PMC6102424_01
(A): Lateral projection radiograph of the flexed stifle reveals severe soft tissue opacity in the cranial stifle region. A round, well-defined mineral opacity is found distal to the patella and cranial to the femoral condyles, consistent with an avulsion fracture of the distal pole of the patella (black arrow). (B): Craniocaudal projection of the extended stifle reveals the patella is proximally displaced suggestive of a patellar tendon rupture (white arrow).
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F1
Flexed lateral and extended craniocaudal radiographic projections of the right stifle were obtained (Figure 1).
Longitudinal ultrasonographic image of the cranial stifle in the region of the normal patellar tendon. (A): A hyperechoic structure distal to the femoral trochlear groove with distal acoustic shadowing is present (white arrow). (B): The patellar tendon has a focal area of fiber disruption and severe thickening (gray arrows). The patellar tendon abruptly tapers (black arrows) and cannot be traced proximally.
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F2
A focal area of fiber disruption and severe thickening of the proximal patellar tendon was identified, and the patellar tendon thickness abruptly decreased to a width of 1 mm proximally (Figure 2).
Intraoperative photograph of FiberWire suture placement using the PARS Achilles Jig System. (1): transversely passed distal suture; (2): first transverse pass of self-locking middle suture; (3 and 4): obliquely passed special loop sutures used to pull the end of the middle suture through the tendon to create a self-locking loop; (5): empty hole (arrow head) for passage of the proximal transverse suture.
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F3
The looped end sutures were pulled through the tendon bringing the terminal ends of the middle suture strand back through the tendon for a second pass forming a self-locking loop on each abaxial aspect of the tendon (Figure 3).
Intraoperative photograph of axial and transverse bone tunnels with 0.035" K-wires in place of tunnels (proximal is to the right).
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F4
The locations of the bone tunnels were maintained by placing 0.9 mm Kirschner wires within each of the bone tunnels (Figure 4).
Postop operative orthogonal radiographic images of the stifle. The patellar tendon remains markedly thickened. The avulsion fracture fragment is now closer to the patellar apex, but otherwise remains unchanged (black arrow). Axial bone tunnels are apparent in both views (white arrows). The transverse patellar tunnel can be seen on the lateral projection (gray arrow). The polyethyl ethyl ketone (PEEK) anchor location can be seen in the proximal tibial (arrow head).
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F5
The oblong button implant was located proximal to the patella with likely soft tissue interposed between the button and the patella (Figure 5).
Lateral projection radiographs of the stifle. (A): preoperative with a PLL:PL of 2.52; (B): post-operative ratio of 2.01; (C): 1 month post-operative, ratio of 2.55; (D): 2 month post-operative ratio of 2.31 Post-operative ratio increased moderately but maintained improved ratio compared to preoperative ratio; (E): 3.6 yr post-operative, ratio of 2.17, bone tunnels are still evident.
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F6
The avulsed fragment off the distal pole of the patella had enlarged and the patella tendon was thickened, but the patella was positioned appropriately in the trochlear groove of the femur and there were no degenerative changes noted in the stifle (Figure 6).
(A): The FiberWire suture from the primary patellar tendon repair is seen distal to the patella. The irregular, well-defined hyperechoic structure causing distal acoustic shadowing distal to the patella is unchanged. (B): The fibers within the patellar tendon are arranged in a more organized fashion and the tendon margins are better defined, consistent with normal healing at the repair site.
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F7
An ultrasound was performed that found the right patellar tendon fibers were arranged in a more organized fashion and were contiguous with the apex of the patella (Figure 7).