UCT engineer and local surgeon design novel prosthesis
A University of Cape Town (UCT) mechanical engineer and a local surgeon have
saved the leg of a young cancer patient by designing and producing a novel
prosthesis that may well become standard use in South Africa.
Dr George Vicatos and colleagues from the Department of Mechanical
Engineering at UCT, at the behest of Vincent Pallotti Hospital surgeon and part
time at Groote Schuur Hospital, Dr Keith Hosking, designed a titanium
"stem" (rod) to replace the cancerous part of the femur (thigh bone)
that doctors planned to cut out (or "resect") from an 18-year old
patient. Other options included amputating the entire left leg from just below
the hip, or replacing the cancerous bit with a segment of cadaver bone, fusing
this at the knee joint.
Vicatos' commission was to come up with a replacement "bone" that
would slot in between the top, remaining part of the femur and the knee.
"We chose this option as the patient would be able to retain function of
his knee and be able to walk without crutches, consistent with current practice
in other orthopaedic oncological units in Europe and North America," said
Hosking.
Vicatos came up with a number of prosthetic parts, as well as the tools to
fit them in to the patient's leg. A cementless system to enhance bone fixation
by use of a specialised sleeve and stem were manufactured from medical grade
titanium.
Vicatos, working against the clock, came up with scientific drawings for the
implants and tools, which he gave to Mr Len Watkins, Principal Technical Officer
in the Mechanical Engineering Department and the man responsible for machining
all the pieces. Watkins, also working against the clock, completed the last
components the night before the scheduled operation. Vicatos and Hosking
completed the "trial" run of inserting the device at 11pm.
In a five-and-a-half hour operation, Hosking successfully resected the
cancerous bone and replaced it with the customised implants.
In total, the operation cost R30 000, far less than what it would have been
had the prosthesis been imported from overseas.
Within two weeks the patient was able to move his leg and hip and he needed
to use crutches for only three months. Now 18 months later the young patient's
life has returned to normal. His stride is in fact so normal that onlookers are
unable to point out which leg contains the titanium implant.
Building on this success story, Vicatos, Hosking and Watkins have
collaborated to design a new range of various prostheses including a shoulder
joint, a distal radius, a proximal tibia, a proximal femur, a hip, as well as a
complete modular system for the replacement of part or even the complete femur.
The new, modular design allows the surgeon (using simple tools) to assemble
the correct length for the prosthesis inside the operating theatre, outside of
the patient. "They are designed to be simple and to make the surgeon's job
easier," Vicatos added.
One of the latest designs is a custom-made humerus (upper arm) including the
shoulder and elbow joints. This very rare prosthesis is ready to be made
through the invaluable contribution of Mr Andrew Parrott of Wits University. The
prosthesis will be manufactured in association with the Cape Town-based foundry,
CastCo Precision Castings (Pty) Ltd.
In close co-operation with Hosking the designs are repeatedly revised and
perfected. Some parts are exceptionally difficult to manufacture at present and
others can be standardised and produced in various sizes and options in advance
so patients need not wait. "We're expecting to manufacture all the
components much faster and with greater precision in the future," Vicatos
added.
Because they are locally designed and manufactured, these components are far
more affordable than the imported overseas equivalent products, which will give
many cancer patients a second chance. According to Hosking, these prostheses
could be highly beneficial to the orthopaedic oncology unit at Groote Schuur,
which serves as a tertiary referral centre for much of the country.
Other patients have subsequently benefited from these specialised implants
and research on new designs is ongoing. This has been made possible by UCT's
scientific knowledge and infrastructure, Vicatos noted. Several UCT engineering
students have become actively involved in this project under the guidance of the
team.
The University has allocated space in the Upper Campus' Old Maintenance
building, to set-up the manufacturing unit. Isiqu, the Xhosa word for
"complete body" is the name the team have chosen for their research
and manufacturing unit.---UCT
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