Büchler, U

Abstract OBJECTIVE AND IMPORTANCE Heterotopic ossification (“neuritis ossificans”) is among the least frequently encountered reactive lesions in peripheral nerves. Only two cases have been described previously, one in the median nerve of a 34-year-old man, and the other in the ulnar nerve of an adult woman. The architecture of this lesion is distinctly zonal. Consisting of a central fibroblastic core, an intervening zone of osteoid production, and a peripheral layer of ossification, the pattern is remarkably similar to that of myositis ossificans. This similarity and the occurrence of the process in superficial nerves have led to speculation that trauma plays a role in its pathogenesis; this hypothesis remains unproved. We describe two additional cases of neuritis ossificans. CLINICAL PRESENTATION One patient, a 41-year-old man, experienced pain and numbness in the left leg for several months but had no history of local trauma. A mass was detected in the saphenous nerve. The second patient, a 16-year-old boy, noted subacute onset of pain in the popliteal fossa and decreased sensation in the distribution of the lateral sural cutaneous nerve. A mass was found within the tibial nerve at the knee level. INTERVENTION In each patient, resection of the mass required sacrifice of a segment of the nerve. CONCLUSION In each patient, the mass was composed of fibrovascular tissue with osteoid and bone deposition arranged in a zonal pattern. The ossifying process was intraneural but encased rather than directly involving nerve fascicles. These exceptionally intact examples of neuritis ossificans underscore its resemblance to myositis ossificans. Nerve-sparing resection of such masses is not always possible.

Six cases of greater arc injury, defined as a perilunate dislocation of the carpus with a fracture of at least both the scaphoid and the capitate, were treated by open reposition and both internal and external fixation. Revascularisation of the capitate by implantation of the first dorsal intermetacarpal artery was attempted in three cases. At a mean follow-up of six years and four months, all patients complained of residual pain in the wrist. Carpal mobility and grip strength were reduced, and all patients showed mild or moderate arthritic changes. Progressive cartilage damage over the proximal pole of the capitate seems to be a determining factor in the outcome. Open reposition and both internal and external fixation are recommended in order to possibly diminish the incidence of arthritis and minimise secondary carpal instability.