ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ASSESSMENT OF SURGICAL VARIABILITY IN TKA USING DIGITAL
ANALYSIS
1. ABSTRACT
A. Henderson 1 , Y. Dai 2 , J. Seebeck 3 , J. Bischoff 4 ,
Clinical variability in implant positioning is an important factor to consider for Total
Knee Arthroplasty (TKA) designs. To determine this surgical variability in TKA
placement 11 cadaver knees were implanted by experienced surgeons. Bone geometries
were segmented from pre and post op CT scans and the implant orientation was found
using image registration techniques. Component resection parameters with respect to
bone landmarks were determined for each individual bone and the mean and standard
deviations across all bones were calculated. AP and ML dimensions, relevant to
determine TKA size selections were compared for the individual component
alignments, their theoretical mean position and a +/- 1 std. dev. perturbation from the
mean to determine their robustness against surgical alignment variability. The average
absolute difference in the AP and ML dimensions of the femur and tibia between the
actual surgical and the mean resection was between 1 and 2 mm. The AP differences
were larger than ML and the femur had larger differences than the tibia. Varying a
single resection parameter by the measured standard deviation change the AP & ML
dimensions by less than 1 mm for the tibia and less than 1.7 mm for the femur.
2. INTRODUCTION
The clinical variability in terms of the implant positioning by surgeons is an important
factor to be understood for designing a Total Knee Arthroplasty (TKA) system. As
statistical shape analysis has gained attention and is used to assess the biomechanical
characteristics of TKA implants [1], such methodology is promising when applied to
resection analysis of TKA in order to motivate component design, enable vigorous
checks of the robustness of current designs, or improve the understanding of surgical
outcomes. However, current analyses ignored the surgical variations as they either
directly use actual TKA resection data [2], or assume a single set of parameters for
resections across the entire specimen investigated [3]. This could be due to lack of
available data in the clinical variability of TKA resections. To obtain such information,
characterizing of clinical resection variability is needed.
This study presents methodology and results for characterizing surgical variability of
the TKA resection. In addition, the impact of such variability on the dimensional
measurements in the resected knee was determined. Specifically, 1) TKA resections
1 Research Engineer, Computational Biomechanics, Zimmer GmbH, Winterthur 8404, Switzerland
2 Research Engineer, Computational Biomechanics, Zimmer Inc, Warsaw IN 46580, US
3 Associate Director, Research, Zimmer GmbH, Winterthur 8404, Switzerland
4 Director, Research, Zimmer Inc, Warsaw IN 46580, US