Perspectives on craniofacial growth.

This article underscores the importance of the growth process in the production of normal and abnormal craniofacial morphology. Although much has been learned over the past century, we still have only a limited appreciation of the 3D changes that occur in the skull during postnatal growth. We have also stressed that the current cooperation between reconstructive surgeons and radiologists is producing a substantive amount of data that could be used to further our understanding of the postnatal growth process. At The Johns Hopkins University we are putting our efforts toward the collection and organization of a large data base of craniofacial images that will allow us to study questions about the role growth plays in mediating the results of reconstructive surgery. Our ultimate goal is to provide information about the future appearance of craniofacial patients based on empirically derived growth patterns. In a recent article Dufresne and Richtsmeier proposed that the results of surgical correction may be predicted based on the etiology of the craniofacial condition, and not necessarily the degree or character of the dysmorphology. The authors hypothesize that a categorization or classification of craniofacial dysmorphology can be proposed, based on the response of individuals to surgery, and that such a classification reflects real differences in etiology. Hence, a poor response to surgery reflects a condition that includes a growth disorder, whereas cases that respond positively to reconstructive surgery are those in which the growth process is not part of the dysmorphology. In the latter cases, a dysmorphic face is surgically transformed into an acceptable morphology, and normative growth vectors maintain or improve postoperative facial appearance. Thus, Dufresne and Richtsmeier13 suggest that this divergence in the response to surgery among patients relates directly to the role of the growth process in various types of dysmorphologies. Using our tools and the data base we are forming, we envision a markedly different preoperative consultation for future craniofacial patients. When a patient is evaluated, images from the data base with a similar diagnosis will be used to calculate a growth pattern for the proper age interval. The patient's scan is then "grown" according to the appropriate growth pattern. The parents and patient can evaluate this new image and see what their child's skull will look like 2, 3, or 4 years from the present, both with and without reconstructive surgery. In addition, our tools will statistically compare the simulated (or "grown") skull to samples of craniofacial images of normal and affected children of an age/sex/ethnic population that matches the patient. This testing will determine whether growth results in the patient becoming more normal, or more different from normal, with time.(ABSTRACT TRUNCATED AT 400 WORDS)

The first rib of hominoids.

Homo sapiens is unique among extant hominoids in displaying a univertebral articular pattern for the first rib; that is, the head of the first rib articulates only with the body of the first thoracic vertebra. All other hominoids, indeed virtually all other mammals, display a bivertebral pattern; that is, the head of the first rib articulates with the bodies of both the seventh cervical and the first thoracic vertebrae, as well as the intervening disk. Two fossil hominid partial first ribs, A.L. 288-lax and A.L. 333-118, show that the univertebral pattern was fully established in the hominid lineage by the appearance of Australopithecus afarensis. Four hypotheses, based in functional anatomy, can be postulated for the evolution of the univertebral pattern: (1), it increases the volume (via increased length) of the neck, which could, in turn, compensate for the functional loss of the laryngeal sac systems in hominid vocalization; (2), it is a consequence of the more barrel-shaped thorax in hominids; (3), it is a consequence of functional modifications in the hominid shoulder girdle; and/or (4), it is a consequence of modifications in hominid first rib motion while breathing in an upright stance. Fossil evidence supports all but the first hypothesis, and most strongly supports the third. However, evidence for the first hypothesis does suggest that the evolution of descent of the upper respiratory system in the hominid lineage may have been permitted by the presence of the univertebral pattern, while the reverse is probably not true. Furthermore, fossil evidence for the third hypothesis shows that, by the appearance of A. afarensis, the hominid upper limb had been freed from locomotor constraints, which concomitantly confirms full adaptation to upright posture. Thus, because of their potential relationship with upright posture, the two remaining hypotheses (i.e., "thoracic shape" and "first rib movement during breathing") also have support from the fossil evidence.

Talocrural joint in African hominoids: implications for Australopithecus afarensis.

Talocrural joints of the African apes, modern humans, and A.L.288-1 are compared in order to investigate ankle function in the Hadar hominids. Comparisons between the hominids and African pongids clearly illustrate the anatomical and mechanical changes that occurred in this joint as a consequence of the evolutionary transition to habitual bipedality. Features which are considered include the obliquity of the distal tibial articular surface, the shape of the talar trochlea, and the location and functional implications of the talocrural axis. In every functionally significant feature examined the A.L.288-1 talocrural joint is fully bipedal. Moreover, the Hadar ankle complex also shows the functional constraints which are necessarily imposed by the adaptation to habitual bipedalism.

Estimation of maxillary alveolar cleft volume by three-dimensional CT.

Reconstruction of cleft lip and palate deformities is a challenging problem involving a variety of the subspecialties of surgery, dentistry, and medicine as well as radiology. This paper outlines the contribution of three-dimensional CT to preoperative treatment planning for bone grafting of a maxillary cleft alveolus.

Cortical bone distribution in the femoral neck of hominoids: implications for the locomotion of Australopithecus afarensis.

Contiguous high resolution computed tomography images were obtained at a 1.5 mm slice thickness perpendicular to the neck axis from the base of the femoral head to the trochanteric line in a sample of 10 specimens each of Homo sapiens, Pan troglodytes, and Gorilla gorilla, plus five specimens of Pan paniscus. Superior, inferior, anterior, and posterior cortical thicknesses were automatically measured directly from these digital images. Throughout the femoral neck H. sapiens displays thin superior cortical bone and inferior cortical bone that thickens distally. In marked contrast, cortical bone in the femoral neck of African apes is more uniformly thick in all directions, with even greater thickening of the superior cortical bone distally. Because the femoral neck acts as a cantilevered beam, its anchorage at the neck-shaft junction is subjected to the highest bending stresses and is the most biomechanically relevant region to inspect for response to strain. As evinced by A.L. 128-1, A.L. 211-1 and MAK-VP-1/1, Australopithecus afarensis is indistinguishable from H. sapiens, but markedly different from African apes in cortical bone distribution at the femoral neck-shaft junction. Cortical distribution in the African ape indicates much greater variation in loading conditions consistent with their more varied locomotor repertoire. Cortical distribution in hominids is a response to the more stereotypic loading pattern imposed by habitual bipedality, and thin superior cortex in A. afarensis confirms the absence of a significant arboreal component in its locomotor repertoire.