Perspectives on craniofacial growth

CURRENT LITERATURE an incidence of one in 100,000. The physical characteristics include a misshapenness to the skull, mitten hand and feet deformities, mental retardation, and blindness. Other syndromes include Carpenter, Pfeiffer, Saethre-Chotzen, and Kleeblattschadel. Brain volume in the normal child triples during the first year of life, and cranial synostosis may restrict this growth with a resultant intracranial pressure elevation. Hydrocephalus, midfacial hypoplasia, increased nasal airway resistance, and oral anomalies compound these problems. The current surgical approach at correction begins with primary cranio-orbital decompression-reshaping in infancy, preferably between 10 months and 1 year of age. Repeat craniotomy-decompression-reshaping is then done in childhood. Total midface osteotomies (the Le Fort III type) may be effectively managed as early as 5 to 7 years of age. Orthognathic deformity completes the surgical corrections and are usually planned for age 14 to 16 years in females, and 16 to 18 years in males. Staged procedures performed at intervals, which coincide with facial growth, visceral function, and psychosocial development are the current approach to the correction of craniofacial deformities associated with craniofacial dysostosis syndromes.--R.H. HAUG Reprint requests to Dr Posnick; Division of Plastic Surgery, Georgetown Craniofacial Center, Georgetown University Medical Center, 3800 Reservoir Rd NV¢, Washington, DC 20007-2197,

Experimental Studies Addressing Rigid Fixation in Craniofacial Surgery. Yaremchuk MJ. Clin Plast Surg 21:517, 1994 During the last decade, plate and screw fixation has evolved as the preferred method of stabilization of the craniofacial skeleton. Because it provides three-dimensional position control for surgical osteotomies or fracture segments, it has gained increased acceptance and application in orthognathic, trauma, and congenital facial reconstruction. Miniaturized plates and screws have become widely used in pediatric patients. However the possible growth-deforming effects of osteotomy and plate and screw fixation on the craniofacial skeleton are not clear. Laboratory studies have been performed to examine the possible effects of rigid fixation on craniofacial growth. In animal studies, growth restriction has been noted with plate and screw fixation across the coronal suture, supraorbital region, and frontal bone, as well as with osteotomies. Increasing restriction was noted with increasing amounts of hardware, the magnitude related to complexity of fixation. However rigid fixation appears to provide threedimensional control, stability, and improved volume maintenance. Improved positional control and contouring of onlay bone grafts and alloplastic materials is made possible with rigid fixation. As well, rigid fixation improves graft volume maintenance, improves neovascularization, and reduces osteoblastic and osteoclastic activity. Titanium implants produce less "starburst" or "streak" artifact with computerized tomographic scans, than does vitalium or stainless steel. As well, titanium causes considerably less "black hole" artifact in magnetic resonance imaging than does vitalium or stainless steel. Heating and plate deflection are not problems with either material. Biocompatible bioresorbable materials would obviate many of the problems associated with metal fixation systems. While experimental and clinical studies show feasibility, these systems are currently too large and too weak to make them functionally stable. Butyl-2-cyanoacrylate may become a useful adhesive which will serve as an adjunct to plate and screw fixation.--R.H. HAUG

634 Reprint requests to Dr Yaremchuk: Massachusetts General Hospital, WACC, Suite 453, Boston, MA 02114.

Perspectives on Craniofacial Growth. Ohman JC, Richtsmeier JT. Clin Plast Surg 21:489, 1994 The two methods of craniofacial bone development, intramembranous and endochondral, are well understood. Large two-dimensional normative data bases exist to characterize growth; however three-dimensional normative data bases do not exist. This results in an inability to determine whether growth patterns in craniofacial anomalies are abnormal or normal in three-dimensional form. Craniosynostosis can result in predictable alterations in head shape because of compensatory growth of unaffected sutures. A variety of authors have previously attempted to describe how cranial base and cranial vault growth interface in normal development to ultimately construct a model explaining craniofacial abnormalities. Accepted theories by Delashaw and coworkers resulted in a unified explanation of compensatory growth describing growth patterns in craniosynostosis, but failed to address the underlying mechanisms of abnormal growth. The need for longitudinal data in three-dimensional form can be satisfied by the use of computerized tomography (CT). Morphomettics, the combination of biology and geometry, allows comparison of strategic landmarks on CT data to define a form. Forms then are quantitatively compared to produce a threedimensional picture of growth. Current methods of comparison include Euclidean Distance Matrix Analysis and finite element scaling analysis. Confidence in landmark position between slices of CT data can be improved by using various interpolation schemes. Interpretation of these data covering a wide range of craniofacial anomalies using a large number of patients may provide information about the future appearance of patients based on empirically derived growth patterns. This information will greatly assist the patient's parents and the surgeon when deciding on reconstructive surgery.--J.P. BRADRICK Reprint requests to Dr Ohman: Cleft and Craniofacial Center, The Johns Hopkins University School of Medicine, JHOC 8152A, 601 North Carolina St, Baltimore, MD 21287-0980.

Craniofacial Computer-Assisted Surgical Planning and Simulation. Lo LJ, Marsh JL, Vannier MW, et al. Clin Plast Surg 21:501, 1994 The authors relate the experience of one center using computer surgical planning and simulation for complex craniofacial surgery. They describe tile evaluation of surgical simulation as a three-phase process: development, validation, and utilization. Development is the process of acquiring and merging the appropriate hardware and software to compare postoperative computerized tomography (CT) scans and surgical outcome with conventional surgical treatment plans. Validation compares a computer-simulated treatment plan to the actual outcome. The simulation can then be modified appropriately to match actual outcome. Utilization uses preoperative scans to simulate different surgical plans, select the proper procedure, and then compare actual outcome as quality control. Conventional surgical treatment planning is bypassed only with the utilization phase. Work stations with as much as 96 megabytes of random access memory are required to manipulate patient image files ranging from 10 to 100 megabytes. Pertinent soft tissue structures, such as ocular globes, are traced on two-dimensional CT slices and then displayed as separate objects along with hard tissue for