Anterior Tibial Translation During Different Isokinetic Quadriceps Torque in Anterior Cruciate Ligament Deficient and Nonimpaired Individuals

Abstract

Study Design: Factorial quasi-experimental design. Objectives: To quantify the effect of different levels of isokinetic concentric and eccentric knee extensor torques on the anterior tibial translation in subjects with anterior cruciate ligament (ACL) deficiency. Electromyogram (EMG) activity of 4 leg muscles was recorded in order to detect any co-activation of extensors and flexors. Background: The rehabilitation after an ACL injury is of importance for the functional outcome of the patient. In order to construct a rehabilitation program after that injury, it is important to understand the in vivo relationships between muscle force and tibial translation. Methods and Measures: Twelve patients with unilateral ACL injury and 11 uninjured volunteers performed 36 repetitions of a quadriceps contraction at different isokinetic concentric and eccentric torque levels, on a KinCom machine (60"-s-I), with simultaneous recordings of tibial translation (CA-4000) and EMG activity from quadriceps and hamstrings muscles. Tibial translations and EMG levels were normalized to the maximum of each subject. Results: The individual anterior tibial translation increased with increased quadriceps torque in a similar manner in both quadriceps contraction modes in all legs tested. During concentric mode, translation was similar in all groups, but during eccentric mode, the mean translation was 38% larger in the ACL injured knees. No quadriceps-hamstrings co-activation occurred in any test or group. Conclusions: An ACL deficient knee can limit the translation within a normal space during concentric muscle activity but not during eccentric activity. That limitation depends on other mechanisms than hamstrings co-activation. ] T he long-term prognosis for sports participation after an anterio r cruciate ligament (ACL) injury is uncertain, both after nonsurgical treatment and after reconstruction of the ruptured ligament.11.27 The rehabilitation after an ACL injury is of importance for the functional outcome of the patient. Various exercises included in a rehabilitation program may produce potentially harmful forces for the knee joint and stretch out the secondary restraints or the reconstructed ligament. Exercises that operate without joint compression produce large anterior shear force~~.~~.~~ and ACL strain14 compared to weight-bearing exercises that have been strongly recommended as the best form of exercise after an ACL injUry.6.14.nv25.28.39 Nanweight-bearing activities using isokinetic dynamometers, such as KinCom or Cybex, are used to quantitatively evaluate the progress of muscle rehabilitation and training.15 The recommendation to avoid non-weight-bearing exercises during the early rehabilita- tion period is not founded on sound data.I0 Specifically, Beynnon et a14 have shown that the ACL strain is almost the same in weight and non-weight-bearing exercises in normal knees. The effect of different exercises on the ACL or the secondary restraints in case of ACL deficiency, can be measured as the degree of anterior translation o...

Eccentric Muscle Contractions: Their Contribution to Injury, Prevention, Rehabilitation, and Sport

“…45,139 While it is difficult to draw unequivocal conclusions from the conflicting evidence following surgical reconstruction of the torn ACL, it appears that eccentric hamstring strength is impaired after ACL reconstruction. 105,108,123 As well, quadriceps weakness following ACL reconstruction is also variable 105,108 and somewhat dependent on the numerous rehabilitation and testing protocols used, making it difficult to draw any consensus from the literature. Clearly, however, eccentric muscle dysfunction does exist around unstable (and painful 141 ) joints, and therefore must be reversed.…”

Frequency content asymmetry of the isokinetic curve between ACL deficient and healthy knee

“…Extension and flexion strength after ACL rupture is assessed by isokinetic dynamometry, which involves measurements mainly of the classical parameters such as peak torque, total work and average power (Benjuya et al, 2000;St. Claire Gibson et al, 2000;Kvist et al, 2001;Verdonck et al, 1994;Wu et al, 1997). This conventional approach is, however, inadequate for the assessment of the quality of torque production throughout the range of motion.…”

Co-contraction during static and dynamic knee extensions in ACL deficient subjects

“…One of the reasons might be that ACLD subjects allow shear displacement in the knee. Kvist et al [17] have examined anterior shear displacement during isokinetic knee extensions and they found that the absolute translation was larger in ACLD subjects. By allowing shear displacement, secondary restraining structures can balance the shear force.…”

“…Only a few isokinetic or isometric studies have been done on ACLD subjects. Osternig et al [19] found more co-contraction in the injured leg, while others found no co-contraction [17] or no difference in co-contraction between normal and ACLD subjects [9].…”