Elsevier

European Journal of Radiology

Volume 84, Issue 12, December 2015, Pages 2564-2570
European Journal of Radiology

Extremity cone-beam CT for evaluation of medial tibiofemoral osteoarthritis: Initial experience in imaging of the weight-bearing and non-weight-bearing knee

https://doi.org/10.1016/j.ejrad.2015.09.003Get rights and content

Highlights

  • The medial tibiofemoral joint space width (JSW) and meniscal extrusion (ME) exhibit measurable change in patients with OA, imaged using a dedicated cone-beam CT (CBCT) scanner in weight bearing (WB) and non-weight bearing (NWB) configurations.

  • There is weak association between the ME measured in a NWB scan and the change in ME exhibited between WB and NWB scans. This suggests that ME measurements obtained in conventional NWB studies (such as MDCT and MRI acquired with the patient in decubitus) are limited in the ability to predict the extent of ME in the WB knee.

  • A dedicated CBCT extremity scanner capable of imaging the WB knee could provide increased functional information relevant to OA compared to plain radiography or NWB imaging.

Abstract

Purpose

To investigate differences in joint space width (JSW) and meniscal extrusion (ME) between non-weight bearing (NWB) and weight bearing (WB) examinations of knee joints with medial compartment osteoarthritis (OA) using a cone-beam CT (CBCT) extremity imaging system.

Materials and methods

In this IRB approved prospective study, informed consent was obtained for 17 patients symptomatic for OA (11 F,6 M; 31–78 years, mean 56 years) and 18 asymptomatic controls (0 F,18 M; 29–48 years, mean 38.5 years) enrolled for CBCT exams in NWB and WB positions. Three independent observers measured medial tibiofemoral JSW and ME. Measurements were compared between NWB and WB images using paired Wilcoxon signed-rank sum test.

Results

OA subjects exhibited a statistically significant reduction in JSW between NWB and WB scans (average JSWNWBOA = 2.1 mm and JSWWBOA = 1.5 mm, p = 0.016) and increase in ME (average MENWBOA = 6.9 mm and MEWBOA = 8.2 mm, p = 0.018)). For non-OA subjects, the change in JSW and ME between NWB and WB exams was reduced (average JSWNWBnonOA = 3.7 mm and JSWWBnonOA = 3.4 mm; average MENWBnonOA = 2.6 mm and MEWBnonOA = 2.7 mm) and was not statistically significant. Inter-observer agreement was evaluated using Bland–Altman limits of agreement, with good agreement for all measurements (correlation coefficient 0.89–0.98).

Conclusion

The ability to conduct NWB and WB exams in CBCT with a dose profile that is favorable in comparison to multidetector CT (MDCT) and with image quality sufficient for morphological analysis of joint space narrowing and meniscal extrusion could provide a valuable tool for OA diagnosis and treatment assessment.

Introduction

Osteoarthritis (OA) of the knee is the most common chronic joint disease, with a rising prevalence of about 15% [1]. Currently, weight bearing plain radiography is the most common imaging modality to monitor the severity and progression of knee OA by demonstrating the narrowing of joint space width (JSW). Accurate and reproducible JSW evaluation using plain radiography requires careful positioning of both the X-ray system and the patient [2] and does not provide information on soft tissue structures or 3D orientation of osseous structures. Multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) provide detailed assessment of cartilage disease and other structural damage in patients with knee OA, such as meniscal or ligamentous injuries [3], which can contribute to joint space narrowing and progression of disease. For example, in addition to cartilage damage, the presence of meniscal extrusion (ME) can contribute to narrowing of knee JSW [4], [5] and is a strong predictor of further cartilage loss in patients with knee OA [6].

Cone-beam computed tomography (CBCT) uses a large-area detector (>1000 detector rows covering ∼30 × 30 cm2) and a pyramid-shaped X-ray beam to acquire a volumetric image in a single rotation. A CBCT system for extremity imaging has been recently developed [7] and translated to a clinical prototype with the ability to acquire both weight bearing (WB) and non-weight bearing (NWB) exams of the lower extremities. Feasibility of CBCT scanning in either configuration was recently confirmed [8], and initial results demonstrated reduced radiation exposure, soft tissue image quality sufficient for visualization of ligaments, cartilage, and menisci, and bone visualization meeting or exceeding the performance of high-resolution MDCT [9], [10]. Other work also demonstrates the ability to acquire images of the lower extremities in a physiologic WB setup, which may improve diagnosis and management of certain pathologies in WB joints, like the ankle and the knee [11].

The purpose of the current study was to test the hypothesis that there is a significant difference in measurements of JSW and ME between NWB and WB examinations of the knee joints with known medial compartment OA using a dedicated CBCT extremity system.

Section snippets

Patient population

Institutional review board approval was obtained for this prospective study. Informed consent was obtained from 17 symptomatic patients (11 females, 6 males; age range: 31–78 years, mean age: 56 years) with diagnosis of OA in their medial tibiofemoral compartment, independent of the CBCT studies reported below, as per the clinical symptoms and findings in plain radiographs. The severity of OA was classified in plain radiographs using a previously described grading classification system [3]

Result

A summary of measurements for JSW and ME is presented in Table 1, Table 2. Disease severity in the OA subjects was graded using radiographs for each subject acquired as part of the standard of care. Of the 17 symptomatic subjects with OA, 3 (17.6%) were severe, 12 (70.6%) were moderate, and 2 (11.8%) were mild in the severity of disease in the medial compartment according to the previously described grading system based on plain radiographs [3]. Additionally, OA severity was graded according to

Discussion

In this study, we demonstrated that the medial tibiofemoral JSW and ME change significantly in patients with OA between a WB and NWB setup using a CBCT extremity scanner. CBCT images provide image data with isotropic spatial resolution, which can be reconstructed in any plane in support of accurate measurements of JSW, as opposed to plain radiographs, where JSW measurements can be highly dependent on the positioning of the patient and X-ray beam [16]. Plain standing radiographs require precise

Conflict of interest

None.

Funding

This project was funded by Carestream Health Inc. and NIH Grant No.R21-AR-062293.

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