Reduction of the frequently extremely delicate proximal fragment can be very difficult, especially in the case of dislocation fractures.
A prerequisite for reduction is that the mandibular ramus is pulled downwards.
For this purpose, a hole is drilled for fixation of a one-pronged hook in the region of the angle of the jaw using a rose-head burr. The bone can then be pulled downwards with a sharp clamp or a wire that is threaded through the bone. Reduction of the articular disk is not usually required, even for dislocation fractures, as demonstrated by post-operative MRI examinations (Eickelt and Klengel 1996).
For auricular access, a bone clamp is attached transcutaneously.
zu sehr guten Konditionen
Methods of reduction of a dislocated fragment
1. using a raspatory (periosteal elevator)
The raspatory is passed upwards medially along the mandibular ramus. With it, the luxated condyle may be repositioned in the fossa. An assistant with a second raspatory exerts pressure laterally on the lower end of the small fragment. Where there is both intra- and extracapsular fractures and auricular access, the dislocated condylar head is repositioned using small hooks.
2. using reduction forceps
After identification of the dislocated condylar head and preparation with a periosteal elevator, the condylar head can sometimes be uprighted using repositioning forceps or angled forceps with which the condylar neck is grasped. The repositioning forceps can then be left in-situ during the ongoing surgical procedure, facilitating the fixation of fragments during osteosynthesis.
3. using a lag screw
In some cases, especially fractures following a more perpendicular course from cranio-lateral to caudo-medial, Eckelt (2000) uses a lag screw for reduction of the condylar head. The screw is inserted through a troachar via a transbuccal approach. It is important to ensure that the screw is inserted into an area of the condylar head such that it will not be in the way of subsequent osteosynthesis plates and screws.
Functionally stable osteosynthesis materials
The plate is fixed using at least 2 screws on both sides of the fracture.
Where there is a high condylar neck fracture, the joint capsule must be opened for this purpose.
In these cases, an alternative is the use of an L-shaped plate or a miniplate modified especially for this joint region (Champy-Magdeburg condylar fracture plate) with a smaller distance between the holes of the plate on the side of the lesser fragment. Insertion of the screws into the lesser fragment may sometimes be extremely difficult. Special instruments such as a rectangular screw driver are particularly useful. Transbuccal insertion of the screws is also possible.
If the miniplate was inserted via an external approach, it must also be removed later through an external access to the joint if the osteosynthesis material is to be removed after healing of the fracture. Due to scar formation following the primary surgical procedure, this is sometimes associated with a higher risk of damage to the facial nerve than the primary access for osteosynthesis. Another option is to remove the plate via an oral approach with transbuccal removal of the screws.
Biomechanically, miniplate osteosynthesis is not the ideal method due to the position of the plate at the lateral margin of the mandibular ramus.
If a pre-auricular approach is selected, the condylar neck is exposed first and then the condylar head is located. Where the condylar head is medially displaced, the fossa is empty; only the distal margin of the condylar fragment located perpendicular to the ascending ramus is visible. Repositioning of the condyle in the fossa is achieved using a hook, periosteal elevator or both and pulling laterally, with caution. Following repositioning of the condyle in the fossa, the distal end of the fragment is aligned to the stump of the ascending ramus and held in place by intermaxillary fixation. The fracture is reduced monocortically with a miniplate on the lateral surface. Because access below the fracture is limited by the pre-auricular access, fixation of the plate may require a transcutaneous trochar to enable insertion of the lower screws. Another alternative is the use of an L-shaped plate in which both screw holes lie at the same horizontal level below the fracture line. In order to achieve functionally stable fixation, preventing flexible movements of the condylar fragment, a minimum of two screws are inserted on each side of the fracture.
Reduction of the condylar fragment is achieved using a clamp or bone holding forceps. A straight four-hole miniplate is used for osteosynthesis. In order to achieve greater stability, screws are recommended with a diameter of 2 mm (Ellis and Dekan, 1993). Bicortical screws may also be used. If the condyle is significantly displaced medially, it is often difficult to locate the fragment.
Lag screw osteosynthesis
In the modified procedure according to Eckelt (1999 a, b), a groove of 15 mm length and 2 mm width is drilled caudally into the mandibular ramus without penetrating the inner cortex. This groove corresponds to the later course of the gliding canal. It is extraordinarily useful for orientation when the gliding canal is prepared. The gliding canal is placed centrally from the lower border of the mandibular ramus. The groove prepared before in the area of the gliding canal will then permit a good view on the fracture line. In the case of oblique fractures and a narrow mandibular ramus, the groove in the outer cortical bone is made to proceed into the proximal fragment and will thus reach areas where sufficient bone is available.
The traction screw can be removed again when healing of the bone fracture is complete after 4 - 6 months through a small stab incision in the area of the scar resulting from osteosynthesis surgery. Removal requires local anaesthesia only and does not require hospitalisation. The relatively simple procedure for removal of osteosynthesis material facilitates the decision for or against removal for the surgeon, and is an advantage over other functionally stable methods for osteosynthesis.
An extremely narrow or curved mandible is considered a contra-indication for lag screw osteosynthesis because in these cases the gliding canal is not sufficiently covered laterally with cortical bone (Welk and Sümnig 1999).
Combination of lag screw and plate
Because of the varying bone thickness of the ascending ramus, reliable fixation and sufficient stability of the fragment cannot always be achieved using lag screws and plates, particularly so in a very narrow mandible. The combination of lag screws and miniplates referred to as Wurzburg lag screw plate system may be an alternative (Reuther J 1999). The gliding hole in this system permits relocation of the screw, so securing improved inter-fragment compression.
The tooth-bearing fragment is exposed via an extra-oral access.
The large fragment is slightly contoured on the outer surface using a bone mill and then a diamond-covered cylindrical drill. The instrument tip is centred on the small fragment, the drill lying parallel to the posterior margin of the ramus. The plate is pre-fixed in this gap at a distance of 5 - 8 mm from the fracture line at the posterior margin of the ramus. The distance between plate and fracture line is determined by the thickness of the condylar neck and the angle of inclination of the guiding sleeve of 10°. As a rule, this distance is 5 - 8 mm, assuming that the condylar neck has a thickness of approx. 5 mm in the area of the fracture. For pre-fixation, the fixation screw lies in the centre of the gliding hole. The guiding sleeve at the upper end of the lag screw plate has an angle of inclination of 10° to the bone surface. Through this guiding sleeve, the lag screw is inserted into the medullary bone of the small fragment after reduction and pre-drilling, if required; then it is fixed to the larger fragment.
Final fixation is achieved by fastening the screws in the gliding and fixation holes of the plate. If the lag screw in the small fragment cannot be sufficiently secured, then the system may be used only for reduction; immobilisation must then be achieved using intermaxilly fixation (Reuther 1999).
Lag screws or small fragment titanium screws for intracapsular fractures
Rasse (1993) described an osteosynthesis procedure using absorbable poly-p-dioxanone (PDS) pins for the fixation of intra-capsular fractures. This procedure enables also the insertion of smaller fragments. For reasons of stability, two titanium mini-traction screws were used later instead of the absorbable pins. Neff et al. (1999) also considered fixation with absorbable pins alone to be insufficient.
While unilateral fractures may often be functionally compensated by neuromuscular adaptation mechanisms following conservative treatment, bilateral fractures will usually result in obvious functional disorders. The pull of the masticatory muscles leads to shortening of the mandibular ramus resulting in a more or less severe anterior open bite with retrusion of the mandible. Auto-elevation of the luxated fragment cannot be expected at all as it is prevented by contraction of the lateral pterygoid muscle after the fracture. Even in unilateral fractures, the vertical loss of height with its changed functional geometry will lead to clinical problems in approx. 40–70 % of the patients in the long term. Neff et al. (2002) recorded connections between clinically and/or axiographically determined limitations their patients suffered, and the kind of osteosynthesis material used. There were limitations following the use of absorbable ostesynthesis materials that were primarily considered the result of the low primary stability of the osteosynthesis that seemed suitable for immediate loading associated with exercise only under certain conditions. Furthermore, their patients suffered limitations following the use of plating systems for osteosynthesis (miniplates, microplates). Clinically, scarring of the capsule and ligaments has been observed in the course of necessary removal of osteosynthesis material, particularly in the case of loosening of material and/or screws. Furthermore, the miniplates used are usually relatively large in order to achieve sufficient primary stability and frequently induce clearly visible scars due to their direct relationship to the lateral ligament. Therefore, Neff et al. (2002) use small-fragment titanium screws (diameter of 1.7 mm, lengths of 13–17 mm). They offer the possibility of immediate physiotherapy with the patient under normal loading conditions as a major prerequisite for optimal functional results.
- Soft tissue defect
- Degree of dislocation
- Impaired air passage
- Number of fractures (multiple fractures, segment fractures)
- Foreign bodies
- Wound contamination
- Insufficient blood supply to fragments and overlying soft tissues
- Malocclusion present prior to the accident
- Concomitant injury in the maxillofacial region
- Pre-trauma complaints and/or disorders of the temporomandibular joint
- Time elapsing prior to treatment of the fracture
- Tendency for formation of keloid or hypertrophic scars
- Pre-trauma bone damage (metabolism, irradiation)
- Change of shape and position of the disk
- Facial deformity
- Skeletal deformity
- Functional disorder (limited incisal edge distance or mandibular excursion)
- Impaired occlusion and/or masticatory function
- Disturbed speech and/or swallowing
- Impaired air passage
- Chronic pain
- Chronic infection
- Chronic neurological functional disorder (motor function and/or sensory function)
- Facial nerve
Some patients suffer from a disturbed motor function of the lower lip immediately following surgery. This damage is transient and is caused by the intra-operative traction of the surrounding soft tissues.
- Auriculo-temporal syndrome (Swanson et al. 1991)
- Bleeding and haematoma development are possible.