An anatomic and 3D study of the development of the proximal humeral physis

Purpose: During maturation, the ossification centers of the proximal humerus form a characteristic pattern consisting of a metaphyseal peak and corresponding epiphyseal valley. The surface topographies of the metaphyseal peak and epiphyseal valley are not well described and may have variation with age and structural importance to the pathogenesis of proximal humeral epiphysiolysis. Methods: High-resolution 3-dimensional surface scans of 24 cadaveric proximal humeral epiphyses and metaphyses in specimens aged 3 to 18 years were obtained. Computer modeling software was used to measure the peak height of the metaphysis and maximal depth of the epiphysis relative to a perpendicular line drawn across the proximal humeral physis. Results: The metaphyseal peak had a mean height of 12.7 ± 1.6 mm while the epiphyseal valley had a mean depth of 13.1 ± 2.1 mm, both consistently positioned in the posterolateral quadrant. Both the absolute metaphyseal peak height (R² = 0.536; p < 0.001) and absolute epiphyseal valley depth (R² = 0.524; p < 0.001) increase with advancing age. Multiple linear regression analysis demonstrated that normalized metaphyseal peak height + sex (adjusted R² = 0.408; p < 0.002) correlated more with age than normalized epiphyseal valley depth + sex (adjusted R² = 0.128; p < 0.091). Conclusion: Prominence of the metaphyseal peak and epiphyseal valley both increase with advancing age, with a lower correlation between normalized sizes with age as compared to the absolute sizes, suggesting that these structures stay relatively proportional with growth.