Aug 31, 2015
Improving Patient Outcomes with Kinematic Alignment in Total Knee Replacement
Total hip replacement is one of the most successful procedures in modern surgery with greater than 95% survivorship at 11 years in Australian registry data1. Similarly, hip replacements enjoy high patient satisfaction rates over 90% at 12 months2.
Despite similar survivorship rates, total knee replacements have never achieved the same level of patient satisfaction. Recent independent reports from the United Kingdom and Canada quote dissatisfaction rates between 18% and 25% with traditional ‘mechanically’ aligned knee replacements3-4.
Traditional mechanically aligned knee replacements aim to create a horizontal joint line and a ‘straight’ 0o hip-knee-ankle angle (the perceived ‘norm’) irrespective of each patient’s individual alignment and natural non-arthritic joint line obliquity. To achieve this, ligament releases and alteration to the level of the joint line are often required to allow acceptable balance and range of motion.
A study by Eckhoff et al has challenged the validity of this concept with only 4 of 180 analysed normal limbs having the ‘ideal’ mechanically aligned 00 hip-knee-ankle angle. 103 normal limbs were in varus and 73 in valgus with a wide normally distributed range from 120 varus to 150 valgus5.
With the advent of computer assisted navigation and improved prosthetic design, it is now possible to accurately restore each patients joint line to their natural ‘kinematic’ alignment. The goal is to simply put back what arthritis has taken away. This reproduces a normal pre-arthritic joint line and restores the rotational axes unique to each patient.
A recent randomized control trial compared the function at 2 years of 60 kinematic to 60 mechanically aligned knee replacements. They clearly demonstrated superior clinical results with patients receiving kinematic aligned knee replacements able to walk further in early post-operative period, 3 to 5 times more likely to be completely pain free at 2 years and significantly better range of motion and knee outcome scores than mechanically aligned knees6.
With the recent advances of computer navigation and robotic assistance in joint replacement surgery, it is now feasible to produce accurate and reproducible implant positioning unique to each individual patient to best restore normal joint line anatomy and more normal joint motion following knee replacement.
1. Australian Orthopaedic Association National Joint Replacement Registry Annual Report 2014
2. Mariconda, Massimo, Olimpio Galasso, Giovan Giuseppe Costa, Pasquale Recano, and Simone Cerbasi. "Quality of life and functionality after total hip arthroplasty: a long-term follow-up study." BMC musculoskeletal disorders 12, no. 1 (2011): 222.
3. Bourne, Robert B., Bert M. Chesworth, Aileen M. Davis, Nizar N. Mahomed, and Kory DJ Charron. "Patient satisfaction after total knee arthroplasty: who is satisfied and who is not?." Clinical Orthopaedics and Related Research® 468, no. 1 (2010): 57-63.
4. Baker, P. N., J. H. Van der Meulen, J. Lewsey, and P. J. Gregg. "The role of pain and function in determining patient satisfaction after total knee replacement Data from the National Joint Registry for England and Wales."Journal of Bone & Joint Surgery, British Volume 89, no. 7 (2007): 893-900.
5. Eckhoff, Donald G., Joel M. Bach, Victor M. Spitzer, Karl D. Reinig, Michelle M. Bagur, Todd H. Baldini, and Nicolas MP Flannery. "Three-dimensional mechanics, kinematics, and morphology of the knee viewed in virtual reality."The Journal of Bone & Joint Surgery 87, no. suppl 2 (2005): 71-80.
6. Dossett, H. G., N. A. Estrada, G. J. Swartz, G. W. LeFevre, and B. G. Kwasman. "A randomised controlled trial of kinematically and mechanically aligned total knee replacements Two-year clinical results." Bone & Joint Journal96, no. 7 (2014): 907-913.
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