Analysis of Multifidus Muscle Atrophy After Minimally Invasive Laminotomy

Presented at SMISS Annual Forum 2014
By Islam Elboghdady
With Kern Singh MD, Sreeharsha Nandyala BA, Alejandro Marquez-Lara MD, Eric Sundberg MD, Hamid Hassanzadeh MD, Anton Jorgensen MD, Khaled Aboushaala MD, Junyoung Ahn ,

Disclosures: Islam Elboghdady None Kern Singh MD A; CSRS Resident Grant. B; DePuy, Zimmer, Stryker, CSRS, ISASS, AAOS, SRS, Vertebral Column - ISASS. D; Avaz Surgical, LLC, Vital 5, LLC. F; Zimmer, Stryker, Pioneer, Lippincott Williams & Wilkins, Th, Sreeharsha Nandyala BA None, Alejandro Marquez-Lara MD None, Eric Sundberg MD None, Hamid Hassanzadeh MD None, Anton Jorgensen MD None, Khaled Aboushaala MD None, Junyoung Ahn None,

Introduction:
The multifidus is the major stabilizing muscle of the posterior spine. Multifidus atrophy has been associated with failed spine surgery syndrome. Postoperative muscle damage after a minimally invasive lumbar decompression has not been fully elucidated.

Aims/Objectives:
The purpose of this study is to characterize the extent and distribution of paraspinal muscle atrophy following a minimally invasive laminotomy with or without discectomy by analyzing the cross-sectional area (CSA) and mean T2 signal intensity of the multifidus.

Methods:
Twelve patients underwent a post-operative MRI following a 1-level to 3-level minimally invasive laminotomy with or without discectomy by a single surgeon for lumbar stenosis or herniated nucleus pulposus. Preoperative and postoperative total muscle CSA, lean muscle CSA, and T2-weighted signal intensity ratio of mutifidus to psoas muscle were measured on MRI. Measurements were made bilaterally at the affected and adjacent disc levels as well as at the ipsilateral pedicle levels.

Results:
Eleven of patients were male and one was female. The mean age was 49.8 years. Six patients underwent a 1-level decompression, 5 patients a 2-level decompression, and a single patient a 3-level decompression. The mean operative time was 49.3 ± 32.3 minutes. Postoperative MRI was obtained at a mean of 6 months after surgery. There were no significant differences between preoperative and postoperative total multifidus muscle CSA. There were significant decreases in lean multifidus muscle CSA at the ipsilteral operative level (25% decrease) the ipsilateral inferior-adjacent disc (24% decrease), the ipsilateral superior-adjacent pedicle (18% decrease),and the ipsilateral inferior-adjacent pedicle (26% decrease) (p<0.05). No significant changes in total or lean mutlifidus muscle CSA were observed on the contralateral side. The change in T2 signal intensity ratio of multifidus to psoas muscle correlated well with the change in lean multifidus muscle CSA, as significant increases were seen at the ipsilateral operative level, the ipsilateral inferior-adjacent disc, and the inferior-adjacent pedicle.

Conclusions:
Minimally invasive laminotomy resulted in significant and substantial decreases in lean multifidus muscle CSA both at the operative level and the inferior-adjacent level. The contralateral and the ipsilateral multifidus muscle at the superior-adjacent level were largely unaffected. The selective distribution of muscle atrophy at the operative level and the inferior adjacent level may indicate a combined mechanism of muscle injury including both direct trauma and denervation.