Trabecular metal spacers as standalone or with pedicle screw augmentation, in posterior lumbar interbody fusion: a prospective, randomized controlled trial.

purposeThis prospective randomized comparative trial compared radiological and clinical outcome of Trabecular Metal™ (TM) spacers in PLIF, used as standalone (SA) devices, to TM spacers in PLIF with pedicle screw fixation (PF), in patients with single-level degenerative disc disease (DDD).

methodsPatients (n = 80) with chronic low back pain and single-level degenerative disc were randomly assigned to the SA PLIF (n = 40) or PLIF with PF (n = 40). The primary radiological outcome was the evaluation of a long-term (±6 years; range 6.0-7.7 years) stable construct measured by dynamic X-rays. CT scan does not allow judging the bony bridging between vertebrae, because of Tantalum artefacts. The clinical evaluation (6 weeks, 6, 12 and 24 months) consisted of the Oswestry Disability Index (ODI) score, intensity of low back pain (Visual Analogue Scale) and quality of life (Short Form-36).

resultsAt 6-year follow-up, X-rays showed a stable construct in 94 % of patients treated by SA TM-500 spacers and in 97 % of those with additional PF. Neither subsidence nor migration was observed in either the SA or the PF group. The average improvement in ODI scores at 24-month clinical follow-up was 14.4 and 13.8 for the SA and PF group, respectively. The VAS score showed an average improvement of 6.4 (SA) and 6.7 (PF), 2 years after implantation. No significant difference between groups was observed at all the evaluation points.

conclusionIn this study, TM spacers were found to provide a solid construct at more than 6-year follow-up after PLIF for DDD both with and without additional pedicle fixation. The clinical, but also radiological results were not significantly different between both cohorts. Future studies focusing on the differences of SA and PF at L4/5 level should be powered to study differences in post-surgery stability at the long term.