Congenital and Developmental Abnormalities 93 7 Congenital and Developmental Abnormalities Karl J. Johnson and A. Mark Davies CONTENTS form. Cavitation occurs between this cell mass and the femur creating the joint space. Any incongruity 7.1 Embryology and Development 93 present at birth is therefore secondary to abnormal 7.2 Normal Variants 93 7.3 Femoral Neck-Shaft Angulation 94 development from 11 weeks onwards. After 11 weeks 7.3.1 Coxa Vara 95 vascular invasion, cartilage formation and liga- 7.3.2 Infantile Coxa Vara 95 ment development become apparent. The hip joint 7.3.3 Coxa Valga 96 is completely developed by 5 months of gestational 7.4 Femoral Anteversion 96 age (Francis 1951). 7.5 Sacral Agenesis (Caudal Regression Syndrome) 97 7.6 Acetabular Protrusion (Protrusio Acetabuli) 97 Ossification is initially seen in the centre of the 7.7 Proximal Focal Femoral Deficiency 98 femur and appears at the level of the lesser trochan- 7.8 Skeletal Dysplasias 99 ter at 4 months of gestational age. Primary ossifica- 7.8.1 Meyer’s Dysplasia (Dysplasia Epiphysealis Capitis tion centres appear in the ilium, ischium and pubis Femoris) 99 at 2, 3 and 4 months respectively. The sacrum is 7.8.2 Multiple Epiphyseal Dysplasia 100 7.8.3 Spondyloepiphyseal Dysplasia 101 formed from five segments each of which constitutes 7.8.4 Accelerated Ossification 101 a vertebral body and paired neural arches. Ossifica- 7.8.5 Delayed Ossification 102 tion occurs in a craniocaudal direction beginning 7.8.6 Increased Bone Density 102 at about 14 weeks’ gestational age. The vertebral 7.8.7 Decreased Bone Density 102 bodies are the first to ossify, followed by the neural 7.8.8 Abnormal Shape and Appearance of Pelvis 102 arches and lateral masses (Caffey and Madell 7.9 Arthrogryposis Multiplex Congenita 103 Osborne 7.10 Neuromuscular Hip Dysplasia 103 1956; et al. 1980). References 104 Following birth ossification of the proximal femoral epiphysis is generally seen in girls between 2 and 6 months of age and in boys between 3 and 7.1 7 months. Femoral head ossification is seen in 50% Embryology and Development of children by 4 months and in 90% by 7 months of age (Pettersson and Theander 1979; Stewart et The lower limb bud develops as an outgrowth from al. 1986). the ventral surface of the embryonic mass at approx- Secondary ossification centres appear in the iliac imately 4 weeks’ gestational age. The club-shaped crest, ischial tuberosity the pubic symphysis, the femoral pre-cursors along with the iliac, ischial and superior acetabulum and the anterior superior and pubic pre-modal centres develop at around 6 weeks. inferior iliac spines around puberty and are usually Between 6 and 11 weeks the femoral head can be fused by early adulthood. Fusion of the posterior identified as a mass of cells interposed between spinal elements of the sacrum fuse in a craniocaudal the distal femur and the pelvis, at the same time direction and is complete by around 17 years of age the primitive femoral neck and greater trochanter (Eich et al. 1992). K. J. Johnson, MD Department of Radiology, Princess of Wales Birmingham 7.2 Children’s Hospital, Steelhouse Lane, Birmingham, B4 6NH, Normal Variants UK A. M. Davies, MD The MRI Centre, Royal Orthopaedic Hospital, Birmingham, The multiple centres of ossification and the varia- B31 2AP, UK tion in their appearance and timing need to be con- 94 K. J. Johnson and A. M. Davies Fig. 7.2. AP radiograph of the pubic bones in a 13-year-old boy. The left ischium pubic synchondrosis is large and prominent. Fig. 7.1. AP radiograph of the pelvis in a 5-year-old boy. There The right is almost absent is asymmetry in the appearances of the ischiopubic synchon- drosis. The left side is larger and more prominent than the right sidered when evaluating radiographs of the pelvis. These normal variants are very well illustrated in Atlas of Normal Roentgen Variants (Keats and Anderson 2001). At birth the pelvis is more rounded with the bony Fig. 7.3. AP radiograph showing two separate ossifi cation cen- outline of the acetabulum appearing shallower. tres in the left proximal femoral epiphysis. This is a normal Minor irregularities in the outline of the acetabu- variant lum, iliac crest and pubic bones can be seen from 3 years of age until early adulthood. In the sacrum transitional vertebrae are com- Fusion of the ischiopubic synchondrosis has a monly seen to involve the sacrococcygeal and very variable appearance and times of closure. It lumbosacral junctions. The L5 vertebrae can be can appear as early as 3 years of age, with complete incorporated into the sacrum (sacralized) or the S1 fusion seen in the majority of children by 12 years vertebrae can be incorporated into the lumbar spine of age. Closure may be preceded by increase in size (lumbarized). These transitional vertebrae retain of the cartilaginous component giving a swollen partial features of the segments involved above and or bubbly appearance which may last up to 3 years below so the total number of vertebra remains con- (Figs. 7.1 and 7.2) (Caffey and Ross 1956). This stant. Transitional vertebrae are usually an inciden- expansion can be unilateral and it may also show tal asymptomatic finding on pelvic and abdominal unequal uptake on bone scintigraphy. The uptake in radiographs. Enlarged transverse processes have the synchondrosis should not be greater than that been described to cause soft tissue irritation (Eich seen around the triradiate cartilage (Kloiber et al. et al. 1992). 1988). Vertical clefts and multiple ossific centres can be seen in the superior pubic ramus and the superior margin of the acetabulum may be irregular with 7.3 beaking of its intra-pelvic portion (Ponseti 1978). Femoral Neck-Shaft Angulation A wide variety of appearances and times of ossifi- cation of the proximal femoral epiphysis can occur, At birth the femoral neck to shaft angle, as mea- asymmetry of 2 mm in height being recognised in sured in the coronal plane, is 150° which decreases any individual (Lemperg et al. 1973). to 120°–130° in the adult. Coxa vara is a smaller and During infancy the ossification centres can have coxa valga is a larger than normal angle (Pavlov a crenated, or stippled outline with vertical clefts et al. 1980; Lincoln and Suen 2003; Staheli et al. within them. There may also be central defect in the 1985). epiphysis due to the ligamentous teres attachment The alteration in neck angle shaft during child- (Ozonoff and Ziter 1987) (Fig. 7.3). hood is as a result of different growth rates of the Congenital and Developmental Abnormalities 95 greater trochanter and femoral neck. This is a con- sequence of the gravitational forces that act on the proximal femur that occur as the child starts to walk upright. 7.3.1 Coxa Vara A Coxa vara deformity is the result of either congeni- tal or acquired conditions, which may be a localised abnormality or associated with a more generalised skeletal disorder. Once coxa vara is identified it is important to find a causative deformity to deter- mine prognosis, any likely associations and plan Fig. 7.4. AP radiograph of a child with Gaucher’s disease. The management. bone density is abnormal. There is fragmentation and irreg- Localised acquired conditions include treated ularity of the left femoral epiphysis as a result of avascular necrosis. There is bilateral coxa vara congenital hip dislocations with or without subse- quent avascular necrosis, Gaucher’s disease, Perthes’ disease, slipped capital femoral epiphysis, trauma and sepsis (Fig. 7.4). Generalised acquired conditions are usually asso- ciated with reduced bone density including osteo- malacia, renal osteodystrophy and rickets. In these children there is remodelling of the femoral necks, metaphyseal widening, irregularity, slipped capital femoral epiphysis and bowed femurs. The coxa vara can be progressive. Fig. 7.5. Congenital coxa vara. The physis is almost vertical. Coxa vara that is present at birth (congenital coxa There is fragmentation around the distal metaphysis, with a small ossifi cation fragment on the inferior aspect vara) can be isolated or associated with other anom- alies. When associated with proximal focal femoral Table 7.1. Causes of Coxa vara (unilateral or bilateral) deficiency, congenital short femur or congenitally bowed femur, there is usually minimal progression Idiopathic coxa vara of childhood (Fig. 7.5). Legg-Perthes’ disease, old A list of the disorders associated with coxa vara is Neuromuscular disorders given in Table 7.1. Malunited fracture Developmental dysplasia of the hip Fibrous dysplasia Paget’s disease 7.3.2 Rheumatoid arthritis Infantile Coxa Vara Rickets; osteomalacia Proximal focal femoral defi ciency Infantile or developmental coxa vara is a localised Diastrophic dwarfi sm abnormality that is usually not detected until Enchondromatosis (Ollier’s disease) the child begins to walk at around 2 years of age, Fibrous dysplasia Hyperparathyroidism, secondary radiographs being normal at birth (Blockey 1969; Amstutz Hyperphosphatasia 1970). It is of unknown aetiology but may Hypothyroidism be the result of a defect in cartilaginous develop- Kniest’s disease ment, with an abnormal transition from resting to Metaphyseal chondrodysplasia proliferating cartilage cells; in the medial portion of Multiple epiphyseal dysplasia the growth plate being described (Bos et al. 1989). Osteogenesis imperfecta There is no sex predilection but familial cases have Osteopetrosis been reported. Bilateral involvement is seen in 30%– Slipped capital femoral epiphysis Spondyloepiphyseal dysplasia 50% of cases (Calhoun and Pierret 1972). 96 K. J. Johnson and A. M. Davies Children often complain of fatigue, thigh pain and an abnormal gait between 1–6 years of age.