Technical note: Resolution of spontaneous electromyographic discharge following disk-space distraction during lateral transpsoas interbody fusion.

Purpose: The lateral transpsoas interbody fusion (LTIF) is an increasingly popular minimally invasive technique for lumbar interbody fusion. Although a posterior approach to the lumbar spine has traditionally been favored for the treatment of canal stenosis and neural foraminal stenosis, a growing body of evidence suggests that indirect decompression of the spinal canal and neural foramen can be achieved using a lateral transpsoas approach to the lumbar spine. We present 2 cases that may suggest a role for spontaneous electromyography (s-EMG) monitoring in assessing the adequacy of decompression during LTIF.

Methods: The 2 cases presented in this technical note illustrate resolution of s-EMG firing during LTIF, following distraction across the disk space. Removal of the distracting device produced the return of s-EMG firing. Both of these cases were operated at the L2-3 level.

Results: In the first case, s-EMG firing was noted in the bilateral tibialis anterior leads. Resolution of EMG firing may suggest indirect decompression of the canal via ligamentotaxis as the L5 root traverses the L2-3 disk space. In the second case, s-EMG firing was noted in the left abductor hallucis and resolved with distraction of the L2-3 disk space. Again, this may be explained by canal decompression via ligamentotaxis as the S1 root traverses the L2-3 disk space.

Conclusion: In both cases, distraction across the disk space resulted in resolution of s-EMG discharges-this correlated with an improvement in symptoms. These findings may suggest a role for s-EMG as a marker for adequacy of decompression in a select subset of patients undergoing LTIF. Further study is needed to determine if resolution of s-EMG is a useful measure of indirect decompression during LTIF.