Is Bone Graft Possible without Limit in Length for Nonunion of Ulna Alone?

Abstract

Background: When either the radius or ulna is united, and the other fails to heal, bone graft and bridge plating can be a choice to treat nonunion of the radius or ulna alone. The length of the bone used to fill the bony defect, however, has not yet been found in terms of biomechanics or biology for healing. The purpose of this study was to find the length of bone grafts possible for operative treatment of bridge plating in nonunion of ulna alone by 3D-finite element method. Method: Using 3D-finite element models based on CT scans of ulna, iliac bone graft and 3.5-locking compression plate(LCP) and screws(10-holes), biomechanical values were obtained to compare them according to 5 to 20mm of lengths of the bone grafts when applied anterior-posterior bending, axial compression and torsion loads. Results: With 5, 10 and 15mm in bone graft lengths, the bending and axial compression forces produced less than 2mm of displacement values of the bone graft. In terms of stiffness, maximum values in the ulna bone under the bending force were greater than those during the testing under axial compression and torsion regardless of lengths of the bone grafts. Conclusion: For stability in nonunions of ulna alone, the recommended length of iliac bone graft associated with bridge plating which can maintain stability is less than 20mm, and it must be paid attention to bending force for postoperative rehabilitation.