The aim of this study was to retrospectively analyse the very long term outcomes of an ultraselected, bias-free cohort of patients operated on by one surgeon, for a simple lumbar central canal stenosis, and to compare these results to those of a cohort of patients who were found to suffer from a perfectly superimposable condition at first outpatient evaluation and who, according to the same surgical indication criteria, were referred for surgical treatment but, due to various reasons, were never operated on.
This feature was shared both by the surgical and non-surgical subset of patients.
Obstacles to this work lie in the multifactorial aetiology of LSS [
17‐
19]: if we consider only the anatomical conditions, it is possible to notice that single factors like lumbar spondylarthrosis, lumbar spine instability, facet malposition and hypertrophy, the different degrees of intervertebral discs degeneration, hypertrophy or calcification of the posterior ligamentous complex (PLC) and anatomical variations of the spinal canal diameter may play roles of a dramatically different weight in different patients affected by a
similar form of LSS.
Key results and Interpretation
As previously reported [
20,
21], the rate of excellent outcomes for surgical treatment over long periods (many years), decreases by about 70%, and this data appears to be confirmed in the present series.
However a detailed and critical review of our data mitigates the disappointment that might initially rise from the long-term results of surgery in the management of this condition.
There was a statistically significant difference between the “self report” outcomes (SSSQ) and the clinical and radiological outcomes as seen from the physician point of view: patients were definitely older when reevaluated at follow up and many of them suffered from other degenerative conditions affecting the quality of their march. Patients did not appear to be completely aware of how much of their reduced physical efficiency could exclusively be attributed to their LS conditions.
In four patients (about 5% of the surgical subgroup), the cranio-caudal extension of the laminectomy had been insufficient, thus results were unsatisfactory; this common surgical complication significantly contributes to the failure of the procedure; at present, with the constantly improving quality of intraoperative imaging, such “failures” can be simply avoided.
In three patients the laminectomy caused delayed lumbar spine instability, significantly contributing to a bad outcome. Two of these patients were later operated on for the newly arisen instability and LS fusion was performed, the remaining patient was deemed unsuitable for surgery and thus referred for physical treatment. Therefore, in the present series, the incidence of iatrogenic spinal instability over a span of 12–17 years was 3.8%, which is not negligible, though not unacceptable.
In the present series, patients underwent a standard laminectomy (“partial laminectomy” with sparing of the medial facet of the articular process). We strongly prefer to spare articular processes because of the evidence-based risk of iatrogenic postoperative instability. In the thoracolumbar spine, instability usually appears in 25% of patients receiving more than 2 level laminectomies if the articular processes are involved in the osteotomies [
21]. Postoperative deformity is reported in 9.4% of patients receiving complete laminectomies compared to 3% in patients whose articular processes are preserved [
22]. When the preoperative imaging rules out the presence of a gross preoperative lumbar spine instability, a laminectomy without fusion can be safely performed, with minor risk of jeopardizing spinal stability [
23].
Avoiding a useless spinal fusion leads to a reduction in surgical and anesthesiological times, intraoperative bleeding, spinal stiffness, iatrogenic neurological and spinal adverse events related to an unnecessary procedure and furthermore, in countries like Italy, in which the National Health System provides full coverage for healthcare expenses, leads to a dramatical case related cost reduction for patients operated on for LSS [
23].
A judicious follow-up, properly hastened in case of painful symptomatology and/or neurological variations, brings to a fast and effective detection of instability; in such cases, when the dural sac and neuroforamina have been previously decompressed, a minimally invasive lumbar arthrodesis can definitely resolve the problem.
If we compare the surgical and the non-surgical subsets of patients, it appears that the management of LSS through surgery, despite several limitations, is the most effective treatment for this condition. Despite some evidence that in the long-term surgery presents the same outcomes of the conservative strategy [
7,
24], our results confirm the majority of previous reports [
4‐
9]: in the long run, patients who undergo surgery preserve better neurological and functional status in respect to non-operated patients.
As previously stated, we investigated the very long term results of a classic surgical technique for the management of LSS: the decompressive laminectomy, but, at present, there are other minimally invasive techniques that are increasingly being used for LSS surgery. Obviously, every procedure that minimizes handling and damage of the tissues, reduces bleeding and reduces the length of surgeries is welcome, but currently we lack strong evidence, large and multicentric prospective trials with very long term follow-up to accurately estimate the effectiveness of the new procedures.
Limitations and generalisability
The main limitations of this study lie in the exiguity of the sample and in its retrospective nature.
Bias are expected from the long range of follow-up, the lack of access to complete psychosocial and other lifestyle factors and paradoxically even from the inclusion and exclusion criteria: the selection of the patients enrols a limited number of highly comparable patients on one side, but on the other may exclude potentially relevant observations since, as reported in the Literature, psychosocial and emotional factors do influence the expression of impairment caused by degenerative lumbar spine conditions in the quality of life [
25‐
28].
Furthermore, while a single surgeon’s experience study depicts what is the real story of a single operator in the management of LSS, and importantly eliminates technique-related bias that may develop among different operators, it may on the other hand exclude relevant observations about the general history of this disease, as well as psychosocial variables that may have affected the operator himself. Though a great effort has been made towards a rigorous methodology in patient’s eligibility, conclusions may suffer from under-representation bias, and prospective randomized large cohorts of patients, treated by a select number of surgeons, are required to provide conclusive findings in regard to the management of this condition. It would be particularly interesting to run at least two parallel, comparative studies on the prospective sample: one that, like ours, takes only take into consideration the anatomical and clinical factors, the other that includes the psychosocial and emotional variables.
What makes this study relevant is that the impact of many types of common bias has been completely removed. Moreover, one the greatest bias, the technique related difference among different physicians has been excluded because all the patients have been operated on by the same surgeon.
The increasing incidence of LSS, its impact on quality of life and on treatment related costs for National Health Systems, compels researchers to urgently propose evidence-based guidelines for the management of this condition. The road to reach this target is not easy because of the large number of confounding factors that must be taken into account.
Surgery appears to be the most effective treatment and the current gold standard for the management of LSS.