Trabecular microstructure at the human scaphoid nonunion

Purpose Scaphoid fractures have the highest prevalence of nonunion in the human body, but despite this, little is known about the microstructure of the bone. Given that microstructural changes in the bone at the site of nonunion define the nonunion, it was our purpose to characterize the trabecular microarchitecture on both sides of the nonunion and compare these to the normal structure. Methods Fifteen human scaphoid nonunions (14 men, 1 woman; average age, 29 years; interval between injury and examination ranged from 7 to 156 months) were excised during surgical reconstruction and assessed by high-resolution micro-computed tomography. Results The bone from the nonunions was clearly different from that of normal scaphoids (obtained from nonreplantable hand amputations or postmortem). Bone on both sides of the nonunions was characterized by higher bone mineral density and an increased number of trabeculae, which were thinner and more tightly packed together compared with the normal scaphoid bones. Further evaluation showed that the bone on the proximal side of the nonunion had higher bone mineral density, higher bone volume fraction, decreased bone surface area, increased trabecular thickness, and increased trabecular number when compared with the distal side. Conclusions These data demonstrate the differing microstructure of the bone at the scaphoid nonunion, particularly on the proximal side, and indicate that the biology also differs from normal. The data also show that scaphoid nonunions produce new bone at the site, which may have positive implications toward hardware fixation and healing stimulation.