MR Imaging of the Knee

MGACA-Net: a novel deep learning based multi-scale guided attention and context aggregation for localization of knee anterior cruciate ligament tears region in MRI images

Anterior cruciate ligament (ACL) tears are a common knee injury that can have serious consequences and require medical intervention. Magnetic resonance imaging (MRI) is the preferred method for ACL tear diagnosis. However, manual segmentation of the ACL in MRI images is prone to human error and can be time-consuming. This study presents a new approach that uses deep learning technique for localizing the ACL tear region in MRI images. The proposed multi-scale guided attention-based context aggregation (MGACA) method applies attention mechanisms at different scales within the DeepLabv3+ architecture to aggregate context information and achieve enhanced localization results. The model was trained and evaluated on a dataset of 917 knee MRI images, resulting in 15265 slices, obtaining state-of-the-art results with accuracy scores of 98.63%, intersection over union (IOU) scores of 95.39%, Dice coefficient scores (DCS) of 97.64%, recall scores of 97.5%, precision scores of 98.21%, and F1 Scores of 97.86% on validation set data. Moreover, our method performed well in terms of loss values, with binary cross entropy combined with Dice loss (BCE_Dice_loss) and Dice_loss values of 0.0564 and 0.0236, respectively, on the validation set. The findings suggest that MGACA provides an accurate and efficient solution for automating the localization of ACL in knee MRI images, surpassing other state-of-the-art models in terms of accuracy and loss values. However, in order to improve robustness of the approach and assess its performance on larger data sets, further research is needed.

Radiological maturation and clinical results of double-bundle and single-bundle anterior cruciate ligament reconstruction. A 5-year prospective case-controlled trial

INTRODUCTION

The aim of the study was to make a prospective comparison of the radiological and clinical outcomes of patients undergoing single-bundle and double-bundle anterior cruciate ligament (ACL) reconstruction.

METHOD

This prospective, case-controlled study included 65 patients, separated into 2 groups as 33 patients undergoing single bundle (SB), and 32 patients undergoing double bundle (DB) ACL reconstruction. The patients were evaluated clinically using the International Knee Documentation Committee (IKDC) and the Lysholm knee scores. Stability was evaluated with the KT-1000 Arthrometer Measurement, the Lachman and pivot shift tests. Magnetic resonance images (MRI) at 1 and 5 years postoperatively were evaluated by a musculoskeletal radiologist. All the operations were performed by a single surgeon and the clinical evaluations were made by an independent researcher.

RESULTS

Evaluation was made of a total of 53 patients (SB: 28, DB: 25). No statistically significant difference was determined between the groups regarding the postoperative IKDC and Lysholm scores. The pivot shift tests were negative in the DB group and positive in two patients of the SB group. The Lachman test was negative in all the patients. No significant difference was determined between the groups. No statistically significant difference was determined between the two groups in respect of the arthrometer measurements. In the SB group, revision surgery was performed in two patients due to graft failure. No graft failure findings were determined in the DB group, and no statistically significant difference was determined between the groups in respect of graft failure. On the MRIs taken at 1 year postoperatively, the ACL was seen to be hyperintense in 16 patients in the DB group and 6 patients in the SB group (p = 0.004). On the 5-year MRIs, ACL hypointensity could not be seen in three patients of the SB group and two of the DB group, with no difference determined between the groups (p > 0.05).

CONCLUSION

In the 5-year follow-up period, no difference was determined between patients undergoing SB ACL reconstruction and those undergoing DB ACL reconstruction regarding clinical scores, knee stability, and MRI findings, but graft maturation occurs later the patients undergoing DB reconstruction.

Assessment of Graft Maturity After Anterior Cruciate Ligament Reconstruction Using Autografts: A Systematic Review of Biopsy and Magnetic Resonance Imaging studies

Purpose

The purpose of this investigation was to evaluate systematically the literature concerning biopsy, MRI signal to noise quotient (SNQ) and clinical outcomes in graft-maturity assessment after autograft anterior cruciate ligament reconstruction (ACLR) and their possible relationships.

Methods

The systematic review was reported and conducted according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Studies through May 2019 evaluating methods of intra-articular ACL autograft maturity assessment were considered for inclusion. Eligible methods were histologic studies of biopsy specimens and conventional MRI studies reporting serial SNQ and/or correlation with clinical parameters.

Results

Ten biopsy studies and 13 imaging studies, with a total of 706 patients, met the inclusion criteria. Biopsy studies show that graft remodeling undergoes an early healing phase, a phase of remodeling or proliferation and a ligamentization phase as an ongoing process even 1 year after surgery. Imaging studies showed an initial increase in SNQ, peaking at approximately 6 months, followed by a gradual decrease over time. There is no evident correlation between graft SNQ and knee stability outcome scores at the short- and long-term follow-up after ACLR.

Conclusions

The remodeling of the graft is an ongoing process even 1 year after ACLR, based on human biopsy studies. MRI SNQ peaked at approximately 6 months, followed by a gradual decrease over time. Heterogeneity of the MRI methods and technical restrictions used in the current literature limit prediction of graft maturity and clinical and functional outcome measures by means of MRI graft SNQ after ACLR.

Level of evidence

Level IV, systematic review, including level III and IV studies.

Spectrum of common and uncommon causes of knee joint hyaline cartilage degeneration and their key imaging features

Hyaline cartilage lining the surfaces of diarthrodial joints is an important construct for transmission of load and to reduce friction between the bones. Normal wear and tear accounts for about 3-5 percent knee cartilage loss ever year in otherwise healthy people after the age of 30 years. Several conditions and diseases lead to premature cartilage degeneration. Standardized description of cartilage loss, detailed evaluation of the joint health and determining the underlying etiology of cartilage loss are important for effective reporting, multidisciplinary communications and patient management. In this article, the authors discuss normal and abnormal imaging appearances of the hyaline cartilage of knee with focus on using controlled terminology and MRI classifications. The reader will benefit and learn key MR imaging features of a spectrum of common and uncommon conditions and diseases affecting the knee cartilage, such as trauma, secondary injury associated with meniscus and ligament injury related instability, arthritis, ischemia, idiopathic, and hereditary conditions including Matrix metalloproteinase-2 (MMP-2) mutations and mucopolysaccharidosis type IX disease with illustrative case examples.

Structural and Anatomic Restoration of the Anterior Cruciate Ligament Is Associated With Less Cartilage Damage 1 Year After Surgery: Healing Ligament Properties Affect Cartilage Damage

BACKGROUND

Abnormal joint motion has been linked to joint arthrosis after anterior cruciate ligament (ACL) reconstruction. However, the relationships between the graft properties (ie, structural and anatomic) and extent of posttraumatic osteoarthritis are not well defined.

HYPOTHESES

(1) The structural (tensile) and anatomic (area and alignment) properties of the reconstructed graft or repaired ACL correlate with the total cartilage lesion area 1 year after ACL surgery, and (2) side-to-side differences in anterior-posterior (AP) knee laxity correlate with the total cartilage lesion area 1 year postoperatively.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixteen minipigs underwent unilateral ACL transection and were randomly treated with ACL reconstruction or bridge-enhanced ACL repair. The tensile properties, cross-sectional area, and multiplanar alignment of the healing ACL or graft, AP knee laxity, and cartilage lesion areas were assessed 1 year after surgery.

RESULTS

In the reconstructed group, the normalized graft yield and maximum failure loads, cross-sectional area, sagittal and coronal elevation angles, and side-to-side differences in AP knee laxity at 60° of flexion were associated with the total cartilage lesion area 1 year after surgery (R² > 0.5, P < .04). In the repaired group, normalized ACL yield load, linear stiffness, cross-sectional area, and the sagittal and coronal elevation angles were associated with the total cartilage lesion area (R² > 0.5, P < .05). Smaller cartilage lesion areas were observed in the surgically treated knees when the structural and anatomic properties of the ligament or graft and AP laxity values were closer to those of the contralateral ACL-intact knee. Reconstructed grafts had a significantly larger normalized cross-sectional area and sagittal elevation angle (more vertical) when compared with repaired ACLs (P < .02).

CONCLUSION

The tensile properties, cross-sectional area, and multiplanar alignment of the healing ACLs or grafts and AP knee laxity in reconstructed knees were associated with the extent of tibiofemoral cartilage damage after ACL surgery.

CLINICAL RELEVANCE

These data highlight the need for novel ACL injury treatments that can restore the structural and anatomic properties of the torn ACL to those of the native ACL in an effort to minimize the risk of early-onset posttraumatic osteoarthritis.

Poly (lactic acid)-based biomaterials for orthopaedic regenerative engineering

Regenerative engineering converges tissue engineering, advanced materials science, stem cell science, and developmental biology to regenerate complex tissues such as whole limbs. Regenerative engineering scaffolds provide mechanical support and nanoscale control over architecture, topography, and biochemical cues to influence cellular outcome. In this regard, poly (lactic acid) (PLA)-based biomaterials may be considered as a gold standard for many orthopaedic regenerative engineering applications because of their versatility in fabrication, biodegradability, and compatibility with biomolecules and cells. Here we discuss recent developments in PLA-based biomaterials with respect to processability and current applications in the clinical and research settings for bone, ligament, meniscus, and cartilage regeneration.

Graft bending angle is correlated with femoral intraosseous graft signal intensity in anterior cruciate ligament reconstruction using the outside-in technique

BACKGROUND

The purposes of this study were as follows: 1) to determine the correlation between the bending angle of the anterior cruciate ligament (ACL) graft at the femoral tunnel and the magnetic resonance imaging (MRI) signal intensity of the ACL graft and 2) to analyze the difference in the MRI signal intensity of the reconstructed ACL graft in different areas of the graft after single-bundle hamstring autograft ACL (SB ACL) reconstruction using an outside-in (OI) technique with bone-sparing retro-reaming.

METHODS

Thirty-eight patients who underwent SB ACL reconstruction with the hamstring tendon autograft using the OI technique were enrolled in this study. All patients were assessed using three-dimensional computed tomography (CT) to evaluate femoral tunnel factors, including tunnel placement, tunnel length, tunnel diameter, and femoral tunnel bending angle. At a mean of 6.3±0.8months after surgery, 3.0-T MRI was used to evaluate the graft signal intensity using signal/noise quotient for high-signal-intensity lesions.

RESULTS

Among various femoral tunnel factors, only the femoral tunnel bending angle in the coronal plane was significantly (p=0.003) correlated with the signal/noise quotient of the femoral intraosseous graft. The femoral intraosseous graft had significantly (p=0.009) higher signal intensity than the other graft zone. Five cases (13.2%) showed high-signal-intensity zones around the femoral tunnel but not around the tibial tunnel.

CONCLUSION

After ACL reconstruction using the OI technique, the graft bending angle was found to be significantly correlated with the femoral intraosseous graft signal intensity, indicating that increased signal intensity by acute graft bending might be related to the maturation of the graft.

LEVEL OF EVIDENCE

This was a retrospective comparative study with Level III evidence.

Changes in the T2 relaxation value of the tibiofemoral articular cartilage about 6 months after anterior cruciate ligament reconstruction using the double-bundle technique

OBJECTIVE

To evaluate T2 relaxation values (T2RVs) of knee joint cartilage after double-bundle anterior cruciate ligament reconstruction (DB-ACLR) in a 6-month follow-up and to correlate changes between T2RVs with meniscal status and clinical findings.

METHODS

27 patients who underwent DB-ACLR and MRI before and 6 months after surgery, and 27 control subjects were enrolled. We compared T2RVs of the control vs pre-operative MR and pre-operative vs post-operative MR using 28 subcompartments, including superficial and deep layers. Correlations between T2RV changes with meniscal status and clinical data were examined.

RESULTS

The pre-operative T2RV was significantly higher than that of the control group in the medial tibia (posterior-superficial), posterior medial femur (superficial) and posterior lateral femur (superficial and deep). The post-operative T2RV was significantly higher than that of pre-operative T2RV in the posterior medial femur (superficial), medial tibia (anterior-deep and central-deep), lateral femur (anterior-deep, anterior-superficial and central-superficial) and posterior medial femur (deep). Moderate positive correlations between pre-operative and post-operative T2RV changes were found at the posterior medial femur (interval between injury and MR examination, and instability) and posterior lateral femur (Lysholm score).

CONCLUSION

Patients with anterior cruciate ligament injury followed by DB-ACLR presented short-term subcompartment T2RV changes at the medial femur, lateral femur and medial tibia. Meniscal status did not affect T2RV; however, clinical findings influenced T2RV at the posterior grooves of the medial and lateral femoral condyles.

ADVANCES IN KNOWLEDGE

Patients submitted to DB-ACLR presented T2RV changes in both femoral and medial tibial condyles 6 months after the surgery, affecting not just the weight-bearing areas, but also the less-weight-bearing areas.

MRI findings of young male soldiers with atraumatic anterior knee pain

The purpose of this study is to investigate abnormal magnetic resonance image (MRI) findings of young active males with atraumatic anterior knee pain (AKP). Targeting young male soldiers, we prospectively gathered and analyzed 157 knee MRIs from patients with atraumatic AKP (AKP group) and 53 knee MRIs from patients without knee pain (control group). Abnormalities of the patellofemoral (PF) joint and extensor mechanism on MRI were more common in the AKP group than the control group (48% vs 13%, P < 0.001). The overall prevalence of medial plica (34% vs 13%, P = 0.004) and the prevalence of the thick medial plica (9% vs 0%, P = 0.023) were considerably higher in the AKP group. The cartilaginous sulcus angle in the AKP group without abnormalities on MRI was significantly higher than both the AKP group with abnormalities and the control group (145° vs 141° vs 142°, respectively, P = 0.001). Our results suggest that careful assessment of young, active males with atraumatic AKP is warranted regarding PF joint abnormalities, particularly the presence of medial plica and/or subtle abnormalities of the articular geometry. The results from the present study could be used for the management of patients with AKP.

Validation of porcine knee as a sex-specific model to study human anterior cruciate ligament disorders

BACKGROUND

Animal models have long been considered an important modality for studying ACL injuries. However, to our knowledge, the value of these preclinical models to study sex-related phenomena associated with ACL injury and recovery has not been evaluated.

QUESTIONS/PURPOSES

We asked whether (1) prominent anatomic and (2) biomechanical factors differ between female and male porcine knees, particularly those known to increase the risk of ACL injury.

METHODS

Eighteen intact minipig knees (nine males, nine females) underwent MRI to determine the femoral bicondylar width, intercondylar notch size (width, area and index), medial and lateral tibial slope, ACL size (length, cross-sectional area, and volume), and medial compartment tibiofemoral cartilage thickness. AP knee laxity at 30°, 60°, and 90° flexion and ACL tensile structural properties were measured using custom-designed loading fixtures in a universal tensile testing apparatus. Comparisons between males and females were performed for all anatomic and biomechanical measures. The findings then were compared with published data from human knees.

RESULTS

Female pigs had smaller bicondylar widths (2.9 mm, ratio=0.93, effect size=-1.5) and intercondylar notches (width: 2.0 mm, ratio=0.79, effect size=-2.8; area: 30.8 mm2, ratio=0.76, effect size=-2.1; index: 0.4, ratio=0.84, effect size=-2.0), steeper lateral tibial slope (4.3°, ratio=1.13, effect size=1.1), smaller ACL (length: 2.7 mm, ratio=0.91, effect size=-1.1; area: 6.8 mm2, ratio=0.74, effect size=-1.5; volume: 266.2 mm3, ratio=0.68, effect size=-1.5), thinner medial femoral cartilage (0.4 mm, ratio=0.8, effect size=-1.1), lower ACL yield load (275 N, ratio=0.81, effect size=-1.1), and greater AP knee laxity at 30° (0.7 mm, ratio=1.32, effect size=1.1) and 90° (0.5 mm, ratio=1.24, effect size=1.1) flexion compared with their male counterparts. These differences were significant for all parameters (p≤0.04). Observed sex-related differences were similar to those reported for the human knee.

CONCLUSIONS

Significant differences exist between knees of male and female pigs with respect to prominent anatomic and biomechanical factors. Our findings strongly agreed with published data regarding human knees.

CLINICAL RELEVANCE

The findings highlight the use of the porcine large animal model to study the role of sex on ACL injuries and surgical outcome. This validated preclinical model may facilitate the development of novel, sex-specific interventions to prevent and treat ACL injuries for male and female patients.

Effect of tunnel placements on clinical and magnetic resonance imaging findings 2 years after anterior cruciate ligament reconstruction using the double-bundle technique

PURPOSE

The purpose of the study reported here was to find out if the clinical and magnetic resonance imaging (MRI) findings of a reconstructed anterior cruciate ligament (ACL) have an association. Our hypothesis, which was based on the different functions of the ACL bundles, was that the visibility of the anteromedial graft would have an impact on anteroposterior stability, and the visibility of the posterolateral graft on rotational stability of the knee.

METHODS

This study is a level II, prospective clinical and MRI study (NCT02000258). The study involved 75 patients. One experienced orthopedic surgeon performed all double-bundle ACL reconstructions. Two independent examiners made the clinical examinations at 2-year follow-up: clinical examination of the knee; KT-1000, International Knee Documentation Committee and Lysholm knee evaluation scores; and International Knee Documentation Committee functional score. The MRI evaluations were made by two musculoskeletal radiologists separately, and the means of these measurements were used.

RESULTS

We found that the location of the graft in the tibia had an impact on the MRI visibility of the graft at 2-year follow-up. There were significantly more partially or totally invisible grafts if the insertion of the graft was more anterior in the tibia. No association was found between the clinical results and the graft locations.

CONCLUSION

Anterior graft location in the tibia can cause graft invisibility in the MRI 2 years after ACL reconstruction, but this has no effect on the clinical recovery of the patient.

Prevalence and incidence of new meniscus and cartilage injuries after a nonoperative treatment algorithm for ACL tears in skeletally immature children: a prospective MRI study

BACKGROUND

The increased risk of long-term osteoarthritis from concomitant injuries to the menisci or cartilage after an anterior cruciate ligament (ACL) injury in adults is well established. In skeletally immature children, ACL reconstruction is often recommended to reduce the risk of new intra-articular injuries. However, the prevalence and incidence of new injuries after nonoperative treatment of ACL injuries in children are unknown.

PURPOSE

To prospectively investigate the incidence of new injuries to the menisci and joint cartilage in nonoperatively treated, skeletally immature children with a known ACL injury by use of bilateral 3.0-T MRI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Forty skeletally immature children with a ruptured ACL (41 knees) followed a nonoperative treatment algorithm and were evaluated with bilateral 3.0-T MRI on 2 occasions (MRI1 and MRI2). The intra-articular structures were analyzed by 2 independent MRI radiologists. Monitoring of participation in physical activities was accomplished through a monthly online activity survey. Descriptive statistics and frequencies were extracted from the scoring forms and compared using the Fisher exact test.

RESULTS

Fourteen girls (35%) and 26 boys (65%) with a mean age of 11.0 ± 1.4 years at the time of injury were included. Time from injury to the final follow-up was 3.8 ± 1.4 years. Eighty-eight percent of the ACL-deficient children confirmed monthly participation in pivoting sports and/or in physical education classes in school. The prevalence of meniscus injuries in the 28 nonreconstructed knees was 28.5% at MRI1 and MRI2, and the incidence of new meniscus and cartilage injuries in the nonreconstructed knees from MRI1 to MRI2 was 3.6%. Thirteen children underwent ACL reconstruction, with a prevalence of meniscus procedures of 46.2%. The incidence of new meniscus injuries from diagnostic MRI to final follow-up was 19.5%. Surgical treatments for meniscus injuries were performed in 8 of the 41 knees.

CONCLUSION

The incidence of new injuries to menisci and joint cartilage was low between MRI1 and MRI2 in the 28 nonreconstructed knees. Thirty-two percent of the knees required ACL reconstruction, and 19.5% required meniscus surgeries during the 3.8 ± 1.4 years of follow-up from injury. Further follow-up is needed to evaluate the long-term knee health in these children.

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

BACKGROUND

Magnetic resonance imaging (MRI) is a noninvasive technology that can quantitatively assess anterior cruciate ligament (ACL) graft size and signal intensity. However, how those properties relate to reconstructed or repaired ligament strength during the healing process is yet unknown.

HYPOTHESIS

Magnetic resonance imaging-derived measures of graft volume and signal intensity are significant predictors of the structural properties of an ACL or ACL graft after 15 weeks and 52 weeks of healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

The current data were gathered from 2 experiments evaluating ACL reconstruction and repair techniques. In the first experiment, pigs underwent unilateral ACL transection and received (1) ACL reconstruction, (2) ACL reconstruction with collagen-platelet composite (CPC), or (3) no treatment. The surgical legs were harvested after 15 weeks of healing. In the second experiment, pigs underwent ACL transection and received (1) ACL reconstruction, (2) ACL reconstruction with CPC, (3) bioenhanced ACL primary repair with CPC, or (4) no treatment. The surgical legs were harvested after 52 weeks. The harvested knees were imaged using a T2*-weighted 3-dimensional constructive interference in steady state (CISS) sequence. Each ligament was segmented from the scans, and the intra-articular volume and the median grayscale values were determined. Mechanical testing was performed to establish the ligament structural properties.

RESULTS

Volume significantly predicted the structural properties (maximum load, yield load, and linear stiffness) of the ligaments and grafts (R (2) = 0.56, 0.56, and 0.49, respectively; P ≤ .001). Likewise, the median grayscale values (ie, signal intensity) significantly predicted the structural properties of the ligaments and grafts (R (2) = 0.42, 0.37, and 0.40, respectively; P < .001). The combination of these 2 parameters in a multiple regression model improved the predictions (R (2) = 0.73, 0.72, and 0.68, respectively; P ≤ .001).

CONCLUSION

Volume and grayscale values from high-resolution T2*-weighted MRI scans are predictive of structural properties of the healing ligament or graft in a porcine model.

CLINICAL RELEVANCE

This study provides a critical step in the development of a noninvasive method to predict the structural properties of the healing ACL graft or repair. This technique may prove beneficial as a surrogate outcome measure in preclinical animal and clinical studies.

Analysis of tunnel widening after double-bundle ACL reconstruction

PURPOSE

The purpose of this study was to evaluate the tunnel widening using a multi-planar reformation of MRI (Magnetic Resonance Imaging) in the orientation of the tunnel. The hypotheses of this study were as follows: (1) tunnel widening would be reduced with the above-mentioned technique, (2) the degree of tunnel widening would be different at the site of the tunnels, and (3) the time interval from surgery to MRI acquisition would affect the magnitude of tunnel widening.

METHODS

Forty double-bundle ACL reconstructed patients who underwent postoperative MRI were enrolled in this study. The postoperative MRI was performed at 26.7 ± 7.4 months in terms of time. The tunnel widening was examined using a multi-planar reformation of MRI in the orientation of the tunnel. Site-specific analysis was performed according to the depth (the entrance, mid, and exit portion) and wall (anterior, posterior, medial, and lateral walls). The correlation between MRI and widening was also evaluated.

RESULTS

The mean tunnel widening of the femoral AM (Anteromedial), femoral PL (Posterolateral), tibial AM, and tibial PL in terms of the most widened diameter was 1.9 (25.4), 2.1 (30.8), 2.5 (32.8), and 3.2 mm (44.5%), respectively. The tibial PL tunnel showed significant widening than the other tunnels. At the entrance, tunnel widening occurred mostly, followed by the order of the mid and exit portion. Correlation analysis of the time interval of MRI acquisition and tunnel widening showed little association.

CONCLUSIONS

Tunnel widening after a double-bundle ACL reconstruction using an outside-in technique with press-fitting of the graft was acceptable compared to previously published studies. The tibial PL tunnel showed the most widening among the 4 tunnels examined with the tunnel entrance being most widened area.

LEVEL OF EVIDENCE

Therapeutic case series, Level IV.

Effect of timing of ACL reconstruction in surgery and development of meniscal and chondral lesions

PURPOSE

To investigate whether a delay in the timing of surgery of > 6 months compared with performing the surgery ≤ 6 months after the anterior cruciate ligament (ACL) injury leads to an increased risk of injuries or degenerative changes in the ACL-deficient knee.

METHODS

Patients who underwent primary ACL reconstruction at an academic tertiary care center, and had preoperative magnetic resonance imaging (MRI) performed within 2 months of the time of the ACL injury were included. The prevalence of degenerative changes at the time of surgery was assessed and related to the timing of ACL surgery, with "early reconstruction" defined as a surgery performed ≤ 6 months and "delayed reconstruction" defined as surgery performed > 6 months after ACL injury. "New" meniscal tears were defined as lesions detected at the time of surgery that were not detected by MRI.

RESULTS

Of 195 patients who were selected based on inclusion criteria, 171 patients underwent surgery ≤ 6 months after their ACL injury, and 24 patients underwent surgery > 6 months after their ACL injury. The prevalence of new medial meniscal tears in the early reconstruction group was 4.1%, while in the delayed reconstruction group, the prevalence was 16.7% (P = 0.012).

CONCLUSION

A delay in the timing of ACL reconstruction from ≤ 6 months to > 6 months following injury is associated with a significant increase in the prevalence of medial meniscal tears (P = 0.012), with a relative risk of 4.07 (CI, 1.29-12.88).

Double-bundle versus single-bundle anterior cruciate ligament reconstruction: randomized clinical and magnetic resonance imaging study with 2-year follow-up

BACKGROUND

One aspect of the debate over the reconstruction of the anterior cruciate ligament is whether it should be carried out with the single-bundle or double-bundle technique.

HYPOTHESIS

The double-bundle technique results in fewer graft failures than the single-bundle technique in anterior cruciate ligament reconstruction.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 153 patients were prospectively randomized into 2 groups of anterior cruciate ligament reconstruction with hamstring autografts using aperture interference screw fixation: single-bundle technique (SB group, n = 78) and double-bundle technique (DB group, n = 75). The evaluation methods were clinical examination, KT-1000 arthrometric measurement, the International Knee Documentation Committee (IKDC) and the Lysholm knee scores, and magnetic resonance imaging (MRI) evaluation. All of the operations were performed by 1 experienced orthopaedic surgeon, and all clinical assessments were made by 2 blinded and independent examiners. A musculoskeletal radiologist blinded to the clinical data made the MRI interpretation.

RESULTS

There were no differences between the study groups preoperatively. Ninety percent of patients (n = 138) were available at a minimum 2-year follow-up (range, 24-37 months). Eight patients (7 in the SB group and 1 in the DB group) had graft failure during the follow-up and had anterior cruciate ligament revision surgery (P = .04). In addition, 7 patients (5 in the SB group and 2 in the DB group) had an invisible graft on the MRI assessment at the 2-year follow-up. Also, the anteromedial bundle was partially invisible in 2 patients and the posterolateral bundle in 9 patients. Together, the total number of failures and invisible grafts were significantly higher in the SB group (12 patients, 15%) than the DB group (3 patients, 4%) (P = .024). No significant group differences were found in the knee scores or stability evaluations at the follow-up.

CONCLUSION

This 2-year randomized trial showed that the revision rate of the anterior cruciate ligament reconstruction was significantly lower with the double-bundle technique than that with the single-bundle technique. However, additional years of follow-up are needed to reveal the long-term results.

The "lateral gutter drive-through" sign: an arthroscopic indicator of acute femoral avulsion of the popliteus tendon in knee joints

Acute avulsions of the popliteus tendon and the lateral collateral ligament of the femur (peel-off lesion) are common and can both be missed during preoperative assessment and later overlooked during surgery if not specifically sought out. Arthroscopic observation of the direct avulsion sign of the torn end of the popliteus tendon occurs less frequently in patients with acute and subacute injuries. This study describes an arthroscopic sign that detects these tears when they either involve only the popliteal tendon or include the lateral collateral ligament assessed from the lateral gutter of the joint. The "lateral gutter drive-through," visualized during diagnostic arthroscopy, is described as entering of the arthroscope into the posterolateral compartment through the interval between the popliteal tendon and the lateral femoral condyle. A positive sign indicates (1) the presence of femoral avulsion tears of the popliteal tendon or concomitant lateral collateral ligament, (2) the presence of repairable posterolateral corner tears, and (3) the enablement of mini-open surgery for the repair of these avulsion tears with a recess or reattachment procedure. In addition, arthroscopic evaluation of the lateral compartment and preoperative magnetic resonance imaging assessment are used to eliminate the multiple-level injuries of the popliteus tendon and lateral collateral ligament.