Study design
This study is a single-arm study with non-probabilistic recruitment of consecutive cases, developed between May 2017 and October 2018, approved by the Research Ethics Committee of Universidade Federal do Rio Grande do Norte (Protocol no. 1,316,438) and registered in the Brazilian Registry of Clinical Trials – ReBEC (RBR-3DDG2K) – Registered in July 5th, 2017 – Retrospectively registered, http://www.ensaiosclinicos.gov.br/rg/RBR-3ddg2k/. All volunteers provided their informed consent after being informed verbally and in writing about the objectives, risks and benefits of the study.
Participants
Participants were recruited from flyers posted in the community and via social media. The inclusion criteria were: 18–60 years old, history of unilateral shoulder pain lasting at least one month, located in the proximal anterolateral shoulder region (27), or in the C5 or C6 dermatome region (28), and at least three of the following positive tests: Neer (29), Hawkins-Kennedy (30), Jobe (31), painful arch (32), external rotation resistance (33), Gerber and Speed (34). Exclusion criteria were: adhesive capsulitis, history of symptom onset due to trauma, multidirectional or anterior glenohumeral joint instability based on positive sulcus sign test and apprehension test, numbness or tingling in the upper extremity, fibromyalgia or rheumatic disease, previous neck and shoulder surgery, systemic disease, body mass index > 28 kg/m2, injection of corticosteroids in the last 3 months or use of analgesics or muscle relaxants 72 hours before the procedures, and symptoms of depression with a score ≥ 13 on the Beck’s depression Inventory (BDI) (35, 36).
There were 56 individuals interested in participating in the study and were initially evaluated according to the eligibility criteria. However, 41 were excluded from this assessment for the reasons described in the study flowchart (Fig. 1), with only 17 individuals able to participate. Of these, 02 individuals did not attend the second day of assessment; thus, 15 individuals participated in the ICT session. Demographic and pain-related characteristics and shoulder functionality of the participants are shown in Table 1.
Table 1
Demographic characteristics and pain and functional status of all individuals.
Variables | Individuals (n = 15) |
Sex | 6 F (40%) / 9 M (60%) |
Age (years) | 34.4 ± 10.43a |
Height (m) | 1.68 ± 0.09a |
Weight (kg) | 69.13 ± 11.78a |
BMI (kg/m2) | 24.20 ± 2.18a |
BDI (0/21) | 6.46 ± 3.70a |
Pain at rest | 1.67 (0.18)b |
Number of positive tests | 4.80 ± 1.08a |
Duration of symptoms (months) | 16 (40)b |
Affected Side (D/ND) | 9 D (60%) / 6 ND (40%) |
Penn Shoulder Score Questionnaire | 74 (25)b |
Evaluation protocol
All individuals included in the study were submitted to the following assessments: 1) pain and general function of the shoulder complex using the Penn Shoulder Score Questionnaire; 2) identification of MTPs; 3) pain assessment, comprising the pressure pain threshold (PPT) and pain during mobility and strength tests, according to the Numerical Pain Rating Scale (NPRS); 4) shoulder mobility; 5) muscle strength of the shoulder complex.
The evaluations were carried out in three moments: a) initial evaluation (baseline); b) 48 hours after the initial assessment and immediately before the ICT session; and c) immediately after the ICT session. The purpose of the baseline was to verify the influence of the evaluation procedures on the variables.
Three evaluators participated in the study, 2 who were in the last year of graduation in Physical Therapy and 1 physiotherapist with 6 years of clinical experience. The physiotherapist performed the screening evaluation of the recruited individuals and performed the ICT session; a second evaluator was responsible for evaluating MTPs and PPT; and the third evaluator was responsible for the other evaluations (mobility, strength and pain due to NPRS). Only the affected side was evaluated.
Reliability of measures
The two evaluators involved in the MTPs, PPT, mobility and shoulder strength evaluations participated in training with a physiotherapist with six years of experience in musculoskeletal evaluation. The examiners carried out an evaluation of 06 subjects (03 symptomatic and 03 asymptomatic), totaling 5 hours for each evaluator. Next, a test-retest reliability study was conducted with 20 asymptomatic individuals only evaluating the dominant side in order to verify the reliability of the evaluators’ measurements. For MTPs, an agreement percentage greater than 70% was verified, being considered acceptable for clinical practice (Bron, Franssen, Wensing, and Oostendorp, 2007). Almost perfect reliability was obtained for the other variables with ICC between 0.91 to 0.98 for the assessments of PPT, ROM and strength, as well as NPRS (ICC: 0.96–0.98).
MTP evaluation
The evaluated muscles were: upper and lower trapezius, supraspinatus, infraspinatus, pectoralis minor and middle deltoid. The following diagnostic criteria proposed by Simons (38) were monitored: identification of a palpable tense band, if the muscle is accessible; local pain to digital compression of a palpable nodule located in a tense band; recognition of pain referred by the individual as familiar when pressing on the sensitive nodule (to identify active MTP); and jump sign. These criteria have obtained good inter-examiner reliability with moderate to almost perfect reliability (39). The report of spontaneous referred pain, local pain upon palpation and recognition of the pain referred to as familiar in the digital compression was associated with active MTP, while a report of local pain and referred pain which was not familiar to the digital compression was associated with latent MTP (7, 14). If the same muscle had latent and active MTP, that muscle was classified as containing active MTP. The evaluation was performed with the individual in the supine or prone position, with the evaluation order of the muscles being randomized for each individual.
Pain evaluation
Pressure Pain Threshold Assessment
The PPT is defined as the minimum amount of pressure that is perceived as painful (40). A digital algometer (Wagner Instruments, model FDX, Greenwich, CT, USA) was used for this assessment, which is a device made up of a 1 cm2 rubber disk connected to a pressure gauge which displays values in kgf/cm2. The individuals were evaluated in the sitting position, and the following muscles were evaluated: lower trapezius (in the muscle belly, halfway between the midpoint of the medial edge of the scapula and the spinous process of the twelfth vertebra), upper trapezius (midway between the spinous process of C7 and the acromion of the scapula), infraspinatus (in the muscular belly below the midpoint of the scapular spine) and middle deltoid (muscle belly, close to the inferolateral insertion) (5, 6).
Assessment of pain during mobility and maximum isometric strength
Individuals were asked about pain according to NPRS (0–10, with 0 being no pain and 10 being the worst possible pain) after each ROM and strength assessment, with an average of 2 values reported for each test.
Evaluation of shoulder ROM
The ROM of arm elevation in the sagittal plane, arm elevation in the scapular plane, internal and external rotation of the shoulder were evaluated using a digital inclinometer (Lafayette Instrument Company, model ACU001, Lafayette, IN, USA). The elevation in the sagittal plane of the shoulder was measured with the individuals sitting with their elbow extended, shoulder in neutral rotation and thumb pointing upwards. The internal and medial rotation ROM were measured with the individuals in the supine position, shoulder abducted at 90° in the frontal plane with the humerus supported on the examination table and elbow flexed at 90° (41). Each test was performed twice and the average between the values was calculated (42).
Isometric strength assessment
The isometric muscle strength test was performed with a manual dynamometer (Lafayette Instrument Company, model 0116, Lafayette, IN, USA) at moments of arm elevation in the scapular plane, medial and external rotation of the shoulder. The individuals were seated in all assessments. The arm was positioned at 90° of elevation in the scapular plane in the neutral rotation with the elbow extended to assess the arm elevation strength (43). Next, the individuals were seated with an arm close to their body, and neutral rotation of the shoulder and elbows flexed at 90° to measure the isometric strength in the medial and external rotation of the shoulder (44). The dynamometer was fixed to the wall and adjusted so that individuals pushed it with the distal part of their forearm. They were instructed to perform maximum isometric contraction for 5 seconds. Each test was performed twice, with an interval of two minutes between attempts, and the average was calculated between the values (45).
Ischemic Compression Therapy Session
All individuals were submitted to an ICT session applied to all active and latent MTPs identified in the assessment. The therapist intermittently applied digital compression to the identified MTPs. Compression was applied over the MTPs until an increase in muscle resistance was perceived by the therapist (6). At this point the individual felt some degree of discomfort and/or pain, evoking a pattern of referred pain. The pressure was maintained until the therapist felt relief from tension under digital palpation or the individual showed a considerable decline in discomfort and/or pain (22). At that moment the therapist increased the intensity of the compression, trying to find a new parameter of referred pain, following the same process. This procedure was repeated until the individual no longer reported an increase in discomfort or referred pain with progression of the compression, or a maximum time of 90 seconds was reached in the entire process.
Statistical analysis
The sample size was calculated using the G* Power 3.1 software program (46) adopting an α of 0.05 and power of 0.80% for paired comparison analysis, with pain as the main outcome variables. The calculated sample size was 12 individuals considering a difference between means of 2.05 and standard deviation of 2.30 in NPRS (47); while the calculated sample size was 10 individuals considering the PPT variable with a difference between the averages of 1 kg/cm² (48, 49) and standard deviation of 1 kg/cm² (50). Thus, we considered the calculation with the largest number (n = 12) and added 25% of this value, totaling 15 individuals.
The data were statistically analyzed in a descriptive and inferential manner using the SPSS 20.0 statistical package (SPSS Inc., Chicago, IL, USA). The sample distribution was assessed using the Shapiro Wilk test. Mean and standard deviation (SD) were calculated for each variable, and the median and interquartile range were also calculated for non-parametric variables.
The Wilcoxon test was used to compare the number of MTPs between baseline and pre-treatment assessments in order to verify the influence of the assessment on the number of MTPs and other variables, and between pre and post-treatment assessments in order to to assess the effect of the ICT session. The paired t-test was used to compare the other variables between baseline and pre-treatment assessments, as well as pre- and post-treatment.
The effect size was then calculated from the differences between the evaluations using the Cohen’s d coefficient in the G* Power software program (51) for parametric variables. An effect size greater than 0.8 was considered large, around 0.5 moderate, and less than 0.2 small (52). A moderate effect size is considered to be clinically important (53). Delta Cliff was used to evaluate the effect size for non-parametric variables (MTPs) using a VBA/Excel calculator, considering 0.43 large, around 0.28 moderate and less than 0.11 small (10).