Background: Many studies have attempted to clarify factors associated with the development of shoulder periarthritis. In its early stage, omalgia impairs normal, everyday life. Due to this pain, muscle force decreases in the affected side of the upper limb, and a change occurs in body composition distribution, especially in the upper limb. Currently, body composition distribution can be measured using dual energy X-ray absorptiometry (DEXA).
Methods: 102 patients with unilateral shoulder pain over 3 months (5 males and 97 females, mean age: 62.5 ± 10.5 years) were assigned to the shoulder pain group (painful group). The control group consisted of 237 patients without shoulder pain (20 males and 197 females, mean age: 59.8 ±14.2 years). These factors were measured using a QDR-4500 DEXA scanner (Hologic Co., Ltd.).
Results: Mean values of bone mineral density were 0.57 ±0.09 g/cm2 on the affected side and 0.59 ± 0.08 g/cm2 on the non-affected side in the painful group. Mean values in the control group were 0.57 ± 0.14 g/cm2 on the left side and 0.58 ±0.09 g/cm2 on the right side. There was no significant difference between the shoulder with and without pain, affected and non-affected side. Mean proportions of the upper limb that was fat were 40.1 ± 9.5% on the affected side and 35.7 ±9.8% on the non-affected side in the painful group. In the control group, the means were 39.2 ±11.1% on the left side and 37.5 ± 10.9% on the right side. The mean muscle masses of the upper limb were 1548.5 ±304.2 g on the affected side and 1723.5 ±321.5 g on the non-affected side in the painful group. There was a significant difference between the affected and non-affected side.
Conclusions: We measured the body composition of the upper limb. Muscle mass of upper limb was significantly different between the affected and non-affected sides.