Gross, computed tomographic, and endoscopic anatomy of the equine carpal extensor tendon sheaths.

Objective: (1) To describe the computed tomography (CT) and gross anatomy of the equine extensor carpi radialis sheath (ECRS) and common digital extensor sheath (CDETS); (2) to describe a single-portal endoscopic examination of the ECRS and CDETS.

Study Design: Ex vivo experimental.

Sample Population: Thirty clinically normal cadaver thoracic equine limbs severed at the humeral diaphysis.

Methods: Ten limbs underwent plain and intrathecal contrast CT examinations and gross dissection of the ECRS and CDETS. Single-portal endoscopic examination of ECRS and CDETS was attempted in 4 limbs and endoscopic examination was performed on 16 limbs. Endoscopic video recordings were reviewed by 3 observers for quality of visualization before dissection and examination for iatrogenic damage. Interobserver agreement for ECRS and CDETS visualization was determined with Fleiss' κ agreement.

Results: Extensor carpi radialis sheath and CDETS anatomy was consistent between gross dissection and CT examinations. The ECRS endoscopic portal was medial at the level of the intersection between the extensor carpi obliquus and extensor carpi radialis tendon. The CDETS endoscopic portal was lateral, 5 cm proximal to the lateral styloid process of the ulna. The ECRS and CDETS were well visualized and interobserver agreement was substantial (κ = .73; P < .0001) and moderate (κ = .53; P < .0001), respectively.

Conclusion: Computed tomography examinations provided useful anatomical information, consistent with gross dissection of the ECRS and CDETS. The described single-portal endoscopic techniques allowed consistent tenoscopic examination of the majority of the ECRS and CDETS.

Clinical Significance: Awareness of the intrathecal anatomy of the ECRS and CDETS should facilitate the treatment of these tendon sheaths. The proposed portals provide good to excellent single-site endoscopic visualization of the majority of the ECRS and CDETS.