Heterotopic ossification is a frequent complication in patients with spinal cord injury. The purpose of this study is to investigate location, the efficacy of diagnostic tools, and risk factors for heterotopic ossification in traumatic spinal cord injury.

Seventy-one patients with traumatic spinal cord injury who were admitted in the department of rehabilitation medicine, Severance hospital, Yonsei university college of medicine, between September 1, 1992 and April 15, 1993, were studied. All were at least 6 months post injury. They were divided into 2 groups: 15 patients with heterotopic ossification and 56 patients without.

The results are as follows:

1) Fifteen (21.1%) of 71 patients with traumatic spinal cord injury developed heterotopic ossification.

2) The most common location of heterotopic ossification was around the hip joint, especially the anteromedial aspect.

3) The risk factors found to be significantly related to heterotopic ossification formation were anemia, presence of pressure sores and spasticity. The risk factors appeared to be cumulative.

4) Serum alkaline phosphatase levels were elevated in all of the patients who were diagnosed with heterotopic ossification within 12 months after injury. The dynamic phase of the 3 phase bone scan showed increased vascularity in areas of ossification before plain roentgenography revealed ossification.

In accordance with the above finding, close clinical observation and serial laboratory tests are needed in patients at risk. Serial serum alkaline phosphatase measurements, roentgenography and 3 phase bone scan are required for early diagnosis and evaluation of the maturity of heterotopic ossification.