What Is Your Diagnosis?

Phanuel Mponda University of Sydney Veterinary Teaching Hospital, Camperdown, NSW, Australia

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 BVSc, MBA
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Rachel Basa University of Sydney Veterinary Teaching Hospital, Camperdown, NSW, Australia

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 BVSc, PhD, ECVS

History

A 3-year-old female spayed Swiss White Shepherd bitch was presented for further investigation of a 4-week history of severe non–weight-bearing right pelvic limb lameness. She had initially presented to an emergency center for assessment of acute lameness associated with a 2-cm-long laceration to the cranial aspect of the right stifle. The laceration was lavaged and closed primarily. Radiographs of the right stifle were taken at the regular vet clinic the next day, and there was noted to be evidence of thickening of the patella ligament. The bitch was discharged with a 2-week course of amoxycillin at 12.5 mg/kg, PO, q 12 h, and meloxicam at 0.1 mg/kg, PO, q 24 h. She was initially grade 4/5 lame; however, this improved to a grade 2/5 lameness.

On referral examination, vitals were within normal limits with moderate to severe weight-bearing lameness of the right pelvic limb. A full orthopedic examination was unable to be performed conscious; however, the bitch had a tendency to hold her right stifle joint in a flexed position. The dog was heavily sedated with a combination of acepromazine at 0.03 mg/kg, medetomidine at 0.01 mg/kg, and methadone at 0.1 mg/kg for stifle radiography (Figure 1) and ultrasonography (Figure 2). While sedated, the only abnormality detected on examination was thickening of the right patella ligament.

Figure 1
Figure 1

A lateral (A) and craniocaudal (B) view of the right stifle of a 3-year-old female spayed Swiss White Shepherd bitch presented for evaluation of a 4-week history of right pelvic limb lameness.

Citation: Journal of the American Veterinary Medical Association 260, 15; 10.2460/javma.22.02.0069

Figure 2
Figure 2

Longitudinal ultrasonographic images of the proximal portion of the patellar ligament (A) and distal portion of the patellar ligament and insertion site (B). Left to right direction represents proximal to distal orientation in the standing animal.

Citation: Journal of the American Veterinary Medical Association 260, 15; 10.2460/javma.22.02.0069

Diagnostic Imaging Findings and Interpretation

On the mediolateral view of the right stifle, there is proximal positioning of the patella in relation to the femoral trochlea (Figure 3). This could also be seen on the craniocaudal view. At the cranial aspect of the right stifle joint, there is an area of soft tissue opacity that extends from the distal portion of the patella proximally to the proximal aspect of the tibia, distally (Figure 3). This is most consistent with thickening of the patellar ligament. There is minimal to no intracapsular soft tissue swelling given the relatively normal size and shape of the infrapatellar fat pad and lack of displacement of fascial planes at the caudal aspect of the stifle joint. Based on these radiographic findings, a presumptive diagnosis of patella ligament injury was made.

Figure 3
Figure 3

Same images as in Figure 1. On the mediolateral projection (A), the patella is proximally displaced (white arrow), could also be seen on the craniocaudal view (B; white arrow). There is marked thickening of the soft tissues at the cranial aspect of the stifle joint, most consistent with thickening of the patellar ligament (circled in white).

Citation: Journal of the American Veterinary Medical Association 260, 15; 10.2460/javma.22.02.0069

Due to the chronicity of the injury and concern regarding the integrity of the patella ligament, ultrasound was performed. Ultrasound of the right patella ligament revealed that the proximal portion of the patella ligament was mildly thickened; however, from mid ligament distally there was complete loss of normal architecture (Figure 4). This extended for a length of 3 cm and ended just proximal to the patella ligament insertion on the tibial crest. There was normal appearance of the cranial cruciate ligament, menisci, and collateral ligaments on ultrasound examination of the right stifle joint. Stifle joint effusion was not identified on ultrasound.

Figure 4
Figure 4

Same images as Figure 2. There is rupture of the distal portion of the patellar ligament with retraction of the ligament fibers (white circle) and small avulsion fragments (white rectangle).

Citation: Journal of the American Veterinary Medical Association 260, 15; 10.2460/javma.22.02.0069

Treatment and Outcome

Due to the ultrasonographic findings being consistent with complete patella ligament rupture interposed with a 3 cm length of scar tissue, augmentation of the ligament with a graft was performed. At the time of surgery there was confirmed to be a defect in the patella ligament 2 cm proximal to the tibial tuberosity. Autogenous fascia lata was harvested and split longitudinally then the medial aspect of the graft was fed through a drill hole in the proximal tibia and fixed to the medial parapatellar fascia. The lateral aspect of the graft was fixed to the lateral parapatellar fascia with both graft ends extending proximal to the patella. A second hole was drilled in the tibial tuberosity and 100-lb nylon encircling suture was fed through this hole and secured proximal to the patella, deep to the ligament. A 2.7 ten-hole locking compression plate was used as an internal splint with screws engaging the patella and proximal tibia; the plate was contoured to permit a 135-degree standing position during weight-bearing. Following surgery, the right pelvic limb was immobilized with a spica splint that was maintained for 6 weeks then both the spica splint and implants were removed 6 weeks postoperatively. At 2 years telephone follow-up postsurgery, the dog was reported to be sound on the affected right pelvic limb with slightly reduced range of motion.

Comments

The quadriceps mechanism is comprised of the quadriceps muscles, the patella, and the patella ligament, and is important for the extension of the stifle joint. Rupture of the patella ligament is an uncommon condition and is often traumatic in etiology leading to failure of extension of the stifle joint and weight bearing due to the inability to fix the stifle joint during loading.15 Conservative treatment of ruptured patella ligament is considered a poor option,1 therefore surgery is recommended for optimal outcomes. Surgical management involves the following 3 steps: primary tenorrhaphy, transpatellar augmentation, and temporary immobilization of the stifle joint.1 Tissue autografts have been utilized in cases of chronic patella ligament rupture.1,3,4 In this particular case, delayed diagnosis and ultimately referral, led to further diagnostic imaging being employed to investigate the full extent of the injury.

Due to the chronicity of the case and delayed imaging, it was not possible to determine whether this was a true tear as opposed to a laceration related to the original traumatic event. Arguably, imaging performed at the time of initial presentation would have probably made it possible to distinguish a true patellar tear from a primary laceration. Immediate imaging based on the clinical examination findings and severity of the lameness at initial presentation can aid in early diagnosis in future cases.

This case highlights the importance of radiography and ultrasonography as complimentary diagnostic modalities in the case of chronic patella ligament injury. The disruption of the patella ligament was clearly identified on ultrasound and definitive ligament repair was performed.

References

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    Farrell M, Fitzpatrick N. Patellar ligament-bone autograft for reconstruction of a distal patellar ligament defect in a dog. J Small Anim Pract. 2013;54(5):269274. doi:10.1111/jsap.12043

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  • 2.

    Archer RM, Sissener TR, Spotswood TC. What Is Your Diagnosis? Patellar ligament rupture. J Am Vet Med Assoc. 2010;237(3):273274. doi:10.2460/javma.237.3.273

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  • 3.

    Gemmill TJ, Carmichael S. Complete patellar ligament replacement using a fascia lata autograft in a dog. J Small Anim Pract. 2003;44(10):456459. doi:10.1111/j.1748-5827.2003.tb00105.x

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    Aron DN, Selcer BA, Smith JD. Autogenous tensor fascia lata graft replacement of the patellar ligament in a dog. Vet Comp Orthop Traumatol. 1997;10(3):141145. doi:10.1055/s-0038-1632585

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  • 5.

    Brunnberg L, Dürr E, Knopse C. Injury to the patella and the patellar ligaments in dogs and cats II. Rupture of the patellar ligament. Eur J Companion Anim Pract. 1993;3:6973.

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