In Situ, noninvasive, T2*-weighted MRI-derived parameters predict ex vivo structural properties of an anterior cruciate ligament reconstruction or bioenhanced primary repair in a porcine model

Vascular Research of Pig Knee from the Perspective of Comparative Medicine

BACKGROUND

Pigs have long been employed as an animal model for knee-related diseases. However, vascular anatomy around the pig knee is rare. The objective of this study was to explore the vascular anatomy around the pig knee from the perspective of comparative medicine.

METHODS

Fifteen fresh cadaveric hindlimbs of hybrid pigs were used in this study. The femoral artery was infused with red- or black-colored latex. The origination, course, and branches of the arteries around the pig knee were observed.

RESULTS

The femoral artery around the pig knee has the following branches: the saphenous artery, the first descending geniculate artery, the second descending geniculate artery, several muscular branches, and the caudal femoral artery. The popliteal artery gives off the following branches: the medial sural artery, lateral sural artery, and 5 articular branches. The caudal tibial artery was very thin, whereas the cranial tibial artery was strong and gave off a cranial recurrent tibial artery running toward the knee joint.

CONCLUSIONS

With the help of 2 classic veterinary anatomy books, we described the vascular anatomy around the pig knee from the perspective of comparative medicine, which was useful for vessel-related studies using pig knees and was conducive to academic communication.

Novel Noninvasive Imaging Techniques to Assess Structural, Functional, and Material Properties of Tendon, Ligament, and Cartilage: A Narrative Review of Current Concepts

Background

Novel noninvasive imaging modalities such as quantitative magnetic resonance imaging (qMRI) and shear wave elastography (SWE) allow for assessment of soft tissue microstructure and composition, which ultimately may be associated with functional and material properties.

Purpose

To provide a narrative review of the scientific techniques and clinical applications of qMRI and SWE for the evaluation of soft tissue about the knee and shoulder, including the meniscus, the anterior cruciate ligament (ACL), and the rotator cuff.

Study Design

Review.

Methods

A literature search was performed in October 2022 via PubMed using the following keywords: "quantitative MRI tendon," quantitative MRI ligament,""quantitative MRI cartilage," or "shear wave elastography tendon." Only articles related to clinical applications were included in this review.

Results

Conventional imaging techniques, including standard morphologic magnetic resonance imaging (MRI) and ultrasound imaging, have limited ability to evaluate the material and functional properties of soft tissue; qMRI builds on the limitations of conventional morphologic MRI by allowing for detection of early articular cartilage changes, differentiation of healed versus unhealed meniscal tissue, and quantification of ACL graft maturity. SWE can evaluate the material properties of rotator cuff and Achilles tendons after injury, which may provide insight into both the chronicity and the healing status of the aforementioned injuries.

Conclusion

Our review of the literature showed that quantitative imaging techniques, including qMRI and SWE, may both improve early detection of pathology and aid in comprehensive evaluation after treatment.

Biological augmentation of anterior cruciate ligament reconstruction with bone marrow aspirate concentrate: a systematic review and meta-analysis of randomised controlled trials

PURPOSE

Biological augmentation of anterior cruciate ligament (ACL) reconstruction with bone marrow aspirate concentrate (BMAC) is gaining attention for its theoretical potential to enhance postoperative healing and recovery. However, its clinical benefits remain uncertain, and its high cost raises questions about efficacy. Hence, we systematically reviewed randomised controlled trials (RCTs) to evaluate the effectiveness of BMAC in ACL reconstruction.

METHODS

Our search included Cochrane, EMBASE, OVID, PubMed, and Scopus databases for RCTs evaluating the use of BMAC in ACL reconstruction. Primary outcomes focused on International Knee Documentation Committee (IKDC) scores and Lysholm scores. Secondary outcomes included MRI-related outcomes and postoperative complications. Statistical analysis was conducted using Review Manager 5.4 (Cochrane Collaboration), with heterogeneity assessed using Cochrane's Q test and I2 statistics.

RESULTS

221 patients from five RCTs were included, with 109 (49.3%) receiving BMAC augmentation. Follow-up ranged from 11.05 to 24 months. No significant differences were found in postoperative IKDC scores between the BMAC and control groups at, three, six and 12 months. The BMAC group had significantly higher IKDC scores at 24 months; however, this difference was unlikely to be clinically significant. No significant differences were observed in postoperative Lysholm scores at 12 or 24 months. MRI-related outcomes suggested potential graft recovery improvement with BMAC, and complication rates were comparable between groups.

CONCLUSION

In summary, biological augmentation with BMAC in ACL reconstruction does not significantly improve early patient-reported outcomes but offers potential benefits in graft recovery without increasing complication rates.

The Vascular Anatomy and Harvesting of the Lateral Femoral Condyle Flap in Pigs

BACKGROUND

 Clinically, there has been increasing employment of the lateral femoral condyle flap. The objective of this study was to explore the vascular anatomy of the lateral femoral condyle in pigs and to explore the feasibility of using pigs as an animal model of the lateral femoral condyle flap.

METHODS

 A total of 20 fresh cadaveric hindlimbs of 4-week-old hybrid pigs were used in this study. The origination, course, and branches of the nourishing vessels of the lateral femoral condyle were observed in 15 specimens. The primary parameters included the variability in the anatomy of the vessels and the length and outer diameter of the vessels. Surgical procedures for the lateral femoral condyle flap were conducted on five specimens.

RESULTS

 The primary nourishing arteries of the lateral femoral condyle in pigs were the first superolateral geniculate artery, which was observed in all 15 specimens and had a diameter and length of 1.99 ± 0.44 mm and 2.27 ± 0.46 cm, respectively, as measured at their origination. The operation was performed in the lateral position. A 10-cm skin incision was made from the lower edge of the patella to the posterior lateral side of the distal femur. After blunt dissection of the intermuscular septum between the biceps femoris and vastus lateralis, the whole course of the first superolateral geniculate artery was exposed.

CONCLUSION

 The vascular anatomy of the lateral femoral condyle in pigs and that of humans exhibited great similarities. The harvesting of the lateral femoral condyle flap in pigs was as easy as that in humans. Pigs could serve as a suitable animal model for the lateral femoral condyle flap.

The vascular anatomy and harvesting of the medial femoral condyle flap in pigs

INTRODUCTION

Clinically, there has been increasing employment of the medial femoral condyle flap. Pigs have been employed as a model of the medial femoral condyle flap. However, related anatomical studies from the perspective of comparative medicine are rare. The objective of this study was to explore the vascular anatomy of the medial femoral condyle in pigs, explore the surgical procedure of the medial femoral condyle flap in pigs, and compare the medial femoral condyle flap in pigs and humans.

MATERIALS AND METHODS

20 fresh cadaveric hindlimbs of hybrid pigs were used in this study. The origination, course, and branches of the vessels nourishing the medial femoral condyle were observed in 15 specimens. The variability in the anatomy of the vessels and the length and outer diameter of the vessels were evaluated. Surgical procedures for the medial femoral condyle flap were conducted on five specimens.

RESULTS

The nourishing artery of the medial femoral condyle in pigs was the second descending geniculate artery, which was observed in all 15 pigs and had a diameter and length of 2.013 ± 0.316 mm and 1.527 ± 0.212 cm, respectively. A skin incision of approximately 10 cm was used to harvest the medial femoral condyle flap of the pig in the supine position. After the adductor muscle was cut, the whole course of the second descending geniculate artery artery and its venae comitantes were exposed.

CONCLUSIONS

The vascular anatomy of the medial femoral condyle in pigs and that of humans exhibited great similarities. The medial femoral condyle flap in pigs was as easily harvested as that in humans. Pigs could serve as a suitable animal model for the medial femoral condyle flap.

Higher Posterior Tibial Slope and Lower Medial Proximal Tibial Angle of the Knee Are Associated With Delayed Graft Maturation After Anterior Cruciate Ligament Reconstruction Surgery With Hamstring Autograft

PURPOSE

To relate bone shape with anterior cruciate ligament (ACL) graft maturation, as evaluated by quantitative magnetic resonance imaging.

METHODS

We retrospectively evaluated patients aged 18 to 60 years who underwent ACL reconstruction with a hamstring autograft with doubled semitendinosus and gracilis at our institution between 2018 and 2020 with isolated ACL injuries. All patients had a minimum follow-up period of 2 years. To evaluate alignment, radiographs of the knee were taken preoperatively. Postoperative 3T magnetic resonance imaging and patient-reported outcome scores were acquired at 2 years after surgery. A combined T1ρ/T2 quantification sequence and a 3-dimensional multiecho ultrashort echo time (UTE) cone sequence were obtained in a sagittal-oblique plane for better assessment of the ACL graft. After acquiring images, a manual segmentation for the ACL graft was performed to assess T1ρ, T2, and UTE T2∗ relaxation times. Correlations between radiographic parameters or patient-reported outcome scores and T1ρ, T2, and UTE T2∗ values were tested with Pearson correlation coefficients. Significance was defined as P < .05.

RESULTS

Participants were 28 patients (12 men and 16 women) who had a mean (SD) age of 34.3 (8.5) years and body mass index of 24.4 (4.5). A significant correlation was found between the preoperative posterior tibial slope (PTS) and the T1ρ, T2, and UTE T2∗ relaxation times (r = 0.41, P = .033; r = 0.47, P = .014; and r = 0.41, P = .030), indicating inferior graft maturation in patients with a higher PTS. Furthermore, a negative correlation was identified between the preoperative medial proximal tibial angle and the T1ρ, T2, and UTE T2∗ relaxation times (r = -0.39, P = .039; r = -0.46, P = .018; and r = -0.43, P = .024), indicating inferior graft maturation in patients with greater varus knee alignment.

CONCLUSIONS

The study findings suggest that an increased PTS and a lower medial proximal tibial angle are associated with inferior graft maturation as per T1ρ, T2, and UTE T2∗ imaging at 2 years post-ACL reconstruction.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Broström ankle ligament repair augmented with suture tape : Results of magnetic resonance imaging evaluation

BACKGROUND

The Broström procedure is an established procedure in cases of primary lateral ankle ligament repair (LALR). To improve postoperative stability an augmentation device, InternalBrace™ (Arthrex, Naples, FL) has been introduced. This study evaluates remodelling of the anterior talofibular ligament (ATFL) in patients undergoing a tape augmented Broström technique as well as clinical outcomes.

METHODS

In this study 32 patients with chronic lateral ankle instability (CLAI) receiving augmented LALR were included. Clinical outcomes were evaluated at a one-time postoperative visit between 12 and 18 months. A 3 T magnetic resonance imaging (MRI) was done to evaluate the morphology of the ATFL. Statistical analysis was completed with the free software and environment R version 3.6.3 (Bell Laboratories, Murray Hill, NJ, USA) and P-values < 0.05 were considered statistically significant.

RESULTS

The mean follow-up time was 15.3 ± 1.8 months with a return to sport time of 4.0 ± 2.4 months. The average AOFAS (American Orthopaedic Foot and Ankle Society Score) score was 94.4 ± 7.2, the FAOS (Foot and Ankle Outcome Score) demonstrated 87.3 ± 10.4 points and the FFI (Foot Function Index - 2 scores (pain and function score)) was 22.9 ± 20.1 and 15.4 ± 10.4, respectively. The MRI findings demonstrated an average length of the ATFL of 18.6 ± 4.3 mm and the width was 3.6 ± 0.9 mm. A clear differentiation between the ATFL and the augmentation device could be shown in 28 cases. The Fisher's exact test could not depict a significant correlation between the presence of a bone marrow edema and the tension of the augmentation device with a level of significance of α = 0.05.

CONCLUSION

An anatomical healing tendency of the ligament repair and good integrity of the augmentation device could be shown based on MRI findings. The lateral ligament repair augmented with suture tape is an effective and safe procedure regarding surgical treatment in chronic lateral ankle instability producing good clinical outcome.

Bridge-Enhanced Anterior Cruciate Ligament Restoration: 6-Year Results From the First-in-Human Cohort Study

Background

Bridge-enhanced anterior cruciate ligament restoration (BEAR) combines suture repair of the anterior cruciate ligament (ACL) with an extracellular matrix implant plus autologous blood to facilitate native ACL healing.

Purpose/Hypothesis

The purpose of this study was to compare the 6-year follow-up outcomes of patients who underwent the BEAR procedure with those of a nonrandomized concurrent control group receiving autograft ACL reconstruction (ACLR) in the first-in-human safety study of the BEAR implant (BEAR I trial). Based on the 2-year results, it was hypothesized that isometric hamstring strength after the BEAR procedure would be greater than that after ACLR and that there would be no other differences in outcomes at 6 years.

Study Design

Cohort study, Level of evidence, 2.

Methods

Ten patients underwent BEAR and 10 received ACLR with a 4-stranded hamstring autograft. Outcomes assessed included the record of subsequent surgeries, the International Knee Documentation Committee (IKDC) Subjective Knee Score, IKDC physical examination grade, the Knee injury and Osteoarthritis Outcome Score, instrumented knee laxity, functional outcomes (ie, muscle strength assessments and hop testing), and qualitative magnetic resonance imaging assessment. Comparisons between treatments were based on computations of the mean differences and the associated 95% CIs.

Results

One patient in the BEAR group and 3 patients in the ACLR group were lost to follow-up. In the period between 2 and 6 years, 1 patient in each group underwent revision surgery. There were no differences between groups at the 6-year follow-up in any of the outcome measures except for isometric hamstring strength, which was approximately equal to that of the contralateral knee in the BEAR group and <44% of that in the contralateral knee in the ACLR group (P < .01).

Conclusion

This preliminary study suggests that the outcomes of BEAR and ACLR with a hamstring tendon graft may be similar at the 6-year follow-up and warrants investigation of the BEAR procedure in a larger cohort of patients.

Comprehensive evaluation of magnetic resonance imaging sequences for signal intensity based assessment of anterior cruciate ligament healing following surgical treatment

Normalized signal intensity (SI) obtained from magnetic resonance imaging (MRI) has been used to track anterior cruciate ligament (ACL) postoperative remodeling. We aimed to assess the effect of MRI sequence (PD: proton density-weighted; T2: T2-weighted; CISS: constructive interference in steady state) on postoperative changes in healing ACLs/grafts. We hypothesized that CISS is better at detecting longitudinal SI and texture changes of the healing ACL/graft compared to the common clinical sequences (PD and T2). MR images of patients who underwent ACL surgery were evaluated and separated into groups based on surgical procedure (Bridge-Enhanced ACL Repair (BEAR; n = 50) versus ACL reconstruction (ACLR; n = 24)). CISS images showed decreasing SI across all timepoints in both the BEAR and ACLR groups (p < 0.01), PD and T2 images showed decreasing SI in the 6-to-12- and 12-to-24-month postoperative timeframes in the BEAR group (p < 0.02), and PD images additionally showed decreasing SI between 6- and 24-months postoperation in the ACLR group (p = 0.02). CISS images showed texture changes in both the BEAR and ACLR groups, showing increases in energy and decreases in entropy in the 6-to-12- and 6-to-24-month postoperative timeframes in the BEAR group (p < $\lt $  0.04), and increases in energy, decreases in entropy, and increases in homogeneity between 6 and 24 months postoperation in the ACLR group (p < 0.04). PD images showed increases in energy and decreases in entropy between 6- and 24-months postoperation in the ACLR group (p < 0.008). Finally, CISS was estimated to require a smaller sample size than PD and T2 to detect SI differences related to postoperative remodeling.

MRI Assessment of Tendon Graft After Lateral Ankle Ligament Reconstruction: Does Ligamentization Exist?

BACKGROUND

No description exists in the literature about the normal evolution of tendon graft after a lateral ankle ligament (LAL) reconstruction.

PURPOSE

To assess the magnetic resonance imaging (MRI) characteristics and the evolution of the tendon graft during different moments in the follow-up after an endoscopic reconstruction of the LAL.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This prospective study included 37 consecutive patients who underwent an endoscopic reconstruction of the LAL with an autograft using the gracilis tendon to treat chronic ankle instability (CAI) resistant to nonoperative treatment (CAI group) and 16 patients without ankle instability (control group). All patients in the CAI group underwent a postoperative assessment at 6, 12, and 24 months using the Karlsson score and MRI examination. Only patients with good and excellent results were included in the study. Graft assessment consisted of qualitative measurements and quantitative evaluations of the reconstructed anterior talofibular ligament (RATFL) and reconstructed calcaneofibular ligament (RCFL), including signal-to-noise quotient (SNQ) and contrast-to-noise quotient (CNQ) measurements in proton density-fat suppressed (PD-FS) and T1-weighted sequences. The analysis of variance test was used to compare the SNQ and the CNQ at different time points for each sequence.

RESULTS

The MRI signal at 6 months was increased compared with that of the control group. Next, a significant signal decrease from 6 to 24 months was noted on PD-FS and T1-weighted images. SNQ measurements on PD-FS weighted images for both the RATFL and the RCFL demonstrated a significantly higher signal (P < .01 and P = .01, respectively) at 6 months compared with that of the control group. Subsequently, the signal decreased from 6 to 24 months. Similarly, CNQ measurements on PD-FS weighted images for both the RATFL and the RCFL demonstrated a significantly higher signal (P < .01 and P < .01, respectively) at 6 months compared with that of the control group. Subsequently, the signal decreased from 6 to 24 months.

CONCLUSION

The present study demonstrated an evolution of the MRI characteristics, suggesting a process of graft maturation toward ligamentization. This is important for clinical practice, as it suggests an evolution in graft properties and supports the possibility of creating a viable ligament.

Augmentation of ACL Autograft Reconstruction With an Amnion Collagen Matrix Wrap and Bone Marrow Aspirate Concentrate: A Pilot Randomized Controlled Trial With 2-Year Follow-up

Background

It is theorized that the lack of a synovial lining after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) contributes to slow ligamentization and possible graft failure. Whether graft maturation and incorporation can be improved with the use of a scaffold requires investigation.

Purpose

To evaluate the safety and efficacy of wrapping an ACL autograft with an amnion collagen matrix and injecting bone marrow aspirate concentrate (BMAC), quantify the cellular content of the BMAC samples, and assess 2-year postoperative patient-reported outcomes.

Study Design

Randomized controlled trial; Level of evidence, 2.

Methods

A total of 40 patients aged 18 to 35 years who were scheduled to undergo ACLR were enrolled in a prospective single-blinded randomized controlled trial with 2 arms based on graft type: bone-patellar tendon-bone (BTB; n = 20) or hamstring (HS; n = 20). Participants in each arm were randomized into a control group who underwent standard ACLR or an intervention group who had their grafts wrapped with an amnion collagen matrix during graft preparation, after which BMAC was injected under the wrap layers after implantation. Postoperative magnetic resonance imaging (MRI) mapping/processing yielded mean T2* relaxation time and graft volume values at 3, 6, 9, and 12 months. Participants completed the Single Assessment Numeric Evaluation Score, Knee injury and Osteoarthritis Outcome Score, and pain visual analog scale. Statistical linear mixed-effects models were used to quantify the effects over time and the differences between the control and intervention groups. Adverse events were also recorded.

Results

No significant differences were found at any time point between the intervention and control groups for BTB T2* (95% CI, -1.89 to 0.63; P = .31), BTB graft volume (95% CI, -606 to 876.1; P = .71), HS T2* (95% CI, -2.17 to 0.39; P = .162), or HS graft volume (95% CI, -11,141.1 to 351.5; P = .28). No significant differences were observed between the intervention and control groups of either graft type on any patient-reported outcome measure. No adverse events were reported after a 2-year follow-up.

Conclusion

In this pilot study, wrapping a graft with an amnion collagen matrix and injecting BMAC appeared safe. MRI T2* values and graft volume of the augmented ACL graft were not significantly different from that of controls, suggesting that the intervention did not result in improved graft maturation.

Registration

NCT03294759 (ClinicalTrials.gov identifier).

A review on the use of porcine in tendon research

PURPOSE OF REVIEW

Large animals have been increasingly employed in tendon research; the objective of this review was to summarize the employment of porcine in tendon research.

RECENT FINDINGS

Literature before 2022-03-31 was searched using the following strategy: (pig[MeSH Terms]) AND (tendon[MeSH Terms]); (pig[MeSH Terms]) AND (tendon[title]); (tendon[MeSH Terms]) AND (porcine[title]); (tendon[title]) AND (porcine[title]); (tendon[MeSH Terms]) AND (pig[title]); (tendon[title]) AND (pig[title]); (tendon[MeSH Terms]) AND (swine[title]); (tendon[title]) AND (swine[title]). 296 studies were included in this review. There were wide application areas of porcine tendon, including tissue engineering tendons, training of surgical skills. Porcine tendon was used both in in vitro studies, such as anatomy, biomechanics, cytology, and material science as well as in in vivo studies. The research techniques of porcine tendon are relatively common.

SUMMARY

In conclusion, pigs have been widely used as a good animal model of tendon research. However, the limitations of porcine tendon research (the lack of anatomical research and in vivo studies) should be given more attention in future studies.

Preclinical tendon and ligament models: Beyond the 3Rs (replacement, reduction, and refinement) to 5W1H (why, who, what, where, when, how)

Several tendon and ligament animal models were presented at the 2022 Orthopaedic Research Society Tendon Section Conference held at the University of Pennsylvania, May 5 to 7, 2022. A key objective of the breakout sessions at this meeting was to develop guidelines for the field, including for preclinical tendon and ligament animal models. This review summarizes the perspectives of experts for eight surgical small and large animal models of rotator cuff tear, flexor tendon transection, anterior cruciate ligament tear, and Achilles tendon injury using the framework: "Why, Who, What, Where, When, and How" (5W1H). A notable conclusion is that the perfect tendon model does not exist; there is no single gold standard animal model that represents the totality of tendon and ligament disease. Each model has advantages and disadvantages and should be carefully considered in light of the specific research question. There are also circumstances when an animal model is not the best approach. The wide variety of tendon and ligament pathologies necessitates choices between small and large animal models, different anatomic sites, and a range of factors associated with each model during the planning phase. Attendees agreed on some guiding principles including: providing clear justification for the model selected, providing animal model details at publication, encouraging sharing of protocols and expertise, improving training of research personnel, and considering greater collaboration with veterinarians. A clear path for translating from animal models to clinical practice was also considered as a critical next step for accelerating progress in the tendon and ligament field.

LigaNET: A multi-modal deep learning approach to predict the risk of subsequent anterior cruciate ligament injury after surgery

Anterior cruciate ligament (ACL) injuries are a common cause of soft tissue injuries in young active individuals, leading to a significant risk of premature joint degeneration. Postoperative management of such injuries, in particular returning patients to athletic activities, is a challenge with immediate and long-term implications including the risk of subsequent injury. In this study, we present LigaNET, a multi-modal deep learning pipeline that predicts the risk of subsequent ACL injury following surgical treatment. Postoperative MRIs (n=1,762) obtained longitudinally between 3 to 24 months after ACL surgery from a cohort of 159 patients along with 11 non-imaging outcomes were used to train and test: 1) a 3D CNN to predict subsequent ACL injury from segmented ACLs, 2) a 3D CNN to predict injury from the whole MRI, 3) a logistic regression classifier predict injury from non-imaging data, and 4) a multi-modal pipeline by fusing the predictions of each classifier. The CNN using the segmented ACL achieved an accuracy of 77.6% and AUROC of 0.84, which was significantly better than the CNN using the whole knee MRI (accuracy: 66.6%, AUROC: 0.70; P<.001) and the non-imaging classifier (accuracy: 70.1%, AUROC: 0.75; P=.039). The fusion of all three classifiers resulted in highest classification performance (accuracy: 80.6%, AUROC: 0.89), which was significantly better than each individual classifier (P<.001). The developed multi-modal approach had similar performance in predicting the risk of subsequent ACL injury from any of the imaging sequences (P>.10). Our results demonstrate that a deep learning approach can achieve high performance in identifying patients at high risk of subsequent ACL injury after surgery and may be used in clinical decision making to improve postoperative management (e.g., safe return to sports) of ACL injured patients.

Association Between Tunnel Position, Tunnel Angle, Graft Signal Intensity, and Graft Thickness in the Reconstructed Posterior Cruciate Ligament

Background

An appropriate tunnel position, tunnel angle, and tunnel-graft angle are important factors for maintaining the stability and mechanical properties of a posterior cruciate ligament (PCL) graft.

Purpose

To evaluate the association between tunnel position, tunnel angle, graft signal intensity ratio (SIR), and graft thickness after remnant-preserving PCL reconstruction.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included were patients who had undergone remnant-preserving single-bundle PCL reconstruction using a tibialis anterior allograft between March 2014 and September 2020 and who had minimum 12-month postoperative magnetic resonance imaging scans. Tunnel position and angle were evaluated via 3-dimensional computed tomography, and their association with graft SIR on both the femoral and the tibial sides was determined. Graft thickness and SIR at 3 areas of the graft were evaluated and compared, and their association with tunnel-graft angle was also determined.

Results

Overall, 50 knees (50 patients; 43 male, 7 female) were included. The mean time to postoperative magnetic resonance imaging was 25.8 ± 15.8 months. The mean SIR of the graft's midportion was higher compared with that of the proximal and distal portions (P = .028 and P < .001, respectively), and the SIR of the proximal portion was higher compared with that of the distal portion (P = .002). The femoral tunnel-graft angle was more acute than the tibial tunnel-graft angle (P = .004). A more anteriorly and distally located femoral tunnel led to a less acute femoral tunnel-graft angle (P = .005) and a decreased SIR of the proximal portion (P = .040), and a more laterally located tibial tunnel was associated with a less acute tibial tunnel-graft angle (P = .024) and a reduced SIR of the distal portion (P = .044). The mean thicknesses of the graft's midportion and distal portion were larger than that of the proximal portion (P < .001). The SIR of the graft's midportion was positively correlated with its thickness (r = 0.321; P = .023).

Conclusion

The SIR of the proximal portion of the graft around the femoral tunnel was higher than that of the distal portion around the tibial tunnel. An anteriorly and distally positioned femoral tunnel and a laterally positioned tibial tunnel resulted in less acute tunnel-graft angles that were associated with decreased signal intensity.

Comparison of Primary Repair of the Anterior Cruciate Ligament and Anterolateral Structures to Reconstruction and Lateral Extra-articular Tenodesis at 2-Year Follow-up

BACKGROUND

Lateral extra-articular procedures have been effective in reducing graft rupture rates after anterior cruciate ligament (ACL) reconstruction (ACLR), but the evidence supporting their role in ACL repair is sparse.

PURPOSE/HYPOTHESIS

The purpose was to compare clinical and radiological outcomes of ACLR and lateral extra-articular tenodesis (LET) (ACLR+LET) against combined repair of the ACL and anterolateral (AL) structures (ACL+AL Repair). It was hypothesized that patients undergoing ACL+AL Repair would have noninferior clinical and radiological outcomes with respect to International Knee Documentation Committee (IKDC) scores, knee laxity parameters, and magnetic resonance imaging (MRI) characteristics. Furthermore, it was hypothesized that patients undergoing repair would have significantly better Forgotten Joint Score-12 (FJS-12) values and shorter times to return to the preinjury level of sport, without any increase in the rate of ipsilateral second ACL injury.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Consecutive patients evaluated with an acute ACL tear were considered for study eligibility. ACLR+LET was only performed when intraoperative tear characteristics contraindicated ACL repair. Patient-reported outcome measures such as the IKDC score, Lysholm score, and Knee injury and Osteoarthritis Outcome Score (KOOS); reinjury rates; anteroposterior side-to-side laxity difference; and MRI characteristics were reported at a minimum follow-up of 2 years. The noninferiority study was based on the IKDC subjective score; side-to-side anteroposterior laxity difference; and signal-to-noise quotient (SNQ). The noninferiority margins were defined using the existing literature. An a priori sample size calculation was performed using the IKDC subjective score as the primary outcome measure.

RESULTS

A total of 100 patients (47 ACLR+LET, 53 ACL+AL Repair) with a mean follow-up of 25.2 months (range, 24-31 months) were enrolled and underwent surgery within 15 days of injury. At the final follow-up, the differences between groups with respect to the IKDC score, anteroposterior side-to-side laxity difference, and SNQ did not exceed noninferiority thresholds. ACL+AL Repair was associated with a shorter time to return to the preinjury level of sport (ACL+AL Repair: mean, 6.4 months; ACLR+LET: mean, 9.5 months; P < .01), better FJS-12 values (ACL+AL Repair: mean, 91.4; ACLR+LET: mean, 97.4; P = .04), and a higher proportion of patients achieving the Patient Acceptable Symptom State (PASS) for the KOOS subdomains studied (Symptoms: 90.2% vs 67.4%, P = .005; Sport and Recreation: 94.1% vs 67.4%, P < .001; Quality of Life: 92.2% vs 73.9%, P = .01). There were no significant differences between groups with respect to ipsilateral second ACL injury rates (ACL+AL Repair group, 3.8% and ACLR+LET group, 2.1% [n = 1]; P = .63).

CONCLUSION

ACL+AL Repair yielded clinical outcomes that were noninferior to (or not significantly different from) ACLR+LET with respect to IKDC subjective, Tegner activity level, and Lysholm scores; knee laxity parameters; graft maturity; and rates of failure and reoperation. However, there were significant advantages of ACL+AL Repair, including a shorter duration of time to return to the preinjury level of sport, better FJS-12 values, and a higher proportion of patients achieving PASS for KOOS subdomains studied (Symptoms, Sport and Recreation, Quality of Life).

Early MRI-based quantitative outcomes are associated with a positive functional performance trajectory from 6 to 24 months post-ACL surgery

PURPOSE

Quantitative magnetic resonance imaging (qMRI) has been used to determine the failure properties of ACL grafts and native ACL repairs and/or restorations. How these properties relate to future clinical, functional, and patient-reported outcomes remain unknown. The study objective was to investigate the relationship between non-contemporaneous qMRI measures and traditional outcome measures following Bridge-Enhanced ACL Restoration (BEAR). It was hypothesized that qMRI parameters at 6 months would be associated with clinical, functional, and/or patient-reported outcomes at 6 months, 24 months, and changes from 6 to 24 months post-surgery.

METHODS

Data of BEAR patients (n = 65) from a randomized control trial of BEAR versus ACL reconstruction (BEAR II Trial; NCT02664545) were utilized retrospectively for the present analysis. Images were acquired using the Constructive Interference in Steady State (CISS) sequence at 6 months post-surgery. Single-leg hop test ratios, arthrometric knee laxity values, and International Knee Documentation Committee (IKDC) subjective scores were determined at 6 and 24 months post-surgery. The associations between traditional outcomes and MRI measures of normalized signal intensity, mean cross-sectional area (CSA), volume, and estimated failure load of the healing ACL were evaluated based on bivariate correlations and multivariable regression analyses, which considered the potential effects of age, sex, and body mass index.

RESULTS

CSA (r = 0.44, p = 0.01), volume (r = 0.44, p = 0.01), and estimated failure load (r = 0.48, p = 0.01) at 6 months were predictive of the change in single-leg hop ratio from 6 to 24 months in bivariate analysis. CSA (βstandardized = 0.42, p = 0.01), volume (βstandardized = 0.42, p = 0.01), and estimated failure load (βstandardized = 0.48, p = 0.01) remained significant predictors when considering the demographic variables. No significant associations were observed between MRI variables and either knee laxity or IKDC when adjusting for demographic variables. Signal intensity was also not significant at any timepoint.

CONCLUSION

The qMRI-based measures of CSA, volume, and estimated failure load were predictive of a positive functional outcome trajectory from 6 to 24 months post-surgery. These variables measured using qMRI at 6 months post-surgery could serve as prospective markers of the functional outcome trajectory from 6 to 24 months post-surgery, aiding in rehabilitation programming and return-to-sport decisions to improve surgical outcomes and reduce the risk of reinjury.

LEVEL OF EVIDENCE

Level II.

Propensity for Clinically Meaningful Improvement and Surgical Failure After Anterior Cruciate Ligament Repair

Background

Primary repair of the anterior cruciate ligament (ACL) confers an alternative to ACL reconstruction in appropriately selected patients.

Purpose

To prospectively assess survivorship and to define the clinically meaningful outcomes after ACL repair.

Study Design

Case series; Level of evidence, 4.

Methods

Included were consecutive patients with Sherman grade 1-2 tears who underwent primary ACL repair with or without suture augmentation between 2017 and 2019. Patient-reported outcomes (Lysholm, Tegner, International Knee Documentation Committee, Western Ontario and McMaster Universities Osteoarthritis Index, and Knee injury and Osteoarthritis Outcome Score [KOOS] subscales) were collected preoperatively and at 6 months, 1 year, and 2 years postoperatively. The minimal clinically important difference (MCID) was calculated using a distribution-based method, whereas the Patient Acceptable Symptom State (PASS) and substantial clinical benefit (SCB) were calculated using an anchor-based method. Plain radiographs and magnetic resonance imaging (MRI) were obtained at 6 months, 1 year, and 2 years postoperatively.

Results

A total of 120 patients were included. The overall failure rate was 11.3% at 2 years postoperatively. Changes in outcome scores required to achieve the MCID ranged between 5.1 and 14.3 at 6 months, 4.6 and 8.4 at 1 year, and 4.7 and 11.9 at 2 years postoperatively. Thresholds for PASS achievement ranged between 62.5 and 89 at 6 months, 75 and 89 at 1 year, and 78.6 and 93.2 at 2 years postoperatively. Threshold scores (absolute/change based) for achieving the SCB ranged between 82.8 and 96.4/17.7 and 40.1 at 6 months, between 94.7 and 100/23 and 45 at 1 year, and between 95.3 and 100/29.4 and 45 at 2 years. More patients achieved the MCID and PASS at 1 year compared with 6 months and 2 years. For SCB, this trend was also observed for non-KOOS outcomes, while for KOOS subdomains, more patients achieved the SCB at 2 years. High-intensity signal of the ACL repair (odds ratio [OR], 31.7 [95% CI, 1.5-73.4]; P = .030) and bone contusions on MRI (OR, 4.2 [95% CI, 1.7-25.2]; P = .041) at 1 year postoperatively were independently associated with increased risk of ACL repair failure.

Conclusion

The rate of clinically meaningful outcome improvement was high early after ACL repair, with the greatest proportion of patients achieving the MCID, PASS, and SCB at 1 year postoperatively. Bone contusions involving the posterolateral tibia and lateral femoral condyle as well as high repair signal intensity at 1 year postoperatively were independent predictors of failure at 2 years postoperatively.

Predicting anterior cruciate ligament failure load with T2* relaxometry and machine learning as a prospective imaging biomarker for revision surgery

Non-invasive methods to document healing anterior cruciate ligament (ACL) structural properties could potentially identify patients at risk for revision surgery. The objective was to evaluate machine learning models to predict ACL failure load from magnetic resonance images (MRI) and to determine if those predictions were related to revision surgery incidence. It was hypothesized that the optimal model would demonstrate a lower mean absolute error (MAE) than the benchmark linear regression model, and that patients with a lower estimated failure load would have higher revision incidence 2 years post-surgery. Support vector machine, random forest, AdaBoost, XGBoost, and linear regression models were trained using MRI T2* relaxometry and ACL tensile testing data from minipigs (n = 65). The lowest MAE model was used to estimate ACL failure load for surgical patients at 9 months post-surgery (n = 46) and dichotomized into low and high score groups via Youden's J statistic to compare revision incidence. Significance was set at alpha = 0.05. The random forest model decreased the failure load MAE by 55% (Wilcoxon signed-rank test: p = 0.01) versus the benchmark. The low score group had a higher revision incidence (21% vs. 5%; Chi-square test: p = 0.09). ACL structural property estimates via MRI may provide a biomarker for clinical decision making.

Automated segmentation of the healed anterior cruciate ligament from T2 * relaxometry MRI scans

Collagen organization of the anterior cruciate ligament (ACL) can be evaluated using T2 * relaxometry. However, T2 * mapping requires manual image segmentation, which is a time-consuming process and prone to inter- and intra- segmenter variability. Automating segmentation would address these challenges. A model previously trained using Constructive Interference in Steady State (CISS) scans was applied to T2 * segmentation via transfer learning. It was hypothesized that there would be no significant differences in the model's segmentation performance between T2 * and CISS, structural measures versus ground truth manual segmentation, and reliability versus independent and retest manual segmentation. Transfer learning was conducted using 54 T2 * scans of the ACL. Segmentation performance was assessed with Dice coefficient, precision, and sensitivity, and structurally with T2 * value, volume, subvolume proportions, and cross-sectional area. Model performance relative to independent manual segmentation and repeated segmentation by the ground truth segmenter (retest) were evaluated on a random subset. Segmentation performance was analyzed with Mann-Whitney U tests, structural measures with Wilcoxon signed-rank tests, and performance relative to manual segmentation with repeated-measures analysis of variance/Tukey tests (α = 0.05). T2 * segmentation performance was not significantly different from CISS on all measures (p > 0.35). No significant differences were detected in structural measures (p > 0.50). Automatic segmentation performed as well as the retest on all segmentation measures, whereas independent segmentations were lower than retest and/or automatic segmentation (p < 0.023). Structural measures were not significantly different between segmenters. The automatic segmentation model performed as well on the T2 * sequence as on CISS and outperformed independent manual segmentation while performing as well as retest segmentation.

Adaptation of the Signal Noise Quotient MRI classification for graft ligamentization analysis following ATFL and CFL anatomical reconstruction: Validation of the SNQA

BACKGROUND

Chronic ankle instability is the most frequent clinical sign of an antero tibiofibular (ATFL) and/or calcaneo fibular ligament (CFL) tear. One common surgical technique is to use the distal tendon of the gracilis muscle to reconstruct both the ATFL and CFL. In the knee, the hamstring tendons used in anterior cruciate ligament (ACL) reconstruction may go through structural modifications called "ligamentization ". A noninvasive MRI technique has been developed using the Signal/Noise Quotient to compare the signal of the graft following reconstruction to that of the posterior cruciate ligament. To our knowledge no studies have ever evaluated radiographic changes in the graft over time. The main goal of this study was to develop a specific MRI protocol to evaluate graft remodeling following ATFL and CFL reconstruction over time.

METHODS

A prospective study of the changes in the MRI signal of the ATFL-CFL graft 3-months postoperatively was performed in 20 patients. The main outcome was a comparison of the graft signal to that of the peroneal fibular tendon and the surrounding noise to determine the Ankle SNQ (SNQA). MRI images were evaluated by two senior radiologists to assess inter-rater reliability and then 2 weeks later for the intra-rater reproducibility.

RESULTS

The intraclass correlation (ICC) showed excellent inter- and intra rater reliability for the ATFL SNQA (0.96 and 0.91, respectively); and for the CFL SNQA, the ICC was 0.97 and 0.99, respectively. Bland-Altman analysis showed very limited bias in the interpretation of SNQA.

CONCLUSION

This preliminary study confirmed the inter- and intra- rater reliability of a new tool using the SNQA.

Quantitative MRI Biomarkers to Predict Risk of Reinjury Within 2 Years After Bridge-Enhanced ACL Restoration

BACKGROUND

Quantitative magnetic resonance imaging (qMRI) methods were developed to establish the integrity of healing anterior cruciate ligaments (ACLs) and grafts. Whether qMRI variables predict risk of reinjury is unknown.

PURPOSE

To determine if qMRI measures at 6 to 9 months after bridge-enhanced ACL restoration (BEAR) can predict the risk of revision surgery within 2 years of the index procedure.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Originally, 124 patients underwent ACL restoration as part of the BEAR I, BEAR II, and BEAR III prospective trials and had consented to undergo an MRI of the surgical knee 6 to 9 months after surgery. Only 1 participant was lost to follow-up, and 4 did not undergo MRI, leaving a total of 119 patients for this study. qMRI techniques were used to determine the mean cross-sectional area; normalized signal intensity; and a qMRI-based predicted failure load, which was calculated using a prespecified equation based on cross-sectional area and normalized signal intensity. Patient-reported outcomes (International Knee Documentation Committee subjective score), clinical measures (hamstring strength, quadriceps strength, and side-to-side knee laxity), and functional outcomes (single-leg hop) were also measured at 6 to 9 months after surgery. Univariate and multivariable analyses were performed to determine the odds ratios (ORs) for revision surgery based on the qMRI and non-imaging variables. Patient age and medial posterior tibial slope values were included as covariates.

RESULTS

In total, 119 patients (97%), with a median age of 17.6 years, underwent MRI between 6 and 9 months postoperatively. Sixteen of 119 patients (13%) required revision ACL surgery. In univariate analyses, higher International Knee Documentation Committee subjective score at 6 to 9 months postoperatively (OR = 1.66 per 10-point increase; P = .035) and lower qMRI-based predicted failure load (OR = 0.66 per 100-N increase; P = .014) were associated with increased risk of revision surgery. In the multivariable model, when adjusted for age and posterior tibial slope, the qMRI-based predicted failure load was the only significant predictor of revision surgery (OR = 0.71 per 100 N; P = .044).

CONCLUSION

Quantitative MRI-based predicted failure load of the healing ACL was a significant predictor of the risk of revision within 2 years after BEAR surgery. The current findings highlight the potential utility of early qMRI in the postoperative management of patients undergoing the BEAR procedure.

MRI signal intensity of anterior cruciate ligament graft after transtibial versus anteromedial portal technique (TRANSIG): A randomised controlled clinical trial

BACKGROUND

Two primary surgical femoral drilling techniques are used to reconstruct the anterior cruciate ligament (ACL): the transtibial (TT) technique and the anteromedial portal (AMP) technique. Currently there is no consensus on which surgical technique elicits the best clinical and functional outcomes. MRI-derived measures of the signal intensity (SI) of the ACL graft have been described as an independent predictor of graft properties. The purpose of this study was to assess MRI-derived SI measurements of the ACL graft one year after ACL reconstruction, in order to compare graft maturation of both AMP and TT ACL reconstruction techniques.

METHODS

This randomised controlled trial included 33 patients admitted for primary unilateral ACL reconstruction. Primary outcome was MRI Signal intensity ratio (SIR) of the ACL graft one year after ACL reconstruction. Differences in MRI SIR were assessed on two MRI sequencies: sagittal Proton Density Turbo Spin Echo weighted images (PDTSE) and 3D T2 Gradient Echo (T2*) weighted images. Analysis of interobserver and intraobserver variability was conducted for the SIR measurements.

RESULTS

No difference in signal intensity of the graft was found between the TT and AMP techniques one year after ACL reconstruction (PDTSE p = 0.665, T2* p = 0.957). Both interobserver and intraobserver variability showed strong agreement (ICC 0.64-0.94).

CONCLUSION

No differences in signal intensity of the graft on MRI were seen between the femoral drilling techniques one year after ACL reconstruction, suggesting similar graft maturation at that time. Follow-up studies are needed to determine whether graft intensity changes in the long term.

LEVEL OF EVIDENCE

Therapeutic study with level of evidence I.

Reproducibility and postacquisition correction methods for quantitative magnetic resonance imaging of the anterior cruciate ligament (ACL)

Quantitative magnetic resonance imaging has been used to evaluate the structural integrity of knee joint structures. However, variations in acquisition parameters between scanners pose significant challenges. Understanding the effect of small differences in acquisition parameters for quantitative sequences is vital to the validity of cross-institutional studies, and for the harmonization of large, heterogeneous datasets to train machine learning models. The study objective was to assess the reproducibility of T2 * relaxometry and the constructive interference in steady-state sequence (CISS) across scanners, with minimal hardware-necessitated changes to acquisition parameters. It was hypothesized that there would be no significant differences between scanners in anterior cruciate ligament T2 * relaxation times and CISS signal intensities (SI). Secondarily, it was hypothesized that differences could be corrected by rescaling the SI distribution to harmonize between scanners. Seven volunteers were scanned on 3T Prisma and Tim Trio scanners (Siemens). Three correction methods were evaluated for T2 *: inverse echo time scaling, z-scoring, and Nyúl histogram matching. For CISS, scans were normalized to cortical bone, scaled by the background noise ratio, and log-transformed. Before correction, significant mean differences of 6.0 ± 3.2 ms (71.8%; p = 0.02) and 0.49 ± 0.15 units (40.7%; p = 0.02) for T2 * and CISS across scanners were observed, respectively. After rescaling, T2 * differences decreased to 2.6 ± 2.7 ms (23.9%; p = 0.03), 1.3 ± 2.5 ms (10.9%; p = 0.13), and 1.27 ± 3.0 ms (19.6%; p = 0.40) for inverse echo time, z-scoring, and Nyúl, respectively, while CISS decreased to 0.01 ± 0.11 units (4.0%; p = 0.87). These findings suggest that small acquisition parameter differences may lead to large changes in T2 * and SI values that must be reconciled to compare data across magnets.

Anterior talofibular ligament remnant quality is important for achieving a stable ankle after arthroscopic lateral ankle ligament repair

PURPOSE

The relationship between ligament remnant quality and postoperative outcomes after arthroscopic lateral ankle ligament repair for chronic lateral ankle instability is controversial. This study aimed to determine whether the signal intensity of the anterior talofibular ligament on preoperative magnetic resonance imaging and ligament remnant quality identified on arthroscopy are associated with recurrent ankle instability after arthroscopic lateral ankle ligament repair.

METHODS

A total of 68 ankles from 67 patients with chronic lateral ankle instability who underwent arthroscopic lateral ankle ligament repair were retrospectively studied. The signal intensity of the anterior talofibular ligament was evaluated using T2-weighted magnetic resonance imaging. Arthroscopy was used to evaluate the thickness and mechanical resistance of the anterior talofibular ligament by hook palpation and to classify ankles into two groups: the present anterior talofibular ligament group with adequate mechanical resistance and the absent anterior talofibular ligament group with no mechanical resistance. The outcomes included recurrent ankle instability (respraining of the operated ankle after surgery) and Self-Administered Foot Evaluation Questionnaire scores.

RESULTS

Thirteen ankles were diagnosed with recurrent ankle instability. Patients with a high anterior talofibular ligament T2 signal intensity experienced more recurrent ankle instability than those with a low intensity. As determined via arthroscopy, the absent anterior talofibular ligament group had a higher rate of recurrent ankle instability than the present anterior talofibular ligament group. There were no significant differences in Self-Administered Foot Evaluation Questionnaire scores between patients with high and low anterior talofibular ligament T2 signal intensity, as well as between absent and present anterior talofibular ligament groups based on arthroscopy.

CONCLUSION

Poor quality of the anterior talofibular ligament remnant could result in recurrent ankle instability after arthroscopic lateral ankle ligament repair. Therefore, when treating chronic lateral ankle instability, surgeons should consider ligament quality.

LEVEL OF EVIDENCE

IV.

Effect of Joint Infection After Arthroscopic Single-Bundle ACL Reconstruction With Autologous Hamstring Tendon: A Retrospective Matched MRI Study

Background:

Joint infection after anterior cruciate ligament (ACL) reconstruction is a rare but serious complication.

Purpose:

To assess the effect of joint infection on the graft, cartilage, and bone tunnel using magnetic resonance imaging (MRI) after arthroscopic single-bundle ACL reconstruction with autologous hamstring tendons.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

This retrospective matched cohort study included 26 patients who underwent arthroscopic single-bundle ACL reconstruction with hamstring tendon graft at the authors’ institute between January 2002 and December 2017 and developed postoperative joint infection. These patients were matched 1:3 to patients who did not sustain joint infection after ACL reconstruction (control group). MRI scans were collected at the time of follow-up. The following parameters were evaluated: graft signal-to-noise quotient (SNQ); graft signal intensity at the bone-graft interface and within the knee joint; bone tunnel enlargement at the tunnel aperture, midsection, and exit of the tibial and femoral tunnels; and cartilage integrity.

Results:

The average follow-up time was 47.8 months in the infection group and 48.5 months in the control group. Compared with the control group, the infection group had a significantly higher SNQ (20.01 ± 12.08 vs 7.61 ± 6.70; P = .014) as well as a higher signal intensity at the bone-graft interface (P = .037) and higher Howell grade (P = .031). The mean enlargement at the femoral tunnel aperture was 31.20% ± 26.76% in the infection group and 19.22% ± 20.10% in the control group (P = .037). The articular cartilage of the patellofemoral and lateral femorotibial joints showed more degenerative change in the infection group.

Conclusion:

Study findings indicated that graft ligamentization and incorporation graft maturity were inferior in patients who experienced a joint infection after ACL reconstruction compared with patients who did not.

Association of Smoking With Graft Rupture After Anterior Cruciate Ligament Reconstruction

Background

The effect of smoking on graft rupture after anterior cruciate ligament (ACL) reconstruction is not well understood.

Hypothesis

It was hypothesized that there will be no relationship between tobacco use and graft rupture after ACL reconstruction, as reflected by postoperative magnetic resonance imaging (MRI) and arthroscopic examination.

Study Design

Cohort study; Level of evidence, 3.

Methods

Included were 233 patients who received primary ACL reconstruction with hamstring tendon autograft between January 1, 2013, and December 31, 2019, and who underwent MRI evaluation at 20.2 ± 1.9 months postoperatively. The patients were categorized by smoking history into 2 groups: 39 smokers and 194 nonsmokers. The 2 groups did not differ significantly in age, sex, operative technique, preinjury Tegner score, or mean time until postoperative MRI. The primary outcome was graft rupture rate, with rupture confirmed by either arthroscopic assessment or postoperative MRI diagnosis. The secondary outcome measure was degree of graft ligamentization, evaluated by measuring the signal-to-noise quotient (SNQ) of the graft.

Results

The overall ACL graft rupture rate was 6.0%. The rupture rate was significantly higher in smokers than in nonsmokers (12.8% vs 4.6%, respectively; P = .0498). Smokers also had a significantly higher whole-graft SNQ compared with nonsmokers (4.7 ± 4.4 vs 3.3 ± 3.7, respectively; P = .028), suggesting less satisfactory ligamentization in smokers.

Conclusion

Smoking was associated with a higher risk of graft rupture of ACL reconstruction and a higher SNQ of the intact graft as shown on postoperative MRI.

Effect of a new remnant-preserving technique with anatomical double-bundle anterior cruciate ligament reconstruction on MRI-based graft maturity: a comparison cohort study

PURPOSE

To investigate the effects of a new remnant-preserving double-bundle anterior cruciate ligament reconstruction (ACLR) technique, focused on avoiding remnant damage and preserving continuity of remnants, on graft maturity using magnetic resonance imaging (MRI).

METHODS

A total of 169 patients were divided into three groups: 41 in the preservation group, 70 in the resection group, and 58 in the absent group. In the preservation group, rather than passing the graft through the remnant tissue, the graft was reconstructed such that the anteromedial and posterolateral bundles sandwiched the remnant to avoid damage to the remnant and maintain its continuity. Based on 1-year postoperative MRI, the grafts were divided into three regions: distal, middle, and proximal. The signal/noise quotient (SNQ) of each region of interest was calculated to evaluate the signal intensity of the graft and was compared among the three groups. Additionally, to identify factors influencing graft maturity, a multiple regression analysis was performed with SNQ as the dependent variable and patient demographics, bone morphology, and surgical factors as independent variables.

RESULTS

In a three-group comparison of mean SNQs, the distal region was 3.3 ± 3.4, 8.9 ± 8.3, and 9.0 ± 8.6 (p < 0.001), the middle region was 5.3 ± 3.7, 10.9 ± 11.1, and 11.3 ± 10.2 (p < 0.001), and the proximal region was 6.8 ± 4.5, 11.1 ± 8.8, and 11.7 ± 10.8 (p = 0.017), in order of the preservation, resection, and absent groups, respectively. That indicated that the remnant-preserving ACLR was more hypointense than ACLR with remnant resection or absent in all three regions. Multiple regression analysis showed that remnant preservation remained the relevant factor affecting SNQ of the graft at the distal and middle levels.

CONCLUSION

The new remnant-preserving anatomic double-bundle ACLR had significantly better graft maturity, measured by SNQ on MRI, than the remnant resection and absent groups. The remnant procedure was the relevant factor affecting graft maturity.

LEVEL OF EVIDENCE

Level III.

The Influence of Suture-Tape Augmentation on Biological Healing of the Anterior Talofibular Ligament in Chronic Ankle Instability: A Quantitative Analysis Using MRI

While the effectiveness of suture-tape augmentation for chronic ankle instability has been supported biomechanically and clinically, little information is available regarding biological changes of the lateral ligaments postoperatively. This study aims to quantitatively evaluate ligament regeneration with MRI after suture-tape augmentation. Forty-six patients underwent MRI scan at follow-up of a minimum of 1 year after lateral ligaments augmentation using suture-tape. The signal-to-noise ratio (SNR) and width of anterior talofibular ligament (ATFL) were measured on preoperative and postoperative MRI by 3 researchers. The degree of biological healing of ATFL was analyzed based on the change of SNR and comparison with normal contralateral ankle. Clinical outcomes were evaluated with the Foot and Ankle Outcome Score, Foot and Ankle Ability Measure. Mean Foot and Ankle Outcome Score and Foot and Ankle Ability Measure scores improved significantly from 63.1 to 92.7, and 59.6 to 91.5 points at final follow-up, respectively (p < .001). Mean SNR and width of ATFL were changed insignificantly from 8.24 to 7.96, and 1.88 mm to 2.05 mm at final follow-up, respectively (p = .391, .509). As compared to contralateral side, there were significant differences in both mean SNR and width of the ATFL, respectively (p < .001, p = .0012). Spearman's correlation analysis revealed no significant association between clinical outcomes and degree of biological healing of ATFL based on MRI. Despite significant improvement in patient-reported clinical outcomes, the influence on ligament regeneration of suture-tape augmentation for chronic ankle instability was insignificant. In addition, there was no significant correlation between clinical outcomes and degree of biological healing of the ATFL.

Postoperative MRI signal intensity correlates functional outcomes after superior capsular reconstruction

PURPOSE

Superior capsular reconstruction (SCR) using fascia lata autograft has been performed for irreparable rotator cuff tear recently. The signal-to-noise quotient (SNQ) of the graft on magnetic resonance imaging (MRI) may reflect the degree of graft maturity and healing. However, how SNQ changes with graft remodelling and time and whether this change correlates with postoperative clinical outcomes after SCR remain unknown. This study aimed to explore the correlation between SNQ of the fascia lata autograft and clinical functional outcomes after SCR.

METHODS

Patients with irreparable posterosuperior rotator cuff tear undergoing SCR using fascia lata autograft between 2013 and 2017 were retrospectively analysed. For clinical outcomes, the American Shoulder and Elbow Surgeons (ASES) score, Constant-Murley score, Single Assessment Numeric Evaluation (SANE), and Visual Analogue Scale (VAS) for pain and range of motion (ROM; forward flexion and external rotation) were evaluated at postoperative 6 and 12 months. Signal intensity of the humeral, mid-substance, and glenoid sites and background were measured to calculate the SNQ values on follow-up MRI at 3 and 12 months. The correlations between clinical outcomes and SNQ at different time points were then analysed.

RESULTS

A total of 15 patients were enrolled in the study. The mean postoperative VAS score significantly increased at postoperative 6 months and significantly decreased at postoperative 12 months. Except for forward flexion, all other functional outcomes were improved at postoperative 6 months. Analysis of MRI showed SNQ at the humeral (SNQh), mid-substance, and glenoid sites decreased from postoperative 3 to 12 months with a statistical significance detected in SNQh (P < 0.01). Correlation analyses showed that the SNQh values negatively correlated with VAS, ASES, Constant-Murley score, SANE, ROM (forward flexion), and ROM (external rotation) (all P < 0.05).

CONCLUSION

SNQ of the fascia lata autograft decreased with time in patients receiving SCR. SNQ at the humeral site was negatively correlated with clinical outcomes.

LEVEL OF EVIDENCE

III.

UTE-T2* versus conventional T2* mapping to assess posterior cruciate ligament ultrastructure and integrity-an in-situ study

Background

Clinical-standard morphologic magnetic resonance imaging (MRI) is limited in the refined diagnosis of posterior cruciate ligament (PCL) injuries. Quantitative MRI sequences such as ultrashort echo-time (UTE)-T2* mapping or conventional T2* mapping have been theorized to quantify ligament (ultra-) structure and integrity beyond morphology. This study evaluates their diagnostic potential in identifying and differentiating partial and complete PCL injuries in a standardized graded injury model.

Methods

Ten human cadaveric knee joint specimens were imaged on a clinical 3.0 T MRI scanner using morphologic, conventional T2* mapping, and UTE-T2* mapping sequences before and after standardized arthroscopic partial and complete PCL transection. Following manual segmentation, quantitative T2* and underlying texture features (i.e., energy, homogeneity, and variance) were analyzed for each specimen and PCL condition, both for the entire PCL and its subregions. For statistical analysis, Friedman’s test followed by Dunn’s multiple comparison test was used against the level of significance of P≤0.01.

Results

For the entire PCL, T2* was significantly increased as a function of injury when acquired with the UTE-T2* sequence [entire PCL: 11.1±3.1 ms (intact); 10.9±4.6 ms (partial); 14.3±4.9 ms (complete); P<0.001], but not when acquired with the conventional T2* sequence [entire PCL: 10.0±3.2 ms (intact); 11.4±6.2 ms (partial); 15.5±7.8 ms (complete); P=0.046]. The PCL subregions and texture variables showed variable changes indicative of injury-associated disorganization.

Conclusions

In contrast to the conventional T2* mapping, UTE-T2* mapping is more receptive in the detection of structural damage of the PCL and allows quantitative assessment of ligament (ultra-)structure and integrity that may help to improve diagnostic differentiation of distinct injury states. Once further substantiated beyond the in-situ setting, UTE-T2* mapping may refine diagnostic evaluation of PCL injuries and -possibly- monitor ligament healing, ageing, degeneration, and inflammation.

Magnetic Resonance Imaging Assessment of Hamstring Graft Healing and Integration 1 and Minimum 2 Years after ACL Reconstruction

BACKGROUND

An increase has been seen in the number of studies of anterior cruciate ligament reconstruction (ACLR) that use magnetic resonance imaging (MRI) as an outcome measure and proxy for healing and integration of the reconstruction graft. Despite this, the MRI appearance of a steady-state graft and how long it takes to achieve such an appearance have not yet been established.

PURPOSE

To establish whether a hamstring tendon autograft for ACLR changes in appearance on MRI scans between 1 and 2 years and whether this change affects a patient's ability to return to sports.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients with hamstring tendon autograft ACLR underwent MRI and clinical outcome measures at 1 year and at a final follow-up of at least 2 years. MRI graft signal was measured at multiple regions of interest using oblique reconstructions both parallel and perpendicular to the graft, with lower signal indicative of better healing and expressed as the signal intensity ratio (SIR). Changes in tunnel aperture areas were also measured. Clinical outcomes were side-to-side anterior laxity and patient-reported outcome measures (PROMs).

RESULTS

A total of 42 patients were included. At 1 year, the mean SIR for the graft was 2.7 ± 1.2. Graft SIR of the femoral aperture was significantly higher than that of the tibial aperture (3.4 ± 1.3 vs 2.6 ± 1.8, respectively; P = .022). Overall, no significant change was seen on MRI scans after 2 years; a proximal graft SIR of 1.9 provided a sensitivity of 96% to remain unchanged. However, in the 6 patients with the highest proximal graft SIR (>4) at 1 year, a significant reduction in signal was seen at final follow-up (P = .026), alongside an improvement in sporting level. A significant reduction in aperture area was also seen between 1 and 2 years (tibial, -6.3 mm², P < .001; femoral, -13.3 mm², P < .001), which was more marked in the group with proximal graft SIR >4 at 1 year and correlated with a reduction in graft signal. The patients had a high sporting level; the median Tegner activity score was 6 (range, 5-10), and a third of patients scored either 9 or 10. Overall, PROMs and knee laxity were not associated with MRI appearance.

CONCLUSION

In the majority of patients, graft SIR on MRI did not change significantly after 1 year, and a proximal graft SIR <2 was a sensitive indicator for a stable graft signal, implying healing. Monitoring is proposed for patients who have a high signal at 1 year (proximal graft SIR >4), because a significant reduction in signal was seen in the second year, indicative of ongoing healing, alongside an improvement in sporting level. A reduction in tunnel aperture area correlated with a reduction in graft SIR, suggesting this could also be a useful measure of graft integration.

Sufficient MRI graft structural integrity at 9 months after anterior cruciate ligament reconstruction with hamstring tendon autograft

PURPOSE

To assess the MRI-measured structural integrity of hamstring autograft at 9 months after anterior cruciate ligament reconstruction (ACLR) surgery.

METHODS

A prospective cohort study was conducted including 34 patients (mean age 36.8 ± 11.8 years; 73.5% males) who underwent ACLR with hamstring autograft. In addition, 36 patients (mean age 39.2 ± 10.5 years; 69.4% males) without any ACL injury were also reviewed and served as control group. The primary outcome used for examining graft maturity at 9 months after ACLR was the MRI-based signal-to-noise quotient (SNQ) of reconstructed ACL. SNQ values were stratified into 3 different categories: excellent: < 0.1; good: ≥ 0.1 and ≤ 0.19; fair: ≥ 0.2. The KT-1000 knee arthrometer was used to measure the side-to-side difference in the anterior tibial translation between the ACLR knee and the contralateral healthy knee in the ACLR group.

RESULTS

Reconstructed ACLs were found with a mean SNQ of 0.078 ± 0.061, while almost all ACL-reconstructed patients (97%; 33 out of 34) were found with excellent or good SNQ values (< 0.019). The mean KT-1000 in the ACLR group was 0.071 mm ± 0.926 mm, while there were no patients in the ACLR cohort with a KT-1000 value > 3 mm. The mean 9-months MRI-based SNQ of ACLR group was significantly higher compared to the mean MRI-based SNQ of the control group (p < 0.001). Multiple regression analysis showed no correlation between SNQ and age, gender, time from injury to ACLR, graft size, or simultaneous treatment of additional intra-articular knee lesions.

CONCLUSIONS

In this cohort of 34 ACL-reconstructed patients, 97% of hamstring tendon autografts demonstrated excellent/good MRI signal intensity and excellent functional results (KT-1000 < 3 mm) at 9 months after surgery. Based on this finding, it is suggested that return to sports after ACLR with hamstring autograft can be considered safe at 9 months post surgery. Furthermore, while structural integrity of the graft has been achieved at this time point, statistical differences found in SNQ values of ACL-reconstructed patients compared to ACLs of healthy individuals highlight the continuing process of graft maturation and remodelling.

LEVEL OF EVIDENCE

Level III.

The Efficacy of Platelet-Rich Plasma for Ligament Injuries: A Systematic Review of Basic Science Literature With Protocol Quality Assessment

Background:

Despite the existence of many clinical studies on platelet-rich plasma (PRP) interventions for ligamentous pathology, basic science consensus regarding the indications, mechanisms, and optimal composition of PRP for treating ligament injuries is lacking.

Purpose:

To (1) compare the efficacy of PRP in animal models of ligament injury with placebo and (2) describe the potential variability in PRP preparation using accepted classification systems.

Study Design:

Systematic review.

Methods:

The Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, PubMed, Embase, and Ovid MEDLINE were queried in April 2020 for in vivo and in vitro basic science studies regarding PRP use for ligament injury. Study design, results, PRP composition, and analyzed cellular and molecular markers were extracted, and outcomes relative to control models were documented. Bias was assessed using the SYRCLE risk-of-bias tool.

Results:

Included were 43 articles (31 in vivo and 12 in vitro studies) investigating the anterior cruciate ligament/cranial cruciate ligament (n = 32), medial collateral ligament (n = 6), suspensory ligament (n = 3), patellar ligament (n = 1), and Hock ligament (n = 1). Platelet concentration was reported in 34 studies (77.3%); leukocyte composition, in 12 (27.3%); and red blood cell counts, in 7 (15.9%). With PRP treatment, 5 of 12 in vitro studies demonstrated significant increases in cell viability, 6 of 12 in gene expression, 14 of 32 in vivo studies reported superior ligament repair via histological evaluation, and 13 in vivo studies reported superior mechanical properties. Variability in PRP preparation methods was observed across all articles, and only 1 study reported all necessary information to be classified by the 4 schemes we used to evaluate reporting. Among the in vivo studies, detection and performance bias were consistently high, whereas selection, attrition, reporting, and other biases were consistently low.

Conclusion:

Conflicting data on the cellular and molecular effects of PRP for ligament injuries were observed secondary to the finding that included studies were heterogeneous, limiting interpretation across studies and the ability to draw meaningful conclusions. Clinical trials and any causal relationship between PRP use in ligament injuries and its potential for regeneration and healing should be pursued with caution if based solely on basic science data.

Correlation between the elastic modulus of anterior cruciate ligament (ACL) and quantitative ultrashort echo time (UTE) magnetic resonance imaging

Conventional magnetic resonance imaging (MRI) often acquires no signal in anterior cruciate ligament (ACL) due to the short apparent transverse relaxation time of ACL. Ultrashort echo time (UTE) MRI is capable of imaging ACL with high signal which enables quantitative ACL assessment. This study aimed to investigate the correlations of the mechanical and microstructural properties of human ACL specimens with quantitative three-dimensional UTE Cones (3D-UTE-Cones) MRI measures. ACL specimens were harvested from cadaveric knee joints of 13 (50.9 ± 21.1 years old, 11 males and 2 female) donors. Specimens were scanned using a series of quantitative 3D-UTE-Cones T₂ * (UTE-T₂ *), T₁ (UTE-T₁ ), Adiabatic T_1ρ (UTE-Adiab-T_1ρ ), and magnetization transfer (UTE-MT) sequences in a wrist coil on a clinical 3T scanner. ACL elastic modulus was measured using a uniaxial tensile mechanical test. Histomorphometry analysis was performed to measure the average fascicle specific surface, fascicle size, and number of cells per unit area. Spearman's rank correlations of UTE-MRI biomarkers with mechanical and histomorphometry measures were investigated. The elastic modulus of ACL showed significant moderate correlations with UTE-Adiab-T_1ρ (R = -0.59, p = 0.01), macromolecular fraction from MT modeling (R = 0.54, p = 0.01), magnetization transfer ratio (R = 0.53, p = 0.01), UTE-T2* (R = -0.53, p = 0.01), and average fascicle specific surface (R = 0.54, p = 0.01). UTE-MRI showed nonsignificant correlations with histomorphometry measures. UTE-MRI biomarkers may be useful noninvasive tools for the ACL mechanical assessment.

Design Features and Rationale of the BEAR-MOON (Bridge-Enhanced ACL Restoration Multicenter Orthopaedic Outcomes Network) Randomized Clinical Trial

Background:

BEAR (bridge-enhanced anterior cruciate ligament [ACL] restoration), a paradigm-shifting technology to heal midsubstance ACL tears, has been demonstrated to be effective in a single-center 2:1 randomized controlled trial (RCT) versus hamstring ACL reconstruction. Widespread dissemination of BEAR into clinical practice should also be informed by a multicenter RCT to demonstrate exportability and compare efficacy with bone--patellar tendon–bone (BPTB) ACL reconstruction, another clinically standard treatment.

Purpose:

To present the design and initial preparation of a multicenter RCT of BEAR versus BPTB ACL reconstruction (the BEAR: Multicenter Orthopaedic Outcomes Network [BEAR-MOON] trial). Design and analytic issues in planning the complex BEAR-MOON trial, involving the US National Institute of Arthritis and Musculoskeletal and Skin Diseases, the US Food and Drug Administration, the BEAR implant manufacturer, a data and safety monitoring board, and institutional review boards, can usefully inform both clinicians on the trial’s strengths and limitations and future investigators on planning of complex orthopaedic studies.

Study Design:

Clinical trial.

Methods:

We describe the distinctive clinical, methodological, and operational challenges of comparing the innovative BEAR procedure with the well-established BPTB operation, and we outline the clinical motivation, experimental setting, study design, surgical challenges, rehabilitation, outcome measures, and planned analysis of the BEAR-MOON trial.

Results:

BEAR-MOON is a 6-center, 12-surgeon, 200-patient randomized, partially blinded, noninferiority RCT comparing BEAR with BPTB ACL reconstruction for treating first-time midsubstance ACL tears. Noninferiority of BEAR relative to BPTB will be claimed if the total score on the International Knee Documentation Committee (IKDC) subjective knee evaluation form and the knee arthrometer 30-lb (13.61-kg) side-to-side laxity difference are both within respective margins of 16 points for the IKDC and 2.5 mm for knee laxity.

Conclusion:

Major issues include patient selection, need for intraoperative randomization and treatment-specific postoperative physical therapy regimens (because of fundamental differences in surgical technique, initial stability construct, and healing), and choice of noninferiority margins for short-term efficacy outcomes of a novel intervention with evident short-term advantages and theoretical, but unverified, long-term benefits on other dimensions.

ACL Size, but Not Signal Intensity, Is Influenced by Sex, Body Size, and Knee Anatomy

Background:

Little is known about sex-based differences in anterior cruciate ligament (ACL) tissue quality in vivo or the association of ACL size (ie, volume) and tissue quality (ie, normalized signal intensity on magnetic resonance imaging [MRI]) with knee anatomy.

Hypothesis:

We hypothesized that (1) women have smaller ACLs and greater ACL normalized signal intensity compared with men, and (2) ACL size and normalized signal intensity are associated with age, activity levels, body mass index (BMI), bicondylar width, intercondylar notch width, and posterior slope of the lateral tibial plateau.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Knee MRI scans of 108 unique ACL-intact knees (19.7 ± 5.5 years, 62 women) were used to quantify the ACL signal intensity (normalized to cortical bone), ligament volume, mean cross-sectional area, and length. Independent t tests were used to compare the MRI-based ACL parameters between sexes. Univariate and multivariate linear regression analyses were used to investigate the associations between normalized signal intensity and size with age, activity levels, BMI, bicondylar width, notch width, and posterior slope of the lateral tibial plateau.

Results:

Compared with men, women had significantly smaller mean ACL volume (men vs women: 2028 ± 472 vs 1591 ± 405 mm³), cross-sectional area (49.4 ± 9.6 vs 41.5 ± 8.6 mm²), and length (40.8 ± 2.8 vs 38.1 ± 3.1 mm) (P < .001 for all), even after adjusting for BMI and bicondylar width. There was no difference in MRI signal intensity between men and women (1.15 ± 0.24 vs 1.12 ± 0.24, respectively; P = .555). BMI, bicondylar width, and intercondylar notch width were independently associated with a larger ACL (R² > 0.16, P < .001). Younger age and steeper lateral tibial slope were independently associated with shorter ACL length (R² > 0.03, P < .04). The combination of BMI and bicondylar width was predictive of ACL volume and mean cross-sectional area (R² < 0.3). The combination of BMI, bicondylar width, and lateral tibial slope was predictive of ACL length (R² = 0.39). Neither quantified patient characteristics nor anatomic variables were associated with signal intensity.

Conclusion:

Men had larger ACLs compared with women even after adjusting for BMI and knee size (bicondylar width). No sex difference was observed in signal intensity, suggesting no difference in tissue quality. The association of the intercondylar notch width and lateral tibial slope with ACL size suggests that the influence of these anatomic features on ACL injury risk may be partially explained by their effect on ACL size.

Registration:

NCT02292004 and NCT02664545 (ClinicalTrials.gov identifier).

A transfer learning approach for automatic segmentation of the surgically treated anterior cruciate ligament

Quantitative magnetic resonance imaging enables quantitative assessment of the healing anterior cruciate ligament or graft post-surgery, but its use is constrained by the need for time consuming manual image segmentation. The goal of this study was to validate a deep learning model for automatic segmentation of repaired and reconstructed anterior cruciate ligaments. We hypothesized that (1) a deep learning model would segment repaired ligaments and grafts with comparable anatomical similarity to intact ligaments, and (2) automatically derived quantitative features (i.e., signal intensity and volume) would not be significantly different from those obtained by manual segmentation. Constructive Interference in Steady State sequences were acquired of ACL repairs (n = 238) and grafts (n = 120). A previously validated model for intact ACLs was retrained on both surgical groups using transfer learning. Anatomical performance was measured with Dice coefficient, sensitivity, and precision. Quantitative features were compared to ground truth manual segmentation. Automatic segmentation of both surgical groups resulted in decreased anatomical performance compared to intact ACL automatic segmentation (repairs/grafts: Dice coefficient = .80/.78, precision = .79/.78, sensitivity = .82/.80), but neither decrease was statistically significant (Kruskal-Wallis: Dice coefficient p = .02, precision p = .09, sensitivity p = .17; Dunn post-hoc test for Dice coefficient: repairs/grafts p = .054/.051). There were no significant differences in quantitative features between the ground truth and automatic segmentation of repairs/grafts (0.82/2.7% signal intensity difference, p = .57/.26; 1.7/2.7% volume difference, p = .68/.72). The anatomical similarity performance and statistical similarities of quantitative features supports the use of this automated segmentation model in quantitative magnetic resonance imaging pipelines, which will accelerate research and provide a step towards clinical applicability.

Anterior cruciate ligament autograft maturation on sequential postoperative MRI is not correlated with clinical outcome and anterior knee stability

PURPOSE

Magnetic resonance imaging (MRI) signal intensity is correlated to structural postoperative changes of the anterior cruciate ligament (ACL) autograft. The purpose of this study was to investigate the ACL autograft maturation process via MRI over 2 years postoperatively, compare it to a native ACL signal and correlate the results with clinical outcome, return to preinjury sports levels, and knee laxity measurements.

METHODS

ACL autograft signal intensity was measured in 17 male patients (age, 28.3 ± 7.0 years) who underwent ACL reconstruction with hamstring autograft at 6 weeks, 3-, 6-, 12-, and 24 months postoperatively by 3 Tesla MRI. Controls with an intact ACL served as control group (22 males, 8 females; age, 26.7 ± 6.8 years). An ACL/PCL ratio (APR) and ACL/muscle ratio (AMR) was calculated to normalize signals to soft tissue signal. APR and AMR were compared across time and to native ACL signal. Clinical outcome scores (IKDC, Lysholm), return to preinjury sports levels (Tegner activity scale), and knee laxity measurement (KT-1000) were obtained and correlated to APR and AMR at the respective time points.

RESULTS

The APR and AMR of the ACL graft changed significantly from the lowest values at 6 weeks to reach the highest intensity after 6 months (p < 0.001). Then, the APR and AMR were significantly different from a native ACL 6 months after surgery (p < 0.01) but approached the APR and AMR of the native ACL at 1- and 2 years after surgery (p < 0.05). The APR changed significantly during the first 2 years postoperatively in the proximal (p < 0.001), mid-substance (p < 0.001), and distal (p < 0.01) intraarticular portion of the ACL autograft. A hypo-intense ACL MRI signal was associated with return to the preinjury sports level (p < 0.05). No correlation was found between ACL MRI graft signal and clinical outcome scores or KT-1000 measurements.

CONCLUSION

ACL grafts undergo a continuous maturation process in the first 2 years after surgery. The ACL graft signals became hyper-intense 6 months postoperatively and approximated the signal of a native intact ACL at 12- and 24 months. Patients with a hypo-intense ACL graft signal at 2 years follow-up were more likely to return to preinjury sports levels. The results of the present study provide a template for monitoring the normal ACL maturation process via MRI in case of prolonged clinical symptoms. However, subjective outcome and clinical examination of knee laxity remain important to assess the treatment success and to allow to return to sports.

LEVEL OF EVIDENCE

III.

Regional Differences in Anterior Cruciate Ligament Signal Intensity After Surgical Treatment

BACKGROUND

Magnetic resonance-based measurements of signal intensity have been used to track healing of surgically treated anterior cruciate ligaments (ACLs). However, it is unknown how the signal intensity values in different regions of the ligament or graft change during healing.

HYPOTHESES

(1) Normalized signal intensity of the healing graft or repaired ACL is heterogeneous; (2) temporal changes in normalized signal intensity values differ among the tibial, middle, and femoral regions; and (3) there are no differences in regional normalized signal intensity values 2 years postoperatively among grafts, repaired ACLs, and contralateral native ACLs.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Magnetic resonance imaging scans were analyzed from patients in a trial comparing ACL reconstruction (n = 35) with bridge-enhanced ACL repair (n = 65). The ACLs were segmented from images acquired at 6, 12, and 24 months postoperatively and were partitioned into 3 sections along the longitudinal axis (femoral, middle, and tibial). Linear mixed modeling was used to compare location-specific differences in normalized ligament signal intensity among time points (6, 12, and 24 months) and groups (ACL reconstruction, repair, and contralateral native ACL).

RESULTS

For grafts, the middle region had a higher mean normalized signal intensity when compared with the femoral region at all time points (P < .01) but compared with the tibial region only at 6 months (P < .01). For repaired ACLs, the middle region had a higher mean normalized signal intensity versus the femoral region at all time points (P < .01) but versus the tibial region only at 6 and 12 months (P < .04). From 6 to 24 months, the grafts showed the greatest reduction in normalized signal intensity in the femoral and middle regions (vs tibial regions; P < .01), while there were no regional differences in repaired ACLs. At 2 years after surgery, repaired ACLs had a lower normalized signal intensity in the tibial region as compared with reconstructed grafts and contralateral native ACLs (P < .01).

CONCLUSION

The results suggest that graft remodeling is location specific. Repaired ACLs were more homogeneous, with lower or comparable normalized signal intensity values at 2 years as compared with the contralateral native ACL and reconstructed grafts.

Quantitative analysis of the ACL and PCL using T1rho and T2 relaxation time mapping: an exploratory, cross-sectional comparison between OA and healthy control knees

Background

Quantitative magnetic resonance imaging (MRI) methods such as T1rho and T2 mapping are sensitive to changes in tissue composition, however their use in cruciate ligament assessment has been limited to studies of asymptomatic populations or patients with posterior cruciate ligament tears only. The aim of this preliminary study was to compare T1rho and T2 relaxation times of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) between subjects with mild-to-moderate knee osteoarthritis (OA) and healthy controls.

Methods

A single knee of 15 patients with mild-to-moderate knee OA (Kellgren-Lawrence grades 2–3) and of 6 age-matched controls was imaged using a 3.0 T MRI. Three-dimensional (3D) fat-saturated spoiled gradient recalled-echo images were acquired for morphological assessment and T1ρ- and T2-prepared pseudo-steady-state 3D fast spin echo images for compositional assessment of the cruciate ligaments. Manual segmentation of whole ACL and PCL, as well as proximal / middle / distal thirds of both ligaments was carried out by two readers using ITK-SNAP and mean relaxation times were recorded. Variation between thirds of the ligament were assessed using repeated measures ANOVAs and differences in these variations between groups using a Kruskal-Wallis test. Inter- and intra-rater reliability were assessed using intraclass correlation coefficients (ICCs).

Results

In OA knees, both T1rho and T2 values were significantly higher in the distal ACL when compared to the rest of the ligament with the greatest differences in T1rho (e.g. distal mean = 54.5 ms, proximal = 47.0 ms, p < 0.001). The variation of T2 values within the PCL was lower in OA knees (OA: distal vs middle vs proximal mean = 28.5 ms vs 29.1 ms vs 28.7 ms, p = 0.748; Control: distal vs middle vs proximal mean = 26.4 ms vs 32.7 ms vs 33.3 ms, p = 0.009). ICCs were excellent for the majority of variables.

Conclusion

T1rho and T2 mapping of the cruciate ligaments is feasible and reliable. Changes within ligaments associated with OA may not be homogeneous. This study is an important step forward in developing a non-invasive, radiological biomarker to assess the ligaments in diseased human populations in-vivo.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04755-y.

Effect of Time on MRI Appearance of Graft After ACL Reconstruction: A Comparison of Autologous Hamstring and Quadriceps Tendon Grafts

Background:

After anterior cruciate ligament (ACL) reconstruction (ACLR), changes in the appearance of the ACL graft can be monitored using magnetic resonance imaging (MRI).

Purpose:

The purpose of this study was to evaluate and compare the MRI signal intensity (SI) of hamstring and quadriceps tendon grafts during the first postoperative year after ACLR. As a secondary aim, the relationship of SI to clinical and anatomic measurements was analyzed.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 78 patients who underwent ACLR with an autologous graft were reviewed; 55 received hamstring grafts and 23 received quadriceps tendon grafts. At 3 and 9 months postoperatively, 3-T MRI was performed using a dedicated knee coil, and the median SI of the intra-articular ACL graft was measured on sagittal-plane images. Postoperative lateral radiographs were analyzed to determine medial and lateral posterior tibial slope (PTS). Side-to-side difference in anterior knee laxity between injured and uninjured limbs was measured at 6 and 12 months postoperatively.

Results:

The median SI of quadriceps grafts was significantly greater than hamstring grafts at 3 months after ACLR (P = .02). Between 3 and 9 months, the median SI of quadriceps grafts decreased (P < .001), while that of hamstring grafts did not significantly change (P = .55). The lateral PTS was significantly correlated with median SI measurements at 3 and 9 months such that greater lateral PTS values were associated with greater median SI. The side-to-side difference in anterior knee laxity decreased for the quadriceps group (P = .04) between 6 and 12 months but did not change for the hamstring group (P = .88).

Conclusion:

The median SI of quadriceps grafts significantly decreased on MRI between 3 and 9 months after ACLR, while the median SI of hamstring grafts did not significantly change. The change in MRI appearance of the quadriceps grafts was paralleled by a reduction in anterior knee laxity between 6 and 12 months after surgery. In the absence of standardized imaging techniques and imaging analysis methods, the role of MRI in determining graft maturation, and the implications for progression through rehabilitation to return to sport, remain uncertain.

Optimizing outcomes of ACL surgery-Is autograft reconstruction the only reasonable option?

Anterior cruciate ligament (ACL) injuries occur at a high frequency in the United States with approximately 400,000 ACL reconstructions being performed each year. While ACL reconstruction is our current gold standard of treatment, it does not restore joint motion, or prevent the premature development of posttraumatic osteoarthritis (PTOA) in many patients. Thus, new treatments for an ACL injury, which are less invasive and minimize patient morbidity, including cartilage damage, are highly desirable. We have used a tissue-engineered approach to stimulate ligament healing, to improve upon current treatment options. In this review, we describe and discuss our work moving a tissue engineering strategy from the concept to bench, preclinical, clinical trials and ultimately FDA 510(k) de Novo approval, providing clinicians and patients with a viable alternative to ACL reconstruction.

Two-year postoperative MRI appearances of anterior cruciate ligament hamstrings autografts are not correlated with functional outcomes, anterior laxity, or patient age

Aims

MRI has been suggested as an objective method of assessing anterior crucate ligament (ACL) graft “ligamentization” after reconstruction. It has been proposed that the MRI appearances could be used as an indicator of graft maturity and used as part of a return-to-sport assessment. The aim of this study was to evaluate the correlation between MRI graft signal and postoperative functional scores, anterior knee laxity, and patient age at operation.

Methods

A consecutive cohort of 149 patients who had undergone semitendinosus autograft ACL reconstruction, using femoral and tibial adjustable loop fixations, were evaluated retrospectively postoperatively at two years. All underwent MRI analysis of the ACL graft, performed using signal-to-noise quotient (SNQ) and the Howell score. Functional outcome scores (Lysholm, Tegner, International Knee Documentation Committee (IKDC) subjective, and IKDC objective) were obtained and all patients underwent instrumented side-to-side anterior laxity differential laxity testing.

Results

Two-year postoperative mean outcome scores were: Tegner 6.5 (2 to 10); Lysholm 89.8 (SD 10.4; 52 to 100); and IKDC subjective 86.8 (SD 11.8; 51 to 100). The objective IKDC score was 86% A (128 patients), 13% B (19 patients), and 1% C (two patients). Mean side-to-side anterior laxity difference (134 N force) was 0.6 mm (SD 1.8; -4.1 to 5.6). Mean graft SNQ was 2.0 (SD 3.5; -14 to 17). Graft Howell scores were I (61%, 91 patients), II (25%, 37 patients), III (13%, 19 patients), and IV (1%, two patients). There was no correlation between either Howell score or SNQ with instrumented anterior or Lysholm, Tegner, and IKDC scores, nor was any correlation found between patient age and ACL graft SNQ or Howell score.

Conclusion

The two-year postoperative MRI appearances of four-strand, semitendinosus ACL autografts (as measured by SNQ and Howell score) do not appear to have a relationship with postoperative functional scores, instrumented anterior laxity, or patient age at surgery. Other tools for analysis of graft maturity should be developed.

Cite this article: Bone Jt Open 2021;2(8):569–575.

Return to sport following anterior cruciate ligament reconstruction: the argument for a multimodal approach to optimise decision-making: current concepts

Existing literature is varied in the methods used to make this determination in the treatment of athletes who have undergone recent anterior cruciate ligament (ACL) reconstruction. Some authors report using primarily time-based criteria, while others advocate for physical measures and kinematic testing to inform decision-making. The goal of this paper is to elucidate the most current medical evidence regarding identification of the earliest point at which a patient may safely return to sport. The present review therefore seeks to examine the evidence from a critical perspective-breaking down the biology of graft maturation, effect of graft choice, potential for image-guided monitoring of progression and results associated with time-based versus functional criteria-based return to play-to justify a multifactorial approach to effectively advance athletes to return to sport. The findings of the present study reaffirm that time is a prerequisite for the biological progression that must occur for a reconstructed ligament to withstand loads demanded by athletes during sport. Modifications of surgical techniques and graft selection may positively impact the rate of graft maturation, and evidence suggests that imaging studies may offer informative data to enhance monitoring of this process. Aspects of both functional and cognitive testing have also demonstrated utility in prior studies and consequently have been factored into modern proposed methods of determining the athlete's readiness for sport. Further work is needed to definitively determine the optimal method of clearing an athlete to return to sport after ACL reconstruction. Evidence to date strongly suggests a role of a multimodal algorithmic approach that factors in time, graft biology and functional testing in return-to-play decision-making after ACL reconstruction.Level of evidence: level V.

The role of magnetic resonance imaging in evaluating postoperative ACL reconstruction healing and graft mechanical properties: a new criterion for return to play?

Background: Disruption of the anterior cruciate ligament (ACL) is a common injury. In active patients, it is routinely treated with ACL reconstruction surgery. Following reconstruction, one of the critical decisions that must be made is the optimal timing of return to sport. While many biomechanical, biological, and functional criteria have been proposed to determine return to play, these methods are limited at best.Reasoning: As criteria for return to play are multifactorial, there is a growing need for noninvasive technologies, such as magnetic resonance imaging (MRI), to objectively track graft healing, to better assess the graft itself. Measuring the changes in the strength of the healing ligament has been shown to be a reliable means of objectively documenting graft healing in preclinical studies. While the initial studies of MR-based modeling of ACL graft healing are promising, this technology is still in its infancy and requires optimization.Purpose: The goals of this review are: 1) to outline the shortcomings of current return to play criteria, 2) to highlight the ability of MRI to determine the status of ACL graft healing, and 3) to discuss the future of imaging technology to determine return to play and its potential role in the clinical evaluation of patientsConclusion: There continues to be a wide variabiltiy regarding adequate return to play criteria, most of which are subjective in nature.

Long-term outcomes of anterior cruciate ligament reconstruction surgery: 2020 OREF clinical research award paper

ACL injuries place the knee at risk for post-traumatic osteoarthritis (PTOA) despite surgical anterior cruciate ligament (ACL) reconstruction. One parameter thought to affect PTOA risk is the initial graft tension. This randomized controlled trial (RCT) was designed to compare outcomes between two graft tensioning protocols that bracket the range commonly used. At 7 years postsurgery, we determined that most outcomes between the two tension groups were not significantly different, that they were inferior to an uninjured matched control group, and that PTOA was progressing in both groups relative to controls. The trial database was also leveraged to gain insight into mechanisms of PTOA following ACL injury. We determined that the inflammatory response at the time of injury undermines one of the joint's lubricating mechanisms. We learned that patients continue to protect their surgical knee 5 years postinjury compared to controls during a jump-pivot activity. We also established that presurgical knee function and mental health were correlated with symptomatic PTOA at 7 years, that there were specific anatomical factors associated with poor outcomes, and that there were no changes in outcomes due to tunnel widening in patients receiving hamstring tendon autografts. We also validated a magnetic resonance imaging technique to noninvasively assess graft strength. In conclusion, the RCT determined that initial graft tensioning does not have a major influence on 7-year outcomes. Therefore, surgeons can reconstruct the ACL using a graft tensioning protocol that is within the window of the two graft tensioning techniques evaluated in this RCT.

Magnetic Resonance Imaging 1 Year After Hamstring Autograft Anterior Cruciate Ligament Reconstruction Can Identify Those at Higher Risk of Graft Failure: An Analysis of 250 Cases

BACKGROUND

There is currently no analysis of 1-year postoperative magnetic resonance imaging (MRI) that reproducibly evaluates the graft of a hamstring autograft anterior cruciate ligament reconstruction (ACLR) and helps to identify who is at a higher risk of graft rupture upon return to pivoting sports.

PURPOSE

To ascertain whether a novel MRI analysis of ACLR at 1 year postoperatively can be used to predict graft rupture, sporting level, and clinical outcome at a 1-year and minimum 2-year follow-up.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Graft healing and integration after hamstring autograft ACLR were evaluated using the MRI signal intensity ratio at multiple areas using oblique reconstructions both parallel and perpendicular to the graft and tunnel apertures. Clinical outcomes were assessment of side-to-side laxity and International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Lysholm, and Tegner activity level scores at 1 year. Repeat outcome measures and detection of graft rupture were evaluated at a minimum of 2 years.

RESULTS

A total of 250 patients (42.4% female) underwent MRI analysis at 1 year, and assessment of 211 patients between 1 year and the final follow-up (range, 24-36 months) detected 9 graft ruptures (4.3%; 5 in female patients). A significant predictor for graft rupture was a high signal parallel to the proximal intra-articular graft and perpendicular to the femoral tunnel aperture (P = .032 and P = .049, respectively), with each proximal graft signal intensity ratio (SIR) increase by 1 corresponding to a 40% increased risk of graft rupture. A cutoff SIR of 4 had a sensitivity and specificity of 66% and 77%, respectively, in the proximal graft and 88% and 60% in the femoral aperture. In all patients, graft signal adjacent to and within the tibial tunnel aperture, and in the mid intra-articular portion, was significantly lower than that for the femoral aperture (P < .001). A significant correlation was seen between the appearance of higher graft signal on MRI and those patients achieving top sporting levels by 1 year.

CONCLUSION

ACLR graft rupture after 1 year is associated with MRI appearances of high graft signal adjacent to and within the femoral tunnel aperture. Patients with aspirations of quickly returning to a high sporting level may benefit from MRI analysis of graft signal. Graft signal was highest at the femoral tunnel aperture, adding further radiographic evidence that the rate-limiting step to graft healing occurs proximally.

Automated magnetic resonance image segmentation of the anterior cruciate ligament

The objective of this study was to develop an automated segmentation method for the anterior cruciate ligament that is capable of facilitating quantitative assessments of the ligament in clinical and research settings. A modified U-Net fully convolutional network model was trained, validated, and tested on 246 Constructive Interference in Steady State magnetic resonance images of intact anterior cruciate ligaments. Overall model performance was assessed on the image set relative to an experienced (>5 years) "ground truth" segmenter in two domains: anatomical similarity and the accuracy of quantitative measurements (i.e., signal intensity and volume) obtained from the automated segmentation. To establish model reliability relative to manual segmentation, a subset of the imaging data was resegmented by the ground truth segmenter and two additional segmenters (A, 6 months and B, 2 years of experience), with their performance evaluated relative to the ground truth. The final model scored well on anatomical performance metrics (Dice coefficient = 0.84, precision = 0.82, and sensitivity = 0.85). The median signal intensities and volumes of the automated segmentations were not significantly different from ground truth (0.3% difference, p = .9; 2.3% difference, p = .08, respectively). When the model results were compared with the independent segmenters, the model predictions demonstrated greater median Dice coefficient (A = 0.73, p = .001; B = 0.77, p = NS) and sensitivity (A = 0.68, p = .001; B = 0.72, p = .003). The model performed equivalently well to retest segmentation by the ground truth segmenter on all measures. The quantitative measures extracted from the automated segmentation model did not differ from those of manual segmentation, enabling their use in quantitative magnetic resonance imaging pipelines to evaluate the anterior cruciate ligament.

Compositional MRI of the anterior cruciate ligament of professional alpine ski racers: preliminary report on seasonal changes and load sensitivity

The purpose of this study was to investigate potential changes in the anterior cruciate ligament (ACL) structure of alpine ski racers over the course of an entire season using quantitative magnetic resonance imaging (T2* mapping). The dominant legs of three alpine ski racers were examined on a 3-T MR scanner four times at 3-month intervals. Multi-echo sequences for T2* maps, which were coregistered with high-resolution morphological sequences for reproducible definition of ACL regions of interest, were acquired. Means and standard deviations of T2* values from the central and femoral portion of the ACL were extracted and presented in a descriptive manner. T2* values were subject to seasonal changes, which were most pronounced in the ligament central region. Substantial increases (+ 41%) occurred between the measurements taken in January and April. A partial recovery of T2* (-19%) was observed in the July follow-up. The increased T2* times may reflect decreased stress tolerance and increased susceptibility for fatigue tears at the end of the competitive season. Further research in larger samples is required. The likeliness of ACL tears may depend on the precedent history of mechanical loading and vary in professional athletes over the course of the competitive season.