Both anatomic (aTSA) and reverse (rTSA) total shoulder arthroplasty are the standard of care for various end-stage degenerative conditions of the glenohumeral joint. Osteoarthritis (OA) is the most common indication for aTSA while Rotator Cuff Tear Arthropathy (CTA) is the most common indication for rTSA. Worldwide, the usage of both aTSA and rTSA has increased significantly due in part, to the predictability of acceptable outcomes achieved with each prosthesis type. The aim of this study is to quantify outcomes using 5 different metrics and compare results achieved for each indication using one platform total shoulder arthroplasty system which utilizes the same humeral component and instrumentation to perform both aTSA or rTSA.
200 patients (70.9 ± 7.3 yrs) were treated by two orthopaedic surgeons using either aTSA or rTSA. 73 patients received aTSA (67.4 ± 8.0 yrs) for treatment of OA (PHF: 64 patients; YM: 9 patients) and 127 patients received a rTSA (72.9 ± 6.1 yrs) for treatment of CTA (PHF: 53 patients; YM: 74 patients). These patients were scored pre-operatively and at latest follow-up using the SST, UCLA, ASES, Constant, and SPADI metrics; active abduction, forward flexion, and external rotation were also measured. The average follow-up for all patients was 31.4 ± 9.7 months (aTSA: 32.5 ± 12.1 months; rTSA: 30.8 ± 8.0 months). A Student's two-tailed, unpaired t-test was used to identify differences in pre-operative, post-operative, and pre-to-post-operative improvements in results, where p < 0.05 denoted a significant difference.
All patients demonstrated significant improvements in pain and function following treatment of OA with aTSA and of CTA with rTSA. No instances of instability or glenoid loosening were reported in either cohort; one instance of infection occurred in the rTSA cohort. The average pre- and post-operative outcome scores and range of motion measurements are presented in Figures 1 and 2, respectively. The average improvement in outcome scores and range of motion measurements are presented in Figure 3, respectively.
Discussion and Conclusions
The results of this study demonstrate that CTA patients had significantly lower pre-operative scores as measured by 3 of the 5 metrics and significantly less active abduction and forward flexion than OA patients. While aTSA and rTSA were used to treat different indications; each treatment method provided a significant improvement in all 5 outcome score measurements and all 3 motion measurements for its respective indication at a similar mean follow-up. Interestingly, a few comparative differences were observed: aTSA was associated with significantly higher post-operative scores according to 2 of the 5 metrics, greater range of motion according to all 3 active motion measurements, and was demonstrated to be significantly more effective at improving active external rotation; whereas, rTSA was associated with significantly larger improvements in outcome scores according to 2 of the 5 metrics and was demonstrated to be significantly more effective at improving active forward flexion. Additional and longer term follow-up is required to confirm these findings.