Computed Tomographic Tenography of the Equine Carpal Flexor Tendon Sheath

Exploratory tenoscopy is considered the gold standard technique to identify intrathecal pathology of the equine carpal flexor tendon sheath (CFTS). Preoperative diagnosis allows for more precise prognostication and surgical planning, potentially associated with improved surgical outcomes. This prospective, descriptive, anatomical study aimed to describe the anatomy of the equine CFTS using noncontrast and contrast CT in clinically normal cadaver limbs. Ten pairs of equine forelimbs free of gross external abnormalities were examined from mid-antebrachium to distal metacarpus. Specimens initially underwent noncontrast CT examination using 135 kVp, dynamic mAs, and 1 mm slice thickness. Contrast media (iohexol) diluted in saline (total 60 mL, final concentration 75 mg/mL) was injected into the CFTS from a lateral approach before the CT examination was repeated. Tenoscopy was then performed using the conventional lateral approach. Dissection was used to compare the gross, tenoscopic, and imaging findings. The combined noncontrast CT and contrast CT examinations provided excellent anatomical detail of intrathecal and extrathecal structures. Detailed anatomy of the previously undescribed proximal mesotenon and manica of the common mesotenon were also identified. The distal termination of the CFTS was beyond the mid-metacarpus in most specimens, which is significantly more distal than previously reported. This is an important consideration when administering local anesthesia in orthopedic examinations to prevent potential iatrogenic CFTS penetration, which may induce sepsis if the aseptic technique is not followed. Noncontrast and contrast CT can be used to accurately identify CFTS anatomy. Documentation of new intrathecal structures provides a greater understanding of CFTS anatomy.