Regional variations in radial head bone volume and density: implications for fracture patterns and fixation

BACKGROUND: Fractures of the radial head are common with most partial articular fractures resulting in an anterolateral fragment. The exact mechanism of radial head fracture is unknown; however, forces transmitted and variations in local bone density are believed important. This study quantifies the regional variations in bone density and volume of the radial head to better understand the pathomechanics of fracture patterns. METHODS: Computer tomography scan data of 18 cadaver elbows were imported into imaging analysis software. The radial head was divided into quadrants based on neutral forearm rotation. Bone density and volume were calculated and compared between quadrants. RESULTS: The regional densities of bone expressed in Hounsfield units (HU) were posteromedial quadrant (PM) 496 ± 87 HU, anteromedial quadrant (AM) 443 ± 72 HU, anterolateral quadrant (AL) 409 ± 60 HU, and posterolateral quadrant (PL) 406 ± 57 HU. The volume of bone in descending order was PM 1138 ± 179 mm(3), PL 1013 ± 213 mm(3), AM 1010 ± 210 mm(3), and AL 938 ± 175 mm(3). The PM quadrant was significantly denser than the AM, AL, and PL quadrants, (P = .001) and the AM quadrant was significantly denser than the AL and PL quadrants (P = .006 and .009). The PM quadrant had significantly more bone volume when compared to the AM, AL, and PL (P = .001). The AM and PL quadrants had significantly greater bone volume compared to AL quadrant (P = .023 and .018, respectively). CONCLUSION: Radial head bone volume and density is highest in the posteromedial quadrant and lowest in the anterolateral quadrant where fractures occur more frequently.