Abstract
Objective
To compare regional body composition, bone mineral density (BMD), and clinical outcome in patients with two different shoulder arthroplasty designs.
Materials and Methods
This cross-sectional study included 54 patients with a total of 63 shoulder arthroplasties. There were 18 men and 45 women with a mean age of 68.9 years SD ± 10.5. Mean follow-up time was 39.2 months SD ± 14.4. The patients were divided into three groups according to their history: 22 patients were diagnosed with a proximal humeral fracture and treated with a stemmed hemi arthroplasty, 11 patients were diagnosed with osteoarthritis and treated with a stemmed hemi arthroplasty, and 30 patients were diagnosed with osteoarthritis and treated with a resurfacing arthroplasty. All patients underwent a one-day protocol: Regional Dual X-ray Absorptiometri (DXA) was used to measure BMD of the distal third of humerus and regional body composition of the upper arm. The clinical outcome was measured using Western Ontario Osteoarthritis of the Shoulder index (WOOS) and Constant-Murley score.
Results
All three groups were comparable regarding demographic data. Mean BMD of the distal third of humerus was 1.029 g/cm2 SD ± 0.204, mean tissue mass of the upper arm was 2.6 kg SD ± 0.7 and mean muscle mass was 1.4 kg SD ± 0.6. BMD of the distal third of humerus, tissue mass and muscle mass were significantly higher in the group diagnosed with osteoarthritis and treated with a resurfacing arthroplasty compared to the group diagnosed with a proximal humeral fracture and treated with a stemmed hemi arthroplasty, P = 0.03, P = 0.01 and P = 0.02 respectively. Median Constant score was 45.0, range 6–89, median WOOS 633, range 28–1824, and median strength 7.0 units, range 0–25. There were no significant differences between the three groups. Nevertheless, there was a trend towards a higher Constant-Murley score and muscle strength in the group of patients diagnosed with osteoarthritis and treated with a resurfacing arthroplasty compared to the group of patients diagnosed with a proximal humeral fracture and treated with a stemmed hemi arthroplasty.
Conclusion
After shoulder arthroplasty BMD of the distal third of humerus and body composition are apparently more dependent on diagnosis rather than arthroplasty design. However, a larger number of patients diagnosed with osteoarthritis and treated with a stemmed hemi arthroplasty are needed to support this.
