David G. Genecov

Clinical experience with the application of distraction osteogenesis for airway obstruction.

Objectives: The objective of this study was to evaluate the long-term success of mandibular distraction osteogenesis in patients with mandibular airway obstruction syndrome (MAOS), defined as obstructive sleep apnea, swallowing abnormalities, and failure to thrive in the presence of micrognathia, glossoptosis, gastroesophageal or laryngeal reflux, and microaspiration. This is a cross-sectional study at the International Craniofacial Institute in the Medical City Hospital, Dallas, TX. From January 1997 to July 2008, a group of 81 patients were examined for MAOS using medical history and physical examination. They all met the criteria for a multidisciplinary team evaluation consisting of upper airway endoscopy, swallowing evaluations, standard overnight polysomnography, and radiologic evaluations of the airway and craniofacial structures. Materials and Methods: In the 81 patients examined, Pierre Robin Sequence was diagnosed in 65; micrognathia and glossoptosis without cleft palate, in 13; and micrognathia as a component of a craniofacial syndrome (Treacher Collins syndrome), in 3. A total of 45 patients were documented to have gastroesophageal or laryngeal reflux. Only 41 patients had yet to receive any treatment at the time of evaluation; 40 patients presented with a tracheotomy. Of the 41 untreated patients, 14 responded to conservative treatment; Pierre Robin syndrome was diagnosed in all of them, and they did not require mandibular distraction or other surgical procedure to improve the MAOS. Bilateral distraction osteogenesis of the mandible was performed in 67 patients; 27 were younger than 6 months at the beginning of the distraction, and 40 were older than 6 months (mean age at distraction, 1.2 yr). Of this group, 26 patients did not have any prior surgical treatment, and 41 patients already had a tracheotomy. The distraction devices used were internal in 33 (49.26%) and external in 34 (50.74%) of 67 patients. The distraction protocol consisted of a 24-hour latency period and then a 1-mm/d activation period. The mean activation period was 19.4 days (range, 10-27 d), the mean consolidation period was 73 days, and the mean length of distraction was 22 mm (range, 10-32 mm). Results: Tracheostomy was prevented in 25 (96%) of 26 patients, and decannulation after distraction was possible in 38 (92%) of 41 patients. Success, defined as decannulation within 1 year of the start of distraction or prevention of tracheostomy in a patient otherwise deemed as a candidate, was found in 63 (94%) of 67 patients. Oral feedings have been resumed in 61 (91%) of 67 patients. Complications observed were mostly related to pin site infections requiring antibiotics. Device failure was experienced in 2 (3%) of 66 internal devices and in 7 (10.2%) of 68 external devices. Distraction osteogenesis of the mandible provides an excellent treatment for mandibular airway obstruction in patients younger than 6 years who do not respond to conservative measures and allows for early decannulation in patients who previously underwent tracheotomy.

Bone Grafts in Craniofacial Surgery

Reconstruction of cranial and maxillofacial defects is a challenging task. The standard reconstruction method has been bone grafting. In this review, we shall describe the biological principles of bone graft healing, as pertinent to craniofacial reconstruction. Different types and sources of bone grafts will be discussed, as well as new methods of bone defect reconstruction.

Unilateral cleft lip-nose repair – long-term outcome

Good to excellent results have consistently been achieved by the authors in primary unilateral cleft lip-nose repair. Modifications and improvements in their original technique have led to better symmetry and balance, with less scarring. This technique, when performed by experienced surgeons, yields consistent, predictable, and achievable outcomes for all patients with unilateral cleft lip and nose, where normal appearance and function at conversational distance is the standard of care. The achievement of excellence in soft tissue and skeletal restoration optimizing each patients growth potential depends on a surgical-orthodontic-speech-oriented treatment plan. Long-term outcomes demonstrating consistently good to excellent results can be achieved using this primary technique if it is backed up with a dedicated, multidisciplinary ongoing treatment protocol.

Positron emission tomography studies confirm the need for early surgical intervention in patients with single-suture craniosynostosis.

Craniosynostosis, the premature fusion of one or more cranial sutures, may occur in isolation or in association with a syndromic constellation. Multiple-suture synostosis has consistently been associated with brain compression and increased intracranial pressure, and frequently decreased cognitive development. Single-suture craniosynostosis, however, has been thought by some to be an aesthetic problem with infrequent consequences on brain function and development. Some studies have disputed this concept and have argued a correlation between single-suture craniosynostosis and abnormalities in development. The purpose of this study was to determine, using an objective radiographic tool, positron emission tomography scans, if patients with single-suture craniosynostosis had any abnormalities in cerebral glucose metabolism that would indicate changes in local brain function. A total of 10 children with single-suture craniosynostosis, eight males and two females, ranging in age from 0.1 to 3.2 years, were enrolled in this prospective study approved by the Internal Review Board. Six of the children had sagittal synostosis, three had metopic synostosis, and one had coronal craniosynostosis. Each of the patients had preoperative positron emission tomography scans performed 1 to 5 weeks before cranial reconstructive surgery and postoperative scans at 6 to 12 weeks after surgery. Surgical treatment consisted of cranial vault remodeling in eight of the children and strip craniectomy with cranial expansion in two of the children. After surgery, the two scans were compared qualitatively and quantitatively by a single radiologist. The results demonstrated variable regional increases and decreases in local post-operative cerebral glucose metabolism. However, in the posterior occipital region, the area of visual development and visual spatial coordination, there was a consistent postoperative increase in all 10 patients. Maximum glucose metabolic rate was increased up to 30.2% with a mean of 9.9%, and average glucose metabolic rates demonstrated a maximum increase of up to 18.8%. The results of this study indicate cerebral glucose metabolism consistently increases in the posterior occipital cortex after surgical release of single-suture craniosynostosis. Future developmental studies are being performed to examine the functional consequences of these metabolic changes.

Recombinant Human BMP-2 Enhances the Effects of Materials Used for Reconstruction of Large Cranial Defects

PURPOSE Cranial defect reconstruction presents 2 challenges: induction of new bone formation, and providing structural support during the healing process. This study compares quantity and quality of new bone formation based on various materials and support frameworks. MATERIALS AND METHODS Eighteen dogs underwent surgical removal of a significant portion of their cranial vault. Demineralized bone matrix was used to fill the defect in all animals. In 9 dogs, recombinant human bone morphogenetic protein-2 (rhBMP-2) was added, while the other 9 served as the non-rhBMP-2 group. In each group, 3 animals were fixed with cobalt chrome plates, 3 with adding platelet-rich plasma, and 3 fixed with a Lactosorb (Walter Lorenz Surgical, Inc, Jacksonville, FL) resorbable mesh. Necropsy was done at 12 weeks postoperative. Histomorphometry, density, and mechanical properties of the regenerate were analyzed. RESULTS The non-rhBMP-2 groups showed minimal substitution of demineralized bone matrix with new bone, while only sporadic remnants of demineralized bone matrix were present in the rhBMP-2 groups. The defect showed more new bone formation (P < .001) and density (P < .001) in the rhBMP-2 groups by Kruskal-Wallis test. The area of new bone was not significantly different among the rhBMP-2 subgroups. The resorbable mesh struts showed no sign of bone invasion or substitution. In the non-rhBMP-2 resorbable mesh group, demineralized bone matrix almost totally disintegrated without replacement by new bone. CONCLUSIONS The addition of rhBMP-2 to demineralized bone matrix accelerated new bone formation in large cranial defects, regardless of the supporting framework or the addition of platelet-rich plasma. The use of a resorbable mesh in such defects is advisable only if rhBMP-2 is added.

Bone generation in the reconstruction of a critical size calvarial defect in an experimental model.

This study was designed to investigate the optimal combination of known osteogenic biomaterials with shape conforming struts to achieve calvarial vault reconstruction, using a canine model. Eighteen adolescent beagles were divided equally into 6 groups. A critical-size defect of 6 x 2 cm traversed the sagittal suture. The biomaterials used for calvarial reconstruction were demineralized perforated bone matrix (DBM), recombinant human bone morphogenetic protein 2 (rhBMP2), and autogenous platelet-rich plasma (PRP). The struts used were cobalt chrome (metal) or resorbable plate. The groupings were as follows: 1) DBM + metal, 2) DBM + PRP + metal, 3) DBM + PRP + resorbable plate, 4) DBM + rhBMP2 + metal, 5) DBM + rhBMP2 + PRP + metal, and 6) DBM + rhBMP2 + resorbable plate. Animals were killed at 3 months after surgery. There was no mortality or major complications. Analysis was performed macroscopically and histologically and with computed tomography. There was complete bony regeneration in the rhBMP2 groups only. Non-rhBMP2 groups had minimal bony ingrowth from the defect edges and on the dural surface, a finding confirmed by computed tomographic scan and histology. Platelet-rich plasma did not enhance bone regeneration. Shape conformation was good with both metal and resorbable plate. rhBMP2, but not PRP, accelerated calvarial regeneration in 3 months. The DBMs in the rhBMP2 groups were substituted by new trabecular bone. Shape molding was good with both metal and resorbable plate.This study was designed to investigate the optimal combination of known osteogenic biomaterials with shape conforming struts to achieve calvarial vault reconstruction, using a canine model. Eighteen adolescent beagles were divided equally into 6 groups. A critical-size defect of 6 × 2 cm traversed the sagittal suture. The biomaterials used for calvarial reconstruction were demineralized perforated bone matrix (DBM), recombinant human bone morphogenetic protein 2 (rhBMP2), and autogenous platelet-rich plasma (PRP). The struts used were cobalt chrome (metal) or resorbable plate. The groupings were as follows: 1) DBM + metal, 2) DBM + PRP + metal, 3) DBM + PRP + resorbable plate, 4) DBM + rhBMP2 + metal, 5) DBM + rhBMP2 + PRP + metal, and 6) DBM + rhBMP2 + resorbable plate. Animals were killed at 3 months after surgery. There was no mortality or major complications. Analysis was performed macroscopically and histologically and with computed tomography. There was complete bony regeneration in the rhBMP2 groups only. Non-rhBMP2 groups had minimal bony ingrowth from the defect edges and on the dural surface, a finding confirmed by computed tomographic scan and histology. Platelet-rich plasma did not enhance bone regeneration. Shape conformation was good with both metal and resorbable plate. rhBMP2, but not PRP, accelerated calvarial regeneration in 3 months. The DBMs in the rhBMP2 groups were substituted by new trabecular bone. Shape molding was good with both metal and resorbable plate.

Norian craniofacial repair system: compatibility with resorbable and nonresorbable plating materials.

Background: Choice of bone replacement materials is important when reconstructing large craniofacial defects. Hydroxyapatite cements are often used for such reconstructions. Recent advances in the development of these cements have produced locally applied, in situ hardening materials excellent for use in craniofacial defects. To date, there has been a paucity of data comparing the use of calcium phosphate cements in combination with titanium or resorbable plating systems and their combined biocompatibility. An experimental dog model was used to compare these systems. Methods: Two 4 × 4-cm calvarial defects were created in each of 18 mongrel dogs, and defects were reconstructed with calcium phosphate cement with either titanium or resorbable mesh sheets to evaluate their interaction. Specimens were harvested and evaluated histologically for the development of new bone formation at 3, 6, and 12 months. Results: At 3 months, no differences were noted in the amount of bone formed between titanium and resorbable plating. By 6 months, the resorbable mesh sheet showed delayed bone formation compared with the titanium mesh. At 12 months, bone formation over the resorbable mesh accelerated to be no different from the titanium mesh. Importantly, new bone formation was seen within the monocalcium phosphate cement Norian Craniofacial Repair System on a reliable basis, regardless of mesh plate used. Conclusions: There are no long-term adverse effects with the use of Norian cement with either titanium or resorbable mesh. However, further studies need to be conducted to determine why there is an arrested healing phase between 3 and 6 months with the Norian cement and resorbable plating materials.

Preoperative screening for coagulopathy using prothrombin time and partial thromboplastin time in patients requiring primary cranial vault remodeling.

Background: The aim of this study was to investigate the prevalence of abnormal preoperative screening prothrombin time and partial thromboplastin time in patients listed for primary cranial vault remodeling that required hematologic workup and their diagnoses and subsequent management. Methods: This retrospective analysis was performed from January of 2000 to December of 2003 at the International Craniofacial Institute, Dallas, Texas, on a total of 168 patients. Results: All patients had a normal prothrombin time. Abnormally raised partial thromboplastin time was found in six patients (prevalence of 3.57 percent), one who had factor XI deficiency, one who had a borderline factor XI deficiency and circulating inhibitor, one who had an intermittent factor XI deficiency and circulating inhibitor, one who had a borderline von Willebrand’s disease with low factor XII, and the remaining two who had a circulating inhibitor of coagulation. Of these six patients, the perioperative management was altered in four of five patients, and one patient declined surgery out of fear of surgical morbidity. The surgery of one patient was aborted intraoperatively because of abnormal bleeding without clot formation after the calvarial burr holes had been drilled. The mean blood loss was 183 ml for the four patients with completed surgery and 100 ml for one patient. Conclusions: The authors conclude that even though the prevalence of abnormal screening partial thromboplastin time in these patients was low (3.57 percent), detection of an abnormal result required preoperative correction of coagulopathy in 80 percent of cases.