CIRCUMFERENTIAL SPINAL FUSION WITH ANTERIOR PEEK CAGES: MORE THAN 4 YEARS FOLLOW-UP

Abstract

Purpose of the study: PEEK (polyetheretherketone)is increasingly used for spinal fusion since its elasticity modulus is close to that of cancellous bone. This favors harmonious force distribution within and around the implant and thus stimulates bone healing by remodeling. The purpose of this work was to report the mid-term radiographic outcome with this material used for sagittal correction.

Material and methods: Fifty-seven patients aged 54.6 years on average were reviewed 4 to 8 years after isolated intervertebral fusion for degenerative disease. Levels varied from L2L3 to L5S1. Posterior instrumentation used a rigid or semi-rigid pedicle screw-plate configuration associated with an anterior approach to install a lordozing intersomatic PEEK cage and a cancellous autograft. Six patients were overweight. Regional lordosis was unchanged postoperatively for 47 patients but increased 8.2° on average for ten. The clinical outcome and radiographic fusion were noted using the Brantigan classification. Multivariate analysis was used to search for correlation between regional sagittal correction at last follow-up and the following variables: age, body weight, level, quantity of intersomatic autograft as assessed by CT, rigidity of the posterior instrumentation, posterior regional correction and size of the cage.

Results: The clinical outcome was excellent for 24 patients, good for 25, fair for 6 and poor for 2. Mean sagittal correction was decreased in 13 (5.6° on average). Multivariate analysis demonstrated a significant correlation (p< 0.01, R2=0.590) between loss of correction and the following variables: degree of initial correction, rigidity of the posterior instrumentation, age, lower level, size of the cage.

Discussion and conclusion: Despite the excellent rate of fusion, sagittal correction of the regional lordosis did not persist over time and tended to return to the initial state irrespective of the patient’s weight or the quality of the initial graft. A rigid posterior instrumentation should be considered in parallel with the effect of the PEEK for explaining its role in the loss of correction.