Dry needling is one of many intervention methods physical therapists can employ to treat neuromuscular and musculoskeletal conditions. Dry needling effects help improve pain, disability, and function. In order to effectively dry needle a specific body region, a therapist uses a thin filiform needle to penetrate the skin into underlying muscle and connective tissue with the goal of eliciting neurophysiological effects that decrease local and central pain responses(Flannagan, 2013). The depth of needle insertion, movement of the needle as well as the amount and force of stimulation applied, and the elicitation of alocal twitch response, or involuntary spinal reflex resulting in a localized contraction of affected muscle fibers, are all important factors that influencethe efficacy of treatment (Cagnie et al., 2013). Dry needling with electrical stimulation can either be performed manually by a therapist pistoning the needle in and out of underlying tissue or electrophysiologically by connecting the needles to an electrical stimulation unit.
Myofascial pain syndrome is a common widespread diagnosis used to classify patients that have pain of musculoskeletal origin associated with active and latent myofascial trigger points, taunt bands of skeletal muscle characterized by hyperirritability that are often the target of dry needling treatment. It is believed that these taut bands develop as a result of excessive acetylcholine release in the neuromuscular junction that cause sustained sarcomere contractures and resultant ischemia and hypoxiain the tissue. Active trigger points elicit pain in response to movement,stretch, or compression whereas latent trigger points elicit pain with compression only (Cagnie et al., 2013). Research suggests that latent trigger points demonstrate distinct physiological properties from healthy muscle tissue,including decreased oxygen saturation, decreased pH with acidic levels below 5 that can cause increased nociceptive activation, and hypersensitivity tohypertonic saline and glutamate which affects central sensitization (Dommerholt& Gerwin, 2015).
Central sensitization can be described as abnormal central nervous system processing of sensory input in the brain and spinal cord that perpetuates pain and dysfunction and can result in hyperalgesia, or increased pain sensation,and allodynia, or pain elicited by non painful stimuli (Cagnie et al., 2013).Patients with chronic pain associated with central sensitization, however,demonstrate altered inhibitory pain control referred to as conditioned pain modulation, where in the presence of two noxious stimuli, the second painful stimulus can lead to inhibition of the first painful stimulus. It is hypothesized that dry needling can stimulate nociceptive fibers intramuscularly and activate inhibitory dorsal horn interneurons that inhibit early nociception, or pain processing, and that sustained trigger point pressure can eliminate the contracture, restore oxygen and pH levels, and promote angiogenesis, vasodilation, and altered glucose metabolism in hypoxic tissues(Cagnie et al., 2013; Dommerholt & Gerwin, 2015). Common conditions tha thave shown to benefit from dry needling treatment include cervicogenic headaches, tennis elbow, shoulder impingement, plantar fasciitis, and hip and knee pain (Flannagan, 2013).
E-stim Dry Needling for Shoulder Pain
In addition to causing increased pain local to the muscle in which they form,trigger points can also cause referred pain into more distal parts of the body due to altered pain processing pathways and central sensitization. Pain in the muscles of the neck and shoulder including the scalenes, subscapularis,supraspinatus and infraspinatus, for example, can refer pain to the lateral elbow. Ebrahimian and colleagues (2015) investigated whether the addition of dry needling to these muscles was superior to conventional treatment consisting of ultrasound, burst TENS, hotpack, and wrist extensor exercises for female patients with lateral epicondylitis (tennis elbow). The researchers found that grip strength and pain pressure thresholds significantly improved in the intervention group following 6 sessions compared to controls, providing further support for the clinical utility of dry needling for altering nociceptive pathways and the potential for improving pain and dysfunction in referral areas other than myofascial trigger points alone.
Dommerholt, J, & Gerwin, RD. (2015). A critical evaluation of Quintner etal: Missing the point. Journal of Bodywork & Movement Therapies;19:193-204.
Ebrahimian, M, Kheradmandi, A, Ghaffarinejad, F, Ehyaii, V, & Farazdaghi,MR. (2015). The Effect of Dry Needling of the Trigger Points of Shoulder Muscles on Pain and Grip Strength in Patients with Lateral Epicondylitis: APilot Study. Journal of Rehabilitation Sciences and Research;2(3):58-62.