Most of the load onto the tibiofemoral joint is transmitted through the menisci. The load distribution and transmission functions are pivotal roles of the meniscus for cartilage protection and joint preservation.
Radial tear of the meniscus disrupts the integrity of the circumferential collagen fibers and has a detrimental effect on the load distribution and transmission functions. The lateral meniscus (LM) complete radial tear drastically deteriorated the biomechanical function.
In the clinical settings, radial tears of the meniscus can be observed at various locations; however, the effect of the tear site on the deterioration of the load distribution and transmission functions remains unclear. The meniscus complete radial tear at different tear sites may cause different impacts on the load distribution and transmission functions. Understanding the association between the radial tear location of the meniscus and the degradation of the biomechanical function must be helpful to estimate the adverse effect on the tibiofemoral joint or decide the appropriate treatment strategies in clinical practice.
This study aimed to compare the effect of the LM complete radial tear at different tear sites on the loaddistribution and transmission functions using a porcine knee model.
Thirty porcine knees were used in this study. The study utilized a 6-degree of freedom (DOF) robotic system which consists of a velocity-control 6-DOF (3 translational-axis and 3 rotational-axis) manipulator with a universal force/moment sensor and a control computer linked with a high-speed motion network. This system can manipulate the physiological 3D motion of the knee joint by calculating and applying the 3D path to eliminate the force/moment on the knee joint except for the operator’s intended direction.
A thin electronic pressure film sensor with a thickness of 0.2 mm was utilized to measure the tibiofemoral contact mechanics (pressure and area) in real time (sampling frequency:100 Hz). The pressure film sensor was inserted between the LM and the tibial articular surface through the capsular incision.
First, an axial compressive load of 300 N was applied to the intact knees at 15°, 30°, 60°, 90°, and 120° of flexion. The tibiofemoral contact pressure and area in the lateral compartment were recorded via the pressure film sensor, while the 3D path of the tibia relative to the femur and the force/moment acting on the knee joint (Fi) were recorded.
Next, the porcine knees were divided into three groups of ten knees each, and the LM complete radial tears were created at the middle portion (group M), the posterior portion (group P), or the posterior root (group R). Subsequently, the same loading and recording procedures were followed by the knees in all the three groups.
Finally, the pressure film sensor was extracted from all the knees, and the LM was totally removed. Then, the previously recorded 3D paths in the intact knees and the knees with the LM complete radial tear were sequentially reproduced on the LM-removed knees recording the force/moment on the knee joint. This process was conducted to calculate the in situ force carried by the LM
The peak contact pressure and the contact area in the lateral compartment were compared among the intact knees, group M, group P, and group R. The in situ force carried by the LM was calculated under the four meniscal conditions (intact, group M, group P, and group R) as the difference of the acquired force/momentvector between before and after the removal of LM based on the principle of superposition. The in situ force carried by the LM under 300 N of axial compressive load was also compared among the four groups.
The peak contact pressure was significantly higher and the contact area was significantly lower after creating the LM complete radial tear as compared to that in the intact state at all the flexion angles (p < 0.01).
At 120° of flexion, group R represented the highest peak contact pressure and the lowest contact area, followed by group P and group M (p < 0.05). In the intact knees, the tibiofemoral contact pressure wasconstantly well distributed in the lateral compartment. On the other hand, the contact pressure was concentrated at the central area in the knees after creating the LM complete radial tear.
The in situ force carried by the LM was significantly decreased by 40–88% after creating the LM complete radial tear as compared to that in the intact state at all the flexion angles (p < 0.01).
The detrimental effect of the LM complete radial tear on the load distribution and transmission functions wasgreatest in the posterior root tear, followed by the posterior portion tear and the middle portion tear in the deep-flexed position. As complete radial tears of the meniscus, especially at the posterior root, have a harmful impact on the load distribution and transmission functions, these tears should be repaired to restore thebiomechanical function and prevent the progression of knee osteoarthritis.
Ohori T et al. (2021) Different effects of the lateral meniscus complete radial tear on the load distribution and transmission functions depending on the tear site. Knee Surgery, Sports Traumatology, Arthroscopy 29, 342–351.
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