8 year-old Neutered Male, Labradoodle

History: This patient jumped off of a deck and would immediately not bear any weight on the right pelvic limb.  The right tarsal joint is swollen.

Images:

     

Answer:

Findings:  Dorsoplantar (Figure 1) and lateral (Figure 2) radiographs of the right tarsus were acquired.  There is marked soft tissue swelling surrounding the tarsus, primarily medially.  There is a fragment at the medial aspect of the joint of uncertain origin (arrow in Figure 1). In the lateral view the tarsometatarsal joint space is slightly wide (arrow in Figure 2) and there is a triangular mineral fragment at the dorsal aspect of the joint, just proximal to the arrow, also of uncertain origin.  There is no evidence of an aggressive bone lesion.  No other abnormalities are seen.

Conclusions: There is evidence of an injury to the right tarsus with the possibility of multiple fractures and subluxation of the tarsometatarsal joint. Acute severe lameness following a jump, as reported for this patient, should always suggest the possibility of a pathologic fracture.  In this patient there is none.  This negative finding should be included in the radiology report.  Although there is evidence of an injury, the extent of tarsal instability is not known and this could have an effect on treatment and prognosis.  Stress radiographs of the tarsus are indicated in this scenario and this should be recommended in the radiology report.  It will also be helpful to provide brief instructions on how to obtain stress views as this may not be understood.

A stress dorsoplantar view was obtained (Figure 3) with force applied as shown. A vertical fracture of the fourth tarsal bone is obvious, and involves the distal intertarsal and tarsometatarsal joints.  There is also a fracture of the first digit, and the tarsometatarsal subluxation is apparent.  It is likely that tarsal fusion will be needed given the extent of the instability.  There may be other radiographically occult fractures that could be identified with CT but the cost of a CT study should be balanced against the need for arthrodesis regardless of other small fractures that are present.

Reference:  Mauragis D and Berry CR.  Imaging Essentials – Small Animal Tarsus and Pes Radiography.  Today’s Veterinary Practice, November/December 2012, pp47-54.

View this PDF for additional information:  Stress Radiographs

One comment

  1. In the lateral projection, the dorsal margin of the fourth tarsal bone is non-parallel to the remainder of the distal tarsus, with dorsal displacement of its distal margin. The lateral aspect of the tarsometatarsal joint is widened. There is an indistinct, oblique linear lucency coursing through the fourth tarsal bone, seen in the dorsoplantar projection. There is increased soft tissue surrounding the distal tarsal joints. The tibiotarsal joint and intertarsal joints are normal. There is moderate focal swelling along the medial aspect of the tarsus.

    Theses findings suggest a fourth tarsal bone fracture and tarsometatarsal joint subluxation, with distal tarsal synovial effusion. Swelling along the medial aspect of the limb is also concerning for collateral ligament injury. Oblique projections of the tarsus may highlight the changes fourth tarsal bone, and medial and lateral stressed projections should also be performed to evaluate collateral ligament integrity. A CT scan may be required to characterize the fourth tarsal bone fracture.

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