Novel Surgical Approaches to the Orbit.

Determining safe surgical access to the orbit can be difficult given the complex anatomy and delicacy of the orbital structures. When considering biopsy or removal of an orbital tumor or repair of orbital fractures, careful planning is required to determine the ideal approach. Traditionally, this has at times necessitated invasive procedures with large incisions and extensive bone removal. The purpose of this review was to present newly techniques and devices in orbital surgery that have been reported over the past decade, with aims to provide better exposure and/or minimally invasive approaches and to improve morbidity and/or mortality.

INTRODUCTION

Safe surgical access to the orbit can be challenging given the complex anatomy and delicacy of the orbital structures. When considering biopsy or removal of an orbital tumor or repair of orbital fractures, careful planning is required to determine the ideal approach.

In traditional approaches to the orbit, anterior orbitotomy is the broad term used to describe the surgical approach to the anterior half of the orbit. The location of the incision is determined by the desired quadrant of the orbit to be accessed. A cutaneous incision is made in various locations to access either the subperiosteal (via the orbital rim) or orbital (via the orbital septum) approach. Examples of orbital rim incisions include the direct brow, subbrow, Lynch, inferior rim, Kronlein, and lateral canthotomy. Eyelid incisions include upper lid crease, vertical lid-split, subciliary, and mid-tarsal.1 Each of these approaches is associated with pros and cons, and several have been abandoned due to their poor cosmetic outcome. The Lynch incision, for example, provides excellent exposure to the medial orbit, but there is a risk of medial canthal web formation and visible scarring.2 The subciliary approach to the orbital floor also allows for broad access, but can cause lower lid retraction and malposition.34

To obviate the morbidity of cutaneous incisions, the transconjunctival incision has been utilized. Originally described in 1924,4 it is used for access to the orbital floor. With this technique, there is no visible scarring and a decreased risk of entropion formation given that the orbital septal plane is not violated.5

Access to the lateral and posterior orbit has generally required more involved strategies. Lateral orbitotomy has been used as a means to access the lateral orbit and retrobulbar space. A lateral canthotomy or extended eyelid crease skin incision is used followed by taking down part of the lateral orbital wall. If this is insufficient, neurosurgical approaches may be implemented. The bicoronal incision is a mainstay of craniofacial surgery involving a long incision with extensive dissection, yet provides broad access to the zygomatic arch as well as the medial, superior, and lateral orbit.36 A neurosurgical approach, the fronto-orbito-zygomatic cranio-orbitotomy, provides a panoramic view of the orbit, orbital apex, optic canal, and adjacent intracranial structures.7 Drawbacks of these approaches, however, are significant operative and recovery time, length of incision, extensive bone removal, and neurosurgical related morbidity.

The purpose of this review was to present newly described and further elucidated techniques in orbital surgery that have been reported over the past decade, with aims to provide better exposure and/or minimally invasive approaches and to improve morbidity and/or mortality.

ENDOSCOPIC APPROACHES

Endoscopy is a technique initially developed and used in fields such as urology, gastroenterology, and otolaryngology to achieve less invasive surgery with improved visualization. In recent years, the use of the endoscope to access and visualize the orbit has also proven to be a huge advancement. In conjunction with otolaryngologists, many new techniques have been developed by ophthalmologists to remove orbital tumors and repair fractures, particularly in the posterior orbit.

The orbital apex and periorbital skull base have long been challenging to access. Murchison et al.8 reviewed 18 patients whereby an endoscopic approach was used to access a range of pathologies including cavernous hemangiomas, juvenile angiofibromas, and invasive cutaneous squamous cell carcinoma. The majority of lesions, 12 (67%), were located in the medial orbit and/or optic canal, 2 (11%) in the cavernous sinus and/or superior orbital fissure, and 4 (22%) in the inferior orbit and/or pterygopalatine fossa. A multidisciplinary team consisting of a neurosurgeon, otolaryngologist, and orbital surgeon worked together to perform ethmoidectomy and sphenoidotomy followed by removal of the posterior lamina papyracea to enter the orbit. The infraorbital canal was used as the lateral limit of dissection when the orbital floor was accessed. Intraoperative computed tomography (CT) image guidance was used in all cases. In their report, complications occurred in 4 (22%) of the patients.8 They included decreased postoperative visual acuity in two, worsening of diplopia in one, and cerebral spinal fluid leak with gyrus rectus contusion in one requiring a postoperative lumbar drain. Given these complications, this technique must be considered carefully, but the challenging underlying condition and anatomic location make any surgery in this location high risk. Koutourousiou et al. described an approach for excisional biopsy of the optic nerve using endoscopic endonasal transorbital approach combined with tranconjunctival medial orbitotomy.9

There have been innovations to operating on intraconal lesions as well. Stamm and Nogueira were the first to demonstrate the feasibility of the endoscopic transnasal approach in 2009 in the resection of an 8-mm cavernous hemangioma of the orbital apex with complete recovery of the patient's preoperative visual loss.10 They were able to demonstrate an alternative to traditional external approaches that may be associated with significant morbidity.11 Since then, a number of surgeons have published their experiences. Chhabra et al.12 reported 5 patients with a diagnosis of orbital cavernous hemangioma who underwent endoscopic surgery between 2007 and 2011 by an otolaryngologist and an orbital surgeon. All tumors were located in the medial orbit with an average tumor size of 1.68-cm in the greatest dimension. Preoperative findings included diplopia in 3 patients. They used the ophthalmic Cryoprobe (MIRA Inc., Waltham, MA, USA) to purchase and manipulate the tumors, a technique initially described by Putterman in 1975.13 Extensive dissection was required to mobilize tumors from this location. Typically, cavernous hemangiomas of the orbit are easily dissected from the orbit, but these lesions may have shared characteristics of variants such as angiomyofibromas14 with features of lyphangiohemangioma15 which can have dense fibrous adherence, especially deep in the orbit, making dissection difficult. In the immediate postoperative period, 2 patients had transient diplopia while one was treated with prism lenses. Enophthalmos occurred in 2 patients (40%), a similar incidence with external approaches.11 Another case series examined the endoscopic approach for intraconal masses in 6 patients. In this report, the authors felt that the endoscopic approach was best applied for benign soft tissue masses located in the medial orbit.16 Healy et al.17 described an endoscopic trans-nasal septal bimanual approach to an intraconal cavernous hemangioma of the orbital apex with the reconstruction of the medial orbital wall with a vascularized nasoseptal flap.17 The flap was constructed from the nasopharynx and the pedicle draped across the choanal arch through a septectomy defect. The medial rectus was covered with surrounding extraconal fat prior to laying the mucoperichondrial side facing the periorbita. Reconstruction of the medial wall was purported to prevent postoperative enophthalmos or diplopia.

IMAGE-GUIDED ORBITAL SURGERY

The use of intraoperative CT image guidance in orbital surgery has been increasingly reported. Due to the high density of critical structures packed into a small space, more precise localization has been coveted. There are a number of different systems available, including InstaTrak (Visualization Technology Inc., Woburn, MA, USA),18 LandmarX (Xomed-Medtronic, Jacksonville, FL, USA),19 Cygnus PFS System (Compass International, Rochester, MN, USA), and Stealth Station (Medtronics, Memphis, TN, USA). Each of these proprietary systems has their own advantages and disadvantages. The InstaTrak system involves placement of a plastic headset (anchored at the external auditory canals bilaterally and the nasal dorsum) followed by the acquisition of a CT or magnetic resonance (MR) scan. At the time of surgery, the plastic headset is placed back on the patient and allows signals to be captured from a probe's transmitter. The Stealth system requires placement of several adhesive fiducials on the scalp followed by a preoperative MR scan. At the time of surgery, a probe with a light-emitting diode registers the markers and allows for localization on the preoperative scan. The Cygnus PFS system is similar in its use of fiducial markers yet uses magnetic special referencing and tracking. The LandmarX system requires preoperative CT scanning but does not need the patient to wear a headset or have fiducial markers placed. Instead, a 3 camera system located 6 feet from the head of the surgical table collect information from light-emitting diodes on a headset placed on the patient's head at the time of surgery. This allows for real-time positioning of surgical instruments using infrared tracking, which allows mobility of the head intraoperatively.

A variety of surgical approaches and indications have been reported. The use of the Cygnus and Stealth stereotactic systems was reported in the use of three large orbital tumors, including an optic nerve glioma, recurrent pleomorphic adenoma of the lacrimal gland, and secondary orbital meningioma.20 Here, the calculated accuracy was reported to 1.2 ± 0.4 mm. The authors believed that image guidance was helpful in realizing the full extent of the tumor and determination of tumor-free margins. In another case series, the Stealth image-guidance system proved useful in localizing and obtaining a biopsy of three orbital apex tumors, two meningiomas, and one osteoblastoma.21 Another useful application is the use of image-guidance in the localization and removal of foreign bodies located in the posterior orbit, which in one case, avoided the need for an open external approach.22

Image-guidance has also been employed in cases of orbital decompression with improved anatomical localization.23 Seven patients underwent lateral wall orbital decompression through a lateral skin crease incision with the aid of image-guidance. It was noted that image-guidance was particularly helpful at the posterior limits of the deep lateral wall decompression and allowed for maximum bone removal without harm to the dura mater.24 We use image guidance (Fusion ENT Navigation System, Medtronic, Jacksonville, FL, USA) surgery for both the medial and lateral orbital wall decompression through endoscopic and open approaches, respectively. The headset is placed in an ideal location for the endoscopic medial wall decompression but can interfere with the open surgical approach to the lateral wall [Figure 1a and b].

Figure 1

Example of image-guided surgical navigation. (a) The Fusion ENT Navigation System (Medtronic, Jacksonville, FL, USA) used for image-guided surgery. (b) An example of the headset used with the Fusion ENT Navigation System

ENDOSCOPIC FRACTURE REPAIR

Endoscopy can also be used in orbital fracture repair, particularly in posterior floor fractures, fractures with a limited posterior shelf, secondary repairs for residual enophthalmos, or medial orbital wall fractures.25 Endoscopy allows for an up close and magnified view of the posterior fracture edge that may be otherwise difficult to visualize. In some cases, all edges of the fracture may be more easily identified with an intraorbital endoscope. In a systematic review of endoscopic management for isolated orbital floor fractures, 9 studies comprising 172 patients were identified. 86% had a resolution of diplopia, and 95% had a resolution of enophthalmos,26 outcomes comparable to traditional external approaches.27 Although the superiority of traditional versus endoscope-assisted surgery of orbital fractures is unclear, there are advantages to the use of endoscopes in select cases.

Endonasal and transantral endoscopic approaches have also been described for fracture repair. The endonasal approach is typically used in medial wall fracture repairs, although has also been reported in orbital floor fracture repairs. It is used in conjunction with a transcaruncular or transconjunctival approach. The endoscope is introduced through the bulla ethmoidalis until the medial orbital wall fracture is seen. When used in combination with CT image guidance, excellent visualization of the medial orbital wall fracture is achieved.2829

The transantral endoscopic technique has been described in the repair of orbital floor fractures.30 An advantage over standard transconjunctival or transcutaneous techniques includes avoidance of an eyelid incision and, therefore, eliminates the risk of postoperative eyelid malposition.31 It also allows for complete visualization of the posterior aspect of the fracture.

In addition to transantral endoscopic surgery for repair of orbital floor fractures, some authors describe the placement of a balloon catheter in the maxillary sinus to aid in fracture reduction.32 The initial use of the maxillary antral balloon technique for use in repairing depressed fractures of the orbital rim was proposed in 194433 but did not gain popularity. More recently, 30 consecutive cases were reported using the maxillary sinus balloon without an orbital implant. The balloon, inflated with saline, was kept in the sinus for 4 weeks and then extracted through a small sublabial incision under local anesthesia.32 The advantages of this technique include obviating the need for an orbital implant and high rates of improvement in extraocular movements, double vision, and enophthalmos. Possible complications include insufficient pressure at the fracture site (given that the balloon applies pressure to the entire maxillary antrum), leakage of the balloon, over-inflation leading to compression of the orbit, and need to remove the balloon after surgery with another incision. Further studies and experience with this technique are needed to determine whether this technique will offer true advantages to standard techniques.

INNOVATIONS IN SURGICAL DEVICES

Traditional tools used to manipulate bone in orbital surgery include manual osteotomes as well as powered saws, drills, and osteotomes. Predictably, several complications have been reported with these devices including ocular laceration, periorbital hemorrhage, and nerve injury.34 Consequently, surgeons have sought after devices with an improved safety profile.

Piezoelectric bone surgery, or piezosurgery, is a relatively new soft tissue-sparing system for precise bone cutting. Initially used in oral and head-neck surgery in 2000,35 the technology has recently gained more traction in fields such as neurological, craniofacial, hand, otologic, and facial reconstructive surgery. The device produces ultrasonic microvibrations at frequencies ranging from 20 to 30 kHz, which cuts via a phenomenon called cavitation. These microvibrations allow for cutting mineralized tissue (such as bone) without damage to surrounding soft tissues. The handpiece [Figure 2] is attached to a peristaltic cooling pump, which continuously irrigates normal saline at room temperature at an adjustable flow rate (0–60 ml/min), cooling the surgical site while improving visibility. A light emitting diode is also built into the device to allow for illumination in areas with poor visibility.

Figure 2

An example of the handpiece used in piezoelectric bone surgery (Synthes Piezoelectric System, Synthes, Oberdorf, Switzerland)

In addition to its safety with soft tissue, piezosurgery also appears to cut bone that preserves osteocytes. By avoiding coagulative necrosis at the bony margin, there is little disruption of osseous vessels with little vascular occlusion and blood flow disruption,36 as demonstrated in a rat model.3738 Some authors have attributed these findings to apparent improved comfort and faster recovery after piezosurgery compared to traditional techniques.39 Bone may, in fact, heal with better realignment and cosmetic results.40 There also appear to be a lower risk of seroma formation at the surgical site compared to traditional bone cutting tools.39 The piezoelectric device also appears to be useful in cases of revision surgery where the presence of more scar tissue can make visualization during osteotomies more difficult. Some surgeons have stated that the device makes blind cutting, when unavoidable, safer given the minimal risk to soft tissues, such as the facial nerve and dura mater.41

In 2007, Gleizal et al.42 proposed the use of piezoelectric bone surgery in the area of craniofacial surgery, such as orbital bone removal.42 Since then, the technology has increasingly become adopted for use in orbital surgery. De Castro et al. reported a case series of 16 patients who underwent orbital surgery with the use the piezoelectric device for indications including orbital decompression, lateral orbitotomy, cranio-orbitotomy, and external dacryocystorhinostomy.43 They felt safe use of the device required minimal training time and allowed for maneuverability and precision in cutting. The overall operative time was comparable to use of more traditional osteotomes and electronic saws. No gross soft tissue damage was observed intraoperatively.

Another group reported a similar experience with piezosurgery. They reported 20 patients who underwent surgery for removal of anterior cranial fossa meningiomas, orbital tumors, and sinonasal lesions with intracranial extension. Surgical approaches included an eyebrow supraorbital access for meningiomas (craniotomy size 2.5 cm), lateral orbitotomy for orbital tumors, and minimally invasive supraorbital approach for sinonasal tumors. Bone was re-fixated with titanium miniplates. Again, the piezoelectric device appeared to have good maneuverability with precise bone cutting and little harm to adjacent tissues. The main observed drawback of piezosurgery was the increased operative time, taking 30–40% longer than with mechanical instruments. The authors concluded that when including the time required to protect the soft tissue and eventual repair of soft tissues if harmed when using more traditional bone cutting tools, it is likely that there was not an overall difference in total operative time.4044 This experience was shared by another group as well.45

The microdebrider (Straightshot M4 microdebrider, Medtronic Surgical Technologies, Minneapolis, MN, USA) is another device previously used by other specialties that has recently proved useful in certain circumstances in orbital surgery. Originally patented by Urban in 1969 as a “vacuum rotary device,”46 it was initially used in acoustic neuroma and arthroscopic surgeries, and more recently in nasal surgery.47 The device consists of an outer shaft with a rotating inner cannula that cuts tissue into small pieces, which are then aspirated through the device. It is powerful and can excise soft tissue and thin bone within seconds. Freitag et al.48 reported the use of the device in three patients. One case involved debulking a gelatinous, infiltrative orbital mass, and the other two cases involved orbital exenteration for infiltrative sino-orbital fungal infection. The microdebrider was felt to be particularly useful when tissue was difficult to grasp and excise. It was cautioned that it should only be used in select cases, e.g., preexisting profound visual loss where preservation of important orbital structures matters little.48

The minimally invasive, sutureless anterior orbitotomy biopsy using a Finger's aspiration cutter device was a newly proposed technique that offers minimal disruption of tissue to achieve sufficient results.49 This technique is more specifically used to obtain tissue biopsy for histopathological analysis. A 3-mm incision is made along the superior eyelid crease or conjunctival fornix. Then the aspiration cutters are introduced into the orbital tumors using a bimanual technique to provide tissue samples in which one finger palpates the tumor while the shaft of the aspiration cutter is guided into the tumor. Settings were typically set at 300-mmHg of suction and a cutting rate of 600 cuts/min. Approximately, 3–5 biopsy passes were completed, removing the aspiration after each pass to collect the specimen.49 Advantages include small sutureless incision with minimal postoperative recovery time; disadvantages include minimal exposure for gross analysis of specimen, possibly smaller tissue samples for pathological analysis, and insufficient approach for some lacrimal fossa tumors such as adenoid cystic carcinoma that would require total excision.49

INNOVATIONS IN ACCESS

Tumors of the orbital apex are inherently difficult to access. If lateral orbitotomy techniques are insufficient, neurosurgical approaches may be necessary. Transcranial approaches include transfrontal, pterional, or cranio-orbital bone flap techniques, which can provide significant exposure.75051525354 However, the invasiveness, duration, and morbidity of this surgery are notable disadvantages.750 Kim et al. proposed a new total lateral orbitotomy that includes a bone flap extending from the supraorbital nerve laterally then inferiorly to the infraorbital nerve. On 10 cadavers and 5 patients, they found that this approach could be done without injury to critical structures or dura mater, and it provided improved exposure of deep orbital lesions without surgical complication.55 One patient had a temporary worsening of preexisting blepharoptosis, and another had temporary diplopia; however, all patients had stable or improved visual acuity.55

Alternative approaches to the lateral orbit have been published. Traditionally, the lateral orbitotomy includes a canthotomy and cantholysis, which can cause abnormalities of the canthus if not repaired correctly. Moe et al. reported a lateral canthal tendon-sparing technique. This retrocanthal orbitotomy includes a conjunctival incision just posterior to the lateral canthal tendon continued laterally toward the lateral orbital wall.56 This approach was used in patients requiring lateral orbitotomy (for fractures, tumors, and wall defects) and was found to be less invasive while more safe and efficient with appropriate surgical exposure.56 In 30 patients evaluated, 3 patients had postoperative lower eyelid asymmetry/malposition all of whom had extensive and prolonged surgery for complicated fracture repair. Two additional patients had persistent diplopia (thought to be related to the fracture repair and not the surgical approach).

As an alternative, the lateral triangle flap may be utilized. This technique involves a lateral eyelid crease incision that is carried laterally and joined with an incision along the “crow's feet” (sparing the canthal angle and tendon) to make a medial based triangle. This triangular flap can then be folded medially to provide access to the lateral orbit. This approach spares the lateral canthal tendon, provides adequate exposure of the lateral orbital rim, and has shown to have cosmetically acceptable results.57 However, it still involves a skin incision posing a risk for visible scars. In addition, the lateral canthus may still need to be opened if more inferior exposure is required.

A novel sinonasal-orbital approach for the treatment of nasolacrimal outflow tumors was also reported. This technique, which uses the expertise of both a lacrimal surgeon and an otolaryngologist, allowed for tumor clearance of malignant lacrimal sac tumors (squamous cell carcinoma, adenoid cystic carcinoma, transitional cell carcinoma, mucoepidermoid carcinoma, and oncocytic adenoma), improved overall survival, and reduced disease relapse.58 The procedure combined a medial orbitotomy with a medial maxillectomy (via a lateral rhinotomy skin incision) for en bloc resection of the tumor and reconstruction with a custom contoured titanium mesh for globe and eyelid support.58 The reported complications were primarily related to the effects of postoperative radiation on wound healing including skin breakdown over the mesh with nasocutaneous fistula (9/14), medial canthal dystopia (2/14), and corneal perforation in a patient with recurrent disease (1/14).58 Half of the patients also reported epiphora. This may be a useful technique in patients with advanced or aggressive tumors.

CONCLUSION

Several novel approaches to the orbit have been developed over the past decade. New or modified routes of access may provide better exposure, improved morbidity and/or mortality, or a more minimally invasive surgery overall. These improvements were designed to offer additional options for orbital access. It is important to remember that the techniques presented each have their own benefits and drawbacks, and it remains to be seen whether these innovations are advantageous. Endoscopic techniques require the availability of equipment with skill and experience in instrumentation. However, in select cases, based on the individual patient and surgeon's experience, these novel approaches may benefit outcomes. We look forward to further innovations in orbital surgery that advance our understanding of orbital diseases and their treatment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.