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Benefit of a Preoperative MRI Including T2 Mapping and Semiquantitative Analysis for Varus Gonarthritis
02 March 2017 (online)
Introduction: This article discusses the preliminary results of a prospective study that compared the analysis of degenerative changes in the tibiofemoral compartment between magnetic resonance imaging (MRI) and X-ray.
Materials and Methods: Patients with a varus malalignment and consecutive knee osteoarthritis in the medial compartment received a MRI and X-ray in two views before total knee arthroplasty. The gonarthritis was graded according to the Kellgren and Lawrence classification. Knee alignment was quantified by the mechanical axis on a full-length leg X-ray. During the MRI the T2 relaxation times were assessed by the Carr-Purcell-Meiboom-Gill sequence using eight echo times (16–96 ms) and morphologic changes in proton-density and T2-weighted images. A semiquantitative analysis for signal and morphology of the cartilage from the Whole-Organ Magnetic Resonance Imaging Score (WORMS) was performed. The segmentation included the lateral tibia (LT) and lateral fibula (LF), each with a superficial (s) and deep layer (d). The T2 relaxation times were calculated using the IntelliSpace cartilage assessment tool (Philips, Amsterdam, Netherlands).
Results: All patients showed a high-grade varus malalignment with a 39.9 ± 10.6-mm medial deviation of the Mikulicz line. Each of them had a significant medial gonarthritis (grade 3–4) and none in the lateral compartment (grade 0–1). The assessment of the cartilage with WORMS resulted in 13.9 ± 1.8 points out of 30. The relaxation times were prolonged in the lateral compartment compared with the recent literature: LFs = 54.5 ± 5.1, LFd = 46.6 ± 3.6, LTs = 42.7 ± 6.0, and LTd=36.0 ± 5.5.
Conclusion: Adding an MRI examination in varus gonarthritis offers additional and clinically valuable information regarding early potential degenerative changes in the lateral compartment that would be underestimated by the single use of X-ray.