Delay of 2 or 6 weeks adversely affects the functional outcome of augmented primary repair of the porcine anterior cruciate ligament

Rate of Revision Surgery and Associated Risk Factors After Primary Arthroscopic ACL Repair With Additional Suture Augmentation

Background

Recent studies have suggested promising patient-reported outcomes after primary anterior cruciate ligament (ACL) repair with additional suture augmentation (SA).

Purpose

To evaluate the risk for revision surgery and identify patient- and injury-related risk factors after ACL repair with SA in a large patient cohort subject to strict patient selection.

Study Design

Case-control study; Level of evidence, 3.

Methods

Included were 86 patients (61 female; 93% follow-up rate) who underwent arthroscopic ACL repair with SA between January 2017 and March 2019 by a single surgeon and had a minimum follow-up of 24 months. Patients were selected for surgery with regard to time to surgery (preferably on the day of injury), tear pattern (limited to Sherman types 1 and 2), and tissue quality (intact synovial coverage). Postoperatively, the patients who needed revision surgery were identified and compared with patients who did not undergo revision surgery, using the Mann-Whitney U test for nonparametric analysis and the Student t test for parametric analysis. A Kaplan-Meier analysis was performed to investigate the survival rate of the ACL repair.

Results

A total of 9 patients (10%; median age, 48 years; interquartile range [IQR], 27-50 years) underwent revision surgery at 12 months postoperatively (IQR, 8-25 months). The median follow-up of patients without revision surgery was 35 months (IQR, 33-44 months). The revision-free survival rate was 97% (95% CI, 93%-100%) after 1 year, 93% (95% CI, 88%-98%) after 2 years, and 90% (95% CI, 83%-97%) after 4 years. Patient-related factors-such as sex (P = .98), age at surgery (P = .459), body mass index (P = .352), and preinjury level of sports (P = .53)-had no significant impact on the survival rate of the ACL repair. Injury-related factors-such as concomitant injuries of the medial (P = .860) and lateral menisci (P = .414) and the medial (P = .801) and lateral collateral ligaments (P = .534) or same-day surgery compared with a delay of surgery of up to 18 days (P = .277)-had no significant impact on the survival rate of the ACL repair.

Conclusion

The revision rate of primary ACL repair with SA at a 2-year follow-up was 10%. Patient- and injury-related factors were not associated with the survival rate of the ACL repair.

Proprioception After Primary Repair of the Anterior Cruciate Ligament

BACKGROUND

Primary repair of the anterior cruciate ligament (ACL) has some potential advantages over the reconstruction technique, which include but are not limited to better knee sensation due to preservation of the natural ACL tissue in patients compared with tendon graft. Proprioception is impaired after ACL injuries and the sense of the joint position is lost.

PURPOSE/HYPOTHESIS

The purpose of this study was to compare arthroscopic ACL primary repair and ACL reconstruction techniques clinically and functionally and analyze the differences in proprioception. It was hypothesized that primary repair would restore knee joint proprioception more successfully because the original tissue of the ACL is preserved.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 63 patients (34 underwent reconstruction and 29 underwent primary repair between 2017 and 2020) and 33 healthy controls, as well as the healthy knees of the operated groups, were evaluated between 24 and 48 months (mean, 29 months) postoperatively. Patients with proximal femoral avulsion tears and stump quality suitable for repair underwent primary repair, and those with tears outside these criteria underwent reconstruction using hamstring tendon autograft. Proprioception was evaluated using the active joint position sensation method during weightbearing, with a digital inclinometer used to measure differences between the target and achieved flexion angles of 15°, 30°, and 60°.

RESULTS

At 15° of knee flexion, the deviation angles for the healthy knee of the reconstruction and primary repair groups were significantly smaller than those of the control group (P < .001), but there was no statistically significant difference between the groups in terms of deviation angle at 30° and 60° of flexion. The deviation angle of the operated knees was statistically significantly larger in the reconstruction group than in the primary repair group at all angles. The deviation angles at 15°, 30°, and 60° were 2.83°, 2.66°, and 2.66° in the reconstruction group and 1.00°, 1.00°, and 1.33° in the primary repair group, respectively (P < .001). There was no statistically significant difference between the reconstruction and primary repair groups in terms of clinical scores.

CONCLUSION

Primary ACL repair can preserve proprioception in a well-selected patient group. In short-term follow-up, primary repair of the ACL in patients with proximal femoral avulsion tears and stump quality suitable for repair appears to be proprioceptively protective. Future studies are needed to clarify the long-term consequences of primary repair on proprioception in a larger population.

Primary anterior cruciate ligament repair: Current concepts

The renewed interest in ACL repair over the last two decades stems from advances in modern arthroscopic techniques and clinical studies that have provided evidence that the ACL can reliably heal, and patients can return to sport at a comparable rate to ACL reconstruction patients. The ability to maintain and utilize native ACL tissue, with proprioceptive capabilities, and the smaller drill tunnels needed to repair an ACL leads to an overall less invasive procedure and improved early rehabilitation. Additionally, repair avoids a variety of comorbidities associated with autograft harvest. This current concept review details modern techniques of ACL repair and their current studies, a review on the use of biologic enhancement in ACL repair, and other considerations to appropriately integrate ACL repair into the sports medicine orthopaedic surgeon's practice.

Red blood cell exposure increases chondrocyte susceptibility to oxidative stress following hemarthrosis

OBJECTIVE

The detrimental effects of blood exposure on articular tissues are well characterized, but the individual contributions of specific whole blood components are yet to be fully elucidated. Better understanding of mechanisms that drive cell and tissue damage in hemophilic arthropathy will inform novel therapeutic strategies. The studies here aimed to identify the specific contributions of intact and lysed red blood cells (RBCs) on cartilage and the therapeutic potential of Ferrostatin-1 in the context of lipid changes, oxidative stress, and ferroptosis.

METHODS

Changes to biochemical and mechanical properties following intact RBC treatment were assessed in human chondrocyte-based tissue-engineered cartilage constructs and validated against human cartilage explants. Chondrocyte monolayers were assayed for changes to intracellular lipid profiles and the presence of oxidative and ferroptotic mechanisms.

RESULTS

Markers of tissue breakdown were observed in cartilage constructs without parallel losses in DNA (control: 786.3 (102.2) ng/mg; RBCINT: 751 (126.4) ng/mg; P = 0.6279), implicating nonlethal chondrocyte responses to intact RBCs. Dose-dependent loss of viability in response to intact and lysed RBCs was observed in chondrocyte monolayers, with greater toxicity observed with lysates. Intact RBCs induced changes to chondrocyte lipid profiles, upregulating highly oxidizable fatty acids (e.g., FA 18:2) and matrix disrupting ceramides. RBC lysates induced cell death via oxidative mechanisms that resemble ferroptosis.

CONCLUSIONS

Intact RBCs induce intracellular phenotypic changes to chondrocytes that increase vulnerability to tissue damage while lysed RBCs have a more direct influence on chondrocyte death by mechanisms that are representative of ferroptosis.

Repair of a meniscus tear within 3 weeks after trauma significantly reduces the likelihood of a recurrent tear compared with later repairs

PURPOSE

To evaluate the potential benefit of meniscus tear repair within 3 weeks after rupture compared with more than 3 weeks after rupture.

METHODS

Ninety-one patients (95 menisci) underwent repair within 3 weeks after meniscus rupture [Group 1] and 15 patients (17 menisci) [Group 2] underwent repair more than 3 weeks after rupture. The posterior part of the ruptured meniscus was repaired with Contour Arrows^®, using a Crossbow as the insertion instrument, whereas the middle third was repaired by inserting PDS 2.0 stitches using a Meniscus Mender^® outside-in device. The patients were followed-up for a mean(SD) 8.9 years (range: 1-12 years).

RESULTS

Of the 91 patients (95 menisci) in Group 1, 88 (96.7%) healed without complications. One meniscus in one patient did not heal after 11 months, requiring resection. Two other menisci in two other patients showed partially healed tears. This part was removed while preserving most of the meniscus (failure rate: 3/91 patients: 3.3%). The other 88 patients recovered without complaints and participated in sports without restraint. Four menisci in four patients experienced a second sports-related incident, resulting in a renewed tear between 12 months and 3 years. These tears were repaired successfully again. Of the 15 patients in Group 2, 12 (80.0%) healed without complications. The ruptured part of the remaining menisci in the other three patients, (20%) was removed, with all patients remaining symptom-free until the end of follow-up. Rates of treatment failure differed significantly in these two groups (3.3% vs 20.0%, p = 0.04).

CONCLUSIONS

The overall failure rate was significantly lower in patients who underwent meniscus repair within 3 weeks than in those who underwent repair at 3 weeks (or more) after the trauma. Thus, early repair of meniscus tears is beneficial, and can prevent failure of meniscus repair surgery.

LEVEL OF EVIDENCE

III.

Arthroscopic biological internal bracing with remnant repair for subacute ACL femoral avulsions

Arthroscopic anterior cruciate ligament (ACL) reconstruction predictably restores sagittal plane knee stability, however its inability to replicate a complex fan-shaped ligament of multiple fascicles, along with deficient restoration of normal rotational knee kinematics, results in failure to reverse a high risk for premature post-traumatic osteoarthritis. Although arthroscopic repair for acute ACL femoral avulsions is proposed to counter these deficiencies, the risk of early failure following non-healing, along with lack of convincing evidence of efficacy has impeded its universal acceptance. Moreover, since ACL repair needs to be performed in the acute phase following injury, it has an increased risk of developing arthrofibrosis, besides precluding any possibility to achieve natural healing of an ACL avulsion with non-operative treatment. The technique of biological internal bracing with remnant repair incorporates the advantages of both reconstruction and repair, and is indicated for patients with persistent ACL deficiency in the subacute phase (6-12 weeks) following an ACL femoral avulsion. This operation essentially involves two steps. The step of biological internal bracing is similar to a conventional ACL reconstruction using a small diameter hamstring graft that is targeted to the centre of the anteromedial ACL bundle on the femur, whereas the tibial socket is located posteriorly within the ACL tibial footprint so as to preserve the anterior fan-shaped morphology of the ACL tibial insertion. The second step involves repairing the remnant ACL tibial stump using one of three techniques. Although technically more complex than an ACL reconstruction, this novel technique provides native anatomy restoration with potential biomechanical and functional advantages, and should be considered for unhealed subacute ACL avulsion injuries.

Promising functional outcomes following anterior cruciate ligament repair with suture augmentation

PURPOSE

There has been a renewed interest in the repair of the torn anterior cruciate ligament (ACL). Purpose of this study was to evaluate the functional outcome of arthroscopic ACL repair with additional suture augmentation (SA), hypothesizing that isolated ACL ruptures would yield superior patient-reported outcome measures (PROMs) compared to those with concomitant meniscal and/or ligamentous injuries.

METHODS

This is a retrospective analysis of 93 consecutive patients (67 female, median age 42 years) who underwent arthroscopic ACL repair with SA between January 2017 and March 2019 for an acute traumatic ACL tear confirmed by magnetic resonance imaging (MRI). Patients with pre- or intraoperative mid-substance or distal ACL tears and/or poor tissue quality of the ACL remnant were not considered for ACL repair but were scheduled for an ACL reconstruction with a tendon autograft. In patients who underwent ACL repair with SA, the SA construct was proximally stabilized with a flip-button and distally with a suture anchor. Surgery was preferably performed on the day of injury and all surgeries were performed by the same surgeon. Postoperative rehabilitation included partial weight-bearing (20 kg) for 6 weeks and immobilization in a brace limited at 90-degrees of knee flexion for 4 weeks. Patient-reported outcome measures (PROMs) were determined using International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Lysholm Score (LS), Tegner Activity Score (TS) and Forgotten Joint Score (FJS). Knee-laxity was assessed using the KT-1000 arthrometer (Med Metrics Corp. Inc., San Diego, USA).

RESULTS

Nine patients underwent revision surgery for a traumatic re-tear (four patients) and chronic instability (five patients) and were excluded from further functional analysis. Functional results of 77 patients (54 female) with a median age of 44 years (IQR 33-51) on the day of surgery were available for follow-up after a median time of 35 months (IQR 33-44). Concomitant injuries were observed in 66 Patients (86%), meniscal injuries in 43 patients (55%) and ligamentous injuries in 50 patients (65%). Median interval from injury to surgery was 1 day (IQR 0-1) with 81% (62/77) of patients being treated within 24 h of injury. The median IKDC was 92 (IQR 86-99), the median LS was 95 (IQR 86-100), the median pre-traumatic TS was 7 (IQR 6-7), the median post-traumatic TS was 6 (IQR 5-7) with a non-significant median difference (TS_Diff) of 0 (IQR 0-1). The median FJS was 95 (IQR 78-98). KT-1000 measurements were available in 34 of 77 patients with a median postoperative laxity compared to the uninjured side of 1 mm (IQR 0-2). Interval from injury to surgery, patients' age, body mass index (BMI), knee laxity and concomitant ligamentous or meniscal injuries had no statistically significant impact on postoperative PROMs (n.s.).

CONCLUSION

Following arthroscopic ACL repair with SA good-to-excellent functional results were observed. However, a failure rate of 10% cannot be neglected and warrants further attention. Concomitant injuries to the meniscus and/or collateral ligaments do not seem to be associated with inferior PROMs.

LEVEL OF EVIDENCE

Level IV.

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

Background:

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

Purpose:

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

Study Design:

Clinical trial.

Methods:

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

Results:

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

Conclusion:

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

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

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

Distal remnant length can be measured reliably and predicts primary repair of proximal anterior cruciate ligament tears

PURPOSE

To assess the reliability and predictive value of quantifying anterior cruciate ligament (ACL) tear location on magnetic resonance imaging (MRI) and assess the predictive value of tear location on the eligibility for arthroscopic primary repair of proximal ACL tears.

METHODS

In this case-control study, all adult patients undergoing acute ACL surgery between 2008 and 2020 were retrospectively reviewed. All patients were treated with the treatment algorithm of undergoing primary repair when proximal tears with sufficient tissue quality were present intraoperatively, and otherwise underwent single-bundle ACL reconstruction. Sagittal MRI images were reviewed to measure proximal and distal remnant lengths along the anterior aspect of the torn ligament, and tear location was calculated as distal remnant divided by total remnant length. Interobserver and intraobserver reliability for remnant measurements were calculated. Then, receiver operating curve analysis (ROC) was performed to calculate the optimal cut-off for the possibility of primary repair with the different measurements.

RESULTS

Two hundred and forty-eight patients were included, of which 151 underwent repair (61%). Inter- and intraobserver reliability ranged between 0.92 and 0.96 [95% confidence interval (CI) 0.55-0.98] and 0.91-0.97 (95% CI 0.78-0.98, respectively). All patients with a tear location of  ≥ 80% on MRI could undergo repair, whereas all patients with tear location of < 60% required reconstruction. The positive predictive value of a proximal quarter tear (≥ 75%) on primary repair was 94%. Older age was correlated with more proximal tear location (p < 0.001), but there was no correlation between tear location and gender, BMI, or timing of surgery (all n.s).

CONCLUSION

This study showed that tear location could reliably be quantified on MRI by assessing distal and proximal remnant lengths. Tear location in the proximal quarter of the ACL was found to have a positive predictive value for repairability of 94%. These findings may assist orthopaedic surgeons in evaluating which patients are eligible for primary ACL repair preoperatively.

LEVEL OF EVIDENCE

III.

Standard MRI May Not Predict Specific Acute Anterior Cruciate Ligament Rupture Characteristics

Background

There has been renewed interest in the concept of anterior cruciate ligament (ACL) suture repair (ACLSR). Morphologic characteristics of the ruptured ACL remnant play a role in deciding whether a patient is eligible for ACLSR. However, no classification of these characteristics of ACL rupture on magnetic resonance imaging (MRI) scans has yet been compared with intraoperative findings in the context of ACLSR.

Purpose

To investigate the value of using preoperative MRI to predict specific characteristics of acute complete ACL rupture.

Study Design

Cohort study (diagnostic); Level of evidence, 2.

Methods

A total of 25 patients were included. Two radiologists classified ACL rupture location and pattern on preoperative 1.5-T MRI scans with a standard sequence; the results were compared with the corresponding findings at arthroscopy conducted by a single surgeon. The agreement between the MRI and surgical findings was calculated using Cohen κ values. Furthermore, the reliability coefficients of the MRI classifications within and between radiologists were calculated.

Results

The agreement between MRI classification and arthroscopic findings for ACL rupture location was slight (Cohen κ, 0.016 [radiologist 1] and 0.087 [radiologist 2]), and for ACL rupture pattern, this was poor to slight (Cohen κ, <0 and 0.074). The intraobserver reliability of MRI classification for ACL rupture location was moderate for radiologist 1 and slight for radiologist 2 (Cohen κ, 0.526 and 0.061, respectively), and for ACL rupture pattern, this was slight for radiologist 1 and 2 (Cohen κ, 0.051 and 0.093, respectively). The interobserver reliability of MRI classification for ACL rupture location and pattern was slight between radiologists (Cohen κ, 0.172 and 0.040, respectively).

Conclusion

In the current study, we found poor to slight agreement between MRI classification and arthroscopic findings of specific ACL rupture characteristics. In addition, the intra- and interobserver reliability for MRI classification of the ACL rupture characteristics was slight to moderate.

Arthroscopic anterior cruciate ligament repair with and without suture augmentation: technical note

Anterior cruciate ligament (ACL) tears are routinely treated with an ACL reconstruction. This is based on historical literature reporting high failure rates after ACL repairs in addition to the limited healing potential of the ACL. Recently, improved understanding of pathophysiology of ligamentous healing has led to increasing interest in treating proximal avulsions with excellent tissue quality in the acute setting, as this technique allows for ACL healing. Potential advantages of ACL repair include preservation of native proprioceptive and kinematics of the knee, avoidance of graft harvesting morbidity and the possibility to perform a primary ACL reconstruction in case of failure. As a consequence, several techniques for ACL repair have been proposed that can be performed in isolation or with suture augmentation. The primary aim of this technical note is to describe step-by-step the ACL repair technique with and without suture augmentation. The secondary aim of the current study is to review the indications, patient selection and advantages of the technique.

Good to Excellent Functional Short-Term Outcome and Low Revision Rates Following Primary Anterior Cruciate Ligament Repair Using Suture Augmentation

The aim of this study was to evaluate the functional outcome of primary anterior cruciate ligament (ACL) repair using suture augmentation (SA) in 93 consecutive patients (67 female) with a minimum follow-up of 12 months. Patients’ outcomes were determined using International Knee Documentation Committee (IKDC) score, Lysholm score (LS) and Tegner score (TS). Knee-laxity was assessed using the KT-1000 arthrometer. Eighty-eight patients (67 female, mean age 42 years ± standard deviation (SD) 13) were available for follow-up after a mean time of 21 months (range 12–39). Three patients (3%) underwent revision surgery and were excluded from functional analysis. The mean IKDC score was 87.4 ± 11, mean LS was 92.6 ± 11, mean pre-traumatic TS was 6 ± 2 and mean postoperative TS was 6 ± 2, with a mean difference (TS_Diff) of 1 ± 1. The interval from injury to surgery had no significant impact on the postoperative IKDC (p = 0.228), LS (p = 0.377) and TS_Diff (p = 0.572). Patients’ age (>40 years), BMI (>30) and coexisting ligament or meniscal injuries did not seem to influence postoperative functional results. Primary ACL repair using SA provides good to excellent functional outcomes with a low probability of revision surgery at a minimum of 12 months.

The multiple ligament-injured knee: When is primary repair an option?

BACKGROUND

Treatment of multiple ligament-injured knees (MLIKs) remains complex and most often requires ligament reconstruction surgery. Reconstruction effectively restores knee stability but the procedure is invasive and can be complicated by stiffness or arthrofibrosis. There has been recent resurgence of interest in primary repair of knee ligaments. The goal was therefore to assess incidence of repairable ligaments in MLIKs, and determine patient and injury characteristics associated with potential for primary repair.

METHODS

A retrospective review of all MLIK patients surgically treated between 2009 and 2018 was conducted. All patients were treated with the same algorithm: primary repair was performed if the ligament was proximally or distally avulsed, and otherwise, reconstruction was performed. Patient characteristics, injury patterns, treatment specifics, and short-term outcomes were compared using independent t-tests and chi-square tests.

RESULTS

Forty-eight patients were included (mean age 32 years ± 14; 54% were male). Ultimately, 55% of ACL, 73% of PCL, 88% of MCL/PMC, and 87% of LCL/PLC injuries were repaired. Patients above 35 years (OR 6.9, P = 0.010) and higher BMI (OR 3.5, P = 0.046) were more likely to undergo ACL repair. No significant correlation was found in other ligaments. At a minimum of six-month follow-up (range 0.5-7.2 years), ACL repair failed in nine percent, PCL repair in 17%, MCL/PMC repair in 0%, and LCL/PLC repair in 18% of patients.

CONCLUSIONS

This study noted high incidences of repairable ligaments when MLIKs are treated within six weeks following injury. Although preliminary outcomes following primary repair in MLIK are good, further long-term follow-up studies are needed.

Editorial Commentary: Anterior Cruciate Ligament Repair Revisited … Do We Need A Paradigm Shift?

This commentary discusses a brief history of anterior cruciate ligament (ACL) repair using a variety of techniques, including open primary repair, arthroscopic repair, and bridge-enhanced ACL repair. Concerns are raised about the current reported outcomes of primary ACL repair. There is a need for controlled prospective studies that assess the structural integrity of the repaired ligament using modern imaging techniques, physical examination, and KT-1000 testing. Caution should be used when interpreting published studies that rely solely on patient-reported outcome measures.

Primary Arthroscopic Repair of the Anterior Cruciate Ligament: A Systematic Review of Clinical Outcomes

PURPOSE

To describe the clinical outcomes after primary arthroscopic anterior cruciate ligament (ACL) repair.

METHODS

A systematic review of the PubMed, Embase, and Cochrane Library databases was performed according to the PRISMA guidelines. All English-language literature published from 2000 to 2018 that reported the clinical outcomes after primary arthroscopic repair (AR) of complete tear of the ACL (without augmentation) with a minimum 2-year follow-up was reviewed by 2 independent reviewers. Outcomes included repair failure, reoperation, postoperative knee stability, and patient-reported outcomes. Descriptive statistics are presented. Study quality was evaluated with the Modified Coleman Methodology Score (MCMS) and the Methodological Index for Nonrandomized Studies (MINORS) score.

RESULTS

Six studies (2 level III, 4 level IV) were included. The mean MCMS was 62.2. The mean MINORS score for noncomparative studies was 11.8, and for comparative studies, 18. Six studies reported outcomes of 89 patients who underwent AR of the ACL from 2007 to 2016 (age, 8 to 67 years; follow-up, 24 to 110 months). All 6 studies included exclusively proximal avulsion tears. Overall, 0% to 25.0% of patients experienced repair failure (I² = 23.7%; 95% confidence interval, 0% to 67.6%), and 0% to 20.0% of patients had a subsequent reoperation (I² = 12.1%; 95% confidence interval, 0% to 77.7%). Similar inconsistent results were shown for postoperative knee stability measures and patient-reported outcomes.

CONCLUSIONS

The literature on clinical outcomes of primary arthroscopic ACL repair is limited. The reported rates of repair failure and reoperation are highly inconsistent. Most studies report relatively high failure rates.

LEVEL OF EVIDENCE

IV, systematic review of level III and IV studies.

Identifying candidates for arthroscopic primary repair of the anterior cruciate ligament: A case-control study

INTRODUCTION

There has been a recent resurgence of interest in arthroscopic primary repair of proximal anterior cruciate ligament (ACL) tears. Patient selection is critical but not much is currently known on what predicts the possibility of repair. Goal of this study was therefore to assess predictive factors for the possibility of arthroscopic primary ACL repair.

METHODS

In this retrospective case-control study, all patients undergoing ACL surgery in a ten-year interval were included. Patients were treated with primary repair if there was a proximal tear and good tissue quality, or otherwise underwent ACL reconstruction. Collected data were age, gender, BMI, injury-to-surgery delay, injury mechanism and concomitant injuries. Receiver operating characteristic curves were used to find cutoff values, and all significant dependent variables were used in multivariate logistic analysis to assess independent predictors for the possibility of primary repair.

RESULTS

Three hundred sixty-one patients were included, of which in 158 patients (44%) primary repair was possible. Multivariate analysis (R² = 0.340, p < 0.001) showed that age > 35 years (Odds ratio [OR] 4.2, 95% CI 2.4-7.5,p < 0.001), surgery within 28 days (OR 3.3, 95% CI 1.9-5.7, p < 0.001), and BMI <26 (OR 1.9, 95% CI 1.1-3.3,p = 0.029) were predictive for the possibility of primary repair, and lateral meniscus injury presence decreased the likelihood of repair (OR 0.5, 95% CI 0.3-0.8, p = 0.008).

CONCLUSION

In this large cohort study, it was noted that 44% of patients had repairable ACL tears. Primary repair was more likely to be possible in older patients, patients with lower BMI and when surgery was performed within four weeks of injury.

The non-reconstructive treatment of complete ACL tear with biological enhancement in clinical and preclinical studies: A systematic review

Introduction

There is still controversy regarding the bio-enhanced non-reconstructive ACL treatment.

Materials and methods

A search for articles in databases was performed in February 2017. The objective and subjective evaluations of clinical studies and biomechanical and histological data of preclinical studies were extracted.

Results

Eighteen articles were included for analysis. In clinical studies, although subjective scores were significantly improved, the rate of re-operation rate was high. In preclinical studies, bio-enhancing techniques demonstrated promotion of the healing of ACL.

Conclusions

The efficacy of biological enhancement cannot be validated in clinical studies. Preclinical studies showed improved biomechanical and healing potential.

Reduced Time to Surgery Improves Patient-Reported Outcome After Achilles Tendon Rupture

BACKGROUND

Patient outcome after an acute Achilles tendon rupture (ATR) continues to be suboptimal and heterogeneous. Thus, prognostic factors are called for to optimize evidence-based ATR treatment protocols; however, the influence of delayed time from injury to surgery (TTS) on patient outcome after ATR remains largely unknown.

PURPOSE

To determine whether patient outcomes and adverse events after surgical repair of acute ATR are related to delayed TTS.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Two hundred twenty-eight patients with ATR who were treated with uniform anesthetic and surgical techniques, within 10 days after injury, were retrospectively assessed. TTS depended on availability of the operating theater, and neither surgeon nor patient could influence the TTS. Patients were assigned to 1 of 3 groups: short TTS (<48 hours), intermediate TTS (48-72 hours), and long TTS (>72 hours). Patient-reported outcome at 1 year was assessed with the validated Achilles tendon Total Rupture Score, with scores higher than 80 on a 0- to 100-point scale indicating an overall good outcome. The incidences of adverse events (perioperative and postoperative) and deep venous thrombosis were assessed.

RESULTS

Short TTS was significantly associated with increased rate of good outcome and reduced risk of adverse events. Seventy-one percent (95% CI, 60%-83%) of the patients with short TTS attained a good outcome compared with 44% (95% CI, 33%-56%) of the patients with long TTS ( P = .002), with the intermediate TTS group in between, 63% (95% CI, 47%-78%). The incidence of adverse events was significantly reduced among patients with short TTS, 1.4% (95% CI, 1%-4%) compared with those with intermediate TTS, 11% (95% CI, 2%-21%) ( P = .035) and those with long TTS, 14.8% (95% CI, 7%-23%) ( P = .003). The risk of sustaining a deep venous thrombosis was not statistically significantly different among the 3 groups ( P = .15).

CONCLUSION

Patients with acute ATR undergoing operation within 48 hours after injury had better outcomes and a lower number of adverse events compared with patients undergoing operation after 72 hours. These results align with evidence-based recommendations from other surgical disciplines and should be used as guidelines for optimizing ATR treatment protocols. Registration: NTC01317160 (ClinicalTrials.gov identifier).

Is There a Role for Internal Bracing and Repair of the Anterior Cruciate Ligament? A Systematic Literature Review

BACKGROUND

Renewed interest has arisen in arthroscopic anterior cruciate ligament (ACL) repair techniques.

HYPOTHESIS

ACL repair with or without some form of internal bracing could lead to good outcomes in a carefully selected subset of patients.

STUDY DESIGN

Systematic review.

METHODS

An electronic database search was performed to identify 89 papers describing preclinical and clinical studies on the outcome of ACL repair.

RESULTS

Proximal ACL tear patterns showed a better healing potential with primary repair than distal or midsubstance tears. Some form of internal bracing increased the success rate of ACL repair. Improvement in the biological characteristics of the repair was obtained by bone marrow access by drilling tunnels or microfracture. Augmentation with platelet-rich plasma was beneficial only in combination with a structural scaffold. Skeletally immature patients had the best outcomes. Acute repair offered improved outcomes with regard to load, stiffness, laxity, and rerupture.

CONCLUSION

ACL repair may be a viable option in young patients with acute, proximal ACL tears. The use of internal bracing, biological augmentation, and scaffold tissue may increase the success rate of repair.

Anterior cruciate ligament repair - past, present and future

Background

This article provides a detailed narrative review on the history and current concepts surrounding ligamentous repair techniques in athletic patients. In particular, we will focus on the anterior cruciate ligament (ACL) as a case study in ligament injury and ligamentous repair techniques. PubMed (MEDLINE), EMBASE and Cochrane Library databases for papers relating to primary anterior cruciate ligament reconstruction were searched by all participating authors. All relevant historical papers were included for analysis. Additional searches of the same databases were made for papers relating to biological enhancement of ligament healing.

Current standard

The poor capacity of the ACL to heal is one of the main reasons why the current gold standard surgical treatment for an ACL injury in an athletic patient is ACL reconstruction with autograft from either the hamstrings or patella tendon. It is hypothesised that by preserving and repairing native tissues and negating the need for autograft that primary ACL repair may represent a key step change in the treatment of ACL injuries.

History of primary ACL repair

The history of primary ACL repair will be discussed and the circumstances that led to the near-abandonment of primary ACL repair techniques will be reviewed.

New primary repair techniques

There has been a recent resurgence in interest with regards to primary ACL repair. Improvements in imaging now allow for identification of tear location, with femoral-sided injuries, being more suitable for repair. We will discuss in details strategies for improving the mechanical and biological environment in order to allow primary healing to occur.

In particular, we will explain mechanical supplementation such as Internal Brace Ligament Augmentation and Dynamic Intraligamentary Stabilisation techniques. These are novel techniques that aim to protect the primary repair by providing a stabilising construct that connects the femur and the tibia, thus bridging the repair.

Bio enhanced repair

In addition, biological supplementation is being investigated as an adjunct and we will review the current literature with regards to bio-enhancement in the form platelet rich plasma, bio-scaffolds and stem cells. On the basis of current evidence, there appears to be a role for bio-enhancement, however, this is not yet translated into clinical practice.

Conclusions

Several promising avenues of further research now exist in the form of mechanical and biological augmentation techniques. Further work is clearly needed but there is renewed interest and focus for primary ACL repair that may yet prove the new frontier in ligament repair.

Rise of the Pigs: Utilization of the Porcine Model to Study Musculoskeletal Biomechanics and Tissue Engineering During Skeletal Growth

Large animal models play an essential role in the study of tissue engineering and regenerative medicine (TERM), as well as biomechanics. The porcine model has been increasingly used to study the musculoskeletal system, including specific joints, such as the knee and temporomandibular joints, and tissues, such as bone, cartilage, and ligaments. In particular, pigs have been utilized to evaluate the role of skeletal growth on the biomechanics and engineered replacements of these joints and tissues. In this review, we explore the publication history of the use of pig models in biomechanics and TERM discuss interspecies comparative studies, highlight studies on the effect of skeletal growth and other biological considerations in the porcine model, and present challenges and emerging opportunities for using this model to study functional TERM.

Collagen application reduces complication rates of mid-substance ACL tears treated with dynamic intraligamentary stabilization

PURPOSE

Dynamic intraligamentary stabilization was recently proposed as an option for the treatment of acute ACL ruptures. The aim of this study was to investigate the feasibility of the procedure in mid-substance ACL ruptures and examine whether the additional application of a bilayer collagen I/III membrane would provide for a superior outcome.

METHODS

The study group consisted of patients presenting with a mid-substance ACL rupture undergoing dynamic intraligamentary stabilization using the Ligamys™ device along with application of a collagen I/III membrane to the surface of the ACL (group A, n = 23). The control group comprised a matched series of patients presenting with a mid-substance ACL rupture also treated by dynamic intraligamentary stabilization Ligamys™ repair, however, without additional collagen application (group B, n = 33). Patients were evaluated preoperatively and at 24-month follow-up for stability as well as Tegner and Lysholm scores. Knee laxity was measured as a difference in anterior translation (ΔAP) and pivot shift. Any events occurring during the follow-up period of 24 months were documented. Logistic regression of complications was performed, and adjustment undertaken where necessary.

RESULTS

A high total complication rate of 78.8 % was noted in group B, compared to group A (8.7 %) (p = 0.002). The addition of a collagen membrane was the only independent prognostic factor associated with reduced complications (OR 8.0, CI 2.0-32.2, p = 0.003, for collagen-free treatment). In group B, 6 patients suffered a re-rupture with subsequent instability requiring secondary hamstring reconstruction surgery, and 11 developed extension loss requiring arthroscopic debridement, whilst in group A, 2 patients required arthroscopic debridement for loss of exension, with no further encountered complication. Median Lysholm score was significantly higher in group A compared to group B (median 100 range 93-100 vs median 95 range 60-100, p = 0.03) at final follow-up.

CONCLUSIONS

A high complication rate following ACL Ligamys™ repair of mid-substance ruptures was noted. Application of a collagen membrane to the surface of the ACL resulted in a reduced incidence of extension deficit and re-ruptures. The results indicate that solitary ACL Ligamys™ repair does not present an appropriate treatment modality for mid-substance ACL ruptures. Collage application proved to provide healing benefits with superior clinical outcome after ACL repair.

LEVEL OF EVIDENCE

Case control study, Level III.

The Location of Anterior Cruciate Ligament Tears: A Prevalence Study Using Magnetic Resonance Imaging

Background:

Over the past decade, there has been a resurgence of interest in anterior cruciate ligament (ACL) preservation. Proximal and distal avulsion tears have been treated with arthroscopic primary repair, while augmented repair, remnant tensioning, primary repair with biological scaffold, and remnant preservation have been proposed for different types of midsubstance tears. Currently, the incidence of these different tear types is unknown.

Purpose:

To propose a magnetic resonance imaging (MRI) classification system for different tear types based on clinical relevance and to assess the distribution of these different ACL tear types.

Study Design:

Case series; Level of evidence, 4.

Methods:

A retrospective search in an institutional radiographic database was performed for patients who underwent knee MRI at our institution between June 2014 and June 2016. Patients younger than 18 years and those with reports of chronic tears, partial tears, multiligamentous injuries, were excluded. Tear types were graded as proximal avulsion (distal remnant length >90% of total ligament length, type I), proximal (75%-90%, type II), midsubstance (25%-75%, type III), distal (10%-25%, type IV), and distal avulsion (<10%, type V). An orthopaedic surgeon, a radiologist, and a research fellow graded the tear type on 30 MRIs to determine reliability, and the research fellow graded all MRIs. Inter- and intraobserver reliability were measured using kappa statistics.

Results:

A total of 353 patients (57% male; mean age, 37.1 years; range, 18.1-81.2 years) were included. Interobserver reliability was 0.670 (95% confidence interval, 0.505-0.836), and intraobserver reliability ranged from 0.741 to 0.934. Incidence of type I tears was 16%, type II tears 27%, type III tears 52%, type IV tears 1%, and type V tears 3% (2.5% with bony avulsion). Type I tears were more common in patients older than 35 years compared with those younger than 35 years (23% vs 8%; P < .001).

Conclusion:

This classification system was reliable in assessing tear location in acute ACL injuries. Type I tears were seen in 16%, type II in 27%, and type III in 52% of patients in our cohort. These data suggest that there may be greater potential application for ACL preservation techniques.

Primary Repair of the Anterior Cruciate Ligament: A Systematic Review

PURPOSE

To describe the clinical and preclinical research conducted on primary repair of the anterior cruciate ligament (ACL) during the past 10 years.

METHODS

A systematic search of PubMed, the Cochrane Central Register of Controlled Trials, and Embase was performed for all English-language studies published between 2003 and April 2014 on primary repair of the ACL.

RESULTS

Twenty-six studies met the inclusion and exclusion criteria. In the clinical research group, 8 studies (166 patients; age range, 10 to 71 years) met the inclusion and exclusion criteria and were largely long-term clinical outcome studies, based on the original cohorts from the 1970s and 1980s, and suggested high failure rates, additional surgery, and revision for instability. A subset of patients, however, achieved good to excellent subjective and objective long-term outcomes. In the preclinical research group, 18 studies met the inclusion and exclusion criteria and were based on an ACL transection model; they suggested that (1) stabilization of the knee with an internal suture strut improved the healing and biomechanical properties of the repaired ACL, (2) "enhancing" the repair with biological collagen-platelet composite augmentation improved healing and mechanical strength, (3) younger age and skeletal immaturity seem to correlate with improved histologic healing and biomechanical properties, (4) enhanced primary repair of the ACL may reduce post-traumatic osteoarthritis, and (5) the native ACL biomechanically outperformed the repaired ACL.

CONCLUSIONS

Although long-term human studies suggest collectively unacceptable outcomes for open primary repair of the ACL, a subset of patients achieved acceptable long-term results. ACL transection model animal studies showed improved healing and biomechanics with primary suture repair stabilization, early intervention, biological augmentation techniques, and younger age. Primary repair of the ACL may be an effective treatment modality for an appropriately selected subset of patients.

LEVEL OF EVIDENCE

Level IV, systematic review of preclinical and clinical Level IV studies.

Effect of low-temperature ethylene oxide and electron beam sterilization on the in vitro and in vivo function of reconstituted extracellular matrix-derived scaffolds

Reconstituted extracellular matrix (ECM)-derived scaffolds are commonly utilized in preclinical tissue engineering studies as delivery vehicles for cells and growth factors. Translation into clinical use requires identifying a sterilization method that effectively removes bacteria but does not harm scaffold function. To determine effectiveness of sterilization and impact on ECM scaffold integrity and function, low-temperature ethylene oxide and 15 kGy electron beam irradiation techniques were evaluated. Scaffold sterility was assessed in accordance to United States Pharmacopeia Chapter 71. Scaffold matrix degradation was determined in vitro using enzymatic resistance tests and gel electrophoresis. Scaffold mechanics including elastic modulus, yield stress and collapse modulus were tested. Lastly, 14 Yorkshire pigs underwent ACL transection and bio-enhanced ACL repair using sterilized scaffolds. Histologic response of ligament, synovium, and lymph nodes was compared at 4, 6, and 8 weeks. Ethylene oxide as well as electron beam irradiation yielded sterile scaffolds. Scaffold resistance to enzymatic digestion and protein integrity slightly decreased after electron beam irradiation while ethylene oxide altered scaffold matrix. Scaffold elastic modulus and yield stress were increased after electron beam treatment, while collapse modulus was increased after ethylene oxide treatment. No significant changes in ACL dimensions, in vivo scaffold resorption rate, or histologic response of synovium, ligament, and lymph nodes with either terminal sterilization technique were detectable. In conclusion, this study identifies two methods to terminally sterilize an ECM scaffold. In vitro scaffold properties were slightly changed without significantly influencing the biologic responses of the surrounding tissues in vivo. This is a critical step toward translating new tissue engineering strategies to clinical trials.

Bio-enhanced repair of the anterior cruciate ligament

Suture repair of the anterior cruciate ligament (ACL) has been widely abandoned in favor of ACL reconstruction, largely because of the high rates of failure and unreliability of the outcomes after suture repair. However, there have been recent basic science studies that suggest that combining a suture repair with a biological adjunct may improve the results of suture repair of the ACL, with several studies in large animal models showing equivalent strength of an ACL treated with bio-enhanced repaired to that of an ACL graft at 3, 6, and 12 months after surgery. In addition, the groups treated with bio-enhanced repair had significantly less osteoarthritis when compared with the animals undergoing ACL reconstruction. These findings have led to a renewed interest in bio-enhanced primary repair as a way to make repair of the ACL a viable option for a select group of patients in the future.

Fresh versus frozen engineered bone-ligament-bone grafts for sheep anterior cruciate ligament repair

Surgical intervention is often required to restore knee instability in patients with anterior cruciate ligament (ACL) injury. The most commonly used grafts for ACL reconstruction are tendon autografts or allografts. These current options, however, have shown failure rates requiring revision and continued instability in the long term. The mismatched biomechanical properties of the current tendon grafts compared with native ACL tissue are thought to contribute to these poor outcomes and potential risk of early onset osteoarthritis. As a possible solution to these issues, our laboratory has fabricated tissue-engineered ligament constructs that exhibit structural and functional properties similar to those of native ACL tissue after 6 months implantation. In addition, these tissue-engineered grafts achieve vascular and neural development that exceeds those of patellar tendon grafts. However, the utility of our tissue-engineered grafts is limited by the labor-intensive method required to produce the constructs and the need to use the constructs fresh, directly from the cell culturing system. Ideally, these constructs would be fabricated and stored until needed. Thus, in this study, we investigated the efficacy of freezing our tissue-engineered constructs as a method of preservation before use for ACL reconstruction. We hypothesized that frozen constructs would have similar histological and biomechanical outcomes compared with our fresh model. Our results showed that 6 months postimplantation as an ACL replacement graft, both our tissue-engineered fresh and frozen grafts demonstrated similar mechanical and histological outcomes, indicating that freezing is a suitable method for preserving and storing our graft before ACL reconstruction. The ability to use frozen constructs significantly increases the versatility of our graft technology expanding the clinical utility of our graft.

Gene expression of catabolic inflammatory cytokines peak before anabolic inflammatory cytokines after ACL injury in a preclinical model

Background

The response of the joint to anterior cruciate ligament (ACL) injury has not been fully characterized. In particular, the characterization of both catabolic factors, including interleukin-6 (IL-6), interleukin-8 (IL-8), and markers of ongoing tissue damage (CRP), and anabolic factors, including vascular endothelial growth factor (VEGF), transforming growth factor β-induced (TGFβI), and the presence of CD163+ macrophages, have not been well defined. In this study, we hypothesized ACL injury would catalyze both catabolic and anabolic processes and that these would have different temporal profiles of expression.

Methods

Adolescent Yucatan minipigs were subjected to ACL transection. Within the joint, gene expression levels of IL-6, IL-8, VEGF, and TGFβI were quantified in the synovium, ligament, and provisional scaffold located between the torn ligament ends at days 1, 5, 9, and 14 post-injury. Macrophage infiltration was also assessed in the joint tissues over the two week period. Serum C-reactive protein (CRP) levels were measured at multiple time points between 1 hour to 14 days after injury.

Results

Increases in IL-6 and IL-8 gene expression peaked at day 1 after injury in the synovium and ligament. CRP levels were significantly increased at day 3 before returning to pre-injury levels. VEGF and TGFβI gene expression did not significantly increase until day 9 in the synovium and were unchanged in the other tissues. CD163+ macrophages increased in the ligament and synovium until day 9.

Conclusion

Taken together, these results suggest that the response within the joint is primarily catabolic in the first three days after injury, switching to a more anabolic phase by nine days after injury. The effect of medications which alter these processes may thus depend on the timing of administration after injury.

Expression of modulators of extracellular matrix structure after anterior cruciate ligament injury

The ability of the anterior cruciate ligament (ACL) to heal after injury declines within the first 2 weeks after ACL rupture. To begin to explore the mechanism behind this finding, we quantified the expression of genes for collagen I and III, decorin, tenascin-C, and alpha smooth muscle actin, as well as matrix metalloproteinase (MMP)-1 and -13 gene expression within multiple tissues of the knee joint after ACL injury in a large animal model over a 2-week postinjury period. Gene expression of collagen I and III, decorin, and MMP-1 was highest in the synovium, whereas the highest MMP-13 gene expression levels were found in the ACL. The gene expression for collagen and decorin increased over the 2 weeks to levels approaching that in the ligament and synovium; however, no significant increase in either of the MMPs was found in the provisional scaffold. This suggests that although the ACL and synovium up-regulate both anabolic and catabolic factors, the provisional scaffold is primarily anabolic in function. The relative lack of provisional scaffold formation within the joint environment may thus be one of the key reasons for ACL degradation after injury.

Updates in biological therapies for knee injuries: anterior cruciate ligament

There have been many advances in anterior cruciate ligament reconstruction (ACLR) techniques incorporating biological treatment. The aim of this review is to discuss the recent contributions that may enlighten our understanding of biological therapies for anterior cruciate ligament (ACL) injuries and improve management decisions involving these enhancement options. Three main biological procedures will be analyzed: bio-enhanced ACL repair, bio-enhanced ACLR scrutinized under the four basic principles of tissue engineering (scaffolds, cell sources, growth factors/cytokines including platelet-rich plasma, and mechanical stimuli), and remnant-preserving ACLR. There is controversial information regarding remnant-preserving ACLR, since different procedures are grouped under the same designation. A new definition for remnant-preserving ACLR surgery is proposed, dividing it into its three major procedures (selective bundle augmentation, augmentation, and nonfunctional remnant preservation); also, an ACL lesion pattern classification and a treatment algorithm, which will hopefully standardize these terms and procedures for future studies, are presented.

Basic science of anterior cruciate ligament injury and repair

Injury to the anterior cruciate ligament (ACL) is one of the most devastating and frequent injuries of the knee. Surgical reconstruction is the current standard of care for treatment of ACL injuries in active patients. The widespread adoption of ACL reconstruction over primary repair was based on early perception of the limited healing capacity of the ACL. Although the majority of ACL reconstruction surgeries successfully restore gross joint stability, post-traumatic osteoarthritis is commonplace following these injuries, even with ACL reconstruction. The development of new techniques to limit the long-term clinical sequelae associated with ACL reconstruction has been the main focus of research over the past decades. The improved knowledge of healing, along with recent advances in tissue engineering and regenerative medicine, has resulted in the discovery of novel biologically augmented ACL-repair techniques that have satisfactory outcomes in preclinical studies. This instructional review provides a summary of the latest advances made in ACL repair. Cite this article: Bone Joint Res 2014;3:20-31.

Loss of extracellular matrix from articular cartilage is mediated by the synovium and ligament after anterior cruciate ligament injury

OBJECTIVE

Post-traumatic osteoarthritis (PTOA) occurs after anterior cruciate ligament (ACL) injury. PTOA may be initiated by early expression of proteolytic enzymes capable of causing degradation of the articular cartilage at time of injury. This study investigated the production of three of these key proteases in multiple joint tissues after ACL injury and subsequent markers of cartilage turnover.

METHODS

ACL transection was performed in adolescent minipigs. Collagenase (MMP-1 and MMP-13) and aggrecanase (ADAMTS-4) gene expression changes were quantified in the articular cartilage, synovium, injured ligament, and the provisional scaffold at days 1, 5, 9, and 14 post-injury. Markers of collagen degradation (C2C), synthesis (CPII) and aggrecan synthesis (CS 846) were quantified in the serum and synovial fluid. Histologic assessment of the cartilage integrity (OARSI scoring) was also performed.

RESULTS

MMP-1 gene expression was upregulated in the articular cartilage, synovium and ligament after ACL injury. MMP-13 expression was suppressed in the articular cartilage, but upregulated 100-fold in the synovium and ligament. ADAMTS-4 was upregulated in the synovium and ligament but not in the articular cartilage. The concentration of collagen degradation fragments (C2C) in the synovial joint fluid nearly doubled in the first five days after injury.

CONCLUSION

We conclude that upregulation of genes coding for proteins capable of degrading cartilage ECM is seen within the first few days after ACL injury, and this response is seen not only in chondrocytes, but also in cells in the synovium, ligament and provisional scaffold.

Biology of anterior cruciate ligament injury and repair: Kappa delta ann doner vaughn award paper 2013

Anterior cruciate ligament (ACL) injuries are currently treated by removing the injured ligament and replacing it with a tendon graft. Recent studies have examined alternative treatment methods, including repair and regeneration of the injured ligament. In order to make such an approach feasible, a basic understanding of ACL biology and its response to injury is needed. Identification of obstacles to native ACL healing can then be identified and potentially resolved using tissue engineering strategies-first, with in vitro screening assays, and then with in vivo models of efficacy and safety. This Perspectives paper outlines this path of discovery for optimizing ACL healing using a bio-enhanced repair technique. This journey required constructing indices of the functional tissue response, pioneering physiologically based methods of biomechanical testing, developing, and validating clinically relevant animal models, and creating and optimizing translationally feasible scaffolds, surgical techniques, and biologic additives. Using this systematic translational approach, "bio-enhanced" ACL repair has been advanced to the point where it may become an option for future treatment of acute ACL injuries and the prevention of subsequent post-traumatic osteoarthritis associated with this injury.

Use of a bioactive scaffold to stimulate anterior cruciate ligament healing also minimizes posttraumatic osteoarthritis after surgery

BACKGROUND

Although anterior cruciate ligament (ACL) reconstruction is the treatment gold standard for ACL injury, it does not reduce the risk of posttraumatic osteoarthritis. Therefore, new treatments that minimize this postoperative complication are of interest. Bioenhanced ACL repair, in which a bioactive scaffold is used to stimulate healing of an ACL transection, has shown considerable promise in short-term studies. The long-term results of this technique and the effects of the bioenhancement on the articular cartilage have not been previously evaluated in a large animal model.

HYPOTHESES

(1) The structural (tensile) properties of the porcine ACL at 6 and 12 months after injury are similar when treated with bioenhanced ACL repair, bioenhanced ACL reconstruction, or conventional ACL reconstruction, and all treatments yield results superior to untreated ACL transection. (2) After 1 year, macroscopic cartilage damage following bioenhanced ACL repair is similar to that in bioenhanced ACL reconstruction and less than in conventional ACL reconstruction and untreated ACL transection.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 64 Yucatan mini-pigs underwent ACL transection and randomization to 4 experimental groups: no treatment, conventional ACL reconstruction, bioenhanced ACL reconstruction using a bioactive scaffold, and bioenhanced ACL repair using a bioactive scaffold. The biomechanical properties of the ligament or graft were examined and macroscopic assessments of the cartilage surfaces were performed after 6 and 12 months of healing.

RESULTS

The structural properties (ie, linear stiffness, yield, and maximum loads) of the ligament after bioenhanced ACL repair were not significantly different from those in bioenhanced ACL reconstruction or conventional ACL reconstruction but were significantly greater than those in untreated ACL transection after 12 months of healing. Macroscopic cartilage damage after bioenhanced ACL repair was significantly less than that in untreated ACL transection and bioenhanced ACL reconstruction, and there was a strong trend (P = .068) for less macroscopic cartilage damage than in conventional ACL reconstruction in the porcine model at 12 months.

CONCLUSION

Bioenhanced ACL repair produces a ligament that is biomechanically similar to an ACL graft and provides chondroprotection to the joint after ACL surgery.

CLINICAL RELEVANCE

Bioenhanced ACL repair may provide a new, less invasive treatment option that reduces cartilage damage following joint injury.

ACL graft healing and biologics

Operative reconstruction of a torn anterior cruciate ligament (ACL) has become the most broadly accepted treatment. An important, but underreported, outcome of ACL reconstruction is graft failure, which poses a challenge for the orthopedic surgeon. An understanding of the tendon-bone healing and the intra-articular ligamentization process is crucial for orthopedic surgeons to make appropriate graft choices and to be able to initiate optimal rehabilitation protocols after surgical ACL reconstruction. This article focuses on the current understanding of the tendon-to-bone healing process for both autografts and allografts and discusses strategies to biologically augment healing.

The potential for primary repair of the ACL

The objective of this work is to assess the feasibility of successfully repairing the torn anterior cruciate ligament (ACL). Two major motivators for developing a new treatment for ACL injuries are the recently reported high rates of osteoarthritis, after conventional ACL reconstruction, and the problem of how to safely treat skeletally immature patients. A key factor in developing such a technique was the identification of the main inhibitor of intrinsic ACL healing-the lack of clot formation between the 2 torn ends of the ligament. A bioactive and biocompatible scaffold, which could be placed in the wound site to enhance cellular proliferation and biosynthesis, was developed. This biomaterial has shown promising functional outcomes in several large animal models of primary repair of partial and complete ACL transection over 4 to 14 weeks, suggesting potential for a successful, future clinical application.