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Bone & Joint Open
Vol. 2, Issue 7 | Pages 476 - 485
8 Jul 2021
Scheerlinck T De Winter E Sas A Kolk S Van Gompel G Vandemeulebroucke J

Aims

Hip arthroplasty does not always restore normal anatomy. This is due to inaccurate surgery or lack of stem sizes. We evaluated the aptitude of four total hip arthroplasty systems to restore an anatomical and medialized hip rotation centre.

Methods

Using 3D templating software in 49 CT scans of non-deformed femora, we virtually implanted: 1) small uncemented calcar-guided stems with two offset options (Optimys, Mathys), 2) uncemented straight stems with two offset options (Summit, DePuy Synthes), 3) cemented undersized stems (Exeter philosophy) with three offset options (CPT, ZimmerBiomet), and 4) cemented line-to-line stems (Kerboul philosophy) with proportional offsets (Centris, Mathys). We measured the distance between the templated and the anatomical and 5 mm medialized hip rotation centre.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_4 | Pages 48 - 48
1 Apr 2018
Kebbach M Grawe R Geier A Winter E Kluess D Woernle C Bader R
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Introduction

Despite decades of clinical research in artificial joints and underlying failure mechanisms, systematical and reproducible identification of reasons for complications in total knee replacements (TKR) remains difficult. Due to the complex dynamic interaction of implant system and biological situs, malfunction eventually leading to failure is multifactorial and remains not fully understood. The aim of present study was to evaluate different TKR designs and positions with regard to joint kinematics and stability under dynamic conditions by using a robot-based hardware-in-the-loop (HiL) setup.

Material & methods

An industrial 6-axis robot with 6-axis force-torque sensor mounted into its end-effector moved and loaded real, commercially available TKR (bicondylar, cruciate-retaining) that were in virtual interaction with a subject-specific computational multibody model representing the anatomical situs of the knee joint while performing passive seated deep knee flexion. The subject-specific musculoskeletal multibody model (MMB) included rigid bones of the lower right extremity. Bone and cartilage geometries were reconstructed from MRT/ CT data sets preserving anatomical landmarks and allowing for the calculation of inertial properties. M. quadriceps femoris was modeled as single passive tensile force elements. Knee ligaments were modelled as elastic spring elements with a nonlinear force-displacement characteristic. Providing the flexion angle, the robot moved and loaded the mounted femoral implant component with respect to the tibial component while being in continuous interaction with the MMB. Several influencing parameters like implant position (internal/external rotation, varus/valgus alignment) and design (fixed vs. mobile bearing, tibia-insert height) as well as ligament insufficiency and joint loading on joint kinematics and stability was systematically analysed.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_4 | Pages 79 - 79
1 Feb 2017
De Winter E Kolk S Van Gompel G Vandemeulebroucke J Scheerlinck T
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Introduction

Natural population variation in femoral morphology results in a large range of offsets, anteversion angles and lengths. During total hip arthroplasty, accurate restoration of hip biomechanics is essential to achieve good functional results. One option is to restore the anatomic hip rotation center. Alternatively, medializing the rotation center and compensating by increasing the femoral offset, reduces acetabular contact forces and increases the abductor lever arm. We investigated the ability of two cemented stem systems to restore hip biomechanics in an anatomic and medialized way. We compared an undersized “Exeter-type” of stem with three offset options and 18 sizes (CPT, Zimmer), to a line-to-line “Kerboul-type” of stem with proportional offset and 12 sizes (Centris, Mathys).

Methods

Thirty CT scans of whole femora were segmented and the hip rotation center, proximal femoral axis and femoral length were determined with Mimics and 3-matic (Materialise). Using scripting functionality in the software, CAD design files of both stems were automatically sized and aligned along the proximal femoral axis to restore an anatomical and a 5 mm medialized hip rotation center. Stem size and position could be fine-tuned manually. The maximum distances between the prosthetic (PRC), the anatomic (ARC) and the medialized hip rotation center (MRC) were calculated (Fig. 1). Variations in femoral offset (ΔFO), anteroposterior (ΔAP) and proximodistal distance (ΔPD) were analyzed. Finally, the number of cases where the hip rotation center could be restored within 5 mm was reported.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_III | Pages 353 - 353
1 Mar 2004
Eingartner C Heigele T Winter E Weise K
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Aims: A femoral stem design (BiCONTACT¨) for cementless þxation is being used without any technical modiþcation since 14 years. The long term results should be evaluated in this study. Methods: A consecutive series was continuously monitored in a prospective follow-up study. A survival analysis was performed, clinical results were rated according to the HARRIS Score. Results: There were 236 patients with 250 hips, mean age at time of implantation was 58.2 years. Indications for THR included osteoarthritis (62.4%), dysplasia (16.8%), trauma (8.4%) and femoral head necrosis (16.8%). Average time of follow-up evaluation was 11.8 years (range 10.6 Ð 13.7 years). At follow-up, 44 patients have died and three could not be located. Eight patients have been revised, 2 for infection, 1 for recurrent dislocation, 2 for component undersizing with rapid subsidence and 1 for aseptic loosening of a varus-malaligned stem. Two stems have been revised during acetabular revision. Survival estimate showed an overall survival of 96.6% after 14 years (conþdence limits: 98.4% (upper) and 92.8% (lower)). The average HARRIS hip score at time of follow-up was 78.3 points. Radiologically, tiny reactive lines (< 2mm) were present in the distal zones of the femoral shaft in 39%, but no radiolucencies could be found in the proximal anchoring zone. Conclusions: The long-term follow-up results with the BiCONTACT¨ femoral component are encouraging and are comparable to those of modern techniques of cementing in primary total hip arthroplasty.