A convenience sample of 10 subjects diagnosed with FS was recruited. Since there is no gold standard to diagnose FS, diagnosis was stablished by a physician based on clinical examination, exclusion of other pathologies and imaging . Patients included should present with primary or idiopathic FS, a limitation in passive external rotation > 50% compared to the unaffected shoulder or less than 30° of passive external rotation, and a ROM loss > 25% in at least two movement planes . Additionally, pain and movement restriction should be present for at least one month having either reached a plateau or worsened  and radiographs had to be normal (with the exception of osteopenia of the humeral head and calcific tendinosis) .
Patients that presented with locked dislocations, arthritis, fractures or avascular necrosis were excluded. Furthermore, those subjects not understanding Spanish language, having previous upper quadrant region surgery during the last year, any skin or medical condition preventing them from receiving tactile stimuli on the shoulder, any neurological or motor disorder, visually impaired or having a diagnosed psychopathology were excluded from the study.
This feasibility study involved a 10-week CNS-focused intervention and periodic assessment of participants. All outcome measurements were performed at baseline (T-1) and after a 2 week period of “washout” with no intervention (T0) . After this initial assessment participants began the treatment and were again measured at the end of treatment (3 months after baseline; T3) and at three months follow-up (T6) (Fig. 1).
The CNS-focused intervention consisted of a 10-week treatment program (1 session/week) delivered as 60 min sessions. In addition, participants performed a 30-minutes home training program five times per week during those 10 weeks. The CNS-focused intervention included discussion of the participant’s shoulder pain experience from a pain neuroscience perspective provided in session 1 plus graded sensory discrimination training and GMI . The physiotherapist performing treatment (SM) had a post-graduate degree in manual therapy and was trained in how to perform the treatment by another researcher (ELL) with 10 years working experience in the use of these interventions.
Primary outcome measure
The primary outcome measured was self-reported shoulder pain and disability measured with the Shoulder Pain and Disability Index (SPADI) . The SPADI is a 13-items shoulder function index assessing pain and disability related to shoulder dysfunction . Each item is scored by a numeric scale (0–10) and the total score ranges from 0 to 100 points. A higher score indicates greater disability. The Spanish version of the SPADI has shown high internal consistency and excellent test-retest reliability . The Minimal Clinically Important Difference (MCID) for the SPADI ranges from 8 to 13 points .
Secondary outcome measures
Different feasibility outcomes were considered as secondary: timely recruitment, number of participants completing treatment, treatment compliance and barriers (with clinic and home training sessions), and number of patients measured at follow-up. To assess treatment adherence patients were provided with a diary to record their compliance with therapy . In addition, patients were asked whether any difficulties with treatment compliance had appeared from one session to another.
Additionally, other secondary outcome measures were collected: self-perceived shoulder pain, active and passive ROM, and changes in tactile acuity and laterality judgement performance, Tampa Scale for Kinesiophobia (TSK-11), Central Sensitization Inventory (CSI) and Pain Catastrophizing Scale (PCS).
Self-perceived shoulder pain
Participants’ self-perceived shoulder pain was evaluated with the Numeric Pain Rating Scale (NPRS) anchored with 0 (“no pain”) and 10 (“pain as bad as you can imagine”). Patients reported their most intense pain over the last week, least intense pain over the last week, average pain intensity over the last week, and pain at that moment. The scores were averaged to calculate a final pain intensity score . NPRS is a valid and reliable measure in patients with shoulder pain . The minimal detectable change (MDC) of the NRPS for patients with shoulder pain is 2.5 points and the MCID is 1.1 points .
Shoulder range of motion (ROM)
Shoulder flexion and active and passive external rotation at 00 of abduction of the affected shoulder were measured with a goniometer with the patient seated. To allow consistency of pre and post-therapy measurements, skin marks were placed for goniometric measurements. There is good reliability and validity of goniometric shoulder ROM measurements . The MDC for shoulder flexion, abduction and external rotation ranges from 11° to 16º .
Tactile acuity was assessed with the two-point discrimination threshold (TPDT). A mechanical sliding calliper with a 1-mm precision (Duratech TA-2081) was used to calculate the TPDT. Participants were positioned in sitting and a point 5 cm distal to the lateral border of the acromion was marked on the painful shoulder. In order to standardize the testing region, this point was always kept between the two calliper points and measurements were performed in the longitudinal direction of the arm . An ascending and a descending run of measurements were completed. The calliper distance was first gradually increased from 0 mm in 5 mm steps until the participant perceived two points instead of one. The descending run began with the calliper points separated 30 mm more than the TPDT value obtained from the ascending run, followed by decrements of 5 mm. A mean TPDT value was obtained from the two threshold scores and used for analysis.
Laterality judgement was assessed with a left/right judgement task (LRJT) using the NOI™ online program. A total of 30 shoulder pictures (context mode) were presented to participants on a laptop in a random order and they were instructed to decide as quickly as possible but without guessing whether the picture showed the right or left shoulder thus making a response. Accuracy and mean response time were recorded. The LRJT was performed twice. The first block of images was used for task familiarization and data from the second block was used for analysis . The normative mean (SD) response time and mean (SD) accuracy of this LRJT is 1738(741) ms and 93.5(9.2)%, respectively .
Fear avoidance was assessed with the Spanish version of the TSK-11 . The TSK-11 is an 11-item questionnaire used to assess fear of movement or (re)injury during movement . The total score ranges from 11 to 44 with higher scores indicating more fear-avoidance behavior. The TSK-11 has shown acceptable internal consistency and validity in both subjects with acute and chronic musculoskeletal pain . The MDC for the TSK-11 is 5.6 . The Spanish version of the CSI was used to assess different symptom dimensions related to central sensitization . The CSI has high test-retest reliability and internal consistency . Pain catastrophization was assessed with the Pain Catastrophizing Scale (PCS). PCS consists of 13 items and the total score ranges from 0 to 52 . A total PCS score of 30 represents a clinically relevant level of catastrophizing .
CNS-focused treatment program
Prior to starting treatment, participants were given an explanation of the study. Patients were shown a picture of the ‘brain map’ (homunculus) and taught how, when people are in pain, the map becomes “less sharp” since it’s not being moved and it is believed that when the map is sharpened, it may help reduce their pain even movements . By using sensory discrimination training and GMI, the therapy aimed to sharpen the brain shoulder map and thus improve pain and movement. The CNS-focused treatment included graded sensory discrimination training and GMI training techniques. A full description of the treatment can be found elsewhere .
Statistical analysis was conducted using IBM SPSS Statistics 21. Normality of the data was assessed using the Shapiro–Wilk test. Study findings are expressed as the mean and standard deviation or 95% confidence interval, or as percentage frequencies. A Student's t-test was used to assess differences between T-1 and T0 (“washout” period). A repeated measure analysis of variance (ANOVA) was used to evaluate within-subjects’ differences for all outcome measures in the different assessment periods and a pairwise analysis was used to compare between the different assessment points. Statistical significance was set at p < 0.05.
The data associated with the paper are not publicly available but are available from the corresponding author on reasonable request.