Bio-enhanced repair of the anterior cruciate ligament

Editorial Commentary: Noninferiority of Anterior Cruciate Ligament Repair With Dynamic Intraligamentary Stabilization at Short- to Mid-Term Follow-Up Does Not Justify Superseding Anterior Cruciate Ligament Reconstruction as the "Gold Standard" for Anterior Cruciate Ligament Surgery

With advances in surgical technology, including the introduction of some kind of mechanical augmentation, there has been a resurgence of interest in primary repair of the anterior cruciate ligament (ACL). If successful, ACL repairs may provide several advantages over reconstruction resulting from the preservation of the native anatomy and proprioception. Recently, augmentation of ACL repair using dynamic intraligamentary stabilization (DIS) has been proposed, to create an optimal biomechanical environment for healing. In the DIS technique, an additional nonresorbable cord is placed along the ACL and attached to a dynamic spring fixed in the proximal tibia, keeping the tibia in a posterior drawer position at every degree of flexion. The analyzed randomized controlled trials comparing ACL repair with DIS to ACL reconstruction found overall similar failure and revision rates, whereas the few observed statistically significant differences in functional scores or knee stability favoring either of the techniques were clearly not clinically relevant. Of course, repair of a torn ACL should be limited to a specific subset of patients presenting with an acute femoral avulsion tear with minimal retraction and good tissue quality. However, the present short- to mid-term results do not justify ACL reconstruction to be superseded by ACL repair with DIS as the "gold standard" for surgical treatment of ACL tears in the future, even in this subset of patients.

Anterior Cruciate Ligament Repair-Here to Stay or History Repeating Itself?

Anterior cruciate ligament (ACL) injuries continue to be a prevalent concern among athletes and individuals with an active lifestyle. Traditionally, the standard of care for ACL tears has involved surgical reconstruction using autograft or allograft. This article aims to provide an overview of the evolving landscape of primary ACL repair, examining the current evidence, surgical techniques, patient selection criteria, outcomes, and potential future directions in this field.

Advanced Graft Development Approaches for ACL Reconstruction or Regeneration

The Anterior Cruciate Ligament (ACL) is one of the major knee ligaments, one which is greatly exposed to injuries. According to the British National Health Society, ACL tears represent around 40% of all knee injuries. The number of ACL injuries has increased rapidly over the past ten years, especially in people from 26-30 years of age. We present a brief background in currently used ACL treatment strategies with a description of surgical reconstruction techniques. According to the well-established method, the PubMed database was then analyzed to scaffold preparation methods and materials. The number of publications and clinical trials over the last almost 30 years were analyzed to determine trends in ACL graft development. Finally, we described selected ACL scaffold development publications of engineering, medical, and business interest. The systematic PubMed database analysis indicated a high interest in collagen for the purpose of ACL graft development, an increased interest in hybrid grafts, a numerical balance in the development of biodegradable and nonbiodegradable grafts, and a low number of clinical trials. The investigation of selected publications indicated that only a few suggest a real possibility of creating healthy tissue. At the same time, many of them focus on specific details and fundamental science. Grafts exhibit a wide range of mechanical properties, mostly because of polymer types and graft morphology. Moreover, most of the research ends at the in vitro stage, using non-certificated polymers, thus requiring a long time before the medical device can be placed on the market. In addition to scientific concerns, official regulations limit the immediate introduction of artificial grafts onto the market.

Efficacy of repair for ACL injury: a meta‑analysis of randomized controlled trials

We aim to compare the curative effect of primary repair for anterior cruciate ligament (ACL) injury with reconstruction and provide the reliable evidence for its clinical application. The literatures were searched in PubMed, EMBASE, Springer, and other medical literature databases published between January 1970 and June 2021. Basic characteristics, surgery technique, clinical outcome scores and physical examination results were recorded and evaluated. Seven randomized controlled trials (RCT) were eligible for inclusion. The results showed that there were no statistically significant differences between arthroscopic ACL repair and ACL reconstruction for Tegner, Lysholm, Lachman, KT-1000, range of motion (ROM), functional outcomes and reoperation rate (P > 0.05), even the result of IKDC scores showed that arthroscopic repair was better than reconstruction (P = 0.04). However, through the subgroup analysis, it was found that the short-term follow-up results of arthroscopic ACL repair were indeed better than those of open ACL repair. Therefore, we can assume that the arthroscopic ACL repair technique is an optional and promising surgical method to treat ACL injury.

Anterior cruciate ligament (ACL) repair using cortical or anchor fixation with suture tape augmentation vs ACL reconstruction: A comparative biomechanical analysis

BACKGROUND

The purpose was to compare knee kinematics in a cadaveric model of anterior cruciate ligament (ACL) repair using an adjustable-loop femoral cortical suspensory (AL-CSF) or independent bundle suture anchor fixation (IB-SAF) with suture tape augmentation to a bone-patellar tendon-bone (BPTB) ACL reconstruction.

METHODS

Twenty-seven cadaveric knees were randomly assigned to one of three surgical techniques: (1) ACL repair using the AL-CSF technique with suture tape augmentation, (2) ACL repair using the IB-SAF technique with suture tape augmentation, (3) ACL reconstruction using a BPTB autograft. Each specimen underwent three conditions according to the state of the ACL (native, proximal transection, repair/reconstruction) with each condition tested at four different angles of knee flexion (0°, 30°, 60°, 90°). Anterior tibial translation (ATT) and internal tibial rotation (ITR) were evaluated using 3-dimensional motion tracking software.

RESULTS

ACL transection resulted in a significant increase in ATT and ITR when compared to the native state (P < 0.001, respectively). ACL repair with the AL-CSF or IB-SAF technique as well as BPTB reconstruction restored native ATT and ITR at all tested angles of knee flexion, while showing significantly less ATT at 0°, 30°, 60°, and 90° as well as significantly less ITR at 30°, 60°, and 90° of knee flexion when compared to the ACL-deficient state. There were no significant differences in ATT and ITR between the three techniques utilized.

CONCLUSION

ACL repair using the AL-CSF or IB-SAF technique with suture tape augmentation as well as BPTB ACL reconstruction each restored native anteroposterior and rotational laxity, without significant differences in knee kinematics between the three techniques utilized.

LEVEL OF EVIDENCE

Controlled Laboratory Study.

Primary Anterior Cruciate Ligament Repair Using Suture Tape Augmentation: A Case Series of 29 Patients With Minimum 2-Year Follow-Up

PURPOSE

To evaluate clinical outcomes and patient-reported outcomes of patients who underwent primary anterior cruciate ligament (ACL) repair using suture tape augmentation.

METHODS

Patients with a proximal tear of the ACL who underwent primary ACL repair with a minimum 2-year follow-up were included. The exclusion criteria included multiligamentous knee injuries, midsubstance tears, tibial avulsion fractures, and distal tears. Demographic characteristics, injury pattern, concomitant injury pattern, and patient-reported outcome measures were recorded. Patients were evaluated at a minimum 2-year follow-up for clinical success, defined as stability not requiring revision ACL reconstruction, and for patient-reported outcome measurements. Failure was defined as the need for revision surgery.

RESULTS

The mean follow-up period was 2.8 ± 0.9 years. Thirty-five patients met the inclusion criteria, with an average age of 32.2 ± 7.2 years, and 2-year follow-up was obtained for 29 of these patients. Revision surgery was required in 2 of the 29 patients (6.9%); successful treatment was achieved in the remaining 93.1%. The Single Assessment Numeric Evaluation score and Knee Injury and Osteoarthritis Outcome Score for the 27 successfully treated patients were recorded, with 70.4% having Single Assessment Numeric Evaluation scores of 80 or greater.

CONCLUSIONS

This case series shows that primary surgical repair of proximal ACL tears using suture tape augmentation results in a low rate of revision surgery.

LEVEL OF EVIDENCE

Level IV, prospective case series.

[Effectiveness of partial anterior cruciate ligament suture repair with wide awake local anesthesia no tourniquet technique]

OBJECTIVE

To investigate the effectiveness of partial anterior cruciate ligament (ACL) suture repair with wide awake local anesthesia no tourniquet (WALANT) technique.

METHODS

Between July 2017 and July 2019, 18 patients with partial ACL injury were admitted. There were 10 males and 8 females, with an average age of 40.5 years (range, 22-57 years). There were 5 cases on the left knee and 13 cases on the right knee. Forteen cases had a clear history of trauma or sports injury, and 4 cases had no obvious cause. The time from injury to operation was 1-6 months (median, 3 months). Partial ligament was sutured using WALANT technique under arthroscopy. The operation time, total hospital stay, and postoperative hospital stay were recorded. Lachman test and anterior drawer test were performed to evaluate the knee joint stability after treatment, and Lysholm and International Knee Documentation Committee (IKDC) scores were used to evaluate the knee function. Five-point Likert scaling were used to evaluate postoperative patient satisfaction.

RESULTS

The operation time was 30-100 minutes (mean, 64.2 minutes). The total hospital stay was 2-12 days (mean, 4.5 days). Postoperative hospital stay was 1-4 days (mean, 1.8 days). All incisions healed by first intention after operation, and no surgery-related complications occurred. All patients were followed up 12-36 months (mean, 19.1 months). Lachman test and anterior drawer test were negative after operation. Lysholm score and IKDC score at 6 and 12 months after operation were significantly higher than those before operation, and at 12 months after operation were higher than those at 6 months after operation, the differences were significant ( P<0.05). At last follow-up, according to five-point Likert scaling of patient satisfaction, 7 cases were very satisfied, 10 cases were relatively satisfied, and 1 case was general. The total patient satisfaction rate was 94.4% (17/18). MRI scan showed the good ligament tension.

CONCLUSION

Using WALANT technique to repair partial ACL injuries under arthroscopy can retain the patient's own ligament tissue to the maximum extent and achieve satisfactory short-term effectiveness.

ACL Repair: A Game Changer or Will History Repeat Itself? A Critical Appraisal

Until the past decade the common thought was that the anterior cruciate ligament (ACL) was not able to heal and restore knee stability. In this manuscript a brief review of studies of the developers and the early adaptors of four different modern ACL repair techniques are presented. The present status and considerations for the future of ACL repair and its research are shared. After promising short- to midterm ACL healing results by the developers, the results of the early adaptors show more variety in terms of rerupture and reintervention for other reasons. Risk factors for failure are a young age, high preinjury sports activity level, midsubstance ruptures and impaired integrity of the ACL bundles and the synovial sheath. There is a call for more clinical data and randomized clinical trials. Conclusion: an important finding of the past decade is that the ACL is able to heal and subsequently restabilize the knee. Patient selection is emphasized: the ideal patient is a non-high athlete older than 25 and has an acute proximal one bundle ACL rupture. Further research will have to show if ACL repair could be a game changer or if history will repeat itself.

Efficacy of Nonaugmented, Static Augmented, and Dynamic Augmented Suture Repair of the Ruptured Anterior Cruciate Ligament: A Systematic Review of the Literature

BACKGROUND

Anterior cruciate ligament suture repair (ACLSR) was abandoned late last century in favor of anterior cruciate ligament (ACL) reconstruction (ACLR) because of overall disappointing results. However, in recent years there has been renewed and increasing interest in ACLSR for treatment of ACL ruptures. Several contemporary ACLSR techniques are being used, but any difference in effectiveness is unclear.

HYPOTHESIS

Contemporary nonaugmented (NA), static augmented (SA), and dynamic augmented (DA) ACLSR leads to (1) comparable outcomes overall and (2) comparable outcomes between proximal third, middle third, and combined ACL rupture locations (a) within and (b) between ACLSR technique categories.

STUDY DESIGN

Systematic review.

METHODS

An electronic search was performed in the MEDLINE and Embase databases for the period between January 1, 2010, and August 7, 2019. All articles describing clinical and patient-reported outcomes for ACLSR were identified and included, and outcomes for NA, SA, and DA ACLSR categories were compared.

RESULTS

A total of 31 articles and 2422 patients were included. The majority of articles (65%) and patients (89%) reported outcomes of DA ACLSR. Overall, there was high heterogeneity in study characteristics and level as well as quality of evidence (19 level 4; 7 level 3; 3 level 2; and 2 level 1). Most studies indicated excellent patient-reported outcomes. Overall, the variability in (and the maximum of) the reported failure rate was high within all ACLSR categories. The variability in (and the maximum of) the reported rate of all other complications was highest for DA ACLSR. Regarding ACL rupture location, the failure rate was highest in proximal ACL ruptures within the SA and DA ACLSR categories; rates of all other reported complications were highest in combined ACL ruptures within the DA ACLSR category. However, no studies in the NA category and only 1 study in the SA ACLSR category evaluated combined ACL ruptures. The majority of studies comparing ACLSR and ACLR found no differences in outcomes.

CONCLUSION

The amount of high-quality evidence for contemporary ACLSR is poor. This makes it difficult to interpret differences among ACLSR categories and among ACL rupture locations and, though promising, to establish the role of ACLSR in the treatment of ACL ruptures. More high-quality large randomized clinical trials with longer follow-up comparing ACLSR and ACLR are needed.

Is Primary Arthroscopic Repair Using the Pulley Technique an Effective Treatment for Partial Proximal ACL Tears?

BACKGROUND

Attention has recently been paid to primary arthroscopic repair to treat ACL tears because of the disadvantages associated with reconstruction. However, there remain many unanswered questions and concerns about its application in the treatment of ACL tears.

QUESTIONS/PURPOSES

(1) Does primary arthroscopic repair using the pulley technique result in satisfactory ROM (a functional ROM with a flexion contracture of 30° or less), knee stability, and functional scores in patients with partial proximal ACL tears? (2) What complications are associated with primary arthroscopic repair using the pulley technique in patients with partial proximal ACL tears?

METHODS

Between January 2014 and March 2016, we treated 23 patients surgically who had partial proximal ACL tears and excellent tissue quality (defined as a remnant with mild interstitial tearing and the ability to hold sutures). All patients meeting those two criteria were treated using primary arthroscopic repair using the pulley technique. During that period, this represented 13% (23 of 183) of the patients we treated surgically for an ACL tear. Patients were excluded if they had other ACL tear types, insufficient tissue quality (defined as a severely torn remnant that was not strong enough to hold sutures), multi-ligamentous injuries, or substantial arthrosis (chondromalacia greater than Outerbridge grade 3, most of which underwent conversion to ACL reconstruction). Clinical outcomes were assessed using ROM, the anterior drawer test, the Lachman test, Lysholm score, Tegner activity score, IKDC subjective score, and radiographs. Twenty-one patients were observed for a mean (range) period of 36 months (25-49), and two were lost to follow-up.

RESULTS

At the most-recent follow-up examination, all patients achieved full extension and only one patient lacked full flexion, with a flexion contracture of 10°. Twenty patients had no instability on the anterior drawer test and Lachman test findings, and one patient had a 1 + anterior drawer test. The mean Lysholm score improved from a mean ± SD of 71 ± 9 before surgery to 94 ± 6 (mean difference 23 points [95% CI 20 to 25]; p < 0.001) at latest follow-up. The IKDC subjective score improved from 64 ± 10 to 86 ± 11 points (mean difference 22 points; p < 0.001). We found no difference in the Tegner score from before surgery to latest follow-up (6.3 ± 1.2 versus 6.1 ± 1.2; mean difference 0.2; p = 0.056). One patient re-ruptured his ACL 2 months after surgery in military training during an obstacle race. No complications such as infection, thrombosis, stiffness, patellofemoral pain, or implant failure were observed.

CONCLUSIONS

Primary arthroscopic repair using the pulley technique can achieve short-term clinical success in a carefully selected (the selection process includes first identifying the ACL injury pattern preoperatively with MRI, then confirming the diagnosis under arthroscopy, and deciding whether to perform a repair intraoperatively) subset of patients with partial proximal ACL tears and excellent tissue quality (defined as a remnant with mild interstitial tearing and the ability to hold sutures). Despite the promising clinical outcomes of our study, this technique should not be widely adopted unless it has been compared directly with ACL reconstruction, so future studies should be conducted to compare the clinical outcomes between this technique and ACL reconstruction, and longer-term follow-up is necessary to identify whether there is deterioration in the clinical outcomes over time.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Anterior cruciate ligament repair versus reconstruction: A kinematic analysis

BACKGROUND

The purpose of this study was to compare the biomechanical properties of an anterior cruciate ligament (ACL) anatomic repair of a true femoral avulsion to an anatomic ACL reconstruction. It was hypothesized that the ACL repair and ACL reconstruction would have comparable biomechanical behavior when compared to the native knee.

METHODS

Ten paired fresh-frozen cadaveric knees (n = 20) were used to investigate knee kinematics when an anterior drawer force, varus, valgus, internal, and external rotational moment were applied at 0, 15, 30, 45, 60, and 90 degrees of flexion. Displacement and rotation were recorded in the following conditions: ACL-intact, ACL-deficient, and ACL-repaired vs reconstructed.

RESULTS

Sectioning of the ACL significantly increased anterior tibial translation (0°, 15°, 30° and 45°) compared to the intact state. The mean anterior displacement difference from intact was lower in the ACL-repaired knees compared to reconstructed knees at 30° and 90°. There were no significant differences between conditions in varus, valgus, internal, or external rotations.

CONCLUSION

ACL repair and ACL reconstruction procedures restored knee anterior tibial translation in matched paired specimens. There were no differences in valgus, varus, internal, or external rotation. Although, ACL-repaired knees (avulsion model) demonstrated less anterior tibial translation when compared to ACL-reconstructed knees, this difference was less than one millimeter. Based on the findings of this study, repair and reconstruction procedures both restored anterior tibial translation in matched-pair specimens. This suggests that the initial functionality of both techniques is similar and that further clinical studies are needed to compare the long-term stability.

Incidence and Risk Factors for a Partial Anterior Cruciate Ligament Tear Progressing to a Complete Tear After Nonoperative Treatment in Patients Younger Than 30 Years

Background:

Partial anterior cruciate ligament (ACL) tears are observed in 10% to 27% of isolated ACL tears. There is currently no consensus on diagnosis and treatment protocols, and the outcomes of nonoperative treatment remain undefined.

Purpose:

To assess the incidence and risk factors for the progression of partial ACL tears to complete ruptures after nonoperative treatment in active patients younger than 30 years.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A total of 41 patients, all younger than 30 years and active in sports, were diagnosed with a partial ACL tear, with no associated meniscal or chondral lesions on magnetic resonance imaging (MRI). All were assigned to a nonoperative treatment program. The Lachman test, ≤4-mm side-to-side difference in laxity by Rolimeter, and MRI were utilized for the diagnosis. Tegner and International Knee Documentation Committee (IKDC) scores were assessed before and after the first lesion, and the Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) score was assessed at last follow-up. Postinjury Tegner and IKDC scores were assessed before the second injury for patients progressing to a complete ACL tear and at last follow-up for patients without progression.

Results:

At a mean of 43 months (range, 24-96 months), the partial ACL injury progressed to a complete ACL tear in 16 (39%) patients. In the remaining 25 patients without progression, the mean Tegner and IKDC scores were 7.0 and 96.0 before the injury and 5.9 and 85.7, respectively, at last follow-up. The mean ACL-RSI score was 69.3. The Tegner and IKDC scores were significantly lower at final follow-up (P = .0002 and P < .0001, respectively). Only 18 (44%) patients returned to their preinjury level of sports activities. A significantly increased risk of progression to a complete ACL tear was seen in patients ≤20 years (odds ratio, 5.19; P = .037) or patients practicing pivoting contact sports (odds ratio, 6.29; P = .026). Meniscal lesions were found in 50% of patients with a partial tear that progressed to a complete ACL tear.

Conclusion:

A partial ACL injury progressed to a complete ACL tear in 39% of young active patients treated conservatively, with half of the complete tears presenting with a concomitant meniscal lesion at the time of reconstruction. Age ≤20 years and participation in pivoting contact sports were identified as significant risk factors for progression to a complete tear.

Micro-scale assessment of the postoperative effect of anterior cruciate ligament reconstruction preclinical study using a 7.1T micro-magnetic resonance imaging

High-field micro-magnetic resonance imaging (MRI) scanning may provide additional information for quantitative analysis of graft bone healing processes, thus serving as a promising supplementary method in graft and bone healing evaluation following anterior cruciate ligament reconstruction (ACLR) surgery during preclinical studies. The present study included 12 New Zealand white rabbits that underwent ACLR with polyethylene terephthalate (PET) ligament. At 4, 8, and 16 weeks following surgery, 4 rabbits were euthanized and knee joint samples were harvested for a 7.1T micro-magnetic resonance imaging (MRI) scan. The graft bone tunnel diameter and signal noise ratio (SNR) at the region of interest (ROI) were measured. Hematoxylin-eosin staining was performed at each time point to verify the graft bone healing process in histology. The bone tunnel diameter at the graft tunnel interface decreased over time in both femoral and tibial parts. Notably, the tunnel size was smaller than the diameter of the drilling Kirschner wire that was used to observe the femoral part and proximal site of the tibial part at 16 weeks following surgery. SNR research demonstrated that both the femoral and tibial part PET ligaments selected in the ROI exhibited a marked increase in SNR from the initial 4-week results. The micro-MRI result was consistent with that of histological analysis. Micro-MRI scanning was applied in an animal model that underwent ACL reconstruction surgery with PET ligament, and it was determined that micro-MRI is promising in quantitatively observing graft bone healing processes directly with a focus on graft tunnel distances and SNRs.

How to Succeed in Arthroscopic Anterior Cruciate Ligament Primary Repair? Step-by-Step Technique

Historically, poor results of open primary repair of anterior cruciate ligament (ACL) injuries have been reported. It has recently been recognized that favorable outcomes of primary ACL repair are possible when selectively performed in patients with proximal tears and good tissue quality. Moreover, with arthroscopic technological advances, primary repair can be a valuable treatment option for patients with proximal tears. Preserving the native ACL has several advantages, including maintenance of native proprioceptive function and biology. The procedure is also minimally invasive and reduces the inflammatory reaction often seen in ACL reconstruction. Recently, it has been suggested that additional suture augmentation of the primary repair technique may be beneficial for protecting ligament healing during early range of motion. In this Technical Note, we present the step-by-step surgical technique of arthroscopic primary repair using a femoral suspensory device with suture augmentation.

Combined Anterior Cruciate Ligament Repair and Anterolateral Ligament Reconstruction

There has been a renewed interest in anterior cruciate ligament (ACL) repairs over the last decade with some early promising results in the right patient population. Additionally, the anterolateral ligament has been extensively studied and has recently been shown to have a protective effect on standard ACL reconstructions in a clinical trial. Given its protective effect on ACL reconstructions, we believe this phenomenon is also relevant to ACL repairs and can decrease rerupture rates. In this publication, we demonstrate a surgical technique for ACL repair using an internal brace combined with an anterolateral ligament reconstruction using a gracilis autograft.

Relation of Anterior Cruciate Ligament Tears to Potential Chronic Cardiovascular diseases

We have enrolled a cohort of former National Football League players (n = 3,506) who played since 1960 to assess potential long term health consequences associated with participating in the sport. Each participant has completed a self-administered questionnaire including reporting of physician-diagnosed health conditions. One of the early assessments was to evaluate whether anterior cruciate ligament (ACL) tears were associated with later life co-morbidities, including cardiovascular effects. We used Cox proportional hazards to estimate hazard ratios (HR) for joint replacement surgeries, myocardial infarction, sleep apnea, arthritis, dementia, and stroke by history of ACL tear during their professional career. For additional outcomes without date of occurrence reported we used logistic regression to estimate odds ratios adjusted for potential confounding variables in all models. After adjusting for covariates, former National Football League players who tore their ACL had approximately a twofold increase in muscular skeletal co-morbidities, including knee joint replacement and arthritis, compared with those without ACL tears. In addition, those with a history of ACL tears also had more than a 50% increased risk of myocardial infarction (HR 1.52; 95% confidence interval 0.97 to 2.38) and a slight increase in sleep apnea (HR 1.15; 95% confidence interval 0.96 to 1.38). ACL tears sustained by athletes may increase the risk of co-morbidities beyond the musculoskeletal system. As there are more than 100,000 ACL reconstructions annually in the United States, our findings could have widespread public health importance if these findings generalize to a population beyond professional football players. In conclusion, enhanced screening for other risk factors for these conditions in patients who have torn their ACL might identify those who could most benefit from prevention strategies.

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.

Partial Anterior Cruciate Ligament Ruptures: Advantages by Intraligament Autologous Conditioned Plasma Injection and Healing Response Technique-Midterm Outcome Evaluation

The historical treatment options for partial anterior cruciate ligament (ACL) ruptures were conservative therapy or ACL reconstruction by injured bundle or entire ACL replacement. In awareness of the regenerative potential of biologic agents such as mesenchymal stem cells or platelet rich plasma (PRP), the healing response technique was developed to preserve the injured ACL with better outcomes than the conservative therapy. Further improvement of this technique seems to be obtained by the additional application of PRP products. Thus, the aim of this study was to evaluate the midterm outcome after intraligament autologous conditioned plasma (ACP) by a clinical, scoring, and functional performance assessment. 42 patients were evaluated in this study. The failure rate was 9.5%. Outcome evaluation showed good to excellent results. The scores were IKDC subjective 83.2 (SD 14.5), Lysholm 85.5 (SD 15.5), Tegner 4.7 (SD 1.7), and Cincinnati 85.4 (SD 15.5) after a mean follow-up of 33 months. Clinical examination showed stable Lachman test, negative pivot shift phenomenon, and a significant reduction in AP-laxity compared to preoperative status (rolimeter preoperative: 1.9 (SD1.4); postoperative 0.6 (SD1.8), p=0.001) in all patients. Functional performance testing showed no significant differences between the injured and healthy side. Return to sport was achieved after a mean of 5.8 months (SD 3.6) in 71.1% of the included patients. In summary, this new treatment option revealed in midterm follow-up promising results to treat partial ACL lesions with a reduced need for conversion to ACL reconstruction and with a high percentage of return to preinjury sport activity.

Clinical Outcomes of Arthroscopic Primary Repair of Proximal Anterior Cruciate Ligament Tears Are Maintained at Mid-term Follow-up

PURPOSE

To assess the mid-term clinical outcomes in patients with proximal avulsion anterior cruciate ligament (ACL) tears undergoing arthroscopic primary repair with suture anchors.

METHODS

The first 11 consecutive patients with proximal avulsion tears treated with arthroscopic primary repair were evaluated at mid-term (minimum 5-year) follow-up. Physical examination was performed; laxity examination consisting of the Lachman, pivot-shift, and anterior drawer tests was performed; and patients were asked to complete the Lysholm, modified Cincinnati, Single Assessment Numeric Evaluation, and International Knee Documentation Committee (IKDC) questionnaires.

RESULTS

Of the 11 patients, 10 were seen at a mean follow-up of 6.0 ± 1.5 years (range, 4.8-9.2 years). One patient was lost to follow-up, in whom failure had already occurred at short-term follow-up. One additional patient underwent reoperation for a medial meniscus tear and also had a partial ACL tear; this patient was clinically stable at last follow-up. All patients had full range of motion. Nine patients had negative Lachman and negative pivot-shift examination findings (IKDC score of A), and 1 patient had a 1A Lachman result and 1+ pivot-shift result (IKDC score of B). The mean Lysholm score was 96.0 ± 4.5 (range, 88-100); modified Cincinnati score, 95.6 ± 7.4 (range, 80-100); Single Assessment Numeric Evaluation score, 95.4 ± 5.4 (range, 85-100); preinjury Tegner score, 7.2 ± 1.2 (range, 5-9); postoperative Tegner score, 6.6 ± 1.8 (range, 3-9); and IKDC subjective score, 92.3 ± 11.3 (range, 64-100).

CONCLUSIONS

The clinical outcomes of arthroscopic primary repair of proximal ACL tears with suture anchors are excellent and are maintained at mid-term follow-up in a carefully selected subset of patients with proximal tears and excellent tissue quality.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Primary Anterior Cruciate Ligament Repair With Augmentation

Anterior cruciate ligament (ACL) tears are usually managed by reconstruction with autograft or allograft, but primary repair in carefully selected patients is a reasonable option. Proximal avulsions presenting early with excellent tissue quality are amenable to repair and healing. Restoration of native ACL preserves its proprioceptive and kinematic functions. A repair is less invasive and avoids graft-related problems, and faster rehabilitation is possible. Protection for the repair in the early stages will allow better healing. We present our technique of ACL repair using knotless suture anchors with high-strength sutures and protection using high-strength sutures tapes inserted through the same anchors.

Factors influencing the success of anterior cruciate ligament repair with dynamic intraligamentary stabilisation

PURPOSE

Primary repair of the anterior cruciate ligament (ACL) has regained interest of clinicians with recent development of novel repair techniques. Dynamic intraligamentary stabilisation was introduced in an attempt to promote healing by shielding cyclic loads acting upon the ACL during the healing phase. The aim of this study was to identify negative factors likely to influence success of this procedure.

METHODS

Between 2009 and 2014, 264 patients with an acute ACL rupture undergoing dynamic intraligamentary stabilisation were included in this study. Patients were evaluated for anterior/posterior laxity; range of motion and patient reported outcome measures. Adverse events and re-operations were noted. Failure was defined as AP Translation >3 mm, re-rupture or conversion to ACL reconstruction. Minimum follow-up was 24 months. Univariate and multivariate regression models were utilized to determine predictors of failure.

RESULTS

An overall complication rate of 15.1% was noted comprising 9.5% (n = 25) re-ruptures, 4.1% (n = 11) persistent instability, and 1.5% (n = 4) > 10° fixed flexion deformity. Two factors were identified as negative predictors of failure: (1) pursuit of competitive sport activities with a Tegner pre-injury score >7 (Odds Ratio (OR) 4.4, CI 1.2-15.9, p = 0.02) and (2) mid-substance ACL rupture location (OR 2.5, 1.1-5.7, p = 0.02). When neither of those risk factors occurred the failure rate was limited to 3.9%.

CONCLUSIONS

Correct patient selection and narrowing of indications are necessary to maintain high success rates of the procedure. Mid-substance ACL ruptures and a high pre-injury sports activity level are two predictors of inferior outcome.

LEVEL OF EVIDENCE

II.

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.

Biologic Approaches for the Treatment of Partial Tears of the Anterior Cruciate Ligament: A Current Concepts Review

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) has been established as the gold standard for treatment of complete ruptures of the anterior cruciate ligament (ACL) in active, symptomatic individuals. In contrast, treatment of partial tears of the ACL remains controversial. Biologically augmented ACL-repair techniques are expanding in an attempt to regenerate and improve healing and outcomes of both the native ACL and the reconstructed graft tissue.

PURPOSE

To review the biologic treatment options for partial tears of the ACL.

STUDY DESIGN

Review.

METHODS

A literature review was performed that included searches of PubMed, Medline, and Cochrane databases using the following keywords: partial tear of the ACL, ACL repair, bone marrow concentrate, growth factors/healing enhancement, platelet-rich plasma (PRP), stem cell therapy.

RESULTS

The use of novel biologic ACL repair techniques, including growth factors, PRP, stem cells, and bioscaffolds, have been reported to result in promising preclinical and short-term clinical outcomes.

CONCLUSION

The potential benefits of these biological augmentation approaches for partial ACL tears are improved healing, better proprioception, and a faster return to sport and activities of daily living when compared with standard reconstruction procedures. However, long-term studies with larger cohorts of patients and with technique validation are necessary to assess the real effect of these approaches.

The past, present and future of ligament regenerative engineering

Regenerative engineering has been defined as the convergence of Advanced Materials Sciences, Stem Cell Sciences, Physics, Developmental Biology and Clinical Translation for the regeneration of complex tissues and organ systems. Anterior cruciate ligament (ACL) reconstruction necessitates the regeneration of bone, ligament and their interface to achieve superior clinical results. In the past, the ACL has been repaired with the use of autologous and allogeneic grafts, which have their respective drawbacks. Currently, investigations on the use of biodegradable matrices to achieve knee stability and permit tissue regeneration are making promising advancements. In the future, utilizing regenerative biology cues to induce an endogenous regenerative response may aid the enhancement of clinical ACL reconstruction outcomes.

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.

Enhanced Bone-Tendon-Bone Approach for Open Anterior Cruciate Ligament Replacement With Conservation of the Joint Capsule

Arthroscopic procedures for ruptured anterior cruciate ligament (ACL) tears are a common standard. However, there are strong alternatives to this standard. The purpose of this study is to present a precise, fast, and minimally invasive but open procedure for reconstruction of the ruptured ACL. The torn ACL is substituted by a widely used bone-patellar tendon-bone (BPTB) autograft. After the BPTB graft has been harvested, the Hoffa body is exposed and mobilized ventrally. The surgeon then has a free view of the remnants of the torn ACL, which are to be removed completely. Through the tibial and femoral footprints of the ACL, a tunnel is drilled under a direct view, thus ensuring optimal anatomic positioning of the BPTB graft. The described approach is simple in handling and advantageous because all steps are performed under a direct view, which improves overall precision and intraoperative functional control.

Editorial commentary: tissue engineering in knee arthroscopic and related surgery

Stem cells are guided by scaffolds, induced by growth factors, and stimulated by biomechanical forces, with a goal of engineering clinically competent cartilage, meniscus, tendon, or ligament tissue. Translational research, to move us from the preclinical to the clinical phase, is today necessary.

Editorial commentary: ACL bioactive scaffold

ACL bioactive scaffolds may be used to bioenhance ACL primary repair, and they show preclinical (porcine) promise. We are extremely interested in ongoing clinical development.

Editorial commentary: ACL tissue bioengineering clinical application is in its infancy

Preclinical ACL tissue engineering studies show promise using a combination of cells, scaffolds, growth factors, and "stimulation," such as ultrasound or shockwave therapy, but clinical application is in its infancy. Bioactive scaffolds may be weak at time zero. A solution could be to add to the combination of cells, scaffolds, growth factors, simulation, and a structural tie.

Editorial commentary: synthetic ACL grafts are more important than clinical nonbelievers may realize

Artificial ACL grafts are structural ties, designed to resist tension, but not designed to undergo biologic ligamentization by the host. Strategically, an artificial ACL graft may be used as reinforcement to augment ACL repair, ACL autograft, ACL allograft, or tissue-engineered ACL. Most artificial ACL grafts have had poor reported outcomes. However, the Ligament Augmentation and Reconstruction System (LARS) artificial ACL graft shows positive clinical outcomes.