Measurement Methods for Humeral Retroversion Using Two-Dimensional Computed Tomography Scans: Which Is Most Concordant with the Standard Method?

BACKGROUND Humeral retroversion is variable among individuals, and there are several measurement methods. This study was conducted to compare the concordance and reliability between the standard method and 5 other measurement methods on two-dimensional (2D) computed tomography (CT) scans. METHODS CT scans from 21 patients who underwent shoulder arthroplasty (19 women and 2 men; mean age, 70.1 years [range, 42 to 81 years]) were analyzed. The elbow transepicondylar axis was used as a distal reference. Proximal reference points included the central humeral head axis (standard method), the axis of the humeral center to 9 mm posterior to the posterior margin of the bicipital groove (method 1), the central axis of the bicipital groove -30° (method 2), the base axis of the triangular shaped metaphysis +2.5° (method 3), the distal humeral head central axis +2.4° (method 4), and contralateral humeral head retroversion (method 5). Measurements were conducted independently by two orthopedic surgeons. RESULTS The mean humeral retroversion was 31.42° ± 12.10° using the standard method, and 29.70° ± 11.66° (method 1), 30.64° ± 11.24° (method 2), 30.41° ± 11.17° (method 3), 32.14° ± 11.70° (method 4), and 34.15° ± 11.47° (method 5) for the other methods. Interobserver reliability and intraobserver reliability exceeded 0.75 for all methods. On the test to evaluate the equality of the standard method to the other methods, the intraclass correlation coefficients (ICCs) of method 2 and method 4 were different from the ICC of the standard method in surgeon A (p < 0.05), and the ICCs of method 2 and method 3 were different form the ICC of the standard method in surgeon B (p < 0.05). CONCLUSIONS Humeral version measurement using the posterior margin of the bicipital groove (method 1) would be most concordant with the standard method even though all 5 methods showed excellent agreements.