Anterior cruciate ligament replacement: a review

The anterior cruciate ligament (ACL) is the major intra-articular mechanical element that limits motion of the tibia with respect to the femur. It is a multi-fasciculated structure composed of crimped aligned collagen fibers. The purpose of this paper is to review the literature on ACL structure and mechanical properties in an effort to stimulate the development of a new generation of more effective replacement devices. Replacement of the ACL is achieved using biologic and synthetic grafts. Biologic grafts include illiotibial band, semitendinosus and gracilis tendons, patellar tendon, and meniscus. Bone-patellar-bone complexes used to replace the ACL are revascularized and ultimately replaced by neo-ligament. Synthetic implants including the Integraft, Leads-Keio ligament, Gore-Tex? ligament and Kennedy Ligament Augmentation Device (LAD) have either not been approved or approved by the FDA for limited use as a replacement for the ACL. The Kennedy LAD has been found to increase the strength of autogenous tissue during revascularization. Based on the success of autografts and the Kennedy LAD, we conclude that the next generation of ACL replacement devices will consist of a scaffold and a biodegradable augmentation device. The scaffold will have a structure that mimics the normal ACL as well as stimulates revascularization and healing. A biodegradable augmentation device will be employed to mechanically reinforce the scaffold without stress shielding the neo-ligament. By combining the advantages of autografts and a biodegradable augmentation device, a new generation of ACL replacements will be achieved.     

兔前交叉韧带保残重建的生物力学研究

目的 应用动物模型评估保留残端对兔前交叉韧带(ACL)重建的生物力学意义. 方法 将50只成年健康新西兰大白兔一侧后肢制作ACL断裂模型后随机分为两组(n=25),一组行保留残端ACL重建术(保残组),另一组行去除残端ACL重建术(去残组).所有手术均采用自体半腱肌腱作为移植物,并于术后12周统一将两组动物处死,行ACL大体观察及生物力学测试. 结果 术后12周取材时,保残组和去残组总计50个标本关节活动度与正常侧相比差异无统计学意义(t=0.440,P＝0.662).所有ACL移植物连续性完整,张力满意.保残组和去残组标本屈膝30°与90°胫骨前移距离、最大拉力载荷、最大拉伸距离以及刚度所占正常侧百分比差异均无统计学意义(P＞0.05);保残组中残端存活组和残端失效组标本屈膝30°与90°胫骨前移距离、最大拉力载荷、最大拉伸距离以及刚度所占正常侧百分比差异均无统计学意义(P＞ 0.05). 结论 保留残端重建ACL不能显著提高术后兔ACL的生物力学性能.     

Anterior cruciate ligament reconstruction in adolescents: a survivorship analysis

There are few reports on the longevity of anterior cruciate ligament (ACL) reconstruction in adolescents. In the study reported here, we performed a survivorship analysis of our experience with ACL reconstructions in adolescents. We retrospectively reviewed the cases of 276 consecutive patients (girls' bone age, > 13 years; boys' bone age, > 14 years; chronological age, < 18 years) who underwent primary ACL reconstruction. All patients underwent transphyseal ACL reconstruction with Achilles tendon soft-tissue allograft using the same technique. Twenty-nine patients (10.5%) were excluded or lost to follow-up. Mean follow-up of the remaining 247 patients was 6.3 years (range, 2-10 years). Data were collected from charts and telephone interviews. Failure was defined as the report of symptomatic knee instability and/or revision ACL surgery. The Kaplan-Meier method showed that 1-year survivorship of ACL reconstruction was 96.4% and 5-year survivorship was 93.1%.     

Anterior cruciate ligament deficiency alters the in vivo motion of the tibiofemoral cartilage contact points in both the anteroposterior and mediolateral directions

BACKGROUND: Quantifying the effects of anterior cruciate ligament deficiency on joint biomechanics is critical in order to better understand the mechanisms of joint degeneration in anterior cruciate ligament-deficient knees and to improve the surgical treatment of anterior cruciate ligament injuries. We investigated the changes in position of the in vivo tibiofemoral articular cartilage contact points in anterior cruciate ligament-deficient and intact contralateral knees with use of a newly developed dual orthogonal fluoroscopic and magnetic resonance imaging technique. METHODS: Nine patients with an anterior cruciate ligament rupture in one knee and a normal contralateral knee were recruited. Magnetic resonance images were acquired for both the intact and anterior cruciate ligament-deficient knees to construct computer knee models of the surfaces of the bone and cartilage. Each patient performed a single-leg weight-bearing lunge as images were recorded with use of a dual fluoroscopic system at full extension and at 15 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion. The in vivo knee position at each flexion angle was then reproduced with use of the knee models and fluoroscopic images. The contact points were defined as the centroids of the areas of intersection of the tibial and femoral articular cartilage surfaces. RESULTS: The contact points moved not only in the anteroposterior direction but also in the mediolateral direction in both the anterior cruciate ligament-deficient and intact knees. In the anteroposterior direction, the contact points in the medial compartment of the tibia were more posterior in the anterior cruciate ligament-deficient knees than in the intact knees at full extension and 15 degrees of flexion (p < 0.05). No significant differences were observed with regard to the anteroposterior motion of the contact points in the lateral compartment of the tibia. In the mediolateral direction, there was a significant lateral shift of the contact points in the medial compartment of the tibia toward the medial tibial spine between full extension and 60 degrees of flexion (p < 0.05). The contact points in the lateral compartment of the tibia shifted laterally, away from the lateral tibial spine, at 15 degrees and 30 degrees of flexion (p < 0.05). CONCLUSIONS: In the presence of anterior cruciate ligament injury, the contact points shift both posteriorly and laterally on the surface of the tibial plateau. In the medial compartment, the contact points shift toward the medial tibial spine, a region where degeneration is observed in patients with chronic anterior cruciate ligament injuries.     

Anterior cruciate ligament reconstruction: a systematic review of polyethylene terephthalate grafts

Background: The ligament advanced reinforcement system (LARS) ligament is an artificial polyester ligament made from polyethylene terephthalate (PET) that is used for primary anterior cruciate ligament (ACL) reconstructive surgery. Recent media attention has resulted in a high awareness of this reconstructive option among patients; however, the outcomes compared with autograft are controversial. Objectives: A systematic review of the literature was undertaken to examine the outcomes following LARS and long‐term PET artificial grafts in ACL reconstructive surgery. The ultimate objective was to determine whether the LARS ligament should be incorporated into routine practice. Methods: A systematic search strategy from 1970 to June 2010 was used to retrieve relevant studies. Inclusion of articles was established through application of a predetermined protocol, independent assessment by two reviewers and a final consensus decision. Results: Twelve articles met the inclusion criteria for the LARS ligament. The methodology of the identified articles was poor. Only short‐term outcomes were available. These results were good with low complication rates. Eleven articles reported on other PET grafts and recorded long‐term follow‐up of more than 4 years. These grafts had poor outcomes and a high rate of complications. No meta‐analysis was possible. Conclusions: There are surprisingly few studies reporting on LARS ligament outcomes. The literature has poor methodological quality. Short‐term results for the LARS ligament appear good, with faster recovery times compared with autografts. Final short‐term results are not significantly different from autograft. There is real concern that late failure and iatrogenic osteoarthritis may occur based on the results of other PET grafts.     

前交叉韧带损伤:3.0TMR影像与关节镜对照分析

目的分析膝关节前交叉韧带损伤的3．0TMRI特征,并与关节镜手术结果对照。方法回顾性分析来我院行3．0T MR膝关节检查的36例前交叉韧带损伤患者的40个膝关节,全部病例经关节镜检查确诊。应用3．0T MR机（Philips Achieva型）,膝关节专用线圈,进行斜矢状位TSE T1WI、TSE T2WI、PD-SPIR和冠状位、轴位TSE T2WI扫描。前交叉韧带损伤分为完全断裂、撕裂（部分断裂）及胫骨端撕脱。将膝关节前交叉韧带损伤的3．0T MR影像特征与关节镜手术结果进行对照分析。结果前交叉韧带完全断裂MRI直接征象表现为韧带连续性中断,断端肿胀（21／25）,间接征象为交叉韧带过度弯曲、T2WI和PD-SPIR股骨髁间窝外侧骨挫伤;MRI与关节镜诊断完全符合率为84．00％。前交叉韧带撕裂（部分断裂）MRI直接征象为ACL矢状T2WI和PD-SPIR显示形态不规则、部分撕裂,ACL局部肿胀增粗,信号增高,仍可见连续存在的纤维低信号;MRI与关节镜诊断完全符合率为66．67％。前交叉韧带胫骨端撕脱MR检查直接征像为胫骨近端可见T1WI、T2WI低信号撕脱骨片（3／3）,ACL水肿、形态不规则,周围可见出血、积液,MRI与关节镜诊断符合率为100％。结论高场强3．0TMR膝关节诊断的多平面、多序列影像相结合可形成ACL立体影像观,结合临床能够有效诊断ACL损伤。     

Anterior cruciate ligament tear patterns in young patients: An arthroscopic multicenter study

IntroductionIn the last decade, there has been a renewed interest in anterior cruciate ligament (ACL) preservation surgeries in the younger patients. Several ACL preservation techniques such as primary repair, augmented repair, and scaffold repair have been described based on the particular tear type and pattern. The purpose of this study was to determine the distribution of tear patterns in young patients presenting with an acute ACL injury.MethodsA prospective observational study was performed at two tertiary children’s hospitals. Patients under 18 years undergoing ACL reconstruction within 8 weeks of initial injury were included from 2017 to 2019. Tear patterns were classified by two orthopedic surgeons from each of the two centers during arthroscopic ACL reconstruction into 4 types: I. Avulsion off the femur, II. <10% of total ACL length tear from femoral end, III. Mid-substance tear and IV. Single bundle tear. For reliability, the four surgeons classified ACL injury (2 rounds each) based on de-identified intraoperative videos of 33 randomly selected surgical ACL cases. Inter and intra-rater reliability studies were calculated using Kappa statistics.Results224 patients (123 males, 101 females) with mean age of 16 (range: 9–18) years were enrolled in this study. Fifty-seven (25%) patients reported contact injury while 167 (75%) reported non-contact. Isolated ACL injury was recorded in 70 (31%) patients, while concomitant injuries were recorded in 154 patients (69%). The most common associated injury was lateral meniscus tear (35%), followed by lateral and medial meniscus tears (20%). According to our classification, 31 (14%) patients were Type I, 30 (13%) were Type II, 139 (62%) were Type III, 18 (8%) were Type IV. The intra-rater reliability was excellent for 2 reviewers, good for 1 and marginal for another. The overall inter-rater reliability for all 4 reviewers was marginal for both readings. There was no statistical difference in the occurrence of type of tear based on the mechanism of injury (contact vs non-contact) or age of the patients.ConclusionsThis is the first multicenter study using an arthroscopic assessment to classify the location of ACL tear in the young population. It gives us further insight on the possible application for surgeries to preserve the ACL in this group. Larger studies incorporating these findings with MRI evaluation and ACL repair techniques are needed to confirm the utility of this information to decide the eligibility for repair in pediatric patients.     

Anterior cruciate ligament reconstruction with the ligament augmentation and reconstruction system: a systematic review

Purpose

The Ligament Augmentation and Reconstruction System (LARS) is a third generation of synthetic ligament, designed to overcome the issues of graft failure and synovitis which led previous generations of synthetic ligaments to fall out of favour. The theoretical benefits of LARS are appealing but this has not led to widespread uptake of the system in preference to autograft. The aim of this systematic review is to assess whether the evidence exists to support the use of LARS with respect to outcomes and complications.

Methods

A systematic search process was undertaken from January 1990 to June 2012 to identify primary evidence relating to the use of LARS in anterior cruciate ligament (ACL) single ligament reconstruction.

Results

Nine studies were found meeting the search criteria including a single randomised controlled trial, two comparative series and six further observational case series. Overall the methodological quality of the studies was poor with follow-up to a maximum of five years. Reported outcome scores were good for LARS and comparable to autograft techniques. Complication rates were low and comparable to those published for autograft techniques within the wider literature. Two reported incidences of synovitis were identified in case reports.

Conclusions

The current literature supports the use of LARS in the short to medium term. However, high-quality studies with long-term follow-up are required to determine whether the use of LARS is preferable to autograft for ACL reconstruction over the longer term. Synovitis appears to be a rare complication closely related to imperfect graft positioning.     

Anterolateral instability in the anterior cruciate ligament deficient knee: A cadaver study

Knee instability was evaluated in 13 normal osteoligamentous knee preparations after transection of the anterior cruciate ligament. Abduction-adduction rotation, coupled tibial translatory movement, and coupled tibial axial rotation were recorded continuously and simultaneously during flexion or extension while applying a well defined valgus directed moment and during extension while applying an anterior tibial force. As a result of the valgus-directed moment, an increase was found in abduction rotation, in coupled anterior tibial translation, and in coupled internal tibial axial rotation. Coupled rotatory and translatory instabilities were larger, and maximum instability was observed at a smaller knee angle during the extension movement than during the flexion movement. The pattern of the instability, excited as a result of the valgus moment, was different from the instability excited as a result of an anterior tibial force.     

Anterior cruciate ligament reconstruction: the diagnostic value of MRI

Summary. A prospective study was carried out in order to evaluate the predictive value of MRI in the early postoperative course after cruciate ligament replacement. Twenty patients who had undergone anterior cruciate ligament reconstruction using autologous patellar tendon/bone grafts were examined clinically and with contrast enhanced MRI at 2, 12 and 24 weeks, and 1 and 2 years after operation. The clinical findings were evaluated according to the scores established by Lysholm, OAK and IKDC. The MRI scans (SP 63, 1.5 Tesla) were assessed in terms of the quality and signal intensity of the reconstructed ligaments. During the first postoperative year there was a significant increase of signal intensity and in homogeneity of the neoligament on in the MRI. Seventeen patients had an average value for signal/noise of 1.1 at two weeks after surgery, which had increased to 7.1 at 1 year. In 14 patients the reconstructed ligament could not be evaluated in MRI scans after 1 year but clinical instability was not suspected in any of these patients. Two years after operation the MRI signal intensity of the neoligament was again decreasing.

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Résumé. Une étude prospective a été faite, afin d’estimer la valeur de pronostic de l’IRM dans la phase postopératoire précoce du remplacement des ligaments croisés. 20 patients, avec des ligaments croisés antérieurs remplacés (transplantation autologue du tendon rotulien) ont été examinés cliniquement et à l’aide d’IRM de contraste, la 2e, 12e, 24e semaine post-opératoire et, 1 et 2 ans post-opératoires. Les examens cliniques ont étéévalués selon le score de Lysholm, OAK et IKDC. Les imageries IRM (SP 63, 1.5 Tesla) ont étéévaluées et mettant en évidence la qualité et l’intensité du signal du ligament reconstitué. Pendant la première année post-opératoire, on a notéà l’IRM une augmentation significative de l’intensité du signal et de la non-homogénéité du nouveau ligament chez 17 patients, avec une valeur moyenne du signal/écho allant de 1.1, 2 semaines postopératoire, jusqu’à 7.1, un an post-opératoire. Chez 14 patients dans la première année post-opératoire, le ligament reconstitué a pu être visualiséà l’IRM, bien qu’aucun de ces patients n’ai eu un examen clinique suspect, quand à l’instabilité. A l’IRM post-opératoire de la deuxième année, l’intenstié du signal du nouveau ligament a à nouveau diminué, selon une constatation régulière.

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Accepted: 24 February 1998     

ACL断裂对膝半月板和软骨应力分布的影响

[目的]采用三维有限元,对比分析前交叉韧带(anterior cruciate ligament,ACL)正常时和断裂后膝关节半月板和软骨的应力分布。[方法]构建胫股关节三维有限元模型,把ACL断裂引起的股骨外旋增加量(5.4°)设置为边界条件,以模拟ACL断裂后膝关节在伸直位的运动状态,同时在股骨上施加700 N向下载荷和134N向后载荷,对比分析ACL正常时和断裂后两种情况下半月板和软骨的应力分布。另一方面,在ACL断裂的胫股关节模型中分析两种工况:应用股骨外旋增加量模拟膝关节运动状态、不模拟运动状态,计算出这两种工况下胫股关节间的应力并进行比较。[结果]当ACL断裂后,除了外侧股骨软骨,内外侧间室中半月板和软骨的应力均比正常时有不同程度的增加,内侧胫骨软骨的应力增幅最大(57.6%),内侧间室的平均应力增幅大于外侧间室(34.1%vs 4.7%)。在ACL断裂胫股关节模型的两种工况之间,胫股关节间的平均应力差异为20%,外侧间室的平均应力差异大于内侧间室(32.6%vs 7.4%)。[结论]ACL断裂使胫股关节间的应力重新分布,主要引起内侧间室的应力明显增加。ACL断裂后膝关节的运动状态本身就可以造成关节间应力改变,所以在有限元分析时模拟膝关节的运动行为是有必要的。     

Partial tears of the anterior cruciate ligament. Progression to complete ligament deficiency

In a prospective seven-year study, we treated 32 patients with partial ruptures of the anterior cruciate ligament (ACL) verified by arthroscopy. Twelve knees (38%) progressed to complete ACL deficiency with positive pivot shift tests and increased anteroposterior translation on tests with the KT-1000 arthrometer. Patients with partial ACL tears frequently had limitation for strenuous sports, while those developing ACL deficiency had additional functional limitations involving recreational activities. Three factors were statistically significant in predicting which partial tears would develop complete ACL deficiency: the amount of ligament tearing--one-fourth tears infrequently progressed, one-half tears progressed in 50% and three-fourth tears in 86%; a subtle increase in initial anterior translation; and the occurrence of a subsequent re-injury with giving-way.