A fixator is an external fixation device used in orthopedic surgery to stabilize bone fragments. This apparatus is applied outside the body to hold fractured or surgically altered bones in a fixed position, promoting healing without internal hardware at the injury site. The device is a mechanical system designed for temporary or definitive skeletal stabilization. Its primary function is to maintain proper alignment, length, and rotation of the bone segments.
The Components and Biomechanics of Fixation
The external fixator system consists of pins, a frame, and connecting clamps that create a rigid, stabilizing framework outside the limb. Pins or wires, often called Schanz pins or half-pins, are surgically inserted through the skin and soft tissues directly into the bone fragments. These pins often have specialized threads or coatings to enhance their grip within the bone tissue and prevent loosening.
The external frame is constructed using rods, bars, or rings made of materials like carbon fiber or metal, connected to the pins via specialized clamps. This scaffolding acts as a rigid support structure, resisting forces that would otherwise displace the bone fragments. Stability is determined by mechanical factors, including the diameter and number of pins used, and the distance between the pins, the bone, and the frame.
The frame counteracts bending, rotational, and compression forces by distributing them across the external framework, thus protecting the healing bone. This design allows surgeons to achieve fracture immobilization without extensive surgical exposure of the fracture site. Minimizing surgical trauma preserves the blood supply to the bone, which is beneficial for the healing process.
Specific Indications for External Fixators
External fixators are often the preferred method of stabilization when internal fixation is compromised or impossible. A primary indication is the temporary stabilization of severe trauma, known as damage control orthopedics. The fixator is rapidly applied to align the bone and stabilize the patient until they are medically stable enough for a definitive procedure.
The device is valuable for open fractures, where the bone is exposed, and in injuries with significant soft tissue swelling or contamination. Since the frame is external, medical staff have immediate access to wounds for frequent dressing changes, cleaning, and monitoring. This access is important for preventing deep infection.
External fixation also serves as a definitive treatment for conditions like infected non-unions, where a fracture has failed to heal and is complicated by chronic infection. Beyond trauma, fixators are indispensable for elective procedures such as limb lengthening and complex deformity correction. In these cases, the frame is used to gradually and precisely adjust the bone’s position over weeks or months.
Major Configurations of Fixators
External fixators are broadly categorized into two main structural configurations. Monolateral or unilateral fixators feature a straight bar or rail positioned along one side of the limb, connected to the bone using half-pins. This configuration is simple, less bulky, and commonly used for temporary stabilization in trauma or for fractures requiring stability primarily in a single plane.
The other major type is the circular or ring fixator, associated with the Ilizarov technique and modern derivatives. These frames consist of full or partial rings that encircle the limb, attached to the bone using thin, tensioned wires and half-pins. The circular design provides greater multi-planar stability and is primarily used for complex limb reconstruction.
Circular frames use a system of adjustable struts between the rings, allowing for precise, dynamic adjustments to the bone alignment over time. This controlled, gradual distraction stimulates new bone formation, known as regenerate bone. This capability allows for complex correction, including gradual limb lengthening and multi-axial deformity correction.
Patient Care and Management
Proper patient care is paramount because the pins penetrate the skin, creating a direct pathway for bacteria. Pin site hygiene is the most important aspect of daily care, typically involving cleaning the insertion sites with an antiseptic solution or saline. This meticulous cleaning helps prevent pin-tract infection, which is the most common complication associated with external fixation.
Patients must manage the discomfort and pain associated with the device, especially during the adjustment phase of a lengthening or correction procedure. Medications are often prescribed, and patients may be advised to take pain relief before performing daily adjustments. Physical therapy is initiated early to prevent joint stiffness and muscle atrophy, as many fixators allow for movement of adjacent joints.
The frame remains in place until the bone has fully consolidated, a process that can take many months, particularly after a lengthening procedure. Frame removal is typically performed under light sedation or a short general anesthetic. A cast or brace may be applied afterward for a short period to protect the newly healed bone as the patient returns to normal activity.