Do Patient-specific Guides Improve Coronal Alignment in Total Knee Arthroplasty?

Department of Orthopaedic Surgery, Washington University School of Medicine, One Barnes-Jewish Hospital Plaza, 11300 West Pavilion, Campus Box 8233, St Louis, MO 63110, USA.
Clinical Orthopaedics and Related Research (Impact Factor: 2.77). 12/2011; 470(3):895-902. DOI: 10.1007/s11999-011-2222-2
Source: PubMed


Coronal alignment may impact clinical outcome and survivorship in TKA. Patient-specific instrumentation has been developed to restore mechanical or kinematic axis and potentially reduce component malpositioning. Although it is clear these instruments add cost, it is unclear whether they improve alignment.
We determined whether the mean coronal alignment after TKA performed with conventional versus patient-specific instrumentation better restored the mechanical and kinematic axes and whether there were more outliers with one of the two methods.
We retrospectively evaluated 150 primary TKAs performed for osteoarthritis: Group 1 (n = 50) conventional instrumentation; Group 2 (n = 50) patient-specific instrumentation restoring the mechanical axis; Group 3 (n = 50) patient-specific instrumentation restoring the kinematic axis, and measured femorotibial angle, hip-knee-ankle angle, and the zone of the mechanical axis from scout CT images taken 0 to 6 weeks postoperatively.
The mean femorotibial angle differed between the groups: Group 1 had the greatest varus mean alignment and most varus outliers. The mean hip-knee angle was similar between Groups 1 and 2, with Group 3 having greater valgus mean alignment and the most valgus outliers. For the zone of the mechanical axis, Groups 1 and 2 had similar percentages of outliers (40% versus 32%), whereas Group 3 had a greater number of outliers (64%) that were valgus.
TKAs with patient-specific instrumentation restoring the mechanical axis had a similar number of outliers as conventional instrumentation with both groups having more varus outliers than TKAs with patient-specific instrumentation restoring kinematic axis, which had more valgus outliers. Therefore, additional studies are needed to determine whether patient-specific instrumentation improves clinical function or patient satisfaction and whether their routine use can be justified in primary TKA.
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Download full-text


Available from: Stephen Miller Howell
  • Source
    • "The geometric fit of PSSGs is different for each patient (i.e., patient specific) and achieved either by three-dimensional printing [5] [6] or by setting a configurable PSSG. Printed PSSGs are already used in clinical practice today [1] [2] [3] [4] whereas configurable PSSGs are still in a more conceptual phase [7]. The downside of printed PSSGs is that they can only be used one time for one patient due to the varying bone geometry. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In joint replacement surgery, patient specific surgical guides (PSSGs) are used for accurate alignment of implant components. PSSGs are designed preoperatively to have a geometric fit with the patient's bone such that the incorporated guidance for drilling and cutting is instantly aligned. The surgeon keeps the PSSG in position with a pushing force, and it is essential that this position is maintained while drilling or cutting. Hence, the influence of the location and direction of the pushing force should be minimal. The extent that the pushing force may vary is what we refer to as docking robustness. In this article, we present a docking robustness framework comprising the following quantitative measures and graphical tool. Contact efficiency gc is used for the quantification of the selected bone-guide contact. Guide efficiency gg is used for the quantification of the whole guide including an application surface whereon the surgeon can push. Robustness maps are used to find a robust location for the application surface based on gradient colors. Robustness R is a measure indicating what angular deviation is minimally allowed at the worst point on the application surface. The robustness framework is utilized in an optimization of PSSG dimensions for the distal femur. This optimization shows that 12 contacts already result in a relatively high contact efficiency of 0.74±0.02 (where the maximum of 1.00 is obtained when the guide is designed for full bone-guide contact). Six contacts seem to be insufficient as the obtained contact efficiency is only 0.18±0.02.
    Full-text · Article · Jun 2015 · Journal of Mechanical Design
  • Source
    • "The incorporation of the system in the polymer insert is to be performed during manufacturing and should not modify the external surface or mechanical behavior of the insert which need to be validated through fatigue testing in the simulator. Patient-specific implants are becoming reality [24–27] and layer-by-layer rapid prototyping method such as laser sintering [28] could allow incorporating the sensors in a custom made implant. Compression molding is common for UHMWPE insert manufacturing and over molding is an option for module incorporation in the insert. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Total knee arthroplasty is a widely performed surgical technique. Soft tissue force balancing during the operation relies strongly on the experience of the surgeon in equilibrating tension in the collateral ligaments. Little information on the forces in the implanted prosthesis is available during surgery and post-operative treatment. This paper presents the design, fabrication and testing of an instrumented insert performing force measurements in a knee prosthesis. The insert contains a closed structure composed of printed circuit boards and incorporates a microfabricated polyimide thin-film piezoresistive strain sensor for each condylar compartment. The sensor is tested in a mechanical knee simulator that mimics in-vivo conditions. For characterization purposes, static and dynamic load patterns are applied to the instrumented insert. Results show that the sensors are able to measure forces up to 1.5 times body weight with a sensitivity fitting the requirements for the proposed use. Dynamic testing of the insert shows a good tracking of slow and fast changing forces in the knee prosthesis by the sensors.
    Full-text · Article · Aug 2014 · Sensors
  • Source
    • "Depuis plus de 30 ans, les ancillaires conventionnels pour la mise en place des prothèses totales de genou (PTG) permettent, avec l'utilisation des guides intra-ou extra-médullaires, un positionnement plus ou moins précis des guides de coupes osseuses [1] [2] [3] [4]. Malgré un avenir prometteur, les ancillaires personnalisés n'ont pas encore suffisamment fait la preuve de leur précision pour devenir une procédure de référence [5] [6] [7] [8] [9]. Avec un recul de plus de 10 ans, Fig. 1. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Introduction Dans l’arthroplastie totale de genou, la chirurgie assistée par ordinateur se définit depuis plus de 10 ans comme l’outil de précision pour aligner les implants dans le plan frontal. Notre hypothèse a été qu’une imprécision sur les repères squelettiques pendant la phase d’acquisition et/ou une variabilité de mesure du système optique infrarouge pouvaient remettre en question la pertinence des informations numériques qui guident le geste opératoire. Matériel et méthode Une modélisation géométrique d’un système de navigation, sans acquisition d’imagerie préopératoire, a permis de simuler les étapes du processus d’acquisition. Le centre de chaque réflecteur optique et les points anatomiques d’acquisition ont été bruités aléatoirement de manière multidirectionnelle dans une sphère d’incertitude dont le diamètre a été préalablement fixé. Trente mille simulations réalisées selon la méthode statistique de Monte-Carlo ont permis à partir du modèle géométrique virtuel et du processus de navigation de calculer la variabilité des référentiels anatomiques qui guident les coupes osseuses. Les variabilités en rotation (α, β et γ) des repères squelettiques fémoral et tibial ont traduit respectivement les erreurs de positionnement des implants en flexion–extension, valgus–varus et rotation. Résultats En considérant les incertitudes du système de mesure optique infrarouge 3D et de l’acquisition des points anatomiques, les repères fémoral et tibial ont montré une erreur maximale alpha (flexion–extension), bêta (valgus–varus) et gamma (rotation axiale) respectivement de 1,65° (0,9°) ; 1,51° (0,98°) et 2,37° (3,84°). La variabilité du système de mesure optique infrarouge n’a pas eu d’influence significative sur les angles d’alignement fémoro-tibiaux. Conclusion Sur la base d’une simulation de Monte-Carlo, les systèmes de navigation démontrent une certaine vulnérabilité pour le guidage en rotation mais une robustesse pour le contrôle de l’alignement frontal et coronal. Niveau de preuve de l’étude IV.
    Full-text · Article · Jun 2014 · Revue de Chirurgie Orthopédique et Traumatologique
Show more