This genetically heterogenous condition with a fragile skeleton has several varieties according to the severity of involvement and genetic inheritance. The severity may vary from a stillborn baby with multiple fractures to a milder variety with slight tendency to fracture.
Osteogenesis imperfecta congenita which is present at birth, often with multiple fractures, will be discussed here. Osteogenesis imperfecta tarda usually develop fracture when the child learns walking, but the condition of osteopenia and cortical thinning of bone are present in a hitherto normal radiograph.
Classification and Incidence
The condition is best described according to Sillence9 classification which is comprehensive and thorough. He has described four types with types I and IV divided into A and B and Type II divided into A, B and C. All are autosomal dominant in inheritance except type IIC and Type III, which are autosomal
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General Aspect of Neonatal Orthopaedics recessive. The type II is osteogenesis imperfecta congenita A and the type III and IVA are congenita B as described by Shapiro.10The incidence varies between 1 in 30,000 in type I and 1 in 62,000 in type II; the incidence of other two varieties is not known yet.
Etiology
Biochemical defects in the genes for collagen A1 and A2 cause this connective tissue disorder. In the congenita A and B varieties of Shapiro, i.e. Type II A, B, C and Type III and Type IVB of Sillence the collagen A1 and A2 produced is mostly structurally abnormal with molecular defect. In the Sillence Type I variety the cause is 50 per cent underproduction of normal collagen A1, i.e. a quantitative change. The defect in both the qualitative and quantitative varieties is in chromosome 7q21.
Clinical Features
Fragility of bones causing fracture is common in all the varieties; but in type I and type IV bone fragility is never severe and fractures occur later in life with a lesser incidence than in other types (Table 6.1).
The incidence and severity of deformities due to fractures is more in type II and III, i.e. in more serious type of the disease. Sometimes babies are born with birth fractures in the long bones, ribs and skull with even subdural haematoma or develop fracture without any significant trauma. One bone may fracture repeatedly, which indicates a milder form of the disease. Fracture are common to occur in the lower limbs. The multiplicity of fractures make the children fearful (Fig. 6.3). Otherwise, the suffering children are bright and intelligent.
fig. 6.3: Clinical photograph of a crying baby with multiple fractures in both upper and lower limbs in osteogenesis imperfecta
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General Abnormalities of Skeletal Development, Evident at Birth
Blueness of sclera, which is due to thinness of scleral collagen, is present in type I and II. The sclera is blue at birth in type III but becomes normal in adulthood and is absolutely normal in type IV. Sometimes the sclera surrounding the cornea is white with a further ring in the periphery of sclera producing what is known as arcus juvenilis. Blue sclera is not associated with any visual impairment.
Hypermobility of joints due to laxity of ligaments is a common finding in osteogenesis imperfecta.
This is again due to collagen abnormality. Pes valgus, genu recurvatum, patello femoral instability, hyperextended elbow, atlantoaxial subluxation and occasional hip and radial head dislocation are found due to laxity of ligaments.
Problems arise with teeth, starting from late eruption, brittleness, proneness to caries to abnormal teeth from deficiency of dentin. The colour of the teeth both deciduous and permanent varies between yellowish brown and translucent blue.
In adults the symptoms like Kyphoscoliosis and deafness from otosclerosis develop in about one- third of cases with osteogenesis imperfecta.
The clinical features of Type II A, B and C and Type III and Type IVA which Shapiro10 described as congenita A and congenita B respectively are given in a tabular form11 in Table 6.3.
Radiographic features: The X-ray findings of osteogenesis imperfecta are characteristic at birth and in the neonatal period. The long bones which are wide at diaphysis equalling metaphysis with thin cortices show multiple fractures at various stages of healing (Fig. 6.4). Some of the long bones are, therefore, angulated and some are accordion-like or crampled. The ribs are beaded with atrophy of the thoracic cage; and the skull shows practically no ossification (Fig. 6.5). The other redeeming feature is osteoporosis. The presence of wormian bones at the suture lines is characteristically present in the nonossified membranous skull bones of osteogenesis imperfecta like cleidocranial dysostosis.
fig. 6.4: Osteogenesis imperfecta with multiple fractures at various stages of healing
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General Aspect of Neonatal OrthopaedicsTable 6.3: Clinical features according to types of Sillence in congenita A and B Congenita A: Type IICongenita B ABCType IIIType IVA InheritanceAutosomal dominantAutosomal dominantAutosomal recessiveAutosomal recessiveAutosomal dominant Incidence1 in 62,000Not knownExtremely rare Very rareUnknown Bone fragilityVery severeVery severeVery severeSevere, numerous fractures by 2 years of ageModerate-newborn fracture-25% Deformity of long bonesBroad, crumpled accordion- like, specially femurs and humerus; beaded ribs Broad, crumpled; beaded ribs; rib fractures Thin, fractured long bones; ribs slightly beaded
Fractures at birth; severe deformities of long bonesModerate Hyperimobility of joints- ligamentous laxityUnknown becasue of perinatal deathUnknown beasue of perinatal deathUnknown because of perinatal deathMarkedModerate Spine deformity???Severe kyphoscoliosis; cod fish vertebraeKyphoscoliosis SkullWormian bones with severe demineralisationWormian bones with severe demineralisation
Wormian bones with severe demineralisation Membranous bones, severe deossification; Wormian bones; occiput, facial bones fairly well ossified; triangular facies
Moderate- deossification; Wormian bones TeethUnknown because of perinatal deathUnknown because of perinatal deathUnknown because of perinatal deathDentinogenesis imperfectaNormal ScleraeBlueBlueBlueBlue at birth and infancy, but becomes normal laterNormal Deafness————Deafness less severe-otosclerosis OtherFlattened acetabuli; microscopic calcification of aorta and endocardium
Flattened acetabuliFlattened acetabuli‘Popcorn’ calcification PrognosisPerinatal lethal respiratory diseaseSurvival possible; respiratory diseasePerinatal lethal respiratory diseaseWheelchair bound; Utmost household ambulator Chondro-osseous and biochemial defectCollagen produced structurally abnormalCollagen produced structurally abnormalCollagen produced Structurally abnormalCollagen produced structurally abnormal—
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General Abnormalities of Skeletal Development, Evident at Birth
Differential Diagnosis
Various other conditions like achondroplasia, camptomelic dwarfism or congenital hypophosphatasia with multiple fractures in the neonatal period or at birth with short limbs and enlarged head must be differentiated from osteogenesis imperfecta by radiological studies and skin biopsy for study of collagen.
The conditions mimicking osteogenesis imperfecta in older children are omitted here.
Treatment
A baby born with multiple fractures in the long bones, ribs and skull needs particular care in handling the baby, maintenance of respiration in multiple rib fractures even by an anaesthesiologist and the help of a neurosurgeon is asked for in case of subdural haematoma following skull fracture.
The problem needs to be discussed with the parents, not only for the initial management of simple splintage for multiple fractures but also regarding the upbringing of the child when the need for correction of bent bones and kyphoscoliosis will arise (Figs 6.6 and 6.7). As the callus formation occurs early (Fig. 6.8) the immobilisation by splintage should be done for a short period to prevent development of osteoporosis.
The osteoporosis in this disease is real problem (Fig. 6.9) and various types of medicines tried for the condition are proved useless. Further development of fractures from osteoporosis is prevented by different types of orthosis, which again help in the locomotion of the child. The difficulty in locomotion arises from improper muscular development due to bone and joint immobilisation by various types of splints and orthosis, so develops a vicious cycle.
In a child of three years or more, the problems arising from the disease like deformity of long bones are treated surgically. Multiple osteotomies of deformed long bones, correction of alignment and holding the fragments with various types of intramedullary rods like Sofield’s and telescoping IM rods of Bailey and Dubow are undertaken at around three to five years of age. The procedure also helps in the better use of orthosis.
fig. 6.5: Skull in osteogenesis imperfecta showing practically no ossification
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General Aspect of Neonatal Orthopaedicsfigs 6.6 and 6.7: Bent bones in osteogenesis imperfecta showing kyphoscoliosis of tibia and fibula at two different stages
fig. 6.8: Early callus formation in fractures in osteogenesis imperfecta
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General Abnormalities of Skeletal Development, Evident at Birth
fig. 6.9: Osteoporosis in osteogenesis imperfecta