- Email: [email protected]
Evaluation of rigid internal fixation of mandible fractures performed in the teaching laboratory
J Oral Maxillofac Surg 51:1315 ·1319.1993
Evaluation of Rigid Internal Fixation of Mandible Fractures Performed in the Teaching Laboratory LEON A. ASSAEL, DMD* Rigid internal fixation of mandible fractures is advocated as an effective means of providing undisturbed healing and immediate function. However, its application in the clinical setting has resulted in many technique-related failures. To determine the reasons for clinical failure and to help develop improved means of providing successful fixation, the results of plate application in'.the teaching laboratory were evaluated. Seventy-four surgeons taking the AO/Association for the Study of Internal Fixation (AO/ASIF) maxillofacial course in Davos, Switzerland and 56 surgeons taking the advanced AO/ASIF course in Naples, FL applied rigid internal fixation devices to a mandibular fracture model. Treatment was evaluated for anatomic morbidity and effectiveness. In Daves, 92 of 121 subcondylar, body, symphysis, and ramus fractures (76%) were treated effectively. This included 22 of 34 symphysis fractures (65%). In Naples, 11 of 28 symphyseal fractures (39%) were fixed effectively with lag screws without anatomic morbidity. Technique failure is a frequent event in the application of rigid internal fixation devices to mandible fractures. Lag screw fixation of symphyseal fractures had a particularly high rate of technique-related failure .
Rigid internal fixation ofmandible fractures has been used as a means of permitting healing under stable conditions with immediate function . I This method of fixation is attractive because it precisely reestablishes the preinjury position of'bones.l" By providing fixation forces that exceed functional forces at all times during the cours e of healing, it is not necessary to place the patient into maxiIIomandibular fixation postoperatively.5.6 A lower incidence of infection due to the absence of interfragmentary mobility also has been reported as an advantage of this technique.I"? Improved systemic recovery in the multiple trauma patient and less significant pulmonary morbidity are seen as other advantages of rigid internal fixation. I I While the goals of rigid internal fixation seem to be well understood, the highly technical nature ofachiev-
ing them in the clinical situation has resulted in a significant incidence of technique-related failure. The most common result of improperly applied rigid internal fixation is infection. Infection after rigid internal fixation of mandible fractures has been variously reported between 5% and 16%.8-10,12 Malocclusion also occurs after inexact application of rigid internal fixation devices. The incidence of malocclusion is as high as 9% in clinical studies. 9 •12 Injury to the inferior alveolar, marginal mandibular, and lingual nerves also has been reported in association with the use of rigid internal fixation for mandible fractures . Conventional wisdom presumes that the rate ofinfection , malocclusion, and nerve injury should decrease as experience with rigid internal fixation increases. Because of the inherent difficulties in applying rigid fixation devices to fractures, "hands on" courses have become an important means of teaching principles of use and the development of psychomotor skills. These courses include lectures, visual demonstration, and simulated procedures performed in the laboratory by the participant. Although it has been assumed that such courses taken by surgeons already familiar with treating facial trauma wiII provide adequate training for them to successfully use these techniques in practice, the ad-
* Department of Oral Surgery, University of Connecticut School of Dental Medicine. John Demp sey Hospital, Farmington, cr. Address correspondence and reprint requests to Dr Assad: Oral Surgery L-7073, Universit y of Connecticut Health Center, 263 Farmin gton Ave, Farmington. cr 0603 2. © 1993 American Association of Oral and Maxillofacial Surgeons 0278-2391/93/5112-0005$3.00/0
1315
1316
RIGID INTERNAL FIXATION OF MANDIBLE FRACfURES
equacy of such instruction has not been studied in a controlled setting. The purpose of this study was to assess the ability of surgeons to perform effective internal fixation of mandible fractures in the teaching laboratory.
Materials and Methods To determine the potential for technique-related failure of rigid internal fixation of mandible fractures in the clinical setting, 74 surgeons taking the Advanced Maxillofacial Course of the Association for the Study of Internal Fixation (Arbeitsgemeinshaft fur Osteosynthese) in Davos, Switzerland in December 1990 and 56 surgeons taking the advanced course in November 1991 in Naples, FL were evaluated in the laboratory. Each surgeon claimed to have used rigid internal fixation of the mandible actively in clinical practice and most had taken a basic course. Participants in Davos were oral and maxillofacial surgeons, otolaryngologists, and plastic surgeons from 29 nations. Participants in Naples, also represented all three specialties, but were all US practitioners. In Davos, the 74 surgeons were divided into teams of two and were given identical fractures to treat on a mounted plastic mandible: right ramus, right symphysis, left body, and left condyle. They were instructed to apply rigid internal fixation techniques according to AO principles that would permit immediate func-
Table 1. Criteria for Effective Selection of Internal Fixation Devices in the Davos Exercise Fracture Site Right ramus
Right symphysis
Left body
Left condyle
Hardware 4-6-hole 2.7 mm OCPor Recon 4-6-hole 2.0 mm 4-6-hole 2.7 mm Recon and 2 hole 2.0 mm 4-6-hole 2.7 mm OCPor EOCP Two 4-6-hole 2.0mm Two lag screws 4-6-hole 2.7 mm OCPor EDCP Two 4-6-hole 2.0mm 4-6-hole 2.0 mm
Location Anterior border Posterior border Anterior border Posteroanterior border
FIGURE I. A cephelad-caudal arc of6° provides safe screw placement without nerve or tooth injury.
tion. 13-2 1 Immediately preceding this exercise, review ofthese techniques had taken place in the didactic portion of the course. A complete set of instruments, plates, and screws was available for each team. This method permitted each surgeon to select from a variety of means of providing stable internal fixation that would permit immediate function (Table 1). At the conclusion of the 2-hour exercise, each mandible was examined and photographed by the same observer. The exercise in Naples was designed to evaluate a single method for treatment of symphysis fractures. Lag screw fixation was selected because ofits presumed simplicity, brevity, and effectiveness.18,19.21 Fifty-six maxillofacial surgeons who were experienced in rigid internal fixation were divided into teams of two and given a plastic mandibular fracture model with a symphysis fracture. The participants were instructed to place a single lag screw across the fracture from facial cortex to facial cortex. Previous evaluation of this model had indicated that an arc of6° cephelad-caudally on the far segment and 8 0 anteroposteriorly would produce a stable screw without anatomic morbidity (Figs 1 and 2). Anatomic morbidity was considered to
Inferior border Midcorpus and inferior border Subapical
Inferior border Midcorpus monocortical and inferior border
Lateral aspect
Associated tension band plates were acceptable in all fractures. Abbreviations: OCP, dynamic compression plate; Recon, reconstruction plate; EDCP, eccentric dynamic compression plate.
FIGURE 2. An anteroposterior arc of8° provides safe screw placement without nerve injury or perforating the lingual cortex. Minimal screw length is 40 mm.
1317
LEON A. ASSAEL
FIGURE 5. Proper treatment ofa symphyseal fracture with a fourhole dynamic compression plate. . FIGURE 3. Proper treatment of a subcondylar fracture with a fourhole 2.0-mm minicompression plate.
The results from the Davos evaluation showed that, of the 148 fractures, 121 had been treated. These included 28 ramus fractures, 34 symphysis fractures, 34 body fractures, and 25 subcondylar fractures. Twentyseven fractures were not treated because the time for the exercise had expired.
Ninety-two of the 121 fractures (76%) were effectively treated without anatomic morbidity (Figs 3-6). Twenty-nine of the 121 fractures (24%) had methods of treatment that would have resulted in clinical failure during function (FigS 7-10). This included one of 28 ramus fractures (4%), 12 of 34 symphysis fractures (35%), 10 of 34 body fractures (29%), and six of 25 subcondylar fractures (24%). The reasons for failure included insufficient screws (less than two on each side of the fracture), misplaced screws (ie, screw in the fracture line), mismatching hardware (ie, the use of 2.7 screws with a 2.0 plate), and poorly contoured plates (producing gross fracture distraction). Of637 screws placed , 43 (7%) would have damaged the teeth and 38 (6%) most likely would have resulted in inferior alveolar nerve injury. In the Naples exercise, 11 of the 28 fractures (39%) were fixed effectively without anatomic morbidity. Of the 17 lag screw fixations with problems (61%), 5 (18%) had comminution due to overtightening of the screw, 3 (11%) had poor reduction, 2 (7%) had screws through
FIGURE 4. Proper treatment of a body fracture with a four-hole eccentric dynamic compression plate.
FIGURE 6. Proper treatment of a ramus fracture with a reconstruction plate and tension band.
have occurred when there was comminution of the fracture caused by application of the screw, gross distraction of the segments, obvious tooth injury, or injury to the mental foramen-mandibular nerve region. A videotape describing lag screw fixation of an identical fracture was shown before the exercise. One faculty member was available for each eight participants. Results were evaluated by three surgeons, each of whom agreed on all findings. Results
1318
RIGID INTERNAL FIXATION OF MANDIBLE FRACTURES
FIGURE 7. Incorrect treatment ofa subcondylar fracture. A single screw in the proximal segment is not stable. This may have resulted from the misdirected position of the plate.
FIGURE 9. Incorrect treatment of a symphyseal fracture.an attempt to treat the symphysis and body fractures with a single plate resulted in insufficient screws in the segments.
the mental foramen, and 13 (46%) had tooth injury on the far side.
The application of rigid internal fixation devices for mandibular fractures in the laboratory produced a high rate of iatrogenic complications. These inciuded predictable mechanical failure (24%), tooth injury (7%), and nerve injury (6%). Failure rates were much higher (32%) in the portion of the mandible involving the dentition (body and symphysis) than in the sites proximal to the dentition (13%; condyle and ramus). This may be due to the more complex anatomy in these sites and the limited dental education of the majority of participants. The presence of teeth makes treatment-
planning options more limited and their successful execution more complex. Lag screw fixation of symphyseal fractures may seem to be a simple means of applying fixation, but the results of the Naples study indicate that its use may be beset by problems. The range ofdirection in which the screw can be safely placed is extremely narrow on the far side. Also, countersinking requires removing a precise amount of bone in the correct direction. Improper or inadequate countersinking is the chief reason for fractures of the outer cortex or distraction of the fracture when the screw is tightened. In addition, the surgeon must drill, measure, tap , and screw precisely in the same direction.Pr" This ability is severely tested in placement of the symphyseal lag screw. Failure to perform these steps correctly results in an enlarged hole
FIGURE 8. Incorrect treatment of a body fracture. The rniniplate extends from the tension zone superiorly, where it grossly injures the first molar, to the neutral zone, producing distraction of the fracture and instability.
FIGURE 10. Incorrect treatment ofa ramus fracture: the use ofa six-hole straight dynamic compression plate places the mandibular nerve unnecessarily at risk.
Discussion
1319
LEON A. ASSAEL
and a loose screw, or the distraction of the fracture. 18 , 19.2 1 When given the option to provide internal fixation of a symphyseal fracture by a variety of means in the Davos course, the failure rate was 34%. When only permitted to perform lag screw fixation in the Naples course, the failure rate was 61 %. It would appear that the symphyseal lag screw should be used only by surgeons who are experienced in the technique and the anatomic exigencies of the area.
10. II.
12.
13.
Acknowledgment
14.
The authors thank Drs Brian Alpert, Michael Ehrenfeld, Daniel Buchbinder, Wilfried Schilli, Peter Stoll, Jochem Prein, and Berton Rahn for serving as advisors and evaluators of these exercises.
15.
References I. Spiessl B: New Concepts in Maxillofacial Bone Surgery. Berlin, Germany, Springer, 1976 2. Allgower M, Border JR: Advances in the care ofmultiple trauma patient-introduction. World J Surg 7:1, 1983 3. Danis R: Theorie et pratique de l'osteosynthese. Paris, France, Masson, 1949 4. Muller ME, Allgower M, Schneider R, et al: Manual ofInternal Fixation. Berlin, Germany, Springer, 1979 5. Schmoker R, von Allmen G, Tschopp HM: Application offunctionally stable fixation in maxillofacial surgery according to the ASIF principles. J Oral Maxillofac Surg 40:457, 1982 6. Spiessl B: Internal Fixation of the Mandible. Berlin, Germany, Springer-Verlag, 1989 7. Assael L: Complications of rigid internal fixation of the facial skeleton. Oral Maxillofac Surg Clin North Am 2:615, 1990 8. Anderson T, Alpert B: Experience with rigid fixation of mandibular fractures and immediate function. J Oral Maxillofac Surg 50:555, 1992 9. Ardary W: Prospective clinical evaluation of the use ofcom pres-
16. 17. 18. 19. 20. 21. 22. 23.
sion plates and screws in the management of mandible fractures. J Oral Maxillofac Surg 47:1150, 1989 Tu H, Tenhulzen D: Compression osteosynthesis of mandibular fractures: A retrospective study. J Oral Maxillofac Surg 43: 597, 1985 Johnson KD, Ladambi A, Seibert GB: Incidence of adult respiratory distress syndrome in patients with multiple musculoskeletal injuries: Effectofearly operative stabilization of fractures. J Trauma 25:375, 1975 Assael L, Hammon K: A comparison of rigid internal fixation with wire osteosynthesis of mandible fractures. ill Case reports and outlines of scientific sessions. American Association of Oral and Maxillofacial Surgeons, Chicago, IL, 1987, p II Schmoker R: Mandibular reconstruction using a special plate. J Maxillofac Surg 11:99, 1983 (suppl) Schmoker R: The eccentric dynamic compression plate. An experimental study as to its contribution to the functionally stable internal fixation of fractures of the lower jaw. AO Bull, 1976 Rahn BA, Cordey H, Prein J, et al: Zur Biomechanik der Osteosynthese der Mandibula. Fortschr Kiefer Gesichtschir 19: 37, 1975 Perren SM, Russenberger M, Steinemann S, et al: A dynamic compression plate. Acta Orthop Scand 125:29, 1969b (suppl) Perren SM, Huggler SM, Russenberger M, et al: The reaction of cortical bone to compression. Acta Orthop Scand 125:3, 1969a (suppl) Niederdellmann H: Rigid internal fixation by means oflag screws, ill Kruger E, Schilli W (eds): Oral and Maxillofacial Traumatology, vol I. Quintescence, 1980 Niederdellmann H, Schilli W: Zugschraubenosteosynthese zurt Behandlung der Kieferwinkelfraktur. Aktuel Traumatol 10: 105, 1980 Champy M, Lodde J, Schmitt R, et al: Mandibular osteosynthesis by miniature screwed plates via a buccal approach. J Maxillofac Surg 6:14, 1978 Ellis E, Ghali G: Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 49: 13, 1991 Ansell RH, Scales JJ: A study of some factors which affect the strength of screws and their insertion and holding power in bone. J Biomech 1:279, 1968 Allgower M: Weichteilprobleme und Infektionsrisiko der Osteosynthese. Langenbecks Arch Chir 329: 1130, 1971
Evaluation of Rigid Internal Fixation of Mandible Fractures Performed in the Teaching Laboratory LEON A. ASSAEL, DMD* Rigid internal fixation of mandible fractures is advocated as an effective means of providing undisturbed healing and immediate function. However, its application in the clinical setting has resulted in many technique-related failures. To determine the reasons for clinical failure and to help develop improved means of providing successful fixation, the results of plate application in'.the teaching laboratory were evaluated. Seventy-four surgeons taking the AO/Association for the Study of Internal Fixation (AO/ASIF) maxillofacial course in Davos, Switzerland and 56 surgeons taking the advanced AO/ASIF course in Naples, FL applied rigid internal fixation devices to a mandibular fracture model. Treatment was evaluated for anatomic morbidity and effectiveness. In Daves, 92 of 121 subcondylar, body, symphysis, and ramus fractures (76%) were treated effectively. This included 22 of 34 symphysis fractures (65%). In Naples, 11 of 28 symphyseal fractures (39%) were fixed effectively with lag screws without anatomic morbidity. Technique failure is a frequent event in the application of rigid internal fixation devices to mandible fractures. Lag screw fixation of symphyseal fractures had a particularly high rate of technique-related failure .
Rigid internal fixation ofmandible fractures has been used as a means of permitting healing under stable conditions with immediate function . I This method of fixation is attractive because it precisely reestablishes the preinjury position of'bones.l" By providing fixation forces that exceed functional forces at all times during the cours e of healing, it is not necessary to place the patient into maxiIIomandibular fixation postoperatively.5.6 A lower incidence of infection due to the absence of interfragmentary mobility also has been reported as an advantage of this technique.I"? Improved systemic recovery in the multiple trauma patient and less significant pulmonary morbidity are seen as other advantages of rigid internal fixation. I I While the goals of rigid internal fixation seem to be well understood, the highly technical nature ofachiev-
ing them in the clinical situation has resulted in a significant incidence of technique-related failure. The most common result of improperly applied rigid internal fixation is infection. Infection after rigid internal fixation of mandible fractures has been variously reported between 5% and 16%.8-10,12 Malocclusion also occurs after inexact application of rigid internal fixation devices. The incidence of malocclusion is as high as 9% in clinical studies. 9 •12 Injury to the inferior alveolar, marginal mandibular, and lingual nerves also has been reported in association with the use of rigid internal fixation for mandible fractures . Conventional wisdom presumes that the rate ofinfection , malocclusion, and nerve injury should decrease as experience with rigid internal fixation increases. Because of the inherent difficulties in applying rigid fixation devices to fractures, "hands on" courses have become an important means of teaching principles of use and the development of psychomotor skills. These courses include lectures, visual demonstration, and simulated procedures performed in the laboratory by the participant. Although it has been assumed that such courses taken by surgeons already familiar with treating facial trauma wiII provide adequate training for them to successfully use these techniques in practice, the ad-
* Department of Oral Surgery, University of Connecticut School of Dental Medicine. John Demp sey Hospital, Farmington, cr. Address correspondence and reprint requests to Dr Assad: Oral Surgery L-7073, Universit y of Connecticut Health Center, 263 Farmin gton Ave, Farmington. cr 0603 2. © 1993 American Association of Oral and Maxillofacial Surgeons 0278-2391/93/5112-0005$3.00/0
1315
1316
RIGID INTERNAL FIXATION OF MANDIBLE FRACfURES
equacy of such instruction has not been studied in a controlled setting. The purpose of this study was to assess the ability of surgeons to perform effective internal fixation of mandible fractures in the teaching laboratory.
Materials and Methods To determine the potential for technique-related failure of rigid internal fixation of mandible fractures in the clinical setting, 74 surgeons taking the Advanced Maxillofacial Course of the Association for the Study of Internal Fixation (Arbeitsgemeinshaft fur Osteosynthese) in Davos, Switzerland in December 1990 and 56 surgeons taking the advanced course in November 1991 in Naples, FL were evaluated in the laboratory. Each surgeon claimed to have used rigid internal fixation of the mandible actively in clinical practice and most had taken a basic course. Participants in Davos were oral and maxillofacial surgeons, otolaryngologists, and plastic surgeons from 29 nations. Participants in Naples, also represented all three specialties, but were all US practitioners. In Davos, the 74 surgeons were divided into teams of two and were given identical fractures to treat on a mounted plastic mandible: right ramus, right symphysis, left body, and left condyle. They were instructed to apply rigid internal fixation techniques according to AO principles that would permit immediate func-
Table 1. Criteria for Effective Selection of Internal Fixation Devices in the Davos Exercise Fracture Site Right ramus
Right symphysis
Left body
Left condyle
Hardware 4-6-hole 2.7 mm OCPor Recon 4-6-hole 2.0 mm 4-6-hole 2.7 mm Recon and 2 hole 2.0 mm 4-6-hole 2.7 mm OCPor EOCP Two 4-6-hole 2.0mm Two lag screws 4-6-hole 2.7 mm OCPor EDCP Two 4-6-hole 2.0mm 4-6-hole 2.0 mm
Location Anterior border Posterior border Anterior border Posteroanterior border
FIGURE I. A cephelad-caudal arc of6° provides safe screw placement without nerve or tooth injury.
tion. 13-2 1 Immediately preceding this exercise, review ofthese techniques had taken place in the didactic portion of the course. A complete set of instruments, plates, and screws was available for each team. This method permitted each surgeon to select from a variety of means of providing stable internal fixation that would permit immediate function (Table 1). At the conclusion of the 2-hour exercise, each mandible was examined and photographed by the same observer. The exercise in Naples was designed to evaluate a single method for treatment of symphysis fractures. Lag screw fixation was selected because ofits presumed simplicity, brevity, and effectiveness.18,19.21 Fifty-six maxillofacial surgeons who were experienced in rigid internal fixation were divided into teams of two and given a plastic mandibular fracture model with a symphysis fracture. The participants were instructed to place a single lag screw across the fracture from facial cortex to facial cortex. Previous evaluation of this model had indicated that an arc of6° cephelad-caudally on the far segment and 8 0 anteroposteriorly would produce a stable screw without anatomic morbidity (Figs 1 and 2). Anatomic morbidity was considered to
Inferior border Midcorpus and inferior border Subapical
Inferior border Midcorpus monocortical and inferior border
Lateral aspect
Associated tension band plates were acceptable in all fractures. Abbreviations: OCP, dynamic compression plate; Recon, reconstruction plate; EDCP, eccentric dynamic compression plate.
FIGURE 2. An anteroposterior arc of8° provides safe screw placement without nerve injury or perforating the lingual cortex. Minimal screw length is 40 mm.
1317
LEON A. ASSAEL
FIGURE 5. Proper treatment ofa symphyseal fracture with a fourhole dynamic compression plate. . FIGURE 3. Proper treatment of a subcondylar fracture with a fourhole 2.0-mm minicompression plate.
The results from the Davos evaluation showed that, of the 148 fractures, 121 had been treated. These included 28 ramus fractures, 34 symphysis fractures, 34 body fractures, and 25 subcondylar fractures. Twentyseven fractures were not treated because the time for the exercise had expired.
Ninety-two of the 121 fractures (76%) were effectively treated without anatomic morbidity (Figs 3-6). Twenty-nine of the 121 fractures (24%) had methods of treatment that would have resulted in clinical failure during function (FigS 7-10). This included one of 28 ramus fractures (4%), 12 of 34 symphysis fractures (35%), 10 of 34 body fractures (29%), and six of 25 subcondylar fractures (24%). The reasons for failure included insufficient screws (less than two on each side of the fracture), misplaced screws (ie, screw in the fracture line), mismatching hardware (ie, the use of 2.7 screws with a 2.0 plate), and poorly contoured plates (producing gross fracture distraction). Of637 screws placed , 43 (7%) would have damaged the teeth and 38 (6%) most likely would have resulted in inferior alveolar nerve injury. In the Naples exercise, 11 of the 28 fractures (39%) were fixed effectively without anatomic morbidity. Of the 17 lag screw fixations with problems (61%), 5 (18%) had comminution due to overtightening of the screw, 3 (11%) had poor reduction, 2 (7%) had screws through
FIGURE 4. Proper treatment of a body fracture with a four-hole eccentric dynamic compression plate.
FIGURE 6. Proper treatment of a ramus fracture with a reconstruction plate and tension band.
have occurred when there was comminution of the fracture caused by application of the screw, gross distraction of the segments, obvious tooth injury, or injury to the mental foramen-mandibular nerve region. A videotape describing lag screw fixation of an identical fracture was shown before the exercise. One faculty member was available for each eight participants. Results were evaluated by three surgeons, each of whom agreed on all findings. Results
1318
RIGID INTERNAL FIXATION OF MANDIBLE FRACTURES
FIGURE 7. Incorrect treatment ofa subcondylar fracture. A single screw in the proximal segment is not stable. This may have resulted from the misdirected position of the plate.
FIGURE 9. Incorrect treatment of a symphyseal fracture.an attempt to treat the symphysis and body fractures with a single plate resulted in insufficient screws in the segments.
the mental foramen, and 13 (46%) had tooth injury on the far side.
The application of rigid internal fixation devices for mandibular fractures in the laboratory produced a high rate of iatrogenic complications. These inciuded predictable mechanical failure (24%), tooth injury (7%), and nerve injury (6%). Failure rates were much higher (32%) in the portion of the mandible involving the dentition (body and symphysis) than in the sites proximal to the dentition (13%; condyle and ramus). This may be due to the more complex anatomy in these sites and the limited dental education of the majority of participants. The presence of teeth makes treatment-
planning options more limited and their successful execution more complex. Lag screw fixation of symphyseal fractures may seem to be a simple means of applying fixation, but the results of the Naples study indicate that its use may be beset by problems. The range ofdirection in which the screw can be safely placed is extremely narrow on the far side. Also, countersinking requires removing a precise amount of bone in the correct direction. Improper or inadequate countersinking is the chief reason for fractures of the outer cortex or distraction of the fracture when the screw is tightened. In addition, the surgeon must drill, measure, tap , and screw precisely in the same direction.Pr" This ability is severely tested in placement of the symphyseal lag screw. Failure to perform these steps correctly results in an enlarged hole
FIGURE 8. Incorrect treatment of a body fracture. The rniniplate extends from the tension zone superiorly, where it grossly injures the first molar, to the neutral zone, producing distraction of the fracture and instability.
FIGURE 10. Incorrect treatment ofa ramus fracture: the use ofa six-hole straight dynamic compression plate places the mandibular nerve unnecessarily at risk.
Discussion
1319
LEON A. ASSAEL
and a loose screw, or the distraction of the fracture. 18 , 19.2 1 When given the option to provide internal fixation of a symphyseal fracture by a variety of means in the Davos course, the failure rate was 34%. When only permitted to perform lag screw fixation in the Naples course, the failure rate was 61 %. It would appear that the symphyseal lag screw should be used only by surgeons who are experienced in the technique and the anatomic exigencies of the area.
10. II.
12.
13.
Acknowledgment
14.
The authors thank Drs Brian Alpert, Michael Ehrenfeld, Daniel Buchbinder, Wilfried Schilli, Peter Stoll, Jochem Prein, and Berton Rahn for serving as advisors and evaluators of these exercises.
15.
References I. Spiessl B: New Concepts in Maxillofacial Bone Surgery. Berlin, Germany, Springer, 1976 2. Allgower M, Border JR: Advances in the care ofmultiple trauma patient-introduction. World J Surg 7:1, 1983 3. Danis R: Theorie et pratique de l'osteosynthese. Paris, France, Masson, 1949 4. Muller ME, Allgower M, Schneider R, et al: Manual ofInternal Fixation. Berlin, Germany, Springer, 1979 5. Schmoker R, von Allmen G, Tschopp HM: Application offunctionally stable fixation in maxillofacial surgery according to the ASIF principles. J Oral Maxillofac Surg 40:457, 1982 6. Spiessl B: Internal Fixation of the Mandible. Berlin, Germany, Springer-Verlag, 1989 7. Assael L: Complications of rigid internal fixation of the facial skeleton. Oral Maxillofac Surg Clin North Am 2:615, 1990 8. Anderson T, Alpert B: Experience with rigid fixation of mandibular fractures and immediate function. J Oral Maxillofac Surg 50:555, 1992 9. Ardary W: Prospective clinical evaluation of the use ofcom pres-
16. 17. 18. 19. 20. 21. 22. 23.
sion plates and screws in the management of mandible fractures. J Oral Maxillofac Surg 47:1150, 1989 Tu H, Tenhulzen D: Compression osteosynthesis of mandibular fractures: A retrospective study. J Oral Maxillofac Surg 43: 597, 1985 Johnson KD, Ladambi A, Seibert GB: Incidence of adult respiratory distress syndrome in patients with multiple musculoskeletal injuries: Effectofearly operative stabilization of fractures. J Trauma 25:375, 1975 Assael L, Hammon K: A comparison of rigid internal fixation with wire osteosynthesis of mandible fractures. ill Case reports and outlines of scientific sessions. American Association of Oral and Maxillofacial Surgeons, Chicago, IL, 1987, p II Schmoker R: Mandibular reconstruction using a special plate. J Maxillofac Surg 11:99, 1983 (suppl) Schmoker R: The eccentric dynamic compression plate. An experimental study as to its contribution to the functionally stable internal fixation of fractures of the lower jaw. AO Bull, 1976 Rahn BA, Cordey H, Prein J, et al: Zur Biomechanik der Osteosynthese der Mandibula. Fortschr Kiefer Gesichtschir 19: 37, 1975 Perren SM, Russenberger M, Steinemann S, et al: A dynamic compression plate. Acta Orthop Scand 125:29, 1969b (suppl) Perren SM, Huggler SM, Russenberger M, et al: The reaction of cortical bone to compression. Acta Orthop Scand 125:3, 1969a (suppl) Niederdellmann H: Rigid internal fixation by means oflag screws, ill Kruger E, Schilli W (eds): Oral and Maxillofacial Traumatology, vol I. Quintescence, 1980 Niederdellmann H, Schilli W: Zugschraubenosteosynthese zurt Behandlung der Kieferwinkelfraktur. Aktuel Traumatol 10: 105, 1980 Champy M, Lodde J, Schmitt R, et al: Mandibular osteosynthesis by miniature screwed plates via a buccal approach. J Maxillofac Surg 6:14, 1978 Ellis E, Ghali G: Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 49: 13, 1991 Ansell RH, Scales JJ: A study of some factors which affect the strength of screws and their insertion and holding power in bone. J Biomech 1:279, 1968 Allgower M: Weichteilprobleme und Infektionsrisiko der Osteosynthese. Langenbecks Arch Chir 329: 1130, 1971