Up to 77% of patients with chronic shoulder pain have a trigger point (TrP) in the infraspinatus muscle. These TrPs can lead to pain, limitation of activities and reduced quality of life. Dry needling (DN) is gaining popularity as a treatment for TrPs in physiotherapy. However, its clinical effects remain poorly understood mechanistically and its neurophysiological effects little studied.

The primary objective of this study is to determine the feasibility of a larger scale study.

The secondary objective of this study is to to explore the immediate neurophysiological, biomechanical and clinical effects of DN and sham needling when applied to TrP of the infraspinatus muscle in people with chronic non-traumatic shoulder pain.

Methodology

In this randomized, double-blind, parallel-group trial, twenty adults with chronic non-traumatic shoulder pain and with a infraspinatus TrP will be recruited according to established criteria. Participants will be randomized into two groups: one group (n = 10) receiving a DN in the infraspinatus TrP and another group (n = 10) receiving a sham needling.

Recruitment strategies

Recruitment will be done through posters that will be posted on bulletin boards of the Faculty of Medicine and Health Sciences of the University of Sherbrooke and in physiotherapy clinics in the region. The persons interested will be invited to contact the research assistant in charge of the study to verify their eligibility to participate.

Data collection procedure

The experimental procedure will take place in a laboratory located at the Research Center on Aging in Sherbrooke, Quebec, Canada. Upon arrival, individuals will be greeted by a research assistant. Verification of the presence of TrP in the infraspinatus to confirm eligibility to participate will be carried out by a physiotherapist with more than 20 years of experience in the identification of TrPs and with the application of DN, according to the following procedure: Participants will be asked to lie in a decubitus lateral position on a treatment table and on the asymptomatic side. The upper arm will be supported on a box placed in front of them, so that the muscles can be relaxed, but the arm will be positioned in a and have a slight horizontal adduction to slightly stretch the fibers of the infraspinatus muscle. Manual palpation with flat fingers and perpendicular to the fibers will be used to identify the tight muscle band. Once a tight muscle band has been identified, the physiotherapist will search within this band for a contraction node, namely the TrP. Once she had identified this TrP with a non-toxic black Sharpie pencil, she will validate with the patient that the compression of this TrP reproduces local or referred pain. This pain should correspond to the pain patterns known to the infraspinatus according to Simons and Travell, 1999 and reproduce the pain known by the patient. This pain should be at least a 1/10 intensity on the visual analog scale (VAS). Ineligible participants will receive advices from the physiotherapist as well as a prescription for exercises related to their condition and a list of physiotherapists they can consult.

The research assistant will explain the nature of the project to the selected participants, he will make sure that the participants have no contraindications to receive DN and/or for transcranial magnetic stimulation (TMS) examination, and he will obtain written informed consent. Participants will then complete a questionnaire used to collect baseline medical information.

Intervention (DN and Sham)

DN will be performed by a certified clinician, experienced with the technique. She will explain the purpose of the intervention and she will review the contraindications and precautions for DN to ensure that the procedure is safe. The technique used is recommended by l'Ordre professionnel de la physiothérapie du Québec (OPPQ). The clinician will insert a sterile disposable acupuncture needle, OPTIMED (non-silicone), 40 mm x 0.30 caliber. The direction of the needle will be slightly oblique, directly in the TrP and in the direction of the muscle fibers. The production of a twitch is expected, gliding and rotation of the needle may be performed to produce this effect, if necessary. The needle will be removed after the twitch. The same procedure will be used for the sham group, except that the needle will be inserted at the subcutaneous level, at the depth of the superficial adipous tissues

Inclusion Criteria:

1. Unilateral, chronic non-traumatic shoulder pain (VAS ≥ 2/10; >3 months)
2. Localized pain in the shoulder region or referred according to the territory of the infraspinatus (Travell and Simons, 1999)
3. Presence of a palpable nodule inside a tight muscle band reproducing the patient's pain

Exclusion Criteria:

1. Cancer or metastasis in organs or tissues above the pelvis (< 5 years)
2. Shoulder capsulitis
3. Shoulder, thorax or mastectomy surgeries
4. Shoulder bone fracture (< 6 months)
5. C4-C5 or C6 radiculopathy
6. Osteoporosis or excessive atrophy of the infraspinous fossa (infraspinatus <10 mm)
7. Body mass index (BMI) > 28

Exclusion (TMS security):

1. Pregnant woman
2. Neurological, psychiatric or epilepsy conditions
3. Implants (e.g. Neurostimulator, pacemaker, cerebral aneurysm clip, screw or plate), metallic foreign body in the eye
4. Head trauma with loss of consciousness