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Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_13 | Pages 40 - 40
1 Oct 2018
Faizan A Scholl L Zhang J Ries MD
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Introduction

Iliopsoas tendonitis after total hip arthroplasty (THA) can be a considerable cause of pain and patient dissatisfaction. The optimal cup position to avoid iliopsoas tendonitis has not been clearly established. Implant designs have also been developed with an anterior recess to avoid iliopsoas impingement. The purpose of this cadaveric study was to determine the effect of cup position and implant design on iliopsoas impingement.

Materials

Bilateral THA was performed on three fresh frozen cadavers using oversized (jumbo) offset head center revision acetabular cups with an anterior recess (60, 62 and 66 mm diameter) and tapered wedge primary stems through a posterior approach. The relatively large shell sizes were chosen to simulate THA revision cases. At least one fixation screw was used with each shell. A 2mm diameter flexible stainless steel cable was inserted into the psoas tendon sheath between the muscle and the surrounding membrane to identify the location of the psoas muscle radiographically. Following the procedure, CT scans were performed on each cadaver. The CT images were imported in an imaging software for further analysis. The acetabular shells, cables as well as pelvis were segmented to create separate solid models of each. To compare the offset head center shell to a conventional hemispherical shell in the same orientation, the offset head center shell was virtually replaced with an equivalent diameter hemispherical shell by overlaying the outer shell surfaces of both designs and keeping the faces of shells parallel. enabled us to assess the relationship between the conventional shells and the cable. The shortest distance between each shell and cable was measured. To determine the influence of cup inclination and anteversion on psoas impingement, we virtually varied the inclination (30°/40°/50°) and anteversion (10°/20°/30°) angles for both shell designs.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_IV | Pages 517 - 517
1 Nov 2011
Brilhault J Carpenter RD Majumdar S Ries MD
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Purpose of the study: Kinetic studies of total knee arthroplasty (TKA) in vivo have provided divergent data but have agreed on one point: knee kinetics is abnormal after TKA. Restitution of a normal kinetics is thus the goal to reach to improve functional outcome after TKA. The Journey® TKA is specifically designed to induce automatic medial rotation of the tibia during flexion. This would align the extensor system during flexion and would reduce mediolateral shear forces applied to the patellofemoral joint. Fluoroscopic dynamic studies have been conducted in vivo to confirm the reality of the femorotibal kinematics but to date there has been no study of the patellofemoral kinematics. Magnetic resonance imaging (MRI) is the gold standard for exploring the knee. The important artefacts caused by metal implants made of chromium-cobalt alloys make it difficult or impossible to interpret the images in patients with TKA. Oxinium® implants are weakly ferromagnetic, allowing the development of a specific MRI sequence which can be used to explore a TKA.

Material and methods: We used this technique in vivo for a 3D exploration of the patellofemoral kinematics of six Jouney® TKA in comparison with five Genesis II® TKA with preservation of the posterior cruciate ligament and with 13 normal knees. We analysed: patellofemoral surface area of contact, patellar translation and shift during weight-bearing flexion.

Results: The results showed that the patellofemoral kinematics of the Journey® TKA are close to that observed in normal knees and that the patellofemoral pressures of the posterior cruciate ligament TKA are significantly higher than with the Journey® TKA.

Discussion: These findings confirm our initial hypothesis and allow hop for better functional outcome and reduced wear of the patellar implant with the Journey® TKA.


The Journal of Bone & Joint Surgery British Volume
Vol. 92-B, Issue 9 | Pages 1306 - 1311
1 Sep 2010
Patten EW Atwood SA Van Citters DW Jewett BA Pruitt LA Ries MD

Retrieval studies of total hip replacements with highly cross-linked ultra-high-molecular-weight polyethylene liners have shown much less surface damage than with conventional ultra-high-molecular-weight polyethylene liners. A recent revision hip replacement for recurrent dislocation undertaken after only five months revealed a highly cross-linked polyethylene liner with a large area of visible delamination. In order to determine the cause of this unusual surface damage, we analysed the bearing surfaces of the cobalt-chromium femoral head and the acetabular liner with scanning electron microscopy, energy dispersive x-ray spectroscopy and optical profilometry. We concluded that the cobalt-chromium modular femoral head had scraped against the titanium acetabular shell during the course of the dislocations and had not only roughened the surface of the femoral head but also transferred deposits of titanium onto it. The largest deposits were 1.6 μm to 4.3 μm proud of the surrounding surface and could lead to increased stresses in the acetabular liner and therefore cause accelerated wear and damage.

This case illustrates that dislocations can leave titanium deposits on cobalt-chromium femoral heads and that highly cross-linked ultra-high-molecular-weight polyethylene remains susceptible to surface damage.