Purpose

To determine if clinical outcomes are correlated with center of rotation (COR) in patients implanted with a viscoelastic total disc replacement (VTDR).

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.

Background and purposes of study The objective of this study is to report the preliminary clinical data from a stand-alone interbody fusion cage (Stabilis™) from two centres.

Methods and results This was a retrospective group comparative study. Anterior lumbar interbody fusion was performed using Brantigan (n=6) or Stabilis™ cages (n=19). Clinical assessment was performed using standardised questionnaires. Lumbar flexion/extension views were used to assess union and implant subsidence. There were no significant differences between the groups for ODI, VAZ, MZ and MSPQ pre-operatively. The Stabilis group showed an improvement in ODI (pre: 49.4; post: 39.3; p=0.024), VAS (pre: 76.1; post: 47.8; p< 0.01) and MZ (pre 32.9; post: 20.6; p< 0.01).

There was no statistical improvement in the Brantigan cage group. Despite clinical improvement, five patients in the Stabilis group failed to unite and six demonstrated subsidence of the implant. The relationship between non-union and subsidence was statistically significant (p = 0.017). Furthermore, the change in ODI between patients who united and those who did not was both statistically significant (p=0.03) and the difference in mean ODI between the two groups was considerable (21%).

Conclusions: Stand-alone cages show promise, involve a shorter operating time and less tissue trauma for the patient. This study has identified a high rate of non-union and implant subsidence. This did not appear to be clinically relevant.