Decreased pain at 12 weeks post-operatively is associated with superior shoulder range of motion after anatomic and reverse total shoulder arthroplasty and is sustained up to two years

Background: While immediate post-operative pain control after total shoulder arthroplasty (TSA) has been associated with improved long-term functional outcomes, the effect of pain levels beyond the initial recovery period remains unclear. This study aimed to evaluate whether decreased pain at 12 weeks post-operatively after anatomic TSA (aTSA) and reverse TSA (rTSA) is associated with improved shoulder range of motion (ROM) and pain control up to 2 years post-operatively compared to patients with elevated pain during the post-operative recovery period. Methods: We performed a retrospective review of 605 primary TSAs (206 aTSA, 399 rTSA) at a single institution from 2007 to 2022. Perioperatively, patients received a cervical paravertebral nerve catheter. Post-operatively, patients were discharged on a multimodal oral analgesic regimen consisting of both opioid and nonopioid medications. Pre-operative to post-operative improvement in ROM was evaluated at 6 weeks, 12 weeks, 6 months, 1 year, and 2 years follow-up. Mixed-effects models were used to evaluate whether minimal post-operative pain (defined as patient-reported pain at worst < 3/10) at 12-week follow-up was associated with improved ROM (forward elevation [FE], abduction, external rotation, and internal rotation [IR]) and pain at each of the next follow-up time point compared to those with elevated pain. Clinical significance was evaluated by comparing improvement to the minimum clinically important difference (MCID) and substantial clinical benefit (SCB). Results: For aTSA, patients with pain < 3/10 at 12 weeks demonstrated significantly greater pre-operative to post-operative improvement in abduction, FE, and IR at all follow-up points, including 2 years post-operatively. For rTSA, patients with minimal pain at 12 weeks had significantly greater pre-operative to post-operative improvement in abduction and IR at all follow-up points, including 2 years post-operatively. For both aTSA and rTSA cohorts, patients with minimal pain at 12 weeks had significantly greater mean improvement in daily pain and pain at worst at all follow-up points, including 2 years post-operatively. Patients with minimal pain after aTSA achieved the MCID earlier for abduction and FE and the SCB earlier for abduction, FE, and IR. Patients with minimal early pain after rTSA achieved the MCID earlier for FE and the SCB earlier for external rotation and IR. Conclusion: Minimal pain at 12 weeks post-operatively is associated with sustained superior ROM gains and reduced pain up to 2 years post-operatively after aTSA and rTSA. Future prospective studies are needed to determine what patient and surgery factors lead to poor early pain control and which can be optimized to improve the functional benefits of TSA.