Tension band wiring
1. General considerations
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.
Every effort should be made to reconstruct the patella. If reconstruction is not possible, a partial or complete patellectomy is performed.
2. Preparation and approach
The direction of the approach is based on the location of the comminution.
3. Reduction
The direction of K-wires or lag screws should be as perpendicular as possible to each fracture line. Additional information on lag screw fixation is available here. This process is repeated with additional fragments, until the patella has two main fragments. The size of the patella and the fragments may limit the possibility of applying the fixation.
The two main fragments are anatomically reduced and stabilized using small pointed reduction forceps.
4. Fixation
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.
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.
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.
Alternative: single orthopedic wire as tension band
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.
5. Closure
6. Aftercare
General considerations
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.
Phase 1: 1-3 days after surgery
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.
Phase 2: 4-14 days after surgery
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.
Phase 3: 14 days-8 weeks after surgery
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.
