Long-term follow-up of functional electromyostimulation–augmented home exercise after primary reverse total shoulder arthroplasty A prospective longitudinal assessment of the original intervention cohort

Abstract Introduction Reverse total shoulder arthroplasty (rTSA) reliably reduces pain and restores function, but shoulder function typically plateaus within the first postoperative year and gradually declines thereafter. Motion-triggered functional electromyostimulation (FES) enhances muscle activation and has shown short-term functional benefits in patients after rTSA. The long-term durability of these effects remains unclear, though sustained improvements would increase the clinical value of this time-limited intervention. Therefore, the aim of this study was to evaluate short-term outcomes after at least six months after completion of an FES program and compare them with baseline and immediate post-intervention results. Methods Ten of the initially fourteen patients previously enrolled in the intervention arm of a prospective randomized controlled trial were re-evaluated after at least six months after completing a six-week home-based, deltoid-focused FES program initiated one year after primary rTSA. Clinical outcomes included Constant Score (primary outcome), Subjective Shoulder Value (SSV), active range of motion (ROM), deltoid strength and scapular kinematics assessed using identical methods to the previous randomized controlled trial. Results Ten participants (71%) completed the follow-up at a median of 18 months (range, 6–24 months) after the intervention. The mean CS improved from 65.7±13.2P at baseline to 79.5±7.9P post-intervention (p<0.001) and remained significantly elevated at follow-up (84.0±4.2P, p<0.001 vs. baseline; p=0.09 vs. post). SSV increased from 70.7±16.9% to 91.1±10.0% post-intervention and was maintained at 92.0±7.9% at follow-up (p<0.001 vs baseline). Abduction ROM and deltoid strength showed additional long-term gains, whereas no decline was observed in any outcome parameter. No device-related complications occurred. Conclusion In this single-arm follow-up, functional outcomes that improved after the FES-augmented program were maintained at mid-term reassessment. Because the control group was not re-evaluated, treatment-specific durability cannot be inferred. No deterioration was observed after discontinuation of device use. Larger controlled studies with long-term comparative follow-up are required before conclusions regarding treatment-specific benefit can be drawn.