Study Confirms Results of Disc Replacement in Lumbar Spine
Total Disc Replacement (TDR) in the lumbar spine (low back) for degenerative disc disease helps reduce pain while preserving motion. There are several different types (brands) of disc replacement devices available now. In this study, patients who received the ProDisc-L are followed for a minimum of 5 years to assess outcomes.
Clinical success was measured in several different ways. They used the Visual Analog Scale (VAS) to measure pain, the Oswestry Disability Index (ODI) for function, and a sporting activity scale score. A minimum of 15-points in improvement on the Oswestry was required for the patient to be considered "improved" or "a success." Patients were also asked two questions at the end: 1) how satisfied were you with the results of surgery? (e.g., satisfied, very satisfied, dissatisfied, or very dissatisfied and 2) If you had to do it over, would you have the surgery again?
Everyone in the study was treated by the same surgeon at one center. Follow-up was conducted at three months after surgery, then again after one year, two years, and finally more than five years later. The results were very similar to results from other studies using this particular implanted device.
First, early improvements were observed in the first two years after the procedure. But a decline in the positive benefits of this device was observed in the later years. To put some numbers to these results, 88 per cent registered at least a 15-point improvement on the ODI from before to after surgery. This number declined to only 71.4 per cent at the end of five years.
Only 60 per cent of the patients said, 'Yes, if given the choice, I would have this surgery again.' The authors expected that statement of satisfaction to be higher to match the increase in function in at least the 71.4 per cent group. There were no complications or adverse events in either group making it seem like the perceived success should be higher longer.
As they looked back over the study, the authors observed several things that might account for the disconnect between functional improvement and patient satisfaction. First of all, the cut off for a threshold of improvement using the ODI (15 points better = success) might be too conservative. A 10-point difference might have given a higher satisfaction rate while still registering significant improvements in function.
It's possible that the decline in improvements seen over time is typical of lumbar disc replacement surgery no matter who does the surgery and/or no matter which device is used. In this study, they only used one implant and therefore did not compare the mid-term results with other devices. At five years out, further study is still needed to assess the long-term (10 years or more) results with all types of artificial disc replacements.
Chun-Kun Park, MD, PhD, et al. Clinical Outcome of Lumbar Total Disc Replacement Using ProDisc-L in Degenerative Disc Disease. In Spine. April 15, 2012. Vol. 37. No. 8. Pp. 672-677.