Orthopaedics

Our group includes scientists, surgeons, students and surgical trainees. We are developing new tools for patient health management, surgery, and surgical training. These include tools for depicting patient density data post operation, patient specific models for computer-assisted surgery, software for a surgical training simulator and tooling for bone graft harvesting. In the clinic, we are engaged in radiostereometric (RSA) analysis to evaluate the microscopic motion of total hip replacement components.

Our laboratory equipment includes a bench Instron test machine, FARO Arm coordinate measuring device, Skyscan 1172 micro-CT, a gait analysis treadmill (instrumented with Kistler load cells and cameras) and RSA equipment.

We are developing a new tool for monitoring the remodelling of the bone around a prosthesis. We can automatically produce models of a patient's bone using computed tomography data (CT). This CT data, assessed with a special osteodensitometry software, enables us to obtain point estimates of density throughout the bone.

Models of the femoral bone of a hip replacement patient scanned post operation (left), at one year follow-up (middle) and at three years follow-up (right).

A novel virtual reality tool for training surgeons is under development. The simulator uses the CT scans of a patient's hip to customise a model allowing the surgeon to virtually operate on a model specific to the patient's anatomy. This customisation (an optional feature) can be performed within minutes on a standard desktop computer.

The simulator provides objective feedback on the surgeon's performance. Once fully developed the simulator may allow comparison between trainees, and assessment of improvements and learning. We are currently assessing the system as a training tool for hip fracture procedures.

Implant malposition remains one of the common causes of TKA failure and increased wear. Computer assisted surgery (CAS) tools can help the surgeon to improve implant position. However the accuracy of CAS systems remains an important question. We have developed a system for assessing the accuracy of CAS systems using a mechanical phantom that represents the leg and a coordinate measuring system (FARO Arm). We can use this tool to assess the accuracy of a CAS system in a leg with normal and abnormal geometry.

The Orthopaedics Project gratefully acknowledges the support of its funding partners:

• Veterans Affairs
• New Economy Research Fund
• Stryker S.A.
• Wishbone Trust (NZ)
• DePuy Johnson & Johnson

• Project members and collaborators
• Project publications