Computed tomographic arthrography, gross anatomy and histology demonstrate a communication between synovial invaginations in the proximal aspect of the third interosseous muscle and the carpometacarpal joint in horses.
Authors: Gerdes Carolin, Morgan Rhiannon, Terry Rebecca, Foote Alastair, Smith Roger
Journal: Frontiers in veterinary science
Summary
# Editorial Summary This anatomical investigation by Gerdes and colleagues has definitively mapped a direct synovial communication between the carpometacarpal joint and synovial invaginations within the proximal aspect of the suspensory ligament (third interosseous muscle) in horses. Using computed tomographic arthrography with contrast medium injection into the middle carpal joint, alongside histological verification and gross anatomical dissection, the researchers demonstrated that contrast material penetrated into both the lateral and medial lobes of the proximal suspensory ligament in all 16 cadaver limbs examined, with significantly elevated Hounsfield units in the ligament tissue between 0.5–2.5 cm distal to the proximal subchondral bone plate of the third metacarpal bone (p < 0.05). The findings offer a mechanistic explanation for the often-puzzling cross-over effects observed when performing diagnostic local anesthesia blocks in the carpal and subcarpal regions, and highlight the critical need to consider potential spread into the suspensory ligament when planning both diagnostic and therapeutic injections into the middle carpal joint. Given that the proximal suspensory ligament was clearly visualised on plain CT imaging, this work provides a foundation for further clinical investigation into whether computed tomography might improve detection and characterisation of soft tissue pathology in this anatomically complex subcarpal region—potentially offering a valuable diagnostic tool for cases where traditional imaging leaves questions unanswered.
Read the full abstract on PubMed
Practical Takeaways
- •When injecting the middle carpal joint therapeutically or diagnostically, expect the medication to reach the proximal suspensory ligament in all horses due to direct synovial communication—this may explain unexpected anesthetic effects in the subcarpal region
- •CT imaging can clearly visualize the proximal suspensory ligament and may be useful for evaluating soft tissue pathology in the subcarpal region, warranting clinical validation studies
- •Consider this anatomical communication when diagnosing or treating carpal region lameness, as joint injections will predictably affect the suspensory ligament
Key Findings
- •Positive contrast medium reached the lateral and medial lobes of the proximal suspensory ligament in 100% (8/8) of cadaver limbs following middle carpal joint injection
- •Hounsfield units within the suspensory ligament were significantly higher in contrast-injected limbs compared to plain CT between 0.5-2.5 cm distal to the proximal subchondral bone plate (p < 0.05)
- •Gross anatomy and histology confirmed a direct synovial-lined cavity communication between the carpometacarpal joint and the proximal suspensory ligament