Case Study

ORTHO – Chronic partial avulsion rupture of the patellar ligament, pre and post surgical repair, in a 9 month old German Wirehaired Pointer dog with a history of traumatic injury

This 9 month old M intact German Wirehaired Pointer dog presented with left hind lameness of several months duration. Suspect traumatic injury to patellar ligament.

Physical exam: Gait/Lameness- Grade III/V left pelvic limb lameness Posture: Off weighting left pelvic limb at a stand. Joint palpation left stifle – Severe patellar ligament swelling, pain on extension of stifle, no cruciate instability, possible defect on the lateral aspect of the origin of the patellar ligament. Healed ~1cm diameter dermal scar over the proximal patellar ligament. Mild muscle atrophy of the left pelvic limb

Image Interpretation

US of the left and right patellar ligaments – Left: An irregular new bone formation is seen at the patellar apex. The patellar ligament reveals marked fusiform thickening at up to 1.5 cm peaking 1.5 cm distal to the patellar apex. Incomplete loss of the regular fibre pattern is noted emphasizing the region next to the patellar apex. The tendon tissue is hypoechoic and heterogenous. Part of the fibre volume is maintained in echoarchitecture and continuous. The infrapatellar recess reveals only scant effusion. There is a mass effect on the infrapatellar fat pad deep to the patellar ligament. The fat pad presents increased echogenicity and heterogeneity. A moderate amount of anechoic effusion is noted within the suprapatellar recess. Mild synovial proliferation is noted here as well. Right: A mild amount of anechoic effusion is noted within the suprapatellar recess. The synovial membrane is thin.

DX

Chronic partial avulsion rupture of the left patellar ligament next to the patellar apex.

Outcome

Secondary stifle joint effusion and synovial proliferation is noted.
The scant effusion within the right stifle may reflect compensatory mechanical load of
the right hind limb or a normal variation.
The history indicates a traumatic injury.
The normal position of the patella suggests maintained biomechanical stability of the
patellar ligament. However the clinical status of the patient appears to be unsatisfying
and progressing disintegration cannot be ruled out.
Temporary fixation of the stifle joint in extended position may be considered to unload
the ligament and allow for healing. However, this requires narrow clinical monitoring
of the patient as irreciprocal quadriceps contracture is a major complication of this
procedure with a reasonable risk in a young dog.
Tendon healing and restoration of the fibre pattern should be monitored
ultrasonographically as it helps determine the earliest point to discontinue the
temporary fixation.

Comments

Addendum: 6 weeks post-tendon reconstruction surgery:

Left stifle joint:

Looping suture material is seen in place within the distal quadriceps tendon and the proximal patellar tendon. The proximal patellar tendon presents marked thickening of up to 1.5 cm over a length of 2.5 cm immediately distal to the patellar apex. The outline of the affected region is largely even. Partial restoration of the fibre pattern with short and moderately long fibres is appreciated. A relative and overall decrease in echogenicity compared with the remainder of the tendon is still noted.

The patella presents marked bony modeling throughout.

The suprapatellar and infrapatellar both contain a mild amount of anechoic effusion. Marked thickening of the synovial fold is noted in the suprapatellar region as well as hypoechoic tissue with a mass effect between the bone surface of the femur and the quadriceps tendon. The layers of the skin present edematous swelling with no free fluid accumultation. Emerging osteophytes are noted at the proximal aspect of the femoral trochlea. The infrapatellar fat pad presents marked heterogeneity. The cranial ligament (CCL) is continuous with even outline and regular echo pattern.

Overall assessment:

Ultrasonographic reevaluation of the left stifle joint 6 weeks after surgical fixation of a patellar tendon avulsion rupture.

The degree of fibre restoration is as expected, there is no evidence of delayed healing. Relative stability is assumed.

The stifle joint presents moderate synovialitis with emerging femoropatellar osteophytosis which is likely to be a consequence of mechanical irritation. There is no evidence of primary articular pathology, the CCL is intact. The hypoechoic tissue deep to the quadriceps tendon is likely consistent with granulation tissue (also likely in conjunction with the mechanical irritation), organizing hematoma is a potential with lower probability here too.