The appropriate management of persisting pain after spine surgery: a European panel study with recommendations based on the RAND/UCLA method

Panel composition was based on an equal representation of the 3 specialties that are most involved in the treatment of patients with PPSS: neurosurgery, pain medicine, and orthopaedic surgery. Individual panellists were selected on the basis of their scientific and clinical expertise, as well as their involvement in guideline development in the field of PPSS. Furthermore, a reasonable geographic spread over Europe was pursued. The panel included 6 neurosurgeons, 6 anaesthetists/pain specialists, and 6 orthopaedic surgeons from 9 European countries (Belgium, France, Germany, Italy, Spain, The Netherlands, Sweden, Switzerland, and the UK).

A literature study was conducted to support shaping the starting points of the study, and to ensure that participants had access to the same body of evidence during the panel process. To avoid interpretation bias, materials were provided as an overview, rather than as a review.

The flow of the panel study is depicted in Fig. 1. During the first panel meeting (Amsterdam, October 2016), the panel discussed the patient population to be considered, treatments to be included, and factors that may be relevant to treatment choice.

The panel agreed to restrict the study to patients with:

The panel acknowledged the importance of psychological aspects of chronic pain, but wished to focus on somatosensory aspects. For that reason, the psychological dimension of PPSS and its impact on treatment choice was not considered in this study.

Selected treatment options for the first round were conservative treatment, spinal cord stimulation, re-operation, and “specialised diagnostic evaluation” (including facet denervation, root blocks, and spinal endoscopy). The panel identified a number of variables that may be relevant to treatment choice: previous spinal surgery (decompression/fusion), onset of pain (remaining/recurrent), location of pain (leg/back/mixed), type of pain (neuropathic/nociceptive/mixed), concordance of signs and symptoms with anatomic abnormalities (yes/no/uncertain), and age (< 50, 50–70, > 70 years).

The panel extensively discussed the definitions of neuropathic and nociceptive pain to be used. It was agreed that the taxonomy of the International Association for the Study of Pain (IASP) is a good concept [36], but that its application in PPSS is sometimes problematic, and may confuse the appropriateness ratings. For that reason, it was decided to use the term neuropathic (like) pain in the ratings, thereby including a broader group of patients with neuropathic signs and symptoms than would fit within the IASP definition. This approximates more the reality of presentation of complaints of patients with PPSS. For reasons of brevity, the term neuropathic pain will be used throughout this manuscript.

By permutation of the clinical variables, a set of 324 mutually exclusive scenarios (unique patient profiles) was constructed. Using an electronic rating program, panellists individually assessed the appropriateness of the 4 treatment options for all 324 scenarios using a 9-point scale (reference values: 1 = inappropriate, 5 = uncertain, 9 = appropriate). According to the RUAM definition, a treatment was considered appropriate if the expected benefits outweigh the expected negative consequences by a sufficient margin [29]. Panellists were instructed to take the clinical perspective as a starting point, and to disregard cost and reimbursement of treatments. The rating results were discussed during the second panel meeting (Paris, April 2017). Panellists received feedback on their own ratings in comparison with the anonymous results of their colleagues. The panel discussion led to a number of adaptations to the clinical variables, treatment options, and definitions. The final set included 1 variable with 2 categories, 3 variables with  3 categories, and 1 variable with 5 categories (Table 1), summing up to (2¹ * 3³ * 5¹ =) 270 scenarios. After exclusion of 60 scenarios that the panel considered to be unrealistic or falling beyond the scope of this study (for example nociceptive leg pain), 210 scenarios remained for which the appropriateness of treatments was assessed during the second round. Final recommendations were established and approved during a web conference (October 2017). An overview of clinical variables and treatment options used in the second round is provided in Table 1.

Similar to most RUAM studies, appropriateness of treatments was classified using the median panel score and extent of agreement between panellists [29]. The outcome was considered appropriate if the median score was between 7 and 9, and inappropriate if the median was between 1 and 3, without disagreement between panellists. Disagreement was defined as the situation in which at least one-third of the panellists scored in each of the sections 1–3 and 7–9 [29]. All other outcomes were deemed “uncertain”. Frequency tables and cross-tabulations were used to describe the appropriateness outcomes by treatment choice, clinical variables, and specialty. Multivariate logistic regression was used to analyse underlying patterns and to determine the internal consistency of the ratings. All statistical analyses were performed using IBM SPSS for Windows version 25.

For all indications together, disagreement after the second round was 8%. Dispersion of opinions was highest for minimally invasive treatment and re-operation in patients with predominant back pain (disagreement 68 and 88%, respectively). Appropriateness outcomes for the theoretical patient population are shown in Fig. 2.

Conservative treatment was considered appropriate for around two-thirds of cases. The choice for minimally invasive treatments showed the highest proportion of uncertainty (84%). Inappropriate indications were seen for neurostimulation (15%) and re-operation (37%). The “rating behaviour” of individual panel members showed large variations: the proportion of ratings in the sections 1–3, 4–6, and 7–9 ranged from 0 to 46%, 3 to 65%, and 15 to 65%, respectively. However, differences in appropriateness outcomes across specialties were modest (Fig. 3). The difference between the mean median scores was at most 1.1 points on the 9-point scale.

The appropriateness of treatments by clinical variables is shown in Table 2.

Evidence for anatomic abnormality appeared to be the most discriminative variable. Conservative treatment was considered appropriate for most patients with pronounced scar tissue or iatrogenic lesion and for those with no or inconclusive evidence for an anatomic abnormality. The same factors were obviously considered as a contraindication for re-operation. Spinal instability proved to be an important factor in favour of re-operation, and against minimally invasive treatment and neurostimulation. The presence of predominant leg pain was the strongest single factor in favour of neurostimulation, while the presence of predominant nociceptive (back) pain was the most important factor against this treatment option. The impact of the type of previous surgery was only significant for minimally invasive treatment: this treatment option was not considered appropriate for most patients with previous instrumented surgery and fusion. Onset of pain was most relevant for the choice of conservative treatment. The appropriateness of this option was substantially higher in patients with new pain, i.e. different from the type of pain for which the initial surgery took place.

Logistic regression analysis, with the outcome appropriate (yes/no) as the dependent variable and including all clinical variables as explanatory factors, confirmed the appropriateness patterns of the 4 treatment options, with predictive values for the statistical models varying between 83 and 94% at a cut-off value of 0.5. Appropriateness outcomes were highly specific. In 48% of the scenarios, only one of the treatment options was appropriate, and in another 39%, at most two options were appropriate. Principal appropriateness patterns are shown in Fig. 4. Detailed tables are provided in “Appendix 1”.

Evidence for anatomic abnormality proved to be the most discriminative variable in relation to the appropriateness of treatments. The absence of an anatomic abnormality or discordance with symptoms clearly and logically rules out surgical intervention, including minimally invasive procedures. Similar results were seen for patients with pronounced scar tissue or an iatrogenic lesion, with the difference that minimally invasive treatments may sometimes be an option here (Fig. 3). Available guidelines and algorithms do not explicitly give recommendations on scar tissue and iatrogenic lesion [6, 23‐27]. However, there is general agreement in the surgical community that an already partially or completely damaged nerve or nerve root causing chronic neuropathic pain cannot be restored with any kind of surgery, and symptomatic pain therapy in a multidisciplinary setting is required [37, 38]. For patients with spinal instability, re-operation is the most appropriate option. Conservative treatment in these patients may also be appropriate, (particularly) if the pain is different from the original pain for which previous spinal surgery took place (see “Appendix 1”). Re-operation was considered an appropriate option for most patients with a recurrent disc herniation or spinal/foraminal stenosis, and having predominant leg or mixed leg/back pain (Table 2, “Appendix 1”). Most currently available guidelines and algorithms do either not mention, or are not very specific on the indications for re-operation [6, 23‐25]. The algorithm by Van Buyten and Linderoth is close to our findings in this respect, as it considers re-operation indicated in patients with (recurrent) disc herniation and leg pain prevailing over back pain [27]. The algorithm suggested by Rigoard and Assaker is also largely in line with our recommendations, albeit that their specification of the related type of symptoms is different (“mixed back pain” or “exclusive/predominant axial back pain”) [26]. According to the panel, neurostimulation is most appropriate in patients with predominant neuropathic leg or mixed leg/back pain, and without clear surgical indications such as spinal instability. This is in accordance with the inclusion criteria of some, but not all RCTs that have studied spinal cord stimulation for “failed back surgery syndrome” [39, 40], albeit that different terms have been used such as “radicular pain” or “neuropathic pain of radicular origin” [39, 40]. The recommendations are also largely in line with the guidelines and algorithms in which neurostimulation was mentioned [6, 23‐27]. Neurostimulation was also considered appropriate in the case of scar tissue or a iatrogenic lesion (Table 2), mostly in patients with a neuropathic leg pain component, but also for patients with exclusively neuropathic or mixed back pain (Fig. 4). The efficacy of SCS for PPSS patients with predominant low back pain is currently under study [41]. Minimally invasive treatments showed some specific indications for patients with (mostly) back or mixed leg/back pain after non-instrumented previous spinal surgery (Fig. 4, “Appendix 1”). Some guidelines and algorithms advise selective root blocks, radiofrequency, and epidural injections as a first (diagnostic) step in specific situations (e.g. suspected facet joint syndrome) [6, 26]. The overall panel recommendations are summarised in Table 3.

Although the use of detailed clinical scenarios and the involvement of different specialties may be considered as strong points of this study, it still is a first step towards an individualised and multidisciplinary approach of managing PPSS.

The panel consisted of 3 different specialities, but there are many other disciplines that are involved in the management of persisting pain after spine surgery, and that all could have had a significant contribution to this project. However, the number of participants had to be limited to allow everyone to be involved in the group discussion. In addition, to be able to detect potential differences between specialities, a minimum number per specialty was needed. For these reasons, the panel was restricted to the primary decision-makers from both the spine and pain perspectives.

Although a variety of patient scenarios was used, the recommendations relate to a theoretical population and the applicability of the clinical factors and the distribution of scenarios need to be determined in daily practice. For reasons of practicability, a set of relatively simple variables without extensive definition was chosen. As was also noticed during the panel discussions, some of these may need further refinement. This is particularly true for the concept of neuropathic (versus nociceptive or mechanical) pain for which there is currently much debate on its precise nature [14, 42‐45] and role in the diagnostic evaluation and treatment choice for patients with PPSS [12‐14, 46, 47]. Further research may also consider the inclusion of additional somatic variables, potentially relevant to treatment choice, such as sagittal balance [15, 16].

The focus of this study was on somatosensory aspects which is surely an important limitation. Psychological and social aspects are very important in the management of PPSS, but including this dimension would have substantially increased the complexity and extensiveness of the study. This study should therefore be considered as a foundation on which further refinements can be made.