Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Role of Central Sensitization in Persistent Pain Post-Knee Replacement: The MOST Study.

Neogi3,  Tuhina, Niu4,  Jingbo, Frey-Law9,  Laura, Arendt-Nielsen1,  Lars, Singh8,  Jasvinder, Scholz2,  Joachim, Woolf2,  Clifford

Aalborg University, Denmark
Boston Childrens Hospital
Boston Univ Schl of Med, Boston, MA
Boston Univ School of Medicine, Boston, MA
Boston University School of Medicine, Boston, MA
UCDavis, Sacramento, CA
UCSF
University of Alabama at Birmingham, Minneapolis, MN
University of Iowa

Purpose:

Pain persists post-knee replacement (KR) in ~20–30% of patients. The reason for this pain persistence is unclear. One possibility is that long-standing mechanical and inflammatory stimuli in osteoarthritis (OA) can lead to changes in the peripheral and central nervous system, with subsequent peripheral and central sensitization resulting in heightened pain sensitivity. We hypothesized that central sensitization may be associated with persistent pain post-KR.

Methods:

The Multicenter Osteoarthritis (MOST) Study is cohort study of persons with or at high risk of knee OA. This analysis was limited to those with KR at any time during the study, confirmed by medical records and/or x-ray. At the 60-month clinic visit, participants had knee x-rays, answered a knee-specific WOMAC pain questionnaire, and had temporal summation (TS) assessed at the wrist. TS is an augmented pain response to repetitive mechanical stimuli thought to reflect central sensitization. TS was defined as being present when, after touching the skin with a 60g monofilament repeatedly at a frequency of 1Hz for 30 seconds, the subject reported increased pain at the site being tested. For cross-sectional analyses, we defined presence of knee pain (of the KR knee) as moderate or greater pain vs none/mild based on the maximal score of any of the 5 WOMAC pain questions. For longitudinal analyses, we defined knee pain improvement post-KR as a decrease of >=5.6/20 in WOMAC pain (of the KR knee) from pre- to post-KR (Escobar, OA&C, 2007) using the closest clinic visits to those time-points. We examined the relation of presence of TS with presence of knee pain among all persons with KR, and with having pain improvement post-KR among those with a new KR during follow-up, using Poisson regression with GEE to obtain prevalence ratios (cross-sectional) and risk ratios (longitudinal). All analyses were adjusted for age, sex, BMI, depressive symptoms, race, clinic site, and time since KR. Only the cross-sectional analysis could be adjusted for catastrophizing due to unstable estimates in the longitudinal analysis.

Results:

There were 114 subjects with 151 knees that had a KR at baseline (22) or during follow-up (129) who also had TS measured at the 60-month visit (mean age 71.2, mean BMI 32.9, 74.6% female, mean time since KR 3.7 yrs (range <1–15 yrs)). Maximal WOMAC knee pain was rated as >=moderate in 26.5% of KR knees. Cross-sectionally, presence of TS was associated with 2.06 times higher prevalence of knee pain compared with no TS (95% CI 1.12–3.79, p=0.02). Pain improvement from pre- to post-KR occurred in 42% of KR knees. In the longitudinal analysis, presence of TS was associated with a 67% lower chance of having a pain improvement post-KR (RR 0.33, 95% CI 0.17–0.63, p=0.0009).

Conclusions:

Temporal summation was associated with presence of, and less improvement in, post-KR pain. Central sensitization may therefore partially explain why some individuals have pain persistence post-KR. These findings suggest that consideration for performing KRs earlier in the course of OA, when central sensitization is still potentially reversible, may be warranted.

To cite this abstract, please use the following information:
Neogi, Tuhina, Niu, Jingbo, Frey-Law, Laura, Arendt-Nielsen, Lars, Singh, Jasvinder, Scholz, Joachim, et al; Role of Central Sensitization in Persistent Pain Post-Knee Replacement: The MOST Study. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1385
DOI: 10.1002/art.29151

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