A comparison of pre-operative evaluation of anterior knee laxity by dynamic X-rays and by the arthrometer KT 1000

Abstract

The comparison of bilateral dynamic X-rays in passive anterior and posterior drawer with a load of 9 kg, and the arthrometer KT 1000 measurements obtained from 100 patients before anterior cruciate ligament reconstruction, confirms the good diagnostic efficiency of the following methods: (1) radiological measurement of the anterior translation of the medial compartment, as an absolute value and especially as a differential value in relation to the opposite, uninjured knee, the normal value limits being respectively 5 and 2 mm; and (2) arthrometric measurement of the maximal manual translation, also as absolute and differential values, the normal value limits being 10 and 2 mm respectively. These two measurements have a predictive value of 90%. No numerical equivalency exists between the radiological and arthrometric values, but their variations in relation to each other are statistically correlated. The arthrometer, simple to use and totally innocuous, is an excellent test device for consultation, while dynamic X-rays allow separate studies of each compartment to look for lesions of the posteromedial or posterolateral corners.

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

“…First, this review excluded non-English-language articles, which may have led to the omission of additional descriptive studies of stress techniques, accuracy and reliability data, and comparative studies not available in the English language literature. Second, this review did not Lerat [29] 100 AP Anterior drawer: the patient is supine on a table with the lower extremity supported in a special leg holder and the thigh free; the foot and ankle are fixed with a strap; the opposite limb is positioned on a stool at a lower level; a free hanging 9-kg weight is hung from the distal femur Posterior drawer: the leg support is turned 180°and moved closer to support the patient and a 9-kg weight is hung from a strap at the proximal tibia …”

“…Three of five studies comparing stress radiography with the KT-1000 or KT-2000 (MEDmetric Corporation, San Diego, CA, USA) for the diagnosis of AP instability concluded that stress radiography is superior, whereas the other two studies showed excellent but equivalent diagnostic ability [7,14,29,31,45]. For diagnosis of ACL injury, stress radiography correlated with results of the pivot shift test but not the Lachman's test [15], was equivalent to the GNRB computerized arthrometer [2], and offered greater sensitivity but similar specificity to the Rolimeter [34].…”

“…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]. Side-to-side differences in the amount of displacement (anterior or posterior) or gapping (varus or valgus) increase suspicion of a functional deficit in knee ligament stability.…”

Anterior cruciate ligament assessment using arthrometry and stress imaging

“…Normal SSD is near zero [20]. Different diagnostic thresholds have been reported in the literature ranging from SSD of 2 to 5 mm [14,17,21]. In patients with complete ACL tear, Panisset et al found average SSD to be 7.4 ± 4.3 mm and used SSD >5 mm as their diagnostic threshold using Telos stress imaging (Sn 80.9 %, sp 81.8 %) [5].…”

Objective measurements of static anterior and rotational knee laxity

“…Reliability of posterior displacement between testers is estimated to reach an ICC of 0.91 and the measurement errors reached 2.77 mm [22]. -Lerat's method [23]: In this invasive method, a mass of 9 kg is attached to the patient's thigh above his patella to induce a posterior translation of the femur compared to the tibia. This technique seems to be reliable with an intra-tester ICC superior to 0.9 [24].…”