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,
195 Reads
  • 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.
    Sensors 08/2014; 14(8):15009-21. DOI:10.3390/s140815009 · 2.25 Impact Factor
  • 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.
    Revue de Chirurgie Orthopédique et Traumatologique 06/2014; 100(4):295–302. DOI:10.1016/j.rcot.2014.01.016
  • Source
    • "With these systems, bone cut guides are positioned, with a variable degree of accuracy [1] [2] [3] [4]. Patient-specific guides may hold promise for the future but have not been proven sufficiently accurate to warrant their use as a reference procedure [5] [6] [7] [8] [9]. Computerassisted orthopaedic surgery was introduced over 10 years ago and has been found to improve implant position accuracy in the coronal plane compared to conventional instrumentation [10] [11] [12] [13] [14] [15] [16]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background For over a decade, computer-assisted orthopaedic surgery for total knee arthroplasty has been accepted as ensuring accurate implant alignment in the coronal plane. Hypothesis We hypothesised that lack of accuracy in skeletal landmark identification during the acquisition phase and/or measurement variability of the infrared optical system may limit the validity of the numerical information used to guide the surgical procedure. Methods We built a geometric model of a navigation system, with no preoperative image acquisition, to simulate the stages of the acquisition process. Random positions of each optical reflector center and anatomic acquisition point were generated within a sphere of predefined diameter. Based on the virtual geometric model and navigation process, we obtained 30,000 simulations using the Monte Carlo statistical method then computed the variability of the anatomic reference frames used to guide the bone cuts. Rotational variability (α, β, γ) of the femoral and tibial landmarks reflected implant positioning errors in flexion-extension, valgus-varus, and rotation, respectively. Results Taking into account the uncertainties pertaining to the 3D infrared optical measurement system and to anatomic point acquisition, the femoral and tibial landmarks exhibited maximal alpha (flexion-extension), beta (valgus-varus), and gamma (axial rotation) errors of 1.65° (0.9°); 1.51° (0,98°), and 2.37° (3.84°), respectively. Variability of the infrared optical measurement system had no significant influence on femoro-tibial alignment angles. Conclusion The results of a Monte Carlo simulation indicate a certain level of vulnerability of navigation systems for guiding position in rotation, contrasting with robustness for guiding sagittal and coronal alignments. Level of evidence Level IV.
    Orthopaedics & Traumatology Surgery & Research 06/2014; 100:395-402. DOI:10.1016/j.otsr.2013.12.029 · 1.26 Impact Factor
Show more