Calcium Hydroxyapatite Deposition Disease
A 54 year old hairdresser comes to your office complaining of right shoulder pain over the past 3 months that seems to be much worse at night. Some pain does occur with abduction of her arm while using scissors. She has already been to her primary care provider and minimally improved with NSAIDs. You order a plain x-ray that shows an ill-defined and fluffy deposit along the supraspinatus. You diagnose her with calcium hydroxyapatite deposition disease. According to this description, which phase of this disease is most likely?
Basic calcium phosphate crystals encompass several types of crystals, including carbonate apatite, octacalcium phosphate and whitlockite crystals. Crystals can deposit in tendons, bursa, muscles or periarticular structures. More recent studies have shown the calcium that deposits of calcific tendinitis is carbonate apatite, as opposed to studies from 1976 and 1990 that described hydroxyapatite [2-5]. The exact etiology is unknown. Some authors have speculated it is due to tendon degeneration, while others describe a cell-mediated process [6-7].
Figure 1. Calcific tendinitis of the supraspinatus in the acute phase, showing a more “fluffy apperance”. (adopted from )
Figure 2. Calcific tendinitis of the shoulder with a more discrete, well defined calcification correlating with the post-calcific stage (adopted from ).
Figure 3. Calcific tendinitis of the hip (adopted from ).
Figure 4. Rotator cuff barbotage and calcific return. Acoutic shadowing is present (adopted from ).
Answer B. The natural progression has been described in 4 stages: precalcific, formative, resorptive and postcalcific. In the precalcific phase, collagen fibers of the tendon undergo metaplasia into fibrocartilage tissue. During the formative phase, chondrocytes begin to develop within the areas of fibrocartilage formation with eventual formation of calcified apatite crystals. The resorptive phase is described as the most inflammatory, although most individuals go through the resorptive stage with mild or no symptoms. At a more cellular level, lymphocytes, leukocytes, and giant cells forming calcium granulomas characterize the inflammatory resorptive phase.
Depending on your practice or the patient’s course, you may have plain radiographs of the shoulder to review. Many times this will greatly aid with the diagnosis and it is important to get external rotation views if CHDD is suspected. Plain radiographs can distinguish calcifications from mature ossifications, which will show a distinct cortical and/or trabecular bone pattern. Calcifications of plain radiographs are described as fluffy, ill-defined (Figure 1), and inhomogeneous or as discrete, homogeneous, and well defined. The ill-defined lesions are thought to be more associated with the acutely symptomatic phase of calcific tendinitis, while the well-defined calcifications tend to be present in patients that are asymptomatic or have chronic pain.
K. Uhthoff, K. Sarkar, and J. A. Maynard, “Calcifying tendinitis. A new concept of its pathogenesis,” Clinical Orthopaedics and Related Research, vol. 118, pp. 164–168, 1976.