Authors of section

Authors

Andrew Howard, Theddy Slongo

Executive Editor

Fergal Monsell

General Editor

Chris Colton

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Minimally invasive cannulated screw fixation

1. Introduction

Goals

The main goals of treatment of these fractures are:

  • Uncomplicated healing
  • No secondary displacement
  • Avoiding overgrowth due to unstable fixation
  • Avoiding secondary complications, such as nonunion, leading to additional problems (eg, ulnar nerve irritation)

Principles

The main principles for this treatment are:

  • Anatomical reduction
  • To get initial stable fixation (by screw fixation)
  • Minimally displaced fractures with a gap up to 2-3 mm are mostly incomplete at the joint level (so-called "hanging fractures"), especially in younger children with very thick joint cartilage. Only such fractures can be treated with closed reduction and insertion of a cannulated screw from behind, to close the gap and stabilize the fracture

Suitable fracture types

13-E/4.1L with no more than 2 mm of metaphyseal displacement, and stable in the joint.

Note: Salter-Harris IV fractures of the medial column are very rare. Care must be taken not to damage the ulnar nerve and they should only be treated by open procedure.

minimally invasive cannulated screw fixation

General considerations

Normally, all undisplaced intraarticular fractures (which in children always are epiphyseal fractures) require absolute anatomical reduction, which can only be performed by an open method. However, for "hanging fractures" minimally invasive treatment can be attempted.

The problem of any nonoperative treatment of this fracture is that the fracture can be completed and displaced by extensor muscle tension, thereby becoming unstable (as illustrated). It is therefore recommended that the fracture be fixed by insertion of a metaphyseal compression screw.

minimally invasive cannulated screw fixation

2. Preparation

Instruments and implants

As this is a minimally invasive surgical technique, only a few instruments are necessary.

3.0 or 3.5 mm cannulated cancellous lag screws (ideally self-drilling, self-tapping titanium screws) should be used.

The following equipment is needed:

  • Cannulated screw set
  • Drill
  • Cannulated screws (length 25-40 mm)
  • 1.25 mm threaded guide wire
  • Image intensifier
  • If necessary, contrast medium for arthrography
minimally invasive cannulated screw fixation

Anesthesia and positioning

General anesthesia is recommended and a sterile tourniquet should be available. Muscle relaxation is not necessary.

The patient is placed supine with the arm draped up to the shoulder.

See also the additional material on preoperative preparation.

minimally invasive cannulated screw fixation

3. Reduction and fixation

Planning of the entry point

In the AP view, a line is drawn from the most prominent part of the visible capitellum and perpendicular to the fracture.

The arm is positioned in a clear lateral view and a line is drawn from the posterior metaphyseal fragment to the anterior cortex (as illustrated).

The crossing point of these two lines on the skin is the entry point for the guide wire.

minimally invasive cannulated screw fixation

Skin incision and approach to the bone

A small (5 mm) skin incision is made using a pointed knife.

minimally invasive cannulated screw fixation

The wound is deepened by blunt dissection using a small artery forceps, down to bone contact.

minimally invasive cannulated screw fixation

Guide wire insertion for cannulated screws

A 1.25 mm threaded guide wire is used for the cannulated screw.

The guide wire is inserted by hand until it has good bone contact.

minimally invasive cannulated screw fixation

The guide wire is then advanced 1-2 mm inside cartilage of the capitellum.

The position and direction are checked in AP and lateral views using an image intensifier.

minimally invasive cannulated screw fixation

Once the position and direction are correct, the guide wire is advanced as far as the anterior cortex in a lateral view.

minimally invasive cannulated screw fixation

Screw insertion

The appropriate screw length and size can be determined in two different ways:

  1. By using a measuring device
  2. By positioning a second guide wire, of the same length, with its tip on the bone at the entry point and measuring the difference between the protruding lengths of the two wires

Note: According to the posterior/anterior orientation of the guide wire, the cortex is perforated in the AP view, not on the medial border, but almost centrally in the humerus.

minimally invasive cannulated screw fixation

The screw is passed by hand over the guide wire, the screw driver is placed over the guide wire, and the screw is fully inserted.

minimally invasive cannulated screw fixation

The screw positon and fragment compression are verified using image intensification.

minimally invasive cannulated screw fixation

The small incision is closed with one suture or a strip.

13 e 41l

4. Postoperative care

Note: According to the age of the child, plaster cast or posterior splint immobilization for two weeks (for pain management) can be useful. In children of school age, an arm sling is sufficient. Depending on the level of pain, early movement is allowed for gentle daily activities only.

minimally invasive cannulated screw fixation

Note: In any case of elbow immobilization by plaster cast, careful observation of the neurovascular situation is essential both in the hospital and at home.

See also the additional material on postoperative infection.

It is important to provide parents with the following additional information:

  • The warning signs of compartment syndrome, circulatory problems and neurological deterioration
  • Hospital telephone number
  • Information brochure

If the child remains for some hours/days in bed, the elbow should be elevated on pillows to reduce swelling and pain.

minimally invasive cannulated screw fixation

The postoperative protocol is as follows:

  • Discharge from hospital according to local practice (1-3 days)
  • First clinical and radiological follow up, depending on the age of the child, is undertaken 4-5 weeks postoperatively
  • In most cases, at this first control, the child is able to move the elbow through a nearly normal range
  • During the first clinical follow-up parents/carers should be informed about the timing of implant removal
  • Physiotherapy is normally not indicated

Screw removal

The screw can be removed after 2-3 months. Screw removal can be performed as a day case under light general anesthesia.