Shin bone's connected to the . . .

May 24, 2007
The Bocemix, a mixing dispenser for orthopedic bone cement, works smoothly and reliably thanks to five key parts, says its maker Bidoia S.a.s. of Peroga di Vigonza near Padua, Italy.

Delrin acetal parts contribute to the smooth, efficient operation of a bone cement mixer: (1) leaf spring as an integral part of the trigger lever; (2) C-shaped anti-screw pull-tab; (3) ribbed driving shaft; (4) mixing blades; and (5) rotary piston.

The self-contained device doesn't need separate injectors and eliminates air and gas bubbles from the mixed cement. This reportedly gives doctors better control while injecting bone cement during reconstruction surgeries.

The dispenser works with all types of cement although there are some limitations for zirconium dioxide, says Bidoia S.a.s executive Roberta Bidoia. The five key parts are made from Delrin acetal and would have been unfeasible or too costly if designed in metals or other materials, says Bidoia.

Delrin, from DuPont, Wilmington, Del., has good elongation at yield and makes it possible to mold the device's leaf springs as an integral part of the trigger levers. This eliminates the need for metal return springs and related assembly operations. Delrin's toughness and stiffness also let designers build a C-shaped anti-screw pull-tab that's held in place with a snap-fit. The inherent lubricity of the acetal together with its high modulus and strength were key for the ribbed driving shaft design, while its flex modulus is essential in the design of its mixing blades. A rotary piston is also Delrin. Mixing is done manually or with an electric power source. The transparent barrel allows visual inspection of the consistency of the cement.

More Information:
Bidoia S.a.s.

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