Sagittal groove (SG) injuries of the proximal phalanx (P1) are an increasingly recognized cause of lameness in equine athletes. Early diagnosis can help optimize rehabilitation programs and prevent further injury. Several publications have described the variable abnormal imaging features of the SG on radiography, magnetic resonance imaging (MRI), computed tomography (CT), and scintigraphy. However, to date, there are no studies evaluating the distribution of lesion type and severity of MRI findings in a large group of horses. This retrospective, cross-sectional study aimed to describe the range of abnormalities present in the sagittal groove in a large group of horses diagnosed with sagittal groove disease (SGD) on low-field MRI.
Researchers searched medical records to identify MRI images of horses diagnosed with SGD. They blindly evaluated these images using a semiquantitative grading scheme and novel SGD MRI classification system reflecting potential pathways of pathological progression and severity of stress injury.
Study Population and Findings
The study included a total of 132 limbs from 111 horses, predominantly warmbloods competing in show-jumping (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 edema-like signal within the subchondral ± trabecular bone and ± subchondral microfissure or demineralization, n = 72).
- 5 (incomplete macrofissure/fracture, n = 23).
- 6 (complete fracture, n = 0).
Classification 4c (bone edema-like signal with demineralization) and 5 had higher proportions in the plantar third of hind limbs (3% and 10%, respectively) compared with forelimbs (0% and 0%, respectively). SGD classification and extent of bone edema-like signal were not significantly different between lame (n = 116) and non-lame limbs (n = 16) (both p > 0.05). The researchers identified (either confidently or suspected) periosteal new bone and edema-like signal at the dorsoproximal aspect of P1 in 25% and 39% of limbs, respectively.
Bottom Line
The researchers successfully applied the SGD MRI classification system to all limbs. The most prevalent classification was 4 (bone edema-like signal within the subchondral ± trabecular bone) and more specifically 4a (bone edema-like signal within the subchondral ± trabecular bone). There was no significant difference in the SGD MRI classifications, sub-classifications, or extent of bone edema-like signal between lame and non-lame limbs.
Related Reading
- Using Information from Cross-Sectional Imaging in Daily Practice
- Fetlock Radiographs: No Association Between Lameness, Pathology
- 10 Radiographic Prepurchase Abnormalities in Sport Horses
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