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Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_3 | Pages 43 - 43
1 Apr 2018
Seitz A Lippacher S Natsha A Reichel H Ignatius A Dürselen L Dornacher D
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Introduction

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.

Material & Methods

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).


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_3 | Pages 44 - 44
1 Apr 2018
Warnecke D Balko J Schild NB Wang P Bieger R Ignatius A Mizaikoff B Reichel H Dürselen L
Full Access

Introduction

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.

Methods

Menisci of 24 TKR-patients (≈67.1 yrs.) were harvested and the degeneration of each region (pars anterior PA, pars intermedia PI, pars posterior PP) classified according to Pauli et al. For biomechanical characterisation, confined compression tests (20% strain; velocity: 3%h0/min, relaxation time: 1h) to determine equilibrium modulus (HA) and hydraulic permeability (k) and tensile tests (velocity: 5%l0/min) to determine the tensile modulus were performed. Therefore, cylindrical (Ø= 4.6mm, initial height h0≈ 2.3mm) and dumbbell-shaped (3.5mm × 1.4mm × 3.5mm) samples were punched out of each region and flattened to achieve parallel surfaces. Additionally, collagen and proteoglycan (PG) content were analysed by calculating the area-under-curve of their specific wavelength ranges (1293–1356cm−1 and 980–1120cm−1, respectively) using infrared (IR) spectroscopy. To identify differences regarding the meniscus regions or its degeneration, a statistically mixed model was used.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_II | Pages 160 - 161
1 May 2011
Majewski M Vögele S Seitz A Dürselen L
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Introduction: Previous work has shown that fixation of meniscus tears supports healing by preventing tears from gapping. However, an anterior cruciate ligament (ACL) insufficiency might increase the loads especially on the posterior horns of the meniscus. The aim of this study was to test an ACL tear results in wider gaps of longitudinal meniscal tears.

Methods: 3 cm longitudinal tears were artificially set in the posterior horn of the medial menisci in 10 human cadaver knee joints. The medial plateau of the joints was replaced by a translucent copy, under which an arthroscope was positioned to observe the gapping phenomenon of the meniscal tears. The knee specimens were flexed and extended in a motion and loading simulator allowing for all degrees of freedom. The maximum gap width occurring during a flexion-extension cycle was registered.

Results: Longitudinal meniscal tears showed significantly wider gaps after cutting the ACL (p< 0.01). However, refixation of the tears with suture anchors significantly reduced the gap width to much lower values (p< 0.01), still higher then with intact ACL.

Conclusion: The results indicate that medial meniscal tears in the posterior horn are exposed to higher loads in case of an ACL insufficiency. A missing ACL leads to increased anterior instability, which obviously results in wider tear gaps also in case of tear fixation with an implant. This confirms from a biomechanical point of view the clinical finding that meniscus repair is significantly enhanced when combined with ACL reconstruction.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 170 - 171
1 Mar 2008
Kessler O Banks S Mannel H Claes L Streicher R Dürselen L
Full Access

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.