A quantitative assessment of bone and cartilage morphology at the glenohumeral joint in manual wheelchair users

• Main Author: LaFrance, Amy Elizabeth
• Language: English
• Published: 2010
• Online Access: http://hdl.handle.net/2429/18295

Debilitating shoulder pain is prevalent among wheelchair users, however the causes remain unknown. Shoulder pain is reported to be greater among those who began wheeling after skeletal maturity (adulthood-onset, AO) than among those who began wheeling prior to skeletal maturity (childhood-onset, CO). It is unclear whether functional load-bearing from manual wheelchair use affects glenohumeral bone and cartilage morphology. Bone is known to adapt to loading, however the literature is conflicting regarding cartilage’s capacity to adapt to loading. We performed a pilot study to quantify bone and cartilage morphology at the glenohumeral joint of manual wheelchair users (nco=3, nao=5) and age- and gender-matched able-bodied controls (nc=8). Bone morphology (volumetric bone mineral density (vBMD) and normalized cross-sectional area (nCSA)) was evaluated using quantitative computed tomography. Bone density distribution was assessed across the glenoid and, for the first time, across the humeral head using a novel quantitative CT-Osteoabsorptiometry method. Cartilage morphology (thickness, volume, and surface area) was evaluated using quantitative magnetic resonance imaging, in the first assessment at 3T MRI. This novel combination of methods provides complementary quantitative data of glenohumeral bone and cartilage morphology. Compared to the AO, the CO in our study had significantly higher (p<0.05) glenoid subchondral nCSA, non-significantly lower glenoid subchondral vBMD, and non-significantly higher humeral head and glenoid trabecular vBMD. A reasonable cross-sectional study (n=22) would likely show higher humeral head and glenoid trabecular vBMD and glenoid subchondral nCSA in CO subjects but would not find differences in nCSA of humeral head total, trabecular, and cortical bone, or glenoid trabecular bone. Surprisingly, vBMD was (non-significantly) lower in the wheelchair users than in the able-bodied controls, however activity levels varied considerably. Significant correlations were found between humeral head and glenoid trabecular vBMD (r=0.94), and between humeral head trabecular vBMD and physical activity scores (r= 0.84). Given the small effect sizes and the large variance in humeral head and glenoid cartilage thickness, volume, and surface area, it is not likely that further study of these parameters would provide insight into wheelchair users’ shoulder pain. Gaining a better understanding of how glenohumeral bone and cartilage respond to wheelchair use would allow for rehabilitation programs and wheelchair-design to be tailored to childhood-onset and adulthood-onset wheelchair users. === Applied Science, Faculty of === Mechanical Engineering, Department of === Graduate