Calcification may occur in tendons due to multiple mechanisms. These include:
ï Degenerative: necrosis of tenocytes due to ischaemia or repetitive trauma
ï ëTraction spursí: endochondral ossification at tendon or ligament insertions
ï Crystallopathy
Calcific tendinosis is a crystal arthropathy which results in abnormal deposition of calcium hydroxyapatite crystals in tendons, most commonly supraspinatus. Other tendons may be affected including flexor carpi ulnaris at the wrist, and the gluteal and rectus femoris tendons at the hip. Involvement of longus colli is a recently described, uncommon cause of acute neck pain.
Regardless of location, the pathogenesis of calcific tendinosis is poorly understood. It is a condition characterised by multiple phases:
ï Pre-calcification: cellular change in tendon
ï Calcification: deposition of crystals to form a partly liquified deposit, which incites an inflammatory response and resorption
ï Post-calcification: repair and restoration of tendon fibres
The inflammatory/ resorptive response produces pain; up until this stage, the process is generally asymptomatic.
Intratendinous calcific deposits may have various appearances on ultrasound including arc shaped, nodular, punctate and cystic. Small, degenerative calcifications are common, particularly in elderly patients. These tend to be sharply defined and arc shaped, with acoustic shadowing. Acutely painful calcifications tend to be larger and more amorphous in shape, without acoustic shadowing.
Various therapeutic options are available. These have variable effectiveness and little in the way of high-level evidence, and include:
ï Nothing: self-limiting
ï Non-steroidal anti-inflammatory drugs (NSAIDS)
ï Physiotherapy
ï Extracorporeal shock wave lithotripsy
ï Needling
ï Surgery: Arthroscopic debridement
Needling is usually performed under ultrasound guidance. It has several advantages including being minimally invasive, generally well tolerated, widely available, relatively inexpensive and quick. Most operators use a standard procedure with minor individual variations. First, there is injection of local anaesthetic into all tissue layers, including the calcification itself. This is followed by aspiration and breakup of the calcification with a larger needle (18 ñ 14 g). Barbotage is a term used to describe wash out of the calcification with saline or local anaesthetic combined with aspiration. This may be a double needle or single needle technique. Aspiration and break up is followed by injection of a combination of steroid and longer acting anaesthetic into the remaining calcification and tendon, and into the overlying subacromial bursa.