From the Journals

New models predict post-op pain in TKA



Researchers have developed models that successfully predict persistent postoperative pain (PPP) after total knee arthroplasty (TKA) two-thirds of the time. Major risk factors include pre-operative pain, sensory testing results, anxiety and anticipated pain.

“The results of this study provide some basis for the identification of patients at risk of PPP after TKA and highlight several modifiable factors that may be targeted by clinicians in an attempt to reduce the risk of developing PPP,” write the authors of the study, which appeared in the British Journal of Anaesthesia.

The authors, led by David Rice, PhD, of Auckland University of Technology, note that moderate to severe levels of PPP affect an estimated 10%-34% of patients at least 3 months after TKA surgery. “PPP adversely affects quality of life, is the most important predictor of patient dissatisfaction after TKA, and is a common reason for undergoing revision surgery.”

The researchers, who launched the study to gain insight into the risk factors that can predict PPP, recruited 300 New Zealand volunteers (average age = 69, 48% female, 92% white, average body mass index [BMI] = 31 kg/m2) to be surveyed before and after TKA surgery. They monitored pain and tracked a long list of possible risk factors including psychological traits (such as anxiety, pain catastrophizing and depression), physical traits (such as gender, BMI), and surgical traits (such as total surgery time).

At 6 months, 21% of 291 patients reported moderate to severe pain, and the percentage fell to 16% in 288 patients at 12 months.

The researchers developed two models that successfully predicted moderate-to-severe PPP.

The 6-month model relied on higher levels of preoperative pain intensity, temporal summation (a statistic that’s based on quantitative sensory testing), trait anxiety (a measure of individual anxiety level), and expected pain. It correctly predicted moderate to severe PPP 66% of the time (area under the curve [AUC] = 0.70, sensitivity = 0.72, specificity = 0.64).

The 12-month model relied on higher levels of all the risk factors except for temporal summation and correctly predicted moderate-to-severe PPP 66% of the time (AUC = 0.66, sensitivity = 0.61, specificity = 0.67).

The researchers noted that other research has linked trait anxiety and expected pain to PPP. In regard to anxiety, “cognitive behavioral interventions in the perioperative period aimed at reducing the threat value of surgery and of postoperative pain, improving patients’ coping strategies, and enhancing self-efficacy might help to reduce the risk of PPP after TKA,” the researchers write. “Furthermore, there is some evidence that anxiolytic medications can diminish perioperative anxiety and reduce APOP [acute postoperative pain] although its effects on PPP are unclear.”

Moving forward, the authors write, “strategies to minimize intraoperative nerve injury, reduce preoperative pain intensity, and address preoperative psychological factors such as expected pain and anxiety may lead to improved outcomes after TKA and should be explored.”

The Australia New Zealand College of Anesthetists and Auckland University of Technology funded the study. The study authors report no relevant disclosures.

SOURCE: Rice D et al. Br J Anaesth 2018;804-12. doi:

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