Risk-Factor Analysis of Disc and Facet Joint Degeneration After Inter-Segmental Pedicle Screw Fixation for Lumbar Spondylolysis

Background: To assess the effects of inter-segment pedicle screw fixation for the treatment of lumbar spondylolysis, and evaluate various risk factors potentially predicting the probability of disc and facet joint degeneration after instrumentation.Methods: The study included 54 male L5 spondylolysis patients who underwent pars repair and inter-segment fixation using pedicle screws. Bony union was evaluated using reconstruction images of computed tomography. Radiographic changes including the disc height, vertebral slip, facet joint and disc degeneration in the grade of adjacent and fixed segments were determined from before to final follow-up. Logistic regression analysis was performed to identify factors associated with the incidence of disc and facet joint degeneration.Results: Bony union was achieved in all cases. Logistic regression analysis revealed that duration of instrumentation of more than 15.5 months and 21.0 months were significant risk factor of the incidence of L4/5 and L5S1 facet degeneration, respectively. Conclusions: Inter-segmental pedicle screw fixation provides good surgical outcomes and good isthmic bony union rates in patients with lumbar spondylolysis. The duration of fixation was confirmed as a risk factor of facet joint degeneration. Once bony union is achieved, remove of the instruments should be recommended.