In 32-B1, lag screw fixation combined with a neutralization plate is the standard technique for fractures with a large reducible wedge. As an alternative to the lag screws, cerclage wires can be applied to reduce the fragment in cases where fracture obliquity allows for application of at least 2 wires.
Note: if the fragment reduction is challenging and there is a risk to detach the fragment from its muscular and soft tissue attachments during the reduction maneuver, it is advisable to switch to an indirect reduction and biological fixation technique (for more information please see "Plate and rod" or “Interlocking nail” fixation).
Reducing the free fragment to one of the main bone segments is recommended. This transforms the 3-piece fracture into a simpler 2-piece fracture that allows for an easier anatomical fracture reduction.
The fragment is secured to one of the main bone segments with a lag screw.
Reduction of the remaining fracture line
Bone holding forceps are applied to the proximal and distal major fragments for distraction.
In an oblique fracture pattern, the bones are slid along the fracture line into perfect anatomical reduction with the help of one or two pointed reduction forceps placed across the fracture line.
Note: care must be taken not to damage the secured fragment during the reduction maneuver.
A second lag screw completes the reconstruction of the bony column.
Lag screws vs. cerclage
In order to achieve interfragmentary compression and counteract the shearing forces, either cortex screws placed in lag fashion, cerclage wires or a combination of both can be used depending on fracture configuration.
Pitfall: If the obliquity of the fracture is too short, a cerclage wire will cause the fracture to shear and cause loss of reduction.
The plate is contoured, applied and preliminary secured to the bone with bone or plate holding clamps. If a locking compression plate is used, temporary stabilization can be achieved with the push-and-pull devices.
The length of the plate should allow for placement of at least 3 screws in each the proximal and distal major fragment. To increase stability of the construct, a plate that spans 75% of the femur length is recommended.
The plate is secured with at least three bicortical screws in each of the major fragments. Avoid screw insertion close or at the level of the fracture line. All screws are placed in a neutral mode.
Fixation with a locking plate
If a locking plate is used, only 2-3 locking bicortical screws per main fragment are needed. One advantage of using a locking plate is that precise contouring is not necessary.
Note: If a combination of cortex and locking screws is used, the plate must be anatomically contoured at the sites of non-locking screw insertion. The non-locking screws must be inserted and tightened before any locking screws are placed.
5. Case example
~2 year old cat with a 32-B1 fracture from unknown trauma.
The fracture was repaired with a 10 hole 2.4 mm LCDCP and a 20 gauge cerclage wire.
The patient did well on follow up but never returned for radiographs.
Phase 1: 1-3 day after surgery
Aim is to reduce the edema, inflammation and pain. Integrative medical therapies, anti-inflammatory and analgesics.
Phase 2: 4-10 days after surgery
Aim is to resolve the hematoma, edema and control pain, and prevent muscle contracture. Anti-inflammatory and analgesic medications may still be needed. Rehabilitation and integrative medical therapies can be used.
Special attention should be given to patients less than 1 year of age with a femoral fracture. Rehabilitation is strongly recommended to help prevent quadriceps muscle contracture.
If the cat is not starting to use the limb within fa few days after surgery, a careful evaluation is recommended.
10-14 days after surgery the sutures are removed.
Radiographic assessment is performed every 4-8 weeks until bone healing is confirmed.
~3-4 months after follow up radiographs surgery check bone healing.