3D craniofacial anthropometry, simplified and accelerated by semi-automatic calliper

Abstract

Anthropometric standard callipers are used in craniofacial conformation assessment of patients with malformations, such as cleft lip and palate, hypoplastic or excessive jaw development, or for aesthetic reasons. Roentgenocephalogram analysis is the mainstay in diagnosing craniofacial osseous and soft-tissue conformation and development. Also called cephalometry, it is based on lateral and posterior- anterior standardized roentgenographs and several insecure landmarks that show considerable intrarater and interrater variation. Moreover, radiation exposure, constant object positioning and the use of costly roentgen equipment is inevitable. Anthropometry, as mostly presented in the literature, is time consuming and cannot reproduce 3D craniofacial conformation. Insecure landmark definitions and soft tissue resilience foster systemic measurement errors. Therefore, a few, easily accessible landmarks, closely related to the underlying bone were selected, measured and reconstructed in their 3D conformation as a wire frame. A soft tissue mask, concentrating on the mid-sagittal profile was added. Facial growth was monitored, growth functions generated and postoperative outcomes evaluated against the preoperative situation. To simplify general anthropometric data acquisition by calliper, a semiautomatic calliper was developed. With its data-input switch connected by optical data cable to a standard personal computer (PC), this calliper permitted completion of standard data sheets, interrater and intrarater validated in test collectives and patients. A major volunteer collective with repeat measurements served for standards and for reliability assessment. Normal growth functions, differentiated by sex, were assessed with 95-percentiles and 5% relative error. Full manual viscerocranial Am was thrice as time-consuming as the semi-automatic calliper-mediated direct data input to the computer. Gauging of the distance of the calliper ends by ruler, taking down the numbers manually, and lastly computer data input were rendered superfluous, and standard relative error decreased. The developed craniofacial Am proved reliable and valid for measurement of craniofacial growth, diagnosis and treatment control. Relative measurement errors are smaller than the systematic magnification and distortion in lateral cephalograms. The Am allowed reliable, objective, independent calculation of cranial bone relations and soft tissue projection, sensitive to facial asymmetry. Easy application, versatility and economy were obvious in the assessment of facial proportions, soft tissue ratios, operation planning and follow-up. Semiautomatic anthropometric callipered data acquisition was shown to be faster than the manual technique and equally reliable: measurement errors were effectively diminished and oversight errors avoided. The craniofacial anthropometric routine has been in use over 10 years and proven valuable in growth comparison of different regimens of cleft lip and palate treatment as well as with jaw development in microsomia and jaw deformity treatment, such as dysgnathia. While treating specific craniofacial syndromes, many specialists have needed to assess postnatal growth patterns as a background consideration. Normal development and knowledge of softtissues- to-bone relationships and their interaction and the interaction between functional-aesthetic regions have been given high importance in prospective treatment rationales and outcome assessments. Using anthropometric standard callipers, craniofacial features, e.g. of patients with malformations such as cleft lip and palate, dysgnathia (hypoplastic or excessive jaw formation), craniosynostosis are assessed today, as are proportions in the trunk and extremities, with dedicated measurement routines.