Biomechanical outcomes after bioenhanced anterior cruciate ligament repair and anterior cruciate ligament reconstruction are equal in a porcine model

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.

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

BACKGROUND

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

PURPOSE

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

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

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

RESULTS

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

CONCLUSION

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

Advanced Gene Therapy Strategies for the Repair of ACL Injuries

The anterior cruciate ligament (ACL), the principal ligament for stabilization of the knee, is highly predisposed to injury in the human population. As a result of its poor intrinsic healing capacities, surgical intervention is generally necessary to repair ACL lesions, yet the outcomes are never fully satisfactory in terms of long-lasting, complete, and safe repair. Gene therapy, based on the transfer of therapeutic genetic sequences via a gene vector, is a potent tool to durably and adeptly enhance the processes of ACL repair and has been reported for its workability in various experimental models relevant to ACL injuries in vitro, in situ, and in vivo. As critical hurdles to the effective and safe translation of gene therapy for clinical applications still remain, including physiological barriers and host immune responses, biomaterial-guided gene therapy inspired by drug delivery systems has been further developed to protect and improve the classical procedures of gene transfer in the future treatment of ACL injuries in patients, as critically presented here.

Bridge-Enhanced Anterior Cruciate Ligament Repair for Mid-Substance Tear With Concomitant Lateral Meniscus Radial Repair

In recent years, repair of the injured anterior cruciate ligament (ACL) has been subject to a renewed interest as novel arthroscopic techniques have been developed. Specifically, the bridge-enhanced ACL repair is a technique composed of a resorbable protein-based implant combined with autologous blood that is used to bridge the gap between 2 torn edges of a mid-substance ACL tear. This implant is believed to help facilitate healing of a primary suture repair and suture cinch and has since demonstrated noninferiority to ACL reconstruction with autograft at 2-year follow-up. The purpose of this Technical Note is to describe a step-by-step surgical technique of a mid-substance ACL repair using the bridge-enhanced ACL repair system in a case with a concomitant lateral meniscus radial repair.

Effects of Male and Female Sex on the Development of Posttraumatic Osteoarthritis in the Porcine Knee After Anterior Cruciate Ligament Surgery

BACKGROUND

Posttraumatic osteoarthritis (PTOA) is a common sequela of anterior cruciate ligament (ACL) injury, even when surgical treatment is selected. The effect of patient sex on cartilage health after ACL injury and surgical treatment has been less studied.

PURPOSE/HYPOTHESIS

The study objective was to compare the macroscopic cartilage damage that develops after ACL surgery in male and female Yucatan minipigs. It was hypothesized that after ACL surgery, the macroscopic cartilage damage of the tibiofemoral joints from female animals would be greater than that from male animals. Additionally, it was hypothesized that the effect of sex on the macroscopic cartilage damage would depend on surgical treatment.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve-month follow-up data were obtained for 55 adolescent Yucatan minipigs (22 female/33 male) that were randomized to 1 of 3 experimental groups: no treatment (ACL transection [ACLT]), ACL reconstruction, and bridge-enhanced ACL restoration. The Osteoarthritis Research Society International guidelines were used to determine a standardized macroscopic cartilage damage score on 5 surfaces of the knee joint.

RESULTS

Females had significantly worse mean total macroscopic cartilage damage scores on the surgical side (adjusted P value [P adj] = .04) and significantly better scores on the contralateral side (P adj = .01) when compared with males. The trochlear damage scores were also significantly worse in females for surgical limbs (P adj = .009) and significantly better for the contralateral limbs (P adj < .001) when compared with males. Although there were no significant differences in total macroscopic cartilage damage scores between sexes within treatment groups on the surgical limbs (ACLT, P adj = 0.45; ACL reconstruction, P adj = .56; bridge-enhanced ACL restoration, P adj = .23), the mean trochlear scores on the surgical limb of females were significantly worse than those of the males in the ACLT group (P adj = .003).

CONCLUSION

Mean total macroscopic cartilage damage scores of Yucatan minipigs were significantly worse in females than males, regardless of treatment. These differences were predominantly found in the trochlear scores across all treatment groups.

CLINICAL RELEVANCE

These data suggest that patient sex could be more influential in the progression of PTOA than surgical treatment after ACL injury. Identifying factors responsible for this discrepancy may prove valuable to identify targets to slow PTOA progression in male and female ACL-injured populations.

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.

Effect of Skeletal Maturity on Fixation Techniques for Tibial Eminence Fractures

Background:

Several fixation methods have been reported for the operative treatment of tibial eminence fractures. Previous biomechanical studies have demonstrated that suture fixation may be a stronger construct; however, the maturity status of these specimens was not scrutinized.

Purpose:

To examine if suture fixation remains a biomechanically superior fixation method to screw fixation in both skeletally mature and immature specimens.

Study Design:

Controlled laboratory study.

Methods:

Sixteen total matched porcine (Yorkshire) knees (8 skeletally immature knees and 8 skeletally mature knees) were procured, and a standardized tibial eminence fracture was created. In each age-matched group of knees, 4 knees underwent randomization to fixation with 2 screws while 4 knees were randomized to fixation using a dual-suture technique. Once fixation was complete, the specimens underwent cyclic loading (200 cycles) in the anteroposterior plane of the tibia and load-to-failure testing, both with the knee positioned at 30° of flexion. Relevant measurements were recorded, and data were analyzed.

Results:

Among mature specimens, load to failure was 1.9 times higher in the suture fixation group compared with the screw fixation group (1318.84 ± 305.55 vs 711.66 ± 279.95 N, respectively; P = .03). The load to failure was not significantly different between the groups in immature specimens (suture: 470.00 ± 161.91 N vs screw: 348.79 ± 102.46; P = .08).

Conclusion:

These findings suggest that suture fixation may represent a better construct choice for fixation of tibial eminence fractures in the skeletally mature population. However, in the skeletally immature population, fixation with screws or suture may be equivalent. Displacement after cyclic loading did not appear to differ by fixation method, nor did stiffness.

Clinical Relevance:

A stronger fixation construct may be beneficial and allow for earlier range of motion to help potentially decrease postoperative stiffness. Clinical studies are warranted to see if these results may be replicated in humans.

Earlier Resolution of Symptoms and Return of Function After Bridge-Enhanced Anterior Cruciate Ligament Repair As Compared With Anterior Cruciate Ligament Reconstruction

Background:

Bridge-enhanced anterior cruciate ligament repair (BEAR) has noninferior patient-reported outcomes when compared with autograft anterior cruciate ligament reconstruction (ACLR) at 2 years. However, the comparison of BEAR and autograft ACLR at earlier time points—including important outcomes such as resolution of knee pain and symptoms, recovery of strength, and return to sport—has not yet been reported.

Hypothesis:

It was hypothesized that the BEAR group would have higher outcomes on the International Knee Documentation Committee and Knee injury and Osteoarthritis Outcome Score, as well as improved muscle strength, in the early postoperative period.

Study Design:

Randomized controlled trial; Level of evidence, 1.

Methods:

A total of 100 patients aged 13 to 35 years with complete midsubstance anterior cruciate ligament injuries were randomized to receive a suture repair augmented with an extracellular matrix implant (n = 65) or an autograft ACLR (n = 35). Outcomes were assessed at time points up to 2 years postoperatively. Mixed-model repeated-measures analyses were used to compare BEAR and ACLR outcomes. Patients were unblinded after their 2-year visit.

Results:

Repeated-measures testing revealed a significant effect of group on the International Knee Documentation Committee Subjective Score (P = .015), most pronounced at 6 months after surgery (BEAR = 86 points vs ACLR = 78 points; P = .001). There was a significant effect of group on the Knee injury and Osteoarthritis Outcome Score-Symptoms subscale scores (P = .010), largely attributed to the higher BEAR scores at the 1-year postoperative time point (88 vs 82; P = .009). The effect of group on hamstring strength was significant in the repeated-measures analysis (P < .001), as well as at all postoperative time points (P < .001 for all comparisons). At 1 year after surgery, approximately 88% of the patients in the BEAR group and 76% of the ACLR group had been cleared for return to sport (P = .261).

Conclusion:

Patients undergoing the BEAR procedure had earlier resolution of symptoms and increased satisfaction about their knee function, as well as improved resolution of hamstring muscle strength throughout the 2-year follow-up period.

Registration:

NCT02664545 (ClinicalTrials.gov identifier)

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.

A Systematic Review of Tissue Engineering Scaffold in Tendon Bone Healing in vivo

Background: Tendon-bone healing is an important factor in determining the success of ligament reconstruction. With the development of biomaterials science, the tissue engineering scaffold plays an extremely important role in tendon-bone healing and bone tissue engineering. Materials and Methods: Electronic databases (PubMed, Embase, and the Web of Science) were systematically searched for relevant and qualitative studies published from 1 January 1990 to 31 December 2019. Only original articles that met eligibility criteria and evaluated the use of issue engineering scaffold especially biomaterials in tendon bone healing in vivo were selected for analysis. Results: The search strategy identified 506 articles, and 27 studies were included for full review including two human trials and 25 animal studies. Fifteen studies only used biomaterials like PLGA, collage, PCL, PLA, and PET as scaffolds to repair the tendon-bone defect, on this basis, the rest of the 11 studies using biological interventions like cells or cell factors to enhance the healing. The adverse events hardly ever occurred, and the tendon bone healing with tissue engineering scaffold was effective and superior, which could be enhanced by biological interventions. Conclusion: Although a number of tissue engineering scaffolds have been developed and applied in tendon bone healing, the researches are mainly focused on animal models which are with limitations in clinical application. Since the efficacy and safety of tissue engineering scaffold has been proved, and can be enhanced by biological interventions, substantial clinical trials remain to be done, continued progress in overcoming current tissue engineering challenges should allow for successful clinical practice.

Suture Tape Augmentation Has No Effect on Anterior Tibial Translation, Gap Formation, or Load to Failure of Anterior Cruciate Ligament Repair: A Biomechanical Pilot Study

Purpose

The purpose of our pilot study was to assess the effect of augmenting anterior cruciate ligament (ACL) repair with suture tape on biomechanical parameters including anterior tibial translation, gap formation, and load to failure.

Methods

Ten fresh-frozen nonpaired cadaveric knees were dissected, and baseline anterior-posterior stability of both ACL-intact and -deficient knees was obtained. The specimens were randomized to undergo ACL repair either with or without suture tape reinforcement, and anterior tibial translation, as well as gap formation, was measured after cyclic loading. Finally, all specimens were subjected to a single pullout force to determine maximum load to failure. We performed t test analysis to compare means between groups, and significance was defined as P < .05.

Results

On t test analysis, no statistically significant difference was found regarding anterior tibial translation between the ACL-intact group and either repair group or between the repair group without suture tape augmentation and the repair group with suture tape augmentation. No significant difference in gap formation was detected between the repair groups with and without suture tape augmentation at 100 cycles (1.25 mm vs 1.02 mm, P = .6), 250 cycles (2.87 mm vs 2.12 mm, P = .3), and 500 cycles (4.5 mm vs 4.55 mm, P = .5). The average load to failure of the repairs without suture tape augmentation was not significantly different from that of the repairs with suture tape augmentation (725.9 N vs 725.7 N, P = .99).

Conclusions

In this pilot study, we did not identify a difference between ACL repairs with and without suture tape augmentation regarding anterior tibial translation, gap formation, or maximum load to failure.

Clinical Relevance

Treatment of ACL tears with primary ACL repair is a highly debated topic, and studies such as this study to further our understanding of the biomechanical properties of augmented ACL repairs are important for surgeons when deciding the best treatments for their patients.

Positive effects of platelet-rich plasma (PRP) and a Sanguisorba officinalis polysaccharide on the proliferation and differentiation of anterior cruciate ligament (ACL) fibroblasts in vitro

Context: Sanguisorba officinalis L. (Rosaceae), a famous traditional Chinese medicine. It was recently reported that its polysaccharide could facilitate collagen production.Objectives: We investigated the mechanism by which S. officinalis polysaccharide (SOWPa) and/or platelet-rich plasma (PRP) promote regenerative potential of anterior cruciate ligament (ACL) in vitro.Materials and methods: ACL fibroblasts were treated with SOWPa (25 and 100 mg/kg), PRP, PRP + SOWPa (25 and 100 mg/kg) or vehicle alone for 24, 48, or 72 h. Cell viability, migration ability and apoptosis were evaluated by MTT, transwell and flow cytometry, respectively. Western blot analysis was performed to assess associated protein expression.Results: PRP, SOWPa (100 mg/kg) or PRP + SOWPa (100 mg/kg) treatment for 72 h significantly improved the cell viability of ACL fibroblasts from 100 ± 7.5% (control) to 156.85 ± 12.82%, 188.08 ± 15.92%, and 223.67 ± 18.82%, respectively, which was evidenced by individual decreased apoptosis rate from 31.26 ± 2.35% (control) to 20.80 ± 1.89%, 18.01 ± 1.55% and 9.33 ± 0.78%. Furthermore, the motility of ACL fibroblasts was significantly improved with increased migrated cell number per field from 5 for control to 26 for PRP, 36 for SOWPa and 44 for PRP + SOWPa, respectively. Moreover, the protein expression of differentiation markers (RUNX2, ALP, BMP2 and Col I) and TLR-4 and phosphorylated p65 (p-p65) was inhibited by the above treatment.Discussion and conclusions: Data suggested that the addition of SOWPa to PRP increased the regenerative ability of ACL fibroblasts by blocking the TLR-4/NF-κB pathway.

Clinical and radiological results after Internal Brace suture versus the all-inside reconstruction technique in anterior cruciate ligament tears 12 to 18 months after index surgery

BACKGROUND

 Anterior cruciate ligament (ACL) injury can lead to reduced function, meniscal lesions, and early joint degeneration. Preservation of a torn ACL using the Internal Brace technique might re-establish normal knee kinematics, avoid donor-site morbidity due to tendon harvesting, and potentially maintain proprioception of the knee.

METHODS

 Fifty subjects were recruited for this study between December 2015 and October 2016. Two groups of individuals who sustained a unilateral ACL rupture were included: those who underwent surgery with preservation of the injured ACL (Internal Brace technique; IB) and those who underwent ACL reconstruction using a hamstring tendon graft (all-inside technique; AI). Subjective self-administered scores were used: the German version of the IKDC Subjective Knee Form (International Knee Documentation Committee), the German version of the WOMAC (Western Ontario and McMaster Universities Arthritis Index), SF-36 (short form), the German version of the KOOS (Knee Osteoarthritis Outcome Score), and the German version of themodified Lysholm Score by Lysholm and Gillquist. Anterior tibial translation was assessed using the KT-1000 Arthrometer (KT-1000 Knee Ligament Arthrometer, MEDmetric Corp., San Diego, CA, USA). Magnetic resonance evaluation was performed in all cases.

RESULTS

 Twenty-three subjects (46 %) were men, and the mean age was 34.7 years. The objective IKDC scores were "normal" in 15 and 14 patients, "nearly normal" in 11 and 7 patients, and "abnormal" in 1 and 2 patients, in the IB and AI groups, respectively. KT-1000 assessment showed a sideto-side difference of more than 3 mm on maximum manual testing in 11 (44 %) and 6 subjects (28.6 %) in the IB and AI groups, respectively. In the postoperative MRI, 20 (74 %) and 22 subjects (96 %) in the IB and AI groups had an intact ACL. Anterior tibial translation was significantly higher in the IB group compared with the AI group in the manual maximum test.

CONCLUSIONS

 Preservation of the native ACL with the Internal Brace primary repair technique can achieve comparable results to ACL reconstruction using Hamstring autografts over a short term. Clinically relevant limitations such as a higher incidence of pathologic laxity, with patients more prone to pivot-shift phenomenon were observed during the study period.

Inter- and Intraobserver Reliability Between Orthopaedic Surgeons for Reparability of the Anterior Cruciate Ligament Using MRI

Background

Anterior cruciate ligament (ACL) reconstruction is the standard of care for patients after an ACL tear, as poor historical outcomes were observed after primary ACL repair. Certain subgroups of patients, however, have been shown to have outcomes equivalent to reconstruction after undergoing ACL repair and therefore may benefit from the potential advantages offered by avoiding reconstruction. It is important to accurately and consistently identify and indicate these candidates for ACL repair.

Purpose/Hypothesis

The purpose of this study was to determine the inter- and intraobserver reliability of magnetic resonance imaging (MRI) evaluation for the reparability of ACL tears and to identify imaging factors that may lead to surgeon uncertainty or disagreement in decision making. Our hypothesis was that the orthopaedic surgeons surveyed would not be able to reliably agree on the reparability of an ACL using MRI scans alone.

Study Design

Cohort study (diagnosis); Level of evidence, 3.

Methods

We administered 2 surveys to 6 fellowship-trained orthopaedic sports medicine surgeons. Each surgeon reviewed preoperative MRI scans for 20 patients and answered a series of questions, ultimately determining whether they would choose an ACL reconstruction or repair for the patient based on the imaging alone. The same survey was repeated 6 weeks later. Kappa values for inter- and intraobserver reliability of their decision making were then calculated.

Results

The average kappa for interobserver reliability in the 2 surveys was 0.22, and the average kappa for intraobserver reliability was 0.34. Interobserver reliability among the surgeons in this group was poor to moderate; intraobserver reliability was slightly better. The choice for ACL repair was significantly correlated with proximal tear locations (r = 0.854; P < .001), good-quality ACL tissue remnant (r = 0.929; P < .001), and how many surgeons believed that the tear only involved a single bundle (r = 0.590; P = .006).

Conclusion

The surgeons surveyed in this study did not consistently agree on candidates for ACL repair using MRI alone.

Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes

PURPOSE

Anterior cruciate ligament (ACL) surgery in the paediatric population has long been a challenge. Non-operative treatment will result in persistent instability which can lead to chondral and meniscal injuries. The results of primary open ACL repair are poor. Concerns of growth plate disturbance with transphyseal techniques and issues with relatively small-diameter grafts in Tanner 1 and 2 patients, which are inadequate, have contributed to these challenges. With advancing instrumentation, there is renewed interest in ACL repair. The minimally invasive approach of arthroscopic primary ACL repair retains the native ligament. The objective and subjective outcomes at 2 years are presented.

METHODS

Paediatric patients, less than 16 years of age, presenting acutely with complete proximal ACL ruptures underwent direct arthroscopic ACL repair, reinforced by a temporary internal brace, which was subsequently removed after 3 months. Patient-reported outcome measures including the Lysholm, Tegner and KOOS scores were collected at 6 months, 1 year and 2 years post-operatively.

RESULTS

Twenty patients (age 6-16) completed data at 2 years post-operatively. There were no failures, no complications and no growth disturbance out to 2 years. The 2-year postoperative outcomes; Lysholm 95 (90-100), Tegner 7 (6-10), KOOS-Child 96.5 (88.9-100) demonstrated statistically significant improvements following surgery (p < 0.001). Objective measurements with an accelerometer did not demonstrate any significant side-to-side difference.

CONCLUSION

ACL repair for proximal ACL tears in the paediatric population demonstrates the potential for excellent outcomes at short-term follow-up. This presents an attractive alternative to ACL reconstruction when an adequate ACL remnant permits direct repair. Our results demonstrate that paediatric ACL repair is safe and effective.

Higher Physiologic Platelet Counts in Whole Blood Are Not Associated With Improved ACL Cross-sectional Area or Signal Intensity 6 Months After Bridge-Enhanced ACL Repair

Background:

A bridge-enhanced anterior cruciate ligament (ACL) repair (BEAR) procedure places an extracellular matrix implant, combined with autologous whole blood, in the gap between the torn ends of the ligament at the time of suture repair to stimulate healing. Prior studies have suggested that white blood cell (WBC) and platelet concentrations significantly affect the healing of other musculoskeletal tissues.

Purpose/Hypothesis:

The purpose of this study was to determine whether concentrations of various blood cell types placed into a bridging extracellular matrix implant at the time of ACL repair would have a significant effect on the healing ligament cross-sectional area or tissue organization (as measured by signal intensity). We hypothesized that patients with higher physiologic platelet and lower WBC counts would have improved healing of the ACL on magnetic resonance imaging (MRI) (higher cross-sectional area and/or lower signal intensity) 6 months after surgery.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 61 patients underwent MRI at 6 months after bridge-enhanced ACL repair as part of the BEAR II trial. The normalized signal intensity and average cross-sectional area of the healing ligament were measured from a magnetic resonance stack obtained using a gradient echo sequence. The results were stratified by sex, and univariate and multivariate regression analyses determined significant correlations between blood cell concentrations on these 2 magnetic resonance parameters.

Results:

In unadjusted analyses, older age and male sex were associated with greater healing ligament cross-sectional area (P < .04) but not signal intensity (P > .15). Adjusted multivariable analyses indicated that in female patients, a higher monocyte concentration correlated with a higher ACL cross-sectional area (β = 1.01; P = .049). All other factors measured, including the physiologic concentration of platelets, neutrophils, lymphocytes, basophils, and immunoglobulin against bovine gelatin, were not significantly associated with either magnetic resonance parameter in either sex (P > .05 for all).

Conclusion:

Although older age, male sex, and monocyte concentration in female patients were associated with greater healing ligament cross-sectional area, signal intensity of the healing ligament was independent of these factors. Physiologic platelet concentration did not have any significant effect on cross-sectional area or signal intensity of the healing ACL at 6 months after bridge-enhanced ACL repair in this cohort. Given these findings, factors other than the physiologic platelet concentration and total WBC concentration may be more important in the rate and amount of ACL healing after bridge-enhanced ACL repair.

Bioaugmentation in the surgical treatment of anterior cruciate ligament injuries: A review of current concepts and emerging techniques

Injuries involving the anterior cruciate ligament are among the most common athletic injuries, and are the most common involving the knee. The anterior cruciate ligament is a key translational and rotational stabilizer of the knee joint during pivoting and cutting activities. Traditionally, surgical intervention in the form of anterior cruciate ligament reconstruction has been recommended for those who sustain an anterior cruciate ligament rupture and wish to remain active and return to sport. The intra-articular environment of the anterior cruciate ligament makes achieving successful healing following repair challenging. Historically, results following repair were poor, and anterior cruciate ligament reconstruction emerged as the gold-standard for treatment. While earlier literature reported high rates of return to play, the results of more recent studies with longer follow-up have suggested that anterior cruciate ligament reconstruction may not be as successful as once thought: fewer athletes are able to return to sport at their preinjury level, and many still go on to develop osteoarthritis of the knee at a relatively younger age. The four principles of tissue engineering (cells, growth factors, scaffolds, and mechanical stimuli) combined in various methods of bioaugmentation have been increasingly explored in an effort to improve outcomes following surgical treatment of anterior cruciate ligament injuries. Newer technologies have also led to the re-emergence of anterior cruciate ligament repair as an option for select patients. The different biological challenges associated with anterior cruciate ligament repair and reconstruction each present unique opportunities for targeted bioaugmentation strategies that may eventually lead to better outcomes with better return-to-play rates and fewer revisions.

Bridge-Enhanced Anterior Cruciate Ligament Repair Is Not Inferior to Autograft Anterior Cruciate Ligament Reconstruction at 2 Years: Results of a Prospective Randomized Clinical Trial

BACKGROUND

Preclinical studies suggest that for complete midsubstance anterior cruciate ligament (ACL) injuries, a suture repair of the ACL augmented with a protein implant placed in the gap between the torn ends (bridge-enhanced ACL repair [BEAR]) may be a viable alternative to ACL reconstruction (ACLR).

HYPOTHESIS

We hypothesized that patients treated with BEAR would have a noninferior patient-reported outcomes (International Knee Documentation Committee [IKDC] Subjective Score; prespecified noninferiority margin, -11.5 points) and instrumented anteroposterior (AP) knee laxity (prespecified noninferiority margin, +2-mm side-to-side difference) and superior muscle strength at 2 years after surgery when compared with patients who underwent ACLR with autograft.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

One hundred patients (median age, 17 years; median preoperative Marx activity score, 16) with complete midsubstance ACL injuries were enrolled and underwent surgery within 45 days of injury. Patients were randomly assigned to receive either BEAR (n = 65) or autograft ACLR (n = 35 [33 with quadrupled semitendinosus-gracilis and 2 with bone-patellar tendon-bone]). Outcomes-including the IKDC Subjective Score, the side-to-side difference in instrumented AP knee laxity, and muscle strength-were assessed at 2 years by an independent examiner blinded to the procedure. Patients were unblinded after their 2-year visit.

RESULTS

In total, 96% of the patients returned for 2-year follow-up. Noninferiority criteria were met for both the IKDC Subjective Score (BEAR, 88.9 points; ACLR, 84.8 points; mean difference, 4.1 points [95% CI, -1.5 to 9.7]) and the side-to-side difference in AP knee laxity (BEAR, 1.61 mm; ACLR, 1.77 mm; mean difference, -0.15 mm [95% CI, -1.48 to 1.17]). The BEAR group had a significantly higher mean hamstring muscle strength index than the ACLR group at 2 years (98.2% vs 63.2%; P < .001). In addition, 14% of the BEAR group and 6% of the ACLR group had a reinjury that required a second ipsilateral ACL surgical procedure (P = .32). Furthermore, the 8 patients who converted from BEAR to ACLR in the study period and returned for the 2-year postoperative visit had similar primary outcomes to patients who had a single ipsilateral ACL procedure.

CONCLUSION

BEAR resulted in noninferior patient-reported outcomes and AP knee laxity and superior hamstring muscle strength when compared with autograft ACLR at 2-year follow-up in a young and active cohort. These promising results suggest that longer-term studies of this technique are justified.

REGISTRATION

NCT02664545 (ClinicalTrials.gov identifier).

Cruciate ligament healing and injury prevention in the age of regenerative medicine and technostress: homeostasis revisited

PURPOSE

This clinical concepts paper discusses the essential elements of cruciate ligament recuperation, micro-trauma repair, and remodeling.

METHODS

Cruciate ligament mechanobiology and tissue heterogeneity, anatomy and vascularity, and synovial membrane and fluid functions are discussed in relationship to deficiency-induced inflammatory responses, nervous and immune system function, recuperation, repair and remodeling, and modern threats to homeostasis.

RESULTS

Cruciate ligament surgical procedures do not appreciate the vital linked functions of the central, peripheral, and autonomic nervous systems and immune system function on knee ligament injury recuperation, micro-trauma repair, and remodeling. Enhanced knowledge of these systems could provide innovative ways to decrease primary non-contact knee injury rates and improve outcomes following reconstruction or primary repair.

CONCLUSIONS

Restoration of knee joint homeostasis is essential to cruciate ligament recuperation, micro-trauma repair, and remodeling. The nervous and immune systems are intricately involved in this process. Varying combinations of high-intensity training, under-recovery, technostress, and environmental pollutants (including noise) regularly expose many athletically active individuals to factors that abrogate the environment needed for cruciate ligament recuperation, micro-trauma repair, and remodeling. Current sports training practice, lifestyle psychobehaviors, and environmental factors combine to increase both primary non-contact knee injury risk and the nervous and immune system dysregulation that lead to poor sleep, increased anxiety, and poorly regulated hormone and cytokine levels. These factors may create a worst-case scenario leading to poor ligament recuperation, micro-trauma repair, and remodeling. Early recognition and modification of these factors may decrease knee ligament injury rates and improve cruciate ligament repair or reconstruction outcomes.

LEVEL OF EVIDENCE

V.

Return to Sports after Anterior Cruciate Ligament Injury: a Matched-Pair Analysis of Repair with Internal Brace and Reconstruction Using Hamstring or Quadriceps Tendons

PURPOSE

 The purpose of this study was to evaluate sports activity before anterior cruciate ligament (ACL) injury and after surgical treatment of ACL rupture comparing ACL repair with an Internal Brace to ACL reconstruction using either a hamstring (HT) or quadriceps tendon (QT) autograft.

METHODS

 Between 12/2015 and 10/2016, we recruited 69 patients with a mean age of 33.4 years for a matched-pair analysis. Twenty-four patients who underwent Internal Brace reconstruction were matched according to age (± 5 years), gender, Tegner activity scale (± 1), BMI (± 1) and concomitant injuries with 25 patients who had undergone HT reconstruction and 20 patients who had undergone QT reconstruction. The minimum follow-up was 12 months.

RESULTS

 Overall, the return-to-sports rate was 91.3 %. There were no significant differences (p ≥ 0.05) in the number of sports disciplines and the time before return to sports within or among the groups. Overall and within the groups, the level of sports participation did not change significantly (p ≥ 0.05) postoperatively. The patients' sense of well-being was excellent after either ACL repair with an Internal Brace or ACL reconstruction with autologous HT or QT.

CONCLUSION

 At short-term follow-up, ACL repair using an Internal Brace enables sports activity and provides a sense of well-being similar to that of classic ACL reconstruction using hamstring or quadriceps tendon autografts in a selected patient population.

LEVEL OF EVIDENCE

Level III Retrospective comparative study.

Primary Anterior Cruciate Ligament Repair With Hyaluronic Scaffold and Autogenous Bone Marrow Aspirate Augmentation in Adolescents With Open Physes

It is well known that the anterior cruciate ligament (ACL) is the main stabilizer to the anterior tibial translation in the knee. The current gold standard of treatment for such lesions is ACL reconstruction. However, there are notable disadvantages to ACL reconstruction that include loss of proprioception, donor site morbidity, incomplete return to high-demand sports, and the inability to restore normal kinematics of the knee joint. Additionally, in adolescents who have open physes, there is a risk of potential iatrogenic growth plate injury. Tibial-sided soft-tissue avulsion is a rare subtype of ACL injuries. This Technical Note presents a method for primary anatomic ACL repair with a bioabsorbable scaffold and bone marrow concentrate augmentation for an acute distal ACL injury. Our technique is an alternative to reconstruction as it allows the preservation of the native insertion site and has the potential to reduce the risk of posttraumatic osteoarthritis.

Cartilage Damage Is Related to ACL Stiffness in a Porcine Model of ACL Repair

Inferior anterior cruciate ligament (ACL) structural properties may inadequately restrain tibiofemoral joint motion following surgery, contributing to the increased risk of post-traumatic osteoarthritis. Using both a direct measure of ACL linear stiffness and an in vivo magnetic resonance imaging (MRI) T₂ *-based prediction model, we hypothesized that cartilage damage and ACL stiffness would increase over time, and that an inverse relationship between cartilage damage and ACL stiffness would emerge at a later stage of healing. After either 6, 12, or 24 weeks (w) of healing after ACL repair, ACL linear stiffness was determined from the force-displacement relationship during tensile testing ex vivo and predicted in vivo from the MRI T₂ *-based multiple linear regression model in 24 Yucatan minipigs. Tibiofemoral cartilage was graded postmortem. There was no relationship between cartilage damage and ACL stiffness at 6 w (R²  = 0.04; p = 0.65), 12 w (R²  = 0.02; p = 0.77), or when the data from all animals were pooled (R²  = 0.02; p = 0.47). A significant inverse relationship between cartilage damage and ACL stiffness based on both ex vivo measurement (R²  = 0.90; p < 0.001) and in vivo MRI prediction (R²  = 0.78; p = 0.004) of ACL stiffness emerged at 24 w. This result suggests that 90% of the variability in gross cartilage changes is associated with the repaired ACL linear stiffness at 6 months of healing. Clinical Significance: Techniques that provide a higher stiffness to the repaired ACL may be required to mitigate the post-traumatic osteoarthritis commonly seen after ACL injury, and MRI T₂ * can be used as a noninvasive estimation of ligament stiffness. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2249-2257, 2019.

The detached stump of the torn anterior cruciate ligament adheres to the femoral notch wall and then to the posterior cruciate ligament within 6 months from injury

PURPOSE

To evaluate the progressive changes in the morphology of traumatic ruptures of the anterior cruciate ligament (ACL) over time. A secondary objective was evaluating their correlation with meniscal tears or chondral lesions.

METHODS

The study included one hundred and one patients who underwent ACL reconstruction surgery of the knee after a definite date of injury. The torn ACL remnant morphological pattern was assessed and classified during arthroscopy. A correlation analysis was performed between the pathological features of the remnant and the time length from injury. In addition, correlation between ACL remnant subtypes and meniscal tears or chondral lesions was evaluated.

RESULTS

At surgery there were four distinct ACL tear morphological patterns that were correlated to the time span from injury (r = 0.61, p < 0.001) and ended with scarring of the femoral remnant to the posterior cruciate ligament. The early pattern was noticed within median time of 2.6 months from injury and appeared as a separate stump with no scar tissue. The following two patterns appeared within 6 months from injury and were characterized by adhesion of scar tissue to different locations in the femoral notch. The last morphological pattern appeared as adherence of the ACL stump to the posterior cruciate ligament. This pattern was seen in some patients within 6 months from injury but was the dominant pattern later on and was also correlated with meniscal tears.

CONCLUSIONS

During the first 3 months from injury the gross morphological features of the torn ACL remnant showed no scar. This phase was followed by scarring of the femoral remnant at first to the femoral notch, and eventually to the posterior cruciate ligament within 6 months from injury and later on. Therefore, further research on the healing potential of the human ACL stump and its biological environment should be focused on the first 3 months from injury.

STUDY DESIGN

Case series; Level of evidence, 4.

Evaluation of a magnesium ring device for mechanical augmentation of a ruptured ACL: Finite element analysis

BACKGROUND

Recently, a ring device was used for mechanical augmentation to aid the healing of ACL. In-vivo study using goat showed improved joint stability after ring repair in comparison to using biological augmentation alone. Objective of this study was to quantify the load and stress levels in the ACL and its femoral insertion site following ring repair.

METHODS

A three dimensional finite element model of a goat stifle joint was developed to find the load and stress level in the ACL and at its femoral insertion site following ring repair.

FINDINGS

Ring repair led to approximately a 50% reduction in anterior-posterior tibial translation over the model with a deficient ACL: 5.2 mm vs 10.6 mm, 4.4 mm vs 9.0 mm, and 2.9 mm vs 5.2 mm at joint flexion angles of 37°, 60° and 90° respectively. After ring repair, the in situ force in the ACL was restored to be nearly 60% of the intact ACL. The maximum Von Mises stress at the femoral insertion site was up to 71% of those for the intact ACL.

INTERPRETATION

This study offers new knowledge on the function of a ring device to mechanically augment ACL repair in order to improve its healing. Quantitative data on loading levels in the repaired ACL and its insertion site that led to its healing could be used as basis for developing novel devices to mechanically augment the healing of ACL in humans.

Predictors of Healing Ligament Size and Magnetic Resonance Signal Intensity at 6 Months After Bridge-Enhanced Anterior Cruciate Ligament Repair

BACKGROUND

Primary repair of the anterior cruciate ligament (ACL) augmented with a tissue engineered scaffold to facilitate ligament healing is a technique under development for patients with ACL injuries. The size (the amount of tissue) and signal intensity (the quality of tissue) of the healing ligament as visualized on magnetic resonance imaging (MRI) have been shown to be related to its strength in large animal models.

HYPOTHESIS

Both modifiable and nonmodifiable risk factors could influence the size and signal intensity of the repaired ligament in patients at 6 months after surgery.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

62 patients (mean age, 19.4 years; range, 14-35 years) underwent MRI of the knee 6 months after ACL repair augmented with an extracellular matrix scaffold. The signal intensity (normalized to cortical bone) and average cross-sectional area of the healing ligament were measured from the MRI stack obtained by use of a gradient echo sequence. Associations between these 2 measures and patient characteristics, which included demographic, clinical, and anatomic features, were determined by use of multivariable regression analysis.

RESULTS

A larger cross-sectional area of the repaired ligament at 6 months was associated with male sex, older age, and the performance of a larger notchplasty ( P < .05 for all associations). A lower signal intensity at 6 months, indicating greater similarity to normal ligament, was associated with a smaller tibial slope and greater side-to-side difference in quadriceps strength 3 months after surgery. Other factors, including preoperative body mass index, mechanism of injury, tibial stump length, and Marx activity score, were not significantly associated with either MRI parameter at 6 months.

CONCLUSION

Modifiable factors, including surgical notchplasty and slower recovery of quadriceps strength at 3 months, were associated with a larger cross-sectional area and improved signal intensity of the healing ACL after bridge-enhanced ACL repair in this preliminary study. Further studies to determine the optimal size of the notchplasty and the most effective postoperative rehabilitation strategy after ACL repair augmented by a scaffold are justified.

REGISTRATION

NCT02664545 (ClinicalTrials.gov identifier).

Bridge-Enhanced Anterior Cruciate Ligament Repair: Two-Year Results of a First-in-Human Study

Background

Bridge-enhanced anterior cruciate ligament repair (BEAR) combines suture repair of the anterior cruciate ligament (ACL) with a specific extracellular matrix scaffold (the BEAR scaffold) that is placed in the gap between the torn ends of the ACL to facilitate ligament healing.

Purpose/Hypothesis

The purpose of this study was to report the 12- and 24-month outcomes of patients who underwent the BEAR procedure compared with a nonrandomized concurrent control group who underwent ACL reconstruction (ACLR) with an autograft. We hypothesized that the BEAR group would have physical examination findings, patient-reported outcomes, and adverse events that were similar to those of the ACLR group.

Study Design

Cohort study; Level of evidence, 2.

Methods

Ten patients underwent BEAR, and 10 underwent ACLR with a 4-stranded hamstring autograft. At 24 months, 9 of the 10 BEAR patients and 7 of the 10 ACLR patients completed a study visit. Outcomes reported included International Knee Documentation Committee (IKDC) subjective and objective results, knee anteroposterior (AP) laxity findings via an arthrometer, and functional outcomes.

Results

There were no graft or repair failures in the first 24 months after surgery. The IKDC subjective scores in both groups improved significantly from baseline (P < .0001) at 12 and 24 months, to 84.6 ± 17.2 in the ACLR group and to 91.7 ± 11.7 in the BEAR group. An IKDC objective grade of A (normal) was found in 44% of patients in the BEAR group and in 29% of patients in the ACLR group at 24 months; no patients in either group had C (abnormal) or D (severely abnormal) grades. Arthrometer testing demonstrated mean side-to-side differences in AP laxity that were similar in the 2 groups at 24 months (BEAR, 1.94 ± 2.08 mm; ACLR, 3.14 ± 2.66 mm). Functional hop testing results were similar in the 2 groups at 12 and 24 months after surgery. Hamstring strength indices were significantly higher in the BEAR group compared with the ACLR group (P = .0001).

Conclusion

In this small, first-in-human study, BEAR produced similar outcomes to ACLR with a hamstring autograft. BEAR may result in knee stability and patient-reported outcomes at 2 years sufficient to warrant longer term studies of efficacy in larger groups of patients.

ACL Repair With Suture Ligament Augmentation Is Associated With a High Failure Rate Among Adolescent Patients

BACKGROUND

The anterior cruciate ligament (ACL) repair technique avoids graft harvest and therefore the risk of donor site morbidity. However, early failure rates after ACL repair with suture ligament augmentation (SLA) remain high.

PURPOSE

To compare surgical failure, functional outcomes, return to sport, and joint laxity between adolescents who underwent ACL repair with SLA and those who underwent ACL reconstruction with quadriceps tendon-patellar bone autograft (QPA).

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Adolescent patients (7-18 years old) underwent ACL repair with SLA or ACL reconstruction with QPA. The authors collected data from those who had postoperative information pertaining to repaired ligament or graft failure, range of motion, complications, and return to sport at a minimum of 6 months after surgery. Participants were contacted after surgery to complete study questionnaires.

RESULTS

The cohort included 22 consecutive patients in the SLA group and 157 in the QPA group. The median duration of follow-up was 2.7 years (interquartile range, 2.0-3.6 years) in the QPA group and 3.2 years (2.2-3.4 years) in the SLA group. After adjustment for sex, age, body mass index, and time from injury to surgery, the hazard of graft failure in the SLA group was 10.66 times (95% CI, 3.41-32.92; P < .0001) that of the QPA group. The cumulative incidence of graft failure in the first 3 years after surgery was 48.8% (95% CI, 28.9%-73.1%) in the SLA group, as opposed to 4.7% (2.1%-10.3%) in the QPA group. There was no difference in return to sport between the groups. Among individuals who did not rerupture their ACL, International Knee Documentation Committee and Lysholm scores were comparable between the groups, as well as range of motion.

CONCLUSION

The risk of failure was significantly increased in the SLA group relative to the QPA group. The high risk of failure for the SLA group in this short-term follow-up should be considered when selecting the treatment for adolescent patients with an ACL injury.

Acute Anterior Cruciate Ligament Rupture: Repair or Reconstruction? Two-Year Results of a Randomized Controlled Clinical Trial

BACKGROUND

Contemporary anterior cruciate ligament (ACL) suture repair techniques have been subject to renewed interest in recent years. Although several clinical studies have yielded good short-term results, high-quality evidence is lacking in regard to the effectiveness of this treatment compared with ACL reconstruction.

HYPOTHESIS

Dynamic augmented ACL suture repair is at least as effective as anatomic single-bundle ACL reconstruction for the treatment of acute ACL rupture in terms of patient self-reported outcomes at 2 years postoperatively.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

After stratification and randomization, 48 patients underwent either dynamic augmented ACL suture repair or ACL reconstruction with a single-bundle, all-inside, semitendinosus technique. The International Knee Documentation Committee (IKDC) subjective score at 2 years postoperatively was the primary outcome measure. Patient-reported outcomes (IKDC subjective score, Knee injury and Osteoarthritis Outcome Score, Tegner score, visual analog scale for satisfaction), clinical outcomes (IKDC physical examination score, leg symmetry index for the quadriceps, hamstrings strength, and jump test battery), and radiological outcomes as well as adverse events including reruptures were recorded. Analyses were based on an intention-to-treat principle.

RESULTS

The lower limit for the median IKDC subjective score of the repair group (86.2) fell within the prespecified noninferiority margin, confirming noninferiority of dynamic augmented ACL suture repair compared with ACL reconstruction. No statistical difference was found between groups for median IKDC subjective score (repair, 95.4; reconstruction, 94.3). Overall, 2 reruptures (8.7%) occurred in the dynamic ACL suture repair group and 4 reruptures (19.0%) in the ACL reconstruction group; further, 5 repeat surgeries-other than for revision ACL surgery-took place in 4 patients from the dynamic ACL suture repair group (20.8%) and in 3 patients from the ACL reconstruction group (14.3%).

CONCLUSION

Dynamic augmented ACL suture repair is not inferior to ACL reconstruction in terms of subjective patient-reported outcomes as measured with the IKDC subjective score 2 years postoperatively. However, for reasons other than revision ACL surgery due to rerupture, a higher number of related adverse events leading to repeat surgery were seen in the dynamic augmented ACL suture repair group within 2 years postoperatively.

CLINICAL RELEVANCE

Dynamic augmented ACL suture repair might be a viable treatment option for patients with an acute ACL rupture.

REGISTRATION

NCT02310854 ( ClinicalTrials.gov identifier).

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.

Emerging Orthobiologic Techniques and the Future

The future of orthopedic surgery appears to be intimately associated with the development of orthobiologics to facilitate healing and the treatment of multiple disease processes. The orthopedic community should understand developmental processes to ensure that products are adequately studied and the effects are fully known before widespread implementation in the clinical setting. Technologies that embrace this paradigm will impact the field the most.

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.

Dynamic augmentation restores anterior tibial translation in ACL suture repair: a biomechanical comparison of non-, static and dynamic augmentation techniques

PURPOSE

There is a lack of objective evidence investigating how previous non-augmented ACL suture repair techniques and contemporary augmentation techniques in ACL suture repair restrain anterior tibial translation (ATT) across the arc of flexion, and after cyclic loading of the knee. The purpose of this work was to test the null hypotheses that there would be no statistically significant difference in ATT after non-, static- and dynamic-augmented ACL suture repair, and they will not restore ATT to normal values across the arc of flexion of the knee after cyclic loading.

METHODS

Eleven human cadaveric knees were mounted in a test rig, and knee kinematics from 0° to 90° of flexion were recorded by use of an optical tracking system. Measurements were recorded without load and with 89-N tibial anterior force. The knees were tested in the following states: ACL-intact, ACL-deficient, non-augmented suture repair, static tape augmentation and dynamic augmentation after 10 and 300 loading cycles.

RESULTS

Only static tape augmentation and dynamic augmentation restored ATT to values similar to the ACL-intact state directly postoperation, and maintained this after cyclic loading. However, contrary to dynamic augmentation, the ATT after static tape augmentation failed to remain statistically less than for the ACL-deficient state after cyclic loading. Moreover, after cyclic loading, ATT was significantly less with dynamic augmentation when compared to static tape augmentation.

CONCLUSION

In contrast to non-augmented ACL suture repair and static tape augmentation, only dynamic augmentation resulted in restoration of ATT values similar to the ACL-intact knee and decreased ATT values when compared to the ACL-deficient knee immediately post-operation and also after cyclic loading, across the arc of flexion, thus allowing the null hypotheses to be rejected. This may assist healing of the ruptured ACL. Therefore, this study would support further clinical evaluation of dynamic augmentation of ACL repair.

Should orthopedic surgeons consider reducing the negative effects of Outerbridge grade 2 patellofemoral chondral lesion on early postoperative recovery during anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to comparatively evaluate the effectiveness of intra-articular PRP and HA injections applied as the treatment of Outerbridge grade 2 chondral lesions in patellofemoral joint during arthroscopic ACL reconstruction.

METHODS

The clinical and radiographic data of 61 patients between 18 and 45 years of age were evaluated. The patients were separated into three groups. Hyaluronic acid injection was applied in 22 knees (Group 1), PRP injection was applied in 18 knees (Group 2), and 21 knees did not have any specific treatment except ACL reconstruction (Group 3). All patients were followed clinically at least for 12 months. Clinical examination of the operated knee, visual analogue scale (VAS) score, Lysholm knee score, and Tegner activity scale were the outcome measures. Routine X-ray and MRI were also performed for all patients at 12-month postoperative follow-up visit.

RESULTS

Although the mean VAS and Lysholm scores at 3-month follow-up were better in Group 1 and 2 than Group 3, the efficacy of intra-articular PRP on healing process regarding progression of the mean VAS and Lysholm scores through 6- and 12-month follow-ups was significantly better and longer than HA. No statistically significant differences were detected according to Tegner activity scale between the groups at 3 and 6 months; however, Group 2 had better activity level than both Group 1 (p < 0.001) and 3 (p < 0.001) at the end of 12 months after surgery.

CONCLUSION

Intra-articular PRP injection applied as the treatment of concomitant Outerbridge grade 2 chondral lesion in patellofemoral joint during ACL reconstruction revealed better and durable clinical outcomes via decreasing the potentially negative effects of chondral pathology on postoperative healing with respect to HA injection.

LEVEL OF EVIDENCE

III-retrospective comparative study.

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.

Magnetic resonance measurements of tissue quantity and quality using T2 * relaxometry predict temporal changes in the biomechanical properties of the healing ACL

The purpose of this study was to develop a magnetic resonance T2 * relaxometry-based multiple linear regression model to predict the structural properties of the healing anterior cruciate ligament (ACL) over a 24-week healing period following ACL repair in Yucatan minipigs. Two hypotheses were tested: (i) that a regression model based on ACL sub-volumes containing short and long T2 * relaxation times would outperform a competing model based on sub-volumes of short T2 * relaxation times only; and (ii) that an optimized regression model would be capable of predicting ACL structural properties between 6 and 24 weeks post-repair. ACLs were imaged in 24 minipigs (8/group) at either 6, 12, or 24 weeks after ACL repair. The structural properties of the ACLs were determined from tensile failure tests. Four multiple linear regression models of increasing complexity were fitted to the data. Akaike Information Criterion values and Bland-Altman tests were used to compare model performance and to test the hypotheses. The structural properties predicted from the multiple linear regression model that was based on the change in ACL sub-volumes of both the short and long T2 * relaxation times over the healing period were in closest agreement to the measured values, suggesting that the amounts of both organized and disorganized collagen, and the change in these quantities over time, are required to predict the structural properties of healing ACLs accurately.

CLINICAL SIGNIFICANCE

our time-specific, T2 *-based regression model may allow us to estimate the structural properties of ACL repairs in vivo longitudinally. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1701-1709, 2018.

Bench-to-bedside: Bridge-enhanced anterior cruciate ligament repair

Anterior cruciate ligament (ACL) injuries are one of the most well-known orthopaedic injuries and are treated with one of the most common orthopaedic procedures performed in the United States. This surgical procedure, ACL reconstruction, is successful at restoring the gross stability of the knee. However, the outcomes of ACL reconstruction can be limited by short and long-term complications, including muscle weakness, graft rupture, and premature osteoarthritis. Thus, new methods of treating this injury are being explored. This review details the pathway of how a tissue engineering strategy can be used to improve the healing of the ACL in preclinical studies and then translated to patients in an FDA-approved clinical study. This review paper will outline the clinical importance of ACL injuries, history of primary repair, the pathology behind failure of the ACL to heal, pre-clinical studies, the FDA approval process for a high risk medical device, and the preliminary results from a first-in-human study. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2606-2612, 2017.

A new simulator model for knee arthroscopy procedures

PURPOSE

Arthroscopy is currently the "gold standard" for various surgeries performed on the knee joint. Therefore, surgeons wishing to operate in this professional field should be able to perform this technique. Arthroscopic training, an experimental laboratory, is important for the surgeons' training, enabling them to increase their skills with the specific instruments and to become familiar with the operating techniques. The aim of this study was to present a new surgical simulator for training in arthroscopic procedures of the knee.

METHODS

The Kneetrainer 1 is a simulator consisting of a type of thermo-retractile, thermo-sensitive synthetic rubber that has texture, colour, consistency, and mechanical resistance that mimic many human tissues. Nine simulators were used, operated by seventeen expert Brazilian surgeons in knee surgery. The surgeons performed arthroscopy, meniscectomy, and reconstruction of the anterior cruciate ligament (ACL), responded to an electronic questionnaire with several variables, and gave an overall score on the ability of the device to perform realistic simulation for the above procedures.

RESULTS

The ability to perform the procedures of meniscectomy and ACL reconstruction was considered adequate by 82 and 100 % of the specialists, respectively. The overall scores for the ability to perform realistic simulation for the procedures meniscectomy and reconstruction of the anterior cruciate ligament by arthroscopy were 64.7 and 82.4 %, respectively. The simulator was therefore considered suitable for practical application with novice surgeons.

CONCLUSION

The Kneetrainer 1 simulator was assessed as an effective tool for recreating accurate arthroscopic knee procedures. In addition, the simulator may be effective as a means of honing the skills of novice surgeons. Future investigations should be performed to validate the reliability of the simulator.

LEVEL OF EVIDENCE

IV.

Tendons and Ligaments: Connecting Developmental Biology to Musculoskeletal Disease Pathogenesis

Tendons and ligaments provide connections between muscle and bone or bone and bone to enable locomotion. Damage to tendons and ligaments caused by acute or chronic injury or associated with aging and arthritis is a prevalent cause of disability. Improvements in approaches for the treatment of these conditions depend on a better understanding of tendon and ligament development, cell biology, and pathophysiology. This review focuses on recent advances in the discovery of transcription factors that control ligament and tendon cell differentiation, how cell and extracellular matrix homeostasis are altered in disease, and how this new insight can lead to novel therapeutic approaches. © 2017 American Society for Bone and Mineral Research.

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

BACKGROUND

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

HYPOTHESES

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

STUDY DESIGN

Controlled laboratory study.

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

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.

Biologic Treatments for Sports Injuries II Think Tank-Current Concepts, Future Research, and Barriers to Advancement, Part 1: Biologics Overview, Ligament Injury, Tendinopathy

Biologic therapies, including stem cells, platelet-rich plasma, growth factors, and other biologically active adjuncts, have recently received increased attention in the basic science and clinical literature. At the 2015 AOSSM Biologics II Think Tank held in Colorado Springs, Colorado, a group of orthopaedic surgeons, basic scientists, veterinarians, and other investigators gathered to review the state of the science for biologics and barriers to implementation of biologics for the treatment of sports medicine injuries. This series of current concepts reviews reports the summary of the scientific presentations, roundtable discussions, and recommendations from this think tank.

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.

The Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR) Procedure: An Early Feasibility Cohort Study

Background:

This study assessed the safety of the newly developed bridge-enhanced anterior cruciate ligament (ACL) repair (BEAR), which involves suture repair of the ligament combined with a bioactive scaffold to bridge the gap between the torn ligament ends. As the intra-articular environment is complex in its response to implanted materials, this study was designed to determine whether there would be a significant rate of adverse reaction to the implanted scaffold.

Hypothesis:

The primary hypothesis was that the implanted scaffold would not result in a deep joint infection (arthrocentesis with positive culture) or significant inflammation (clinical symptoms justifying arthrocentesis but negative culture). The secondary hypotheses were that patients treated with BEAR would have early postoperative outcomes that were similar to patients treated with ACL reconstruction with an autologous hamstring graft.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 20 patients were enrolled in this nonrandomized, first-in-human study. Ten patients received BEAR treatment and 10 received a hamstring autograft ACL reconstruction. The BEAR procedure was performed by augmenting a suture repair with a proprietary scaffold, the BEAR scaffold, placed in between the torn ends of the ACL at the time of suture repair. The BEAR scaffold is to our knowledge the only device that fills the gap between the torn ligament ends to have current Investigational Device Exemption approval from the Food and Drug Administration. Ten milliliters of autologous whole blood were added to the scaffold prior to wound closure. Outcomes were assessed at 3 months postoperatively. The outcomes measures included postoperative pain, muscle atrophy, loss of joint range of motion, and implant failure (designated by an International Knee Documentation Committee grade C or D Lachman test and/or an absence of continuous ACL tissue on magnetic resonance images).

Results:

There were no joint infections or signs of significant inflammation in either group. There were no differences between groups in effusion or pain, and no failures by Lachman examination criteria (BEAR, 8 grade A and 2 grade B; ACL reconstruction, 10 grade A). Magnetic resonance images from all of the BEAR and ACL-reconstructed patients demonstrated a continuous ACL or intact graft. In addition, hamstring strength at 3 months was significantly better in the BEAR group than in the hamstring autograft group (mean ± SD: 77.9% ± 14.6% vs 55.9% ± 7.8% of the contralateral side; P < .001).

Conclusion:

The results of this study suggest that the BEAR procedure may have a rate of adverse reactions low enough to warrant a study of efficacy in a larger group of patients.

Magnesium ring device to restore function of a transected anterior cruciate ligament in the goat stifle joint

A bioresorbable, mono-crystalline magnesium (Mg) ring device and suture implantation technique were designed to connect the ends of a transected anterior cruciate ligament (ACL) to restabilize the knee and load the ACL to prevent disuse atrophy of its insertion sites and facilitate its healing. To test its application, cadaveric goat stifle joints were evaluated using a robotic/universal force-moment sensor testing system in three states: Intact, ACL-deficient, and after Mg ring repair, at 30°, 60°, and 90° of joint flexion. Under a 67-N anterior tibial load simulating that used in clinical examinations, the corresponding anterior tibial translation (ATT) and in-situ forces in the ACL and medial meniscus for 0 and 100 N of axial compression were obtained and compared with a control group treated with suture repair. In all cases, Mg ring repair reduced the ATT by over 50% compared to the ACL-deficient joint, and in-situ forces in the ACL and medial meniscus were restored to near normal levels, showing significant improvement over suture repair. These findings suggest that Mg ring repair could successfully stabilize the joint and load the ACL immediately after surgery, laying the framework for future in vivo studies to assess its utility for ACL healing. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2001-2008, 2016.