Pathogenesis (disease development)
Tendinosis calcarea is thought to result from degenerative processes, such as those triggered by reduced blood flow to the tendon attachment to bone. Mechanical causes such as an anatomically narrow space may also promote degeneration. It is likely that the development of calcifications is multifactorial. The calcification foci can cause discomfort due to a local increase in pressure in the tendon tissue. In the shoulder joint, for example, the calcium crystals cause thickening of the supraspinatus tendon (attachment tendon of the supraspinatus muscle). When the arm is raised, the tendon is then pinched between the shoulder joint and the acromion (subacromial constriction syndrome). The immune system reacts to the embedded calcium crystals by macrophages (“scavenger cells”) breaking them down to the greatest possible extent. The resulting resorption cavities are replaced by scar tissue.
The following are the stages of tendinosis calcarea using calcific shoulder as an example:
Precalcific stage (phase of cell transformation).
- Metaplasia (differentiation (conversion) of one type of cell into another) of tendon tissue into fibrocartilage or tendinocytes (tendon cells) into chondrocytes (mediators (“mediators”) of tissue calcification and ossification (ossification)).
- No or only very mild pain
- Radiologically, no changes are yet detectable.
Calcification (phase of calcification).
- Partial death of the cartilage tissue
- Calcification
- Diagnosable by sonography (ultrasound) as well as X-ray examination.
- Painful limited mobility of the shoulder and nocturnal pain
Postcalcifying stage (phase of resorption).
- Resorption – giant cells and macrophages (phagocytes) approximately degrade the calcium crystals.
- Carry-over of calcium particles into adjacent bursa (bursa subacromialis) is possible → bursitis (bursitis).
- Often highly acute symptomatology (probably due to increased intratendinous pressure).
Repair stage (phase of repair))
- Once the calcification has resolved, recurrence (recurrent calcification) is extremely rare. The calcification is replaced by new scar tissue that fills the remaining tendon injury.
Not every calcified shoulder goes through this cycle completely.
The individual stages can last for years. It is also possible that the disease does not go through all the stages previously described. It may also remain in one stage.
Etiology (causes) of tendinitis calcarea of the shoulder (calcific shoulder)
Biographic causes
- Anatomic variants – variations in the shape of the involved bones and soft tissues that drive degenerative processes.
Behavioral causes
- High-risk sports such as throwing sports
Disease-related causes
Injuries, poisonings and other consequences of external causes (S00-T98).
- Trauma (injury) of the shoulder, unspecified.
