Background Inlay total shoulder arthroplasty (iTSA) serves as a stemless shoulder reconstruction option. While current literature has demonstrated improved patient reported outcomes (PROs) with minimal postoperative revisions and high rates of return to activity, supporting long-term evidence is limited. The purpose of this study was to evaluate the trends in PROs following iTSA over an eleven-year period.

Methods A historical cohort of our institutional database was used to investigate outcome trends. Inclusion criteria consisted of patients with advanced osteoarthritis treated with iTSA. Patients had preoperative PROs and a minimum of one follow-up assessment between 1-11 years. Outcomes assessments included WOOS%, ASES, activities of daily living (ADLs), VAS pain, patient satisfaction, and range of motion (ROM). Descriptive analyses were conducted using Stata (v.15, College Station, TX). Join-point regression analysis (version 5.0.2, National Cancer Institute) was used to explore trends in functional outcomes, pain relief, and ADLs to determine whether a change in temporal trend was statistically significant. WOOS%, ASES, ADLs, and VAS pain were entered into the model and were assessed at five timepoints: preoperative, 1 year, 2-3 years, 4-7 years, and 8-11 years.

Results Since 2011, 583 shoulders were treated with iTSA at our institution and 97 met the inclusion criteria, with 10 patients being bilateral. The mean age was 63.7 years ± 10.5 (31 females, 66 males). The average length of follow-up was 60.5 months ± 37.8. Along the postoperative period of up to 2-3 years, there was significant improvement in WOOS% (84.97 AYPPC), ASES (78.22 AYPPC), and VAS pain (-74.50 AYPPC), after which gains were sustained. ADLs improved over time, but there was no significant change in the trend. The median PROs improved at all five timepoints: WOOS% 26(16-40), 85(56-95), 93(77-97), 89(75-97), 92(77-97), ASES 27(17-40), 83(67-93), 88(68-95), 87(70-97), 90(78-98), VAS pain 8(6-9), 1(0-3), 1(0-2), 0(0-3), 0(0-0) and ADLs 4(2-6), 8(6-10), 9(6-10), 8(6-8), 9(6-10). Mean ROM improved by 46.49 degrees ± 37.28 on forward elevation and 26.95 degrees ± 18.90 on external rotation.  Mean patient satisfaction on a scale of 1-10 (10=best) for each follow-up timepoint was 8.6 ± 2.4, 9.2 ± 1.6, 8.7 ± 1.8, and 9.6 ± 0.7 respectively (p <0.001).

Conclusion iTSA demonstrated significant improvement in pain relief and functional outcomes within 2-3 years, after which gains were sustained over an eleven-year period. ROM improved and patient satisfaction remained high over time. These findings support the use of stemless shoulder reconstruction as a reliable solution for advanced shoulder osteoarthritis.