Congenital kyphosis

Kyphosis is a curvature of the spine in the sagittal plane with the formation of a bulge facing backwards.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ]

What causes congenital kyphosis?

According to the classification of R. Winter et al., congenital kyphosis is divided into three main groups:

• kyphosis due to formation anomalies;
• kyphosis due to segmentation anomalies;
• kyphosis due to mixed anomalies.

McMaster et al. introduced a group of unclassifiable deformities into it. Dubousset singled out special kyphotic deformities into a separate group, which he called rotational dislocation of the spine.

Kyphosis based on anomalies of vertebral formation is the most common type of congenital kyphosis, accounting for 61 to 76%. These deformities are based on the following types of anomalies: anterior and anterolateral wedge-shaped vertebrae, posterior hemivertebrae, posterolateral quadrant of the vertebral body, butterfly vertebra, and agenesis of the vertebral body.

Kyphosis due to segmentation anomalies. Segmentation anomalies are the second most common after formation anomalies and account for 11-21%. Patients with these deformities can be divided into two subgroups depending on the symmetry of the lesion - anterior or anterolateral non-segmented block. The length of the block can vary from two to eight or nine vertebral bodies. It can be localized at any level, but most often in the thoracolumbar and lumbar spine.

If the segmentation defect is located in the front, a "pure" kyphosis is formed, if asymmetrically - kyphoscoliosis. The progression of the deformation is variable and depends on the symmetry of the block and the preservation of the posterior sections.

Kyphosis due to mixed anomalies is the result of the simultaneous existence of a non-segmented block of vertebrae with formation disorders at one or two adjacent levels, usually located contralaterally. The frequency of such kyphosis varies from 12 to 15%.

Kyphosis due to unclassifiable anomalies can be found in any part of the spine. The purity is 5-7%.

Rotational dislocation of the spine. The deformation may be based on any anomaly. The main feature is that the kyphosis is located between two congenital lordoscoliotic arcs of different directions. It occurs at any level, but most often in the upper thoracic and thoracolumbar regions. Kyphosis is pointed in shape, usually rough, its development is accompanied by a collapse of the spinal column. The spinal cord is deformed in accordance with the deformation of the spinal canal, that is, it is twisted over a short distance, and sharply.

Symptoms of Kyphosis

Kyphotic deformation (kyphosis) can have a peak at almost any level, be flat or pointed, often (up to 70% of cases) has a scoliotic component. Congenital kyphosis is almost always rigid, and in most cases is accompanied by neurological symptoms of varying severity. Quite often (up to 13% of cases) combined with various congenital anomalies of extravertebral localization.

Clinical and radiological classification of kyphosis

The classification was developed on the basis of literature data.

The type of anomaly on the basis of which the deformation frolicked

• Posterior (posterolateral) vertebrae (hemivertebrae).
• Absence of a vertebral body - asoma.
• Microspondyly.
• Concretion of the vertebral bodies - partial or complete.
• Multiple anomalies.
• Mixed anomalies.

Type of deformation.

• Kyphosis,
• Kyphoscoliosis.

Localization of the deformation peak.

• Cervicothoracic.
• Upper thoracic.
• Mid-chest.
• Lower thoracic.
• Thoracolumbar.
• Lumbar.

The magnitude of kyphotic deformity.

• Up to 20° - 1st degree.
• Up to 55° - II degree.
• Up to 90° - III degree.
• Over 90° - IV degree.

Type of progressive deformation.

• Slowly progressing (up to 7° and a year).
• Rapidly progressing (more than 7° per year).

Age of initial detection of deformity.

• Infantile kyphosis.
• Kyphosis in young children.
• Kyphosis in adolescents and young men.
• Kyphosis in adults.

The presence of involvement of the contents of the spinal canal in the process.

• Kyphosis with neurological deficit.
• Kyphosis without neurological deficit.

Associated spinal canal anomalies.

• Diastematomyelia.
• Diplomyelia.
• Dermoid cysts.
• Neuroenteric cysts.
• Dermal sinuses.
• Fibrous constrictions.
• Abnormal spinal roots.

Associated anomalies of extravertebral localization.

• Anomalies of the cardiopulmonary system.
• Anomalies of the chest and abdominal wall.
• Anomalies of the urinary system.
• Limb anomalies.

Secondary degenerative changes in the spine.

1. None.
2. Present in the form of:
   • osteochondrosis;
   • spondylosis;
   • spondyloarthrosis.

[ 7 ], [ 8 ]

Diagnosis of kyphosis

The radiographic picture of congenital kyphosis is very characteristic and does not pose any particular difficulties in diagnosis.

The magnitude of kyphotic deformity is determined using the Cobb method based on profile spondylograms.

Kyphosis diagnostics does not only involve conducting a general spondylography. MRI and CT can be useful here. Functional spondylography is used to determine the functions of the intervertebral discs in the parasagittal sections of the spine - in the lateral projection, in the position of maximum possible flexion and extension of the patient's spine. In all cases of congenital spinal deformities, an examination of the contents of the spinal canal is indicated - a contrast study, MRI, CT. A neurological examination is mandatory.

[ 9 ], [ 10 ], [ 11 ]

Treatment of kyphosis

Conservative treatment of kyphosis is clearly recognized as ineffective, since at best it can only slightly slow down the progression of the deformation.

Modern surgical treatment of congenital kyphosis is based on the collective experience of the world's leading clinics.

Congenital kyphosis type I (due to formation anomalies)

[ 12 ]

Treatment of early deformities

Usually, patients under 5 years of age with a kyphosis of less than 75° are effectively treated with posterior fusion alone. The method is based on the principle of preserving the growth potential of the vertebral bodies while "arresting" their dorsal parts. The posterior fusion zone should be larger than the abnormal zone by one segment cranially and caudally. This is necessary to form lordoses above and below the kyphosis zone, compensating for any residual kyphosis.

If kyphoscoliosis rather than kyphosis is detected, the treatment is similar. However, even with a good posterior block, the growth of the apical vertebrae can continue laterally and in the horizontal plane. This is the crankshaft phenomenon described by Dubousset. The development of this complication means progression of the deformation. In this case, there are urgent indications for anterior-posterior epiphysiospondylodesis along the convex side of the deformation.

Another issue is the patient's age. Given the nature of congenital kyphosis, dynamic observation of the patient is pointless. Early posterior fusion and reliable posterior spondylodesis before the development of gross deformation are necessary. The earlier the patient is operated on, the better. The earliest permissible age for surgical intervention is 6 months.

The principle of solving the problem depending on the magnitude of deformation (according to Cobb) is not reliable in relation to kyphosis. A gentle kyphosis of 30° in the mid-thoracic region is practically normal, the same kyphosis in the thoracolumbar region is already a pathology, and a kyphosis of 10° in the lumbar region is a gross pathology. A sharp-apical kyphosis of 50° in the mid-thoracic region is a pathology, and a gentle kyphosis of the same magnitude in the same region is only the upper limit of the norm. The results obtained indicate a high efficiency of the method. Not only is there no progression, but self-correction of the deformation is constantly revealed. However, even in children under 5 years of age, the development of a pseudoarthrosis of the block is possible and quite real. Therefore, after 6 months, a repeat operation with revision of the spondylodesis zone and placement of additional bone-plastic material is indicated in all cases. There are no cases of hypercorrection, but if there is such, blocking of the anterior spine is indicated. Criticism of the method is based on the fact that early siondylodesis causes some shortening of the trunk. However, a large loss of trunk height occurs during the growth of the deformed spine and is emphasized by progressive kyphosis.

Treatment of late-formed deformities

These cases are much more complex, as they require two-stage treatment - anterior and dorsal spondylodesis. Accordingly, the risk of complications increases.

Preliminary traction, performed to "soften" the deformation, is pointless before anterior spondylodesis. The ligamentous apparatus and cartilaginous tissue in the area of the apex of the kyphosis are inelastic, therefore, nothing can be obtained beyond the correction determined on functional spondylograms in the hyperextension position. Traction is indicated only in a few patients in whom decreased lung function is combined with sufficient mobility of the spine, which allows for some correction during the period of pulmonary rehabilitation. The best form is halo-pelvic traction, which allows the patient to move independently, which is very important in terms of preventing thromboembolic complications and osteoporosis. Usually, the duration of traction is no more than 2 weeks. Since the use of traction in congenital kyphosis is dangerous due to the high risk of paraplegia due to spinal cord tension, it should be used rarely and accompanied by neurological monitoring at least twice a day.

The type of anterior fusion depends on the severity and extent of the kyphosis. Relatively mild deformities, the smallest of those subject to anterior intervention, can be effectively corrected by anterior fusion surgery of the partial vertebral body replacement type. It is extremely important to adequately expose the anterior sections with the removal of the anterior longitudinal ligament, discs, and cartilage at the apex of the deformity. One normal disc is removed proximally and caudally from the kyphosis zone. After this, the deformity becomes more mobile. In order to install the graft spacer, simultaneous traction behind the patient's head and manual pressure on the apex of the kyphosis from behind are necessary. Additionally, spongy bone is placed in the intervertebral spaces. Posterior fusion is performed on the same day. For more severe kyphosis, the use of a spacer is necessary. The more severe the kyphosis, the more bone-plastic material is used. In case of large deformations, a gross error would be to use one graft-spacer by creating an "empty" space between it and the apex of the kyphosis. In such cases, it is necessary to use several rigid autografts from the tibial crest.

The posterior intervention includes spinal fixation with segmental instrumentation (CDI) and fusion with autogenous bone. Planning of the posterior stage includes determination of hook placement points.

Treatment of intermediate deformities

A patient with such a deformation presents a serious challenge, since with early deformations a posterior spondylodesis is sufficient, and with severe kyphosis a combined treatment of kyphosis is necessary. If there are doubts, it is better to perform a posterior spondylodesis, and after 6 months revise the block and supplement it with bone-plastic material, regardless of how strong it seems to the surgeon. Immobilization with a corset is carried out for a period of 1 year. If a false joint of the block develops, anterior spondylodesis is indicated.

The choice of the anterior and dorsal fusion zone is primarily a biomechanical issue, since the goal of central fusion surgery is to place a strong bone graft in the most biomechanically favorable position so that the spine can effectively withstand vertical loads. If we use the experience gained in the surgical treatment of patients with scoliosis, the ideal fusion zone should extend along the line of the center of gravity from top to bottom, i.e. both the upper and lower ends of the fusion zone should lie on the same line.

Congenital kyphosis is most rigid in its central part, the parahybrid sections are more mobile. The length and boundaries of these sections (rigid and mobile) can be determined on a spondylogram taken in the hyperextension position. Anterior spondylodesis should cover the entire zone of structural changes, but should not reach the terminal vertebrae if the line of the center of gravity passes dorsal to them on the spondylogram in the hyperextension position. The posterior bone block should reach the line of the center of gravity, even if it is far from the terminal vertebrae of the kyphotic arch. After anteroposterior spondylodesis, a single bone conglomerate is formed, the ends of which lie along the line of the center of gravity.

Congenital kyphosis of the II tile (due to segmentation anomalies)

[ 13 ], [ 14 ], [ 15 ], [ 16 ], [ 17 ], [ 18 ]

Early treatment

In young children, the basis of treatment is slowing the growth of the posterior vertebrae. Until severe kyphosis has developed, the operation of choice is posterior bilateral spondylodesis. Its length is one normal vertebra above and below the zone of the anterior congenital block.

[ 19 ], [ 20 ], [ 21 ]

Late treatment

Correction of the formed deformation is a very complex task. It is necessary to osteotomize the anterior block at the levels corresponding to the disappeared disks. Experience shows that these levels can usually be determined by spondylograms or intraoperatively - by the elements of the fibrous rings. Then, interbody spondylodesis and dorsal spondylodesis are performed using modern segmental CPI instrumentation or its analogues.

Operation Tomita

In 1994, a group of Japanese orthopedists led by K. Tomita developed and introduced into practice an operation they called "total spondylectomy." The authors proceeded from the fact that the usual two-stage intervention on the anterior and posterior sections of the spine does not allow for a sufficient degree of correction due to the rigidity of the chest.

The operation consists of two stages: en bloc resection of the posterior elements of the vertebrae, en bloc resection of the anterior column.

Stage I. Resection of the posterior vertebrae.

Access. The patient is in the prone position. Linear midline incision along the length necessary for future reliable fixation of the spine with Cotrel-Dubousset instrumentation. The paraspinal muscles are displaced laterally, exposing the facet joints and transverse processes. At the selected levels, the ribs are transected 3-4 cm lateral to the costotransverse joints, after which the pleura is carefully separated from the vertebral bodies on both sides. To expose the superior articular processes of the upper vertebra to be removed, the spinous and inferior articular processes of the adjacent vertebra are osteotomized and removed together with the yellow ligament.

Insertion of the flexible saw guide. The soft tissues are separated from the lower part of the pars interarticularis with extreme care so as not to damage the spinal root. This prepares the entrance for the saw guide. The flexible C-shaped guide is then inserted into the intervertebral foramen in the craniocaudal direction. The tip of the guide should move along the medial endplate of the semi-arch and the root of the arch so as not to damage the spinal cord and the root. Finally, the tip of the guide appears under the lower edge of the pars interarticularis. A thin flexible multi-fiber wire saw with a diameter of 0.54 mm is then passed along the guide, and its ends are fixed with grips. The guide is removed, the saw is tensioned, and this tension is maintained.

Intersection of the arch roots and resection of the posterior elements of the vertebrae. While continuing to tension the saw, it is placed below the superior articular and transverse processes around the arch root. The latter is intersected with rocking movements of the saw at all necessary levels. After this, the posterior elements of the vertebrae are removed as a single block, including the articular, spinous, transverse processes and arch roots. To maintain the stability of the spinal column, the upper and lower "knees" of the kyphosis are fixed with CDI instrumentation.

Stage II. Resection of the anterior column of the spine.

Blunt dissection of the vertebral bodies. At the beginning of this stage, it is necessary to identify the segmental arteries on both sides. The spinal branch of the segmental artery running along the spinal root is ligated and transected. In the thoracic spine, the spinal root is transected on the side through which it is intended to remove the elements of the anterior column of the spine. Blunt dissection is continued in the anterior direction between the pleura (or m. psoas tajor) and the vertebral bodies. Usually, the lateral surfaces of the vertebral bodies are easily exposed with a curved vertebral spatula. Then it is necessary to separate the segmental vessels - arteries and veins - from the vertebral body. Next, the aorta is carefully separated from the anterior surface of the vertebral body with a spatula and fingers. The dorsal surface of the finger of the surgeon's left hand feels the pulsations of the aorta. When the tips of the fingers of the surgeon's right and left hands meet on the anterior surface of the vertebral body, a series of spatulas of varying sizes are used, which are inserted sequentially (starting with the smallest) to widen the access. The two largest spatulas are held between the vertebral bodies and the internal organs to prevent damage to the latter and to obtain maximum freedom of manipulation.

Insertion of a wire saw. Two such saws are inserted at the levels of the proximal and distal sections of the anterior column of the spine. The correctness of the selected levels is verified using marking radiography; small cuts are made in the bone tissue with a chisel so that the saw does not shift.

Freeing the spinal cord and removing elements of the anterior column. Using a thin spatula, the spinal cord is mobilized from the surrounding venous plexuses and ligaments. Then a protector with teeth at the edges is inserted to prevent the saw from slipping. Using the latter, the anterior vertebral column with longitudinal ligaments is transected. The mobility of the excised segment should then be checked to ensure that the transection is complete. The excised fragment of the anterior column is rotated around the dural sac and removed.

Correction of kyphotic deformity. The rods of the CDI instrumentation are crossed at the apex of the deformity. The resulting fragments, each of which is fixed to one of the "knees" of the kyphosis, are connected in the position of deformity correction with "domino" connectors. During the correction, the dural sac is under constant visual control. Correct calculation of the required volume of resection of the anterior and posterior columns of the spine will allow, as a result of the correction, to achieve closure of the bone surfaces of the vertebral bodies and restore the continuity of the posterior wall of the spinal canal. If this is not possible, before the correction stage it is necessary to fill the anterior "empty" space with a cage-type implant or allograft bone. It is mandatory to perform posterior spondylodesis with autografts along the entire length of the CDI instrumentation.

Postoperative management. The patient is allowed to get up and walk a week after the operation. Then a rigid corset is prepared for the thoracic and lumbosacral spine, which the patient should wear for 6 months.