Islandic horse, male castrated, 8 years of age. Presented 2 months before for lameness front left, suspected fracture of P3. The horse was treated with anti-inflammatory drugs and rest, there was no improvement in the following weeks. At the time of presentation there was a soft tissue swelling lateral to the PIP joint not painful with a mild hoof imbalance. Positive diagnostic anesthesia at the level of the medial fetlock joint (90% positive) and on the medial hoof cartilage (70%). Radiographs of the region were taken. From the left: Distal front left limb, mediolateral, dorsomedial-palmarolateral and dorsolateral-palmaromedial view. Radiographic changes
- There is moderate new bone formation, solid and irregular, on the dorsal aspect of P2 and accentuated medially (arrow). Corresponding moderate soft tissue swelling.
- There is moderate new bone formation, solid and irregular, on the dorsal aspect of P2 and accentuated medially (arrow). Corresponding moderate soft tissue swelling.
- There is moderate new bone formation, solid and irregular, on the dorsal aspect of P2 and accentuated medially (arrow). Corresponding moderate soft tissue swelling.
Close up of the DL-PM view of the distal left front limb. New bone proliferation on the dorsomedial border of P2 with corresponding soft tissue swelling Radiographic diagnosis
- Considering the positive anesthesia at the level of the PIP joint and the soft tissue swelling, the list of differential diagnosis include chronic fissure/fracture of P2 or chronic active periostitis secondary to lesion of the soft tissue, particularly of the collateral ligaments inserting in this anatomical region.
- For a better evaluation of the soft tissue, a MRI examination was performed.
Transverse and dorsal plane of the left front limb at the level of P1. PD fat suppressed sequences. Medial is to the left. Radiologic findings
- There is a loss of definition of the medial collateral ligament of the PIP joint. The ligament (white arrow)is only partially visible, much thinner than the contralateral (white empty arrowhead) and with an increasead signal intensity.
- The findings are compatible with a chronic severe desmitis (almost complete rupture) of the medial collateral ligament of the PIP joint and accompanying soft tissue swelling.
Comments
- The PIP joint is a low motion joint.
- The collateral ligaments of the PIP joint originate from the medial and lateral eminences and adjacent depression of distal P1 and insert on the medial and lateral eminences of proximal P2.
- In early or acute disease, the radiographic examination may be normal.
- Avulsion fracture from the insertion are quite rare.
- In chronic injuries, enthesophyte formation at the origin and insertion of the collateral ligaments is usually present.
- The horse did not undergone to an ultrasonographic examination, probably the lesion would have been visible.
