ObjectiveTo investigate the application of lateral malleolus hook-plate for the treatment of stageⅡsupination-adduction type medial malleolus fractures. MethodsBetween January 2011 and June 2013, 21 patients with stageⅡsupination-adduction type ankle fractures were treated with lateral malleolus hook-plate, including 12 males and 9 females with an average age of 55.5 years (range, 27-65 years). The injury causes were sprain in 17 cases and traffic accident in 4 cases. The mean time between injury and admission was 12.4 hours (range, 2-72 hours). The tibial distal medial articular surface collapse was found in 7 cases by CT examination and in 3 cases by X-ray film. Of 21 cases, there were 12 cases of low transverse fractures of lateral malleolus, 7 cases of short oblique fractures of lateral malleolus, and 2 cases of ankle joint lateral collateral ligament injury without fractures of lateral malleolus. After operation, the clinical outcome was evaluated according to the talus-leg angle, the recovery of Coin-sign continuity, inside-outside and top ankle gap, talus slope, American Orthopedic Foot and Ankle Society (AOFAS) score, Olerud-Molander score, Kofoed evaluation standards, and patient satisfaction. ResultsSeventeen cases were followed up 18.7 months on average (range, 12-25 months). Primary healing was obtained in 16 cases except 1 case of delayed healing. Fracture healed at an average of 14.6 weeks (range, 12-16 weeks). All cases achieved anatomical reduction, the continuity of Coin-sign, and consistency of inside and outside joint gap; no talus tilt occurred. There was no complication of reduction loss, loosening or breakage of internal fixation, or osteoarthritis during follow-up. The talus-leg angle of the affected side was significantly improved to (83.4±1.8)° at 1 week after operation from preoperative (74.8±7.1)° (t=5.370, P=0.000), but no significant difference was found when compared with normal side (83.8±2.3)° (t=0.676, P=0.509). The AOFAS score, Olerud-Molander score, and range of motion at 1 week, 3 months, and 1 year after operation were significantly improved when compared with preoperative ones (P < 0.05). According to Kofoed evaluation standard, the outcome was excellent in 15 cases and good in 2 cases; the excellent and good rate was 100%. According to patient satisfaction, the outcome was excellent in 13 cases, good in 3 cases, and poor in 1 case; the excellent and good rate was 94.1%. ConclusionThe use of lateral malleolus hook-plate for fixation of stageⅡsupination-adduction type medial malleolus fracture not only can effectively maintain anatomical reduction and supporting function, but also can prevent re-collapsing of the reset joint surface. The surgical method can not increase soft tissue complication, so it is a safe and effective method.