Abstract
Summary
The posterolateral overhang of the femoral component was measured using 3-D templating software. Rounded and reduced shape of the posterolateral corner in the femoral component would be beneficial.
Introduction
In total knee arthroplasty, patients sometimes have pain in the posterolateral part of the knee. One possible cause is the impingement of the popliteus tendon against femoral components. In the literature, the incidence has been reported to be 1–4%. The purpose of this study was to compare of two prostheses on the amount of posterolateral overhang of the femoral component using Three-dimensional (3-D) templating software.
Methods
We investigated 50 knees with varus osteoarthritic knees (male 11 knees and female 39 knees), all cases were grade 2 or lower in Kellgren Lawrence classification.
We compared of two prostheses, symmetrical design (Vanguard RP prosthesis?Zimmer-Biomet, Warsaw, IN, USA?; V group) and asymmetrical design (FINE Total Knee System (Teijin-Nakashima medical, Okayama, Japan); F group), on the amount of posterolateral overhang of the femoral component using 3-D preoperative planning software.
The distal femur was simulated to cut 9mm thickness on the lowest point of the medial condyles with 6 degrees valgus. The femoral mediolateral axis was simulated to be parallel to the surgical epicondylar axis. The size of femoral components was decided by anteroposterior dimension of distal femur. Mediolateral location of the femoral component was that the lateral edge of the femoral components is just on the lateral cortex of the femur. In coronal plane, amount of M-L overhang of the femoral component was measured in 3 Zones (distal, proximal, center) on the surface of the posterior condyle cut.
Results
The mean amounts of M-L overhang averaged of 3 zone were 3.5±1.6mm in the proximal zone, 1.6±1.7mm in the central zone and −0.2±1.5mm in the distal zone in V group, 0.2±1.9mm in the proximal zone, 1.4±1.7mm in the central zone and 0.0±1.5mm in the distal zone in F group. V group (symmetrical design) had significantly higher component overhung than F group (asymmetrical design) in proximal zone of posterolateral condyle. (P<0.01).
In the proximal zone of lateral condyles, over 3mm overhanging cases were only 3 knees (6.0%) in F group, but were 30 knees (60.0%) in V group.
Discussion and Conclusion
There is the popliteal sulcus in proximal zone of the posterolateral part of the femur. Rounded and reduced shape of the posterolateral corner in the femoral component like FINE Total Knee System would be beneficial in decreasing overhang and complication in posterolateral part of femur.
