A Comparative Animal Study of Tendon Grafts Healing After Remnant-Preserving Versus Conventional Anterior Cruciate Ligament Reconstruction

Primary Repair for Treating Acute Proximal Anterior Cruciate Ligament Tears: A Histological Analysis and Prospective Clinical Trial

Reconstruction surgery for acute proximal anterior cruciate ligament (ACL) tears remains controversial. Recently, ACL primary repair has received increasing attention in ACL treatment. This study aimed to explore the histological characteristics of ACL healing in primary repair and compare its therapeutic and prognostic results with the reconstruction of acute proximal ACL tears. Histological experiments using rabbits and a prospective clinical trial were conducted. We established a rabbit model of ACL primary repair, and histological changes were observed using haematoxylin and eosin (HE) and toluidine blue staining. We performed immunohistochemical analysis of CD34 and S-100 and measured the expression of collagen I and II using qRT-PCR, Western blotting, and immunohistochemistry. The prospective clinical trial involved performing ACL primary repair and reconstruction in patients with acute proximal ACL tears to detect proprioception and evaluate the function of joints. We discovered that primary repair promoted cell proliferation in the tendon-bone transition and ligament portions, reduced osteoarthritis-like pathological changes, and maintained blood vessels and proprioceptors within the ACL. In the clinical trial, primary repair achieved similar therapeutic outcomes, including recovery of knee function and proprioception, in the follow-up period as ACL reconstruction. However, the primary repair had a significantly shorter operative time and lower cost than reconstruction. Therefore, doctors should consider the benefit of primary repair in treating acute proximal ACL tears.

Remnants-preserving ACL reconstruction using direct tendinous graft fixation: a new rat model

BACKGROUND

Anterior cruciate ligament (ACL) repair techniques are new emerging strategies prevailing, in selected cases, over standard reconstruction of the ACL with excision of its remnants. Mid-substance ACL tears represent a challenge for ACL repair techniques, and remnants-preserving ACL reconstruction (rp-ACLR) using an autograft remains the recommended treatment in this situation. However, morbidity associated with the autograft harvesting prompts the need for alternative surgical strategies based on the use of synthetic scaffolds. Relevant small animal models of mid-substance tears with ACL remnants preservation and reconstruction are necessary to establish the preliminary proof of concept of these new strategies.

METHODS

A rat model of rp-ACLR using a tendinous autograft after complete mid-substance ACL transection was established. Twelve weeks following surgery, clinical outcomes and knee joints were assessed through visual gait analysis, Lachman tests, thigh perimeter measurements, magnetic resonance imaging, micro-computed tomography, and histology, to evaluate the morbidity of the procedure, accuracy of bone tunnel positioning, ACL remnants fate, osteoarthritis, and autograft bony integration. Results were compared with those obtained with isolated ACL transection without reconstruction and to right non-operated knees.

RESULTS AND DISCUSSION

Most operated animals were weight-bearing the day following surgery, and no adverse inflammatory reaction has been observed for the whole duration of the study. Autograft fixation with cortical screws provided effective graft anchorage until sacrifice. Healing of the transected ACL was not observed in the animals in which no graft reconstruction was performed. rp-ACLR was associated with a reduced degeneration of the ACL remnants (p = 0.004) and cartilages (p = 0.0437). Joint effusion and synovitis were significantly lower in the reconstructed group compared to the transected ACL group (p = 0.004). Most of the bone tunnel apertures were anatomically positioned in the coronal and/or sagittal plane. The most deviated bone tunnel apertures were the tibial ones, located in median less than 1 mm posteriorly to anatomical ACL footprint center.

CONCLUSION

This study presents a cost-effective, new relevant and objective rat model associated with low morbidity for the preliminary study of bio-implantable materials designed for remnants-preserving ACL surgery after mid-substance ACL tear.

Ligamentization and Remnant Integration: Review and Analysis of Current Evidence and Implications for Scapholunate Reconstruction

Background  Scapholunate interosseous ligament injuries are common but remain a therapeutic challenge. Current treatment modalities prioritize restoration of normal anatomy with reconstruction where appropriate. To date no reconstructive technique has been described that discusses the potential benefit of preservation of the scapholunate ligament remnant. Little is known about the "ligamentization" of grafts within the wrist. However, a growing body of knee literature suggests that remnant sparing may confer some benefit. In the absence of wrist specific studies, this literature must guide areas for potential augmentation of current surgical practices. Objective  The purpose of this study was to perform a review of the process of ligamentization and a systematic review of the current literature on the possible role of ligament sparring and its effect on ligamentization. Methods  A systematic search of the literature was performed to identify all the studies related to remnant sparing and the ligamentization of reconstructed tendons, regardless of graft type or joint involved from MEDLINE, EMBASE, and PubMed until February 1, 2016 using the following keywords: ligamentization, graft, remodelling, reconstruction, biomechan*, histolo∗, scapholunate ligament. Each selected study was evaluated for methodological quality and risk of bias according to a modified Systematic Review Center for Laboratory Animal Experimentation criteria. Conclusions  The available literature suggests that ligament sparring demonstrated a trend toward improvements in vascularity, mechanoreceptors, and biomechanics that lessens in significance over time. Clinical Relevance  This review suggests that remnant sparing may be one way to improve outcomes of scapholunate ligament reconstructive surgery. Level of Evidence  This is a level I/II, review study.

Effect of Remnant Tissues on Outcomes of Anterior Cruciate Ligament Reconstruction at Follow-up Arthroscopy

BACKGROUND

Remnant-preserving anterior cruciate ligament reconstruction (ACLR) is sought to enhance vascularization and maturation of a graft and to produce positive clinical outcomes after reconstruction.

OBJECTIVE

The purpose of this study was to investigate an effect of remnant anterior cruciate ligament (ACL) tissues on outcomes of ACLR 1 year after reconstruction in younger populations.

DESIGN

Retrospective chart review.

SETTING

Inpatient orthopedic surgical and rehabilitation clinic.

SUBJECTS

The subjects were 644 patients who underwent primary ACLR.

INDEPENDENT VARIABLES

The independent variables were age, height, and body weight of the subjects, and the presence of remnant tissue.

MAIN OUTCOME MEASURES

The outcome measure was the number of subjects with secondary infra-articular injuries at a follow-up arthroscopy after ACLR. The odds ratio was calculated and compared between the remnant-preserving ACLR (ACLR-P) and remnant-resecting (ACLR-R) groups to investigate the effect of remnant tissues on postoperative outcomes.

RESULTS

A total of 416 cases met our inclusion criteria and were included in this study. There were 136 cases (49 males and 87 females) in the ACLR-P group with the mean age (±SD) of 17.86 ± 2.85 years. There were 280 cases (106 males and 174 females) in the ACLR-R group, and the mean age (±SD) was 18.13 ± 2.73 years. Of 136 cases in the ALCR-P group, 54 (39.7%) had abnormal arthroscopic findings that lead to a surgical intervention. Of 280 patients in the ACLR-R group, 128 (45.7%) had abnormal findings. Odds ratio was 0.78 [95% confidence interval (CI), 0.51-1.18; P = 0.24]. Four cases in the ACLR-P group and 8 in the ACLR-R group were diagnosed with ACL retear during follow-up arthroscopy. Odds ratio was 1.03 (95% CI, 0.30-3.48; P = 0.96).

CONCLUSIONS

The presence of ACL remnant tissues did not have a significant effect on outcomes 1 year after reconstruction. However, there was a trend that lower percentage of patients with remnant-preserving ALCR had abnormal arthroscopic findings that lead to a surgical treatment at follow-up arthroscopy 1 year after initial reconstruction. The presence of remnant tissues did not have a significant effect on retear rate.

Anterior cruciate ligament remnant-preserving and re-tensioning reconstruction: a biomechanical comparison study of three different re-tensioning methods in a porcine model

BACKGROUND

With the developments in the arthroscopic technique, anterior cruciate ligament (ACL) remnant-preserving reconstruction is gradually gaining attention with respect to improving proprioception and enhancing early revascularization of the graft. To evaluate the mechanical pull-out strength of three different methods for remnant-preserving and re-tensioning reconstruction during ACL reconstruction.

METHODS

Twenty-seven fresh knees from mature pigs were used in this study. Each knee was dissected to isolate the femoral attachment of ACL and cut the attachment. An MTS tensile testing machine with dual-screw fixation clamp with 30° flexion angle was used. The 27 specimens were tested after applying re-tensioning sutures with No. 0 polydioxanone (PDS), using the single stitch (n = 9), loop stitch (n = 9), and triple stitch (n = 9) methods. We measured the mode of failure, defined as (1) ligament failure (longitudinal splitting of the remnant ACL) or (2) suture failure (tearing of the PDS stitch); load-to-failure strength; and stiffness for the three methods. Kruskal-Wallis test and Mann-Whitney U-test were used to compare the variance of load-to-failure strength and stiffness among the three groups.

RESULTS

Ligament failure occurred in all cases in the single stitch group and in all but one case in the triple stitch group. Suture failure occurred in all cases in the loop stitch group and in one case in the triple stitch group. The load-to-failure strength was significantly higher with loop stich (91.52 ± 8.19 N) and triple stitch (111.1 ± 18.15 N) than with single stitch (43.79 ± 11.54 N) (p = 0.002). With respect to stiffness, triple stitch (2.50 ± 0.37 N/mm) yielded significantly higher stiffness than the other methods (p = 0.001).

CONCLUSIONS

The results suggested that loop stitch or triple stitch would be a better option for increasing the mechanical strength when applying remnant-preserving and re-tensioning reconstruction during ACL reconstruction.

Osteoprotegerin/bone morphogenetic protein 2 combining with collagen sponges on tendon-bone healing in rabbits

INTRODUCTION

The aim was to investigate the effect of collagen sponges (CS) as a delivery device for osteoprotegerin (OPG)/bone morphogenetic protein 2 (BMP-2) and support matrix on the tendon-bone healing after anterior crusicate ligament (ACL) reconstruction in modeled rabbits.

MATERIALS AND METHODS

Sixty New Zealand white rabbits were randomly divided into four groups based on treatments they received at the tendon-bone interface after left knee ACL reconstruction: the control group, OPG/BMP-2, CS, and OPG/BMP-2/CS combination. At 4, 8 and 12 weeks post-surgery, five rabbits from each group were euthanized to examine the tendon-bone healing. Levels of OPG and BMP-2 in synovial fluid, the bone tunnel enlargement value, the histomorphological typing of tendon-bone interface, and the bone tunnel area of the tendon-bone interface were compared among different treatments.

RESULTS

The OPG/BMP-2/CS combination treatment group had the highest levels of OPG and BMP-2 in synovial fluid (both P < 0.05), the greatest number of Sharpey-like collagen fibers at all test points (P < 0.05), the most fibrocartilage enthesis on week 12, the greatest bone tunnel area (P < 0.05), and the greatest decrease in bone tunnel enlargement on week 12 (P < 0.05). Histomorphological typing of tendon-bone interface of all groups showed changes varying from tendon-bone separation to firm healing, and the change was most significant in the OPG/BMP-2/CS combination treatment group.

CONCLUSION

CS treatment alone serves as a fixing support, and CS combining with growth factors OPG/BMP-2 ensures slow and stable release of OPG/BMP-2, significantly improves the tendon-bone healing in the rabbit ACL model.

Anterior cruciate ligament reconstruction with remnant preservation: current concepts

Anterior cruciate ligament (ACL) tears are a common knee injury, and anatomic ACL reconstruction (ACLR) is now the standard of care to restore knee stability. Nevertheless, re-tear rates exceeding 5% are commonly reported, with an even higher percentage of patients unable to achieve preinjury knee function. As the torn ACL remnant contains elements (eg, cells, blood vessels and mechanoreceptors) essential to ACL function, it has been hypothesised that ACLR with remnant preservation may improve graft remodelling, in turn more quickly and completely restoring ACL structure and function. In this Current Concepts review, we summarise the present understanding of ACLR with remnant preservation, which includes selective bundle reconstruction of partial (one-bundle) ACL tears and single- and double-bundle ACLR with minimal to partial debridement of the torn ACL stump. Reported benefits of remnant preservation include accelerated graft revascularisation and remodelling, improved proprioception, decreased bone tunnel enlargement, individualised anatomic bone tunnel placement, improved objective knee stability and early mechanical support (with selective bundle reconstruction) to healing tissues. However, clinical studies of ACLR with remnant preservation are heterogeneous in the description of remnant characteristics and surgical technique. Presently, there is insufficient evidence to support the superiority of ACLR with remnant preservation over the standard technique. Future studies should better describe the ACL tear pattern, remnant volume, remnant quality and surgical technique. Progress made in understanding and applying remnant preservation may inform, and be reciprocally guided by, ongoing research on ACL repair. The goal of research on ACLR with remnant preservation is not only to achieve anatomic structural restoration of the ACL but also to facilitate biologic healing and regeneration to ensure a more robust and functional graft.

The effect of interleukin-8 in the early stage after anterior cruciate ligament reconstruction with remnant preservation

PURPOSE

We studied the effect of interleukin-8 (IL-8) as the factor for angiogenesis in the joint fluid of remnant-preserved anterior cruciate ligament reconstruction (RP-ACLR).

MATERIALS AND METHODS

We measured 12 cytokines in joint fluid by multiplex assay and assessed the relationship between IL-8 and vascular endothelial growth factor (VEGF) concentrations. The signal intensity and mean sagittal diameter via postoperative magnetic resonance imaging (MRI) scans were evaluated and the stress X-ray image was analyzed at 3, 6, and 12 months after operation.

RESULTS

The IL-8 concentration was highest 3 months postoperatively in those patients who underwent RP-ACLR. Clinical data also showed that the signal intensity and stress radiography of the knee graft were significantly better at the early postoperative stage.

DISCUSSION

Our results show that IL-8 plays an important role in angiogenesis within 3 months after RP-ACLR. This effect yields better recovery after operation. RP-ACLR patients with high knee stability in clinical data were identical to those with high expression of IL-8 in experimental data. Therefore, IL-8 has been shown to help revascularization and ligamentization of the grafted tendon. These results indicate that IL-8 in RP-ACLR is an important factor for angiogenesis after operation. Unfortunately, the relationship of IL-8 and VEGF in vivo has not been studied.

CONCLUSION

Our results showed that the IL-8 concentration was very high within 3 months after RP-ACLR operation. The increase in concentration of IL-8 over time was consistent with the increase in VEGF concentration. In the IL-8 clinical setting, MRI analysis showed that ACL synovialization and tension were better in patients who underwent the remnant preservation method. In addition, it was shown that RP-ACLR may be advantageous for early anterior stability within 1 year post operation and beneficial for tendon graft in the early stage post operation. Taken together, our findings suggest that IL-8 may contribute to angiogenesis which is helpful for revascularization and ligamentization of the graft tendon in the early stages of RP-ACLR.

Proprioceptive Changes in Bilateral Knee Joints Following Unilateral Anterior Cruciate Ligament Injury in Cynomolgus Monkeys

BACKGROUND The anterior cruciate ligament (ACL) is one of the most important structures maintaining stability of knee joints, and the proprioception of the ACL plays a key role in it. If the ACL is injured in the unilateral knee joint, it changes nerve electrophysiology, morphology, and quantity of the proprioceptors in the bilateral ACL. The aim of this study was to explore the proprioceptive changes in the bilateral knee joints following unilateral ACL injury, and to provide a theoretical foundation and ideas for clinical treatment. MATERIAL AND METHODS Nine normal cynomolgus monkeys were chosen and used to developed a model of unilateral ACL injury, and 3 monkeys without modeling were used as blank control. At the 4th, 8th, and 12th weeks, the changes in ACL nerves were inspected using electrophysiology [somatosensory evoked potentials (SEPs) and motor nerve conduction velocity (MCV)], and the changes of morphology and quantity of the proprioceptors in ACL were observed and measured under gold chloride staining. RESULTS On the injured and contralateral knee joints, the incubations were extended and the amplitudes were decreased over time. In addition, with the extension of time, the total number of proprioceptors in the ACL decreased, and the variable number of proprioceptors in the ACL increased. CONCLUSIONS ACL injury leads to attenuation of proprioception on the injured side, and also leads to the attenuation of proprioception on the contralateral side, and there is a tendency could get worse over time.

Second-Look Arthroscopic Evaluation and Clinical Outcomes of Anatomic Anterior Cruciate Ligament Reconstruction with Autograft and Hybrid Graft: A Retrospective Study

BACKGROUND Graft choice is very controversial. This study compared the second-look evaluation and clinical outcomes of anatomic ACL-R using a thin autograft versus a thick hybrid graft. MATERIAL AND METHODS Sixty-eight patients who had received ACL-R with hamstring autograft or autograft-allograft hybrid graft accepted second-look arthroscopy were grouped (autograft: n=31, age: 32.8±8.9, Male/Female: 16/15, and hybrid graft: n=37, age: 33.9±8.4, Male/Female: 27/10). Patients were evaluated with the functional score and KT-1000 test before reconstruction. The re-examination and second-look evaluation were performed at 2-year follow-up. Results were compared and further comparisons were made for grafts size >8.5 mm. RESULTS The hybrid group showed thicker graft size and bigger graft occupancy (9.0±0.5 mm vs. 8.5±0.7 mm, P=.003; 80.1±7.0% vs. 69.9±6.9%, P8.5 mm were selected and compared (autograft, n=16; hybrid, n=29). Graft tension and Synovial coverage showed a significant difference (P=.036 and P=.029). The Lysholm, IKDC, and KT-1000 test were significantly superior for the autograft than the hybrid graft (P=.036, P=.004, and P=.003, respectively). CONCLUSIONS A pure autograft is superior to a hybrid graft with same diameter in ACL-R because the augmenting allografts may be null and void. Therefore, a homogenous graft is recommended.