Development and Persistence of Suspected Neuropathic Pain After Total Knee Arthroplasty in Individuals With Osteoarthritis.

BACKGROUND

Despite the effectiveness of total knee arthroplasty (TKA) for osteoarthritis (OA), up to 20% will report knee pain 1 year after surgery. One possible reason is the development of neuropathic pain before or after TKA.

OBJECTIVE

To longitudinally describe suspected neuropathic pain in patients pre- and post-TKA and to explore relations between pre-TKA suspected neuropathic pain and post-TKA outcomes.

DESIGN

Prospective observational study.

SETTING

Participants were recruited from orthopedic surgery clinics prior to inpatient elective primary TKA.

PARTICIPANTS

Convenience sample of 135 patients were assessed for eligibility; 99 were enrolled and 74 completed the 6-month follow-up.

METHODS

Participants completed the Self-Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) and outcome measures at baseline (pre-TKA) and 1 and 6 months post-TKA by postal survey. Demographic variables included age, gender, and comorbidities. Descriptive statistics were calculated for the presence of suspected neuropathic pain at each assessment and course of outcomes for various suspected neuropathic pain trajectories. Further, t-tests were used to compare outcomes between those with and without suspected neuropathic pain at each assessment. Multiple linear regressions assessed the relationship between baseline suspected neuropathic pain and 6-month outcomes.

MAIN OUTCOME MEASUREMENTS

Intermittent and Constant Osteoarthritis Pain (ICOAP), Pain Catastrophizing Scale (PCS), and the Patient Health Questionnaire (PHQ-9) for depression.

RESULTS

Suspected neuropathic pain was present in 35.5% of pre-TKA patients, 39.0% at 1 month, and 23.6% at 6 months post-TKA. Those with suspected neuropathic pain had higher scores for ICOAP total pain (P = .05), pain catastrophizing (P < .01), and depression (P < .01) at each assessment. After adjusting for potential confounding, pre-TKA suspected neuropathic pain did not predict ICOAP total pain or PHQ-9 depression scores at 6 months.

CONCLUSIONS

Although 14% of individuals with knee OA had suspected neuropathic pain that persisted 6 months post-TKA and those with suspected neuropathic pain had higher levels of pain, catastrophizing, and depression, the clinical identification of neuropathic pain remains enigmatic. Preoperative suspected neuropathic pain, as measured by S-LANSS, may have limited prognostic value for post-TKA outcomes.

LEVEL OF EVIDENCE

II.