We measured satisfaction, pain, and disability in a cohort of 406 patients submitted to surgery for DDL. Based on PROMs combination, we created four operational definitions of S&F in the following terms: Success (patients satisfied with no or only mild to tolerable pain, and no or only borderline disability),Incomplete success (patients are satisfied despite levels of pain and/or disability worse than ideal for success),Incomplete failure (patients are not satisfied despite levels of pain and/or disability better than expected for failure) and Failure (patients are unsatisfied with moderate to severe pain and disability).
The clinical profile of Success (ODI 8.0 [2.0–16.0], NPRS back 1.0 [0.0–3.0], NPRS leg 0.0 [0.0–1.0]) is comparable to normal healthy population, that is, pain in the range of “no pain” (10) and ODI in the range of healthy population (9). At the same time, the clinical profile of Failure (ODI 44.4 [38.0–54.0], NPRS back 7.0 [6.0–9.0], NPRS leg 7.0 [1.0–9.0]) demonstrates that these patients remain as sick as before surgery. This model seems well adjusted to the commonsense ideas of Success (suggestive of normal life) and Failure (continuation or worsening of the disease).
These definitions describe the results of surgery in terms that are precise, simple and meaningful.The operational definitions of Incomplete success and Incomplete failure can be considered relatively vague. But they make sense when presented together with respectively S&F. It is intuitive that there is not a sharp limit between S&F. All the pertinent literature relies on satisfaction as the primary anchor of S&F. All success patients are satisfied, and all failures are unsatisfied. Disability and pain quantify the robustness of each subcategory.
Methodological issues
Our S&F model is based on satisfaction, disability, and pain, having satisfaction as the main criterion. The choice of satisfaction as the primary anchor may be debated. Some authors demonstrate that there is a discrepancy between satisfaction and PROMS(21), while others demonstrate that they correlate well (22). It is clear that satisfaction correlates better with the final raw scores than with improvement(17). It was hypothesized that PROMS may not be the best instruments to evaluate satisfaction (23), for satisfaction depends on a complex and wider array of variables such as physical and mental health, expectations and lifestyle(22,23). Some authors chose satisfaction as the main translation ofsuccess(22)and were praised for that(24).Even the concept of minimal clinically important difference (MCID) is based on satisfaction. Satisfaction represents the patient’s most comprehensive evaluation of what occurred (25).
We then chose ODI and NPRS (26) as complementary criteria, for they are directly related to the disease. Quality of life is also important in this evaluation, but it is dependent on other social and health factors. EQ5D varies among countries, and is difficult to be explained in simple words. In the same manner, drug use and work status are also important, but were left out of the model because they evaluate the consequences of the disease and not the disease itself.
For the method of this study, we adopted the final raw score of pain and disability as outcomes. Many authors base their studies on pre-to-postoperative variation as well as on MCID (27)(14)(20). Previous studies demonstrated that the analysis S&F based on pre-to-postoperative differences or MCID may have some flaws (6). The results obtained with this strategy are strongly influenced by the severity of preoperative symptoms (18)(28). Final raw scores correlate better with S&F are more simple and objective, and they are not influenced by the intensity of preoperative symptoms (18). Our model describes “how patients will be at the end of treatment” (final raw scores) and avoids referring to an elusive “minimum clinically significant” improvement.
Another peculiarity of our study was to assess pain considering the highest value between back and leg pain. We assume that the patient’s suffering is better assessed in this manner. Other authors have previously done the same(4).
The option for an operational definition of S&F
The precise concept (or diagnostic criteria) of S&F after low back surgery has never been, and probably will never be defined(4)(5)(6). Nonetheless, S&F happen and are widely studied. One review at PUBMED with the terms “lumbar spine surgery AND failure” showed 3.268 results. Another one with “lumbar spine surgery AND success”, 2.882 results. Concepts or definitions of S&F are based on many PROMs that measure different constructs, so their results are almost never coincident(29). As a result, patients face a myriad of numbers which are difficult to understand. According to some authors, even doctors have difficulty to fully understand the meaning of these numbers(13).
A process of shared decision based on concepts like “33.0% improvement in ODI” or “to reach MCID in leg pain” is almost impossible. This difficulty is more visible in people with low literacy but can happen in more educated people (30). According to Werner et al.(13), patients have more ability to understand percentages of definite types of outcomes than continuous variables. Our method responds to these problems by two ways: a) it divides the possible outcomes into four intuitive types (Success, Incomplete Success, Incomplete failure and Failure), and b) the myriad of numeric variables was replaced by simple equivalent words.
We emphasized the importance of our operational definitions for the communication among all stakeholders of spine surgery. But there is one specific scenario where this type of definition reaches its most relevant moment: this is the preoperative discussion between patient and doctor concerning the indication of surgery(31). Patients have the right to be informed, and doctors must be in charge of giving the information concerning all possible outcomes, that is, their relative incidences and clinical characteristics. This information must be as precise as possible, and be presented in simple and meaningful terms. This is a prerequisite to assure that patients can exert their freedom of choice (32)(33).
Possible deficiencies of the study
This study was based on a single institution, so our results need to be replicated and tested to obtain better validation. Our cohort includes different diseases (disc herniation, stenosis, etc…), surgical techniques, approaches, and surgeons in one single group. This is in pace with a recent tendency of the surgical literature, the so-called science of practice(34,35). With this approach, it was already demonstrated, for example, that return to work (36), improvement of pain, disability and quality of life depend more on the patients’ characteristics than on thetype of approach, number of levels, the use of fusion, thesurgeon experience and other(37).
Another criticism can be made to the relatively short follow-up in patients submitted to fusion. The objective of this study, however, is not to describe the rates of success and failure (which really may depend on time) but to describe a manner (simple and communicable) of reporting the basic endpoints of success and failure. The rates of S&F may change with time, the way they are described may not.
Finally, the problem of reducing all possible outcomes into only 4 categories. The complexity of degenerative disc disease and the heterogeneity of treatments and results deserve a very granular subdivision of possible outcomes. Such a “perfect” definition, on the other hand, would be cumbersome during the process of decision making. It must be recognized that the broader aim of developing a completely truthful and sophisticated definition of S&F has not proven feasible in the context of lumbar spine surgery. The more complex and sophisticated the definition, the more difficult it is to be understood and communicated, and vice-versa. This tradeoff is inevitable. It is the opinion of the authors that the simplicity and communicability of our operational definitions were obtained without compromising precision.