Tibial Crest Avulsion

Also known as: Tibial tubercle avulsion — Tibial tuberosity avulsion

Introduction

The tibial crest is the insertion point for the straight patellar tendon and it forms as a separate centre of ossification. Hyperflexion of the stifle joint can cause avulsion of the growth plate of the tibial crest in immature animals, less than about 10 months of age.

It can occur in cats and dogs, and the Greyhound and Terrier breeds are overrepresented.

Avulsion fractures are uncommon in skeletally mature animals, although they can occur.

Clinical Signs

The animal will be unable to fix the stifle during weight-bearing, leading to lameness and decreased weight-bearing on the affected leg.

Other signs include pain and swelling on the cranial aspect of the joint.

The displaced tubercle can sometimes be palpated proximal to its normal position, and the patella will be positioned proximally in the trochlear groove.

The condition can be bilateral, and in those cases the animal will have a crouched position and will be reluctant to move.

Diagnosis

Radiography provides a definitive diagnosis. Lateral and craniocaudal views are usually all that is necessary.

There is a normal radiolucent line between the tubercle and the tibia prior to fusion of the tubercle, and this should not be mistaken for a fracture.

The tibial tubercle will be displaced proximally if it is avulsed.

In unilateral cases, it may be helpful to compare with radiographs of the contralateral side.

Treatment

Surgical repair is the treatment of choice as there is loss of function of the affected stifle joint.

In chronic cases, if healing is already evident radiographically, conservative management can be attempted, and the limb and stifle joint can be immobilised for 2-3 weeks in a cast or bandage, keeping the stifle in slight extension.

Surgery permits anatomic reduction of the avulsed fragment and return to function of the stifle joint.

The tibial crest is reattached using several different techniques:

Kirchner wire fixation: two Kirchner wires are driven through the tubercle and into the tibia, placed at divergent angles.

Tension band wire fixation: a tension band can be applied to the avulsed tubercle and counteracts the pull of the quadriceps muscle. Two small Kirchner wires are placed through the tubercle and into the tibia. Orthopaedic wire is then placed in a figure of eight fashion around the exposed ends of the Kirchner wires and through a hole drilled more distally into the tibia.

The tension band principle is the ideal method of treatment, however the compression at the fracture site can lead to early closure of the physis and subsequent limb deformities in growing animals.

In patients approaching skeletal maturity, at 8-10 months of age, the implants can be left in place.

In younger patients, implants should be removed after about 5 weeks to try and prevent early closure of the physis.

Post-operatively, the limb should be immobilised in a padded bandage for 2 weeks and exercise should be restricted for a further 2 weeks.

Physiotherapy can be used to help promote joint motion.

Prognosis

The prognosis is good to excellent if the condition is treated early and anatomic and rigid fixation are achieved.

Complications include: implant failure such as pin bending or migration, wire breakage, and growth deformities.

Tibial Crest Avulsion Learning Resources
Flashcards Test your knowledge using flashcard type questions	Small Animal Emergency and Critical Care Medicine Q&A 19

References

Denny, H. (2008) A guide to canine and feline orthopaedic surgery John Wiley and Sons

Scott, H. (2007) Feline Orthopaedics Manson Publishing

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