Davos Courses

Executive Editor: James Hunter General Editor: Fergal Monsell

Authors: Andrew Howard, Peter Schmittenbecher, Theddy Slongo

Pediatric proximal forearm 21r-E/3 + 21r-E/4

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Glossary

1 General considerations top

Radial head lag screw enlarge

Fixation principles for the radial head

Choice of fixation depends on the size of the fragment and on the degree of comminution. A lag screw or screws, or a headless screw with variable pitch, will provide the most stable fixation because compression can be achieved. (See also the lag screw principles.)

For smaller fracture fragments K-wires may be used, or bioabsorbable pins if available. (See also the K-wire principles.)

Because the radial head is completely covered by articular cartilage the screw heads must be countersunk just below the level of the articular cartilage.

The screw tip must not protrude medially, as it will contact the ulna and interfere with supination/pronation.


Radial head lag screw enlarge

In the last two years of growth do not hesitate to place implants across the growth plate and into the metaphysis if required to achieve fracture stability.

2 Screw positioning top

Radial head lag screw - Screw positioning enlarge

For the insertion of the screws, choose a location in the radial head that causes the least compromise of full pronation and supination (see below). Insert the screw(s) as perpendicularly to the fracture plane as possible.


Radial head lag screw - Safe zones enlarge

Safe zone for screw insertion

To determine the location of the “safe zone”, place reference marks along the radial head and neck, to mark the midpoint of the visible bone surface. Place three such marks with the forearm in neutral rotation (A), full pronation (B), and full supination (C) as shown in the illustration. The posterior limit of the safe zone lays halfway between the reference marks A and B made with the forearm in neutral rotation and full pronation. The anterior limit lays nearly two thirds of the distance between the neutral mark A and the mark made in full supination C.

Note: The nonarticulating portion of the safe zone for the application of implants to the radial head (or safe zone for prominent fixation) consistently encompasses a 90° angle localized by palpation of the radial styloid and Lister’s tubercle.

3 Choice of implant top

Radial head lag screw - Screw selection enlarge

1.5 mm up to 2.7 mm screws, or headless compression screws (Herbert or similar screws) are used.

With smaller fracture fragments or higher degrees of comminution, fixation with K-wires or bioabsorbable pins may be preferred.

4 Patient preparation and approach top

Patient preparation enlarge

Patient preparation

This procedure is normally performed with the patient in a supine position.


Lateral approach enlarge

Approach

For this procedure a lateral approach is normally used.

5 Reduction and preliminary fixation top

Radial head lag screw - Reduction enlarge

Reduction of stable fractures

In minimally displaced and stable fractures, there is no need to open the fracture site. Use a tamp to correct the displacement.


Radial head lag screw - Reduction of unstable fractures enlarge

Reduction of unstable fractures

In unstable fractures, open the fracture site to clear out soft tissue, hematoma and interposed fragments.

Expose the fracture ends with minimal soft-tissue dissection.

If the radial head has been dislocated posteriorly, confirm that it is satisfactorily reduced to the capitellum.


Radial head lag screw - Temporary fixation enlarge

Reduction is achieved directly.

If the annular ligament is still intact, cut and retract it to achieve better access to the fracture site.

Reduce and provisionally fix the fracture with the help of small pointed reduction forceps and one or two K-wires.

Anticipate the final screw position prior to temporary K-wire placement.

6 Headless compression screw top

Radial head lag screw - Headless compression screw enlarge

Insertion of guide pins

Ideally direct the screw perpendicular to the fracture plane.

Guide pins for the screws are used to achieve preliminary fixation.

If one screw is used place the guide pin centrally in the small fragment. If two screws are planned place both guide pins before inserting the first screw.


Radial head lag screw - Headless compression screw enlarge

Insertion of screw

When headless compression screws (eg Herbert or HCS) are used, there is no need for countersinking as the screw head engages inside the bone.

Compression is based on variable thread pitch. The distal threads should therefore cross the fracture and completely engage the opposite fragment.

7 Alternative: lag screw top

Radial head lag screw - Screw sizes enlarge

Screw and drill sizes

Plan the number and location of screws.


Radial head lag screw - Drilling enlarge

Drilling

Drill a gliding hole into the free fragment with the appropriate drill, determined by the screw size.


Radial head lag screw - Drilling enlarge

Insert the appropriate drill sleeve into the gliding hole until it reaches the fracture plane.


Radial head lag screw - Drilling enlarge

Drill the epiphysis of the intact radial head with the appropriate drill bit.


Radial head lag screw - Countersinking enlarge

Countersinking and measuring

It may be necessary to countersink the cartilage covering the free fragment to prevent protrusion of the screw head.

Measure the depth of the hole and place the screw. If self-tapping screws are not available, tap the far epiphysis with the appropriate cortical tap and protection sleeve.

Note: Always measure after countersinking to prevent penetration of the screw tip into the joint.


Radial head lag screw insertion enlarge

Lag screw insertion

Closely observe the compression effect on the fracture line while tightening the lag screw.

Any K-wire(s) should be removed just before the final tightening of the screw.


Radial head lag screw enlarge

Second lag screw

If fragment size permits, a second lag screw will improve strength of fixation. Insert it as described for the first screw.

Note: Check reduction and screw length with supination/pronation exam. The screws should not obstruct rotation.

8 Fixation of small fragments top

Radial head fractures - Fixation of small fragments enlarge

A fragment that is too small or comminuted to be fixed by a screw can be stabilized by one or two K-wires. If two K-wires are used they should diverge.

If K-wires are used they are typically bent and cut and left beneath the skin. They must be removed before full motion can be restored.

Bioabsorbable pins may be used instead to avoid a second operation for K-wire removal.

Very small fragments may require excision.

9 Ligament repair and wound closure top

Radial head lag screw - Ligament repair enlarge

Repair the annular ligament using non-absorbable sutures.

Close the wound in layers with resorbable sutures.

10 Final assessment top

Radial head lag screw - Checking supination/pronation enlarge

Check supination/pronation. The fixation should be stable. Crepitus or restricted motion should be absent.

Check fracture reduction and fixation with image intensifier or x-ray.

v1.0 2019-08-19