Is lag screw fixation superior to plate fixation to treat fractures of the mandibular symphysis

1. EDWARD ELLIS III. IS LAG SCREW FIXATION SUPERIOR
TO PLATE FIXATION TO TREAT FRACTURES OF THE
MANDIBULAR SYMPHYSIS?. J ORAL MAXILLOFAC SURG
70:875-882, 2012
PRESENTED BY –
DR. SHEETAL KAPSE
GUIDED BY –
DR. RAJASEKHAR G.

2. Professor and Chair, Department of Oral and
Maxillofacial Surgery, University of Texas Health
Science Center, San Antonio, TX.
EDWARD ELLIS III

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

4. • 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.

5. • 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.

6. • 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)

7. 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.

8. 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.

9. • 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).

11. • 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.

13. 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 mandibular
fractures. J Oral Maxillofac Surg 49:13, 1991

14. 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.

15. 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.

16. • 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.

17. • 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.

18. • 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.

19. Fixation of
group with lag
screw technique,
with A, frontal
and B, side
views.
Fixation of
group with 2
perpendicular
miniplates, with
A, frontal and B,
inferior-superior
views.
Fixation of group with 1
miniplate in the tension
zone. 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.

20. 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.

21. • 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.

22. • 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.

23. 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.