Clinical and radiographic outcomes of lumbar decompression and fusion with a novel metal-free cortico-pedicular fixation device: A comparative cohort study.

Background: There is ongoing interest in less invasive fixation strategies for lumbar fusion that can achieve comparable biomechanical stability and patient outcomes to traditional pedicle screws. The purpose of this study was to compare the novel metal-free polyether ether ketone cortico-pedicular fixation device (Karma Fixation System; Spinal Elements) with conventional pedicle screw fixation in the largest clinical series reported to date. Methods: This retrospective comparative cohort study included 20 consecutive patients who underwent lumbar fusion with the cortico-pedicular fixation device and 20 consecutive controls treated with conventional pedicle screw fixation. Outcome measures included same-level reoperation rate within 12 months, radiographic fusion assessed on computed tomography, and patient-reported outcomes (Oswestry Disability Index and Visual Analog Scale for back and leg pain) at 12 months. Results: In the cortico-pedicular fixation group, 5 patients (25%) required reoperation with pedicle screw fixation for pseudarthrosis and recurrent symptoms at a mean of 7.6 months (reoperation rate at L2-L3 was 50%). Among patients with computed tomography imaging at ≥6 months (range 6-17 months), fusion was observed in only 3 of 16 assessable levels (18.8%), with inferior articular process fractures identified in 9 levels. In the control group, no structural reoperations were required, and posterolateral fusion was achieved in 10 of 11 assessable levels (91%). After excluding cases requiring revision, there were no significant differences in patient-reported outcomes between groups. Conclusions: The cortico-pedicular device demonstrated high rates of pseudarthrosis and inferior articular process fractures. Its use in conjunction with open laminectomy may be inadvisable.