Mini-Open Versus Conventional Open Posterior Lumbar Interbody Fusion for the Treatment of Lumbar Degenerative Spondylolisthesis Comparison of Paraspinal Muscle Damage and Slip Reduction

Study Design. A comparative analysis of paraspinal muscle damage and radiographic parameters after mini-open and conventional open posterior lumbar interbody fusion (PLIF). Objective. To determine whether mini-open PLIF decreases paraspinal muscle damage and yields the same radiographic results as those in conventional open PLIF. Summary of Background Data. Compared with conventional open PLIF, mini-open PLIF using a paramedian approach reduces intraoperative hemorrhage and decreases postoperative back pain. However, whether the latter produces less paraspinal muscle damage than the former remains unclear. No comparative study has investigated slip reduction and segmental lordosis at the fusion level in the 2 techniques. Methods. We studied 20 patients (10 in each group) who had undergone single-level conventional (midline approach) or mini-open (bilateral Wiltse approach) PLIF with pedicle screws and interbody cages at the L4-L5 level for lumbar degenerative spondylolisthesis. The rate of improvement in the Japanese Orthopedic Association score; radiographic parameters, including %slip; segmental lordotic angle at the L4-L5 level; and fusion rate were examined. Postoperative multifidus (MF) atrophy and degeneration were evaluated using magnetic resonance imaging. Results. No significant differences were detected between the 2 groups with respect to the rate of improvement in the Japanese Orthopedic Association score, segmental lordotic angle, and fusion rate. Both groups showed significant reduction in %slip after surgery. The degree of MF atrophy and the increase in T2-signal intensity in the MF muscle after mini-open PLIF were significantly lesser than those following open PLIF. Conclusion. Mini-open PLIF is safe and effective. Mini-open PLIF was less invasive than open PLIF with regard to the MF muscle.