Darrick Lo

Reliability of Navigated Lower Limb Alignment in High Tibial Osteotomies

Background Navigation allows for determination of the mechanical axis of the lower extremity during high tibial osteotomy (HTO) procedures. The objectives of this study were to (1) evaluate the reliability of noninvasive registration with an image-free navigation system for HTO and (2) determine the accuracy of the navigation system to monitor changes in lower limb alignment as compared with alignment measured with a novel 3-dimensional computed tomography method. Hypothesis Navigated limb alignment demonstrates good reliability and accuracy in all 3 planes. Study Design Descriptive laboratory study. Methods Thirteen cadaver legs were used to examine the intra- and interobserver registration reliability of 3 observers. Initial coronal, sagittal, and axial alignment was measured on 6 legs, 3 times each, at intervals >36 hours. Navigated HTOs were then performed on all 13 legs, pre- and postoperative alignment was recorded, and data were compared with equivalent measures obtained by 3-dimensional computed tomography. Reliability and accuracy data were both analyzed using intraclass correlation coefficients with the following established thresholds: good, >0.75; fair, 0.4 to 0.75; and poor, <0.4. Results Intraclass correlation coefficients for intraobserver reliability were categorized as follows: varus-valgus, good; flexion-extension fair; and femoral-tibial rotation, poor. For interobserver reliability, results were varus-valgus, fair; flexion-extension, fair; and femoral-tibial rotation, poor. Intraclass correlation coefficients for navigation accuracy were varus-valgus, good; tibial slope, good; and tibial torsion, poor. Maximum differences in navigation-computed tomography measurements were Δ varus-valgus angle, 4.5°; Δ tibial slope, 8.8°; and Δ tibial torsion, 16.5°. Conclusion and Clinical Relevance Navigation may be reliable and clinically useful for dynamic monitoring of coronal leg alignment but has limits in determination of sagittal and axial plane alignment.

Ausblick: Biomechanik des Ellenbogenkunstgelenks

Die Entwicklung von Kunstgelenken fur Hufte und Knie hat einen kontinuierlichen Verbesserungsprozess durchlaufen. Der Entwicklungsstand von Ellenbogenprothesen weist im Vergleich dazu jedoch trotz der erheblichen mechanischen Belastung auf solchen Gelenken einen deutlichen Ruckstand auf. Die Ergebnisse nach Ellenbogenarthroplastik (TEA) sind im Vergleich zu den Resultaten nach Huft- und Kniearthroplastik weniger dauerhaft und schlechter voraussehbar mit Versagerquoten, die 30 % nach 5 Jahren erreichen konnen (Skytta et al. 2009). Alternative Methoden zur Behandlung der Ellenbogenarthrose/-arthritis und komplexen Traumafolgen sind sogar noch weniger erfolgreich. Die Interpositionsarthroplastik des Ellenbogens beispielsweise ist selten erfolgreich; nur ein Viertel der Patienten weist nach 6 Jahren ein ausgezeichnetes Resultat auf (Larson und Morrey 2008). Unglucklicherweise bedeutet eine fehlgeschlagene Ellenbogenarthroplastik meist eine Katastrophe fur den betroffenen Patienten mit schwerer Beeintrachtigung der Funktion der ganzen oberen Extremitat.