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Purpose: Osteoarthritis of the knee (KOA) leads to severe and often debilitating symptoms such as pain, constrained movement, immobility, and reduced quality of life and the incidence is still increasing. Previous randomized controlled trials (RCT) have shown a significant pain reduction using leeches for the treatment of KOA. The way how leeching improves the symptoms of KOA is still unclear. The aim of this study was to pilot if the measurement of somatosensory function is a way to investigate the mechanism of action of leech therapy treating KOA.
Methods: 42 patients with bilateral KOA participated in the case series pilot study. Neurophysiological measures of local pain perception at the knee were subtests obtained from the QST (Quantitative sensory testing) protocol: MDT (mechanical detection threshold), VDT (Vibration detection threshold) and PPT (Pressure pain threshold). All QST subtests were obtained at defined areas of both knees and at the hands as a control area for systematic treatment effects. Moreover, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was obtained before and seven days after therapy in addition to pain measured by a visual analogue scale (VAS, day 0 and day 7). Based on the QST results a case number was calculated.
Results: MDT was generally lowered after treatment indicating a better discrimination of mechanical stimuli. The effect was significant (p=0.008) for the area close to the pain. In order to prove the standardized difference with a statistical power of β=80% in a following RCT 170 patients are needed. Whereas a statistical power of β=80% requires 228 patients. There was a general significant treatment effect for VDT resulting in less vibration discrimination for all sites (p<0.05) with the exception of the most affected knee. No consistent effects were seen for PPT. Clinical pain improved significantly (WOMAC global, pain, function, and VAS: p<0.001).
Discussion: Due to the study design it can not be concluded that leeching improves somatosensory function. However, there are essential findings concerning feasibility, methodologies and results along with the corresponding case number calculation. These findings can then be implemented in a following RCT.