A congenital kyphosis or kyphoscoliosis is an uncommon deformity in which there is an abnormal posterior convex angulation of a segment of the spine due to developmental vertebral anomalies that impair longitudinal growth anterior or anterolateral to the transverse axis of vertebral rotation in the sagittal plane. These vertebral anomalies are present at birth, hence the term congenital, but the deformity may not become clinically apparent until later in childhood.
Congenital kyphosis and kyphoscoliosis are much less common than congenital scoliosis9,22, but they are potentially more serious because they sometimes lead to compression of the spinal cord and paraplegia7,8. The first description of congenital kyphosis was by Von Rokitansky20 in 1844; however, it was not until 1932 that Van Schrick19 differentiated a failure of vertebral-body formation from a failure of vertebral-body segmentation as a cause of congenital kyphosis. He reported on four patients and reviewed the literature, in which he identified the cases of fourteen patients. In 1955, James7 described twenty-one patients who had a congenital kyphoscoliosis; five became paraplegic. To our knowledge, the only study on the natural history of congenital kyphosis and kyphoscoliosis in a large series was that by Winter et al.23, published in 1973. Those authors reported on 130 patients from several centers, but only thirty of the patients were followed without treatment for more than one year.
The goal of the present study was to further evaluate the natural history of congenital kyphosis and kyphoscoliosis. It should be kept in mind that once a patient begins treatment (which may consist only of follow-up evaluations and observation) the course of the deformity is, by definition, no longer the natural history.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Edinburgh Spine Deformity Centre, Princess Margaret Rose Orthopaedic Hospital, Fairmilehead, Edinburgh EH10 7ED, Scotland.
‡39 Jalan 22/44, 46300 Petaling Jaya, Malaysia.
The radiographic classification of congenital kyphosis and kyphoscoliosis used in the present series (Table I) is based on the vertebral anomalies that cause the deformity (Fig. 2) and is an expansion of the classification used by Winter et al.23. We added the subgroups of butterfly (sagittal cleft) and anterior or anterolateral wedged vertebrae, and we differentiated between an anterior and an anterolateral unsegmented bar, as these were not described in the system of Winter et al. The number and sites of the vertebral anomalies were assessed (Fig. 3). Thirteen patients had extra thoracic vertebrae. Vertebral anomalies occurred at the thirteenth thoracic level in five patients and at the fourteenth level in two patients. The present classification system identifies the different types of congenital kyphosis and kyphoscoliosis and can be used to prognosticate about the natural history and the possibility of neurological complications.
The deformity usually progresses more rapidly during the adolescent growth spurt. We estimated the median rate of progression in degrees per year, rather than the mean, for each subgroup of patients: those who were less than ten years old and those who were ten years old and older. We believed that these values were more representative of each subgroup as a whole and were less distorted by widely divergent outliers.
Type I: Anterior Failure of Vertebral-Body Formation
Sixty-eight (61 percent) of the patients had a failure of formation of the anterior segment of the vertebral body. These patients were divided into four subgroups (Table I), depending on the pattern of failure of formation: posterolateral quadrant vertebra, posterior hemivertebra, butterfly (sagittal cleft) vertebra, and anterior or anterolateral wedged vertebra.
Posterolateral Quadrant Vertebra
This anomaly is due to a complete failure of formation of the anterolateral portion of a vertebral body, leaving a posterolateral fragment of bone of varying size attached to one pedicle and the neural arch (Fig. 2). An anteroposterior radiograph of the spine shows the posterolateral quadrant vertebra as a lateral triangle of bone containing a single pedicle with disc spaces cephalad and caudad (Fig. 4-A). A lateral radiograph shows the varying severity of the anterior failure of formation (Fig. 4-B), which ranges from a near absence of the vertebral body to a tapering of the vertebral body toward the anterior longitudinal ligament.
Thirty-four patients had a single posterolateral quadrant vertebra, and five patients had two adjacent posterolateral quadrant vertebrae. These anomalies occurred at all levels of the spine, but most were at the thoracolumbar junction (Fig. 3), and all patients had a sharply angled kyphoscoliosis. The associated scoliosis was on the left side in twenty-three patients and on the right in sixteen. The mean extent of the measured kyphosis was five vertebrae (range, three to seven vertebrae).
Of the thirty-four patients who had a single posterolateral quadrant vertebra, nineteen were less than ten years old (mean age, three years; range, four months to eight years and seven months) when they were first evaluated; the kyphosis measured a mean of 42 degrees (range, 23 to 88 degrees) at that time. Four patients had an arthrodesis of the spine soon after the initial visit, and the other fifteen patients were observed without treatment for a mean of four years and eight months (range, one year to nine years and two months) before the age of ten years, during which time the median rate of progression of the kyphosis was 2.5 degrees per year (range, 0 to 6 degrees per year) (Figs. 4-A, 4-B, 4-C and 4-D). Of the nineteen patients, nine had an arthrodesis before the age of ten years (mean age, four years and four months; range, nine months to nine years and seven months), when the kyphosis was a mean of 50 degrees (range, 30 to 93 degrees). The other ten patients had not been treated by the age of ten years, at which time the mean kyphosis was 51 degrees (range, 21 to 92 degrees). One of these patients (Case 4, Table II), who had a 92-degree kyphosis at the age of ten years and four months, had a spastic paraparesis. She was managed with a localizer cast and a posterior arthrodesis, and she had a complete recovery.
After the age of ten years, ten patients were seen without treatment for a mean of three years and six months (range, one to six years), during which time the median rate of progression of the kyphosis was 5 degrees per year (range, 2.4 to 12 degrees per year). Ten patients had an arthrodesis of the spine at a mean age of twelve years and eight months (range, eleven years and one month to sixteen years and six months), when the mean kyphosis was 81 degrees (range, 52 to 126 degrees). Two additional patients (Cases 2 and 7, Table II) were seen with a spastic paraparesis at the ages of fourteen years and eight months and sixteen years and ten months, when the kyphosis measured 111 and 60 degrees, respectively. Both patients were managed with an anterior decompression of the spine and arthrodesis combined with a posterior arthrodesis, and they had a complete recovery. Ten patients were seen untreated at skeletal maturity, at which time the mean kyphosis was 62 degrees (range, 40 to 120 degrees). One of the ten patients (Case 6, Table II) was seen with a spastic paraparesis at the age of seventeen years. No treatment was given because of severe congenital cardiac abnormalities, and complete paraplegia developed.
Of the five patients who had two adjacent posterolateral quadrant vertebrae, four were first seen untreated before the age of ten years (mean age, two years and five months; range, nine months to four years and seven months), when the mean kyphosis measured 53 degrees (range, 38 to 73 degrees). One of these patients, who was one year old, had a 50-degree kyphosis and was managed with an immediate arthrodesis of the spine. The other three patients were observed untreated for a mean of six years and ten months (range, five years and five months to nine years and three months) before the age of ten years, during which time the median rate of progression of the kyphosis was 5 degrees per year (4, 5, and 5.5 degrees per year). One of these patients (Case 1, Table II) had a 101-degree kyphosis and a gradual onset of a spastic paraparesis, which was treated with an anterior transthoracic strut-graft arthrodesis and a posterior arthrodesis when she was nine years and two months old. The patient had a partial neurological recovery. The other two patients had an arthrodesis of the spine when they were ten years and twelve years and ten months old and the kyphosis measured 68 and 78 degrees, respectively.
The fifth patient who had two adjacent posterolateral quadrant vertebrae (Case 3, Table II) was seen untreated when he was seventeen years and five months old, at which time he had a 127-degree kyphosis and spastic paraparesis. He was managed with an anterolateral decompression of the spine and a posterior arthrodesis, but he had no improvement and became completely paraplegic.
Posterior Hemivertebra
This anomaly is a complete failure of formation of the anterior portion of the vertebral body, leaving a residual wedged posterior portion attached to both pedicles and the neural arch (Fig. 2). Eight patients had this anomaly: four had a single posterior hemivertebra, and four had two adjacent posterior hemivertebrae. These anomalies all occurred in the caudad thoracic region (Fig. 3) and resulted in a sharply angled kyphosis; any associated scoliosis was less than degrees. The mean extent of the measured kyphosis was five vertebrae (range, four to seven vertebrae).
Two of the four patients who had a single posterior hemivertebra were diagnosed at birth. One patient had a 50-degree kyphosis, which progressed to 54 degrees at one year and was treated with an arthrodesis of the spine. The second patient had a 40-degree kyphosis associated with a forward subluxation of the eleventh thoracic vertebra on the twelfth thoracic vertebra, producing a bayonet-type deformity, and was managed with an arthrodesis of the spine. This deformity, which occurred in only one patient in the present series, has been described as a congenital dislocated spine5,26 or a congenital vertebral displacement16. Of the two patients who were not diagnosed at birth, one was three years and six months old and had an 18-degree kyphosis at the initial evaluation. The kyphosis progressed 5 degrees per year to become 55 degrees at the age of ten years and eight months, when the patient had an arthrodesis of the spine. The other patient was seen untreated at skeletal maturity and had a 57-degree kyphosis.
Of the four patients who had two adjacent posterior hemivertebrae, one (Case 5, Table II) was seven years and seven months old at the initial visit and had a 69-degree kyphosis. This kyphosis progressed 9 degrees per year to become 89 degrees at the age of nine years and nine months, at which time the patient had a spastic paraparesis. She had an anterior transthoracic decompression of the spine and arthrodesis combined with a posterior arthrodesis, after which she had increased spasticity. Another patient was eight years and seven months old at the initial visit, at which time she had a 62-degree kyphosis; this progressed 7 degrees per year to become 96 degrees at the age of thirteen years and three months, when she had an arthrodesis of the spine. The remaining two patients were seen untreated at skeletal maturity with kyphoses of 32 and 88 degrees.
Butterfly (Sagittal Cleft) Vertebra
This anomaly consists of a partial or complete failure of formation of the anterior and central portions of the vertebral body, leaving two posterolateral fragments of bone attached to the neural arch (Fig. 2). These residual pieces of bone are wedged anteriorly and medially and are separated by a sagittal cleft. This gives the typical butterfly appearance seen on anteroposterior radiographs of the spine, where the wings of the butterfly are represented by the two triangular fragments of the vertebral body, each containing a single pedicle (Fig. 5-A).
All fifteen patients in this subgroup had a single butterfly vertebra. These anomalies occurred mainly at the thoracolumbar junction (Fig. 3) and produced an angular deformity. The posterolateral fragments of bone were symmetrical and produced a pure kyphosis in ten patients, and the fragments were asymmetrical and produced kyphoscoliosis in five patients. The mean extent of the kyphosis was five vertebrae (range, three to seven vertebrae).
Ten patients were first evaluated when they were less than ten years old (mean age, three years and nine months; range, three months to nine years and ten months); the mean kyphosis was 32 degrees (range, 21 to 52 degrees). Seven of the ten patients were observed untreated for a mean of four years and eight months (range, one year and ten months to nine years) before the age of ten years, during which time the median rate of progression of the kyphosis was 1.5 degrees per year (range, 1 to 4 degrees per year). Four patients had an arthrodesis of the spine at a mean age of three years and four months (range, two years and four months to four years and eight months), when the mean kyphosis was 40 degrees (range, 32 to 46 degrees). Six patients had not been treated by the age of ten years, at which time they had a mean kyphosis of 40 degrees (range, 23 to 58 degrees).
After the age of ten years, five patients were observed untreated for a mean of five years and four months (range, three years to seven years and two months), during which time the median rate of progression of the kyphosis was 4 degrees per year (range, 0 to 12 degrees per year) (Figs. 5-A, 5-B, 5-C and 5-D). A sixth patient, who was thirteen years old at the time of the first evaluation, had not been treated and had a 90-degree kyphosis. Six patients had an arthrodesis of the spine after the age of ten years (mean age, thirteen years; range, eleven years to fifteen years and six months), when the mean kyphosis was 61 degrees (range, 37 to 90 degrees). Five patients who were seen untreated at skeletal maturity had a mean kyphosis of 47 degrees (range, 23 to 96 degrees).
Anterior and Anterolateral Wedged Vertebrae
These anomalies are characterized by a partial failure of formation, usually affecting the anterolateral segment of the vertebral body (Fig. 2). The anterior wedging always extends forward to the anterior longitudinal ligament, where the anterior height of the wedged vertebra is reduced to between 30 and 50 percent of the posterior height. These anomalies, which were present in six patients, all occurred in the caudad thoracic and cephalad lumbar regions (Fig. 3). The mean extent of the measured kyphosis was six vertebrae (range, three to twelve vertebrae).
A single wedged vertebra was present in two patients: an eleven-year-old who had a 33-degree kyphosis and a seventeen-year-old who had a 43-degree kyphosis. Both of these patients were managed with an arthrodesis of the spine.
There were two adjacent anterolateral wedged vertebrae in four patients. One patient was two years and four months old and had an 85-degree kyphosis, which progressed to 99 degrees by the age of nine years and seven months. The remaining three patients were first seen untreated when they were ten years old or older. One patient had an 85-degree kyphosis at the age of fifteen years and ten months, and two had kyphoses of 90 and 91 degrees at skeletal maturity.
Type II: Anterior Failure of Vertebral-Body Segmentation
Twenty-four patients (21 percent) had an anterior bar of bone extending across the intervertebral disc spaces joining adjacent vertebral bodies. These patients could be divided into two subgroups (Table I) depending on whether the anterior bar of bone lay symmetrically in the sagittal plane, producing a pure kyphosis, or anterolaterally, producing a kyphoscoliosis.
Anterior Unsegmented Bar
This anomaly lay symmetrically in the sagittal plane in fifteen patients; it involved a mean of 3.5 vertebrae (range, two to eight vertebrae) and produced a smooth pure kyphosis extending over a mean of five vertebrae (range, three to eleven vertebrae). This anterior failure of segmentation occurred at all levels from the fifth thoracic vertebra to the sacrum (Fig. 3). The anterior-to-posterior depth of the bar relative to the affected disc space was 30 percent in two patients, 50 to 75 percent in twelve patients, and more than 80 percent (a block vertebra) in one patient.
Eight patients were less than ten years old (mean age, five years and two months; range, three months to nine years and five months) when they were first seen, at which time the mean kyphosis was 42 degrees (range, 26 to 48 degrees). Six of these patients were observed without treatment for a mean of eight years and two months (range, five years and three months to nine years and nine months) before the age of ten years, during which time the median rate of progression was 1 degree per year (range, 0 to 1.6 degrees per year). One patient, who was six years old at the time of the initial visit, had an immediate arthrodesis of the spine, when the kyphosis was 67 degrees. The eighth patient, who had a kyphosis of 54 degrees when she was eight years and six months old, was seen only once. Thus, seven of these patients, with a mean kyphosis of 42 degrees (range, 23 to 54 degrees), were still untreated by the age of ten years.
Thirteen patients remained untreated after the age of ten years. Six of these patients were less than ten years old when they were first evaluated, and they were observed for a mean of six years and eight months (range, one year and eight months to nine years) after the age of ten years, during which time the median rate of progression of the kyphosis was 1.5 degrees per year (range, 0 to 7 degrees per year) (Figs. 6-A, 6-B, and 6-C). One of the six had an arthrodesis at the age of ten years and one month, one had an arthrodesis at the age of eleven years, and four remained untreated at maturity. Seven of the thirteen patients were first seen when they were at least ten years old. Two of these seven patients had an immediate arthrodesis, one was followed untreated until maturity, and the remaining four were first seen untreated at maturity. The four patients (of the thirteen) who had an arthrodesis were operated on at a mean age of twelve years (range, ten years and one month to fifteen years and four months), when the mean kyphosis was 73 degrees (range, 51 to 90 degrees). The remaining nine patients, who were untreated at skeletal maturity, had a mean kyphosis of 64 degrees (range, 27 to 140 degrees) at that time.
Anterolateral Unsegmented Bar
This anomaly, which is asymmetrical and lies anterolaterally, involved a mean of three vertebrae (range, two to three vertebrae) and produced a smooth kyphoscoliosis that extended over a mean of seven vertebrae (range, four to ten vertebrae). The scoliosis was to the right in six patients and to the left in three patients. The anterolateral failure of segmentation affected all levels from the third thoracic vertebra to the third lumbar vertebra (Fig. 3). It was not possible to measure the depth of the bar on the lateral radiographs of the spine because of the kyphoscoliosis.
Two of the nine patients were first seen untreated before they were ten years old. One patient was nine years old and had a 26-degree kyphosis, which was treated with an arthrodesis of the spine. The second patient was six years and ten months old and had a 38-degree kyphosis, which progressed to 42 degrees by the time that the child was ten years old.
Eight patients were seen untreated after the age of ten years. One patient was observed untreated for four years, during which time the kyphosis progressed 4 degrees per year. Three patients had an arthrodesis of the spine at a mean age of fourteen years (range, thirteen years and ten months to fourteen years and two months), when the mean kyphosis was 90 degrees (range, 65 to 109 degrees). Overall, five of the nine patients were untreated at skeletal maturity, at which time they had a mean kyphosis of 92 degrees (range, 58 to 109 degrees).
Type III: Mixed Anomalies
A combination of an anterolateral unsegmented bar and one or more contralateral posterolateral quadrant vertebrae (Fig. 2) was present in twelve patients (11 percent). The anterolateral bar extended over three adjacent vertebrae in nine patients, four vertebrae in two patients, and five vertebrae in one patient. Nine patients had a single posterolateral quadrant vertebra, two patients had two posterolateral quadrant vertebrae, and one patient had three posterolateral quadrant vertebrae. Localized oblique radiographs of the spine were usually necessary to identify these anomalies, which produced a sharply angular kyphoscoliosis. The anomalies occurred only between the ninth thoracic and the fourth lumbar vertebra (Fig. 3). The degree of the scoliosis, which was to the left in six patients and to the right in six patients, was usually similar to that of the kyphosis. The mean extent of the measured kyphosis was 5.5 vertebrae (range, four to nine vertebrae).
Seven patients were first seen untreated when they were less than ten years old, at a mean age of two years (range, birth to six years), when the mean kyphosis was 29 degrees (range, 11 to 44 degrees). These seven patients were observed untreated for a mean of seven years and two months (range, four years and one month to nine years) before the age of ten years, during which time the median rate of progression of the kyphosis was 5 degrees per year (range, 2.6 to 6 degrees per year). Three patients had an arthrodesis of the spine at a mean age of eight years (range, six years and nine months to nine years and seven months), when the mean kyphosis was 66 degrees (range, 60 to 70 degrees). At the age of ten years, four patients were still untreated and had a mean kyphosis of 76 degrees (range, 70 to 85 degrees).
Three patients were observed untreated for a mean of two years and three months after the age of ten years, during which time the median rate of progression of the kyphosis increased to 8 degrees per year (Figs. 7-A, 7-B, 7-C and 7-D). Seven patients had an arthrodesis of the spine at a mean age of thirteen years (range, ten years and seven months to sixteen years and four months), when the mean kyphosis was 92 degrees (range, 85 to 106 degrees). The remaining two patients were seen untreated at skeletal maturity with kyphoses of 60 and 97 degrees.
Type IV: Unclassifiable Anomalies
In eight patients (7 percent), the radiographic characteristics of the congenital anomalies lying at the apex of the curve were obscured by the severity of the deformity; six patients had an angular kyphoscoliosis, and two patients had an angular kyphosis. These curves occurred in all regions of the spine.
Three of the eight patients were first seen between the ages of eight and ten years old. The kyphoses measured 90, 112, and 130 degrees and were treated with an arthrodesis of the spine. A fourth patient (Case 11, Table II), who was eight years and six months old, had a 121-degree kyphosis and a spastic paraparesis. She was managed with an anterior transthoracic strut-graft arthrodesis combined with a posterior arthrodesis and had a partial neurological recovery.
The remaining four patients, who were seen untreated at or near skeletal maturity, had a mean kyphosis of 132 degrees. Three of these patients (Cases 8, 9, and 10, Table II) had a spastic paraparesis when they were between sixteen and twenty-eight years old. Two were managed with an anterior transthoracic strut-graft arthrodesis combined with a posterior arthrodesis; one had a partial recovery, and one had no change in the neurological status and died of respiratory failure. The third patient had an anterior transthoracic spinal decompression and became paraplegic.
Intraspinal Anomalies
A myelogram or a magnetic resonance imaging scan was made for fifty-one patients either before operative intervention or when there was a spontaneous neurological deficit. Only one of these patients was found to have an occult congenital intraspinal anomaly. This was a ten-year-old boy who had a type-II anterior failure of segmentation extending from the second lumbar vertebra to the sacrum and producing a lumbar kyphosis with its apex at the fourth thoracic vertebra. He had had mild nonprogressive unilateral neurological abnormalities of the lower limb from birth. At the time of exploration, he was found to have a large lumbar extradural lipoma and a tight filum terminale.
Other Congenital Anomalies
Other congenital anomalies were present in thirty-three patients (twenty who had type-I kyphosis or kyphoscoliosis, five who had type-II, and eight who had type-III). None of these anomalies were specific to any one type of congenital kyphosis or kyphoscoliosis.
Anomalies of the lower limb were present in fifteen patients. Five of these patients had a talipes equinovarus, two had a unilateral cavus foot, and five had mild unilateral hypoplasia of the lower limb. None of these anomalies were associated with a neurological deficit. Other anomalies of the lower limb, each affecting one patient, were unilateral coxa vara and short femur, unilateral slipped capital femoral epiphysis, and syndactyly of the toes.
Cardiac anomalies were diagnosed in five patients; renal anomalies, in four; intestinal abnormalities, in four; esophageal atresia, in two; imperforate anus, in one; and rectovaginal fistula, in one. A Goldenhar syndrome was present in three patients; a scimitar syndrome, in one; and a Prader-Willi syndrome, in one. A Sprengel deformity of the shoulder was found in four patients, and another patient had hypoplasia of the arm.