Is Adding Extracorporeal Shock Wave Therapy to Physiotherapy and Corticosteroid Injection Beneficial for Frozen Shoulder?

Frozen shoulder, or adhesive capsulitis of the shoulder, is a common clinical problem characterized by pain, loss of both passive and active range of motion (ROM) of glenohumeral joint (GHJ), leads to functional limitation, and reduces quality of life. Primary frozen shoulder occurs without any obvious connection to any other condition, and secondary frozen shoulder is related to some medical problems, such as an injury, inflammatory, immunological, and endocrine conditions, or surgery of the shoulder. The prevalence of frozen shoulder is 2%-5% in general population, usually between 40 to 60 years old, and more in female. Diabetes patients have more chance of developing frozen shoulder than general population and the prevalence was 13.4%.

Frozen shoulder is clinically divided into 3 overlapping phases. The painful freezing phase has a duration of 10 to 36 weeks and is characterized by pain and stiffness around the shoulder, which may worsen at night. The frozen phase is characterized by restricted ROM with a gradual relief of pain, which occurs at 4 to 12 months. The thawing phase with spontaneous improvement in the ROM takes 12 to 42 months. .Although frozen shoulder is a self-limited condition, the recovery may be slow and incomplete.

Treatment of frozen shoulder consists of physiotherapy, oral medication (nonsteroidal anti-inflammatory drugs or corticosteroid), intra-articular corticosteroid injection, hydrodilatation, suprascapular nerve block, mobilization, manipulation under anesthesia, and operative intervention (arthroscopic release or open release). Because of the uncertainty of the efficacy and risk of surgical treatment, nonsurgical treatments are more likely chosen by patients. Among them, intra-articular steroid injection and physical therapy are commonly used nonsurgical treatments and have shown some benefits. .Because the clinical picture of frozen shoulder may be similar to, or combining with chronic subacromial bursitis, especially in the freezing stage, concomitant subacromial/subdeltoid (SASD) bursa injection may be needed for treatment of frozen shoulder. In addition, the 3 stages of frozen shoulder often overlap and the clinical symptoms of patients are complex, adjuvant therapy is often needed throughout the course of treatment. Even after physical therapy (PT) and corticosteroid injection, mild to moderate contracture, especially external rotation, abduction, and internal rotation may still be present.

Over the past few years new evidence has emerged on the effectiveness of extracorporeal shock wave therapy (ESWT) in the treatment of many musculoskeletal disorders. Briefly, ESWT has been shown to promote neovasculization, amplify growth factor and protein synthesis, increase of pain inhibiting substance, alteration of pain receptor neurotransmission, and intensification of tissue regeneration. Furthermore, ESWT can produce a cavitation effect between tissues, cause intertissue release, promote the separation of adhesion, and release the adhesive tissue. Because of its analgesic, anti-fibrotic, and anti-inflammatory effect, application of ESWT as main treatment or an adjunct to other interventions has been tried. Knoblock et al found that focused ESWT can reduce pain in painful nodules in Dupuytren's disease; in a randomized controlled trial Chen et al showed focused ESWT was superior to oral corticosteroid for frozen shoulder, although oral corticosteroid is not commonly prescribed for patients with frozen shoulder. Vahdatpour compared ESWT with sham ESWT on treatment of frozen shoulder after 40mg triamcinolone intra-articular injection, and found that ESWT group seemed to have positive effects on treatment, and quicker return to daily life. Another two studies investigating application of radial shock wave to patients with frozen shoulder showed improvement of ROM, even for diabetic patients. A systemic review and meta-analysis also showed ESWT seems beneficial to patients with frozen shoulder and could be used as an adjunct therapy to routine treatments. However, the authors mentioned that the quality of the included randomized controlled trials were hampered by significant heterogeneity regarding long-term analgesia and joint ROM.

Because the effect of ESWT against frozen shoulder has not been well established, we aim to investigate whether adding ESWT to corticosteroid injection and routine PT beneficial for patients with frozen shoulder? We hypothesize that ESWT would be a positive adjunctive therapy in the treatment of frozen shoulder.