Over the last 15 years, the use of internal rigid fixation in oral and maxillofacial surgery has become widely utilized. Miniplate osteosynthesis is a standard method for the surgical treatment of mandibular fractures . Miniplates provide functionally stable fixation unlike rigid fixation that prevents micromotion of the bony fragments under function. Functionally stable fixation applies to internal fixators that allow bone alignment and permit healing during function .

The loosening of one or more screws during the convalescent period following miniplate osteosynthesis is a problem especially in mandibular fracture osteosynthesis where loosening of screws requires removal of the fixation appliance. As a rule this does not compromise the result as the fracture or osteotomy has healed underneath , but it leads to a second minor operative procedure. This problem has been overcome by the development of the locking plate/screw system, which offers advantages over other plating systems . Locking 2.0 miniplates utilize double threaded screws, which lock to the bone and the plate, creating a mini-internal fixator. This results in a more rigid construction with less distortion of the fracture or osteotomy, less screw loosening and less interference with bone circulation since the plate is not too tightly pressed against the bone .

The locking screw plate system also reduces compressive forces between the undersurface of the plate and lateral bony cortex compared with a conventional mandibular plate. In a locking screw plate system, forces are generated between the threaded portion of the plate and the screw. This limits stress shielding and creates a more stable fixation over time . Theoretical advantages proposed include: less precision required in plate adaptation because of the internal/external fixator; less alteration in osseous or occlusal relationship on screw tightening; greater stability across the fracture site; and less screw loosening .

H erford and E llis concluded that the use of a locking plate/screw system was simple, and it offers advantages over conventional bone plates by not requiring the plate to be compressed to the bone to provide stability. In 1999, G utwald performed the first biomechanical comparison of locking plates applied to the mandible. They concluded that higher stability was achieved with the locking plates. H aug et al. performed a study with intentional maladaptation of the plates. They concluded that the degree of adaptation affected the mechanical behaviour of nonlocking systems, but it did not affect the locking system.

The biomechanical and technical advantages of locking miniplate systems over conventional miniplate systems prompted the current study. The purpose of this prospective randomized study was to evaluate the efficacy of 2.0-mm locking miniplate/screw systems compared with 2.0-mm nonlocking miniplate/screw systems in mandibular fractures.

Materials and methods

A prospective randomized clinical trial was conducted for 18 months, from November 2007 to June 2009. Fifty patients ( Tables 1 and 2 ) with isolated mandibular fracture (single or multiple) without pre-existing infection and comminution were selected. Excluded were patients in whom a brief period of maxillomandibular fixation (MMF) was medically contraindicated (epilepsy, severe asthma, psychiatric condition, and smoker, alcohol or drug abuse). Patients were randomly divided according to a computer generated randomizer into two equal groups of 25 patients each. Group A patients underwent osteosynthesis using 2.0 mm locking miniplates while group B patients underwent osteosynthesis using 2.0 mm non-locking miniplates. They were informed of the need for 3 month follow-up. The patients had to give informed consent to participate in the study. The patient information was documented in a consent form. The study design had been approved by the local ethics committee.

Table 1

Patient details for group A.

Sr. No.	Age/sex	Aetiology	Time lapse (days)	Site distribution	MMF if required (5 days)	Pain third month	Morbidity	Treatment
1	22 M	RTA	6	Body + angle	–	5	None	–
2	24 M	RTA	7	Body alone	–	5	None	–
3	26 M	RTA	3	Parasymphysis + angle	Required	0	None	–
4	42 M	RTA	6	Angle alone	–	4	None	–
5	26 F	Assault	4	Angle alone		3	None	–
6	19 F	RTA	4	Body + U/L condyle	Required	4	None	–
7	25 M	RTA	6	Body + parasymphysis	Required	3	None	–
8	22 M	RTA	13	Parasymphysis alone	–	4	Infection	Local Curettage
9	52 M	Assault	6	Angle alone	–	0	None
10	33 M	RTA	5	Body alone	Required	8	Infection	Incision and drainage with plate removal
11	30 M	RTA	7	Angle alone	–	1	None	–
12	17 M	Fall	8	Body + angle	–	4	None	–
13	24 M	RTA	6	Body alone	–	0	None	–
14	32 M	RTA	7	Angle alone	–	3	None	–
15	33 M	Assault	15	Parasymphysis alone	–	0	None	–
16	30 M	RTA	8	Angle alone	–	0	None	–
17	34 M	RTA	4	Body + U/L condyle	Required	6	None
18	24 M	RTA	9	Parasymphysis + angle	–	1	None	–
19	26 M	Fall	5	Body + angle	–	1	None	–
20	45 M	RTA	6	Body alone	–	0	None	–
21	28 M	RTA	4	Angle alone	–	2	None	–
22	29 M	RTA	9	Angle + body + U/L condyle	Required	1	None	–
23	47 M	RTA	3	Body alone	–	2	None	–
24	30 M	RTA	7	Parasymphysis + U/L condyle	Required	0	None	–
25	32 M	RTA	7	Body alone	–	1	None	–

 

Table 2

Patient details for group B.

Sr. No.	Age/sex	Aetiology	Time lapse (days)	Site distribution	MMF if required (5 days)	Pain third month	Complication	Treatment
1	26 M	RTA	6	Angle alone	–	0	None	–
2	24 M	RTA	6	Body alone	–	6	None	–
3	23 M	RTA	7	Parasymphysis + angle	Required	0	None	–
4	16 M	Assault	3	Parasymphysis alone	Required	0	None	–
5	32 M	RTA	7	Angle alone	Required	3	Infection	Local curettage
6	42 M	RTA	6	Body + angle	Required	2
7	33 M	Fall	7	Parasymphysis	–	2	Infection	Local curettage
8	18 F	RTA	4	Parasymphysis + angle	Required	0	None	–
9	34 M	Assault	8	Body alone	Required	2	None	–
10	46 M	RTA	6	B/L Body	Required	6	None	–
11	28 M	RTA	14	Body + angle	Required	3	None	–
12	20 M	Fall	3	B/L Body	Required	4	None	–
13	30 F	Assault	7	Angle alone	–	3	Infection	Incision and drainage; plate removal
14	26 M	RTA	6	Parasymphysis + angle	–	2	None	–
15	40 M	RTA	4	Parasymphysis alone	–	0	None	–
16	48 M	RTA	8	Parasymphysis + angle	Required	0	None	–
17	29 M	Assault	7	Body + angle	Required	4	None	–
18	34 M	RTA	6	B/L Body	Required	0	None	–
19	36 M	RTA	5	Body + angle	Required	2	None	–
20	32 M	RTA	8	Angle alone	–	3	Occlusal disturbance	Occlusal grinding
21	30 M	Assault	7	Body + angle	Required	7	None	–
22	19 M	RTA	5	Parasymphysis	Required	2	Infection	Local curettage
23	52 M	RTA	6	Parasymphysis + B/L condyle	Required	0	None	–
24	27 M	RTA	6	B/L Body	Required	4	None
25	25 M	RTA	4	Parasymphysis alone	–	0	None	–

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