An optimised injection technique for the navicular bursa that avoids the deep digital flexor tendon.

The paper describes a new technique for injecting the navicular bursa in a horse’s leg that avoids damaging the deep digital flexor tendon (DDFT). The technique involves injecting from the side of the limb rather than from the back, as is traditionally done.

Introduction and Objectives

• This study aims to introduce a new approach for injecting the navicular bursa (a fluid-filled sac found in the horse’s hoof) to avoid injuring the deep digital flexor tendon (DDFT). This is carried out by using a lateral (side) approach instead of the traditional palmar (back) approach.
• The main objective was to assess whether this method could avoid the puncture of the DDFT and to check for potential penetration into the synovial and soft tissue by the needle.

Methods

• The research was a combination of a clinical study involving actual patients and a cadaveric study using horses’ legs after euthanasia.
• The navicular bursa was injected from the side in both real clinical cases and cadaver limbs, and the positions of the needles evaluated with radiographs.
• Contrast agents were injected to better visualize the needle position.
• None of the cadaver limbs used for testing were distended, meaning they did not have excess fluid causing swelling. However, the study also explored injection in limbs with distension of the distal interphalangeal (DIP) joint, the digital flexor tendon sheath (DFTS), or the navicular bursa.
• For the cadaver limbs, magnetic resonance imaging (MRI) with the needle still in place was also used.

Results

• All injections into the navicular bursa were successful across all tested limbs (n = 71).
• It was found that there was a much higher risk of puncturing the DIP joint when it was distended than when it was normal.
• The study also revealed a higher risk of puncturing the DFTS if it was distended, though this was not as severe as for the DIP joint.
• Approximately half of the clinical cases resulted in syvovial fluid being aspirated.

Conclusions

• The lateral approach to navicular bursa injection can successfully avoid penetrating the DDFT.
• The research found that this method may also increase the risk of synovial penetration, especially when the DIP joint or DFTS is distended, meaning there is a higher risk of injecting into a swollen or infected area.