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. A longitudinal K-wire and figure of 8 wire 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.
The direction of the approach is based on the location of the comminution.
The fragments are reduced and evaluated for reconstruction based on their size and shape.
Non-reconstructible fragments are removed using forceps.
The two main fragments are clamped with pointed reduction forceps. The smaller fragment is reduced in the proximal or distal part of the patella based on what achieves maximal stability.
The fixation of small fragments often relies on one or two K-wires. Bone screws in lag fashion are used for larger fragments.
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.
Note: Attention should be paid to preserve the patellar ligament fibers.
A K-wire is introduced centrally from the smaller fragment, cranial to the articular cartilage. A power drill is used 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 or a cat.
Both ends of the K-wire should be accessible. 5 cm of K-wire should be accessible to facilitate wire placement and K-wire bending.
Orthopedic wire is wrapped in a figure of 8 pattern over the ends of the K-wire and twisted. 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.
Note: The K-wire is directed perpendicular to the main fracture line, making sure to avoid the articular surface. The K-wire should be as caudal as possible, to minimize distraction of the articular surface.
The articular surface is evaluated to make sure that it is anatomically reduced.
The K-wires ends are cut and bent away from the articular surface and the patellar ligament.
The end of the K-wire 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