Restore Stability & Motion: Fixation of Fracture-Dislocations

Comprehensive Introduction and Patho-Epidemiology

Simple dislocations of the elbow, characterized by a loss of ulnohumeral congruency without associated fractures, can most often be treated successfully with closed means. The standard of care involves prompt concentric reduction, short-term immobilization (typically less than one week), and the immediate initiation of early active motion to prevent debilitating stiffness. However, fracture-dislocations of the elbow represent a vastly more troublesome clinical entity, demanding a high index of suspicion, sophisticated preoperative planning, and, almost invariably, operative intervention. These complex injuries typically involve disruptions of both the primary osseous stabilizers and the secondary ligamentous restraints, creating a profoundly unstable joint that will rapidly subluxate or redislocate if managed nonoperatively.

The most notorious of these complex instability patterns is the "terrible triad" of the elbow, a term coined by Hotchkiss to describe a posterior elbow dislocation associated with fractures of both the radial head and the coronoid process. This specific constellation of injuries obliterates the anterior, lateral, and valgus buttresses of the elbow. Historically, the terrible triad was associated with dismal outcomes, characterized by chronic instability, severe arthrosis, and profound stiffness resulting from prolonged cast immobilization in a desperate attempt to maintain joint reduction. The contemporary principle of treating fracture-dislocations of the elbow is to provide sufficient mechanical stability through meticulous reconstruction of bony and ligamentous restraints such that early motion (within 2 weeks postoperatively) can be safely instituted without the risk of recurrent instability.

The pathogenesis of elbow fracture-dislocations typically involves high-energy trauma, such as falls from a significant height, motor vehicle collisions, or falls onto an outstretched hand (FOOSH) during sporting activities. The mechanism of injury follows a predictable cascade of soft tissue and osseous failure, classically described by O'Driscoll as the "Circle of Horii." This sequence begins laterally and progresses medially as the forearm is subjected to a combination of axial loading, supination, and valgus stress. As the patient falls, the body rotates internally against the planted hand, applying a supination torque to the forearm that sequentially strips the lateral collateral ligament (LCL) complex, disrupts the anterior and posterior capsule, and finally compromises the medial collateral ligament (MCL).

When an axial load is superimposed upon this rotational force, the radial head is driven into the capitellum, resulting in a shear or impaction fracture. Concurrently, as the humerus is driven anteriorly over the ulna, the coronoid process impacts the trochlea, fracturing the anterior buttress of the ulnohumeral joint. A variant mechanism involving a varus posteromedial rotational force leads to a different injury pattern: the anteromedial facet fracture of the coronoid, combined with an LCL avulsion, leading to varus posteromedial rotatory instability. Recognizing the specific forces at play—whether valgus-posterolateral or varus-posteromedial—is absolutely critical for the operating surgeon, as it dictates the surgical approach and the specific structures requiring repair.

Detailed Surgical Anatomy and Biomechanics

A profound understanding of elbow anatomy and biomechanics is the bedrock of successful surgical management. The elbow is a highly constrained, modified hinge joint relying on a delicate interplay between primary and secondary stabilizers. The primary stabilizers include the highly congruent ulnohumeral articulation, the anterior bundle of the medial collateral ligament (MCL), and the lateral collateral ligament (LCL) complex. Posterolateral dislocations of the elbow are universally associated with disruption of the LCL and, in severe cases, the MCL. The MCL is the primary stabilizer to valgus stress. It originates from the anteroinferior surface of the medial epicondyle and inserts onto the sublime tubercle at the base of the coronoid.

The LCL complex, specifically the lateral ulnar collateral ligament (LUCL), is the primary stabilizer against posterolateral rotatory instability (PLRI). The LUCL originates from the lateral epicondyle, sharing a footprint with the common extensor origin, and inserts onto the supinator crest of the proximal ulna. Most often, the LCL disruption occurs as a proximal avulsion from the lateral epicondyle of the humerus, which creates a characteristic, easily identifiable "bare spot" during surgical exposure. Less commonly, the ligament may rupture midsubstance or avulse from its ulnar insertion. Secondary restraints on the lateral side that may also be disrupted include the common extensor origin and the posterolateral capsule, both of which must be meticulously repaired to restore lateral tension.

The radial head serves as a crucial secondary stabilizer to valgus stress and posterior translation, particularly when the MCL is compromised. It also functions as a longitudinal stabilizer of the forearm, preventing proximal radius migration. Radial head fractures have been classically described by the Mason classification: Type I (small or marginal fracture with minimal displacement), Type II (marginal fracture with displacement), Type III (comminuted fractures of the head and neck), and Type IV (radial head fracture associated with elbow dislocation—the Johnson modification). In the setting of a fracture-dislocation, the radial head must never be excised without replacement; doing so in the absence of a competent MCL and coronoid will universally lead to catastrophic recurrent instability.

Coronoid fractures are equally critical to evaluate, as the coronoid provides the anterior buttress preventing posterior subluxation of the ulna. These have been traditionally classified by Regan and Morrey: Type I (tip avulsions, often representing capsular avulsions rather than true osseous stabilizers), Type II (less than 50% of the coronoid height), and Type III (more than 50% of the coronoid, often involving the sublime tubercle and MCL insertion). However, modern biomechanical understanding emphasizes the anteromedial facet fracture, a distinct entity caused by a primary varus force. The medial facet is paramount for varus stability of the elbow. These fractures are inherently unstable and are best treated with open reduction and internal fixation utilizing a medial buttress plate, as failure to recognize and stabilize the anteromedial facet will lead to rapid articular wear and chronic varus instability.

Exhaustive Indications and Contraindications

The natural history of elbow fracture-dislocations treated nonoperatively is unacceptably poor. Closed treatment invariably leads to a failure to maintain concentric reduction, resulting in chronic subluxation, rapid onset of post-traumatic osteoarthritis, and profound functional deficits. Therefore, the presence of a fracture-dislocation of the elbow—specifically the terrible triad or a varus posteromedial rotatory instability pattern—is an absolute indication for surgical intervention. The overarching goal of surgery is to obtain and maintain a concentric, perfectly stable reduction of both the ulnohumeral and radiocapitellar joints, allowing the patient to safely initiate a flexion-extension arc of 30 to 130 degrees within two weeks postoperatively.

While surgery is indicated in almost all cases of complex elbow instability, the timing of the intervention requires clinical judgment. Acute surgical intervention (within 7-10 days) is highly recommended to prevent the severe soft tissue contractures and heterotopic ossification that complicate delayed reconstructions. If a joint is completely dislocated and cannot be reduced closed in the emergency department, emergent operative intervention is required to relieve tension on the neurovascular bundle and prevent irreversible cartilage necrosis. Repeated, forceful attempts at closed reduction should be strictly avoided, as they exacerbate soft tissue trauma, strip remaining periosteal hinges, and significantly increase the risk of massive heterotopic ossification.

Contraindications to immediate surgical fixation are relatively few but clinically significant. Patients who are medically unstable or polytraumatized with life-threatening injuries (e.g., severe traumatic brain injury, massive hemorrhage) must be stabilized prior to orthopedic reconstruction. In such damage-control scenarios, the elbow should be reduced, splinted, or temporarily spanned with a static external fixator. Severe local soft tissue compromise, such as extensive blistering, open wounds with gross contamination, or active infection, represents a relative contraindication to immediate definitive internal fixation. In these cases, a staged approach utilizing temporary external fixation and delayed definitive osteosynthesis is the safest course of action.

Pre-Operative Planning, Templating, and Patient Positioning

Meticulous preoperative planning is the cornerstone of a successful surgical outcome in elbow fracture-dislocations. High-quality plain radiographs in the anteroposterior (AP) and lateral planes must be obtained before and after any closed reduction attempts. However, cast material and overlapping osseous structures often obscure critical bony detail. Therefore, computed tomography (CT) scanning with thin cuts, multiplanar reformatted images, and three-dimensional (3-D) reconstructions is considered the gold standard and is mandatory for surgical planning. 3-D CT allows the surgeon to precisely understand the size, comminution, and spatial orientation of the coronoid and radial head fragments, dictating whether primary osteosynthesis is feasible or if arthroplasty will be required.

Before the patient enters the operating theater, the surgeon must ensure that a comprehensive armamentarium of implants is available. Coronoid fractures may require small fragment screws, cannulated headless compression screws, or specialized mini-fragment buttress plates. For the radial head, standard mini-fragment plates and countersunk Herbert screws should be available for osteosynthesis. Crucially, a modular, metallic radial head arthroplasty system must be in the room and ready for use. If a comminuted radial head (typically >3 fragments) cannot be robustly fixed to withstand early motion, the surgeon must immediately pivot to replacement. Attempting heroic but flimsy fixation of a severely comminuted radial head in a terrible triad injury is a common pitfall that leads to early fixation failure and recurrent instability.

Patient positioning must be carefully selected based on the anticipated surgical approaches and the potential need for intraoperative fluoroscopy. Most commonly, the patient is positioned supine on the operating table under general anesthesia, with the operative limb supported on a radiolucent hand table. A sterile tourniquet is applied to the proximal arm to provide a bloodless field. This position provides excellent access for a lateral approach and allows for easy extension to a medial approach if necessary. The arm can be freely manipulated to assess stability under fluoroscopy.

Alternatively, the lateral decubitus position can be utilized, with the operative limb supported by a padded bolster or a dedicated arm positioner. This position is particularly advantageous if the application of a dynamic hinged external fixator is deemed highly likely based on preoperative imaging, as it provides unimpeded access to the axis of rotation for pin placement. Furthermore, the lateral decubitus position facilitates a universal posterior skin incision, allowing the surgeon to elevate full-thickness fasciocutaneous flaps to access both the medial and lateral aspects of the joint simultaneously without repositioning. Regardless of the position chosen, an examination under anesthesia (EUA) should be performed prior to incision to document the specific arcs of instability.

Step-by-Step Surgical Approach and Fixation Technique

Surgical Approaches

The lateral approach is the workhorse for the treatment of terrible triad injuries, providing access to the LCL complex, the radial head, and, in many cases, the coronoid. A direct lateral incision is made, typically utilizing the Kocher interval between the anconeus and the extensor carpi ulnaris (ECU). However, the astute surgeon will often abandon formal anatomic intervals and instead utilize the traumatic dissection that occurred at the time of injury. In most cases, the LCL and common extensor origin have been avulsed from the lateral epicondyle, creating a massive traumatic window directly into the joint. If an anteromedial facet fracture is present, a separate medial incision is utilized. The medial approach involves identifying and protecting the ulnar nerve, followed by splitting the flexor carpi ulnaris (FCU) or utilizing an "over-the-top" approach anterior to the medial epicondyle to gain orthogonal access to the coronoid.

The Standardized Fixation Protocol

Management of elbow fracture-dislocations must follow a rigid, established protocol, pioneered by Pugh and Schemitsch, working from deep to superficial and from inside out.

Step 1: Fix the Coronoid Fracture. The coronoid is addressed first, often through the lateral traumatic window after the fractured radial head fragments have been temporarily excised or retracted. Small transverse tip fractures (Type I) are often capsular avulsions and can be secured using heavy nonabsorbable sutures passed through the anterior capsule and tied over the dorsal aspect of the proximal ulna via drill holes (the "capsular lasso" technique). Larger fragments (Type II) can be fixed with retrograde cannulated screws from the dorsal ulna. Anteromedial facet fractures demand a medial approach and rigid fixation with a mini-fragment buttress plate to resist varus shear forces.

Step 2: Fix or Replace the Radial Head. Once the anterior buttress is restored, attention turns to the radial column. If the radial head fracture consists of two or three large, non-comminuted fragments, osteosynthesis is performed using countersunk headless compression screws or a low-profile "safe zone" plate. If the fracture is highly comminuted, radial head arthroplasty is mandatory. The radial head implant must be carefully sized; "overstuffing" the radiocapitellar joint will lead to capitellar wear, lateral elbow pain, and a failure to regain terminal flexion and extension. The implant should track smoothly against the capitellum and sit flush with or slightly proximal to the lateral edge of the intact coronoid.

Step 3: Repair the LCL Complex. With the osseous stabilizers reconstructed, the lateral ligamentous tension must be restored. The avulsed LUCL and common extensor origin are repaired back to their anatomic footprint on the lateral epicondyle—the isometric point located at the center of capitellar curvature. This is typically achieved using robust suture anchors or transosseous bone tunnels. The repair must be tied with the forearm in pronation and the elbow at 90 degrees of flexion to ensure appropriate tensioning of the lateral structures.

Step 4: Assess Intraoperative Stability. Following LCL repair, the elbow is taken through a gentle range of motion. The surgeon must assess stability within a functional arc of 30 to 130 degrees of flexion-extension with the forearm in full pronation. If the joint remains concentrically reduced without subluxation or gapping on fluoroscopy, the procedure is concluded.

Step 5 & 6: Address Residual Instability. If the elbow demonstrates residual valgus instability or posterior subluxation during the functional arc, the surgeon must proceed to Step 5: exploration and repair of the MCL via a medial approach. If, after MCL repair, the joint remains unstable (a rare occurrence if the osseous anatomy was correctly restored), Step 6 is invoked: the application of a dynamic hinged external fixator. This highly specialized device maintains concentric reduction while allowing for early, protected motion, neutralizing deleterious shear forces during the critical early phases of ligamentous healing.

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