Clinical Trials

The MIMO Study Group proposes to conduct a prospective randomized controlled trial in order to determine whether a low implant density cohort has equivalent clinical and radiographic results to a high implant density cohort. This study is proposed as a trial of equivalence. The null hypothesis is that significant differences exist in percent major Cobb angle correction between high- and low-implant density cohorts for Lenke 1A curve types, the most common scoliotic curve pattern (73). Consecutive qualifying patients will be screened and enrolled by high-volume spine surgeons at 14 sites and randomized to spinal instrumentation with a low- or high-density screw pattern. Patients will return at 3-months, 1-year, and 2-years for exam, radiographs, and collection of patient-reported outcome scores. The Harms Study Group Foundation will serve as a collaborating organization and will provide database development and management, secure online data collection, centralized radiographic measurements, and data quality control. The University of Minnesota team will lead study design, protocol development, IRB/data use agreement contracts, patient randomization, and statistical analysis, including quarterly data review. Imaging will be obtained either with an EOS system or using a calibration belt during the radiographs, which allows for subsequent with the 3D modeling of the deformity. Six enrolling sites currently have this capability (EOS - Montreal, St. Louis, Iowa, Mayo, DuPont, and San Diego). An additional five sites already have calibration belts - Dallas, New York, Baltimore, Boston, U. of Rochester), and new calibration belts will be fabricated for the additional sites. The Montreal site will supervise collection of radiographic data with 3D capability and assist with troubleshooting and radiographic quality control. Although the study is primarily powered to detect change in percent correction of the major coronal curve, preliminary data will be gathered on axial and sagittal plane correction as well as complications, surgical factors, and patient-reported outcomes.