Technique Spotlight: Static, Hinged, and Internal Elbow Joint Fixators

Indications

Damage to bony, muscular, and ligamentous structures from injuries such as simple but unstable elbow dislocations or fracture-dislocations may result in elbow instability. Attempts to repair these structures may not address the resultant elbow instability. When instability persists, the use of an elbow fixator may be necessary to maintain ulnohumeral joint reduction and/or protect the repaired structures. Elbow fixators may also be indicated for instability compounded by delayed treatment. When dislocated elbows remain unreduced for >2 weeks, elastic forces (laxity) from fibrosing soft tissues must be overcome and the joint often requires supplemental stabilization to maintain reduction. Patients undergoing surgery for elbow contracture or heterotopic ossification may require extensive soft tissue release or excision resulting in instability. Therefore the use of an elbow fixation device may be necessary.

Static elbow fixation methods include transarticular pinning and static external fixators. These stabilize but also completely immobilize the elbow joint. Static fixation is simple to apply but has considerable potential drawbacks such as cartilage necrosis, poor soft tissue maturation, and joint stiffness. Therefore they are best indicated for shorter periods of immobilization or when other methods are not available. Hinged external fixators and internal joint stabilizers are indicated when early motion is particularly desired or longer fixation times are needed. ^, Early joint motion has been documented to preserve cartilage integrity, improve the maturation and remodeling of healing ligaments, and prevent joint contracture. Hinged external fixators are indicated for distraction interposition arthroplasty, in which the joint is distracted and stabilized to minimize shear forces on the biological resurfacing.

Generally, all elbow fixation devices are relatively contraindicated in the presence of poor bone quality. Bone loss in the humerus or ulna may not allow the use of these devices. The use of transarticular pinning in pediatric patients should be avoided to avoid disturbing growth plates.

Preoperative Evaluation

The nature of elbow instability should be determined by evaluating the patient’s history, including the mechanism of injury and the magnitude of energy involved. Also, mechanical symptoms, prior elbow surgery, and peripheral nerve deficits must be investigated and documented. Understanding normal elbow stability is essential for formulating an effective treatment plan. The ulnohumeral articulation, medial collateral ligament (MCL), and lateral collateral ligament (LCL) are considered the primary static elbow joint constraints. The radiocapitellar articulation, joint capsule, and the common flexor and extensor tendon origins are considered secondary static constraints. Diagnostic maneuvers can help elucidate subtle instability patterns. Valgus instability, from injury to the MCL, can be identified through a valgus stress test. Posterolateral rotatory instability, resulting from injuries to the LCL, can be identified through the lateral pivot-shift test or posterolateral rotatory drawer test. Varus posteromedial rotatory instability can be identified through the gravity-assisted varus stress test. Instability can be acute, recurrent, chronic, or surgically induced.

Preoperative planning is enhanced by imaging. Radiographs in multiple views should be acquired to examine fracture pattern, bone defects, or joint malalignment. Computed tomography may also be used for high-resolution characterization of bony structures. Magnetic resonance imaging can be used to assess soft tissue and osteochondral structures. Ultrasonography can also be a valuable tool for identifying concomitant ligamentous damage.