Abstract
Introduction Current evidence suggests that, in the short and medium term, total disc arthroplasty (TDA) is at least as good as fusion for the management of discogenic low back pain. The optimum kinematic design of TDA, however, at this stage has not been identified. This paper compares the clinical outcomes of two TDA prostheses with different kinematic properties.
Methods A randomised comparative clinical study with prospective data collection was performed. Two groups of patients with low back pain who were treated surgically with TDA were compared. All patients had primary symptoms of low back pain without significant facet degeneration. All patients had MRI evidence of disc degeneration and positive discography at the target level. The two surgical groups were treated consecutively by the one surgeon. The first chronological group consisted of 23 cases of SB Charité (CHR) prostheses (DePuy Spine) and the second group consisted of 18 cases of Maverick (MAV) disc replacements (Medtronic Sofamor Danek). The CHR group consisted of 16 males and 7 females with an average age of 37.1 years. The MAV group consisted of 10 males and 8 females with an average age of 41.3 years. 17 (74%) of the CHR group were single level cases. 6 (24%) cases were performed at the same time as an adjacent level anterior fusion. There were no two level prostheses performed. One case in the CHR group was lost to follow-up. 10 (55%) of the MAV group were single level cases. 7 (38%) of the MAV group were double level prosthesis cases. There was 1 case performed adjacent to a fusion in this group. Patients were assessed by visual analogue pain scores (VAS), Low-Back outcome score (LBOS), and SF12 health outcomes that were collected preoperatively and at 6 months.
Results There was a mean improvement of 3.4 VAS points with the CHR group compared to a mean improvement of 5.1 points with the MAV group (p=0.039). There was a mean percentage improvement in VAS scores of 42.1% with the CHR group compared to a 70.1% improvement in the MAV group (p=0.003). The mean LBOS scores improved by 12.3 points in the CHR group, compared to an improvement of 25.6 points in the MAV group (p=0.016). Percentage improvement in LBOS score was 67.8% for the CHR group compared to 210% for the MAV group (p=0.006). The mean improvement in the PCS score of the SF12 measure was 7.3 for the CHR group compared to 15.6 for the MAV group (p=0.055). The percentage improvement in PCS scores was 23.1% for the CHR group compared to 56.0% for the MAV group (p=0.047). There was no significant difference in the improvement in MCS score of the SF12 measure (6.3 compared to 8.1 p=0.7).
Discussion On all outcome measures of pain and physical disability the MAV cases improved by a statistically greater amount than the CHR cases. This difference appears to be clinically important. There are a number of possible reasons for this difference, including the fact that the cases were not performed concurrently (learning curve affect) and that there were a number of fusions performed simultaneously in the CHR group. However one possible explanation is the difference in the kinematic behaviour of the two prostheses.
The abstracts were prepared by Professor Bruce McPhee. Correspondence should be addressed to him at Orthopaedics Division, The University of Queensland, Clinical Sciences Building, Royal Brisbane & Women’s Hospital, Herston, Qld, Australia
