oinical Radiology (1982) 33, 445 -452 © 1982 Royal College of Radiologists

0009-9260/82/00910445502.00

Severe Kyphosis Due to Congenital Dorsal Hemivertebra FRANK WILLIAMS*, IAIN W. McCALL, JOHN P. O'BRIEN and WILLIAM M. PARK

Departments of Radiology and Spinal Disorders, Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire

Kyphotic deformity arising from failure of the formation of a vertebral body is described in nine patients. The study of the natural history demonstrates the progressive nature of this disorder resulting in severe deformity and neurological embarrassment. Early radiological recognition of this congenital deformity is essential and tomography is important in the early assessment. Tomography combined with myelography is essential to delineate the extent o f bony abnormality and cord compression in severe kyphosis in order that adequate decompression and reconstructive surgery can be performed.

Kyphotic deformity arising from the failure in forma- tion of a vertebral body is an uncommon orthopaedic condition showing late complications o f gross spinal angulation, paraplegia and reduced pulmonary func- tion. These complications result from the failure to recognise the lesion radiologically and to appreciate the natural history of this condition (Winter, 1973). This paper presents nine patients with this condition, in order to demonstrate the natural history and to stress the importance of careful radiological manage- ment.

CLINICAL FINDINGS

Nine patients have been studied, five female and four male; their ages ranged from 6.4 to 25 years at the time of review. All patients presented initially with a kyphotic deformity of t he thoracic spine of a variable degree. Three patients had been observed from the first year of life allowing the natural history of this disorder to be extensively followed. Seven patients had an associated scoliosis. Seven patients developed neurological abnormalities of the lower limbs ranging from mild intermittent paraparesis to spastic paraplegia. Four patients had diminished pul- monary function with associated pulmonary hyper- tension. Clinically detectable associated congenital heart disease was present in two patients.

graphs. The final range at the time of the review was 4 5 - 1 7 0 °. The angle o f the kyphosis was measured by the Cobb method. Five of the hemivertebrae were located at the lower dorsal and thoraco-lumbar region; three lesions were in the mid-thoracic region and one was mid-lumbar. One patient had two dorsal hemi-

vertebrae at the thoraco-lumbar junction. The developmental defect of the vertebral body varied and took the form of almost total absence (Fig. 1) or, more usually, failure of the anterior half to develop (Fig. 2). A butterfly vertebra was present in the mid-thoracic region in one patient who had a diastematomyelia with a bony spur at the L5 level. Two patients had associated spina bifida occulta defects. In two cases, the scoliosis was greater than 40 ° . Lateral flexion and extension films were per- formed and no movement was demonstrated at the kyphotic segment in any of the cases.

Serial radiographs showed that the rate of deterioration was variable but a marked deterioration of the deformity often occurred at the time of the growth spurt (Fig. 2). This deterioration continued after posterior fusion in five cases. These features are summarised in Table 1.

Table 1 - Analysis of cases of congenital kyphosis

Level Age at P e r i o d Initial Post- Final of HV pres. o fobs. angle fusion angle

R A D I O L O G I C A L FINDINGS T6

Plain F i l m R a d i o g r a p h y T8 T8

On initial presentation the angle ofkyphosis ranged T9 from 18 ° to 70 ° on the lateral thoraco-lumbar radio- T12

T12 *Present address: Nevill Hall Hospital, Abergavenny, L1

Gwent, UK. L1 Address for reprints: lain W. McCall, Robert Jones and L3

Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire, UK.

14.6 1.8 49 60 95 0.1 12.0 20 - 147 3.0 11.6 30 80 170 8.1 8.0 - - 25 0.6 3.8 30 - 42 0.7 9.3 25 55 79 2.0 16.0 25 - 130 2.5 13.0 18 49 105 7.0 18.0 - - 87

446 C L I N I C A L R A D I O L O G Y

(a) (b) Fig. 1 - (a) Failure of development of most of the body of T12 with only a very small portion of its posterior wall present. The kyphosis is 25 ° at 7 months. (b) The kyphosis has progressed to 79 °. T l l and L1 have pivoted around the hemivertebra and reactive changes and re-alignment of the bodies axe demonstrated.

Tomography Lateral tomography was an essential part of the

radiological assessment. In four cases, tomography demonstrated a dorsal hemivertebra which was not clearly discernable on the AP or lateral radiographs, and enabled the extent of the vertebral defect to be accurately assessed. As the kyphosis increased, marked distortion of the vertebral bodies above and below the dorsal hemivertebra occurred and this was also well demonstrated by tomography.

Myelography

Metrizamide myelography was performed in seven cases. The remaining two patients did not have metri- zamide examinations, but had had myelography previously employing iophendylate. In four cases, metrizamide myelography was combined with lateral tomography which assisted the assessment of the extradural cord compression. This had significant bearing on the surgical approach and extent of anterior decompression. All patients who had metriz-

amide myelography showed extradural compression at the apex of the kyphosis; the more extensive the kyphotic angle, the greater the extrinsic cord com- pression. Myelography was also useful in assessing the extent of the diastematomyelia and the state of the ilium terminale (Fig. 3). As a high incidence of anomalies of the renal tract is associated with con- genital spinal disorders, all patients received intra- venous urograms, one of which showed horse-shoe kidney (Fig. 4). Complete situs inversus was observed in one patient.

CASE REPORTS Case 1. A.W. (Fig. 1). This girl was seen at the age of

7 months with a thoracic kyphosis measuring 25 ° . She re- mained asymptomatic until the age of 10 years when she developed mild paraparesis; the kyphosis at this stage was 550. A posterior fusion operation was performed but a gradual neurological deterioration occured with development of lower limb spasticity and later, loss of bladder function. At the age of 14 years, her kyphosis had progressed to 79 o. Tomograms showed virtually no development of the 1)12 vertebral body with only a small triangle of bone posteriodY~

S E V E R E KYPHOSIS DUE TO CONGENITAL DORSAL HEMIVERTEBRA 447

2 - (a) The anterior half of the vertebral body has failed to develop. The kyphosis develops slowly until the growth spurt when Progression becomes rapid (b-d).

448 C L I N I C A L R A D I O L O G Y

Fig. 3 - Numerous vertebral anomalies are associated with a diastematomyelia demonstrated with Myodil.

Anterior spinal decompression and fusion were Performed with a marked improvement in the neurological state of the patient's lower limbs.

Case 2. E.M. (Fig. 5). This girl, a good swimmer, was first seen at the age of 8 years with transient paraparesis followiag diving into a swimming pool. Neurological examination at the time demonstrated brisk lower limb reflexes and equivocal Babinski responses. A mild thoracic scoliosis was observed but was not investigated at this stage. At the age of 16 Years 10 months, following further and more frequent transient paretic episodes, she was shown to have a mild thoracic kyphosis of 25 °. At investigation a D9 dorsal hemivertebra was found with significant anterior cord compression on myelography. Following excision of the dorsal hemivertebra and anterior spinal fusion, the patient had no further syrup. toms and her neurological assessment returned to normal.

Case 3. N.W. (Fig. 6). This child presented at 6 months of age with a minor thoracic kyphosis. He was observed at intervals and at the age of 3 years, the kyphosis was noted to have progressed by some 15 ° . No neurological abnormality of the lower limbs was observed at any stage. Investigation showed at two level dorsal hemivertebrae at the thoraco. lumbar junction. In view of the poor prognosis of these lesions, anterior decompression and fusion, followed several months later by a posterior fusion, was performed and the patient made a completely uneventful recovery.

Case 4. B.W. (Fig. 7). This boy presented at birth with congenital heart disease which necessitated cardiac surgery during the neo-natal period. He made a good recovery but at that time was noted to have a very mild thoracic kyphosis. Follow~up of his cardiac condition also showed that the kyphosis was progressing, especially between the ages of 8 and 12 years (70-140°). During this period he was prescribed a Milwaukee brace. From the age of 12 years he developed a progressive spastic paraplegia with loss of bladder function. ~ The mid-thoracic kyphosis deteriorated to 147 ° and myelo- graphy demonstrated a complete myelographic block at the~ apex of the kyphosis. Pulmonary function studies showed a~ marked reduction in vital capacity; clinical examination and i ECG changes indicated a fairly severe pulmonary hyper- tension. Owing to the length of period over which the kyphosis i~ had developed, the degree of angulation and the lack o f mobility at the level of the kyphosis, only anterior decom- pression with anterior fusion was performed. A considerable reduction in the lower limb spasticity followed surgery, but the kyphosis was unchanged.

Fig. 4 - The medial re-orientation of the calyces, the lateral position of the pelvi-ureteric junction and the presence of functioning renal tissue joining the lower renal poles all indicate a horseshoe kidney.

DISCUSSION

Congen i t a l k y p h o s i s results f rom a d i s tu rbance in t h e early d e v e l o p m e n t o f the spine at a b o u t the fifth to s ix th embryo log ica l week . Two types o f abnor- ma l i t y have b e e n d is t inguished ( V a n Schr ick 1932), e i the r a fai lure o f f o r m a t i o n or a fai lure o f segmenta- t i o n o f o n e or m o r e ve r tebra l bodies . A combinat ion o f these t w o processes may also occur . Failure of f o r m a t i o n o f one or more ve r t eb ra l bod ies is the c o m m o n cause o f congen i ta l kyphos i s and is d u e e i the r to a fai lure in t h e d e v e l o p m e n t o f t h e cart i lage base o f the b o d y or , in the less severe f o r m of par t ia l h e m i v e r t e b r a , to a de fec t in oss i f ica t ion. Oss i f ica t ion in t h e ve r t eb ra l b o d y occurs f rom t w o cent res ; o n e an t e r i o r and o n e pos t e r i o r and the non-development~

S E V E R E K Y P H O S I S D U E TO C O N G E N I T A L D O R S A L H E M I V E R T E B R A 449

Fig. 5 - (a) The plain film demonst ra tes the hemiver tebra with only 25 ° of kyphosis . (b) Myelography from above shows marked obstruct ion of the co lumn at the lower margin o f the hemiver tebra which is the apex of the kyphosis .

of the anterior ossification centre produces a hemi- vertebra. The kyphosis is accentuated by the con- tinued normal growth of the posterior elements in the presence of anterior instability. As the kyphosis develops, the vertebral bodies above and below the hemivertebra become distorted due to interference with their normal growth stresses. The classical dorsal hemivertebra occurred in eight of the nine patients reviewed. The final case, however, showed a different initial pattern with several dysplastic anterior elements in the mid-thoracic region; one of these underwent growth arrest providing the final result identical to the classical dorsal hemivertebra. The importance of the dorsal hemivertebra lies in its paralytic potential. Lombard and Le Genissel (1938) were first ~o demonstrate compression of the spinal cord with Opaque myelography. Bingold (1953), in the English literature, described paraplegia as a complication and James (1955) reporting a further five cases, stressed the progressive nature of this condition if left un- treated. The malignant nature of the disorder was

31

confirmed by Winter e t al. (1973) who found that marked deterioration of the kyphosis often occurred during the growth spurt. The long period of review in three of our cases enabled us to confirm these find- ings. The end result of this condition is almost invariably some degree of cord compression and spastic paraparesis; this is often associated with con- siderable thoracic distortion, fixity and respiratory failure. The dangers of cord compression are increased if the hemive(tebra involves the mid-thoracic region (Winter e t al., 1973). One of our cases (Case 2) demonstrates how neurological signs may occur after a minor spinal insult and illustrates that the signs may be intermittent. This particular case also stresses that, even with a minor kyphosis of 25 °, significant neuro- logical changes may occur. Failure of formation of a vertebral body may be asymmetrical thus leading to a degree of associated scoliosis; in the true dorsal hemi- vertebra, however, this is usually of only a mild degree.

In view of the severe and progressive nature of this

450 C L I N I C A L R A D I O L O G Y

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Fig. 6 - (a) Six months. Two adjacent vertebral bodies are affected with a hemivertebra of T12 (large arrow) and almost total absence of L1 vertebral body (small arrow). The initial kyphosis is 30 °. (b) Three years four months. The kyphosis has progressed to 38 °. Metrizamide myelography shows considerable pressure deforming the conus medullaris. (e) Anterior decompression with removal of the hemivertebra and strut grafting has been performed combined with pos- terior fusion.

disorder, it is important to correctly diagnose the underlying cause of any childhood kyphosis. Careful scrutiny of good lateral plain films may reveal the lesion, but even at this early stage, tomography may be required to confirm the failure of vertebral body development. Instabil i ty at the kyphosis in the first year of life has been reported (Winter et al., 1973) and is related to defects in the pars interarticularis or to failure of development of the articular processes. Movement in the established kyphosis is rare but if mobi l i ty is demonstrated, then gentle and carefully moni tored traction may be of value in the initial pre-operative programme. Extra-dural compression of the cord may extend considerably from the apex o f the curve, due to the secondary growth anomalies of the proximal and distal vertebral bodies as the kyphosis develops. As the treatment of these severe lesions initially involves removal of the block of bone

S E V E R E K Y P H O S I S D U E T O C O N G E N I T A L D O R S A L H E M I V E R T E B R A 451

Fig, 7 - (a) Rounding of the anterior parts of the bodies of D7-9. The kyphosis is 70 ° and is evenly distributed in the mid-dorsal spine. (b) Growth arrest of the anterior part of D8 has occurred. The kyphosis is now 100 °. (e) The AP view shows a mild scoliosis. (d) and (e) over page.

compressing the spinal canal, it is clearly essential to demonstrate the extent of the compression, and metrizamide myelography with tomography will provide such information. A decompression opera- tion is followed by anterior and posterior fusion. In the early stages of deformity, posterior fusion will prevent a severe kyphosis (Winter and Hall, 1978), but in the more severe cases, posterior fusion alone is insufficient to halt the relentless progress (Winter and Hall, 1978).

When anterior surgery is contemplated, particularly in the severe cases, extensive studies of lung function should be performed and the exclusion of renal and cardiac anomalies is essential.

In conclusion, the dorsal hemivertebra when un- treated commonly results in paraplegia and severe respiratory l imitat ion. Early radiological recognition and effective t reatment are required. Where severe deterioration has occurred, full radiological evalua- t ion is required prior to reconstructive surgery.

452 CLINICAL R A D I O L O G Y

Fig. 7 - (d) The kyphosis has progressed to 147 ° and metrizamide is completely obstructed at the kyphus. (e) Tomographs performed during the metrizamide myelogram, demonstrates clearly the hemivertebra at the apex, the exact extent of the cord compression and complete obstruction of the canal.

REFERENCES

Bingold, A. C. (1953). Congenital kyphosis. Journal of Bone and Join t Surgery, 35B, 579 - 583.

James, J. I. P. (1955). Kypho~coliosis. Journal of Bone and Joint Surgery, 3711, 414-426.

Lombard, P. & Le Genissel, M. (1938). Cyphoses congenitales. Revue d'orthopddie, 25, 532-550.

Van Schrick, F. G. (1932). Die Angeborene Kyphose. Zeit- schrift ffir orthopddische Chirurgie, 56,238-258.

Winter, R; B. & Hall, J. E. (1978). Kyphosis in childhood and adolescence. Spine, 3, 285-308.

Winter, R. B., Moe, J. H. & Wang, J. F. (1973). Congenital kyphosis. Journal of Bone and Joint Surgery, 55A, 223- 256.