The contact condition in the human knee joint must play important roles especially in dynamic loading situations where the loads transfer in the knee. In this study, the impact stress propagations through the inside of the knee joint were simulated using the three-dimensional finite element analysis (FEA). And the differences in the stress distribution were investigated between the intact knee and the total replacement condition. The finite element (FE) models of an intact human knee joint and a total replaced knee joint were constructed with high shape fidelity. The intact model included the cortical bone, cancellous bone, articular cartilage, bone marrow, and meniscus. And the total replacement knee FE model, which is consisted of the artificial femoral and tibial components were also prepared to compare the impact propagations with the intact model (Figure 1). Impact load were applied to the proximal femur of the FE models under the same conditions as those of the weight-drop experiments with the knee joint specimens. The FEA results showed that the impact stress propagated to the tibia through the knee joint for several milliseconds. The values and the time dependent change of the compressive strain on the cortical surface had good agreement with the experimental results. The compressive stress mainly propageted at the medial side, with 1.0 MPa at 1.2 milliseconds. Especially, the impact stress propagated not only in the cortical surface area which has hard material property but also in the soft cancellous bone region inside the knee joint. The mass density of the cancellous bone has similar to that of the cortical bone, and thus the role of the load bearing in the cancellous area must be much increasing under the impact condition. In the total replacement model, concentration of the impact compressive stress was observed with 2.8 MPa at the tibial region, while not under the normal intact conditions (Figure 2). Since the total replacement model is formed of different materials and the impact propagations were inhibited by the interfacial condition, such as sliding or debonding, it is considered that the contact condition between such materials have a great effect on the stress propagation.
Biomechanical knowledge of the medial collateral ligament (MCL) is important for MCL release during knee arthroplasty. The purpose of this study was to define the influences of the deep medial collateral ligament (dMCL) and the posterior oblique ligament (POL) on valgus and rotatory stability in knee arthroplasty. Six cadaveric knees were divided into 2 groups with unique sequential sectioning sequences of the dMCL and the POL. Group A (n = 2) first received femoral arthroplasty only, and thereafter sequentially received medial half tibial resection with spacer, ACL cut, dMCL cut, POL cut, and finally tibial arthroplasty. Group B (n = 4) first received femoral arthroplasty only, and thereafter sequentially received medial half tibial resection with spacer, ACL cut, tibial arthroplasty, dMCL cut, and finally, POL cut. A CT-free navigation system monitored motion after application of valgus loads (10 N-m) and internal and external rotation torques (5 N-m) at 0°, 20°, 30°, 60°, and 90°of knee flexion.Purpose:
Methods:
Quantitative knowledge on the anatomy of the medial collateral ligament (MCL) is important for preventing MCL damage during unicompartmental knee arthroplasty (UKA). The objective of this study was to quantitatively determine the morphology of the medial capsule and deep MCL on tibias. 24 cadaveric human knees (control: 19, OA: 5) were dissected to investigate the deep MCL and capsule anatomy. The specimens were fixed in full extension and this position was maintained during the dissection and morphometric measurements. The distance from the tibial insertion sites of the medial capsule including deep MCL to the medial joint surface were measured at anterior, middle, and posterior sites. Posterior capsule slope and posterior tibia slope to the anterior tibia cortex was also measured. In control, the distance from the tibia insertion sites of the medial capsule including deep MCL to the anterior 1/3, middle 1/3, and posterior 1/3 of medial joint surface were 12.5 ± 1.5 mm and 8.0 ± 1.6 mm and 9.4 ± 1.6 mm, respectively. Posterior capsule slope and posterior tibia slope to the anterior tibia cortex were 6.3 ± 3.3 degree and 12.7 ± 2.1 degree, respectively. In OA, the distance from the tibia insertion sites of the medial capsule including deep MCL to the anterior 1/3, middle 1/3, and posterior 1/3 of medial joint surface were 14.0 ± 1.7 mm and 9.6 ± 1.9 mm and 10.8 ± 1.5 mm, respectively. Posterior capsule slope and posterior tibia slope to the anterior tibia cortex were 8.0 ± 3.5 degree and 14.5 ± 2.2 degree, respectively.METHODS
RESULTS
562 osteoarthritic knees rated as stage 1 or more according to Kellgren's osteoarthritic knee classification were selected randomly and analyzed radiologically. Eighty cases with the height of 155 cm-160 cm, for which a large number of male and female cases are available (34 male cases, 46 female cases) were extracted for analysis. The values measured were significantly larger in male than in female in any region. In order to clarify differences in morphology between the sexes, the ratio between the values measured of various regions was computed. As a result, the value obtained by dividing the length of medial femoral condyle in anterior-posterior direction and the depth of medial femoral condyle in proximal-distal direction by the width of femur at articular level was 0.87±0.03, 0.56±0.03 in female against 0.81±0.04, 0.52±0.03 in male, respectively. The value obtained by dividing the length of medial tibia condyle in anterior-posterior direction by the width of tibia at articular level was 0.61±0.05 in female against 0.59±0.04 in male. Anteversion of the femur in female was higher than that in male. When the differences between the sexes were studied, the values measured of various regions were significantly larger in males than in females even in the group of the same height. Morphologically, the knee of males tended to have a larger width than that of females.
