[Cone beam computed tomography and cross-sectional anatomy of the carpal region in the horse].

This study shows that cone beam CT (CBCT) can clearly depict the bones and, with joint contrast, many soft-tissue details of the horse’s carpus. By matching CBCT images to exact anatomical cross-sections, the authors provide an atlas to help clinicians interpret carpal CBCT in practice.

What the researchers asked and why it matters

• Question: Can CBCT reliably display clinically important anatomy of the equine carpus (knee) and be cross-validated against true sectional anatomy?
• Rationale: Radiography and ultrasonography can miss or incompletely characterize complex carpal pathology; a cross-sectional modality that is practical in equine practice could improve diagnosis and case management.
• Goal: Create an anatomical atlas aligning CBCT images with matched anatomical sections to guide everyday clinical interpretation.

Study design and specimens

• Specimens: 28 forelimbs from 15 adult horses without orthopedic disease.
• Design: Ex vivo imaging followed by anatomical sectioning to validate imaging findings.
• Planes assessed: Dorsal, sagittal, and transverse planes, with sections cut to correspond to selected CBCT slices.

Imaging protocol and contrast arthrography

• Native CBCT: Each limb underwent non-contrast CBCT to establish baseline visualization of osseous and soft-tissue structures.
• Contrast-enhanced CBCT: A hyperattenuating intra-articular contrast mixture (combined with a blue epoxy dye for later anatomical identification) was injected into the antebrachiocarpal joint (proximal) and the middle carpal joint.
• Post-processing: Soft-tissue window adjustments were applied to optimize visualization of tendons and ligaments.
• Validation: Limbs were frozen and sectioned in planes matching the CBCT to enable direct, slice-by-slice anatomical correlation and photography.

Key anatomical findings on CBCT

• Bone detail: Carpal bones and adjacent osseous structures were sharply delineated on CBCT across all planes.
• Soft tissues (native CBCT): With appropriate windowing, extensor tendons, flexor tendons, and carpal collateral ligaments were identifiable, though with lower conspicuity than bone.
• Intracarpal ligaments: Indirectly visualized after intra-articular contrast injection, as contrast outlined joint spaces and interfaces adjacent to these ligaments.
• Articular cartilage: Became assessable after contrast arthrography, with best visibility proximally (antebrachiocarpal joint) and progressively reduced toward the distal carpometacarpal joint.
• Sectional correlation: Matched anatomical sections confirmed the identity and spatial relationships of structures seen on CBCT, enabling atlas-style reference images.

What the atlas contributes

• Provides side-by-side CBCT slices and true anatomical sections in standard planes to improve structure recognition.
• Clarifies expected appearance of key carpal components (bones, articular surfaces, tendons, collateral ligaments, and intracarpal ligament regions with contrast).
• Serves as a practical guide for clinicians transitioning from 2D modalities to cross-sectional imaging of the carpus.

Clinical relevance and use cases

• Adjunct to radiography and ultrasound when findings are equivocal or anatomy is complex.
• Assessment of osseous injury: Small osteochondral fragments, subchondral bone changes, and complex fracture morphology can be delineated in multiple planes.
• Cartilage and joint-space evaluation: Contrast arthrography can highlight cartilage surfaces and help infer intracarpal ligament status via contrast distribution.
• Soft-tissue appraisal: Major tendons and collateral ligaments can be identified; however, fine soft-tissue detail remains less conspicuous than bone, guiding expectations and modality selection.

Strengths of the study

• Direct anatomical validation: Exact plane-matched sections bolster confidence in structure identification on CBCT.
• Comprehensive planes: Dorsal, sagittal, and transverse coverage mirrors clinical problem-solving views.
• Practical focus: Outputs an atlas aimed at everyday clinical interpretation, not just research characterization.

Limitations to consider

• Ex vivo design: Image quality and soft-tissue appearance may differ in live horses due to motion, perfusion, and positioning.
• Population: Only healthy limbs; no assessment of diagnostic accuracy for specific pathologies.
• Comparators: No direct head-to-head with multidetector CT or MRI for soft-tissue sensitivity.
• Soft-tissue constraints: Intrinsic CBCT limitations in soft-tissue contrast mean some ligaments and tendon pathology may remain challenging without contrast or complementary imaging.

Implications and recommendations

• Adopt CBCT as a problem-solving tool when radiographs or ultrasound are insufficient, especially for osseous and osteochondral pathology.
• Consider intra-articular contrast when evaluating cartilage or intracarpal ligament-related questions, noting best results in the antebrachiocarpal and middle carpal joints.
• Use the atlas to standardize interpretation, training, and reporting across practices implementing CBCT for carpal issues.

Future directions

• In vivo studies to optimize protocols (positioning, motion mitigation, dose) and confirm diagnostic utility.
• Diagnostic performance research against gold standards for fractures, osteochondral lesions, ligament injuries, and synovial pathology.
• Protocol refinement for contrast arthrography to enhance cartilage and intracarpal ligament assessment, particularly in the distal carpometacarpal joint.
• Development of 3D reconstructions and automated segmentation tools to streamline clinical workflows.

Take-home points

• CBCT provides high-quality visualization of equine carpal bone anatomy and, with intra-articular contrast, improves assessment of cartilage and intracarpal ligament regions.
• Soft tissues are detectable with optimized windowing but remain less conspicuous than bone, so expectations should be calibrated accordingly.
• The CBCT–anatomy atlas offers a practical foundation for clinical interpretation and supports broader use of cross-sectional imaging in equine carpal diagnostics.