J Oral Maxillofac

Surg

50:1075-1080,199Z

Location of the Nasolacrimal Canal in Relation to the High Le Fort Osteotomy I

ZHI-HAO YOU,

DDS, AND

MS,

WILLIAM H. BELL, A. FINN, DDSS

PHD,*

RICHARD

DDS,t

The positional relationship between the high-level Le Fort I osteotomy and the nasolacrimal canal was studied in standard posteroanterior and lateral cephalograms made of 100 adult dry skulls after orienting the Frankfort horizontal of each skull to the natural horizontal plane. The simulated high-level Le Fort I osteotomy in all of the 100 skulls was under the level of the inferior orifice of the nasolacrimal canal by a mean distance of 5.2 mm (range, 0.5 to 11.5 mm). The average distance between the canal orifice and a line which extended from the lacrimal fossa to the anterior attachment of the inferior turbinate was 0.7 mm (range, 2.0 mm medially to 3.5 mm laterally). The maxillary height was strongly correlated to the height of the infraorbital foramen (r = 59, P < .OOl) and the simulated osteotomy (r = .57, P < .OOl). The results indicate that the osteotomy, when made just beneath the infraorbital foramen and extending into the piriform rim at the level of anterior attachment of the inferior turbinate, will usually not jeopardize the nasolacrimal duct within its bony canal. A line drawn from the lacrimal fossa to the anterior attachment of the inferior turbinate on the anterior aspect of the maxilla is a good approximation of the course of the nasolacrimal canal.

The high-level Le Fort I osteotomy is usually made directly inferior to the infraorbital foramen extending from the piriform aperture rim to the root of the zygoma. Osteotomies inferior to the infraorbital nerve have a very close positional relationship with the nasolacrimal apparatus and transient or permanent epiphora secondary to injury of the nasolacrimal apparatus

Received from the Division of Oral and Maxillofacial Surgery, Baylor College of Dentistry, and Southwestern Medical Center, Dallas. * Research Scholar; Assistant Professor, Department of Oral and Maxillofacial Surgery, School of Stomatology, Beijing Medical University, Beijing, The People’s Republic of China. t Professor. $ Associate Professor. Presented at the 73rd Annual Meeting of the American Association of Oral and Maxillofacial Surgeons in Chicago, IL, September 2529, 1991. Address correspondence and reprint requests to Dr Bell: Department of Oral and Maxillofacial Surgery, Baylor College of Dentistry, 3302 Gaston Ave, Dallas, TX 75246-2098.

FIGURE I. View of lateral nasal wall in a cadaver. The cut edge of the inferior turbinate is shown by the small arrows. The inferior orifice of the nasolacrimal canal (large arrow) is located at the top of the curved insertion of the inferior turbinate, and is higher than the anterior attachment of the inferior turbinate (triangle). A periosteal elevator is inserted between the mucoperiosteum, which contains the meatal portion of the nasolacrimal duct, and the bony lateral nasal wall.

0 1992 American Association of Oral and Maxillofacial Surgeons 0278-2391/92/501 O-0010$3.00/O

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NASOLACRIMAL CANAL-HIGH

LEFORT I OSTEOTOMY

has been documented occasionally with high Le Fort I osteotomy. I,’ The lacrimal drainage system consists of canaliculi, lacrimal sac, and nasolacrimal duct. The nasolacrimal duct commences from the lacrimal sac, passes within the bony nasolacrimal canal, and empties into the inferior meatus. After exiting from the bony canal, the meatal portion of the duct extends about 5 mm beneath the mucosa of the lateral nasal wa11.3-5The canal and meatal portions of the nasolacrimal duct are the two parts of the lacrimal apparatus that are potentially put in jeopardy by high-level Le Fort I osteotomy. The aim of this investigation was to study the positional relationship of the high-level Le Fort I osteotomy to the nasolacrimal canal. An understanding of the anatomic relationships between the nasolacrimal conduit and the anticipated osteotomy site is essential for safe execution of this midfacial procedure. Materials and Methods One hundred dry skulls collected from the Department of Anatomy and Cell Biology, University of Texas, Southwestern Medical Center at Dallas, were studied. All skulls were from persons approximately 18 years of age or older as determined by partial or complete ossification of the sphenooccipital synchon-

FIGURE 2. Measurements on the P-A cephalogram. Two reference lines were made: PAB, piriform aperture base line; x. a line drawn from the intersection of nasolacrimal canal axis with the infraorbital rim to the anterior attachment of the inferior turbinate. The heights of the infraorbital foramen (1) simulated osteotomy (2), anterior attachment of the inferior turbinate (3) and the inferior orifice of the nasolacrimal canal (4) were measured. The distance of the inferior orifice of the canal to the x line (a), the length of the canal relative to the x line (b), and the length of the x line (c) were also determined. OL, Simulated high-level Le Fort I osteotomy; LC, axis of the nasolacrimal canal.

FIGURE 3. Measurements on the lateral cephalogram. The heights of the following structures were measured from the palatal plane (PP): the infraorbital foramen (1). the simulated osteotomy (2) the anterior attachment of the inferior turbinate (3). the inferior orifice of the nasolacrimal canal (4). orbitale (5) and nasion (6). The distance from the inferior orifice of the canal to the anterior attachment of the inferior turbinate (7) was measured. OL, Simulated high-level Le Fort I osteotomy; LC, axis of the nasolacrimal canal.

drosis.6 The sex of these skulls was not specified. The lacrimal fossa and canal were grossly intact. A high Le Fort I osteotomy (a horizontal line about 3 mm inferior to the center of the infraorbital foramen extending from the piriform aperture rim posteriorly into the root of the zygoma, approximately 5 to 7 mm above the inferior aspect of the zygomatic arch) was simulated on each skull. The following structures were then identified with metal markers on both the right and the left sides: 1) nasolacrimal canal: the bony canal beginning at the infraorbital rim and terminating at its inferior orifice; 2) infraorbital foramen: the center of the infraorbital foramen; 3) anterior attachment of the inferior turbinate: the most anterior point of the inferior turbinate bone terminating on the lateral nasal wall (Fig 1). The anterior attachment of the inferior turbinate usually extends to the piriform rim or to a location 1 to 3 mm behind the piriform rim. In this study, it was defined as the point on the piriform rim at the same level of the anterior attachment of the inferior turbinate.

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YOU. BELL. AND FINN

Variation in Position of Nasolacrimal Canal Orifice FIGURE 4. Diagram showing the heights (means and ranges) from the piriform aperture base (PAB) of the infraorbital foramen (I), the simulated osteotomy (2). the anterior attachment of the inferior turbinate (3). and the inferior orifice of the nasolacrimal canal (4). The inset illustrates the variation in position of the nasolacrimal canal orifice relative to the x line drawn between the lacrimal fossa (A) and the anterior attachment of the inferior turbinate (8).LC, Nasolacrimal canal; OL, simulated high-level Le Fort I osteotomy.

16.6(12.0-22.0) mm .

12.0(7.0-18.5)

mm

I

-----_

11.3(6.0 - 16.5) mm

‘0.7(-2.0-3.5) mm 10

.3(6.5 - 15.0;

15.5(10.0

Standard posterior-anterior (P-A) and lateral cephalograms were made of each skull by orienting the Frankfort Horizontal to the natural horizontal plane by means of a cephalostat. When exposing P-A radiographs, the bony structures were marked bilaterally: when exposing lateral cephalograms, only those on left side were marked and this side was placed adjacent to the radiographic film. All measurements were made directly on the radiographs. Two reference lines were made on the P-A cephalograms (Fig 2). The first was the piriform aperture base line (PAB), which was a horizontal line through the lowest point of the piriform aperture base. The second was the X line (x), which was a line drawn from the intersection of the nasolacrimal canal axis with the infraorbital rim to the anterior attachment of the inferior turbinate. The vertical distance from PAB to the infraorbital foramen, simulated osteotomy, anterior attachment of the inferior turbinate, and the inferior orifice of the nasolacrimal canal was measured. The distance between the inferior orifice of the nasolacrimal canal and the X line, the length of the nasolacrimal canal relative to the X line, and the length of the X line were also determined. On the lateral cephalogram (Fig 3) a reference line, palatal plane (PP), was drawn through the anterior nasal spine and the posterior nasal spine. The distances of the following structures from PP were measured: the infraorbital foramen, the simulated osteotomy, the anterior attachment of the inferior turbinate, the inferior orifice of the nasolacrimal canal, the orbitale (maxillary

- 21.0) mm

height), and the nasion (midfacial height). The distance from the inferior orifice of the canal to the anterior attachment of the inferior turbinate also was measured. Student’s t test was used to compare the difference between the right and left sides. Pearson product moment correlations were computed to examine the relationship of the height of the maxilla or the height of the midface to the heights of the other related structures. Results No statistically significant difference was found between the observations on the right and left sides so that only the data from the left side was used for analysis. Vertical relationship of high Le Fort I osteotomy to related unatomic structures. The heights of the infraorbital foramen, the simulated osteotomy, the anterior attachment of the inferior turbinate, and the in-

Table 1. Vertical Distances (mm) From the Inferior Orifice of the Nasolacrimal Canal to Other Related Structures n= 100

Mean

Range

SD

Simulated osteotomy Infraorbital foramen Anterior attachment of inferior turbinate

5.2 I.4

0.5-l I.5 -3.5-9.0

2.10 2.14

4.4

0.0-8.0

I .92

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NASOLACRIMAL CANAL-HIGH

ferior orifice of the nasolacrimal canal from the piriform aperture base are shown in Figure 4. The average values and ranges of the vertical distances from the inferior orifice of the nasolacrimal canal to the infraorbital foramen, the simulated osteotomy, and the anterior attachment of the inferior turbinate are listed in Table 1. The simulated high Le Fort I osteotomy in all of the 100 skulls was under the inferior orifice of the nasolacrimal canal with a mean distance of 5.2 mm (range, 0.5 to 11.5 mm). The inferior orifice of the nasolacrimal canal was almost at the same level as the infraorbital foramen (mean, 1.4 mm; range, 3.5 mm inferiorly to 9 mm superiorly). The inferior orifice of the canal was, on the average, 4.4 mm above the anterior attachment of the inferior turbinate (range, 0 to 8 mm). The simulated osteotomy was an average of 1 mm under the anterior attachment of the inferior turbinate, but ranged from 4 mm superiorly to 4.5 mm inferiorly. There were 25 specimens in which the simulated osteotomies were at or above the level of the anterior attachment of the inferior turbinate. Appro.ximution of the course of the nasolacrimal canal on the anterior aspect of the maxillary bone. The distance between the inferior orifice of the nasolacrimal canal and the X line, and the length of the nasolacrimal canal relative to the X line are shown in the inset of Figure 4. The inferior orifice of the nasolacrimal canals in the 100 skulls was positioned in an area that extended 2 mm medially and 3.5 mm laterally along the X line.

Table 2. Linear Correlation of the Maxillary Height (0r:PP) to the Other Heights of Measured Structures

LEFORT I OSTEOTOMY

n = 100

r

P

Infraorbital foramen Simulated osteotomy Anterior attachment of inferior turbinate Inferior orifice of nasolacrimal canal

59 51