Heterotopic Ossification (HO) & Cysts
Heterotopic ossification (HO) is the development of abnormal bone in soft (non-skeletal) tissue, primarily in the region of the hip and knee joints. It occurs in many spinal cord injured individuals and may develop within days following the injury or several months later. HO occurs below the level of injury and the cause is unknown. Most cases cause no significant additional physical limitations, but in a minority of patients, HO may result in a major limitation of joint motion. Symptoms you may notice is difficulty or limitation in your ability to perform activities of daily living, especially activities that require you to bend at the hips. However, sometimes the onset of HO is more rapid, and symptoms at that time may be swelling of one hip and warmth and redness overlying the swelling. In addition to decreased range of motion and swelling in the area of the HO, other symptoms may include increased spasticity, swelling of the entire leg, and/or elevated temperature. If you suspect you have HO, contact your physician. He or she will do an X-ray of your hips and knees, a special isotope bone scan, and blood tests.
If you have HO, watch your skin closely. The HO can increase the amount of pressure applied to the tissue under certain bony prominences. A significant loss of motor function could strongly suggest a cyst. The changes in sensation or motor function may develop gradually. You may notice that it is more difficult to do some of your functional activities, such as holding a cup or putting on your clothes, or you may notice a change in your balance or find that you are burning yourself in places where you previously had sensation. Be aware of your sensory level and muscle strength. If you notice significant changes, contact your physician, and give him or her specific information about the changes you have notices. A muscle and sensory test will be conducted and if you have neurologic deterioration due to a cyst, it may be corrected with surgery. The earlier HO is detected, the easier the treatment.
More Technical: A condition not well understood that occurs in acute spinal cord injury and consists of the laying down of bone outside the normal skeleton, usually occurring at large joints such as the hips or knees. The primary problem with heterotopic ossification, or HO, is the risk for joint stiffening and fusion. Should the hip or knee become fused in a certain position, a surgical release is necessary to allow range of motion to occur. Unfortunately, it takes between 12 and 18 months for heterotopic bone to mature once it has developed. Activities that are used to prevent the development of HO include range of motion programs and other functional activities that move the joints within a functional range. Currently treatment is limited with the exception of preventing the joint fusion (termed ankylosis).