Minimally invasive surgery versus open surgery in the treatment of lumbar spondylolisthesis: study protocol of a multicentre, randomised controlled trial (MISOS trial)

INTRODUCTION Patients with symptomatic spondylolisthesis are frequently treated with nerve root decompression, in addition to pedicle screw fixation and interbody fusion. Minimally invasive approaches are gaining attention in recent years, although there is no clear evidence supporting the proclamation of minimally invasive spine surgery (MISS) being better than open surgery. We present the design of the MISOS (Minimal Invasive Surgery versus Open Surgery) trial on the effectiveness of MISS versus open surgery in patients with degenerative or spondylolytic spondylolisthesis. METHODS AND ANALYSIS All patients (age 18-75 years) with neurogenic claudication or radicular leg pain based on low-grade degenerative or spondylolytic spondylolisthesis with persistent complaints for at least 3 months are eligible. Patients will be randomised into mini-open decompression with bilateral interbody fusion with percutaneous pedicle screw fixation (MISS), or conventional surgery with decompression and instrumented fusion with pedicle screws and bilateral interbody fusion (open). The primary outcome measure is Visual Analogue Scale of self-reported low back pain. Secondary outcome measures include improvement of leg pain, Oswestry Disability Index, patients' perceived recovery, quality of life, resumption of work, complications, blood loss, length of hospital stay, incidence of reoperations and documentation of fusion. This study is designed as a multicentre, randomised controlled trial in which two surgical techniques are compared in a parallel group design. Based on a 20 mm difference of low back pain score at 6 weeks (power of 90%, assuming 8% loss to follow-up), a total of 184 patients will be needed. All analyses will be performed according to the intention-to-treat principle. ETHICS AND DISSEMINATION The study has been approved by the Medical Ethical Review Board Southwest Holland in August 2014 (registration number NL 49044.098.14) and subsequently approved by the board of all participating hospitals. Dissemination will include peer-reviewed publications and presentations at national and international conferences. TRIAL REGISTRATION NUMBER NTR 4532, pre-results.