A 60 y.o. woman with a history of renal failure presents with shoulder swelling and pain.

Serum calcium was normal

what is wrong?

Our patient had a Milwaukee shoulder.  This is a neuropathic joint caused by crystal deposition in the joint.  It was previously called pseudogout since the crystals are not uric acid but  rather calcium phosphate or pyrophosphate. Severe articular surface destruction occurs  with total rotator cuff disruption. 

This was first described in 1857 by  an Irish surgeon .  In 1981 a group of Milwaukee-based researchers  reported four cases of rotator cuff loss and shoulder arthropathy  with calcium phosphate crystals on aspiration of the shoulder effusion. The crystals are most easily seen with an alizarin red stain but  they are often missed on light microscopy.  The crystals have been shown to induce prostaglandin E2, a potent inducer of osteoclast formation.

 MRI findings mirror plain radiographs and include:

—large joint effusions

—complete rotator cuff tears

—narrowing of the glenohumeral joint

—destruction of subchondral bone

although they can sometimes be needle like , most often calcium phosphate crystals are rhomboid and not always birefingent on polarized light

 Calcium phosphate crystals are deposited when levels of calcium and phosphorus exceed a saturation point . This can happen in kidney disease, genetic disorders of phosphate metabolism , hyperparathyroidism or excess Vit D ingestion. Less common causes of calcium phosphate deposition include  hypophosphatasia, a condition which is associated with low levels of alkaline phosphatase, hypothyroidism, hypomagnesemia and even high iron concentrations like those found in hemochromatosis.

CPPD   can sometimes be seen on plain film both with calcific periarthritis as in our patient  or meniscal calcification.

meniscal calcium can be seen in calcium phosphate crystal disease.

This process also occurs  in calciphylaxis.  End stage renal failure can lead to calcium and phosphate building up in  arterioles deep in the skin causing blockage with necrosis of the overlying skin.

CALCIPHYLAXIS

TREATMENT

The first line therapies include NSAIDS and steroid injection. Pyrophosphate analogs have been shown to be useful in some settings.  Complete destruction of the humeral head can occur in which case a reverse total shoulder replacement is often recommended. A reverse prosthesis exchanges the ball and socket using the deltoid rather than the rotator cuff for movement.

reverse shoulder replacement

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https://radiopaedia.org/articles/milwaukee-shoulder

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