A Trial of Mechanical Axis vs Kinematic Alignment in Total Knee Replacement

To demonstrate, through calculation of Oxford Knee Score (OKS) post operatively, that total knee replacement (TKR) performed using the ShapeMatch® Cutting Guide provides improvement from preoperative levels of patient pain and function comparable to the improvement obtained with TKR performed using computer-assisted Navigation. Oxford Knee Scores will be calculated pre-operatively and at 6 weeks, 6 months, 12 months, 2 years and 5 years. The OKS is a participant completed 12 question form on activities of daily living that assess function and pain. Scores can range from 0 to 48 with lower scores indicating a poor outcome and higher scores indicating a more satisfactory joint outcome.

Skin to skin time is the time in minutes from initial skin incision to skin closure. Anaesthesia time is the time in minutes that anaesthesia administration is started to the time it is stopped. Data for anaesthesia time is not available due to an error on the original case report form that did not correctly capture anaesthesia time.

To compare the cost-effectiveness and cost-utility of the procedure between the ShapeMatch® Cutting Guide group and the computer-assisted Navigation control group the surgical incision length is reported in mm.

To compare the cost-effectiveness and cost-utility of the procedure between the ShapeMatch® Cutting Guide group and the computer-assisted Navigation control group. The data for the cost of consumable items used during the operating procedure is not available. Due to limited site resources, a decision was made not to collect this secondary outcome measure data.

To compare the cost-effectiveness and cost-utility of the procedure between the ShapeMatch® Cutting Guide group and the computer-assisted Navigation control group the length of stay in number of days spent in the hospital is reported..

A quality-adjusted life-year (QALY) takes into account both the quantity and quality of life generated by healthcare interventions. It is the arithmetic product of life expectancy and a measure of the quality of the remaining life-years. A QALY places a weight on time in different health states. A year of perfect health is worth 1 and a year of less than perfect health is worth less than 1. Death is considered to be equivalent to 0; however,some health states may be considered worse than death and have negative scores.

Pain at rest and pain during mobilization was measured using a 10 centimeter Visual Analogue Scale (VAS). Participants are asked to indicate their level of pain with 0 being no pain and 10 being the worst pain.

The WOMAC is completed by the participant and measures five items for pain (score range 0-100), two for stiffness (score range 0-100), and 17 for functional limitation (score range 0-100). The total score is the sum of these three categories.

The EQ-5D-3L descriptive system comprises the following 5 dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension has 3 levels: no problems, some problems, extreme problems. The participant is asked to indicate his/her health state by indicating the most appropriate level for each of the 5 dimensions. Responses may be converted into a single summary index by applying a formula that essentially attaches values (also called weights) to each of the levels in each dimension. The index can be calculated by deducting the appropriate weights from 1= the value for full health.

The EQ VAS records the participant's self-rated health on a vertical, visual analogue scale where the endpoints are labelled from 100 ='Best imaginable health state' to 0= 'Worst imaginable health state'.

The Forgotten Joint Score (FJS) is a 12 question form that asks the patient their level of awareness of their artificial joint in 12 scenarios commonly encountered in daily life. Scores can range from 0 to 100 with a higher score indicating a better outcome (high degree of forgetting the joint in everyday life).

The Knee Society Clinical Rating System is comprised of two distinct sub-scores: one for pain, range of motion (ROM) and joint stability, and one for functional parameters. Sub-scores range from a minimum score of 0 to a maximum of 100 points. Although the specific scores are not distinguished as "excellent," "good," "fair," or "poor," a higher value represents a better outcome.

The Perth CT protocol is a comprehensive assessment of total knee replacement (TKR) component position and orientation. The alignment of the TKR components is measured against the mechanical axis and the transepicondylar axis of the lower extremity. The posted data represents the mean angle between the femoral component and mechanical axis of the femur, the angle between tibial component and mechanical axis of the tibia, the tibial component slope relative to the sagittal mechanical axis, and the femoral component rotation relative to surgical epicondylar axis (positive value=external rotation). For all degree values posted a positive (+) value= valgus and a negative (-) value = varus.