Injuries about the ankle joint resulted in not only fractures of the bone but also ruture of the ligamentous and soft tissue structures and it is important that accurate reduction and rigid internal fixation of fracture as well as repair of ruptured ligament should be performed.

The author analyzed 35 cases of the trimalleolar fractures of the ankle which were admitted and treated in Department of Orthopaedic Surgery, Hanyang University Hospital from january 1984 to December 1988.

The results obtained from this study were as follows;

1. Among the 35 cases, male was 25 cases(71.4%), female was 10 cases(28.6%), and average age was 37.43 years.

2. The main cause of the fracture was 18 cases of slip down(51.43%), and other causes were traffic accident(22.86%), fall from a height(17.14%), sports injury(5.71%), and other injuries(2.86%).

3. Open fractures were 2 cases(5.7%), and closed fractures 33 cases(94.3%).

4. According to the classification of Lauge-Hansen, the pronation-external rotation type was 22 cases(62.86%), and the supination-external rotation type, 13 cases(37.14%).

5. Open reduction was performed in 25 cases(71.43%), and closed reduction 10 cases(28.57%).

6. The average period of the cast immobilization after open reduction was 10.7 weeks, and

8. Fractures with a posterior marginal fragment invoving 25 percent of more of the tibial articular surface, open reduction was recommended.