Tibial Bowing

This section has significant overlap with the section "Bowed Tubular Bones" in this chapter. Most of the general comments provided in that section apply to tibial bowing, including the fact that bowing can be congenital or acquired; confined to the tibia or extended to other long bones; related to a focal defect,

Neurofibromatosis Bone Deformities

Fig. 5.32. Neurofibromatosis type 1 in a 2-year-old child. Observe anterolateral bending of the distal end of the left tibia and, to a lesser extent, of the fibula. Bowing deformities can either precede or follow pseudarthrosis, or can exist as a manifestation of the disease in the absence of bone discontinuity. (Courtesy of Dr. P. Balestrazzi, University of Parma, Italy)

Fig. 5.32. Neurofibromatosis type 1 in a 2-year-old child. Observe anterolateral bending of the distal end of the left tibia and, to a lesser extent, of the fibula. Bowing deformities can either precede or follow pseudarthrosis, or can exist as a manifestation of the disease in the absence of bone discontinuity. (Courtesy of Dr. P. Balestrazzi, University of Parma, Italy)

or part of a systemic disorder. In this section, the conditions with selective or preferential involvement of the tibia are briefly reviewed.

Unilateral tibial bowing in children may be seen after plastic bending fractures of the tibial shaft, or after injuries to the epiphysis, whether traumatic or infectious in origin. In the first case bowing is typically transitory, while in the second case it tends to be permanent. Unilateral, congenital tibial bowing may be secondary to a faulty intrauterine position or be the result of congenital pseudarthrosis. Bowing deformities related to faulty intrauterine positions tend to resolve spontaneously over time (Reed 1992), while those secondary to congenital pseudarthrosis do not. The term 'pseudarthrosis' refers to discontinuity of the bone, which is characterized by nonunion and abnormal bending at the site. Mechanisms underlying congenital pseudarthrosis include abnormalities of the primary cartilaginous anlage, trauma, amniotic bands, genetic causes, vascular anomalies, and metabolic and nutritional disturbances (Newell and Durbin 1976). However, the ultimate reason for bony nonunion often remains obscure. Congenital pseudarthrosis has been related to the presence of neurofibromatosis type 1 (OMIM 162220) in about 50% of cases (Brown et al. 1977) (Fig. 5.32). Hence, whenever pseudarthrosis of the tibia is found, neurofibromatosis type 1 must be excluded. Since an intraosseous neurofibroma or schwannoma at the site of nonunion is found only rarely, the bony defect probably reflects abnormal or deficient bone formation of the basic mesodermal dysplasia (Andersen 1976). In under 20% of cases pseudarthrosis has been related to the presence offibrous dysplasia and fibrous tissue has been found at the site of the fracture (Brown et al. 1977). The lesion usually develops during the first 2 years of life, although cases of later onset have been observed. Fibular bowing and limb length discrepancy can be associated features (Swis-chuk and John 1995). In another 30 % of cases neither neurofibromatosis nor fibrous dysplasia can be documented (Brown et al. 1977). Pseudarthrosis can also occur with osteofibrous dysplasia, a benign fibro-os-seous lesion of bone similar to fibrous dysplasia, with selective involvement of the tibia and fibula (Cam-panacci and Laus 1981). Involvement of other bones, notably the ulna, is rare (Goto et al. 2001). Cortical irregularities with alternating lytic and sclerotic lesions are seen radiographically. Spontaneous resolution is common in the long term, and surgical removal is indicated only in patients with a high risk of impending fracture and progressive deformity (Ozaki et al. 1998). The lesions tend to recur after surgery. The differential diagnosis against fibrous dysplasia is based on lesion location (maxilla, frontal bone, and femur in fibrous dysplasia; tibia and fibula in osteofibrous dysplasia), patient age (on average 24.0 years for fibrous dysplasia; 13 years for osteofibrous dysplasia), and histological appearance (resting osteoblasts and cartilage differentiation in fibrous dysplasia; fibroblast-like spindle cells, and osseous tissue in osteofibrous dysplasia) (Maki et al. 2001). A possible involvement of neurofibromin, the product of the tumor suppressor NF1 (neurofibromatosis type 1) gene in the development of osteofibrous dysplasia, has been suggested (Sakamoto et al. 2001).

Bilateral tibial bowing may occur in isolation or, more commonly, in association with other defects, including fibular hemimelia, shortening of the ipsi-lateral femur, equinovalgus deformity of the foot, deficiency of the lateral rays in the foot, and tarsal coalition (Hootnick et al. 1977). With isolated tibial bowing, the tibial convexity is usually posteromedial, dorsiflexion deformity of the foot may be present, and bowing of the fibula commonly coexists. In the case of fibular hemimelia, the tibia is usually bowed in a ventral and medial direction. Tibial bowing occurs in the context of disorders characterized by inherent bone weakening, including rickets and osteomalacia. In osteogenesis imperfecta (OMIM 166200, 166210,166220,259420) both osteomalacia and multiple fractures can be responsible for tibial bowing. Bilateral bowing of the tibias and fibulas, often associated with bowing of other tubular bones, is typically encountered in the autosomal dominant Weis-mann-Netter-Stuhl syndrome (OMIM 112350) (Francis et al. 1991). As in neurofibromatosis type 1, tibial curvature is anterior and medial and is associated with thickening of the posterior tibial cortex. However, 'tibialization' of the fibula in Weismann-NetterStuhl syndrome is clearly different from the gracile and hypoplastic fibular appearance in neurofibromatosis type 1. In Melnick-Needles syndrome (OMIM 309350), lateral bowing of both tibias, with a characteristic S-shaped configuration, is striking (Melnick and Needles 1966).

Hearing Aids Inside Out

Hearing Aids Inside Out

Have you recently experienced hearing loss? Most probably you need hearing aids, but don't know much about them. To learn everything you need to know about hearing aids, read the eBook, Hearing Aids Inside Out. The book comprises 113 pages of excellent content utterly free of technical jargon, written in simple language, and in a flowing style that can easily be read and understood by all.

Get My Free Ebook


Responses

  • SEMIRA
    What deficiency causes posteromedial bowing of tibia and fibula in newborn?
    3 years ago
  • Hope Hamilton
    What syndromes cause tibial bowing?
    1 month ago

Post a comment