Description of Intervention
Transcutaneous electrical nerve stimulation (TENS) is a therapeutic modality in which a low-voltage electric current is applied to treat pain. Treatment involves careful placement of electrodes on the skin, either at or near nerves associated with the painful area, which are connected to the TENS unit. Once the electrodes are placed in the correct location, the unit is turned on and an electric current is sent to the electrodes. Each treatment session is highly adjustable, as the therapist or patient can control the pulse width, intensity, and/or frequency, depending on the patient’s presentation. Low frequencies (<10Hz) combined with high intensity will produce muscle contractions, while high frequencies (>50 Hz) combined with low intensity will lead to paresthesia without muscle contractions.1,2
TENS is a noninvasive and easy-to-use modality, with some devices being small enough to fit in a pocket. TENS units are also titratable, which allows for a high degree of user tolerance with very few side effects. There are two main two theories about how TENS works. According to one theory, its electric current stimulates nerve cells that block the transmission of pain signals, which modifies the patient’s perception of pain. The other theory suggests that stimulating nerves raises the body’s level of endorphins, which then block the perception of pain.1-3
Indications for Intervention
TENS may be indicated for any injury or condition that is associated with acute or chronic pain in the hand, wrist, or elbow. Patients recovering from surgery may also be candidates for TENS therapy.
Diagnosis
- Ask the patient to describe their medical history, including any recent injuries to the hand/fingers, wrist, or elbow, or any recent surgeries performed.
- Ask if the patient has any comorbidities, including smoking, diabetes, or osteopenia.
- Perform a physical examination of the area of interest. If range of motion (ROM) is impaired, measure the active and passive ROM of any involved joint(s) and compare these measurements to the contralateral side.
- Ask the patient to rate their pain on the visual analogue scale (VAS) or a similar outcome measure.
- Consider using the DASH (Disabilities of the Arm, Shoulder, and Hand) questionnaire to evaluate the patient’s subjective impairment of the upper extremity.
- If the patient presents with pain anywhere in the upper extremity, consider utilizing TENS therapy.
Intervention Options1,2,4
TENS should be integrated into a comprehensive, individualized treatment program designed by a physical therapist or hand therapist. Depending on the patient’s diagnosis, the program may also include strengthening exercises, stretching exercises, manual therapy, functional training, and/or other therapeutic modalities to alleviate symptoms and increase physical function.
TENS can be performed either under the care of a therapist at a clinic or by the patient at their convenience; however, the patient should not use TENS while operating heavy machinery, driving, bathing, showering, or swimming. Electrodes should be placed ≥1 inch apart in the appropriate dermatomal region of the targeted pain, and the underlying skin must have intact sensation. The exact placement of the electrodes should be based on the target muscle or muscle group, either independently or in relation to other muscles. The main configuration patterns for electrodes are as follows:
- Unilateral: stimulates one limb or half of a muscle pair
- Bilateral: stimulates both limbs or both halves of a muscle pair
- Unipolar: only one of two essential leads and the electrode provide stimulation to the target area
- Quadripolar: involves two sets of electrodes, each originating from its own channel
After powering on the TENS unit, set the parameters according to the manufacturer’s recommendations and based on the patient’s condition and tolerance. For example, TENS treatment for a patient with complex regional pain syndrome affecting the forearm may involve the following parameters: frequency of 100 Hz, pulse duration of 50–100 ms, and amplitude that does not cause discomfort or muscle contraction.4 For lateral epicondylitis, a lower frequency of 3–20 Hz may be appropriate, and the amplitude should be increased to a point where the patient is most comfortable while visible muscle contractions are occurring.2
Each TENS session lasts for about 15–20 minutes, and the therapist may recommend 3–4 sessions per week for several weeks, depending on the treatment plan.
