Research into Radiographic Changes of the Equine Proximal Third Metatarsal Bone

A recent study found that horses with proximal suspensory desmopathy (PSD) had more increased radiopacity in the lateral aspect of the metatarsus and a multifocal distribution pattern was more common in hindlimbs with PSD.

feet and legs of several horses
A recent study found that horses with proximal suspensory desmopathy (PSD) had more increased radiopacity in the lateral aspect of the metatarsus and a multifocal distribution pattern was more common in hindlimbs with PSD. iStock

The tarsus and proximal suspensory origin of the metatarsus are commonly imaged regions for lameness. Common radiographic findings in the proximal third metatarsal bone (MtIII) include increased trabecular and endosteal bone density (sclerosis), areas of decreased bone density, and enthesophyte formation.

A recent study found that horses with proximal suspensory desmopathy (PSD) had more increased radiopacity in the lateral aspect of the metatarsus and a multifocal distribution pattern was more common in hindlimbs with PSD. Comparison of radiography to magnetic resonance imaging (MRI) can help objectively assess the value and limitations of radiographs in orthopedic disease processes.

The study was titled, “Radiographic changes of the proximal third metatarsal bone do not predict presence or severity of proximal suspensory desmopathy in a predominately Quarter Horse population” was published in the Equine Veterinary Journal. The authors were Frances E. Hinkle, Kurt T. Selberg, David D. Frisbie and Myra F. Barrett.

Focus of Study

The aim of this retrospective observational study was to compare the radiographic and MRI findings of the proximal third metatarsal bone (MtIII) and proximal suspensory ligament, using MRI as the gold standard.

Single hindlimbs of 35 horses (32 Quarter Horses) with radiographic and high-field (3Tesla (3T)) MRI studies were blindly evaluated by two board-certified veterinary radiologists and a radiology resident. Severity and location of the following parameters were assessed: radiographic MtIII sclerosis and lucent regions, MRI endosteal metatarsal sclerosis and bone marrow lesions, plantar cortical proliferation and resorption, and proximal suspensory desmopathy (PSD).

Radiographic osseous changes of MtIII were identified in 54% of limbs, whereas 40% limbs had osseous changes on MRI. In addition, 43% of limbs had PSD on MRI. No significant association was found between the presence of radiographic changes in MtIII and PSD on MRI. A statistically significant association and positive correlation was found between the severity of radiographic changes and MtIII plantar cortical proliferation and resorption on MRI (P=0.01).

Bottom Line

Radiographic bony changes of proximal MtIII do not reliably predict presence or severity of PSD but are associated with osseous changes at the proximal MtIII. The presence of radiographic changes should warrant additional diagnostics in the region prior to making conclusions about the presence or absence of PSD.

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