Case Series
Changes in pain and pressure pain sensitivity after manual treatment of active trigger points in patients with unilateral shoulder impingement: A case series

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Summary

The aim of this case series was to investigate changes in pain and pressure pain sensitivity after manual treatment of active trigger points (TrPs) in the shoulder muscles in individuals with unilateral shoulder impingement. Twelve patients (7 men, 5 women, age: 25 ± 9 years) diagnosed with unilateral shoulder impingement attended 4 sessions for 2 weeks (2 sessions/week). They received TrP pressure release and neuromuscular interventions over each active TrP that was found. The outcome measures were pain during arm elevation (visual analogue scale, VAS) and pressure pain thresholds (PPT) over levator scapulae, supraspinatus infraspinatus, pectoralis major, and tibialis anterior muscles. Pain was captured pre-intervention and at a 1-month follow-up, whereas PPT were assessed pre- and post-treatment, and at a 1-month follow-up. Patients experienced a significant (P < 0.001) reduction in pain after treatment (mean ± SD: 1.3 ± 0.5) with a large effect size (d > 1). In addition, patients also experienced a significant increase in PPT immediate after the treatment (P < 0.05) and one month after discharge (P < 0.01), with effect sizes ranging from moderate (d = 0.4) to large (d > 1).A significant negative association (rs = −0.525; P = 0.049) between the increase in PPT over the supraspinatus muscle and the decrease in pain was found: the greater the decrease in pain, the greater the increase in PPT. This case series has shown that manual treatment of active muscle TrPs can help to reduce shoulder pain and pressure sensitivity in shoulder impingement. Current findings suggest that active TrPs in the shoulder musculature may contribute directly to shoulder complaint and sensitization in patients with shoulder impingement syndrome, although future randomized controlled trials are required.

Introduction

Shoulder pain is a common health problem that has a multi-factorial underlying pathology with high direct costs for the society (Meislin et al., 2005). The one-year prevalence of shoulder pain ranges from 20% to 50% in the general population (Pope et al., 1997, Luime et al., 2004). Among the different causes of shoulder pain, the most prevalent diagnosis is shoulder impingement (13%) (Pribicevic et al., 2009).

The aetiology of shoulder impingement is not completely understood, but there is evidence showing the role of the shoulder musculature as a potential factor (Tyler et al., 2005). Different studies have shown the presence of muscle imbalance of the shoulder musculature in this painful condition (Ludewig and Cook, 2000, Moraes et al., 2008). Due to this imbalance, Simons et al. (1999) suggested that muscle trigger points (TrP) can play a relevant role in shoulder impingement syndrome. TrPs are defined as hypersensible spots in a taut band of a skeletal muscle, painful on contraction, stretching or manual stimulation which give rise to a referred distant pain. Active TrPs are those which their local and referred pains are responsible for the patients’ symptoms. There is preliminary evidence suggesting that referred pain from active TrPs may be implicated in the clinical picture of shoulder impingement. Ingber (2000) described 3 patients with shoulder impingement syndrome who were successfully treated with TrPs injection of the subscapularis muscle. Ge et al. (2008) described the presence of active TrPs within the infraspinatus muscle in individuals with shoulder pain, without specific diagnosis. A recent study reported that the referred pain elicited by active TrPs in the supraspinatus, infraspinatus, pectoralis mayor and subscapularis muscles reproduced the pain pattern in subjects with shoulder impingement (Hidalgo-Lozano et al., 2010). The hypothesis that active TrPs may be relevant for shoulder pain has been supported by the study of Hains et al. (2010) where myofascial therapy using ischemic compression on shoulder TrPs reduced the symptoms of patients experiencing chronic shoulder pain. Therefore, these studies suggest that referred pain from active TrPs may be relevant for shoulder pain.

Hidalgo-Lozano et al also found that patients with shoulder impingement exhibit generalized pressure pain hypersensitivity as compared to controls (Hidalgo-Lozano et al., 2010). In addition, the presence of mechanical pain hypersensitivity was related to the presence of active TrPs, suggesting that active TrPs may be involved in sensitization mechanisms in individuals with impingement syndrome (Hidalgo-Lozano et al., 2010). The aim of this case series was to investigate changes in pain and pressure pain sensitivity after manual treatment of active muscle TrPs in the shoulder musculature in patients with unilateral shoulder impingement.

Section snippets

Patients

Consecutive patients with diagnosis of strictly unilateral impingement syndrome stage I (acute inflammation and either tendonitis or bursitis) (Frieman et al., 1994) within the dominant-right hand were recruited. Patients were eligible if: 1) they had unilateral shoulder complaints with duration of at least 3 months; 2) an intensity of at least 4 on an 11-point numerical pain rating scale (NPRS) during arm elevation; 3) positive Neer test, that is, pain during passive abduction (Neer, 1983);

Clinical data of the participants

Twelve patients, 7 men and 5 women, aged 20–38 years (mean: 25 ± 9 years) diagnosed with unilateral shoulder impingement participated. All patients reported pain located in the anterior and posterior parts of the shoulder and the dorso-lateral aspect of the forearm in 5 patients (42%). The mean duration of shoulder pain history was 8.7 ± 4.8 months (95%CI 5–12.4), and the mean intensity of pain experienced during arm active elevation was 5.1 ± 1.9 (95% CI 3.9–6.4).

Changes in pain

The Wilcoxon signed test

Discussion

The current case series has shown that manual treatment of active TrPs within the shoulder muscles reduces spontaneous pain and increases PPT levels in individuals with shoulder impingement. Current results underline the importance of inspection and inactivation of active muscle TrPs in the shoulder musculature in patients with shoulder impingement syndrome as they may contribute to the overall picture of pain; however, future randomized controlled trials are required to further confirm this

Conclusion

This case series suggests that manual treatment of active TrPs may reduce spontaneous pain and increase PPT in patients with shoulder impingement. Effect sizes were large for pain and moderate-large for changes in PPT. Current findings suggest that active TrPs in the shoulder musculature may contribute to shoulder complaint and sensitization in patients with shoulder impingement syndrome. However, due to a small sample size and the absence of a control group, these assumptions should be

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