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Chapter 7 Internal orbit
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Exposure
Proper repositioning of the globe requires exposure and anatomic reconstruction of the internal orbit. A transconjunctival retroseptal incision, often with
a lateral canthotomy extension, provides excellent exposure to approach the
orbital floor and lower medial and lateral walls. The transcaruncular approach
affords added exposure to the medial wall. Skin and skin–muscle flaps that
delaminate and relaminate the lower lid can result in lid malposition when
used in the trauma setting.6 Extensive subperiosteal dissection of the lateral
orbit will detach the lateral canthus. It should be repositioned at closure.
Mobilization and retrieval of orbital contents
A small conical space and fragile contents make surgery in the internal orbit
challenging. Using loupe magnification, the soft tissue contents of the orbit are
freed from the injured skeleton by subperiosteal dissection. Care is taken to
avoid damaging the lacrimal sac and structures in the inferior orbital fissure.
Intact bone edges are identified for orientation and provide stable constructs on
which to position grafts or implants. Once the prolapsed contents of the orbit
are retrieved, a piece of silicone sheeting is useful to maintain soft tissue retraction (Fig. 7.4). This maneuver prevents the soft tissues from falling back into
the sinus, lessens repeated handling, and improves the operative field. Once
reconstruction is complete, the silicone sheet is removed.
7
This dissection can be exceedingly difficult in extensive injuries, particularly
when surgery has been delayed and prolapsed orbital soft tissues have healed to
damaged mucosa in the maxillary or ethmoid sinuses or to the temporalis muscle in
the temporal fossa. The orbital contents must be separated from these structures and
replaced in the orbit. An inferior orbitotomy increases internal orbit access, thereby
simplifying soft tissue mobilization during complex reconstructions8 (Fig. 7.5).
PEARL
Periorbital fractures should be
reduced and xed prior to internal
orbit reconstruction.
Internal orbit reconstruction
The internal orbit is reconstructed to restore its preinjury anatomy with the
anticipation that proper globe position will result.
9–12
This requires definition
of the injured area, which is best accomplished by identifying intact bone and
Fig. 7.4 A thick piece of silicone sheeting is placed beneath the retrieved
orbital contents to prevent the soft tissues from prolapsing into the
maxillary antrum when the retractor is repositioned.
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hence the limits of the defect. This process is complicated by the location and
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extent of the injury. The bony landmark that is usually most difficult to identify
is the posterior ledge of the remaining intact orbital floor. When the orbital floor
disruption extends far posterior and intact bone cannot be visualized, it can be
located by placing the end of an elevator against the posterior wall of the maxillary sinus and elevating it until it meets resistance, which indicates contact with
the intact posterior remnant of the orbital floor. This structure is usually 35 to 40
mm from the infraorbital rim (Fig. 7.6).
Operative technique
A
Fig. 7.5 Inferior orbitotomy simplies retrieval of prolapsed orbital contents from the maxillary sinus and identication of intact bony
landmarks. Anatomic replacement of the osteotomized rim segment is simplied by adapting a microplate to the rim, drilling holes,
and temporarily xing the intact rim prior to making the osteotomy. (A) Location of orbitotomy. (B) Replacement of rim segment after
reconstruction of defect.
Periosteal elevator
B
Fig. 7.6 Identication of the intact posterior ledge can be simplied
by placing an elevator against the posterior wall of the maxillary
antrum and elevating it until it meets the restriction of the intact
posterior ledge. Presence of an intact ledge must be conrmed
preoperatively by CT scans to avoid putting the optic nerve at risk.
An implant placed on this ledge provides a posterior landmark for
orientation and a stable construct for implant placement.
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Chapter 7 Internal orbit
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A B
Fig. 7.7 (A) Defect of orbital oor. (B) Orbital oor reconstructed with graft spanning the defect. Stable adjacent ledges make bone graft or
implant positioning relatively straightforward.
When reconstructing injuries to one orbital wall, the surgeon first defines
the defect by identifying intact bone edges and then spans the defect with
an implant or autogenous graft (Fig. 7.7). The size of the defect and the
normal configuration of the injured area will dictate the dimensions, thickness, and number of grafts. For example, a small floor defect is usually
reconstructed with a single thin implant, replicating the relatively flat shape
of the orbital floor. A similarly dimensioned inferomedially located defect
usually requires a thick implant or stacked implants to recreate the convex
shape of the orbit in this area. Failure to replicate this convexity effectively
increases the volume of the orbit from normal and tends towards enophthalmos. Similarly, placement of an overly thick implant to reconstruct the floor
would also create an internal orbit shape different from normal. In this case,
the abnormal convexity beneath the globe would elevate it, resulting in an
ocular dystopia. For injuries involving only the floor, the senior author routinely uses an alloplastic implant. Implants are immobilized with titanium
screws.
Injuries involving two or more walls of the orbit are problematic. Rigid fixation techniques allow these complex injuries to be subdivided into a series of
smaller, more manageable areas for reconstruction. Implants designed to mimic
the contours of the orbital floor and medial wall allow combined floor and
medial wall injuries to be reconstructed with a single implant13 (Fig. 7.8).
Implant materials
Materials available for reconstruction include bone, cartilage, smooth and
porous plastics, as well as metal.
Reconstruction with autogenous bone has the conceptual advantage
that it will, in time, become vascularized and incorporated into the skeleton, thereby resisting migration, extrusion, and infection. Revasculariza-
80
tion, however, also predisposes the graft to resorb, with a concomitant
PEARL
Denition of intact skeletal ledges is
key to placing implants.
Operative technique
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Fig. 7.8 Method of spanning large orbital defects. Titanium mesh is
molded to the appropriate contour, bridges the defect, and is xed to the
orbital rim. The mesh, often coated with porous polyethylene, may serve
as a platform for additional implant placement.
change in internal orbit architecture – hence, volume and globe position.
Clinical experience has shown that cranial grafts tend to resorb less than
grafts taken from other donor sites. Cranial bone grafts have more dense
cortical bone than ilium or rib, which tend to be predominantly cancellous.
Experimental evidence suggests that the volume persistence of cranial grafts
may result from the fact that cortical bone is less susceptible to revascularization than cancellous bone, thus less susceptible to osteoclastic activity
(see Chapter 3).14 Cranial bone can be difficult to shape and control during
internal orbit reconstruction.
To avoid changes in graft shape and volume, as well as to avoid the
morbidity and operative time associated with autogenous graft harvest,
alloplastic implants have long been used for orbital floor reconstruction.
These include polytetrafluoroethylene (PTFE), silicone, dense and porous
polyethylene, resorbable materials, metal plates, and polymethylmethacrylate. High rates of extrusion have been documented for the rigid smoothsurfaced implants made of silicone (3.1%) and nylon (12%). There are also
many reports of late complications, especially with silicone, PTFE, and nylon
plates. These have been noted to occur as late as 21 years after placement,
and include infection, extrusion, migration with hematoma formation, and
lower eyelid deformity.15 Clinical experience obtained from treating these
complications suggests that these problems are related to capsule formation
around smooth-surfaced implants with the concomitant tendency towards
implant migration.
Porous polyethylene is the senior author’s preferred non-metallic orbital
implant. In a personal experience with over 200 patients since 1987, there has
been no known instance of infection or graft extrusion using this material for
internal orbit reconstruction. Clinical experience suggests that the soft tissue
ingrowth into the material limits the tendency for migration seen with smoothsurfaced implants. Others have presented anecdotal data suggesting that
this soft tissue ingrowth has the potential to include adjacent ocular motility
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Chapter 7 Internal orbit
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Fig. 7.9 A exible titanium infrastructure is laminated with porous
polyethylene. Courtesy Matrix Surgical, Atlanta, GA.
muscles with the possibility of ocular motility disorder. To avoid this potential
problem, polyethylene implants are now available with a smooth surface on the
inner side of the orbit and a porous surface on the other. The smooth surface
is designed to face the orbital soft tissue contents and the porous side to face
the sinuses. The smooth surface is intended to prevent soft tissue ingrowth and
possible motility problems, while the porous side allows soft tissue ingrowth
with concomitant immobilization.
Laminated implants of titanium metal and polyethylene are available (Fig.
7.9). A titanium infrastructure is sandwiched between a sheet of smooth poly-
ethylene on one side and a sheet of porous polyethylene on the other. The metal
facilitates implant conformability and screw fixation. The smooth laminate is
intended to interface with the soft tissue while the porous laminate is intended
to interface with the mucosal surface.
Video 7.1 demonstrates the reconstruction of an orbital floor blowout frac-
ture using a titanium mesh implant.
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CLINICAL EXAMPLES
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Clinical examples of patients treated with the techniques described are presented in Figs. 7.10 and 7.11).
A
Clinical examples
B
D
E
C
F
Fig. 7.10 A 30-year-old man was assaulted with a pipe. Surgery was performed through coronal, transconjunctival with lateral canthotomy,
and intraoral incisions. The internal orbit was reconstructed with titanium mesh. (A) Preoperative coronal CT scan. (B) Preoperative sagittal
CT scan. The arrow points to the intact ledge of the posterior orbital oor discussed in Fig. 7.6. (C) Postoperative coronal CT scan. (D)
Postoperative sagittal CT scan. (E) Postoperative axial CT scan. (F) Postoperative three-dimensional CT scan. (G) Postoperative worm’s eye
view.
G
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Chapter 7 Internal orbit
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A
C
E
B
D
F G
Fig. 7.11 A 32-year-old woman was struck by an automobile and suered multiple injuries including a right orbital fracture. The internal
orbit was not reconstructed acutely and the patient developed enophthalmos as well as a loss of malar prominence. The patient presented
for secondary reconstruction 9 months after her initial repair. Surgery was performed through a transconjunctival retroseptal with lateral
canthotomy and intraoral incisions. The internal orbit as well as the lateral and inferior orbital rims were reconstructed with porous
polyethylene implants immobilized with titanium screws. (A) Preoperative frontal view. (B) Postoperative frontal view. (C) Preoperative
worm’s eye view. (D) Postoperative worm’s eye view. (E) Three-dimensional CT scan showing initial reconstruction. (F) Preoperative coronal
CT scan showing enlarged, unrepaired internal orbit. (G) Intraoperative view of internal orbit reconstruction with screw-immobilized porous
polyethylene implants.
REFERENCES
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orbital injuries and their treatment by quantitative computed tomography. Plast Reconstr Surg
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techniques. In: Yaremchuk MJ, Gruss JS, Manson PN, editors. Rigid fixation of the
craniomaxillofacial skeleton. Boston: Butterworth-Heinemann; 1992.
13. Gordon CR, Susarla SM, Yaremchuk MJ. Quantitative assessment of medial orbit fracture
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References
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Video 7.1 Orbital oor repair. This video demonstrates the reconstruction of an orbital oor
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blowout fracture using a titanium mesh implant. Forced duction tests at onset and nish of
surgery demonstrate soft tissue entrapment and subsequent release, respectively.
86.e1
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