Neurologic adverse event avoidance in lateral lumbar interbody fusion: technical considerations using muscle...

The retroperitoneal trans-psoas extreme lateral interbody fusion (XLIF) technique has improved over the last decade with increased efficiency and an emphasis on complication avoidance. After all known procedural safeguards are enacted, the most common failure of neuro-monitoring precision may be the use of non-depolarizing muscle relaxants (MR) for induction that is standard of care for anesthesia. Even when non-depolarizing MRs are minimized there is often a small dose given to decrease risk of vocal cord injury with intubation. The most common neurological adverse events (AE) attendant to the lateral approach are thigh dysesthetic pain and hip flexor weakness. The purpose of this study is to present a consecutive series of L3-4 and L4-5 XLIF patients treated by a single surgeon using all procedural safeguards with and without the use of a low dose of non-depolarizing MRs prior to intubation.

A retrospective review of 74 consecutive patients treated at 150 levels with XLIF and no muscle relaxants (NMR) were compared to a group of 124 consecutive XLIF patients treated at 238 levels with MR. The surgeon upon discovering a small dose of rocuronium was used for intubation, questioned the effect on the neuromonitoring and NMR group was begun. All procedural technique details remained the same. All patients had XLIF at L3-4, L4-5, or both levels. Perioperative variables were collected, including evoked and free-run EMG readings and postoperative neural and muscular side effects. Hospital records including progress notes describing postoperative symptoms and anesthesia records describing the drugs, dosages, and timing were studied. Clinical records were reviewed at 1, 3 and 6 months for complaints of neurologic AE.

NMR patients had a perfect twitch test (>99%) immediately. MR patients had slower arrival of the twitch and often settled at a lower level (80-92%). No surgery was attempted until the twitch test was at least 80%. NMR had 8/74 (10.8%) and MR 36/125 (28.8%) thigh AE (thigh dysthetic pain) at 1 month (P<0.005). No lower extremity weaknesses (femoral nerve injury) were observed in the NMR group and three in the MR group. All NMR thigh AEs resolved by the third month postoperative visit compared with 17/125 at 3 months (P=0.001) and 6/125 at 6 months (P=0.176) with persistent thigh AEs in the MR group.

Eliminating MRs altogether appears to have allowed the evoked and free running EMG to be more reliable and accurate in predicting the proximity of the neurologic structures. Thigh AEs related to neural and muscular integrity in NMR patients were limited and eliminated by the 3rd month. The MR group was significantly more likely to have a thigh AE at 1 month and persistent at 3 months. Neurologic AEs may be limited or eliminated when MRs are avoided in lateral lumbar fusion surgery.