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The objective of the clinical study was to evaluate the efficacy of locking plates and conventional miniplates in mandibular fractures. The site of fracture, osteosynthesis, post operative functional ability and complications of fracture after osteosynthesis were evaluated. 21 patients were treated with 2mm locking miniplates (Group1) and 22 patients were treated with 2 mm conventional miniplates (Group 2).
The increasing road traffic accidents have led to a significant increase in maxillofacial trauma. Numerous investigators have reported studies on populations on all continents. Fractures of the mandible have been reported to account for 36-70% of all maxillofacial fractures.1, 2, 3, 4 All reports apparently show a higher frequency in males aged 21-30 years.5 Other contributing factors such as socioeconomic status, environment, alcohol use and mechanisms show greater variability.6, 7
Rigid internal fixation with plates and screws is now standard for the treatment of fractures, osteotomies and reconstruction of the cranio-maxillofacial skeleton. The technique of rigid internal fixation was developed and popularized by Arbeitsgemeinschaft fur Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) in Europe in the 1970s. Champy et al in France developed the concept of adaptive osteosynthesis. Champy8 advocated transoral placement of small, thin malleable stainless steel miniplates with monocortical screws along an ideal osteosynthesis line of the mandible.
These guide lines of AO rigid internal fixation and the Champy method of monocortical miniplates revolutionized the treatment approach to mandibular fractures. An example of this evolution is the treatment of comminuted mandibular fractures. These were thought to be treated best by closed reduction to minimize stripping of the periosteum of small bone fragments. Although this treatment modality is still used, rigid fixation now enables the clinician to avoid closed reduction with the use of reconstruction plates and good soft tissue coverage.9
Mini plates are being used for last several years. With the introduction of locking plates, the disadvantages of conventional mini plates are mostly overcome. In conventional miniplates system the stability is achieved when the head of the screw compresses the fixation plate to the bone as the screw is tightened. In locking plates the screw locks not only to the bone but to the bone plate also. This is accomplished by having a screw with a double thread. One thread will engage the bone; another will engage a threaded area of the bone plate which results in providing mini-internal fixator. The first biomechanical comparison of locking plates to appear in the maxillofacial surgical literature was made by Gutwald17 in 1999; he concluded that a higher stability was achieved with the locking plates.
To evaluate the efficacy, a clinical study was done to compare effectiveness of 2.0 mm locking miniplates and screws with 2.0 mm standard miniplates and screws in treating mandible fractures.
PATIENTS AND METHODS
43 patients with single unilateral fracture of mandible were operated from June 2008 to February 2010. Twenty one patients were treated using 2.0mm locking plates (Group-1) and another 22 patients were treated using conventional 2.0mm mini plates (Group-2). The patients were in the age group of 20- 65 years. A thorough history was taken and meticulous clinical examination was performed on all patients. All subjects who had sustained mandibular fracture were advised a standard orthopantomogram (OPG) and a postero-anterior view of the mandible. A definitive diagnosis of mandibular fracture was established with the aid of clinical and radiographic findings. Data collected included etiological factors, localization of the fracture, time from injury to surgery, osteosynthesis, postoperative occlusion, need for IMF and complications like failure of the hardware and infection at the fracture site.
All the patients were followed for 12 weeks postoperatively. The evaluation was done at 1st week, 4rd week, 8th week and 3rd month.
Table-1: Age Distribution of Patients
Age Range (Years)
No. of Patients
Table-2: Aetiology of Injuries
No. of Cases
Hit by a Bull
Table-3: Site Distribution
No. of Patients
Condylar & Subcondylar
Table 4: Complications (in % of patients)
Number of patients N=21
Number of patients N=22
A total of 43 patients were included in the study. Of the 43 patients, there were 4 females and 39 males. The average age was 34.05+ 3.08 with a range of 22 to 63 years. The cause of trauma was road traffic accident in 33 patients, fall in 4 and assault in 3. All the patients were treated within one week after injury.
The anatomic distribution of fracture site was 24 parasymphysis, 11 angle, 5 body and 2 condyle. 21 fracture sites were treated with 2.0-mm locking miniplates and 22 with 2.0-mm nonlocking miniplates.
After application of the bone plates, all fractures appeared to be well reduced and stable. There were no intraoperative difficulties associated with placement of the fixation hardware. Postoperative radiographs taken within the first 2 days showed excellent reduction in all cases.
Number of patients in which postoperative inter-maxillary fixation required varied in both groups. In group- A, 2 out of 21 patients required IMF postoperatively while the number of patients requiring IMF in group- B was 11 out of 22. Occlusal discrepancy was noticed in one patient of Group B at the third month follow up.
There was significant decrease in pain (VAS) on progressive follow up in both groups although in Group B, 3 patients complained of pain in relation to the fractured site during follow up which was related to infection at the site. No such episode of pain was detected in Group A.
Postoperative infection developed in 4 patients; 1 in group A and 3 in group B. Hardware in 2 fractures had to be removed in group B (angle & parasymphysis region). Both patients had good occlusion and healed fractures at the time of hardware removal. The bone plate was found to be loose from the bone, with granulation tissue around the screw-bone interface. No such complication was found in group A.
The term rigid internal fixation can be defined as "Any form of bone fixation in which otherwise deforming biomechanical forces are either countered or used to advantage to stabilize the fracture fragments and to permit loading of the bone so far as to permit active motion."1 A more basic definition is "Any form of fixation applied directly to the bones which is strong enough to prevent inter-fragmentary motion across the fracture when actively using the skeletal structure2.
Over the past 10 years, there has been an introduction of locking plate-screw systems into maxillofacial surgery. These plates function as internal fixators, achieving stability by locking the screw to the plate. Bone plate-screw systems require precise adaptation of the plate to the underlying bone. Without this intimate contact, tightening of the screws will draw the bone segments toward the plate, resulting in alterations in the position of the osseous segments and the occlusal relationship. Locking plate-screw systems offer certain advantages over other plates in this regard.
The most significant advantage may be that it becomes unnecessary for the plate to intimately contact the underlying bone in all areas. As the screws are tightened they "lock" to the plate, thus stabilizing the segments without the need to compress the bone to the plate. This makes it impossible for the screw insertion to alter the reduction. This theoretical advantage is certainly more important when using large bone plates, such as reconstruction plates, which can be very difficult to perfectly adapt to the contours of the bone.
Another theoretical advantage to the use of locking bone plate-screw systems is that the screws are unlikely to loosen from the bone. This means that even if a screw is inserted into a fracture gap, loosening of the screw will not occur. The possible advantage to this property of a locking plate-screw system is a decreased incidence of inflammatory complications from loosening of the hardware. It is known that loose hardware propagates an inflammatory response and promotes infection. For the hardware or a locking plate-screw system to loosen, loosening of a screw from the plate or loosening of all of the screws from their bony insertions would have to occur. Both of these are unlikely.
A third advantage to a locking screw-plate system is that the amount of stability provided across the fracture gap is greater than when standard non-locking screws are used.
In the present study of fractured patients, the age group most commonly affected was 30-40 years and it was mainly due to road traffic accidents i.e. 55.8%. The number of male patients was higher (91%) than that of female patients (9%), which was in accordance with the other studies.10, 11, 12, 14
One of the interesting findings in our study was that the postoperative IMF was required in lesser number of cases if osteosynthesis was done with locking system. But this finding alone cannot prove the higher stability of locking plate system. The severity of displacement of fracture segments and precise anatomical reduction achieved should be taken into consideration for successful treatment.
In a prospective study10 the efficacy of the treatment of mandibular fractures using a 2.0 mm nonlocking miniplate and 2 weeks of maxillomandibular fixation (IMF) with a complication rate of 4.52% whereas complication rate in our study in nonlocking group was 18.2% with postoperative IMF period of 7 days. The higher complication rate in our study cannot be directly attributed to the lesser period of IMF. Other factors related to patient, operator, and surgical technique may also influence the complication rate.
In another study on 2.0 mm locking miniplate screw system in the treatment of mandibular fractures with 1 week period of maxillomandibular fixation, they found that a single 2.0-mm locking mini plate placed along Champy's line of ideal osteosynthesis plus one week of IMF fixation is a reliable and effective treatment modality for mandibular fractures.11
Several researchers advocated that postoperative MMF should be done for a period of 2 weeks to 4 weeks, 10, 12, 13 but early active mobilization cannot be achieved if postoperative IMF is kept for such a long period, which is one of the main goals of functional rigid fixation.
In our study, it was observed that only 2 patients out of 21 (group- A) required postoperative IMF; that too for a period of 5 days and complication rate was 4.7%. The result of our study also supports the concept of higher stability of the locking miniplate plate system as compared to nonlocking miniplate system. We strongly recommend no postoperative IMF or if required, IMF for a period of 5 days, can be used in both groups, which is supported by many other studies.14, 15
As observed in our study the infection rate was higher in nonlocking group (13.6%) as compared to locking group (4.7%). In patients with persistent infection, it was found that loosening of more number of screws were present on surgical exploration in nonlocking group as compared to locking group. This can be attributed to the greater amount of granulation tissue around the screw bone interface in nonlocking plates. This observation supports the proposed theoretical advantages of locking plate/screw system.
Total infection rate observed in our study was 9.3% and similar kind of observations were being recorded in other studies with the almost similar rate of infection.14, 15, 16 Overall complication rate in our study is 11.6%; with 4.7% in 2.0-mm locking group and 18.2% in 2.0-mm nonlocking group.
From this study we concluded that locking plates are superior to conventional miniplates taking into account its various advantages. The use of locking miniplates in mandibular fracture is efficacious enough to bear masticatory loads during the osteosynthesis of fracture. It has greater stability, less precision required in plate adaptation because of the "internal/external fixator", less alteration in periosteal blood supply and reducing the need and duration of IMF.