Tension band wiring

The patella fracture is under tension and distracted apart by the pull of the quadriceps muscle group. Acute patella fractures can be reduced. Chronic patella fractures may not be reducible.

The fixation method must resist the large tension forces constantly acting on the patella. Longitudinal K-wires and tension bands can be an effective method to counteract the tension on the patella.

The patient is positioned in dorsal recumbency. The pelvic limb is extended.

A lateral parapatellar or medial parapatellar approach is performed along the patellar ligament and patella proximally to the quadriceps muscle.

An arthroscopic assisted minimally invasive approach can be used for some fractures.

The proximal fragment migrates proximally under the tension of the quadriceps muscles. It can be repositioned distally by extending the leg and by using pointed reduction forceps.

The stifle is fully extended, and traction is applied to the proximal fragment to reduce it.

The reconstructible fragments are anatomically reduced and stabilized using small pointed reduction forceps.

A hole is drilled transversally in the extra-articular portion of the patella.

Orthopedic wire is pre-placed in the hole. As a guideline, the dimensions of the wire for a German shepherd breed is 18 gauge (1.25 mm).
Smaller wires are used in medium and small breeds. For example, 20 gauge wire (1.0 mm) is used in a border collie, and a 22 gauge wire (0.8 mm) is used in a miniature poodle.

Two K-wires are introduced from the proximal or distal aspect of the patella, based on fracture configuration.

K-wires are placed:

• From the smaller to the larger fragment
• At the medial and lateral edges of the patellar ligament
• Cranial to the articular surface

The K-wires are directed along the long axis of the patella, making sure to avoid the articular surface.

The K-wires are placed using a power drill, at low speed (less than 300 rpm), using irrigation to minimize heat generation.
As a guideline, the dimension of the K-wire for a German shepherd is 0.062'' (1.55 mm). Smaller K-wires are used in medium and small breeds. For example, 0.045'' (1.15 mm) is used in a border collie, and a 0.032'' (0.8 mm) is used in a miniature poodle.

In small dogs and cats, placing two K-wires may not be feasible due to the small patellar size and a single K-wire may be sufficient.

A second orthopedic wire is slid under the K-wires. This wire should be placed in close contact with the K-wires and remain cranial to the articular surface.

The two wires are tightened using two twists, in a figure of 8 pattern.

The excess length of the twist is trimmed. Care must be taken to avoid interference between the remaining twists and the articular surface.

The K-wires are cut and bent on the near end away from the articular surface. Far ends may also be bent, if accessible.

A single longer piece of orthopedic wire can be used to create the tension band.

The wire is threaded through the patella; one end is wrapped cranial to the patella under the K-wires and twisted onto the other end of the wire.

The excess length of the twist is trimmed.

The articular surface is evaluated to make sure that it is anatomically reduced.

The K-wires are cut and bent on the near end, away from the articular surface. Far ends may also be bent, if accessible.

The end of the K-wires should not interfere with the patellar ligament.

The stifle joint is sutured using monofilament absorbable suture material. The wound is closed in layers.

Limb disuse after the repair of a patellar fracture is unusual. Most dogs start weight bearing within 3 days of surgery.

The focus of physical rehabilitation is to:

• Avoid loss of stifle joint motion, particularly loss of extension
• Avoid excessive stress on the surgical repair during the healing period
• Promote low-impact weight bearing pelvic limb exercise

The stifle joint is protected and partially immobilized if deemed necessary for approximately 14 days.

Cryotherapy and passive range of motion are indicated but not possible if immobilization is used.

Activity is limited to leash walks until bone healing is radiographically evident.

The aim is to reduce the edema, inflammation and pain using cryotherapy anti-inflammatory and analgesic medications.

Gentle passive range of motion of the hip and stifle joint can be initiated to promote mobility and joint health.

The aim is to resolve the hematoma, edema, control pain and prevent muscle contracture.

Anti-inflammatory and analgesic medications may still be needed.

If the dog is not starting to use the limb within a few days after surgery, re-evaluation is recommended.

Rehabilitation therapy is continued.

10-14 days after surgery the sutures are removed.

Radiographic assessment is performed every 4-8 weeks until bone healing is confirmed.