Predictive Value of Preoperative Pain Sketches in Lower Extremity Amputees Undergoing Secondary Targeted Muscle Reinnervation for Treatment of Neuropathic Pain.

ABSTRACT

BACKGROUND: Targeted Muscle Reinnervation (TMR) is an effective surgical treatment for neuropathic pain in amputees. Qualitative descriptions of pain, depicted by pain sketches, could enhance the understanding of symptomatic improvement following surgery. Our aim is to assess whether pre-operative pain sketches, drawn by lower extremity (LE) amputees, can predict surgical outcomes following Secondary TMR surgery. STUDY DESIGN: Eligible patients were LE amputees who underwent Secondary TMR surgery between 2017 and 2023. Pain sketches and pain scores were prospectively collected both before and after surgery. The pain trajectory, as categorized by pre-operative pain sketches, was analyzed and assessed for improvement, defined as reaching the Minimal Clinically Important Difference (MCID). The transition into different pain sketches and the occurrence of phantom drawings were evaluated for their association with improvement. RESULTS: Fifty-eight patients were included, of which 18 (31.1%) depicted diffuse pain (DP), 26 (44.8%) depicted focal pain (FP), and 18 (24.1%) depicted radiating pain (RP) in their pre-operative sketch. FP sketches were associated with the lowest pre- and post-operative pain scores and most frequently developed into sketches indicating "no pain". RP sketches were associated with the least pain improvement, the lowest likelihood of achieving the MCID, and were more prevalent in patients with diabetes or depression. RP sketches were associated with phantom drawings; no other sketch types developed into RP sketches at the final follow-up. CONCLUSIONS: In LE amputees who underwent Secondary TMR, pre-operative pain sketches could serve as a helpful tool in predicting pain outcomes. RP sketches seemed to be associated with worse outcomes, and FP sketches with the most improvement.