A biomechanical comparison of scaphoid fixation with bone grafting using iliac bone or distal radius bone

Abstract

Purpose: Although many scaphoid fractures may be treated by immobilization, complex scaphoid fractures generally require bone grafting with internal fixation. A preferred source of bone graft for scaphoid grafting is the iliac crest. Donor site morbidity from iliac crest harvest, however, is a known complication, and the comparable strength and osteogenic properties of bone harvested from other sites are unclear. To this end, we have conducted a cadaveric comparative investigation of the strength of scaphoid nonunions with bone graft and internal fixation using either iliac crest bone or distal radius bone.

Methods: Ten paired, human, fresh-frozen cadaveric wrists were used to create a standard midwaist wedge osteotomy into which identically shaped distal radius or iliac crest bone wedges were internally fixed using headless compression screws. After bone density and computed tomography assessment of the bones, benchtop biomechanical testing was conducted to compare the strength of the scaphoids after iliac and distal radius grafting, at 2-mm displacement, and at failure.

Results: Analysis of scaphoid length, width, height, weight, density, and screw placement revealed no statistical differences between both bone graft groups. Although not significant, scaphoid nonunions grafted with distal radius bone evidenced a reduced load (3.23 +/- 0.26 Nm) to 2-mm displacement compared with iliac crest bone (5.97 +/- 0.68 Nm). Similarly, though not significant, scaphoids grafted with distal radius bone showed a reduced load (4.18 +/- 0.30 Nm) to failure compared with iliac crest bone grafting (6.42 +/- 0.66 Nm). Although no significance was found between the 2 grafting methods, a trend toward greater strength in the iliac crest graft group was observed.

Conclusions: Given the comparable biomechanical strength shown between iliac and distal radius bone in this study and the simplified surgical technique of distal radius harvesting, the data justify use of distal radius bone as a viable alternative donor source in scaphoid fracture treatment.