Correction of Angular Deformities in Knee Arthrosis

For participants whose leg bones don't line up properly, extra stress is placed on either the inner or outer side of the knee joint due to uneven transfer of body-weight. Gradually, this extra pressure wears away the smooth cartilage, resulting in osteoarthritis on that side of the knee joint. This problem is particularly common in young athletes and places them at risk of early osteoarthritis.

An operation exists whereby one of the bones either side of the knee is cut ( an osteotomy) and hinged open to straighten the leg. This alteration redistributes body-weight more equally across the knee joint and is known to be effective in delaying and possibly preventing, the progression of knee osteoarthritis- especially in younger and physically more active patients in whom a knee replacement is undesirable.

Currently it is possible to ( accurately) calculate the precise position of the bone cut and number of degrees correction required to straighten a leg using digital x-rays and three-dimensional CT scans. However there is no method of implementing this pre-operative plan during surgery so that the majority of surgeons rely on relatively crude and ipso facto unreliable intra-operative measurements as a guide.

To improve the accuracy of this operation, the investigator propose the use of a custom-made 'cutting block', tailored for each individual patient and its shape will match the contour of the patient's bone to ensure it can only be placed in one position. Pre-cut slots and holes will then guide the saw cut and the number of degrees the bone in hinged open, as per the pre-operative plan; it functions as an intra-operative template for the surgeon.

This study will primarily examine whether there is a close match between the planned and actual correction of leg deformities when using a patient-matched cutting-block.