Knee instability after injury to the anterior cruciate ligament

Abstract

We have measured anterior and posterior displacement in 563 normal knees and 487 knees with chronic deficiency of the anterior cruciate ligament (ACL). We performed stress radiography using a simple apparatus which maintained the knee at 20 degrees of flexion while a 9 kg load was applied. There was no significant difference in posterior translation dependent on the condition of the ACL. Measurement of anterior translation in the medial compartment proved to be more reliable than in the lateral compartment for the diagnosis of rupture of the ACL, with better specificity, sensitivity and predictive values. We have classified anterior laxity based on the differential anterior translation of the medial compartment and identified four grades in each of which we can further distinguish four subgrades for laxity of the lateral compartment. Within each of these subgroups, either internal or external rotation may dominate and sometimes there is a major translation of both compartments. Radiological evaluation of displacement of the knee in 20 degrees of flexion provides conclusive evidence of rupture of the ACL. A detailed study of pathological displacement is the basis for a classification of laxity. It is then possible to decide for each type of laxity, the surgical treatment which is specifically adapted to the lesion, and to define a reference value for judging outcome.

Stress Radiography for the Diagnosis of Knee Ligament Injuries: A Systematic Review

“…Only two studies in this review reported results for comparison of measurement techniques using different landmarks and reference points on stress radiographs [28,30]. Although we recognize that the choice of landmarks may influence the accuracy and reliability of measurements in stress radiography, this was beyond the scope of the present review.…”

“…No diagnostic accuracy data were reported for diagnosis of isolated varus knee injuries on stress radiography. Overall, excellent intrarater and interrater ICCs were reported for the diagnosis of ACL [28,30], PCL [28,42], varus [12,26], and valgus [25] injuries on stress radiography. However, only six studies included analysis of intrarater and interrater reliability [12,25,26,28,30,42].…”

“…In addition, the calculated diagnostic accuracy of stress radiography techniques changes depending on the side-to-side difference limit that defines a nonfunctional ligament. For the ACL, the threshold varied from 2 mm [6] to 6 mm [30] and from 3 mm [8] to 12 mm [8] for the PCL. The inconsistent threshold for side-to-side difference for ACL and PCL injuries clouds any comparison of the diagnostic accuracy among studies and techniques.…”

“…Lerat [30] KT-1000 Both KT-1000 and stress radiography provide excellent diagnostic value of ACL integrity with predictive values of 90%; stress radiographs provide superior precision and independent evaluation of medial and lateral compartments…”

“…Its applications include diagnosing acute and chronic injuries [1,21,30,32], comparing instability preoperatively and postoperatively [20,24,39,55], and monitoring stability in nonoperatively treated patients [17]. A variety of stress techniques have been described that assess ligament stability using an anteriorly, posteriorly, varus-, or valgus-directed force to the knee [10,14,17,28,29,37,40,41,43,45].…”