Effect of the presence of the articular cartilage on the femoral component rotation in total knee arthroplasty in female and varus osteoarthritis knees

Abstract

Purpose Surgical techniques for total knee arthroplasty (TKA) require femoral rotational corrections that alter the position of the surface of the posterior femoral joint especially in kinematic alignment. However, preoperative planning of TKA based on computed tomography (CT), without knowing the femoral cartilage thickness, may cause post-surgery failures in femoral rotation. Therefore, this study aimed to evaluate the effects of posterior condyle cartilage thickness on rotational alignment in the femoral component. Methods Three-dimensional magnetic resonance imaging (MRI) scans were obtained for 139 male and 531 female osteoarthritis patients. The angles defined by the femoral posterior condylar axis (PCA) and the surgical transepicondylar axis (TEA) were evaluated with respect to the presence of cartilage. Additionally, these effects were evaluated with respect to patient gender and varus/valgus condition. Results In all patients, the angle between the TEA and PCA was significantly greater in the presence of cartilage than in the absence of cartilage. This result was also seen in female patients. However, there was no difference in the TEA/PCA angle in male patients based on the presence of cartilage. The TEA/PCA angle was significantly greater in the presence of cartilage than in the absence of cartilage in the female varus group. However, there were no differences in the TEA/PCA angle based on the presence of cartilage in the male varus/valgus and female valgus groups. Cartilage thickness in the posterior femoral condyle was significantly greater on the lateral side than on the medial side in all and male patients. However, there was no difference between the genders regarding cartilage thickness. Conclusion Surgical planning for TKA based on CT does not consider articular cartilage and could lead to external malrotation of the femoral implant. Therefore, the effect of the remaining posterior condylar cartilage should be considered by surgeons to prevent over-rotation of the femoral component, especially in female varus knees.

The Presence of Cartilage Affects Femoral Rotational Alignment in Total Knee Arthroplasty

“…Koh et al indicated that the PCA was 2.2 ± 1.0° internally rotated relative to the sTEA through 3D bony and cartilaginous models based on MRI scans of end-stage osteoarthritis patients ( 13 ). Nam et al also reported that the PCA was 2.4 ± 0.9° with cartilage and 2.6 ± 1.0° without via femoral 3D MRI constructed models, and the variation was more evident in females, similar to our results ( 9 ). When performing femoral rotational resection, the same cutting angle leads to over 10% outliers, possibly resulting in malalignment.…”

“…We also evaluated the cartilage thickness in the distal and posterior femoral condyles and found no difference between the lateral and medial sides. Nam et al reported that the lateral posterior cartilage thickness (2.2 ± 1.0 mm) was significantly greater than the medial side (1.8 ± 0.4 mm), and Asada et al reported 1.5 ± 0.39 mm ( 9 , 10 ). However, both studies enrolled arthritic subjects where pathological cartilage wear or defects were expected.…”

“…Further, our institute's senior surgeon noticed that patients with mild to moderate arthritis scheduled to undergo TKA had cartilage remnants or intact in the femoral posterior condyles and the unilateral distal femoral condyle, which may result in inaccurate prosthesis implantation. Nam et al and Asada et al noted that cartilage remnants influenced Korean and Japanese populations with arthritis ( 9 , 10 ). However, if cartilage thickness affected the distal femoral resection was unknown, and studies focused on these measurements in the normal Chinese population are lacking.…”

The femoral anterior tangent line could serve as a reliable alternative reference axis for distal femoral rotational alignment in total knee arthroplasty: an MRI-based study

“…Various degrees of cartilage wear, osteophyte hyperplasia, and bone-end deformity may occur in different stages of knee osteoarthritis, and these changes may lead to the alteration of the position of femoral rotational reference axes ( 28 , 29 ). The posterior femoral condyles are in the load-bearing area of the femur, where cartilage wear is very common in patients with knee osteoarthritis, making the PCA susceptible to the deterioration of the knee joint circumstance ( 30 ). By analyzing more than 2,000 cases of femur CT data, Jang et al pointed out that, when compared with other rotational reference axes, the external rotation of the PCA by 3° was the most accurate reference to the sTEA, but it had the highest intersubject variability ( 6 ).…”

Lateral distal femoral condyle has more uniform cartilage wear in varus knee osteoarthritis

“…Residual cartilage in patients with osteoarthritis may affect the accuracy of the osteotomy. Nam et al proposed surgical planning for TKA based on CT does not consider articular cartilage and could lead to external malrotation of the femoral implant 13 .…”