Objective knee evaluation using the Genucom Knee Analysis System

Abstract

The Genucom Knee Analysis System was used in a clinical setting to study the clinical practicality of the Genucom instrument, and the degree of correlation between Genucom and clinical knee examinations. The Genucom evaluation performed by an experienced ex aminer required 25 to 30 minutes for a 14 test bilateral examination. The instrument provided detailed graphi cal and tabular data of the test results.

One hundred "normal knees" were examined in a series of seven Genucom tests. Normal "laxity bands" for both males and females were generated for a range of load applications for the seven tests. There was no significant difference observed between the male and female laxity distributions. However, a slightly lesser laxity was observed for the male population in general.

A group of 38 subjects with 1 injured knee were assessed concurrently using clinical and instrument techniques. Comparisons were made for the 90° an terior-posterior (AP) drawer, the 30° AP drawer (Lach man), and the varus/valgus stress test. For the 90° AP drawer test, 16 subjects were found clinically to have less than or equal to 5 mm of excess laxity based on comparison with the opposite normal knee. The instru mented measurement concurred in 10 cases. In the other six cases it was noted that laxity on the uninjured knee reached the maximum of the "normal" instru mented population, that is with higher than normal laxities. Fifteen subjects were clinically tested with greater than 5 mm of excess laxity. The instrumented test concurred in all but one.

For the Lachman test (30° AP drawer), 19 subjects were found with an excess laxity of less than or equal to 5 mm. The instrument concurred in all cases but one. Fifteen subjects had a clinical Lachman of greater than 5 mm of excess laxity. The instrumented meas urements concurred in all cases. For the varus/valgus stress test, five subjects were found with excess lateral joint opening of less than or equal to 5 mm. The instrumented test concurred in all but one case in which the varus laxity was clinically described as "subtle." Four clinical cases of medial joint opening of less than or equal to 5 mm were found in the group. The instru ment concurred in all cases.

It was also found that 17 of 18 patients with a clinically positive pivot shift demonstrated a greater than 5 mm of excess laxity on the 30° AP drawer Genucom test. In this study, it was found that the results of the instrument evaluation correlated to a high degree with the clinical evaluations of the knees of the subjects. It appears that the computer-based instrument provides a significant contribution to objective measurement of knee joint stability (laxity).