Quantitative bone single photon emission computed tomography/computed tomography in symptomatic and asymptomatic foot and ankle osteoarthritis

Purpose The purpose of this study was to evaluate and quantify the prevalence of increased uptake in SPECT/CT in symptomatic and asymptomatic foot and ankle joints in patients with osteoarthritis. Methods In 63 patients with osteoarthritis (OA), the painful symptomatic foot (SF) and asymptomatic contralateral foot (AF) were imaged with bone SPECT/CT. Presence, localization, and maximum standardized uptake value (SUVmax) of the active joints were assessed for SF and AF. CT OA grade (grade 1: mild, grade 2: moderate, grade 3: severe) and presence of five morphological features of OA (joint space narrowing, subchondral sclerosis, subchondral cysts, irregular joint margins, and osteophytes) were evaluated. Results In total 32 (51%) patients showed additional uptake in the AF, whereas 31 (49%) patients showed it only in the SF. SF showed more active joints than AF (106 vs. 43). CT OA grades positively correlated with SUVmax (Kendall's tau b = 0.62, P < 0.001). SUVmax values (per foot) in SF were higher in patients with uptake in bilateral feet (SF+, AF+) [median (IQR): 17.9 (10.7-23.3)] as compared with patients with active sites only in the SF (SF+, AF-) [10.4 (6.4-19.1); P < 0.001]. Number of active OA joints in SF was higher in patients with bilateral uptake (P = 0.017). Conclusion In conclusion, half of the patients exhibited increased uptake in the contralateral asymptomatic foot. SUVmax showed a significant correlation to CT osteoarthritis grade, in the symptomatic and asymptomatic foot. Future follow-up studies will provide further insights into the prognostic and therapeutic value of these findings.