【Abstract】 Objective To evaluate the cl inical effect of excising the radial head, repairing or reconstructing themedial collateral l igament (MCL) in treating comminuted fracture of the radial head accompanying by MCL injury. Methods From September 2000 to April 2006, 18 patients with comminuted fractures of radial head accompanying by MCL injury were treated by excision of the radial head, repair or reconstruction of the MCL. Of them, there were 12 males and 6 females,aged 21 to 57 years. Injury was caused by high fall ing in 10 cases and by traffic accidents in 8 cases. According to Mason classifications,13 fractures were of type Ⅲ and 5 of type Ⅳ . Fifteen cases of fresh fractures were operated within 2 weeks, 3 cases of old fractures at 4, 6, and 14 months after injury respectively. Four cases underwent MCL repair and 14 cases underwent MCL reconstruction. Results All the 18 cases were followed up 1-5 years (mean 3 years ). According to Broberg and Morrey scoring system, 4 patients were rated as excellent, 12 as good, 1 as fair, and 1 as poor. The excellent and good rate was 88.9%.Three patients had l ight pain of elbow, 1 patient had moderate pain and the other 14 had no pain. The range of elbow motion was from 110 to 140°(mean 130°). The pronation averaged 75° (35-85°). The supination averaged 80° (65-89°). Compared with normal l imbs, the grip strength decreased by 3% to 28% (mean 15%); the extension strength decreased by 8% to 39% (mean 30%); the flexion strength decreased by 7% to 29% (mean 18%); the pronation strength decreased by 7% to 31% (mean 20%);the supination strength decreased by 15% to 45% (mean 25%). The X-ray films showed that carrying angle increased by 0 to 11°(mean 5° ) under two-newton-meter valgus torque. There were significant differences between injured l imbs and normal l imbs (P lt; 0.05). Conclusion The MCL was the primary valgus stabil izer of the elbow. If the radial head replacement could not becarried out, the repair or reconstruction of the medial collateral l igament was effective.