Anatomy and Ultrasound-Guided Injection of the Deep Branch of the Lateral Palmar Nerve in the Horse: A Cadaveric Study.

Overview

• This study investigated the nerve supply of the proximal suspensory ligament (PSL) in horses, focusing on the deep branch of the lateral palmar nerve (DBLPaN).
• The researchers developed and tested a landmark-based, ultrasound-guided technique to inject the DBLPaN to aid in diagnosis and treatment of PSL-related lameness.

Background and Purpose

• Proximal suspensory ligament (PSL) injuries are a frequent cause of lameness in horses, but pinpointing the exact source of pain in the proximal metacarpal and carpal regions is challenging.
• Existing diagnostic analgesic methods lack specificity for the PSL, complicating effective treatment.
• The study aimed to clarify the nerve supply to the PSL, especially focusing on the deep branch of the lateral palmar nerve (DBLPaN), and to create an accurate injection technique to target this nerve under ultrasound guidance.

Methods

• The study was conducted using cadaver limbs from euthanized horses.
• A total of 18 limbs were dissected to examine the anatomy of the DBLPaN and its accessory branches.
• Distances were measured from the distal margin of the accessory carpal bone (ACB) to both the origin of the DBLPaN and its insertion on the PSL.
• These anatomical findings were then used to develop a landmark-based, ultrasound-guided injection protocol.
• The injection technique was tested on an additional 20 limbs to evaluate success rates.

Key Anatomical Findings

• There was considerable variability in the anatomy of the DBLPaN, with 2 to 6 accessory branches identified per nerve.
• The average distance from the distal margin of the accessory carpal bone to the origin of the DBLPaN was approximately 2.5 cm.
• The mean distance from this bony landmark to the insertion point of the nerve on the proximal suspensory ligament was about 5.1 cm.

Injection Technique Results

• The ultrasound-guided injection method was assessed for accuracy in targeting the DBLPaN.
• Injections were judged successful in 65% of the tested limbs, partially successful in 25%, and unsuccessful in 10%.
• These results demonstrate a relatively high degree of accuracy, indicating clinical relevance for diagnosis and treatment.

Conclusions and Clinical Implications

• This study provided new, detailed anatomical knowledge about the DBLPaN and its role in PSL innervation.
• The ultrasound-guided injection technique offers a promising, more specific diagnostic tool compared to current non-specific analgesic methods.
• The results lay a foundation for further research aimed at improving diagnostic precision and potentially optimizing treatments for PSL-related lameness issues in horses.
• Future investigations are warranted to refine the technique and validate its clinical effectiveness in live animals.