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Exploring Bone Ageing Mr James Olding details how facial bones change over time and provides considerations for dermal filler treatment Contemporary concepts in facial aesthetics have shifted the focus to rejuvenation through revolumisation and identifying age-related volume loss, with the objective of re-establishing the ideal or previous facial dimensions. The facial skeleton provides the structural support for overlying soft tissues, and changes to facial appearance manifesting as hollowing, folds, creases and rhytids, are usually preceded by bony changes. It is therefore of great importance that any structural deficit is addressed. Facial ageing follows a predictable process, with specific areas of the facial skeleton undergoing resorption, resulting in the appearance of some of the most common stigmata of ageing. The mid-face, the orbit and the mandible are three important areas of the facial skeleton implicated in ageing, and the signs of bony changes in these regions include under-eye hollowing, altered brow position, deepening facial folds, and the appearance of jowls.1,2
The biology of bone remodelling
only two thirds of the amount that women lose over their lifetimes, in addition to reaching peak bone mass later (around aged 30) and having a higher adult peak bone mass.4 In women, in addition to gradual progressive loss of cortical and trabecular bone from the third decade onwards, additional bone loss occurs precipitously within a year of the menopause; a process which is sex hormone linked and attenuated by hormone replacement therapy.9 The idea of selective bone resorption alludes to the site-specific changes in certain areas of the face, while resorption elsewhere is less pronounced or not present at all.1 Despite being regulated by different growth factors, facial bone undergoes a decrease in bone mineral density with age, similar to axial bone.2 In the adult facial skeleton, it has been observed that bone resorption occurs in a predictable manner, commonly affecting the mid-face, orbit and mandible, though each area is not necessarily affected by the same pathophysiological process.2,10 Differences in bone density are well reported between ethnicities and black individuals have been shown to experience less pronounced dimensional changes to the face than white individuals as they age.10 It is not possible to fully assess the reasons underlying these observed differences between ethnicities, though genetics is likely to be central, in conjunction with other factors including body mass, hormones and diet.11
Bone is a living tissue maintained through a delicate balance of osteoid deposition by osteoblasts, and resorption by osteoclasts. Understanding bone biology and its clinical relevance requires an understanding of some important terms; namely, peak bone mass (PBM) and bone mineral density (BMD). Bone mass will depend on bone density and bone size.3,4 Each individual has a bone mass potential which is largely determined by genetics.3 Within this genetic potential, the actual peak bone mass reached as an adult will depend The mid-face on lifestyle, hormonal and environmental factors.5 Research has shown that even within a single area of the face, Differences between sexes are also notable, with the peak bone bone resorption is highly site specific.1,2,12 The bony mid-face mass achieved by males being greater due to increased periosteum consists principally in the maxillary and the zygomatic bones, with a deposition on account of the fact of males having larger and longer predilection for age-related resorption at the maxilla, even in dentate bones in general.6 Sex hormones and the IGF-1 system have been patients.1,2 Maxillary bone resorption leads to reduced anterior 7 implicated in this sexual dimorphism. Bone mineral density is a measure of the inorganic mineral content of bone, and is a surrogate for measuring bone mass and strength. It can be Inferiorlateral measured as a snapshot using a DEXA scan orbital to diagnose conditions such as osteoporosis. It is important to understand that the peak Glabella angle adult bone mass achieved will influence Pyriform angle the risk of sequelae arising from bone loss, Maxilla 6 including osteoporotic fractures, in adulthood. Maxilliary angle Bone responds to mechanical stress, undergoing remodelling, which involves Prejowl suculus resorption followed by deposition, in what is of mandible known as a basic multicellular unit of bone remodelling (BMU).5 The adult skeleton is entirely replaced in this way every 10 years.8 Starting from the middle of the third decade, Figure 1: Areas of the facial skeleton prone to Figure 2: Age-related resorption has been analysed women lose 35% of their cortical bone and age-related bone resorption in longitudinal studies using CT, where the glabella, 4 50% of their trabecular bone. Men lose pyriform, and maxillary angles are measured over time
Reproduced from Aesthetics | Volume 7/Issue 10 - September 2020
