In the embryonic stage, the hemivertebral system is underdeveloped or the cartilage center is asymmetrically developed, and it appears without fusion. Hemivertebral bodies are common in vertebral deformities and can be single or multiple, mostly on one side, and mostly posterior or lateral. Congenital scoliosis is mostly caused by hemivertebral bodies. However, if two adjacent vertebrae have hemivertebral bodies on different sides at the same time, they can compensate for each other and maintain the balance of the axis without significant scoliosis.
Hemivertebral deformity is classified according to anatomical morphology: 1. Simple redundant hemivertebral body There are round and oval bone blocks between two adjacent vertebral bodies, and when the development is completed, it is fused with one or two adjacent vertebral bodies, and there are often pedicles and extra ribs in the thoracic vertebrae at the same time. 2. The simple wedge-shaped hemivertebral body is roughly a triangular bone block, and there is no excess rib bone in the thoracic vertebrae, which can be regarded as a component of the complete spine. 3. Multiple hemivertebral bodies combined with one side fusion Fusion can occur in the vertebral body or adnexa. with rib closure or other deformities. 4. The multiple hemivertebral bodies are round, oval or wedge-shaped. 5. Balanced hemivertebral body Two or more hemivertebral bodies on opposite sides cancel each other out and do not produce obvious scoliosis. 6. Posterior vertebral body Only the osteogenic center on the posterior side of the vertebral body develops, while the osteogenic center does not develop, causing the posterior half of the vertebral body, which is wedge-shaped in lateral view, often causing kyphosis.
A "free" hemivertebral body (defined as a normal disc and pedicle above and below the hemivertebral body) is a risk factor for the progression of the deformity. The fusion of the hemivertebral body with the adjacent vertebral body will greatly reduce the likelihood of the deformity progressing. After fusion of the hemivertebral body and adjacent vertebral bodies on both sides, the deformity almost never progresses.
Diagnosis is made with a careful history and a rigorous physical examination, as well as complete imaging and electrophysiology studies. The history should note the child's birth, growth, development, and family history, particularly for concomitant musculoskeletal problems, genitourinary anomalies, or cardiac abnormalities. If motor dysfunction is present, cerebral palsy should be considered; If a child with normal intelligence has motor retardation, he or she may have spinal cord dysfunction; Older children should be aware of neurological deficits. Back pain, limited spinal mobility, weakness in walking, numbness of limbs, ability to control bowel and bowel movements, presence of concomitant foot deformities, differences in lower limb length or foot size, and congenital scoliosis with genitourinary tract deformities. Family history is also important because children with certain bone disorders are associated with familial and childbirth, such as sacral hypoplasia and maternal diabetes. However, the genetic predisposition to thoracolumbar deformity is not predisposition, and no clear genetic predisposition has been found so far.
The examination should expose the child to the fullest. Starting from the head, the range of motion and hairline of the cervical spine, whether there are abnormalities in the eyes, ears and face, whether there are lumps, depressions and hair spots on the back and buttocks. A complete neurological examination is also performed, including rectal tone, sensation, and autonomic control.
Radiography of the spine is the basis for classifying and assessing the risk of thoracolumbar deformity and scoliosis progression. Anterolateral x-rays of the spine should be routinely taken, and standing x-rays should be taken in children who are able to stand. CT has a good indication of the extent of thoracolumbar deformity and compensation of surrounding vertebral bodies, axial CT can provide spinal canal abnormalities and defects such as spina bifida, and CT 3D reconstruction has a better indication of congenital malformations. MRI is the best way to determine the presence of neuraxial malformations, which can occur in about 15% of patients with congenital spinal deformities.
The efficacy of non-surgical hemivertebral surgery** is not ideal, and most children require surgery**. Scoliosis caused by hemivertebral body is congenital scoliosis, which is a structural scoliosis, and the angle of scoliosis is large, which can lead to severe curvature and imbalance of the spine, and the hemivertebral body of the lumbosacral segment will also produce pelvic tilt and unequal length of lower limbs. If kyphosis is present, the usual orthodontic treatment is not satisfactory. If hemivertebral resection is performed, the fusion segments can be reduced and better correction can be achieved. However, hemivertebral resection is not necessarily necessary for thoracic hemivertebral bodies, unless progressive and significant deformity, and lumbosacral hemivertebral bodies are an absolute indication for resection. Intraoperative neural evoked potential monitoring or arousal testing may be done. Patients with lumbosacral hemivertebral body resection and compensatory thoracolumbar scoliosis require a long period of external fixation with a brace after surgery to control the compensatory thoracolumbar scoliosis.
The easiest to remove with surgery is a single segmented hemivertebral body, which can be better corrected. Hemivertebral body excision has two functions: one is to control the development of the curvature, and the other is to correct the curvature. Hemivertebral bodies with complete segmentation without significant curvature may not be excised, but those with significant spinal imbalance or trunk tilt may need to be excised to achieve an effect similar to that of a spinal osteotomy. The lumbosacral hemivertebral body must be removed as soon as possible to prevent progressive compensatory curvature of the thoracolumbar segment and worsening pelvic tilt.