A new condylar positioning technique in orthognathic surgery Technical note Hans-Albert Merten, Frank Halling
Dept of Maxillofacial Surgery (Head: Prof. H.-G. Luhr, AID, DMD), University Hospital, Gdttingen, Germany SUMMAR Y. In two-jaw surgery, special importance must be attached to the maintenance of the condylar position, particularly in combination with rigid fixation, not only to enhance the stability of the post-operative result but also to avoid iatrogenic temporomandibular joint complications. The new positioning method reported herein is based on a mini fragmentation plate, which can be easily adapted to the bone surface. Reinforcement of the plate by autopolymerizing acrylate, injected into a silicone tube which is pushed over the plate, prevents any unnoticed deformation of the positioning device during surgery. In clinical use, this positioning method has proved to be more versatile and technically less difficult to perform than previous techniques, without any decrease in reliability.
KEY WORDS: Two-jaw surgery - Condylar position control - New positioning device - Rigid fixation.
INTRODUCTION
which is reinforced by the application of autopolymerizing acrylate.
Maintenance of the anatomical position of the mandibular condyles within the glenoid fossa during surgery avoids a built-in relapse potential, minimizes serious temporomandibular joint complications or functional impairment of the masticatory system. The difficulty of maintaining intra-operative centric relation under general anaesthesia and muscular relaxation has been previously described (Luhr, 1989). Most of the condylar positioning techniques fail to fix the condylar segment in three dimensions during the intra-operative application of the miniplates or bimaxillary surgery. These aims have been achieved by a positioning technique using a long right-angled miniplate to join the ascending ramus and the anterolateral aspect of the zygomatic buttress together (Luhr, 1989). Despite several years clinical experience, some problems are hard to solve with this system:
SURGICAL PROCEDURE INCLUDING CONDYLAR POSITIONING We take one mini fragmentation plate for each side to position the condyles (Fig. 1). To facilitate the intraoperative handling, the plates can be adapted on a skull pre-operatively. It is important that the fixation sites of the positioning plates be placed away from the osteotomy lines and the final rigid fixation sites (Fig. 2). Before definitive screw fixation, a silicone tube (inside diameter 5 mm) is drawn with friction over each plate leaving blank the last two screw holes on
• Under special surgical conditions (high level maxillary osteotomy) even the long positioning plate is too short. • Adaptation of the plate to the bony structures often requires connection of the maxillary and mandibular soft tissue-incisions. • After extensive forward advancement of the maxilla the re-application of the positioning plate is sometimes very difficult. • Because of the extraordinary length, the positioning miniplate shows a higher tendency to distortion and twisting during the positioning procedures. For these reasons we have developed a modified technique for condylar positioning based on a mini fragmentation plate (Howmedica International, Inc.),
Fig. 1 The mini fragmentationplate and the completecondylar positioning devicebeforereapplication. 310
A new condylarpositioningtechnique in orthognathicsurgery
311
the post-operative splint. After reapplication of the positioning devices the centric relation of the condylar segments can be re-established exactly (Fig. 3). The gaps at the osteotomy sites must be maintained to avoid any change in the TMJ position even after bridging by miniplate fixation (Luhr, 1989). Finally, in addition to the post-operative splint, guiding elastics are inserted. They help the patient to find his new occlusion and facilitate the neuromuscular adaptation to the changed situation. DISCUSSION Connection of the lateral surface of the ascendingramus and the zygomawith the condylarpositioningdeviceand four screws. Notice the placement of the screws behind the sagittal split osteotomyline and above the Le Fort I--osteotomy line!
Fig. 2 -
Intraoperative situation of the left side after rigid fixation of the Le Fort I osteotomy(osteotomyline [$"]) and sagittal split osteotomy of the mandible (ascendingramus [*]). After reapplication of the positioningdevice, bridging of the sagittaI split osteotomiesis performed. Fig. 3 -
each side of the plate. Now the plates are secured with two 2 x 6 mm self-tapping screws on the lateral cortex of the ascending ramus and the zygoma. Subsequently, the lateral openings of the silicone tubes are closed by means of surgical clamps. To achieve additional rigidity of the positioning plate fluid autopolymerizing methylmetacrylate is injected into the tube with a 10 ml syringe and a steel canula (Strauss canula; 1.8 ram; Braun, Melsungen). The procedure is repeated on the opposite side. After the removal of the positioning devices the Le Fort I - o s t e o t o m y is performed. Passively adapted miniplates at the zygomatic buttresses and beside the piriforme aperture fix the maxilla in the desired position. Now the sagittal split ramus osteotomy of the mandible is performed bilaterally. Subsequently, the toothbearing segment of the mandible is placed into
The basis for good results in combined orthodontic and surgical treatment is the maintenance of the presurgical position of the condyles. Errors in condylar positioning during surgery are hard to correct post-operatively. Due to the stability of rigid internal fixation, wrongly positioned condyles show a higher tendency to relapse into the presurgical position. This 'self-repositioning' (Luhr, 1989) leads to an error in occlusion. Both aspects are good reasons to make every effort to maintain the position of the condyles in the centric relation. The positioning method described above allows precise intra-operative control of the condylar position. It is especially suitable for bimaxillary corrections, but can also be applied in one-jaw surgery. In contrast to other positioning techniques (Hiatt et al. 1988; Luhr, 1989; Schwestka et al., 1990) there is no need for a special positioning plate or condylar positioning appliances. The versatility of the fragmentation plate enables the surgeon to choose the best position for screw fixation, which is of special importance in the tiny bone structure of the maxilla (Ewers and Schilli, 1977). The small connecting bars of the plate permit easy bending in order to obtain optimal adaptation to the patient's individual bone surfaces. Because of the extraordinary length of the plate there is no need for connection of the maxillary and mandibular soft tissue incisions. Thereby restrictive scar formation can be avoided. The reinforcement with autopolymerizing methylmethacrylate reduces the resilience of the plate to a minimum in order to prevent any unobserved deformation of the plate during the reapplication procedures with certainty. The cold-curing acrylate shows only minimal contraction during polymerization (Franz, 1982) and is easy to handle. The silicone tube keeps the acrylate in place and protects the surrounding tissue against the heat of polymerization. This 'trick' renders additional cooling (Hiatt et al. 1988) superfluous. CONCLUSIONS This new condylar positioning method combines easy applicability, versatility and reliability and represents an improved technique for condylar positioning during two-jaw surgery. It maintains the presurgical hinge axis position of the mandibular condyles and
312
Journal of Cranio-Maxillo-Facial Surgery
helps to avoid post-operative occlusal disturbances and adverse effects on the temporomandibular joints. References
Schwestka, R., D. Engelke, D. Kubein-Meesenburg : Condylar
position control during maxillary surgery: the condylar positioning appliance and three-dimensional double splint method. Int. J. Adult Orthodont, Orthognath. Surg. 5 (1990b) 161
Ewers, R., W. Schilli: Die Knochenstrukturen der Maxilla und
ihre Bedeutung ffir die Methoden der Osteosynthese. Dtsch. Z. Mund Kiefer GesichtsChir. I (1977) 148 Franz, G. : Zahn/irztliche Werkstoffkunde. In: Schwenzer, N. (ed.): Zahn-Mund-Kiefer-Heilkunde. Vol. 3. Thieme, Stuttgart, New York 1982, p. 83 Hiatt, W. R., P. M. Schelkun, D. L. Moore: Condylar positioning in orthognathic surgery. J. Oral Maxillofac. Surg. 46 (1988) II10 Luhr, H. G. : The significance of condylar positioning using rigid fixation in orthognathic surgery. Clin. Plast. Surg. 16 (1989) 147
Dr F. Hailing, MD, DMD Dept of Maxillofacial Surgery University Hospital, G6ttingen Robert-Koch-Str. 40 W-3400 G6ttingen Germany
Paper received: 26 March 1992 Accepted: 4 May 1992
Dept of Maxillofacial Surgery (Head: Prof. H.-G. Luhr, AID, DMD), University Hospital, Gdttingen, Germany SUMMAR Y. In two-jaw surgery, special importance must be attached to the maintenance of the condylar position, particularly in combination with rigid fixation, not only to enhance the stability of the post-operative result but also to avoid iatrogenic temporomandibular joint complications. The new positioning method reported herein is based on a mini fragmentation plate, which can be easily adapted to the bone surface. Reinforcement of the plate by autopolymerizing acrylate, injected into a silicone tube which is pushed over the plate, prevents any unnoticed deformation of the positioning device during surgery. In clinical use, this positioning method has proved to be more versatile and technically less difficult to perform than previous techniques, without any decrease in reliability.
KEY WORDS: Two-jaw surgery - Condylar position control - New positioning device - Rigid fixation.
INTRODUCTION
which is reinforced by the application of autopolymerizing acrylate.
Maintenance of the anatomical position of the mandibular condyles within the glenoid fossa during surgery avoids a built-in relapse potential, minimizes serious temporomandibular joint complications or functional impairment of the masticatory system. The difficulty of maintaining intra-operative centric relation under general anaesthesia and muscular relaxation has been previously described (Luhr, 1989). Most of the condylar positioning techniques fail to fix the condylar segment in three dimensions during the intra-operative application of the miniplates or bimaxillary surgery. These aims have been achieved by a positioning technique using a long right-angled miniplate to join the ascending ramus and the anterolateral aspect of the zygomatic buttress together (Luhr, 1989). Despite several years clinical experience, some problems are hard to solve with this system:
SURGICAL PROCEDURE INCLUDING CONDYLAR POSITIONING We take one mini fragmentation plate for each side to position the condyles (Fig. 1). To facilitate the intraoperative handling, the plates can be adapted on a skull pre-operatively. It is important that the fixation sites of the positioning plates be placed away from the osteotomy lines and the final rigid fixation sites (Fig. 2). Before definitive screw fixation, a silicone tube (inside diameter 5 mm) is drawn with friction over each plate leaving blank the last two screw holes on
• Under special surgical conditions (high level maxillary osteotomy) even the long positioning plate is too short. • Adaptation of the plate to the bony structures often requires connection of the maxillary and mandibular soft tissue-incisions. • After extensive forward advancement of the maxilla the re-application of the positioning plate is sometimes very difficult. • Because of the extraordinary length, the positioning miniplate shows a higher tendency to distortion and twisting during the positioning procedures. For these reasons we have developed a modified technique for condylar positioning based on a mini fragmentation plate (Howmedica International, Inc.),
Fig. 1 The mini fragmentationplate and the completecondylar positioning devicebeforereapplication. 310
A new condylarpositioningtechnique in orthognathicsurgery
311
the post-operative splint. After reapplication of the positioning devices the centric relation of the condylar segments can be re-established exactly (Fig. 3). The gaps at the osteotomy sites must be maintained to avoid any change in the TMJ position even after bridging by miniplate fixation (Luhr, 1989). Finally, in addition to the post-operative splint, guiding elastics are inserted. They help the patient to find his new occlusion and facilitate the neuromuscular adaptation to the changed situation. DISCUSSION Connection of the lateral surface of the ascendingramus and the zygomawith the condylarpositioningdeviceand four screws. Notice the placement of the screws behind the sagittal split osteotomyline and above the Le Fort I--osteotomy line!
Fig. 2 -
Intraoperative situation of the left side after rigid fixation of the Le Fort I osteotomy(osteotomyline [$"]) and sagittal split osteotomy of the mandible (ascendingramus [*]). After reapplication of the positioningdevice, bridging of the sagittaI split osteotomiesis performed. Fig. 3 -
each side of the plate. Now the plates are secured with two 2 x 6 mm self-tapping screws on the lateral cortex of the ascending ramus and the zygoma. Subsequently, the lateral openings of the silicone tubes are closed by means of surgical clamps. To achieve additional rigidity of the positioning plate fluid autopolymerizing methylmetacrylate is injected into the tube with a 10 ml syringe and a steel canula (Strauss canula; 1.8 ram; Braun, Melsungen). The procedure is repeated on the opposite side. After the removal of the positioning devices the Le Fort I - o s t e o t o m y is performed. Passively adapted miniplates at the zygomatic buttresses and beside the piriforme aperture fix the maxilla in the desired position. Now the sagittal split ramus osteotomy of the mandible is performed bilaterally. Subsequently, the toothbearing segment of the mandible is placed into
The basis for good results in combined orthodontic and surgical treatment is the maintenance of the presurgical position of the condyles. Errors in condylar positioning during surgery are hard to correct post-operatively. Due to the stability of rigid internal fixation, wrongly positioned condyles show a higher tendency to relapse into the presurgical position. This 'self-repositioning' (Luhr, 1989) leads to an error in occlusion. Both aspects are good reasons to make every effort to maintain the position of the condyles in the centric relation. The positioning method described above allows precise intra-operative control of the condylar position. It is especially suitable for bimaxillary corrections, but can also be applied in one-jaw surgery. In contrast to other positioning techniques (Hiatt et al. 1988; Luhr, 1989; Schwestka et al., 1990) there is no need for a special positioning plate or condylar positioning appliances. The versatility of the fragmentation plate enables the surgeon to choose the best position for screw fixation, which is of special importance in the tiny bone structure of the maxilla (Ewers and Schilli, 1977). The small connecting bars of the plate permit easy bending in order to obtain optimal adaptation to the patient's individual bone surfaces. Because of the extraordinary length of the plate there is no need for connection of the maxillary and mandibular soft tissue incisions. Thereby restrictive scar formation can be avoided. The reinforcement with autopolymerizing methylmethacrylate reduces the resilience of the plate to a minimum in order to prevent any unobserved deformation of the plate during the reapplication procedures with certainty. The cold-curing acrylate shows only minimal contraction during polymerization (Franz, 1982) and is easy to handle. The silicone tube keeps the acrylate in place and protects the surrounding tissue against the heat of polymerization. This 'trick' renders additional cooling (Hiatt et al. 1988) superfluous. CONCLUSIONS This new condylar positioning method combines easy applicability, versatility and reliability and represents an improved technique for condylar positioning during two-jaw surgery. It maintains the presurgical hinge axis position of the mandibular condyles and
312
Journal of Cranio-Maxillo-Facial Surgery
helps to avoid post-operative occlusal disturbances and adverse effects on the temporomandibular joints. References
Schwestka, R., D. Engelke, D. Kubein-Meesenburg : Condylar
position control during maxillary surgery: the condylar positioning appliance and three-dimensional double splint method. Int. J. Adult Orthodont, Orthognath. Surg. 5 (1990b) 161
Ewers, R., W. Schilli: Die Knochenstrukturen der Maxilla und
ihre Bedeutung ffir die Methoden der Osteosynthese. Dtsch. Z. Mund Kiefer GesichtsChir. I (1977) 148 Franz, G. : Zahn/irztliche Werkstoffkunde. In: Schwenzer, N. (ed.): Zahn-Mund-Kiefer-Heilkunde. Vol. 3. Thieme, Stuttgart, New York 1982, p. 83 Hiatt, W. R., P. M. Schelkun, D. L. Moore: Condylar positioning in orthognathic surgery. J. Oral Maxillofac. Surg. 46 (1988) II10 Luhr, H. G. : The significance of condylar positioning using rigid fixation in orthognathic surgery. Clin. Plast. Surg. 16 (1989) 147
Dr F. Hailing, MD, DMD Dept of Maxillofacial Surgery University Hospital, G6ttingen Robert-Koch-Str. 40 W-3400 G6ttingen Germany
Paper received: 26 March 1992 Accepted: 4 May 1992
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