Metacarpophalangeal Joint Lesions Identified on Magnetic Resonance Imaging with Lameness That Resolves Using Palmar Digital Nerve and Intra-Articular Analgesia

It is possible for a palmar digital nerve block to resolve lameness caused by a metacarpophalangeal joint lesion. Therefore, complementary blocks prior to magnetic resonance imaging may provide additional information beneficial to planning a magnetic resonance study.

1. Introduction

Perineural analgesia is used to localize lameness, and MRI is often pursued when other modalities do not provide a diagnosis. However, a lack of specificity has been demonstrated with this diagnostic technique. This study describes lameness cases that subjectively improved ≥90% with a palmar digital nerve block (PDN) that were diagnosed with primary metacarpophalangeal (MCP) joint lesions based on MRI and subsequent intra-articular MCP joint analgesia.

2. Materials and Methods

Cases were selected from those presented for MRI of the front feet with lameness that resolved after a PDN. From lameness cases that blocked to PDN analgesia and presented for MRI of the front feet, cases were selected if an MCP joint lesion was the most significant MRI finding and the lameness resolved with both PDN and intra-articular MCP joint analgesia. 

3. Results

On MRI, 15 horses had a primary MCP joint lesion. The medial aspect of the joint was affected in 13 horses, and 2 horses had a midline lesion. PDNs were performed using 2.5 mL of anesthetic agent per site, and horses were reevaluated within 10 minutes.

4. Discussion

Consider the possibility of a lesion located at the proximal pastern and/or fetlock when planning MR studies in horses with lameness that resolves with a PDN. Complementary or intra-articular blocks should be performed before MRI to ensure the proper anatomic region is imaged.