MR imaging of avascular scaphoid nonunion before and after vascularized bone grafting

Objective: To investigate the magnetic resonance (MR) imaging appearances of chronic nonunion of the scaphoid with proximal pole avascular necrosis before and after insertion of a vascularized bone graft, using computed tomography (CT) as the imaging gold standard. Design and patients: A retrospective study was performed involving MR imaging (n=26), CT scans (n=37) and radiographs (n=52) of 13 men (mean age 29 years, age range 20-38 years) with avascular scaphoid nonunion. Avascular necrosis of the scaphoid proximal pole was confirmed intraoperatively (n=13). MR images were acquired preoperatively and following placement of a vascularized bone graft. Scaphoid MR signal characteristics were assessed for evidence of vascular bone graft incorporation and revascularization of the bone marrow of the proximal pole of the scaphoid and compared with the gold standard of CT. Surgical and clinical notes were reviewed with a minimum 3 year imaging and clinical follow-up in all patients. Results: Graft incorporation with revascularization of the proximal pole of the scaphoid was documented in 9 patients (69%). Graft failure with persistent pseudoarthrosis and avascular necrosis of the scaphoid was seen in 4 patients (31%). Conclusions: MR imaging is useful to determine whether vascularized bone graft incorporation and revascularization of the proximal pole of the scaphoid has occurred in the setting of avascular scaphoid nonunion.