Kinematic Alignment Compared to Mechanical Alignment Techniques for Total Knee Replacement Surgery (KARMA)

In order to be able to undertake a randomized controlled trial (RCT) comparing the efficacy of kinematic alignment versus conventional mechanical alignment for total knee replacement a robust assessment of the expected standard deviation of the primary outcome measure (Oxford Knee Score [OKS]) in both arms of the proposed RCT must be undertaken, hence this pilot study.

To determine whether there are improved postoperative outcomes in the investigative arm using the following patient reported outcomes: Knee Implant Performance (PKIP - pre and post surgical), Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), Knee Noise and Front of Knee Pain Score and Quality of Life score EQ-5D which will be completed at baseline(pre-operatively) and post-operatively at 6 weeks (normal clinical follow up), 1 year (normal clinical follow up) and 2 years. In addition, x-rays of the knee (AP, lateral & skyline) will be taken at the same time. These outcomes are identical to the data collected in the previous mechanically aligned study which will be used as the control arm.

Much attention has been given to the alignment of the components in total knee replacement (TKR) and this is relatively easy to quantify, particularly in the coronal plane. However, due to the development and use of computer navigation and patient-specific instrumentation systems that achieve neutral mechanical alignment, the conventional assumption that mechanically aligned TKR leads to the best implant survival has been brought into doubt. Although mechanically aligned TKR improves function, 20 % of patients remain dissatisfied according to reports from Canada, England and Wales. The relationship between in-range and varus (turned inward toward the mid line of the body to an abnormal degree) and valgus (turned outward) outlier categories of the limb and implant survival of a primary total knee replacement is weak at 15 years. Leaving a limb, knee, or tibial component within a natural range of varus does not reduce implant survival at 3, 5, 7, and 10 years.

With the development of individualization of component alignment and the goal of achieving pre-arthritic alignment through restoration of the axes of rotation, the kinematic alignment technique has shown in case series and one RCT in the USA a substantial benefit in postoperative patient pain relief and function.

For direct comparison between kinematic aligned and mechanically aligned surgical techniques for total knee replacement, the investigators will conduct a pilot study prior to a larger RCT and recruit a cohort of 15 patients undergoing kinematic aligned TKR. The investigators will use the same device as was used in a previous mechanically aligned study undertaken at our hospital (REC ref: 12/NE/0293 Attune, DePuy, Warsaw IN, in 35 patients based on the same eligibility criteria who will act as controls), which will allow the opportunity to estimate the standard deviation in the control arm in preparation for the larger RCT.