Healio
Healio
April 14, 2015
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Physiologic variation in anatomic landmarks may result in malalignment of TKA components

Due to a known high degree of physiologic variation between patients, assuming a standard relationship for anatomic landmarks when placing components for a total knee arthroplasty procedure could result in rotational malalignment with regard to the individual patients’ naïve anatomy, according to researchers.

The MRIs of 114 patients (average age: 64 years) with arthritic knees who underwent total knee arthroplasty (TKA) using patient-specific cutting guides were reviewed retrospectively by two orthopedic surgeons and two musculoskeletal radiologists. The main goal of the study was to evaluate the accuracy and precision of anatomic landmarks often used to determine rotational alignment for TKA. The researchers calculated interobserver and intraobserver intraclass correlation coefficient (ICC) to measure reliability.

Results showed the average external rotation of the posterior condylar angle was 1.34°. According to the researchers, 13% of the knees studied deviated from the mean by more than 3°. None of the knees deviated by more than 5°. Interobserver ICC and intraobserver ICC were found to be good and good-very good, respectively. The average range of variability measurement made by the four independent observers was 3.47°.

The external rotation angle for the tip of the tubercle to geometric center of tibia was 25.08°, with an average range of variability measurement of 12.36°. A deviation from the mean of more than 5° was observed in 49% of knees, and a deviation of more than 10° was seen in 15%.

On average, the external rotation angle from the medial third of the tubercle to center of tibia was on average 12.36°. Interobserver ICC and intraobserver ICC were moderate to good and good to very good, respectively, with an average range of variability of 10.18°.

According to the researchers, the high magnitude of variability between the observers demonstrates an intrinsic risk of inconsistency when the landmarks are used for the fabrication of patient-specific guides. – by Monica Jaramillo

Disclosure: The researchers report no relevant financial disclosures.

Sources/Disclosures

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Source:

Park A, et al. J Arthroplasty. 2015;doi:10.1016/j.arth.2014.08.015.