Stiffness was a consistent but nonspecific symptom of primary frozen shoulder. Theories and descriptions of the pathological condition had not yet been determined. Severe pain was observed in the early stage: freezing phase and global limitation of shoulder motion was recognized in the next stage: frozen phase. Complex regional pain syndrome type I: CRPS type I was known as presenting post-traumatic chronic pain and autonomic nervous abnormalities and was reported to present bone scintigraphic abnormalities. We hypothesized that primary frozen shoulder resembled CRPS and the aim of this study was to investigate the characteristics of bone metabolism with scintigraphy in this disease. We retrospectively evaluated bone scintigraphic findings in 25 cases of frozen shoulder: 15 cases of freezing phase and 10 cases of frozen phase. Quantitative computerized analyses of each scintigraphic image were performed in three areas: anterior, posterior and inferior scapula. Each data was revised with the reference determined at the healthy humeral bone. Scintigraphic comparisons between affected shoulders and healthy shoulders and those between freezing phases and frozen phases were statistically evaluated. Scintigraphic uptake in the affected side was significantly increased compared to the healthy side. Those in the freezing phases were significantly increased than in the frozen phases. Bone metabolism in frozen shoulders determined by bone scintigraphy was significantly increased in the affected shoulders and in the freezing phases.
