Dynamic palmar dislocation of the ulnar head at the distal radioulnar joint (DRUJ) after radius shaft malunion

Abstract

Introduction: Palmar instability of the distal radioulnar joint (DRUJ) is a rare condition, which is, in contrast to the dorsal dislocation, scarcely represented in the literature. This palmar instability can result from a dorsally angulated malunion of the radial shaft after forearm fracture in childhood. Treating such a condition is controversial in the literature and was described in small case series. This study represents the largest case series in the literature that dealt with this condition, alongside a review of the key papers in the English literature.

Materials and methods: This is a retrospective case series. Ten patients were operated between 2007 and 2014. Six patients could be followed up clinically and radiologically after radius corrective osteotomy at the site of malunion with a mean time of 5.6 years. Patient history revealed a conservatively treated forearm fracture in childhood, a symptom-free period of several years [mean of 21.5 (min-max: 9.4-26.5) years] and a minor trauma as a trigger for clinical symptoms. All patients had clinically a DRUJ instability with palmar luxation of the ulnar head at supination. A diagnostic key feature is a radiograph of the whole forearm, revealing malunion of the radius at shaft level. Retrospective patient history, diagnostic imaging, operative technique and clinical results (DASH, modified Mayo Wrist Score, pain, grip strength, range of motion) were analyzed.

Results: Four patients were lost to follow-up. In all patients, a radius corrective osteotomy could stabilize the DRUJ. In one patient, the osteosynthesis was revised due to metal failure after one month. In all the six patients, bony union of the osteotomy was achieved. In another patient, an additional ulnar shortening osteotomy was done one year later due to a positive ulnar variance. Postoperative range of motion of the wrist had an average of 136° in extension/flexion and 149° in pronation/supination, and grip strength was 89% of the opposite side. With an average of 12.5 points at the DASH score and 82 at the modified Mayo Wrist Score, patients rated their hand function as good.

Conclusions: In this patient cohort, a simple corrective osteotomy of the radial shaft at the malunion site was adequate to treat the dynamic palmar instability of DRUG. A soft tissue procedure was not required. Forearm radiographs are the mainstay of diagnostic tools.

Keywords: Distal radioulnar joint; Instability; Palmar dislocation; Radius malunion; Wrist joint.