A computer-aided bone-implant technique is coming on line that will increase the accuracy of implant insertions and decrease operating room time for hip, shoulder, knee and ankle replacements - especially for younger patients.

The novel technology relies on software newly developed by the Human Mobility Research Center in Kingston, Ontario. It also depends on computed tomography (CT) scans of a patient's damaged joint. The software creates an exact, patient-specific, 3-D image of the joint and nearby bones, which can then be turned into a plastic model. This, in turn, is used for precise alignment and placement of the metal implants needed to redo the patient's joint with - in the case of hip surgery - so-called hip resurfacing arthroplasty.

The procedure is usually geared toward younger, more active patients who would likely outlive a traditional joint replacement, leaving them with considerable incapacitation.

Resurfacing is a less drastic form of joint replacement than traditional arthroplasty. In hip replacement surgery, resurfacing involves shaving off the damaged cartilage on the head of the leg bone, and replacing it with a metal cap - instead of cutting off the head and end of the bone and replacing them with a prosthesis. Resurfacing ultimately allows the patient greater mobility and range of motion.

In this sort of surgery, however, the implants must be inserted with great precision to avoid excessive strain on the healthy bone tissue that remains. Surgeons have always been challenged to do this unaided.

"The three-dimensional advantage of the CT scan is incorporated into the design to create a customized form that increases accuracy and efficiency in the [operating room]," says Dr. John Rudan, orthopedic surgeon at Kingston General Hospital and professor of surgery at Queen's University. In addition, Rudan is vice president of clinical relations at iGO Technologies Inc., the Kingston-based company that helped develop the customized surgical-planning software. "The virtual representation in this form of computer-assisted surgery allows for better reproducibility and a reduction in errors."

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