Retrospective Study: A Study Evaluating the Anatomical Variances of the Pterygomaxillary Junction and its Impact on Pterygoid Plate Fractures With Le Fort I Osteotomies
LeFort 1 osteotomies are used to correct a variety of maxillofacial deformities. Its technical ease and relatively low complication rates have made this procedure dependable and stable in resolving functional and aesthetic issues. However, a Le Fort 1 osteotomy may be associated with untoward pterygoid plate fractures that extend cephalad at the time of maxillary down fracture. It is the goal of the authors to determine if there are any anatomical variances that may contribute to these untoward fractures.
87 Patients who underwent LeFort 1 Osteotomies from the dates of 02/10/10 to 12/22/11. Prior to downfracture, surgery at the pterygomaxillary junction was carried out with an osteotome, oscillating saw, or nothing. Computer tomography scans were done before surgery and 6 weeks postoperatively and evaluated. The pterygoid plates were evaluated for fracture. If a fracture occurred it was recorded as either a low or high fracture. High fracture was determined if higher than half way up pterygoid plate. The reference points for evaluation included the length of the maxilla (from piriform rim to pterygomaxillary junction), the lateral plate, the medial plate, anterior-posterior and medial-lateral length of the pterygomaxillary junction, the distance from the lateral maxillary sinus wall to pterygomaxillary junction, the angle to the pterygoid plate in relation to the lateral maxillary sinus wall, the surface area of the lateral pterygoid plate (mm2), and bone density in Hounsfield Units (HU) at the pterygomaxillary junction, piriform rim, and zygomatic buttress.
Of the 87 patients, 47 were females and 40 were males. Age ranged from 14-68 and the median age was 22. Fractures of the pterygoid plates occurred in 48% (N=42) of patients. Of those, 17% (N=7) had high pterygoid plate fracture and 83% (N=35) had low pterygoid plate fractures. Of the 7 cases with high pterygoid plate fracture, 3 occurred with an oscillating saw, 2 with osteotome and 2 with manual down fracture. Mean of the reference points were done on all 87 patients.
Table I: Anatomical mean values of fracture population:
Reference Points |
R |
L |
Piriform-Base Line |
35.1 |
34.9 |
Lateral Plate |
11.2 |
11.3 |
Medial Plate |
9.0 |
8.8 |
A-P Thickness PMJ |
3.7 |
4.0 |
M-L Thickness PMJ |
7.5 |
7.0 |
Lateral Wall-PMJ |
31.2 |
31.4 |
Angle of PMJ |
100.6 |
94.3 |
Area of Lateral Wall (mm2) |
211.7 |
205.3 |
HU PMJ |
352.5 |
252.2 |
HU Zygomatic Buttress |
486.7 |
508.7 |
HU Piriform |
735.7 |
729.7 |
Table II: Anatomical mean values of non-fracture population:
Reference Points |
R |
L |
Piriform-Base Line |
34.8 |
34.6 |
Lateral Plate |
12.2 |
11.8 |
Medial Plate |
9.0 |
9.5 |
A-P Thickness PMJ |
5.0 |
4.3 |
M-L Thickness PMJ |
7.2 |
6.8 |
Lateral Wall-PMJ |
31.2 |
30.9 |
Angle of PMJ |
99.9 |
96.1 |
Area of Lateral Wall (mm2) |
208.1 |
204.5 |
HU PMJ |
311.9 |
277.7 |
HU Zygomatic Buttress |
491.3 |
438.1 |
HU Piriform |
713.8 |
723.9 |
The incidence of untoward pterygoid plate fracture has been reported to be as high as 87%1. Pterygoid plate fracture happens nearly 50% of the time and 17% were high-level fractures. Based on our data, neither surgical technique nor anatomical variability played a significant contributing role to pterygoid plate fracture pattern or incidence. Nevertheless, understanding the etiology of pterygoid plate fracture may help decrease the occurrence of neurological-ophthalmologic complications and their associated morbidities.
References:
- Precious, D.S. Pterygoid Plate Fracture in LeFort 1 Osteotomy With and Without Pterygoid Chisel: A Computer Tomography Scan Evaluation of 58 Patients. J Oral Maxillofacial Surgery 51: 151-153. 1993
- Fonseca, R.J. Oral and Maxillofacial Surgery. Volume 2: 232-248.
Authors:
David Wilson DMD, MD
Sharon Aronovich DMD
Sean P. Edwards DDS, MD