Acute Sports Injuries - MYOSITIS OSSIFICANS and ACUTE COMPARTMENT SYNDROME

Myositis ossificans (MO) is a form of heterotrophic ossification and refers to the formation of bone within a muscle. It is an infrequent complication of a contusion injury wherein bone-forming osteoblasts invade the haematoma and begin to lay down bone. The cause remains unknown; however, risk factors include severe contusions that limit the joint's range of movement (e.g. thigh contusions that limit knee flexion to <45%), repeat contusion injury and inappropriate initial management that causes a rebleed. MO should be suspected in muscle contusions that do not resolve in the expected time.

Particular signs and symptoms include initial improvements in range and pain followed by subsequent deterioration and ongoing or reappearance of inflammatory symptoms (i.e. resting, morning and night pain). The bone grows from 2 - 4 weeks after injury at which time an area of calcification may be visible on an X-ray or ultrasound and a firm lump may be felt. Once active bone formation ceases, the area of calcification gets slowly reabsorbed. As MO is self-limiting , management is typically conservative and consists of anti-inflammatory approaches and non-painful stretching and strengthening.

Acute compartment syndrome occurs when interstitial pressure within a compartment exceeds perfusion pressure leading to the onset of ischaemia and, ultimately, cellular anoxia and death. Muscles in the extremities are surrounded by a strong, thick connective tissue called fascia. The fascia serves as an attachment site for muscle, aids in force transmission and forms non-distensible compartments that facilitate muscle-pump mediated venous return. Injury leading to swelling or bleeding into one of the fascial compartments (usually the flexor compartment in the forearm or anterior compartment of the lower leg) can result in the development of acute compartment syndrome. This is characterised by pain that is out of proportion to the inciting injury, pain on passive stretching and at rest, paraesthesia and pulselessness (although the latter is a late finding as the interstitial pressure needs to be high enough to occlude arterial flow). Acute compartment syndrome represents a medical emergency that may require urgent fasciotomy (release of fascia surrounding muscle compartment) in order to prevent permanent, irreversible damage.

REFERENCES

Brukner, P., 2012. Brukner & Khan's clinical sports medicine. North Ryde: McGraw-Hill.