L. Greaney, J.G. Cowpe, C. Clokie, F. Kienle, T. Meisami

Keywords: Mandibular fractures, epidemiology, trauma, jaw fractures, treatment methods

Short Title: Mandibular Fractures: UK vs. Canada.

A retrospective 5 year study was carried out at the Toronto General Hospital and the Bristol Royal Infirmary of 394 patients who were admitted for surgical treatment of mandibular fractures between January 1995 and June 2000. Patients were analysed with respect to age, gender, presence of separate dento-alveolar fractures and method of treatment (closed or open reduction).

Aim

To assess whether there were any significant differences between the two centres and to suggest possible explanations.

Methods

Data was collected from patient notes and computer databases. Chi squared statistics were used for analysis.

Results

The majority of mandibular fractures occurred in males in the 20-29 age group. Dento-alveolar fractures were infrequent. Both centres used open, closed and combination reduction methods to differing extents with BRI using open reduction more commonly and TGH using combination of open and close methods.

Conclusion

The two hospitals did not significantly differ in their results.

Mandibular fractures are among the most common facial fractures and their treatment is routinely managed by Oral and Maxillofacial Surgeons. According to Lentrodt¹ mandibular fractures present in 55% of facial and skull fractures, with 8% of these occurring in conjunction with midface fractures.

Rowe and Williams found that the peak age for facial fractures lay between 20-29 years of age, and that there was a far greater incidence in males than females². These observations are supported by other authors^3-6. Routine methods of fixation for mandibular trauma consist of open reduction where the fracture site is accessed directly during surgery, closed reduction when the fracture is reduced without exposing the fractured bones, or by a combination of both methods of treatment⁷.

This retrospective study compared several aspects of the demographics and treatment of mandibular fractures in two separate population bases, the Toronto General Hospital (TGH) in Canada, and the Bristol Royal Infirmary (BRI), UK. Despite the distance between the centres, different populations and cultures, there are a number of similarities between the centres. They are both teaching hospitals and supported by government health insurance plans, the Ontario Health Insurance Plan (OHIP) in Canada and the National Health Service (NHS) in Britain.

The aim of this study was to investigate demographic factors and the methods of treatment of mandibular fractures, to determine whether there were any significant differences between the two Maxillofacial centres having noted the obvious geographical and cultural differences.

All patients requiring surgical treatment for mandibular fractures and admitted to the operating theatre between January 1995 and June 2000 were included in the analysis. A total of 245 records were analysed at the BRI and 149 records at the TGH. A proforma was produced for each patient and the surgical database at the BRI used to assimilate the necessary data in the UK. This is a computerised database which contains information regarding each operation. As patient notes and radiographs were scrutinised in Canada, the required approval from the local Human Ethics Committee was obtained.

The proforma recorded the following information:

Age was categorised as <20 years; 20 – 29 years; 30 – 39 years and >40 years. Gender was recorded. The presence of a separate dento-alveolar component was recorded as was the method of reduction - open, closed or combination. No attempt was made to classify the mandibular fractures by site to reduce the number of categories into which individuals may have fallen. Aetiology was unfortunately not available from case notes and could not be included.

The demographics of the two study groups are displayed in Table 1.

Ages ranged from 12 to 95 years. The data indicate a peak incidence in the age range for patients with mandibular fractures of 20 – 29 years of age. TGH also displayed a slightly higher incidence in the >40 age group. Chi-squared analysis applied to the data found no statistically significant difference between the centres (p = 0.065). No consideration was given to categorising age above 40 years because of the small number of subjects found above this age.

In both hospitals 16% of patients were female and 8% were male with 41 of 245 patients at BRI and 24 of 149 patients at TGH. The preponderance of males was highly signficant (p<0.001).

Charts 1 and 2 compare age distribution within the confines of gender. Chi squared analysis displayed no statistically significant difference in the incidence of fractures among males (p = 0.20) or females (p = 0.16) in the two hospitals.

Chart 1

Chart 2

No dentoalveolar fractures were seen at the TGH despite there being 149 patients treated for mandibular fractures. At the BRI three of the cases included a separate dentoalveolar component. No formal statistical analysis was carried out because of the small number of dentoalveolar fractures.

Data were unavailable for 3 patients at both the BRI and at the TGH (1.2% and 2.0% respectively). The percentage number of patients receiving closed, open or both methods of reduction in the two centres are displayed in Table 2.

Open reduction was carried out more frequently at the BRI whereas a combination of both methods of treatment were used most commonly at the TGH. The difference in treatment methods between the two study centres was found to be statistically significant (p < 0.001).

DISCUSSION

Most patients in this study group were in the 20 – 29 year age group, which coincides with the findings of many other authors^2-6. Mandibular fractures were also significantly more common in the male population, which was again expected given that males are commonly more involved in inter-personal violence, often due to alcohol imbibition, falls and sport injuries.²

When one separates gender to consider age, it is interesting to note that the incidence of mandibular fractures in females from both countries peak in the >40 age group. This might possibly reflect the number of females in our ageing world population, with females generally living longer than males. The prevalence of osteoarthritis leading to falls in the female patient group could also be relevant, as could an increased exposure to domestic violence. There was an apparent small difference in the distribution of ages that occurred between the two hospitals but this was not statistically significant.

There was a statistically significant difference in age distribution within the genders when comparing the two centres, but population numbers do not allow any meaningful conclusions to be extrapolated.

It is unusual to apply a force to the mandible, being fixed at two points, the temporomandibular joints, which will only cause a single fracture line. Fractures tend to be present in the opposite side of the mandible, but not necessarily in the corresponding contralateral site ⁸. The second site of fracture depends on the site of impact, the direction and magnitude of the force encountered, the density and shape of the object involved and where the weakest points are in each individual mandible ^2,8. The surrounding musculature will also influence the site of fracture as well as influencing the displacement of the fragments, and it is generally found that tensile strain is less resistant to fracture than compressive strain⁸. The position of the lower alveolus in relation to the upper alveolus allows a partial state of physical protection at rest, as does the spatial orientation of the alveolus, being tilted in towards the oral cavity. Initial contact with the mandible is very unlikely to encounter any alveolar bone. This supports the findings of the present survey that dentoalveolar involvement is infrequent.

No single type of treatment was considered appropriate in all cases due to the range of injuries encountered, each having their own specific treatment considerations such as the presence of a suitable dentition ⁷. Open reduction served the vast majority of patients at the BRI, with a small number of clinicians utilising closed reduction and only a few patients having a combination of treatment modalities. At the TGH all three categories of treatment were used to a more equal extent, but a combination of treatment methods were used most frequently. Open reduction tends to be used for the more severe fractures where there may be insufficient teeth for wiring or splinting, where fragments of bone cannot be satisfactorily repositioned by closed reduction, or where the patient’s medical condition contraindicates long-term immobilisation of the jaws or when mobilisation is necessary as soon as possible ³. Differences found between the modalities of treatment in the two centres would likely be due to the proportions of fracture types encountered. Another contributing factor may be that both centres are teaching hospitals, with current treatment under constant supervision, course contents constantly monitored and re-written, and new techniques often explored.

It is also noticeable that the results from both hospitals are surprisingly similar despite obvious geographical and culture differences. This might be related to similarities in funding, both being centrally funded. Many females over forty were treated as were several young patients, some who might not necessarily be able to afford private treatment and therefore may not have presented at the hospitals had state care not been available.

This study has examined aspects surrounding the patients presenting with mandibular fractures at the Bristol Royal Infirmary and the Toronto General Hospital between the period of April 1995 and June 2000. Many of the results found agree with those of previous authors. Mandibular fractures were seen most frequently in males in the 20 – 29 years age range. Dentoalveolar fractures were infrequently seen, and a mixture of open and closed reduction was used to a greater or lesser extent at both hospitals. Both hospitals shared common findings and a few possible contributors to this were suggested in the discussion. However more research is needed to fully establish whether these conjectures are appropriate.

I would like to thank the Toronto General Hospital for their kindness and for hosting me over the summer of 2001. I would especially like to thank Dr Clokie, Paddy and Drs Kienle and Meisami. I would also like to thank Professor Cowpe and Professor Addy for their patience.

1. Lentrodt J: Maxillofacial Injuries – statistics and causes of accidents, in Kruger, E, Schilli W: Oral Maxfac Traumatol. Chicago, Quintessence, 1982, vol 1, p 43
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7. Donoff, R. B.: Facial Trauma, L. L. Duncan, Manual of Oral and Maxillofacial Surgery, Missouri, 3^rd Ed., Mosby, 1997, 299-303
8. Rowe NL, Killey HG: Fractures of the Facial Skeleton, Edinburg, 2^nd ed., Livingstone, 1968: 180