Chronic postoperative pain after total knee replacement (TKR) in knee osteoarthritis (KOA) implies clinical challenges. Widespread hyperalgesia, facilitated temporal summation of pain (TSP), and impaired conditioned pain modulation (CPM) have been found in painful KOA. This exploratory study investigated postoperative pain relief 12 months after TKR in 4 subgroups of patients preoperatively profiled by mechanistic quantitative sensory testing. In 103 patients with KOA, pressure pain detection threshold (PDT) and tolerance thresholds (PTT) were assessed at the lower leg using cuff algometry. Temporal summation of pain was measured as an increase in pain intensity scores during 10 repeated (2 seconds intervals) painful cuff stimuli. Conditioned pain modulation was calculated as the relative increase in PDT during painful conditioning stimulation. The grand averages of TSP and CPM were calculated and values below or above were used for subgrouping: facilitated TSP/impaired CPM (group A, N = 16), facilitated TSP/normal CPM (group B, N = 15), normal TSP/impaired CPM (group C, N = 44), and normal TSP/normal CPM (group D, N = 28). Clinical VAS pain intensity scores were collected before and 12 months after TKR surgery and the pain relief calculated. Less pain relief was found in group A (52.0% ± 14.0% pain relief) than in group B (81.1% ± 3.5%, P = 0.023) and group C (79.6% ± 4.4%, P = 0.007), but not group D (69.4% ± 7.9%, P = 0.087). Low preoperative PDT was associated with a less postoperative pain relief (R = −0.222, P = 0.034), whereas TSP or CPM alone showed no associations with postoperative pain relief. This explorative study indicated that patients with osteoarthritis with facilitated TSP together with impaired CPM are more vulnerable to experience less pain relief after TKR.
Patients with knee osteoarthritis with low conditioned pain modulation and high temporal summation have more pain 12 months after total knee replacement surgery.
aSMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark
bCenter for Neuroplasticity and Pain (CNAP), SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark
cOrthopaedic Surgery Research Unit, Aalborg University Hospital, Aalborg, Denmark
Corresponding author. Address: SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Fredrik Bajers Vej 7 D3, DK-9220 Aalborg, Denmark. Tel.: +45 9940 8831; fax: +45 9815 4008. E-mail address: firstname.lastname@example.org (L. Arendt-Nielsen).
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
Received December 07, 2015
Received in revised form January 23, 2016
Accepted February 09, 2016