1 General considerations top
Isolated coronoid fractures are extremely rare. The coronoid is almost always fractured in association with a dislocation of the ulnohumeral joint. Repair of the coronoid fracture may be necessary for restoring elbow joint stability after fracture dislocation.
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. Most involve avulsion of the anterior elbow capsule. Particularly deceiving are small anteromedial coronoid fractures , which may be associated with posteromedial subluxation of the elbow. Coronoid tip fractures, in isolation, may not produce elbow instability. Generally, the larger the coronoid fragment, the greater its 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 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, a separate medial collateral ligament tear will be identified during a medial approach. If so, it should be repaired.
Coronoid fractures may be approached from laterally, through the site of a radial head or neck fracture, or medially by reflection of the flexor-pronator muscle origin (protect the ulnar nerve). Either approach can be an extension of the posterior approach. Additionally, coronoid fractures associated with olecranon fractures can sometimes be reduced and fixed via the olecranon fracture site, through a posterior approach.
This x-ray shows screw fixation of a coronoid fracture, via medial approach with epicondylar osteotomy.
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. Alignment must be checked with satisfactory x-rays or image intensifier.
Fixation principles according to fracture type
Transverse fractures (O’Driscoll 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 (O’Driscoll 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 subluxation, are best fixed with an anteromedial plate.
Basilar fractures (O’Driscoll 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.
2 Suture repair topenlarge
In small type I and II, and multifragmentary, fractures of the coronoid process, the fragments with joint capsule 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 the coronoid fragment(s) and if possible through the capsule that is attached to it.
Place a cross suture in the brachialis tendon at its insertion.
Drill holes for sutures
Drill two holes with the drill aimed from the dorsal aspect of the ulna into the bed of the fractured coronoid, close to the articular surface.
Reduction and fixation
Pass the sutures through the holes with a suture passer.
Reduce the fragments and tie the sutures.
3 Fixation of larger, simple coronoid fracture topenlarge
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 lag screws.
Use a washer at least in one of the lag screws.
This is difficult because of the soft-tissue anatomy in this area. 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 topenlarge
For larger anteromedial facet coronoid fractures (O’Driscoll type II), an anteromedial plate with or without additional lag screws provides good stability. This requires a medial exposure.
The forces acting on the fractured coronoid fragments are axial distraction by the brachialis and anterior shearing forces created by the distal humerus pushing forward. The anterior plate counteracts these shearing forces (buttress effect), increasing stability and permitting early motion. This can be done with a properly contoured three-hole one-third tubular plate.
5 Fixation of Type III coronoid fracture topenlarge
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.
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.
Occasionally, a small comminuted fragment may require suture fixation as described above.