Congenital radioulnar synostosis.

Congenital radioulnar synostosis is a rare disorder resulting in the fusion of the radius and ulna from birth. Management is conservative. Operative treatment rarely succeeds.

Radioulnar synostosis is divided into two types: post-traumatic radioulnar synostosis and congenital radioulnar synostosis (CRS). Radioulnar synostosis is the failure of segmentation of the adjacent radius and ulna. Radioulnar synostosis affects the supination and pronation movements of the elbow joint. The elbow flexion and extension is unaffected and the inconvenience is often only moderate [1]. However, potential consequence of restricted elbow movement includes excessive strain on the shoulder joint above and the wrist joint below. In contrast to radioulnar synostosis resulting from trauma, I present a case of congenital CRS.

Case report

A 29-year-old right-handed woman 10 months postpartum presented with 6 months of pain in the right wrist. The pain is starting to affect her care of the 10-month-old baby. She also started a new job that involved typing. Examination showed mild tender wrist and no other abnormality except the elbows were moderately restricted in supination and pronation. Patient indicated that she was born with the restricted elbows and learnt to live with it. For example, she types by moving the elbows to the sides. X-ray and computed tomography confirmed bilateral radioulnar synostosis (Figs. 1 and 2). The woman was treated with indomethacin, activity modification, occupational therapy, and advice for an ergonomic keyboard. An improvement in the wrist pain was noted at a clinic follow-up visit.

Fig. 1

Anteroposterior and lateral radiographs of both forearms, demonstrating bilateral proximal congenital radioulnar synostoses (Acknowledgement: Dr David Mitchell, Qscan Radiology).

Fig. 2

Three-dimensional tomographic reformation of both elbows, demonstrating bilateral proximal congenital radioulnar synostoses (Acknowledgement: Dr Mark Bergin, Qscan Radiology).

Discussion

CRS is a rare congenital disorder with approximately 350 cases reported in the literature [2]. Sixty per cent of them are bilateral. CRS is caused by the failure of separation of the fused cartilaginous precursors of the radius and ulna during the seventh week of gestation. CRS may be associated with other congenital musculoskeletal disorders such as congenital hip dislocation, clubfeet, polydactyly, or syndactyly [2], [3]. If the deformity is mild, the patient often compensates well with adjusted movements of the adjacent joints, wrists, and shoulders. However, to avoid excessive strain on other joints, occupational therapy, activity modification, and ergonomic working environment are recommended. Surgery to regain rotatory movement rarely succeeds [1]. Poor surgical outcomes occur because of the poorly developed supporting structures, neurovascular compromise, and recurrence of the synostosis [2].