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.