a comparative review of 266 mandibular fractures with

$: A comparative review of 266 mandibular fractures with$
A comparative review of 266 mandibular fractures with internal fixation using rigid (AO/ASIF) plates or mini-plates

M. A. Kuriakose, M. Fardy, M. Sirikumara, D. W. Patton, A. W. Sugar

MasilloJirciul Unit, Welsh Centre,for Burns, Plastic Surgery md Mrrsillojkial Surgery, Morriston Hospitul, Snmsecr

SUMMARY. This study compares the internal fixation of mandibular fractures using either rigid 2.7 mm AO/ASIF plates or mini-plates. In the rigid plate group, 88 fractures were fixed with 88 plates. In the mini-plate group, 116 fractures were fixed with 170 plates. All the cases were consecutive and were treated in two South Wales hospitals during a 3-year period from 1988 to 1991.

The aetiology of injury, timing of surgery, site of fracture, antibiotic policy and demographic features were evenly distributed between the two groups but there was a higher incidence of females in the mini-plate group.

Both plating systems were successful in restoring functional occlusion. Rigid plates avoided the use of postoperative elastics better than mini-plates but the difference was not significant. There was a significantly higher incidence (P=O.O13) of infection in the mini-plate (12.9%) compared with the rigid plate (2.3%) group but 7.9% of the rigid group developed facial nerve weakness. A significantly higher proportion of mini-plates needed to be removed (P = 0.00019). A better treatment outcome for angle and comminuted fractures was noted with rigid plates.

INTRODUCTION

The objectives of mandibular fracture management include the restoration of the pre-existing anatomical form, functional occlusion and facial aesthetics. Even though these objectives can often be achieved by closed reduction and inter-maxillary fixation (IMF), unfavourable displaced fractures require open reduction and internal fixation. This method is also indicated when IMF is undesirable. There are many situations in which JMF is contra-indicated or rela- tively contra-indicated. These include the treatment of epileptics, alcoholics and others with drug addic- tion, those with chronic obstructive airways disease and any condition in which the airway is compromised or potentially compromised. Williams and Cawood’ have shown that tidal volume may be reduced by up to 40% in patients whose teeth are wired together. Cawood’ has also demonstrated improved mouth opening after treatment of mandibular fractures with small plate osteosynthesis.

Internal fixation of mandibular fractures using plates and screws is now an established method of treatment. Two fundamentally different phil- osophies have evolved. Spiessl and the AO/ASIF group (Arbeitsgemeinschaft fiir Osteosynthesefragen/ Association for the Study of Internal Fixation) introduced the use of rigid plates with 2.7 mm bicortical screws in 1972.3 This was an adaptation of the experience with internal fixation in long bones with particular modifications for the mandible. A method of stable fixation with mini-plates and 2 mm monocortical screws was advocated by Michelet in 1973’ for the midface and was applied to the mandible by Champy in 1975.5

There is a lack of consensus on which type of plating system to use in different clinical circum- stances or of the relative merits of the two philosophical approaches. No published studies have so far attempted to compare the effectiveness of these two methods of internal fixation. The aim of this study was to review mandibular fractures treated by these two types of plating system to evaluate treatment outcome.

MATERIALS AND METHODS

All patients with mandibular fractures treated by internal fixation in the Departments of Maxillofacial Surgery of two South Wales hospitals, St Lawrence Hospital, Chepstow (SLH) and Morriston Hospital, Swansea (MH), during the 3-year period from 1988 to 1991 were reviewed. This was a retrospective study of hospital notes, radiographs, hospital theatre records and out-patient reviews. Only those patients for whom all records were available remained in the study.

The two hospitals involved treated patients from the same geographical region but had different catch- ment areas. The period 1988-91 was chosen because at that time these hospitals had different philosophical approaches to the internal fixation of mandibular fractures. AO,/ASIF rigid plates were the principal method at SLH and Champy plates at MH. This made it an ideal situation in which to study the treatment outcome for these two methods.

At SLH, the principal method of treatment was the use of 2.7 mm bicortical screws and AO/ASIF plates although some fractures were managed with

315

3 16 British Journal of Oral and Maxillofacial Surgery

mini-plates. The plates and screws were inserted according to the principles laid down by Spies4 and the A0 group, although an application of these techniques which permitted only one plate to be used per fracture was adopted.

At MH, Champy mini-plates with 2.0 mm monocortical screws were used as the principal technique, although some fractures were managed with rigid AO/ASIF plates. The mini-plates were inserted according to the guide-lines laid down by Michelet4 and Champy et al.’

Both centres were actively involved in the training of maxillofacial surgeons with staff working at the level of Registrar and Senior Registrar. All these higher surgical trainees were involved in the treatment of mandibular fractures in both units under the supervision of consultants.

During the period of the study at SLH, 74 consecutive patients were treated by internal fixation but the records of 3 patients were not available and these were excluded from the study. Complete records were thus available for 71 patients with 117 fractures reflecting a very high retrieval rate. At Morrison Hospital, 133 consecutive patients with mandibular fractures were treated during this period by internal fixation. Complete records were available for 97 patients with 149 fractures and only these patients were included in the study.

Demographic features, aetiology, nature of fracture, method of treatment and treatment outcome were compared between the two groups which, for ease of description, we shall refer to as the ‘Rigid’ (AO/ASIF plates with 2.7 mm bicortical screws) and ‘Mini’ (mini-plates with 2.0 mm monocortical screws) groups. The distribution of cases according to centre is shown in Table 1. All the patients in both centres received a single dose of a broad spectrum intra- venous antibiotic at induction of anaesthesia followed by oral antibiotics.

Patients were followed up for a minimum period of 3 months and up to 18 months if there were complications. The data was analysed using the Chi- Square test. A ‘P’ value less than 0.05 was considered to be significant.

RESULTS

The results are reported on a total of 168 consecutive patients with 266 mandibular fractures, of which 204

Table 1 -Patient distribution

were fixed internally. Of these internally fixed fractures, 88 belonged to the ‘Rigid’ group and 116 to the ‘Mini’ group.

The mean age of patients was similar in both groups but the sex distribution showed a higher proportion of females among the ‘Mini’ group (25% compared with 9.4%) which was significant (P = 0.01) (Table 1). Assault was the cause of over half of the cases (Fig. 1). Evaluation of the site of fracture showed an even distribution in both groups, with the angle and body being the most common sites (Fig. 2). These included untreated fractures (stable undis- placed or condylar neck fractures when another fracture in the same patient was fixed). 6.5% of the ‘Rigid’ and 6.9% of the ‘Mini’ group were compound extra-orally. Cornminuted fractures were encountered in 6.5% of ‘Rigid’ and 7.6% of the ‘Mini-plate groups. Consequently, and with the exception of the sex distribution, it appears that the two groups were comparable in relation to the types of patient treated and fractures fixed.

In the ‘Rigid’ group, out of the 88 fractures that were fixed, 45 reconstruction plates (RP), 36 eccentric dynamic compression plates (EDCP), 6 dynamic compression plates (DCP) and in 1 case a lag screw alone were used. It should be noted that in no case was more than one plate used for a fracture. The tension band principle was generally applied with the use of an arch bar when a DCP was used and in most cases when an EDCP was applied. RPs were generally inserted without the use of tension banding at the upper border and angle fractures were usually managed in this way.

In the ‘Mini’ group, in the 116 fractures which were fixed, 170 plates were used. 67 fractures received one plate, 46 received two plates, one had three plates and two had four plates. The distributions of plates is listed in Table 2. The only patient to be treated with micro-plates (two) was a 2-year-old girl with an unstable displaced body fracture in the tooth bear- ing area.

Over 70% of all fractures were treated within 24 h (Fig. 3). An oral approach was adopted in 12% of the ‘Rigid’ and 93% of the ‘Mini’ groups. Whereas 82% of the ‘Rigid’ group required an extraoral approach, this was only adopted in 5% of the ‘Mini’ group. The remaining fractures were treated by a combined approach. The difference in surgical approaches was statistically highly significant (P = <O.OOl).

MH ‘Mini’ MH ‘Rigid’ plates plates

SLH ‘Mini’ plates

SLH ‘Rigid’ plates

‘Mini’ plates total

‘Rigid’ plates total

No. of patients 129 4 11 63 140 67 Patients with complete records 93 4 11 60 104 64 No. of fractures 144 5 14 103 158 108 No. of treated fractures* 104 4 12 84 116 88 Male 70 3 8 55 78 58 Female 23 1 3 55 26 6 Age range 5-84 70-82 2-89 13-55 2-89 13-82 Mean age 30 77 37 33 33 36

MH = Morriston Hospital, SLH = St Lawrence Hospital. * Fractures of the condyle were not treated by internal fixation.

A comparative review of 266 mandibular fractures 317

Aetiology of injury* 70

63

32 33

Assault RTA sports Fall Industrial Others

*in percentages of patients

Fig. 1.

Site Distribution of All Fractures

Rigid (treated and untreated)

Mini Plate Plate

Group Group

36 13 11 38

in percentages

Fig. 2.

Table 2 - Types of plate used

‘Mini’ plate ‘Rigid’ plate (II = 170) (~2=88)

Champy 83.5* 0 Luhr mini 7.1 0 A0 craniofacial mini 8.2 0 Micro-plates 1.2 0 RP 0 51.1 EDCP 0 40.9 DCP 0 6.8 Lag screws (2.7 mm) 0 1.2

RP = A0 2.7 mm reconstruction plate. EDCP = A0 2.7 mm eccentric dynamic compression plate. DCP = A0 2.7 mm dynamic compression plate. * Data in percentages.

Postoperative IMF was not used in any of the ‘Rigid’ group but one of the surgeons at that time electively placed his mini-plated patients into IMF immediately post operatively for up to 10 days. This represented 25% of the ‘Mini’ group. In addition, 12.5% of the ‘Rigid’ group and 21.2% of the ‘Mini’ required light elastic traction to optimise the occlusion at some stage post-operatively. This difference was not statistically significant (P=O.2).

Analysis of treatment outcome showed that in over 90% of fractures, functional occlusion was restored. ‘Rigid’ fixation resulted in occlusal interference in 3 (4.7%) of the fractures in comparison to 10 (9.6%) in the ‘Mini’-plate group. However, there was no statistically significant difference between the two groups. None of these patients required further surgery to correct this malocclusion. It was treated primarily by selective occlusal adjustments.

3 18 British Journal of Oral and Maxillofacial Surgery

Time elapsed from injury to surgery 80 ,

c 24hrs 24 to 48 hrs > 48 hrs unknown ‘Mini’ plates, n=104 patients; ‘Rigid’ plates, n= 64 patients

Data in percentages

Fig. 3.

Further analysis of the group of patients with malocclusion was carried out to identify the risk factors. In the ‘Rigid’ group, 2 out of the 3 patients had associated condylar fractures. In the ‘Mini’ group, of the 10 patients, 5 of the fractures that were internally fixed were at the angle and 3 of the patients had associated condylar fractures (Table 3). Mini- plates were employed to treat 12 patients with comminuted fractures. Four of these patients (33%) developed malocclusion. In contrast none of the 7 patients with cornminuted fractures treated by ‘Rigid’ plates developed occlusal interferences.

Infection was recorded when it was manifested by abscess formation. Some of these cases also had a discharging sinus and others had frank osteomyelitis. It did not include cases of wound dehiscence alone. Only 2 cases of infection (2.3%) resulted in the ‘Rigid’ group and 15 ( 12.9%) in the ‘Mini’ group. The difference was statistically significant (P=O.O13). The most common sites of infection were at the angle and symphysis and in association with an intraoral approach (Table 4). There was no association to the timing of treatment or to the number of plates used.

Of the two infected cases in the ‘Rigid’ group, one required removal of loose plates and screws as well as sequestra and antibiotic irrigation but at the time of exploration the fracture had united. In the other case it was considered likely that the infection had

Table 3 -Analysis of cases with post-operative malocclusion

Site of fracture ‘Mini’ plates ‘Rigid’ plates

Angle 2 1 Angle and condyle 0 1 Angle and parasymphysis 1 0 Body 1 0 Body and condyle 3 1 Body and ramus 1 0 Angle and body 2 0 Total 10 (9.5%) 3 (4.7%)

Table 4 -Analysis of infection

Site and surgical ‘Mini’ plates ‘Rigid’ plates Chi Sq. approach (n=15) (n=2) (P=O.O13)

Angle 8 1 Body 2 1 Symphysis 5 0 Extra-oral 1 2 Intra-oral 14 0

arisen from an abscessed tooth which had not been removed at the time of fracture treatment. The 15 patients in the ‘Mini’ plate group who developed infections were treated by antibiotics and removal of the plates. In 3 patients additional sequestrectomy was required. One of these patients was treated by replacing the ‘mini’ plate with a ‘rigid’ plate’.

Eight plates (9.1%) in six patients were removed in the ‘Rigid’ group. All but one of the plates/screws were firm at the time of removal. In the ‘Mini’ group, 56 mini- and micro-plates (48.3%) in 32 patients were removed. The difference was statistically highly significant (P=O.O0019). The reasons for plate removal are listed in Table 5.

Weakness of the marginal mandibular branch of the facial (VII) nerve, which was not recorded as having recovered eighteen months after treatment, complicated 7 (7.9%) of patients in the ‘Rigid’ group. The actual long term figure could be a little lower because of the failure of some patients to attend out- patient follow-up appointments. None of the ‘Mini’ group had this complication. This difference was statistically significant (P = 0.007). It was always associated with an extra-oral approach.

Treatment outcome was further analysed in relation to the type and site of fracture. Significant differences were identified in cornminuted and angle fractures. There were 7 cornminuted fractures (8.2%) in the ‘Rigid’ group and 12 (10.3%) in the ‘Mini’ group.

A comparative review of 266 mandibular fractures 319

Table 5 - Analysis of plates removed

No. of patients No. of plates No. of fractures

Site (in ‘Xl) Angle Body Symphysis Ramus

Reason (in ‘%I) Infection Pain Non-union Exposed plates Elective

‘Mini’ plates ‘Rigid’ plates

32 6 56 8 37 8

40.5 31.5 35.1 25 18.9 37.5

5.5 0

37.8 25 8.1 75 8.1 0

16.3 0 29.7 0

Table 6 -Complications of comminuted fractures

Use of IMF Infection Malocclusion Plate removal VII nerve damage

‘Mini’ plates ‘Rigid’ plates (n= 12) (n=7)

2 0 4 1 4 0 5 1 0 1

Table 7 - Complications of angle fractures

Use of IMF Infection Malocclusion Plate removal VII nerve damage

‘Mini’ plates (n=58)

II 6 6

15 0

‘Rigid’ plates (n=34)

0 I

2 3 4

Over all, complications rates were significantly higher in the ‘Mini’ group (P=O.O17). The distribution of the complications is listed in Table 6. There were 34 angle fractures in the ‘Rigid’ group and 58 in the ‘Mini’ group. Analysis of the complications is given in Table 7, which showed a significantly higher incidence of complications in the latter group (P= 0.00091).

DISCUSSION

Ewers and Harle6 quote the first description of mandibular fracture fixation using plates and screws by Hausmann in 1886. Several authors have advocated the use of different types of plating system. The results of such modes of fixation were initially incon- sistent and consequently acceptance of this method was slow. However, the introduction of better bio- compatable and well-designed plates and screws has led to improved success rates. Additionally, modifications in surgical techniques and better understand- ing of the biomechanics of bone repair have produced more acceptable results and these techniques are now practised widely and routinely.

During function of the lower jaw, tension occurs

at the level of the dentition whereas compression will be observed along the lower border. In the symphyseal region, torsional forces produce a combination of tension and compression.’ It is known that osteo- syntheses are most effective if they are carried out in the zone of tension.’ In the mandible, however, the presence of teeth and the inferior alveolar nerve prevents surgeons inserting plates in the ideal zones. Based on these principles, different methods of plate fixation for the mandible have been developed to solve the problem of stabilisation of displaced fracture segments.

Spiessl and Schroll” described a plate-fixation system which was applied to the lower border of the mandible. the biomechanically most unfavourable site. However, special gliding holes in these plates were designed to provide a dynamic compression system of plates and bicortical screws which gave perfect stability to the fracture segments. The increased stability at the fracture site is produced by tight approximation and larger contact surfaces gen- erated by the compressive forces.” Primary bone healing occurs when axial compression yields tight approximation of the fragments at the fracture site, promoting direct extension of osteocytes across the small bone gap. This type of primary bone healing occurs without external callus formation, thereby shortening the time period for remodelling and consolidation. 11,”

Champy+’ introduced a mini-plate system based on the plates developed by Michelet’ to treat midface fractures. The plates are applied close to the tension zone of the mandible. Because of the dentition and alveolar nerve, the screws have to be monocortical. Champy states that this mini-plate system also gives sufficient support and stability to the bone fragments to allow immediate function.’

Although studies comparing wire osteosynthesis and plating have proved the superiority of the latter,‘” no studies so far have attempted to compare treatment results of different plating systems. Reports on separate plating systems have claimed varying success rates,‘.14.15

In this study, and despite the limitations of a retrospective review of this kind, demographic features, aetiology, types of fracture and the time from injury to operation were comparable in both groups as were the populations from whom the patients were drawn. Assault was the cause of fracture in over half of the patients in both groups. Many of the patients abused alcohol and these patients are known to have reduced healing capacity and poor co-operation.‘”

There was an uneven distribution of patients by sex between the two groups with a higher proportion of females in the Mini-plate group and this was statistically significant (P=O.Ol). This was thought to have been due to a wish to avoid an external scar in such patients. It is likely that this would produce a small bias in favour of the results in the Mini-plate group as it has been shown that females apply less force to the mandible during function than do males.” The main variable factor which could have

320 British Journal of Oral and Maxillofacial Sur~erv

affected treatment outcome was the method of plating used.

There was a significant difference in the surgical approaches. In most situations, mini-plates could be inserted through an intra-oral incision. This avoided two important drawbacks of rigid fixation-facial nerve weakness and facial scar. The incidence of facial nerve damage (7.9%) in this study was in agreement with the reported incidence of nerve damage of O-12% elsewhere.15*i8 Most of this injury probably resulted from traction of soft tissue at the time of surgery. This can be avoided by using a careful soft-tissue technique. l5 A higher proportion of such plates may now be inserted intra-orally with improved trans-buccal instrumentation and experience.

None of the patients in our study developed hypertrophic scars or required scar revision. Other authors have also reported that satisfactory scars in this region can be obtained. “J Placing the incision along the lateral neck skin creases reduces the incidence of unacceptable scars. Post-traumatic swelling can however make it difficult to identify natural skin creases. There is also individual variation in the predisposition to hypertrophic scars. This factor needs to be taken into consideration when treating populations with increased risk of developing such poor scars.

This study has revealed a significant difference in the incidence of infection (2.3% vs 12.9%) between the two plating systems in favour of the ‘rigid’ system. Infection rates between 3% and 13% have been reported with rigid plate ostosynthesis20-22 and with mini-plates the reported incidences of infection vary from 4% to 32%.2,23,24 Infection at a fracture site can have serious sequelae. It can initiate delayed union, non-union and in some cases malunion’* as well as bone and tooth loss. It may increase the need for plate and screw removal as reported in this series. Prevention of infection and, if it occurs, prompt identification of the cause as well as treatment, are thus essential principles of fracture management.

Most of the infected fractures in this series belonged to the angle region as reported by other authors.2s However in the mini-plate group, a significant number of plates at the symphyseal region also developed infection. Another predisposing factor for infection identified in our series was cornminuted fractures treated with mini-plates. The superiority of rigid plates in preventing infection in cornminuted fractures may be related to the stability of fixation achieved by this technique and has been reported by other authors. 26 Ezsias and Sugar 27 have reported similar better results for pathological fractures managed by Reconstruction plates. Mobility of fragments has been shown by other authorslg to predispose to infection. The angle and symphyseal regions have been shown to produce torsional forces.28 At the angle region, in addition, the cross sectional area is less than in the middle part of the mandible, decreas- ing the area of medullary bone contact. In one series, tapping of the hole seemed to reduce the rate of infection by 10% but the infection rate in this report was very high at 32% with the use of 2.4 mm com-

pression plates. 22 The same authors have also reported a high incidence of 18 and 25% infection with mini-plate fixation at the angle.23,25

Both the plating systems were successful in restoring a functional occlusion. However the Rigid plating system was more reliable at avoiding the postoperative use of elastics, and IMF was not used in any of the patients in this group. Mini-plates should be regarded as a semi-rigid fixation system allowing the use of elastic traction to correct small occlusal discrepancies post operatively. This flexibility in treatment is lacking in rigid fixation.

CONCLUSIONS

Both plating systems were successful in restoring functional occlusion. Rigid plates in this series usually required an extra-oral approach with the risk of facial nerve damage. The incidence of infection and plate removal was higher in the mini-plate group. A better treatment outcome for angle and comminuted fractures was observed with rigid plates.

Acknowledgements

The authors wish to thank Professor S. S. Prime and Dr B. G. H. Levers for their assistance in the statistical analyses.

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The Authors

M. A. Kuriakose, BSc, MB, ChB, FDSRCS, FFDRCS Senior Registrar Catherine Cookson Maxillofacial Unit Newcastle General Hospital, Newcastle-upon-Tyne, UK M. Fardy, FRCS, FDSRCS Senior Registrar Department of Maxillofacial Surgery Queen Victoria Hospital, East Grinstead, Sussex, UK M. Sirikumara, MBBS, FDSRCS, FFDRCS Associate Specialist in Oral and Maxillofacial Surgery Royal Gwent Hospital, Newport, UK D. W. Patton, FRCS, FDSRCS Consultant Oral and Maxillofacial Surgeon A. W. Sugar, FDSRCS Consultant Oral and Maxillofacial Surgeon Maxillofacial Unit Welsh Centre for Burns, Plastic Surgery and Maxillofacial Surgery Morriston Hospital. Swansea. UK

Correspondence and requests for offprints to Mr A. W. Sugar, Consultant Oral and Maxillofacial Surgeon, Maxillofacial Unit, Welsh Centre for Burns, Plastic Surgery and Maxillofacial Surgery Morriston Hospital, Swansea SA6 6NL

Paper received 8 December 1994 Accepted 17 July 1995

a comparative review of 266 mandibular fractures with

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