Clinical Manifestations. The patient’s
appearance varies with the level of the vertebral lesion. Although partial
sacral agenesis may not be noticeable, lumbar or complete sacral agenesis is a
The posture of the lower limbs has been likened to that of the “sitting
Buddha” and is characterized by flexion-abduction contractures of the hips and
severe knee flexion, with popliteal webbing; the feet are in equinovarus and
tucked under the buttocks. Inspection of the back reveals a bony prominence,
which is the last vertebral segment, and often gross motion between this and
the pelvis. Flexion-extension may occur at the junction of the spine and pelvis
rather than at the hips. When the patient sits unsupported, the pelvis rolls up
under the thorax. Scoliosis, hemivertebrae, spina bifida, and meningocele are
common associated spinal anomalies.
With low-level lesions, deformities of the foot and lower limb resemble
those of resistant clubfoot or arthrogryposis. Children may be misdiagnosed for
several years or until problems with toilet training call attention to the
sacral anomalies. Although the clinical signs resemble those of arthrogryposis,
patients with arthrogryposis have full sensation in the lower limbs, bowel and
bladder control, and normal vertebral architecture.
The neurologic deficit is one of the most unusual features of this
condition. Motor paralysis is profound, with no voluntary or reflex activity,
and it corresponds anatomically within one level to what might be expected from
the vertebral loss. Even patients with the most severe involvement have
sensation to the knees and spotty hypesthesia distally. Trophic ulceration of
the feet is quite uncommon, suggesting at least protective sensation.
Bladder dysfunction is a consistent finding in all patients, even those
with a relatively minor hemisacral defect, but the patterns of urinary function
vary. Patients exhibit individual mixtures of upper and/or lower motor neuron
disorders; perineal electromyography is necessary to obtain the correct
diagnosis. Severe constipation with absence of the normal sensation of rectal
distention is a common bowel abnormality.
The visceral anomalies are usually confined to the anogenital region
(imperforate anus is the most common) and urinary tract (e.g., bladder
dysfunction, hydronephrosis, vesical reflux and diverticulum, fused or absent
kidney, exstrophy of the bladder, and hypospadias).
Radiographic Findings. A lesion at the level
of the lumbar spine results in the complete absence of all vertebral
development below it, including the sacrum and coccyx. However, lesions of the
sacrum are less consistent; and in about one third of patients the defect
occurs on one side only. In lumbar or complete sacral agenesis there is usually
no bony connection of the spine to the pelvis. The spinopelvic articulation
should be examined with flexion-extension radiographs because its stability has
important implications in treatment and rehabilitation.
Treatment. Treatment measures vary with the level of
involvement; and the management plan, based on the following broad concepts,
must be highly individualized.
If the sacropelvic ring is intact, the spinopelvic junction is usually
stable and the patient can walk with minimal or no brace support. Patients with
significant deformities of only the feet and legs requirevigorous correction,
begun at birth, including serial plaster casts in conjunction with stretching
and exercises to position the feet plantigrade and the knees in extension.
Surgical release may be necessary if conservative measures are inadequate.
Because of the high incidence of associated defects that may lead to
serious renal impairment, recognition and treatment of urinary abnormalities
are an important part of management. Delay in diagnosis and treatment may lead
to upper tract deterioration and severely limit