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Strengths, weaknesses of axis options should be weighed for TKA
Although Whiteside’s Line approximated the transepicondylar axis well among patients undergoing total knee arthroplasty, the posterior condylar axis demonstrated a lower variability and lower likelihood of being internally rotated compared with transepicondylar axis, according to study results.
Using MRI-based planning software, researchers assessed the relationship of Whiteside’s Line (WSL) and the posterior condylar axis (PCA) to the transepicondylar axis (TEA) in 560 knees undergoing total knee arthroplasty (TKA) for osteoarthritis. The researchers aimed to determine whether the relationships were influenced by preoperative coronal deformity.
Study results showed WSL did not approximate a line perpendicular to the TEA but instead demonstrated a mean rotational deviation of 0.361° of external rotation. Additionally, PCA did not approximate a line 3° internally rotated to the TEA, but instead rotated internally an average 2.38°.
Compared with the WSL group, significantly more patients in the PCA group deviated by more than 1° from TEA. However, PCA had significantly fewer outliers when evaluated for more than 3° of rotational deviation compared with WSL, whereas WSL had significantly more likelihood of being internally rotated compared to the TEA than the PCA, according to the researchers.
Age did not affect the rotational relationship between WSL or the PCA and TEA, whereas gender did not affect the relationship of WSL to TEA, according to the researchers. On average, however, women experienced significantly more internal rotation of the PCA to the TEA than men.
Disclosure: Stulberg received royalties from Peachtree Publishers, Aesculap and IntraMed; is on the speakers bureau for Zimmer and Stryker; and has stock options with Blue Belt Technologies.