Ligament and Tendon Enthesis: Anatomy and Mechanics - Structural Interfaces and Attachments in Biology - page 72

Fig. 4.5 Schematic description of the changes in the tensile properties and failure modes of the
rabbit femur-MCL-tibia complex (FMTC) with age
tensile failure of the FMTC by midsubstance failure, as the strength of the
MCL-tibia insertion increased with skeletal maturity.
A schematic representation of the effects of maturation on the biomechanical
properties of the FMTC is shown in Fig. 4.5 . Prior to skeletal maturity, the strength
of the MCL substance reached its peak value, while the bone-ligament junction,
especially at the proximal tibial insertion site, was being established. Therefore, the
MCL substance was stronger, and the FMTC failed by tibial avulsion. Once skeletal
maturity was reached, the proximal tibial insertion site became solidly established,
while the tensile strength of the MCL substance changed minimally.
4.3.2 Aging
With aging, there are significant changes in the periosteum, as the superficial
fibrous layer becomes comprised of fibroblasts and fibrocytes interposed between
multidirectional collagen layers permeated by elastic tissue. The deeper osteogenic
layer now contains precursor osteogenic cells and mature osteoblasts, changes that
are coupled with a loss of organelles. Aging is also characterized by a loss of cells
and organelles associated with normal functional activities. Lipofuscin also appears
in all of aged cells, including osteocytes. Despite these severe ultrastructural