Value of SPECT-CT Imaging for Middle-Aged Patients with Chronic Anterior Knee Pain

BACKGROUND Single-photon emission computed tomography-computed tomography (SPECT-CT) is a highly sensitive tool for detecting bone metabolism. We determined whether subchondral bone metabolism, as indicated by SPECT-CT in the patellofemoral (PF) joint, predicts response to conservative management in middle-aged patients with chronic anterior knee pain (AKP), and whether SPECT-CT results correlate with arthroscopic assessments of chondral lesions in the PF joint. METHODS The study group comprised 74 middle-aged patients with chronic AKP. All of the patients underwent SPECT-CT, and the results were graded along a scale of 0 to 3°. After 8 weeks of conservative management, they were grouped as responders (n = 40) or non-responders (n = 34) according to symptom improvement. We compared the median scintigraphic uptake of the PF joint between the two groups, and evaluated the positive predictive value (PPV) of uptake for treatment response in each patient. In non-responders, cartilage condition was assessed during arthroscopy, and the correlation of scintigraphic uptake with severity of the chondral lesion was assessed. RESULTS The median scintigraphic uptake in the patella was higher in non-responders than in responders (2 vs. 1). Among patients with higher patella uptake (grade 2 or 3), the PPV for non-response to conservative therapy was 62-67 %, whereas it was 24-25 % in patients with lower uptake (grade 0 or 1). Patella uptake corresponded strongly with arthroscopic assessment of patellar chondral lesions; the correlation was less strong for the femoral trochlea. CONCLUSIONS Increased subchondral bone metabolism in the patella is associated with responsiveness to conservative therapy. SPECT-CT can benefit clinicians by predicting the treatment response from conservative management.