Non-union of the ulnar styloid process in children is common but long-term morbidity is rare: a population-based study with mean 11 years (9-15) follow-up.

Background and purpose - Fracture of the ulnar styloid process (USP) is common in children in connection with distal radius fracture. The long-term morbidity of USP non-union following a childhood distal radius fracture is unclear. We evaluated long-term clinical and radiographic findings of USP non-union. Patients and methods - All 208 children (< 16 years) who had suffered from distal radius fracture with or without a diagnosed concomitant ulnar fracture during 1992-1999 in the study institution were invited to follow-up at mean of 11 years (9-15) after the injury. Radiographs of both wrists of all 139 participants (67%) were taken; 22 patients showed USP non-union and they made up the study population. Distal radioulnar joint (DRUJ) instability, decreased range of motion (ROM), and weakened grip strength as compared with the uninjured side were the main functional outcomes. Elements of the "Disability of Arm, Shoulder and Hand" questionnaire were used for subjective symptoms. Results - The rate of USP non-union following childhood distal forearm fracture was 16% (22/139) and only 9 of the ulnar styloid fractures were visible in the radiographs primarily. At follow-up wrist flexion-extension ROM and ulnar and radial deviation ranges did not differ between the injured and uninjured sides. Grip strengths were similar. 6 patients reported pain during exercise. 7 had ulna minus (mean 2.3 mm) but none showed degenerative radiographic findings. Interpretation - The long-term clinical results of USP non-union following a childhood wrist fracture were good. However, one-third of the patients with USP non-union had ulnar shortening, which may predispose them to degenerative processes later in life.