Re: Arthroscopic Subacromial Decompression versus Placebo Surgery for Subacromial Pain Syndrome: 10 Year Follow-Up of the FIMPACT Randomised, Placebo Surgery Controlled Trial

Why It Matters

Understanding the true estimand and appropriate outcome measures is crucial for clinicians deciding whether to recommend ASD, and for policymakers shaping guidelines on shoulder surgery reimbursement.

Key Takeaways

• 10‑year FIMPACT trial retained 87% of participants.
• Crossovers turned the 10‑year contrast into “ASD now vs ASD later.”
• Trial powered for superiority; results do not prove equivalence.
• Cumulative surgery incidence (4/59 ASD, 13/63 placebo) is clinically key.
• Per‑protocol analysis cannot resolve crossover bias without advanced estimand methods.

Pulse Analysis

Subacromial pain syndrome remains a leading cause of shoulder disability, prompting surgeons to perform arthroscopic subacromial decompression (ASD) despite mixed evidence. Early trials suggested modest pain relief, but the rise of placebo‑controlled designs—most notably the FIMPACT study—has forced a re‑examination of ASD’s true efficacy. By embedding a sham surgery arm, researchers aimed to isolate the procedural effect from postoperative rehabilitation, offering a clearer picture for clinicians and insurers alike.

The recent 10‑year follow‑up of FIMPACT is remarkable for its 87% retention rate, yet the letter highlights a methodological shift: numerous participants crossed over from placebo to ASD or required additional surgery, converting the original intention‑to‑treat contrast into a comparison of early versus delayed decompression. This estimand drift, coupled with the trial’s superiority‑focused power calculation, means the null finding cannot be interpreted as proof of equivalence. Moreover, the confidence interval for pain scores (‑19.0 to 0.3) skirts zero, underscoring the statistical nuance that “no superiority” is not synonymous with “no benefit.”

For practitioners, the most actionable metric may be the cumulative incidence of subsequent surgery—four of 59 ASD patients versus thirteen of 63 placebo patients required further intervention. Reporting this outcome as primary would better inform shared decision‑making and health‑policy debates. Future shoulder trials should adopt explicit target‑trial frameworks and estimand‑driven analyses to handle time‑varying intercurrent events, ensuring that long‑term results remain clinically interpretable and policy‑relevant.