The vascular basis of the hemi-hamate osteochondral free flap. Part 1: vascular anatomy and clinical correlation.

Purpose: The treatment of comminuted fractures of the proximal interphalangeal joint is highly challenging due to the complexities of joint bio-mechanics and stability. The hemi-hamate osteochondral auto-graft has been popularised in this role, able to replace articular loss and restore joint stability. Recent evaluation of their long-term follow-up however has shown the early development of osteoarthritis and potential early cartilage loss, which may be due to the non-vascularised nature of the graft. We offer a new technique that maintains vascularisation of the transferred hamate fragment, and investigate the anatomical vascular basis for the technique.

Methods: Dissection and angiographic studies of ten cadaveric specimens were undertaken, exploring the vascular anatomy of the dorsal hamate. A clinical case of hemi-hamate osteochondral free flap is presented, including preoperative, intraoperative and postoperative investigation of the relevant vasculature.

Results: Cadaveric studies demonstrated dorsal vascular supply to the hamate from the central of three dorsal carpal arches. The arch was supplied by the dorsal branch of the ulnar artery. Multiple supracapsular veins are present for use in flap venous drainage. This vascular pattern was found to be constant. A clinical case of hemi-hamate osteochondral free flap harvest demonstrated the same vascular anatomy intraoperatively. The digital artery was used as a recipient for microvascular anastomosis. Postoperative computed tomographic angiography and nuclear bone scan confirmed flap perfusion.

Conclusions: The hemi-hamate osteochondral flap has a reliable anatomical vascular basis, and is clinically feasible as a technique for early vascularisation of the osteochondral fragment to sustain the transferred articular cartilage.