Michael W. Hartman
Scott P. Steinmann
Radial head fractures represent the most common fracture of the elbow in the adult population, accounting for 1.7% to 5.4% of all adult fractures. Approximately 85% of these fractures occur in young, active individuals ranging in age from 20 to 60 years old. Radial head fractures may occur in isolation or may be part of a more extensive traumatic elbow injury. An estimated 20% of all acute elbow injuries have an associated radial head fracture (Fig. 55-1). In elbow dislocations, a radial head fracture is commonly associated with other traumatic pathologies including medial collateral ligament (MCL) rupture, olecranon fracture, and/or coronoid fracture. Therefore, in the setting of trauma, the elbow must be carefully evaluated to rule out associated ligamentous and bony pathology.
Radial head fractures usually result from a fall onto the outstretched hand with the elbow slightly flexed and the forearm in a pronated position. Biomechanical studies have demonstrated that the greatest amount of force is transmitted from the wrist to the radial head when the elbow and forearm are oriented in this position. During a fall, the body rotates internally on the elbow; the weight of the body contributes an axial load to the radius; and a valgus moment is applied to the elbow since the hand becomes laterally displaced from the body. The resultant combination of axial, valgus, and external rotatory loading mechanisms forces the anterolateral margin of the radial head to come into contact with the capitellum, resulting in a fracture of the radial head and/or capitellum.
Surgical Indications and Other Options
The modified Mason classification is useful in predicting the surgical management of radial head fractures. Type I fractures include nondisplaced or minimally displaced fractures of the head and neck, fractures with intra-articular displacement of <2 mm, or marginal lip fractures. There should be no mechanical block to forearm rotation; however, rotation may be limited by acute pain and swelling. The mainstay of treatment of type I fractures involves nonoperative measures that encourage early elbow and forearm range of motion. In the acute setting, the elbow hemarthrosis should be aspirated and injected with local anesthetic to allow a better assessment of forearm rotation, improve patient discomfort, and encourage earlier range of motion. The patient is placed into a sling for comfort and instructed to begin active and passive range of motion as tolerated within 7 days. Protected weight bearing of the upper extremity for a period of 6 weeks is encouraged to prevent fracture displacement. Serial x-ray views are obtained on a weekly basis to assess for fracture displacement. Open reduction internal fixation (ORIF) is indicated if the fracture displacement subsequently occurs. Good to excellent results are expected in most type 1 fractures managed nonoperatively with a program of early elbow and forearm range of motion.
Type II fractures include displaced (>2 mm) fractures of the radial head or neck without severe comminution. These fractures may have mechanical block to motion or be incongruous. Nonoperative management of type II fractures should be considered only if elbow stability is not dependent on fracture fixation and no significant block to elbow motion is present. In the absence of comminution, these fractures are usually amenable to ORIF (Fig. 55-2). Recent data suggest that ORIF should be reserved for minimally comminuted fractures with three or fewer articular fragments.1 These data also suggest that fracture-dislocations of the elbow or forearm managed with ORIF result in less optimal results, especially with regard to forearm rotation. Other surgical options for type II fractures include fragment excision, head excision, or radial head replacement arthroplasty. Fragment excision alone may be indicated when a fracture fragment blocks forearm rotation but is too small, comminuted, or osteoporotic to adequately gain fixation (Fig. 55-3). The fracture fragment should not involve the lesser sigmoid notch or involve more than one third of the circumference of the head's articular surface. Most elbow surgeons discourage fragment excision because of the possibility of subsequent radial head subluxation.
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Figure 55-1 Type III radial head fracture. A: Anteroposterior view. B: Lateral view. |
Type III fractures include severely comminuted radial head or neck fractures that are deemed unreconstructable based on radiographic and/or intraoperative appearance. Surgical options include radial head excision with or without radial head replacement arthroplasty. Prosthetic head replacement is indicated under associated conditions of instability such as complex elbow instability, Essex-Lopresti lesion, Monteggia lesion with instability, or a fracture of a major portion of the coronoid (Fig. 55-4).
Radial head excision alone may be indicated in elderly, low-demand patients without ligamentous instability. Numerous series report good to excellent results in terms of pain relief and elbow range of motion after head excision alone. The potential disadvantages of head excision include decreased grip strength, weak forearm rotation, and radial shortening with resultant wrist pain. Altered load transfer at the elbow joint may also lead to the development of early ulnar trochlear arthrosis and elbow pain. When compared with head excision, results of metal prosthetic radial head replacement demonstrate similar range of motion, better clinical scores, less proximal radial migration, and decreased elbow arthritis (Fig. 55-5).
Surgical Techniques
Preoperative planning is essential in the surgical management of radial head fractures. A full selection of internal fixation and reconstructive options should be available at the surgeon's disposal. Options for internal fixation include various combinations of threaded K-wires, screws, and plates. The ultimate goal of these hardware devices is to obtain rigid fixation and hence, allow early postoperative range of motion. The surgeon should be prepared to replace the radial head if indicated, preferably with a metallic prosthesis. The patient is positioned supine on the operating table and general or regional anesthesia is administered. A sandbag is placed under the ipsilateral scapula to facilitate positioning of the upper extremity across the chest. Prophylactic antibiotics are administered 30 minutes prior to making the incision. An examination under anesthesia is performed prior to prepping and draping the involved extremity. Examination under anesthesia is absolutely essential in evaluating elbow and forearm stability and range of motion prior to proceeding. A skin incision is centered laterally over the lateral epicondyle and extended distally over the radial head and neck. Alternatively, a posterior elbow incision just lateral to the tip of the olecranon may be used in complex injuries in which access to the radial head, coronoid, medial collateral ligament, and/or lateral collateral ligament may be required (Fig. 55-6). Full-thickness flaps are developed down to the level of the fascia.
The classic approach to the radial head uses the Kocher interval between the anconeus and extensor carpi ulnaris. This approach is disadvantageous for two reasons. First, the approach tends to expose the radial head too posteriorly, making internal fixation of the commonly fractured anterolateral head difficult, if not impossible. Second, iatrogenic injury to the lateral ulnar collateral ligament is difficult to avoid and may lead to posterolateral rotatory instability. An alternative approach that splits the extensor digitorum communis is the preferred approach. This approach is more anterior and hence avoids disruption of the posterolateral
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collateral ligamentous complex (Fig. 55-7). The lateral epicondyle is identified, and the elbow capsule is elevated subperiosteally off its anterior aspect. Anterior capsular elevation is continued distally to the level of the capitellum and elbow joint taking care to avoid the collateral ligamentous complex posteriorly. Dissection next proceeds through the annular ligament exposing the radial head. If the fracture involves only the radial head, minimal distal (1 to 2 cm) dissection is usually necessary. If the radial neck is involved, further distal exposure is required. The forearm is fully pronated and the posterior portion of the extensor digitorum communis is divided. To avoid placing the posterior interosseous nerve at risk, distal dissection should not proceed more than two fingerbreadths from the radial head. If the location of the posterior interosseous nerve is in doubt, definitive identification of the nerve may be required.
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Figure 55-2 A: Lateral radiograph of fracture dislocation of elbow type II fracture radial head. B: Anteroposterior radiograph type II fracture radial head. C: Postoperative view: pin and screw fixation of radial head fracture (lateral view). D: Postoperative view: pin and screw fixation of radial head fracture (anteroposterior view). |
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Figure 55-3 Attempted screw fixation of radial head fracture. |
Once sufficient exposure is obtained, the character of the fracture is thoroughly assessed. The capitellum is also visually assessed for the presence of an associated chondral injury or osteochondral fracture. The decision to proceed with fragment excision, head excision, ORIF, or radial head replacement arthroplasty can be made at this point. At the time of closure, the annular ligament and the posterolateral collateral ligament complex (if disrupted) are repaired. The fascial layer over the common extensor group is closed to augment lateral elbow stability. Elbow and forearm range of motion and stability are carefully assessed and recorded.
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Figure 55-4 Radial head fracture type III with associated coronoid fracture. The radial head was replaced with a prosthesis and the coronoid fracture repaired with suture (second smaller, posterior incision). |
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Open Reduction Internal Fixation
The concept of an anatomic “safe zone” must be understood when attempting hardware placement into the radial head. Hardware may be placed into this zone without causing impingement of the proximal radioulnar joint. The safe zone is defined by a 110-degree arc centered anterolaterally over the equator of the radial head with the forearm in neutral rotation. Alternatively, one may identify the safe zone as a 90-degree arc defined by the right angle from the radial styloid to the Lister tubercle. Surface anatomy can also help to identify the proper location for hardware placement.
Once the fracture has been reduced, K-wires may be used for provisional fixation. K-wires should be absolutely avoided for definitive fixation given their tendency for migration postoperatively. For fractures that do not involve the radial neck, definitive fixation is typically obtained by using small screws (sizes 1.5, 2.0, or 2.7 mm) and 3.0-mm cannulated screws. Screws should be countersunk beneath the articular surface but not protrude through the opposite cortex. Fractures involving the radial neck are often impacted and require bone grafting to elevate the radial head. These fractures may be amenable to screw and/or plate fixation. One technique that has been successful in the authors' experience avoids the inherent problems associated with plate fixation for impacted neck fractures. In this technique, the radial head is first elevated to its anatomic position and temporarily secured using threaded K-wires. Screws are then placed obliquely from the radial head proximally to the opposite cortex of the radial neck distally. This arrangement may be likened to a bar stool in which the seat (the radial head) is supported by the eccentrically
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arranged legs (the screws). The resultant bony defect in the radial neck secondary to impaction is filled with autogenous bone graft or bone graft substitute. This technique has several advantages over plate fixation for radial neck fractures. First, screws are less bulky than plates and may decrease annular ligament impingement. Second, placement of screws generally requires less dissection and periosteal stripping, which may lessen the amount of blood supply disruption to the neck and decrease risk of injury to the posterior interosseous nerve. These advantages should theoretically result in decreased postoperative stiffness, painful hardware, heterotopic ossification, proximal radioulnar synostosis, and nonunion rates. If plate fixation is chosen, low-profile plates are necessary given the close proximity of the annular ligament and paucity of overlying soft tissues. Minicondylar L-plates, T-plates, and fixed-angled blade plates are all available for radial head and neck fixation.
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Figure 55-5 A: Type III radial head fracture. Attempt at open reduction internal fixation was unsuccessful. B: Radial neck has been prepared for implantation of radial head prosthesis. |
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Figure 55-6 Postoperative photograph of posterior incision for radial head fracture. This is the standard approach used by the authors because of the pleasing cosmetic result. |
There are few studies comparing internal fixation devices. A recent biomechanical study compared the average stiffness of several radial neck fracture plate fixation constructs axially loaded in compression.2 The study demonstrated statistically greater stiffness with a 2.7-mm T-plate modified with a fixed-angle blade when compared with a 2.0-mm T-plate and 2.0-mm fixed-angle blade. The investigators also noted increased proximal screw hole toggle when a fixed-angle device was not used. Contouring of the plate to the radius was observed to be the most important factor affecting overall construct stiffness. In another biomechanical study, investigators found no statistically significant difference in fixation stiffness when a low-profile blade plate and 3.0-mm cannulated screws were compared, but both constructs were statistically stiffer when compared with a 2.7-mm T-plate.3
Radial Head Replacement Arthroplasty
For all practical purposes, metal radial head prostheses have replaced silicone radial heads as the implant of choice in radial head replacement arthroplasty. When compared with metal radial heads, silicone implants are associated with worse clinical scores, increased elbow arthritis, and increased radial shortening. Furthermore, silicone implants are associated with increased failure secondary to fracture, fragmentation, and production of silicone synovitis. Both monoblock and modular radial head prostheses are now available. Anthropometric studies of cadaver proximal radii demonstrate that the head is inconsistently elliptical in shape, the head is variably offset from the axis of the neck, and the head diameter correlates poorly with the diameter of the medullary canal of the neck.4 These findings may support the use of modular implants that allow improved sizing options that more closely approximate the anatomy of the proximal radius.
The radial head is approached in the manner previously described. The annular ligament is incised transversely to expose the radial head. The appropriate radial head resection guide is used to determine proper alignment and resection level. The neck should be osteotomized proximal to the bicipital tuberosity. The medullary canal of the proximal
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radius is then prepared with a starter awl, burrs, and broaches to accept the implant. Exposure may be improved by applying varus stress and placing the forearm in supination. Serial sized broaches are used until a snug fit is obtained in the canal at the appropriate depth. The appropriate-sized trial stem is inserted, ensuring that the collar of the prosthesis is flush with the resected neck. In modular designs, the trial head is secured to the trial stem, and the elbow and forearm are placed through a full arc of motion. Tracking as well as the relationship between the prosthesis and the capitellum are carefully assessed. Once acceptable alignment and tracking are determined, the trial components are removed and the final prosthesis is inserted. The stem may be press-fit or cemented in place depending on the design and stability of the stem in the medullary canal. The head is inserted over the taper of the stem and secured using an impactor. Final assessment of motion and stability of the elbow and forearm is performed.
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Figure 55-7 A: Type III fracture. Severe comminution noted at surgery. Surgical approach involved posterior skin incision with split of the extensor digitorum communis (EDC) tendon origin to gain exposure. B: Radial head prosthesis. Note metallic head centered on capitellum. |
Conclusion
Radial head and neck fractures are common injuries that require a thorough understanding of elbow anatomy and biomechanics for proper management. The goals of current management are aimed at restoring the normal anatomic and biomechanical relationships of the elbow in an effort to prevent the development of elbow stiffness, instability, and arthritis. Preservation of the radial head should be attempted in fractures that are amenable to internal fixation. Severely comminuted fractures that are not salvageable should be managed with radial head replacement. Regardless of the type of fracture and chosen method of management, a program of early range of motion should be incorporated.
References
Suggested Readings
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