Microcurrent Therapy in the Management of Chronic Tennis Elbow
Microcurrent therapy (MCT) involves the application of sub-sensory electric current and can promote tissue repair, possibly by mimicking endogenous electrical cues for healing. It has been used successfully to treat recalcitrant bone fractures and skin ulcers, but its effects on other forms of tissue have received little attention. This study aimed to investigate the potential of MCT to promote healing and alleviate symptoms in a selected soft connective tissue disorder. A systematic review of human studies involving MCT for soft connective tissue damage was conducted. A survey of 93 musculoskeletal physiotherapists was used to help select a common, recalcitrant disorder to treat with microcurrent in a clinical trial. Novel sonographic scales to quantify tendon structural abnormality and tissue healing were developed, and their measurement properties evaluated along with several clinical and patient-rated outcome measures. Two preliminary clinical trials, involving 62 people with the selected disorder – chronic tennis elbow - were conducted, comparing four different types of microcurrent applied daily for 3 weeks. The review found fair quality evidence that certain forms of MCT can relieve symptoms, and low quality evidence that they can promote healing, in several soft connective tissue disorders, including those affecting tendons. Optimal treatment parameters are unknown. In the survey, clinicians identified frozen shoulder, plantar fasciitis and tennis elbow as particularly problematic, and tennis elbow was selected for treatment in the trials. The sonographic scales of hyperaemia had fair-to-good inter-rater and test-retest reliability. Minimum Detectable Change values are calculated for the sonographic scales and for pain-free grip strength measurements. The trials suggest that monophasic microcurrent of peak amplitude 50 µA applied for 35 hours was most effective in symptom alleviation, with a 93% treatment success rate three months after treatment. By final assessment, pain-free grip strength increased by 31% (95%CI:5,57%), pain measured on a multiple-item questionnaire reduced by 27% (95%CI:16,38%) and patient-rated functional disability by 26% (95%CI:14,28%). MCT with a current amplitude of 500 µA was significantly less effective, and varying the waveform appeared less important in determining outcomes. Differences between groups were non-significant on several measurs, though there was a risk of type II error in the tests used. No significant differences between any groups were seen in sonographic assessments, although consistent patterns in bloodflow chage suggested that MCT may modulate hyperaemia levels. Higher baseline hyperaemia was associated with sustained falls in hyperaemia levels after treatment, and with improved clinical outcome. MCT’s analgesic effect does not rely on sensory stimulation, and further investigation of its influence on tendinous blood flow and vascularity, or on the local biochemical milieu, may help elucidate its mechanism of action. On the basis of this investigation, a fully-powered controlled clinical trial is justified. A protocol, combining MCT with an exercise programme, is proposed.