Tardy posterolateral rotatory instability of the elbow due to cubitus varus

Background: Cubitus varus has long been considered merely a cosmetic deform ity. The purpose of this paper is to demonstrate a causal relationship betw een cubitus varus and instability of the elbow. Methods: In twenty-four patients (twenty-five limbs) with a cubitus varus d eformity following a pediatric distal humeral fracture or resulting from a congenital anomaly (three limbs of two patients), tardy posterolateral rota tory instability of the elbow developed approximately two to three decades after the deformity occurred. All patients presented with lateral elbow pai n and recurrent instability. The average varus deformity was 15 degrees (ra nge, 0 degrees to 35 degrees). Surgery was performed in twenty-one patients (twenty-two limbs). Treatment consisted of reconstruction of the lateral c ollateral ligament and osteotomy in seven limbs, ligament reconstruction al one in ten, osteotomy alone in four, and total elbow arthroplasty in one. Results: In three patients, the triceps muscle was dynamically stimulated i ntraoperatively to contract while resisting extension of the elbow. This pr oduced posterolateral rotatory subluxation of the elbow, which was reversed by corrective osteotomy and lateral transposition of a portion of the medi al head of the triceps that originally had been attached to the elongated, deformed medial aspect of the olecranon. At an average of three years (mini mum, one year) after the operation, the result was good or excellent for ni neteen of the twenty-two limbs that had undergone an operation; three limbs had persistent instability. Conclusions: With cubitus varus, the mechanical axis, the olecranon, and th e triceps line of pull are all displaced medially. The repetitive external rotation torque on the ulna permitted by these deformities can stretch the lateral collateral ligament complex and lead to posterolateral rotatory ins tability. Thus, cubitus varus deformity secondary to supracondylar malunion or congenital deformity of the distal part of the humerus may not always b e a benign condition and may have important long-term clinical implications . Operative correction can relieve symptoms of instability. The indications for preventive corrective osteotomy remain to be determined.