The preferred treatment for 31-B2 physeal fractures of the femoral head is internal fixation with parallel K-wires. The use of K-wires avoids compression of the growth plate and minimizes the risk of premature closure.
Unlike cervical or basicervical fractures, Salter-Harris type I fractures of the femoral head are generally stable after reduction. This is due to the “L” shaped physis and its proximity to the point of application of the weight bearing forces.
In animals with minimal growth potential left, this fracture can also be repaired using a screw in lag fashion and anti-rotational K-wires.
4. Surgical technique when using a craniolateral approach
Anatomical reduction of the fragments is mandatory for the correct placement of the K-wires.
The femoral head remains in the acetabulum due to its attachment to the ligament of the head of the femur, while the femoral neck is displaced cranial and dorsally.
If parts of the joint capsule remain intact, the displacement may be minimal.
K-wire insertion in the femoral neck
The K-wires are started at a point slightly distal and just cranial to the third trochanter. The wires are directed dorsally and slightly cranially to follow the direction of the femoral neck and avoid the trochanteric fossa.
Three K-wires are pre-inserted in the femoral neck. The K-wires are placed parallel to one another with the points visible at the fracture surface.
The wires can be driven in a retro or normograde fashion. Retrograde fashion ensures easier positioning of the pins within the femoral neck but requires a more aggressive exposure of the proximal femur to expose the fracture surface.
The use of an aiming device can also ensure accurate placement.
To reduce the fracture, the femur is distally retracted, derotated, and slid caudally into the matching surface of the femoral head.
The pins are driven into the femoral epiphysis.
Note: Care is taken to avoid penetrating the articular surface. The visible portion of the articular surface is visualized by applying gentle lateral traction on the femur to open up the joint space. The non-visible part of the articular surface can be palpated using a small curved instrument like a curved hemostatic forceps or a Freer periosteal elevator.
Pins protruding through the articular surfaces are retracted below the level of the cartilage.
The lateral ends of the pins are bent and cut short.
5. Surgical technique when using a ventral approach
The fracture is reduced by distal distraction of the femur and its gentle manipulation.
One K-wire is inserted through the fovea capitis femoris with a low speed power drill towards the third trochanter.
A second pin is inserted cranially to the first one and directed laterally.
Both pins are cut and countersunk below the level of the articular cartilage.
6. Surgical technique when using MIO
Minimally invasive osteosynthesis can be used to treat capital physeal fractures using K-wires. The use of fluoroscopy is mandatory to ensure adequate reduction and K-wire placement. Preservation of blood supply is an advantage of using this method.
Reduction is performed in a closed manner and visualization is done via fluoroscopy.
The pins are positioned percutaneously from lateral to medial into the femoral head under fluoroscopic visualization.
7. Validation of fixation
Postoperative orthogonal radiographs are taken to assess fixation.
8. Case example Salter-Harris type I
8-month-old domestic shorthair cat with a B2 physeal fracture from an unknown trauma.
The fracture was repaired using 2 parallel k-wires of 1mm diameter.
Note: the pins did penetrate the trochanteric fossa because they were placed too high.
Postoperative radiographs at 1 month.
Successful repair despite pin malpositioning. Note the apple coring effect that commonly occurs at the femoral neck.
Clinically, the cat was doing well.
Activity restriction is indicated until radiographs indicate bone healing of the fracture.
Phase 1: 1-3 day after surgery
Aim is to reduce the edema, inflammation and pain.
Integrative medical therapies, anti-inflammatory and analgesic medications.
Note: Nonsteroidal anti-inflammatory medications can be toxic in the cat and should only be used as labeled for the cat.
Phase 2: 4-10 days after surgery
Aim is to resolve the hematoma, edema and control pain, and prevent muscle contracture.
Anti-inflammatory (see nonsteroidal warning) 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 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.
Implants may cause discomfort of the adjacent soft tissue. If this occurs, implants can be removed after bone healing is observed. In case of infection, implants must be removed after healing.
If there is no implant failure or infection, there is no need for implant removal.