Quarter horse 16 Years of age Male castrated Presented for a history of lameness diagnosed 2 months before and localised in the front right DIP joint. The joint was treated and horse rested. 3 weeks later after uncontrolled movement, progressive lameness on the same region was noted. Radiographs of the distal front right limb were taken. Radiographic examination Dorsopalmar and lateromedial view of the distal right front limb. Radiographic examination As comparison, the lateromedial view of the distal left front limb was also taken. Radiographic findings
- There is a moderate soft tissue swelling at the level of the coronary band medially and dorsally front right (arrow).
- There is focal new bone proliferation on the dorsal border of the diaphysis of P2 on both sides, in the area of the eminence for attachment of the collateral ligament of the DIP joint.
- This new bone proliferation, however, on the right side is more amorphous, irregulary and ill defined, almost cloudy (arrowhead). On the left side, it is more solid and smooth, of a homogenous radioopacity.
- Mild ill definition and irregularity of the Processus extensorius of the front right P3 compared to the left side (empty arrow).
Radiographic diagnosis Close up of the lateromedial view of the DIP joint right (on the left image) and left (on the right image)
- The diagnosis was active entesiophytosis of the collateral ligaments of the DIP joint front right with associated soft tissue swelling, compatible with desmopathy of medial lateral collateral ligament. Additionaly mild OA of the DIP joint front right.
- Chronic enthesiopathy of the collateral ligament of the DIP joint front left, most likely inactive.
Radiographic diagnosis The horse underwent a MRI examination of the distal front limbs. T2 transverse image (on the left) and STIR (fat suppressed) coronal image of the left front right distal limb, medial is on the right of the images. Comments
- The MRI findings confirmed the diagnosis of the radiographic examination. There is an almost complete loss of definition of the medial collateral ligament of the DIP joint front right, replaced by amorphous tissue of very high signal intensity on T2w images (arrows).
- There is a region of focal high signal intensity on the STIR image in the mid and medial region of P2.
- All in all the signal intensity also of the lateral collateral ligament is more than expected in a normal structure on both the T2w and STIR images .
- The DIP joint is widened medially (arrowhead).
- The findings are consistant with rupture of the medial collateral ligament of the DIP joint front right and bone like edema, subluxation of the DIP joint, synovitis.
- Mild desmopathy of the lateral collateral ligament same joint.
- Radiographic changes in 22 horses were desmopathy of the collateral ligaments of the DIP joint were confirmed (Turner et al., 2002) are subtle, if present.
- The most common finding was mild osteolysis or bony irregularity around the origin of the collaterals on the third phalanx
- Ostophyte formation along the estensor process may be present
- Mild new bone formation along the body of the second phalanx was also reported.
- Ultrsonographic examination may be challenging because the location of the collateral ligaments: Lack of identification of the ligaments, loss of parallel long fibers or increased echogenicity is expected in case of lesions.
