The preferred treatment for 32-A2 fractures is internal fixation with lag screws and/or cerclage wires across the fracture line, combined with a neutralization plate. The screws/wires applied across the fracture generate friction between the fragments and counteract shearing forces, while the plate protects the fixation from collapsing.
Anatomical reconstruction of the fragments is mandatory for the correct placement of lag screws and/or cerclage wires.
Note: If anatomical reconstruction cannot be accomplished, then a bridging technique should be used.
Lag screws vs. cerclage wires
In order to achieve compression and counteract the shearing forces, either lag screws, cerclage wires or a combination of both can be used depending on fracture configuration.
Lag screws are the preferred technique because they provide greater interfragmentary compression than cerclage wires.
Cerclage wires should only be used if the fracture configuration allows for placement of at least two wires and should not be used on short oblique fractures.
A singular lag screw can be used on short oblique fractures as long as it is directed at a right angle to the fracture plane.
Bone holding forceps are applied to the proximal and distal fragment for distraction. This is necessary to counteract the strong muscles surrounding the bone.
Once distraction is achieved, the bone fragments are pulled, toggled or levered along the fracture line into perfect anatomical reduction with the help of one or two pointed reduction forceps placed across the fracture line.
The fracture is preliminary fixed with one or two pointed reduction forceps while the lag screw(s) or cerclage wires are applied.
Note: take care to avoid placing the forceps at the planned lag screw or cerclage wire sites.
Anatomical reduction and the stability of preliminary fixation are carefully checked before applying the implants.
Lag screw fixation
The screws are inserted in lag fashion. To achieve maximal interfragmentary compression, the screws must be directed perpendicular to the fracture plane.
Depending on the fracture configuration, 1-2 additional screws are inserted in the same fashion.
Note: The screws should be evenly spaced and care should be taken to avoid placing them too close to each other. Safe distance is at least 1 screw diameter away from any fracture line and 2 screws should be separated by 2 x their diameter.
Cerclage wires application
Indications for the use of cerclage wires are long oblique fracture, in which at least two wires can be applied.
Pitfall: Placing cerclage wires on a short oblique fracture will generate larger shear forces and will cause the fracture to shear and collapse.
The length of the plate should allow the placement of at least 3-4 screws in each major fragment.
Note: a traditional non-locking or locking plate (DCP, LCDCP or the LCP) can be used. If using a LCP, the dynamic compression unit (DCU) part of the combi hole can be used with locking screws.
The contoured plate is applied to the lateral surface (tension surface) of the bone and 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.
Pitfall: in spiral fractures it may be difficult to determine the exact location of the fracture line once the bone is reduced. Careful examination of the fracture configuration and pre-planning is necessary to avoid placing a screw too close to or at the level of a fracture line.
5. Case example
6 month old cat with an 32-A2 fracture from falling ~ 10 feet.
The fracture was repaired with a 8 hole 2.4 LCDCP.
Alignment: anatomical Apposition: fair/adequate Activity: PO
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.