Abstract
Introduction: Surgical management of discogenic low back pain has in the past been limited to spinal fusion. Recently disc arthroplasty has become available. The rationale for disc arthroplasty is that it may avoid the long term consequences of adjacent segment degeneration. Avoidance of long term consequences is of no value unless the short term outcome is at least equivalent between fusion and arthroplasty.
Methods: A series of patients with chronic low back pain with concordant lumbar discography and a negative control discogram were surgically treated. Prospective data was collected preoperatively and at regular intervals during the post-operative period for a historical series of combined anterior and posterior lumbar fusion (n =24), a series of SB Charité (DePuy Spine) disc replacements (n =23), and recently, a series of Maverick (Medtronic Sofamor Danek) artificial disc replacements (n =9). Self assessed outcome measures of visual analog pain score (VAS), Low Back Outcome Score (LBOS) and SF12 general health data was obtained at intervals after the surgery. This paper presents the results of the consecutive series that have a minimum of 3 months follow-up.
Results: The data for the two groups of arthroplasty was combined and compared to the fusion group. The mean age for the fusion group was 37.6 years and the mean age for the arthroplasty group was 38.6 years. There were 5 compensation cases (20.8 %) in the fusion group and 5 cases (15.6 %) in the arthroplasty group. Both groups had 69% male patients. The mean VAS dropped from 7.5 to 3.7 (p< 0.001) in the arthroplasty group and from 7.3 to 3.5 (p< 0.001) in the fusion group. The mean LBOS improved from 22.0 to 36.5 (p< 0.001) in the arthroplasty group and from 19.6 to 37.1 (p< 0.001) in the fusion group.
There was no apparent difference between the clinical improvement in VAS and LBOS (p=0.91 and p=0.45 respectively) for each group. Analysis of the power of the comparison showed an 86% power for comparison of VAS improvement using a clinically important difference (delta) of 1 VAS point and there was 98% power for the LBOS improvement comparison using a clinically important difference (delta) of 10 LBOS points. Complications appeared higher in the arthroplasty group with foraminal encroachment requiring revision in 3 cases and one case of polyethylene failure in the Charité group at 3 years. This case occurred with an 8mm polyethylene insert (since removed from inventory by the manufacturer)
Discussion: Disc arthroplasty in the lumbar spine appears to offer similar short term results to that of fusion for chronic low back pain. The surgical complication rate may be higher in the early learning curve of the procedure.
The abstracts were prepared by I. B. McPhee. Correspondence should be addressed to the Spine Society of Australia Secretariat, The Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science, PO Box 14, Rundle Mall, Adelaide SA 5000, Australia.
