The medial patellofemoral ligament (MPFL) is the main stabilizer of the patella and therefore mostly reconstructed in the surgical correction of patellofemoral dislocation. Various biomechanical and clinical studies have been conducted on MPFL reconstruction, while the patellofemoral contact pressure (PFCP) which is indicated as one of the predictors of retropatellar osteoarthritis was neglected. Therefore, the aim of this study was to investigate how different MPFL reconstruction approaches affect PFCP. After radiographic examination and preparation six human cadaveric knee joints (52.1 ± 8.4yrs) were placed in a 6-DOF knee simulator. Three flexion-extension cycles (0–90°) were applied, while the extensor muscles (175N) and an axial joint load (200N) were simulated. PFCP was measured in knee flexion of 0°, 30° and 90° using a calibrated pressure measurement system (K-Scan, Tekscan Inc., USA). The following MPFL conditions were examined: native (Pnat), anatomical reconstruction (Pa), proximal and distal patellar single-bundle reconstruction (Pp, Pd), proximal and ventral femoral reconstruction (Fp, Fv). The cohesive gracillis graft of each knee was used for MPFL reconstruction. Further, the effect of three different graft pre-tensioning levels (2N, 10N, 20N) on the PFCP were compared. Nonparametric statistical analysis was performed using SPSS (IBM Inc., USA).Introduction
Material & Methods
With processing age, meniscus degeneration occurs which is often associated with osteoarthritis. Existing data about the influence of degeneration on the biomechanical properties of the meniscus are still contradictory, or completely unknown regarding the hydraulic permeability. Thus, the aim of this study was to characterise the biomechanical properties and structural composition of the meniscal tissue depending on its degree of degeneration. Menisci of 24 TKR-patients (≈67.1 yrs.) were harvested and the degeneration of each region (Introduction
Methods
Kinematic evaluation of the knee after total joint arthroplasty plays an important role to analyze and understand the post operative outcome of the surgical procedure. The objective of the study was to quantify in vivo kinematics of two different knee designs (dual radius, single radius) by combining video fluoroscopy and helical axis of motion analysis. 3D position of the finite helical axis (FHA) of the displacement of the tibial component of the prosthesis relative the femoral component during a knee extension from 55° to 20° flexion underweight bearing conditions was computed. The motion data were extracted from in vivo fluoroscopy measurement. Angular deviations as angles between each FHA and the mediolateral axis of the femoral component of the prosthesis, and the localization deviation as the distance between each FHA and the center of the femoral component of the prosthesis were calculated. The median and the interquartile range (IQR) of the angular deviation and the localization deviation were computed. Non-parametric Wilcoxon test compared the values of the two designs. The angular and localization deviations of the dual radius design were bigger than of the single radius design. Median localization deviation, IQR Angle deviation, IQR localization deviation showed highly significant differences between the two designs (p<
0.01). Compared to the dual radius design the single radius design modified the knee kinematics in vivo. Since it is asingle axis design FHA is therefore concentrated near this unique single axis. On the contrary the dual radius design has two axes, and the FHA floated between these two axes.
