Trabecular Pattern of the Proximal Ulna: A Morphological Study

Abstract

Background The trabecular architecture of the olecranon and proximal ulna has not been studied in detail. We undertook a primarily cadaveric study aiming to link with the theory of biomechanics. Methods Eight pairs of ulnae were obtained from cadavers. Half of the ulnae were sliced longitudinally, each slice 2 mm to 3 mm thick (Group I), and the remaining half were sliced vertically (Group II) and radiographed to study the trabecular orientation of the olecranon and proximal ulna. Computerized tomography (CT) scans of eight patients (Group III) were studied to determine the real-life trabecular pattern. Results In Group I, two main sets of trabeculae were observed. The first set of trabeculae consists of three bundles, which arise from the anterior cortex. Anterior and middle bundles support the subarticular subchondral area. The posterior bundle curves and spreads to posterior cortex. The second set arises from posterior cortex and terminates under subchondral area. In Group II, trabeculae subtend a 90° angle to the articular surface. CT (Group III) confirmed the cadaveric observations. Conclusions Trabeculae of the olecranon and proximal ulna comprise a cluster that resists compressive loading and a further cluster that resists tensile stresses, which should be taken into consideration in the prosthetic design of elbow replacement to facilitate stress absorption.