Comparison of 18 F-sodium fluoride positron emission tomography and computed tomography for imaging of the fetlock in 25 nonracehorses

Charlene Pige; Mathieu Spriet; Marcos Perez-Nogues; Scott Katzman; Sarah Le Jeune; Larry Galuppo

doi:10.1111/evj.14015

Comparison of ¹⁸ F-sodium fluoride positron emission tomography and computed tomography for imaging of the fetlock in 25 nonracehorses

Equine Vet J. 2023 Oct 23. doi: 10.1111/evj.14015. Online ahead of print.

Authors

Charlene Pige¹, Mathieu Spriet², Marcos Perez-Nogues¹, Scott Katzman², Sarah Le Jeune², Larry Galuppo²

Affiliations

¹ Veterinary Medical Teaching Hospital, University of California, Davis, California, USA.
² Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, California, USA.

PMID: 37872742
DOI: 10.1111/evj.14015

Abstract

Background: ¹⁸ F-sodium fluoride (¹⁸ F-NaF) positron emission tomography (PET) has been validated as a useful imaging technique in the racehorse fetlock. The use of ¹⁸ F-NaF PET in the nonracehorse fetlock has not been reported.

Objectives: To describe ¹⁸ F-NaF PET findings in nonracehorse fetlocks, to compare with computed tomography (CT) findings and to compare PET findings between horses with and without fetlock pain.

Study design: Retrospective observational study.

Methods: All horses undergoing ¹⁸ F-NaF PET and CT imaging of the fetlock between October 2016 and March 2021 were included in the study. Medical records were reviewed for associated lameness information.

Results: Thirty-six fetlocks (33 front and 3 hind) from 25 horses were included. The interobserver agreement for PET [0.62 (95% confidence interval [CI] 0.59-0.65)] was higher than for CT [0.47 (95% CI 0.43-0.51)]. Increased ¹⁸ F-NaF uptake was most common in the medial subchondral bone of the proximal phalanx (23/36), the dorsomedial (20/36) and dorsosagittal (16/36) metacarpal/metatarsal distal subchondral bone, whereas sclerosis was identified on CT in these areas in 22 of 36 (p > 0.9), 33 of 36 (p = 0.001) and 23 of 36 (p = 0.15), respectively. Significant correlations were found between PET grades and both subchondral sclerosis and resorption CT grades (p < 0.001, Spearman r = 0.19 and 0.21, respectively). Abnormal ¹⁸ F-NaF uptake in the proximal sesamoid bones (PSBs) was identified in 12 of 36 of the fetlocks, which was more common than CT abnormalities (3/36, p = 0.02). Periarticular increased uptake was seen in 7 of 36 fetlocks, whereas osteophytosis was recognised on CT in 20 of 36 (p = 0.1). Maximal standardised uptake values (SUVmax) were significantly higher in painful than in nonpainful fetlocks (22.0 and 11.9, respectively, p = 0.038).

Main limitations: Retrospective study and limited sample size.

Conclusions: Overall PET and CT findings follow a similar distribution in their location. PET identified more abnormalities in the PSBs than CT. SUVmax is a pertinent factor to take into consideration for the assessment of the clinical significance of findings.

Keywords: 18F-NaF; horse; metacarpophalangeal joint; proximal sesamoid bone; subchondral bone.