Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis.
This study published by the late Dr. Harry Herkowitz, from William Beaumont Hospital in 1991, is one of the most influential papers of its time. His contributions to the field of degenerative spinal surgery continue to influence current research and treatment of many spinal disorders. This paper in particular, has been referenced over 800 times since it’s publishing.
Surgical treatment options for degenerative lumbar spondylolisthesis with spinal stenosis in the early 1990s was mixed between a lumbar decompressive laminectomy alone or combined with a fusion. The paper by Herkowitz and Kurz sought to compare the results of these surgical options for degenerative spondylolisthesis and stenosis confined to one level. The authors concluded that the results of this prospective study have demonstrated that the treatment of choice for patients with degenerative spondylolisthesis with stenosis is a decompressive laminectomy with intertransverse process arthrodesis.
Applying todays standards of evidence based medicine in reviewing this study, finds many methodological concerns. This study is based on a small sample size of 50 patients. From the onset, it is unclear about the clinical symptoms that these patients had prior to surgery. While we know about the average age and sex of the patients pre-op, we really know nothing about their functional levels, use of narcotics, and severity of their complaints. Utilizing the primary outcome measure (operative results), this pre-op information is vital to determining degree of improvement. The study does not truly identify how patients were “assigned alternatively” into the two treatment groups. Were they randomized? If not, who decided the treatment for each patient? This could be considered selection bias. Since the patients did not have to sign informed consent for the study, as both surgical treatments were accepted procedures, were the patients masked to their treatment?
The authors state that the range of follow-up was from 2.4 to 4 years. Again, it is not clear at what point primary and secondary outcomes were determined. A “last” follow-up visit for one patient may have been months or years later than another. This leads to the concern for the possible loss due to follow-up and a detection bias.
Several of the outcome measures, pain scale and operative results are subjective. It is unclear if the treating surgeon was the one to determine operative outcome. If this were the case, this would introduce further bias into the study.
While these are some of the major methodological concerns identified, there are several other potential issues. Taking into account the advancements that have been made and clearer identification of outcomes from the surgical management of degenerative lumbar spondylolisthesis with spinal stenosis in the last twenty years, the results of this study are not necessarily generalizable to modern day practice. However, this study can certainly be credited for opening the door for further research in this area and has helped achieve the level of knowledge that we currently have in this area.