The Orthopaedic management of Scheuermann's kyphosis

St Mary's Orthopaedic Hospital,
Cappagh,
Dublin 11.

Lunn J, Byrne S, Morris S, Mc Cormack D.

Introduction:

H.W. Scheuermann, a Danish surgeon working in Copenhagen published a report in 1921 describing a "fixed dorsal kyphosis, a true sagittal deformity different from the postural hunchback which can be corrected actively."1 First described by Schanz in 1911 it was originally known as apprentices kyphosis or kyphosis muscularis. (This term is now only used to describe type 2 curves). Scheuermann described radiological findings showing three wedged vertebra at the apex of the curve. Sorenson in 1965 modified this definition to say that the kyphosis should include three adjacent vertebra with anterior wedging of at least 5 degrees (Figure 1). In practice a fixed kyphosis showing features of Scheuermann's is the criteria required for inclusion in many studies. Interestingly Scheuermann submitted his dissertation on juvenile dorsal kyphosis to the university of Copenhagen for his doctoral thesis, this was rejected.

Figure 1

Lateral radiograph showing characteristic anterior wedging of the thoracic vertebrae.

The Roundback Deformity:

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 roundback deformity is either postural or due to Scheuermann's, other rarer causes should be ruled out ie neurofibromatosis or heriditary conditions such as achondroplasia or developmental vertebral anomalies.
The incidence in the population of Scheuermanns 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 roundback 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 patients appearance.

Classification of Scheuermanns Kyphosis:

Type 1
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.

Type 2
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.

Radiographic Assessment:

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 material3, Typically anterior in Scheuermanns and posterior in scoliotic patients), decreased disc space and wedging of at least three adjacent vertebra greater than 5 mm
It is important to note that clinical appearance and radiographic findings often correlate poorly.
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.4

Pathogenesis

The exact cause of Scheuermanns kyphosis is unknown.An autosomal dominant mode of inheritance has been described in some families.5 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 felt that the problem was due to an 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.6
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 Scheuermanns kyphosis.7

Treatment Options

1) Observe for progression: If they have only a minimal curve and are still skeletally immature; If they are skeletally mature and asymptomatic and not pushing for correction of a cosmetic deformity no prolonged follow-up is necessary.

2) Postural exercises are often recommend however these have no scientific validation. Importantly they do no harm and do not dramatically affect the patient's lifestyle. Exercises include hamstring and pectoral stretching, postural awareness and trunk strengthening.

3) Cast and/or bracing. This is often prolonged and psychologically traumatic for the patient. It also requires a lot of time, effort and resources.
The Milwaukee brace8 was used in skeletally immature patients with a kyphosis of greater than 45 degrees. This requires a dedicated orthotist, regular assessment and alteration of the brace. Patients nearing the end of skeletal growth (Rissers sign 3 or 4) can be successfully treated with bracing unlike idiopathic scoliosis patients at this stage.
The brace is ideally worn for 23 hours a day for the first year and then night-time only for the second year. Patient compliance often reduces this to 16 hours per day. Modifications i.e. low profile neckpiece or an under arm corrective orthosis try to avoid the social stigma of a visible brace above the collar line. Bracing is rarely used nowadays as the treatment is often felt to be worse than the disease.
The use of traction is minimal but has been used in the past prior to fitting the brace.

4) Surgery.

Indications: As progression in adulthood is rarely a problem the indications for surgery are not fixed. Typically patients, who are unhappy with their appearance, are skeletally mature and whose kyphosis measures at least 60 degrees can be considered for surgery. Importantly these patients must understand the magnitude of the surgery, the risks involved in even the most experienced hands and the likelihood that the kyphosis may not be able to be corrected to an unnoticeable degree. Surgical correction is not common for Scheuermann's kyphosis.
Patients rarely present with neurological signs. Those that do should have surgery to correct their kyphosis after having MRI studies (Figure 2) to outrule other causes or exacerbating factors. It should be noted that unlike cord compression from stenosis of the spinal canal, laminectomy has no alleviating effect.

Figure 2:

MRI scan illustrating the position of the spinal cord lying away from the posterior elements.

The 'Gold standard' for surgical correction of a thoracic kyphosis is anterior discectomy and grafting via a thoracotomy plus posterior spinal instrumentation.)Initially treatment by posterior fusion and/or instrumentation had problems with long term stability. Rods fractured or bent and loss of correction occurred.9
Modern posterior instrumentation uses stiffer rods and segmental fixation. Anterior disc excision and grafting provides increased stability.

First stage-Thoracotomy

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.

Figure 3:

Lateral radiograph showing the pedicle screws and the sub-laminar wires at the lower limit of the fixation.

Second stage-Posterior fusion and discectomy

This is either done at the same sitting10 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 (Figure 3 and 4). Distally pedicle screws provide a firm hold (Figure 4). 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 kyphosis12. Following surgery patients are allowed to walk without the support of bracing or plaster jackets.

Figure 4:

AP radiograph following 2-stage fixation of the thoracic spine.

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.

Conclusion:

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.13

References:

1) Scheuermann HW: The classic: kyphosis dorsalis juvenilis. Clin Orthop 1977 Oct;(128):5-7.

2) Murray PM, Weinstein SL, Spratt KF: The natural history and long-term follow-up of Scheuermann kyphosis. J Bone Joint Surg Am 1993 Feb;75(2):236-48

3) Resnick D, Niwayama G: Intravertebral disk herniations: cartilaginous (Schmorl's) nodes. Radiology 1978 Jan;126(1):57-65

4) Wood KB, Garvey TA, Gundry C, Heithoff KB: Magnetic resonance imaging of the thoracic spine. Evaluation of asymptomatic individuals. J Bone Joint Surg Am 1995 Nov;77(11):1631-8

5) Halal F, Gledhill RB, Fraser C: Dominant inheritance of Scheuermann's juvenile kyphosis. Am J Dis Child 1978 Nov;132(11):1105-7

6) Ippolito E, Ponseti IV: Juvenile kyphosis: histological and histochemical studies. J Bone Joint Surg [Am] 1981 Feb;63(2):175-82.

7) Sward L The thoracolumbar spine in young elite athletes. Current concepts on the effects of physical training. Sports Med 1992 May;13(5):357-64

8) Sachs B, Bradford D, Winter R, Lonstein J, Moe J, Willson S: Scheuermann kyphosis. Follow-up of Milwaukee-brace treatment. J Bone Joint Surg [Am] 1987 Jan;69(1):50-7

9) Bradford DS, Moe JH, Montalvo FJ, Winter RB: Scheuermann's kyphosis. Results of surgical treatment by posterior spine arthrodesis in twenty-two patients. J Bone Joint Surg [Am] 1975 Jun;57(4):439-48

10) Powell ET 4th, Krengel WF 3rd, King HA, Lagrone MO. Comparison of same-day sequential anterior and posterior spinal fusion with delayed two-stage anterior and posterior spinal fusion. Spine 1994 Jun 1;19(11):1256-9.

11) Hall BB, Asher MA, Zang RH, Quinn LM. The safety and efficacy of the Isola Spinal Implant System for the surgical treatment of degenerative disc disease. A prospective study. Spine 1996 Apr 15;21(8):982-94

12) Reinhardt P, Bassett GS: Short segmental kyphosis following fusion for Scheuermann's disease. J Spinal Disord 1990 Jun;3(2):162-8

13) Lowe TG: Scheuermann's disease Orthop Clin North Am 1999 Jul;30(3):475-87, ix