EARLY CLINICAL RESULTS WITH A VISCOELASTIC ARTIFICIAL LUMBAR DISC

Abstract

Purpose: To evaluate the safety of a novel polymeric one-piece disc arthroplasty.

Introduction: A polymeric disc that can replicate the native function of the natural disc, including three dimensional motion, dynamic stiffness, load sharing capability, and proper maintenance of lordosis provides a promising alternative for management of lumbar back pain caused by symptomatic degenerative disc.

Methods: Forty-four patients with disabling back pain that were unresponsive to non-operative strategies were enrolled in a clinical trial at three sites. Each patient underwent an L4/L5 or L5/S1 lumbar disc replacement with the study device, via a transperitoneal or retroperitoneal approach. Patients were assessed clinically and radiographically at 6 weeks, 12 weeks, 6 months, and 1 year, and 2 years. Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), and SF-36 questionnaires were used to assess patient outcomes. The X-rays were independently analyzed for implant position, subsidence and radiolucency.

Results: For the 26 patients with follow up data at the time of writing, there were no intra-operative complications. An assessment of quantitative radiographic data indicate that the FLD maintains lumbar lordosis, restores and maintains a ‘physiologically appropriate’ disc height and angle, and provides flexion/extension range of motion and translation similar to those provided by the natural disc. Mean ODI scores decreased from 49% pre-operatively to 23 and 26% at 6 months and one year follow up, respectively. Mean VAS scores decreased from 7.7 to 3.1 and 3.0 cm for back pain at 6 and 12 months; from 4.1 to 0.8 and 0.5 cm for right leg pain at 6 and 12 months; and from 3.5 to 0.7 and 2.0 cm for left leg pain at 6 months and one year follow up, respectively. SF-36 component scores also improved significantly, from 31 pre-operatively to 45 and 44 at 6 and 12 months for the physical component, and from 45 pre-operatively to 54 and 51 at 6 and 12 months, respectively.

Conclusions: Although clinical experience is limited to date, results for these pilot patients, while early, indicate that the study device is safe and efficacious in the treatment of symptomatic lumbar degenerative discs. Longer term results will demonstrate the value of a viscoelastic total disc replacement that mimics the performance of the natural disc.