Experimental studies of the fracture behaviour of the mandibular condylar process

"Crack under pressure"-Inducing life-like mandible fractures as a potential benefit to surgical education in oral and maxillofacial surgery

The aim of this study was to investigate whether life-like fractures of human cadaveric mandibles with a focus on the condylar process and the intact soft tissue envelope could be simulated. A total of nine fresh-frozen human head specimens were fractured in a custom-made drop-test bench. This reproducible method is based on a weight falling from a defined height onto the fixed specimens, simulating a direct blow to the symphysis of the mandible. All the fractures were analyzed by fluoroscopy and CT-scans. In all the specimens that were included in this study, several typical lesions could be created, resulting in a total of 27 mandible fractures. Seven condylar head fractures with intracapsular fracture patterns, three high, two low and five subcondylar fractures as well as different corpus fractures occurred. Human cadaveric mandibles as part of a complete head specimen with intact soft tissue can be successfully fractured by means of a drop-test bench setup. The amount of load and the exact angle at which the load is applied seem to be of high relevance. Such fractured specimens can be implemented in surgical education courses to teach and improve osteosynthetic techniques.

An unusual anterior dislocation of fractured mandibular condyle leading to psuedo-ankylosis in a 8 yr old child-A distinct case report

INTRODUCTION

Literature reviews are replete with discussions focusing on the incidence, types, and patterns of disruption in TM joint function, besides enumerating and classifying its causes. However, atypical situations do present, such situations warranting a detailed, methodical assessment before therapeutic institution.

PRESENTATION OF CASE

Described here is management of a unique case of post-traumatic pseudo-ankylosis in a 8year old child that had an old fractured condyle, displaced and dislocated anteriorly into the sigmoid notch, with eventual fusion to the ipsilateral zygomatic arch on its medial side.

DISCUSSION

Although conventional imaging tools still have relevance, but the significance of multi detector CT scan with multiplanar reformation and three dimensional images have a become unequivocally a standard part of assessment of such complex facial injuries regardless of therapeutic setting. The probable explanation for the condylar fracture and unusual anterior dislocation of the condylar segment is also hypothesized.

CONCLUSION

Although Post traumatic ankylosis is common in developing countries like India, distinct cases do present rarely which requires a disciplined approach in the management of such cases.

Mechanics in the Production of Mandibular Fractures: A Clinical, Retrospective Case-Control Study

As the mandible is susceptible to fracture, the aim of this study was to use multivariate logistic regression analysis to identify and distinguish various internal factors that may influence the location of mandibular fractures. The study included 1131 patients with maxillofacial fractures during the period from January 2000 to December 2009 to evaluate the association of mandibular fracture location (unilateral symphysis, body, angle, condylar, or bilateral condylar fractures) with various internal factors. Among the 1131 patients, 869 had mandibular fractures. Data on age, sex, soft tissue injuries, dental trauma, and maxillofacial fracture type were collected and analyzed using multivariate logistic regression. In total, 387, 210, 139, 319, and 172 patients were diagnosed with unilateral symphysis, body, angle, unilateral, or bilateral condylar fractures, respectively. The dental trauma in patients with bilateral condylar fractures differed from that in patients with unilateral condylar fractures. Patients with mandibular fracture (unilateral symphysis, body, unilateral or bilateral condylar) possessed an approximately equal risk of soft tissue injuries in the mandible. Patients with either unilateral or bilateral condylar fractures were associated with a low risk of mandibular angle fracture (OR < 1). Similarly, patients with mandibular angle fracture were associated with a low risk of unilateral or bilateral condylar fractures (OR < 1). Moreover, patients with symphysis fracture were associated with a low risk of bilateral condylar fractures (90 of 387 [23.3%], OR 0.899). By contrast, patients with bilateral condylar fractures were associated with a high risk of symphysis fracture (90 of 172 [52.3%], OR 17.38). Patients with condylar fractures, particularly those with bilateral condylar fractures, were infrequently associated with secondary mandibular fractures. Mandibular fractures tended to have less of an association with midfacial fractures. The occurrence of mandibular fractures is strongly correlated with age, sex, soft tissue injuries, dental trauma, and the pattern and position of the maxillofacial fractures in patients.

Mandibular fracture patterns consistent with posterior maxillary fractures involving the posterior maxillary sinus, pterygoid plate or both: CT characteristics

OBJECTIVES

The aim of this study was to determine the incidence of posterior maxillary fractures involving the posterior maxillary sinus wall, pterygoid plate or both, unrelated to major midface fractures in patients with mandibular fractures, and to characterize associated fractures.

METHODS

A CT study was performed in patients with mandibular fractures to identify posterior maxillary fractures. Patients aged under 16 years, those with mandibular fractures involving only dentoalveolar components and those with concurrent major midfacial fractures were excluded.

RESULTS

13 (6.7%) of 194 patients with mandibular fractures also had posterior maxillary fractures (case group). The injury pattern correlated with the external force directed to the lateral side of the mandible (p < 0.001), alcohol consumption (p = 0.049), the presence of multifocal fractures (p = 0.002) and the fracture regions in the symphysis/parasymphysis (p = 0.001) and the angle/ramus (p = 0.001). No significant difference between the case and non-case groups was seen for age, sex or cause of trauma. Non-displaced fractures in the ipsilateral posterior mandible occurred with significant frequency (p = 0.001) when the posterior maxillary fractures involved only the sinus.

CONCLUSIONS

Mandibular fractures accompanied by posterior maxillary fractures are not rare. The finding of a unilateral posterior maxillary fracture on CT may aid the efficient radiological examination of the mandible based on possible patterns of associated fractures, as follows: in the ipsilateral posterior region as a direct fracture when the impact is a medially directed force, and in the symphysis/parasymphysis or contralateral condylar neck as an indirect fracture.

Clinical experience with osteosynthesis of subcondylar fractures of the mandible using TCP plates

AIM

To evaluate the clinical and radiological results obtained with a new kind of osteosynthesis device (Modus TCP) plates, Medartis, Basel, Switzerland), especially designed for low subcondylar fracture (LSCF) and high subcondylar fracture (HSCF) of the mandible in association with the high submandibular approach (HSMA).

METHOD

A prospective clinical and radiological study was carried out over a 41-month period. All adult patients suffering from a displaced LSCF or HSCF who consented to the surgical treatment were included in the study. All fractures were operated on using an HSMA and were stabilised using a 4- or 9-hole TCP((R)) plate. No intermaxillary fixation was used and a soft diet was started on the 1st postoperative day. Clinical examinations and control X-rays were carried out on the 10th postoperative day, in the 1st, the 3rd and, at least, in the 6th postoperative months.

MATERIAL

Sixty-four patients (12 females, 52 males - mean age: 28.3) with a total of 75 fractures (54 LSCF, 21 HSCF) were included in the study. Mean postoperative follow-up was 14 months.

RESULTS

In the 6th postoperative month, all fractures were consolidated in 79% of the cases in an anatomical position. A secondary displacement of the fracture occurred in 6.6% of the cases. Plate fracture was not observed. Dental occlusion remained unchanged in 94% of the patients. The mandibular movements (mouth opening, protrusion, lateral movements on the unfractured and fractured side) had normal mean values (49.5, 10.4, 12.8, 12.1mm, respectively). These movements were symmetrical in 95% of the patients. No patient complained about articular pain or noise. No facial nerve palsy was noticed, not even a transiently one. All patients but one found the scars acceptable.

CONCLUSION

TCP plates, in association with HSMA, were found to be an efficient osteosynthesis device for stabilising subcondylar fractures.

Experimental evaluation of three osteosynthesis devices used for stabilizing condylar fractures of the mandible

INTRODUCTION

The purpose of the study is to evaluate experimentally the quality of the primary stability achieved in treating low subcondylar fractures by means of three different osteosynthesis devices.

MATERIAL AND METHODS

The devices, a standard four-hole plate, an axial lag screw and a three-dimensional rectangular plate were tested on fresh isolated human mandibles. Testing was done on a test bench by reproducing static biting exercises between the first molars on the side of the fracture. The quality of the osteosynthesis was assessed by measuring the macroscopic amount of fragment displacement and on the device's ability to diffuse the mechanical strain within the fractured area by photoelastic stress analysis.

RESULTS

The straight plates provided the worst restoration. This was explained by the unfavourable position of the plate along compression lines. The axial lag screws allowed average stability. This was due to the difficulty of intra-medullary positioning of the screw, and by the compression of the fracture line. Rectangular plates allowed good stability associated with rather good restitution of the strains. These good results were assigned to the shape of the plate, one of its arms approximating the tensile strain lines.

CONCLUSION

Positioning and shape of the osteosynthesis device are of prime importance for condylar fracture stabilization. None of the three tested devices was optimal but the three-dimensional plate was the best. There is a need to develop the geometry of new plates.

Ballistic Impact to the Forehead, Zygoma, and Mandible: Comparison of Human and Frangible Dummy Face Biomechanics

BACKGROUND

Currently, there is a greater use of nonlethal force in law enforcement and military operations. Because facial injuries have been observed, there is a need to understand the human response to ballistic impacts involving various regions of the face. This study aimed to establish blunt ballistic response corridors for high-speed, low-mass facial impacts to the forehead, zygoma, and mandible, and to determine how these responses compare with those of the frangible Hybrid III headform. Correlation of the human and dummy responses allows injury risk assessment for munitions used in the field.

METHODS

Facial impacts to the forehead, zygoma, and mandible of six cadavers at 42 +/- 10 m/sec were conducted using a 25- to 35-g projectile 37 mm in diameter that was instrumented with an accelerometer to determine impact force. High-speed video analysis determined penetration of the projectile, and autopsy determined the facial fractures. Force and deflection were normalized for the 50% tile response, and corridors were determined for blunt ballistic impacts. Similar tests were conducted on the frangible face of the Hybrid III dummy.

RESULTS

Peak normalized force of 3.5 +/- 0.9 kN on the forehead and 3.0 +/- 1.0 kN on the mandible did not result in fractures, whereas an impact force of 2.3 +/- 0.5 kN on the zygoma caused anterior maxilla fractures. The frangible Hybrid III face developed similar force levels, but with less penetration of the projectile. Its stiffness was 43% greater than that of the cadaver.

CONCLUSIONS

Higher impact force can be tolerated on the forehead and mandible than on the zygoma. Normalized force-deflection and force-time corridors were established for the human response. The frangible Hybrid III face is an effective surrogate for assessing ballistic injury risks, but greater compliance would make it more biofidelic. Initial human tolerance levels of 6.0 kN for the forehead, 1.6 kN for the zygoma, and 1.9 kN for the mandible have been established for ballistic impacts to the face.

Deformation characteristics of the human mandible in low impact experiments

A total of 11 human mandibles were subjected to physical impacts under standardised conditions. Two impact sites and directions were tested and the impact load was varied in four steps. Two occlusional strengths were applied and the influence of simulated soft tissue covering was recorded. The deformation of the bones was measured using strain gauge strips located at eight defined sites. In a series of frontal to occipital impacts the frontal areas and the collum showed the largest length changes. Increasing impact intensities led to a proportional increase of the length changes. An increase of the occlusional strength was either protective (at the collum) or it increased the deformation (frontal area). The soft tissue covering was only partly protective. Lateral impact was characterised by a compression on the side of the impact and stretching on the other side only. The intensity and speed of deformation increased with increasing distance from the site of impact. A fixed occlusion caused an increase of compression at the site of impact and an increasing stretching in the frontal part of the bone and at the opposite collum.

Stability of the mandibular condylar process after functionally stable traction-screw-osteosynthesis (TSO) with a self-tapping screw-pin

The behaviour under stress of the condylar processes of the mandible was examined as to possible physiological and pathological influence after traction screw osteosynthesis of experimental condylar neck and base fractures. Stresses were applied in a sagittal direction and laterally in a load device fitted with an electronic power recorder. The behaviour under stress was recorded in load-path diagrams. The interfragmentary compression which can be applied intuitively under operating conditions was measured with an electronically calibrated torque wrench and compared with the maximum resistance to tensile stress, i.e. the force necessary to rip the screw out of the proximal fragment. Compared with the strain on the joint resulting from masticatory pressure and the possible performance of the masticatory muscles traction-screw osteosynthesis of condylar neck and base fractures was seen to be functionally stable, but not mastication stable.