EDWARD ELLIS III. IS LAG SCREW FIXATION SUPERIOR TO PLATE FIXATION TO TREAT FRACTURES OF THEMANDIBULAR SYMPHYSIS?. J ORAL MAXILLOFAC SURG 70:875-882, 2012

PRESENTED BY – DR. SHEETAL KAPSE

GUIDED BY – DR. RAJASEKHAR G.

AUTHOR

Professor and Chair, Department of Oral and

Maxillofacial Surgery, University of Texas

Health Science Center, San Antonio, TX.

EDWARD ELLIS III

CONTENTS

• Introduction• Aim of the study• Patients and methods• Surgical technique• Results • Discussion• Cross references• Conclusion• References

INTRODUCTION• Fractures of the mandibular symphysis are extremely common

injuries.

• When open reduction and internal fixation is chosen as treatment, many internal fixation schemes can be used. Perhaps the most common is the application of bone plates with or without an arch bar.

• However, the mandibular symphysis is uniquely shaped for the application of lag screws.

• There are no studies in the literature comparing lag screw fixation with bone plate fixation for fractures of the mandibular symphysis.

Aim of the study

• The specific aims of this study were to 1. design and implement a retrospective cohort study,2. estimate and compare the frequencies of complications between

the 2 treatment groups, 3. compare the types of complications in the 2 treatment groups.

• The investigator hypothesized that there would be no difference in the frequency of postoperative complications between the 2 fixation techniques, but that there might be a difference in the types of complications.

PATIENTS AND METHODS

• All patients treated by open reduction and internal fixation of a symphysis fracture

of the mandible using bone plates from January 1, 1998 to December 31, 2009 and

those treated by lag screw fixation from January 1, 1989 to December 31, 2009 at

Parkland Hospital, Dallas, Texas.Inclusion criteria 1. An intraoral surgical approach

2. Simple (linear, noncomminuted) fracture of the symphysis (defined as the region between but not including the

mental foramina)

3. Teeth present in area of fracture

4. 1 of the following fixation techniques was used: lag screws or bone plates secured with locking or nonlocking

screws an arch bar placed during surgery and maintained postoperatively for at least 5 weeks

5. No postoperative intermaxillary fixation

6. A minimum follow-up of 5 weeks

7. Sufficient documentation to be included (medical records, radiographs, photographs)

Evaluation parameters

1. Infection (diagnosed clinically—not with cultures), dehiscence of the

incision not related to infection (no purulence),

2. Duration from surgery to dehiscence of incision and/or infection,

exposure of bone plate(s),

3. Need for plate removal,

4. Damage to tooth roots (based on postoperative images and/or information

available from the records),

5. Malocclusion attributable to symphysis fracture,

6. Clinical union at last visit.

Surgical techniqueTwo methods of internal fixation

C, Intraoperative photograph showing application of 1 larger, stronger plate.

A, Intraoperative photograph showing 2 lag screws inserted across the mandibular symphysis.

B, Intraoperative photograph showing the application of 2 miniplates.

A bur was used to place a hole through the outer cortex of the mandible on each side of the fracture, just below the apices of the roots, and a bone reduction clamp was placed to further reduce and temporarily stabilize the fracture.

Results

• Total patients = 887 • Bone plates (223 with 2 miniplates and 253 with a single large/strong plate) - n =

476• Lag Screws – n = 411

• Two lag screws were used in the vast majority of cases (n = 407) and 3 were used in 4 fractures.

• Of the 826 lag screws placed, the vast majority of lag screws entered the buccal cortex on 1 side of the fracture and exited the buccal cortex on the other (n = 738 screws).

• In the others, the fracture was oblique, so the screw entered the buccal cortex and exited the lingual cortex (n = 88 screws).

Results

Discussion

• Many choices for internal fixation of symphysis fractures are available, including reconstruction bone plates, lag screws, geometric bone plates, double miniplates, and a single strong nonreconstruction bone plate.

• The application of an arch bar and 2 lag screws, 2 miniplates, or 1 larger, stronger bone plate can be considered “rigid” fixation, meaning that the fixation is stable enough to prevent interfragmentary motion even with active use of the mandible.

• Therefore, any differences in outcomes between groups in this study would unlikely be due to differences in stability imparted to the fracture.

Cross references

Example of a symphysis fracture treated with 2 lag screws. Note that the upper lag screw is placed from buccal cortex to buccal cortex, whereas the lower lag screw is placed from the buccal cortex to the lingual cortex. Also note that the screws are placed perpendicular to the direction/bevel of the fracture.

A, Intraoperative photograph. Dashed line shows direction of lag screw crossing from one buccal cortex to the other on opposite side of fracture.

B, Postoperative occlusal radiograph.

Ellis E, Ghali GE: Lag screw fixation of anterior mandibularfractures. J Oral Maxillofac Surg 49:13, 1991

A case in which overcountersinking occurred. A, Intraoperative photograph showing the lower screw entering the medullary cavity.

B, A single hole was cut off an adaptation plate and used as a “washer” to provide a larger diameter of the screw head.

C, Intraoperative photograph showing the screw and washer in place.

Edward Ellis III. Lag Screw Versus Plate Fixation. J Oral Maxillofac Surg 2012.

A case in which gross overcountersinking occurred. A, Photograph showing a 2-hole adaptation plate bent in the middle to act as a “hook” when placed under the head of the lag screw. B, Intraoperative photograph showing that the upper screw has been salvaged using a 2-hole adaptation plate bent acutely to serve as a “hook” to “grab” the cortical bone. C, Postoperative panoramic and D, occlusal radiographs showing the 2-hole adaptation plate.

Edward Ellis III. Lag Screw Versus Plate Fixation. J Oral Maxillofac Surg 2012.

• The purpose of this investigation was to evaluate and compare the

biomechanical behaviour of 5 different methods used to repair mandibular

symphysis/parasymphysis fractures on Sixty synthetic polyurethane mandible

replicas.

• Ten controls and 10 each of the experimental groups were tested by subjecting

5 constructs in each group to vertical loading at the incisal edge and 5

constructs to torsional loading at the molar region.

• The 5 methods of reconstruction include: 1. arch bars using 18-gauge stainless steel wire with an acrylic

lingual splint, 2. 2 2.4-mm lag screw technique, 3. 2 2.0-mm 4-hole locking miniplates, 4. 2 2.0-mm 6-hole nonlocking miniplates, 5. 2 2.4-mm 6-hole limited-contact dynamic-compression plates.

• Although statistically significant differences were noted between each of the fixation systems in their abilities to resist loads under the conditions tested, when placed in the context of functional parameters, all systems met the requirements for incisal edge loading.

• When molar loading was considered, the lag screw technique performed more favorably than the other systems.

• The aim of this study was to make a comparative evaluation of the mechanical behaviour of 4 different internal fixation systems for mandibular symphysis fractures.

• 40 polyurethane mandible replicas (Nacional, Jaú, SP, Brazil) were used. The load resistance values were measured at load application displacements of 1, 3, 5, and 10 mm.

Fixation of group with lag

screw technique, with A, frontal

and B, side views.

Fixation of group with 2 perpendicular

miniplates, withA, frontal and B, inferior-superior

views.

Fixation of group with 1 miniplate in the tensionzone. Fracture reduction

was achieved with relief of the acrylic devices.

Fixation of group with 2 parallel miniplates, 1 in the tension zone and the other in the compression zone.

Distortion of the mandible during unilateral molar loading. The distortion of the mandibular body can be described as a combination of sagittal bending, torsion and lateral transverse bending. Patterns of stress and deformation at the mandibular symphysis. Jaw deformation during function. MC, medial convergence; CR, corporal rotation; DVS, dorso-ventral shear.

• Assael performed a study examining the outcomes of a laboratory exercise

in the application of lag screws for symphysis fractures and found a 61%

failure rate, indicating that experience is necessary for the proper

application of lag screws for these fractures.

• The application of bone plates is probably more easily accomplished by the

novice surgeon.

Conclusion

• There were no statistically significant differences in occlusal or osseous

healing outcomes. However, there were significant differences in

treatment outcomes for several variables, including wound dehiscence,

plate exposure, and the need for hardware removal between the groups.

• Plating and lag screw techniques showed very good outcomes.

• There were more intraoperative difficulties placing lag screws than bone

plates, but the application of lag screws was associated with fewer

postoperative complications.

References

1. Ellis E, Ghali GE: Lag screw fixation of anterior mandibular fractures. J Oral Maxillofac Surg 49:13, 1991

2. Matthew J. Madsen, Christopher A. McDaniel, Richard H. Haug. A Biomechanical Evaluation of Plating Techniques Used for Reconstructing Mandibular Symphysis/ Parasymphysis Fractures. J Oral Maxillofac Surg 66:2012-2019, 2008.

3. R. C. W. Wong, H. Tideman, L. Kin, M. A. W. Merkx: Biomechanics of mandibular reconstruction: a review. Int. J. Oral Maxillofac. Surg. 2010; 39: 313–319.

4. Assael LA: Evaluation of rigid internal fixation of mandible fractures performed in the teaching laboratory. J Oral Maxillofac Surg 51:1315, 1993.