Osteosynthesis of Craniofacial Fractures

11.1  Biomechanics: Facial Skeleton

The craniofacial skeleton comprises 22 different bones and exhibits remarkable stability, although it is partly composed of pneumatized bones. The bony areas delimit the cranial vault, the orbital cavities, the paranasal sinuses and the oral cavity. Within the craniofacia l skeleton there are thicker load-bearing and thinner nonloadbearing bony regions (Ewers et al. 1995).

The osseous facial skeleton is supported by three vertical struts:

•Naso-maxillary-frontonasal strut

•Zygomatico-maxillary strut

•Pterygo-maxillary strut

and three horizontal transverse struts:

•Maxillary alveolar process

•Infraorbital-nasal rim

•The fronto-cranial skull base/frontofacial bandeau

Their arrangement corresponds to that of the micro-­ trajectory configuration of cancellous bone (Schilli et al. 1981; Manson et al. 1980; Manson et al. 1990; Härle et al. 1999; Ernst et al. 2004) (see Figs. 1.10 and 1.11).

•As a bony framework, the transverse and vertical struts determine the vertical facial height, the transverse facial width, the sagittal midfacial position and, consequently, the symmetry and projection of the facial skeleton (Manson 1986; Härle et al. 1999).

infection (Gruss et al. 1989; Joss et al. 2001) (Figs. 11.1 and 11.2).

Consequences of defective positioning of these skeletal structures are:

•Occlusal dysfunction — dysgnathic maxillary posi­ tion­

•Dish face - midfacial retrusion — pseudoprogenia

•Occlusal disturbances — open-bite

•Elongated or shortened midface

•Broadening of the facial skeleton

Functional impairments

•Obstruction of the nasal airways with reduced aeration of the paranasal sinus system

•Insufficient function of the naso-lacrimal duct

•Ophthalmic problems — diplopia, enophthalmus, etc.

•Masticatory insufficiency

•Chronic pain

•The anatomical reconstruction and stabilization of the facial struts is essential in reestablishing the normal midfacial relation with the skull base and for restoring the midfacial projection, including normal occlusion (Rowe and Williams 1985; Gruss et al. 1985a, b; Gruss and Mc Kinnon 1986; Klotch and Gilliand 1987; Gruss and Philipps 1989; Manson et al. 1995; Weerda 1995; Joss et al. 1996, 2001; Manson 1998)

Fractures with dislocation of the midfacial complex in the sagittal, transverse, and vertical dimensions induce the loss of the three-dimensional midface projection.

If these structures are not adequately repositioned and stabilized, this consequently results not only in varying degrees of disfiguration and deformation but also in functional disability and a relevant danger of

11.2  Principles of Biomechanical

Reconstruction

An understanding of the structure and biomechanics of the maxilla and midface, accompanied by an anatomically orientated therapy, has resulted in significant

Fig.11.1  Malalignement of midface fractures with loss of facial symmetry. (a) Depression of right zygomatic region, deviation of osseous nasal pyramid and enophthalmus following zygomaticoorbital and naso-maxillary fracture. (b) Dish-face deformity following a severe central midface fracture (Le Fort I and II).

Fig.11.2  Facial asymmetry after severe cranio-orbito-nasal fracture with comminution of the left orbital walls. Alteration in globe position (enophthalmus), disturbance of eye motility (diplopia), narrow palpebral fissure, pseudoptosis, deviation of nasal skeleton, increase of intercanthal distance

(c) Severe asymmetry of the lateral midface with malalignement of the bony orbit, loss of orbital soft tissue with low-lying globe, enophthalmus and significant disturbance of eye motility after comminuted zygomatico-orbital fracture on the left

improvements in maxillofacial traumatology (Manson et al. 1980, 1985; Manson 1986; Gruss 1990; Dufresne et al. 1992; Prein et al. 1998; Hausamen and Schierle 2000; Ward-Booth et al. 2003).

The midfacial framework composed of an external and internal skeletal frame is the key to rigid fixation of the midface skeleton using varying plate thicknesses. A primarily correct and stable reconstruction of the osseous structures exhibits numerous advantages:

•Aesthetic improvement and functional stability

•Reduced risk of infection

•Uncomplicated fracture healing

•Transplant healing with minimal resorption

•Reduction of pain

11.2.1  External Midfacial Skeletal

Framework

Gruss and Mc Kinnon (1986) stress the importance of a precise initial reconstruction of the external skeletal frame in order to establish correct facial dimensions. This midfacial framework comprises the transverse frontofacial junction, the zygomatico-orbital complex and the external, lateral midfacial strut (lateral zygo- matico-maxillary strut).

•The frontofacial and zygomatico-orbital regions biomechanically form an important subcranial structure at the intersection between the visceroand

neurocranium and are, therefore, important corner struts for the three-dimensional reconstruction of the subordinate midface complex

The frontofacial region plays a key role in a correct transverse and sagittal reconstruction of facial width and depth. Dislocated fractures of this compartment result in a loss of anatomical orientation for reconstructing the fractured midfacial complex (Sailer and Graetz 1991) (Fig. 11.3).

The zygomatico-facial compartment forms the basis for reconstructing facial width and orbital depth and the fronto-facial compartment for the sagittal position of the naso-orbito-ethmoidal (NOE) complex (Prein et al. 1998). Only if the fronto-facial junction is anatomically correctly reconstructed, is it possible to correctly position the zygomatico-maxillary and naso-ethmoidal complexes and to reconstruct the orbital cavity (Wolfe and Berkowitz 1989; Gruss et al. 1990; Kraft et al. 1991; Hardt et al. 1992; Prein et al. 1998).

The zygomatico-orbital complex influences facial width as well as sagittal projection of the midface (Gruss et al. 1992; Gruss 1995; Manson et al. 1999; Brisett and Hilger 2005). Postero-lateral displacement of the ­zygomatico-orbito-maxillary complex results in broadening of the midface with a postero-lateral curvature of the zygomatic arch region and reduction of facial ante- ro-posterior projection (Brisett and Hilger 2005). A correctsagittalmidfacialprojectionisassuredifreconstruction of the zygomatic arch is anatomically correct.

•The position of the zygomatic arch determines the depth and the position of the zygomatic bone and the horizontal dimension of the midface

Correct primary positioning and fixation of the zygomatic complex in relation to the skull base assures not only the correct facial width but also the correct position of the naso-ethmoidal complex. In this respect, it is the key to correct sagittal and transverse reconstruction of the midface, including vertical height. Consequently, the position of the zygomatic complex is also responsible for symmetry and ventral projection of the midface (Gruss et al. 1985 b; Gruss and Mc Kinnon 1986; Sailer and Graetz 1991; Prein et al. 1998; Manson et al. 1999).

11.2.2  Internal Midfacial Skeletal

Framework

The internal skeletal frame comprises the central naso- ethmoido-orbital complex and the ventro-median struts. After reconstruction of the external frame, the successive reconstruction of the internal frame follows by progressive osteosynthesis of the central midface and its integration into the stable external frame. The reconstruction process begins in the region of the NOE complex with fixation of the central midface complex