coronoid fractures

A 43-year-old, active man presents to your clinic with a chief complaint of elbow pain. He tells you that he came down awkwardly onto an extended arm the previous evening in a soccer game. He denies dislocating his elbow and says he was able to finish the game but also says that his arm felt strange, and he had to repeatedly “shake out” the elbow through the remainder of the game. Following the game he went to a local emergency department because of persistent pain, where x-rays were taken (Fig. 6–14). He was told by the Emergency Physician that there was only a very small fracture of his ulna and likely nothing to worry about. He was given a

sling and told to follow-up with you.

 

 

 

Figure 6–14

 

Multiple plain radiographic views of the elbow were reviewed and there appears to be a small fracture of the coronoid with no other fractures identified. His elbow examination in clinic is difficult to interpret due to swelling and pain with stability examination, although there is slight laxity noted with varus stress despite his guarding.

What injury are you concerned about and what would be an appropriate imaging workup at this point?

1. Coronoid tip fracture; no further imaging as plain films are sufficient

2. Anteromedial facet fracture; order a CT of the elbow

3. MCL injury; order an MRI of the elbow

4. Coronoid tip fracture; order a CT of the elbow

 

Discussion

The correct answer is (B). The plain radiograph shows a fracture line through the tip of the coronoid process, however a fracture of the coronoid tip and one involving the anteromedial facet of the coronid can occasionally be difficult to differentiate on plain radiographs alone. The lack of a dislocation event in the clinical history and the varus laxity on clinical examination should raise suspicion for a fracture of the anteromedial facet of the coronoid. A fracture of the coronoid tip is more frequently associated with an elbow dislocation and valgus instability. It is suggested that a CT of the elbow be ordered to further characterize all coronoid fractures in order to determine an appropriate treatment plan. Above is a summary of the O’Driscoll classification of coronoid fractures in Table 6–2. The O’Driscoll

system differs from the classic Regan and Morrey system in that it focuses on the importance of the anteromedial facet rather than classifying strictly based on the level of the coronoid process fracture.

 

Table 6–2 O’DRISCOLL CORNOID FRACTURE CLASSIFICATION

 

Fracture	Subtype	Description
Tip	1	≤2 mm of cornoid height
	2	>2 mm of cornoid height
Anteromedial	1	Anteromedial rim
	2	Anteromedial rim and tip
	3	Anteromedial rim and sublime tubercle (± tip)
Basal	1	Cornoid body and base
	2	Transolecranon basal coronoid fracture

 

What type of elbow instability is associated with fractures of the anteromedial facet of the coronoid?

1. Varus posteromedial rotatory instability

2. Recurrent posterior elbow dislocations

3. Anteromedial instability

4. Posterolateral rotatory instability

 

Discussion

The correct answer is (A). The various types of coronoid fractures are associated with predictable elbow instability patterns. Coronoid tip fractures are frequently seen as part of a terrible triad elbow injury (LCL rupture, radial head fracture, and coronoid fracture), which often results in posterolateral rotatory instability (PLRI). Anteromedial facet fractures are seen when there is a varus force on the extended elbow, leading to failure of the LCL and impingement of the anteromedial coronoid under the trochlea. As up to 60% of the anteromedial facet is unsupported by the ulnar metaphysis, it is prone to fracture under strong varus force. It is important to recognize the sometimes subtle anteromedial facet fracture and accompanying varus instability, as this has been shown to progress to ulnohumeral arthritis when left untreated. Figure 6–15 depicts the three types of coronoid fractures as described by O’Driscoll, with “ii” outlining the various fractures of the anteromedial facet.

 

 

 

Figure 6–15 (Illustrated by David Beavers.)

 

Which of the coronoid fracture patterns listed warrants surgical fixation?

1. Transversely oriented tip fracture measuring 2 mm in height which is associated with posterolateral rotatory instability of the elbow (PLRI)

2. Base fracture involving approximately 60% of the coronoid height

3. Anteromedial facet fracture associated with varus instability

4. Fracture of the tip which measures 5 mm in height on plain radiographs which also show slight anterior elbow subluxation

5. All of the above fracture patterns warrant surgical fixation

 

Discussion

The correct answer is (E). Historically it was suggested that the coronoid process only needed to be addressed surgically if a fracture involved at least 50% of the process, however the importance of the coronoid as a contributor to elbow stability is now more understood. Any fracture of the coronoid, if associated with elbow instability, warrants surgical fixation. This includes very small tip fractures, which can be fixed with a suture lasso technique if they are too small to accept screw fixation. The only coronoid fractures which have acceptable outcomes with nonsurgical management are small fractures without associated elbow subluxation and without radiocapitellar joint opening on stress radiographs. This change in practice with respect to coronoid fractures is due to the high percentage of unacceptable clinical outcomes including chronic instability and early arthritis seen with nonsurgical management of coronoid fractures.

 

Objectives: Did you learn...?

 

Anatomy of the coronoid process?

 

 

Importance of recognizing elbow instability associated with coronoid fractures? Indications for operative management of coronoid fractures?