Feasibility of a medial tenoscopic portal in the equine carpal flexor tendon sheath in cadavers.

Overview

• This study investigated the feasibility and ideal placement of a medial tenoscopic portal into the equine carpal flexor tendon sheath (CFTS) using cadaver forelimbs and contrast computed tomography (CT) imaging.
• The goal was to determine if a medial portal could be safely established without damaging anatomical structures, to improve surgical access during tenoscopy.

Background

• The carpal flexor tendon sheath (CFTS) in horses is a synovial structure enclosing tendons that control carpal (wrist) movement.
• Tenoscopy is a minimally invasive technique to visualize and treat tendon sheath disorders, traditionally performed using a lateral portal.
• A medial portal could potentially improve visualization and instrument triangulation but risks damaging important structures such as tendons and veins.
• Therefore, defining a safe and effective medial portal location is critical before its clinical application.

Methods

• Twenty forelimbs from adult Standardbred horse cadavers were used.
• A lateral approach was used initially to inject diluted contrast media into the CFTS.
• The limb was manually flexed and extended 20 times to disperse the contrast evenly within the sheath.
• With the limb in lateral recumbency, a capped 21-gauge needle was placed approximately 5 mm proximal and 32 mm caudal to the palpable distal medial radial physis into the medial aspect of the CFTS to simulate the medial portal.
• Contrast-enhanced CT imaging was then performed to visualize the position of the needle and check for impingement on intrathecal structures, the cephalic vein (CV), and the flexor carpi radialis tendon (FCRT).
• After CT imaging, conventional tenoscopy was done through the lateral portal.
• Following tenoscopy, gross dissection was conducted to check for any needle-induced damage to superficial or intrathecal structures.

Results

• No damage was observed either inside the sheath (intrathecal) or on superficial structures related to the needle placement site.
• CT imaging showed impingement on the flexor carpi radialis tendon in 7 out of 20 specimens (35%).
• Impingement on the cephalic vein was identified in only one specimen (5%).
• The findings suggest that while minor risk of contact with tendons and veins exists, the proposed medial portal placement is generally safe.

Conclusions and Implications

• This study successfully identified a feasible anatomical location for a medial tenoscopic portal in the equine CFTS.
• Using contrast CT in cadaver limbs allowed precise visualization of needle placement relative to important structures.
• The medial portal could enhance surgical access by improving triangulation (angle of instrument entry), fluid egress, and visualization compared to the conventional lateral approach alone.
• These improvements may facilitate better diagnosis and treatment of tendon sheath diseases in horses.
• Further in vivo studies and clinical trials would be necessary to confirm the safety and efficacy of the medial portal in live horses before widespread clinical use.