Andrew Wolfenden

With so many people now enjoying good health into their nineties and beyond, there is a growing need for bone conserving hip replacements that preserve as much of the host bone as possible so that future surgeons can implant a standard hip replacement if the original implant works loose. As Lead Design Engineer I was responsible for every aspect of the engineering design, from concept right through to training the first surgeons on the correct technique for implantation.

Computer navigated surgery is a state-of-the-art surgical technique which is reported to enhance the accuracy of knee replacement surgery. Navigated surgery maps the position of the patient’s bones and the positions of the instruments in surgery using sensors, not unlike a small GPS system. These create a detailed 3D image and then provide real-time information on a computer screen which helps the surgeon accurately guide the implant into position.

I worked with German navigation software designers Localite to develop a series of adapters that would allow our existing suite of hip resurfacing instruments to be used in navigated surgery.

Occasionally, a surgeon will ask for a bespoke set of instruments which deviates from the standard issue kit, usually to accomodate a unique or innovative surgical approach. In this instance, a surgeon required a narrow, 'minimally invasive' cup positioner in place of the standard, larger one shown above, to allow him to position and impact the implant through a very small incision in the patient's hip. The instrument was designed, validated and in use in 8 weeks.

The Medial Referencing Jig allows a surgeon to visualise, adjust, then drill the desired stem axis of the femoral head implant (the 'ball' part of the ball and socket joint). The patented jig design prevents the surgeon from creating a potential bone fracture as a result of malpositioning the axis or choosing an implant which is too small for the patient. A leading surgeon reported 0% femoral neck fracture in 420 cases (compared with 4% in 1000 cases using the previous instrumentation).