Results from a randomized controlled study between total disc replacement and fusion compared with results from a spine register

Background

Difficulties in performing randomized controlled trials (RCTs) to evaluate new treatment options are increasing. Higher costs and patient unwillingness are the main obstacles. A spinal surgery register has been in use in Sweden for 11 years. Our aim was to determine whether this register can provide the same information as an RCT and whether register data compare favorably with RCT data, making RCTs unnecessary. If not the case, was patient selection or follow-up frequency the cause of any differences?

Materials and methods

We compared baseline data and outcome, retrieved from our register, between 2 surgical groups, total disc replacement (TDR) and fusion at 1 or 2 levels, performed for degenerative disc disease. One hundred fifty-two patients were part of an RCT, whereas four hundred fifty-five patients had been treated according to an active decision. These 2 subgroups were the subjects for comparison.

Results

The 2 subgroups were not similar at baseline. Patients who were fused in the non-RCT subgroup were older, had a higher Oswestry Disability Index, and were more frequently smokers than the other patients. The outcome for the non-RCT group showed larger differences in favor of TDR than the RCT did. The nonresponders in the non-RCT group showed worse life quality and disability at baseline, and patients who answered the 1-year follow-up questionnaire but not the 2-year follow-up questionnaire had an inferior clinical result compared with the other patients at 1 year.

Conclusion

Data from our register showed results similar to the RCT, but a register cannot fully replace an RCT study when evaluating a new treatment option if the RCT has narrower selection than just the diagnosis. In this RCT comparing TDR with posterior fusion, the normal exclusion criteria for TDR were used. These were not registered, so the register could not prevent a possible selection bias, which might also be caused by the nonresponders.