Graft failure in intra-articular anterior cruciate ligament reconstructions: a review of the literature

Application and optimization of bioengineering strategies in facilitating tendon-bone healing

Tendon-bone insertion trauma is prevalent in both rotator cuff and anterior cruciate ligament injuries, which are frequently encountered conditions in the field of sports medicine. The main treatment for such injuries is reconstructive surgery. The primary determinant impacting this process is the graft's capacity to integrate with the bone tunnel. In recent years, researchers have attempted to use a variety of methods to facilitate tendon-bone healing after reconstructive surgery. Such as the implantation of biological materials, cytokines and the local application of permanently differentiated cells from various sources. However, there are limitations to the efficacy of one therapy alone in facilitating tendon-bone healing. Therefore, researchers are trying to combine strategies to overcome this conundrum. At present, most studies are based on biomaterial combined with other therapeutic strategies for tissue repair and regeneration. Biomaterials mainly include the application of bioengineering scaffolds, hydrogels and bioabsorbable interference screws. By conducting a thorough review of relevant literature, this study provides a comprehensive overview of the present research progress in enhancing tendon-bone healing using biomaterials. Additionally, it explores the potential benefits of combining biomaterials with other approaches to promote tendon-bone healing. The ultimate goal is to offer insights for future basic research endeavors and establish a solid groundwork for advancing clinical applications in the near future.

An Aligned-to-Random PLGA/Col1-PLGA/nHA Bilayer Electrospun Nanofiber Membrane Enhances Tendon-to-Bone Healing in a Murine Model

BACKGROUND

The challenge of achieving effective tendon-to-bone healing remains a significant concern in sports medicine, necessitating further exploration. Biomimetic electrospun nanomaterials present promising avenues for improving this critical healing process.

PURPOSE

To investigate the biological efficacy of a novel aligned-to-random PLGA/Col1-PLGA/nHA bilayer electrospun nanofiber membrane in facilitating tendon-to-bone healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

The bilayer membrane's composition, combining PLGA/Col1 for tendon attachment and PLGA/nHA for bone integration, was examined using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical testing. Positioned between the Achilles tendon and bone, its design aimed for harmonious integration with both types of tissue. In vitro, biocompatibility, cell adhesion, and proliferation of the biomaterial were evaluated using live/dead staining and the CCK-8 assay. Collagen secretion and mineralization were measured for 2 cell types. In vivo, tendon-to-bone insertion samples harvested from mice were analyzed: micro-computed tomography assessed bone formation; histological staining evaluated chondrogenesis, tendinogenesis, and the 4-layer structure of the insertion; and biomechanical testing measured insertion strength. Real-time polymerase chain reaction identified genes involved in tendon-to-bone healing, and transcriptome analysis elucidated the underlying cellular and molecular mechanisms.

RESULTS

The optimal composition was determined as 10% 3:1 for aligned PLGA/Col1 and 9% 5:1 for PLGA/nHA. Coculture showed minimal cell death, firm cell adherence, and steady proliferation, with PLGA/Col1 enhancing collagen secretion. In vivo, the material promoted bone and cartilage formation and improved tendon-to-bone interface strength. Transcriptome analysis indicated links to TNF and NF-κB pathways and to genes IL-1β, ADAM8, and EGR2.

CONCLUSION

The novel aligned-to-random PLGA/Col1-PLGA/nHA bilayer nanofiber membrane outperformed other materials in both in vitro and in vivo evaluations, significantly enhancing tendon-to-bone healing. It notably improved cartilage and bone formation, tendon maturation, and biomechanical strength at the surgical interface. These effects may be associated with the TNF and NF-κB pathways and with the genes IL-1β, ADAM8, and EGR2.

CLINICAL RELEVANCE

This study introduces a biomimetic nanofiber membrane enhancing tendon-to-bone healing, which is crucial for sports medicine. Its efficacy in improving healing outcomes, including bone and cartilage formation and biomechanical strength, could significantly lower failure rates in surgical procedures such as rotator cuff repair and anterior cruciate ligament reconstruction. This advancement offers promising implications for patient recovery and the effectiveness of surgical interventions in tendon-to-bone injuries.

Intra-Articular Surgical Reconstruction of a Canine Cranial Cruciate Ligament Using an Ultra-High-Molecular-Weight Polyethylene Ligament: Case Report with Six-Month Clinical Outcome

The intra-articular reconstruction of the cranial cruciate ligament (CrCL) by an organic graft or a synthetic implant allows the restoration of physiological stifle stability. This treatment is still marginal in routine practice. A Rottweiler presented an acute complete CrCL rupture treated using an ultra-high-molecular-weight polyethylene (UHMWPE) implant. The latter was positioned under arthroscopic guidance and fixed with interference screws through femoral and tibial bone tunnels. The dog was weight-bearing just after surgery and resumed normal standing posture and gait after one month, with mild signs of pain upon stifle manipulation. At three months postoperatively, minimal muscle atrophy and minimal craniocaudal translation were noted on the operated hindlimb, with no effects on the clinical outcome. The stifle was painless. At six months postoperatively, standing posture and gait were normal, muscle atrophy had decreased, the stifle was painless, and the craniocaudal translation was stable. On radiographs, congruent articular surfaces were observed without worsening of osteoarthrosis over the follow-up, as well as stable moderate joint effusion. Replacement of a ruptured CrCL with a UHMWPE ligament yielded good functional clinical outcome at six months postoperatively. This technique could be considered an alternative for the treatment of CrCL rupture in large dogs, but it needs confirmation from a prospective study with more dogs.

Anterior cruciate ligament femoral side retained stump technique reduces enlargement of the femoral bone tunnel after anterior cruciate ligament reconstruction

BACKGROUND

Enlargement of the bone tunnel has become an unavoidable early complication after anterior cruciate ligament (ACL) reconstruction, whether it is a single or double-bundle ACL reconstruction. Preservation of the ACL stump in ACL reconstruction reduces enlargement of the bone tunnel. The purpose of this study was to investigate the question of whether single-bundle ACL reconstruction using the ACL femoral side retained stump technique reduces enlargement of the femoral tunnel.

METHODS

Forty patients who underwent single-bundle reconstruction of the ACL were included in this study. The patients were categorized into a Remnant preservation group (Group R) and the Non-remnant preservation group (Group N). In the Remnant preservation group, a high-flexion femoral side retained stump technique was used intraoperatively for the establishment of the femoral side bone tunnel, and in the Non-remnant preservation group, the conventional femoral positioning method was used (we used a femoral positioning drill for localization and drilling of the femoral bone tunnel), and MRI of the operated knee joints was performed at 6 months postoperatively. We measured the internal diameter of the femoral bone tunnel at 5 mm from the intra-articular outlet of the femoral bone tunnel on an MRI scan image perpendicular to the femoral bone tunnel. The size of the tunnel was compared between the intraoperative drilling of the bone tunnel and the size of the bone tunnel at 6 months postoperatively. Postoperative clinical assessment was Lysholm score.

RESULTS

After a 6-month follow-up of 40 patients, the diameter of the femoral tunnel at a distance of 5 mm from the inner opening of the femoral tunnel was 10.96 ± 0.67 mm and 10.11 ± 0.62 mm in patients of group N and group R, respectively, and the difference was statistically significant (P < 0.05).The diameter of the femoral tunnel at 6 months postoperatively in group N and group R compared to the intraoperative bone tunnel increased by 2.58 ± 0.24 mm and 1.94 ± 0.31 mm, and the difference was statistically significant (P < 0.05).The femoral tunnel enlargement rates of group N and group R were 30.94 ± 3.00% and 24.02 ± 5.10%, respectively, and the differences were significant (P < 0.05).

CONCLUSION

ACL femoral side retained stump technique does not sacrifice the ideal location of the femoral tunnel and is able to preserve the possible benefits of the ACL stump: reduced femoral tunnel enlargement.

Risk Factors for Ipsilateral Versus Contralateral Reinjury After ACL Reconstruction in Athletes: A Systematic Review and Meta-analysis

Background

Anterior cruciate ligament (ACL) reinjury after ACL reconstruction (ACLR) can occur on the ipsilateral or contralateral side. Limited evidence exists regarding the difference between the incidence of reinjury to either knee, which is important in developing interventions to prevent ACL reinjury.

Purpose

To compare the reinjury rate of the ACL on the ipsilateral side versus the contralateral side in athletes after ACLR and investigate the risk factors that may cause different reinjury rates between the sides.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic review was performed based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Studies that involved ACL reinjury in athletes after ACLR were reviewed. Considering several risk factors, including age and sex, a comparison of ACL reinjury incidence on the ipsilateral and contralateral sides was performed using a meta-analysis.

Results

Of the 17 selected studies, 3 were found to be at high risk of bias, and thus, 14 (n = 3424 participants) studies were included in the meta-analysis. In this athletic population, the contralateral ACL had a significantly higher rupture rate than the ipsilateral graft (risk ratio [RR], 1.41; P < .0001). Female athletes were found to have a greater risk of ACL reinjury on the contralateral versus the ipsilateral side (RR, 1.65; P = .0005), but different results were found in male athletes. (RR, 0.81; P = .21). There was no statistical difference in the incidence rate of ACL reinjury to either side in adolescent athletes (RR, 1.15; P = .28).

Conclusion

The contralateral ACL was more vulnerable to reinjury than the ipsilateral side in athletes after ACLR. Female athletes were more likely to reinjure their contralateral native ACL, while the same trend was not found in their male counterparts. The reinjury rate was comparable in both knees in adolescent athletes.

Combining return to sport, psychological readiness, body mass, hamstring strength symmetry, and hamstring/quadriceps ratio increases the risk of a second anterior cruciate ligament injury

PURPOSE

To investigate the combinations of variables that comprise the biopsychosocial model domains to identify clinical profiles of risk and protection of second anterior cruciate ligament injury.

METHODS

One hundred and forty-five patients for return-to-sport testing after anterior cruciate ligament (ACL) reconstruction (ACLR) were contacted, and 97 were deemed eligible. All were evaluated between 6 and 24 months and followed up for 2 years. Participants answered the International Knee Documentation Committee (IKDC) and Anterior Cruciate Ligament-Return to Sport after Injury Scale (ACL-RSI), performed the postural stability assessment using the Biodex Balance System, and assessed muscle strength at 60° and 300°/s on the isokinetic dynamometer. Personal factors (age, gender, body mass index), body structures (graft type and concomitant injuries), and environmental factors (time between surgery and evaluation) were also collected. The participants were asked about the occurrence of a second ACL injury and return to sport after 2 years of follow-up. Classification and regression tree (CART) analysis was used to determine predictors of a second ACL injury. The receiver operating characteristic (ROC) curve was performed to verify the accuracy of the CART analysis, in addition to the sensitivity, specificity, and relative risk (RR) of the model.

RESULTS

Of the initial 97 participants, 88 (89.8%) responded to follow-up and 14 (15.9%) had a second ACL injury (11 graft ruptures and three contralateral ACL). CART analysis identified the following variables as predictors of second ACL injury: return to sport, hamstring strength symmetry at 300°/s, ACL-RSI score, hamstrings/quadriceps ratio at 60°/s, and body mass index (BMI). CART correctly identified 9 (64.3%) of the 14 participants who were reinjured and 71 (95.9%) of the 74 participants who were not. The total correct classification was 90.9%. The area under the ROC curve was 0.88 (95% CI 0.72-0.99; p < 0.001), and the model showed a sensitivity of 75% (95% CI 42.8-94.5), specificity of 93.4% (95% CI 85.3-97.8), and RR of 15.9 (95% CI 4.9-51.4; p < 0.0001).

CONCLUSION

The combination of hamstring strength symmetry, hamstring/quadriceps ratio (body functions); return to sport (activity and participation); psychological readiness; and BMI (personal factors) could identify three clinical risk profiles for a second ACL injury with good accuracy.

LEVEL OF EVIDENCE

IV.

Tubularization of Bone-Tendon-Bone Grafts: Effects on Mechanical Strength and Postoperative Knee Stability in Anterior Cruciate Ligament Reconstruction

Background and Objectives: The study addresses a significant limitation in applying bone-patellar tendon-bone (BTB) grafts in anterior cruciate ligament (ACL) surgery. By exploring the tubularization of grafts, the study extends the understanding of this surgical technique. The dual approach of the study-focusing on biomechanical properties using an animal model and postoperative outcomes in humans-offers a comprehensive perspective. Materials and Methods: The experimental cohort encompassed ten pairs of fresh porcine bone-tendon-bone grafts. One graft in each pair underwent modification through sutures that transformed the flat graft into a cylindrical structure. Testing determined the force required for the modified graft to rupture mechanically, expressed as N/mm2, compared to conventionally prepared bone-tendon-bone grafts. The second phase of the research involved a prospective randomized clinical trial comprising 120 patients undergoing operative ACL reconstruction. For half the cases, grafts were tubularized using a random selection process. Clinical evaluations preoperatively and 12 months postoperatively employed the Tegner, Lysholm, and IKDC scoring scales for knee assessment. Results: Experiments showed that ligaments made using the tubularized surgical technique have statistically significantly higher values of measured force and higher maximum elongation values than ligaments made using the classical method. The clinical study concluded that there was no significant difference between the two groups of patients in the average score on the Tegner, Lysholm, and IKDC scales before and after surgery. Conclusions: The study results showed that suturing the graft does not negatively affect its biomechanical properties, and tubularization significantly increases the values of force required to cause rupture and the values of maximum elongation during rupture. Given the possibility of the one-year follow-up period being insufficient, future investigations should extend this period to acquire objective functional insights post-surgery.

Increased Bone Plug Depth From the Joint Increases Tunnel Enlargement in Anterior Cruciate Ligament Reconstruction Using Bone-Patellar Tendon-Bone Autograft With Suspensory Femoral Fixation

Purpose

To determine a safe bone plug depth fixation zone based on early tunnel enlargement rates in anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon-bone (BPTB) autograft with suspensory femoral fixation.

Methods

Patients who had undergone rectangular tunnel ACL reconstruction using BPTB autograft with suspensory femoral fixation were retrospectively identified. Femoral and tibial tunnel aperture areas were measured on computed tomography 2 weeks and 6 months after surgery to calculate rates of femoral and tibial tunnel enlargement (FTE and TTE), respectively. Femoral bone plug depth (FBPD) and tibial bone plug depth (TBPD) were defined as the distance of the tip of the plug from the respective joint lines. Optimal FBPD and TBPD cutoff values were calculated for the following rates of FTE and TTE, respectively: 0%, 15%, 30%, and 50%.

Results

Sixty-four patients (19 females, 45 males; mean age, 29.5 ± 12.3 years) were included in the study. The femoral and tibial tunnel apertures significantly enlarged over time. FBPD (P < .001; r = 0.607) and TBPD (P = .013; r = 0.308) were positively correlated with FTE and TTE, respectively. The optimal FBPD cutoff value was 2.8 mm for FTE rates of 0% and 15%, 3.6 mm for 30%, and 6.0 mm for 50%. The optimal TBPD cutoff value was 1.48 mm for a 0% TTE rate and 5.1 mm for those higher. The cutoff value specificities were lower for the tibial tunnel than the femoral tunnel for each tunnel enlargement rate.

Conclusion

Early tunnel enlargement and bone plug depth were significantly correlated in bone the femoral and tibial tunnels. The degree of correlation was higher in the femoral tunnel. To minimize bone tunnel enlargement, the distal end of the femoral bone plug should be placed less than 2.8 mm from the tunnel aperture.

Level of Evidence

Level IV, therapeutic case series.

Strategies for promoting tendon-bone healing: Current status and prospects

Tendon-bone insertion (TBI) injuries are common, primarily involving the rotator cuff (RC) and anterior cruciate ligament (ACL). At present, repair surgery and reconstructive surgery are the main treatments, and the main factor determining the curative effect of surgery is postoperative tendon-bone healing, which requires the stable combination of the transplanted tendon and the bone tunnel to ensure the stability of the joint. Fibrocartilage and bone formation are the main physiological processes in the bone marrow tract. Therefore, therapeutic measures conducive to these processes are likely to be applied clinically to promote tendon-bone healing. In recent years, biomaterials and compounds, stem cells, cell factors, platelet-rich plasma, exosomes, physical therapy, and other technologies have been widely used in the study of promoting tendon-bone healing. This review provides a comprehensive summary of strategies used to promote tendon-bone healing and analyses relevant preclinical and clinical studies. The potential application value of these strategies in promoting tendon-bone healing was also discussed.

Pediatric Revision Anterior Cruciate Ligament Reconstruction: Current Concepts Review

OBJECTIVE

We present a review of revision anterior cruciate ligament (ACL) reconstruction in pediatric patients, discussing risk factors for rerupture, physical examination and imaging, treatment principles and surgical techniques, postoperative rehabilitation, and clinical outcomes.

DATA SOURCES

PubMed, Cochrane, and Embase databases were queried for relevant articles about revision ACL topics. All types of manuscripts, including clinical studies, basic science studies, case series, current concepts reviews, and systematic reviews were analyzed for relevant information. Current concepts on risk factors for rerupture, physical examination and imaging, treatment principles and surgical techniques, postoperative rehabilitation, and clinical outcomes were synthesized.

MAIN RESULTS

Surgical treatment should be individualized, and the graft type, fixation devices, tunnel placement, and complementary procedures (eg, extra-articular tenodesis) should be tailored to the patient's needs and previous surgeries. Rehabilitation programs should also be centered around eccentric strengthening, isometric quadriceps strengthening, active flexion range of motion of the knee, and an emphasis on closed chain exercises. Despite adherence to strict surgical and postoperative rehabilitation principles, graft refailure rate is high, and return to sports rate is low.

CONCLUSION

Rerupture of the ACL in the pediatric population is a challenging complication that requires special attention. Diagnostic evaluation of repeat ACL ruptures is similar to primary injuries. Although outcomes after revision ACL reconstruction are expectedly worse than after primary reconstruction, athletes do return to sport after proper rehabilitation. Further research is needed to continue to improve outcomes in this high-risk population, aimed at continued knee stability, graft survivorship, and improved quality of life.

Stem cell therapies in tendon-bone healing

Tendon-bone insertion injuries such as rotator cuff and anterior cruciate ligament injuries are currently highly common and severe. The key method of treating this kind of injury is the reconstruction operation. The success of this reconstructive process depends on the ability of the graft to incorporate into the bone. Recently, there has been substantial discussion about how to enhance the integration of tendon and bone through biological methods. Stem cells like bone marrow mesenchymal stem cells (MSCs), tendon stem/progenitor cells, synovium-derived MSCs, adipose-derived stem cells, or periosteum-derived periosteal stem cells can self-regenerate and potentially differentiate into different cell types, which have been widely used in tissue repair and regeneration. Thus, we concentrate in this review on the current circumstances of tendon-bone healing using stem cell therapy.

A steep coronal graft bending angle is associated with bone tunnel enlargement of the posterolateral bundle after anterior cruciate ligament reconstruction

PURPOSE

The correlation between the graft bending angle (GBA) of the anteromedial bundle and posterolateral bundle after anterior cruciate ligament reconstruction (ACLR) and postoperative tunnel enlargement was evaluated.

METHODS

Two hundred fifty-eight patients (137 males, 121 females; mean age 27.3 years) who had undergone double-bundle ACLR were included. Computed tomographic scans of the operated knee were obtained at 2 weeks and 6 months postoperatively. The area of the tunnel aperture for femoral anteromedial tunnel (FAMT) and femoral posterolateral tunnel (FPLT) was measured; the area at 2 weeks after ACLR was subtracted from the area at 6 months after ACLR and then divided by the area at 2 weeks after ACLR. The femoral tunnel angles were obtained with Cobb angle measurements. The femoral tunnel angle in the coronal plane was measured relative to the tibial plateau (coronal GBA). On the median value, the patients were divided into two groups in each of FAMT and FPLT; those with a coronal GBA of FAMT of ≥27° were classified as group A, while those with a coronal GBA of <27° were classified as group B, those with a coronal GBA of FPLT of ≥23° were classified as group C, while those with a coronal GBA of<23° were classified as group D.

RESULTS

Group A included 129 knees, while group B included 129 knees. Groups A and B did not significantly differ regarding FAMT enlargement. Group C included 133 knees, while group D included 125 knees. The percentage of FPLT enlargement in group C was significantly smaller than that in group D (p = 0.001).

CONCLUSIONS

A steep coronal GBA of the FPLT after ACLR results in greater FPLT enlargement. The present findings suggest that surgeons should avoid creating a steep GBA of the FPLT in the outside-in technique.

Does Manual Drilling Improve the Healing of Bone-Hamstring Tendon Grafts in Anterior Cruciate Ligament Reconstruction? A Histological and Biomechanical Study in a Rabbit Model

Background:

Heat necrosis due to motorized drilling during anterior cruciate ligament (ACL) reconstruction could be a factor in delayed healing at the bone–tendon graft interface.

Hypothesis:

The process of osteointegration could be enhanced using manual drilling. It reduces the invasiveness of mechanical-thermal stress normally caused by the traditional motorized drill bit.

Study Design:

Controlled laboratory study.

Methods:

ACL reconstruction using semitendinosus tendon autografts was performed in 28 skeletally mature female New Zealand white rabbits, which were randomly divided into 3 groups. In group A (n = 12), the tunnels were drilled using a motorized device; in group B (n = 12), the tunnels were drilled using a manual drill bit; and group C (n = 4) served as a control with sham surgical procedures. The healing process in the tunnels was assessed histologically at 2, 4, 8, and 12 weeks and graded according to the Tendon–Bone Tunnel Healing (TBTH) scoring system. In addition, another 25 rabbits were used for biomechanical testing. The structural properties of the femur–ACL graft–tibia complex, from animals sacrificed at 8 weeks postoperatively, were determined using uniaxial tests. Stiffness (N/mm) and ultimate load to failure (N) were determined from the resulting load-elongation curves.

Results:

The time course investigation showed that manual drilling (group B) had a higher TBTH score and improved mechanical behavior, reflecting better organized collagen fiber continuity at the bone–fibrous tissue interface, better integration between the graft and bone, and early mineralized chondrocyte-like tissue formation at all the time points analyzed with a maximum difference at 4 weeks (TBTH score: 5.4 [group A] vs 12.3 [group B]; P < .001). Stiffness (23.1 ± 8.2 vs 17.8 ± 6.3 N/mm, respectively) and ultimate load to failure (91.8 ± 60.4 vs 55.0 ± 18.0 N, respectively) were significantly enhanced in the specimens treated with manual drilling compared with motorized drilling (P < .05 for both).

Conclusion:

The use of manual drilling during ACL reconstruction resulted in better tendon-to-bone healing during the crucial early weeks. Manual drilling was able to improve the biological and mechanical properties of bone–hamstring tendon graft healing and was able to restore postoperative graft function more quickly. Tunnel drilling results in bone loss and deficient tendon-bone healing, and heat necrosis after tunnel enlargement may cause mechanical stress, contributing to a delay in healing. Manual drilling preserved the bone stock inside the tunnel, reduced heat necrosis, and offered a better microenvironment for faster healing at the interface.

Clinical Relevance:

Based on study results, manual drilling could be used successfully in human ACL reconstruction, but further clinical studies are needed. A clinical alternative, called the original “all-inside” technique, has been developed for ACL reconstruction. In this technique, the femoral and tibial tunnels are manually drilled only halfway through the bone for graft fixation, reducing bone loss. Data from this study suggest that hamstring tendon–to–bone healing can be improved using a manual drilling technique to form femoral and tibial tunnels.

Arthrofibrosis Following Anterior Cruciate Ligament Reconstruction

Introduction: Anterior cruciate ligament (ACL) tear is a frequent injury and its reconstruction is among the most commonly performed orthopaedic surgical procedures. ACL reconstruction generally yields good results. However, its recovery can be hampered by the development of postoperative complications. The aim of this study was to review complications following arthroscopic ACL reconstruction done in Hospital Raja Permaisuri Bainun, Ipoh and Hospital Teluk Intan, Perak with the emphasis on arthrofibrosis. Arthrofibrosis is defined as a loss of 15 degrees extension or more, with or without flexion loss compared to the contralateral knee. Materials and Methods: The study is based on a series of retrospective cases, on which medical records of 200 patients who underwent ACL reconstruction surgeries between March 2007 and December 2014 were reviewed. Follow-up treatment records were available for 166 patients (83%). The data was analysed to identify the risk factors for developing complications with an emphasis on arthrofibrosis. Results: Eight patients (5%) developed arthrofibrosis in the post-operative period. Early surgical intervention, preoperative limited range of motion and female gender are the risk factors correlate with arthrofibrosis. However, the type of graft used and meniscal procedure do not have a significant correlation with the development of arthrofibrosis. Other complications encountered are local infections, hypertrophic scar and chronic regional pain syndromes. Conclusion: The 5% incidence of arthrofibrosis following an ACL reconstruction in our centres can be reduced with proper preventive measures which include thorough preoperative evaluation, proper patient selection, restoration of ROM prior to surgery and proper timing of surgery.

Bacterial DNA is associated with tunnel widening in failed ACL reconstructions

PURPOSE

To determine if tunnel widening, defined as change in maximal tunnel diameter from the time of initial bone tunnel drilling to revision surgery is associated with bacterial deoxyribonucleic acid (DNA) presence and concentration in torn graft tissue from failed anterior cruciate ligament reconstructions (ACLRs).

METHODS

Thirty-four consecutive revision ACLRs were included (mean age 27.3 years SD 10.9; median time to failure 4.9 years range 105 days-20 years). Graft selection of the failed reconstruction was 68% autograft, 26% allograft, and 6% autograft/allograft hybrid with a mean drilled tunnel diameter of 8.4 mm SD 0.8. Maximal tunnel diameters prior to revision were measured on pre-operative three-dimensional imaging and compared to drilled tunnel diameters at the time of the previous reconstruction. Tissue biopsies of the failed graft were obtained from tibial, femoral, and intraarticular segments. Sterile water left open to air during revision ACLRs and tissue from primary ACLRs were used as negative controls. Clinical cultures were obtained on all revision ACLRs and PCR with universal bacterial primer on all cases and negative controls. Fluorescence microscopy was used to confirm the presence and location of biofilms in two patients with retrieved torn graft tissue and fixation material. Amount of tunnel widening was compared to bacterial DNA presence as well as bacterial DNA concentration via Welch ANOVA.

RESULTS

Bacterial DNA was present in 29/34 (85%) revision ACLRs, 1/5 (20%) of primary ACLR controls and 0/3 (0%) sterile water controls. Cultures were positive (coagulase negative Staphylococcus sp.) in one case, which also had the greatest degree of tunnel widening. Femoral widening was greater in cases with detectable bacterial DNA (mean widening 2.6 mm SD 3.0) versus without (mean 0.3 mm SD 0.6) (p = 0.003) but was unaffected by bacterial DNA concentration (p = 0.44). Tibial widening was not associated with the presence of bacterial DNA (n.s.); however, higher bacterial DNA concentrations were observed in cases with tibial widening ≥ 3.0 mm (median 2.47 ng bacterial DNA/µg total DNA) versus widening < 3.0 mm (median 0.97 ng bacterial DNA/µg total DNA) (p = 0.046). Tunnel widening was not associated with time to failure, graft selection, or number of prior surgeries (n.s., all comparisons). Fluorescence microscopy confirmed the presence of biofilms on ruptured tendon graft as well as fixation material in 2/2 cases.

CONCLUSION

Bacterial DNA is commonly encountered on failed ACLR grafts and can form biofilms. Bacterial DNA does not cause clinically apparent infection symptoms but is associated with tunnel widening. Further research is needed to determine whether graft decontamination protocols can reduce graft bacterial colonization rates, ACLR tunnel widening or ACLR failure risk.

LEVEL OF EVIDENCE

Therapeutic III.

Fibrochondrogenic differentiation potential of tendon-derived stem/progenitor cells from human patellar tendon

Background

Bone–tendon junction (BTJ) is a unique structure connecting tendon and bone through a fibrocartilage zone. Owing to its unique structure, the regeneration of BTJ remains a challenge. Here, we study the fibrochondrogenic differentiation of human tendon-derived stem/progenitor cells (TSPCs) both in vitro and in vivo.

Methods

TSPCs were isolated from human patellar tendon tissues and investigated for their multidifferentiation potential. TSPCs were cultured in chondrogenic medium with transforming growth factor beta 3 (TGF-β3) and BMP-2 in vitro ​and examined for the expression of fibrochondrogenic marker genes by quantitative real-time reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, and immunofluorescence. TSPCs pretreated were also seeded in collage II sponge and then transplanted in immunocompromised nude mice to examine if the fibrochondrogenic characteristics were conserved in vivo.

Results

We found that TSPCs were differentiated towards fibrochondrogenic lineage, accompanied by the expression of collagen I, collagen II, SRY-box transcription factor 9 (Sox 9), and tenascin C. Furthermore, after TSPCs were seeded in collagen II sponge and transplanted in immunocompromised nude mice, they expressed fibrochondrogenic genes, including proteoglycan, collagen I, and collagen II.

Conclusion

Taken together, this study showed that TSPCs are capable of differentiating towards fibrocartilage-like cells, and the fibrochondrogenic characteristics were conserved even in vivo, and thus might have the potential application for fibrocartilage regeneration in BTJ repair.

The translational potential of this article

TSPCs are able to differentiate into fibrocartilage-like cells and thus might well be one potential cell source for fibrocartilage regeneration in a damaged BTJ repair.

No difference in the graft shift between a round and a rounded rectangular femoral tunnel for anterior cruciate ligament reconstruction: an experimental study

INTRODUCTION

We developed a novel technique of creating a rounded rectangular femoral bone tunnel for anatomical, single-bundle, autologous hamstring tendon anterior cruciate ligament (ACL) reconstruction. Although this tunnel has many advantages, its non-circular shape has raised concerns regarding excessive graft shift within the bone tunnel. This study aimed to compare the graft shift between round and rounded rectangular tunnels using a graft diameter tester for simulating the femoral bone tunnel.

MATERIALS AND METHODS

Seven semitendinosus tendon grafts harvested from fresh-frozen cadavers were prepared by removing all excess soft tissue. The two ends of a double-fold hamstring tendon were sutured using a baseball stitch and then looped over a TightRope (Arthrex Co., Ltd., Naples, Florida, USA) to make a fourfold graft. The diameter of the graft was standardized to 8 mm using a round graft diameter tester. A round and an original rounded rectangular graft diameter tester were used for simulating the respective femoral bone tunnels. The graft was inserted into the tunnel, with the TightRope positioned on the outside of the tunnel. The distal end of the graft was tensioned to 40 N at an angle of 75° to reproduce the most severe graft bending angle. Digital photographs of the tunnel aperture taken at each simulated tunnel and the range of graft shift in the simulated tunnel were analyzed by ImageJ software. Statistical analyses were performed using the Tukey test. P < 0.05 was considered to be significant.

RESULTS

There were no significant differences between the round and the rounded rectangular tunnel groups (P > 0.05) in terms of graft shift, gap area, and graft shift ratio.

CONCLUSION

In a simulated ACL reconstruction, there is no difference in the graft shift between a round and a rounded rectangular bone tunnel.

Patient age as a preoperative factor associated with tunnel enlargement following double-bundle anterior cruciate ligament reconstruction using hamstring tendon autografts

PURPOSE

A few studies have detected associations of post-operative tunnel enlargement with sex, age, and the timing of anterior cruciate ligament reconstruction (ACLR). The aim of the present study was to investigate the correlation between post-operative tunnel enlargement following ACLR using hamstring tendon autografts and preoperative factors. The authors hypothesized that tunnel enlargement is associated with age in patients undergoing ACLR.

METHODS

One hundred and six patients (male, n = 57; female, n = 49; mean age, 26.9 years) who underwent double-bundle ACL reconstruction were included in the present study. The time between injury and surgery was 26.3 ± 71.4 weeks. Computed tomographic scans of the operated knee were obtained at 2 weeks and 6 months after surgery. The area of the tunnel aperture was measured for the femoral anteromedial tunnel (FAMT), femoral posterolateral tunnel (FPLT), tibial anteromedial tunnel (TAMT), and tibial posterolateral tunnel. The percentage of tunnel area enlargement was defined as the area at 2 weeks after ACLR subtracted from the area at 6 months after ACLR and then divided by the area at 2 weeks after ACLR. Spearman's correlation coefficient was calculated for each factor. The patients were divided into two groups based on age. Patients aged <40 and ≥40 years were assigned to Groups A and B, respectively. The differences in the outcomes and characteristics of the two groups were evaluated.

RESULTS

The percentage of enlargement of the FAMT, FPLT, and TAMT was correlated with patient age (r = 0.31, p = 0.001; r = 0.24, p = 0.012; and r = 0.30, p = 0.002, respectively). In total, 87 and 19 knees were classified into Groups A and B, respectively, based on patient age. The percentage of enlargement of the FAMT was significantly higher in Group B than A (78 vs. 60%, respectively; p = 0.01). The percentage of enlargement of the TAMT was significantly higher in Group B than A (53 vs. 36%, respectively; p = 0.03).

CONCLUSION

The percentage of enlargement of the FAMT and TAMT was associated with patient age. These findings suggest the need to consider the possibility of tunnel enlargement when double-bundle ACLR is performed for patients aged >40 years. Age was a preoperative factor associated with tunnel enlargement.

LEVEL OF EVIDENCE

III.

Minimum Two-Year Follow-up of Anterior Cruciate Ligament Reconstruction in Patients with Generalized Joint Laxity

BACKGROUND

The purposes of this investigation were to compare outcomes of anterior cruciate ligament (ACL) reconstruction between patients with generalized joint laxity and those without it and to investigate the effect of generalized joint laxity on outcomes of ACL reconstruction from 2 to 8 years postoperatively.

METHODS

We retrospectively reviewed 163 patients who had undergone unilateral ACL reconstruction from January 2001 to December 2008. Patients were divided into 2 groups according to presence or absence of generalized joint laxity. The proportions of patients with meniscectomy, graft rupture, and contralateral ACL rupture were compared. Rupture rates were compared with Kaplan-Meier analysis. The Lachman test, pivot-shift test, and anterior translation measured with the KT-2000 arthrometer were evaluated. The Lysholm knee score and International Knee Documentation Committee (IKDC) subjective score were compared. The IKDC objective grade and radiographic grade were also evaluated. Follow-up assessments were performed at 2, 5, and 8 years postoperatively.

RESULTS

The proportions of meniscectomy, graft rupture, and contralateral ACL rupture in patients with generalized joint laxity were higher than in patients without generalized joint laxity during the whole evaluation period. However, differences in proportions and cumulative rupture rates did not reach significance (p > 0.05). Patients with generalized joint laxity had less stability and poorer functional outcomes at the 8-year follow-up compared with patients without generalized joint laxity. With regard to the Lachman test and anterior translation, poorer results were shown in patients with generalized joint laxity than in patients without generalized joint laxity during the whole evaluation period. The results of pivot-shift testing differed significantly at 5 years (p = 0.002) and 8 years (p = 0.007). Patients with generalized joint laxity also had worse Lysholm knee scores and IKDC subjective scores during the whole evaluation period; these differences may not be clinically important. Comparisons between serial outcomes measured at 2, 5, and 8-year follow-ups within each patient group showed that anterior translation (p = 0.002), Lysholm knee score (p = 0.014), and IKDC subjective score (p = 0.002) deteriorated over time, although the values at 8 years were similar to those at 5 years, in patients with generalized joint laxity.

CONCLUSIONS

Generalized joint laxity as an inherent physiologic characteristic of patients was related to a significant adverse effect on stability and functional outcomes of ACL reconstruction for patients followed for 2 to 8 years. Generalized joint laxity should be considered a risk factor for poor outcomes after ACL reconstruction.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

The remnant preservation technique reduces the amount of bone tunnel enlargement following anterior cruciate ligament reconstruction

PURPOSE

The aim of the present study was to investigate the correlation between postoperative tunnel enlargement after ACLR and remnant tissue preservation using the hamstring tendon.

METHODS

One hundred and ninety-two subjects (male, n = 101; female, n = 91; mean age 27.1) who had undergone double-bundle ACL reconstruction were included in the present study. The patients were divided into two groups: the remnant tissue preservation group (Group R) and the non-remnant tissue preservation group (Group N). Computed tomographic scans of the operated knee were obtained at 2 weeks and 6 months after surgery. The area of the tunnel aperture for the anteromedial femoral tunnel (FAMT), posterolateral femoral tunnel (FPLT), anteromedial tibial tunnel (TAMT), and posterolateral tibial tunnel (TPLT) was measured. The area at 2 weeks after ACLR was subtracted from the area at 6 months after ACLR and then divided by the area at 2 weeks after ACLR. The differences in the outcomes and characteristics of the two groups were evaluated.

RESULTS

Seventy-seven knees were classified into Group R, and 115 knees were classified into Group N. The age, gender, and body mass index did not differ to a statistically significant extent. The percentages of FAMT and TAMT enlargement in Group R were significantly smaller in comparison with Group N (P = 0.003 and P = 0.03, respectively). The percentage of FPLT and TPLT enlargement in the two groups did not differ to a statistically significant extent.

CONCLUSION

The remnant-preserving technique reduces the amount of bone tunnel enlargement. The present findings indicate the advantages of the remnant-preserving ACLR technique, and therefore the remnant-preserving technique should be recommended.

LEVEL OF EVIDENCE

II.

Increased bone tracer uptake in symptomatic patients with ACL graft insufficiency: a correlation of MRI and SPECT/CT findings

PURPOSE

Magnetic resonance imaging (MRI) and single-photon emission computerised tomography/computerised tomography (SPECT/CT) are used as diagnostic tools in symptomatic patients after reconstruction of the anterior cruciate ligament (ACL). The benefit of SPECT/CT in comparison with MRI is under debate. The purpose of this study was to investigate whether and how bone tracer uptake (BTU) intensity and distribution in SPECT/CT correlate with MRI findings in symptomatic patients after ACL reconstruction.

METHODS

Twenty-nine patients (male:female = 22:7, mean age ± SD 26 ± 10 years) with symptoms of pain and instability after ACL reconstruction were retrospectively investigated using prospectively acquired SPECT/CT and MRI. On MRI graft tear, graft signal intensity, bone marrow oedema, tunnel cyst formation, roof impingement, roof osteophytes, local arthrofibrosis, joint effusion and synovial thickness were analysed by two readers blinded to the BTU results. BTU was anatomically localised and volumetrically quantified. Spearman's rho test was used for correlation of BTU in SPECT/CT and MRI findings (p < 0.05).

RESULTS

SPECT/CT showed increased femoral and tibial BTU in patients with MRI-confirmed graft tear, signal hyperintensity of the intraarticular graft section, joint effusion, synovial thickening, roof osteophytes and bone marrow oedema. Cyst formation in the femoral tunnel results in significantly reduced BTU in femur and tibia. No correlation of increased BTU was found for graft impingement and graft arthrofibrosis.

CONCLUSIONS

Bone tracer uptake in SPECT/CT and defined MRI findings in symptomatic patients after ACL reconstruction were correlated. Both imaging modalities have a definite role in post-operative diagnostic and have established their value in those patients. This study provides a better understanding of the clinical value of SPECT/CT versus MRI in the clinical decision-making process. SPECT/CT provides a window into the in vivo loading of the joint as well as bone remodelling and graft incorporation process. In addition, ACL graft insufficiency can be detected by increased BTU.

LEVEL OF EVIDENCE

Retrospective cohort study, Level III.

Underappreciated Factors to Consider in Revision Anterior Cruciate Ligament Reconstruction: A Current Concepts Review

Primary anterior cruciate ligament (ACL) reconstructions (ACLRs) are being performed with increasing frequency. While many of these will have successful outcomes, failures will occur in a subset of patients who will require revision ACLRs. As such, the number of revision procedures will continue to rise as well. While many reviews have focused on factors that commonly contribute to failure of primary ACLR, including graft choice, patient factors, early return to sport, and technical errors, this review focused on several factors that have received less attention in the literature. These include posterior tibial slope, varus malalignment, injury to the anterolateral ligament, and meniscal injury or deficiency. This review also appraised several emerging techniques that may be useful in the context of revision ACL surgery. While outcomes of revision ACLR are generally inferior to those of primary procedures, identifying these potentially underappreciated contributing factors preoperatively will allow the surgeon to address them at the time of revision, ideally improving patient outcomes and preventing recurrent ACL failure.

Tunnel widening after single- versus double-bundle anterior cruciate ligament reconstruction: a randomized 8-year follow-up study

OBJECTIVE

The purpose of this study was to compare the single-bundle (SB) and double-bundle (DB) surgical techniques for anterior cruciate ligament (ACL) reconstruction with regard to tunnel widening, isokinetic muscle strength, and clinical outcomes over an 8-year follow-up period.

METHODS

This study included 31 patients with ACL injury who underwent ACL reconstruction via the SB (n = 16) or the DB (n = 15) technique. Isokinetic and concentric strength measurements of the quadriceps and hamstring muscles were conducted at postoperative 6 months and postoperative 8 years, and 3D-CT scans of the knee joints were performed on the 2nd, 3rd and 6th month, and the 8th year postoperatively. Clinical evaluations were performed at 8 years postoperatively with the International Knee Documentation Committee (IKDC), Tegner, and Lysholm knee scoring systems.

RESULTS

There was marked widening of the parts of the femoral tunnel close to the knee joint in both the SD and the DB groups. There was no difference between the two groups in terms of clinical results and isometric muscle strength at postoperative 8 years; however, there was a significant difference between the preoperative and 6 months postoperative clinical and strength results in both group (P < 0.05). There was no difference between the groups in IKDC score, Lysholm score, Tegner activity scale, and anterior drawer test at postoperative 8 years. On evaluation of the anteromedial bundles alone, the DB group had greater widening than the SB group.

CONCLUSION

In this study, we have found that the tunnels continue to enlarge after 6 months. However, that has no impact in patients comfort and that did not made any change in our daily routine. On the other hand, we found that the reconstruction of the double-band ligament technique is useless for non-professional athletes.

Bone tunnel enlargement following hamstring anterior cruciate ligament reconstruction: a comprehensive review

Nowadays, bone tunnel enlargement (BTE) after anterior cruciate ligament reconstruction is a well-known phenomenon. It has been identified, investigated and described by many authors during the last thirty years. Nevertheless, the etiology of bone tunnel enlargement still remains unclear. It is known that the causes are multifactorial and may include the surgical technique, the method of fixation, materials used, type of graft as well as biological factors. Due to the recent popularization of the use of hamstring grafts in anterior cruciate ligament reconstruction, the bone tunnel enlargement phenomenon is becoming increasingly common. In this review article, the authors focus on compiling current knowledge about the etiology, diagnosis, and the possibility of reducing the occurrence of this phenomenon by using the latest methods of supporting reconstruction surgery.

Generalised ligamentous laxity and revision ACL surgery: Is there a relation?

BACKGROUND

The aim of the present study was to investigate the relationship between generalised ligamentous laxity (GLL) and requirement for revision anterior cruciate ligament (ACL) reconstruction.

METHODS

The study cohort consisted of 139 patients undergoing primary ACL reconstruction, 44 patients undergoing revision ACL surgery and a control group of 70 patients without any knee ligament injury. A Beighton score of four or more was classified as generalised ligamentous laxity.

RESULTS

The primary and revision ACL surgery groups had an increased incidence of GLL compared to the control group (p<0.05). The revision ACL surgery group also had higher incidence of GLL as compared to primary ACL surgery group (p<0.05). There was a sub group within the revision cohort, who had failure of the original surgery without an identifiable cause (biological failure). The incidence of GLL in this group was significantly higher than the primary surgery group (p<0.05).

CONCLUSIONS

The findings of this study suggest that GLL may be associated with a higher risk of ACL injury and an increased risk of graft failure after primary ACL reconstruction. Based on the results of our study we feel that in the presence of GLL an autogenous graft may not be the best option for either primary or revision ACL reconstruction.

LEVEL OF EVIDENCE

3 (III).

Computed tomography value and tunnel enlargement of round and rounded rectangular femoral bone tunnel for anterior cruciate ligament reconstruction

INTRODUCTION

We developed a novel technique for anatomical single-bundle anterior cruciate ligament (ACL) reconstruction: creation of a rounded rectangular femoral bone tunnel. The purpose of this study was to compare the computed tomography (CT) value and tunnel enlargement ratio of the femoral bone tunnel with those of round tunnel ACL reconstruction.

MATERIALS AND METHODS

We included 39 knees that underwent round tunnel ACL reconstruction and 42 that underwent rounded rectangular ACL reconstruction. To evaluate the CT value, we compared the CT images approximately 1 week after surgery. Making a parallel slice toward the opening of bone tunnels to a depth of 3 mm, we evaluated the CT value of eight directions in the bone tunnel wall. To evaluate tunnel enlargement, we compared CT images approximately 1 week after surgery with images taken 3 months after surgery. Using a parallel slice toward the opening of the bone tunnel, we measured the bone tunnel area and calculated the tunnel enlargement ratio. The level of significance was P < 0.05, and the t test was used for statistical analyses.

RESULTS

The CT value was significantly increased for the rounded rectangular tunnel in comparison with the round tunnel in almost all directions (P < 0.05). The rounded rectangular tunnel area enlargement ratio was significantly lower (round, 110 ± 38 %; rounded rectangular, 73 ± 37 %; P = 0.001).

CONCLUSION

The rounded rectangular tunnel could have a compression effect on the cancellous bone and reduce enlargement of the bone tunnel.

Stem cell therapy: a promising biological strategy for tendon-bone healing after anterior cruciate ligament reconstruction

Tendon-bone healing after anterior cruciate ligament (ACL) reconstruction is a complex process, impacting significantly on patients' prognosis. Natural tendon-bone healing usually results in fibrous scar tissue, which is of inferior quality compared to native attachment. In addition, the early formed fibrous attachment after surgery is often not reliable to support functional rehabilitation, which may lead to graft failure or unsatisfied function of the knee joint. Thus, strategies to promote tendon-bone healing are crucial for prompt and satisfactory functional recovery. Recently, a variety of biological approaches, including active substances, gene transfer, tissue engineering and stem cells, have been proposed and applied to enhance tendon-bone healing. Among these, stem cell therapy has been shown to have promising prospects and draws increasing attention. From commonly investigated bone marrow-derived mesenchymal stem cells (bMSCs) to emerging ACL-derived CD34+ stem cells, multiple stem cell types have been proven to be effective in accelerating tendon-bone healing. This review describes the current understanding of tendon-bone healing and summarizes the current status of related stem cell therapy. Future limitations and perspectives are also discussed.

Tibial and Femoral Tunnel Changes After ACL Reconstruction: A Prospective 2-Year Longitudinal MRI Study

BACKGROUND

Tunnel widening after anterior cruciate ligament reconstruction (ACL-R) is a well-accepted and frequent phenomenon, yet little is known regarding its origin or natural history.

PURPOSE

To prospectively evaluate the cross-sectional area (CSA) changes in tibial and femoral bone tunnels after ACL-R with serial MRI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients underwent arthroscopic ACL-R with the same surgeon, surgical technique, and rehabilitation protocol. Each patient underwent preoperative dual-energy x-ray absorptiometry and clinical evaluation, as well as postoperative time zero MRI followed by subsequent MRI and clinical examination, including functional and subjective outcome tests, at 6, 12, 24, 52, and 104 weeks. Tibial and femoral tunnel CSA was measured on each MRI at tunnel aperture (ttA and ftA), midsection (ttM and ftM), and exit (ttE and ftE). Logistic regression modeling was used to examine the predictive value of demographic data and preoperative bone quality (as measured by dual-energy x-ray absorptiometry) on functional outcome scores, manual and instrumented laxity measurements, and changes in tunnel area over time.

RESULTS

Eighteen patients (including 12 men), mean age 35.5±8.7 years, underwent ACL-R. There was significant tunnel expansion at ttA and ftA sites 6 weeks postoperatively (P=.024 and .0045, respectively). Expansion continued for 24 weeks, with progressive tunnel narrowing thereafter. Average ttA CSA was significantly larger than ftA CSA at all times. The ttM significantly expanded after 6 weeks (P=.06); continued expansion to week 12 was followed by 21 months of reduction in tunnel diameter. The ftM and both ttE and ftE sites decreased in CSA over the 2 years. Median Lysholm and International Knee Documentation Committee scores significantly improved at final follow-up (P=.0083 and <.0001, respectively), and patients returned to preoperative activity levels. Pivot shift significantly decreased (P<.0001). Younger age (<30 years), male sex, and delayed ACL-R (>1 year from time of injury) predicted increased tunnel widening and accelerated expansion in CSA (P<.005).

CONCLUSION

Tunnel expansion after ACL-R occurs early and primarily at the tunnel apertures. Expansion may not affect clinical outcome. Younger age, male sex, and delay from injury to ACL-R may be potential risks for enlargement.

Adolescent differences in knee stability following computer-assisted anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) surgery is being increasingly performed in the adolescent population. Computer navigation offers a reliable way to quantitatively measure knee stability during ACL reconstruction. A retrospective review of all adolescent patients (<18 years old) who underwent computer-assisted primary single bundle ACL reconstruction by a single surgeon from 2007 to 2012 was performed. The average age was 15.8 years (SD 3.3). Female adolescents were found to have higher internal rotation than male adolescents both pre- (25.6° vs 21.7°, P=0.026) and post-reconstruction (20.1° vs 15.1°, P=0.005). Compared to adults, adolescents demonstrated significantly higher internal rotation both pre- (23.3° vs 21.5°, P=0.047) and post-reconstruction (17.1° vs 14.4°, P=0.003). They also had higher total rotation both pre- (40.9° vs 38.4°, P=0.02) and post-reconstruction when compared to adults (31.56° vs 28.67°, P=0.005). In adolescent patients, anterior translation was corrected more than rotation. Females had higher pre- and residual post-reconstruction internal rotation compared to males. When compared to adults, adolescents had increased internal rotation and total rotation both pre-and post-reconstruction.

In vitro investigation of a tissue-engineered cell-tendon complex mimicking the transitional architecture at the ligament-bone interface

Restoration of the transitional ligament-bone interface is critical for graft-bone integration. We postulated that an allogenic scaffold mimicking the fibrogenic, chondrogenic, and osteogenic transition gradients could physiologically promote ligament-bone incorporation. The aim of this study was to construct and characterize a composite tendon scaffold with a continuous and heterogeneous transition region mimicking a native ligament insertion site. Genetically modified heterogeneous cell populations were seeded within specific regions of decellularized rabbit Achilles tendons to fabricate a stratified scaffold containing three biofunctional regions supporting fibrogenesis, chondrogenesis, and osteogenesis. The observed morphology, architecture, cytocompatibility, and biomechanics of the scaffolds demonstrated their improved bio-physico-chemical properties. The formation of the transitional regions was augmented via enhanced delivery of two transcription factors, sex determining region Y-box 9 and runt-related transcription factor 2, which also triggered early up-regulated expression of cartilage- and bone-relevant markers, according to quantitative PCR and immunoblot analyses. Gradient tissue-specific matrix formation was also confirmed within the predesignated regions via histological staining and immunofluorescence assays. These results suggest that a transitional interface could be replicated on an engineered tendon through stratified tissue integration. The scaffold offers the advantages of a multitissue transition involving controlled cellular interactions and matrix heterogeneity, which can be applied for the regeneration of the ligament-bone interface.

Gender differences following computer-navigated single- and double-bundle anterior cruciate ligament reconstruction

PURPOSE

Female patients not only demonstrate an increased risk for injury, but also a poorer response following anterior cruciate ligament (ACL) rupture. However, no study has investigated gender-related differences between computer-navigated single-bundle (SB) and double-bundle (DB) ACL reconstruction. The aim of this study was to evaluate the effects of gender on the outcome of computer-navigated SB and DB ACL reconstruction and to present reference values.

METHODS

A retrospective review of 55 consecutive patients who underwent SB (15 males, 12 females) and DB (18 males, 10 females) ACL reconstruction with autogenous hamstring tendon grafts and showed a minimum follow-up of 24 months was conducted. Intraoperatively, the anteroposterior and rotational laxity were measured and the follow-up examination included pivot-shift testing, KT-1000 arthrometer testing, International Knee Documentation Committee (IKDC) form, the Lysholm score and Tegner score.

RESULTS

Pre-operatively, female patients showed a significant higher internal rotation in (p < 0.001) both the SB and DB group. Regarding the post-operative reduction in internal rotation, females in the SB group revealed a greater reduction compared to males (p < 0.001), whereas females in the DB group revealed a significantly greater post-operative reduction in anterior-posterior translation (p = 0.04). Female patients following DB ACL reconstruction presented a significant worse IKDC score, Lysholm score and Tegner score compared to male patients. All score values of the female DB group were worse than in the female SB group. In contrast, male patients showed better results of all examined clinical scores following DB procedure compared to SB technique.

CONCLUSION

Female patients who underwent computer-navigated DB ACL reconstruction exhibited significantly worse outcome scores than males who underwent DB ACL reconstruction. The gender-based relationship between joint function and outcome after ACL reconstruction remains unclear and requires further investigation.

LEVEL OF EVIDENCE

Retrospective case-control series, Level III.

Pediatric anterior cruciate ligament reconstruction using low-profile hybrid tibial fixation

The authors introduce the application of a low-profile hybrid fixation technique for pediatric anterior cruciate ligament graft fixation into the tibia using both an interference screw and knotless anchors. This technique allows for physeal avoidance while maintaining fixation strength.

Anatomic and nonanatomic double-bundle anterior cruciate ligament reconstruction: an in vivo kinematic analysis

BACKGROUND

There have been no direct in vivo biomechanical comparisons performed between an anatomic double-bundle (ADB) and a nonanatomic double-bundle (NADB) anterior cruciate ligament (ACL) reconstruction.

HYPOTHESIS

There are differences in kinematic outcomes between ADB and NADB ACL reconstruction techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-six consecutive patients (mean age, 30 years; range, 18-32 years; 23 men, 3 women; 17 right knees, 9 left knees) with an isolated ACL injury were included in the study. The first 13 consecutive patients underwent NADB reconstruction (combination of a single-bundle and an over-the-top reconstruction), and the following 13 consecutive patients were treated with an ADB approach (using 2 tibial tunnels and 2 femoral tunnels placed in the center of the native femoral and tibial insertion sites). Grafts were pretensioned at 80 N and secured with cortical fixation systems under manual maximum force tension. Standard clinical laxity and pivot-shift tests were quantified at time zero before and after ACL reconstruction by means of a surgical navigation system dedicated to kinematic assessment; displacement of the medial and lateral compartments during the tests was also analyzed.

RESULTS

The ADB-reconstructed knees showed a larger preoperative-to-postoperative difference in anterior-posterior tibial plateau displacement of the medial and lateral compartments when compared with the NADB-reconstructed knees during the internal-external rotation test at 30° of flexion (P < .050). No other significant differences in laxity or pivot-shift values were noted. The mean surgical time for ADB reconstruction was significantly higher than that for NABD reconstruction (62 ± 13 and 43 ± 10 minutes, respectively; P < .0001).

CONCLUSION

Results showed a greater anterior-posterior translation of both compartments during the rotational passive laxity test in the ADB reconstruction group or overconstraint caused by the NADB technique. The 2 analyzed double-bundle ACL reconstructions did not show any significant quantitative difference in isolated anterior-posterior laxity and pivot-shift phenomenon at time zero.

CLINICAL RELEVANCE

Nonanatomic double-bundle ACL reconstruction can control anterior-posterior laxity and the pivot-shift phenomenon as well as ABD ACL reconstruction.

Biocompatibility and enhanced osteogenic differentiation of human mesenchymal stem cells in response to surface engineered poly(D,L-lactic-co-glycolic acid) microparticles

Tissue engineering strategies can be applied to enhancing osseous integration of soft tissue grafts during ligament reconstruction. Ligament rupture results in a hemarthrosis, an acute intra-articular bleed rich in osteogenic human mesenchymal stem cells (hMSCs). With the aim of identifying an appropriate biomaterial with which to combine hemarthrosis fluid-derived hMSCs (HF-hMSCs) for therapeutic application, this work has investigated the biocompatibility of microparticles manufactured from two forms of poly(D,L-lactic-co-glycolic acid) (PLGA), one synthesized with equal monomeric ratios of lactic acid to glycolic acid (PLGA 50:50) and the other with a higher proportion of lactic acid (PLGA 85:15) which confers a longer biodegradation time. The surfaces of both types of microparticles were functionalized by plasma polymerization with allylamine to increase hydrophilicity and promote cell attachment. HF-hMSCs attached to and spread along the surface of both forms of PLGA microparticle. The osteogenic response of HF-hMSCs was enhanced when cultured with PLGA compared with control cultures differentiated on tissue culture plastic and this was independent of the type of polymer used. We have demonstrated that surface engineered PLGA microparticles are an appropriate biomaterial for combining with HF-hMSCs and the selection of PLGA is relevant only when considering the biodegradation time for each biomedical application.

Biomechanical evaluation of augmented and nonaugmented primary repair of the anterior cruciate ligament: an in vivo animal study

PURPOSE

The purpose of this study was to evaluate in a sheep model the biomechanical performance of augmented and nonaugmented primary repair of the anterior cruciate ligament (ACL) following transection at the femoral end during a 12-month postoperative observation.

METHODS

Forty sheep were randomly assigned to nonaugmented or augmented primary ACL repair using a polyethylene terephthalate (PET) band. At two, six, 16, 26 and 52 weeks postoperatively four sheep in each group were sacrificed and biomechanical testing performed.

RESULTS

Compared with nonaugmented primary ACL repair, the PET-augmented repair demonstrated superior biomechanical results from 16 weeks postoperatively onwards in terms of anterioposterior (AP) laxity, tensile strength and ligament stiffness. The augmentation device works as a stress shield during the ligament healing process. The nonaugmented ACL repair also resulted in ligament healing, but the biomechanical properties were at a significantly lower level.

CONCLUSION

These results support the previously reported histological findings following augmented primary ACL repair. This animal study on the healing capacity of the ACL may provide some important contributions to how primary healing in certain types of ruptures can be achieved.

CLINICAL RELEVANCE

I.

Radiographic findings in revision anterior cruciate ligament reconstructions from the Mars cohort

The Multicenter ACL (anterior cruciate ligament) Revision Study (MARS) group was developed to investigate revision ACL reconstruction outcomes. An important part of this is obtaining and reviewing radiographic studies. The goal for this radiographic analysis is to establish radiographic findings for a large revision ACL cohort to allow comparison with future studies. The study was designed as a cohort study. Various established radiographic parameters were measured by three readers. These included sagittal and coronal femoral and tibial tunnel position, joint space narrowing, and leg alignment. Inter- and intraobserver comparisons were performed. Femoral sagittal position demonstrated 42% were more than 40% anterior to the posterior cortex. On the sagittal tibia tunnel position, 49% demonstrated some impingement on full-extension lateral radiographs. Limb alignment averaged 43% medial to the medial edge of the tibial plateau. On the Rosenberg view (45-degree flexion view), the minimum joint space in the medial compartment averaged 106% of the opposite knee, but it ranged down to a minimum of 4.6%. Lateral compartment narrowing at its minimum on the Rosenberg view averaged 91.2% of the opposite knee, but it ranged down to a minimum of 0.0%. On the coronal view, verticality as measured by the angle from the center of the tibial tunnel aperture to the center of the femoral tunnel aperture measured 15.8 degree ± 6.9% from vertical. This study represents the radiographic findings in the largest revision ACL reconstruction series ever assembled. Findings were generally consistent with those previously demonstrated in the literature.

Interference screws should be shorter than the hamstring tendon graft in the bone tunnel for best fixation

PURPOSE

Interference screw fixation of hamstring tendon grafts in bone has to overcome the challenges that tendons have a slippery surface and viscoelastically adapt under pressure. As the typical failure mode of the graft is to slip past the interference screw, it was hypothesized that the position and configuration of the graft end may be of influence on the fixation strength.

METHODS

Different configurations of the graft ending and its effect to primary fixation with interference screws after viscoelastic adaptation were tested in six groups: I: graft and the screw inserted at the same depth, II/III: the graft overlaps the tip of the screw (interference screw of 28 and 19 mm in length, respectively), IV: strengthening of the graft ending with additional suture knots, V: Endopearl, respectively, and VI: effect of partial retraction of the screw after excessive insertion. In vitro tests were performed with fresh calf tendon grafts and interference screws in bone tunnels (fresh porcine distal femur) all of 8 mm in diameter.

RESULTS

The relative position of the graft ending to the tip of the interference screw thereby was recognized as a significant factor on pullout forces. Further strengthening at the graft endings with additional suture knots or an Endopearl device could improve primary hold as well.

CONCLUSIONS

Better fixation strength is achieved if the tip of interference screw does not extend past the end of a tendon graft. Enforcement of the tendon end with sutures or an implant can further improve fixation.

Effects of graft pretensioning in anterior cruciate ligament reconstruction

PURPOSE

Graft pretensioning is used in anterior cruciate ligament (ACL) reconstruction to prevent secondary slackening. Its effects on collagen fibrillar ultrastructure are not known. In this study, we hypothesized that graft pretensioning in ACL reconstruction creates ultrastructural changes detectable in scanning electron microscopy (SEM).

METHODS

A prospective comparative study was carried out on 38 ACL reconstructions using a 4-strand semitendinosus graft. Samples were harvested intra-operatively before and after pretensioning for 30 s, 2 or 5 min. The images produced in SEM were analyzed using an original semi-quantitative «CIP» score taking into account collagen cohesion, integrity, and parallelism. Intra- and inter-tester reliability for the CIP score were tested.

RESULTS

The CIP scores decreased by 3.5 (1.6) points after pretensioning (P < 0.05). Significant differences were found in the 5, 2 min and 30 s subgroups for the global CIP score. Relative decrease (Delta CIP) was significantly higher in the 2 and 5 min subgroups after pretensioning in comparison with the 30 s subgroups. Intra- and inter-tester reliability for the CIP score were 0.85 and 0.92 (P < 0.05).

CONCLUSION

Pretensioning ACL grafts resulted in alteration of the collagen fibrillar ultrastructure, detectable using SEM. These results confirm the existence of collagen ultrastructural changes after pretensioning that may be related to its duration.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

The accuracy of bone tunnel position using fluoroscopic-based navigation system in anterior cruciate ligament reconstruction

PURPOSE

The first purpose of this study was to examine whether fluoroscopic-based navigation system contributes to the accuracy and reproducibility of the bone tunnel placements in single-bundle anterior cruciate ligament (ACL) reconstruction. The second purpose was to investigate the application of the navigation system for double-bundle ACL reconstruction.

METHODS

A hospital-based case-control study was conducted, including a consecutive series of 55 patients. In 37 patients who received single-bundle ACL reconstruction, surgeries were performed with this system for 19 knees (group 1) and without this system for 18 knees (group 2). The positioning of the femoral and tibial tunnels was evaluated by plain sagittal radiographs. In 18 patients who received double-bundle ACL reconstruction using the navigation system (group 3), the bone tunnel positions were assessed by three-dimensional computed tomography (3D-CT). Clinical assessment of all patients was followed with the use of Lysholm Knees Score and IKDC.

RESULTS

Taking 0% as the anterior and 100% as the posterior extent, the femoral tunnels were 74.9 ± 3.0% in group 1 and 71.5 ± 5.8% in group 2 along Blumensaat's line, and the tibial tunnels were 42.3 ± 1.4% in group 1 and 42.5 ± 4.6% in group 2 along the tibia plateau. The bone tunnel positions in group 1 were located significantly closer to the position planned preoperatively and varied less in both femur and tibial side, compared with those without navigation (group 2). (Femur: P < 0.05, Tibia: P < 0.001) 3D-CT evaluation of double-bundle ACL reconstruction (group 3) also demonstrated that the bone tunnel positions of both anteromedial (AM) and posterolateral (PL) were placed as we expected.

CONCLUSION

The fluoroscopic-based navigation system contributed to the more reproducible placement of the bone tunnel during single-bundle ACL reconstruction compared with conventional technique. Additionally, this device was also useful for double-bundle ACL reconstruction.

LEVEL OF EVIDENCE

Case-control study, Therapeutic study, Level III.

MR imaging of the postoperative knee

Advances in orthopedic and arthroscopic surgical procedures of the knee such as, knee replacement, ligamentous reconstruction as well as articular cartilage and meniscus repair techniques have resulted in a significant increase in the number of patients undergoing knee arthroscopy or open surgery. As a consequence postoperative MR imaging examinations increase. Comprehensive knowledge of the normal postoperative MR imaging appearances and abnormal findings in the knee associated with failure or complications of common orthopedic and arthroscopic surgical procedures currently undertaken is crucial. This article reviews the various normal and pathological postoperative MR imaging findings following anterior and posterior cruciate ligament, medial collateral ligament and posterolateral corner reconstruction, meniscus and articular cartilage surgery as well as total knee arthroplasty with emphasis on those surgical procedures which general radiologists will likely be faced in their daily clinical routine.

Most british surgeons would consider using a tissue-engineered anterior cruciate ligament: a questionnaire study

Donor site morbidity, poor graft site integration, and incorrect mechanical performance are all common problems associated with autografts for anterior cruciate ligament (ACL) reconstructions. A tissue-engineered (TE) ligament has the potential to overcome these problems. We produced an online questionnaire relating to tissue engineering of the ACL to obtain input from practising clinicians who currently manage these injuries. 300 British orthopaedic surgeons specialising in knee surgery and soft tissue injury were invited to participate. 86% of surgeons would consider using a TE ACL if it were an option, provided that it showed biological and mechanical success, if it significantly improved the patient satisfaction (63%) or shortened surgical time (62%). 76% felt that using a TE ACL would be more appropriate than a patellar tendon, hamstring, or quadriceps autograft. Overall, most surgeons would be prepared to use a TE ACL if it were an improvement over the current techniques.

EVIDENCE OF TIME-DEPENDENT TENSILE RESPONSE IN INTACT HUMAN TENDON

The present study was performed to establish whether intact human tendons exhibit time-dependent tensile properties, as they do in the in vitro state. Measurements were taken in seven men and involved ultrasound-based recording of the gastrocnemius tendon elongation during three sets of five repeated isometric plantarflexion contractions elicited by tetanic electrical stimulation. The plantarflexion moment corresponding to the tendon elongation in the fifth contraction presented a pattern dependent on the voltage applied: it was approximately constant when applying 50% of maximal voltage, but it decreased curvilinearly as a function of contraction number when applying 70 and 100% of maximal voltage, reaching in the fifth contraction 84% of the plantarflexion moment corresponding to the elongation examined in the first contraction. These results suggest that, once a threshold tendon elongation is undergone, in vivo tendons may exhibit substantial viscoelasticity. The present findings have implications for muscle and joint function and need to be accounted for by musculoskeletal models.

Pre-operative versus post-operative gait variability in patients with acute anterior cruciate ligament deficiency

Change in gait variability at least 6 months after surgical reconstruction of the anterior cruciate ligament (ACL) was assessed in 20 male patients with acute ACL deficiency and compared with pre-operative data and that from 20 healthy male controls. Gait was measured using a triaxial accelerometer and data were analysed by the Gait Evaluation Differential Entropy Method (GEDEM) to determine gait variability. Pain was assessed with a visual analogue scale and functional ability with the Oswestry Disability Index and the International Knee Documentation Committee score. Mean gait variability was significantly lower after than before surgery, with values for the anterior-posterior axis being in the normal range of controls after 6 months, whereas in the mediolateral axis mean gait variability remained significantly higher, indicating that some rotational instability remained in the time-frame of the study. Pain and functional ability scores improved after surgery compared with before surgery. The combination of accelerometry and GEDEM may be a useful orthopaedic tool for the post-operative evaluation of patients who have undergone ACL reconstruction.

Anatomic double-bundle anterior crucial ligament reconstruction with G-ST

The anterior cruciate ligament (ACL) consists of two primal functional bundles, anteromedial bundle and posterolateral bundles. Those two bundles play different functional roles and contribute differently to knee stability throughout the range of motion. Recent advancement in studies of anatomy and biomechanics of ACL has led surgeons to perform double-bundle ACL reconstruction to obtain better stability and kinematics. Consequently, variable surgical techniques of double-bundle ACL reconstruction have been reported to replicate native ACL. In addition, various surgical key points and problems in double-bundle ACL reconstruction techniques have also been reported. There has been a trend to more anatomically replicate native ACL bundles, not simply creating two bundles. We summarize the basic knowledge and current concepts of anatomic double-bundle ACL reconstruction using hamstrings tendons.

The fixation strength of a novel ACL soft-tissue graft fixation device compared with conventional interference screws: a biomechanical study in vitro

Anterior cruciate ligament reconstruction using autologous hamstring tendons is an established surgical procedure but some grafts fail due to poor fixation. This study compared the fixation of a new ACL graft fixation device (the EZ KneeSpan) to conventional soft-tissue threaded titanium interference screws (IS). The EZ device was designed to provide secure fixation while avoiding soft-tissue graft damage associated with use of an IS. Eight paired fresh-frozen cadaveric human knees and bovine digital extensor tendons were used. Two tunnels were placed in each tibia and femur, and grafts were fixed using the EZ device and the IS in each bone. Cyclic tensile loading and pull-out testing measured graft slippage (mm) and ultimate strength (N) of the fixation. The results were compared using the non-parametric Wilcoxon signed-rank test. Graft slippage after cyclic loading was significantly lower in the EZ group at 2.4 ± 0.1 mm versus 9.5 ± 6.2 mm for the IS group in the femur and 3.3 ± 1.4 mm versus 17.7 ± 13.6 mm in the tibia. The mean ultimate load for the femoral EZ group was significantly higher than the IS group (769 ± 223 N versus 468 ± 60 N), but they did not differ significantly in the tibia (518 ± 48 N versus 546 ± 139 N). Our results indicate that with the EZ device the initial fixation of cyclically loaded hamstring grafts could be superior to that with an IS. The EZ KneeSpan device also had similar tibial and higher femoral ultimate fixation strength than an IS.

Detached femoral bone plug following anterior cruciate ligament repair

We report the case of a 16-year-old woman who experienced failure of her bone-patellar tendon-bone (BPTB) reconstruction of her left anterior cruciate ligament (ACL) due to detachment of the femoral bone plug from the endobutton. We have only found one prior report of this unusual complication. This case is also notable in that evidence of this complication is visible radiographically. Most postoperative complications of ACL reconstruction can be visualized only with the assistance of magnetic resonance imaging (MRI).

Anterior cruciate ligament repair with LARS (ligament advanced reinforcement system): a systematic review

BACKGROUND

Injury to the anterior cruciate ligament (ACL) of the knee is common. Following complete rupture of the ACL, insufficient re-vascularization of the ligament prevents it from healing completely, creating a need for reconstruction. A variety of grafts are available for use in ACL reconstruction surgery, including synthetic grafts. Over the last two decades new types of synthetic ligaments have been developed. One of these synthetic ligaments, the Ligament Advanced Reinforcement System (LARS), has recently gained popularity.The aim of this systematic review was to assess the current best available evidence for the effectiveness of the LARS as a surgical option for symptomatic, anterior cruciate ligament rupture in terms of graft stability, rehabilitation time and return to pre-injury function.

METHOD

This systematic review included studies using subjects with symptomatic, ACL ruptures undergoing LARS reconstruction. A range of electronic databases were searched in May 2010. The methodological quality of studies was appraised with a modified version of the Law critical appraisal tool. Data relating to study characteristics, surgical times, complication rates, outcomes related to knee stability, quality of life, function, and return to sport as well as details of rehabilitation programs and timeframes were collected.

RESULTS

This review identified four studies of various designs, of a moderate methodological quality. Only one case of knee synovitis was reported. Patient satisfaction with LARS was high. Graft stability outcomes were found to be inconsistent both at post operative and at follow up periods. The time frames of rehabilitation periods were poorly reported and at times omitted. Return to pre-injury function and activity was often discussed but not reported in results.

CONCLUSIONS

There is an emerging body of evidence for LARS with comparable complication rates to traditional surgical techniques, and high patient satisfaction scores. However, this systematic review has highlighted several important gaps in the existing literature that require future prospective investigation. The findings of this review were equivocal with regards to other measures such as graft stability and long term functional outcomes. While the importance of rehabilitation following LARS is well recognised, there is limited evidence to guide rehabilitation protocols.