RESEARCH DESIGN
The research design for this experimental study will be a repeated measures design. The outcome variables collected in this study are the following: peak systolic velocity, end diastolic velocity, resistive index, pulsatile index, of the infraspinatus, shoulder range of motion (ROM) of internal and external rotations, and Pain pressure threshold (PPT).
PROCEDURE
Eligible participants will be asked to complete an intake form (see Section 6 and 9), asking them about their demographic data, including age, gender, height, weight, occupation, past medical history, and questions related to their shoulder pain (onset, injury mechanism if any, location, duration, type, and nature). The participant's eligibility will be confirmed by the Principal Investigator (PI). Next, each participant will complete the shortened Disabilities of the Arm, Shoulder and Hand Questionnaire (QuickDASH) to determine the participants disability level due to their shoulder pain. After gathering the subjective information and confirming presence of MTrP using palpation, blood flow parameters, shoulder ROMs and PPTs will be collected from the most painful side. If both sides are equally painful, a coin-flip will be used to determine the side of testing. In a subgroup of the first 15 participants in each group, the outcome measures will be assessed twice with a 5-minute break between each measure to establish the reliability prior to the dry needling intervention. The outcome measurements will be administered in an order of shoulder ROMs, followed by PPT and blood flow parameters before the dry needling and in a reverse order of blood flow parameters, PPT and shoulder ROM after dry needling in order to minimize the position changes and to capture immediate changes of blood flow.
SHOULDER RANGE OF MOTION
Range of motion testing will be performed with the individual in supine with the shoulder at 90° abduction and 10° of horizontal abduction with 90° of elbow flexion. Two examiners (The PI and a research assistant) will be responsible for all the measurements, one to measure the shoulder ROM and the other to read the measurements off the goniometer. The center of rotation of the goniometer will be placed over the olecranon while one arm of the goniometer will be positioned along the length of the ulna, aligned with the ulnar styloid process. The other arm will be positioned perpendicular to the ground. For both measurement of shoulder internal and external rotation, scapular compensation will be monitored by using the thumb on the coracoid process and fingers along the spine of the scapula. Each measurement will be repeated three times with the average measurements used for data analysis.
PRESSURE PAIN THRESHOLD TESTING
During the PPT testing, the participant will be placed in the prone position with upper extremities relaxed at their sides. PPT of the infraspinatus will be tested in the muscle belly below the midpoint of the spine of scapula. The participants will be given a stop button and instructed to stop the test as soon as the pressure becomes uncomfortable or painful, and not to allow a painful or uncomfortable sensation to continue. The participants will be familiarized with the algometer, which will consist of a single trial on the non-painful side to ensure that the participant understands the process. An average of three trials will be used for data analysis.
ULTRASOUND IMAGING
Each participants will remain in the same position for ultrasound imaging. The ultrasound transducer will be placed perpendicular to the infraspinous fossa to visualize arterioles or arteries in the vicinity of the MTrPs and to quantify the velocity of blood flow at the MTrPs of the infraspinatus determined by palpation by the PI (JB) during the eligibility screen. The location of the transducer will be outlined after initial placement to ensure consistent placement of the transducer between the testing sessions. The spectral Doppler waveforms will be analyzed to trace the velocities throughout the cardiac cycle. The peak systolic (PSV), end diastolic velocity (EDV), resistive index (RI) and pulsatile index (PI) will be calculated using software available on the device. On a Doppler waveform, the PSV corresponds to each "peak" within the spectral window, whereas the EDV corresponds to the point marked at the end of the cardiac cycle just prior to the systolic peak. These values will be used to calculate the RI with the formula RI = (PSV - EDV)/PSV and the PI with the formula PI = (PSV - EDV)/mean velocity, where mean velocity is the average flow velocity during the cardiac cycle.
INTERVENTION
Following the baseline testing, the PI will perform the dry needling intervention. A sterile, disposable, solid filament needle (Seirin Corp., Shizuoka, Japan) will be inserted manually into the MTrP of the infraspinatus muscle. Once the needle has been inserted, the needle will be pistoned in an up-and-down motion within the infraspinatus muscle at approximately 1Hz for 10 seconds, Individuals with shoulder pain will receive dry needling to the two to four most tender points in the infraspinatus based on examiner palpation (JB). The control group will receive dry needling to two points in the muscle belly of the infraspinatus near the insertion and below the midpoint of the spine of the scapula.
REASSESSMENT
Immediately following the interventions, measures of the three outcomes will be collected in the following order to minimize position changes for all participants (blood flow parameters, infraspinatus PPT, and shoulder range of motion). Additionally, any adverse events following the dry needling procedures will be assessed immediately, such as bruising, nausea, dizziness, or post-needling soreness. If bleeding occurs, the participant will be informed.
