PEEK Rods for Posterior Lumbar Fixation: Pros and Cons: The First French Series
Authors: Desjardins Thierry 
Published: April 2016

Introduction The ideal lumbar spine fixation system should provide sufficient stability while preserving natural posturing and spinal alignment with limited risk of adjacent level degeneration. While rigid fixation systems may contribute to stress shielding in anterior column increasing consecutively adjacent segment degeneration, Polyetherethrketone (PEEK) Rods provide a modulus of elasticity close to cancellous bone that may decrease these risks. Biomechanical studies comparing rigid fixation using titanium Rods with PEEK Rods posterior systems have shown a comparable intervertebral stability with the two systems nevertheless PEEK was associated with a lower risk of screw mobilization in poor bone, an increased anterior physiological load and a reduced stress on bone-screw interface that may predict lower risk of adjacent level degeneration. We performed a retrospective study in a french cohort of patients who underwent posterior lumbar fixation using PEEK Rods to investigate clinical indications and clinical outcomes in real life settings. Material and Methods Between June 2011 and July 2014, 48 patients who underwent posterior lumbar fixation using PEEK Rods were included in our study for retrospective review. Surgery was performed using 5,5mm pre-bent PEEK Rods with Titanium monoaxial screws for 1 to 4 level posterior lumbar fixation with a maximum length of 160 mm. Clinical outcomes were assessed using Oswestry Disability Index (ODI), reoperation rate, complications, radiographs and MRI. The patients satisfaction was also evaluated using the Patient Satisfaction Index (PSI). Results The population included 28 males and 20 females with an average age of 61 years. The main indication for surgery was spinal decompression with stabilization (44,6%). A majority of patients (29/60,4%) presented surgical antecedents including recurrent disc herniation, posterior decompression, posterior fusion with instrumentation and stabilization with interspinous devices. Patients underwent surgery on one (18/37,5%) or multiple levels (30/62,5%). Patients had surgery with anterior cages for fusion (PLIF), posterior dynamic fixation or hybrid systems combining fusion and non-fusion. The most frequent surgeries were performed on L4L5S1 as hybrid systems. At 2 years follow-up, the mean ODI score was improved by 29% (from 67% to 38%) and the mean PSI was 1,8 on a scale ranging from 1 to 4 (1: completely satisfied. 4: same or worse condition than before surgery). There was no reoperation for 89,7% patients, no migration for 94,7%, no screw breakage for 84,2% (never for one single level fixation) and no rod breakage. We reported 15% patients with post-operative adjacent level degeneration. For 21% patients with pre-operative signs, the degeneration was no more observed on the last MRI evaluation after 2 years. Conclusion PEEK Rods provide a safe and effective system that can be either used as a fusion system promoting anterior fusion with decreased risk of implant failure, as dynamic system protecting adjacent levels, or as hybrid system combining both advantages, with a stability comparable to Titanium rods. Further studies on larger populations and longer term follow-up are needed to confirm these data.