The Cybex II evaluation of lateral ankle ligamentous reconstructions

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Abstract
Chronic lateral ankle instability is a costly disability to the athlete. The Chrisman-Snook and Evans lateral ligamentous reconstructions are two procedures fre quently performed to correct ligamentous instability. The entire peroneus brevis tendon is transected in the Evans procedure, thus sacrificing its eversion strength and power. The importance of preserving the eversion function of the peroneus brevis muscle is speculative, but may be of significance for good long-term results. The ankle eversion strength and power of 10 patients with Chrisman-Snook and 10 patients with Evans lat eral ligamentous reconstructions were objectively eval uated with the Cybex II Isokinetic Dynamometer. The mean postoperative time to testing was 4.2 years. The uninvolved ankle was also tested and used as the normal strength of the patient. Twenty normal controls matched for age, sex, and physical activity were tested to assure maximum test reproducibility. The eversion strength was tested at several speeds, but torque values at speeds of 30 and 120 deg/sec were selected for analysis. At slow speeds, 30 deg/sec, and ankles that had Evans and Chrisman-Snook reconstruction were 4% and 7% weaker, respectively, than the contralateral normal ankles. At 120 deg/second the ankles were 8% and 9% weaker with the Evans and Chrisman-Snook reconstructions, respectively. A three factor analysis of variance with repeated measures on two of the factors was used to analyze the data. The analysis indicated that the estimated mean difference in peak torque values between the control and surgical ankles for the Evans procedure at 30 deg/sec, the Chrisman-Snook procedure at 30 deg/sec, the Evans procedure at 120 deg/sec, and the Chrisman-Snook procedure at 120 deg/sec were not significantly different (F = 0.49, df = 1/18, P = 0.491). Thus, the surgical loss of the peroneus brevis muscle in the Evans lateral ligamentous reconstruction does not appear to result in a significant loss of eversion strength and power when compared to the contralateral normal ankle. Therefore, the authors contend that the loss of the peroneus brevis tendon should not be a factor in the selection of an operative procedure for lateral ankle instability.

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