Internal Fixation of the Mandible : A Manual of AO/ASIF Principles

The rigid internaI fixation of mandibular fractures has become a widely ac­ cepted practice among European surgeons. The caution or even outright re­ jection voiced at a congress of the German Society of Maxillofacial Sur­ 1970s is no longer prevalent. Through a process of geons held in the late critical review and implementation, rigid internaI fixation has become an established treatment modality at numerous centers, especially in Switzer­ land, the Federal Republic of Germany, and the Netherlands. By comparison, the method has received very little attention in North America and the Anglo-Saxon countries. By and large, surgeons in these countries continue to treat mandibular fractures by intermaxillary fixation, possibly supplemented by the use of interosseous wires. Many recent edi­ tions of surgical texts confirm this. Lately, however, there appears to be a surge of interest in methods of functionally stable internaI fixation, especially in the United States of America, and AO/ ASIF instruction courses are increasingly in demand. This book is intended to aid course participants in their lessons and practi­ cal exercises and also to guide the clinical practitioner in the application of AO/ ASIF principles. Basel, September 1988 B.SPIESSL VII Acknowledgments I have received help from many sources. The colleagues of the past 20 years who have contributed to the case material upon which this manual is based are too numerous to credit by name.

I: Basic Principles.- 1 Goals of the AO/ASIF Technique.- 2 The Stability Principle.- 2.1 Instability and Its Consequences.- 2.2 Experimental Investigations of Stability and Instability.- 2.3 Significance of the Stability Principle.- 2.3.1 Indirect (Secondary) and Direct (Primary) Bone Healing.- 3 Biomechanics.- 3.1 Anatomic Aspects of Biomechanics.- 3.1.1 Form and Structure of the Mandible.- 3.1.2 Muscular Apparatus of the Mandible.- 3.1.3 Implications for the Biomechanics of Internal Fixation.- 3.2 Biomechanics of Fracture Treatment: Experimental Background (B. Rahn).- 3.2.1 Mechanisms of Stabilization.- 3.2.1.1 Stabilization by Splinting.- 3.2.1.2 Stabilization by Compression.- 3.2.2 Special Situation in the Mandible.- 3.2.3 Bone Healing.- 3.2.3.1 Indirect Bone Healing.- 3.2.3.2 Direct Bone Healing.- 3.2.3.3 Plate-Induced Porosis, “Stress Protection”.- 3.2.3.4 Disturbed Healing Process.- 3.2.4 Implant Design.- 4 Principles of the ASIF Technique.- 4.1 Interfragmental Compression for Functionally Stable Internal Fixation.- 4.1.1 Static Compression.- 4.1.1.1 Static Compression with a Prestressed Plate (DCP).- 4.1.1.2 Eccentric Dynamic Compression Plate (EDCP) for Creating Uniform Pressure on the Oral Side.- 4.1.1.3 Overbending the Plate to Improve Compression on the Lingual Side.- 4.1.1.4 Static Compression with a Lag Screw.- 4.1.2 Dynamic Compression.- 4.1.2.1 Application of the Tension Band Principle in the Mandible.- 4.1.2.2 Tension Band Plate and Tension Band Splint.- 4.1.2.3 Experimental Studies of the Tension Band Splint.- 4.1.2.4 Tension Band Plate.- 4.1.2.5 Plate and Tension Band System.- 4.1.2.6 Interfragmental Compression Without a Tension Band.- 4.1.2.7 Applications of the EDCP.- 4.1.2.8 Applications of the Reconstruction Plate.- 4.2 Principle of Surgical Splinting.- 4.2.1 Internal Splinting.- 4.2.1.1 Buttressing.- 4.2.1.2 Bridging.- 4.2.1.3 Internal Bone Splinting Combined with Interfragmental Compression.- 4.2.2 External Splinting: External Fixator.- 4.2.2.1 Principle, Design, and Advantages.- 4.2.2.2 Clinical Significance.- 4.2.2.3 Indications.- 4.2.2.4 Historical Aspects of External Fixation.- 4.2.2.5 Biomechanics of External Fixation.- 4.2.2.6 One-Bar External Fixator.- 4.2.2.7 Indications for External Fixation.- 5 ASIF Instrumentation.- 5.1 Instrument Sets for Mandibular Surgery.- 5.2 Materials.- 5.2.1 Materials for Mandibular Implants.- 5.2.2 Materials for Instruments.- 5.3 Mandibular Instruments.- 5.3.1 Reduction and Compressing Instruments.- 5.3.2 Instruments for Screw Insertion.- 5.3.2.1 Instruments for Direct Screw Insertion.- 5.3.2.2 Instruments for Transbuccal Screw Insertion.- 5.3.2.3 Small Air Drill with Quick Coupling.- 5.3.2.4 Instruments for Bending and Twisting.- 5.4 Mandibular Implants.- 5.4.1 Mandibular Plates.- 5.4.1.1 Linear System: DCP and EDCP.- 5.4.1.2 Universal Plate System: Reconstruction Plate.- 5.4.1.3 Principles of Plate Bending.- 5.4.2 Mandibular Screws.- 5.4.2.1 Cortex Screw.- 5.4.2.2 Emergency Screw.- 5.4.2.3 Technique of Screw Insertion.- 5.4.3 Wire as a Fixation Material.- 5.5 Wire Acrylic Splint (Schuchardt Splint).- 5.5.1 Functions: Reduction, Retention, Tension Band.- 5.5.2 Materials and Instrumentation.- 5.5.3 Splinting Technique.- 5.5.3.1 Placement of the Arch Bar.- 5.5.3.2 Wiring the Arch Bar to the Teeth.- 5.5.3.3 Stiffening the Arch Bar.- 6 Preoperative, Intraoperative, and Postoperative Guidelines.- 6.1 Organizational Requirements.- 6.2 Priorities in the Care of Multiple Trauma Patients.- 6.3 Timing of Operation.- 6.3.1 Plan of Operation.- 6.3.2 Preparation of the Operative Field.- 6.4 Postoperative Care.- 6.5 Atraumatic Operating Technique.- 6.5.1 Handling of the Soft Tissues.- 6.5.1.1 Value of the Scalpel Technique.- 6.5.2 Prevention of Infection.- 6.5.3 Handling of the Bone.- 6.6 Antibiotic Prophylaxis (General).- 6.7 Interaction Between the Implant and Tissue.- 6.7.1 Mechanical Interactions.- 6.7.2 Chemical-Physiologic Interactions.- 6.7.3 Observations in Mandibular Implants.- 6.7.4 Implant Removal.- 6.7.5 Timing of Implant Removal.- 6.7.6 Technique of Implant Removal.- 6.8 Complications.- 6.8.1 Posttraumatic Bone Infection.- 6.8.2 Postoperative Hematoma.- 6.8.3 Postoperative Pain and Inflammatory Edema.- 6.8.4 Postoperative Osteitis.- 6.8.4.1 Definition and Pathogenesis.- 6.8.4.2 Early Infection.- 6.8.4.3 Late Infection.- 6.8.4.4 Summary of Therapeutic Principles.- II: Internal Fixation of Fresh Fractures.- 1 Introduction.- 2 Classification of Fractures.- 2.1 Definition of Fracture.- 2.2 Approaches to Classification.- 2.3 Findings Relevant to Internal Fixation.- 2.4 Classification Scheme.- 2.4.1 Classification of Fractures by the Number of Fragments and the Presence of a Bone Defect (F1-F4).- 2.4.2 Classification of Fractures by Site (L1-L8).- 2.4.3 Classification of Fractures by Displacement (O0-O2).- 2.4.4 Fracture Formula.- 2.4.5 Classification of Fractures by Soft-Tissue Involvement (S0-S4).- 2.4.6 Associated Fractures (A0-A6).- 2.4.7 Summary of the Constituent Findings in Mandibular Fractures and the Fracture Formula.- 2.4.8 Grouping of Open and Closed Fractures by Grades of Severity and Clinical Categories (FS Formula).- 3 Indications for Internal Fixation.- 3.1 Priority of Early Treatment in Multiple Trauma Patients.- 3.2 Sequencing of Priorities in Patients with Life-Threatening Hemorrhage.- 3.3 Early Stabilization in Concomitant Craniocerebral Trauma.- 3.4 Priorities in the Treatment of Concomitant Le Fort and Mandibular Fractures.- 3.5 Parallel Care in Multiple Trauma Patients.- 3.6 Contraindications to Internal Fixation and Exceptions.- 3.7 Absolute Indications.- 3.8 Condylar Neck Fractures: Their Significance as an Indirect Indication for Internal Fixation.- 4 Surgical Approaches.- 4.1 Inadequacy of Unilateral Fracture Treatment.- 4.2 Principle of Combined Fracture Treatment.- 4.3 Anatomic Landmarks for the Extraoral Approaches.- 4.4 Position of the Head.- 4.5 Classification of Approaches.- 4.6 Purpose of a Systematic Technique of Fracture Exposure.- 4.7 Directions of the Incision.- 4.7.1 Closed Fractures.- 4.7.2 Open Fractures.- 4.8 Angle of the Incision.- 4.9 Surgical Anatomy of the Approaches.- 4.9.1 Submandibular Approach.- 4.9.1.1 Sulcus Incision: Incision in the Natural Cervical Crease (Hyoid Sulcus).- 4.9.1.2 Paramandibular Incision.- 4.9.2 Subangular Approach.- 4.9.3 Submental Approach.- 5 Closed Fractures.- 5.1 Definition of Terms.- 5.2 Classification.- 5.3 Single Fracture (F1S0, Grade I).- 5.3.1 Internal Fixation of Transverse and Oblique Fractures in the Precanine Region (Median, Paramedian, and Canine Fractures).- 5.3.1.1 Intraoral Approach: Indication for DCP.- 5.3.1.2 Extraoral Approach: Indication for EDCP.- 5.3.2 Internal Fixation of Transverse and Oblique Fractures in the Postcanine Region (Fractures of the Lateral Mandible).- 5.3.2.1 Extraoral Approach.- 5.3.3 Internal Fixation of Angle Fractures.- 5.3.3.1 Statistics.- 5.3.3.2 Central Angle Fractures.- 5.3.3.3 Peripheral Angle Fractures.- 5.3.3.4 Marginal Angle Fractures.- 5.3.3.5 Rules for Electing the Internal Fixation of Angle Fractures.- 5.3.3.6 Problems Specific to the Mandibular Angle.- 5.3.3.7 Technique of Internal Fixation of the Angle.- 5.3.4 Internal Fixation of Oblique-Surface Fractures.- 5.4 Multiple Fractures (F2S0, Grade II A).- 5.4.1 Internal Fixation of a Double Fracture in the Dentulous Mandible.- 5.4.1.1 Indications.- 5.4.1.2 Techniques of Internal Fixation.- 5.4.2 Internal Fixation of a Double Fracture in the Edentulous Mandible.- 5.4.2.1 Indications.- 5.4.2.2 Techniques of Internal Fixation.- 5.4.3 Unilateral Segmental Fracture.- 5.4.4 Unilateral Segmental Fracture and Contralateral Single Fracture.- 5.5 Comminuted Fractures (F3 S0).- 6 Open Fractures.- 6.1 Definition of Terms.- 6.2 Classification.- 6.3 Statistics.- 6.4 Wound Treatment and Splinting in Preparation for Definitive Stabilization of the Fracture.- 6.4.1 Emergency Treatment.- 6.4.2 Preoperative Preparation.- 6.4.3 Intraoral Wound Care and Splinting.- 6.4.4 Extraoral Wound Treatment and Debridement.- 6.5 Internal Fixation of the Open Fracture.- 6.5.1 Indications for Bone Plating.- 6.5.2 Indications for External Fixation.- 6.6 Antibiotic Prophylaxis.- 6.7 Illustrative Case Reports.- 6.8 Gunshot Fractures.- 7 Treatment of Mandibular Fractures in Children.- III: Reconstructive Surgery.- 1 Introduction.- 2 Nonunion.- 2.1 Causes.- 2.2 Classification.- 2.3 Clinical Aspects and Treatment of Noninfected Nonunions.- 2.4 Clinical Aspects and Treatment of Nonreactive, Avascular Nonunions.- 2.5 Clinical Aspects and Treatment of Infected Nonunions.- 2.5.1 Previously Infected Nonunion.- 2.5.2 Infected, Draining Nonunion.- 3 Reconstruction of Segmental Defects in Tumor Surgery.- 3.1 Introduction to the Problem.- 3.2 Technical Principles.- 3.2.1 Bridging Without an Autogenous Bone Graft.- 3.2.1.1 THRP or Reconstruction Plate for Definitive Reconstruction.- 3.2.1.2 Bridging as Definitive Treatment for Mandibular Metastases.- 3.2.1.3 Reconstruction Plate for Interim Bridging.- 3.2.1.4 Covering Soft-Tissue Defects and Bridging Segmental Defects.- 3.2.2 Bridging with an Autogenous Bone Graft.- 3.2.2.1 Revascularization.- 3.2.2.2 Heterotopia.- 3.2.2.3 Secondary Interpositional Corticocancellous Bone Graft.- 3.2.2.4 Primary Interpositional Autogenous Bone Graft.- 4 Prophylactic Use of the Neutralization Plate.- 4.1 Use of the Plate for Extensive Bone Cysts.- 4.2 Plating for the Removal of an Impacted Wisdom Tooth.- 5 Partial Prosthetic Arthroplasty.- 5.1 Indications.- 5.2 Principle and Usefulness of the Prosthesis.- 5.3 Design and Function of the Prosthesis.- 5.4 Technique of Insertion.- 6 Osteotomies.- 6.1 Sagittal Split Osteotomy of the Ascending Ramus (Laminotomy).- 6.1.1 Advantages.- 6.1.2 Disadvantages.- 6.1.3 Planning.- 6.1.4 Instrumentation.- 6.1.5 Anatomic Aspects of the Sagittal Split Osteotomy.- 6.1.6 Technique of the Sagittal Split Osteotomy (Laminotomy).- 6.1.7 Lag Screw Fixation.- 6.1.8 On Lag Screw Fixation as a Possible Cause of Sensory Disturbances.- 6.1.9 Removal of the Lag Screws.- 6.1.10 Indications: Shortening and Lengthening Osteotomy.- 6.1.11 Details on the Forward Sagittal Split.- 6.1.12 Functionally Stable Advancement with a Bone Graft.- 6.1.12.1 Method.- 6.1.12.2 Preliminary Fixation of the Fragments.- 6.1.12.3 Functionally Stable Fixation.- 6.2 Lateral Ostectomy.- 6.2.1 Principle.- 6.2.2 Indications.- 6.2.3 Preoperative Planning.- 6.2.4 Operation.- 6.2.5 Preliminary Fixation of the Fragments.- 6.2.6 Functionally Stable Internal Fixation.- 6.3 Anterior Ostectomy Combined with Sagittal Split.- 6.3.1 Principle.- 6.3.2 Indication.- 6.3.3 Preoperative Planning.- 6.3.4 Operation.- 6.3.4.1 Technique of Osteotomy.- 6.3.4.2 Internal Fixation.- 6.4 Triple Basoalveolar Ostectomy.- 6.4.1 Principle.- 6.4.2 Indication.- 6.4.5 Preoperative Planning.- 6.5 Operation.- 6.5.1 Internal Fixation.- 6.6 Genioplasty.- 6.5.1 Lag Screw Fixation.- 6.6 Concluding Remarks.- Foldout “AO Classification of Mandibular Fractures”.