Morphological changes of intervertebral foramen after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF): a radiographic and clinical study

Abstract Objective In the present study, we aimed to investigate the morphological changes in the intervertebral foramen after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF), and analyze the necessity of routinely performing contralateral intervertebral foraminal decompression in cases of degenerative lumbar spondylolisthesis with bilateral symptoms. Methods 72 single-level degenerative lumbar spondylolisthesis patients (17 males and 55 females) with bilateral lower extremity symptoms were included in this study, all of whom underwent unilateral approach MIS-TLIF from December 2012 to December 2017. The average age was 52±11 years. Among them, 49 and 23 cases were associated with Meyerding grade I and II spondylolisthesis. Preoperative and last follow-up surgical and contralateral side foraminal height (FH) and width (FW), disc height (DH), distance from the existing nerve root to the upper edge of the lower pedicle (RTP), and contralateral side spinal canal area (CSCA) were measured by computed tomography (CT). Clinical outcomes were evaluated using the visual analog scale (VAS) score for low back pain (LBP) and leg pain, Oswestry Disability Index (ODI) and Japanese Orthopaedic Association (JOA) score. Results The preoperative values for FH on operative and contralateral sides were 13.02±2.66 mm and 12.97±2.88 mm, for FW were 10.56±2.30 mm and 10.43±2.12mm, for DH were 6.14±1.50 mm and 6.51±1.37 mm, for RTP were 5.97±2.04 mm and 6.70±2.05 mm and the CSCA of the spinal canal on the contralateral side were 164.36±37.13 mm2. The difference between these was not statistically significant (p>0.05). The mean follow-up period was 30.5±13.9 months. At the last follow-up visit, the values for FH on operative and contralateral sides were 16.23±2.48 mm and 16.10±2.42 mm, for FW were 11.36±2.58 mm and 11.31±2.71 mm, for DH were 8.18±1.58 mm and 8.42±1.54 mm, for RTP were 8.58±1.26 mm and 9.14±1.77 mm and the CSCA of the spinal canal on the contralateral side were 211.59±48.12 mm2. The difference between these was also not statistically significant (p>0.05) Not only did the index on the surgical side increased significantly, the index on the contralateral side also increased significantly. The VAS for LBP and leg pain, JOA and ODI improved significantly at the 2-year follow-up visit. One patient (1%) experienced transient pain and numbness in the contralateral leg after the operation, which was gradually relieved within 1 month. Conclusions Unilateral MIS-TLIF can effectively improve the contralateral FH, DH, FW, RTP, and CSCA. It is not necessary to routinely perform contralateral intervertebral foramen decompression in degenerative lumbar spondylolisthesis (Meyerding grade: I, II) with bilateral symptoms when symptoms are mild on one side.