Risk factors for heterotopic ossification in spinal cord injury.

Heterotopic ossification (HO) is a complication in 16% to 53% of spinal cord injured (SCI) patients. One third of these patients have moderate to severe HO that adversely affects function or health. Pharmacologic prophylaxis of HO for all SCI patients continues to be controversial. High-risk criteria for HO formation identified in total hip replacement patients are not applicable to SCI. A review of the literature did not reveal specific risk factors for HO with SCI. The charts of 100 randomly selected SCI patients, 50 with HO and 50 without HO, were reviewed retrospectively to learn if criteria which would predict high-risk patients could be identified. A total of 14 variables, seven demographic (age, sex, race, level of lesion, completeness of lesion, cause of injury, and geographic locus of patient) and seven medical (bladder stones, fractures, pressure sores, deep vein thrombosis, pulmonary embolism, spasticity, and urinary tract infections) were studied. Four of the 14 variables (age, completeness of lesion, presence of pressure sores, and spasticity) were significantly related to HO formation. The risk factors appear to be additive. When all were present, 92% of patients were found to have HO. Before the findings are applied clinically, it is suggested that a prospective study be conducted to confirm the risk predictive value of these factors in HO.