Limits...
Kinematic analysis of a posterior-stabilized knee prosthesis.

Zhao ZX, Wen L, Qu TB, Hou LL, Xiang D, Bin J - Chin. Med. J. (2015)

Bottom Line: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments.The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopedics, Beijing Chao Yang Hospital, Capital Medical University, Beijing 100020, China.

ABSTRACT

Background: The goal of total knee arthroplasty (TKA) is to restore knee kinematics. Knee prosthesis design plays a very important role in successful restoration. Here, kinematics models of normal and prosthetic knees were created and validated using previously published data.

Methods: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. The data from the three-dimensional models of the normal knee joint and a posterior-stabilized (PS) knee prosthesis were imported into finite element analysis software to create the final kinematic model of the TKA prosthesis, which was then validated by comparison with a previous study. The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.

Results: Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses. The PS knee prosthesis underwent an abnormal forward displacement compared with the normal knee and has insufficient, or insufficiently aggressive, "rollback" compared with the lateral femur of the normal knee. In addition, a certain degree of reverse rotation occurs during flexion of the PS knee prosthesis.

Conclusions: There were still several differences between the kinematics of the PS knee prosthesis and a normal knee, suggesting room for improving the design of the PS knee prosthesis. The abnormal kinematics during early flexion shows that the design of the articular surface played a vital role in improving the kinematics of the PS knee prosthesis.

Show MeSH

Related in: MedlinePlus

(a) The kinematics model of normal knee. (b) The kinematics model total knee arthroplasty prosthesis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4837841&req=5

Figure 2: (a) The kinematics model of normal knee. (b) The kinematics model total knee arthroplasty prosthesis.

Mentions: The data from the 3D model of the normal knee joint were imported into MD Adams R3 software (MSC Software, Newport Beach, CA, USA), and the properties of different bone structures were assigned. Next, the simulation unit was established to simulate the forces of the ligaments and muscle strength based on the settings described above. Because the MD Adams software could not simulate deformation, we designed the study to better simulate the real physiology. First, the medial and lateral menisci were divided into anterior and posterior parts based on the location of the centroid. These two parts of the menisci were then connected to the spring unit, and a damping coefficient of 0.5 N s/mm[19] was applied to the spring unit to ensure that the distal femur cartilage was in contact with the meniscus at the same time. The rotational axis during flexion of the femur (femur flexion center [FFC] axis) was based on the medial and lateral FFC. The rules of the coordinate frame were defined as the FFC axis as the X-axis, the mechanical axis of the lower limb as the Z-axis, and the Y-axis was identified using the “right-hand rule.” Together, the X, Y, and Z axes constitute a cartesian coordinate system in a certain space. As flexion increased, the displacements of the medial and lateral femur (forward and backward) were identical to the displacements of the medial and lateral femur along the Y-axis. The internal rotation of the tibia was reflected by the rotation around the Z-axis. Thus, the model of normal knee joint kinematics was established [Figure 2a]. With this model, the knee could be simulated within a ROM of 0–135° of flexion. The output of the model consisted of the displacements of the medial and lateral femur and the internal rotation angle of the tibia.


Kinematic analysis of a posterior-stabilized knee prosthesis.

Zhao ZX, Wen L, Qu TB, Hou LL, Xiang D, Bin J - Chin. Med. J. (2015)

(a) The kinematics model of normal knee. (b) The kinematics model total knee arthroplasty prosthesis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837841&req=5

Figure 2: (a) The kinematics model of normal knee. (b) The kinematics model total knee arthroplasty prosthesis.
Mentions: The data from the 3D model of the normal knee joint were imported into MD Adams R3 software (MSC Software, Newport Beach, CA, USA), and the properties of different bone structures were assigned. Next, the simulation unit was established to simulate the forces of the ligaments and muscle strength based on the settings described above. Because the MD Adams software could not simulate deformation, we designed the study to better simulate the real physiology. First, the medial and lateral menisci were divided into anterior and posterior parts based on the location of the centroid. These two parts of the menisci were then connected to the spring unit, and a damping coefficient of 0.5 N s/mm[19] was applied to the spring unit to ensure that the distal femur cartilage was in contact with the meniscus at the same time. The rotational axis during flexion of the femur (femur flexion center [FFC] axis) was based on the medial and lateral FFC. The rules of the coordinate frame were defined as the FFC axis as the X-axis, the mechanical axis of the lower limb as the Z-axis, and the Y-axis was identified using the “right-hand rule.” Together, the X, Y, and Z axes constitute a cartesian coordinate system in a certain space. As flexion increased, the displacements of the medial and lateral femur (forward and backward) were identical to the displacements of the medial and lateral femur along the Y-axis. The internal rotation of the tibia was reflected by the rotation around the Z-axis. Thus, the model of normal knee joint kinematics was established [Figure 2a]. With this model, the knee could be simulated within a ROM of 0–135° of flexion. The output of the model consisted of the displacements of the medial and lateral femur and the internal rotation angle of the tibia.

Bottom Line: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments.The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopedics, Beijing Chao Yang Hospital, Capital Medical University, Beijing 100020, China.

ABSTRACT

Background: The goal of total knee arthroplasty (TKA) is to restore knee kinematics. Knee prosthesis design plays a very important role in successful restoration. Here, kinematics models of normal and prosthetic knees were created and validated using previously published data.

Methods: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. The data from the three-dimensional models of the normal knee joint and a posterior-stabilized (PS) knee prosthesis were imported into finite element analysis software to create the final kinematic model of the TKA prosthesis, which was then validated by comparison with a previous study. The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.

Results: Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses. The PS knee prosthesis underwent an abnormal forward displacement compared with the normal knee and has insufficient, or insufficiently aggressive, "rollback" compared with the lateral femur of the normal knee. In addition, a certain degree of reverse rotation occurs during flexion of the PS knee prosthesis.

Conclusions: There were still several differences between the kinematics of the PS knee prosthesis and a normal knee, suggesting room for improving the design of the PS knee prosthesis. The abnormal kinematics during early flexion shows that the design of the articular surface played a vital role in improving the kinematics of the PS knee prosthesis.

Show MeSH
Related in: MedlinePlus