Calcium Hydroxyapatite Crystal Deposition Disease

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Calcium Hydroxyapatite Crystal Deposition Disease (Calcific tendonitis/periarthritis)

http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=101028

Calcium hydroxyapatite (HA) – Ca5(PO4)3.2H20 (often referred to as BCP – basic calcium phosphate) – found in bone and teeth, but can deposit in soft tissues. Affects periarticular structures more than joints – most commonly tendons. Deposition of calcium phosphate crystals  acute calcific periarthritis. More common in hypercalcaemia, chronic renal failure and hyperparathyroidism. Present with acute onset of pain, swelling, erythema, tender to pressure and limitation of movement (may mimic gout). Self limited in most cases. Usually middle aged females. Not known if deposition occurs as result of a chronic strain in an area that is poorly vascularised or if the deposition causes the ‘tendonitis’ (ie cause vs effect).

Shoulder is commonest site – but has been reported around almost all joints. Can be seen on x-ray – often only an incidental x-ray finding. 10 cases reported affecting first metatarsophalangeal joint and surrounding structures . Case report of hydroxyapatite deposition in achilles tendon – onset of pain was sudden with palpable tender lump.

Stages:
• Silent stage - deposit is within tendon with no or minimal symptoms. On x-ray – a sharply defined circumscribed deposit.
• Mechanical stage – deposit enlarges  impingement like symptoms. Deposit liquefies  on x-ray it is less well defined, but still within tendon
• Adhesive periarthritis stage – adhesive bursitis develops  pain and limitation of movement

Occasionally get bony erosions beneath tendon.
Can occur as an intraarticular disease  destructive arthropathy.

Management:
No treatment if asymptomatic
Physical therapy and NSAID’s for symptoms
Corticosteroid injection (needle may disrupt the deposition  ?stimulate phagocytosis)

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