Anterior knee motion analysis. Measurement and simultaneous radiography.

Sixteen patients with a clinically diagnosed chronic ACL deficient knee on one side and a contralateral ACL intact knee were evaluated by arthrometry and simultaneous radiography after epidural anesthesia was induced. The posterior cruciate ligament was intact in all knees. This paper reports only the anterior position of the tibia at the 89 N anterior force level of the KT-1000 arthrometer (as read from the dial) and the anterior tibial position recorded simultaneously by radiography at the 89 N dial tone. A 3 mm difference in anterior tibial position between the two knees of the same patient was considered diagnostic for ACL deficiency. Arthrometrically, 13 of the 16 patients were diagnosed accurately; radiographically, 13 of the 16 met the criterion. Moderately high significant positive correlation of paired values was obtained in ACL deficient knees by the two methods (correlation, 0.58 and two-tail probability, 0.02). In ACL intact knees there was no correlation of paired values (correlation, 0.01 and two-tail probability, 0.98). We found no numerical equivalency between the measurements obtained by the KT-1000 and simultaneous radiography. Neither did we find an apparent pattern to the differences, or formula we could use to interpolate findings of anterior tibial position from one measurement system to the other. We conclude that an examiner can substantiate a clinical diagnosis of chronic ACL deficiency with both methods. Arthrometry alone may be used to repeatedly follow conservatively treated ACL deficient knees without exposing the patient to radiation. Radiographs obtained under known anterior force levels provide a retrievable record to document the exact tibial position in relation to the femur.