Incidence of chronic postsurgical pain in high risk patients. A prospective observational study and statistical analysis of risk factors
Authors: Aerts M , Mertens D , Vanlinthout L , Gryp I , Casaer S 
Published: February 2025

Background and Objectives: Chronic postsurgical pain (CPSP) is a common complication of surgery with significant consequences. Identifying and addressing risk factors for CPSP can enhance shared decision-making between clinicians and patients. It can significantly improve patient outcomes and overall quality of care. The aim of this study was to evaluate the predictive value of the preoperative modified risk index for CPSP (RICP-4) score along with independent risk factors for CPSP. These independent risk factors include early postoperative pain, sex, age, and type of surgery.

Design and Setting: This prospective observational cohort study included 200 adult patients, who underwent either elective total hip arthroplasty or total knee arthroplasty or mastectomy at our hospital group (GZA Hospitals, campus Sint-Augustinus and Sint-Vincentius, Antwerp), from February 2022 until December 2022.

Methods: The combination of descriptive analysis and longitudinal analysis of repeated pain measurements using general estimating equations contributes to a more thorough understanding of postoperative pain dynamics. Multivariable statistical models were used to identify potential characteristics associated with (a) postoperative Numeric Rating Scale (NRS) scores and (b) the incidence of CPSP. As a final step, a prediction model for the occurrence of CPSP was developed using receiver operating characteristic analysis.

Main Outcome Measures: The primary outcome was the incidence of CPSP. As cut-off, we define a NRS score ≥3 at three months postoperatively as CPSP. As a secondary outcome, we used the results of the 15-item quality of recovery questionnaire within 48 hours and at three months postoperatively. And as a tertiary outcome, we evaluated the RICP-4 and Althaus’ scores for each surgical group.

Results: The overall incidence of CPSP during movement and at rest was 35.50% and 16,50%, respectively. An increased incidence of CPSP and lower quality of recovery scores at three months were associated with (a) higher NRS scores in the immediate postoperative period (≤48 hours) and with (b) TKA patients who received loco-regional anaesthesia. The modified RICP-4 score demonstrates poor predictive ability and should not be used as a tool for predicting CPSP. Using the median postoperative (≤48 hours) NRS score with a threshold of a NRS score ≥5 provides a correct prediction of CPSP in 61% of cases. Using Althaus’ composite Risk Index for CPSP (RICP-5) with a threshold of ≥3, a correct prediction of CPSP could be made in 59.50% of cases.

Conclusions: In conclusion, while the RICP-4 score currently in use in our hospital shows more promise for predicting severe acute postoperative pain, its use for predicting CPSP remains limited. Further research and additional studies are needed to improve its predictive capabilities and overall usefulness in clinical settings.

Trial Registration: This study is in accordance with the latest version of the Helsinki Declaration and GDPR guidelines, unfortunately the research protocol was not registered at clinicaltrial.gov before the study began.