DISCAL PROSTHESIS: RESULTS FROM A COHORT OF 24 PATIENTS WITH AT LEAST SIX MONTHS FOLLOW-UP

Abstract

Purpose: The intervertebral disc prosthesis has been proposed as an alternative to fusion in cases of severe discal degeneration. The purpose of this study was to analyse long-term results in patients treated with a Charity III SB intervetebral disc prosthesis.

Material and methods: Clinical and radiological outcome were reviewed in 24 patients (66% women); 86% of the prostheses were L5–S1. Three patients had discectomy or nucleotomy. One patient underwent implantation at two levels. Mean age at surgery was 42 years (26–50). Eighty percent of the patients had an occupational activity and 70% were on sick leave for more than six months. Minimum follow-up was six years. Mean follow-up was eight years six months and was greater than ten years for thirteen patients. The Oswestry score, a visual analogue scale (VAS), and time to resumed occupational or sports activities were used to assess clinical outcome. Radiologically, prosthetic height, and status of adjacent discs were analysed.

Results: Outcome was considered good in 83% of the patients with an improvement in the VAS in 60% and in the Oswestry score in 50%. These results persisted at last follow-up. Twelve patients achieved excellent outcome with VAS at 0 and Oswestry at 10. For the occupationally active patients, 90% resumed their activities, 70% at three months and 80% at the same activity level. Only two patients were on disability compensation. Radiologially, prosthesis flexion-extension was scored 8 at level L4–L5, and 5 at level 5-S1 and persisted at last follow-up. There were no cases of spontaneous fusion or decreased prosthetic height. The status of a suprajacent disc degenerated in one patient requiring L4–L5 fusion nine years after disc implantation. There were two complications (8%): one eventration and one anterior dislocation six days after insertion of an L5–S1 prosthesis in the one patient who underwent a two-level procedure and required secondary fusion.

Conclusion: In light of this series with a sufficient follow-up, intervertebral disc prosthesis appears to be a satisfactory alternative to arthrodesis in well selected young patients with a single level of disc degeneration.