A modified Chrisman-Snook procedure for reconstruction of the lateral ligaments of the ankle: review of 18 cases.

The outcome of 18 ankles of 16 patients who underwent a modification of the Chrisman-Snook lateral ligamentous reconstruction was analyzed. The modification described herein attempts a more anatomic reconstruction of the calcaneofibular ligament, while the anterior talofibular ligamentous reconstruction remains unchanged. All patients were evaluated before and after surgery by physical examinations and stress inversion radiographs were taken to measure the degree of talar tilt. Additional postoperative assessment consisted of a questionnaire, inversion and eversion isokinetic strength measurements, subtalar joint inversion stress radiographs (stress Brodén's views), and a hop test to assess ankle confidence. An average preoperative talar tilt of 13.7 degrees was reduced to an average of 2.3 degrees after surgery. Post-operative subtalar stress radiographs revealed an average of 2.8 degrees of subtalar tilt compared with the "normal" average of 7.2 degrees in the nonoperative ankles. While no ankles were found before surgery to have a 3+ anterior drawer sign, 11 ankles had 3+ inversion laxity. Excessive inversion laxity, which can occur through both the ankle and subtalar joints, more than anterior drawer laxity, may appear to be the primary determinant of functional ankle instability in the chronic setting. We recommend subtalar stress radiographs, in addition to routine talar stress radiographs, to quantify the relative contributions of each of these joints to inversion laxity in a symptomatic patient to guide appropriate treatment. The described procedure will anatomically stabilize both joints to inversion stress.