Silfverskiold's test in total ankle replacement with gastrocnemius recession.
BACKGROUND: For patients undergoing primary total ankle replacement (TAR) with an equinus contracture, gastrocnemius recession may be performed to increase dorsiflexion. We examined whether gastrocnemius recession would significantly increase dorsiflexion even with a negative Silfverskiöld test. METHODS: Data were prospectively collected on a consecutive series of 29 patients who underwent TAR. All were deemed to require lengthening of the posterior soft tissue structures for unacceptable equinus contracture. Once each patient was under anesthesia, Silfverskiöld's test was performed. A digital photograph was taken with the ankle at maximum passive dorsiflexion with the knee at 0 degrees of flexion and again with the knee at 30 degrees of flexion. Strayer gastrocnemius recession was then performed in standard fashion in every patient. After recession, Silfverskiöld's test was again performed with photographs obtained in the same manner. The digital photographs demonstrating the results of the preoperative and postoperative Silfverskiöld's tests in both knee positions were analyzed and the degree of ankle dorsiflexion measured. RESULTS: Regardless of the results of Silfverskiöld's test, after gastrocnemius recession, patients had an average increase of 12.6 ± 1.6 degrees of dorsiflexion with the knee extended compared to the same position preoperatively (P < .0001) and an increase of 10.1 ± 2.0 degrees with the knee flexed (P < .001). In 6 patients Silfverskiöld's test was markedly positive preoperatively; in this group, recession resulted in an average increase of dorsiflexion of 17.8 ± 3.6 degrees with the knee extended (P = .004) and 13.4 ± 5.4 degrees with the knee flexed (P = .055). For the remaining 23 patients with a negative preoperative Silfverskiöld's test, dorsiflexion increased by 11.3 ± 1.6 (P < .0001) and 9.3 ± 2.2 degrees (P = .0003) with the knee extended and flexed, respectively. CONCLUSION: Our data show that a gastrocnemius recession resulted in a significant, reproducible increase in dorsiflexion regardless of the results of the Silfverskiöld test while avoiding potential push-off and plantarflexion weakness associated with an Achilles lengthening. LEVEL OF EVIDENCE: Level IV, case series.
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