High-field magnetic resonance imaging enables diagnosis of central tarsal bone fractures in performance horses with lameness localized to the proximal metatarsus and tarsus.

Overview

• This study reports on the use of high-field (3 Tesla) magnetic resonance imaging (MRI) to diagnose fractures of the central tarsal bone (CTB) in performance horses that show lameness localized around the proximal metatarsus and tarsus regions.
• The research highlights how MRI helps in identifying and characterizing these fractures, which are difficult to detect using traditional radiographs, and supports better clinical management and surgical planning.

Background and Purpose

• CTB fractures in horses are typically challenging to diagnose due to the complex anatomy and subtle fracture presentations.
• Cross-sectional imaging techniques, such as MRI, provide detailed internal views of bone and soft tissue, enabling definitive diagnosis and evaluation of fracture characteristics.
• The goal of this retrospective case series was to describe the MRI features of CTB fractures in performance horses and correlate these findings with clinical signs and other concurrent pathologies.

Study Design and Population

• The study retrospectively reviewed cases from a single tertiary referral hospital gathered between 2013 and 2023.
• A total of 8 horses (9 limbs) diagnosed with CTB fractures on high-field (3-T) MRI were included.
• The horses consisted of:
  • 6 Quarter Horses involved in Western performance disciplines.
  • 1 Lusitano used for Dressage.
  • 1 Thoroughbred used for polo.
  • Age range was 3 to 20 years (mean age 8.4 years).

Clinical Presentation

• Most horses had chronic onset of lameness (5 of 8 cases).
• Lameness grades ranged from moderate (3/5) to nearly severe (4/5).
• Lameness was localized in the following areas based on clinical examination:
  • Proximal metatarsus in 4 of 6 cases.
  • Distal tarsal joints in 1 of 6 cases.
  • Tarsocrural joint in 1 of 6 cases.
• Traditional radiographs suspected a CTB fracture in only one limb prior to MRI, indicating standard imaging lacks sensitivity.

MRI Findings

• Fracture types observed:
  • Complete fractures in 6 of 9 limbs.
  • Incomplete fractures in 3 of 9 limbs.
• Fractures showed a characteristic orientation from dorsomedial to plantarolateral, angled between 36° and 62° medial to the sagittal plane (mean angle 52°).
• Severe sclerosis (increased bone density/hardening) was present in all fractures (9 of 9 limbs).
• Bone edema-like signal, indicative of inflammation or bone bruising, was present with varying severity:
  • 4 limbs showed mild edema.
  • 4 limbs showed moderate edema.
  • 1 limb showed severe edema.
• MRI also revealed concurrent bone and soft tissue pathologies associated with the fractures, contributing to comprehensive assessment.

Conclusions and Implications

• High-field (3-T) MRI proves valuable for accurately diagnosing CTB fractures and defining fracture configuration and associated tissue pathology in performance horses.
• Due to poor sensitivity of standard radiography, particularly in detecting obliquely oriented fractures, an improved radiographic technique is suggested.
• The authors recommend using dorsomedial-plantarolateral oblique radiographic projections around 50° medial to the sagittal plane to enhance initial CTB fracture identification.
• Better diagnostic accuracy supports more informed surgical planning and ultimately may improve treatment outcomes in affected horses.