Authors of section

Authors

Arnold Besselaar, Daniel Green, Andrew Howard

Executive Editor

James Hunter

General Editor

Fergal Monsell

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Open reduction; screw fixation

1. General considerations

Introduction

Similar principles apply to treatment of avulsion fractures on the lateral and medial side of the distal femur.

The following example describes reduction and fixation of a medial collateral avulsion injury using a lag screw.

If the bony fragment is very small then a suture anchor may be used for fixation.

Lag screw fixation of a medial avulsion fracture of the distal femur

Injury types

Twisting injuries may result in disruption of the medial or lateral collateral (MCL, LCL), anterior or posterior cruciate ligaments (ACL, PCL).

The MCL and ACL are most commonly injured.

Small avulsion fractures may represent markers of significant injuries, including knee dislocation and require MRI to determine the extent of the injury.

Ligaments of the knee

2. Instruments and implants

The following equipment is needed:

  • Cannulated screw set
  • Drill
  • Ligament washer
  • Threaded guide wire
  • Image intensifier
Instruments and implants for screw fixation

4.0–7.3 mm cannulated lag screws (ideally self-drilling, self-tapping) should be used.

To secure the ligament and small avulsion fragments, a metal or plastic ligament washer can be used with the screw.

Partially threaded screw and ligament washer

3. Patient preparation and approach

Patient positioning

Place the patient supine on a radiolucent table with a C-arm.

Supine patient position

Approaches

For avulsion fractures of the lateral epicondyle, the lower end of the standard lateral/anterolateral approach is used.

For avulsion fractures of the medial epicondyle, a direct medial longitudinal incision is used, deepened to expose the medial face of the medial condyle.

Pearl: Take care to avoid the saphenous nerve and its infrapatellar branch.

4. Reduction

Reduce the fracture and secure the reduction with the guide wire.

Reduced avulsion fracture secured with the guide wire

5. Fixation

Insert a screw with or without a ligament washer.

Lag screw fixation of a medial avulsion fracture of the distal femur

6. Final assessment

Assessment of ligament stability

Gently examine the knee under anesthesia to test for ligament instability.

X-ray assessment

Check correct implant positioning and anatomical reduction with image intensification.

7. Aftercare

Immediate postoperative care

The patient should get out of bed and begin ambulation with crutches on the first postoperative day.

In most cases the postoperative protocol will be touch-weight bearing for the first 4 weeks.

Touch-weight bearing with crutches

Analgesia

Routine pain medication is prescribed for 3–5 days postoperatively.

Neurovascular examination

The patient should be examined regularly, to exclude neurovascular compromise.

With displaced high-energy fractures watch for signs of delayed vascular problems.

Compartment syndrome, although rare, should be considered in the presence of severe swelling, increasing pain, and changes to neurovascular signs.

Discharge care

Discharge from hospital follows local practice and is usually possible after 1–3 days.

Follow-up

Clinical and radiological follow-up is usually undertaken 2 weeks postoperatively.

Follow-up for growth deformity

All patients with physeal fractures of the distal femur should have clinical and radiological examination 8–12 weeks postoperatively to assess for signs of physeal growth disturbance or resumption of growth.

Examination should be repeated at intervals until resumption of normal growth is documented. This can be seen as a horizontal growth line (Harris line) that is parallel to the entire physis on both AP and lateral views.

A growth line that converges towards the growth plate may be the earliest sign of growth arrest and should prompt investigation/treatment or referral as appropriate.

X-ray of the knee showing growth lines

Clinical assessment of leg length and alignment is recommended at one-year.

Clinical assessment of leg length uses a tape measure from the ASIS to the medial malleolus.

Clinical assessment of leg length

If there is any concern about leg length discrepancy or malalignment, long leg x-rays are recommended.

Leg length is measured from the femoral head to the ankle joint.

Radiological assessment of leg length

Implant removal

If symptoms develop, the screw can be removed once the fracture is completely healed, usually 6–12 months postoperatively.