Correction of Angular Deformities in Knee Arthrosis

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.