Purpose
To study the intraosseous 3-dimensional microvasculature of the capitate bone using a novel high-resolution micro-computed tomography (μCT) imaging technology, and to examine the blood supply as it relates to the most common fracture types.

Methods
Ten cadaveric wrists were injected with a lead-based contrast agent. The capitates were harvested and imaged using a μCT scanner. The intraosseous vascularity was incorporated into a 3-dimensional image. We measured the vascular pattern as well as the vessels’ cross-sectional area, number, and distribution. An average capitate fracture line was calculated using clinical data from 22 patients with capitate fractures. The fracture line was projected on the representative capitate to assess its relation with the nutrient vessels’ entry points.

Results
The capitate is a well-vascularized carpal supplied by dorsal and volar vascular systems that anastomose in 30% of cases. There was no predominance of one vascular system over the other. Most vessels enter the capitate at the distal half and supply the proximal pole in a retrograde fashion. In addition, most specimens (70%) also had at least one vessel entering the proximal pole through the volar capitate ligaments and supplying the proximal pole directly. The average fracture line had an oblique orientation, and 90% of the specimens had a blood vessel entering proximal to that line.

Conclusions
This μCT vascular study further verifies that the capitate receives most of its vasculature in a retrograde fashion, but the study also shows that most capitates have vessels supplying the proximal pole directly. These findings might explain why most capitate waist fractures do not progress to proximal pole avascular necrosis.

Clinical relevance
This study characterizes the microvasculature of the capitate and might shed light on processes involved in bone healing and the etiology of capitate avascular necrosis.