Executive Editor: Peter Trafton, Michael Baumgaertner

Authors: Peter Kloen, David Ring

Proximal forearm Ulna, articular, coronoid

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Glossary

1 General considerations top

Preliminary remark

Isolated coronoid fractures are extremely rare and when seen, suspect a spontaneously reduced dislocation and look for elbow instability. The coronoid is almost always fractured in association with a dislocation of the ulnohumeral joint or a more complex proximal ulna or olecranon fracture. Repair of - even a small - coronoid fracture may be necessary for restoring elbow joint stability.


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Coronoid fractures occur in several patterns (described below). They must be assessed with care.

Fragments which appear small on a lateral x-ray may be larger than suspected. A CT is warranted to better determine the fragment’s exact size. Particularly deceiving are small anteromedial facet impaction fractures, which may be associated with posteromedial varus instability of the elbow. In general, the larger the coronoid fragment, the greater its potential effect on elbow stability.

The above x-rays, before and after reduction of a dislocated elbow, show a large coronoid fragment, still displaced after the elbow joint is reduced.


Associated ligament injuries

Coronoid fractures are often associated with ligament disruption. Lateral collateral ligament tears should be repaired routinely. The medial collateral ligament may be attached to a large coronoid fragment. Fracture fixation repairs the ligament in this case. Occasionally - with small anteromedial facet fractures and complete elbow dislocation - the medial collateral ligament is avulsed from the medial epicondyle and it can be repaired.


Surgical approach

Coronoid fractures may be approached from laterally, through the site of a radial head or neck fracture, or medially by reflection or splitting of the flexor-pronator muscle origin (protect the ulnar nerve). A medial epicondylar osteotomy is another - but seldom used - option. Either approach can be done thru and posterior skin incision. Additionally, coronoid fractures associated with olecranon fractures can sometimes be reduced and fixed via the olecranon fracture site, through a posterior approach.


Reduction

Anatomical reduction of a larger coronoid process fracture is important for elbow joint stability and congruity. This is particularly true, when the coronoid fracture is part of a comminuted olecranon fracture. Reduction may be visualized through the medially extended posterior incision, through the olecranon fracture site, or through a lateral incision if a proximal radius fracture can be retracted or an unsalvageable radial head fracture is replaced.

2 Fixation principles according to fracture type top

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Transverse fractures

Transverse fractures (Mayo type I) of the coronoid tip include the capsular attachment and average more than 1/3 of the total coronoid height. They may have smaller or larger bone fragments. Repair, usually with sutures, is necessary if the elbow is unstable.


Anteromedial facet fractures

Anteromedial facet fractures (Mayo type II) may be small or large. The small fractures are best repaired with suture reattachment of the capsule through a medial exposure. Larger fractures, often associated with varus posteromedial instability, are best fixed with an anteromedial buttress plate.


Basilar fractures

Basilar fractures (Mayo type III), typically one or two large fragments. These may often be repaired with lag screws through or beside a dorsal plate. A medially extended exposure may be necessary for reduction and fixation. Occasionally, an additional anteromedial plate may be required.

Irreparable coronoid fractures, because of extreme comminution and/or osteoporosis, are occasionally encountered. Restoration of elbow stability may require additional use of a hinged external fixator.

3 Lasso suture repair for small Type I coronoid (tip) fractures top

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Prepare tendon

In small type I and II, and multifragmentary, fractures of the coronoid process, the fragments with joint capsule and/or brachialis tendon can be reattached with sutures. For smaller anteromedial fractures, this requires a medial approach.

Pass one or two Nr. 2 or Nr. 5 nonabsorbable sutures through or around the coronoid fragment(s) and if possible through the capsule and/or brachialis tendon that are attached to it.


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Drill holes for sutures

Drill two holes with the drill aimed from the dorsal aspect of the ulna on either side of the crista into the bed of the fractured coronoid, close to the articular surface. The drill holes should be as wide apart as possible yet still be within the fracture bed.


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Reduction and fixation

Pass the sutures through the holes with a suture passer.

Reduce the fragments as well as possible and tie the sutures with the elbow in flexion. It is often not possible or necessary to have the fragments exactly reduced.


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Fixation of larger, simple coronoid fracture

In simple fractures where at least 50% of the coronoid process is involved, the fracture fragment may be reinserted and held with one or two 2.7 mm antegrade lag screws.

Use a washer at least in one of the lag screws.

Alternatively, the screws can be placed retrograde.

Note: Antegrade screws are difficult in this area because of the soft-tissue anatomy. The coronoid process is a very deep structure and it may be difficult to place the drill and screws optimally. Additional soft-tissue dissection is necessary, perhaps with flexor-pronator origin release using a medial epicondylar osteotomy.

4 Fixation of larger Type II coronoid fracture top

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Plate selection

The forces acting on the fractured coronoid fragments are proximal distraction by the brachialis and a distally directed shearing force created by the humerus pushing forward. An anterior plate counteracts the shearing force (buttress effect), increasing stability and permitting early motion.

For larger anteromedial facet coronoid fractures (Mayo type II), the following can be used:

  • Precontoured anatomic plate with or without additional lag screws
  • Properly contoured three-hole one-third tubular plate
  • T-plate

Selection of approach

A single midline posterior approach provides access to nearly the entire elbow. Alternatively, a medial approach can be used.

This decision depends on associated elbow fracture components that need treatment. For example, most fractures of the anteromedial facet have an associated LCL injury that needs repair. A midline posterior approach with elevation of medial and lateral flaps might be better in these cases.

Identify the ulnar nerve.

Decompress the ulnar nerve where it enters the flexor carpi ulnaris.

The anteromedial facet is best approached via the natural split in the flexor carpi ulnaris, between the two heads of this muscle.


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Reduction

Flex the elbow to relax the brachialis and thereby facilitate coronoid reduction.


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Reduce the coronoid and fix it temporarily with a pointed reduction clamp and/or a K-wire.


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Apply the buttress plate by inserting the proximal screw but not fully tightened.


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Rotate the plate so that it compresses against the anteromedial facet fragment.


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A second screw is then placed more distally to increase the stability of fixation, but not fully tightened.

Fracture compression is achieved, and fixation is completed by first fully tightening the proximal, then the distal screw.


Even if there is no screw in the fragment itself, the buttressing effect of the plate will prevent loss of fixation when the capsule pulls on the fragment in extension.

Note: Transposition (subcutaneous) of the ulnar nerve at the end is optional, but probably not needed.

5 Fixation of Type III coronoid fracture top

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In basilar coronoid fractures, usually associated with olecranon fracture dislocations, a single large fragment might be fixable with one or more small lag screws inserted in a postero-anterior direction. These may be through, or separate, from a posterior plate.


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Reduction

Open the fracture by reflecting the olecranon proximally.

Flex the elbow to relax the brachialis and thereby facilitate coronoid reduction.


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Fixation of large coronoid fragments

Reduce the coronoid and fix it temporarily with a pointed reduction clamp and/or a K-wire.

If it is not planned to fix the coronoid fracture with a lag screw through a plate, the coronoid is now fixed with either a threaded K-wire or a small lag screw inserted outside of the planned plate position.


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The olecranon fracture is then reduced and fixed with a plate.


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If not already fixed, the coronoid is now fixed with a small lag screw inserted through the plate.


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Fixation of comminuted coronoid

Comminution or instability may be addressed by adding an anterior plate over the front of the coronoid process (buttress effect) to increase the stability and allow early motion. This can be done with a contoured three-hole one-third tubular plate or a custom plate as described above.

Medial and/or lateral fragments can be buttressed onto the distal shaft with small plates (2.0/2.4/2.7) to augment stability and help with alignment and reduction.


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Occasionally, a small comminuted fragment may require suture fixation as described above. In this case, the suture is tied after the plate has been fixed.

v2.0 2018-04-30