Martin Chin

Distraction osteogenesis in maxillofacial surgery using internal devices: Review of five cases

PURPOSE The purpose of this report is to show the feasibility and potential advantages of using internal devices for distraction osteogenesis in the management of maxillofacial skeletal deficiencies. PATIENTS AND METHODS Distraction osteogenesis was used to correct a variety of maxillofacial skeletal deformities in five patients. One patient underwent bilateral Le Fort III advancement aided by distraction, three patients underwent mandibular ramus lengthening, and one patient underwent segmental alveolar reconstruction by distraction. The devices were activated by either a transcutaneous or transmucosal pin. After achievement of the desired skeletal transport, the activating pins were disengaged and removed from the distraction device. This allowed the distraction device to remain submerged and to stabilize the site of the consolidating bone. RESULTS All patients achieved lengthening of their jaws. However, premature consolidation was noted in two patients, and one patient had significant relapse. CONCLUSIONS Development of internal distraction devices is important to address the limitations of currently available biphasic systems. Potential benefits of internal devices include 1) elimination of skin scarring caused by translation of transcutaneous fixation pins, 2) improved patient compliance during the fixation or consolidation phase because there is no external component, and 3) improved stability of the attachment of the device to the bone.

Le Fort III Advancement with Gradual Distraction Using Internal Devices

&NA; The purpose of this report is to demonstrate a practical clinical method for advancement of the midface using a combination of Le Fort III osteotomy and gradual distraction. Use of internal, submergible distraction devices and modification of the Ilizarov distraction protocol are presented. Case reports show the effect of departing from the Ilizarov protocol by eliminating the latency period, initiating distraction intraoperatively, and rapidly distracting the segments postoperatively. A method of controlling fragment distraction rate by regulating pressures within the osteotomy site is described. The design and surgical application of internal distraction devices are shown. Nine patients with midface hypoplasia related to craniofacial anomalies underwent Le Fort III osteotomies assisted by gradual distraction. Ages ranged from 4 to 13 years. Custom internal distraction devices were employed to meet the unique requirements of each patient. Activation of the distraction device was accomplished by a percutaneous pin that remained in place for 3 to 5 days. The rate of transport was determined by regulating the forces within the distraction site. The internal devices remained in place for 6 months for fixation of the transported fragment. Midface advancement, measured as the anterior displacement of the infraorbital rim, ranged from 16 to 30 mm, with a mean of 20 mm. The typical force required to produce incremental movement of the Le Fort III osteotomy was found to be between 7 and 9 kg as transport exceeded 10 mm. Four patients with obstructive sleep apnea prior to surgery had resolution of the disorder. All the midface advancements remained clinically stable. Establishment of osseous continuity was verified by surgical examination in the four patients in whom the distraction devices have been removed. Combining intraoperative advancement of the Le Fort III osteotomy with gradual distraction consistently resulted in larger movements than could be achieved with conventional osteotomies and rigid fixation alone. The pediatric craniofacial skeleton responds differently to distraction than does the orthopedic skeleton. Eliminating the latency period, establishing a substantial bone gap intraoperatively, and rapidly distracting the fragment postoperatively did not adversely affect the osseous union in these patients. The internal, submergible feature of the device design offers advantages in patient acceptance, fixation stability, and wound management. This method of Le Fort III midface advancement has been shown to be clinically practical and effective. (Plast. Reconstr. Surg. 100: 819, 1997.)

Repair of alveolar clefts with recombinant human bone morphogenetic protein (rhBMP-2) in patients with clefts.

This article demonstrates the feasibility of using recombinant human bone morphogenetic protein (rhBMP-2) as a substitute for autogenous iliac crest bone for repair of congenital facial clefts in humans. In this series, 50 cleft sites were repaired in 43 patients using rhBMP-2 without the use of autogenous graft tissue. Successful osseous union was achieved in 49 of the 50 sites. In one patient, the graft failed to consolidate. Severe clefts were managed by combining distraction osteogenesis and rhBMP-2. Eliminating the need to harvest autogenous iliac crest bone resulted in substantial decrease in morbidity. The constructed alveolus performed clinically as normal bone and responded to natural tooth eruption and orthodontic movement. Histology of the tissue constructed showed normal, vital bone. Although additional investigation is warranted to determine the optimum protocol for the use of this material in alveolar cleft repair, the technique should be considered as a viable treatment option in cases in which avoiding iliac crest harvesting is desirable.

Distraction osteogenesis and its application to the midface and bony orbit in craniosynostosis syndromes.

The purpose of this study was to demonstrate the potential advantages of applying distraction osteogenesis techniques to the correction of orbital and midfacial hypoplasia in craniosynostosis syndromes. Fifteen children with various craniosynostosis syndromes underwent Le Fort III advancement assisted by gradual distraction utilizing a pair of internal distraction devices custom-fabricated for each child. The surgical procedure consisted of a Le Fort III osteotomy, implantation of internal devices with initiation of distraction intraoperatively, and an accelerated rate of midfacial advancement over the next 3 to 5 days. Activation of the distraction hardware was accomplished by a percutaneous pin, which was removed at the end of the distraction protocol, allowing the internal devices to fixate the fragment for a minimum of 6 months during the period of consolidation. With follow-up ranging between 3 to 38 months, the average orbital and midfacial advancement was 19.7 mm (range, 12.0–30.0 mm). Proptosis was lessened and facial proportions significantly improved in all patients. Serious complications were not encountered. The modified distraction protocol utilized in this group of patients was aimed at addressing the unique requirements of pediatric craniofacial surgery, and resulted in almost twice the amount of correction previously reported for traditional rigid fixation techniques.

Reconstruction of #7 facial cleft with distraction-assisted in situ osteogenesis (DISO): role of recombinant human bone morphogenetic protein-2 with Helistat-activated collagen implant.

A case involving concomitant presentation of a #7 lateral facial cleft with a complete cleft of the ipsilateral lip, alveolus, and palate is presented. The mandibular defect was Pruzansky III with a foreshortened body, absent ramus and absent masseter. Taking advantage of developmental field theory, reconstruction of the osseous defect was undertaken using the autogenous periosteum as a source of mesenchymal stem cells. Expansion of the periosteum was followed by implantation of Helistat (Integra Life Sciences, Plainsboro, NJ) collagen sponge saturated with recombinant human bone morphogenetic protein-2. Stimulation of this distraction-induced envelope by rhBMP-2 resulted in abundant production of bicortical membranous bone in situ within 12 weeks. The neoramus was subsequently suspended from the cranial base, and a temporalis muscle transfer was used to provide motor control of the jaw. Synthesis of bone in this manner is termed DISO (distraction-assisted in situ osteogenesis). The biologic rationale and clinical implications of DISO are discussed.

Distraction of rhBMP-2-generated mandible: how stable is the engineered bone in response to subsequent surgeries?

Congenital craniofacial abnormalities and pediatric maxillofacial trauma present special management challenges for the reconstructive surgeon. The presenting structures of a child are naturally quite small. Many of the conditions require multiple staged surgeries throughout the lifetime of the patient to compensate for continued growth. If reconstruction of the pediatric patient is carried out, this will only provide a temporary solution, as children outgrow their correction through maturation and normal development. One alternative to carrying out multiple surgeries is to wait for skeletal maturity. However, the negative psychologic and social impact of the deformity must be taken into consideration when delaying surgery. In current practice, a reconstructive surgeon replaces missing bone with harvested autogenous bone to help provide for structural support and strength. The problem with harvesting bone in a child is the limited amount of available bone, the creation of a second surgical site in the patient, the additional time for rehabilitation, and the increase in morbidity. Further, when future surgeries are necessary the available bone volume is compromised by the prior harvesting. Some patients simply run out of viable sites from which bone can be obtained. rhBMP-2 technology is a new and exciting clinical solution that may alleviate the need for harvesting the patient’s own bone. Studies have shown that new bone can be grown predictability. In the studies where INFUSE Bone Graft (Medtronic, Memphis, TN) was used as a bone graft material before placement of dental implants, the bone formed by rhBMP-2/ACS was able to successfully accept and support implants. It behaved like normal bone and continued to become more dense in response to loads, osseointegrated with the implants, and had equivalent functional loading rates to the autograft control group. Histologic samples provided further evidence of this normal bone formation. No studies have been undertaken, however, to specifically evaluate the response of this regenerated bone to subsequent surgery for distraction. Although there has been concern about the potential for antibody formation, there has been little antibody response when measured in clinical trials (0.7% to 6%), and the antibody response was transitory and h a d n o clinical effects. In a recent review assessing patients who received 2 separate exposures to rhBMP-2, no clinical complications or effects were reported although antibodies were not measured 3 (Dr Y.A. Cillo, personal communication, April 2007). This article presents a case of mandibular bone that has been generated entirely with rhBMP-2. This mandible has subsequently been osteotomized and distracted again with consolidation and growth of this bone.

Primary reconstruction of alveolar clefts using recombinant human bone morphogenetic protein-2: clinical and radiologic outcomes.

Surgical management of cleft lip and palate has a long history dating back at least to the fourth century. At each stage in the evolution of cleft treatment, innovation has been limited by the existing understanding of general biology. Scientific discovery, however, does not automatically result in the advancement of clinical practice. Realizing better patient care has always depended on the union of improved insight into biology and the dedication of the motivated clinician/scientist. The work presented by Drs Fallucco and Carstens represents a major step in the specific treatment of cleft palate and the general understanding of craniofacial disorders. The article emphasizes the interdependence of embryology, emerging biotechnology, and surgery to provide the best potential for a favorable treatment outcome. It also sets the stage for future progress in surgical technology by defining the limitations of past assumptions about craniofacial pathogenesis. Presentation of this material poses a difficult challenge because it confronts a number of treatment practices and developmental anatomy concepts that clinicians have grown accustomed to. The 2 principal innovations are (1) the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) to promote bone formation during primary cleft repair and (2) soft-tissue reconstruction based on a novel model of craniofacial pathogenesis. Each of these concepts represents a significant independent topic and could justify being discussed in separate articles. By presenting the concepts together, it becomes clearer that they are 2 components of a single clinical problem. Contrasting the daunting prospect of rethinking embryology, the authors present straightforward, compelling, and objective clinical results. The article shows the ability of rhBMP-2 to produce de novo skeletal construction in primary cleft repair. Preoperative and postoperative computed tomography studies provide definitive evidence that the use of rhBMP-2 devices will construct missing facial bone segments without grafting tissue. The implication is that the use of autogenous bone grafting may be obsolete, although the authors make no such claim. The prospect that the criterion standard for skeletal reconstruction, autogenous bone, may no longer be needed will be undoubtedly met with major resistance. In our center, we offer the off-label use of rhBMP-2 as an alternative to autogenous bone grafting and as an essential part of informed consent.1 Our patients undergo secondary alveolar cleft grafting between 3 and 6 years of age. When given the choice, 99% of all patients and parents chose rhBMP-2. In our experience, the efficacy of rhBMP-2 treatment exceeded that of autogenous bone and without any donor site morbidity. Our oldest follow-ups are 7 years postoperative and show no obvious growth disturbance. The absence of apparent growth impairment may be partly related to the quality of soft tissue that forms adjacent rhBMP-2Ytreated sites. Quantifying scar tissue formation is difficult in the clinical setting. A qualitative assessment of scar tissue formation might be reflected by impairment of adjacent tissue function. As an example, a segment of mandibular nerve may be exposed and preserved during reconstructive surgery. If bone grafts are placed around the nerve to restore the original housing, paresthesia is often the result. Scar tissue and a damaged nerve are evident on subsequent surgical examination. If instead of a bone graft, an rhBMP-2 device is placed in direct contact with the nerve, bone forms restoring the missing mandible and paresthesia does not occur. Further study is needed to define the effect of this agent on soft-tissue healing. An abundance of clinical data supports the safety and efficacy of rhBMP-2 in a wide variety of surgical applications. There is obvious value in its application to the craniofacial patient. To eliminate or at least decrease the extent of surgery is a goal just as important as to provide surgical care. On its most superficial level, this article demonstrates a surgical procedure that will produce predictable results with reduced morbidity and no apparent adverse effects. This is a valuable contribution in itself. As with all pediatric procedures, long-term observation is still needed. On a more conceptual level, the authors propose that optimal reconstruction and long-term function are improved by surgical design that respects the developmental origin of the defect. This concept is not new. Harvold studied the process of skeletal development in the embryo and then applied theoretical neuromuscular principles to the treatment of cleft palate and hemifacial microsomia. The authors propose surgical repositioning of abnormally placed anatomic structures of the cleft to normal relationships as part of comprehensive reconstruction. Unfortunately, this objective demands that we understand how the cleft formed in the first place and where the normal structures came to rest. All craniofacial surgeons recognize the limitations of the conventional embryologic model of cleft formation. This is most obvious in the Tessier 5 and Tessier 7 clefts, which cannot be explained by the theory of process fusion failure. Carstens conceptualized an alternative model for cleft formation that could accommodate clefts of the lip, palate, and face. This concept is based on a modern understanding of embryology. The model provides a blueprint for surgical planning. It aims to improve on the prior techniques that were based mostly on experience with trauma repair. Long-term observation will be needed to fully understand the impact of these technical changes. Science promotes the concept that, as our knowledge base improves, so does our insight of how the world works. History, DISCUSSION

Pretreatment of Distraction Docking Sites With Bone Morphogenetic Protein (rhBMP-2)

This paper demonstrates a method to achieve osseous union at distraction docking sites without secondary surgery. The efficacy of pretreating anticipated docking sites with recombinant human bone morphogenetic protein (rhBMP-2) at the time of initial osteotomy is shown. Combining the bone induction properties of rhBMP-2 and the local, environmental effects of a converging distraction procedure provides a markedly enhanced situation for bone formation and successful skeletal element construction.

Distraction of the Midface

Distraction osteogenesis has emerged as an important surgical modality in the management of complex problems of the cranio-maxillofacial skeleton. In combination with the standard LeFort III osteotomy it offers the potential of significantly improved results in the treatment of severe midface hypoplasia. Moreover, it has become common for the authors to double the amount of advancement (distance), when compared to the classical LeFort III surgical procedures.