Background and Goal of Study: Incidence of persistent post-surgical pain (PPP) after total knee arthroplasty (painful prosthesis) is vaguely estimated1. Preoperative endogenous analgesia (EA) efficiency has been proposed as a valid tool to predict PPP after surgery2.
Our hypothesis suggests that patients with a preoperative incompetent EA are more prone to develop PPP. We are conducting a study aimed to establish the relationship between the preoperative efficiency of EA and persistent post surgical pain (PPP) after total knee arthroplasty (TKA). We show the descriptive preliminary data.
Materials and Methods: Prospective observational study in patients older than 18, scheduled for TKA. EA efficiency was measured during the month previous to surgery using quantitative sensory testing (QST)3. Variables: primary variable: 1. Presence of pain in a 0-10 numerical scale in the operated knee, 3 months after surgery. Secondary variables: 2. Preoperative EA efficiency measured with QST. 3. Presence of generalised hyperalgesia. 4. Preoperative pain measured by a 0-10 numerical scale.
Results and Discussion: Mean age of patients was 72 years old (95% CL 69-75), 70.4% of them female. The incidence of PPP at 3 months was 30%. 37% of patients showed a preoperative inefficient EA, and 25.9% generalised hyperalgesia. Percentage of patients with a preoperative pain intensity superior to 3 was 51.9% (rest) and 85.2% (movement). Anxiety and depression was present in a 23.1% and 25.9% of patients, respectively. Most of patients were treated with paracetamol/NSAID (55.6%) and only 14.8% with weak opioids. Interestingly, 29.6% of patients didn't follow any preoperative analgesic treatment.
Conclusion(s): Our preliminary data show a PPP incidence after orthopaedic surgery (TKA) similar to that of other better-studied surgeries. An inefficient preoperative EA was present in 37% of patients, probably at risk to develop PPP. The relevance of preoperative EA as a predictor of PPP after TKA will be established at the end of the study.
1. Puolakka PA, Rorarius MG, Roviola M, Puolakka TJ, Nordhausen K, Lindgren L. Eur J Anaesthesiol. 2010;27:455-60.
2. Yarnitsky D, Crispel Y, Eisenberg E, Granovsky Y, Ben-Nun A, Sprecher E, Best LA, Granot M. Pain. 2008 15;138:22-8.
3. Granot M, Weissman-Fogel I, Crispel Y, Pud D, Granovsky Y, Sprecher E, Yarnitsky D. Pain. 2008;136:142-9.
Supported by ISCIII Grant # PI12/01422