Rejuvenation of the aging face and skeleton with implants

Soft Tissue Aging

Soft tissue ptosis secondary to gravity has long been considered the major mechanism responsible for facial aging. There is no doubt that gravity and ptosis are the main factors leading to facial aging. Lambros and others have concluded that changes in volume of cheek fat, both loss and gain, rather than ptosis account for an aged appearance. Numerous anatomical studies, however, show that there are also many changes to the craniofacial skeleton as patients age that contribute to the aging process.

The aging face typically shows the following changes: descent of the brow, changes in contour of the upper eyelid, medialization of the lateral canthus, lower eyelid descent, deflated infraorbital skin envelope, increased visibility of the lid–cheek junction and nasojugal crease, increased prominence and depth of the nasolabial fold, and increased prominence of the labiomandibular crease. These signs of aging have been related to changes in skin and soft tissue.

In addressing soft tissue ptosis and volume changes, many facelifting techniques involve the removal of excess skin and also fat grafting and sculpturing. The main purpose of this chapter is to address the skeletal changes in the face that contribute to aging. Other chapters discuss the techniques available to address and reconstruct the facial skeleton for a more youthful appearance as a sole procedure or in addition to other techniques.

Facial Skeleton Aging

In addition to soft tissue changes, it has been demonstrated that there is remodeling of the craniofacial skeleton with age, for example, bony remodeling in the orbit. These will be discussed separately in the remainder of this chapter.

One of the theories behind the skeletal changes is mechanotransduction, which is the process of skeletal remodeling due to mechanical forces of soft tissue on bone.

The functional matrix hypothesis states that “epigenetic, extra skeletal factors and processes are the prior, proximate, extrinsic, and primary cause of all adaptive, secondary responses of skeletal tissues and organs.” This is, in essence, a restatement of Wolff’s Law, which is the observation that a long bone changes its external shape and internal architecture in response to stresses acting on it. A recent revision of the functional matrix hypothesis stresses the importance of mechanotransduction, which is defined as the process of intercellular transaction of mechanical information into osteoblastic changes.

Several studies have shown craniofacial changes as a result of facial muscle and nerve ablation. Sinsel et al. in a laboratory study on rabbits demonstrated misdirection of bony growth and changes in bony shape after ablating the buccal branches of the facial nerve and the muscles innervated by these branches. Matic et al. also demonstrated a decrease in bone volume of the mandible and zygoma in rabbits after paralyzing the masseter muscle unilaterally with botulinum toxin.

A study conducted on patients with Moebius syndrome by Instrum et al. exemplifies the relationship between musculature and bony changes. In this neuromuscular syndrome, patients suffer congenital facial paralysis that is usually bilateral and involves cranial nerves VI and VIII. In some patients, cranial nerve V is also involved, causing paralysis of the muscles of mastication. Skeletal changes are evident on cephalograms of patients with Moebius syndrome and research has shown that these changes are more apparent in the cephalograms of patients with cranial nerve V involvement. These patients were found to exhibit an “extreme pattern of vertical growth, clockwise rotation of the mandible, and an anterior open bite.”

Craniofacial skeletal changes, including significant lengthening of the face and an anterior flare of the upper incisors, has been found to occur in patients with spinal muscular atrophy and myotonic dystrophy, both syndromes that cause weakening of the muscles of mastication.

The above studies indicate that muscle functionality is important to the development of the bones on which they insert. When comparing the craniofacial skeletal changes that occur in aging with the changes that occur with neuromuscular syndromes, it becomes apparent that the two are quite similar. Therefore, we can conclude that normal facial muscle strength is important in maintaining a youthful craniofacial skeleton.