Visualization of stress fractures of the foot using PET-MRI: a feasibility study

Abstract

BackgroundDiagnosis and treatment of stress fractures still remains to be a clinical and radiological challenge. Therapeutic options vary from conservative treatment to surgical treatment without a clear treatment concept. Recently the combination of PET and MRI has been introduced, aiming a superior diagnostic accuracy in clinical practice. Therefore the aim of our study was to analyse whether PET-MRI would be a feasible technique to recognize stress fractures of the foot and to analyse if our conservative treatment plan leads to a good clinical outcome.MethodsTherefore, 20 patients with suspected stress fractures of the foot and ankle underwent plain radiography and 18F-Fluoride PET-MRI. Two blinded readers assessed in consensus both imaging techniques for the presence of stress fracture, stress reaction or osteoarthritis. Patients with stress fractures or stress reactions in the foot and ankle area underwent our conservative treatment plan, with immobilization in a VACO®ped cast for 6 weeks under partial weight bearing on forearm crutches. The benefit of our conservative therapeutic concept was evaluated by the patients on the basis of VAS and FAOS scoring systems before and after treatment.Results8 out of 20 patients underwent conservative treatment after diagnosis of either a stress fracture or a stress reaction of the foot and ankle area. PET-MRI identified four stress fractures and seven stress reactions. In all cases, no pathological findings were present on plain X-ray. FAOS and VAS significantly improved according to the patients’ records.ConclusionsPET-MRI seems to be a useful modality to diagnose stress fractures and stress reactions of the foot and ankle area, especially when conventional modalities, such as plain radiographs fail. Conservative management is a promising therapeutic option for the treatment of stress fractures. To rule out the benefits compared to a surgical treatment plan, further studies are needed.

Applications of PET‐MRI in musculoskeletal disease

“…9). 145 A separate study in patients with foot pain of unclear cause showed that in cases of stress fracture, PET-MRI performed better than PET/CT due to earlier depiction of T 1 -weighted MRI changes than changes on CT, which provided higher diagnostic confidence. 146 Overall, the authors saw that 18 F-NaF PET-MRI provided more diagnostic information and higher diagnostic confidence compared with PET/CT for evaluation of foot pain of unclear cause.…”

“…PET‐MRI was shown to be useful for diagnosis of stress fractures and stress reactions in cases where no pathological findings were present on X‐ray (Fig. ) . A separate study in patients with foot pain of unclear cause showed that in cases of stress fracture, PET‐MRI performed better than PET/CT due to earlier depiction of T 1 ‐weighted MRI changes than changes on CT, which provided higher diagnostic confidence .…”

“…On MRI, a fracture line in the dorsal calcaneus with little edema is seen, due to an older stress fracture that corresponds to elevated 18 F‐NaF PET uptake (red arrow). Additionally, another stress fracture is shown on PET‐MRI in the mediodorsal parts of the cuboid with bone marrow edema on MRI and elevated uptake on 18 F‐NaF PET (dotted arrow) . Reprinted from Cronlein et al Visualization of stress fractures of the foot using PET‐MRI: a feasibility study.…”

Novel Musculoskeletal and Orthopedic Applications of 18F-Sodium Fluoride PET

“…The feasibility of imaging stress fractures with NaF-PET/ MR was investigated in 20 patients with foot pain by Crö nlein and colleagues. 24 Despite negative findings on radiography, 4 stress fractures and 7 stress reactions involving the foot and ankle were identified by PET/MR. A comparative study between PET/CT and PET/MR by the same group found that both hybrid modalities identified the same 42 lesions across 22 subjects with foot pain of unclear cause.…”

PET-MRI for the Study of Metabolic Bone Disease

“…Additionally, 18 F-NaF has been shown to detect increased bone turnover at areas of new bone formation around stress fractures. It was demonstrated that PET-MRI may be able to diagnose stress fractures and stress reactions in cases where no pathological findings are present on X-ray (32). These studies collectively demonstrate that 18 F-NaF can be a useful marker for the assessment of bone turnover to study metabolic bone diseases.…”