A quantitative study of humeral cartilage in individuals with spinal cord injury

Study design: Cross-sectional design. Objectives: In this in vivo study, we investigated the influence of different load situations on humeral cartilage thickness in individuals with paraplegia and quadriplegia. Setting: ETH Zurich and Swiss Paraplegic Centre Nottwil, Switzerland. Methods: A previously validated three-dimensional (3D) gradient echo MRI-sequence with selective water excitation was used. Three groups were compared: individuals with paraplegia with high shoulder demand (n = 11), individuals with quadriplegia with reduced load on the shoulder joint (n = 8) and a control group (n=9). After 3D reconstruction, the mean cartilage thickness, local thicknesses (superior, medial, inferior) and the minimum joint space were calculated. Results: The mean humeral cartilage thickness (1.40±0.14 mm) as well as the minimum joint space (2.57±0.50 mm) did not differ between groups. In individuals with paraplegia, the superior cartilage thickness was significantly greater than in individuals with quadriplegia (1.47mm compared to 1.28mm, P<0.05). In the control group, there was a significant negative correlation between mean cartilage thickness and age (r=-0.81). Conclusion: Neither higher shoulder demand nor reduced shoulder loading leads to thinning of humeral cartilage. It is hypothesized that higher local stresses prevent local cartilage degeneration, as in normal load situations humeral cartilage thinning is occurring with age. Furthermore, joint space narrowing was only associated with inferior cartilage thickness and cartilage thickness is not related to shoulder pain.