Biometrical analysis of the shoulder joint regarding glenoid implant dimensions for arthroplasty.

ABSTRACT

PURPOSE: Reduced bone stock and difficult intraoperative orientation are challenges in glenoid replacement surgery. New implant designs and methods for fixation, such as locking screws, extra-long central pegs and/or central compression screws are targeting these issues. The objective of this study is the analysis of the glenoid dimension regarding maximum central peg diameter and peg length (PL), and maximum screw length (SL) for glenoid fixation. METHODS: Retrospective analysis of magnetic resonance imaging (n = 50) scans. Measurement of the maximum inferior glenoid diameter (GD), SL, maximum length of a 9.9, 10 and 11.4 mm central peg (PL) in the transverse plane; glenoid version (GV), humeral head diameter (HHD). Two independent measurements. RESULTS: Mean age 49.0 ± 15.7 years (17-80) (n = 20 female, 49.6 ± 16.0; n = 30 male, 48.6 ± 15.7). Mean values of measurement were GD 28.9 ± 3.7 mm (21-39); SL 34.1 ± 4.9 mm (26-44); PL 9.9 mm 19.4 ± 4.3 mm (9-30); PL 10 mm 19.0 ± 4.4 mm (8-30); PL 11.4 mm 16.5 ± 4.1 mm (7-26) with significant gender differences (p = 0.001; p = 0.022; p = 0.001); GV -0.6° ± 4.9° (-10 to 11); HHD 50.0 mm ± 4.9 (41-61). There was good correlation between PL and SL (r = 0.32, p = 0.024) and for GD and PL (r = 0.61, p = 0.001; r = 0.57, p = 0.001; r = 0.96, p = 0.001). The ratio of HHD and GD was very constant with 0.6 ± 0.07. CONCLUSIONS: These data indicate the high interindividual variability of glenoid morphology including significant gender-related differences. The good correlation between humeral head size and GD and maximum central PL can be helpful for cases with reduced bone stock in decision-making about implant size and bone grafting.