- Design
- multicentre retrospective cohort from an electronic health record network, Mantel-Haenszel stratified analysis
- Population
- 38,433 adults undergoing elective below-knee amputation, 2016-2025; 7,430 received a perioperative peripheral nerve block
- Primary outcome
- coded phantom limb syndrome diagnosis within 12 months of surgery
- Effect
- 18.8% with blocks against 15.1% without (absolute difference 3.7 points; Mantel-Haenszel RR 1.24, 95% CI 1.20-1.28); shorter length of stay with blocks
Whether perioperative regional anaesthesia prevents or provokes phantom limb syndrome has been argued for decades without resolution. This study queried a large electronic health record network for adults having elective below-knee amputation between 2016 and 2025, identified 38,433 patients, and compared the 7,430 (19.3%) who received a perioperative peripheral nerve block against the 31,003 who did not, looking for a phantom limb syndrome diagnostic code within 12 months.
Coded phantom limb syndrome was commoner in the block group: 18.8% against 15.1%, an absolute difference of 3.7 percentage points, with a Mantel-Haenszel relative risk of 1.24 (95% CI 1.20-1.28) after adjustment for age, sex and race. The association held across comorbidity subgroups. Length of stay was shorter with blocks.
The authors are unusually clear that this should not be read as causal, and they are right. Adjustment covered age, sex and race only - not indication, not pain severity before amputation, not opioid history, not diabetes or vascular disease severity, all of which predict both receiving a block and developing phantom pain. And there is a second mechanism that generates exactly this pattern without any biology: patients who get a block are under the care of an anaesthetic pain service, which means someone is asking about phantom sensations and coding them. What the study usefully establishes is that peripheral nerve blocks are not demonstrably preventing phantom limb syndrome, which is a claim sometimes made for them. It does not establish that they cause it, and it is not a reason to withhold effective perioperative analgesia from an amputation.
- Continue offering peripheral nerve blocks for below-knee amputation - acute analgesia and shorter stay are the established benefits
- Do not counsel a patient that a block will prevent phantom limb pain; that claim is not supported
- Ask about phantom sensations at follow-up in every amputee, blocked or not, since detection is part of what this study is measuring
- Note the adjustment covered only age, sex and race - vascular disease severity, prior pain and opioid history were not accounted for
- Treat this as a reason for a prospective trial, not as a reason to change technique
Why it matters
It removes a claim regional anaesthetists have made for years, without replacing it with a reason to stop doing blocks.
Don't overread it
Coded diagnoses in a record database with adjustment for age, sex and race only - this shows an association, and confounding by indication and by surveillance are the likelier explanations.
The statistics, in plain English
A relative risk of 1.24 with an interval of 1.20 to 1.28 is extremely precise, and precision here is a product of 38,433 patients rather than of good confounding control - the adjustment covered three demographic variables and nothing clinical. The outcome is a diagnostic code, not an assessed diagnosis, which means the study measures who got coded as much as who developed the syndrome; patients under an anaesthetic pain service are more likely to be asked, and therefore more likely to be coded. Both problems push in the same direction as the finding.
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