Morphometric analysis of the lateral column of the distal humerus with an interest on radio-capitellar arthroplasty design. A computed tomography anatomical study on 50 elbows

Purpose To perform a morphometric analysis of the distal humerus lateral column medullary canal (LCMC). Methods Fifty computed tomography(CTs) from 24 males and 26 females were examined. Two observers measured: (1) the capitellum sagittal (R-S) and axial (R-T) radii of curvature; (2) the sagittal(Sd) and coronal(Cd) diameters of the LCMC in 5 different disto-proximal sites spaced 4 mm apart; (3) the capitellum and LCMC axis offsets on the sagittal (capSO,axSO) and coronal (capCO,axCO) planes; (4) the sagittal (Si) and coronal (Ci) inclination of the LCMC axis. Results The mean R-S and R-T were 1.07 cm (SD, 0.11) and 1.30 cm (SD, 0.11), respectively. The mean Sd and Cd values were 1.17 cm (SD, 0.17) and 1.58 cm (SD, 0.24), respectively, with a disto-proximal decrease on both planes. The capSO, capCO, axSO and axCO mean values were 0.76 (SD, 0.21), 1.60 (SD, 0.27), - 0.16 (SD, 0.30) and 0.79 cm (SD, 0.30), respectively. Si and Ci were 70 degrees and 72 degrees, respectively. A strong correlation (r = 0.78) was found between R-S and R-T and between adjacent levels of Sd and Cd. AxSO and axCO yielded a strong inverse correlation. Male patients showed higher values than female ones in all variables (p < 0.03). The intra-class correlation coefficient (ICC) was always > 0.9. Conclusion The dimensions of the LCMC decrease disto-proximally, with the coronal diameters being greater than the sagittal diameters, resembling a portion of an elliptic torus with an antero-medial concavity. The articular surface of the humeral capitellum is non-spherical, with two strongly correlated radii of curvature. The results of this study may be relevant to the stem design of radiocapitellar arthroplasty.