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Clinical application of bone biology to mandibular and maxillary reconstruction
346 patients. The authors conclude that a follow-up time of 2 years is optimal in these patients, following which there should be no further adaptation and muscles will have regained a stable myoelectric activity state.--R.E. ALEXANDER Reprint requests to Dr Raustia: Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Oulu, Aapistie 3, SF-90220 Oulu, Finland.
Fractures of the C-2 Vertebral Body. Benzel EC, Hart BL, Bali PA, et al. J Neurosurg 81:206, 1994 Although rarely reported, C-2 cervical vertebrae fractures are not uncommon. Vertical C-2 vertebral body fractures are retrospectively evaluated in 15 patients over a 3-year period and they suggest the existence of a variety of injury mechanisms. Previous authors have defined three types of odontoid fractures. Their scheme is misleading and confusing (in the opinions of this study's authors) because their type III fracture is not a fracture through the dens but rather a horizontal rostral C-2 body fracture. In this series, clinical and imaging correlations were derived by four different methods: 1) defining the point of impact via clinical examination; 2) defining the point of impact via soft-tissue changes on magnetic resonance image (MRI) or computed tomography (CT); 3) obtaining an accurate history of the mechanism of injury; and 4) hard and soft tissue spinal imaging (x-ray, CT, and MRI). The authors note that C-2 body fractures cannot be differentiated on the basis of a single imaging technique; It requires a combination of plain x-ray studies, CT, and MRI to accurately establish the nature of most C-2 fractures. The cases presented in this series involve injuries between the dens (odontoid process) and the pars interarticularis of the axis and attempt to impart understanding of the mechanistic etiology of upper cervical spine trauma. A spectrum of causative mechanisms was observed, and the authors conclude that the type of injury is determined by the force vector applied during impact and the intrinsic strength and anatomy of C-2 and its surrounding spinal elements. Two types of vertical C-2 body fractures are clearly defined and presented: a coronally oriented (type 1) C-2 body fracture and a sagittally oriented (type 2) fracture. Another type, the horizontal rostral fracture (type 3), is added for completeness (previously identified by others as a type Ill odontoid process fracture.) Twelve of the cases in this series were type 1 fractures. The authors describe and illustrate the findings and causative mechanisms with each type.--R.E. ALEXANDER Reprint requests to Dr Benzel: Division of Neurosurgery, University of New Mexico School of Medicine, Albuquerque, NM 87131.
Unstable Angina: Pharmaceutical versus Invasive Therapy. Prisant LM, Houghton JL, Bottini PB, et al. Postgrad Med 96:88, 1994 Unstable angina is a medical emergency, is often a precursor of myocardial infarction and/or death, and is often indicative of multivessel disease or intraluminal thrombi. Only 10% of patients with unstable angina have normal coronary arteries. Patients who have persistent chest pain or are refractory to sublingual nitroglycerin should be hospitalized in intensive care with continuous monitoring, and given appropriate pharmacologic therapy (nitroglycerin, a beta blocker, heparin infusion, and aspirin.) A new classification system has been proposed to decrease confusion in terminology.
CURRENT LITERATURE This system defines a type I, II, and III unstable angina based on the severity and duration of symptoms, presence or absence of electrocardiogram changes, and intensity of therapy. There are also subtypes of each category, based on the clinical circumstances (primary, secondary, and postinfarction). If symptoms persist despite adequate drug therapy, coronary arteriography should be performed and consideration given to an invasive procedure (eg, angioplasty, balloon counterpulsation, bypass grafting, etc). If possible, the invasive procedures should be delayed until the patient's condition has improved. The authors provide many useful management tips (eg, when nitroglycerin and heparin are both given, heparin resistance occurs if nitroglycerin is infused at a rate exceeding 350 /zg/min, requiring a larger heparin dose). They also discuss many of the commonly used drugs, such as beta blockers, calcium antagonists (which should be given with a beta blocker), antiplatelet agents, heparin, and thrombolytic therapy (the latter is without value in treating unstable angina). Anticoagulation is appropriate in many cases for up to 3 months.--R.E. ALEXANDER
Reprint requests to Dr Prisant: AF-2053, Section of Hypertension and Vascular Diseases, Medical College of Georgia, Augusta, GA 30912-3150.
Clinical Application of Bone Biology to Mandibular and Maxillary Reconstruction. Marx RE. Clin Plast Surg 21:377, 1994 Jaw reconstruction differs greatly from reconstruction of other bones. The goals of jaw reconstruction are to 1) establish continuity, 2) establish alveolar height, 3) establish arch form, 4) establish arch width, 5) maintain bone, and 6) improve facial contours. Patients 12 years old and younger have endosteum and periosteum capable of fully regenerating a resected jaw in which new bone arises from endosteal cells of the host bone edges. Therefore, early bone grafting may not be needed for children after tumor resection; instead, the remaining jaw should be stabilized rigidly and allow for 1 year of spontaneous osteogenesis. The biologic potential for spontaneous osteogenesis is eliminated by radiotherapy, chronic infection, and induced scar. These children should be reconstructed like adults by using a "bone graft." Cancellous marrow grafts are the most successful in jaw reconstruction. For every 1 cm length of reconstruction, 10 mL of uncompressed cancellous bone is required. Cancellous marrow grafts require a crib for support during the bone regeneration-consolidation phase. The hyperbaric oxygen protocol of 100% oxygen at 2.4 absolute atmospheres for 90 minutes per session for 20 preoperative sessions and 10 postoperative sessions is indicated for grafts with irradiated tissue beds. Secondary "preprosthetic surgeries" are often required; such as, vestibuloplasties which are performed 4 months after graft healing, and osseointegrated fixtures that are placed 6 months after graft healing. There are two types of costochondral grafts: 1) the adult graft, which is an articulating graft, and 2) the childhood graft which is a growth center transplant. The rapid revascularization of cranial bone grafts makes them ideal for midfacial, nasal, and orbital reconstruction. Today, implants are placed into reconstructed and irradiated jaws with favorable results and modified implants are used to anchor maxillofacial prostheses. Free vascular transfers of bone will transfer osteocytes and osteon which bypasses the need for cellular bone regeneration; unfortunately, these donor bones are volumetrically much smaller
CURRENT LITERATURE
347
than the mandibular grafts required. They are mostly used for immediate reconstruction in cancer resection.--J.P. MORGAN
Molecular Basis of Osteogenesis Imperfecta and Related Disorders of Bone. Prockop D J, Kuivaniemi H, Tromp G.
Reprint requests to Dr Marx: 6000 Chapman Field Drive, Miami, FL 33156.
Osteogenesis imperfecta (OI) is a heritable defect that makes bones brittle because of a generalized decrease in bone mass (osteopenia) not ascribable to any defect of hormone regulation or mineral metabolism. It may be sufficient to classify OI as type I (mild with blue sclera), type II (lethal) and type lII (moderately severe). Research has identified more than 150 specific gene mutations that cause OI. All of the mutations presently defined are in either the gene for proc~l (I) chain of type I procollagen or the proc~2(I) chain for the same protein. The current estimate is that more than 90% of patients with OI have mutations of either of these two genes. Most of the mutations that cause OI are caused by the gene for type I procollagen, because collagen fibrils are the principle source of the structural strength of bone. Recently, several preliminary experiments have raised the possibility of gene therapy for OI and related disorders. Results raise the distant possibility that an antisense gene strategy might eventually be useful to treat OI by converting the phenotype of a severe form of the disease to a milder f o r m . - R.H. HAUG
Bone Grafting in Craniofacial Surgery. Habal MB. Clin Plast Surg 21:349, 1994 The autograft is the only acceptable bone graft for use in craniofacial surgery today. Allografts and xenografts have no application in craniofacial surgery. Bone grafts are divided into cortical or cancellous grafts. Cortical grafts are dense and their vascular canaliculi require a longer revascularization time. Cancellous grafts are less dense which allows for faster revascularization and can stimulate neovascularization; although, both graft types undergo a remodeling and adaptation period. Ribs and hip bone provide other sources of bone grafting in craniofaciai surgery though the morbidity of a distant operative site reduces the indications for these grafts. In craniofacial surgery, bone grafts fill two needs 1) structural boundaries are expanded and changed for enhancement purposes, and 2) the grafts fill out structural defects with or without advancement. The principle of advancement is used mostly in craniofacial surgery of children and these bone grafts provide immobilization and obstruction as indicated. The authors have developed their principles of bone grafting which are based on 1) experience obtained in 25 years of extensive bone grafting, 2) experience learned from scientific literature, and 3) basic scientific knowledge. Craniofacial bone grafts should be assessed over a period of several years regarding their final outcome. The basis of craniofacial surgery is to use bone grafting and immobilization of all grafted materials while producing a change in the craniofacial skeleton.--J.P. MORGAN Reprint requests to Dr Habal: Tampa Bay Craniofacial Center, 801 West Dr, Martin Luther King, Jr, Blvd, Tampa, FL 33603-3301.
Effects of Prostaglandins on the Skeleton. Miller SC, Marks SC. Clin Plast Surg 21:393, 1994 The prostaglandins (PG) are a family of 20-carbon, unsaturated fatty acids with a cYClopentane ring structure. The ability of PGs to stimulate bone resorption has been established in several in vitro assay systems. The first suggestion that PGs might be involved with bone formation came from clinical studies in the 1970s involving indomethacin. In vivo studies have firmly established the powerful osteogenic actions of systemically administered prostaglandin E (PGE). One of the initial responses of isolated osteoblast-like cells in vitro to mechanical strain is the production of PGs, leading to the suggestion that they may be involved in the transduction of mechanical signals. It is now evident that the PGEs have dose-related effects on bone formation and bone resorption. Higher doses are usually associated with increased bone resorption, usually expressed as increased bone remodeling where formation is also increased. Lower doses are associated with bone formation; particularly bone modeling. In vivo data shows that PGEs can promote osteogenesis in a variety of circumstances especially bone modeling and remodeling.--R.H. HAUG Reprint requests to Dr Miller: RadiobiologyDivision, Building 586, University of Utah, Salt Lake City, UT 84106.
Clin Plast Surg 21:407, 1994
Reprint requests to Dr Prockop: Department of Biochemistry and Molecular Biology, Jefferson Institute of Molecular Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107.
Anorganic Bovine Bone and Ceramic Analogs of Bone Mineral as Implants to Facilitate Bone Regeneration. Spector M. Clin Plast Surg 21:437, 1994 Bone substitute materials were initially developed to serve as temporary scaffolds or templates to facilitate osteogenesis. Ultimately the bone substitute material was to be resorbed. The beta form of tricalcium phosphate received attention for oral and maxillofacial applications with investigations that evaluated the time course of bone incorporation and rate of body absorption. As research in this area became more sophisticated, natural bone products were developed. Bone substitute materials should serve as a substitute for osteogenesis, become incorporated in the body or resorb, and provide enough strength for a particular clinical situation. Synthetic hydroxylapatite analogs are limited in being able to serve as analogs of bone mineral for use as implants to facilitate bone regeneration. Hydroxylapatite ceramics do not replicate the chemistry and crystalline structure of natural bone mineral. Deorganified bovine bone may produce bone mineral in form that can be employed as implants.--R.H. HAUG Reprint requests to Dr Spector: Department of Orthopedic Surgery, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.
Quantitative Light Microscopy: A powerful tool to assess bone. Hollinger JO, Buck D, Schmitz JP. Clin Plast Surg 21:463, 1994 The optical light microscope is a complex device that allows for the observation of diminutive structures. Despite the advances in modern optics and lens crafting since the 19th century, there are a few inescapable obstacles. Optical diffraction causes single structures in cells to appear blurry.
Fractures of the C-2 Vertebral Body. Benzel EC, Hart BL, Bali PA, et al. J Neurosurg 81:206, 1994 Although rarely reported, C-2 cervical vertebrae fractures are not uncommon. Vertical C-2 vertebral body fractures are retrospectively evaluated in 15 patients over a 3-year period and they suggest the existence of a variety of injury mechanisms. Previous authors have defined three types of odontoid fractures. Their scheme is misleading and confusing (in the opinions of this study's authors) because their type III fracture is not a fracture through the dens but rather a horizontal rostral C-2 body fracture. In this series, clinical and imaging correlations were derived by four different methods: 1) defining the point of impact via clinical examination; 2) defining the point of impact via soft-tissue changes on magnetic resonance image (MRI) or computed tomography (CT); 3) obtaining an accurate history of the mechanism of injury; and 4) hard and soft tissue spinal imaging (x-ray, CT, and MRI). The authors note that C-2 body fractures cannot be differentiated on the basis of a single imaging technique; It requires a combination of plain x-ray studies, CT, and MRI to accurately establish the nature of most C-2 fractures. The cases presented in this series involve injuries between the dens (odontoid process) and the pars interarticularis of the axis and attempt to impart understanding of the mechanistic etiology of upper cervical spine trauma. A spectrum of causative mechanisms was observed, and the authors conclude that the type of injury is determined by the force vector applied during impact and the intrinsic strength and anatomy of C-2 and its surrounding spinal elements. Two types of vertical C-2 body fractures are clearly defined and presented: a coronally oriented (type 1) C-2 body fracture and a sagittally oriented (type 2) fracture. Another type, the horizontal rostral fracture (type 3), is added for completeness (previously identified by others as a type Ill odontoid process fracture.) Twelve of the cases in this series were type 1 fractures. The authors describe and illustrate the findings and causative mechanisms with each type.--R.E. ALEXANDER Reprint requests to Dr Benzel: Division of Neurosurgery, University of New Mexico School of Medicine, Albuquerque, NM 87131.
Unstable Angina: Pharmaceutical versus Invasive Therapy. Prisant LM, Houghton JL, Bottini PB, et al. Postgrad Med 96:88, 1994 Unstable angina is a medical emergency, is often a precursor of myocardial infarction and/or death, and is often indicative of multivessel disease or intraluminal thrombi. Only 10% of patients with unstable angina have normal coronary arteries. Patients who have persistent chest pain or are refractory to sublingual nitroglycerin should be hospitalized in intensive care with continuous monitoring, and given appropriate pharmacologic therapy (nitroglycerin, a beta blocker, heparin infusion, and aspirin.) A new classification system has been proposed to decrease confusion in terminology.
CURRENT LITERATURE This system defines a type I, II, and III unstable angina based on the severity and duration of symptoms, presence or absence of electrocardiogram changes, and intensity of therapy. There are also subtypes of each category, based on the clinical circumstances (primary, secondary, and postinfarction). If symptoms persist despite adequate drug therapy, coronary arteriography should be performed and consideration given to an invasive procedure (eg, angioplasty, balloon counterpulsation, bypass grafting, etc). If possible, the invasive procedures should be delayed until the patient's condition has improved. The authors provide many useful management tips (eg, when nitroglycerin and heparin are both given, heparin resistance occurs if nitroglycerin is infused at a rate exceeding 350 /zg/min, requiring a larger heparin dose). They also discuss many of the commonly used drugs, such as beta blockers, calcium antagonists (which should be given with a beta blocker), antiplatelet agents, heparin, and thrombolytic therapy (the latter is without value in treating unstable angina). Anticoagulation is appropriate in many cases for up to 3 months.--R.E. ALEXANDER
Reprint requests to Dr Prisant: AF-2053, Section of Hypertension and Vascular Diseases, Medical College of Georgia, Augusta, GA 30912-3150.
Clinical Application of Bone Biology to Mandibular and Maxillary Reconstruction. Marx RE. Clin Plast Surg 21:377, 1994 Jaw reconstruction differs greatly from reconstruction of other bones. The goals of jaw reconstruction are to 1) establish continuity, 2) establish alveolar height, 3) establish arch form, 4) establish arch width, 5) maintain bone, and 6) improve facial contours. Patients 12 years old and younger have endosteum and periosteum capable of fully regenerating a resected jaw in which new bone arises from endosteal cells of the host bone edges. Therefore, early bone grafting may not be needed for children after tumor resection; instead, the remaining jaw should be stabilized rigidly and allow for 1 year of spontaneous osteogenesis. The biologic potential for spontaneous osteogenesis is eliminated by radiotherapy, chronic infection, and induced scar. These children should be reconstructed like adults by using a "bone graft." Cancellous marrow grafts are the most successful in jaw reconstruction. For every 1 cm length of reconstruction, 10 mL of uncompressed cancellous bone is required. Cancellous marrow grafts require a crib for support during the bone regeneration-consolidation phase. The hyperbaric oxygen protocol of 100% oxygen at 2.4 absolute atmospheres for 90 minutes per session for 20 preoperative sessions and 10 postoperative sessions is indicated for grafts with irradiated tissue beds. Secondary "preprosthetic surgeries" are often required; such as, vestibuloplasties which are performed 4 months after graft healing, and osseointegrated fixtures that are placed 6 months after graft healing. There are two types of costochondral grafts: 1) the adult graft, which is an articulating graft, and 2) the childhood graft which is a growth center transplant. The rapid revascularization of cranial bone grafts makes them ideal for midfacial, nasal, and orbital reconstruction. Today, implants are placed into reconstructed and irradiated jaws with favorable results and modified implants are used to anchor maxillofacial prostheses. Free vascular transfers of bone will transfer osteocytes and osteon which bypasses the need for cellular bone regeneration; unfortunately, these donor bones are volumetrically much smaller
CURRENT LITERATURE
347
than the mandibular grafts required. They are mostly used for immediate reconstruction in cancer resection.--J.P. MORGAN
Molecular Basis of Osteogenesis Imperfecta and Related Disorders of Bone. Prockop D J, Kuivaniemi H, Tromp G.
Reprint requests to Dr Marx: 6000 Chapman Field Drive, Miami, FL 33156.
Osteogenesis imperfecta (OI) is a heritable defect that makes bones brittle because of a generalized decrease in bone mass (osteopenia) not ascribable to any defect of hormone regulation or mineral metabolism. It may be sufficient to classify OI as type I (mild with blue sclera), type II (lethal) and type lII (moderately severe). Research has identified more than 150 specific gene mutations that cause OI. All of the mutations presently defined are in either the gene for proc~l (I) chain of type I procollagen or the proc~2(I) chain for the same protein. The current estimate is that more than 90% of patients with OI have mutations of either of these two genes. Most of the mutations that cause OI are caused by the gene for type I procollagen, because collagen fibrils are the principle source of the structural strength of bone. Recently, several preliminary experiments have raised the possibility of gene therapy for OI and related disorders. Results raise the distant possibility that an antisense gene strategy might eventually be useful to treat OI by converting the phenotype of a severe form of the disease to a milder f o r m . - R.H. HAUG
Bone Grafting in Craniofacial Surgery. Habal MB. Clin Plast Surg 21:349, 1994 The autograft is the only acceptable bone graft for use in craniofacial surgery today. Allografts and xenografts have no application in craniofacial surgery. Bone grafts are divided into cortical or cancellous grafts. Cortical grafts are dense and their vascular canaliculi require a longer revascularization time. Cancellous grafts are less dense which allows for faster revascularization and can stimulate neovascularization; although, both graft types undergo a remodeling and adaptation period. Ribs and hip bone provide other sources of bone grafting in craniofaciai surgery though the morbidity of a distant operative site reduces the indications for these grafts. In craniofacial surgery, bone grafts fill two needs 1) structural boundaries are expanded and changed for enhancement purposes, and 2) the grafts fill out structural defects with or without advancement. The principle of advancement is used mostly in craniofacial surgery of children and these bone grafts provide immobilization and obstruction as indicated. The authors have developed their principles of bone grafting which are based on 1) experience obtained in 25 years of extensive bone grafting, 2) experience learned from scientific literature, and 3) basic scientific knowledge. Craniofacial bone grafts should be assessed over a period of several years regarding their final outcome. The basis of craniofacial surgery is to use bone grafting and immobilization of all grafted materials while producing a change in the craniofacial skeleton.--J.P. MORGAN Reprint requests to Dr Habal: Tampa Bay Craniofacial Center, 801 West Dr, Martin Luther King, Jr, Blvd, Tampa, FL 33603-3301.
Effects of Prostaglandins on the Skeleton. Miller SC, Marks SC. Clin Plast Surg 21:393, 1994 The prostaglandins (PG) are a family of 20-carbon, unsaturated fatty acids with a cYClopentane ring structure. The ability of PGs to stimulate bone resorption has been established in several in vitro assay systems. The first suggestion that PGs might be involved with bone formation came from clinical studies in the 1970s involving indomethacin. In vivo studies have firmly established the powerful osteogenic actions of systemically administered prostaglandin E (PGE). One of the initial responses of isolated osteoblast-like cells in vitro to mechanical strain is the production of PGs, leading to the suggestion that they may be involved in the transduction of mechanical signals. It is now evident that the PGEs have dose-related effects on bone formation and bone resorption. Higher doses are usually associated with increased bone resorption, usually expressed as increased bone remodeling where formation is also increased. Lower doses are associated with bone formation; particularly bone modeling. In vivo data shows that PGEs can promote osteogenesis in a variety of circumstances especially bone modeling and remodeling.--R.H. HAUG Reprint requests to Dr Miller: RadiobiologyDivision, Building 586, University of Utah, Salt Lake City, UT 84106.
Clin Plast Surg 21:407, 1994
Reprint requests to Dr Prockop: Department of Biochemistry and Molecular Biology, Jefferson Institute of Molecular Medicine, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107.
Anorganic Bovine Bone and Ceramic Analogs of Bone Mineral as Implants to Facilitate Bone Regeneration. Spector M. Clin Plast Surg 21:437, 1994 Bone substitute materials were initially developed to serve as temporary scaffolds or templates to facilitate osteogenesis. Ultimately the bone substitute material was to be resorbed. The beta form of tricalcium phosphate received attention for oral and maxillofacial applications with investigations that evaluated the time course of bone incorporation and rate of body absorption. As research in this area became more sophisticated, natural bone products were developed. Bone substitute materials should serve as a substitute for osteogenesis, become incorporated in the body or resorb, and provide enough strength for a particular clinical situation. Synthetic hydroxylapatite analogs are limited in being able to serve as analogs of bone mineral for use as implants to facilitate bone regeneration. Hydroxylapatite ceramics do not replicate the chemistry and crystalline structure of natural bone mineral. Deorganified bovine bone may produce bone mineral in form that can be employed as implants.--R.H. HAUG Reprint requests to Dr Spector: Department of Orthopedic Surgery, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.
Quantitative Light Microscopy: A powerful tool to assess bone. Hollinger JO, Buck D, Schmitz JP. Clin Plast Surg 21:463, 1994 The optical light microscope is a complex device that allows for the observation of diminutive structures. Despite the advances in modern optics and lens crafting since the 19th century, there are a few inescapable obstacles. Optical diffraction causes single structures in cells to appear blurry.