This study aims to explore the cutoff points for CPSP at one-year post-TKA by employing indicators of functional disability and patient satisfaction.
The study involved 283 participants (42 males, 241 females; mean age 73.1 ± 7.8 years, BMI 26.3 ± 4.1) who had undergone TKA and were assessed one year postoperatively. Evaluation parameters included VAS scores at rest and movement-evoked pain, functional disability measured by the Oxford Knee Score (OKS), and patient satisfaction categorized as “very satisfied,” “somewhat satisfied,” “somewhat dissatisfied,” or “very dissatisfied.” The OKS was based on a minimum clinically meaningful change of 5 points or more, and satisfaction was dichotomized into satisfied or not satisfied. Receiver Operating Characteristic (ROC) curves were utilized to determine VAS cutoff points about OKS and satisfaction, with the Area Under the Curve (AUC) calculated accordingly. The Youden Index was used to establish the optimal cutoff values.
The cutoff points distinguishing the two groups for OKS were 5.0 mm for rest pain (AUC: 0.669, sensitivity: 0.533, specificity: 0.743) and 8.0 mm for movement-evoked pain (AUC: 0.706, sensitivity: 0.700, specificity: 0.692). For satisfaction, the cutoff values were 9.0 mm for rest pain (AUC: 0.768, sensitivity: 0.571, specificity: 0.844) and 16.0 mm for movement-evoked pain (AUC: 0.907, sensitivity: 0.857, specificity: 0.833).
The cutoff points for rest pain and movement-evoked pain related to functional disability and patient satisfaction were both below 30 mm. This suggests that pain intensity scores lower than 30 mm may still be associated with considerable postoperative functional disability and dissatisfaction. Consequently, a reconsideration of the current CPSP criterion, which defines clinically significant pain as being above 30% intensity one year post-TKA, is necessary.
Instead of categorizing patients based solely on whether their pain intensity exceeds 30 mm on the VAS, there is a need to consider treatment for those with lower pain scores as well.
Chronic post-surgical pain
Cutoff value
