Tibia Vara Affects the Aspect Ratio of Tibial Resected Surface in Female Japanese Patients Undergoing TKA

Abstract

Background Tibia vara seen in Japanese patients reportedly influences the tibial component alignment when performing TKA. However, it is unclear whether tibia vara affects the component position and size selection. Questions/purposes We therefore determined (1) the amount of medial tibial bow, (2) whether the tibia vara influences the aspect ratio of the tibial resected surface in aligning the tibial component with the tibial shaft axis, and (3) whether currently available tibial components fit the shapes of resected proximal tibias in terms of aspect ratio. Methods We measured the tibia vara angle (TVA), proximal varus angle (PVA), and the mediolateral and middle AP dimensions of the resected surface using threedimensional preoperative planning software in 90 knees of 74 female patients with varus osteoarthritis. We determined the correlations of the aspect ratio with TVA or PVA and compared the aspect ratios to those of five prosthesis designs. Results The mean TVA and PVA were 0.6°and 2.0°, respectively. The aspect ratio negatively correlated with both TVA and PVA (r = À0.53 and À0.55, respectively). The mean aspect ratio of the resected surface was 1.48 but gradually decreased with increasing AP dimension, whereas four of the five prostheses had a constant aspect ratio. Conclusions The aspect ratio of resected tibial surface was inversely correlated to the degree of tibia vara, and currently available prosthesis designs do not fit well to the resected surface in terms of aspect ratio. Clinical Relevance The design of a tibial component with a smaller aspect ratio could be developed to obtain better bone coverage in Japanese patients.

Popliteus impingement after TKA may occur with well-sized prostheses

“…In a TKA, the thickness of the tibial component is selected to restore the joint line and to match the contours of the resected surfaces [ 13 , 14 , 31 , 36 ]. Therefore, a superstructure of polyethylene is generally built above the posterolateral area of the tibial plateau, leading to a potential risk of popliteus impingement (Fig.…”

Satisfactory long-term survival, functional and radiological outcomes of open-wedge high tibial osteotomy for managing knee osteoarthritis: Minimum 10-year follow-up study

“…Such that, studies have shown a lower prevalence of osteoporosis being found in the Chinese population than their Japanese counterparts [ 24 , 25 ]. Individual studies have also described the difference in morphologies of knee and proximal tibia between the Japanese and Korean population [ 26 , 27 ]. However, a study on the direct comparison among these Asian ethnicities remains to be further elucidated.…”

Proximal tibia vara involves the medial shift of the tibial articular surface

“…[2][3][4][5] It has been reported that the proximal tibia vara involved the medial shift of the tibial articular surface (TAS). 4,[6][7][8] However, it is still obscure that the varus inclination of the TAS has a correlation with the medial shift of the TAS. The constitutional varus knee could be the consequence based on Hueter-Volkmann's law, which states that growth at the epiphyses is retarded by increased compression, whereas reduced loading accelerates growth.…”