Bone Implant Design

Feb, 2018·
Jake Bewick
Jake Bewick
,
Eugene Chen
,
Jacob Holme
,
Lazar Kirov
,
Gregor Miklosic
· 1 min read
Abstract
This project proposes a novel fixation system for complex femoral fractures in osteoporotic patients, combining an inflatable intramedullary nail and an expanding, cementing lag screw—both made from bioresorbable PLA/phosphate glass composite. The system improves biomechanical stability, reduces surgical invasiveness, and promotes bone healing without the need for implant removal.
Type
This project was a collaborative design study to develop a two-part bone fracture fixation system. My contribution was to design a cementing lag screw inspired by rawl plugs to facilitate secure implant fixation into weak cancellous bone.

This project presents the design of a two-part bone fracture fixation system tailored for a complex femoral fracture in an osteoporotic patient. The system includes:

  1. An inflatable intramedullary nail (IMN) for stabilizing the femoral shaft, designed for minimally invasive insertion and manufactured from bioresorbable PLA reinforced with phosphate glass fibers.

  2. An expandable, cementing lag screw for securing the distal fracture, optimized for use in weak cancellous bone, featuring channels for controlled expansion and bone cement injection to enhance pullout resistance.

Both devices were modeled in CAD and assessed using clinical data, decision matrices, and mechanical theory. The bioresorbable material selection ensures gradual load transfer to healing bone, eliminates the need for secondary surgeries, and reduces stress shielding. This design is particularly suited to osteoporotic patients, addressing limitations in traditional metallic implants such as infection risk and fixation failure.

Engineering drawing of proposed lag screw for fixation into cancellous bone.
Figure: Engineering drawing of proposed lag screw for fixation into cancellous bone.
Jake Bewick
Authors
Jake Bewick
Doctoral Student