Tracer uptake pattern around the scapula after reverse total shoulder arthroplasty: stress analysis using single-photon emission computed tomography/computed tomography imaging.

BACKGROUND: The purpose of this study was to investigate distribution and pattern of tracer uptake on single-photon emission computed tomography/computed tomography (SPECT/CT) images around the scapula after reverse total shoulder arthroplasty (rTSA) and to determine the correlation between tracer uptake values and clinical parameters.

METHODS: Thirty-five patients treated with primary rTSA (21 lateralized type vs. 14 medialized type) were retrospectively reviewed. All patients were taken SPECT/CT preoperatively and postoperatively at 6 months. Maximum standardized uptake value (SUVmax) was measured at the 4 regions of interest (ROIs): anterior acromion, posterior acromion (PA), scapular spine (SS), and coracoid process (CP). Demographic data and clinical parameters were prospectively evaluated before surgery and at postoperative 6 months.

RESULTS: During the postoperative 6-month follow-up evaluation, 2 cases with nondisplaced scapular stress fracture (5.7%) and 1 case with scapular stress reaction (2.8%) were diagnosed. Mean postoperative SUVmax for 3 ROIs including PA, SS, and CP were significantly increased compared to preoperative values (PA: 9.6 ± 9.0 vs. 5.3 ± 2.2, SS: 7.0 ± 2.8 vs. 5.9 ± 2.0, and CP: 7.3 ± 2.1 vs. 6.3 ± 2.0). PA had the highest mean postoperative SUVmax among 4 ROIs and the largest SUVmax difference between before and after rTSA. Bone mineral density, activity of daily living score, American Shoulder and Elbow Surgeons score, forward flexion, and abduction at postoperative 6 months were negatively correlated with postoperative SUVmax for PA. Visual analog scale pain score at postoperative 6 months was positively correlated with postoperative SUVmax for PA. However, after correction for multiple testing using the Benjamini-Hochberg false discovery rate method, none of the associations remained statistically significant.

CONCLUSION: This SPECT/CT study demonstrated increased tracer uptake in PA, SS, and CP after rTSA to indicate stress concentration. In particular, PA was the most vulnerable area for stress concentration following rTSA. These findings may support the potential role of SPECT/CT in early detection of stress-related changes in symptomatic patients.