Focused Shockwave Therapy for Neck and Shoulder Myofascial Pain

Effectiveness of Second-Generation Focused Extracorporeal Shockwave Therapy Combined With Ultrasonographic Assessment in Myofascial Pain Syndrome of the Neck and Shoulder: A Pilot Randomized Controlled Trial

Myofascial pain syndrome of the neck and shoulder is a common condition characterized by persistent muscle pain, tenderness, stiffness, and limitations in daily activities. Focused extracorporeal shockwave therapy is a noninvasive treatment that may reduce pain and improve muscle function. However, additional clinical evidence is needed regarding the effectiveness of second-generation focused shockwave therapy and whether ultrasound imaging can objectively detect changes in muscle function after treatment.

This pilot randomized controlled trial will enroll 60 adults with chronic neck and shoulder myofascial pain syndrome. Participants will be randomly assigned to either a focused shockwave therapy group or a home-based neck exercise group.

Participants in the focused shockwave therapy group will receive one treatment session per week for three consecutive weeks. Participants in the control group will perform a standardized home exercise program designed to improve neck mobility and reduce muscle tightness.

Assessments will be performed before the intervention, after the intervention, and at follow-up. Study outcomes will include pain intensity measured using the Visual Analogue Scale, neck-related disability measured using the Neck Disability Index, pressure pain threshold measured using an algometer, and upper trapezius muscle thickness and contraction-related changes measured using ultrasound imaging.

The primary objective is to determine whether focused shockwave therapy is more effective than a home-based neck exercise program in reducing pain and improving neck function. The study will also evaluate whether ultrasound-derived muscle measurements are associated with changes in pain, pressure sensitivity, and functional disability.

Myofascial pain syndrome of the neck and shoulder is a common musculoskeletal pain condition characterized by painful and sensitive areas within tight bands of muscle, commonly referred to as myofascial trigger points. These trigger points frequently occur in the upper trapezius and levator scapulae muscles and may cause localized pain, referred pain, muscle stiffness, reduced neck movement, sleep disturbance, and limitations in work and daily activities. Persistent symptoms may also contribute to altered posture, reduced muscle performance, and decreased quality of life.

Focused extracorporeal shockwave therapy is a noninvasive treatment that delivers acoustic energy to painful soft tissues. Proposed effects include improved local circulation, modulation of pain-related nerve signaling, reduction of abnormal muscle tension, and stimulation of tissue repair. Second-generation focused shockwave systems use piezoelectric technology to provide a stable and precisely focused energy field. This technology may be particularly suitable for treating relatively superficial muscles, such as the upper trapezius.

Ultrasound imaging provides a noninvasive method for evaluating muscle structure and function. In addition to measuring resting muscle thickness, ultrasound can be used to assess changes in muscle thickness during different levels of contraction. These measurements may provide objective information regarding muscle function that cannot be obtained from pain questionnaires alone. In this study, ultrasound imaging will be used only as an outcome assessment tool and will not be used to guide the location of shockwave treatment.

This study is a pilot randomized controlled trial designed to evaluate the effectiveness of second-generation focused extracorporeal shockwave therapy in adults with chronic neck and shoulder myofascial pain syndrome. Approximately 60 participants will be enrolled and randomly assigned in a 1:1 ratio to either a focused shockwave therapy group or a home-based neck exercise group.

Eligible participants will be adults older than 20 years who have had nonspecific neck and shoulder pain for at least 3 months. The pain must primarily arise from muscles and soft tissues in the upper trapezius or levator scapulae region, as determined by a physical medicine and rehabilitation physician. Participants must also have a Neck Disability Index score greater than 5 and must not have recently received pain medication, muscle relaxants, injections, physical therapy, or other related treatment.

Individuals will be excluded if their neck or shoulder pain is primarily caused by a neurologic disorder, cervical radiculopathy, clinically significant cervical degenerative joint disease, rheumatic disease, previous head or neck trauma, cervical spine surgery, or whiplash injury. Individuals with contraindications to shockwave therapy will also be excluded. These contraindications include pregnancy, malignancy, bleeding disorders, use of anticoagulant medication, acute infection or inflammation at the treatment site, an implanted cardiac pacemaker or defibrillator, or another condition considered unsuitable for shockwave therapy by the study physician.

Participants assigned to the focused shockwave therapy group will receive treatment to clinically identified tight and painful regions of the upper trapezius and levator scapulae muscles. Treatment will be administered once weekly for 3 consecutive weeks using a second-generation Richard Wolf PiezoWave focused shockwave system. Each session will include approximately 3,000 shockwave pulses. The treatment depth will generally be set between 20 and 25 mm, the treatment frequency will be approximately 2 to 4 Hz, and the energy level will begin at a lower setting and may be gradually increased according to the participant's clinical response and tolerance. Treatment will be performed by a qualified member of the rehabilitation team in a designated treatment area.

Participants assigned to the control group will receive instruction in a standardized home-based neck exercise program for 3 weeks. The program is intended to improve neck mobility, reduce muscle tightness, and maintain flexibility of the neck and shoulder muscles. It will include movements in cervical flexion, extension, right and left rotation, right and left lateral flexion, and upper cervical rotation performed with the neck in a flexed position. Participants will receive initial instruction and correction from a qualified physical therapist, together with written educational materials. Adherence and difficulties with the exercises may be monitored through telephone or in-person follow-up.

Clinical assessments will be performed before the intervention, after completion of the intervention period, and at the scheduled follow-up visit. The assessments will include both patient-reported and objective measures.

Pain intensity will be measured using the Visual Analogue Scale. Participants will indicate the intensity of their neck and shoulder pain on a 100-mm line ranging from no pain to the worst imaginable pain.

Neck-related functional limitation will be evaluated using the Neck Disability Index. This questionnaire evaluates the effect of neck pain on areas such as personal care, lifting, reading, concentration, work, driving, sleep, and recreation. Higher scores indicate greater disability.

Pressure pain threshold will be measured using an electronic pressure algometer. Pressure will be applied gradually to the identified painful area until the participant first reports discomfort or pain. The measurement will be repeated, and the average value will be used for analysis. A lower pressure pain threshold indicates greater local pressure sensitivity.

Ultrasound imaging will be used to assess the upper trapezius muscle. Measurements will be obtained with the participant seated in a standardized position. Muscle thickness will be measured at the midpoint between the seventh cervical vertebra and the acromion. Ultrasound measurements will be obtained under three conditions: complete rest, an anti-gravity shoulder contraction, and maximal voluntary contraction.

The ultrasound outcomes will include resting muscle thickness and contraction-related changes in muscle thickness. The percentage change from rest to anti-gravity contraction will be used to reflect muscle activation during a low-level functional contraction. The additional percentage increase from anti-gravity contraction to maximal voluntary contraction will be used to reflect the muscle's capacity to generate a stronger contraction.

The primary objective of this study is to determine whether focused shockwave therapy provides greater improvement in pain than a home-based neck exercise program. Additional objectives are to compare changes in neck disability, pressure pain threshold, resting upper trapezius thickness, and ultrasound-derived muscle contraction measures between the two groups. The study will also explore whether changes in ultrasound measurements are associated with changes in pain intensity, pressure sensitivity, and neck-related disability.

Participant characteristics and study outcomes will be summarized using appropriate descriptive statistics. Changes over time within each group and differences between groups will be examined using statistical methods appropriate for repeated measurements. Group-by-time interactions will be evaluated to determine whether the pattern of improvement differs between the focused shockwave therapy and exercise groups. If the data do not meet the assumptions required for conventional parametric analyses, nonparametric methods or linear mixed models may be used. Correlation analyses will be performed to evaluate relationships between clinical outcomes and ultrasound measurements. Statistical significance will be assessed using a two-sided significance level of 0.05.

Adverse events and participant tolerance will be monitored throughout the intervention and follow-up periods. Participants may withdraw from the study at any time without affecting their usual medical care. All study data will be coded and stored securely to protect participant confidentiality.

Inclusion Criteria:

• Adults older than 20 years.
• Clinical diagnosis of nonspecific neck and shoulder pain primarily arising from muscles and soft tissues in the upper trapezius or levator scapulae region, as determined by a physical medicine and rehabilitation physician.
• Neck and shoulder pain lasting for at least 3 months.
• Neck Disability Index score greater than 5.
• No use of analgesic medication or muscle relaxants within the previous month.
• No injection therapy, physical therapy, or other treatment for neck and shoulder pain within the previous month.
• Ability to understand the study procedures and provide written informed consent.

Exclusion Criteria:

• Neck or shoulder pain caused by a neurologic disorder, including cervical radiculopathy.
• Clinical or imaging diagnosis of cervical degenerative joint disease.
• History of a rheumatic disease, including rheumatoid arthritis or systemic lupus erythematosus.
• History of head or neck trauma.
• History of cervical spine surgery.
• History of whiplash injury.
• Pregnancy.
• Current or previous malignancy considered clinically relevant to shockwave therapy.
• Bleeding disorder.
• Current use of anticoagulant medication, including warfarin.
• Acute inflammation or infection at the treatment site.
• Implanted cardiac pacemaker or implantable cardioverter-defibrillator.
• Any other condition judged by the study physician to make participation or focused shockwave therapy inappropriate or unsafe.