Lumbosacral agenesis: a new classification correlating spinal deformity and ambulatory potential

Lumbosacral agenesis is a rare congenital anomaly. There is no consensus regarding the optimal orthopaedic management of the spinal anomaly and the concomitant lower-extremity deformities. We propose a method to predict ambulatory potential and to identify patients who will benefit from early operative treatment of the lower-extremity deformities to facilitate walking.

We reviewed the records and radiographs of eighteen patients with total or partial absence of the lumbar spine and total absence of the sacrum. Thirteen patients (Group I) had lumbosacral agenesis alone, and five patients (Group II) had a concomitant myelomeningocele. Three types of spinal deformity were identified. In Type A, there was either a slight gap between the ilia or the ilia were fused in the midline. One or more lumbar vertebrae were absent. The caudad aspect of the spine articulated with the pelvis in the midline, maintaining its vertical alignment. In Type B, the ilia were fused together, some of the lumbar vertebrae were absent, and the most caudad lumbar vertebra articulated with one of the ilia, with the most caudad aspect of the spine shifted away from the midline. In Type C, there was a total agenesis of the lumbar spine, the ilia were fused together, and there was a visible gap between the most caudad intact thoracic vertebra and the pelvis.

In Group I, all seven patients with Type-A deformity were community ambulators and one patient with Type-B was a household ambulator. No other patient in the series was able to walk. Nine patients had cervical spine anomalies, and seven patients had scoliosis. No patient was managed with a spinopelvic fusion.

We believe that all Group-I, Type-A patients should have correction of lower-extremity deformities as they have a very good potential to walk. The other patients should have operations on the lower extremities only if the deformities preclude sitting or wearing shoes or braces. The cervical spine should be examined radiographically for atlantoaxial instability or congenital anomalies.