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Rigid internal fixation of mandibular fractures
Trauma and reconstructivesurgery
R gid !nternal fixation of mandibular fractures
Tateyuki lizuka, Christian Lindqvist Department of Oral and Maxiliofacial Surgery, IV Department of Surgery, Helsinki University Central Hospital, Helsinki, Finland
An analysis of 270 fractures treated using the A0/ASIF method T. Iizuka, C. Lindqvist: Rigid internal fixation of mandibular fractures. An analysis of 27Ofractures treated using the AO/ASIF method. Int. J. Oral Maxillofac. Surg. 1992; 21: 65-69. Abstract. The results are reported on 214 patients treated for 270 mandibular fractures, using rigid internal fixation. Of these, 172 fractures (63.7%) in 131 patients had been re-evaluated at final follow-up in connection with plate and screw removal, on average 15.2 months, postoperatively. Although one-third of the patients had a history of alcohol abuse, and 86% were treated with a delay of more than 24 h (mean 3.2 days), good primary bone healing was observed in 93.9% of the patients. Infections, seen in 6.1% of the patients, were related exclusively to inadequate stability of the fracture. Malocclusion, observed in 18.2% of 159 dentate patients, was caused by incorrect plate bending and insufficient fracture reduction. Immediate postoperative dysfunction of the inferior alveolar nerve in 58.1% of the cases, and of the mandibular branch of the facial nerve in 12.7%, was followed by almost total recovery 1 year after operation. It is concluded that rigid internal fixation is a reliable method of treatment, especially indicated for patients with reduced healing capacity and poor co-operation.
Fractures of the mandible are generally treated by closed or open reduction4'21. Open reduction, involving internal fixation, is used in displaced fractures. Common methods of fracture fixation include the use of wires, pins or plates, and screws. Sufficient stability of the fracture is always necessary for bone healing. If internal fixation does not result in rigid stability at the fracture, some form of supplementary fixation may be necessary. Traditional methods involve additional intermaxillary fixation (IMF), using arch bars and splints. There are, however, several disadvantages associated with IMF, including: compromised airway, poor oral hygiene, speech difficulties, impaired nutritional intake with weight loss, and disuse atrophy of the masticatory muscles. Problems in relation to I M F in patients with multiple injuries or with generalized disease, such as diabetes, alcoholism and epilepsy are well known. In recent years, rigid internal fixation allowing immediate mobilization of the mandible has won increasing acceptance as a method for treatment of man-
dibular fractures 2,16,18-2°,22,26. In our department the A O / A S I F (AO Study Group for Internal Fixation) technique of rigid internal fixation24 was introduced in 1983. Up to the end of 1989, 270 mandibular fractures in 241 patients had been treated with this method. In the same period 1,823 patients with fractures of the mandible were seen. The annual percentages of open reduction and osteosynthesis varied between 18% and 29% (mean 25%). In general, open surgery was used in fractures with displacement and/or instability of the horizontal part of the mandible. Nondisplaced fractures and condylar fractures were usually treated by I M F alone. Helsinki University Central Hospital serves the 1.5 million inhabitants of the greater Helsinki area and the southern part of Finland. The object of this paper is to report the results of an analysis on the treatment of mandibular fractures using rigid internal fixation with the A O / A S I F plates. Special attention was paid to the technical problems which could affect the number of complications and out-
Key words: trauma; mandibular fracture; rigid fixation. Accepted for publication 14 January 1992
come of treatment and to factors related to patients' general health and drug habits.
Material and methods Patients with mandibular fractures treated following the AO/ASIF principle of rigid internal fixation at the Department of OMF Surgery, Helsinki University Central Hospital, between 1983 and 1989 were reviewed. Fractures with substantial comminution and defects, usually resulting from gunshot injury, were excluded because the special characteristics of such fractures influence the analysis relating to fracture site. Sites and numbers of fractures, surgical approach, presence of a tooth in the line of fracture, and whether or not tooth extraction was undertaken were recorded. Complications were defined as infection, delayed union or non-union, malocclusion and postoperative nerve injuries (motor disturbance affecting the mandibular branch of the facial nerve and sensory disturbance affecting the inferior alveolar nerve). Fracture sites were categorized as I) symphyseal, 2) canine, 3) relating to the anterior body (in the region of the premolar teeth and the mental foramen), 4) relating to the
66
I i z u k a et al.
posterior body (in the region of the molar teeth), and 5) relating to the angular region. Associated condylar fractures were also taken into account. Postoperative follow-up examinations were performed at intervals of 1 or 2 weeks for 3 16 weeks (mean 7.1 weeks). Up until April 30, 1991, 172 fractures (63.7%) in 131 patients had been re-evaluated at final followup in connection with plate and screw removal, on average 15.2 months postoperatively (range 8 to 62 months). Twelve symphyseal fractures, 23 fractures of the canine region, 28 fractures of the anterior part of the body, 26 fractures of the posterior part of the body and 83 angular fractures were assessed. Panoramic radiographs were taken pre- and postoperatively in all cases. Surgical technique
In patients in whom the fiacture involved the tooth-bearing area of the mandible, intravenous antimicrobial therapy consisting of penicillin G (1 million IU), usually combined with metronidazole (500 mg) was administered on admission and given every 6 h preand intraoperatively. Antimicrobial therapy was continued perorally (penicillin V 1 million IU and metronidazole 500 mg evey 6 h) until the 7th day after surgery. The operation was performed under general anaesthesia with nasotracheal intubation. The occlusion was re-established by bimanual manipulation, and secured using dental arch bars and IME Fixation was reinforced, if necessary, with cold-cure acrylic resin. The fracture sites were approached transorally (58 cases) or extraorally (212 cases). The transoral approach was chosen only in cases where, in the opinion of the surgeon, sufficient reduction and stabilization of the fracture could be achieved using this approach. For the extraoral approach, a submandibular incision as described by SPmSSL24was used, taking care not to damage the mandibular branch of the facial nerve by isolating it in the superior site of the wound. A nerve detector was always used. The periosteum was elevated from the mandible, exposing the fracture line. Final fracture reduction and osteosynthesis were performed using the instruments of the Synthes ® mandibular bone plate system (Synthes, Paoli, PA, USA) and AO/ASIF technique24. The repositioning was performed using reduction forceps, usually of the compression-reduction type, fixed with ~10 mm cortical screws (o 2.7 mm) at the lower border of the mandible. An interdental wire ligature was always applied when the fracture was located within the dental arch. In angular fractures and fractures in edentulous mandibles, a tension band plate was used only in cases in which fracture reduction at the upper border of the mandible could not be achieved by use of reduction forceps. Fractures were stabilized using rigid stainless steel plates bent to fit the contour of the buccal aspect of the mandible and fixed by bicortical screws. At least 2 screws were
79 150 t
[]
INTRAORAL
IN r ~'T~AnRAI 100"
<10
10-19 20-29
30-39
40-49
50-5g
60-69 70-79
AGE GROUP
OSymphysis
Cani~
Anterior Body
Posterior Body
Angle
FRACTURE SITE
Fig. 1. Age and sex distributions of 214 patients with 270 mandibular fractures treated following the principles of AO/ASIF rigid internal fixation.
placed on each side of the fracture. After repeated irrigation, the wound was closed in layers, and suction drains were used for the first 24 h after operation. Results Patients' profile
The age and sex distributions of the 175 male and 39 female patients are shown in Fig. 1. The mean age of the patients was 33.9 years (range 8 to 83 years). In over half o f the cases (59.8%) external blows or kicks during assaults or fights were the cause of the fracture. Traffic accients (17.3%), slipping (9.8%) and falling (3.7%) were the next most common causes of fracture (Fig. 2). In 123 patients (57.5%) the accidents occurred at weekends, between Firday afternoon and Sunday evening. M o s t patients (154, 72.0%) at the time of the accident and 92 patients (43.0%) still on hospital admission had been under the influence of alcohol. One-third of the patients (72, 33.6%) had a history of alcohol abuse, often associated with unemployment a n d / o r vagrancy (29, 13.6%). According to the interview and evaluation by hospital social workers, patients with a history of alcohol abuse were defined as patients accustomed to ingesting large quantities of alcohol in an uncontrolled
Fig. 3. Fracture sites and surgical approach.
fashion and'regularly showing impaired social or occupational functioning. Because o f this, further social care or therapy had to be organized after primary fracture treatment. M o r e than half of the patients (119, 55.6%) had 2 or more fractures of the mandible. O f the 270 fractures treated using rigid fixation, 197 (73%) were located in a dentate mandible and 73 (27%) in an edentulous mandible. Fractures which were operated were most often angular (44.8%), followed by body (33.3%), canine (14.4%) and symphyseal fractures (7.4%) (Fig. 3). Sixty patients (28%) also had fractures in the subcondylar region. Bimaxillary fractures were diagnosed in 29 patients. Twenty-seven patients exhibited multiple injuries, including brain and thoraco-abdominal injuries, together with injuries to the extremities. Treatment using rigid fixation
The mean delay between accident and admission to hospital was 2.0 days (range 0 to 22 days). The average delay before surgery was 3.2 days (range 0 to 31 days). In only 30 patients was the fracture operated on within 24 h (14%) (Fig. 4). In most cases (212, 78.5%) the extraoral appf6ach was used, via submandib-
CAUSES OF INJURIES Fight
128 (59.8%)
and a~aug
37 (17.3%1
Traff¢ accident Slipping m
21 (9.8%1
Fallingfrom a height
g (3,7%)
BloWfrom an object
8 (3.7%)
latrogenlc
(o.9%1
Gunshot
2 (0.9%)
Miscelaneous
I. V3-7 ,,............ 20
40
60
80
100
120
NO. OF PATIENTS
Fig. 2. Causes of mandibular fracture.
~40
<24h 1-2 days2-3 days3-4 days4*5 days 5-6 days 6-7 days>lvazsk TREATMENT DELAY
Fig. 4. Delay between trauma and surgery.
AO rigid fixation o f mandibular fractures Table 1. Types of fixation used in the treatment of 270 mandibular fractures in 214 patients Site of mandibular fracture Body Type of fixation
Symphysis n = 20
Canine n = 39
Anterior n = 44
Posterior n = 46
14 1 1 . 4 -
28
18 2 10 2 1
16 20 2
10 1
8
DCP4 DCP4 + 2 DCP6 EDCP4 EDCP5 EDCP6 RP Lag screw
3 3 1 .
.
Angle n = 121 27 32 *(2) 23 2 2 10 22 3
.
3 1
Total n = 270 103 35 57 7 6 10 47 5
DCP = dynamic.compression plate; EDCP = eccentric dynamic compression plate; RP = reconstruction plate. Number indicates number of holes in plate. * Number in parenthesis indicates use of EDCP4 instead of DCP4. ular incision. Fifty-eight fractures (21.5%), mostly in the anterior region of the mandible, were treated using an intraoral approach. The types of plates used in relation to fracture site are shown in Table 1. In 56 patients (26.2%), 2 separate plating procedures were undertaken. The mean operation time was 2.5 h, excluding the time for installation of dental arch bars and intermaxillary fixation. Rigid I M F was not used postoperatively. In 48 patients (22.4%) with associated facial b o n e fractures, elastic I M F was employed for 1 4 weeks. A total of 172 patients (80.4%) required hospitalization for less than 7 days. The mean in-patient time was 5.1 days (range 2 to 12 days), excluding cases with multiple injuries. Postoperative follow-up
During postoperative follow-up of the 270 fractures in 214 patients, on average 7.1 weeks postoperatively, infection and delayed u n i o n or n o n - u n i o n occurred in 13 patients (6.1%). In all these cases, removal of the plate was necessary. Of the 13 fractures, 8 were situated in the
angular region and 4 in the posterior part of the mandible. In one edentulous patient, infection occurred in the parasymphyseal region (Fig. 5). Teeth (5 third molars and 4 second molars) had been extracted from the area of the fracture before bone plates were placed in 9 of 10 dentate patients. The mean delay from accident to surgery was 3.8 days (range 0 to 13 days) in the infection group. This delay did not significantly differ from that (3.2 days) of the patient group in which bone healing was normal. Postoperative malocclusion was seen in 29 patients (18.2% of the 159 dentate patients). Most (23) had 2 or more fractures in the mandible. Sixteen patients had an angular fracture. Of these, 11 had other fractures of the horizontal part of the mandible. These fractures were also treated by rigid fixation. In 4 cases, the angular fracture was isolated. In one there was a subcondylar fracture on the other side. Subcondylar fractures were diagnosed in a total of 10 patients with postoperative malocclusion.
150 -
E] NORMS_ •
,&
MOTORWEAKNES~
67
Motor disturbance of the mandibular branch of the facial nerve was observed immediately postoperatively in 27 cases (12.7% of t h e 212 cases operated on extraorally). In most instances (23), the fracture was located in the angular region (Fig. 6). Disturbed skin sensation, with a central zone of anaesthesia in the mental region under the lower lip, was observed in 50 fractures in 41 patients (19.2%). In 107 fractures in 9! patients (42.5%) there was slight hypaesthesia characterized by an asymmetry of skin sensation in the region of the chin with otherwise n o r m a l reaction to light touch and s h a r p / b l u n t differentiation. Sensory disturbance was observed most frequently in cases of angular fracture and fractures of the posterior part of the mandibular body (Fig. 7). Final examination
D u r i n g final follow-up examinations of 131 patients, on average 15.2 months postoperatively, motor weakness of the lower lip was observed in only 4 patients (3.1%). Hypaesthesia, with a detectable anaesthetic zone in the mental region, was still observable in 13 patients (9.96/0). Four patients (3.1%) expressed dissatisfaction because of unsightly skin scar at the incision line. A secondary correction of the scar was subsequently necessary in these cases. Hypersensitivity to cold or sensation of a foreign body was recorded in relation to 53 fracture sites in 49 patients (37.4). N o correlation between the frequency of such sensation and location of the fracture was found. During plate removal, good bone healing was observed in all cases. There were no signs of n o n - u n i o n or infection. Almost all screws were tight and bone often covered at least part of the plate.
150
100
[] • •
NORMAL SLIGHTHYPAESTHESIA ANAESTHESIA
92 (76%)
i t00' 5O 50.
Syrnphysis
Canine
Anterior Posterior Body
Symphysis Canine
Anterior
Posterior
Body
Body
Angle
FRACTURE SITE
Fig. 5. Incidence of postoperative infection (13 cases) in relation to fracture site.
Angle
Body
FRACTURE EITE
Fig. 6. Incidence of weakness of mandibular branch of the facial nerve on average 7.1 weeks, postoperatively, in 212 extraorally operated patients.
0 Symphysis
(2.,o, ,3;~o, (75., Canine
Anterior Body
Posterior Body
Angle
FRACTURE SITE
Fig. 7. Incidence of sensory disturbance in the lower lip on average 7.1 weeks postoperatively.
68
I i z u k a et al.
Discussion
Many of the patients studied abused alcohol t o a degree that often gave rise to psychosocial handicap. Despite this, acceptable results were obtained because delayed or non-union as a result of postoperative infection occurred in only 6.1% of the patients. F o u r of 5 patients were hospitalized for less than 7 days. Mandibular fractures and alcohol abuse are closely related as regards aetiology and incidence of complications 1437'25. It has been suggested that the most significant factor relating to delayed healing is chronic alcohol abuse, because of patients' reduced healing capacity' and poor co-operation 1'23. A detailed analysis by E D et al. 9 also showed that patients who experienced delayed healing had more frequently been intoxicated by alcohol at the time of the trauma and at the first visit. In this study we were often confronted with this problem. Patients were often unlikely to keep appointments and apt to remove their IMF. Some patients even refused I M F and medication. They often arrived for treatment several days after injury. It is also well known that patients who suffer from chronic alcohol abuse often have poor oral hygiene. There were, consequently, a number of factors which might have adversely affected the treatment results. Nevertheless, rigid fixation proved to be a reliable method for treating mandibular fractures in these patients. Mandibular fractures are often contaminated with oral bacteria. Postoperative infection, however, is not only the result of contamination, but can also be due to insufficient fracture stability1~. Factors contributing to decreased stability were: involvement of the angular region (because the bone is thinner than in the anterior region), extraction of a tooth in the line of fracture (because there is less bone contact) and edentulousness (because of bone atrophy). No significant effect on delay in treatment was found, however, in cases in which postoperative infection occurred. All of these findings support the view expressed by A O / A S I F investigators 24that susceptibility to infection depends on mobility of the fragments. The presence of infection has therefore even been considered as an indication for rigid internal fixation by some investigators 3'22. The results of a previous study" also showed that mandibular reconstruction could be successfully achieved by rigid internal
fixation during an acute stage of postoperative infection. CANN~LL& BOYO5 have reported high rates of infection in conservatively treated vagrant alcoholics despite hospitalization for a month or more, heavy antimicrobial treatment and the use of additional fixation, such as metal cap splints. Thus, conservative fracture treatment does not appear to be indicated in this patient group. Miniplate osteosynthesis of mandibular fractures also showed an infection rate of 25% in patients with chronic alcohol abuse 13. Postoperative infection with abscess formation was commonly observed in patients with a treatment delay of some days, and osteosynthesis with miniplates should ideally be performed within 12 h of trauma v. A comparative study of angular fractures ~s showed that increased stability by using 2 miniplates, significantly reduced the complication rate compared to only one miniplate. This also suggests that rigid stabilization is decisive for successful treatment. The fracture stability achieved by using I M F or miniplate fixation may in some cases be insufficient, Postoperative monitoring of C-reactive protein (CRP), a taboratory parameter of infection and tissue destruction, showed that fixation of mandibular fractures with miniplates was associated with larger increases in CRP level than AO rigid fixation ~°. The more elevated CRP levels suggest some movement of fragments in cases of miniplate fixation. We therefore believe that rigid fixation should be preferred to IMF, or the use of miniplates, in infection-prone patients, such as alcoholics and patients in whom co-operation is likely to be poor. Postoperative malocclusion has often been observed in patients treated by rigid internal fixation 8'16'2°'26. In most cases, the occlusal change is minimal and can be adjusted by grinding. In the present study, postoperative malocclusion was found to be associated with 2 fracture patterns. In one pattern the fracture was located in the anterior part of the mandible and associated with a subcondylar fracture. When a rigid plate is used, compression occurs at the labial or buccal cortex and at the lower border of the mandible. This compression produces tensile forces which tend to open a gap on the lingual side and at the upper border. To avoid asymmetric stress distribution over the fracture site, overbending of the plate and use of a tension band is necessary 24. In the first pattern,
the overbending of the plate was probably insufficient in some patients, resulting in buccal displacement of the mandibular fragment on the side of the condylar fracture. Although the gap was small at the fracture, displacement was observable in the mol~,r region, resulting in malocclusion. The second pattern included angular fractures associated with fracture of the horizontal part of the mandible. In such cases, the 2 fractures were treated separately• The angular fracture was first treated via an extraoral approach. The other, usually in the anterior part of the mandible, was then treated via an intraoral approach• Control of the fragment between the 2 fractures was therefore inadequate, because there is no simultaneous control of the fractures. When 2 or more fractures have to be stabilized, they should all be exposed and reduced, irrespective of the surgical approach, prior to osteosynthesis. Common complications associated with an extraoral approach are development of hypertrophic skin scar at the incision line and motor weakness of the mandibular branch of the facial nerve 16'2°,24.N o preoperative damage to the facial nerve was recorded in any of our patients. The nerve damage was caused only secondarily by surgery. The results of this study show, however, that the functional weakness of the facial nerve was temporary. The injury probably resulted from tension of the surrounding soft tissues during operation• Full recovery of nerve function may therefore be expected in almost all cases within approximately 1 year of surgery. This type of complication can be avoided by using a careful soft-tissue technique. In most cases, the cervical branch of the facial nerve does not have to be severed. In the 4 patients in which motor weakness of the lower lip was still observed at the ,.final follow-up examination, the weakness was slight• Hypertrophic scar characterized by thickened fibrous tissue along the incision line, with a width of several millimetres and a surface raised above the level of the adjacent skin was frequently observed• The formation of a hypertrophic scar could not be avoided, even though the incision was placed along the lateral neck crease• It appears-that the predisposition of patients to develop such scars differs individually,. Posttraumatic swelling at the fracture site also makes it difficult to determine a suitable natural skin crease. Only 4 patients
AO rigid fixation o f mandibular fractures stated their dissatisfaction due to the visible scar at final follow-up. As SPIESSL24reported, the skin scar was generally well accepted. Sensory disturbance in the mental skin region could be caused by damage to the nerve at the time of injury or, secondarily, by sugery. In most studies on rigid internal fixation, the incidence o f postoperative sensory deficits have been lower, f r o m 0.9% to 34%, than in the present study 2'16'2°26. One reason for the high incidence o f sensory disturbance in our patients may have been the relatively large numbers of displaced body and angular fractures. The sensory status was always evaluated critically using objective testing o f light touch and sharp/ blunt differentiation which is not always the case in other studies. M o s t patients regarded their sensation as normal, even though objective testing revealed a sensory disturbance. The disturbances were therefore slight and well accepted. N o further treatment was considered necessary in any patient. We routinely remove plates about 1 year postoperatively because there is no sound medical reason for leaving a large foreign object inside the body once bone healing has occurred. In our unit, plate removal is performed under general anaesthesia except in a few cases with symphysis fracture. The procedure always necessitates hospitalization for at least 2 or, more usually, 3 days. Exceptions for the routine plate removal include patients in w h o m further surgery would result in a risk (heart disease, the elderly). Hypersensitivity to cold or symptoms o f local irritation are always indications for plate removal 24. The high rate o f hypersensitivity to cold recorded in this study has not been previously reported. This symptom occurred especially in winter which is understandable in Finland and was the most c o m m o n indication for plate removal. A large number of studies concerning both rigid internal fixation 2,16,18~0,22,26 and miniplate fixation 6,7,13,I5 o f mandibular fractures have been published in recent years. However, the questions of whether bicortical screws and rigid plates are necessary or whether monocortically fixed miniplates are adequate have not been fully answered. Because of inconsistent study results, variations in patient material and differences in surgical techniques, it is difficult to compare the 2 plate systems. Some of the complications observed in this study were, however, directly associated with
the rigid plate system. These complications include injury of the facial nerve and development of the visible skin scar following an extraoral approach, postoperative malocclusion with difficulties relating to bending of the rigid plate, and problems relating to sensitivity to cold because o f the large quantity of metal involved. Previous observations 12 also suggest that bicortical screws could increase the risk of inferior alveolar nerve damage. In view of this, it seems that monocortical miniplate fixation avoiding extraoral incision may offer some advantages. On the other hand, rigid internal fixation is indicated in patients with a predisposition to infection, and a significant number of patients with mandibular fractures, in our unit at least, fall into this category. References 1. ADELL R, ERIKSSONB, NYLIN O, RIDELL
A. Delayed healing of fractures of the mandibular body. Int J Oral Maxillofac Surg 1987: 16: 1554. 2. ARDARYWC. Prospective clinical evaluation of the use of compression plates and
screws in the management of mandible fractures. J Oral Maxillofac Surg 1989: 47: 1150-3. 3. BECKE;RSHL. Treatment of initially infected mandibular fractures with bone plates. Oral Surg 1979: 37: 310-3. 4. BRUCER, FONSECARJ. Mandibular fractures. In'. Fonseca RJ, Walker RV, eds. Oral and maxillofacial trauma. Philadelphia: W B. Saunders, 1991: 389. 5. CANNELLH, BOYDR. The management of
maxillofacial injuries in vagrant alcoholics. J Maxillofac Surg 1985: 13: t21 4. 6. CAWOODJI. Small plate osteosynthesis of mandibular fractures. Br J Oral Maxillofac Surg 1985: 23: 77-91. 7. CHAMPY M, PAPE H-D, GERLACH KL, LODDE JP. The Strasbourg miniplate osteosynthesis. In: Krfiger E, Schilli W, eds. Oral and maxillofacial traumatology. Chicago: Quintessence, 1986: 19. 8. DoosoN TB, PERROTTDH, KABAN LB, GORDON NC. Fixation of mandibular fractures. A comparative analysis of rigid internal fixation and standard fixation techniques. J Oral Maxillofac Surg 1990: 48: 362-6. 9. EID K, LYNCHDJ, WHITAKERLA. Mandibular fractures: the problem patient. J Trauma 1976: 16:658 61. 10. IIZUKA T, LINDQVIST C. Changes in C-
reactive protein associated with surgical treatment of mandibular fractures. J Oral Maxillofac Surg 1991: 49: 464-7. 11. IIZUKAT, LINDQVISTC, HALLIKAINEND,
PAUKKU P. Infection after rigid internal fixation of mandibular fractures. J Oral Maxillofac Surg 1991: 49:585 93.
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12. IIZUKAT, LINDQVISTC. Sensory disturbances associated with rigid internal fix-
ation of mandibular fractures. J Oral Maxillofac Surg 1991:49: 1264-68. 13. JOHANSSONB, KREKMANOVL, THOMSSON
M. Miniplate osteosynthesis of infected mandibular fractures. J Craniomaxillofac Surg 1988: 16: 22-7. 14. LAMBERG MA. Causes of maxillo-facial fractures in hospitalized patients. Proc Finn Dent Soc 1978: 74:1 35. 15. LEVYFE, SMITHRW, ODLANDRM, MAR-
ENTETTELJ. Monocortical miniplate fixation of mandibular angle fractures. Arch Otolaryngol Head Neck Surg 1991: 117: 149 54. 16. LINDQVIST C, KONTIO R, PIHAKARI A,
SANTAVIRTAS. Rigid internal fixation of mandibular fractures. An analysis of 45 patients treated according to the ASIF method. Int J Oral Maxillofac Surg 1986: 15: 657-64. 17. MCDADE AM, McNIcoL RD, WARDBOOTH P, CHESWORTH J, MOOS F. The
etiology of maxillofacial injuries with special reference to the abuse of alcohol. Int J Oral Surg 1982: 11: 152-5. 18. PELEDM, LAUFERD, HELMANJ, GUTMAN
D. Treatment of mandibular fractures by means of compression osteosynthesis. J Oral Maxillofac Surg 1989: 47: 566-9. 19. POGRELMA. Compression osteosynthesis in mandibular fractures. Int J Oral Maxillofac Surg 1986: 15: 521-24. 20. RAVEH J, VUILLEMIN T, L.g,DRACH K, Roux M, SUTTERE Plate oste0synthesis of 367 mandibular fractures. J Craniomaxillofac Surg 1987: 15: 244-53. 21. ROWE NL, WILLIAMS JL. Maxillofacial injuries. Edinburgh: Churchill Livingstone, 1985: 232-336. 22. SCHWIMMERA, GREENBERGA. Management of mandibular trauma with rigid internal fixation. Oral Surg 1986: 62:630 7. 23. SILBERMAN M, MALONEY C, DUKO C. Mandibular osteomyelitis in the patient with chronic alcoholism. Etiology, management and statistical correlation. Oral Surg 1974: 47: 530-4. 24. SPIESSL B. Internal fixation of the mandible. A manual of AO/ASIF principles. Berlin: Springer-Verlag, 1989: 151. 25. THORN J, MOGELTAFT M, HANSEN PK. Incidence and etiological pattern of jaw fractures in Greenland. Int J Oral Maxillofac Surg 1986: 15: 372-9. 26. Tu HK, TENHULZEND. Compression osteosynthesis of mandibular fractures. A retrospective study. J Oral Maxillofac Surg 1985: 43:585 9.
Address:
Tateyuki Iizuka MD, DDS Department of Oral & Maxillofacial Surgery IV Department of Surgery Helsinki University Central Hospital Kasarmikatu 11-13 SF-O0130 Helsinki 13 Finland
R gid !nternal fixation of mandibular fractures
Tateyuki lizuka, Christian Lindqvist Department of Oral and Maxiliofacial Surgery, IV Department of Surgery, Helsinki University Central Hospital, Helsinki, Finland
An analysis of 270 fractures treated using the A0/ASIF method T. Iizuka, C. Lindqvist: Rigid internal fixation of mandibular fractures. An analysis of 27Ofractures treated using the AO/ASIF method. Int. J. Oral Maxillofac. Surg. 1992; 21: 65-69. Abstract. The results are reported on 214 patients treated for 270 mandibular fractures, using rigid internal fixation. Of these, 172 fractures (63.7%) in 131 patients had been re-evaluated at final follow-up in connection with plate and screw removal, on average 15.2 months, postoperatively. Although one-third of the patients had a history of alcohol abuse, and 86% were treated with a delay of more than 24 h (mean 3.2 days), good primary bone healing was observed in 93.9% of the patients. Infections, seen in 6.1% of the patients, were related exclusively to inadequate stability of the fracture. Malocclusion, observed in 18.2% of 159 dentate patients, was caused by incorrect plate bending and insufficient fracture reduction. Immediate postoperative dysfunction of the inferior alveolar nerve in 58.1% of the cases, and of the mandibular branch of the facial nerve in 12.7%, was followed by almost total recovery 1 year after operation. It is concluded that rigid internal fixation is a reliable method of treatment, especially indicated for patients with reduced healing capacity and poor co-operation.
Fractures of the mandible are generally treated by closed or open reduction4'21. Open reduction, involving internal fixation, is used in displaced fractures. Common methods of fracture fixation include the use of wires, pins or plates, and screws. Sufficient stability of the fracture is always necessary for bone healing. If internal fixation does not result in rigid stability at the fracture, some form of supplementary fixation may be necessary. Traditional methods involve additional intermaxillary fixation (IMF), using arch bars and splints. There are, however, several disadvantages associated with IMF, including: compromised airway, poor oral hygiene, speech difficulties, impaired nutritional intake with weight loss, and disuse atrophy of the masticatory muscles. Problems in relation to I M F in patients with multiple injuries or with generalized disease, such as diabetes, alcoholism and epilepsy are well known. In recent years, rigid internal fixation allowing immediate mobilization of the mandible has won increasing acceptance as a method for treatment of man-
dibular fractures 2,16,18-2°,22,26. In our department the A O / A S I F (AO Study Group for Internal Fixation) technique of rigid internal fixation24 was introduced in 1983. Up to the end of 1989, 270 mandibular fractures in 241 patients had been treated with this method. In the same period 1,823 patients with fractures of the mandible were seen. The annual percentages of open reduction and osteosynthesis varied between 18% and 29% (mean 25%). In general, open surgery was used in fractures with displacement and/or instability of the horizontal part of the mandible. Nondisplaced fractures and condylar fractures were usually treated by I M F alone. Helsinki University Central Hospital serves the 1.5 million inhabitants of the greater Helsinki area and the southern part of Finland. The object of this paper is to report the results of an analysis on the treatment of mandibular fractures using rigid internal fixation with the A O / A S I F plates. Special attention was paid to the technical problems which could affect the number of complications and out-
Key words: trauma; mandibular fracture; rigid fixation. Accepted for publication 14 January 1992
come of treatment and to factors related to patients' general health and drug habits.
Material and methods Patients with mandibular fractures treated following the AO/ASIF principle of rigid internal fixation at the Department of OMF Surgery, Helsinki University Central Hospital, between 1983 and 1989 were reviewed. Fractures with substantial comminution and defects, usually resulting from gunshot injury, were excluded because the special characteristics of such fractures influence the analysis relating to fracture site. Sites and numbers of fractures, surgical approach, presence of a tooth in the line of fracture, and whether or not tooth extraction was undertaken were recorded. Complications were defined as infection, delayed union or non-union, malocclusion and postoperative nerve injuries (motor disturbance affecting the mandibular branch of the facial nerve and sensory disturbance affecting the inferior alveolar nerve). Fracture sites were categorized as I) symphyseal, 2) canine, 3) relating to the anterior body (in the region of the premolar teeth and the mental foramen), 4) relating to the
66
I i z u k a et al.
posterior body (in the region of the molar teeth), and 5) relating to the angular region. Associated condylar fractures were also taken into account. Postoperative follow-up examinations were performed at intervals of 1 or 2 weeks for 3 16 weeks (mean 7.1 weeks). Up until April 30, 1991, 172 fractures (63.7%) in 131 patients had been re-evaluated at final followup in connection with plate and screw removal, on average 15.2 months postoperatively (range 8 to 62 months). Twelve symphyseal fractures, 23 fractures of the canine region, 28 fractures of the anterior part of the body, 26 fractures of the posterior part of the body and 83 angular fractures were assessed. Panoramic radiographs were taken pre- and postoperatively in all cases. Surgical technique
In patients in whom the fiacture involved the tooth-bearing area of the mandible, intravenous antimicrobial therapy consisting of penicillin G (1 million IU), usually combined with metronidazole (500 mg) was administered on admission and given every 6 h preand intraoperatively. Antimicrobial therapy was continued perorally (penicillin V 1 million IU and metronidazole 500 mg evey 6 h) until the 7th day after surgery. The operation was performed under general anaesthesia with nasotracheal intubation. The occlusion was re-established by bimanual manipulation, and secured using dental arch bars and IME Fixation was reinforced, if necessary, with cold-cure acrylic resin. The fracture sites were approached transorally (58 cases) or extraorally (212 cases). The transoral approach was chosen only in cases where, in the opinion of the surgeon, sufficient reduction and stabilization of the fracture could be achieved using this approach. For the extraoral approach, a submandibular incision as described by SPmSSL24was used, taking care not to damage the mandibular branch of the facial nerve by isolating it in the superior site of the wound. A nerve detector was always used. The periosteum was elevated from the mandible, exposing the fracture line. Final fracture reduction and osteosynthesis were performed using the instruments of the Synthes ® mandibular bone plate system (Synthes, Paoli, PA, USA) and AO/ASIF technique24. The repositioning was performed using reduction forceps, usually of the compression-reduction type, fixed with ~10 mm cortical screws (o 2.7 mm) at the lower border of the mandible. An interdental wire ligature was always applied when the fracture was located within the dental arch. In angular fractures and fractures in edentulous mandibles, a tension band plate was used only in cases in which fracture reduction at the upper border of the mandible could not be achieved by use of reduction forceps. Fractures were stabilized using rigid stainless steel plates bent to fit the contour of the buccal aspect of the mandible and fixed by bicortical screws. At least 2 screws were
79 150 t
[]
INTRAORAL
IN r ~'T~AnRAI 100"
<10
10-19 20-29
30-39
40-49
50-5g
60-69 70-79
AGE GROUP
OSymphysis
Cani~
Anterior Body
Posterior Body
Angle
FRACTURE SITE
Fig. 1. Age and sex distributions of 214 patients with 270 mandibular fractures treated following the principles of AO/ASIF rigid internal fixation.
placed on each side of the fracture. After repeated irrigation, the wound was closed in layers, and suction drains were used for the first 24 h after operation. Results Patients' profile
The age and sex distributions of the 175 male and 39 female patients are shown in Fig. 1. The mean age of the patients was 33.9 years (range 8 to 83 years). In over half o f the cases (59.8%) external blows or kicks during assaults or fights were the cause of the fracture. Traffic accients (17.3%), slipping (9.8%) and falling (3.7%) were the next most common causes of fracture (Fig. 2). In 123 patients (57.5%) the accidents occurred at weekends, between Firday afternoon and Sunday evening. M o s t patients (154, 72.0%) at the time of the accident and 92 patients (43.0%) still on hospital admission had been under the influence of alcohol. One-third of the patients (72, 33.6%) had a history of alcohol abuse, often associated with unemployment a n d / o r vagrancy (29, 13.6%). According to the interview and evaluation by hospital social workers, patients with a history of alcohol abuse were defined as patients accustomed to ingesting large quantities of alcohol in an uncontrolled
Fig. 3. Fracture sites and surgical approach.
fashion and'regularly showing impaired social or occupational functioning. Because o f this, further social care or therapy had to be organized after primary fracture treatment. M o r e than half of the patients (119, 55.6%) had 2 or more fractures of the mandible. O f the 270 fractures treated using rigid fixation, 197 (73%) were located in a dentate mandible and 73 (27%) in an edentulous mandible. Fractures which were operated were most often angular (44.8%), followed by body (33.3%), canine (14.4%) and symphyseal fractures (7.4%) (Fig. 3). Sixty patients (28%) also had fractures in the subcondylar region. Bimaxillary fractures were diagnosed in 29 patients. Twenty-seven patients exhibited multiple injuries, including brain and thoraco-abdominal injuries, together with injuries to the extremities. Treatment using rigid fixation
The mean delay between accident and admission to hospital was 2.0 days (range 0 to 22 days). The average delay before surgery was 3.2 days (range 0 to 31 days). In only 30 patients was the fracture operated on within 24 h (14%) (Fig. 4). In most cases (212, 78.5%) the extraoral appf6ach was used, via submandib-
CAUSES OF INJURIES Fight
128 (59.8%)
and a~aug
37 (17.3%1
Traff¢ accident Slipping m
21 (9.8%1
Fallingfrom a height
g (3,7%)
BloWfrom an object
8 (3.7%)
latrogenlc
(o.9%1
Gunshot
2 (0.9%)
Miscelaneous
I. V3-7 ,,............ 20
40
60
80
100
120
NO. OF PATIENTS
Fig. 2. Causes of mandibular fracture.
~40
<24h 1-2 days2-3 days3-4 days4*5 days 5-6 days 6-7 days>lvazsk TREATMENT DELAY
Fig. 4. Delay between trauma and surgery.
AO rigid fixation o f mandibular fractures Table 1. Types of fixation used in the treatment of 270 mandibular fractures in 214 patients Site of mandibular fracture Body Type of fixation
Symphysis n = 20
Canine n = 39
Anterior n = 44
Posterior n = 46
14 1 1 . 4 -
28
18 2 10 2 1
16 20 2
10 1
8
DCP4 DCP4 + 2 DCP6 EDCP4 EDCP5 EDCP6 RP Lag screw
3 3 1 .
.
Angle n = 121 27 32 *(2) 23 2 2 10 22 3
.
3 1
Total n = 270 103 35 57 7 6 10 47 5
DCP = dynamic.compression plate; EDCP = eccentric dynamic compression plate; RP = reconstruction plate. Number indicates number of holes in plate. * Number in parenthesis indicates use of EDCP4 instead of DCP4. ular incision. Fifty-eight fractures (21.5%), mostly in the anterior region of the mandible, were treated using an intraoral approach. The types of plates used in relation to fracture site are shown in Table 1. In 56 patients (26.2%), 2 separate plating procedures were undertaken. The mean operation time was 2.5 h, excluding the time for installation of dental arch bars and intermaxillary fixation. Rigid I M F was not used postoperatively. In 48 patients (22.4%) with associated facial b o n e fractures, elastic I M F was employed for 1 4 weeks. A total of 172 patients (80.4%) required hospitalization for less than 7 days. The mean in-patient time was 5.1 days (range 2 to 12 days), excluding cases with multiple injuries. Postoperative follow-up
During postoperative follow-up of the 270 fractures in 214 patients, on average 7.1 weeks postoperatively, infection and delayed u n i o n or n o n - u n i o n occurred in 13 patients (6.1%). In all these cases, removal of the plate was necessary. Of the 13 fractures, 8 were situated in the
angular region and 4 in the posterior part of the mandible. In one edentulous patient, infection occurred in the parasymphyseal region (Fig. 5). Teeth (5 third molars and 4 second molars) had been extracted from the area of the fracture before bone plates were placed in 9 of 10 dentate patients. The mean delay from accident to surgery was 3.8 days (range 0 to 13 days) in the infection group. This delay did not significantly differ from that (3.2 days) of the patient group in which bone healing was normal. Postoperative malocclusion was seen in 29 patients (18.2% of the 159 dentate patients). Most (23) had 2 or more fractures in the mandible. Sixteen patients had an angular fracture. Of these, 11 had other fractures of the horizontal part of the mandible. These fractures were also treated by rigid fixation. In 4 cases, the angular fracture was isolated. In one there was a subcondylar fracture on the other side. Subcondylar fractures were diagnosed in a total of 10 patients with postoperative malocclusion.
150 -
E] NORMS_ •
,&
MOTORWEAKNES~
67
Motor disturbance of the mandibular branch of the facial nerve was observed immediately postoperatively in 27 cases (12.7% of t h e 212 cases operated on extraorally). In most instances (23), the fracture was located in the angular region (Fig. 6). Disturbed skin sensation, with a central zone of anaesthesia in the mental region under the lower lip, was observed in 50 fractures in 41 patients (19.2%). In 107 fractures in 9! patients (42.5%) there was slight hypaesthesia characterized by an asymmetry of skin sensation in the region of the chin with otherwise n o r m a l reaction to light touch and s h a r p / b l u n t differentiation. Sensory disturbance was observed most frequently in cases of angular fracture and fractures of the posterior part of the mandibular body (Fig. 7). Final examination
D u r i n g final follow-up examinations of 131 patients, on average 15.2 months postoperatively, motor weakness of the lower lip was observed in only 4 patients (3.1%). Hypaesthesia, with a detectable anaesthetic zone in the mental region, was still observable in 13 patients (9.96/0). Four patients (3.1%) expressed dissatisfaction because of unsightly skin scar at the incision line. A secondary correction of the scar was subsequently necessary in these cases. Hypersensitivity to cold or sensation of a foreign body was recorded in relation to 53 fracture sites in 49 patients (37.4). N o correlation between the frequency of such sensation and location of the fracture was found. During plate removal, good bone healing was observed in all cases. There were no signs of n o n - u n i o n or infection. Almost all screws were tight and bone often covered at least part of the plate.
150
100
[] • •
NORMAL SLIGHTHYPAESTHESIA ANAESTHESIA
92 (76%)
i t00' 5O 50.
Syrnphysis
Canine
Anterior Posterior Body
Symphysis Canine
Anterior
Posterior
Body
Body
Angle
FRACTURE SITE
Fig. 5. Incidence of postoperative infection (13 cases) in relation to fracture site.
Angle
Body
FRACTURE EITE
Fig. 6. Incidence of weakness of mandibular branch of the facial nerve on average 7.1 weeks, postoperatively, in 212 extraorally operated patients.
0 Symphysis
(2.,o, ,3;~o, (75., Canine
Anterior Body
Posterior Body
Angle
FRACTURE SITE
Fig. 7. Incidence of sensory disturbance in the lower lip on average 7.1 weeks postoperatively.
68
I i z u k a et al.
Discussion
Many of the patients studied abused alcohol t o a degree that often gave rise to psychosocial handicap. Despite this, acceptable results were obtained because delayed or non-union as a result of postoperative infection occurred in only 6.1% of the patients. F o u r of 5 patients were hospitalized for less than 7 days. Mandibular fractures and alcohol abuse are closely related as regards aetiology and incidence of complications 1437'25. It has been suggested that the most significant factor relating to delayed healing is chronic alcohol abuse, because of patients' reduced healing capacity' and poor co-operation 1'23. A detailed analysis by E D et al. 9 also showed that patients who experienced delayed healing had more frequently been intoxicated by alcohol at the time of the trauma and at the first visit. In this study we were often confronted with this problem. Patients were often unlikely to keep appointments and apt to remove their IMF. Some patients even refused I M F and medication. They often arrived for treatment several days after injury. It is also well known that patients who suffer from chronic alcohol abuse often have poor oral hygiene. There were, consequently, a number of factors which might have adversely affected the treatment results. Nevertheless, rigid fixation proved to be a reliable method for treating mandibular fractures in these patients. Mandibular fractures are often contaminated with oral bacteria. Postoperative infection, however, is not only the result of contamination, but can also be due to insufficient fracture stability1~. Factors contributing to decreased stability were: involvement of the angular region (because the bone is thinner than in the anterior region), extraction of a tooth in the line of fracture (because there is less bone contact) and edentulousness (because of bone atrophy). No significant effect on delay in treatment was found, however, in cases in which postoperative infection occurred. All of these findings support the view expressed by A O / A S I F investigators 24that susceptibility to infection depends on mobility of the fragments. The presence of infection has therefore even been considered as an indication for rigid internal fixation by some investigators 3'22. The results of a previous study" also showed that mandibular reconstruction could be successfully achieved by rigid internal
fixation during an acute stage of postoperative infection. CANN~LL& BOYO5 have reported high rates of infection in conservatively treated vagrant alcoholics despite hospitalization for a month or more, heavy antimicrobial treatment and the use of additional fixation, such as metal cap splints. Thus, conservative fracture treatment does not appear to be indicated in this patient group. Miniplate osteosynthesis of mandibular fractures also showed an infection rate of 25% in patients with chronic alcohol abuse 13. Postoperative infection with abscess formation was commonly observed in patients with a treatment delay of some days, and osteosynthesis with miniplates should ideally be performed within 12 h of trauma v. A comparative study of angular fractures ~s showed that increased stability by using 2 miniplates, significantly reduced the complication rate compared to only one miniplate. This also suggests that rigid stabilization is decisive for successful treatment. The fracture stability achieved by using I M F or miniplate fixation may in some cases be insufficient, Postoperative monitoring of C-reactive protein (CRP), a taboratory parameter of infection and tissue destruction, showed that fixation of mandibular fractures with miniplates was associated with larger increases in CRP level than AO rigid fixation ~°. The more elevated CRP levels suggest some movement of fragments in cases of miniplate fixation. We therefore believe that rigid fixation should be preferred to IMF, or the use of miniplates, in infection-prone patients, such as alcoholics and patients in whom co-operation is likely to be poor. Postoperative malocclusion has often been observed in patients treated by rigid internal fixation 8'16'2°'26. In most cases, the occlusal change is minimal and can be adjusted by grinding. In the present study, postoperative malocclusion was found to be associated with 2 fracture patterns. In one pattern the fracture was located in the anterior part of the mandible and associated with a subcondylar fracture. When a rigid plate is used, compression occurs at the labial or buccal cortex and at the lower border of the mandible. This compression produces tensile forces which tend to open a gap on the lingual side and at the upper border. To avoid asymmetric stress distribution over the fracture site, overbending of the plate and use of a tension band is necessary 24. In the first pattern,
the overbending of the plate was probably insufficient in some patients, resulting in buccal displacement of the mandibular fragment on the side of the condylar fracture. Although the gap was small at the fracture, displacement was observable in the mol~,r region, resulting in malocclusion. The second pattern included angular fractures associated with fracture of the horizontal part of the mandible. In such cases, the 2 fractures were treated separately• The angular fracture was first treated via an extraoral approach. The other, usually in the anterior part of the mandible, was then treated via an intraoral approach• Control of the fragment between the 2 fractures was therefore inadequate, because there is no simultaneous control of the fractures. When 2 or more fractures have to be stabilized, they should all be exposed and reduced, irrespective of the surgical approach, prior to osteosynthesis. Common complications associated with an extraoral approach are development of hypertrophic skin scar at the incision line and motor weakness of the mandibular branch of the facial nerve 16'2°,24.N o preoperative damage to the facial nerve was recorded in any of our patients. The nerve damage was caused only secondarily by surgery. The results of this study show, however, that the functional weakness of the facial nerve was temporary. The injury probably resulted from tension of the surrounding soft tissues during operation• Full recovery of nerve function may therefore be expected in almost all cases within approximately 1 year of surgery. This type of complication can be avoided by using a careful soft-tissue technique. In most cases, the cervical branch of the facial nerve does not have to be severed. In the 4 patients in which motor weakness of the lower lip was still observed at the ,.final follow-up examination, the weakness was slight• Hypertrophic scar characterized by thickened fibrous tissue along the incision line, with a width of several millimetres and a surface raised above the level of the adjacent skin was frequently observed• The formation of a hypertrophic scar could not be avoided, even though the incision was placed along the lateral neck crease• It appears-that the predisposition of patients to develop such scars differs individually,. Posttraumatic swelling at the fracture site also makes it difficult to determine a suitable natural skin crease. Only 4 patients
AO rigid fixation o f mandibular fractures stated their dissatisfaction due to the visible scar at final follow-up. As SPIESSL24reported, the skin scar was generally well accepted. Sensory disturbance in the mental skin region could be caused by damage to the nerve at the time of injury or, secondarily, by sugery. In most studies on rigid internal fixation, the incidence o f postoperative sensory deficits have been lower, f r o m 0.9% to 34%, than in the present study 2'16'2°26. One reason for the high incidence o f sensory disturbance in our patients may have been the relatively large numbers of displaced body and angular fractures. The sensory status was always evaluated critically using objective testing o f light touch and sharp/ blunt differentiation which is not always the case in other studies. M o s t patients regarded their sensation as normal, even though objective testing revealed a sensory disturbance. The disturbances were therefore slight and well accepted. N o further treatment was considered necessary in any patient. We routinely remove plates about 1 year postoperatively because there is no sound medical reason for leaving a large foreign object inside the body once bone healing has occurred. In our unit, plate removal is performed under general anaesthesia except in a few cases with symphysis fracture. The procedure always necessitates hospitalization for at least 2 or, more usually, 3 days. Exceptions for the routine plate removal include patients in w h o m further surgery would result in a risk (heart disease, the elderly). Hypersensitivity to cold or symptoms o f local irritation are always indications for plate removal 24. The high rate o f hypersensitivity to cold recorded in this study has not been previously reported. This symptom occurred especially in winter which is understandable in Finland and was the most c o m m o n indication for plate removal. A large number of studies concerning both rigid internal fixation 2,16,18~0,22,26 and miniplate fixation 6,7,13,I5 o f mandibular fractures have been published in recent years. However, the questions of whether bicortical screws and rigid plates are necessary or whether monocortically fixed miniplates are adequate have not been fully answered. Because of inconsistent study results, variations in patient material and differences in surgical techniques, it is difficult to compare the 2 plate systems. Some of the complications observed in this study were, however, directly associated with
the rigid plate system. These complications include injury of the facial nerve and development of the visible skin scar following an extraoral approach, postoperative malocclusion with difficulties relating to bending of the rigid plate, and problems relating to sensitivity to cold because o f the large quantity of metal involved. Previous observations 12 also suggest that bicortical screws could increase the risk of inferior alveolar nerve damage. In view of this, it seems that monocortical miniplate fixation avoiding extraoral incision may offer some advantages. On the other hand, rigid internal fixation is indicated in patients with a predisposition to infection, and a significant number of patients with mandibular fractures, in our unit at least, fall into this category. References 1. ADELL R, ERIKSSONB, NYLIN O, RIDELL
A. Delayed healing of fractures of the mandibular body. Int J Oral Maxillofac Surg 1987: 16: 1554. 2. ARDARYWC. Prospective clinical evaluation of the use of compression plates and
screws in the management of mandible fractures. J Oral Maxillofac Surg 1989: 47: 1150-3. 3. BECKE;RSHL. Treatment of initially infected mandibular fractures with bone plates. Oral Surg 1979: 37: 310-3. 4. BRUCER, FONSECARJ. Mandibular fractures. In'. Fonseca RJ, Walker RV, eds. Oral and maxillofacial trauma. Philadelphia: W B. Saunders, 1991: 389. 5. CANNELLH, BOYDR. The management of
maxillofacial injuries in vagrant alcoholics. J Maxillofac Surg 1985: 13: t21 4. 6. CAWOODJI. Small plate osteosynthesis of mandibular fractures. Br J Oral Maxillofac Surg 1985: 23: 77-91. 7. CHAMPY M, PAPE H-D, GERLACH KL, LODDE JP. The Strasbourg miniplate osteosynthesis. In: Krfiger E, Schilli W, eds. Oral and maxillofacial traumatology. Chicago: Quintessence, 1986: 19. 8. DoosoN TB, PERROTTDH, KABAN LB, GORDON NC. Fixation of mandibular fractures. A comparative analysis of rigid internal fixation and standard fixation techniques. J Oral Maxillofac Surg 1990: 48: 362-6. 9. EID K, LYNCHDJ, WHITAKERLA. Mandibular fractures: the problem patient. J Trauma 1976: 16:658 61. 10. IIZUKA T, LINDQVIST C. Changes in C-
reactive protein associated with surgical treatment of mandibular fractures. J Oral Maxillofac Surg 1991: 49: 464-7. 11. IIZUKAT, LINDQVISTC, HALLIKAINEND,
PAUKKU P. Infection after rigid internal fixation of mandibular fractures. J Oral Maxillofac Surg 1991: 49:585 93.
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12. IIZUKAT, LINDQVISTC. Sensory disturbances associated with rigid internal fix-
ation of mandibular fractures. J Oral Maxillofac Surg 1991:49: 1264-68. 13. JOHANSSONB, KREKMANOVL, THOMSSON
M. Miniplate osteosynthesis of infected mandibular fractures. J Craniomaxillofac Surg 1988: 16: 22-7. 14. LAMBERG MA. Causes of maxillo-facial fractures in hospitalized patients. Proc Finn Dent Soc 1978: 74:1 35. 15. LEVYFE, SMITHRW, ODLANDRM, MAR-
ENTETTELJ. Monocortical miniplate fixation of mandibular angle fractures. Arch Otolaryngol Head Neck Surg 1991: 117: 149 54. 16. LINDQVIST C, KONTIO R, PIHAKARI A,
SANTAVIRTAS. Rigid internal fixation of mandibular fractures. An analysis of 45 patients treated according to the ASIF method. Int J Oral Maxillofac Surg 1986: 15: 657-64. 17. MCDADE AM, McNIcoL RD, WARDBOOTH P, CHESWORTH J, MOOS F. The
etiology of maxillofacial injuries with special reference to the abuse of alcohol. Int J Oral Surg 1982: 11: 152-5. 18. PELEDM, LAUFERD, HELMANJ, GUTMAN
D. Treatment of mandibular fractures by means of compression osteosynthesis. J Oral Maxillofac Surg 1989: 47: 566-9. 19. POGRELMA. Compression osteosynthesis in mandibular fractures. Int J Oral Maxillofac Surg 1986: 15: 521-24. 20. RAVEH J, VUILLEMIN T, L.g,DRACH K, Roux M, SUTTERE Plate oste0synthesis of 367 mandibular fractures. J Craniomaxillofac Surg 1987: 15: 244-53. 21. ROWE NL, WILLIAMS JL. Maxillofacial injuries. Edinburgh: Churchill Livingstone, 1985: 232-336. 22. SCHWIMMERA, GREENBERGA. Management of mandibular trauma with rigid internal fixation. Oral Surg 1986: 62:630 7. 23. SILBERMAN M, MALONEY C, DUKO C. Mandibular osteomyelitis in the patient with chronic alcoholism. Etiology, management and statistical correlation. Oral Surg 1974: 47: 530-4. 24. SPIESSL B. Internal fixation of the mandible. A manual of AO/ASIF principles. Berlin: Springer-Verlag, 1989: 151. 25. THORN J, MOGELTAFT M, HANSEN PK. Incidence and etiological pattern of jaw fractures in Greenland. Int J Oral Maxillofac Surg 1986: 15: 372-9. 26. Tu HK, TENHULZEND. Compression osteosynthesis of mandibular fractures. A retrospective study. J Oral Maxillofac Surg 1985: 43:585 9.
Address:
Tateyuki Iizuka MD, DDS Department of Oral & Maxillofacial Surgery IV Department of Surgery Helsinki University Central Hospital Kasarmikatu 11-13 SF-O0130 Helsinki 13 Finland