Part 1. Surgical Anatomy and General Considerations


■ Part 1. Surgical Anatomy and General Considerations

The central upper face is at the intersection of the cranium and face and may be divided into four compartments: nasal-nasoseptal, nasomaxillary, orbitoethmoid, and or-bitosphenoid . Part is exposed (the nasal-nasoseptal), as cartilage and nasal bones project beyond the plane of the face. A second part (the nasomaxillary) is protected by serrations of the nasofrontal bony suture at the base of the frontal boss and by thick buttresses, constituting the medial orbital frame. And the third and fourth segments of the central upper face (lacrimal, ethmoid, and sphenoid bones) are relatively sheltered and couched beneath the frontal boss ( Fig. 7.1A,B ).

The Concept of Central Upper Facial Compartments

Support for this arbitrary compartmentalization into four segments is substantiated by embryologic, histologic, anatomic, and physiologic considerations1 4 ( Fig. 7.2 ).

The pathomechanics of central upper facial injury also seem to corroborate this arbitrary compartmentalization, as the nasal-nasoseptal, nasomaxillary, orbitoethmoid, and orbitosphenoid compartments progressively and serially collapse or fracture as load stresses cascade to ever more penetrating depths.5 11

The Nasal and Nasoseptal Compartment

The nasal bones and cartilages are cradled by three of the seven craniomaxillofacial buttresses of the midface that arise from the palatal platform. As such, the anterior medial buttresses (the frontal processes of the maxilla), the posterior sagittal buttress (vomer-sphenoidal-frontal buttress), and palate (see Chapter 4) form a triangulated platform on which the nasal bones and nasal cartilages reside. As noted in Chapter 1, Cryer considered the posterior sagittal buttress to be a “flying” buttress, spanning the palate and cranial base to support the floor of the sphenoid sinus.

Fig. 7.1 (A,B)
Fig. 7.2

The nasal-nasoseptal compartment is further divided into subcompartments or vaults: lower vault (I), middle vault (II), and upper vault (III). Each vault contains a defined portion of the nasal septum.10 An inferior strut of cartilage is in the lower vault, and the cartilaginous midseptum is included in and is continuous with both lateral nasal cartilages. The superior strut and adjacent bone of the ethmoid plate are beneath the nasal bones in the upper vault. The latter ascends to the base of the cribriform plate ( Fig. 7.3 ).

In the distal vault (I) are the greater alar cartilages, the septal angle, and the caudal strut of the nasal septum.

Fig. 7.3

In the middle compartment (II) are the lateral nasal cartilages, the septal dorsal strut, and a thin, central partition of cartilage that rests on the maxillary crest. In the proximal vault (III) are the nasal bones, the thickened superior strut of septal cartilage, and the keel-like vomer.

The cartilaginous struts (caudal, dorsal, and superior) and a thin central partition are depicted. The lateral nasal cartilages, dorsal strut, and central partition are in continuity in the mid-septum (middle vault). The superior strut in the upper vault is thick relative to other areas of the septum and is embryo-logically in continuity with the ethmoid plate. The superior strut and the underlying vomer are “key” structures11 in the event of trauma to the upper vault of the nose ( Fig. 7.4 ).

A fascial aponeurosis, the domal suspensory ligament, interconnects the alar cartilaginous components and anchors the lower vault to proximal structures. The fascial sleeve is Y-shaped and envelops the greater and minor cartilages, sweeping from lateral to medial. The portion of fascia that anchors the lower vault to the underlapping lateral cartilage is lax and delicate. In other areas, particularly between tip-identifying points (the domes and columellar jut), the fascia is thick and tendinous10 13 ( Fig. 7.5 ).

The upper border of each nasal bone is deeply serrated for articulation with the nasal notch of the frontal bone at the base of the frontal boss. The inferior margin of the nasal bone is thin and gives attachment on its undersurface to the upper lateral cartilage of the nose by way of the dorsal suspensory ligament . The lateral border of each bone is also serrated, beveled at the expense of the inner surface above and of the outer below, to articulate with the frontal process of the maxilla.14 The medial border, notably thicker above than below, articulates with its fellow of the opposite side.

The biomechanical advantage of the upper vault, favoring distribution of equilibrium circuits of stress, is clear: it is stabilized by early ossification of the internasal suture, girded by merger with the frontal processes of the maxilla ( transitioning to the nasal sidewalls and the medial components of the orbital frame), and locked into position at the midline by the heavy serrations, at the nasofrontal suture ( Fig. 7.6A,B ).

Fig. 7.4
Fig. 7.5
Only gold members can continue reading. Log In or Register to continue

Jul 2, 2020 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Part 1. Surgical Anatomy and General Considerations
Premium Wordpress Themes by UFO Themes