Authors of section


Tomas Guerrero

Executive Editor

Amy Kapatkin

General Editor

Noel Moens

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Lag screw and K-wire

1. Principles

The preferred treatment for 31-C2 fractures is internal fixation with a screw and an interfragmentary K-wire, and removal of small fragments not amenable for fixation. Anatomical reconstruction is required to minimize secondary degenerative changes. Implants applied from the articular surface must be countersunk.

lag screw and k wire

2. Patient positioning

This procedure is performed with the patient in either lateral recumbency....

combined treatment options

3. Approach

This fracture may be exposed using a craniolateral approach. If further visualization is needed the approach is combined with a dorsal approach and greater trochanter osteotomy. Transection of the ligament of the femoral head may be needed to allow reduction and stabilization of the fragments.

craniolateral approach combined with a dorsal approach

Alternatively, a ventral approach can be used. This approach has the advantage of avoiding the transection of the ligament of the femoral head.

lag screw and k wire

4. Surgical technique

Implant selection

A cortical screw applied in lag fashion combined with an antirotational K-wire is used.

lag screw and k wire


The fracture is reduced and secured with pointed reduction forceps.

lag screw and k wire


One lag screw is used to stabilize the fracture.

A glide hole is drilled through the cis or near fragment. The drill sleeve is inserted into the glide hole and the thread hole is drilled.

lag screw and k wire

A countersink is used carefully in the glide hole to prepare the bone to accept the screw head. The hole is measured, the thread hole is tapped and an appropriate length screw inserted.

Read more about lag screw fixation.

lag screw and k wire

An antirotational K-wire is applied and countersunk under the articular cartilage.

Note: Care must be taken to ensure that no implants are protruding in the articular surface.

lag screw and k wire


Capsulorrhaphy is performed. If the ligament of the femoral head was transected, additional stabilization of the hip joint is generally required.

lag screw and k wire

Validation of fixation

Postoperative orthogonal radiographs are taken to assess fixation.

lag screw and k wire

5. Aftercare

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.

Robinson and Ehmer slings

After transecting the ligament of the femoral head for visualization, capsulorrhaphy is carefully performed for stability. Additional stabilization of the hip joint is sometimes required (see other resources for surgical techniques).

If after surgical treatment additional stability is required or the internal stabilization must be protected, a Robinson or an Ehmer sling may be applied.

The Robinson sling allows range of motion of the pelvic limb but prevents full weight bearing and full extension of the limb.

The Ehmer sling abducts and internally rotates the femoral head, preventing craniodorsal luxation.

These two slings must be carefully monitored after application to avoid complications such as skin irritation, abrasions, swelling of the foot, and slippage of the sling.

Further information on the correct application of these slings can be found in the literature.

Note: Some cats will not tolerate a sling and can cause self-harm when wearing one.

femoral head and neck ostectomy

Implant removal

If there is no implant failure or infection, there is no need for implant removal.