PD positive, Xray negative, what next?
Review of the Seldom was a question easier answered. This horse needs an MRI scan. The palmar digital nerve block is non specific. It will usually anaesthetises all of the sole of the foot, the coffin joint, often the pastern joint and sometimes the fetlock joint. X-Rays are unhelpful in the diagnosis of foot lameness. Bone conditions such as navicular flexor cortical erosions are difficult to detect, and soft tissue conditions such as deep digital flexor tendonitis, which cause most foot lameness, are undetectable. Analgesia of the coffin joint is not specific to the joint, and anaesthetises the navicular bursa, the sole, and the deep digital flexor tendon. This is not time dependent, but a positive response may confirm the lameness is within the foot. Several papers have shown a good response to medication of the navicular bursa with corticosteroids and the duration of soundness was up to 18 months.
- The lack of specificity of the common nerve blocks such as the palmar digital
- The overwhelming lack of value from foot radiography
- The need for MRI for accurate diagnosis
- The potential for exploratory medication of the navicular bursa