Disease Prevalence:
Orthopaedic surgeons are frequently asked to evaluate patients with stiff and painful shoulders. Among the most common causes for such clinical condition is adhesive capsulitis (or frozen shoulder), which is thought to affect approximately 2-5% of the general population. The incidence in patients with diabetes is much higher, up to 29% in some studies.
Clinical Summary of Adhesive Capsulitis:
Adhesive Capsulitis may be summarized briefly as the clinical syndrome of shoulder pain and progressive loss of motion and eventual improvement of symptoms. The cause is classified as either primary (idiopathic) or secondary, if due to a known precipitating condition. Risk factors associated with developing adhesive capsulitis include diabetes, female sex, middle to older age, and thyroid disease. Secondary causes of adhesive capsulitis include trauma, shoulder surgery, degenerative arthritis, rotator cuff tears, or prolonged immobilization.
The condition is characterized functionally by loss of both active and passive range of motion and anatomically by thickening and contracture of the joint capsule. The term "Adhesive Capsulitis" was coined by Neviaser when he noted the contracted capsule peeled from the humeral head like "adhesive plaster from skin". A broader term "Frozen Shoulder" was used by Codman in 1934 to describe this and related conditions. There is a commonly accepted progression of three clinical phases: painful freezing, stiff/frozen phase, and eventually thawing with slow return of motion. Many patients will have some residual loss of motion for several years. For people with diabetes, residual, permanent loss of motion can be as much as 50%. The natural history of the disease has been shown to be more dismal than once thought.
Pathology of the Disease:
Histopathologic changes that occur in the joint capsule and synovial lining are cellular changes of chronic inflammation, fibrosis, perivascular infiltration in the subsynovial layer and increased vascularity. There is some debate as to whether the disease is primarily inflammatory or fibrotic in nature and there is support for both, depending on the stage of disease. Some have shown that arthroscopy reveals a highly vascular, red, inflamed synovium. Neviaser defined four stages of arthroscopic adhesive capsulitis ranging from acute synovitis to chronic adhesions. The pathology is not clearly understood and this makes optimal treatment more difficult to determine.
Limitations of Current Imaging Studies:
Imaging modalities commonly used to evaluate the shoulder such as x-ray (to rule out arthritic changes or fractures) are unremarkable in primary adhesive capsulitis. Traditional arthrograms or contrast Magnetic Resonance Imaging may show decreased capsular volume and edema but are invasive and expensive tests. Magnetic Resonance Arthrogram shows thickening of the coracohumeral ligament and the joint capsule in the area of the rotator interval. Although MRI can demonstrate edema and inflammatory changes, its cost seems prohibitive to follow clinical disease on a serial basis, perhaps monthly as the disease progresses. Ultrasound is a much more likely candidate for serial examination.
Successful Use of Ultrasound in Rheumatoid Wrist Studies:
Recent reports in the literature have shown color doppler ultrasound (CDUS) to be a promising tool for estimation of synovial inflammatory activity in rheumatoid arthritis. Researchers used specific quantitative criteria to measure the resistivity index of small blood vessels in the synovium and color pixel fraction. Both measures attempt to quantify vascularity as a surrogate indicator of inflammation in the joint capsule. In a subsequent study they injected the wrists with corticosteroid and then obtained ultrasound images one month later which showed changes in the resistivity index and color pixel fraction that correlated with the improved clinical evaluation and functional improvements.
Ultrasound in Adhesive Capsulitis:
Ultrasound study of the shoulder has many benefits over MRI/MRA including: no contraindications or risk to patients, non-invasive, and relatively low cos. Ultrasound is comparable to MRI in studying the synovium with much less downside. Despite is theoretical advantages; there are limited studies in the literature reporting on color doppler ultrasound to evaluate adhesive capsulitis of the shoulder. In one study, researchers correlated ultrasound findings with arthroscopic findings and concluded that ultrasound can provide an early, accurate diagnosis of adhesive capsulitis. Their criteria, however, were qualitative using echotexture and increased doppler flow to indicate increased vascularity. No quantitative measurements were made.
Clinical Importance of Proposed Study:
Although the objective in treating patients with adhesive capsulitis is clear (to restore full, pain-free motion and unrestricted shoulder function) the optimal treatment remains unclear. This is due in part because there is no clear consensus on diagnosis, poor understanding of the pathology, and difficulty comparing the effectiveness of treatment regimens. As in many poorly defined medical conditions, multiple, different empiric treatments are employed with varying success. If we could more clearly identify diagnostic criteria and reproducibly stage the disease we could then more reliably and scientifically compare treatment approaches and thus provide a real benefit to many patients with this common condition. Our proposed study is an important step in this process.
