The anterior cruciate ligament

Our knowledge of the anterior cruciate ligament has expanded rapidly over the last decade. Recent advances in arthroscopic techniques, the development and release of synthetic stents and prostheses, increasing laboratory and clinical data involving allograft implantation, and biomechanical research in knee rehabilitation have led to a bewildering array of choices for treatment of anterior cruciate ligament deficiency. As new information and techniques are presented, and new synthetic and biological materials become available, orthopedic surgeons must judge their value and modify treatment recommendations accordingly. A thorough knowledge of the basic science and clinical information is necessary to appropriately evaluate these new advances. A review of our current knowledge of the anterior cruciate ligament is presented to facilitate this evaluation process.     

Revision anterior cruciate ligament reconstruction

Revision ACL surgery is indicated in patients who present with pathologic anterior laxity on clinical examination that reproduces their symptoms of instability during activities of daily living or athletic activities. The goals of the revision ACL surgery are to stabilize the knee, prevent further injury to the articular cartilage and menisci, and maximize the patient's function. Successful revision ACL surgery requires a thorough preoperative evaluation, including a detailed history, physical examination, and radiographic evaluation. Preoperative planning begins with a determination of the mechanisms of failure for the initial ACL reconstruction. Often a primary, as well as secondary cause, for failure can be identified. The determination of the cause of failure is the first step in a carefully-constructed treatment plan, which includes consideration of skin incisions to be used, method of graft removal, hardware removal, the need for a staged procedure or concomitant surgery, graft material selection, tunnel placement, graft fixation, and postoperative rehabilitation protocol. Despite the most meticulous planning, unanticipated findings may be encountered in the operating room, and the preoperative plan should have enough flexibility to accommodate these developments. Finally, it is crucial to counsel the patient preoperatively to limit his or her expectations regarding their surgical outcome. Given the complexity of revision ACL reconstruction, patient expectations must be adjusted to realistically match the potential for success. With proper planning, attention to detail, and appropriate patient expectations, revision ACL surgery can result in a beneficial and satisfying patient outcome.     

Arthroscopic anterior cruciate ligament repair: preliminary results and instrumented testing for anterior stability

The authors present their preliminary results of arthroscopic primary repair of anterior cruciate ligament tears performed on five patients, with a mean follow-up time of 9.2 months. All patients were re-evaluated by subjective questionnaire and clinical examination, and tested for anterior drawer at 20 degrees flexion using the KT-1000 Knee Ligament Arthrometer and the UCLA Instrumented Clinical Knee Testing Apparatus. Subjectively, four patients were rated as fair and one as good. The Lachman test was negative in two and trace or mildly positive in three patients. Pivot shift test was negative in all. Instrumented testing demonstrated three patients with increased anterior laxities outside the normal range, and two of these patients also showed reduced anterior stiffnesses which were beyond the normal range. Based on these results, the authors question the feasibility of arthroscopic repair of anterior cruciate ligament tears and suggest a more objective evaluation of this procedure.     

Imaging the anterior cruciate ligament

MR imaging has surpassed all other imaging modalities to become the "gold standard" for imaging evaluation of ACL injury. The accuracy and sensitivity of MR imaging for evaluation of ACL tears is excellent when correlated with clinical tests and arthroscopic findings, and is improved in equivocal cases with assessment of secondary signs for ACL tear. The MR imaging assessment of partial and chronic ACL tears is less accurate but is clinically useful. MR imaging provides information about associated injuries prior to surgery. Radiologic diagnostic methods for the assessment of ACL tears on MR images are well established; recent techniques such as dedicated cartilage imaging offer new information of use to clinicians about the sequelae of ACL injuries.     

Proprioception in anterior cruciate ligament deficient knees and its relevance in anterior cruciate ligament reconstruction

Injury to the anterior cruciate ligament (ACL) not only causes mechanical instability but also leads to a functional deficit in the form of diminished proprioception of the knee joint. “Functional” recovery is often incomplete even after “anatomic” arthroscopic ACL reconstruction, as some patients with a clinically satisfactory repair and good ligament tension continue to complain of a feeling of instability and giving way, although the knee does not sublux on clinical testing. Factors that may play a role could be proprioceptive elements, as the intact ACL has been shown to have significant receptors. Significant data have come to light demonstrating proprioceptive differences between normal and injured knees, and often between injured and reconstructed knees. ACL remnants have been shown to have proprioceptive fibers that could enhance functional recovery if they adhere to or grow into the reconstructed ligament. Conventionally the torn remnants are shaved off from the knee before graft insertion; modern surgical techniques, with remnant sparing methods have shown better outcomes and functional recovery, and this could be an avenue for future research and development. This article analyzes and reviews our understanding of the sensory element of ACL deficiency, with specific reference to proprioception as an important component of functional knee stability. The types of mechanoreceptors, their distribution and presence in ACL remnants is reviewed, and suggestions are made to minimize soft tissue shaving during ACL reconstruction to ensure a better functional outcome in the reconstructed knee.     

Replacement of the anterior cruciate ligament with a bone-ligament-bone anterior cruciate ligament allograft in dogs

Acute replacement of the canine anterior cruciate ligament (ACL) with a frozen, bone-ligament-bone anterior cruciate ligament preparation was studied using biochemical, immunologic, and biomechanical testing methods. Nine dogs were used for the study, six dogs received allografts and three received autografts. No tissue antigen matching was performed. All nine dogs were killed nine months after surgery. Necropsy examination revealed that the ACL was not present in three joints (one autograft, two allografts). The two autograft and four allograft ligaments available for mechanical testing sustained mean maximum loads that were 10% and 14%, respectively, of the mean maximum loads sustained by the contralateral ACL. Autoradiography indicated that cellular activity was more pronounced in the autograft specimens. Hydroxyproline uptake was 200% and 45% of normal in the autograft and allograft ligaments, respectively. Both autograft and allograft specimens were producing Type I collagen at the time of killing. Antidonor dog leukocyte antigen (DLA) antibody was detected in the synovial fluid taken at the time of killing from six of six dogs that received allografts and in zero of three dogs that received autografts.     

Imaging of the anterior cruciate ligament

The anterior cruciate ligament (ACL) is an important structure in maintaining the normal biomechanics of the knee and is the most commonly injured knee ligament. However, the oblique course of the ACL within the intercondylar fossa limits the visualization and assessment of the pathology of the ligament. This pictorial essay provides a comprehensive and illustrative review of the anatomy and biomechanics as well as updated information on different modalities of radiological investigation of ACL, particularly magnetic resonance imaging.     

Complications in anterior cruciate ligament surgery

There are many potential problems associated with ACL surgery; however, careful attention to detail can prevent problems from occurring or provide corrective options in the event they do occur. Multiple backup options are not only desirable but also essential to a successful outcome. By following these guidelines, ACL surgery can have good long-term results and return the recreational or higher-level athlete to sports participation.     

Lengthening of anterior cruciate ligament graft

32 patients with old anterior cruciate ligament injuries were operated on with patellar tendon-prepatellar tissue-quadriceps tendon graft over the top without and with augmentation (Kennedy-LAD). The anteroposterior (AP) laxity was assessed preoperatively, and at 6, 12, and 24 months after the operation with roentgen stereophotogrammetry. 6 months postoperatively the instability had decreased 5.4 mm in the nonaugmented and 1.9 mm in the augmented group, but not to normal values. During the following 18 months the AP laxity increased and returned to the preoperative level. At 2 years, 28 of the 32 patients were considered good or excellent, according to the Lysholm score. There was a lack of correlation between AP laxity and functional tests.     

Innervation of the anterior cruciate ligament

Summary The innervation of 21 human anterior cruciate ligaments (ACL) obtained at autopsy or during operation was studied by light microscopy. Nerves and nerve endings were found in the synovium and interfascicular connective tissue. The nerves were myelinated and/or unmyelinated and had terminal nerve structures with free nerve endings which provide nociception and supply the blood vessels, Ruffini corpuscles and Pacini corpuscles, which are mechanoreceptors in the ligaments.

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Résumé Etude en microscopie optique de l'innervation du ligament croisé antérieur à l'aide de 21 spécimens obtenus lors d'une intervention ou d'une autopsie. Des nerfs et des terminaisons nerveuses ont été trouvés dans la synoviale et dans le tissu conjonctif intra-fasciculaire. Les nerfs sont myélinisés et/ou non, et présentent des structures terminales libres qui assurent la nociception et innervent les vaisseaux sanguins, ainsi que les corpuscules de Ruffini et de Pacini, qui constituent les récepteurs de l'allongement de ces ligaments.

     

Instability after anterior cruciate ligament rupture

Manual tests and 2 external devices were used together with roentgen stereophotogrammetry (RSA) and an active weight-bearing radiographic method to measure the sagittal laxity in 11 knees with anterior-cruciate-ligament rupture. In 5 knees no ligament surgery had been performed (unstable knees) and in 6 knees a reconstruction had been performed one year before the examination (stable knees). There were positive correlations between all methods, including the manual tests when all knees, both stable and unstable, were analyzed together. However, the mean values of the total displacement differed between the methods, especially when comparing the weight-bearing radiographs with the three other methods. Some knees with substantial displacement during passive loading did not show any displacement when weight bearing; the measurements thus depended on both the ligamentous laxity and the patient's neuromuscular control of the joint. When the stable knees were analyzed separately, higher mean values were recorded with the external devices than with RSA using 180 N load. This could be explained by an error from soft tissue deformation which added to the skeletal displacement when the external devices were used.     

Insufficiency of the anterior cruciate ligament

Summary Recurrent anterior and internal rotatory subluxation of the tibial plateau is a disabling symptom in patients with insufficiency of the anterior cruciate ligament.Since 1970 we have used the N-test, a special jolt test to detect the characteristic instability. One hundred eighteen cases with anterior-internal rotatory instability of the knee seen at the Kanto Rosai Hospital and the University of Tokyo Hospital and diagnosed by arthroscopy and arthrotomy from 1973 to 1978 were reviewed. Most of the patients were athletes or sportsmen and the injuries commonly occurred in deceleration-injury mechanism and 81% of the cases were associated with meniscal tear.Thirty-two cases were reconstructed by iliotibial tract transfer, twenty of whom had been evaluated from 1–5 years after operation. Postoperatively, giving-way incidents disappeared in eleven, markedly decreased in five, and were unchanged in four patients. The anterior and internal rotatory subluxation of the tibial plateau disappeared or decreased in seventeen and was unchanged in two cases.Some type of defective anterior cruciate ligament was recognized in all our 118 cases and the capsular lesions were considered to play only a secondary role in exhibiting the instability.

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Zusammenfassung Die periodisch rezidivierende Subluxation des Tibiakopfes nach vorne and innen ist ein charakteristisches Syndrom bei Patienten mit einer Insuffizienz des vorderen Kreuzbandes. Um these Instabilitat ermitteln zu können, verwenden wir seit 1970 den sogenannten N-Test, eine von uns entwickelte Variante des Pivot-shift-Testes.Im Kanto Rosai Hospital und in der Universitätsklinik Tokio konnten von 1973–1978 118 Fälle mit dieser Instabilitat untersucht and durch Arthroskopie und Arthrotomie diagnostisch gesichert werden. Die Mehrzahl der Patienten waren Sportler, bei denen es bei Decelerationsmechanismen zum Unfall kam. In 81% der Fälle lag gleichzeitig ein Meniskusriß vor. Von 32 durch Verlagerung des Tractus iliotibialis behandelten Patienten werden 20 1–5 Jahre post operationem nachuntersucht. In 11 Fällen verschwand das giving-way, das unsichere, plötzliche Nachgeben im Knie vollständig; in 5 Fällen nahm es deutlich ab und nur 4mal blieb es unverändert. In 17 Fällen verschwand oder verringerte sich die Rotationssubluxation nach vorne and innen und nur in 2 Fällen trat keine Veränderung ein. Ein Defekt des vorderen Kreuzbandes wurde in all unseren 118 Fällen festgestellt wohingegen Kapselverletzungen beim Zustandekommen der Instabilität als zweitrangig angesehen werden.

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Read in part at the SICOT Meeting, Kyoto, 1978     

Replacement of the anterior cruciate ligament

Summary Eighty-seven patients have been examined 2 years on average after knee ligament reconstruction for a torn anterior cruciate ligament. The patients were divided into four groups according to the type of operation that had been carried out. In the first group an extra-articular lateral repair (MacIntosh tenodesis) had been performed, in the second group an intra-articular over-the-top repair using the quadriceps and the patellar tendon, in the third group a modified Eriksson procedure using the patellar tendon, and in the fourth group a combined intra- and extra-articular repair using carbon fibres as a graft. The results of the operations in the different groups are compared. The best results were obtained with the Eriksson procedure, closely followed by the over-the-top repair. Limited range of motion and retropatellar pain resulting from changes in the alignment of the patella were the main problems. The results after the use of carbon fibres were less good. In two cases the graft tore without further trauma, and there were also problems because of restricted range of motion and retropatellar pain. The worst results were found after extra-articular lateral repair, due to insufficient stability in many cases. However, the best results with regard to the range of motion were found in this group.

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Zusammenfassung Es wurden 87 Patienten im Durchschnitt 2 Jahre nach Ersatzplastik bei zerrissenem vorderem Kreuzband und chronischer Instabilität nachkontrolliert. Die Patienten wurden in vier Gruppen eingeteilt. In jeder Gruppe war eine andere Art von Ersatzplastik durchgeführt worden. In der ersten Gruppe war es ein extraartikulärer lateral repair (sog. MacIntosh-Plastik), in der zweiten Gruppe eine intraartikuläre over the top geführte Plastik mit der Quadriceps- und der Patellarsehne, in der dritten eine modifizierte Eriksson-Plastik unter Verwendung der Patellarsehne und in der vierten Gruppe eine kombinierte intra- und extraartikuläre Plastik mit Carbon fibres. Die Resultate der Operationen in allen vier Gruppen werden miteinander verglichen. Die besten Ergebnisse zeigte das Vorgehen nach Eriksson, dicht gefolgt vom over the top-repair. Probleme, die in diesen zwei Gruppen auftraten, betrafen eingeschränkte Kniebeweglichkeit und retropatelläre Schmerzen wegen veränderter Führung der Patella. Die Resultate in der Gruppe mit Verwendung der carbon fibres waren weniger gut. In zwei Fällen ist das Transplantat ohne Trauma gerissen, zudem traten auch hier Beschwerden auf wegen eingeschränkter Beweglichkeit und retropatellärer Schmerzen. Am wenigsten gut waren die Resultate nach extraartikulärem lateral repair. In vielen Fällen konnte durch these Methode keine genügende Stabilität erreicht werden. Andererseits war die Beweglichkeit des Kniegelenkes nach dieser Operation kaum je eingeschränkt.

     

Rehabilitation of anterior cruciate ligament injuries

The previously outlined exercise program for the knee is for the instability that results from the loss of the anterior cruciate ligament and/or capsular ligaments laterally. Its success depends on communication between surgeon, therapist, and trainer. Each must understand what the other is doing and must follow the biomechanical and healing restraints of the surgery. The understanding of soft tissue healing is ongoing. Research in this field will greatly enhance the rehabilitation programs of the future.     

Rehabilitation after anterior cruciate ligament reconstruction

The "Frankfurt rehabilitation regimen" following anterior cruciate ligament reconstruction is presented. ACL rehabilitation is discussed in the light of knowledge on knee biomechanics and proprioception as well as clinical results of reconstruction. Special emphasis is given to exercise therapy.