Anterior Tibial Displacement Research Articles

Comparison of Anterior Laxity Measurements in Anterior Cruciate Deficient Knees with Two Instrumented Testing Devices

We measured anterior tibial displacements in 21 anterior cruciate ligament deficient patients using two instrumented testing devices, the KT-1000 and the KSS. A comparison of values obtained from testing was done using statistical analysis. The two tests common to both devices were the 20 lb pull and the manual maximum. The involved normal (I-N) values showed that there was no significant difference between the two devices for both the manual maximum and the 20 lb force level. There was also no significant difference between devices for the manual maximum absolute values. The significant difference between the absolute values for the 20 lb force level is probably due to the different testing techniques for both devices. When testing with the KSS, the patella remains free; testing with the KT-1000 requires that the examiner maintain pressure to hold the patella down. The manual maximum absolute values showed no significant difference because the testing techniques for both devices were identical. Comparable data for both devices are the I-N values for the 20 lb and manual maximum values.

Coactivation of the hamstrings and quadriceps during extension of the knee

The electromyographic activities of six muscles of the thigh were recorded, using bipolar surface electrodes, during active extension of the knee by six healthy men. The signal amplitudes were normalized to those recorded during isometric maximum voluntary contractions. Extension of the knee from 90 to 0 degrees (full extension) was performed at the rate of 10 degrees per second with the leg unimpeded and with weights of 1.8, 3.6, 5.4, or 7.2 kilograms attached to the ankle. The hamstrings were found to coactivate with the quadriceps during the terminal phase of extension. Coactivation of all three hamstrings was found to occur at joint angles of as much as 9 degrees, with the maximum at full extension of the knee and the strength of the signals ranging to as much as 20 per cent. The signals of all of the flexors and extensors increased with increasing loads on the ankle and, with the exception of the rectus femoris at 9 degrees of flexion, they also increased as the knee extended. The results of this study support the hypothesis that the hamstrings function synergistically with the anterior cruciate ligament to prevent the anterior tibial displacement that is produced by active contraction of the quadriceps in the terminal degrees of extension of the knee. This information is important for the physical conditioning of healthy individuals in preparation for athletic endeavors. Furthermore, if coactivation of the hamstrings with the quadriceps is mediated by sensors other than, or in addition to, those of the anterior cruciate ligament, then strengthening of the hamstrings appears to be an important adjunct to rehabilitation programs after repair or reconstruction of that ligament.

Kappa Delta Award paper. Anterior cruciate ligament: its normal response and replacement.

This article reviews our research studies on the anterior cruciate ligament (ACL). The human ACL was found to be a primary restraint to anterior tibial displacement at both 90 degrees and 30 degrees of flexion. Geometric measurements of the ligament showed it to have a complex macrostructure, consisting of bundles of different lengths, curvatures, and orientations. Similar material properties were measured for subunits from the human anterior and posterior cruciate and lateral collateral ligaments. However, the linear modulus, maximum stress, and strain energy density to maximum stress of the ACL were significantly less than similar properties for patellar tendons. These tissue subunits exhibited nonuniform axial strain during tensile loading, which was partially attributed to differences in bundle crimp period and crimp angle. The structural mechanical properties (stiffness, strength, and energies and elongations to maximum force and failure) of nine commonly used human ACL substitutes were also compared. Only the bone-patellar tendon-bone unit had maximum force and stiffness greater than that of the ACL. The patellar tendon, when used as an ACL replacement in the dog and primate, exhibited significant loss in structural mechanical and material properties early after implantation. These properties showed only a gradual improvement up to 1 year after surgery. Maintaining a vascular supply to these grafts or using intermittent passive motion immediately after surgery produced no significant improvement in graft properties in the primate model.

Exercise-induced knee joint laxity in distance runners.

The objectives of this study were to evaluate the effect of exercise on knee joint laxity. If exercise induced laxity is physiological, incorporation of this quality into a ligament replacement material would be indicated. Twenty recreational long distance runners average age 41 (range 24 to 50 yr) were tested before and immediately after 30 minutes of running. Using a computerized goniometer type instrument (Acufex KSS), knee flexion, axial tibial rotation and anterior-posterior tibial displacement were simultaneously recorded, while the runners underwent tests of static as well as dynamic knee joint laxity. At 30 degrees of knee flexion, a maximum increase of 16 per cent in mean total anterior-posterior laxity post-exercise was found. At the examination 30 minutes post-exercise, laxity at 30 degrees of knee flexion was still increased. However, laxity at 90 degrees of knee flexion had decreased to pre-exercise levels or below. Anterior tibial displacement, recorded during eccentric quadriceps activity (0 to 90 degrees of knee flexion) with weights attached to the foot, showed a maximum of 18 per cent increase in total anterior-posterior laxity post-exercise. It is suggested that the laxity increase is caused in part by a true ligamentous laxity increase, and in part by a decreased resting tone of the fatigued muscles.

Instrumented Lachman tests for the evaluation of anterior laxity after reconstruction of the anterior cruciate ligament.

Using a KT-1000 arthrometer, in fifty subjects were measured the anterior ligamentous laxity in a knee in which the anterior cruciate ligament had been reconstructed and in the normal, contralateral knee. We also determined the anterior tibial displacement and anterior compliance, using the Lachman test. The subjects were divided into groups according to the type of autogenous intra-articular substitute (either the central one-third of the patellar tendon or the semitendinosus tendon) that had been used for the anterior cruciate ligament and according to the duration of follow-up (range, twenty-four to 101 months). Lachman tests were performed, applying sixty-eight and ninety newtons of force, and indices for anterior compliance were calculated. Although significantly more anterior laxity was demonstrated with both sixty-eight and ninety newtons of force in the reconstructed knees than in the contralateral, normal knees (p less than 0.001), thirteen subjects, of whom eight lacked full extension of the reconstructed knee, had more anterior laxity in the normal knee. Analyses of variance showed no significant differences in the results of the Lachman tests as related to either the type of reconstruction or the length of postoperative follow-up. The results suggested that the two types of ligamentous substitute that were used in this study were equally efficient in limiting anterior tibial displacement, as demonstrated by the Lachman test. The study also demonstrated that the substitutes did not elongate significantly during the period of the study.

Coactivation of the hamstrings and quadriceps during extension of the knee.

The electromyographic activities of six muscles of the thigh were recorded, using bipolar surface electrodes, during active extension of the knee by six healthy men. The signal amplitudes were normalized to those recorded during isometric maximum voluntary contractions. Extension of the knee from 90 to 0 degrees (full extension) was performed at the rate of 10 degrees per second with the leg unimpeded and with weights of 1.8, 3.6, 5.4, or 7.2 kilograms attached to the ankle. The hamstrings were found to coactivate with the quadriceps during the terminal phase of extension. Coactivation of all three hamstrings was found to occur at joint angles of as much as 9 degrees, with the maximum at full extension of the knee and the strength of the signals ranging to as much as 20 per cent. The signals of all of the flexors and extensors increased with increasing loads on the ankle and, with the exception of the rectus femoris at 9 degrees of flexion, they also increased as the knee extended. The results of this study support the hypothesis that the hamstrings function synergistically with the anterior cruciate ligament to prevent the anterior tibial displacement that is produced by active contraction of the quadriceps in the terminal degrees of extension of the knee. This information is important for the physical conditioning of healthy individuals in preparation for athletic endeavors. Furthermore, if coactivation of the hamstrings with the quadriceps is mediated by sensors other than, or in addition to, those of the anterior cruciate ligament, then strengthening of the hamstrings appears to be an important adjunct to rehabilitation programs after repair or reconstruction of that ligament.

Augmentation with the longitudinal patellar retinaculum in the repair of an anterior cruciate ligament rupture

Most authors advocate repair of the acutely ruptured ACL by augmentation or some form of primary reconstruction. Strong autogenous tissues like the patellar and semitendinosus tendons and the iliotibial band are often used when augmentation is the surgical choice. This paper describes a surgical procedure using a strip of the longitudinal patellar retinaculum as an augmentation of the repaired ACL. The retinaculum adds stability and strength to the repaired ACL during the healing period. Moreover, the retinaculum may enhance the healing process of the ruptured ACL by revascularization. It may also increase the stimulation of synovial tissue proliferation over the repaired ACL. Twenty-eight patients have been clinically and objectively evaluated at a mean follow-up time of 78 months (range, 63 to 94 months). The patients' own evaluation of their knee function was excellent or good in 86% (24 patients). Eighty-two percent (23 patients) could return to their preinjury activities at the same intensity level as before injury, whereas at an intermediate followup at 18 months only 64% (18 patients) had done so. Anterior tibial displacement was objectively evaluated at both followups by means of the anterior drawer test, with 20 degrees to 30 degrees and 90 degrees of knee flexion, in a testing device. The operated knee usually showed a tendency to a slightly increased anterior displacement when compared with the uninjured knee. The repair of a ruptured ACL with an augmentation using the longitudinal patellar retinaculum has been shown to give good results after more than 5 years.

Arthroscopic partial meniscectomy in the anterior cruciate deficient knee.

One hundred ACL insufficient knees were followed for an average of 3.5 years after arthroscopic partial meniscectomy had been performed. Fifty-two percent of the patients obtained a satisfactory result and 41% were able to participate in strenuous sports activities. The arthroscopic partial meniscectomy reduced pain and swelling in a high proportion of cases, but stability was only marginally improved. Negative prognostic factors were: sex (female), generalized laxity, contralateral recurvatum of more than 10 degrees, complete as opposed to partial ACL lesions, Grade III tibiofemoral or patellar chondromalacia, associated peripheral ligamentous laxity, pivot shift of Grade II or greater, and anterior tibial displacement of more than 5 mm as measured with the KT-1000 knee arthrometer.

Instrumented testing of functional knee braces

The ability of seven functional knee braces to control anterior tibial displacement in three severely lax ACL deficient knees using two instrumented testing devices was studied. Some braces were statistically shown to be much better in this regard than others, but not all data obtained was statistically significant. This material should aid one in determining which braces offer the greatest degree of control of anterior tibial displacement in patients with ACL insufficiency.

Posterior instability of the knee joint. An experimental study.

We investigated the importance of the posterior cruciate ligament (PCL) and the medial and lateral compartmental structures for translatory and simultaneous axial rotatory instability in 25 osteoligamentous knee preparations. Instability was registered continuously from 0 degree to 90 degrees of flexion with application of a constant force to the tibia. Isolated transection of the PCL increased the posterior tibial displacement with flexion to a maximum of 10 mm at 90 degrees of flexion; when combined lesions to the lateral structures were included, the popliteal tendon (PT) in particular turned out to have a major secondary stabilizing function. The posterior tibial displacement in flexion was doubled when all lateral structures were included in the lesions. Transection of the PCL and all the medial structures led to a notable increment in posterior displacement increasing with flexion. Major increments in simultaneous tibial rotation were recorded only after combined lesions to either medial or lateral structures. A reverse pivot shift was provoked after combined lateral lesions when the PT was included. Even an anteromedial subluxation was released after lesions to the medial structures. Regardless of the type of lesion, the specimens remained stable concerning anterior-posterior displacement in extension. No changes in the anterior tibial displacement were observed.

Objective anterior cruciate ligament testing.

We examined subjects with the Stryker knee laxity tester as part of the clinical examination to determine its usefulness in evaluating the anterior cruciate ligament. We measured 123 athletes with no history of knee injury, as well as 30 patients with ACL injury proven by arthroscopy, and 11 injured patients with intact ACL at arthroscopy. We recorded anterior and posterior tibial displacement at 20 degrees of knee flexion and 20 lbs force in each direction. Anterior laxity and side to side difference correlated with ACL injury; posterior and total AP laxity did not. In normal subjects, mean anterior laxity was 2.5 mm. Only 8% of normal knees had anterior laxity of 5 mm or more. Ten percent of normal subjects had a side to side difference of 2 mm or more. In ACL tears, mean laxity was 8.1 mm, with 94% measuring 5 mm or more. Of the subjects, 89% with unilateral ACL injury had an increase of 2 mm or more on the injured side. Ten of ten acute ACL tears were detected by these criteria, with no false positives. In injured knees with intact ACL, measurements did not differ significantly from normal. We found the objective knee laxity measurement to be a useful complement to clinical knee examination.

The static stabilizing function of the popliteal tendon in the knee. An experimental study.

We investigated the importance of the anterior cruciate ligament (ACL), its two components (the AMP and PLP), and the lateral compartment ligaments with special attention to the popliteal tendon (PT) in relation to valgus-varus, axial rotation, and anterior-posterior instability. Mobility patterns were drawn from 15 osteoligamentous knee preparations after successive transection of the structures. Even when combined lesion involved the lateral collateral ligament (LCL), the PT, and the posterolateral capsule (PLC), anterior tibial displacement was not effected until the ACL was cut. The lateral structures acted as secondary restraints to anterior displacement, and prevented simultaneous anterolateral rotation during application of the anterior force. LCL and PLC transection affected varus stability in full extension, and instability improved on additional section of the PT, even if the ACL remained intact. Maximum instability after combined lateral lesion occurred at 40 degrees of flexion, whether the ACL was transected or not. Further flexion caused a rapid decrease of instability. The PT was shown to effectively restrain varus instability from 0 to 90 degrees of flexion. It was experimentally established with regard to axial rotation that marked posterolateral instability was impossible with an intact PT. Maximum instability was recorded at 30 degrees of flexion after combined lesion to the lateral structures. Even in the extension, considerable posterolateral instability was observed. The restraining effect of the PLC was prominent in extension.

Biomechanics of the knee-extension exercise. Effect of cutting the anterior cruciate ligament.

We conducted this study to determine the effective moment arm of the knee extensor mechanism and the conditions under which the anterior cruciate ligament is loaded during knee-extension exercises. The moment arm was calculated from measurement of the quadriceps force required to extend the knee with and without resistive weights placed at the foot, the leg weight, and the location of its center of gravity. Changes in three-dimensional joint motion after the anterior cruciate ligament was removed were considered to be an indication that the ligament was loaded. The quadriceps force rose during the initial phase of knee extension and remained nearly constant at an average value of 177 newtons between 50 and 15 degrees. With extension past 15 degrees it rose rapidly, reaching an average of 350 newtons at zero degrees of extension, and continued to increase with hyperextension. The addition of thirty-one newtons (seven pounds) at the foot approximately doubled the quadriceps force that was required to extend the knee. The effective moment arm of the extensor mechanism increased with knee extension, peaked at approximately 20 degrees, and rapidly decreased with further extension. No change was found in the quadriceps force or its effective moment arm when the anterior cruciate ligament was sectioned except in hyperextension, where the quadriceps force decreased in two of five specimens. There was, however, an increased anterior tibial displacement in the range of 30 degrees to full extension, suggesting that the anterior cruciate ligament is loaded in that flexion arc. This study demonstrates that very large quadriceps forces are required to accomplish the last 15 degrees of extension during leg-raising exercises, typically twice those required to reach 30 degrees of flexion. The large forces that are required to obtain full extension explain why an extensor lag occurs with quadriceps weakness even though a full passive range of motion is possible. Since thirty-one newtons (seven pounds) of resistive weight added at the foot approximately doubles the quadriceps forces required to extend the leg alone, using such weights can produce very large quadriceps forces and concurrent patellofemoral and tibiofemoral contact forces. Because the quadriceps force increases little as the leg is extended from 50 to 15 degrees, in patients with patellofemoral chondroses for whom a full range of joint motion is not desired, quadriceps exercises can be limited to the amount of extension without decreasing quadriceps force.(ABSTRACT TRUNCATED AT 400 WORDS)

A clinical and stress radiographical follow-up investigation after Jones' operation for replacing the anterior cruciate ligament

Measurements have been made on knee radiographs exposed during stress displacement by controlled hydraulic forces using a specially designed apparatus. This accurately records the amount of anterior and posterior tibial displacement (drawer sign) and the degree of medial and lateral collateral ligament laxity on radiographs. The findings in 25 patients have been analysed following the Jones' procedure for the repair of the anterior cruciate ligaments. The operative results were judged to be completely successful in 72 per cent of patients and the value of stress radiographic measurements is discussed.