Sodium fluoride PET/CT with arthrography for cartilage evaluation of the knee

Abstract

The presence of healthy cartilage in the knee joint, featuring smooth articular surfaces, is crucial for normal physiological knee function. However, noninvasive in-vivo assessment of cartilage quality in the knee remains challenging and has not been thoroughly investigated. We aimed to illustrate two clinical cases, a 62-year-old male and a 67-year-old male, presented to the orthopaedic outpatient clinic with severe knee complaints. The novel combination of sodium fluoride-18 positron emission tomography/computed tomography and intra-articular injection of a contrast agent (Na[¹⁸F]F-PET/CT arthrography) was performed to evaluate cartilage defects of the knee as part of a prospective patient study. The lesion size observed on the Na[¹⁸F]F-PET was substantially larger compared to the findings on CT. This might indicate that Na[¹⁸F]F-PET/CT arthrography was able to image osseous and chondral pathological changes in an early stage and in a single procedure. Na[¹⁸F]F-PET/CT arthrography is a promising imaging technique and might extend the diagnostic potential of nuclear and radiological imaging in the evaluation of cartilage defects.

Keywords: Arthrography; Cartilage degeneration; Knee; Na[18F]F-PET/CT; [18F]-sodium fluoride.

Fig. 1

Sagittal images of a sodium fluoride-18 PET/CT (Na[¹⁸F]F-PET/CT) scan with intra-articular contrast (A, PET; B, CT; C PET/CT fusion) with an intense Na¹⁸F focus (16 × 15 mm) with Grade 4 cartilage defect, mild sclerosis, and a small subchondral cyst (arrow). Small spike-like indentations filled with contrast, consistent with degenerative cartilage, are present elsewhere in the retropatellar cartilage.

Fig. 2

Coronal images of a sodium fluoride-18 PET/CT (Na[¹⁸F]F-PET/CT) scan with intra-articular contrast (A, PET; B, CT; C PET/CT fusion) with extensive subchondral cyst formation in the medial femoral condyle, accompanied by an associated cartilage defect (Grade 4) and heightened Na¹⁸F uptake (arrows). Osteophyte formation on the lateral side of the lateral femoral condyle, along with eminence spurring, was noted, all indicative of degeneration.