IMPLICATIONS OF BRAIN ACTIVITY IN THE TREATMENT DECISION OF KNEE OSTEOARTHRITIS

BackgroundChronic pain related to knee osteoarthritis (KOA) is a common health problem and functional magnetic resonance imaging (fMRI) is a useful technique which can determine different brain activation (1).ObjectivesThe main purpose of our study was to observe whether there is different risk to central sensitization and different brain activation in patients with KOA according to the treatment followed (conservative (CNV) Vs. total knee replacement (TKR))MethodsPatients diagnosed of primary KOA following a CNV treatment or undergoing TKR were recruited. The two groups were matched by age, sex and BMI. Clinical central sensitization was considered if patients presented spread tenderness, evaluated with an algometer, in more than 1 site of the extended peripatellar map (2) (notice that pain at points 3, 7 and 8 were not counted) fMRI testing involved pressure painful stimulation to the articular interline and to a commonly sensitized site (tibial surface, point 10).To evaluate the associations between central sensitization and the risk to undergo a TKR; logistic regression was performed to estimate OR and 95% confidence intervals (95%CI). Models were adjusted by sex, age and BMI (R (R v.3.5.2).Whole-brain activation maps were compared between groups using Statistical Parametric Mapping software (SPM12 http://www.fil.ion.ucl.ac.uk/spm).ResultsWomen have a significant higher risk to present central sensitization than men (OD 12,11 (95% CI 4,32-33,95) p-value:2,09*106), but no differences were observed between CNV and TKR group (OR TKR 0,69 (95% CI 0,24-1,98)) (Table 1). The differences observed in brain activation between the treatment groups in the interline fMRI test (point 7) did not correspond to any specific brain area. However, TKR group showed a higher activation that implicated the region of the amygdala and anterior hippocampus during the tibial fMRI test (point 10).Table 1.Central sensitization Odds Ratio (OR) with 95% Confidence Interval (95%CI)O.R. (95% CI)p-valueTreatment0.69 (0.24- 1.98)0,494Sex12.11 (4.32- 33.95)2,09*10-6Age0.72 (0.26- 1.97)0,525BMI1.88 (0.69- 5.17)0,219ConclusionPresenting central sensitization is not a risk for KOA patients to undergo a TKR, but the mechanism underlaying sensitization in both treatment groups might be different, with amygdala playing an important role in TKR patients. The amygdala is an important element of the brain systems that both express emotions and modulate pain. The activation of the amygdala in response to pressure stimulation on a sensitized knee site is interpreted as a failure of the descending pain inhibitory systems, and the occurrence of a major emotional response during the painful experience in patients that ultimately received TKR.References[1]Pujol, J. et al., 2017. Brain imaging of pain sensitization in patients with knee osteoarthritis. Pain, 158(9), pp.1831–1838.[2]Arendt-Nielsen L, Nie H, Laursen MB, Laursen BS, Madeleine P, Simonsen OH, Graven-Nielsen T. Sensitization in patients with painful knee osteoarthritis. Pain 2010;149:573-8Extended peripatellar map including the points tested for tenderness, and brain areas differently activated between both treatments groups during painful stimulation to point 7 (interline) and point 10 (tibial surface, a commonly sensitized site).Disclosure of InterestsNone declared