Patients With High Chronic Postoperative Knee Pain 5 Years After Total Knee Replacement Demonstrate Low-grad Inflammation, Impairment of Function, and High Levels of Pain Catastrophizing.

OBJECTIVES: Total knee replacement (TKR) normally provides improvements of physical function and reduces pain. However, ∼20% of the patients report chronic postoperative knee pain. The aims of the present study were to assess the pain, physical function, and physiological characteristics 5 years after TKR surgery. MATERIALS AND METHODS: Eighty patients were recruited 5 years after TKR and divided into 2 groups based on their average 24-hour knee pain intensity assessed on a visual analog scale (VAS 0 to 10) ("high pain group": VAS≥3; "low pain group": VAS<3). The patients completed the PainDETECT Questionnaire (PDQ), Oxford Knee Score (OKS), Pain Catastrophizing Scale, and Forgotten Joint Score-12. Furthermore, the patients underwent a clinical examination of the knees and high-sensitivity serum C-reactive protein was measured as an inflammatory marker. RESULTS: A total of 53% of the patients in the high pain group were not satisfied with the outcome, while only 11% of the patients in the low pain group was not satisfied, and the pain intensities in the 2 groups were 5.1 (4.6 to 5 to 6) and 1.1 (0.6 to 1.5) (P<0.001), respectively. Furthermore, the high pain group demonstrates worse scores in: Forgotten Joint Score-12 (P=0.001), OKS function (P<0.001), OKS pain (P<0.001), and Pain Catastrophizing Scale (P<0.001).The high pain group demonstrated increased level of high-sensitivity serum C-reactive protein (4.3 mg/L [3.2 to 5.5] vs. 1.7 mg/L [1.2 to 2.2], P<0.001), and decreased range of motion in the knee (110 vs. 119-degree range of motion, P=0.013). DISCUSSION: Patients with high chronic postoperative knee pain 5 years after TKR demonstrate decreased physical function, higher levels of catastrophizing thoughts, and increased levels of inflammation.

Investigating the Effect of Perioperative Chlorzoxazone on Acute Postoperative Pain After Total Hip and Knee Replacement Surgery.

BACKGROUND AND AIMS: Severe preoperative and acute postoperative pain have been associated with the development of chronic postoperative pain. Chlorzoxazone (a muscle relaxant) has been suggested to enhance acute postoperative pain recovery, but the lack of larger randomized controlled trials has, however, questioned the continued use. Despite this, chlorzoxazone is still used for acute postoperative pain management following total knee replacement (TKR) or total hip replacement (THR). The current randomized, double-blinded, placebo-controlled, parallel-group, clinical trial aimed to assess the effect of chlorzoxazone for postoperative pain management following TKR or THR. METHODS: A total of 393 patients scheduled for TKR or THR were included in the trial. Patients were assigned to 250 mg chlorzoxazone 3 times daily for the first 7 days postoperatively or to placebo. The primary outcome was pain after 5 m walk assessed 24 hours postoperatively. Secondary outcomes included changes in preoperative pain at rest, worst pain in the last 24 hours, and Oxford Knee or Hip Score compared with 12 months' follow-up. In addition, adverse events were assessed in the perioperative period. RESULTS: No significant differences were found for any of the outcome parameters after TKR or THR. As regards TKR or THR, no effects were demonstrated for pain after 5 m walk 24 hours after surgery (P>0.313), or for any of the secondary outcomes (P>0.288) or adverse events (P>0.112) in the group receiving chlorzoxazone compared with placebo. CONCLUSION: The current study demonstrated no analgesic effects of postoperative chlorzoxazone administration compared with placebo on acute or chronic postoperative pain 12 months following TKR and THR.

Presurgical Comorbidities as Risk Factors For Chronic Postsurgical Pain Following Total Knee Replacement.

OBJECTIVES: Chronic postsurgical knee pain (CPSP) is a burden for ∼20% of the patients following total knee replacement (TKR). Presurgical pain intensities have consistently been found associated with CPSP, and it is suggested that comorbidities are likewise important for the development of CPSP. This study aimed to identify presurgical risk factors for the development of CPSP 5 years after TKR on the basis of medical records containing information with regard to comorbidities. MATERIALS AND METHODS: Patients undergoing primary TKR surgery were contacted 5 years after TKR. Presurgical Knee Society Score and comorbidities were evaluated. Postsurgical knee pain at 5 years of follow-up was assessed on a Numeric Rating Scale (NRS, 0 to 10). Logistic regression models were utilized to identify patients with moderate-to-severe (NRS≥3) and mild-to-no (NRS<3) CPSP at 5-year follow-up. Odds ratio (OR) for significant factors was calculated. RESULTS: A total of 604 patients were contacted, 493 patients responded, 352 patients provided a completed questionnaire. A total of 107 patients reported NRS≥3 at follow-up. Significant presurgical factors associated with CPSP were fibromyalgia (OR=20.66; P=0.024), chronic pain in body parts other than the knee (OR=6.70; P=0.033), previous diagnosis of cancer (OR=3.06; P=0.001), knee instability (OR=2.16; P=0.021), younger age (OR=2.15; P=0.007), and presurgical knee pain (OR=1.61; P=0.044). Regression analysis identified 36 of 107 (33.6%) patients with CPSP on the basis of presurgical factors, and 231 patients (94.3%) without CPSP were classified correctly. DISCUSSION: The current study found that a variety of presurgical clinical factors can correctly classify 33.6% of patients at risk for developing CPSP 5 years following TKR.