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A transcoronoidal approach of fractures of the condylar neck
348
J. Cranio-Max.-Fac.Surg. 18 (1990)
j. Cranio-Max.-Fac. Surg. 18 (1990) 348-351 © Georg Thieme Verlag Stuttgart • New York
Summary
A Transcoronoidal Approach of Fractures of the Condylar Neck
Open reduction of condylar neck fractures is a contentious issue. The majority of these fractures can be treated conservatively. There are, however, specific situations, where open reduction is indicated. In recognition of the high morbidity associated with extra-oral procedures, we advocate an intra-oral transcoronoidal approach to gain direct access to the fracture site.
Georg Habel i, Barry O'Regan e, Johannes Hidding i, Alfons Eissing i 1Dept. of Oral and Maxillo-Facial Surgery (Head: Prof. R. Becket, M.D., D.M.D.), Westf. Wilhelms-University,Miinster, West Germaw 2Dept. of Oral and Maxillo-Facial Surgery (Head: Prof. G. R. Seward, C.B.E., M.D.S., M.B.B.S., F.R.C.S. (Ed.), F.D.S., F.R.C.S. (Eng.), F.F.A,, The London Hospital, Whitechapel, London, Great Britain
Key words Condylar neck fracture - Transcoronoidal approach - Wire osteosynthesis
Submitted 20.12.89; accepted 19.6.90
Introduction Our personal experience and a comprehensive review of the literature confirm the impression that no general consensus exists as to the management of fractures of the condylar neck. In the past, most fractures of the condylar neck have been treated successfully conservatively (MacLennan, 1952, 1969; Miiller, 1967; Rowe and Killey, 1968). However, more recently some authors have reviewed the indications for open reduction of fractures of the condylar neck, and have demarcated sub-groups, which in their opinion warrant open reduction (Messer, 1972; Petzel, 1982; Zide and Kent, 1983; Kitayama, 1989; Takenoshita et al., 1989). Zide and Kent (1983) suggested the following absolute indications for open reduction of fractures of the condylar neck. 1. Failure to achieve an adequate occlusion by conservative means. 2. Lateral extra-capsular displacement of the condylar head. 3. Compound condylar fractures (i. e. gunshot wounds: foreign body). 4. Displacement of the condylar head into the middle cranial fossa. We regard these indications as relevant today, but would suggest, that condylar neck fractures with medial, anteromedial and posterior luxation of the condylar head should be included in this group, when conservative treatment has failed. We would add a note of caution with respect to high sub-condylar and intra-capsular fractures. We believe, that these fractures are best treated conservatively. Much has been written about extra-oral access (Thoma, 1945; Wassmund, 1951) to condylar neck fractures. The obvious disadvantages of this route have stimulated many authors to consider surgical access via the intra-oral route. We present this technique as a further development of hitherto described intra-oral approaches to the condylar neck (Obwegeser, 1963; Steinhh'user, 1964; Kitayama, 1989).
Surgical Technique Any attempt to reduce a condylar neck fracture intra-orally is hampered by inadequate access to the fracture site itself.
This is mainly because of the coronoid process, which prevents direct visualisation and manipulation of the proximal and distal fragments. Using a vertical anterior ramus incision, we reflect buccal and lingual periostal flaps as described by Obwegeser (1963). After identification and protection of the inferior dental bundle, transverse and vertical sub-sigmoid osteotomy cuts are marked on the buccal aspect of the coronoid process (Fig. I a). The horizontal osteotomy cut is placed 2 - 4 mm above the level of the lingula, and extends to the mid-ramus point A antero-posteriorly. The vertical osteotomy cut runs from the sub-sigmoid through to this point A. Prior to completing a temporary osteotomy of the coronoid process, a miniscrew of appropriate length and breadth (at least 5 mm longer than the horizontal osteotomy length and 1.5-2 mm in diameter) is driven into the anterior margin of the coronoid process (Fig. lb). This ensures accurate repositioning of the osteotomised coronoid process upon completion of the fracture reduction. A transosseous wire secures the mobile osteotomised coronoid process. Thus, direct surgical access to the fracture site is achieved (Fig. 1 c). Reduction and fixation of the fragments is carried out under direct vision using a transosseous wire (Fig. 1 d). The proximal fragment, i.e. the condylar head, is repositioned into the condylar fossa using a condylar retaining hook or forceps (Kitayama, 1989). This can be verified digitally or using intra-operative radiography. Finally, the osteotomised coronoid process is repositioned and fixed in place using the afore-mentioned screw technique (Fig. I e). The patient is put into intermaxillary fixation which is retained for two weeks. Case Report A 22-year-old soldier presented to the Department of Oral and Maxillo-facial Surgery having sustained a blow to the chin during a football game. On clinical examination the patient had a tender swelling in the right condylar region with trismus (maximal inter-incisal distance 15 mm) and complete disocclusion. Lateral and protrusive mandibular movements were restricted and extremely painful.
A TranscoronoidalApproach of Fractures of the Condylar Neck
J. Cranio-Max.-Fac. Surg. 18 (1990)
349
Fig. 1 a Bone cuts - vertical and anteroposterior - with interception at point A, Fig.1 b
Screw in position (arrow),
Fig. 1 c Access to fractures illustrated after temporary displacement of the coronoid process. Fig. 1 d thesis.
Reduced fracture - wire osteosyn-
Fig. 1 e Coronoid process repositioned using a screw.
Fig.2 P.A. radiograph showing luxation of condylar head (arrows) and displacement of the fragments.
Fig.3 intraoperative reduced fracture and repositioned coronoid process.
Radiographs showed a condylar neck fracture with anteromedial luxation of the condylar head and separation of the proximal and distal fragments at the fracture site (Fig. 2). Two days later, the condylar neck fracture was approached intra-orally using the technique described above. Intra-operatively, it was possible to reposition the condylar head in the fossa, using a condylar retaining forceps. The fracture was reduced and fixed with a transosseous wire. The coronoid process was subsequently replaced and fixed with a screw (Fig. 3). The patient was put into intermaxillary fixation for two weeks, upon release of which, near-normal
Fig.4 Patient 6 months postoperatively showing mandibular opening.
mandibular opening was achieved and the patient was painfree. Clinial examination of the patient carried out 6 months postoperatively showed that function of the right temporomandibular joint had returned to normal. The patient had no restriction of movement over the full range of mandibular excursion and the interincisal distance was recorded as 37mm (Fig. 4). Neurological examination showed completely normal facial nerve and trigeminal nerve function on the right side. There was no impairment of the activity of the right temporalis muscle.
350
J. Cranio-Max.-Fac. Surg. 18 (1990)
G. Habel et aL Fig.Sa Lateral radiographic view of the reduced fracture. Fig.5b P, A. radiograph view of the reduced fracture.
Postoperative radiographs show the condylar head in the glenoid fossa and the alignment of the proximal and distal fragments is acceptable (Figs. 5 a and 5 b). Discussion and Conclusions
The majority of condylar fractures may be treated conservatively (Cook and MacFarlane, 1969); i. e. by closed reduction and physiotherapy. In those cases, where open reduction is indicated, the relative advantages and disadvantages of extra-oral versus intra-oral access must be clearly elaborated. The benefits of extra-oral access, and in particular the preauricular approach (AI-Kayat and Bramley, 1979-1980; Timmel, 1982) include direct fracture site visibility, good control, especially of the proximal fragment, with ease of exact anatomical fracture reduction, using the full range of available osteosynthesis techniques (Tboma, 1945; Messer, 1972; Koberg and Momma, 1978; Brown and Obeid, 1984). In contrast to these clear advantages, the simple presence of a facial scar concerns ma W patients. In addition, iatrogenic facial nerve damage, whether temporary or permanent, is a further deterrent to pre-auricular or submandibular access (Kitayama, 1989). In an attempt to lessen the risk of damage to the facial nerve, the use of the submandibular route has been advocated (Messer, 1972; Peters et al., 1976), although the attendant restriction of poor fracture site visibility is recognised. The problems common to extra-oral approaches have led many authors to explore the intra-oral route when dealing with sub-condylar fractures (Steinhduser, 1964; Pape et al., 1980; Kitayama, 1989). The stimulus to this development was in part the success of the routine approach to the ascending ramus as described by Obwegeser (1963). All subsequently described techniques using these methods have suffered restriction of access to the fracture site, because of the presence of the coronoid process (Steinhduser, 1964). To overcome the difficulty, we decided to attempt a transcoronoidal approach.
We believe that the use of a temporary coronoidotomy, as described here, addresses one of the basic problems, i.e. the restriction of access occasioned by the coronoid process itself. The advantages of this procedure are numerous: - The risk of facial nerve damage is substantially reduced. - There are no facial scars. - Surgical trauma is within acceptable limits, direct access to the condylar fracture is achieved with relative ease. - Repositioning of the condylar head in the glenoid fossa is facilitated. We would like to emphasise, that we do not advocate routine open reduction of sub-condylar fractures. This procedure should be reserved for those cases, few in number, which on critical reflection, warrant open reduction. Acknowledgements We wish to thank Frau Brigitte Schulte for her help in typing this paper and Frau Anne M~inster-Erkeling for her photographic assistance. References
A1-Kayat, A., P. Bramley: A modified pre-auricular approach to the temporomandibular joint and malar arch. Br. J. Oral Surg. 17 (1979-1980) 91 Brown, A. E., G. ObeM: A simplified method for the internal fixation of fractures of the mandibular condyle. Br. J. Oral Maxillofac. Surg. 22 (1984) 145 Cook, IL M., W. I. MacFarlane: Subcondylar fracture of the mandible. Oral Surg. 27 (1969) 297 Kitayama, S.: A new method of intraoral open reduction using a screw applied through the mandibular crest of condylar fractures. J. Cran.-Max.-Fac. Surg. 17 (1989) 16 Koberg, W. R., W. G. Momma: Treatment of fractures of the articular process by functional stable osteosynthesis using miniamrised dynamic compression plates. Int. J. Oral Surg. 7 (1978) 256 MacLennan, W. D.- Consideration of 180 cases of typical fracture of the mandibular condylar process. Br. J. Plast. Surg. 5 (1952) 122
A TranscoronoidalApproach of Fractures of the Condylar Neck MacLennan, W. D.: Fractures of the mandibular condylar process. Br.J. Oral Surg. 7 (1969) 31 Messer, E. J.: A simplified method for fixation of the fractured mandibular condyle. J. Oral Surg. 30 (1972) 442 Miiller, W.: Die Therapie der Gelenkfortsatzfrakturen. Zahn-, Mund- und Kieferheilk. 64 (1976) 496 Obwegeser, H.: The indications for surgical correction of mandibular deformity by the sagittal splitting technique. Br. J. Oral Surg. 1 (1963) 157 Pape, H. D., H. Hauenstein, K. L. Gerlach: Chirurgische Versorgung der Gelenkfortsatzfrakturen mit Miniplatten. Fortschr. Kiefer-Gesichts-Chir. 25 (1980) 81 Peters, A. R., J. B. Caldwell, T. W. Olsen: A technique for open reduction of subcondylar fractures. Oral Surg. 41 (1976) 273 Petzel, J. R.: Functional stable traction-screw osteosynthesis of condylar fractures. J. Oral Maxillofac. Surg. 40 (1982) 108 Rowe, N. L., H. C. Killey: Fractures of the facial skeleton. 2nd Ed. Livingstone, Edinburgh and London (1968) 164 Steinh~iuser, E.: Eingriffe am Processus articularis auf dem oralen Weg. Dtsch. Zahnfirztl. Z. 19 (1964) 694
J. Cranio-Max.-Fac. Surg. 18 (1990)
351
Takenoshita, Y., M. Oka, H. Tashiro: Surgical treatment of fractures of the mandibular condylar neck. J. Cran.-Max.-Fac. Surg. 17 (1989) 119 Thoma, K. H.: Fractures and fracture dislocation of the mandibular condyle: A method for open reduction and internal wiring and one for skeletal fixation with a report of 32 cases. J. Oral Surg. 3 (1945) 3 Timmel, R.: Die operative Behandlung der Luxationsfraktur des Kieferk6pfchens. Ost. Z. Stom. 79 (1982) 190 Wassmund, M.: Die Chirurgie des Kiefergelenkes. Zahn-, Mund-, Kieferheilk. In: Vortrfigen, Hanser, Mfinchen (1951) 6 Zide, M. F., J. M. Kent: Indications for open reduction of mandibular condylar fractures. J. Oral Maxillofac. Surg 41 (1983) 89 Prof. Dr. Dr. G. Habel Klinik u. Poliklinik fiir Mund- u. Kiefer-Gesichtschirurgie Westfdlische Wilhelms-Universita't Waldeyerstr. 30 D4400 Miinster Germany
J. Cranio-Max.-Fac.Surg. 18 (1990)
j. Cranio-Max.-Fac. Surg. 18 (1990) 348-351 © Georg Thieme Verlag Stuttgart • New York
Summary
A Transcoronoidal Approach of Fractures of the Condylar Neck
Open reduction of condylar neck fractures is a contentious issue. The majority of these fractures can be treated conservatively. There are, however, specific situations, where open reduction is indicated. In recognition of the high morbidity associated with extra-oral procedures, we advocate an intra-oral transcoronoidal approach to gain direct access to the fracture site.
Georg Habel i, Barry O'Regan e, Johannes Hidding i, Alfons Eissing i 1Dept. of Oral and Maxillo-Facial Surgery (Head: Prof. R. Becket, M.D., D.M.D.), Westf. Wilhelms-University,Miinster, West Germaw 2Dept. of Oral and Maxillo-Facial Surgery (Head: Prof. G. R. Seward, C.B.E., M.D.S., M.B.B.S., F.R.C.S. (Ed.), F.D.S., F.R.C.S. (Eng.), F.F.A,, The London Hospital, Whitechapel, London, Great Britain
Key words Condylar neck fracture - Transcoronoidal approach - Wire osteosynthesis
Submitted 20.12.89; accepted 19.6.90
Introduction Our personal experience and a comprehensive review of the literature confirm the impression that no general consensus exists as to the management of fractures of the condylar neck. In the past, most fractures of the condylar neck have been treated successfully conservatively (MacLennan, 1952, 1969; Miiller, 1967; Rowe and Killey, 1968). However, more recently some authors have reviewed the indications for open reduction of fractures of the condylar neck, and have demarcated sub-groups, which in their opinion warrant open reduction (Messer, 1972; Petzel, 1982; Zide and Kent, 1983; Kitayama, 1989; Takenoshita et al., 1989). Zide and Kent (1983) suggested the following absolute indications for open reduction of fractures of the condylar neck. 1. Failure to achieve an adequate occlusion by conservative means. 2. Lateral extra-capsular displacement of the condylar head. 3. Compound condylar fractures (i. e. gunshot wounds: foreign body). 4. Displacement of the condylar head into the middle cranial fossa. We regard these indications as relevant today, but would suggest, that condylar neck fractures with medial, anteromedial and posterior luxation of the condylar head should be included in this group, when conservative treatment has failed. We would add a note of caution with respect to high sub-condylar and intra-capsular fractures. We believe, that these fractures are best treated conservatively. Much has been written about extra-oral access (Thoma, 1945; Wassmund, 1951) to condylar neck fractures. The obvious disadvantages of this route have stimulated many authors to consider surgical access via the intra-oral route. We present this technique as a further development of hitherto described intra-oral approaches to the condylar neck (Obwegeser, 1963; Steinhh'user, 1964; Kitayama, 1989).
Surgical Technique Any attempt to reduce a condylar neck fracture intra-orally is hampered by inadequate access to the fracture site itself.
This is mainly because of the coronoid process, which prevents direct visualisation and manipulation of the proximal and distal fragments. Using a vertical anterior ramus incision, we reflect buccal and lingual periostal flaps as described by Obwegeser (1963). After identification and protection of the inferior dental bundle, transverse and vertical sub-sigmoid osteotomy cuts are marked on the buccal aspect of the coronoid process (Fig. I a). The horizontal osteotomy cut is placed 2 - 4 mm above the level of the lingula, and extends to the mid-ramus point A antero-posteriorly. The vertical osteotomy cut runs from the sub-sigmoid through to this point A. Prior to completing a temporary osteotomy of the coronoid process, a miniscrew of appropriate length and breadth (at least 5 mm longer than the horizontal osteotomy length and 1.5-2 mm in diameter) is driven into the anterior margin of the coronoid process (Fig. lb). This ensures accurate repositioning of the osteotomised coronoid process upon completion of the fracture reduction. A transosseous wire secures the mobile osteotomised coronoid process. Thus, direct surgical access to the fracture site is achieved (Fig. 1 c). Reduction and fixation of the fragments is carried out under direct vision using a transosseous wire (Fig. 1 d). The proximal fragment, i.e. the condylar head, is repositioned into the condylar fossa using a condylar retaining hook or forceps (Kitayama, 1989). This can be verified digitally or using intra-operative radiography. Finally, the osteotomised coronoid process is repositioned and fixed in place using the afore-mentioned screw technique (Fig. I e). The patient is put into intermaxillary fixation which is retained for two weeks. Case Report A 22-year-old soldier presented to the Department of Oral and Maxillo-facial Surgery having sustained a blow to the chin during a football game. On clinical examination the patient had a tender swelling in the right condylar region with trismus (maximal inter-incisal distance 15 mm) and complete disocclusion. Lateral and protrusive mandibular movements were restricted and extremely painful.
A TranscoronoidalApproach of Fractures of the Condylar Neck
J. Cranio-Max.-Fac. Surg. 18 (1990)
349
Fig. 1 a Bone cuts - vertical and anteroposterior - with interception at point A, Fig.1 b
Screw in position (arrow),
Fig. 1 c Access to fractures illustrated after temporary displacement of the coronoid process. Fig. 1 d thesis.
Reduced fracture - wire osteosyn-
Fig. 1 e Coronoid process repositioned using a screw.
Fig.2 P.A. radiograph showing luxation of condylar head (arrows) and displacement of the fragments.
Fig.3 intraoperative reduced fracture and repositioned coronoid process.
Radiographs showed a condylar neck fracture with anteromedial luxation of the condylar head and separation of the proximal and distal fragments at the fracture site (Fig. 2). Two days later, the condylar neck fracture was approached intra-orally using the technique described above. Intra-operatively, it was possible to reposition the condylar head in the fossa, using a condylar retaining forceps. The fracture was reduced and fixed with a transosseous wire. The coronoid process was subsequently replaced and fixed with a screw (Fig. 3). The patient was put into intermaxillary fixation for two weeks, upon release of which, near-normal
Fig.4 Patient 6 months postoperatively showing mandibular opening.
mandibular opening was achieved and the patient was painfree. Clinial examination of the patient carried out 6 months postoperatively showed that function of the right temporomandibular joint had returned to normal. The patient had no restriction of movement over the full range of mandibular excursion and the interincisal distance was recorded as 37mm (Fig. 4). Neurological examination showed completely normal facial nerve and trigeminal nerve function on the right side. There was no impairment of the activity of the right temporalis muscle.
350
J. Cranio-Max.-Fac. Surg. 18 (1990)
G. Habel et aL Fig.Sa Lateral radiographic view of the reduced fracture. Fig.5b P, A. radiograph view of the reduced fracture.
Postoperative radiographs show the condylar head in the glenoid fossa and the alignment of the proximal and distal fragments is acceptable (Figs. 5 a and 5 b). Discussion and Conclusions
The majority of condylar fractures may be treated conservatively (Cook and MacFarlane, 1969); i. e. by closed reduction and physiotherapy. In those cases, where open reduction is indicated, the relative advantages and disadvantages of extra-oral versus intra-oral access must be clearly elaborated. The benefits of extra-oral access, and in particular the preauricular approach (AI-Kayat and Bramley, 1979-1980; Timmel, 1982) include direct fracture site visibility, good control, especially of the proximal fragment, with ease of exact anatomical fracture reduction, using the full range of available osteosynthesis techniques (Tboma, 1945; Messer, 1972; Koberg and Momma, 1978; Brown and Obeid, 1984). In contrast to these clear advantages, the simple presence of a facial scar concerns ma W patients. In addition, iatrogenic facial nerve damage, whether temporary or permanent, is a further deterrent to pre-auricular or submandibular access (Kitayama, 1989). In an attempt to lessen the risk of damage to the facial nerve, the use of the submandibular route has been advocated (Messer, 1972; Peters et al., 1976), although the attendant restriction of poor fracture site visibility is recognised. The problems common to extra-oral approaches have led many authors to explore the intra-oral route when dealing with sub-condylar fractures (Steinhduser, 1964; Pape et al., 1980; Kitayama, 1989). The stimulus to this development was in part the success of the routine approach to the ascending ramus as described by Obwegeser (1963). All subsequently described techniques using these methods have suffered restriction of access to the fracture site, because of the presence of the coronoid process (Steinhduser, 1964). To overcome the difficulty, we decided to attempt a transcoronoidal approach.
We believe that the use of a temporary coronoidotomy, as described here, addresses one of the basic problems, i.e. the restriction of access occasioned by the coronoid process itself. The advantages of this procedure are numerous: - The risk of facial nerve damage is substantially reduced. - There are no facial scars. - Surgical trauma is within acceptable limits, direct access to the condylar fracture is achieved with relative ease. - Repositioning of the condylar head in the glenoid fossa is facilitated. We would like to emphasise, that we do not advocate routine open reduction of sub-condylar fractures. This procedure should be reserved for those cases, few in number, which on critical reflection, warrant open reduction. Acknowledgements We wish to thank Frau Brigitte Schulte for her help in typing this paper and Frau Anne M~inster-Erkeling for her photographic assistance. References
A1-Kayat, A., P. Bramley: A modified pre-auricular approach to the temporomandibular joint and malar arch. Br. J. Oral Surg. 17 (1979-1980) 91 Brown, A. E., G. ObeM: A simplified method for the internal fixation of fractures of the mandibular condyle. Br. J. Oral Maxillofac. Surg. 22 (1984) 145 Cook, IL M., W. I. MacFarlane: Subcondylar fracture of the mandible. Oral Surg. 27 (1969) 297 Kitayama, S.: A new method of intraoral open reduction using a screw applied through the mandibular crest of condylar fractures. J. Cran.-Max.-Fac. Surg. 17 (1989) 16 Koberg, W. R., W. G. Momma: Treatment of fractures of the articular process by functional stable osteosynthesis using miniamrised dynamic compression plates. Int. J. Oral Surg. 7 (1978) 256 MacLennan, W. D.- Consideration of 180 cases of typical fracture of the mandibular condylar process. Br. J. Plast. Surg. 5 (1952) 122
A TranscoronoidalApproach of Fractures of the Condylar Neck MacLennan, W. D.: Fractures of the mandibular condylar process. Br.J. Oral Surg. 7 (1969) 31 Messer, E. J.: A simplified method for fixation of the fractured mandibular condyle. J. Oral Surg. 30 (1972) 442 Miiller, W.: Die Therapie der Gelenkfortsatzfrakturen. Zahn-, Mund- und Kieferheilk. 64 (1976) 496 Obwegeser, H.: The indications for surgical correction of mandibular deformity by the sagittal splitting technique. Br. J. Oral Surg. 1 (1963) 157 Pape, H. D., H. Hauenstein, K. L. Gerlach: Chirurgische Versorgung der Gelenkfortsatzfrakturen mit Miniplatten. Fortschr. Kiefer-Gesichts-Chir. 25 (1980) 81 Peters, A. R., J. B. Caldwell, T. W. Olsen: A technique for open reduction of subcondylar fractures. Oral Surg. 41 (1976) 273 Petzel, J. R.: Functional stable traction-screw osteosynthesis of condylar fractures. J. Oral Maxillofac. Surg. 40 (1982) 108 Rowe, N. L., H. C. Killey: Fractures of the facial skeleton. 2nd Ed. Livingstone, Edinburgh and London (1968) 164 Steinh~iuser, E.: Eingriffe am Processus articularis auf dem oralen Weg. Dtsch. Zahnfirztl. Z. 19 (1964) 694
J. Cranio-Max.-Fac. Surg. 18 (1990)
351
Takenoshita, Y., M. Oka, H. Tashiro: Surgical treatment of fractures of the mandibular condylar neck. J. Cran.-Max.-Fac. Surg. 17 (1989) 119 Thoma, K. H.: Fractures and fracture dislocation of the mandibular condyle: A method for open reduction and internal wiring and one for skeletal fixation with a report of 32 cases. J. Oral Surg. 3 (1945) 3 Timmel, R.: Die operative Behandlung der Luxationsfraktur des Kieferk6pfchens. Ost. Z. Stom. 79 (1982) 190 Wassmund, M.: Die Chirurgie des Kiefergelenkes. Zahn-, Mund-, Kieferheilk. In: Vortrfigen, Hanser, Mfinchen (1951) 6 Zide, M. F., J. M. Kent: Indications for open reduction of mandibular condylar fractures. J. Oral Maxillofac. Surg 41 (1983) 89 Prof. Dr. Dr. G. Habel Klinik u. Poliklinik fiir Mund- u. Kiefer-Gesichtschirurgie Westfdlische Wilhelms-Universita't Waldeyerstr. 30 D4400 Miinster Germany