MRI evaluation of the effect of minimally invasive transforaminal lumbar interbody fusion (MIS-TILF) on lumbar multifidus muscle / 中华骨科杂志

ABSTRACT

Objective:To explore the effect of minimally invasivetransforaminal lumbar interbody fusion (MIS-TLIF) on lumbar multifidus muscle using MRI techniqueandits clinical significance.Methods:From September 2016 to July 2019, 23 patients who underwent MIS-TLIF surgery for unilateral symptomatic disc herniation in unilateral segments (L 3,4, L 4,5, L 5S 1) of Qingdao University Affiliated Hospital were studied. Their lumbar MR examination was performed 1 week before surgery, and 3 and 6 months after surgery. The axial section of multifidus muscle cross section area (AxCSA) was measured on the axial T2WI image of each intervertebral disc level before and after the operation. The ratio of long and short lines (RLS) was calculated, andthe ratio of axial section of muscle fat infiltration cross section area (FLSA) and AxCSAwasrecorded as FLSA/AxCSA. The changes of various indexes of multifidus muscle in the affected side and the healthy side of the lumbar spine before and after the operation were compared, and the effect of the MIS-TLIF procedure on the morphology of the multifidus muscle was observed. Magnetic resonance spectroscopy (MRS) measurements of the muscle cross-section of the affected side were performed before and 6 months after the operation. The integral value of intracellular lipid (IMCL) and extracellular lipid (EMCL) of 1H spectrum muscle cells was compared, while the degree of fat infiltration was measured. Results:Patients with single-segment lumbar disc herniation had larger AxCSAin the healthy side than the affected side before surgery in surgical level ( t=6.611, P<0.05), and the muscle AxCSAin the healthy side was larger than the affected side in non-surgical levels ( t=-6.682, P<0.05), both suggested preoperative muscle volume advantage in the healthy side; no difference in bilateral AxCSA at 3 months was found after surgeryin surgical levels ( t=0.197, P> 0.05)and non-surgical levels ( t=-1.631, P> 0.05), which suggested bilateral muscle volume equal advantageat short-term follow-up. The FLSA/AxCSA of affected segment before and after 3 months was 9.5%±3.8% and 8.7%±1.5%, and the difference was statistically significant ( t=3.163, P<0.05); the RLS of affected segment before and after 3 months was 3.3%±0.24% and 2.7%±0.83%, and the difference was statistically significant ( t=3.42, P<0.05). The medians of EMCL/IMCL before and after 6 months of MRS were 2.010 and 1.475, respectively, and EMCL decreased after 6 months ( Z=0.48, P<0.05). Conclusion:Patients with single-segment lumbar disc herniation have different morphology of bilateral multifidus muscle before surgery. MIS-TLIF has little effect on the multifidus muscle of the surgical side. MIS-TLIF significantly reduces extracellular lipid accumulation, promotes intracellular transfer, and increases intracellular fat metabolism. Its retention of muscle attachment points and limited fixation can also reshape compensatory muscle atrophy.