Use of Routine Motor-Evoked Potentials (MEPs) is Superior to Routine Running Electromyographic (EMG) and Somatosensory Evoked Potential (SSEP) Monitoring during Lateral Lumbar Interbody Fusion (LLIF) Procedures for Intraoperative Detection of Postoperative Neurological Deficits

Presented at SMISS Annual Forum 2018
By Larry Khoo MD
With Roya Gheissari MS, Ji Lee , P. Emmanuel ,

Disclosures: Larry Khoo MD B; Globus Spine, Zimmer Biomet, Medacta Spine, Burst Biologics. F; Globus Spine, Zimmer Biomet Roya Gheissari MS None, Ji Lee None, P. Emmanuel None,

Introduction:

The reported incidence of postoperative thigh weakness and numbness after lateral interbody fusion (LLIF) range from 0-38% in the literature. Similarly, previous standard intraoperative monitoring during such cases have been shown to have a low sensitivity for detecting neural injury.

Aims/Objectives:

We sought to assess the improved efficacy of adding MEPs to LLIF neuromonitoring for detecting postoperative neurological deficits.

Methods:

In a prospective study group, 108 patients with segmental listhesis and sagittal imbalance were treated via a 1 or 2 level LLIF procedure during which an interbody fusion cage and a plate was inserted (74 cases) and/or posterior instrumented fusion as well (82 cases). Peri-operative data, radiographic and standardized clinical outcomes were collected. Intraoperative SSEP, EMG, and MEP changes were recorded and then correlated with the presence of absence of postoperative sensory or motor deficits. The intensity time to recovery for such deficits was also recorded. These data were compared to a historical same institution cohort of 164 LLIF patients monitored only with SSEP and EMGs.

Results:

Preop data: mean age 68, BMI 29.75, CMI 1.6, T-scores -0.7, ODI 45, VAS leg 8.25, VAS back 9.35. OR data: Surgical time- 62 min/level (LLIF) 57 min (PSF/decompression), ebl total 95cc, LOS 2.75 days, Complications (major 2.7%, minor 8.3%). Clinical Outcomes: 12 mo ODI change -25, VAS back -6.8, VAS leg -7.4. Radiographic Outcomes: Lordotic correction +11.5 at 12 mos, Pelvic tilts improved at -7.75 at 12 mos. Rigid fusion with 1 yr dynamic xrays and CT scan was observed in 101/108 (93.5%). 12 (11%) of patients demonstrated documented thigh weakness, numbness and difficulty with ambulation. All 12 cases demonstrated a decrease in MEP potentials in some combination from the quadriceps, tibialis anterior or posterior which occurred at a mean time interval of 42+/- 11 min. SSEPs changed only in 1 case and EMGs changed in none of them. There were 3 cases of false positive MEP decreases which had no deficit after surgery. For cases with deficits, the average motor strength was 2.5/5 in the psoas, 3.25 in the tibialis anterior immediately after surgery and lasted on average 3.5 weeks before cessation with all cases resolved by 7 weeks. This is improved compared to our historical controls (9.5 wks avg all resolved by 16 weeks).

Conclusions:

The use of MEP is superior to that of routine SSEP-EMGs alone during LLIF procedures for intraoperative detection of documented postoperative neurological deficits.