The Lacrimal Keyhole, Orbital Door Jamb, and Basin of the Inferior Orbital Fissure Three Areas of Deep Bone in the Lateral Orbit

CLINICAL SCIENCES The Lacrimal Keyhole, Orbital Door Jamb, and Basin of the Inferior Orbital Fissure Three Areas of Deep Bone in the Lateral Orbit

Robert Alan Goldberg, MD; Alexander J. Kim, MD; Kristine M. Kerivan

Objectives: To calculate the volume of bone in 3 areas 3 areas of potential bone were delineated within it. of the deep lateral orbit that are available for removal in decompression surgery and to demonstrate these 3 ar- Results: The average volumes of the basin of the inferior eas within a 3-dimensional computed tomographic re- orbital fissure, the sphenoid door jamb, the lacrimal key- construction of the orbit. hole, and the total of the 3 regions were 1.2, 2.9, 1.5, and 5.6 cm3, respectively. The 3 areas of bone contributed vari- Design: The 3 areas of bone in the deep lateral orbit were ably to the total, with the door jamb contributing the most designated the lacrimal keyhole, the sphenoid door jamb, and volume of the 3, nearly twice the value of the other 2. There the basin of the inferior orbital fissure. By means of digi- was, however, a significant amount of interpatient vari- tized computed tomographic scans, these 3 areas of bone ability, especially for the door jamb region. were analyzed by measuring preoperative and postoperative orbital volumes and predicted bony expansion vol- Conclusion: Orbital decompression surgery of the deep umes in 9 patients (17 orbits) who underwent deep lat- lateral wall can provide adequate volume expansion be- eral orbital decompression surgery. We also calculated the cause of the amount and location of potential space that volume of bone that could be removed from 11 normal exists in the 3 areas of deep bone. orbits. A 3-dimensional computer reconstruction of an orbital computed tomographic scan was created, and the Arch Ophthalmol. 1998;116:1618-1624

RBITAL decompression sion surgery. These areas are conceptual surgery is indicated in rather than anatomical structures, and we Graves orbitopathy for find them helpful in surgical planning. The optic nerve compres- 3 areas of thick bone are designated the sion, corneal exposure, lacrimal keyhole, sphenoid door jamb, and Odisfiguring proptosis, and compressive or- the basin of the inferior orbital fissure.By bitopathy. Traditional lateral orbital de- means of digitized computed tomogra- compression involves removal of the an- phy (CT), these 3 areas of bone were ana- terior portion of the lateral orbital wall and lyzed by measuring preoperative and post- is limited in the degree of orbital expan- operative orbital volumes and predicted sion that can be achieved.1 There is, how- bony expansion volumes in 9 patients (17 ever, considerable room for orbital expan- orbits) who underwent deep lateral or- sion in the lateral part of the orbit if the bital decompression surgery. We also cal- thicker, deep areas of lateral wall are re- culated the volume of bone that could po- moved. These are the surfaces that were tentially be removed from 11 normal removed in the historic neurosurgical ap- orbits. A 3-dimensional computer recon- proaches; they can be successfully re- struction of an orbital CT scan was cre- moved through an orbital approach with ated, and the 3 areas of potential bone were adequate anatomical knowledge. The deep delineated within the 3-dimensional or- lateral wall can be accessed through a coro- bital image. nal, lateral cutaneous (for example, eyelid crease), or lateral transconjunctival From the Division of Orbital RESULTS and Ophthalmic Plastic (subcanthal) approach. Surgery, Jules Stein Eye We have found it helpful to concep- Eleven normal orbits were sampled to es- Institute, University of tualize the 3 separate areas of thick bone timate the amount of potential bone avail- California–Los Angeles School in the lateral orbit that are amenable to re- able in the deep lateral orbit. The total of Medicine. moval in deep lateral orbital decompres- amount of potential bone available in the 3

ARCH OPHTHALMOL / VOL 116, DEC 1998 1618

©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/03/2021 MATERIALS AND METHODS keyhole (Figure 2). It is a wedge-shaped section of bone in the superior orbit that begins with a full-thickness notch in the superolateral rim. It extends into the entire fossa of CT SCANNING the lacrimal gland. It is limited externally by the temporalis muscle, medially by the point at which the orbital roof Volume measurements of orbital bony and soft tissue struc- thins as the thin frontal bone, and posteriorly by the fron- tures were obtained by importing axial orbital CT scans tal cranial fossa and the posterior thick border of the lesser (1.5-mm or 3-mm thickness, contiguous slice) into the NIH wing of the sphenoid; inferiorly it blends into the thick tri- Image computer program (National Institutes of Health, gone of the greater wing of the sphenoid (the door jamb) Bethesda, Md). With the use of NIH Image, consecutive CT (Figure 3). The lacrimal keyhole forms a potential space scan slices were displayed on a computer monitor and a “draw” in which the lacrimal gland and the associated fibroadi- function was used to outline the perimeters of the struc- pose structures can prolapse laterally and superiorly; the tures, either bone or soft tissue, from which computer- lacrimal gland can actually prolapse outside of the orbital generated area measurements were obtained (Figure 1). The boundary, providing substantial volume expansion. The volume of each structure was calculated by multiplying the thick posterior portion of the lesser wing of sphenoid in area of the outlined structure by the thickness of each scan the region that separates the frontal and middle cranial fos- slice; the sum of volumes from the scan slices were added to sae is a rich area of thick bone that is responsible for much compute the volume occupied by the measured structure. The of the decompression achieved by the transcranial ap- scans were measured by 3 independent observers (R.A.G., proach; it can be removed from the orbital side, providing A.J.K., and K.M.K.); a high level of interobserver consis- substantial orbital volume expansion. tency was found, with agreement within 2%. The door jamb is formed of the greater wing of the For 9 patients who underwent bilateral decompression sphenoid. The thick trigone of the greater wing is a large of the lateral wall only, preoperative and postoperative CT marrow-filled bone that laterally borders the inferotempo- scans were analyzed. First, preoperative CT scans were ex- ral fossa (temporalis muscle) and posteriorly borders the amined and the volume was calculated for each of the 3 ar- middle cranial fossa (Figure 4). Not only is this the most eas of deep bone to be removed. These measurements served voluminous bony area of the 3 deep regions of bone, but as predictions of the volume available for potential orbital ex- also this bone lies almost directly posterior to the globe. pansion. Measurements of orbital soft tissue volume were then In the case of a “woody” orbit, removal of the door jamb calculated on each preoperative scan. The postoperative or- can allow posterior displacement of the globe in an orbit bital soft tissue volumes were also calculated. The postop- that has little ability to expand its lateral shape. Therefore, erative scans were also examined to determine the extent of in these fibrotic orbits, the door jamb area may be the only soft tissue expansion into the newly created orbital spaces. area of bone that can effectively reduce proptosis. Inferi- Axial CT scans of 11 orbits with normal bony anatomy orly, the door jamb consists of the thick part of the greater were also examined. The scans were from 7 women and 4 wing of the sphenoid that borders the inferior orbital fis- men, ranging in age from 30 to 84 years. The perimeters sure on its superolateral edge. In a maximal deep lateral of each of the 3 areas of deep bone that could potentially orbital decompression, the inferior orbital fissure is com- be removed for deep lateral orbital decompression were out- pletely deskeletonized. lined, and the volumes of the bony areas were calculated. The basin of the inferior orbital fissure consists pri- Including the 17 preoperative orbits from our 8 surgical marily of zygomatic bone and part of the lateral maxilla patients, a total of 28 orbits were sampled. (Figure 5). The body of the zygoma can be sculpted un- A 3-dimensional reconstruction of a normal orbit high- til there is only a thin rim of bone along the lateral orbital lighting the 3 bony areas available for deep lateral orbital rim and face of the zygoma, allowing a large segment of decompression was obtained by downloading an axial CT space for inferolateral prolapse of orbital adipose tissue. Me- scan (1.5-mm thickness, contiguous slices) into a 3- dially, the basin of the inferior orbital fissure can be re- dimensional graphic computer workstation. The lacrimal moved all the way to the zygomatic-maxillary suture. The keyhole, sphenoid door jamb, and basin of the inferior or- lateral portion of the maxillary sinus roof can also be re- bital fissure were then highlighted, allowing for visualiza- moved, and the sinus can be entered for some additional tion from different angles. prolapse of tissue. Near the inferior orbital fissure the zygoma thins, and removal of bone in this region typically SURGICAL ANATOMY exposes the buccal fat; the buccal fat can be cauterized both to reduce its volume, allowing outward prolapse of orbital The frontal bone, part of the lesser wing of the sphenoid, tissues, and also to keep the buccal fat from flowing into and a small portion of the greater wing form the lacrimal the surgical field and obstructing further drilling.

regions ranged from a low of 4.3 cm3 to a high of 6.8 cm3, ments are shown in the scatterplot (Figure 6). These are with an average of 5.6 cm3. The average volumes of the ba- idealized measurements; for practical purposes, it would sin of the inferior orbital fissure, the sphenoid door jamb, be difficult to remove all of this bone. and the lacrimal keyhole were 1.2, 2.9, and 1.5 cm3, re- Surgical patients’ preoperative orbital volumes, pre- spectively. The 3 areas of bone contributed variably to the dicted bony expansion volumes, postoperative orbital vol- total, with the door jamb contributing the most volume of umes, and degree of proptosis reduction are displayed the 3, nearly twice the value of the other 2. There was, how- in the Table. As one would expect, more volume ex- ever, a considerable amount of interpatient variability, es- pansion was achieved through the coronal approach, pecially for the door jamb region. The individual measure- which provides the widest access to all 3 areas of thick

ARCH OPHTHALMOL / VOL 116, DEC 1998 1619

©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/03/2021 bone. Preoperative and postoperative CT scans demon- COMMENT strate adequate expansion of soft tissue into the newly created orbital spaces (Figure 7). Consecutive or worsened strabismus after orbital de- A 3-dimensional reconstruction of a normal orbit compression is the most frequent risk of surgery, and our was obtained by downloading an axial CT scan of a nor- interest in the lateral part of the orbit is precipitated by mal orbit into a 3-dimensional graphic computer. The 3 a continual search for techniques that minimize the risk areas of bone—lacrimal keyhole, orbital door jamb, and of new-onset or worsened double vision. In large se- inferior orbital fissure—were then highlighted in differ- ries,2,3 inferomedial orbital decompression into the max- ent colors, allowing visualization from different angles illary and ethmoid sinuses has resulted in consecutive (Figure 8 and Figure 9). The highlighted portions of strabismus at least one third of the time. Balanced tech- bone within the 3-dimensional reconstruction provide niques4 and strut creation5 may decrease the risk but still a graphic representation of the 3 areas of thick bone and have a notable incidence of new or worsened diplopia. their relationships to surrounding structures. Because the inferomedial shift of the muscle cone is less- ened, isolated lateral orbital decompression should fur- A ther reduce the risk of new or worsened strabismus. Lateral orbital decompression has been described with the use of several techniques.3,6-12 Traditional ophthalmic techniques primarily involved removal of ante- rior portions of the lateral orbital wall.1 Studies de- signed to calculate increases in orbital volume or the degree of reduction of proptosis after lateral decompres- sions resulted in the belief that lateral wall decompression does not achieve adequate volume expansion.1,7,13,14 However, recent reports describe lateral wall decompression techniques that involve removal of thick B areas of bone from the posterior lateral wall, specifically from the area that we designate the door jamb and the deep lacrimal keyhole. The removal of this trigone posteriorly as far as the inner table of the cortical bone can achieve substantial expansion and reduction of proptosis as well as relief of optic nerve compression.3,4,10,11,15,16 The posterior location of the door jamb allows posterior displacement of the orbit, even in fibrotic orbits that can- not expand medially or laterally. Our surgical cases demonstrated that deep lateral wall decompression can achieve successful volume ex- Figure 1. Preoperative (A) and postoperative (B) axial computed tomographic scans. Blue outline indicates perimeter of soft tissue structures pansion and reduction of proptosis (up to 8 mm in 1 case used for measurement. Copyright 1997, Regents of the University of with orbital rim advancement), with the absence of com- California, reprinted with permission. plications such as hypoglobus or dystopia. Analysis of

A C

Figure 2. A, Transilluminated skull showing thick and thin bone. B, C, and D, The 3 areas of thick bone indicated by color coding. Yellow indicates lacrimal keyhole; red, door jamb of the greater wing of the sphenoid; and green, basin of the inferior orbital B D fissure. Copyright 1997, Regents of the University of California, reprinted with permission.

ARCH OPHTHALMOL / VOL 116, DEC 1998 1620

Figure 3. The lacrimal keyhole. Preoperative axial (A) and coronal (B) computed tomographic scans show the lacrimal keyhole outlined in yellow. C and D, Postoperative computed tomographic scans demonstrating bony removal. Copyright 1997, B D Regents of the University of California, reprinted with permission.

A C

Figure 4. The orbital door jamb. Preoperative axial (A) and coronal (B) computed tomographic scans show B D the orbital door jamb (red) and basin of the inferior orbital fissure (green). C and D, Postoperative computed tomographic scans demonstrating bony removal. Copyright 1997, Regents of the University of California, reprinted with permission.

ARCH OPHTHALMOL / VOL 116, DEC 1998 1621

Figure 5. Basin of the inferior orbital fissure. Preoperative axial (A) and coronal (B) computed tomographic scans show the basin of the inferior orbital fissure (green) and door jamb (red). C and D, Postoperative computed tomographic scans B D demonstrating bony removal. Copyright 1997, Regents of the University of California, reprinted with permission.

8 age is present at the end of surgery, it is generally self- limited. Intracranial bleeding associated with dural lac- 7 eration could be life threatening; although this should

3 6 be a rare complication with careful technique, neurosurgical backup should be available. Numbness in the 5 distribution of the zygomaticotemporal and zygomati- 4 cofacial nerves is common, and patients should be warned of this. We had 1 patient who developed oscil- 3 lopsia with chewing; we now avoid complete exposure of the temporalis muscle and, rather, leave a thin shell Potential Bone Volume, cm Potential Bone Volume, 2 of bone over as much of the muscle as possible. Double 1 vision can still occur, even in isolated decompression of

0 the lateral wall only. Interestingly, although one might Total Basin Door Jamb Keyhole have hoped that stretching the lateral rectus muscle would induce some exodeviation to counterbalance the Figure 6. Scatterplot demonstrating the potential bony volume available in the basin of the inferior orbital fissure, the sphenoid door jamb, the lacrimal esotropia that characterizes Graves strabismus, we have keyhole, and the sum of the volumes. Copyright 1997, Regents of the noted several cases of consecutive strabismus after University of California, reprinted with permission. lateral-wall-only decompression in which lateral rectus weakness worsened the esotropia, and we have had no orbital volume changes in postoperative scans not only cases of postoperative exotropia. None of our patients demonstrated the ability to effectively remove a suffi- have sustained orbital trauma after lateral decompres- cient amount of bone from the deep lateral wall for ad- sion; the lateral orbital buttresses are certainly thinned equate volume expansion, but also demonstrated the abil- after aggressive lateral decompression, and we presume ity of the soft tissue to expand into the newly created that the orbit may be more susceptible to traumatic lat- spaces. eral fractures. The complications of lateral orbital decompression Deep lateral wall decompression surgery can pro- have been discussed in previous articles.3 The bone is vide adequate volume expansion because of the amount drilled in the region of the frontal and middle cranial and location of the potential space that exists in the 3 fossa, and small exposures of dura are common in areas of bone. The small sample of patients and normal aggressive bony removals. Leaks of cerebrospinal fluid subjects in this study was not stratified for skull size, can occur if small dural perforations are created. These sex, or age, and a large study would provide a more can be patched intraoperatively, and even if slight leak- accurate estimate. However, these measurements do

ARCH OPHTHALMOL / VOL 116, DEC 1998 1622

Soft Tissue Volume, cm3 Hertel Exophthalmometry, mm Patient No./ Volume Potential Bony Surgical Eye Preoperative PostoperativeChange, cm3 Volume, cm3 Preoperative Postoperative Approach (Notes) 1/OS 26.4 28.6 2.2 5.1 29.0 23.0 Eyelid crease OD 25.1 27.8 2.7 5.1 29.0 24.0 2/OS 20.0 22.3 2.3 4.4 26.0 25.5 Eyelid crease OD 20.0 22.4 2.4 4.6 27.5 22.5 3/OS 20.0 25.7 5.7 7.1 25.0 19.0 Coronal (onlay rim implant OU) OD 19.1 24.4 5.3 6.8 24.5 16.5 4/OS 26.0 29.0 3.0 5.5 24.0 19.0 Eyelid crease OD 27.0 29.2 2.2 5.4 23.0 18.5 5/OS 20.0 25.7 5.7 6.3 24.0 17.0 Coronal (onlay rim implant OS) OD 20.0 26.2 6.2 6.7 21.0 19.0 6/OS 20.8 25.3 4.5 5.5 21.0 16.0 Eyelid crease OD 20.9 22.6 1.7 5.8 20.5 19.0 7/OD 22.2 24.2 2.0 5.0 29.0 26.0 Eyelid crease 8/OS 21.7 23.0 1.3 5.8 26.0 22.0 Eyelid crease OD 21.6 24.0 2.4 4.8 25.0 21.0 9/OS 27.0 30.2 3.2 5.5 23.0 19.0 Eyelid crease OD 27.8 30.2 2.4 5.4 22.0 20.0

Figure 8. Frontal view of 3-dimensional computed tomographic reconstruction of the orbit highlighting the 3 areas of bone: lacrimal keyhole (yellow), door jamb (red), and basin of inferior orbital fissure (green). Copyright 1997, Regents of the University of California, reprinted with permission.

Figure 7. A, Preoperative computed tomographic scan demonstrating significant proptosis. B, Postoperative computed tomographic scan be used in part or in full. We remove orbital fat in most of demonstrating soft tissue expansion into the newly created spaces. Copyright 1997, Regents of the University of California, reprinted with our cases. This is readily accomplished through the lat- permission. eral orbital approach. Removal of intraconal fat aug- ments the proptosis reduction in orbital decompres- provide a useful and reasonably representative estimate sion.17,18 Inferomedial decompression can be added, if of potential bony volume. The average total potential necessary, for additional volume expansion. volume for the 3 areas of bone was 5.6 cm3, with the We hope that the anatomical descriptions and 3- door jamb contributing nearly twice the volume of the dimensional images can provide a better understanding other 2 areas. For surgical purposes, we tend to think of of the substantial amount of potential space that exists the lacrimal keyhole and basin of the inferior orbital fis- in the deep lateral orbit and facilitate more extensive use sure as each contributing about one quarter of the total. of deep lateral orbital decompression. In our experience, every 1 cm3 of bone removed results in approximately 0.8 mm of proptosis reduction. This Accepted for publication July 31, 1998. type of analysis is helpful for grading the amount of de- Reprints: Robert Alan Goldberg, MD, 100 Stein Plaza, compression: in any individual case, 1, 2, or 3 areas can Los Angeles, CA 90095-7006.

ARCH OPHTHALMOL / VOL 116, DEC 1998 1623

©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/03/2021 3. Goldberg RA, Weinberg DA, Shorr N, Wirta D. Maximal 3 wall orbital decompression through a coronal approach. Ophthalmic Surg. 1997;28:832-843. 4. Leone CR Jr, Piest KL, Newman RJ. Medial and lateral wall decompression for thyroid ophthalmopathy. Am J Ophthalmol. 1989;108:160-166. 5. Goldberg RA, Shorr N, Cohen MS. The medial orbital strut in the prevention of postdecompression dystopia in dysthyroid ophthalmopathy. Ophthalmic Plast Reconstr Surg. 1992;8:32-34. 6. Wirtschafter JD, Chu AE. Lateral orbitotomy without removal of the lateral orbital rim. Arch Ophthalmol. 1988;106:1463-1468. 7. McCord CD Jr, Putnam JR, Ugland DN. Pressure volume orbital measurement comparing decompression approaches. Ophthalmic Plast Reconstr Surg. 1985; 1:55-63. 8. Wolfe SA, Hemmy D. How much does moving the lateral wall help in expanding the orbit? Ophthalmic Plast Reconstr Surg. 1988;4:111-114. 9. Goldberg RA, Hwang MM, Garbutt MV, Shorr N. Orbital decompression for non- Graves’ orbitopathy: a consideration of extended indications for decompression. Ophthalmic Plast Reconstr Surg. 1995;11:245-252. 10. Thaller SR, Kawamoto HK. Surgical correction of exophthalmos secondary to Graves’ disease. Plast Reconstr Surg. 1990;86:411-418. 11. Wulc AE, Popp JC, Bartlett SP. Lateral wall advancement in orbital decompression. Ophthalmology. 1990;97:1358-1369. Figure 9. Sagittal cut through the orbit demonstrates the volume available 12. Rootman J, Stewart B, Goldberg RA. Orbital Surgery: A Conceptual Approach. posteriorly in the basin of the inferior orbital fissure and the sphenoid door New York, NY: Raven Press; 1995. jamb. Yellow indicates the lacrimal keyhole; red, door jamb; and green, basin 13. Stabile JR, Trokel SL. Increase in orbital volume obtained by decompression in of inferior orbital fissure. Copyright 1997, Regents of the University of dried skulls. Am J Ophthalmol. 1983;95:327-331. California, reprinted with permission. 14. McCord CD Jr. A combined lateral and medial orbitotomy for exposure of the optic nerve and orbital apex. Ophthalmic Surg. 1978;9:58-66. 15. Kennerdell JS, Maroon JC. An orbital decompression for severe dysthyroid exophthalmos. Ophthalmology. 1982;89:467-472. REFERENCES 16. Hurwitz J, Rosenstock T. Management of inadequate transantral orbital decompression with extended lateral orbitotomy. Can J Ophthalmol. 1983;18:194-196. 17. Trokel SL, Kazim M, Moore S. Orbital fat removal: decompression for Graves 1. McCord CD Jr. Current trends in orbital decompression. Ophthalmology. 1985; orbitopathy. Ophthalmology. 1993;100:674-682. 92:21-33. 18. Olivari N. Transpalpebral decompression of endocrine ophthalmopathy (Graves’ 2. Shorr N, Seiff SR. The four stages of surgical rehabilitation of the patient with disease) by removal of intraorbital fat: experience with 147 operations over 5 dysthyroid ophthalmopathy. Ophthalmology. 1986;93:476-483. years. Plast Reconstr Surg. 1991;87:627-641.

Notes From Our Ophthalmic Heritage

A look at the past...

Graiae iterally, “the old women.” Also called Phorcydes. They first appear in Hesiod (Theog.) and are by him declared to be daughters of the sea-god, Phoreys, by his sister, Ceto, and sisters of the three Gorgons. They are beautiful, well- L dressed, and white of hair from birth. In Æschylus (Prom. Vinc.) they are described as monsters, swan-shaped, and possessing in common but one eye and one tooth, which neither the sun nor the moon had ever shone upon, and which they borrowed from one another as occasion demanded. Some of the poets make them guardians of the Gorgons. Their names are: Pephredo, Enyo, and Dino. The Graiae have been thought to symbolize the clouds, the transferable eye and tooth rep- resenting the flash of the lightning and its rapid interchange from one cloud to another. For the connection of the Phorey- des, or Graiae, with the Perseus myth, see Gorgon.

Reference: Wood CA. Exophthalmometer to Gyrus, Angular. Chicago: Cleveland Press; 1917:5629. American Encyclopedia and Dictionary of Ophthalmology; vol 7.

ARCH OPHTHALMOL / VOL 116, DEC 1998 1624