Investigation of the geometries of the coronoid process and the fibular allograft as a potential surgical replacement.

Background: The proximal tibiofibular joint can be used as a source of osteochondral autograft with little to no morbidity at the harvest site.

Methods: CT scans of fourteen left and seven right fibular heads, seven right and six left ulnas obtained from healthy subjects were volume-scaled and analyzed. Ipsilateral ulnar articular surfaces were compared between subjects and contralateral ulnas were compared within the same subject. The average deviations between the surfaces were measured. Manual registration and best-fit alignment were used to locate the area on the fibular heads that would best-fit the 50% coronoid process surface.

Findings: The average deviations in the articular surface between subjects were (mean (SD) 0.79mm (0.17) and 0.76mm (0.14) for the left and right ulnas respectively and 0.35mm (0.07) in the same subject. The average coronoid process height of the scaled ulnas was 15.92mm (1.15). When comparing the 50% coronoid process with the ispsilateral fibular head geometries, the maximum deviations for all subjects were smaller than 2.0mm. Two locations were identified as the best-fit locations.

Interpretation: When volume-scaled, the articular congruency of the proximal ulna articular surfaces between subjects is within the allowable limit for a typical intra-articular fracture step. Results suggest it is possible to use the CT scan of a patient's contralateral elbow as a template to estimate the morphology of the affected side. The fibular head could be an alternative replacement for damaged coronoid process since it is covered by articular cartilage and has locations with a similar curvature as the coronoid process.