Bone marrow oedema-type signal in the proximal phalanx of Thoroughbred racehorses

Fractures in Thoroughbred racing and the potential for pre-race identification of horses at risk

Risk rates for and predisposing factors to fractures occurring in Thoroughbred racing that have been published in peer reviewed journals are documented. The potential for currently available techniques to identify horses at increased risk for fracture is discussed on the bases of principles, practicalities, advantages, disadvantages and current data. All are reviewed in light of justifiable decision making and importance of fractures to horseracing's social license.

Low-field magnetic resonance imaging of sagittal groove disease of the proximal phalanx in non-racing sport horses

BACKGROUND

Injuries of the sagittal groove of the proximal phalanx (P1) in equine athletes are considered to predominantly occur due to chronic bone stress overload.

OBJECTIVES

To describe the range of abnormalities that is present in the sagittal groove in a large group of horses diagnosed with sagittal groove disease (SGD) on low-field MRI.

STUDY DESIGN

Retrospective, cross-sectional.

METHODS

Medical records were searched to identify initial MRI images of horses diagnosed with SGD and these were blindly evaluated using a semi-quantitative grading scheme and novel SGD MRI classification system reflecting potential pathways of pathological progression and severity of stress injury.

RESULTS

A total of 132 limbs from 111 horses were included in the study; predominantly warmbloods competing in showjumping (n = 83) and dressage (n = 18). SGD MRI classifications were: 0 (normal, n = 0), 1 (small subchondral defect, n = 2), 2 (osseous densification, n = 28), 3 (subchondral microfissure with osseous densification, n = 7), 4 (bone oedema-like signal within the subchondral ± trabecular bone and ± subchondral microfissure or demineralisation, n = 72), 5 (incomplete macrofissure/fracture, n = 23) and 6 (complete fracture, n = 0). Classification 4c (bone oedema-like signal with demineralisation) and 5 had higher proportions in the plantar third of hindlimbs (3% and 10%, respectively) compared with forelimbs (0% and 0%, respectively). SGD classification and extent of bone oedema-like signal were not significantly different between lame (n = 116) and non-lame limbs (n = 16) (both p > 0.05). Periosteal new bone and oedema-like signal were identified (either confidently or suspected) at the dorsoproximal aspect of P1 in 25% and 39% of limbs, respectively.

MAIN LIMITATIONS

Inclusion via diagnoses in original MRI reports, variable clinical history, small size of some classification groups.

CONCLUSIONS

The presence or absence of lameness is not a dependable measure of the severity of SGD. The periosteal oedema-like signal of P1 has not previously been described in MRI of SGD and further supports the concept of bone stress injury.

Post-mortem feasibility of dual-energy computed tomography in the detection of bone edema-like lesions in the equine foot: a proof of concept

Introduction

In this proof-of-concept study, the post-mortem feasibility of dual-energy computed tomography (DECT) in the detection of bone edema-like lesions in the equine foot is described in agreement with the gold standard imaging technique, which is magnetic resonance imaging (MRI).

Methods

A total of five equine cadaver feet were studied, of which two were pathological and three were within normal limits and served as references. A low-field MRI of each foot was performed, followed by a DECT acquisition. Multiplanar reformations of DECT virtual non-calcium images were compared with MRI for the detection of bone edema-like lesions. A gross post-mortem was performed, and histopathologic samples were obtained of the navicular and/or distal phalanx of the two feet selected based on pathology and one reference foot.

Results

On DECT virtual non-calcium imaging, the two pathological feet showed diffuse increased attenuation corresponding with bone edema-like lesions, whereas the three reference feet were considered normal. These findings were in agreement with the findings on the MRI. Histopathology of the two pathologic feet showed abnormalities in line with bone edema-like lesions. Histopathology of the reference foot was normal.

Conclusion

DECT virtual non-calcium imaging can be a valuable diagnostic tool in the diagnosis of bone edema-like lesions in the equine foot. Further examination of DECT in equine diagnostic imaging is warranted in a larger cohort, different locations, and alive animals.

Follow-Up Magnetic Resonance Imaging of Sagittal Groove Disease of the Equine Proximal Phalanx Using a Classification System in 29 Non-Racing Sports Horses

Evolution of magnetic resonance imaging (MRI) findings in horses with sagittal groove disease (SGD) of the proximal phalanx is relatively sparsely described. This retrospective, descriptive, longitudinal study describes the findings of sequential low-field MRI fetlock examinations in horses with SGD of the proximal phalanx using a classification system. Twenty-nine horses were included, predominantly warmbloods used for show jumping (79%). For 29 limbs re-examined during the initial rehabilitation period, classification remained constant (n = 18), increased (n = 2), decreased (n = 7), and fluctuated (n = 2). Notably, two limbs with initial classification 4b (bone oedema-like signal with subchondral microfissure) and one with 4c (bone oedema-like signal with subchondral demineralisation) progressed to classification 5 (incomplete macrofissure/fracture), highlighting their potential as prodromal or imminent fissure pathology. Following conservative (n = 28) and surgical (n = 1) treatment, 86% of the horses re-entered full training and competition with a mean ± sd recovery time of 9.4 ± 4.4 months. In total, 20% of horses in the study subsequently presented for repeat MRI due to recurrent lameness after resuming full work, with classification that was the same (n = 2), increased (n = 2), or decreased (n = 2) compared with the last scan. This study underscores the variability in progression of SGD MRI findings, emphasising the need for further larger-scale research into patterns of progression.