Distal Ulna Reconstruction using the Second Metatarsal: Anatomical Study.

Abstract

Background The ulnar head is a key stabilizer of the wrist and forearm. The authors investigated the possibility of using the second metatarsal bone to replace the distal ulna in an anatomical study. Methods The morphology of the distal ulna and the head of the second metatarsal (MT2) were studied using three-dimensional computerized tomographic (CT) scans of the wrist and foot in 52 patients without pathology related to these two areas, and 11 cadaveric specimens. The radius and height of the best-fit cylinder for both epiphyses were measured in the CT scans and compared. In the cadaveric specimens an osteotomy of the metatarsal neck was performed to rotate 90 degrees the head of the MT2 to match the shape of the distal ulna. Results The osseous morphology of the distal ulna and the head of the MT2 are roughly cylindrical, but differently oriented relative to the diaphyseal axes. In the osteotomized cadaveric MT2specimens, the overall morphology was relatively similar that of the distal ulna. The mean length of the MT2 after the osteotomy was 65 mm. Conclusion The head of the MT2 was found to have a similar cylindrical morphology to that of the ulnar head, with a different orientation. The radius of the cylinder was similar, although the height was bigger for the MT2. After a rotation osteotomy of the neck of the MT2 the overall shape and orientation of the epiphysis was more similar to the distal ulna. A vascularized transfer of an osteotomized MT2 would be an option for autologous reconstruction of the distal ulna in selected patients, but further study is needed in terms of the vascular supply, ligamentous reconstruction, and reconstruction of the sigmoid notch. Level of Evidence Therapeutic, level IV.