congenital absence of sacrum and lumbar vertebrae, an abnormal condition present at birth and characterized by varying degrees of deformity, ranging from the absence of the lower segment of the coccyx to the absence of the entire sacrum and all lumbar vertebrae. Congenital absence of the sacrum and the lumbar vertebrae is relatively rare. Lesser degrees of this anomaly may present so few signs that marked deformities are not present, and the condition may not be diagnosed unless accidentally found on radiographic examination. More severe forms display gross deformities and neurological deficits. Signs and symptoms of the more severe kinds include short stature, flattened buttocks, muscle paralysis to varying degrees, muscle atrophy in the lower extremities, foot deformities, contractures of the hips and knees, and varying degrees of loss of sensation, especially sensation distal to the knees. The treatment varies greatly for the congenital absence of the sacrum and lumbar vertebrae and depends on severity. Surgical intervention may be reconstructive or may involve disarticulation procedures at various spinal levels and subsequent fusion of the remaining vertebrae. Depending on the severity, many patients with this anomaly gain enough stability to sit and to walk with assistance through surgery. The most severe forms are usually fatal.
