The Efficacy of a Pain Neuroscience Education Program in Chronic Shoulder Pain: A Randomized, Single - Blinded Trial

1. Introduction

Shoulder pain (SP) is the third most common musculoskeletal disorder, with an incidence from 7.7 to 62.0 per 1000 persons per year, and a point prevalence from 0.7 to 55.2% in the general population [1]. The recovery from shoulder pain can be slow and recurrence rates are high, with 25% of those affected by shoulder pain reporting previous episodes, and 40-50% reporting persistent or recurrent pain at a 12- months follow-up [2].

This prognosis may be influenced by age, a low educational level, a long duration of symptoms, previous episodes, high rates of disability, pain in other body areas [3], and the presence of psychosocial factors [4]. These psychosocial factors may be risk factors and triggers for the onset and development of shoulder pain, may be facilitators of or barriers to patient recovery [5], and appear to play a key role in explaining why musculoskeletal pain becomes chronic after the normal period of tissue healing has elapsed [5]. The presence of these psychosocial factors may suggest that a pain neuroscience education (PNE) approach could be considered as part of the treatment for these patients, as there is a growing body of research on its efficacy and effectiveness for different pathologies [6].

PNE is an educational strategy that focuses on teaching people in pain more about the neurobiological and neurophysiological processes involved in their pain experience, especially for chronic pain, to influence their beliefs and behaviors [7]. PNE could have a positive effect on pain, disability, catastrophizing, and kinesiophobia [8]. However, the effectiveness of PNE as an isolated treatment technique is limited and on its own may not help to improve the impaired movement and muscle performance observed in individuals with shoulder pain [9]. Thus, exercises (EX) [10] and manual therapy (MT) [11] may be indicated to address such impairments: MT in addition to EX may, in the short term, further reduce pain and improve function [12].

Moreover, manual therapy is based on Mulligan's Movement Mobilization[1]. Mulligan’s mobilization with movement (MWM) technique is a manual therapy approach involving the application of a sustained gliding force (passive mobilization component) with a concurrent active movement or a functional task performed by the patient (active movement component) [14]. The application of MWM, when precisely indicated, has beneficial effects on painful movements and, thereby, function is immediately improved [15].

In this regard, exercise therapy for shoulder pain is effective and consistently recommended, but in general, there is no consensus on the type, intensity, frequency, or duration of the exercises used [16]. Some of the most recommended types of exercises are strengthening exercises, as they have been shown to be effective in reducing pain and disability in people with shoulder pain [17].

In view of this, the aim of this randomized clinical trial is to compare the effects between of two interventions for people diagnosed with shoulder pain: MT and EX, and PNE, MT, and EX. The primary outcomes were to compare the pre-treatment and post-treatment scores of the experimental versus control groups on the level of pain, disability, and mobility. Our secondary outcomes included the comparisons of scores of catastrophizing, kinesiophobia, and satisfaction with the working alliance. We hypothesized that the addition of a PNE program for exercise and manual therapy could improve outcomes in patients with chronic shoulder pain.

2. Materials and Methods

2.1. Study Design

A repeated- measures, single-blind, randomized controlled trial was conducted following the CONSORT guidelines. The study protocol was approved by the Ethics Committee of León University Hospital, Spain, and its internal registry number was 21179. This research was conducted in accordance with the World Medical Association Declaration of Helsinki. Patients were informed about the study and provided their written consent, and the study was registered at ClinicalTrials.gov with the identifier NCT06739694.

2.2. Participants

The study population consisted of 56 patients with shoulder pain selected from the waiting list for Primary Care in León (Castilla y León Public Health Service, SACYL).

The inclusion criteria were as follows: (1): age of being 18–70; (2) history of shoulder pain of more than 3 months’ duration; (3) presence of a painful arc; (4) medical diagnosis of shoulder pain with at least 2 positive impingement tests including Neer, Hawkins, or Jobe tests [18]. The exclusion criteria included (1) a diagnosis of fibromyalgia; (2) pregnancy; (3) a history of traumatic onset of shoulder pain; (4) other histories of shoulder injury; (5) torn tendons; (6) ligamentous laxity based on a positive sulcus and apprehension tests; (7) numbness or tingling in the upper extremity; (8) previous shoulder or cervical spine surgery; (9) systemic illness; (10) corticosteroid injection in the shoulder within 1 year of the study; and (11) physical therapy 6 months before the study.

2.3. Randomization and Blinding

Concealed allocation was performed using a computer-generated randomized table of numbers (Random.org) created before the start of data collection by a researcher not involved in the recruitment and/or treatment of the patients. Individual and sequentially numbered index cards with random assignment were prepared. The index cards were folded and placed in sealed opaque envelopes. A second therapist, blinded to baseline examination findings, opened the envelope and proceeded with treatment according to the group assignment. The participants were randomly assigned to either the experimental group (PNE + MT + EX) or the control group (MT + EX).

Due to the type of study carried out, it was not possible to blind the physiotherapist in charge of the interventions, which may have been a limitation of the study. Participants were unaware of the purpose of the study, and were informed that the study was a comparison between two physiotherapy treatments. The lack of prior experience in pain neuroscience of all participants contributed to the blinding. The statistical analysis was also performed by a blinded researcher who had no knowledge of the groups to which each patient be-longed.

2.4. Interventions

A physiotherapist with 20 years of experience administered the treatment program. For the control group, the MT and EX program lasted 5 weeks with one session per week, while in the experimental group, the program started four weeks earlier with one session per week of PNE, followed by the addition of MT and EX therapy (Figure 1). Measurements were taken prior to the start of treatment and five weeks after the end of manual therapy and exercises.

2.4.1. Manual Therapy

Although used as a treatment technique, MWM is also considered an assessment procedure [19]. The starting point is to select a movement or activity that reproduces the patient's symptoms. Once the provocative activity is known, one or more techniques that reduce the symptoms, either by reducing pain and/or in-creasing movement, are identified [20]. Based on the information gathered during the clinical interview and physical examination, a decision is made as to which joint to treat and the direction of the physiotherapist's performance of the passive technique [21]. Exploratory and/or treatment techniques target the humeral head [22], scapula [23], and cervical [24] and thoracic regions [25]. During the sessions, passive accessory gliding was applied while the patient performed the active movement or function that reproduced their symptoms. Each exercise was performed in three sets of 10 repetitions, with a total duration of 15-30 minutes [26].

2.4.2. Exercises

Participants were instructed to perform a home-based program of progressive shoulder- strengthening exercises [27] involving concentric and eccentric contractions with elastic resistance bands. The exercises targeted the humeral internal/external rotators, abductors and scapular muscles [28]. The exercises were per-formed in 3 sets of 10 repetitions, four times per week, with a 1-minute interval be-tween repetitions during the first week. From the second week onwards, the exercises were increased to 12 repetitions, and from the third week onwards, they were increased to 15 repetitions.

2.4.3. Pain Neuroscience Education

In addition to MT and EX treatment, a PNE protocol was administered to the ex-perimental group for a full 4-week period (1 session/week, 75 minutes per session, 5/6 patients per group) by a physiotherapist with 6 years of experience. PNE aimed to re-conceptualize pain perception from a biomedical or structural model to a biopsychosocial pain model through education on the neurophysiological aspects of pain [29]. All sessions used a slide presentation (PowerPoint, Microsoft Corp., Redmond, WA) prepared by the instructor based on previous studies and modified to address the shoulder that was causing pain [30,31]. The full content of the education is shown in Table 1.

2.5. Outcome Measures

The study participants were assessed at baseline and at the end of the interventions by a physiotherapist who was not involved in the study and who was blinded to the treatment performed. Prior to the start of the study, a series of socio-demographic variables were collected: age, sex, dominance, location of pain, and duration of symptoms (months).

2.5.1. Shoulder Function

The primary outcome measure was the Shoulder Pain and Disability Index (SPADI). The SPADI is a self-reported questionnaire that evaluates the pain and disability associated with shoulder diseases [32]. This questionnaire comprises 2 subclasses (pain and disability) with 13 items (5 items in the pain domain and 8 items in the disabilities domain). The SPADI is scored between 0 and 100, and the SPADI score is calculated by averaging the scores from the 2 subclasses. A higher SPADI score indicates more severe symptoms and a greater level of disability. The questionnaire has been validated for use in Spain [33]. In patients with shoulder pain, the minimal detectable change (MDC) for the SPADI is reported to be 18.1, and the minimum clinically important difference (MCID) has been established as 13.2 [34].

2.5.2. Shoulder flexion active range of motion (AROM)

Shoulder flexion active range of motion (AROM) was measured according to international guidelines using a goniometer [35]. AROM measurement using a goniometer has excellent intra-inspector reliability (ICC = 0.91–0.99) [36]. The minimum detectable change (MDC) for shoulder flexion has been reported as 8°, and the calculation of the minimum clinically important difference (MCID) depends on the patient's pathology, but it is generally accepted that a change of 6° to 11° is needed to be certain that a true change has occurred with goniometric shoulder measurements [37].

2.5.3. Catastrophizing

The Spanish version of the Pain Catastrophizing Scale (PCS) will be used [38]. This is a brief 13-item questionnaire that assesses pain- related behaviors and cognition. Scores range from 0 to 52, with higher scores indicating a higher level of catastrophizing [39]. In patients with shoulder pain, the MDC for the PCS is reported to be 7.97 [40].

2.5.4. Kinesiophobia

The Spanish version of the Tampa Scale of Kinesiophobia (TSK-11) was used [41]. This is a self-reported questionnaire containing 11 items designed to assess a patient’s fear of moving and reinjury. Scores range between 11 and 44 points, with a higher score indicating higher levels of kinesiophobia. The MCD for this tool in patients with shoulder pain has been reported to be 5.6 points [42].

2.5.5. Therapeutic alliance

Therapeutic alliance was measured with the Working Alliance Inventory (WAI) [43]. The WAI is a measure of therapeutic alliance that assesses three aspects: agreement on therapy tasks, agreement on therapy goals and bonding. It consists of 36 items with scores ranging from 36 to 252. Higher scores indicate a higher level of therapeutic alliance.

2.6. Sample Size

With reference to Kararti et al.’s [44] results of the SPADI scores after 6 weeks of treatment and using G*Power Software (Version 3.1.9.7, Düsseldorf University, Düsseldorf, Germany), the minimum required sample size was calculated as 50 participants for the anticipated effect size of 0.82 with a probability level of 0.05 and statistical power level of 80%. Considering a dropout rate of 10%, 55 participants were recruited.

2.7. Statistical Analysis

All statistical analyses were performed using IBM SPSS Statistics version 27.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were expressed as mean ± standard deviation (mean ± SD) for continuous variables, and ratios (%) for categorical variables. The Kolmogorov–Smirnov test showed a normal distribution of all quantitative data (P >.05). Basic parameters of the groups were com-pared using a chi-square test for categorical variables, and an independent t-test for continuous variables. An independent t-test was performed to determine when the interaction between groups appeared over time. A 2 × 2 repeated- measures analysis of variance (ANOVA) with time (pre-treatment vs. post-treatment) as the within-subjects factor and the group (experimental vs. control group) as the between-subjects factor was used to determine the effects of the intervention. When an interaction was detected, a post hoc test was performed using the Bonferroni test. The partial eta square was calculated to classify effect size (ηp2)[45]. The statistical analysis was conducted at the 95% confidence level, and P< .05 was considered statistically significant.

3. Results

Sixty-seven (n = 67) consecutive patients with shoulder pain were screened using the eligibility criteria. Fifty-five patients satisfied the eligibility criteria, agreed to participate, and were randomized into the experimental group (n = 27; mean ± SD age, 57.22 ± 1.57) or the control group (n = 28; mean ± SD age, 56.18 ± 1.71). A study flowchart was is presented in Figure 2.

All of the demographics were similar between the groups (Table 2). There was no difference between the groups in terms of the baseline clinical outcomes (p > .05).

Comparison of the outcome measurements within and between the groups were shown in Table 3. There were significant within-group differences for the experimental and control groups (p < .05) in terms of the range of motion, SPADI (total, pain and disability), catastrophizing and therapeutic alliance. There were significant within-group differences in the experimental group in terms of kinesiophobia, while there were no significant within-group differences in the control group regarding this variable.

The 2 × 2 ANOVA revealed a significant group × time interaction for the range of motion during shoulder flexion (F = 15.27; p < .001; ηp2 = .22), SPADI-total (F = 6.28; p = .015; ηp2 = .06) and SPADI-disability (F = 6.14; p = .01; ηp2 = .10), but not for SPADI-pain (F = 3.94; p = .052; ηp2 = .06). There was also a significant group × time interaction for catastrophizing (F= 8.79; p = .005; ηp2 = .14) and kinesiophobia (F = 7.62; p = .008; ηp2 = .12). Between the groups, the effect sizes varied from medium (0.06) to large (0.14) in favor of the experimental group.

4. Discussion

This study compared a PNE treatment combined with MT and EX with a physio-therapy treatment utilizing MT and EX in patients with shoulder pain. Our results indicated that the PNE program associated with MT and EX was more effective than an MT and EX program for improving the range of motion, disability, catastrophizing and kinesiophobia, but not for reducing pain. In addition, a better therapeutic alliance between the physiotherapist and patient was established in the experimental group compared to the control group. The range of motion improved in both groups, exceeding the MCID score, although there were statistically significant differences in favor of the PNE group. Overall, our results were better than those of a previous study evaluating the efficacy of PNE as an adjunct to a physical rehabilitation protocol after arthroscopic rotator cuff repair, which showed better overall scores for active ROM in shoulder flexion, but no statistically significant differences between groups [46]. Our results were also superior to those from a study by Louw et al. [47], which examined the application of PNE before shoulder surgery, where the participants showed an increase in the AROM during flexion of the affected shoulder after PNE of 5° on average, compared to 29° in our study. The difference in these results in favor of our study could be due to the fact that the patients in the Kim et al. [46] and Louw et al. [47] studies were either having shoulder surgery or awaiting surgery, which would increase kinesiophobia, leading to a decrease in movement due to the correlation between kinesiophobia and range of motion [48]. Furthermore, the study by Louw et al. [47] only included a PNE treatment, and it has been shown that PNE as a stand-alone treatment is not as effective, while PNE combined with other therapeutic treatments, especially exercises, produces significant improvements [49].

Compared to the baseline values of the SPADI scores associated with pain and disability and the total scores, both of the groups improved statistically significantly, exceeding the MCID score, and with statistically significant differences in favor of the experimental group in the total and disability score, but not in the SPADI score associated with pain. Previous studies have reported unsatisfactory results on the efficacy of PNE in directly reducing pain and functional limitations in shoulder pain [30,44,50]. The trial by Kararti et al. examined the efficacy of PNE as an adjunct to clinical outcomes in patients undergoing arthroscopic rotator cuff repair, and compared the results to those from a control group treated with conventional physiotherapy [44]. The study by Myers et al. evaluated the impact of a cognitive-behavioral intervention to improve expectations towards physiotherapy and reduce the likelihood of opting for surgery [50]. Also, Ponce-Fuentes et al. investigated the effectiveness of PNE compared to Biomedical Education as part of a rehabilitation program following arthroscopic rotator cuff repair [30]. None of the trials [30,44,50] found improvements in pain and disability between the groups assessed. Moreover, in our study, no group-–time interaction was observed in the SPADI-pain value but there was an interaction with the SPADI-disability value, which may be because the reduction in the fear of movement led to early functional improvements through an increased tolerance to physical activities, before pain showed significant changes, as the final measurement was taken 5 weeks after the start of the treatment [51,52].

As we expected, PNE associated with MT and EX was more effective than MT and EX alone in reducing catastrophizing and kinesiophobia, with the MCD score being exceeded. Although certain studies that specifically performed PNE interventions for shoulder pain prior to or after surgery found no significant differences in these variables [30,46,47], systematic reviews of interventions that have combined PNE with exercise in chronic musculoskeletal pain have shown clinically relevant reductions in catastrophizing [53] and kinesiophobia [54]. The differences in results with the Louw et al. [47], Kim et al. [46], and Ponce-Fuentes et al. [30] studies may be due to the characteristics of the participants, since in our study the patients had not undergone shoulder surgery, nor were they awaiting this surgical intervention, and the PNE program we carried out was at group level, and not individual as in the aforementioned studies. Reduced levels of kinesiophobia may have led to increased adherence to exercise, thus improving pain intensity and disability outcomes [55].

Finally, significant differences were also found in the therapeutic alliance between the experimental and control groups. The therapeutic alliance can influence the patient's expectations, commitment to the treatment program, motivation and self-efficacy, thus creating the ideal environment for a biomechanical exercise intervention [56].

Our study has several limitations. Differences in the number of sessions between groups (in favor of the experimental group) may have influenced the results of this study due to factors related to the therapist-–patient relationship. Even so, the treatment received by the control group is supported by clinical practice guidelines for the treatment of shoulder pain. A long-term follow-up (6- and 12- months post-treatment) was not performed, which should be considered for future studies.

5. Conclusions

In conclusion, this trial demonstrated that PNE improved the range of motion, disability, catastrophizing, and kinesiophobia, as well as the therapeutic alliance. PNE could be an intervention option associated with MT and EX treatment in the management of shoulder pain.