The Optimal Donor Site From the Foot as a Nonvascularized Osteochondral Graft for the Reconstruction of Lunate Facet Defects in Distal Radius Intra-Articular Fracture: A Computed Tomography and Cadaveric Study.

Purpose: This study aimed to identify the best donor sites for a nonvascularized osteochondral graft from the foot to reconstruct lunate facet defects in malunited distal radius fractures.

Methods: Fifty-six wrist computed tomography (CT) scans, obtained from scaphoid fracture patients, assessed the lunate facet's articular surface for dorsal and volar width, dorsovolar length, and concavity depth. Additionally, 60 foot CT scans, obtained from calcaneus fracture patients, assessed the second and third metatarsals and cuneiforms for dorsal and plantar width, dorsoplantar length, concavity/convexity, inflection point, and articular cartilage thickness. A cadaver study of 20 feet recorded the same parameters along with cartilage thickness using ultrasound and further examined the accessory fibular and tibial facets of the four bones.

Results: The lunate facet measured 11.4 mm dorsally, 13.9 mm volarly, and 17.4 mm long with a 3 mm concavity. The sizes of dorsal and plantar width and dorsoplantar length of articular surfaces of all four foot bones were large enough for lunate facet reconstruction. The second metatarsal and second cuneiform showed concave and convex surfaces in 100% of the cases, respectively. The third metatarsal was concave in 21.7% and convex in 78.3% of the cases. The third cuneiform was concave in 78.3% and convex in 21.7% of the cases. The cadaver study confirmed similar results, with cartilage thickness ranging from 0.5 to 0.7 mm. The dorsofibular accessory facet was oval and larger on the base of the third metatarsal.

Conclusions: The third metatarsal base and third cuneiform are the best donor sites for lunate facet reconstruction. A convex donor site is suboptimal for reconstructing the concave lunate facet; therefore, a preoperative CT scan is mandatory for identifying an appropriate concave donor site.

Clinical relevance: The study recommends the third metatarsal base or third cuneiform for lunate facet reconstruction in distal radius fractures.