Biology of autograft and allograft healing in anterior cruciate ligament reconstruction

Biologic Impact of Anterior Cruciate Ligament Injury and Reconstruction

Surgical intervention after anterior cruciate ligament (ACL) tears is typically required because of the limited healing capacity of the ACL. However, mechanical factors and the inflammatory response triggered by the injury and surgery can impact patient outcomes. This review explores key aspects of ACL injury and reconstruction biology, including the inflammatory response, limited spontaneous healing, secondary inflammation after reconstruction, and graft healing processes. Understanding these biologic mechanisms is crucial for developing new treatment strategies and enhancing patient well-being. By shedding light on these aspects, clinicians and researchers can work toward improving quality of life for individuals affected by ACL tears.

Hamstring Anterior Cruciate Ligament Autograft Contributes to a Delayed Symptomatic Cyclops Lesion: A Case Report

Cyclops lesions are characterized as fibroid nodules with granulation tissue that looks similar to a cyclops eye during arthroscopy. These are rare postoperative complications following anterior cruciate ligament reconstruction (ACLR), presenting typically within six months of their reconstruction. This case report presents a 21-year-old male, three years following hamstring autograft ACLR, with a symptomatic cyclops lesion. Contrary to the reported literature, this delayed presentation showed a painful flexion contracture of the knee and intraoperative findings consistent with a cyclops lesion. The treatment consisted of surgical debridement and notchplasty with subsequent posterior medial and lateral meniscal horn repairs. This case report presents a lesson to indicate that cyclops lesions can occur in a delayed setting following ACLR and to show a technique for successful surgical management of the lesion.

Autograft Demonstrates Superior Outcomes for Revision Anterior Cruciate Ligament Reconstruction When Compared With Allograft: A Systematic Review

BACKGROUND

Multiple studies have compared outcomes among patients undergoing revision anterior cruciate ligament reconstruction (ACLR) with autograft versus allograft, but these data are inconsistently reported and long-term outcomes depending on graft type are yet to be determined.

PURPOSE

To perform a systematic review of clinical outcomes after revision ACLR (rACLR) with autograft versus allograft.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review of the literature was performed by searching PubMed, the Cochrane Library, and Embase to identify studies that compared the outcomes of patients undergoing rACLR with autograft versus allograft. The search phrase used was autograft allograft revision anterior cruciate ligament reconstruction. Graft rerupture rates, return-to-sports rates, anteroposterior laxity, and patient-reported outcome scores (subjective International Knee Documentation Committee, Tegner, Lysholm, and Knee injury and Osteoarthritis Outcome Score) were evaluated.

RESULTS

Eleven studies met inclusion criteria, including 3011 patients undergoing rACLR with autograft (mean age, 28.9 years) and 1238 patients undergoing rACLR with allograft (mean age, 28.0 years). Mean follow-up was 57.3 months. The most common autograft and allograft types were bone-patellar tendon-bone grafts. Overall, 6.2% of patients undergoing rACLR experienced graft retear, including 4.7% in the autograft group and 10.2% in the allograft group (P < .0001). Among studies that reported return-to-sports rates, 66.2% of patients with an autograft returned to sports as opposed to 45.3% of patients with an allograft (P = .01). Two studies found significantly greater postoperative knee laxity in the allograft group as compared with the autograft group (P < .05). Among all patient-reported outcomes, 1 study found 1 significant difference between groups: patients with an autograft had a significantly higher postoperative Lysholm score when compared with patients with an allograft.

CONCLUSION

Patients undergoing revision ACLR with an autograft can be expected to experience lower rates of graft retear, higher rates of return to sports, and less postoperative anteroposterior knee laxity when compared with patients undergoing revision ACLR with an allograft.

Functional Outcomes in Anterior Cruciate Ligament (ACL) Reconstruction: A Nine-Month Follow-up Study Using Lysholm Score in a Rural Tertiary Care Center in India

Introduction The knee joint, an extraordinary feat of biomechanics, is prone to injuries, with the anterior cruciate ligament (ACL) often being a common victim. The intricate coordination of joint movements relies heavily on the ACL's screw-home mechanism, a crucial element for synchronizing knee movement with neighboring joints. Despite its indispensable role, the ACL is susceptible to injury, necessitating surgical intervention. While many patients experience positive outcomes following ACL reconstruction surgeries, a significant proportion face the challenge of procedure failure. The key to success lies in the healing process within the tibial and femoral bone tunnels. The post-ACL reconstruction phase introduces its own set of challenges, particularly in the context of returning to sports (RTS), underscoring the importance of reinstating neuromuscular and motor function. The trajectory of rehabilitation is influenced by factors such as graft healing, patient age, gender, pain levels, and concurrent injuries. Materials and methods This prospective observational study spanned 2.5 years, enrolling 71 patients with diagnosed ACL injuries. Arthroscopic reconstruction utilized hamstring autografts and peroneus longus autografts. A nine-month post-surgery follow-up employed the Lysholm scoring system for comprehensive evaluations. Results Over 2.5 years, 87.3% of male and 12.6% of female participants underwent arthroscopic reconstruction. Lysholm scores revealed 28.1% excellent, 45.0% good, and 26.7% fair outcomes, with no participants in the unsatisfactory range. Lysholm scores demonstrated positive outcomes, indicating the efficacy of arthroscopic reconstruction in enhancing knee function. Findings align with existing literature, emphasizing positive results from ACL reconstruction techniques and specific implants. Comparisons with related studies highlight challenges in standardized return-to-sport guidelines and underscore the need for outcome measure standardization. Conclusion The study contributes nuanced insights into ACL reconstruction outcomes, emphasizing positive functional recovery trends at the nine-month follow-up. Lysholm scores indicate favorable outcomes, supporting the procedure's effectiveness. Consideration of specific implants adds practical value. Despite limitations, this study enriches ACL reconstruction research, promoting advancements in patient care and outcomes. Ongoing research with extended follow-ups and larger cohorts will enhance understanding and refine ACL reconstruction strategies.

Short-Term Evaluation of Bone-ACL-Bone Complex Allograft in ACL Reconstruction in a Rabbit Model

The study is to evaluate incorporation of a bone-anterior cruciate ligament-bone (B-ACL-B) allograft in anterior cruciate ligament (ACL) reconstruction in a rabbit model. A total of 61 New Zealand white rabbits were used, with 23 donor rabbits for harvesting B-ACL-B allografts and 38 recipient rabbits undergoing unilateral ACL reconstruction with B-ACL-B allograft. Animals were euthanized for biomechanical testing, micro-computed tomography examination, histological analysis, multi-photon microscopy and transmission electron microscopy testing at 2, 4 and 8 weeks after surgery. Gross inspection and radiographs confirmed the intact ACL allograft in the proper anatomic position. Progressive healing occurred between the bone block and the bone tunnel as demonstrated by a gradual increase in average bone volume fraction and total mineral density at 4 and 8 weeks. Histological analysis showed new bone formation at the bone block-tunnel interface, with maintenance of the native ACL enthesis. Ultrastructural analysis demonstrated the maintenance of overall collagen matrix alignment, while there was repopulation with smaller diameter collagen fibrils. There was no significant difference between 4 and 8 weeks in mean failure force (p = 0.39) or stiffness (p = 0.15) for the B-ACL-B allografts. This study demonstrates the restoration of the normal anatomy of the ACL and progressive graft incorporation and remodeling using a B-ACL-B allograft for ACL reconstruction in the rabbit knee.

Nanofibrous scaffolds for the healing of the fibrocartilaginous enthesis: advances and prospects

With the current developmental advancements in nanotechnology, nanofibrous scaffolds are being widely used. The healing of fibrocartilaginous enthesis is a slow and complex process, and while existing treatments have a certain effect on promoting their healing, these are associated with some limitations. The nanofibrous scaffold has the advantages of easy preparation, wide source of raw materials, easy adjustment, easy modification, can mimic the natural structure and morphology of the fibrocartilaginous enthesis, and has good biocompatibility, which can compensate for existing treatments and be combined with them to promote the repair of fibrocartilaginous enthesis. The nanofibrous scaffold can promote the healing of fibrocartilaginous enthesis by controlling the morphology and ensuring controlled drug release. Hence, the use of nanofibrous scaffold with stimulative response features in the musculoskeletal system has led us to imagine its potential application in fibrocartilaginous enthesis. Therefore, the healing of fibrocartilaginous enthesis based on a nanofibrous scaffold may be a novel therapeutic approach.

Bone-ACL-bone allograft for anterior cruciate ligament reconstruction: Short-term evaluation in a rabbit model with microcomputed tomography

The standard grafts used for anterior cruciate ligament (ACL) reconstruction are tendon, either patellar tendon, hamstring, or quadriceps. However, the microstructure and composition of tendon differs from ligament. Ideally, the ACL would be replaced with the same tissue. To evaluate the incorporation of a bone-ACL-bone (B-ACL-B) graft for ACL reconstruction, we performed a controlled laboratory study in a rabbit model with microcomputed tomography (μCT). Forty-six New Zealand white rabbits were used, with 17 donor rabbits to harvest bilateral B-ACL-B allografts and 29 rabbits undergoing unilateral ACL reconstruction with B-ACL-B allograft. Knee specimens were collected for biomechanical testing (n = 14) at 4 and 8 weeks and for μCT analysis (n = 15) at 2, 4, and 8 weeks after surgery. Gross inspection and μCT examination confirmed bone blocks in the appropriate anatomic position. Biomechanical tests revealed no difference in mean load-to-failure force for B-ACL-B allografts between 4 and 8 weeks. Progressive healing occurred between the bone block and the tunnel as demonstrated by a gradual increase on average bone-volume fraction and total mineral density (TMD) in both femoral and tibial tunnels. Remodeling of the bone block was evidenced by a significant decrease in TMD of both tibial and femoral bone blocks. This is a report of a novel rabbit B-ACL-B allograft reconstruction model demonstrating early signs of graft remodeling and incorporation. Clinical Relevance: This study demonstrates ACL reconstruction using an anatomically matched ACL allograft, rather than a tendon graft, may be possible based on early findings in this lapine model.

Graft Selection Between Tendon Autograft and Allograft in Anterior Cruciate Ligament Reconstruction Based on the Histological Perspective: A Meta-Analysis

Objective:  The purpose of this meta-analysis is to compare ligament healing on autograft and allograft in anterior cruciate ligament (ACL) reconstruction. Methods:  The selection of appropriate studies was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We made a statistical analysis using a review manager. Electronic reports were searched using the PubMed, Medline, and Cochrane Library databases. The inclusion criteria were animal studies and cellular histology of both grafts as an outcome. Results:  The initial search revealed 412 potential articles. After duplicates were removed, 246 articles remained. Then, 14 articles were obtained and screened for relevance and eligibility. The relevant articles were searched manually, checking for eligibility and details in order not to miss included reports. Subsequently, 5 studies were included, with a total of 232 samples, reporting the biopsied results with quantitative histology of ligament healing between allograft and autograft. The biopsy samples in those studies were examined under light or electron microscope, to analyze the cellular distribution area and ligamentization stages in each group. Meta-analyses found significant difference between autograft and allograft (Heterogeneity, I2 = 89%; Mean Difference, 95% confidence interval [CI] = -34.92, -54.90, -14.93; p  = 0.0006). There is also a significant difference on both graft in cellular count at over 24 weeks (Heterogeneity, I2 = 26%; Mean Difference, 95% CI = -14.59, -16.24, -12.94; p  < 0.00001). Conclusion:  In the current meta-analysis, autograft shows a significant difference when compared to allograft, with more cellular accumulation and faster remodeling response on the ligamentization process being noticed in the former. However, a larger clinical trial will be needed to emphasize this literature's result.

Functional Outcomes of Anterior Cruciate Ligament Reconstruction Using Titanium Adjustable Loop Button and Poly-L-co-DL-Lactic Acid-Beta Tricalcium Phosphate (PLDLA-bTCP) Interference Screws: A Single-Center, Retrospective, Observational Study

Background The anterior cruciate ligament (ACL) reconstruction is a standard surgery in patients with instability of the knee caused by ACL insufficiency. Several differential procedures using grafts and implants such as loops, buttons, and screws have been described. This study aimed to assess the functional outcomes of ACL reconstruction surgery using titanium adjustable loop buttons and poly-L-co-DL-lactic acid-beta tricalcium phosphate (PLDLA-bTCP) interference screws. Methodology This was a retrospective, observational, single-center, and clinical study. A total of 42 patients who underwent ACL reconstruction at a tertiary trauma center in northern India between 2018 and 2022 were recruited. Data including demographics, details of the injury, surgery, implants, and surgical outcomes were collected from the patients' medical records. Further, post-surgery details such as re-injury, adverse events, International Knee Documentation Committee (IKDC) profiles, and Lysholm knee score were recorded from the enrolled patients through a telephonic follow-up. Pain score and Tegner activity scale were used to compare the knee status before and after surgery. Results At the time of surgery, the mean age of the recruited patients was 31.1 ± 8.8 years, with a male preponderance of 93%. About 57% of patients had left knee injuries. The common symptoms were instability (67%), pain (62%), swelling (14%), and giving away (5%). During surgery, titanium adjustable loop button and PLDLA-bTCP interference screw implants were used in all patients. The mean follow-up time was 21.2 ± 14.2 months. Based on patient responses, the mean IKDC and Lysholm scores were found to be 54.02 ± 5.93 and 94.4 ± 4.73, respectively. Further, the proportion of patients reporting pain decreased from 62% before surgery to 21% after surgery. The mean Tegner score revealed a significant increase in the activity levels of the patients post-surgery compared to pre-surgery (p < 0.05). Lastly, no adverse events or re-injuries were reported in any of the patients during follow-up. Conclusions Our findings revealed a significant improvement in Tegner activity levels and pain scores after surgery. In addition, patient-reported IKDC and Lysholm scores fell under the category of good knee status and function, suggesting a satisfactory functional outcome of ACL reconstruction. Hence, titanium adjustable loop and PLDLA-bTCP interference screws may be a good choice of implants for successful ACL reconstruction surgery.

Therapeutic potential and mechanisms of mesenchymal stem cell-derived exosomes as bioactive materials in tendon-bone healing

Tendon-bone insertion (TBI) injuries, such as anterior cruciate ligament injury and rotator cuff injury, are the most common soft tissue injuries. In most situations, surgical tendon/ligament reconstruction is necessary for treating such injuries. However, a significant number of cases failed because healing of the enthesis occurs through scar tissue formation rather than the regeneration of transitional tissue. In recent years, the therapeutic potential of mesenchymal stem cells (MSCs) has been well documented in animal and clinical studies, such as chronic paraplegia, non-ischemic heart failure, and osteoarthritis of the knee. MSCs are multipotent stem cells, which have self-renewability and the ability to differentiate into a wide variety of cells such as chondrocytes, osteoblasts, and adipocytes. Numerous studies have suggested that MSCs could promote angiogenesis and cell proliferation, reduce inflammation, and produce a large number of bioactive molecules involved in the repair. These effects are likely mediated by the paracrine mechanisms of MSCs, particularly through the release of exosomes. Exosomes, nano-sized extracellular vesicles (EVs) with a lipid bilayer and a membrane structure, are naturally released by various cell types. They play an essential role in intercellular communication by transferring bioactive lipids, proteins, and nucleic acids, such as mRNAs and miRNAs, between cells to influence the physiological and pathological processes of recipient cells. Exosomes have been shown to facilitate tissue repair and regeneration. Herein, we discuss the prospective applications of MSC-derived exosomes in TBI injuries. We also review the roles of MSC-EVs and the underlying mechanisms of their effects on promoting tendon-bone healing. At last, we discuss the present challenges and future research directions.

High Levels of Satisfaction and Adequate Patient-Reported Outcomes After Operative Reconstruction of Multiligament Knee Injury With Allograft Among Patients Aged 40 Years and Older

Purpose

To describe injury characteristics and patient-reported outcomes (PROs) among patients aged 40 years and older who underwent allograft reconstruction for multiligament knee injury (MLKI).

Methods

Records of patients aged 40 years and older who underwent allograft multiligament knee reconstruction at a single institution between 2007 and 2017 with a minimum of 2 years of follow-up were retrospectively reviewed. Demographic information, concomitant injuries, patient satisfaction, and PROs including International Knee Documentation Committee and Marx activity scores were obtained.

Results

Twelve patients were included with a minimum follow-up time of 2.3 years (mean, 6.1; range, 2.3-10.1 years) and a mean age at surgery of 49.8 years. Seven patients were male, and the most common mechanism of injury was sport-related. The most frequently reconstructed MLKIs were anterior cruciate ligament and medial collateral ligament (4), anterior cruciate ligament and posterolateral corner (2), and posterior cruciate ligament and posterolateral corner (2). The majority of patients reported satisfaction with their treatment (11). Median International Knee Documentation Committee and Marx scores were 73 (interquartile range, 45.5-88.0) and 3 (interquartile range 0-5), respectively.

Conclusions

Patients aged 40 years and older can expect a high level of satisfaction and adequate PROs at 2-years follow-up after operative reconstruction for a MLKI with allograft. This demonstrates that allograft reconstruction for a MLKI in older patients may have clinical utility.

Level of Evidence

IV, therapeutic case series.

Synergistic Effect of Reverse Drilling and Bone Dust on Femoral Tendon-Bone Healing After Anterior Cruciate Ligament Reconstruction in a Rabbit Model

BACKGROUND

Anterior cruciate ligament (ACL) injuries and bone tunnel enlargement (BTE) after ACL reconstruction (ACLR) remain frequent issues. Bone dust (BD) produced by tunnel preparation with osteogenic ability and reverse drilling (RD), an easy compaction technique, make it accessible to enhance tendon-bone healing in the clinic.

HYPOTHESIS

RD and BD synergistically promote tendon-bone healing by improving peritunnel bone and preventing BTE in femurs.

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 96 New Zealand White rabbits underwent ACLR. The semitendinosus tendon was freed before medial parapatellar arthrotomy. After the native ACL was transected, bone tunnels were prepared through the footprint of the native ACL. All animals were randomly assigned to 1 of 4 groups according to different tunnel preparation methods: group 1 (irrigation after extraction drilling [ED]; control group), group 2 (irrigation after RD), group 3 (no irrigation after ED), and group 4 (no irrigation after RD). BD was harvested by irrigating tunnels and was characterized by morphology and size. The specimens underwent microarchitectural, histological, and biomechanical evaluations at 4, 8, and 12 weeks postoperatively.

RESULTS

Micro-computed tomography demonstrated more peritunnel bone and less BTE in the femurs of group 4 compared with the other groups. Histologically, BD possessed osteogenic activity in bone tunnels postoperatively. Meanwhile, group 4 regenerated a higher amount of the tendon-bone interface and more peritunnel bone than group 1. Biomechanically, group 4 showed higher failure loads and stiffness than group 1. However, peritunnel bone loss, active osteoclasts, and significant BTE were found in the femurs of group 1 and group 3 at 12 weeks postoperatively, while no strong correlation was found between BTE and inflammatory cytokines. Scanning electron microscopy and particle size analysis suggested that BD produced by ED and RD had no difference in size.

CONCLUSION

Tendon-bone healing was facilitated by the synergistic effect of RD and BD in femurs.

CLINICAL RELEVANCE

This study provides a more accessible and effective surgical strategy to promote tendon-bone healing after ACLR by increasing peritunnel bone and preventing BTE in femurs.

Graft Intra-Articular Remodeling and Bone Incorporation in ACL Reconstruction: The State of the Art and Clinical Implications

The knee is one of the most frequently affected joints in sports trauma, and anterior cruciate ligament (ACL) injury and meniscal tears are the most common lesions. ACL reconstruction (ACLR) remains the treatment of choice for patients willing to return to their previous activity. There are different surgical techniques and different possible usable grafts. The graft used for ACLR surgery undergoes a bone incorporation process and an intra-articular remodelling named ligamentization until it reaches characteristics similar to the native ligament. After the first incorporation stage, the remodelling process is divided into an early stage that could last 4 weeks, a proliferative stage that lasts 4 to 12 weeks, and a final stage of ligamentization that could last over 1 year. The period of return to sport (RTS) after ACLR, which is becoming shorter and shorter, can be a high-risk period for athletes due to the risk of graft failure. This systematic review aims to define the phases of the ligamentization process considering graft type and fixation techniques, as well as the graft's anatomopathological and biomechanical characteristics, to evaluate a criterion-based rehab progression and maximize patient outcomes for an RTS respecting graft biology. The rehabilitative program has to promote and optimize the graft remodelling and incorporation processes; moreover, it has to accommodate physiological graft healing and avoid overloading. An early RTS and noncompliance with the biological characteristics of the graft in the various phases are associated with a high incidence of re-injury.

Management of Patella Fracture Nonunion and Large Bone Defect After Bone-Patellar Tendon-Bone Autograft: A Case Report

CASE

A 32-year-old patient was diagnosed with a vertical patella fracture nonunion after a bone-patellar tendon-bone (BTB) anterior cruciate ligament reconstruction. In addition, a 1 × 2 × 1 cm patellar bone defect was noticed at the graft harvesting site. The patient was treated surgically with open reduction and internal fixation and iliac crest bone autograft which resulted in fracture union.

CONCLUSION

Many intraoperative and postoperative risk factors for iatrogenic patella fracture when harvesting BTB autograft were identified. Surgeons should be aware of technical skills needed to prevent this complication and should treat the fracture appropriately to avoid nonunion and optimize the outcome.

Exosomes derived from magnetically actuated bone mesenchymal stem cells promote tendon-bone healing through the miR-21-5p/SMAD7 pathway

Graft healing after anterior cruciate ligament reconstruction (ACLR) involves slow biological processes, and various types of biological modulations have been explored to promote tendon-to-bone integration. Exosomes have been extensively studied as a promising new cell-free strategy for tissue regeneration, but few studies have reported their potential in tendon-to-bone healing. In this study, a novel type of exosome derived from magnetically actuated (iron oxide nanoparticles (IONPs) combined with a magnetic field) bone mesenchymal stem cells (BMSCs) (IONP-Exos) was developed, and the primary purpose of this study was to determine whether IONP-Exos exert more significant effects on tendon-to-bone healing than normal BMSC-derived exosomes (BMSC-Exos). Here, we isolated and characterized the two types of exosomes, conducted in vitro experiments to measure their effects on fibroblasts (NIH3T3), and performed in vivo experiments to compare the effects on tendon-to-bone integration. Moreover, functional exploration of exosomal miRNAs was further performed by utilizing a series of gain- and loss-of-function experiments. Experimental results showed that both BMSC-Exos and IONP-Exos could be shuttled intercellularly into NIH3T3 fibroblasts and enhanced fibroblast activity, including proliferation, migration, and fibrogenesis. In vivo, we found that IONP-Exos significantly prevented peri-tunnel bone loss, promoted more osseous ingrowth into the tendon graft, increased fibrocartilage formation at the tendon-bone tunnel interface, and induced a higher maximum load to failure than BMSC-Exos. Furthermore, overexpression of miR-21-5p remarkably enhanced fibrogenesis in vitro, and SMAD7 was shown to be involved in the promotive effect of IONP-Exos on tendon-to-bone healing. Our findings may provide new insights into the regulatory roles of IONPs in IONP-Exos communication via stimulating exosomal miR-21-5p secretion and the SMAD7 signaling pathway in the fibrogenic process of tendon-to-bone integration. This work could provide a new strategy to promote tendon-to-bone healing for tissue engineering in the future.

Cellular Augmentation of Anterior Cruciate Ligament Surgery Is Not Currently Evidence Based: A Systematic Review of Clinical Studies

PURPOSE

To perform a systematic review of clinical outcome studies exploring cellular augmentation of anterior cruciate ligament (ACL) surgery, including stem cell techniques.

METHODS

A systematic search was performed according to the Preferred Reporting Items of Systematic Reviews and Meta-analyses (PRISMA) guidelines using the Cochrane, PubMed, MEDLINE, SPORTDiscus, and CINAHL (Cumulative Index to Nursing and Allied Health Literature) databases from 2000 to 2019. The inclusion criteria were clinical studies that reported on ACL surgery augmented with stem cells or cellular therapy and patient-reported outcome measures or graft healing. Risk of bias was assessed using the Cochrane risk-of-bias tool for randomized clinical trials, and nonrandomized trials were assessed using the Methodological Items for Non-randomized Studies (MINORS) tool. Methodologic assessment was performed according to the Modified Coleman Methodology Score.

RESULTS

Four studies were found: 2 randomized clinical trials, 1 cohort study with a matched historical control group, and 1 case series. The mean Modified Coleman Methodology Score in these studies was 59, and there was a low risk of bias in 1 study. One study reported outcomes of augmented ACL repair, and 3 studies reported the results of augmented ACL reconstruction. Cellular therapies varied and included concentrated bone marrow aspirate, collagenase/centrifuge processed adipose, and marrow stimulation combined with platelet-rich plasma, as well as cells cultured from allograft bone marrow aspirate. The concentrated bone marrow aspirate and adipose tissue study results did not support their use. The marrow stimulation technique combined with repair led to promising clinical results. The use of allograft cultured cells improved patient-reported outcomes and postoperative radiographic findings.

CONCLUSIONS

Augmentation of ACL surgery with cellular therapy is not supported by clinical evidence at this time.

LEVEL OF EVIDENCE

Level IV.

Graft Choice for Anterior Cruciate Ligament Reconstruction in Women Aged 25 Years and Younger: A Systematic Review

CONTEXT

Although anterior cruciate ligament (ACL) tears are relatively common in athletic populations, few studies have systematically reviewed graft choice in young women.

OBJECTIVE

To quantitatively and qualitatively examine reported outcomes for graft choice in women aged 25 years and younger undergoing primary ACL reconstruction.

DATA SOURCE

A systematic review was performed using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. An electronic search in the PubMed (includes MEDLINE) and EMBASE databases was completed using a combination of key terms.

STUDY SELECTION

Studies were included if they reported graft choice outcomes in women aged 25 years and younger.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

The following information was extracted: title, author, year of publication, number of female patients and age, graft type, follow-up, and patient-reported outcome measures. The following outcome scores were identified as being reported or not reported by each study: graft failure, contralateral ACL (CACL) rupture, IKDC (International Knee Documentation Committee), graft survival (Kaplan-Meier), Lysholm, Tegner, KT-1000, kneeling pain, return to sport, and Lachman.

RESULTS

Of 1170 identified articles, 16 met inclusion criteria, reporting on 1385 female patients aged 25 years and younger. Comparison of 655 bone-patellar tendon-bone (BPTB) versus 525 hamstring tendon (HT) autografts showed significant differences in mean failure rate between BPTB autografts (6.13% ± 2.58%) and HT autografts (17.35% ± 8.19%), P = 0.001. No statistically significant differences in CACL failure rates were found between BPTB autografts and HT autografts (P = 0.25). Pooled results for IKDC were possible in 3 of the HT autograft studies, showing a mean score of 88.31 (95% CI 83.53-93.08). Pooled Lysholm score results were possible in 2 of the HT autograft studies, showing a mean score of 93.46 (95% CI 91.90-95.01).

CONCLUSION

In female patients aged 25 years and younger, BPTB autografts showed significantly less graft failure compared with HT autografts. However, BPTB autografts had comparable patient-reported outcomes compared with HT autografts with the available data. The overall state of evidence for graft choice in female patients aged 25 years and younger is low. Future studies should report statistics by age and sex to allow for further analysis of graft choice for this specific population that is known to be more vulnerable to ACL injury.

Prospective Comparison of Functional and Radiological Outcomes of Arthroscopic Anterior Cruciate Ligament Reconstruction by Hamstring Graft Alone and Platelet-Rich Plasma Added to the Hamstring Graft

Aims and objectives: To measure the additional effect of platelet-rich plasma (PRP) on functional outcome of anterior cruciate ligament tear managed by augmenting anterior cruciate ligament (ACL) reconstruction with PRP.

Methods: The present study was conducted on patients with ACL tear admitted in the department of orthopaedics, King George’s Medical University, Lucknow wherein a total of 70 subjects were assigned into two groups of 35 patients each randomly, viz Group 1 in which the patients were treated by quadruple hamstring graft alone and Group 2 in which the patients were treated with augmented hamstring graft with PRP. The standardized anterior drawer test, Lachman’s test, Lysholm knee score were quantified both preoperatively and postoperatively at different follow-ups and also tibial tunnel widening was measured postoperatively at different follow-ups.

Result: The present study had 70 patients with ACL tears. The mean age of patients in non-PRP groups was 29.71 ±2.99 years while that in the PRP group was 28.34±4.32 years. On comparing the improvement in grades at pre-op, immediate postop, 6 weeks, and 3 months follow-ups, there was no statistically significant difference between the two groups. The tibial tunnel widening also showed no significant difference between the two groups.

Conclusion: In our study, it was found that both the groups showed improvements in grades of anterior drawer test and Lachman’s test postoperatively but the difference between both the groups was not significant. Similarly, while comparing the improvements in Lysholm knee score and tibial tunnel widening among both the groups, the difference was not significant. Follow up of 3 months was a limiting factor in our study. This technique needs further clinical evaluation to assess the long-term results.

Infrapatellar Fat Pad Mesenchymal Stromal Cell-Derived Exosomes Accelerate Tendon-Bone Healing and Intra-articular Graft Remodeling After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Exosomes derived from mesenchymal stromal cells (MSCs) reportedly enhance the healing process. However, no studies have investigated the effect of exosomes from infrapatellar fat pad (IPFP) MSCs on tendon-bone healing and intra-articular graft remodeling after anterior cruciate ligament reconstruction (ACLR).

PURPOSE

To evaluate the in vivo effect of exosomes from IPFP MSCs on tendon-bone healing and intra-articular graft remodeling in a rat model of ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 90 skeletally mature male Sprague Dawley rats underwent unilateral ACLR using an autograft. All rats were randomly divided into 3 groups: sham injection (SI) group (n = 30), control injection (CI) group (n = 30), and IPFP MSC-derived exosome injection (IMEI) group (n = 30). At 2, 4, and 8 weeks postoperatively, tendon-bone healing and intra-articular graft remodeling were evaluated via biomechanical testing, micro-computed tomography, and histological analysis; macrophage polarization was evaluated using immunohistochemical staining.

RESULTS

Biomechanical testing demonstrated a significantly higher failure load and stiffness in the IMEI group than in the SI and CI groups at 4 and 8 weeks postoperatively. Moreover, a thinner graft-to-bone healing interface with more fibrocartilage was observed in the IMEI group at both time points. Micro-computed tomography revealed greater new bone ingrowth in the IMEI group than in the other groups, as demonstrated by smaller mean bone tunnel areas and a larger bone volume/total volume ratio. Additionally, more cellular infiltration was observed in the intra-articular graft in the IMEI group than in the other groups at 4 weeks, followed by more regularly organized fibers with mature collagen at 8 weeks. Notably, similar trends of macrophage polarization were found at both the graft-to-bone interface and the intra-articular graft in the IMEI group, with significantly fewer proinflammatory M1 macrophages and larger numbers of reparative M2 macrophages than in the SI and CI groups.

CONCLUSION

IPFP MSC-derived exosomes accelerated tendon-bone healing and intra-articular graft remodeling after ACLR, which may have resulted from the immunomodulation of macrophage polarization.

CLINICAL RELEVANCE

The IPFP can be easily harvested by most orthopaedic surgeons. Exosomes from IPFP MSCs, constituting a newly emerging cell-free approach, may represent a treatment option for improving tendon-bone healing and intra-articular graft remodeling after ACLR.

Anatomic reconstruction of lateral ankle ligaments: is there an optimal graft option?

PURPOSE

Different graft options are available for the reconstruction of lateral ankle ligaments to treat chronic ankle instability (CAI), which fall in two categories: allografts and autografts. This study aims to provide an updated comparison of the clinical outcomes after stabilisation procedures using allografts and autografts, to correctly advise the clinician during the choice of the best material to be used for the reconstruction of the lateral ligamentous complex of the ankle.

METHODS

A systematic review was performed to analyse the use of autografts and allografts for anatomic reconstruction of the lateral ligamentous complex of the ankle in CAI patients. The presence of a postoperative assessment through outcome measures with proofs of validation in the CAI population or patient's subjective evaluation on the treatment were necessary for inclusion. The quality of the included studies was assessed through the modified Coleman Methodology Score (mCMS). Relevant clinical outcome data were pooled to provide a synthetic description of the results in different groups or after different procedures.

RESULTS

Twenty-nine studies (autograft: 19; allograft: 9; both procedures: 1) accounting for 930 procedures (autograft: 616; allograft: 314) were included. The average mCMS was 55.9 ± 10.5 points. The Karlsson-Peterson scale was the most frequently reported outcome scale, showing a cumulative average post- to preoperative difference of 31.9 points in the autograft group (n = 379, 33.8 months follow-up) and of 35.7 points in the allograft group (n = 227, 25.8 months follow-up). Patient satisfaction was good or excellent in 92.8% of autograft (n = 333, 65.2 months follow-up) and in 92.3% of allograft procedures (n = 153, 25.0 months follow-up). Return to activity after surgery and recurrence of instability were variably reported across the studies with no clear differences between allograft and autograft highlighted by these outcomes.

CONCLUSIONS

The systematic analysis of validated CAI outcome measures and the patient's subjective satisfaction does not support a specific choice between autograft and allograft for the reconstruction of the ankle lateral ligamentous complex in CAI patients. Both types of grafts were associated to a postoperative Karlsson-Peterson score superior to 80 points and to a similar rate of patient's subjective satisfaction.

LEVEL OF EVIDENCE

Level IV.

Anterior Cruciate Ligament Reconstruction: Is Biological Augmentation Beneficial?

Surgical reconstruction in anterior cruciate ligament (ACL) ruptures has proven to be a highly effective technique that usually provides satisfactory results. However, despite the majority of patients recovering their function after this procedure, ACL reconstruction (ACLR) is still imperfect. To improve these results, various biological augmentation (BA) techniques have been employed mostly in animal models. They include: (1) growth factors (bone morphogenetic protein, epidermal growth factor, granulocyte colony-stimulating factor, basic fibroblast growth factor, transforming growth factor-β, hepatocyte growth factor, vascular endothelial growth factor, and platelet concentrates such as platelet-rich plasma, fibrin clot, and autologous conditioned serum), (2) mesenchymal stem cells, (3) autologous tissue, (4) various pharmaceuticals (matrix metalloproteinase-inhibitor alpha-2-macroglobulin bisphosphonates), (5) biophysical/environmental methods (hyperbaric oxygen, low-intensity pulsed ultrasound, extracorporeal shockwave therapy), (6) biomaterials (fixation methods, biological coatings, biosynthetic bone substitutes, osteoconductive materials), and (7) gene therapy. All of them have shown good results in experimental studies; however, the clinical studies on BA published so far are highly heterogeneous and have a low degree of evidence. The most widely used technique to date is platelet-rich plasma. My position is that orthopedic surgeons must be very cautious when considering using PRP or other BA methods in ACLR.

Return to sport following anterior cruciate ligament reconstruction: the argument for a multimodal approach to optimise decision-making: current concepts

Existing literature is varied in the methods used to make this determination in the treatment of athletes who have undergone recent anterior cruciate ligament (ACL) reconstruction. Some authors report using primarily time-based criteria, while others advocate for physical measures and kinematic testing to inform decision-making. The goal of this paper is to elucidate the most current medical evidence regarding identification of the earliest point at which a patient may safely return to sport. The present review therefore seeks to examine the evidence from a critical perspective-breaking down the biology of graft maturation, effect of graft choice, potential for image-guided monitoring of progression and results associated with time-based versus functional criteria-based return to play-to justify a multifactorial approach to effectively advance athletes to return to sport. The findings of the present study reaffirm that time is a prerequisite for the biological progression that must occur for a reconstructed ligament to withstand loads demanded by athletes during sport. Modifications of surgical techniques and graft selection may positively impact the rate of graft maturation, and evidence suggests that imaging studies may offer informative data to enhance monitoring of this process. Aspects of both functional and cognitive testing have also demonstrated utility in prior studies and consequently have been factored into modern proposed methods of determining the athlete's readiness for sport. Further work is needed to definitively determine the optimal method of clearing an athlete to return to sport after ACL reconstruction. Evidence to date strongly suggests a role of a multimodal algorithmic approach that factors in time, graft biology and functional testing in return-to-play decision-making after ACL reconstruction.Level of evidence: level V.

Porcine bone-patellar tendon-bone xenograft in a caprine model of anterior cruciate ligament repair

The use of human tissue-derived autografts and allografts continues to be the gold standard in anterior cruciate ligament (ACL) repair. However, autografts and allografts have their own set of associated risks. Many alternative options, including synthetic replacements, have failed to demonstrate long-term success. In this study, sterile acellular porcine bone-tendon-bone (BTB) xenografts were created using a proprietary process and tested against BTB autografts in goats for 13 and 52 weeks. At 13 weeks, all xenograft-implanted animals (n = 9) had subjective hind leg motor function (HLMF) that was categorized as either normal (score = 0) or a slight limp (score = 1) compared with two of nine autograft-implanted animals having a moderate limp (score = 2). At 39 weeks, there was HLMF improvement with each autograft-implanted and xenograft-implanted animal having normal HLMF or only a slight limp. At 13 weeks, six of nine animals in each group achieved normal anterior drawer scores, which increased to nine of nine animals in each group by 39 weeks. Both autografts and xenografts exhibited minimal inflammation with excellent integration of the fibrous tendon portion of the graft to host bone, as evidenced histologically by Sharpey's fiber formation. At 52 weeks, maximum mechanical load at failure for xenografts was 1092.0 ± 586.4 N compared with 1037.0 ± 422.6 N for autografts. These results demonstrate that a sterile acellular porcine BTB xenograft can perform equivalently to BTB autograft in a caprine model of ACL repair.

Editorial Commentary: Autograft Beats Allograft for Most Knee Ligament Surgery

Knee ligament reconstruction can be performed with autograft or allograft. The use of an autograft has been shown to improve outcomes in primary anterior cruciate ligament reconstruction for young, active patients, and also in revision anterior cruciate ligament reconstruction surgery. A systematic review of posterior cruciate ligament reconstruction showed no difference in outcomes between autograft and allograft tissue. There is a paucity of data comparing autograft versus allograft for fibular collateral ligament and posterolateral corner reconstructions, alone or combined with other ligament surgery. Allograft advantages include no donor site morbidity and reduced operative time. Disadvantages include increased cost and higher failure rates in younger patients. Autograft tissue should be considered in younger, active patients whenever possible.

Improved rotator cuff healing after surgical repair via suppression of reactive oxygen species by sustained release of Se

Porous Se@SiO₂ nanocomposites showed effective results in promoting rotator cuff healing after surgical repair and have great potential in relevant clinical applications.

Mechanically superior matrices promote osteointegration and regeneration of anterior cruciate ligament tissue in rabbits

The gold standard treatment for anterior cruciate ligament (ACL) reconstruction is the use of tendon autografts and allografts. Limiting factors for this treatment include donor site morbidity, potential disease transmission, and variable graft quality. To address these limitations, we previously developed an off-the-shelf alternative, a poly(l-lactic) acid (PLLA) bioengineered ACL matrix, and demonstrated its feasibility to regenerate ACL tissue. This study aims to 1) accelerate the rate of regeneration using the bioengineered ACL matrix by supplementation with bone marrow aspirate concentrate (BMAC) and growth factors (BMP-2, FGF-2, and FGF-8) and 2) increase matrix strength retention. Histological evaluation showed robust tissue regeneration in all groups. The presence of cuboidal cells reminiscent of ACL fibroblasts and chondrocytes surrounded by an extracellular matrix rich in anionic macromolecules was up-regulated in the BMAC group. This was not observed in previous studies and is indicative of enhanced regeneration. Additionally, intraarticular treatment with FGF-2 and FGF-8 was found to suppress joint inflammation. To increase matrix strength retention, we incorporated nondegradable fibers, polyethylene terephthalate (PET), into the PLLA bioengineered ACL matrix to fabricate a "tiger graft." The tiger graft demonstrated the greatest peak loads among the experimental groups and the highest to date in a rabbit model. Moreover, the tiger graft showed superior osteointegration, making it an ideal bioengineered ACL matrix. The results of this study illustrate the beneficial effect bioactive factors and PET incorporation have on ACL regeneration and signal a promising step toward the clinical translation of a functional bioengineered ACL matrix.

Bone ingrowth into open architecture PEEK interference screw after ACL reconstruction

PURPOSE

Open or fenestrated interference screw design that allow bone ingrowth is a concept for improved bone healing to softtissue graft and bone filling in bone tunnels after anterior cruciate ligament reconstruction (ACLR) The aim of the current study was to assess CT scanning evaluated bone ingrowth into an open architecture interference screws in the tibial tunnel of patients undergoing ACL with soft tissue grafts. It was hypothesized that open architecture interference screws would stimulate bone ingrowth into the screw cavities.

METHODS

Twelve patients requiring ACLR were included. They underwent arthroscopic ACLR with semitendinosus-/gracilis tendon graft and an open architecture polyetheretherketone (PEEK) interference screw. The patients were scanned with a multi-slice CT scanner two weeks, six and twelve months postoperatively. On CT reconstruction slices bone ingrowth into the screw was measured. Subjective and objective clinical outcome international knee documentation committee score and instrumented knee laxity determination were collected.

RESULTS

At six months no implants demonstrated more than 10% bone ingrowth. At twelve months 42% (5/12) implants had more than 10% bone ingrowth (p = 0.009). The average bone filling into the screws was 7.7%. There was no tunnel widening or cyst formation seen in relation to any of the implants. Subjective IKDC score improved significantly from 50.6 baseline to 80.1 at 24 month follow-up. Preoperative side-to-side knee laxity improved from 3.7 (2.1) to 1.4 (1.2) mm at twelve months. There were no serious adverse events in relation to the new open architecture thread PEEK interference screw during or after hamstring ACL reconstruction.

CONCLUSION

The present study demonstrated that open architecture thread PEEK interference screw can stimulate bone ingrowth into the screws after soft tissue ACL reconstruction with at 12 months with an average bone filling into screws was 7.7%. Knee stability, functional, subjective and objective outcomes were similar to large volume ACL outcome studies.

TRIAL REGISTRATION

The study was registered at ClinicalTrials # NCT02382341 . 12-09-2014.

LEVEL OF EVIDENCE

IV.

Evaluation of a bioengineered ACL matrix's osteointegration with BMP-2 supplementation

A poly (l-lactic) acid bioengineered anterior cruciate ligament (ACL) matrix has previously demonstrated the ability to support tissue regeneration in a rabbit ACL reconstruction model. The matrix was designed for optimal bone and ligament regeneration by developing a matrix with differential pore sizes in its bone and ligament compartments. Building upon past success, we designed a new bioengineered ACL matrix that is easier to install and can be used with endobutton fixation during ACL reconstruction. To achieve this, a new braiding procedure was developed to allow the matrix to be folded in half, making two-limbs, while maintaining its bone and ligament compartments. The osteointegration of the matrix with and without bone morphogenetic protein 2 (BMP-2) supplementation was evaluated in a rabbit ACL reconstruction model. Two doses of BMP-2 were evaluated, 1 and 10 μg, and delivered by saline injection into the bone tunnel at the end of surgery. A fibrous matrix-to-bone interface with occasional Sharpey’s fibers was the primary mode of osteointegration observed. The matrix was also found to support a fibrocartilage matrix-to-bone interface. In some cases, the presence of chondrocyte-like cells was observed at the aperture of the bone tunnel and the center of the matrix within the bone tunnel. Treatment with BMP-2 was associated with a trend towards smaller bone tunnel cross-sectional areas, and 1 μg of BMP-2 was found to significantly enhance osteoid seam width in comparison with no BMP-2 or 10 μg of BMP-2 treatment. Regenerated tissue was well organized within the bioengineered ACL matrix and aligned with the poly (l-lactic) acid fibers. Disorganized tissue was found between the two-limbs of the bioengineered ACL matrix and hypothesized to be due to a lack of structural scaffolding. This study suggests that the bioengineered ACL matrix can undergo similar modes of osteointegration as current autografts and allografts, and that BMP-2 treatment may enhance osteoblastic activity within the bone tunnels.

A multi-chamber tissue culture device for load-dependent parallel evaluation of tendon explants

Background

Injuries in the musculoskeletal system, such as tendon and ligament ruptures, are challenging to manage and often require surgical reconstructions with limited long-term success. Thus, characterizations of these tissues are urgently needed to better understand cellular mechanisms that regulate tissue homeostasis and healing. Explant culturing systems allow for ex vivo analysis of tissues in an environment that mimics the native microenvironment in vivo.

Methods

Collaborative efforts within our institution facilitated the establishment of a novel explant culturing system. Tissue specimens cultured in single wells, with individual applied loading and/or biological environment, allowed characterization of tissue cultured under a variety of biological loading conditions. Quantitative PCR analysis for selected gene markers was our primary outcome.

Results

Data were stratified for analysis by either culture environment or loading condition. Our gene expression results show that specimens clustered by culture condition may differ in molecular markers related to ECM production (e.g., Col1a1, Adamts4) and/or organization (e.g., Tnc, Dnc). In contrast, loading condition did significantly alter the median gene expression levels of tissues in comparison to unloaded control samples, although gene expression values related to ECM degradation (e.g., Mmp1, Mmp10) were altered in tendons cultured under tension in the device.

Conclusion

Our study demonstrates promising utility of a novel explant culturing system for further characterization of musculoskeletal tissues such as native tendons and ligaments, as well as pathologic fibrotic tissues resulting from arthrofibrosis or Dupuytren’s disease.

Magnetic resonance imaging of the quadriceps tendon autograft in anterior cruciate ligament reconstruction

BACKGROUND

Quadriceps tendon (QT) autograft is emerging as a popular technique for primary anterior cruciate ligament (ACL) reconstruction. Studies have shown that it has comparable outcomes to bone-patellar tendon-bone (BPTB) and hamstring tendon (HT) autografts while mitigating post-operative complications associated with these grafts.

PURPOSE

To provide a literature summary of the important pre- and post-operative magnetic resonance imaging (MRI) findings of the quadriceps tendon and pertinent postoperative complications associated with the QT harvest. Radiologists should be familiar with MR findings after autologous graft harvest of the quadriceps tendon for reconstruction of the ACL.

LEVEL OF EVIDENCE

Level IV.

BIOLOGICAL ENHANCEMENTS FOR ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

The anterior cruciate ligament (ACL) is mostly responsible for providing knee stability. ACL injury has a marked effect on daily activities, causing pain, dysfunction, and elevated healthcare costs. ACL reconstruction (ACLR) is the standard treatment for this injury. However, despite good results, ACLR is associated with a significant rate of failure. In this context, the mechanical and biological causes must be considered. From a biological perspective, the ACLR depends on the osseointegration of the graft in the adjacent bone and the process of intra-articular ligamentization for good results. Here, we discuss the mechanisms underlying the normal graft healing process after ACLR and its biological modulation, thus, presenting novel strategies for biological enhancements of the ACL graft. Level of evidence III, Systematic review of level III studies.

In vivo assessment of high-molecular-weight polyethylene core suture tape for intra-articular ligament reconstruction: an animal study

AIMS

Options for the treatment of intra-articular ligament injuries are limited, and insufficient ligament reconstruction can cause painful joint instability, loss of function, and progressive development of degenerative arthritis. This study aimed to assess the capability of a biologically enhanced matrix material for ligament reconstruction to withstand tensile forces within the joint and enhance ligament regeneration needed to regain joint function.

MATERIALS AND METHODS

A total of 18 New Zealand rabbits underwent bilateral anterior cruciate ligament reconstruction by autograft, FiberTape, or FiberTape-augmented autograft. Primary outcomes were biomechanical assessment (n = 17), microCT (µCT) assessment (n = 12), histological evaluation (n = 12), and quantitative polymerase chain reaction (qPCR) analysis (n = 6).

RESULTS

At eight weeks, FiberTape alone or FiberTape-augmented autograft demonstrated increased biomechanical stability compared with autograft regarding ultimate load to failure (p = 0.035), elongation (p = 0.006), and energy absorption (p = 0.022). FiberTape-grafted samples also demonstrated increased bone mineral density in the bone tunnel (p = 0.039). Histological evaluation showed integration of all grafts in the bone tunnels by new bone formation, and limited signs of inflammation overall. A lack of prolonged inflammation in all samples was confirmed by quantification of inflammation biomarkers. However, no regeneration of ligament-like tissue was observed along the suture tape materials. Except for one autograft failure, no adverse events were detected.

CONCLUSION

Our results indicate that FiberTape increases the biomechanical performance of intra-articular ligament reconstructions in a verified rabbit model at eight weeks. Within this period, FiberTape did not adversely affect bone tunnel healing or invoke a prolonged elevation in inflammation. Cite this article: Bone Joint J 2019;101-B:1238-1247.

Outcomes of the Adams-Berger Ligament Reconstruction for the Distal Radioulnar Joint Instability in 95 Consecutive Cases

Objective  The objective of this article is to evaluate the outcomes and complication rate for Adams-Berger anatomic reconstruction of the distal radioulnar joint (DRUJ), in addition, to determine the role of sigmoid notch anatomy on failure. Methods  We conducted a retrospective chart review to evaluate adult patients that had undergone reconstruction of the DRUJ for instability with the Adams-Berger procedure between 1998 and 2015 within our institution with > 24 months follow-up. Charts were reviewed for patient demographics, mechanism of injury, outcome, and complications. Results  Ninety-five wrists in 93 patients were included. Mean age at surgery was 37.3 years with 65.2 months follow-up. At the last follow-up, 90.8% had a stable DRUJ, 5.3% did not, and 3.4% had some laxity. Postoperatively, 75.9% described either no pain or mild pain. Grip strength increased while pronosupination decreased. Procedure success was 86.3%, as 12 patients underwent revision at 13.3 months postoperatively. Reconstructive failure was more common in females when an interference screw was utilized for tendon fixation. Age, timing of surgery, type of graft, sigmoid notch anatomy, and previous surgery did not affect revision or failure rate. Conclusion  Our findings demonstrate that Adams-Berger reconstruction of the DRUJ provides reliable long-term results with an overall success of 86% at > 5 years follow-up. Level of evidence/Type of study  This is a Level IV, therapeutic study.

The use of allograft tendons in primary ACL reconstruction

PURPOSE

Graft choice in primary anterior cruciate ligament (ACL) reconstruction remains controversial. The use of allograft has risen exponentially in recent years with the attraction of absent donor site morbidity, reduced surgical time and reliable graft size. However, the published evidence examining their clinical effectiveness over autograft tendons has been unclear. The aim of this paper is to provide a current review of the clinical evidence available to help guide surgeons through the decision-making process for the use of allografts in primary ACL reconstruction.

METHODS

The literature in relation to allograft healing, storage, sterilisation, differences in surgical technique and rehabilitation have been reviewed in addition to recent comparative studies and all clinical systematic reviews and meta-analyses.

RESULTS

Early reviews have indicated a higher risk of failure with allografts due to association with irradiation for sterilisation and where rehabilitation programs and post-operative loading may ignore the slower incorporation of allografts. More recent analysis indicates a similar low failure rate for allograft and autograft methods of reconstruction when using non-irradiated allografts that have not undergone chemically processing and where rehabilitation has been slower. However, inferior outcomes with allografts have been reported in young (< 25 years) highly active patients, and also when irradiated or chemically processed grafts are used.

CONCLUSION

When considering use of allografts in primary ACL reconstruction, use of irradiation, chemical processing and rehabilitation programs suited to autograft are important negative factors. Allografts, when used for primary ACL reconstruction, should be fresh frozen and non-irradiated. Quantification of the risk of use of allograft in the young requires further evaluation.

LEVELS OF EVIDENCE

III.

Anterior Cruciate Ligament Reconstruction in a Rabbit Model Using a Decellularized Allogenic Semitendinous Tendon Combined with Autologous Bone Marrow-Derived Mesenchymal Stem Cells

As a regular adoptable material for anterior cruciate ligament (ACL) reconstruction, free tendon allograft exhibits unsatisfactory outcomes, such as retarded ligamentization and tendon–bone integration. The application of bone marrow‐derived mesenchymal stem cells (BMSCs), as well as a decellularized free tendon allograft developed by our group, was proven to be effective in improving ACL reconstruction results. This study aimed to investigate the efficacy and feasibility of decellularized allogenic semitendinous tendon (ST) combined with autologous BMSCs used as a substitute to free tendon allograft in a rabbit model. This study finally shows that the decellularized allogenic ST combined with autologous BMSCs could significantly improve ACL reconstruction results compared with allograft. stem cells translational medicine2019;8:971&982

Mesenchymal Stem Cells Decrease Tunnel Widening of Anterior Cruciate Ligament Reconstruction in Rabbit Model

Background and Objectives

The study investigated the effect of mesenchymal stem cells (MSCs) or fibrin glue on tunnel widening after anterior cruciate ligament (ACL) reconstruction compared with biologic free control without any biologic agents in the rabbit model.

Methods and Results

ACL reconstructions were performed in 18 New Zealand white rabbits. All animals were divided into 3 groups according to the following reconstruction conditions and euthanized 12 weeks postoperatively for radiologic and histologic analyses. Thirty-two knees (control group=10; fibrin group=11; MSCs group=11) were finally evaluated. On micro-CT scan, mean femoral tunnel widening on oblique-sagittal image was 0.7±0.4 mm in the control group, 0.22±0.1 mm in the fibrin group and 0.25±0.1 mm in the MSCs group (p=0.001). Fibrin group and MSCs group showed significant differences compared with control group (p=0.002, 0.002). Mean tibial tunnel widening on oblique-sagittal image was 0.76±0.5 mm, 0.27±0.1 mm and 0.29±0.2 mm in the control, fibrin and MSCs group. Fibrin and MSCs group showed significant differences compared with control group (p=0.017, 0.014). Hounsfield Units (HU) were not significantly different between 3 groups (p>0.05). Histological analysis revealed that the architecture of graft in the MSCs group featured hypercellularity and compact collagen deposit.

Conclusion

ACL reconstruction using MSCs seemed decrease tunnel widening in rabbit model. Further study with large animals is required to confirm efficacy on decreasing tunnel widening.

Negative effect of zoledronic acid on tendon-to-bone healing

Background and purpose - Outcome after ligament reconstruction or tendon repair depends on secure tendon-to-bone healing. Increased osteoclastic activity resulting in local bone loss may contribute to delayed healing of the tendon-bone interface. The objective of this study was to evaluate the effect of the bisphosphonate zoledronic acid (ZA) on tendon-to-bone healing. Methods - Wistar rats (n = 92) had their right Achilles tendon cut proximally, pulled through a bone tunnel in the distal tibia and sutured anteriorly. After 1 week animals were randomized to receive a single dose of ZA (0.1 mg/kg IV) or control. Healing was evaluated at 3 and 6 weeks by mechanical testing, dual-energy X-ray absorptiometry and histology including immunohistochemical staining of osteoclasts. Results - ZA treatment resulted in 19% (95% CI 5-33%) lower pullout strength and 43% (95% CI 14-72%) lower stiffness of the tendon-bone interface, compared with control (2-way ANOVA; p = 0.009, p = 0.007). Administration of ZA did not affect bone mineral density (BMD) or bone mineral content (BMC). Histological analyses did not reveal differences in callus formation or osteoclasts between the study groups. Interpretation - ZA reduced pullout strength and stiffness of the tendon-bone interface. The study does not provide support for ZA as adjuvant treatment in tendon-to-bone healing.

Biological augmentation of graft healing in anterior cruciate ligament reconstruction: a systematic review

Aims

The success of anterior cruciate ligament reconstruction (ACLR) depends on osseointegration at the graft-tunnel interface and intra-articular ligamentization. Our aim was to conduct a systematic review of clinical and preclinical studies that evaluated biological augmentation of graft healing in ACLR.

Materials and Methods

In all, 1879 studies were identified across three databases. Following assessment against strict criteria, 112 studies were included (20 clinical studies; 92 animal studies).

Results

Seven categories of biological interventions were identified: growth factors, biomaterials, stem cells, gene therapy, autologous tissue, biophysical/environmental, and pharmaceuticals. The methodological quality of animal studies was moderate in 97%, but only 10% used clinically relevant outcome measures. The most interventions in clinical trials target the graft-tunnel interface and are applied intraoperatively. Platelet-rich plasma is the most studied intervention, but the clinical outcomes are mixed, and the methodological quality of studies was suboptimal. Other biological therapies investigated in clinical trials include: remnant-augmented ACLR; bone substitutes; calcium phosphate-hybridized grafts; extracorporeal shockwave therapy; and adult autologus non-cultivated stem cells.

Conclusion

There is extensive preclinical research supporting the use of biological therapies to augment ACLR. Further clinical studies that meet the minimum standards of reporting are required to determine whether emerging biological strategies will provide tangible benefits in patients undergoing ACLR. Cite this article: Bone Joint J 2018;100-B:271-84.

There is no difference between quadriceps- and hamstring tendon autografts in primary anterior cruciate ligament reconstruction: a 2-year patient-reported outcome study

PURPOSE

Graft choice for anterior cruciate ligament (ACL) reconstruction is crucial, however the optimal graft source remains a topic of controversy. The purpose of this study is to compare subjective and functional patient-reported outcomes (PRO) after single-bundle ACL reconstruction using quadriceps tendon (QT) or hamstring tendon (HT) autografts for single-bundle ACL reconstruction. We hypothesize that there is no difference in patient-reported functional outcomes after ACL reconstruction using either HT- or QT autograft.

METHODS

All data were extracted from a prospectively collected ACL registry. A total of 80 patients with at least 2-year follow-up were included in this study. A total of 40 patients with primary ACL reconstruction using a QT autograft harvested via a minimally invasive technique were matched by sex, age and pre-injury Tegner and Lysholm score to 40 patients who received HT autografts. Subjective and functional PRO scores including Lysholm score, Tegner activity level and visual analogue scale for pain were obtained at 6, 12 and 24 months after index surgery.

RESULTS

No significant difference between the QT and the HT group was seen at any follow-up in regard to any of the PRO scores for function or pain. 24 months post-surgery the mean Tegner activity score of the HT group was significantly (p = 0.04) lower compared to the pre-injury status. At final follow-up, 27 patients (67.5%) in the QT group and 32 patients (80.0%) in the HT returned to their pre-injury activity level (n.s.). A total of 37 patients (92.5%) of the QT cohort and 35 patients (87.5%) of the HT cohort reported "good" or "excellent" results according to the Lysholm score (n.s.). "No pain" or "slight pain" during severe exertion was reported by 33 patients (82.5%) with QT autograft and 28 patients (82.4%) with HT autograft (n.s.).

CONCLUSION

There is no significant difference between PRO 2 years post-operative using either QT or HT autografts. Both QT and HT grafts show acceptable and comparable PRO scores making the QT a reliable graft alternative to HT for primary ACL reconstruction.

LEVEL OF EVIDENCE

III.

Tibial tunnel enlargement and joint instability after anterior cruciate ligament reconstruction. A prospective comparison between autograft and allograft

PURPOSE

To investigate tibial tunnel widening and knee instability after ACL reconstruction with hamstring autograft or irradiated soft tissue allograft.

METHODS

Eight-two patients were divided into two groups: autograft group and allograft group. Radiographic and clinical evaluations were performed.

RESULTS

Seventy patients were followed up with median of 36.3 months (range 36-38 months). Tibial tunnel widening was at or greater than 30% for nine patients in the autograft group and 15 patients in the allograft group (P = 0.0417). The average percentage of tibial tunnel widening was 26.7 ± 4.0 % and 29.7 ± 5.3 % in autograft and allograft groups, respectively (P = 0.0090). Knee range of motion was not affected by the reconstruction operation or different grafts. Thigh atrophy improved significantly within 24 months after ACL reconstructions in both groups. ACL reconstruction with the allograft leaded to less knee stability than that with the autograft from one year after operation (P = 0.0023). There was no significant difference between two groups with respect to Lysholm score (P = 0.1925) and Tegner score (P =0 .0918) at the final follow-up.

CONCLUSION

The allograft group reported significantly more tibial tunnel widening and knee instability compared with the autograft group.

Current Evidence of Adult Stem Cells to Enhance Anterior Cruciate Ligament Treatment: A Systematic Review of Animal Trials

PURPOSE

To systematically review the available preclinical evidence of adult stem cells as a biological augmentation in the treatment of animal anterior cruciate ligament (ACL) injury.

STUDY DESIGN

Systematic review.

METHODS

PubMed (MEDLINE) and Embase were searched for the eligible studies. The inclusion criteria were controlled animal trials of adult stem cells used in ACL treatment (repair or reconstruction). Studies of natural ACL healing without intervention, in vitro studies, ex vivo studies, and studies without controls were excluded. Evidence level, methodologic quality, and risk of bias of each included study were identified using previously established tools.

RESULTS

Thirteen animal studies were included. Six of 7 studies using bone marrow-derived mesenchymal stem (stromal) cells (BMSCs) reported a positive enhancement in histology, biomechanics, and biochemistry within 12 weeks postoperatively. Four studies using ACL-derived vascular stem cells showed a promoting effect in histology, biomechanics, and imaging within 8 weeks postoperatively. Two studies focusing on animal tendon-derived stem cells (TDSCs) and human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) reported promotable effects for the early healing in a small animal ACL model.

CONCLUSIONS

BMSCs, ACL-derived vascular stem cells, TDSCs, and hUCB-MSCs were shown to enhance the healing of ACL injury during the early phase in small animal models.

CLINICAL RELEVANCE

Results of clinical trials using adult stem cells in ACL treatment are conflicting, and a systematic review of the current best preclinical evidence is crucial to guide further application.

Injectable hydrogels for delivering biotherapeutic molecules

To date, numerous delivery systems based on either organic or inorganic material have been developed to achieve efficient and sustained delivery of therapeutics. Hydrogels, which are three dimensional networks of crosslinked hydrophilic polymers, have a significant role in solving the clinical and pharmacological limitations of present systems because of their biocompatibility, ease of preparation and unique physical properties such as a tunable porous nature and affinity for biological fluids. Development of an in situ forming injectable hydrogel system has allowed excellent spatial and temporal control, unlike systemically administered therapeutics. Injectable hydrogel systems can offset difficulties with conventional hydrogel-based drug delivery systems in the clinic by forming a drug/gene delivery or cell-growing depot in the body with a single injection, thereby enabling patient compliance and comfort. Carbohydrate polymers are widely used for the synthesis of injectable in situ-forming hydrogels because of ready availability, presence of modifiable functional groups, biocompatibility and other physiochemical properties. In this review, we discuss different aspects of injectable hydrogels, such as bulk hydrogels/macrogels, microgels, and nanogels derived from natural polymers, and their importance in the delivery of therapeutics such as genes, drugs, cells or other biomolecules and how these revolutionary systems can complement existing therapeutic delivery systems.

Autogenous Hamstring-Bone Graft Preparation for Anterior Cruciate Ligament Reconstruction

Despite the popularity of anterior cruciate ligament (ACL) reconstruction procedures, the ideal graft for reconstruction remains a matter of controversy. The ideal graft for ACL reconstruction should have histologic and biomechanical characteristics similar to those of the native ACL; should be quickly and fully incorporated within the bony tunnels; should maintain its viscoelastic properties for a long time; should have minimal donor-site morbidity; should be of sufficient length and diameter; should have minimal adverse effects on the extensor mechanism; should have no risk of rejection or disease transmission; and should be cost-effective and readily available. Synthetic grafts are not widely accepted because of their dangerous complications. The main sources of grafts for ACL reconstruction are allografts and autografts. Each type of graft has its own relative advantages and disadvantages. Allografts are not available in every country, besides being expensive, and there are many concerns regarding disease transmission. Autografts, particularly bone-patellar tendon-bone (BPTB), and hamstring tendon grafts have been the standard for ACL reconstruction. The main advantage of autogenous BPTB grafts is the direct bone-to-bone healing in the tunnel, whereas the main disadvantages of such grafts are related to donor-site morbidity, anterior knee pain, and extensor mechanism dysfunction. The popularity of autogenous hamstring tendon grafts for ACL reconstruction is increasing, but there are still concerns regarding the slow soft tissue-to-bone healing, with delayed healing and incorporation of the graft. We describe a technique for ACL reconstruction with autogenous hamstring-bone graft, aiming to produce a type of graft that combines the main advantages of BPTB and hamstring grafts, with avoidance of the main disadvantages of these 2 most commonly used graft types in ACL reconstruction.

Magnetic resonance imaging after anterior cruciate ligament reconstruction: A practical guide

Anterior cruciate ligament (ACL) reconstruction is one of the most common orthopedic procedures performed worldwide. In this regard, magnetic resonance imaging (MRI) represents a useful pre-operative tool to confirm a disruption of the ACL and to assess for potential associated injuries. However, MRI is also valuable post-operatively, as it is able to identify, in a non-invasive way, a number of aspects and situations that could suggest potential problems to clinicians. Graft signal and integrity, correct tunnel placement, tunnel widening, and problems with fixation devices or the donor site could all compromise the surgical outcomes and potentially predict the failure of the ACL reconstruction. Furthermore, several anatomical features of the knee could be associated to worst outcomes or higher risk of failure. This review provides a practical guide for the clinician to evaluate the post-surgical ACL through MRI, and to analyze all the parameters and features directly or indirectly related to ACL reconstruction, in order to assess for normal or pathologic conditions.

Is There a Difference in Graft Motion for Bone-Tendon-Bone and Hamstring Autograft ACL Reconstruction at 6 Weeks and 1 Year?

BACKGROUND

Bone-patellar tendon-bone (BTB) grafts are generally believed to heal more quickly than soft tissue grafts after anterior cruciate ligament (ACL) reconstruction, but little is known about the time course of healing or motion of the grafts within the bone tunnels.

HYPOTHESIS

Graft-tunnel motion will be greater in hamstring (HS) grafts compared with BTB grafts and will be less at 1 year than at 6 weeks.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve patients underwent anatomic single-bundle ACL reconstruction using HS or BTB autografts (6 per group) with six 0.8-mm tantalum beads embedded in each graft. Dynamic stereo x-ray images were collected at 6 weeks and 1 year during treadmill walking and stair descent and at 1 year during treadmill running. Tibiofemoral kinematics and bead positions were evaluated. Graft-tunnel motion was based on bead range of motion during the loading response phase (first 10%) of the gait cycle.

RESULTS

During treadmill walking, there was no difference in femoral tunnel or tibial tunnel motion between BTB or HS grafts at 6 weeks (BTB vs HS: 2.00 ± 1.05 vs 1.25 ± 0.67 mm [femoral tunnel]; 1.20 ± 0.63 vs 1.27 ± 0.71 mm [tibial tunnel]), or 1 year (BTB vs HS: 1.62 ± 0.76 vs 1.08 ± 0.26 mm [femoral tunnel]; 1.58 ± 0.75 vs 1.68 ± 0.53 mm [tibial tunnel]). During stair descent, there was no difference in femoral or tibial tunnel motion between BTB and HS grafts at 6 weeks or 1 year. With running, there was no difference between graft types at 1 year. For all results, P values were > .05. Knee kinematics were consistent with the literature.

CONCLUSION

During walking and stair descent, ACL reconstruction using suspensory fixation yielded no difference between graft types in femoral or tibial tunnel motion at 6 weeks or 1 year. All subjects were asymptomatic with knee kinematics similar to that of the literature. The significance of persistent, small (1 to 3 mm) movements at 1 year for healing or graft performance is unknown.

CLINICAL RELEVANCE

These study results may have significant implications for graft choice, rehabilitation strategies, and timing for return to sports.

Allograft integration in a rabbit transgenic model for anterior cruciate ligament reconstruction

BACKGROUND

Tissue engineering strategies include both cell-based and cell homing therapies. Ligamentous tissues are highly specialized and constitute vital components of the musculoskeletal system. Their damage causes significant morbidity and loss in function.

HYPOTHESIS

The aim of this study is to analyze tendinous graft integration, cell repopulation and ligamentization by using GFP+/- allografts in GFP+/- transgenic New Zealand white (NZW) rabbits.

MATERIAL AND METHODS

Graft implantation was designed to closely mimic anterior cruciate ligament (ACL) repair surgery. Allografts were implanted in 8 NZW rabbits and assessed at 5 days, 3 weeks and 6 weeks through: (1) arthroCT imaging, (2) morphological analysis of the transplanted allograft, (3) histological analysis, (4) collagen type I immunochemistry, and (5) GFP cell tracking. Collagen remodeling was appreciated at 3 and 6 weeks.

RESULTS

Graft repopulation with host cells, chondrocyte-like cells at the tendon-bone interface and graft corticalization in the bone tunnels were noticed at 3 weeks. By contrast we noticed a central necrosis aspect in the allografts intra-articularly at 6 weeks with a cell migration towards the graft edge near the synovium.

DISCUSSION

Our study has served to gain a better understanding of tendinous allograft bone integration, ligamentization and allograft repopulation. We believe that both cell-based therapies and cell homing therapies are beneficial in ligament tissue engineering. Future studies may elucidate whether cell repopulation occurs with pre-differentiated or progenitor cells. We believe that both cell-based therapies and cell homing therapies are beneficial in ligament tissue engineering.

LEVEL OF EVIDENCE

Level V (animal study).

Distal biceps tendon repair: comparison of clinical and radiological outcome between bioabsorbable and nonabsorbable screws

BACKGROUND

Distal biceps tendon repair to the radial tuberosity can be conducted by means of an interference screw in combination with a transosseous button. Bioabsorbable interference screws have been associated with complications such as severe osteolytic reactions. We questioned whether patients with a distal biceps tendon repair with bioabsorbable poly-L-lactide (PLLA) screws had different functional, clinical, and radiologic outcome than patients with nonabsorbable poly-ether ether ketone (PEEK) screws.

METHODS

Between 2010 and 2014, 23 patients with an acute distal biceps tendon rupture were treated with reinsertion of the distal biceps tendon in a bone tunnel at the radial tuberosity through a single anterior incision using a transosseous button combined with an interference screw. A PLLA screw was used in 12 patients and a PEEK screw in 11 patients. All patients were retrospectively evaluated with a minimal follow-up of 1 year clinically and by means of the visual analog scale for pain, Mayo Elbow Performance Score, and Disabilities of Arm, Shoulder and Hand Outcome Measure score. Bone tunnel volume was measured with computed tomography segmentation.

RESULTS

Elbow mobility and arm and forearm circumference were symmetric for all patients. The visual analog scale for pain was 0.2 in the PLLA group and 0.7 in the PEEK group. The Disabilities of Arm, Shoulder and Hand score and Mayo Elbow Performance Score were 5.4 and 98.7 in the PLLA group vs. 3.1 and 95.9 in the PEEK group. Bone tunnel enlargement of 43% in the PLLA and 38% in the PEEK group was noted.

CONCLUSIONS

Clinical and functional outcome at more than 1 year after distal biceps tendon repair was excellent in both groups. Bone tunnel widening occurred in all patients.

Tendon Graft Healing in Multiligament Reconstructed Knee Detected by FDG-PET/CT: A Pilot Study

Background and Aims:

The detection of graft viability is challenging in the multiligament reconstructed knee. Magnetic resonance imaging gives structural information but lacks the capability to assess biological activity of the grafts. 18F-labeled fluorodeoxyglucose positron emission tomography combined with computer tomography is shown to be a sensitive method for imaging tissue metabolism and viability. The aim of the present study was to evaluate the feasibility of fluorodeoxyglucose positron emission tomography combined with computer tomography imaging in the detection of the replacement graft metabolism in multiligament reconstructed knees.

Materials and Methods:

Seven patients (17–44 years) with multiligament reconstructed knee underwent fluorodeoxyglucose positron emission tomography combined with computer tomography to evaluate the biological activity of replacement grafts. The degree of fluorodeoxyglucose uptake reported as standard uptake values from the region of interest was analyzed 3–24 months postoperatively.

Results:

In all patients, the fluorodeoxyglucose positron emission tomography combined with computer tomography showed increased fluorodeoxyglucose uptake in all replacement grafts at different follow-up time points. Furthermore, fluorodeoxyglucose was higher at femoral condyles of operated knees compared to contralateral reference values.

Conclusion:

This pilot study shows a significant increase in tendon graft metabolism during two first years of postoperative healing. The fluorodeoxyglucose positron emission tomography combined with computer tomography imaging seems to be adequate method of assessment of graft metabolism and viability during postoperative healing. The clinical value of fluorodeoxyglucose positron emission tomography combined with computer tomography imaging, however, warrants further evaluation with longitudinal studies with a larger patient population.

Decellularized Versus Fresh-Frozen Allografts in Anterior Cruciate Ligament Reconstruction: An In Vitro Study in a Rabbit Model

BACKGROUND

The common fresh-frozen allografts that are used for anterior cruciate ligament (ACL) reconstructions behave slower during the remodeling process and produce weaker tendon-bone integrations than do autografts. Decellularization of allogenic tendons results in a clean and porous collagen scaffold with low antigenicity and high compatibility, which may be more suitable for ACL reconstructions.

HYPOTHESIS

Allograft decellularization will result in a tissue structure with suitable mechanical characteristics for ACL reconstruction, thereby promoting graft remodeling and enhancing tendon-bone healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

Decellularized allograft tissues were prepared with a pH-modified decellularization process and evaluated for their biocompatibility and biomechanical character in vitro. Eighty New Zealand White rabbits were divided into 2 groups, with 40 in each group, to receive ACL reconstruction with either fresh-frozen (common) allografts or decellularized allografts on both knees. At 2, 4, 8, and 12 weeks postoperatively, the rabbits were euthanized for biomechanical testing, micro-computed tomography analysis, and histologic analysis.

RESULTS

The pH-modified decellularized allograft tissues kept excellent biocompatibility and biomechanical character during the in vitro study. Biomechanical testing indicated that the decellularized allograft had significantly higher ultimate load (P = .02) and stiffness (P = .01) levels than the common allograft at 12 weeks, and there was no significant difference between the 2 groups at any other time point. The micro-CT evaluation determined significantly higher bone mineral density (P < .01) in the decellularized allograft group than that in the common allograft group at 12 weeks, but no difference between the 2 groups was observed at any other time point. Regarding bone volume/total volume, there was no difference between the 2 groups at any time point. Fibroblast ingrowths, vascular formation, and connective tissue formation in the tendon-bone interface were better in the decellularized group within 8 weeks. New bone formation was more common in the decellularized allograft group. The collagen birefringence was restored more quickly in the decellularized allograft group than in the common allograft group at all time points.

CONCLUSION

The use of pH-modified decellularized allografts compared with the common allografts resulted in better cellularity, vascularity, collagen matrix remolding, new bone formation around the graft, enhanced tendon-bone healing, and higher ultimate failure load and stiffness of the graft after ACL reconstruction in the rabbit model.

CLINICAL RELEVANCE

The pH-modified decellularized allograft may be a better graft option than the common fresh-frozen allograft for knee ligament reconstructions.