Asif M. Ilyas and Jesse B. Jupiter
DEFINITION
Capitellar fractures are uncommon, accounting for less than 1% of all elbow fractures and 6% of all distal humerus fractures.3
They often are associated with radial head fractures and posterior elbow dislocations.
A classification system for capitellar fractures has been proposed by Bryan and Morrey3 and modified by McKee:
Type 1: complete fractures of the capitellum11
Type 2: superficial subchondral fractures of the capitellar articular surface22
Type 3: comminuted fractures2
Type 4: coronal shear fractures that include a portion of the trochlea as well as the capitellum as one piece17 (FIG 1)
Ring and Jupiter21 have proposed a new classification, expanding on the growing understanding that isolated capitellum fractures are rare and often are involved as part of articular shear fractures of the distal humerus. The classification includes five anatomic components:
The capitellum and lateral aspect of the trochlea
The lateral epicondyle
The posterior aspect of the lateral column
The posterior aspect of the trochlea
The medial epicondyle
FIG 1 • Type 4 coronal shear fractures of the distal humerus. (Adapted from McKee MD, Jupiter JB, Bosse G, et al. Coronal shear fractures of the distal end of the humerus. J Bone Joint Surg Am 1996;78A:49–54.)
ANATOMY
The two condyles of the distal humerus diverge from the humeral shaft to form the lateral and medial columns, which support the trochlea between them. The anterior aspect of the lateral column is covered with articular cartilage, forming the capitellum. Distally, these two condyles can be visualized as forming a triangle at the end of the humerus.
The capitellum is the first epiphyseal center of the elbow to ossify.
It is covered by articular surface anteriorly but devoid of it posteriorly.
The capitellum is directed distally and anteriorly at an angle of 30 degrees to the long axis of the humerus.
The radial head rotates on the anterior surface of the capitellum in elbow flexion and articulates with its inferior surface in elbow extension.
The lateral collateral ligament inserts next to the lateral margin of the capitellum.
The blood supply of the capitellum is derived posteriorly. It arises from the lateral arcade, which is the anastomosis of the radial collateral arteries of the profunda brachii and the radial recurrent artery.23
PATHOGENESIS
Capitellar fractures usually result from a fall on an outstretched hand or forearm as the radial head impacts the capitellum on impact.
Capitellar–trochlear shear fractures involve impaction of the radial head against the lateral column of the distal humerus in a semi-extended position, resulting in a shearing mechanism of the distal humerus.
Fracture fragments vary in size and displace superiorly and anteriorly into the radial fossa, resulting in impingement with elbow flexion.
NATURAL HISTORY
Capitellar fractures occur almost exclusively in adults. These fractures do not occur in children, because in that age group the capitellum is largely cartilaginous, and a similar mechanism of injury would instead cause a supracondylar or lateral condyle fracture.
Capitellar fractures are more common in females, a finding that has been attributed to the higher carrying angle of the elbow.
Elderly patients of both genders are more susceptible to capitellum and complex capitellar–trochlear shear fractures because of the metabolic susceptibilities of osteoporosis.
Displaced fractures that go untreated can have a poor outcome owing to progressive loss of motion and posttraumatic arthrosis.
PATIENT HISTORY AND PHYSICAL FINDINGS
Symptoms of capitellar fractures are similar to those of radial head fractures, including pain and swelling along the lateral elbow and pain with elbow motion.
Although there may be variable loss of forearm rotation, loss of flexion and extension is common, often accompanied by crepitus and pain.
The association of concomitant radial head fractures and ligamentous injuries with capitellar fractures is high.18
The shoulder and wrist should be examined for concomitant injury.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Standard radiography is inadequate for accurate assessment of capitellar fractures.
Lateral radiographs are best for obtaining an initial evaluation of capitellar fractures.
Anteroposterior views do not reliably show the fracture, because the outline of the distal humerus is not consistently affected.
The radial head–capitellum view can help identify fractures of the capitellum. This view is a lateral oblique projection taken with the x-ray beam pointing 45 degrees dorsoventrally, thereby eliminating the ulnoand radiohumeral articulation shadows.10
A type 1 fracture appears as a semilunar fragment sitting superiorly with its articular surface pointing up and away from the radial head in most cases.
Type 2 fractures are more difficult to diagnose, depending on the amount of subchondral bone accompanying the articular fragment. They may appear as a loose body lying in the superior part of the joint.
Type 3 fractures display variable amounts of comminution.
Coronal shear fractures show a characteristic “double arc” sign on lateral radiographic views (FIG 2A).
CT scans are necessary for delineating the fracture pattern and should be performed in all cases.
CT scanning of the elbow should be done at 1- to 2-mm intervals using axial or transverse cuts.
Three-dimensional (3D) CT reconstructions provide the best detail and ability to appreciate the anatomic orientation of the fracture patterns and should be ordered if 3D imaging is available (FIG 2B,C).
DIFFERENTIAL DIAGNOSIS
Radial head fracture
Distal humeral lateral condyle fracture
Elbow dislocation
NONOPERATIVE MANAGEMENT
Truly nondisplaced and isolated capitellum fractures can be splinted for 3 weeks, followed by protected motion. We do not advocate nonoperative management for any other type of capitellum fracture.
Closed reduction techniques, which have been described in the literature, should be performed with caution, and only complete anatomic reduction should be accepted.4,19
Capitellar–trochlear shear fractures should not be treated nonoperatively because of their inherent instability and articular incongruity.
SURGICAL MANAGEMENT
The goal of surgery is anatomic reduction and fixation of the fracture to allow for early motion without mechanical block.
Long-term goals are pain-free and maximal motion with minimal stiffness.
Capitellar fractures are uncommon, and the wide array of treatment options presented in the literature is based on relatively small series.
Treatment options include closed reduction,4,19 open excision,1,8,16 open reduction and internal fixation (ORIF), and arthroplasty.5,9
With the improvement in techniques for fixation of small fragments and management of articular surfaces, ORIF has become the mainstay of treatment.
Advantages of ORIF include restoration of anatomy and stability.
Disadvantages include stiffness and failed fixation.
In elderly patients, we do consider total elbow arthroplasty for complex intra-articular distal humerus fractures.
Advantages include early return to function and motion.
Disadvantages include functional limitations.
Preoperative Planning
Before proceeding with surgery, a thorough understanding of the fracture and its orientation should be obtained with the help of a CT scan, and, if possible, 3D reconstructions.
FIG 2 • A. Characteristic “double arc” sign on lateral radiographs of coronal shear fractures. B,C. 3D CT reconstructions of a coronal shear fracture of the distal humerus.
The timing of surgery is important. Fractures preferably should be approached within 2 weeks, before osseous healing sets in, but after swelling has gone down.
Ensure that the necessary implants and hardware are available.
Reduction and fixation of the fracture will require K-wires, articular or headless screws, and small-fragment AO screws.
An image intensifier should be used during surgery to confirm reduction of the fracture and proper positioning of implanted hardware.
Positioning
General anesthesia is recommended.
The patient usually is positioned supine on the operating table, with a radiolucent hand table.
Alternatively, a lateral or prone position can be considered, with the anterior surface of the elbow supported by a padded bolster to use the universal posterior approach.
Approach
Either a lateral or posterior midline incision should be used, depending on the nature of the fracture, followed by a lateral approach into the elbow joint.
Multiple intervals that can be exploited in the lateral approach to the elbow.
We advocate the Köcher approach, which uses the interval between the extensor carpi ulnaris and the anconeus and affords greater protection of the posterior interosseous nerve.
To increase exposure, the origin of the extensor carpi ulnaris (ECU), extensor digitorum communis, and extensor carpi radialis longus can be raised off of the lateral epicondyle anterior to its interval with the triceps.
In many cases, a capsular violation has occurred. This can be exploited and used as the interval to expose the fracture, thereby avoiding the need to cause an additional soft tissue defect.
TECHNIQUES
CAPITELLAR FRACTURES
Exposure
The incision should begin 2 cm proximal to the lateral epicondyle and extend 3 to 4 cm distal toward the radial neck.
If no large soft tissue or capsular defect is present, a direct lateral Köcher approach between the anconeus and ECU interval is recommended.
The common extensor origin is sharply raised off the lateral epicondyle and reflected anteriorly to expose the lateral elbow joint.
Care must be taken to avoid damage to the radial nerve traveling between the brachialis and brachioradialis.
Often the lateral ligamentous complex will be avulsed from the distal aspect of the humerus, with or without some aspect of the lateral epicondyle.
This ligamentous violation can be exploited to improve exposure by hinging open the joint on the medial collateral ligament with a varus stress.
The capitellar fracture usually is displaced proximally and rotated and has no soft tissue attachments.
Reduction and Fixation
The fragment is reduced under direct visualization, held with reduction tenaculums, and provisionally fixed with 0.045-inch K-wires from an anterior-to-posterior direction.
Internal fixation options include fixation from posterior to anterior with AO cancellous screws or from either direction with headless compression screws.
Cancellous screws are best for fracture fragments with a large subchondral component, as in type 1 fracture fragments. However, extending the dissection posteriorly around the lateral column theoretically increases the risk of osteonecrosis (TECH FIG 1).
Headless compression screws, such as the Herbert screw, are best for fragments with less subchondral bone, such as type 2 and small type 1 fracture fragments. The head of the screw must be buried below the articular surface.
TECH FIG 1 • Fixation of a type 1 capitellum fracture with a headless screw anteriorly and AO screws from posterior to anterior.
Excision of fracture fragments is recommended in type 2 fractures with small, thin articular pieces and type 3 comminuted fractures where the fragments are not amenable to internal fixation.
Fragment reduction and hardware position should be confirmed by image intensifier.
Unrestricted forearm rotation and elbow flexion– extension without mechanical block or catching should be confirmed intraoperatively.
If the lateral collateral ligament is found to be avulsed, it should be repaired back to the lateral epicondyle with drill holes and nonabsorbable no. 2 suture or suture anchors.
The capsule should be closed.
The retracted extensor origin should be relaxed and closed to the surrounding soft tissue.
CAPITELLAR–TROCHLEAR SHEAR FRACTURES
Exposure
A posterior midline incision should be made, and fullthickness flaps should be raised medially and laterally off of the extensor mechanism.
This incision provides extensile exposure, access to both sides, and ease of osteotomy if necessary (TECH FIG 2A).
Beginning medially, the ulnar nerve should be decompressed in situ behind the medial epicondyle (TECH FIG 2B).
Returning laterally, the interval between the anconeus and the ECU should be developed. In many cases, a capsular violation can be exploited (TECH FIG 2C).
The common extensor origin, including the ECU, extensor digitorum communis, and extensor carpi radialis longus, is then sharply raised off the lateral epicondyle and reflected anteriorly to expose the lateral elbow joint and improve visualization medially.
Care must be taken to avoid injury to the radial nerve proximally as it travels between the brachialis and brachioradialis, and to the posterior interosseous nerve distally when raising the ECU anteriorly. This may be done by keeping the forearm pronated.
In many cases, the lateral epicondyle will have avulsed off of the distal humerus, and this traumatic osteotomy can be exploited.
Otherwise, a formal lateral epicondyle osteotomy can be performed to enhance visualization while maintaining the integrity of the lateral ligamentous complex.
Additionally, an olecranon osteotomy may be performed to improve visualization and fixation of fractures extending medially and posteriorly.
The fracture fragments should now be visualized and accounted for. They are most commonly displaced proximally and internally rotated (TECH FIG 2D).
TECH FIG 2 • A. Posterior midline incision used to for capitellar–trochlear shear fractures. B. Ulnar nerve compression medially. C. Lateral approach to elbow taking advantage of violation of the capsule and extensor muscles at the level of the extensor carpi ulnaris (ECU) and anconeus. D. The fracture fragments tend to displace proximally and become internally rotated.
Reduction and Fixation
The fragment is reduced under direct visualization, held with reduction tenaculums, and provisionally fixed with 0.045-inch K-wires from anterior to posterior (TECH FIG 3A).
Inability to reduce the fracture anatomically may represent fracture impaction, requiring either disimpaction or bone grafting, or both.
Options for internal fixation include fixation from posterior-to-anterior with AO screws or from either direction with headless compression screws.
Cancellous screws are best when the fracture fragment has a large subchondral component, but they make it necessary to extend the dissection posteriorly around the lateral column, theoretically increasing the risk of osteonecrosis.
Headless compression screws, such as the Herbert screw, are best for fragments with less subchondral bone and provide the added benefit that they can be used in either direction, anteriorly or posteriorly. Diligence must be maintained to confirm that the head of the screw is buried below the articular surface when placed anteriorly.
Fragment reduction and hardware position should be confirmed by image intensifier.
Unrestricted forearm rotation and elbow flexion–extension without mechanical block or catching should be confirmed intraoperatively.
The lateral epicondyle, if avulsed or osteotomized, should be repaired with a tension band technique or plate and screws (TECH FIG 3A,B).
The capsule should be closed.
The interval and released extensor origin should be relaxed and closed to the surrounding soft tissue.
TECH FIG 3 • A. The fracture is reduced and pinned with 0.045-inch K-wires. B. Postoperative radiographs illustrate repair of the lateral epicondyle and fracture fixation.
PEARLS AND PITFALLS
POSTOPERATIVE CARE
If secure fixation has been obtained, immediate mobilization can be initiated postoperatively.
If fixation is tenuous, splint or cast the elbow for 3 to 4 weeks, followed by active and assisted range-of-motion exercises.
OUTCOMES
Focusing initially on outcomes after ORIF of types 1 and 2 capitellar fractures, multiple small series have shown good results using Herbert screws in an anterior to posterior direction.6,13,14,20
More recently, Mahirogullari et al15 reported on 11 cases of type 1 capitellum fractures treated with Herbert screws, which yielded 8 excellent and 3 good results. They recommended fixation in a posterior-to-anterior direction with at least two Herbert screws.
Reported outcomes on type 4 capitellar–trochlear shear fractures are limited. McKee et al17 originally described this pattern and reported on 6 cases.
Each case involved an extended lateral Köcher approach and fixation with Herbert screws from an anterior to posterior direction. Good or excellent results were achieved in all cases, with average elbow motion of 15 to 141 degrees, and forearm rotation of 83 degrees pronation and 84 degrees supination.
Ring and Jupiter examined 21 cases of articular fractures of the distal humerus treated with Herbert screw fixation and found 4 excellent results, 12 good results, and 5 fair results.
All of the fractures healed and had an average range of motion of 96 degrees. No ulnohumeral instability, arthrosis, or osteonecrosis was reported.
The authors stressed the importance of proper evaluation of these fractures and awareness that apparent capitellum fractures often are complex articular fractures of the distal humerus.21
Dubberley et al7 further subclassified type 4 fractures in their series of 28 cases. They achieved an average range of motion of flexion–extension of 25 degrees less than the contralateral elbow and 4 degrees of supination–pronation less than the contralateral elbow.
Two comminuted cases required conversion to a total elbow arthroplasty.
Varied fixation methods were used, including Herbert screws, cancellous screws, absorbable pins, and supplementation with K-wires.
COMPLICATIONS
The most common complication of capitellar fractures is loss of elbow motion and residual pain. The compromised motion most commonly is manifested in loss of flexion and extension.
Ulnar neuropathy has been noted after ORIF, and some recommend routine ulnar nerve decompression.21
Osteonecrosis may occur from the initial fracture displacement or surgical exposure. Blood is supplied to the capitellum from a posterior to anterior direction and may be compromised by surgical dissection.
In symptomatic cases in which revascularization after fixation has not occurred, delayed excision is indicated.
Malunions may occur when the patient has delayed seeking treatment, when inadequate reduction or loss of closed reduction occurs, or after ORIF. Malunions result in loss of motion and may require excision of the fragment and soft tissue releases.
Nonunions may occur, although this is uncommon. They most likely result secondary to inadequate reduction or lack of revascularization of the fragment.
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