Scoliosis is a three-dimensional spinal deformity in which lateral curvature and spinal rotation result, among others, in decreased kyphosis (hypokyphosis) or thoraco-lumbar kyphosis in the sagittal plane. The most common form in children and adolescents is adolescent idiopathic scoliosis (AIS) with a prevalence of 1.7% (95% CI: 1.1%-2.4%). (Li, 2024)
In some cases when the curvature is likely to cause cosmetic deformity or in the future, affect lung function, surgical intervention is indicated. Many children who suffer from severe scoliosis also suffer from back pain. However, according to Julien-Marsollier et al. more than 50% of juveniles who have undergone scoliosis surgery, will continue to suffer from post-surgical pain one-year after surgery. (Julien-Marsollier F, 2017)
Pain before and after scoliosis surgery
Researchers from Rotterdam’s Sophia Children’s Hospital in The Netherlands set to find out whether post-operative pain can be predicted pre-operatively (de Leeuw, 2024). All in all, 45 children undergoing spinal surgery were included in the study. Thirty-nine children had completed the study with one-year follow up, of them 26 girls (mean age: 13.9, SD: 1.9). Most (72%) of these children had indeed AIS, while the rest had congenital or musculoskeletal disorder. Almost 90% of children reported pain before the surgery, and in 7 of them this pain reached Numerical Rating Scale (NRS) >4. The pain reported during rest was median 2 NRS, while during movement reached a median 8 NRS. Seven children of the cohort had mild cognitive impairment.
Thermal Quantitative Sensory Testing (T-QST) was conducted using Medoc’s TSA-II, where sensation thresholds were measured with the reaction-time-exclusive Method of Levels and pain thresholds were assessed with the common reaction-time-inclusive Method of Limits on the non-dominant thenar eminence.
Can we predict who is going to suffer from chronic post-operative pain?
At one year post-surgery, ten children suffered chronic (more than 3 months) post-surgical pain. For all these children pain was present during movement (median NRS 6), and two children complained of pain also during rest. Of them, two children had neuropathic pain as assessed using the DN4 7-items questionnaire. Two other children developed chronic neuropathic pain post-surgery. Even though many children who reported pain prior to surgery, did not have significant chronic pain after surgery, from these data we can gather that this treatment success in terms of pain was not applicable to all.
Preoperative cold pain thresholds were associated with one-year chronic post-surgical pain (CPSP), in such that children with CPSP (NRS ≥4) had significantly lower cold pain thresholds (CPT) (decreased sensitivity to cold) at baseline than those without CPSP, median CPT: 8 (IQR 0.8-16) vs. 19.0 (IQR: 12.7-22.5) p= 0.002, respectively.
With regard to acute post-operative pain, cold (r= -0.426 p= 0.0096) and heat pain thresholds (r= 0.392, p= 0.016) were significantly correlated to the number of times pain at NRS level 4 or higher was reported in the week after surgery. However, these thresholds were not related to cumulative analgesic use post-op.
QST, static or dynamic?
Surprisingly to the authors, pain thresholds were associated with chronic post-operative pain, but not in the way they expected. Expectation was set to higher sensitivity to pain would be predicate to chronic pain, but the opposite was true. These expectations may have been based on findings by findings by Müller et al. who found that cold pain hypersensitivity was a predictor for chronic pain after low back surgery (Müller, 2021). For acute pain the correlations met expectations. In other studies in the past, dynamic QST measures like Conditioned Pain Modulation or Temporal Summation showed indicative of post-operative chronic pain (Dürsteler, 2021). In this study (de Leeuw, 2024), and with this specific cohort which included youth with mild cognitive impairment, authors concluded that conducting dynamic QST would not have been viable.
Future studies with a larger cohort and, possibly including dynamic QST measures, could shed light on the intricate relationships between sensory function pre-operatively, to post-operative recovery and chronic pain. Such findings could be then integrated into a comprehensive peri-operative treatment scheme for the preventions of the development of chronic post-operative pain.
References
de Leeuw, T. G. (2024). Pain during the first year after scoliosis surgery in adolescents, an exploratory, prospective cohort study. Frontiers in Pediatrics, 1293588.
Dürsteler, C. S. (2021). Conditioned pain modulation predicts persistent pain after knee replacement surgery. Pain reports, e910.
Julien-Marsollier F, D. R. (2017). Predictors of chronic neuropathic pain after scoliosis surgery in children. Scand J Pain, 339–344.
Li, M. N. (2024). Prevalence of scoliosis in children and adolescents: a systematic review and meta-analysis. Frontiers in Pediatrics, 1399049.
Müller, M. B.-N. (2021). Cold pain hypersensitivity predicts trajectories of pain and disability after low back surgery: a prospective cohort study. Pain, 184-194.