Functional outcome of patients with unstable single- level/ two- level lumbar stenosis treated with decompression plus divergent screws (cortical bone trajectory) or percutaneous convergent pedicle screws

BACKGROUND: The aim of this prospective comparative study is to assess the functional outcome in two groups of patients suffering from spinal lumbar instability and treated by decompression and stabilization with posterior lumbar interbody fusion using percutaneous pedicle screws (PCT) or a novel technique of divergent pedicle screws insertion using a cortical bone divergent trajectory (CBT). Functional outcome after surgery has been evaluated using Numeric Rating Scale (NRS), Modified Rankin Scale (MRS), Smiley-Webster Scale, and Oswestry Disability Index (ODI). METHODS: Seventy-two consecutive patients were treated at our department from February 2013 to February 2018 for one-two levels unstable stenosis with one year follow-up. Forty-one patients were treated with percutaneous screws and thirty-one patients were treated with divergent cortical bone trajectory screws. Functional outcome and complications were analysed with logistic regression analysis. No funding was received for this research. RESULTS: Pain significantly improved in both groups. Charlson Comorbidity Index (CCI>=3) was the only variable associated with increased risk of complications (OR 5.73, p=0.04). Patients with BMI >=27.4 (median value) and patients with percutaneous screws had an increased risk of a worse Smiley-Webster Score (OR=3.675; p=0.029 and OR=3.747; p=0.05, respectively). Patients with BMI >=27.4, patients with percutaneous screws and patients with more comorbidities (CCI>/=3) showed a higher risk of presenting severe/crippling Oswestry Disability Index score (OR=6; p= 0.027, OR=10.747; p=0.04 and OR=6.310; p=0.043, respectively). CONCLUSIONS: Cortical bone trajectory screws technique could represent a valid alternative to the traditional percutaneous pedicle screws technique in posterior lumbar interbody fusion.