Repair of Cranial Tibial Tuberosity Avulsion Fracture in a Pitbull Puppy

 

The case

        A four-month-old female Pitbull, Tiana with a history of jumping from a cot two hours ago and limping on the left hind limb ever since. Physical examination revealed grade 3 lameness, pain on palpation of the left stifle and an unusual, mobile bony prominence at the level of cranial tibial tuberosity. Radiograph of lateral view of the left stifle joint revealed avulsion and displacement of the cranial tibial tuberosity physis.

        The defect was surgically corrected through a cranio-lateral approach to the stifle joint and proximal tibia. The skin, subcutaneous fascia and the fascia lata were incised in successive layers. Two 1.8 mm K-wires were drilled through the avulsed fragment into the tibia directed caudo-ventrally. A transverse bone tunnel was created in the proximal tibial body using a 1mm drill bit and the orthopedic wire was passed through the tunnel. The wire was tightened around the proximally placed K-wire which was bent slightly proximally in a figure of ‘8’ fashion using a wire twister. The protruding portion of the K-wires were cut and further embedded / smoothened using a mallet. The capsular fascia, subcutaneous tissue were opposed in two successive layers using polyglactin 910 2-0. Skin was closed routinely, and a modified Schroeder Thomas splint was applied to prevent jerky flexion of the stifle joint for 2 weeks.

        The recovery was uncomplicated and smooth, attributable to the age of the dog. The Thomas splint was removed 20 days post-surgery and the dog regained limb function completely a week after removal of the splint.

Right Stifle

                                     Left Stifle                                                

  Photographs depicting the sharp angulation observed at  the level of cranial tibial tuberosity which is more pronounced in the fractured left stifle joint than the normal right stifle

Partial weight bearing or 'toeing' noted in the fractured left hind limb

                   

      Left Stifle Joint                                                                             Right Stifle Joint

Lateromedial radiographs of the the left (fractured) and right stifle joints clearly depicting the avulsion of the cranial tibial tuberosity

Advancement of the first K-wire and the second K-wire proximal to the first one through the avulsed fragment and into the proximal tibia. 

Final post-operative radiograph depicting the placement of two K-wires and a Tension Band Wire for reduction and stabilization of the fracture

                                                     

 

        

 

                                

Intraoperative photograph and video showing the fracture site - Avulsion of the physis of the cranial tibial tuberosity

                                    Intraoperative images showing the insertion of K-wires

`                Drilling of the intraosseous canal using Drill bit and passing of K-wire through the canal.

                                                       Gait of the puppy 3 weeks post surgery

Emendations to the procedure performed

1) The K-wires could have been applied in a more caudo-ventral direction.

2.     2) Ideally, a bigger size of orthopedic wire could have used (20-22G) instead of 24G

3.    3)The tension applied after tying a figure of ‘8’ around the K-wire was less than ideal, because of which it might have loosened on post-operative radiographic evaluation.

4.    4) The proximal K-wire shouldn’t have been advanced as further as it was to avoid damaging the popliteal vessels.

5.   5)  The bone-tunnel for passing the orthopedic wire could have been made more distally in the tibia. The bone tunnel had fractured on post-operative radiographic evaluation either owing to the shallow depth of the tunnel created or the tension of the orthopedic wire.

        In our defense, the puppy was hyperactive and ‘broke’ the Thomas Splint twice in three weeks! and might have been the reason for partial implant failure. But as a surgeon, you just get a feeling that such bubbly, excited dogs ultimately make it in the end and that’s what happened in this case too!

OVERVIEW

The tibia has four separate epiphyses: proximal epiphysis, tibial tuberosity epiphysis, distal Epiphysis, and medial malleolar epiphysis. The tibial tuberosity is a traction epiphysis that forms the prominence to which the patellar ligament attaches. At some point in development (between 6 and 8 months in large-breed dogs), the proximal epiphysis fuses to the tibial tuberosity epiphysis.

Tibial tuberosity avulsion and physeal fracture are the two most common types of proximal tibial fractures. Avulsion of the tibial tuberosity occurs relatively infrequently and is limited to younger animals, usually between 4 and 8 months of age (as was Tiana) during which age the physeal plates haven’t fused. The tibial tuberosity serves as the insertion site of the quadriceps femoris muscle tendon, and avulsion of the tuberosity can result from contraction of the muscle while the stifle joint is flexed, and when the foot is set firmly on the ground. (In the present case, Tiana jumped from a cot). Clinically, lameness, pain, stifle joint effusion, and soft tissue swelling are noted. The proximally displaced avulsed tuberosity may be palpable along with crepitus. Avulsion of the tibial tuberosity is best demonstrated on a lateral radiograph while the knee is flexed.

Conservative management with external coaptation (cast or splint maintained for 2-3 weeks) should be considered only when the displacement is minimal, and the patient is a small-breed dog. In most cases, open reduction and internal fixation with two Kirshner wires alone or Kirshner wire and tension band wire is recommended for a better prognosis, but pin and tension band wire fixation is the preferred technique over the other for better stability and strength. Strict exercise restriction is recommended for 1 to 2 weeks, followed by progressive limited leash walking over 2 to 3 weeks.