Further development of titanium miniplate fixation for mandibular fractures. Experience gained and questions raised from a prospective clinical pilot study with 2.0 mm fixation plates Rainer Schmelzeisen, 1 Terry McIff,2 Berton Rahn 2
t Department of Oral and Maxillo-Facial Surgery, Medical University of Hannover (Head." Prof. J.-E. Hausamen, MD, DMD), Hannover, Germany, 2Laboratory for Experimental Surgery (Head: Prof. S. M. Perren, MD, DD), Davos, Switzerland.
S U M M A R Y . Miniplate systems are often used instead of more rigid systems for the treatment of mandibular fractures. While the most stable fixation method for all mandibular fractures is the 2.7 mm plate, most fracture sites and types are eminently suitable for miniplate fixation via an intraoral approach. However, the relatively low stability of the miniplate systems compared with rigid plate systems limits the indications for their use in mandibular fracture treatment, especially when immediate postoperative function is desired. A more rigid miniplate which provides increased stability was studied. The results of a preliminary study and a clinical trial of a 2.0 mm titanium miniplate system are presented in this paper. The therapeutic consequences of the lesser stability afforded by small plate systems are discussed. Indications for miniplate fixation without additional immobilization are reviewed.
KEY W O R D S : Mandibular fractures- Miniplate fixation- Titanium 2.0 miniplates
INTRODUCTION The 2.7 mm AO plate system developed in the 1970's for the surgical treatment of lower jaw fractures allowed immediate mobilization and function following mandibular surgery (Spiessl and Schargus, 1971; Sehilli, 1975). Thereby, the disadvantages of postoperative intermaxillary immobilization (IMF), such as compromised speech, difficulty in feeding, employment disability, social isolation and weight loss, could be avoided. Smaller plate systems which use monocortical screws (Champy and Eodde, 1976; Pape et al., 1983 ; Champy et al., 1986) as well as new surgical techniques favouring the intraoral approach (Sehilli, 1975; Raveh and Neiger, 1978; Gerlach and Pape, 1980; Gauthier and Allaire 1983; Luhr et al., 1985) offered new advantages. This approach minimizes tissue traumatization in anterior fracture sites and facilitates preservation of the periosteal btood supply. In general, operation time was shortened and damage to the facial nerve was avoided. Excellent clinical results have been obtained from large patient groups (Gerlach et al., 1985) who were treated by small plate fixation of mandibular fractures using this simplified surgical technique. These results demonstrate the feasibility of utilizing, in many cases, less rigid 1.5 mm or 2.0 mm plate systems (Champy and Lodde, 1976; Champy et al., 1976, Ewers and Hiirle, 1982; Brown et al., 1989) in place of the rigid 2.7 mm AO plate system. Although some surgeons use no additional postoperative IMF following miniplate fixation (Gerlach et al., 1985), others frequently use immobilization (Mommaerts and Engelke, 1986) to ensure stability,
particularly for complicated fractures with unfavourable soft tissue conditions (Weber et al., 1990). Since 1979, miniplate fixation has been the treatment of choice at the Department of Oral and Maxillofacial Surgery at the Medical University of Hannover; it has been performed in more than 300 mandibular fractures. Provided that there is no additional fracture of the condyle, postoperative intermaxillary immobilization is generally maintained for 7 days. This allows undisturbed wound healing and maintenance of fracture alignment even under unfavourable conditions in the initial phase. In contrast to the miniplates, there is no need for intermaxillary fixation when the 2.7 mm plates are used. The bulky 2.7 mm system provides very rigid fixation, but the stiffness of the plates and the extraoral technique makes for a much more demanding technique. Thus, the aim of our study was to test an implant with intermediate properties, i.e. having smaller dimensions than the 2.7 mm system while still possessing greater rigidity than conventional miniplates. MATERIALS AND METHODS A 2.0 mm titanium plate prototype was developed to provide sufficient resistance to bending for immediate or early postoperative function in selected fracture cases. Four- and six-hole miniplates with and without mid-span extension bars were manufactured. The plate set includes specially pre-bent six-hole plates for angle fractures to avoid weakening of the plate by multiple bending/adaptation procedures. 2 mm di251
252
Journal of Cranio-Maxillo-Facial Surgery
Fig. 2 - Opening of the inferior fracture gap with load applied in front of the fracture in a three dimensional in vitro model.
Fig. 1 - 2.0 m m p l a t e prototypes for mandibular fractures. Prebent 6-hole plates for fractures of the angle of the mandible and 2.4 m m emergency screw.
n 29
30
ameter screws from the existing AO maxillofacial 2.0 mm plate set were inserted and tightened in 1.5 mm drill holes to fix the plate to the bond. 2.4 mm diameter screws were employed as emergency screws (Fig. 1). In vitro investigations were performed using the titanium prototypes for fixation of standardized fractures (Rozema et al. 1989, Kroon et al., 1991) in a three-dimensional model. In this model, the condyles of polyurethane mandibles are positioned in a testing machine in silicone rubber sockets, which simulate the condylar fossae (Fig. 2). Muscle forces acting on the mandible are simulated through a system of wires attached to the mandible and running over pulleys. 'Biting forces' are applied by loading the mandible at different locations. Force transducers are used to measure the various loads and strain gauge transducers are used to measure the opening of the fracture gaps at the superior and inferior border and at the lingual surface of the mandible. The mandibles are loaded and continuous measurements are taken using a computer.
25
22
20 15 10 5 0 Median/Paramedian
Body
Angle
Fig. 3. - Sites of mandibular fractures treated with the 2.0 m m prototype plate, n = 66.
In a pilot clinical study, various residents from our department treated 43 patients with a total of 66 mandibular fractures, using 92 of the 2.0 titanium prototypes. The male/female ratio was 4:1 and patient ages ranged from 15-65 years. Fracture sites are listed in Figure 3. There were 23 unilateral and 20 multiple fractures. 12 patients had unilateral and 4 had additional bilateral fractures of the condyle, 3
Days of IMF 6 5 4 3 2
2
2
1 0
o
o
o
o
o
o1-1
1
2
3
4
5
6
[] Isolated Fractures
o
7
8
9
o
o
o
o
o
o
o
o
10 11 12 13 14. 15 16 17 18 19 20
[ ] Multiple Fractures
Fig. 4 - Duration of intermaxillary fixation and fracture types < 5 days. n = 2.
[] Fractures and Plate Fixation of Condylar Fracture
Further development of titanium miniplate fixation for mandibular fractures
253
Days of IMF 30
28
28
1
2
28
20
10
0
3
4
5 6 7 No. of Patient
[ ] Isolated Fractures
8
9
10
[] Multiple Fractures
Fig. 5 - Duration of intermaxillary fixation > 5 days n = 10.
Days of IMF 5O 42 40
35 28
30
28
21 10
f
0
N®~,4
0V-- q 1
2
3
4
[] Unilateral Fig. 6
5
7 8 6 No. of Patient
9
10
11
12
13
[] Bilateral Condylar Fracture
Duration of intermaxillary fixation. Isolated fractures and condylar fractures, n = 13.
unilateral condylar fractures were also treated surgically with the 2.0 mm plates. In general, plate fixation was performed 7 days following trauma. Prior to plate fixation, Ernst ligatures for intermaxillary fixation were applied, in order to re-establish the occlusion. In 20 patients, the ligatures were removed immediately postoperatively usually after radiological checking of fracture alignment, and if no concomitant fractures of the condyle were present (Fig. 4). In 13 patients, IMF was maintained for 2 weeks on average because of additional condylar fractures, 10 patients without additional condylar fractures were forbidden immediate postoperative mouth opening according to the individual surgeon's impression of the fracture conditions (Figs 5 and 6). The patients were put on a liquid or soft diet for three weeks. 42 of the plates were removed 4-6 months postoperatively.
RESULTS
Measurements of the fracture gap in the in vitro model demonstrated that the 2.0 mm mandibular plate prototypes provided a significantly higher resistance to displacement compared with that provided by conventional stainless steel plates (Champy system). In the case of fractures located at the angle of the mandible, a site which demands a plate with a high bending strength in order to compensate for the masticatory forces, the superior bending resistance of the 2.0 prototype was apparent, especially when simulated biting forces exceeding 60 N were applied (Fig. 7). During our clinical pilot study in which 92 titanium prototype implants were used, bone healing took place in all cases without evidence of osteomyelitis.
254 Journal of Cranio-Maxillo-Facial Surgery
DISLOCATION (exp. fractures)
inferior border
lingual
N
Ti-plate (prototype)
N
t
/
Ti-plate (prototype) q
/
IO0
///~ . . . .
Champy
q
100
/ / ./ / / / " /I
// !/
5O
O
0
P
50
I
I
I
~ 1
I
5
I
I
10 mm
0
0
5
10 mm
Fig. 7 - In vitro results of the plate resistance to bending for an experimental fracture in the angle of the mandible.
No. of complications 14
Total 13
12 10
Total 9
8
Total 7
Total 7
I i
Duration of IMF
0
I M 5 days
[] Wound Healing Imp.
Isolated Fractures Multiple Fractures Fracture + Condyla Fracture(s)+ Bilate
Complications following 2.0
25
F+C
I M > 5 days
Angle
treatment concept, n = 43.
Nonunion occurred in one patient with a bilateral fracture of the mandible. No plate had to be removed in the immediate postoperative period due to infection or screw loosening. Although all prototype plates provided reliable anatomical reduction and stable fixation of the fractures, plate application was slightly more demanding compared with conventional miniplates due to the higher bending resistance of the prototype plate. Application of the pre-bent plates for fractures in the mandibular angle required less bending than usual (i.e. for conventional plates) and was therefore less demanding. None of the 42 plates which were removed 4-6 months postoperatively showed signs of screw loosening. There were 3 mucosal wound healing impairment which had had no apparent influence on bone healing of the mandibular fracture. These were treated and all resolved within 5-6 days post-
Further development of titanium miniplate fixation for mandibular fractures
operatively. All 3 wound healing impairments appeared in association with multiple fractures. 4 minor occlusal disharmonies occurred, of which 3 could be corrected by occlusal adjustment. The other occlusal disturbance was treated by the insertion of a repaired fixed denture. In this case, an anterior multifragmentary fracture with loss of bone fragments was treated with miniplates (Figs 8 and 9). Temporary mental nerve hyperaesthesia with a tendency for improvement of sensibility was seen in one patient 2 months after plate fixation of a paramedian fracture.
DISCUSSION In a three-dimensional in vitro model, it was shown that the new 2.0 mm titanium prototype plate has increased bending resistance compared with conventional stainless steel plates. In our pilot clinical study of the treatment of mandibular fractures with this 2.0 mm plate, reliable bone healing took place in all cases but one. In this patient, primary intraoperative anatomical alignment of the fracture had not been achieved. In comparison, studies of other miniplate systems found either zero (Ikemura et al., 1988; Weber et al., 1990) or low rates of malunion (Gerlach et al., 1985; Wald et al., 1988) following fixation. A low malunion rate following rigid internal fixation has also been reported with the Luhr system (Ardary, 1989) as well as with the 2.7 mm AO plate system (Raveh et al., 1987). Results in the literature cannot be compared directly (because the indications for the choice of treatment and all treatment modalities are not always stated) but the cited causes of complications following each type of surgical procedure are similar. Although interfragmentary compression of a lower jaw fracture is not a necessary precondition for bone healing (Worthington and Champy, 1987; Ewers and Hiirle, 1982) and can even lead to fracture gap opening at the superior and lingual aspects of the mandible (Schlien et al., 1988), sufficient stability of the fragment is mandatory for undisturbed healing (Prein and Beyer, 1990). On the other hand the pre-existence of infection in itself is not necessarily correlated with disturbance in bone healing, even in miniplate fixation of mandibular fractures (Johansson et al., 1988). In accordance with other authors, we believe severe complications such as osteomyelitis or malunion to be the result of a combination of several factors of which a lack of stability in combination with pre-existing or new infection is significant (Jackson et al., 1986; Krebs, 1988; Ardary, 1989; Prein and Beyer, 1990). A lack of stability can result from the inadequate stiffness of the plating system (Raveh et al., 1987) frequently requiring additional intermaxillary immobilization, especially for complicated fractures. Instability can also occur with a highly rigid but technically more demanding system such as the 2.7 mm plate system when it is applied incorrectly (Prein and Beyer, 1990). Post-fixation complications occur more often in the angle region of the mandible (Gerlach, 1982; Kai Tu
255
and Tenhulzen, 1985; Jackson et al., 1986; Ikemura et al., 1988; Ardary, 1989); This is particularly important because fractures in this region comprise 23~42 % of all mandibular fractures (Pape et al., 1983; Wald et al., 1988). Klotch and Prein (1987) describe 4 out of 5 delayed fractures of reconstruction plates following reconstruction of resections of the angle of the mandible, demonstrating the great forces acting in this region due to normal mandibular function. We conclude that, if immediate postoperative function is desired, the surgeon must use judgement in selecting the appropriate fixation system for different types of fracture. In our clinical experience, most of the mandibular fractures are suitable for fixation via an intraoral approach, using plates which offer less stability than the 2.7 mm system. Many fracture sites and conditions also allow for the removal of I M F immediately postoperatively. Although we have seen good results in the treatment of displaced fractures of the mandibular angle using small dimension plates (i.e. using the Champy system and the titanium prototypes), the necessary stability which allows for immediate postoperative function can, in some cases, only be achieved through the use of the 2.7 mm system. Many complex lower jaw fractures demand rigid stabilization with the 2.7 mm fixation plates or with reconstruction plates. Defect fractures of the lower jaw are also not considered suitable for any kind of miniplate osteosynthesis. In general, treatment of edentulous jaw fractures should be performed predominantly with rigid internal fixation methods using 2.7 mm plates. Regardless of the fixation method being used, the intraoral approach should be used whenever possible due to the low overall complication rate (Luhr et al., 1985; Raveh et al., 1987) and the better aesthetic results afforded by such an approach. Also, titanium plates should be preferred, as the metal released from titanium plates used in mandibular fractures is significantly lower than that from stainless steel plates (Moberg et al., 1989). Depending on the patient's individual preference, we would prefer intermaxillary fixation for 7 days after miniplate fixation in addition, instead of creating an extraoral scar, especially in fractures of the angle of the mandible where fixation by the 2.7 mm plate from an intraoral approach is technically extremely demanding. Clinical results from large patient group trials (Gerlach et al., 1985) show low complication rates following miniplate fixation. Nevertheless, experiments must be continued to obtain more information about the causes of complications following miniplate fixation and to clarify the indications for the use of the various plates. The preliminary results from our clinical pilot study do not serve as a proven general treatment recommendation; an enlarged clinical trial, involving several maxillofacial centres, is in progress to evaluate further the new 2.0 mm plates. This study should be regarded as a basis for further discussion of mandibular fracture stabilization using either the 2.0 mm miniplate or 2.7 mm plate systems. While the fixation systems which are already on the
256 Journal of Cranio-Maxillo-Facial Surgery
market are quite reliable, the surgeon must aim to promote the patient's quality of life postoperatively by choosing a fixation method which avoids encumbrances such as long periods of intermaxillary fixation, extraoral scars and nerve and tissue damage during placement and removal of the osteosynthesis device.
CONCLUSIONS Minip[ate fixation is the treatment of choice in the Department of Oral and Maxillofacial Surgery at the Medical University of Hannover. A lack of stability is associated with many complications following plate fixation of mandibular fractures, especially if immediate postoperative function is desired. A preliminary report on the results of a clinical pilot study using specially designed 2.0 mm titanium miniplates with increased resistance to bending is presented. Summarizing our clinical experience, we consider miniplate fixation to be the method of choice for treatment of most mandibular fractures when proper selection of patients and fracture types is made. If immediate postoperative function is desired, the more stable titanium 2.0 mm plates seem to be indicated. A 2.7 mm plate is not always needed, but also a miniplate is not always sufficient.
Acknowledgements We wish to thank Professor Prein, Kantonsspital Basel, and Franz Kroon, Amsterdam for scientific cooperation on this paper.
References Ardary, W. C. : Treatment of mandibular fractures. J. Oral Maxillofac. Surg. 47 (1989) 1153 Brown, J. S., M. Trotter, J. Cliffe, R. P. Ward-Booth, E. D. Williams: The fate of miniplates in facial trauma and orthognathic surgery: A retrospective study. Br. J. Oral Maxillofac. Surg. 27 (1989) 306 Champy, M., or. P. Lodde : Syntheses mandibulaires. Localisation des syntheses en fonction des contraintes mandibulaires. (Justification de la position des plaques d'osteosynthese en fonction de la Iocalisation des contraintes). Rev. Stomat. (Paris) 77 (1976) 971 Champy, M., H. D. Pape, K. D. Gerlach, J. P. Lodde ." Mandibular fractures. The Strasbourg Miniplate Osteosynthesis. In: Krtiger, K. (ed.): Oral and Maxillofacial Trauma. Quintessence, Chicago-Berlin, 1986, p. 19 Ewers, R., F. Hiirle: Biomechanics of the midface and mandibular fractures: Is a stable fixation necessary? Proceedings from the 8th International Conference on Oral and Maxillofaciai Surgery. Quintessence, Chicago-Berlin, 1985, p. 207 Gauthier, P., D. Allaire: Un nouveau mode de traitement des fractures mandibulaires: microplaques et vis. Union Med. Canada 112 (1983) 1028 Gerlach, K. L., H. D. Pape : Prinzip und Indikation der Miniplattenosteosynthese. Dtsch. Zahngrztl. Z. 35 (1980) 346 Gerlach, K. L.." Miniplattenosteosynthese bei Unterkiefer- und Mittelgesichtsfrakturen. Med. Diss, Universit/it K61n, 1982 Gerlach, K. L., M. Khouri, H. D. Pape, M. Champy: The Strasbourg miniplate osteosynthesis. Proceedings from the 8th International Conference on Oral and Maxillofacial Surgery. Quintessence, Chicago-Berlin, 1985, p. 138 Ikemura, K., H. Hidaka, T. Etoh, K. Kabata: Osteosynthesis in
facial bone fractures using miniplates. Clinical and experimental studies. J. Oral Maxillofac. Surg. 46 (1988) 10 Jackson, L 7"., D. C. Somers, J. G. Kjar : The use of Champy miniplates for osteosynthesis in craniofacial deformities and trauma. Plast. Reconstr, Surg. 77 (1986) 729 Johansson, B., L. Krekmanov, M. Thomsson ." Miniplate osteosynthesis in infected mandibular fractures. J. CranioMax.-Fac. Surg. 16 (1988) 22 Kai Tu, H., D. Tenhulzen : Compression osteosynthesis of mandibular fractures: A retrospective study. J, Oral Maxillofac. Surg. 43 (1985) 585 Klotch, D. IV., J. Prein : Mandibular reconstruction using AO plates. Am. J. Surg. 154 (1987) 384 Krebs, F. J. : Dynamic compression plating in treatment of the fractured edentulous mandible. Laryngoscope 98 (1988) 198 Kroon, F. H., M. Mathison, J. R. Cordey, B. A, Rahn." The use of miniplates in mandibular fractures. J. Cranio-Max-Fac Surg. 19 (1991) 199 Luhr, H. G., R. Drommer, V. H6lscher, H. W. Schauer: Comparative studies between the extraoral and intraoral approach in compression - osteosynthesis of mandibular fractures. Proceedings from the 8th International Conference on Oral and Maxillofacial Surgery. Quintessence, ChicagoBerlin, 1985, p. 133 Moberg, L. E., A. Nordenram, O. Kjellmann : Metal release from plates used in jaw fracture treatment. Int. J. Oral Maxillofac. Surg. 18 (1989) 311 Mommaerts, M. Y., W. Engelke : Erfahrungen mit der Osteosyntheseplatte nach Champy/Lodde bei Unterkieferfrakturen. Dtsch. Z. Mund-Kiefer-Gesichstchir. I0 (1986) 94 Pape, H. D., M. Herzog, K. L. Gerlach ." Der Wandel der Unterkieferfrakturversorgung yon 1950-1980 am Beispiel der K61ner Klinik, Dtsch. Zahn~irztl. Z. 38 (1983) 301 Prein, J., M. Beyer: Management of infection and nonunion in mandibular fractures. Oral Maxillofac. Surg. Clin. North Am. 2 (1990) 187 Raveh, or., M. Neiger : Zur Behandlung der Unterkieferfrakturen mit Kompressionsosteosynthese. Aktuel. Probl. Otorhinolaryngol. 1 (1978) 23 Raveh, J., 7". Vuillemin, K. Liidrach, M. Roux, F. Sutter. Plate Osteosynthesis of 367 mandibular fractures. J. CranioMaxFac. Surg. 15 (1987) 244 Rozema, F. R., R. R. M. Bos, G. Boering, J. W. Leenslag, A. J. Pennings." Experimental fractures of the mandibular body of sheep and dogs. A new technique. Br. J. Oral Maxillofac. Surg. 27 (1989) 163 Schilli, W.: Indikation und Technik der stabilen Osteosynthese im Unterkiefer. Fortschritte Kiefer-Gesichtschirurgie 19 (1975) 79 Schlien, H. P., W. Hillebrand, R. Becker, G. Habel: Vergleichende Untersuchungen mit osteosynthesen am frakturmodell. Dtsch. Z. Mund-, Kiefer-Gesichtschir. 12 (1988) 120 tunktionsstabilen Osteosynthese des bezahnten Unterkiefers. Dtsch. Z. Zahn-, Mund- Kieferheilk. 57 (1971) 295 Wald, R. M., E. Abemayor, J. Zemplenyi, C. Mannai, M. A. Lesavoy: The transoral treatment of mandibular fractures using noncompression miniplates: A prospective study. Ann. Plast. Surg. 20 (1988) 409 Weber, N., J. Reuther, C. Michel, J. Mfihling : Erfahrungen bei der Versorgung von Gesichtssch/idelfrakturen mit dem Wfirzburger Titan-miniplattensystem. Dtsch. Z. Mund-KieferGesichts.chir. 14 (1990) 46 Worthington, P., M. Champy : Monocortical miniplate osteosynthesis. Otolaryngol. Clin. North Am. 20 (1987) 607 Rainer Schmelzeisen, MD, DDS Department of Oral and Maxillo-Facial Surgery Medical University of Hannover Konstanty-Gutschow-Str. 8 3000 Hannover 61 Germany Paper submitted 15 November 1991 Accepted 3 February 1992
t Department of Oral and Maxillo-Facial Surgery, Medical University of Hannover (Head." Prof. J.-E. Hausamen, MD, DMD), Hannover, Germany, 2Laboratory for Experimental Surgery (Head: Prof. S. M. Perren, MD, DD), Davos, Switzerland.
S U M M A R Y . Miniplate systems are often used instead of more rigid systems for the treatment of mandibular fractures. While the most stable fixation method for all mandibular fractures is the 2.7 mm plate, most fracture sites and types are eminently suitable for miniplate fixation via an intraoral approach. However, the relatively low stability of the miniplate systems compared with rigid plate systems limits the indications for their use in mandibular fracture treatment, especially when immediate postoperative function is desired. A more rigid miniplate which provides increased stability was studied. The results of a preliminary study and a clinical trial of a 2.0 mm titanium miniplate system are presented in this paper. The therapeutic consequences of the lesser stability afforded by small plate systems are discussed. Indications for miniplate fixation without additional immobilization are reviewed.
KEY W O R D S : Mandibular fractures- Miniplate fixation- Titanium 2.0 miniplates
INTRODUCTION The 2.7 mm AO plate system developed in the 1970's for the surgical treatment of lower jaw fractures allowed immediate mobilization and function following mandibular surgery (Spiessl and Schargus, 1971; Sehilli, 1975). Thereby, the disadvantages of postoperative intermaxillary immobilization (IMF), such as compromised speech, difficulty in feeding, employment disability, social isolation and weight loss, could be avoided. Smaller plate systems which use monocortical screws (Champy and Eodde, 1976; Pape et al., 1983 ; Champy et al., 1986) as well as new surgical techniques favouring the intraoral approach (Sehilli, 1975; Raveh and Neiger, 1978; Gerlach and Pape, 1980; Gauthier and Allaire 1983; Luhr et al., 1985) offered new advantages. This approach minimizes tissue traumatization in anterior fracture sites and facilitates preservation of the periosteal btood supply. In general, operation time was shortened and damage to the facial nerve was avoided. Excellent clinical results have been obtained from large patient groups (Gerlach et al., 1985) who were treated by small plate fixation of mandibular fractures using this simplified surgical technique. These results demonstrate the feasibility of utilizing, in many cases, less rigid 1.5 mm or 2.0 mm plate systems (Champy and Lodde, 1976; Champy et al., 1976, Ewers and Hiirle, 1982; Brown et al., 1989) in place of the rigid 2.7 mm AO plate system. Although some surgeons use no additional postoperative IMF following miniplate fixation (Gerlach et al., 1985), others frequently use immobilization (Mommaerts and Engelke, 1986) to ensure stability,
particularly for complicated fractures with unfavourable soft tissue conditions (Weber et al., 1990). Since 1979, miniplate fixation has been the treatment of choice at the Department of Oral and Maxillofacial Surgery at the Medical University of Hannover; it has been performed in more than 300 mandibular fractures. Provided that there is no additional fracture of the condyle, postoperative intermaxillary immobilization is generally maintained for 7 days. This allows undisturbed wound healing and maintenance of fracture alignment even under unfavourable conditions in the initial phase. In contrast to the miniplates, there is no need for intermaxillary fixation when the 2.7 mm plates are used. The bulky 2.7 mm system provides very rigid fixation, but the stiffness of the plates and the extraoral technique makes for a much more demanding technique. Thus, the aim of our study was to test an implant with intermediate properties, i.e. having smaller dimensions than the 2.7 mm system while still possessing greater rigidity than conventional miniplates. MATERIALS AND METHODS A 2.0 mm titanium plate prototype was developed to provide sufficient resistance to bending for immediate or early postoperative function in selected fracture cases. Four- and six-hole miniplates with and without mid-span extension bars were manufactured. The plate set includes specially pre-bent six-hole plates for angle fractures to avoid weakening of the plate by multiple bending/adaptation procedures. 2 mm di251
252
Journal of Cranio-Maxillo-Facial Surgery
Fig. 2 - Opening of the inferior fracture gap with load applied in front of the fracture in a three dimensional in vitro model.
Fig. 1 - 2.0 m m p l a t e prototypes for mandibular fractures. Prebent 6-hole plates for fractures of the angle of the mandible and 2.4 m m emergency screw.
n 29
30
ameter screws from the existing AO maxillofacial 2.0 mm plate set were inserted and tightened in 1.5 mm drill holes to fix the plate to the bond. 2.4 mm diameter screws were employed as emergency screws (Fig. 1). In vitro investigations were performed using the titanium prototypes for fixation of standardized fractures (Rozema et al. 1989, Kroon et al., 1991) in a three-dimensional model. In this model, the condyles of polyurethane mandibles are positioned in a testing machine in silicone rubber sockets, which simulate the condylar fossae (Fig. 2). Muscle forces acting on the mandible are simulated through a system of wires attached to the mandible and running over pulleys. 'Biting forces' are applied by loading the mandible at different locations. Force transducers are used to measure the various loads and strain gauge transducers are used to measure the opening of the fracture gaps at the superior and inferior border and at the lingual surface of the mandible. The mandibles are loaded and continuous measurements are taken using a computer.
25
22
20 15 10 5 0 Median/Paramedian
Body
Angle
Fig. 3. - Sites of mandibular fractures treated with the 2.0 m m prototype plate, n = 66.
In a pilot clinical study, various residents from our department treated 43 patients with a total of 66 mandibular fractures, using 92 of the 2.0 titanium prototypes. The male/female ratio was 4:1 and patient ages ranged from 15-65 years. Fracture sites are listed in Figure 3. There were 23 unilateral and 20 multiple fractures. 12 patients had unilateral and 4 had additional bilateral fractures of the condyle, 3
Days of IMF 6 5 4 3 2
2
2
1 0
o
o
o
o
o
o1-1
1
2
3
4
5
6
[] Isolated Fractures
o
7
8
9
o
o
o
o
o
o
o
o
10 11 12 13 14. 15 16 17 18 19 20
[ ] Multiple Fractures
Fig. 4 - Duration of intermaxillary fixation and fracture types < 5 days. n = 2.
[] Fractures and Plate Fixation of Condylar Fracture
Further development of titanium miniplate fixation for mandibular fractures
253
Days of IMF 30
28
28
1
2
28
20
10
0
3
4
5 6 7 No. of Patient
[ ] Isolated Fractures
8
9
10
[] Multiple Fractures
Fig. 5 - Duration of intermaxillary fixation > 5 days n = 10.
Days of IMF 5O 42 40
35 28
30
28
21 10
f
0
N®~,4
0V-- q 1
2
3
4
[] Unilateral Fig. 6
5
7 8 6 No. of Patient
9
10
11
12
13
[] Bilateral Condylar Fracture
Duration of intermaxillary fixation. Isolated fractures and condylar fractures, n = 13.
unilateral condylar fractures were also treated surgically with the 2.0 mm plates. In general, plate fixation was performed 7 days following trauma. Prior to plate fixation, Ernst ligatures for intermaxillary fixation were applied, in order to re-establish the occlusion. In 20 patients, the ligatures were removed immediately postoperatively usually after radiological checking of fracture alignment, and if no concomitant fractures of the condyle were present (Fig. 4). In 13 patients, IMF was maintained for 2 weeks on average because of additional condylar fractures, 10 patients without additional condylar fractures were forbidden immediate postoperative mouth opening according to the individual surgeon's impression of the fracture conditions (Figs 5 and 6). The patients were put on a liquid or soft diet for three weeks. 42 of the plates were removed 4-6 months postoperatively.
RESULTS
Measurements of the fracture gap in the in vitro model demonstrated that the 2.0 mm mandibular plate prototypes provided a significantly higher resistance to displacement compared with that provided by conventional stainless steel plates (Champy system). In the case of fractures located at the angle of the mandible, a site which demands a plate with a high bending strength in order to compensate for the masticatory forces, the superior bending resistance of the 2.0 prototype was apparent, especially when simulated biting forces exceeding 60 N were applied (Fig. 7). During our clinical pilot study in which 92 titanium prototype implants were used, bone healing took place in all cases without evidence of osteomyelitis.
254 Journal of Cranio-Maxillo-Facial Surgery
DISLOCATION (exp. fractures)
inferior border
lingual
N
Ti-plate (prototype)
N
t
/
Ti-plate (prototype) q
/
IO0
///~ . . . .
Champy
q
100
/ / ./ / / / " /I
// !/
5O
O
0
P
50
I
I
I
~ 1
I
5
I
I
10 mm
0
0
5
10 mm
Fig. 7 - In vitro results of the plate resistance to bending for an experimental fracture in the angle of the mandible.
No. of complications 14
Total 13
12 10
Total 9
8
Total 7
Total 7
I i
Duration of IMF
0
I M 5 days
[] Wound Healing Imp.
Isolated Fractures Multiple Fractures Fracture + Condyla Fracture(s)+ Bilate
Complications following 2.0
25
F+C
I M > 5 days
Angle
treatment concept, n = 43.
Nonunion occurred in one patient with a bilateral fracture of the mandible. No plate had to be removed in the immediate postoperative period due to infection or screw loosening. Although all prototype plates provided reliable anatomical reduction and stable fixation of the fractures, plate application was slightly more demanding compared with conventional miniplates due to the higher bending resistance of the prototype plate. Application of the pre-bent plates for fractures in the mandibular angle required less bending than usual (i.e. for conventional plates) and was therefore less demanding. None of the 42 plates which were removed 4-6 months postoperatively showed signs of screw loosening. There were 3 mucosal wound healing impairment which had had no apparent influence on bone healing of the mandibular fracture. These were treated and all resolved within 5-6 days post-
Further development of titanium miniplate fixation for mandibular fractures
operatively. All 3 wound healing impairments appeared in association with multiple fractures. 4 minor occlusal disharmonies occurred, of which 3 could be corrected by occlusal adjustment. The other occlusal disturbance was treated by the insertion of a repaired fixed denture. In this case, an anterior multifragmentary fracture with loss of bone fragments was treated with miniplates (Figs 8 and 9). Temporary mental nerve hyperaesthesia with a tendency for improvement of sensibility was seen in one patient 2 months after plate fixation of a paramedian fracture.
DISCUSSION In a three-dimensional in vitro model, it was shown that the new 2.0 mm titanium prototype plate has increased bending resistance compared with conventional stainless steel plates. In our pilot clinical study of the treatment of mandibular fractures with this 2.0 mm plate, reliable bone healing took place in all cases but one. In this patient, primary intraoperative anatomical alignment of the fracture had not been achieved. In comparison, studies of other miniplate systems found either zero (Ikemura et al., 1988; Weber et al., 1990) or low rates of malunion (Gerlach et al., 1985; Wald et al., 1988) following fixation. A low malunion rate following rigid internal fixation has also been reported with the Luhr system (Ardary, 1989) as well as with the 2.7 mm AO plate system (Raveh et al., 1987). Results in the literature cannot be compared directly (because the indications for the choice of treatment and all treatment modalities are not always stated) but the cited causes of complications following each type of surgical procedure are similar. Although interfragmentary compression of a lower jaw fracture is not a necessary precondition for bone healing (Worthington and Champy, 1987; Ewers and Hiirle, 1982) and can even lead to fracture gap opening at the superior and lingual aspects of the mandible (Schlien et al., 1988), sufficient stability of the fragment is mandatory for undisturbed healing (Prein and Beyer, 1990). On the other hand the pre-existence of infection in itself is not necessarily correlated with disturbance in bone healing, even in miniplate fixation of mandibular fractures (Johansson et al., 1988). In accordance with other authors, we believe severe complications such as osteomyelitis or malunion to be the result of a combination of several factors of which a lack of stability in combination with pre-existing or new infection is significant (Jackson et al., 1986; Krebs, 1988; Ardary, 1989; Prein and Beyer, 1990). A lack of stability can result from the inadequate stiffness of the plating system (Raveh et al., 1987) frequently requiring additional intermaxillary immobilization, especially for complicated fractures. Instability can also occur with a highly rigid but technically more demanding system such as the 2.7 mm plate system when it is applied incorrectly (Prein and Beyer, 1990). Post-fixation complications occur more often in the angle region of the mandible (Gerlach, 1982; Kai Tu
255
and Tenhulzen, 1985; Jackson et al., 1986; Ikemura et al., 1988; Ardary, 1989); This is particularly important because fractures in this region comprise 23~42 % of all mandibular fractures (Pape et al., 1983; Wald et al., 1988). Klotch and Prein (1987) describe 4 out of 5 delayed fractures of reconstruction plates following reconstruction of resections of the angle of the mandible, demonstrating the great forces acting in this region due to normal mandibular function. We conclude that, if immediate postoperative function is desired, the surgeon must use judgement in selecting the appropriate fixation system for different types of fracture. In our clinical experience, most of the mandibular fractures are suitable for fixation via an intraoral approach, using plates which offer less stability than the 2.7 mm system. Many fracture sites and conditions also allow for the removal of I M F immediately postoperatively. Although we have seen good results in the treatment of displaced fractures of the mandibular angle using small dimension plates (i.e. using the Champy system and the titanium prototypes), the necessary stability which allows for immediate postoperative function can, in some cases, only be achieved through the use of the 2.7 mm system. Many complex lower jaw fractures demand rigid stabilization with the 2.7 mm fixation plates or with reconstruction plates. Defect fractures of the lower jaw are also not considered suitable for any kind of miniplate osteosynthesis. In general, treatment of edentulous jaw fractures should be performed predominantly with rigid internal fixation methods using 2.7 mm plates. Regardless of the fixation method being used, the intraoral approach should be used whenever possible due to the low overall complication rate (Luhr et al., 1985; Raveh et al., 1987) and the better aesthetic results afforded by such an approach. Also, titanium plates should be preferred, as the metal released from titanium plates used in mandibular fractures is significantly lower than that from stainless steel plates (Moberg et al., 1989). Depending on the patient's individual preference, we would prefer intermaxillary fixation for 7 days after miniplate fixation in addition, instead of creating an extraoral scar, especially in fractures of the angle of the mandible where fixation by the 2.7 mm plate from an intraoral approach is technically extremely demanding. Clinical results from large patient group trials (Gerlach et al., 1985) show low complication rates following miniplate fixation. Nevertheless, experiments must be continued to obtain more information about the causes of complications following miniplate fixation and to clarify the indications for the use of the various plates. The preliminary results from our clinical pilot study do not serve as a proven general treatment recommendation; an enlarged clinical trial, involving several maxillofacial centres, is in progress to evaluate further the new 2.0 mm plates. This study should be regarded as a basis for further discussion of mandibular fracture stabilization using either the 2.0 mm miniplate or 2.7 mm plate systems. While the fixation systems which are already on the
256 Journal of Cranio-Maxillo-Facial Surgery
market are quite reliable, the surgeon must aim to promote the patient's quality of life postoperatively by choosing a fixation method which avoids encumbrances such as long periods of intermaxillary fixation, extraoral scars and nerve and tissue damage during placement and removal of the osteosynthesis device.
CONCLUSIONS Minip[ate fixation is the treatment of choice in the Department of Oral and Maxillofacial Surgery at the Medical University of Hannover. A lack of stability is associated with many complications following plate fixation of mandibular fractures, especially if immediate postoperative function is desired. A preliminary report on the results of a clinical pilot study using specially designed 2.0 mm titanium miniplates with increased resistance to bending is presented. Summarizing our clinical experience, we consider miniplate fixation to be the method of choice for treatment of most mandibular fractures when proper selection of patients and fracture types is made. If immediate postoperative function is desired, the more stable titanium 2.0 mm plates seem to be indicated. A 2.7 mm plate is not always needed, but also a miniplate is not always sufficient.
Acknowledgements We wish to thank Professor Prein, Kantonsspital Basel, and Franz Kroon, Amsterdam for scientific cooperation on this paper.
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