Quantitative sensory testing in Achilles tendinopathy

Abstract

Introduction: Achilles tendinopathy (AT) is a prevalent injury in the adult population, causing persistent pain and disability. Although, recent literature proposes peripheral and central nervous system alterations as one of the underlying processes of persistent pain in tendinopathies, the evidence in people with AT is limited. The primary aim of this study was to assess differences in detection and pain threshold between people with AT and healthy controls. Methods: Thirty people with a clinical diagnosis of AT and 11 healthy controls were recruited. All participants were free from other musculoskeletal injuries, diabetes or other systemic conditions. Quantitative sensory testing (QST) measures were performed by an assessor blinded to their condition. Testing in patients and controls was performed at two standardized locations: the mid-Achilles tendon (most affected or randomly allocated leg respectively) and the lateral elbow (side randomly selected). We determined thermal detection and pain thresholds, thermal sensory limen, mechanical detection thresholds to von Frey filaments and vibration, mechanical pain thresholds to pinprick stimuli and blunt pressure, stimulus-response-functions for pinprick and dynamic mechanical allodynia (pain to light touch), and wind up ratio using repetitive pinprick stimulation. Participants also completed VISA-A, Health-related Quality of Life (EQ-5D), Hospital Anxiety and Depression Scale (HADS), Active Australia and Mental Toughness (MTQ-48) questionnaires. ANCOVA was performed to compare groups adjusting for sex, age and BMI. Results: There were no significant differences for age and sex between the AT group (mean age 45.7 years, range 21–63, 43% female) and the controls (mean age 40.9 years, range 19–68, 46% female). Body mass index was greater in the AT group (BMI 28.3 kg/m2; SD 5.4) compared to the controls (BMI 23.4 kg/m2; SD 2.7, P < 0.005). Those with AT had an average VISA-A score of 57/100, average duration of symptoms of 38.6 months, present at mid-tendon (73%) or insertional (37%) regions. Quality of life was significantly lower in the AT group (mean: 0.74; SD 0.06) compared to the control group (mean 0.96; SD 0.08, P < 0.001). The AT group did not show significant differences compared to the controls on any of the QST measures at either site. Discussion: Based on the limited sample, this study did not find significant peripheral- or central somatosensory changes in people with AT compared to healthy controls. This is in contrast with other studies that found evidence of peripheral sensitization in people with AT.