David A. Staffenberg

Effect of Mandibular Distraction on the Temporomandibular Joint: Part 2, Clinical Study

Mandibular lengthening by gradual distraction has been gaining popularity. However, the effect of osteodistraction on the temporomandibular joint has been evaluated in patients with craniofacial anomalies who underwent mandibular distraction. Five patients had unilateral expansion and five had bilateral expansion. The mandibles were expanded 1 mm per day until the pogonion was in the midline. Preoper-ative, immediate, 6-month, and 12-month panoramic and cephalometric radiographs were evaluated. In unilaterally expanded mandibles, the ipsilateral condyle increased in size and volume, became more upright, and was oriented in a more normal vertical axis. The contralateral unexpanded condyle did not show deformational changes. In those mandibles that were bilaterally expanded, both condyles increased in size and volume and became more symmetrical and upright. Osteodistraction appears to affect bone in both local and distant sites. The expanded condyles were stimulated to ensure a more nearly normal shape, size, and configuration.

Bioabsorbable plates and screws in pediatric craniofacial surgery: a review of 22 cases.

The purpose of this study was to evaluate the application of bioabsorbable fixation devices in reconstructive craniofacial procedures in the pediatric population. We reviewed 22 cases in which bioabsorbable plates and screws were used in craniofacial surgery for reconstruction. The procedures were performed in a 7-month period. The patients ranged in age from 5 to 228 months at the time of surgery (mean, 76.7 months). The postoperative clinical follow-up ranged from 2 to 16 weeks. The fixation devices were evaluated with regards to satisfactory fixation at the time of procedure. The postoperative follow-up evaluated clinical wound healing, signs of infection or local inflammation, and visibility or palpability of plates through the skin. All patients except one showed satisfactory wound healing with no sign of infection or local inflammation. The plates provided satisfactory fixation and were not visible through the skin. Two patients had plates that were palpable at the 4-month follow-up period. One patient with repair of a blow-out fracture of the orbit with resorbable mesh had redness and swelling over the wound site 2 weeks postoperatively with resolution 4 weeks postoperatively. Our early experience suggests reabsorb-able fixation is an attractive option in pediatric plastic and craniofacial surgery. With further experience, this technology may represent the standard of care in reconstruction of the infant calvarium.

Introduction of an intraoral bone-lengthening device.

It has been demonstrated that distraction osteogenesis is an effective clinical tool with applications for the entire human skeleton. Therapeutic exploitation in the correction of the asymmetrical and hypoplastic mandible has been reported previously. However, the main criticism of this technique has been the residual cutaneous scars resulting from the surgical incision and the path of the expansion device. In order to obviate the need for skin incisions, we have developed and demonstrated the feasibility of a miniaturized mandibular bone lengthener that is suitable for intraoral placement. Ten growing mongrel dogs were studied. Under general anesthesia, a buccal mucosal incision was made along the oblique line, and the body and ramus of the mandible were exposed in a supraperiosteal plane. Two 2.0-mm half-pins were placed percutaneously in the area of the angle of the mandible, and two other pins were placed 3.5 cm anteriorly. The clamps of the lengthening device were then attached to the half-pins in an intraoral position. An osteotomy was made by connecting percutaneously made drill holes between the clamps in a line positioned posterior to the third molar. The mucosa was closed loosely over the device. Distraction was commenced on the eighth postoperative day. The results were assessed with pre- and post-lengthening photographs, cephalograms, and CT scans with three-dimensional reconstruction. All animals demonstrated a contralateral cross-bite. The newly developed bone also was examined histologically. The intraoral method of mandibular lengthening offers the same advantages of extraoral lengthening but without the need for a cutaneous incision and resulting scar.

Histopathologic and biochemical changes in the muscles affected by distraction osteogenesis of the mandible

&NA; Lengthening of the canine mandible using an intraoral distraction device was performed in order to study the effects of distraction on the associated muscles of mastication. Biopsies of the masseter and digastric muscles were taken after lengthening at four different time intervals to assess the temporal changes in the masticatory muscles of 10 dogs. Biopsies of the muscles on the contralateral side also were taken from 6 of these dogs before lengthening to establish a control group. Each biopsy was analyzed histologically and spectophotomerically for RNA, DNA, and protein content. The digastric muscle underwent transient atrophy with initiation of distraction but regenerated completely after 48 days of fixation. The masseter muscle was unchanged initially but showed evidence of atrophy only after 20 mm of distraction; it continued to exhibit evidence of atrophy during fixation. Protein synthesis was decreased significantly during periods of atrophy in the masseter; no such change was noted in the digastric. Unlike the masseter, the digastric fibers lie in a plane parallel to the vector of distraction. These findings suggest that any muscle affected by skeletal distraction in the same plane or vector (e.g., digastric) adapts with compensatory regeneration and hypertrophy. Moreover, those muscles lying in a different plane (e.g., masseter) show persistent evidence of atrophy with decreased protein synthesis.

Midface distraction advancement in the canine without osteotomies

Midface hypoplasia, often associated with exorbitism and malocclusion, has been traditionally corrected by using Le Fort advancement osteotomies through wide surgical exposure. These procedures suffer the disadvantages of hemorrhage, unpredictable bone graft resorption, the need for retained hardware, and bone graft donor-site morbidity. We present an investigation of midface distraction in the canine without osteotomies. Five canines were the subjects of this study and were divided into two groups. At the time of placement of the lengthening devices, Group 1 animals were 10 weeks of age and Group 2 animals were 5 years of age. Under general anesthesia, four modified Hoffman bone distractors were mounted on 2-mm half pins placed individually across the nasofrontal and the zygomaticotemporal sutures on each side of the craniofacial skeleton. Distraction of all devices was begun on postoperative day 1 at the rate of 0.5 mm/day for 4 days and then 1.0 mm/day for 28 days, after which interval the devices were removed. The dogs were serially monitored and examined for 3 months. One dog in the first group served as a sham control. The results were assessed by standardized cephalograms, and craniofacial computed tomographic scans with three-dimensional reconstruction performed before device placement as well as after removal of the device. In one Group 1 animal, computed tomographic scanning was performed every 2 to 4 weeks for 3 months. Gross examination of the Group 1 animals demonstrated the development of enophthalmos, dolichocephaly, and a class II malocclusion-overbite. No evidence of distraction or advancement of the midface was observed in the Group 2 dogs. Midface distraction is feasible in the immature animal. If miniaturized devices could be developed, the clinical implications for young patients with midface hypoplasia may be significant.

A study of intracranial volume in apert syndrome

The present study was undertaken to characterize the intracranial volume in patients with Apert syndrome. Radiographic and CT-based techniques for measuring intracranial volume were found to show close correlation when validated in dry normal adult skulls. A standard-deviation score of intracranial volume, determined from CT scans in 20 patients with Apert syndrome from birth to 30 years of age, was calculated with reference to a normative database of age- and sex-matched controls. Analysis of the data showed no significant difference in standard-deviation score between Apert patients with or without ventriculomegaly, before or after cranial vault surgery, or between male and female patients. The mean standard-deviation score among all Apert CT scans compared with normative data was 3.1, which was highly significant (p < 0.001). However, the growth curves showed no significant difference in intracranial volume between Apert and normal patients below 3.5 months of age. In summary, intracranial volume in Apert syndrome is within normal range at birth but increases to greater than 3 standard deviations above normal after 3.5 months of age, a finding independent of cranial vault surgery.

MULTIDIMENSIONAL DISTRACTION OSTEOGENESIS : THE CANINE ZYGOMA

The principle of distraction osteogenesis, well-established in the enchondral bones of the axial skeleton, has recently been applied to the membranous bones (mandible, cranium) of the craniofacial skeleton in the experimental animal and in the human. In the craniofacial skeleton, however, the technique has been used only to lengthen bone in a direction along its major axis, i.e., unidimensional distraction. A canine model is presented to demonstrate the feasibility of distracting membranous bone away from its dominant axis, i.e., multidimensional distraction. Four mongrel dogs, 5 months of age, were the subjects of this study. Two osteotomies were made in the zygomatic arch, and the bone-lengthening device was fixed to the zygoma. After 7 days of external fixation, the osteotomized segment was lengthened 1 mm/day away from the long axis of the bone for 15 days. External fixation was then maintained for a minimum of 4 weeks, after which the dogs were sacrificed. Craniofacial CT with three-dimensional reconstruction documented multidimensional bone lengthening, and histologic analysis of the specimen confirmed the presence of new cortical bone in the expanded areas. Refinement in technique and miniaturization and internalization of the bone-lengthening device may allow for more precise changes in the amount and direction of lengthening, thus making distraction osteogenesis more widely applicable for use in the human craniofacial skeleton.

Tricalcium phosphate and osteogenin: A bioactive onlay bone graft substitute

The disadvantages of autogenous bone grafts has prompted a search for a dependable onlay bone graft substitute. A combination of tricalcium phosphate, a resorbable ceramic, and osteogenin, an osteoinductive protein, was evaluated as an onlay bone graft substitute in a rabbit calvarial model. Twenty-eight tricalcium phosphate implants (15 mm diameter x 5 mm; pore size, 100-200 microns) were divided into experimental and control groups and placed on the frontal bone of 14 adult New Zealand White rabbits. In the experimental animals, 185 micrograms of osteogenin was added to each implant. In the control animals, the implants were placed untreated. Implants were harvested at intervals of 1, 3, and 6 months, and evaluated using hematoxylin and eosin histology, microradiography, and histomorphometric scanning electron microscope backscatter image analysis. At 1 month there was minimal bone ingrowth and little tricalcium phosphate resorption in both the osteogenin-treated and control implants. At 3 months, both the osteogenin-treated and control implants showed a modest increase in bone ingrowth (8.85 percent versus 5.87 percent) and decrease in tricalcium phosphate (32.86 percent versus 37.08 percent). At 6 months, however, the osteogenin-treated implants showed a statistically significant increase in bone ingrowth (22.33 percent versus 6.96 percent; p = 0.000) and decrease in tricalcium phosphate (27.25 percent versus 37.80 percent; p = 0.004) compared with the control implants. The bone within the control implants was mostly woven at 6 months, whereas the osteogenin-treated implants contained predominantly mature lamellar bone with well-differentiated marrow. All implants maintained their original volume at each time interval studied. The tricalcium phosphate/osteogenin composite, having the advantage of maintaining its volume and being replaced by new bone as the tricalcium phosphate resorbs, may be applicable clinically as an onlay bone graft substitute.

The histomorphologic changes in vascularized bone transfers and their interrelationship with the recipient sites : A 1-year study

&NA; In 13 New Zealand White rabbits with a mean age of 6 months, vascularized bone transfers incorporated as paired auricular anterior myo‐osseous flaps were harvested; they were placed in either an inlay or an onlay position relative to the zygomatic arch. The onlay bone transfers were placed either in full contact or in partial contact with the zygomatic arch. The animals were sacrificed 1 year after transfer. At 1 year, the inlay transfers simulated the adjacent zygoma in width and thickness. Onlay full contact transfers maintained significant augmentation in thickness of the zygoma, while the onlay partial contact transfers did not; the thickness of the augmented zygoma in the onlay full contact subgroup was significantly greater than that in the onlay partial contact transfers. The onlay partial contact grafts had remodeled into the zygoma in the areas of bone contact, where the orientation of mismatched osteons within the bone transfers had transformed to match that of the native zygoma. In areas of bone contact between the onlay and the host bone, full‐thickness conversion from a cortical to a trabecular architecture had occurred in both the transfer and host bones. These findings have numerous implications regarding mechanisms that could be exploited clinically to optimize the survival of a bone transfer; they also raise questions regarding alteration of the recipient bed after placement of an onlay bone transfer. (Plast. Reconstr. Surg. 97: 1001, 1996.)

Total Face, Eyelids, Ears, Scalp, and Skeletal Subunit Transplant: A Reconstructive Solution for the Full Face and Total Scalp Burn

BACKGROUND Reconstruction of extensive facial and scalp burns can be increasingly challenging, especially in patients that have undergone multiple procedures with less than ideal outcomes resulting in restricting neck and oral contractures, eyelid dysfunction, and suboptimal aesthetic appearance. METHODS To establish a reconstructive solution for this challenging deformity, a multidisciplinary team was assembled to develop the foundation to a facial vascularized composite allotransplantation program. The strategy of developing and executing a clinical transplant was derived on the basis of fostering a cohesive and supportive institutional clinical environment, implementing computer software and advanced technology, establishing a cadaveric transplant model, performing a research facial procurement, and selecting an optimal candidate with the aforementioned burn defect who was well informed and had the desire to undergo face transplantation. RESULTS Approval from the institutional review board and organ procurement organization enabled our face transplant team to successfully perform a total face, eyelids, ears, scalp, and skeletal subunit transplant in a 41-year-old man with a full face and total scalp burn. CONCLUSIONS The culmination of knowledge attained from previous experiences continues to influence the progression of facial vascularized composite allotransplantation. This surgical endeavor methodically and effectively synchronized the fundamental principles of aesthetic, craniofacial, and microvascular surgery to restore appearance and function to a patient suffering from failed conventional surgery for full face and total scalp burns. This procedure represents the most extensive soft-tissue clinical face transplant performed to date. CLINICAL QUESTION/LEVEL OF EVIDEMCE Therapeutic, V.