Is Neuromonitering needed for Oblique Lateral Interbody Fusion?

Presented at SMISS Annual Forum 2014
By Richard Hynes MD
With

Disclosures: Richard Hynes MD B; Metronic, SpineWave, Celling, F; Medtronic, DePuy

Introduction:
Lateral lumbar interbody fusion (LLIF) has been evolving for the past decade and the use of neuromonitering (NM) for the transpsoas approach mitigates risk to neural elements at risk within the muscle. Other LLIF techniques such as shallow docking with direct visualization and dissection withing the muscle and Oblique lateral interbody fusion (OLIF), accessing the intervetebral disk space external to the muscle may not be dependent upon NM. The approach to the disk space by a retroperitoneal method historically entered the disk anterior to the psoas muscle with gentle retraction on the muscle. NM was not needed for the historical approach and becasue OLIF does not routinely enter the psoas, is NM needed for OLIF?

Aims/Objectives:
The primary goal is to determine if NM is needed for OLIF. If NM is not utilized then the muscle dissection can be done with pharmacologically relaxed muscle which may improve the feel during the approach. This is a retrospective review of patients who underwent LLIF using the DLIF and OLIF approaches from 2007 - 2013

Methods:
217 DLIF patients with NM, 184 OLIF patients with NM and 151 OLIF patients without NM were reviewed retrospectively for the frequency of emg responses during the procedure using NM and then postoperatively for neural injury. All DLIF patients had NM. The first 184 OLIF patients had NM but due to the minimal emg response a subsequent 151 patients underwent OLIF without NM and the patients recieved paralytics to relax the muscle during the exposure. Permanent motor neural injury was recorded and the three groups were compared.

Results:
The DLIF group experienced 139 emg responses. In this group there was one permanent femoral nerve injury. In the NM OLIF group there were 3 emg responses and no long term permanent injuries to motor nerves. In the non NM OLIF group there were no permanentt motor nerve injuries identified. Post operative numbness, dysethesia and weakness were temporary and not significantly different between both OLIF groups.  Comparison of these post operative temporary complaints resolved within 3-6 months in both OLIF groups and may be less than resolution time when compared to the transmuscular LLIF method.

Conclusions:
NM is not likely necessary for LLIF using the OLIF technique. The ability to relax the muscle during the procedure is possible if NM is not needed. The tactile feel may be enhanced due to relaxed muscle during the dissection.