Summary

In this study, trends in reduced pain, increased mobility, and improved shoulder function were observed in patients who underwent inlay total shoulder arthroplasty, marking phases of early significant improvement and maintenance over a ten-year period.

Abstract

Background

Identification of long-term outcomes trends after primary total shoulder arthroplasty is critical to guide patients and manage their expectations. There is little longitudinal data for inlay total shoulder arthroplasty (iTSA) available. The purpose of this study was to analyze trends in patient reported outcomes (PROs) over a long-term observational period. We hypothesized that post-operative improvement would be most pronounced in the first six months and be maintained thereafter.

Methods

The study included patients with advanced shoulder osteoarthritis who were refractory to conservative care and were treated with iTSA. PROs included the American Shoulder and Elbow Surgeon’s (ASES) score, a visual analog scale for pain (VAS-Pain), and shoulder range of motion (ROM). Descriptive analyses were conducted using Stata (v.15, College Station, TX). Normally distributed data was reported as mean and standard deviation, non-normal data as median and interquartile range (IQR). A joinpoint regression analysis (JPRA) (Version 5.0.2, National Cancer Institute) was used to determine temporal trends for ASES and VAS pain from baseline to 120 months. Estimating the monthly percent change (MPC), JPRA uses a trending timeline to mark statistically significant (alpha=0.05 level) changes until an inflection point is reached, resulting in the detection of improvement, maintenance, and declining phases on outcomes.

Results

From 2011-2024, 583 shoulders were treated at our institution with iTSA and 510 (88%) were included in this study (156 bilateral). The mean age was 64.8 years ±10.8 (132 females, 300 males). The mean follow-up was 32.4 months ±32.4. Between baseline and 120 months, 1385 ASES scores and 1395 VAS-Pain scores were collected and included in regression analysis. Two ASES phases were observed: Significant improvement from baseline to 6 months, at an MPC of 14.2% and ASES maintenance from 6 months to 120 months at an MPC of 0.07%. Similarly, the reduction in VAS-Pain scores showed 2 phases with a significant improvement from baseline to 12 months at an MPC of -13.2% and maintenance from 12 to 120 months by a 0.6% MPC. Gender stratification resulted in similar trends on ASES scores; significant improvement on VAS-pain was observed for female patients from 0-6 months and male patients from 0-12 months. No deterioration in PROs was observed for either sex over the 120-month postoperative period. At last follow-up, median PROs improved significantly (p < 0.001) from 35 (22-48) to 80 (58-92) on ASES and 7 (5-8) to 2 (0-4) on VAS-pain. Shoulder ROM improved significantly (p < 0.001) from 95o (80-130) to 160o (140-170) and 20o (10-30) to 50o (40-60) on forward elevation and external rotation at last follow-up.

Conclusion

Inlay total shoulder arthroplasty demonstrated significant improvement trends in patient reported outcomes within 6 to 12 months and provided sustained improvement over a 10-year postoperative period. These findings support the use of iTSA as a reliable, long-term treatment option for advanced shoulder osteoarthritis.