Basic Principles for Approaches to the Facial Skeleton
Maximum success in skeletal surgery depends on adequate access to and exposure of the skeleton. Skeletal surgery is simplified and expedited when the involved parts are sufficiently exposed. In orthopaedic surgery, especially of the appendicular skeleton, the basic rule is to select the most direct approach possible to the underlying bone. Therefore, incisions are usually placed very near the area of interest while major nerves and blood vessels are retracted. This involves little regard for esthetics but allows the orthopaedic surgeon greater leeway in the location, direction, and length of the incision.
Surgery of the facial skeleton, however, differs from general orthopaedic surgery in several important ways. The first factor in incision placement is not surgical convenience but facial esthetics. The face is plainly visible to everyone, and a conspicuous scar may create a cosmetic deformity that can be as troubling to the individual as the reason for which the surgery was performed. Cosmetic considerations are critical in light of the emphasis that most societies place on facial appearance. Therefore, as we will see in this book, all the incisions made on the face must be placed in inconspicuous areas, sometimes distant from the underlying osseous skeleton on which the surgery is being performed. For instance, placement of incisions in the oral cavity allows superb exposure of most of the facial skeleton, with a completely hidden scar.
The second factor that differentiates incision placement on the face from incisions placed anywhere else on the body is the presence of the muscles and nerve (cranial nerve VII) of facial expression. The muscles are subcutaneous structures, and the branches of the facial nerve that supply them can be traumatized if incisions are made in their path. This can result in a “paralyzed” face, which is not only a severe cosmetic deformity but can also have great functional ramifications. For instance, if the ability to close the eye is lost, corneal damage can ensue, affecting vision. Therefore, placement of incisions and dissections that expose the facial skeleton must ensure that damage to the facial nerve is minimized. Many dissections to expose the skeleton require care and electrical nerve stimulation to identify and protect the nerve. Approaches using incisions in the facial skin must also take into consideration the muscles of facial expression. This is especially important for approaches to the orbit, where the orbicularis oculi muscle must be traversed. Closure of some incisions also affects the muscles of facial expression. For instance, if a maxillary vestibular incision is closed without proper reorientation of the perinasal muscles, the nasal base will widen.
The third factor in facial incision placement is the presence of many important sensory nerves exiting the skull at multiple locations. The facial soft tissues have more sensory input per unit area than soft tissues anywhere else in the body. Loss of this sensory input can be a great inconvenience to the individual. Therefore, the incisions and approaches used must avoid injury to the sensory nerves. An example is dissection of the supraorbital nerve from its foramen/notch in the coronal approach.
Other important factors are the patient’s age, existing unique anatomy, and expectations. The age of the patient is important because of the possible presence of the wrinkles that come with age. Skin wrinkles serve as a guide and offer the surgeon the opportunity to place incisions within or parallel to them. Existing anatomic features that are unique to the individual can also facilitate or hamper incision placement. For instance, pre-existent lacerations can be used or extended to provide surgical exposure of the underlying skeleton. The position, direction, and depth of a laceration are important variables in determining its utility. The presence of old scars may also direct incision placement; the old scar may be excised and used to approach the skeleton. Sometimes, an old scar may not lend itself to use and may even cause the new incision to be positioned such that the old scar is avoided. Hair distribution may also direct the position of incisions. For instance, the incision for the coronal approach is largely determined by the patient’s hairline. Ethnic characteristics also have a bearing on whether an incision will be placed in a conspicuous area. History or ethnic propensity for hypertrophic scarring, keloid formation, and hyper- or hypopigmentation may alter the decision as to whether or where to place an incision.