Keywords:
Musculoskeletal soft tissue, MR, Ultrasound, Conventional radiography, Education, Inflammation
Authors:
C. Azzopardi1, G. Kiernan2, J. Teh2; 1Oxford /UK, 2Oxford/UK
DOI:
10.26044/essr2019/P-0100
Background
Hydroxyapatite deposition (HAD) is a common condition predominantly seen in the rotator cuff tendons.
It has been described in association with metabolic disorders such as diabetes and thyroid disease.
The pathogenesis is uncertain and different theories have been proposed [1].
In our review we aim to discuss the condition of hydroxyapatite deposition while focussing on the less described appearance of associated myositis.
Epidemiology:
The shoulder joint is most commonly affected by HAD and while 3% of the population may be asymptomatic,
7% will present with shoulder pain.
This condition primarily affects patients who are between 40 and 70 years old,
affecting both genders to the same extent [2].
Migration towards the myotendinous junction is rare and few cases have been reported in the literature [2].
Clinical presentation:
HAD can both symptomatic and asymptomatic and symptoms are often present in only 31% [3].
Pain is the most common presenting feature and this may be both acute or chronic in nature.
Examination usually reveals a limited range of motion especially in relation to the shoulder joint [2].
Pathophysiology:
Several theories have been proposed regarding the pathogenesis of HAD.
The most popular theory suggests that HAD occurs in stages.
The first stage is a result of longstanding hypoxia which results in transformation of the tendon to fibrocartilage.
Triggers may be mechanical or vascular in nature and tend to affect what is known as the ‘critical zone’ [4].
The clinically painful stage is known as the resorptive phase on a pathological level.
The pain results as a consequence of increased blood flow [4].
It is during this phase that calcium may migrate into adjacent soft tissues or bone. The co-existing acute inflammatory response is the soft tissue or osseous oedema seen on MRI.
The resorptive phase is followed by clinical resolution of symptoms and associated disappearance of the calcific deposits.
The calcium is replaced by scar-like tissue [2].
This is known as the post calcific phase.