Introduction
Orbital fracture surgery is difficult to perform and associated with a high risk of complications in the restoration and reconstruction of the orbital rim and orbital and craniofacial bones, as well as in the functional reconstruction of the globe, extraocular muscles, the lacrimal system, and other structures. Minor errors during surgery can damage the optic nerve and other important structures, causing blindness and other serious consequences. Exposing deep orbital wall fractures and conveniently and accurately repairing orbital wall defects with implants are difficult because of the complex orbital anatomy and restricted operational space, which may affect treatment outcomes. Endoscopic techniques applied in orbital fracture repair can clearly show deep fractures and incarcerated soft tissue, guide accurate implant placement, and prevent injury to important orbital structures with minimal invasiveness.
The development of endoscopic techniques
Endoscopy refers to the use of medical instruments inserted into a variety of channels in the body to observe internal structures. Some endoscopic techniques are used for repairing diseased or injured tissue, such as cystoscopy, gastroscopy, and colonoscopy. The main components of an endoscope include a light source, an imaging system, and a working conduit. Over the past 100 years, the evolution of optical technology and electronic technology has allowed endoscopy to evolve, such as the development of hard-tube endoscopy to semi-flexible endoscopy and ultrasound-guided endoscopy to electronic endoscopy, which has been gradually applied for clinical diagnosis and treatment. Furthermore, the range of applications has evolved from initial medical examinations to various clinical applications.
In 1806, in Frankfurt, Germany, Bozzini [
1] manufactured an instrument using a candle as a light source and a series of lenses in a vase-like structure to observe the bladder and rectum. Although his instrument was not applied to human subjects, Bozzini is still referred to as the inventor of endoscopy. In 1957, Hirschowitz
et al. [
2] applied glass fibers, which transfer light from one end to the other, regardless of whether the fiber is straight or curved, into an endoscope to successfully observe intragastric structures for the first time. Endoscopic technology has become more widely used with the continuous development of light conduction and image transmission.
In 1981, Norris [
3] used endoscopic techniques for the first time in orbital surgery. Later, Braunstein [
3] formed an optical cavity by injecting hyaluronic acid and saline solution through the tip of an endoscope to observe orbital tissue. However, this method was incapable of forming a safe, stable, and expandable cavity, which limited the application of endoscopy in orbital surgery. The wide application of endoscopic surgery in otolaryngology gradually launched transnasal and transantral endoscopic orbital surgery in ophthalmology. In recent years, endoscopy-assisted orbital surgery via the orbital subperiosteal approach has significantly progressed [
4].
Components of an orbital surgical endoscopic system
Endoscopic systems for orbital surgery include an elongated shaft, handle, digital probe imaging system, and coaxial light source. The handle and probe imaging system are the main operating equipment used by the surgeon. One application of endoscopic orbital surgery is nasal endoscopy using a rigid mirror, steel fiber optic lighting system, and lenses. The optical system is similar to a periscope, with an eyepiece and objective lens at both ends. The objective lens forms an inverse image, which passes through the full length of the mirror to allow the transmission of most of the light from the objective lens to the eyepiece. A prism is connected to the distal end with a 0°–100° visual angle range. The light source is a 300 W xenon bulb, and the image is collected and processed using a charge-coupled device (CCD) camera at the proximal end and transferred to a television monitor. The images can be recorded and printed. Four-millimeter rigid endoscopes with 0°, 30°, and 45° visual angles are most commonly used in orbital surgery [
5].
Application of endoscopic techniques in the blowout fracture
Endoscopy is a safe and effective surgical method. Endoscopy-assisted orbital fracture repair surgery fully exposes the edge of orbital wall fractures, especially the posterior edge under the endoscope, to completely replace prolapsed orbital contents and precisely guide the reconstruction of orbital wall defects and fixation of implants. If the orbital wall fractures are deep, the optic foramen and the surrounding bone wall can be identified through endoscopy to avoid injury to the optic nerve and other important orbital structures, which improves the safety and accuracy of minimally invasive orbital surgery.
Traditional orbital wall fracture surgery is performed via the subciliary or medial canthus approach, which leave scars and affect cosmesis and may lead to postoperative ectropion [
6]. Applying endoscopic techniques in orbital fracture repair prevents scarring and enables the surgeon to clearly view the severity and shape of the fractures, which contributes to precise orbital wall fracture repair and implant fixation [
7]. However, endoscopy-assisted orbital fracture repair surgery has the following shortcomings: (1) Larger orbital defect repair implants cannot be placed from the nasal cavity; thus, an additional incision is required; (2) Exposure of the orbital implant material to the full communion of the orbital and nasal cavities may increase the risk of infection; (3) The procedure may injure nasal turbinates and other nasal structures. Shi [
8] reported endoscopy-assisted reconstruction of orbital medial wall and floor fractures via a combined transconjunctival and transnasal approach. The edge of the orbital wall fracture was clearly exposed and directly viewed via endoscopy to completely replace the prolapsed orbital contents. Implants for rebuilding both the orbital medial wall and the floor were inserted into the orbit through a conjunctival incision and fixed with titanium nails and/or glue. The method achieved good clinical outcomes without facial scarring or tissue trauma, and with fewer complications, increased safety, and higher accuracy.
Medial orbital wall fracture
Anatomically, the orbital medial wall is rectangular and consists of the frontal process of the maxilla, lacrimal bone, and sphenoid bone, and the lamina papyracea of the ethmoid bone. The superior medial orbital wall is adjacent to the ethmoidal labyrinth, which contains the anterior fossa of the lacrimal gland, the nasolacrimal duct to the nasal cavity, and the superior margin, which is anterior to the ethmoid canal and the canalis orbitoethmoideus. Through the absorbing action of the ethmoidal sinus, the medial wall tolerates much higher pressure than the orbital floor. However, the orbital medial wall is so thin that the lamina orbitalis is susceptible to fracture along with the orbital wall.
Generally, repairing orbital medial wall factures include subciliary and medial canthus, transnasal-transethmoidal, and transcaruncular approaches with medial brow and conjunctival incisions. The transnasal-transethmoidal and transcaruncular approaches and conjunctival incisions are the most common approaches for endoscopic orbital wall repair. The transnasal and conjunctival approaches avoid skin incisions and maintain cosmesis (Figs. 1 and 2). Hinohira [
9] performed reduction surgery on 23 patients with isolated medial blowout fractures that did not involve the medial wall using an endoscopic endonasal approach and reported that preoperative symptoms were resolved in 22 (95.5%) patients within 6 months post operation. The single transnasal approach with sinus packing is often used for repairing minor defects [
10], whereas larger defects are repaired using rigid materials or prolonging the packing period [
11]. However, placing a large amount of implant material transnasally into the orbit is difficult. Wu [
12] applied an endoscopic transcaruncular approach for repairing large medial orbital wall fractures near the orbital apex with porous polyethylene in 93 patients and achieved very good results. Hence, the outcomes of endoscopic transcaruncular and transnasal approaches for restoring orbital blowout fractures with large or minor defects are encouraging.
Orbital floor fracture
Anatomically, the orbital floor is triangular and consists of the orbital plates of the maxilla, the zygoma, and the palatine bone. Inferior to the orbital floor is the maxillary sinus, which has an infraorbital canal that houses the infraorbital nerve that runs anteriorly to the infraorbital foramen and posteriorly to the inferior orbital fissure. The resistance of orbital floor fractures is proportional to the number of maxillary sinus septa, and inversely proportional to the area of the orbital floor surface. Thus, the orbital floor is weak. In car accidents, falls, and sports injuries, a high-energy external force on the orbit transmitted to the weak orbital wall causes a blowout fracture, but leaves the orbital rim intact. The morbidity of orbital floor blowout fractures is as high as 85%.
For orbital floor fracture repair, most ophthalmologists choose the transconjunctival approach over the transmaxillary, and subciliary approaches [
14]. Endoscopic orbital floor fracture surgery clearly reveals the posterior edge of the orbital floor fracture, completely replaces prolapsed soft tissue, clears blood clots, and carefully handles the maxillary sinus mucosa, and restores orbital defects using implants, while preserving the infraorbital and optic nerves and other important structures (Figs. 3 and 4). Hinohira [
13] endoscopically corrected diplopia caused by orbital floor fractures in 55 of 62 patients (88.7%) within 6 months post operation. This high success rate indicates that the endoscopic endonasal approach may be used as an alternative to extranasal methods. Transantral and transnasal approaches are often applied for minor orbital floor fractures with autologous materials [
14,
15] or for minimal packing of the maxillary sinus [
16–
18].
Simultaneous floor and medial wall fractures are also considered as blowout fractures. The endoscopic surgical approach for compounded blowout fractures includes a conjunctival incision with transnasal, transconjunctival, and transcaruncular approaches to replace the prolapsed soft tissue and expose all edges of the fractures. Generally, a piece of implant material is used to simultaneously rebuild the orbital medial wall and floor [
8].
Problems
Complications may develop during endoscopic orbital surgery because of the complex anatomy of the optic nerve, vessels, and other vital structures at the narrow orbital apex. Common complications include strabismus and diplopia caused by extraocular muscle injury, decreased visual acuity or blindness caused by optic nerve injury, and lacrimal system injury, as well as intraorbital hematomas and emphysema [
19–
25]. Moreover, the patient is at risk of iatrogenic injury related to anatomical variations, fracture scope and depth, the extent of damage to the surrounding tissue caused by trauma, and surgical proficiency [
26]. Considering endoscopy is a relatively new surgical approach, surgeons must undergo a rigorous training program to prevent damage to the optic nerve and other serious complications.
Higher Education Press and Springer-Verlag Berlin Heidelberg
PDF
(177KB)
