Patients posture affects clinical outcomes and range of motion after reverse total shoulder arthroplasty: A clinical study.

BACKGROUND

Movement limitations following implantation of reverse total shoulder arthroplasty (rTSA) have been observed in some patients postoperatively, with implant design and positioning recognized as important influential factors. Recent analyses have identified patient's posture, measured as scapula internal rotation on computed tomography (CT), as an additional factor influencing the functional outcome after rTSA. However, no clinical study has correlated the preoperatively photo-documented posture to functional outcome. It was the aim of this study to correlate preoperatively photo-documented posture to scapula orientation using CT and analyze the influence on functional outcome following rTSA implantation.

METHODS

A prospectively enrolled rTSA database was retrospectively reviewed to include a total of 360 patients with a minimum follow-up of 2 years. Patient's posture was analyzed using standardized preoperative photo and video documentation. The posture was defined following the classification system of Moroder et al as type A (upright posture, retracted scapulae), type B (intermediate), and type C (kyphotic posture with protracted scapulae). In addition, CT data were used to measure scapula position (internal rotation). Correlation analyses between them were conducted. Postoperative range of motion (ROM) and clinical outcomes (absolute Constant-Murley Score and relative Constant-Murley Score) were compared between the different posture types.

RESULTS

According to the photo-documented posture types, the patients were divided into posture types A (n = 59), B (n = 253) and C (n = 48). Average absolute Constant-Murley Score differed significantly among the groups (69 ± 16 vs. 69 ± 14 vs. 64 ± 16,  < .05) favoring patients with posture types A and B over type C. In terms of ROM, flexion, abduction, and internal rotation significantly differed among the groups. Types A and B exhibited better flexion and abduction (flexion 124 ± 26° and 123 ± 23° vs. 113 ± 25°, abduction 140 ± 34° and 137 ± 30° vs. 128 ± 34°). Patients with posture type A demonstrated superior internal rotation (CS points: 5.9 ± 2.9 vs. 5.0 ± 2.7 vs. 4.4 ± 2.8,  < .05). External rotation was better for type A compared to type C (A: 33 ± 17° vs. B: 30 ± 16° vs. C: 28 ± 18°). Correlation analysis of posture classification using photo documentation and CT scan showed poor reliability (r = 0.35).

CONCLUSION

Patients with clinical posture types A and B exhibited improved ROM values compared to type C postures. Clinical outcome scores were also notably superior in types A and B. However, the measurement of scapula internal rotation on supine CT does not reliably correlate with photo documentation of patient's posture. Preoperatively, patient's posture should be considered in rTSA planning because of the potential influence on ROM and clinical outcomes.