Hubbard A M, Meyer J S, Davidson R S, Mahboubi S, Harty M P
Department of Radiology, Children's Hospital of Philadelphia, University of Pennsylvania 19104.
AJR Am J Roentgenol. 1993 Oct;161(4):849-53. doi: 10.2214/ajr.161.4.8372773.
Although many reports have documented when ossification centers can first be visualized on radiographs, few studies have evaluated the position of the ossification center within its cartilaginous anlage. In the skeletally immature child, the ossification centers of the tarsals are used to evaluate the positions of the tarsals and their interrelationships. It is convenient to assume that tarsal ossification begins in the center of its cartilaginous anlage and proceeds in a radial fashion; however, this may not be the case. Accordingly, we used MR imaging to evaluate the location of the ossification centers of the tarsals within their cartilaginous anlage in the mid and hindfoot in children.
MR studies of 69 feet in 40 children, 3 months to 7 years old (mean, 2.5 years), were reviewed retrospectively. The location of the ossification center within its cartilaginous anlage and the percentage of ossification of the cartilaginous anlagen of the talus, calcaneus, cuboid bone, and navicular bone were determined from coronal and sagittal images. In the talus, the difference between the orientation of the long axis of its ossification center and the long axis of its cartilaginous anlage was measured on coronal and sagittal images.
Early talar ossification was centered on the neck of the talus; the proximal aspect of the bone ossified last. The long axis of the talar ossification center and the long axis of its cartilaginous anlage differed in orientation. Early calcaneal ossification was centered on the distal two thirds of the cartilaginous anlage of the calcaneus; the proximal aspect and the area of the subtalar joint ossified last. Early navicular ossification was centered on the central or lateral third of the navicular cartilaginous anlage; the medial aspect ossified last. The ossification center of the cuboid bone was in the middle of the cuboidal cartilaginous anlage.
Our results show that early ossification in the talus, calcaneus, and navicular bones does not begin in the center of the bones' cartilaginous anlagen. The orientations of the long axis of the talar ossification center and the long mid axis of its cartilaginous anlage are different. Therefore, part of the changes in the alignment of the tarsals seen on radiographs with growth is due to ossification beginning and proceeding eccentrically within the cartilaginous anlage and not to a true change in the alignment of the tarsals. These data provide new information about the normal development of the child's hindfoot and midfoot.
尽管许多报告记录了骨化中心最早可在X线片上显影的时间，但很少有研究评估骨化中心在其软骨原基内的位置。在骨骼未成熟的儿童中，跗骨的骨化中心用于评估跗骨的位置及其相互关系。人们通常认为跗骨骨化始于其软骨原基的中心并呈放射状进行；然而，实际情况可能并非如此。因此，我们使用磁共振成像（MR）来评估儿童中足和后足跗骨的骨化中心在其软骨原基内的位置。
回顾性分析了40名年龄在3个月至7岁（平均2.5岁）儿童的69只足的MR研究资料。从冠状位和矢状位图像确定骨化中心在其软骨原基内的位置以及距骨、跟骨、骰骨和舟骨软骨原基的骨化百分比。在距骨，在冠状位和矢状位图像上测量其骨化中心长轴与软骨原基长轴的方向差异。
距骨早期骨化集中在距骨颈部；骨的近端最后骨化。距骨骨化中心的长轴与其软骨原基的长轴方向不同。跟骨早期骨化集中在跟骨软骨原基的远端三分之二；近端和距下关节区域最后骨化。舟骨早期骨化集中在舟骨软骨原基的中央或外侧三分之一；内侧最后骨化。骰骨的骨化中心位于骰骨软骨原基的中部。
我们的结果表明，距骨、跟骨和舟骨的早期骨化并非始于骨软骨原基的中心。距骨骨化中心的长轴与其软骨原基的长轴方向不同。因此，X线片上所见的跗骨排列随生长的部分变化是由于骨化在软骨原基内偏心开始并进行，而不是跗骨排列的真正变化。这些数据为儿童后足和中足的正常发育提供了新的信息。
