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Proximal ulna fracture dislocations encompass a spectrum of injuries defined by the presence of a fracture to the proximal ulna and associated subluxation or dislocation of the ulnohumeral joint and/or the proximal radioulnar joint. These injuries are important to understand as they usually require surgical management and are associated with a high rate of complications particularly when treated incorrectly.
Several terms are currently used to describe the myriad of injuries that fall under the umbrella term “proximal ulna fracture dislocation” including “Monteggia variants,” “trans-olecranon fracture dislocations,” and “ulna basal fracture dislocations” to name a few.
Classification of any injury should ideally be simple, descriptive of all variations, guide management, and be of prognostic value; however, currently used classification systems for these injuries either concentrate on one aspect of the injury such as the coronoid or olecranon, or at the other extreme are too complex for use in clinical practice.[1] [2] [3] [4] [5] Furthermore, only a few of the current systems robustly report interobserver reliability or demonstrate prognostic value.[3] [4] [6]
These issues with classification can lead to confusion for surgeons as they try to “name” the fracture rather than concentrate on understanding the pathoanatomy of a particular injury and how this affects surgical planning and execution. This is reflected by studies that demonstrate a high complication rate following treatment of these injuries.[7]
It became apparent while treating patients and analyzing their imaging that our thought process should move away from overarching classification and toward achieving a better anatomic understanding of the injuries we are faced with. We found that by looking at these injuries more critically with this mindset led to better outcomes for the patients and improved our ability to teach others.
It was, hence, our aim to rationalize this approach by developing a framework that I could use as a basis to share my thoughts.
We named the system CURL (coronoid, ulna, radial head, ligaments) ([Fig. 1]) because it was felt that these were the key anatomic components that determined patient outcome and were important to recognize and quantify as they directly influence surgical planning in terms of implant choice, surgical approach, and patient positioning.
Fig. 1 The coronoid, ulna, radial head, ligaments (CURL) framework. The four critical components of a proximal ulna fracture dislocation (coronoid, ulna, radial head, ligaments) can be subdivided into intact, simple, or complex based on the individual injury characteristics. Copyright: Joideep Phadnis.Indeed, in a prognostic study of 182 patients that is pending publication we demonstrated the presence of a coronoid, radial head, or ligament injury was all independently associated with inferior outcome and that the presence of multiple CURL components was associated with inferior patient reported outcome. In a separate study, we have also demonstrated CURL to have strong inter- and intraobserver reliability both overall and for each individual component.
For a given injury, not all CURL components are present (apart from the ulna that is a prerequisite of a proximal ulna fracture dislocation), and if present they are injured to differing extents. While it is tempting to name each subtype of fracture for the radial head or coronoid for instance, what really matters is knowing if that component is injured and if it can be fixed with standard techniques or may require adjunctive methods. Hence, within CURL, each component is subclassified as either “simple” or “complex.” In this way, every possible injury that falls under the umbrella term of “proximal ulna fracture dislocation” is included, but in a very simple and logical way. Simple fractures are essentially noncomminuted fractures such as a transverse olecranon fracture or a partial articular radial head fracture, whereas complex fractures are those with comminution, multiple fragments, or bone loss. This distinction is crucial for surgical planning. For example, a comminuted radial head fracture will require a radial head prosthesis to be available and the mere presence of a coronoid fracture may push surgeons to position the patient supine rather than lateral to allow a more optimal exposure.
The coronoid comes first in CURL as it is the component that affects outcome most when mismanaged. It is also the component that most surgeons have least experience of treating and can be overlooked with detrimental consequences.
Our understanding of coronoid fractures has evolved steadily over the past 15 years thanks to work by some of the pioneers of elbow surgery.[8] We much better understand that the coronoid acts not only as a bony buttress but is also crucial in providing rotatory and varus stability to the ulnohumeral joint. The coronoid is particularly important in the context of a proximal ulna fracture dislocation as when present it tends to be large, often termed a basal fracture, and should not be ignored by the surgeon. Because of the size of fracture, the coronoid fragment frequently includes the sublime tubercle and insertion of the anterior bundle of the medial collateral ligament (MCL). The MCL itself remains uninjured and consequently the relationship of the sublime tubercle to the medial trochlea is preserved. Even in a highly complex fracture dislocation this may be the only normal anatomy with the rest of the forearm falling away from the coronoid ([Fig. 2]). Hence, we advocate that the thought process should be to bring the forearm back to this fragment by prioritizing it with independent fixation separate to the dorsal ulna plate.
Fig. 2 A “simple” coronoid fracture typically includes the sublime tubercle. The medial collateral ligament is intact and note how the forearm has fallen away from the coronoid fragment that remains correctly articulated with the medial trochlea.The ulna fracture is ubiquitous but highly variable. It can range from a “simple” two-part olecranon fracture to a “complex” multifragmentary articular and metaphyseal fracture that has bone loss and cortical blow-out fragments. When the ulna fracture is complex, the surgeon needs to have a variety of techniques and implants available to help achieve reduction, a congruent greater sigmoid notch and stable fixation.
The radial head is known to be an important valgus stabilizer of the elbow, but in a proximal ulna fracture dislocation its role as a longitudinal stabilizer of the forearm is even more crucial due to the relative increase in load when the ulna is badly fractured. For this reason, we have a lower threshold to replace the radial head in these injuries to guarantee a stable lateral column. Judging correct radial head prosthetic length can be a challenge when the proximal ulna fracture includes comminution of the lesser sigmoid notch and care is required to get this right. We typically prepare the radial head implant, place a trial, and then provisionally reduce the ulna to confirm length and alignment before committing to the definitive prosthesis.
The bony components of CURL are readily identified and categorized on preoperative computed tomographic scans that are essential for planning; however, the presence of concurrent ligamentous injury is more difficult to predict. Nevertheless, this component is included in CURL to make surgeons think about the collateral ligaments which when unrecognized or mismanaged can lead to poor outcome. A “simple” ligament injury constitutes one of the collateral ligaments being torn. Invariably, this is the lateral collateral ligament (LCL) as the MCL is rarely torn in isolation. A “complex” ligament injury denotes that both LCL and MCL are torn. The presence of an LCL injury may be predicted when a lateral epicondyle avulsion or supinator crest fragment is seen on preoperative imaging. The latter is much more common in proximal ulna fracture dislocations compared with other forms of elbow instability. When a LCL injury is suspected preoperatively, it should be looked for intraoperatively and stabilized. While the MCL is rarely torn in isolation and can be tolerated better than the LCL if all other structures are stabilized, the exception to the rule is the “complex” injury where both LCL and MCL are torn. The cardinal feature of this injury on preoperative imaging is when the proximal ulna is fractured, but in addition, the distal humerus is also dislocated outside the greater sigmoid notch and has no congruity with the coronoid ([Fig. 3]). Experience has shown that this injury is not uncommon in older patients and in these cases, consideration should be given to treating both ligaments.
Fig. 3 An example of a patient with a “complex” ligament injury. Note how on both the anteroposterior X-ray and the three-dimensional computed tomography reconstruction, the distal humerus is dislocated outside the greater sigmoid notch in addition to the proximal ulna fracture with no congruency with the coronoid.It is important to remember that the intention of CURL is to promote a framework of thinking for these injuries. The intention is not to create another classification or to help score or name a particular injury, but rather to utilize CURL as a planning and decision-making algorithm. The individual components of CURL can be managed using multiple techniques, but awareness of their presence and importance is key.
We would recommend applying this pathoanatomical approach to all orthopaedic injuries and advocate a move away from nomenclature for the sake of it.
Publication HistoryArticle published online:
26 December 2023
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