Pyriform aperture





A relative deficiency in lower midface projection may be congenital or acquired, particularly after cleft surgery and maxillary fractures. Since the majority of white faces are convex, midface concavity is often considered less attractive. Fig. 10.1 shows the average midface inclination of white North Americans as determined by Farkas. Patients with satisfactory occlusion and lower midface concavity can have their aesthetic desires satisfied with skeletal augmentation. Augmentation of the pyriform aperture area is usually performed to move the lower midface profile from one of concavity to relative convexity.




Fig. 10.1


The inclination of the midface, i.e., glabella (g) to upper lip (ls), in men and women. (A) In men g–ls is 1.3 ± 3.5 degrees. (B) In women g–ls is 1.6 ± 2.5.

Data from Farkas et al. 1994, with permission.


Implantation of alloplastic material in the pyriform aperture area can simulate the visual effect of Le Fort I advancement and other skeletal manipulations. It is often a useful adjunct during the rhinoplasty procedure. Augmenting the skeleton in this area can alter the projection of the nasal base, the nasolabial angle, and the vertical plane of the lip. Fig. 10.2 shows the average nasolabial angle in white North Americans as determined by Farkas. It also tends to efface the nasolabial fold of the overlying soft tissue envelope.




Fig. 10.2


The nasolabial angle in men and women. (A) In men the nasolabial angle is 99.8 ± 11.8 degrees. (B) In women the nasolabial angle is 104.2 ± 9.8 degrees.

Data from Farkas et al. 1994, with permission.


The implant design and surgical techniques described here are extensions of others’ previous efforts to improve paranasal aesthetics. Severe cases of nasomaxillary deficiency, seen with Binder’s syndrome, have been treated with bone and cartilage grafts alone or together with ostesotomies. Lower midface deficiency has also been treated with cartilage grafts or silicone implants as adjuncts to aesthetic rhinoplasty.


Surgical anatomy ( fig. 10.3 )


The surface of the maxilla is very irregular. Inferiorly, this is due to a series of eminences and corresponding depressions reflecting the apices of the teeth. The incisive fossa is the depression above the prominent incisors. This depression gives rise to the origin of the depressor septi. The canine tooth forms a vertical ridge that separates the incisive fossa from the canine fossa, which is deeper and larger than the incisive fossa. The canine fossa gives rise to the levator anguli oris. The infraorbital foramen is located just above the canine fossa. It allows exit of the infraorbital nerve and vessels. They travel beneath the levator superioris and above the levator anguli oris. The infraorbital nerve supplies the skin of the lower lid, the side of the nose, most of the cheek and upper lip. Medial to the infraorbital foramen is the nasal notch, which is a concavity whose margin gives rise to the dilator naris as it ends below as the anterior nasal spine.




Fig. 10.3


Midface skeletal, nervous, and muscular anatomy.




The Implant


Pyriform aperture (or paranasal) implants are available from Matrix Surgical Inc. (Atlanta, GA) as Omnipor and from Stryker (Kalamazoo, MI) as Medpor. They are designed as right and left crescents and come in two sizes. The smaller implant is 27 mm long by 25 mm high and provides 4.5 mm of projection. The larger implant, which is 30 mm long by 28 mm high, provides 7 mm of projection. These implants are designed to be tailored to the patient’s particular aesthetic needs. The implant is positioned to sit flush on the bone. Patient anatomy will determine whether the entire crescent or just the horizontal or vertical limb of the crescent are used ( Fig. 10.4 ).




Fig. 10.4


Porous polyethylene paranasal implants are designed to augment both the lateral and inferior aspects of the pyriform aperture. Implants can be carved to allow selective augmentation. Screw fixation prevents movement of the implant and allows in-place contouring. (A) Implant augments pyriform aperture skeleton (maxilla lateral to the pyriform aperture and alveolus). (B) Implant contoured and positioned to selectively augment alveolus. (C) Implant contoured and positioned to selectively augment maxilla lateral to the pyriform aperture.




Operative Technique ( fig. 10.5 )


Paranasal augmentation can be done under local or general anesthesia. After sterile preoperative preparation and draping, a local anesthetic with 1:200,000 epinephrine is infiltrated at the surgical site. An upper gingivobuccal sulcus incision is made just lateral to the pyriform aperture to avoid placing incisions directly over the implant. The incision is made at least 1 cm above the sulcus to provide an adequate cuff of mucosa inferiorly to allow layered closure. The lip elevators can be seen after the mucosa is incised. These muscles are not divided but, rather, retracted during the exposure of the maxilla.



Pearl


Avoid making the incision directly over the area to be augmented.




Fig. 10.5


Diagrammatic overview of paranasal implant surgery. The incision is made on the labial side of the buccal sulcus and lateral to the area to be augmented. The grey area indicates the area of subperiosteal dissection. Note the proximity of the infraorbital nerve. Note that the root of the canine tooth lies below the area to be augmented. It must be avoided during screw immobilization of the implant.

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Feb 9, 2020 | Posted by in Craniofacial surgery | Comments Off on Pyriform aperture
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