Metaphyseal Bands
► [Radiodense and/or radiolucent striations about the metaphyses, oriented transversely or longitudinally]
Transverse radiodense bands, also referred to as Park or Harris lines (Park and Richter 1953; Harris 1926), stress lines, or growth arrest lines (Garn et al. 1968), are common in both children and adults. They may be present at birth or appear during infancy, do not form after skeletal growth has ceased, and tend to persist into adulthood. Radiodense lines are more frequent at sites of rapid bone growth, such as the distal femurs and proximal tibias, and are not associated with any clinical symptomatology. In the tubular bones, they run parallel to the provisional zone of calcification. Although their pathogenesis is not completely understood, there is some evidence supporting the idea that they represent periods of renewed or increased growth of the bone following a period of inhibited growth. Therefore, the term 'recovery' lines seems more appropriate than 'arrest'lines (Garn et al. 1968). Transverse radiodense bands can be found in healthy (anatomical variation) individuals and in those with symptoms, especially patients who have been poisoned with any of a variety of heavy metals. In particular, lead poisoning is associated with the presence of thick radiodense bands in the metaphy-ses of the tubular bones. Single bands are more typical, but multiple bands can result from several episodes of lead poisoning. These lines have been related to a disturbance in arterial blood supply to the cartilage plate, with secondary deposition of calcium within the cartilaginous matrix. Additional manifes tations of chronic lead poisoning include metaphy-seal widening of the tubular bones and increased in-tracranial pressure (Resnick 1995). Virtually every insult to the growing skeleton, whether from a systemic or a local (trauma, infection) disorder, can produce metaphyseal recovery bands, owing to a transient failure of bone growth. In cases in which no such episodes are recognized, radiodense lines are likely to represent exuberant calcification of the provisional zone. Anatomically, radiodense lines consist of transversely oriented trabeculae crossing the medullary cavity partially or completely (Pease and Newton 1962). In the initial stage of bone growth arrest they appear as thin bony bands lying beneath the proliferating zone of the growth plate. During the recovery phase, cartilaginous proliferation and increased osteoblastic activity lead to thickening of the transverse lines and their migration towards the metaphysis. Thick, transverse metaphyseal lines of increased density are typically found in children with scurvy. These lines correspond histologically to areas of calcified cartilage matrix lying beneath an area of irregular arrangement of cartilage cells in the proliferating zone of the growth plate. The calcified matrix might eventually extend laterally to form small beak-like outgrowths. Under this line a radi-olucent transverse band (the 'scurvy' line) is recognized, which corresponds to decreased trabecular structure in the junctional area. Other radiographic changes in scurvy include periostitis, caused by sub-periosteal hemorrhage with elevation and stimulation of the periosteum, and a peculiar appearance of the epiphyses,with a central radiolucency (atrophy of central spongiosa) surrounded by a sclerotic shell (prominent provisional zone of calcification) (Garn et al. 1968). Radiodense lines extending part-way or right across the marrow cavity in the metaphysis or in the diaphysis of the tubular bones are found in association with chronic osteoporosis, usually secondary to limb disuse of neurological or traumatic origin or to prolonged bed rest. The origin of these lines, also commonly termed 'bone bars' or 'reinforcement lines,' is unknown. They may well be preexisting normal structures disclosed by the intervening osteopenia; or they may represent an abnormal bony response to biomechanical stress (Ogden 1984).
While radiodense bands reflect rapid bone deposition of the recovery phase, radiolucent transverse bands usually reflect deficient endochondral bone formation. Symmetrical metaphyseal radiolucent bands are found in childhood leukemia. Since histo-logically these bands are not associated with leukemic cell infiltration, they probably reflect a nu-
Fig. 5.52. Leukemia in a 3-year-old child. Note typical transverse metaphyseal lucent bands in the distal femoral and proximal tibial metaphyses. Also observe the radiodense bands adjacent to the areas of increased radiolucency, probably reflecting periods of cessation and acceleration of bone growth. (From Wihlorg et al. 2001)
Fig. 5.52. Leukemia in a 3-year-old child. Note typical transverse metaphyseal lucent bands in the distal femoral and proximal tibial metaphyses. Also observe the radiodense bands adjacent to the areas of increased radiolucency, probably reflecting periods of cessation and acceleration of bone growth. (From Wihlorg et al. 2001)
Fig. 5.53. Osteopetrosis: a 4-year-old girl affected by the asynchronous asymmetrical form of heterogeneous osteopetrosis (same case as in Fig. 4.30). Observe the single sclerotic band in the distal left radius, in contrast with the multiple alternating sclerotic bands in the distal right radius. Also observe meta-physeal clubbing of the right radius. (From Young and Lach-man 2001)
Fig. 5.53. Osteopetrosis: a 4-year-old girl affected by the asynchronous asymmetrical form of heterogeneous osteopetrosis (same case as in Fig. 4.30). Observe the single sclerotic band in the distal left radius, in contrast with the multiple alternating sclerotic bands in the distal right radius. Also observe meta-physeal clubbing of the right radius. (From Young and Lach-man 2001)
- Fig. 5.54. Osteopathia striata with cranial sclerosis in an 8-year-old girl.There are vertical linear densities in metaphyses of proximal tibias and distal femurs bilaterally. (From Gay et al. 1994)
tritional deficit interfering with normal osteogenesis. The radiolucent bands are areas of bone weakening, and as such can undergo pathologic fracture or epi-physeal separation and displacement. Associated areas of radiodensity, probably reflecting alternating periods of arrest and acceleration of bone growth, may be seen adjacent to the areas of increased radi-olucency in children with leukemia (Nixon and Gwinn 1973) (Fig. 5.52). Epiphyseal destruction, osteolytic lesions, diffuse osteopenia, periostitis, and osteosclerosis are other common skeletal features in childhood leukemia. Radiolucent metaphyseal bands are also encountered, although less frequently, in adult acute leukemia. Again, osteopenia and discrete osteolytic lesions are additional possible manifestations (van Slyck 1972). Bilateral and symmetrical band-like metaphyseal radiolucencies can be seen in children with neuroblastoma, representing secondary localization of the disease. The femur and tibia are most commonly involved. Sclerotic bands are less frequent in this disease, usually appearing in late stages (McAlister and Lester 1971). Lytic lesions and periostitis are other skeletal manifestations of the disease.
Alternating radiolucent and sclerotic transverse metaphyseal bands are consistent features in both the benign (OMIM 166600) and the malignant (OMIM 259700) forms of osteopetrosis. They repre-
Fig. 5.55 a,b. SPONASTRIME dysplasia. a In a 24-month-old boy the metaphyses of distal femur and proximal tibia are lined with a dense transverse band, but no vertical stria-tions can be seen. b In this 8-year-old girl note increased metaphyseal irregularities and vertical striation of alternating dense and lucent areas next to the metaphyseal margins. (From Langer et al. 1997)
Fig. 5.55 a,b. SPONASTRIME dysplasia. a In a 24-month-old boy the metaphyses of distal femur and proximal tibia are lined with a dense transverse band, but no vertical stria-tions can be seen. b In this 8-year-old girl note increased metaphyseal irregularities and vertical striation of alternating dense and lucent areas next to the metaphyseal margins. (From Langer et al. 1997)
sent areas of mature bone interspersed with disorganized, sclerotic osseous tissue. In rare instances, the transverse bands develop in an asynchronous and asymmetrical fashion between the sides (Young and Lachman 2001) (Fig. 5.53). Occasionally, vertical striations are also seen, probably representing blood vessels surrounded by connective tissue (McAlister and Herman 1995). Diffuse bone sclerosis, lack of corticomedullary differentiation, defective modeling with Erlenmeyer flask deformity, and splayed, radi-olucent metaphyses are important skeletal changes in the long bones in these conditions.
Dense vertical striations about the metaphyses are less common than transverse bands and are found in a selected group of disorders. However, prominent vertical trabecular formation may also represent normal anatomical variation in otherwise normal subjects. Osteopathia striata is a rare disease, probably with an autosomal dominant pattern of inheritance, which is characterized by vertical, fine bands of increased radiodensity extending from the meta-physes of the long bones for a variable distance into the diaphyses and alternating with areas of bone rarefaction. The iliac bones are also involved, with dense striations, while the small bones in the hands and feet, the skull and facial bones, and the vertebrae are usually spared. The lesions are most commonly bilateral and symmetrical, but unilateral distribu tions can be seen (Carlson 1977). Osteopathia striata can occur in association with other sclerosing disorders, such as osteopoikilosis, melorheostosis, and osteopetrosis (Cantatore et al. 1991). Osteopathia striata with cranial sclerosis (OMIM 166500) has been identified as a separate entity. Vertical striations of the long bones in both diseases are remarkably simi-lar,but cranial sclerosis, especially involving the skull base, cranial nerve palsies, macrocephaly, cleft palate, and mental retardation are distinct features in the latter condition (Winter et al. 1980) (Fig. 5.54).A disorder in which the radiographic appearance may not be distinguishable from osteopathia striata is SPONASTRIME dysplasia (OMIM 271510). The acronym SPO-NA-STRI-ME summarizes the principal features of the condition, namely spondylar and nasal alterations, and striations about the metaphy-ses. However, the metaphyseal striations are usually not present in infancy, and they may be inconspicuous in childhood (Fig. 5.55a,b) (Langer et al. 1997). In the first report by Fanconi et al. (1983), the characteristics of the condition were listed as short-limb dwarfism, moderate deformity of the vertebral bodies, mildly striated metaphyses, saddle nose, frontal bossing, large head with midfacial hypoplasia (oriental look), and normal intelligence. Further reports outlined a variety of SPONASTRIME dysplasia with mental retardation (Camera et al. 1993; Verloes et al.
1995). Vertical striations of the metaphyses crossing the epiphyses are also seen in focal dermal hypoplasia (Goltz syndrome, OMIM 305600), together with osteopenia and multiple bone lesions resembling giant cell tumors. Vertical dense metaphyseal spicules representing calcified lines of cartilage projecting from the metaphysis into the growth plate are seen also in phenylketonuria (OMIM 261600). Growth 'arrest' lines can also be present. Metaphyses, especially about the wrist, are widened and cup-shaped.
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