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Evaluation of condylar neck fracture plating techniques
Journal of Cranio-MaxillofacialSurgery (1999)27, 109 112
© 1999EuropeanAssociationfor Cranio-MaxillofacialSurgery
Evaluation of condylar neck fracture plating techniques Byung-Ho Choi, l Kyung-Nam Kim, 2 Hee-Jin Kim, 3 Moon-Key Kim 1
~Department of Oral and Maxillofacial Surgery, 2Department of Dental Materials; 3Department of Oral Biology, Yonsei University, South Korea S U M M A R Y The purpose of this study was to compare the biomechanical stability of four different plating techniques used to fix condylar neck fractures and to decide which fixation systems are strong enough to withstand the functional load. Ten recently acquired formalin-fixed cadaver mandibles were used for this study. Each of the four sets of osteotomized condylar processes was fixed by one of four different fixation systems. The mandibles were then held in an angle vice so that the mandibles were oriented to simulate actual masticatory force loading on the temporomandibular joint and were loaded with an Instron loading machine. Data demonstrated that a two-miniplate system applied to the anterior and posterior regions of the condylar neck was more stable than single-plate repairs using either mini-dynamic compression plates or 2.4 mm plates. The two-miniplate-fixation technique is indicated in cases of condylar neck fracture to achieve early mobility of the jaw and stability of the fracture site.
INTRODUCTION
five osteotomized condylar processes) was fixed by one of four different fixation systems (Table 1). The fixation systems tested included: (1) a 4-hole miniplate at the posterior region of the lateral cortex of the condylar neck with monocortical screws; (2) a 4-hole mini-dynamic compression plate at the posterior region of the lateral cortex of the condylar neck with bicortical screws; (3) a 4-hole 2.4 mm plate at the posterior region of the lateral cortex of the condylar neck with bicortical screws; and (4) a 4-hole miniplate as before and an additional 4-hole miniplate at the anterior region of the lateral cortex of the condylar neck (Fig. 1). Figure 2 shows the type of plates. All plates and screws used in this experiment were made from titanium alloy (Osteomed M3 rigid fixation system, Osteomed Co., Texas, USA), The stability of the fixation was measured according to Ziccardi et al.'s method (1997) in which condylar load directions during mastication were simulated by an angle vice. The mandibles were held in an angle vice so that the resolved forces on the condylar segment were directed as determined in a previous mathematical analysis (Koolstra et al., 1991). The mandibles were oriented at a 15° inferior tilt in the sagittal plane and at a 10° lateral in the coronal plane to simulate actual masticatory force loading on the temporomandibular joint (Fig. 3). This model results
The use of plate and screw fixation in the management of mandibular fractures is a performanceproven technique, as patients resume normal function of the mandible immediately after surgery (Zide and Kent, 1983). However, there is a question whether its application in condylar neck fractures is rigid enough to dispense with maxillomandibular fixation. Hammer et al. (1997) reported that inadequate stability, either causing plate failure or screw loosening was observed in more than one third (35%) of the group stabilized with a single adaptation miniplate. Others have also reported the fracture of plates used in condylar neck fracture fixation (Ellis and Dean, 1993; Klotch and Lundy, 1991; Iizuka et al., 1991). Ellis and Dean (1993) proposed that plates in the management of condylar neck fractures should be stronger and thicker than the thinner adaptation plates. To our knowledge, there are no published reports about which fixation systems provide functionally stable fixation in fractures of the condylar neck of the mandible. The aim of the present article is to compare the biomechanical stability of four different plating techniques used to stabilize condylar neck fractures and to decide which fixation systems are strong enough to withstand the functional load.
MATERIALS AND M E T H O D S
Table I
Ten recently acquired formalin-fixed cadaver mandibles were used for this study. Osteotomy was made bilaterally on a line 5 mm above and parallel to a tangent drawn along the posterior border of the coronoid process. Each of the four sets of osteotomized mandibular condylar processes (1 set =
Type of stabilization of condylar neck fractures
Type of osteosynthesis Miniplate (four screws)* Mini-dynamic compression plate (four screws)** 2.4 m m plate (four screws)** Double miniplate* * Monocortical screws with a length of 6 mm; **Bicortical screws. 109
110 Journalof Cranio-Maxillofacial Surgery
A
B
Fig. 2 - Typeof plates used in condylarneck fracture fixation. (A) 2.4 mm plate. (B) mini-dynamiccompressionplate. (C) miniplate. C
D
Fig. 1 - Schematicrepresentationof the differentfixationsystems. (A) miniplate. (B) mini-dynamiccompressionplate. (C) 2.4 mm plate. (D) double miniplate.
Table 2 Load for permanent deformation and maximum load of differenttypes of plates
Miniplate Mini-dynamiccompression plate 2.4 mm plate Double miniplate
Experimentalset-up showingthe mandible placed in the angle vice and loading of the condyle.
Fig. 3 -
in the condyle exerting a force upwards and somewhat forwards and medially. The vice was fixed on the load actuator of an Instron machine (Instron Inc, Canton, MA, USA). The action point of the compressive forces was located at the condyle. A load was then applied at a rate of 1.0 cm/min. The load vs displacement relationship, load for permanent deformation and maximum load at fracture were recorded using the lnstron chart recorder. Permanent deformation was defined as the initial point that the load-displacement relationship was no longer linear. Maximum load was defined as the greatest load recorded just before any sudden decrease in load level. Data analyses were done by means of the Kruskal-Wallis test, the nonparametric equivalent of one-way analysis of variance.
RESULTS
The fixation stability of the individual systems are summarized in Table 2. Of the plating systems tested,
Load for permanent deformation (N)
Maximum load (N)
I5.0 (+6.1)
27.8 (+4.4)
29.0 (_+5.4) 44.1 (_+10.2) 93.3 (_+21.0)
37.7 (÷5.6) 103.0 (+12.8) 122.0 (+24.7)
the two-miniplate system provided the greatest functional stability under the simulated functional loading. Fractures reduced by a single miniplate appeared to be most vulnerable to the functional loading. Fracture fixation with a mini-dynamic compression plate was more stable than fixation by a miniplate. Fracture fixation with a 2.4 mm plate was more stable than fixation by a mini-dynamic compression plate. The mean loads for permanent deformation were 15 N for the single miniplate, 29 N for the mini-dynamic compression plate, 44 N for the 2.4 mm plate and 93 N for the two miniplates. The mean maximum loads were 28 N for the single miniplate, 37 N for the minidynamic compression plate, 103 N for the 2.4ram plate and 122 N for the two miniplates. An analysis of variance showed significant differences (P<0.01) between the fixation stability provided by the four different fixation systems.
DISCUSSION The current experimental study showed that the twominiplate system provided the greatest functional stability to reduced condylar neck fractures under simulated functional loading. The greater thickness of 2.4 mm plates and mini-dynamic compression plates applied at the posterior border of the condylar neck did not confer any benefits over the two-miniplate system. This would imply that the efficacy of the
Evaluationof condylarneck fractureplating techniques 111 two-miniplate system derives largely from their ability to neutralize functional stresses that are imposed upon the condylar neck. In vitro strain measurements in the condylar process showed that the highest level of tensile strain was shown to occur on the anterior and lateral surfaces and the highest compressive strain was shown to occur on the posterior surface (Throckmorton and Dochow, 1994). The two miniplates applied at the posterior and anterior border of the condylar neck seem to have the beneficial effect of restoring the tension and compression trajectories. The results of this experimental study provide an estimate of the fixation strengths to be expected from various fixation techniques used to stabilize condylar neck fractures. What remains for discussion is whether the fixation techniques are strong enough to withstand functional loads encountered during the period of bone healing. The actual amount of the functional loads is unknown. However, one can deduce the functional loads from data already known. In 1996, Tate et al. measured bite forces in patients at 6 weeks after rigid fixation for fractures of the mandibular angle. They noted that the maximum bite forces was 63 N (6.4 kp) in the incisor region and 135 N (13.8 kp) in the molar region. When we consider that a retromandibular approach in cases of condylar neck fractures necessitates the masseter muscle being stripped from its attachment to the mandible, surgical damage to the masseter muscle after rigid fixation of fractures of the condylar neck seems to be similar to that after rigid fixation of fractures of the mandibular angle. And, therefore, the maximum bite forces in patients at 6 weeks after rigid fixation of condylar neck fractures may be similar to those after rigid fixation of mandibular angle fractures. Koolstra et al. (1991) estimated joint reaction forces relative to the corresponding bite forces using a three-dimensional mathematical model of the human masticatory system. They reported that a bite force in the open position at the incisors may yield joint reaction forces larger than the corresponding bite force itself. And during molar bites, the joint reaction force may reach up to 65% of the corresponding molar bite force. The force that produced the yield stress of the two miniplates in this study was in the range of 71-118 N. This is of an order of magnitude larger than the joint reaction forces encountered in the healing period of condylar neck fractures. However, fixation by single plate such as a miniplate, a mini-dynamic compression plate, and a 2.4 mm plate would be inadequate for the joint reaction forces. H a m m e r et al. (1997) reported, based on their clinical observation, that a high failure rate was observed with a single miniplate. In addition, they reported that adequate stability could be obtained with either a single mini-dynamic compression plate or a single 2.4 mm plate. An important factor may be that the
soft diets that were recommended to these patients caused the chewing forces to be below the joint reaction forces. Due to the very limited number of patients in their observation using mini-dynamic compression plates or 2.4 mm plates, it cannot be decided if adequate stability can be obtained with those plates. Further investigations on the results of clinical series using these plates are desirable to decide whether the results of our experimental study are in accord with clinical findings. The analytic methods used for quantifying postreduction stability would be expected to contribute to variations in the biomechanical stability of the fixation systems. In contrast to the simpler cantilever beam used customarily to describe the behaviour of the mandible, the mandibles in this study were held in an angle vice and were oriented at a 15 ° inferior tilt in the sagittal plane and 10° posterior to the coronal plane to simulate actual masticatory force loading on the temporomandibular joint (Fig. 3). Thereby the resolved forces on the condylar segment were inferiorly and somewhat posteriorly and laterally directed as determined in a previous mathematical analysis (Koolstra et al., 1991). This arrangement might permit a more accurate assessment of the biomechanical strength of fixation systems. Several authors have reported on open reduction with two miniplates which can be technically performed on condylar neck fractures with no significant morbidity. Sargent and Green (1992) reported that the subcondylar fractures were approached via a retromandibular incision and were fixed with two miniplates. H a m m e r et al. (1997) reported that the extended preauricular incision provided sufficient exposure to reduce and stabilize the condylar neck fractures adequately and allowed exposure of almost the entire ascending ramus after detachment of the masseter muscle from the zygomatic arch. A technique for removal and replantation of the condylar segment using the ramus osteotomy can also be used (Ellis et al,, 1989; M i k k o n e n et al., 1989; Choung and N a m , 1998). Although two-miniplate fixation might be a more traumatic procedure than one-plate fixation, we conclude that the two-miniplate-fixation technique is indicated to achieve early mobility of the jaw and stability of the fracture site when open reduction is indicated in cases of condylar neck fractures. References
Choung, P.H., I. W. Nam: An intraoral approach to treatmentof
condylarhyperplasiaor high condylarprocess fracturesusing the intraoral vertico-sagittalramus osteotomy.J. Oral Maxillofac.Surg. 56 (1998) 563 Ellis, E., S. 7FReynolds H.S. Park: A method to rigidlyfix high condylarfractures.Oral Surg. Oral Med. Oral Pathol. 68 (1989) 369 Ellis, E., J. Dean: Rigid fixationof mandibularcondylefractures. Oral Surg. Oral Med. Oral Pathol. 76 (1993) 6
112 Journal of Cranio-Maxillofacial Surgery Hammer, B., P. Schier, ,1..Prein: Osteosynthesis of condylar neck fractures: a review of 30 patients. Br. J. Oral Maxillofac. Surg. 35 (1997) 288 [izuka, T, O. Lindqvist, D. Hallikainen, P. Mikkonen, P. Paukku: Severe bone resorption and osteoarthrosis after miniplate fixation of high condylar fractures. A clinical and radiologic study of thirteen patients. Oral Surg. Oral Med. Oral Pathol. 72 (1991) 4O0 Klotch, D. W., L.B. Lundy: Condylar neck fractures of the mandible. Otolaryngol. Clin. North Am. 24 (1991) 181 Koolstra J, J Van E(iden, W.A. We(is, et al: A three dimensional mathematical model of the human masticatory system predicting maximum possible bite forces, J. Biomech. 21 ( 1991) 563 Mikkonen, P., C. Lindqvist, A. Pihakari, et a1: Osteotomyosteosynthesis in displaced condylar fractures. Int. J. Oral Maxillofac. Surg. 18 (1989) 267 Sargent, L.A., J.F Green: Plate and screw fixation of selected condylar fractures of the mandible. Ann. Plast. Surg. 28 (1992) 2356 Tate, GS., E. Ellis, G Throckmorton: Bite forces in patients treated for mandibular angle fractures: implications for fixation recommendations. J. Oral Maxillofac. Surg. 52 (1994) 734 Throckmorton, G S., P. C. Dechow: In vitro strain measurements in the condylar process of the human mandible. Archs. Oral Biol. 39 (1994) 853
Ziccardi, V.R, tL E. Schneider, F J Kummer: Wurzburg lag screw plate versus four-hole miniplate for the treatment of condylar process fractures. J. Oral Maxillofac. Surg. 55 (1997) 602 Zide, M.F, J.N. Kent: Indications for open reduction of mandibular condyle fractures. J. Oral Maxillofac. Surg. 41 (1983) 89
Byung-Ho Choi Department of Oral and Maxillofacial Surgery Wonju Christian Hospital Yonsei University 162 IIsan-Dong, Wonju Kangwon-Do South Korea Tel: +82371 741 1430 Fax: +82371 748 2025 Paper received 5 November 1998 Accepted 8 February 1999
© 1999EuropeanAssociationfor Cranio-MaxillofacialSurgery
Evaluation of condylar neck fracture plating techniques Byung-Ho Choi, l Kyung-Nam Kim, 2 Hee-Jin Kim, 3 Moon-Key Kim 1
~Department of Oral and Maxillofacial Surgery, 2Department of Dental Materials; 3Department of Oral Biology, Yonsei University, South Korea S U M M A R Y The purpose of this study was to compare the biomechanical stability of four different plating techniques used to fix condylar neck fractures and to decide which fixation systems are strong enough to withstand the functional load. Ten recently acquired formalin-fixed cadaver mandibles were used for this study. Each of the four sets of osteotomized condylar processes was fixed by one of four different fixation systems. The mandibles were then held in an angle vice so that the mandibles were oriented to simulate actual masticatory force loading on the temporomandibular joint and were loaded with an Instron loading machine. Data demonstrated that a two-miniplate system applied to the anterior and posterior regions of the condylar neck was more stable than single-plate repairs using either mini-dynamic compression plates or 2.4 mm plates. The two-miniplate-fixation technique is indicated in cases of condylar neck fracture to achieve early mobility of the jaw and stability of the fracture site.
INTRODUCTION
five osteotomized condylar processes) was fixed by one of four different fixation systems (Table 1). The fixation systems tested included: (1) a 4-hole miniplate at the posterior region of the lateral cortex of the condylar neck with monocortical screws; (2) a 4-hole mini-dynamic compression plate at the posterior region of the lateral cortex of the condylar neck with bicortical screws; (3) a 4-hole 2.4 mm plate at the posterior region of the lateral cortex of the condylar neck with bicortical screws; and (4) a 4-hole miniplate as before and an additional 4-hole miniplate at the anterior region of the lateral cortex of the condylar neck (Fig. 1). Figure 2 shows the type of plates. All plates and screws used in this experiment were made from titanium alloy (Osteomed M3 rigid fixation system, Osteomed Co., Texas, USA), The stability of the fixation was measured according to Ziccardi et al.'s method (1997) in which condylar load directions during mastication were simulated by an angle vice. The mandibles were held in an angle vice so that the resolved forces on the condylar segment were directed as determined in a previous mathematical analysis (Koolstra et al., 1991). The mandibles were oriented at a 15° inferior tilt in the sagittal plane and at a 10° lateral in the coronal plane to simulate actual masticatory force loading on the temporomandibular joint (Fig. 3). This model results
The use of plate and screw fixation in the management of mandibular fractures is a performanceproven technique, as patients resume normal function of the mandible immediately after surgery (Zide and Kent, 1983). However, there is a question whether its application in condylar neck fractures is rigid enough to dispense with maxillomandibular fixation. Hammer et al. (1997) reported that inadequate stability, either causing plate failure or screw loosening was observed in more than one third (35%) of the group stabilized with a single adaptation miniplate. Others have also reported the fracture of plates used in condylar neck fracture fixation (Ellis and Dean, 1993; Klotch and Lundy, 1991; Iizuka et al., 1991). Ellis and Dean (1993) proposed that plates in the management of condylar neck fractures should be stronger and thicker than the thinner adaptation plates. To our knowledge, there are no published reports about which fixation systems provide functionally stable fixation in fractures of the condylar neck of the mandible. The aim of the present article is to compare the biomechanical stability of four different plating techniques used to stabilize condylar neck fractures and to decide which fixation systems are strong enough to withstand the functional load.
MATERIALS AND M E T H O D S
Table I
Ten recently acquired formalin-fixed cadaver mandibles were used for this study. Osteotomy was made bilaterally on a line 5 mm above and parallel to a tangent drawn along the posterior border of the coronoid process. Each of the four sets of osteotomized mandibular condylar processes (1 set =
Type of stabilization of condylar neck fractures
Type of osteosynthesis Miniplate (four screws)* Mini-dynamic compression plate (four screws)** 2.4 m m plate (four screws)** Double miniplate* * Monocortical screws with a length of 6 mm; **Bicortical screws. 109
110 Journalof Cranio-Maxillofacial Surgery
A
B
Fig. 2 - Typeof plates used in condylarneck fracture fixation. (A) 2.4 mm plate. (B) mini-dynamiccompressionplate. (C) miniplate. C
D
Fig. 1 - Schematicrepresentationof the differentfixationsystems. (A) miniplate. (B) mini-dynamiccompressionplate. (C) 2.4 mm plate. (D) double miniplate.
Table 2 Load for permanent deformation and maximum load of differenttypes of plates
Miniplate Mini-dynamiccompression plate 2.4 mm plate Double miniplate
Experimentalset-up showingthe mandible placed in the angle vice and loading of the condyle.
Fig. 3 -
in the condyle exerting a force upwards and somewhat forwards and medially. The vice was fixed on the load actuator of an Instron machine (Instron Inc, Canton, MA, USA). The action point of the compressive forces was located at the condyle. A load was then applied at a rate of 1.0 cm/min. The load vs displacement relationship, load for permanent deformation and maximum load at fracture were recorded using the lnstron chart recorder. Permanent deformation was defined as the initial point that the load-displacement relationship was no longer linear. Maximum load was defined as the greatest load recorded just before any sudden decrease in load level. Data analyses were done by means of the Kruskal-Wallis test, the nonparametric equivalent of one-way analysis of variance.
RESULTS
The fixation stability of the individual systems are summarized in Table 2. Of the plating systems tested,
Load for permanent deformation (N)
Maximum load (N)
I5.0 (+6.1)
27.8 (+4.4)
29.0 (_+5.4) 44.1 (_+10.2) 93.3 (_+21.0)
37.7 (÷5.6) 103.0 (+12.8) 122.0 (+24.7)
the two-miniplate system provided the greatest functional stability under the simulated functional loading. Fractures reduced by a single miniplate appeared to be most vulnerable to the functional loading. Fracture fixation with a mini-dynamic compression plate was more stable than fixation by a miniplate. Fracture fixation with a 2.4 mm plate was more stable than fixation by a mini-dynamic compression plate. The mean loads for permanent deformation were 15 N for the single miniplate, 29 N for the mini-dynamic compression plate, 44 N for the 2.4 mm plate and 93 N for the two miniplates. The mean maximum loads were 28 N for the single miniplate, 37 N for the minidynamic compression plate, 103 N for the 2.4ram plate and 122 N for the two miniplates. An analysis of variance showed significant differences (P<0.01) between the fixation stability provided by the four different fixation systems.
DISCUSSION The current experimental study showed that the twominiplate system provided the greatest functional stability to reduced condylar neck fractures under simulated functional loading. The greater thickness of 2.4 mm plates and mini-dynamic compression plates applied at the posterior border of the condylar neck did not confer any benefits over the two-miniplate system. This would imply that the efficacy of the
Evaluationof condylarneck fractureplating techniques 111 two-miniplate system derives largely from their ability to neutralize functional stresses that are imposed upon the condylar neck. In vitro strain measurements in the condylar process showed that the highest level of tensile strain was shown to occur on the anterior and lateral surfaces and the highest compressive strain was shown to occur on the posterior surface (Throckmorton and Dochow, 1994). The two miniplates applied at the posterior and anterior border of the condylar neck seem to have the beneficial effect of restoring the tension and compression trajectories. The results of this experimental study provide an estimate of the fixation strengths to be expected from various fixation techniques used to stabilize condylar neck fractures. What remains for discussion is whether the fixation techniques are strong enough to withstand functional loads encountered during the period of bone healing. The actual amount of the functional loads is unknown. However, one can deduce the functional loads from data already known. In 1996, Tate et al. measured bite forces in patients at 6 weeks after rigid fixation for fractures of the mandibular angle. They noted that the maximum bite forces was 63 N (6.4 kp) in the incisor region and 135 N (13.8 kp) in the molar region. When we consider that a retromandibular approach in cases of condylar neck fractures necessitates the masseter muscle being stripped from its attachment to the mandible, surgical damage to the masseter muscle after rigid fixation of fractures of the condylar neck seems to be similar to that after rigid fixation of fractures of the mandibular angle. And, therefore, the maximum bite forces in patients at 6 weeks after rigid fixation of condylar neck fractures may be similar to those after rigid fixation of mandibular angle fractures. Koolstra et al. (1991) estimated joint reaction forces relative to the corresponding bite forces using a three-dimensional mathematical model of the human masticatory system. They reported that a bite force in the open position at the incisors may yield joint reaction forces larger than the corresponding bite force itself. And during molar bites, the joint reaction force may reach up to 65% of the corresponding molar bite force. The force that produced the yield stress of the two miniplates in this study was in the range of 71-118 N. This is of an order of magnitude larger than the joint reaction forces encountered in the healing period of condylar neck fractures. However, fixation by single plate such as a miniplate, a mini-dynamic compression plate, and a 2.4 mm plate would be inadequate for the joint reaction forces. H a m m e r et al. (1997) reported, based on their clinical observation, that a high failure rate was observed with a single miniplate. In addition, they reported that adequate stability could be obtained with either a single mini-dynamic compression plate or a single 2.4 mm plate. An important factor may be that the
soft diets that were recommended to these patients caused the chewing forces to be below the joint reaction forces. Due to the very limited number of patients in their observation using mini-dynamic compression plates or 2.4 mm plates, it cannot be decided if adequate stability can be obtained with those plates. Further investigations on the results of clinical series using these plates are desirable to decide whether the results of our experimental study are in accord with clinical findings. The analytic methods used for quantifying postreduction stability would be expected to contribute to variations in the biomechanical stability of the fixation systems. In contrast to the simpler cantilever beam used customarily to describe the behaviour of the mandible, the mandibles in this study were held in an angle vice and were oriented at a 15 ° inferior tilt in the sagittal plane and 10° posterior to the coronal plane to simulate actual masticatory force loading on the temporomandibular joint (Fig. 3). Thereby the resolved forces on the condylar segment were inferiorly and somewhat posteriorly and laterally directed as determined in a previous mathematical analysis (Koolstra et al., 1991). This arrangement might permit a more accurate assessment of the biomechanical strength of fixation systems. Several authors have reported on open reduction with two miniplates which can be technically performed on condylar neck fractures with no significant morbidity. Sargent and Green (1992) reported that the subcondylar fractures were approached via a retromandibular incision and were fixed with two miniplates. H a m m e r et al. (1997) reported that the extended preauricular incision provided sufficient exposure to reduce and stabilize the condylar neck fractures adequately and allowed exposure of almost the entire ascending ramus after detachment of the masseter muscle from the zygomatic arch. A technique for removal and replantation of the condylar segment using the ramus osteotomy can also be used (Ellis et al,, 1989; M i k k o n e n et al., 1989; Choung and N a m , 1998). Although two-miniplate fixation might be a more traumatic procedure than one-plate fixation, we conclude that the two-miniplate-fixation technique is indicated to achieve early mobility of the jaw and stability of the fracture site when open reduction is indicated in cases of condylar neck fractures. References
Choung, P.H., I. W. Nam: An intraoral approach to treatmentof
condylarhyperplasiaor high condylarprocess fracturesusing the intraoral vertico-sagittalramus osteotomy.J. Oral Maxillofac.Surg. 56 (1998) 563 Ellis, E., S. 7FReynolds H.S. Park: A method to rigidlyfix high condylarfractures.Oral Surg. Oral Med. Oral Pathol. 68 (1989) 369 Ellis, E., J. Dean: Rigid fixationof mandibularcondylefractures. Oral Surg. Oral Med. Oral Pathol. 76 (1993) 6
112 Journal of Cranio-Maxillofacial Surgery Hammer, B., P. Schier, ,1..Prein: Osteosynthesis of condylar neck fractures: a review of 30 patients. Br. J. Oral Maxillofac. Surg. 35 (1997) 288 [izuka, T, O. Lindqvist, D. Hallikainen, P. Mikkonen, P. Paukku: Severe bone resorption and osteoarthrosis after miniplate fixation of high condylar fractures. A clinical and radiologic study of thirteen patients. Oral Surg. Oral Med. Oral Pathol. 72 (1991) 4O0 Klotch, D. W., L.B. Lundy: Condylar neck fractures of the mandible. Otolaryngol. Clin. North Am. 24 (1991) 181 Koolstra J, J Van E(iden, W.A. We(is, et al: A three dimensional mathematical model of the human masticatory system predicting maximum possible bite forces, J. Biomech. 21 ( 1991) 563 Mikkonen, P., C. Lindqvist, A. Pihakari, et a1: Osteotomyosteosynthesis in displaced condylar fractures. Int. J. Oral Maxillofac. Surg. 18 (1989) 267 Sargent, L.A., J.F Green: Plate and screw fixation of selected condylar fractures of the mandible. Ann. Plast. Surg. 28 (1992) 2356 Tate, GS., E. Ellis, G Throckmorton: Bite forces in patients treated for mandibular angle fractures: implications for fixation recommendations. J. Oral Maxillofac. Surg. 52 (1994) 734 Throckmorton, G S., P. C. Dechow: In vitro strain measurements in the condylar process of the human mandible. Archs. Oral Biol. 39 (1994) 853
Ziccardi, V.R, tL E. Schneider, F J Kummer: Wurzburg lag screw plate versus four-hole miniplate for the treatment of condylar process fractures. J. Oral Maxillofac. Surg. 55 (1997) 602 Zide, M.F, J.N. Kent: Indications for open reduction of mandibular condyle fractures. J. Oral Maxillofac. Surg. 41 (1983) 89
Byung-Ho Choi Department of Oral and Maxillofacial Surgery Wonju Christian Hospital Yonsei University 162 IIsan-Dong, Wonju Kangwon-Do South Korea Tel: +82371 741 1430 Fax: +82371 748 2025 Paper received 5 November 1998 Accepted 8 February 1999