Multifidus muscle changes and clinical effects of one-level posterior lumbar interbody fusion: minimally invasive procedure versus conventional open approach

We set out to determine whether a minimally invasive approach for one-level instrumented posterior lumbar interbody fusion reduced undesirable changes in the multifidus muscle, compared to a conventional open approach. We also investigated associations between muscle injury during surgery (creatinine kinase levels), clinical outcome and changes in the multifidus at follow-up. We studied 59 patients treated by one team of surgeons at a single institution (minimally invasive approach in 28 and conventional open approach in 31, voluntarily chosen by patients). More than 1 year postoperatively, all the patients were followed up with the visual analogue scale (VAS) and Oswestry disability index (ODI), and 16 patients from each group were evaluated using MRI. This enabled the cross-sectional area (CSA) of lean multifidus muscle, and the T2 signal intensity ratio of multifidus to psoas muscle, to be compared at the operative and adjacent levels. The minimally invasive group had less postoperative back pain (P