We experienced one case of posterolateral rotatory instability (PLRI) in post-traumatic cubitus varus. The patient was a 15-year-old male, motocross player who injured his right elbow while riding his motorcycle. He had a history of supracondylar fracture of the right humerus at nine years of age. He was treated with open reduction. Unstableness of his right elbow has been noticed since 13 years. On his visit to our clinic, the range of motion of his right elbow was three to 140 degrees. He presented deformity of the right elbow which was 20 degrees of the cubitus varus. Radiogram showed ulnar deviation of the orecranon and hypertrophy of the radial head, enlarged curvature of the trochlea notch, free bone fragment at the lateral epicondyle of the right humerus. He showed both 14-degree varus instability and posterolateral rotatory instability. Correction domed osteotomy of the humerus and reconstruction of the lateral collateral ligament with use of a triceps tendon were performed. Eight months postoperatively, there has been no recurrence of deformity and posterolateral rotatory instability.
