Holger Werfel Scheuermann, Danish surgeon), an osteochondrosis of unknown cause involving the the spine and frequently causing lower thoracic kyphosis.
The term juvenile kyphosis has sometimes been used to designate this condition. Currently the diagnostic criteria include the presence of abnormalities in at least three contiguous vertebrae, each of which must have wedging of 5 or more. Some patients have vertebral irregularity without wedging, however. The kyphotic deformity may become progressively more fixed in position.
Radiographically, the affected vertebral bodies show an undulant superior and inferior surface with cartilaginous or Schmorls nodes and surrounding sclerosis. Other findings may include loss of intervertebral disc height, wedging of the anterior portion of the vertebral bodies, and prolapse of large foci of intervertebral disc tissue anteriorly. This may lead to formation of a limbus vertebra as a result of extension of the extruded anterior discal material beneath the apophyseal centres of ossification, separating them from the vertebral body. Synostosis of one vertebral body with its neighbour may also occur.
A condition sharing some features with Scheuermann's disease but without the thoracic deformity, which is localized to the lower thoracic and lumbar spine, has been described as juvenile lumbar.
The normal thoracic spine is moderately kyphotic. The amount of kyphosis varies greatly between individuals; the normal range is from 20-40 degrees. The appearance of a round back deformity is either postural or due to Scheuermann's, other rarer causes should be ruled out i.e. neurofibromatosis or hereditary conditions such as achondroplasia or developmental vertebral anomalies.
The incidence in the population of Scheuermann’s kyphosis is between 4-8%. Males are affected more commonly than females. A familial tendency has been noted with some incidences of autosomal dominant inheritance being reported
The appearance of a round back deformity is exacerbated by other postural changes. Round shoulders, contracted pectoral muscles, a forward protruding neck with tight cervical extensors, increased lumbar lordosis with an anterior pelvic tilt, tight hip flexors and tight hamstrings. All these factors are associated to a lesser or greater extent and all contribute to the patient’s appearance.
Classification of Scheuermann's Kyphosis
A thoracic kyphosis with its apex typically at thoracic vertebra 8. There is often a gradual onset of wedging of the vertebra. This condition is at this time felt to be idiopathic.
A low thoracic-upper lumbar kyphosis occurring in a predominantly male population. This is much less common and less severe in magnitude however patients are more likely to present with low back pain. This group is also known as apprentice's kyphosis due to its association with strenuous muscular activity.
The Natural History
The diagnosis is usually established in early adolescence. Growth exacerbates the thoracic kyphosis with progression occurring until growth ceases. In adult life mild to moderate progression occurs, this is seldom severe. Late problems are mainly due to degenerative spondylolysis in the hyperlordotic lumbar region. Patients with type 2 disease rarely have symptoms as an adult.2
Presentation and Clinical Findings
The presenting problem is principally one of appearance. This is often noted by the parents or at school. Pain with type 1 curves is uncommon and is rarely severe enough to warrant surgical intervention. Type 2 patients are more likely to present with lumbo-sacral pain. Very rarely a patient may present with neurological symptoms of upper motor neurone origin.
Physical examination looks principally for three factors. The kyphosis, is it fixed or flexible, does it have an element of scoliosis to it. The presence or absence of neurological signs. Most importantly to what degree is this kyphosis altering this person appearance when compounding factors (which are not surgically correctable) such as goose-necking and round shoulders are taken into account.
Standing AP and Lateral radiographs of the entire thoraco-lumbar spine. This should show the pelvis to allow for assessment of iliac crest ossification (Risser's sign). The AP film allows for assessment of any scoliotic element present. The curve is measured using a method analogous to Cobb's on the lateral film.
Associated findings include end plate irregularity, Schmorls nodes (invagination of the end plates by disc material 3, Typically anterior in Scheuermann’s and posterior in scoliotic patients), decreased disc space and wedging of at least three adjacent vertebra greater than 5 mm.
MRI scanning of the thoracic spine is carried out preoperatively to out rule any associated spinal cord problems. This modality is not a diagnostic tool as the incidence of false positive vertebral changes in normal patients is high.
The exact cause of Scheuermann’s kyphosis is unknown. An autosomal dominant mode of inheritance has been described in some families. The final common pathway in all theories is a disturbance of growth between the front and the back of the vertebra, with growth anteriorly being decreased. Scheuermann’s felt that the problem was due to a vascular necrosis of the cartilage ring apophysis. This has since been shown not to be the cause, as it is now known that growth occurs at the end-plate epiphysis of the vertebral body.
Schmorl felt that the problem was due to disc protrusion into the vertebrae anteriorly leading to decreased anterior growth.
Disordered endochondral ossification of the endplates is associated with proteoglycan abnormalities. It is not known if these are the cause of the problem or an effect.
Decreased bone density is not a cause. The typical changes in osteoporotic bone show a uniform flattening not just anteriorly.
Abnormalities of the vertebral bodies including abnormal configuration, Schmorl's nodes and apophyseal changes are found among athletes. These abnormalities are similar to those found in Scheuermann's disease. These findings have lead people to surmise that excessive loading of the immature thoracic spine may be a causative factor in the aetiology of Scheuermann’s kyphosis.
The approach is through a left lateral rib excising incision. The lung is deflated and the anterior thoracic spine is clearly visualised lying adjacent to the pulsating descending aorta. The contracted anterior longitudinal ligament is divided at each intervertebral level and multiple discectomies are carried out. It us usually possible to do this proximally and distally inside the thoracic cavity from T5 to T12. The vertebral endplate is also removed. The rib is then morcelized and used as graft.
Alternatively anterior decompression can be done thoracoscopically. Whilst this is minimally invasive it is technically difficult to gain access to the narrowed anterior disc spaces and removal of all the disc material may not be possible
Second stage-Posterior fusion and discectomy
This is either done at the same sitting or 1-2 weeks later. All facet joints in the area to be fused are excised. Sub-laminar hooks are placed at intervals. Proximally a claw configuration is used for extra stability of fixation. Distally pedicle screws provide a firm hold. The use of sublaminar wires to suplement fixation is an option. The rods are pre bent before application to the spine. Spinnous processes and interspinous ligaments are excised, followed by decortication of the laminae. Cancellous bone harvested from the posterior iliac crest is used to graft the posterior spine.11
Care must be taken to ensure fixation extends both sufficiently proximally and distally. This usually is as far as the first lordotic segment. Failure to do this will result in an acute junctional kyphosis. Following surgery patients are allowed to walk without the support of bracing or plaster jackets.
Complications of surgery
Two-stage fixation of the spine is a demanding procedure, both technically and for the patient. All the usual complications of spinal surgery may occur ranging from dural tears to neurological impaiment. Iatrogenic neurological injury may be due to a number of factors. Direct impingement by metal implants i.e. pedical screws, sublaminar wires or it may be due to the correction itself which may cause an infolding of the ligamentum flavum onto the spinal cord. Of note is the fact that the onset of these symptoms may be several days after surgery thus all patients require careful observation for the first week following surgery.
Scheuermanns kyphosis is a common finding in adolescents. The majority of problems are due to the effect the roundback posture can have on body image. Symptoms warranting surgery are rare. Two-stage surgical correction is the definitive treatment however this should not be undertaken without the patient being fully informed of the operative risks. For suitable patients surgery can provide good and lasting correction of their objective deformity with a high level of patient satisfaction.