Authors of section

Editors

Peter Kloen, David Ring

Executive Editors

Peter Trafton, Michael Baumgaertner

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Radius, extraarticular, oblique - Lag screw

1. Principles

Lag screw principles

In oblique fractures of the radial neck, fixation is achieved by lag screws. Longer oblique fractures allow two screws. This is more secure, and should be preplanned.

The thread pulls the opposite bone fragment towards the head of the screw, placing the fracture ends under compression. The portion of the thread in the gliding hole does not purchase in the surrounding bone. Insert the lag screw(s) as perpendicularly to the fracture plane as possible.

Note: Lag screw fixation may prove unsatisfactory for short oblique fractures of the radial neck. If so, plate fixation may be required.

radius extraarticular oblique lag screw

Choice of implant

1.5 mm, 2.0 mm, 2.4 mm or 2.7 mm screws are used.

2. Reduction and provisional fixation

Expose the fracture ends with minimal soft tissue dissection off the bone. Irrigate to remove debris and interposing tissues.

Reduction is direct, aided by supination-pronation of the forearm. Reduce and provisionally fix the fracture with the help of small pointed reduction forceps.

If reduction is difficult to achieve without subluxation, rule out ulnar malreduction as the cause.

Oblique radial neck – lag screw principles

3. Lag screw insertion

Drilling

Drill a gliding hole (sized according to chosen screw size, see fig.) for the lag screw into the proximal fragment.

Insert the appropriate drill sleeve into the gliding hole until it reaches the far cortical bone.

Now drill the far cortex with the appropriate drill bit.

Oblique radial neck – lag screw drilling

Measuring

Measure the depth of the hole with the hook of the depth gauge pointing distally.

Oblique radial neck – lag screw hole depth

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

Oblique radial neck – lag screw insertion

Second lag screw

If the fracture configuration allows the insertion of a second lag screw, it can be inserted now, using the same technique as described above.

Oblique radial neck – lag screw fixation

4. Final assessment

Finally, assess the range of motion in pronation, supination, flexion and extension. Fixation should be stable and crepitus or restricted motion should be absent. Radiocapitellar and ulnohumeral joints should remain located through a full range of motion.

Check fracture and screws with image intensifier or x-ray.