Purpose: Congenital radioulnar syntosis (CRUS) is a rare malformation caused by the fusion of the proximal extremities of the radius and ulna associated with anomalies of the adjacent soft tissues. The purpose of this work was to analyse a series of 36 non-operated cases of CRUS in order to evaluate the functional impact and compensatory mechanisms.

Material and methods: Twenty-five patients (16 male, 9 female) presenting 36 CRUS (14 unilateral, 11 bilateral) were collected over a period of eight years (1994–2002). None of the patients underwent surgery. Mean age at evaluation was 8.3 years (range 2–25) Active and passive motion of the shoulder, elbow, wrist, and fingers was assessed clinically. The modified Jebsen and Taylor test was used to assess function. The size of the synostosis was assessed on plain x-rays of the forearm.

Results: The mean position of the fixed forearm was 35° pronation (range 10° supination to 90° pronation). Thirty-one percent of the patients had deficient elbow extension (5–15°). Shoulder motion was normal in all patients and all except two presented compensatory wrist laxity (two patients had a stiff wrist with CRUS associated with Poland syndrome). Function was normal except for four patients who complained of difficulties in certain activities (volleyball, cutting with scissors, face washing, lifting heavy objects). None of the patients requested corrective surgery.

Discussion: Reports in the literature discuss the technical difficulty of corrective surgery for CRUS and the problems in establishing appropriate indications. Fortunately, most of these patients do not have sufficiently serious impairment to justify surgical intervention. The degree of fixed pronosupination is not the only factor to be considered since function is also related to the bilateral or unilateral nature of the malformation as well as the side (dominant or non-dominant) and also with the efficacy of compensatory shoulder, wrist, and finger movements. The subject’s occupational activity must also be taken into account. In our series, functional impairment was minimal.

Conclusion: CRUS is a well tolerated malformation which only rarely requires surgical correction.