STATIC FUNCTIONAL FEMOROTIBIAL ALIGNMENT FROM A KNEE KINESIOGRAPHY IS EQUIVALENT TO LONG-LEG RADIOGRAPH ALIGNMENT MEASUREMENT

While emerging technologies in total knee arthroplasty (TKA) have improved orthopedists' precision, the lack of input from reliable functional data pre- and post-surgery limits the ability to define accurate treatment targets and assess post-TKA functional outcomes. The mechanical hip-knee-ankle (HKA) alignment assessed on long-leg radiographs is a static parameter of interest in TKA, but it cannot predict the knee dynamic behavior during weight-bearing activities. It is now understood that dynamic malalignment and kinematic biomechanical markers are associated with patient-reported outcomes (i.e., pain, function, satisfaction) pre- and post-TKA. The knee kinesiography exam allows to accurately quantify the knee dynamic alignment as well as kinematic biomechanical markers in all three planes of movement while the patient is walking on a treadmill (Figure 1). The exam begins with a functional and postural registration process which identifies joints' centers and defines a static standing functional HKA (fHKA) alignment before proceeding with the capture of dynamic data. The relationship between fHKA and mechanical HKA (mHKA) alignments is still unknown. The aim of this study was to assess whether the static functional femorotibial alignment from a knee kinesiography exam (i.e., fHKA) is equivalent to the mHKA alignment measured on radiographs. This cross-sectional analysis was performed on 144 healthy knees (79 subjects). There was 54.4% of women and the mean age was 32.3 years (SD: 10.6). The mHKA was measured from a standardized long-leg weight-bearing radiograph with a digital radiology imaging software. All participants underwent a knee kinesiography exam to determine the fHKA. For both measures, the HKA angle is 180° for a neutrally aligned knee. The HKA angle is lower than 180° for a varus knee and greater than 180° for a valgus knee. A paired T-test including Cohen's effect size estimation was used to compare measures from both assessments. Bivariate Pearson correlation and linear regression were used to assess the association between mHKA and fHKA. Box and scatter plots are displayed in Figure 2. There was no difference between mean mHKA and fHKA (178.2° vs 178.3° respectively, p=0.57). This was confirmed by the very small Cohen's D (i.e., 0.04) and mean difference between both measures (0.1°; 95%CI: [−0.3; 0.5]). There was a good to strong significant association between both alignment measures (r=0.651, p Results show that static fHKA from a knee kinesiography exam was equivalent to mHKA alignment taken from radiographs. This demonstrates that the knee kinesiography exam provides a reliable functional measure of the static standing knee alignment while allowing the assessment of the dynamic alignment behavior and the quantification of kinematic biomechanical markers during gait. Therefore, results reinforce the reliability and relevance of this exam and support the use of such dynamic functional assessment for orthopedists to complement static parameters in their decision-making process both before and after TKA. For any figures or tables, please contact the authors directly.