R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

284 Medical modelling
a precision screw mechanism. Adjusting the screw mechanism on a daily
basis maintains the required gap. Typically the device is removed after the
desired growth has occurred and been allowed to heal fully. The technique
can be used in three dimensions to correct any number of skeletal abnormalities
and has been used successfully in orthopaedic and maxillofacial
surgery.
Benjamin’s double osteotomy
Benjamin’s double osteotomy was a double transverse cut, one cut through
the distal femur and one through the proximal tibia. The rationale was that
it would relieve the inter-osseous pressure underneath the subchondral
bone, which was thought to accelerate the degeneration of the cartilage and
sever the nerve in the subchondral bone plate, which was also thought to
contribute to pain relief. A Charnley compression clamp was used to fi x
the osteotomy. The procedure developed a poor reputation because the
condyles and tibial plateaux blood supplies were compromised, and bone
necrosis led to above knee amputations in some cases. In addition, a long
rehabilitation period was required for a minimal benefi t.
Vertebrae
The 33 human vertebrae are named and numbered according to their anatomical
position starting at the head and working downwards. They are split
into three categories, cervical (neck), thoracic (chest) and lumbar (lower
body). The seven cervical vertebrae are therefore referred to as C1 to C7.
The 12 thoracic vertebrae are attached to the ribs and referred to as T1 to
T12. The lower spine consists of fi ve lumbar vertebrae (L1 to L5), the
sacrum and the coccyx. The sacrum is made up of fi ve fused vertebrae and
it forms the rear of the pelvic area. The coccyx is made of four fused vertebrae
that are an evolutionary remnant of a tail.