Transabdominal muscle action potential lessons learned: when should decompression precede fusion? Illustrative cases

Single-position prone lateral lumbar interbody fusion (pLLIF) enables interbody placement, posterior instrumentation, and adjunct decompression to be performed without repositioning. Beyond operative efficiency, prone positioning provides flexible surgical sequencing and intraoperative decision-making. While sequencing might not influence outcomes in most cases, particular scenarios may warrant more careful consideration. Advanced intraoperative neuromonitoring, like transabdominal muscle action potential (TMAP) monitoring, offers real-time feedback and identifies the neurological implications of operative sequencing decisions.

Two patients with nearly identical pathology, proximal lumbar canal stenosis and distal degenerative pathology, underwent pLLIF with concomitant proximal decompression but in opposite operative sequences. In the first case, interbody fusion preceded decompression and was associated with TMAP threshold elevations and postoperative motor deficit. In the second case, proximal decompression performed first resulted in stabilization and improvement of TMAP signals, followed by completion of interbody fusion without neurological complication. Aside from surgical sequence, these cases were otherwise comparable.

The flexibility of surgical sequencing with prone positioning may be clinically meaningful in patients with proximal canal stenosis. Event-based TMAP monitoring provides real-time insight into sequence dependent neural stress that might otherwise go unrecognized. Thoughtful surgical sequencing and integration of sensitive neuromonitoring enhance intraoperative decision-making and neurological safety. https://thejns.org/doi/10.3171/CASE2680.