Overview
External fixation is useful across trauma care, from damage control to definitive treatment. Its versatility allows use in many fractures, but it needs closer clinical and radiographic monitoring than internal fixation and should not be used when screws, plates or nails are more suitable (Campbell). Stability is relative, so healing occurs with callus (AO). In polytrauma it is a key part of damage control surgery because it gives rapid stabilization with minimal additional surgical trauma; other main indications are fixation in bone infection, deformity correction and bone transport (AO).
Indications (Campbell, AO)
There are no absolute indications; an unstable fracture with soft-tissue compromise that precludes safe internal fixation is a near-absolute indication (Campbell).
Accepted: severe type II and III open fractures; fractures with severe burns; fractures requiring later cross-leg flaps, free vascularized grafts or other reconstruction; certain fractures requiring distraction; fractures with severe bone loss; paired-bone fractures where equal length is important; limb deformity or lengthening; arthrodesis; infected fractures or nonunions; correction of malunion; unstable pelvic ring fractures.
Possible: damage-control orthopaedics; certain pelvic fractures or dislocations; open infected pelvic nonunions; reconstructive pelvic osteotomy; fixation after radical tumor excision with graft replacement; femoral osteotomies in children; fractures with vascular or nerve repair; limb reimplantation; multiple closed fractures; severely comminuted or certain intra-articular fractures; patients with head injuries or needing frequent transport; floating knee; fractures with associated ligament injuries.
Occasional: some closed long-bone fractures when reduction cannot be obtained safely by conventional means; periprosthetic fractures with limited bone stock.
Contraindications: extreme obesity precluding safe pin placement; noncompliance or refusal; patient unable to tolerate the procedure medically or psychologically.
(Adapted from Campbell Table 58.13.)
AO adds: open fractures with severe soft-tissue injury; closed fractures with severe contusion or degloving, where a temporary spanning frame outside the zone of injury and outside the future surgical field protects the soft tissues; articular fractures and fracture-dislocations as temporary treatment; bone and soft-tissue loss (acute shortening followed by distraction osteogenesis); and use as an indirect reduction tool during minimally invasive plating or nailing.
Frame Types (Campbell, AO, Rockwood)
Pin fixators: unilateral one-plane, unilateral two-plane (delta), bilateral one-plane (transfixion pins) and bilateral two-plane configurations (Campbell).
Ring fixators: complete or partial rings anchored with half-pins or tensioned 1.5-2.0-mm wires; hinged frames for nonunion and malunion (Campbell).
Hybrid fixators: tensioned wires and a ring (usually 3/4 ring) at the joint level combined with diaphyseal half-pins; used mainly in proximal and distal tibial fractures (Campbell, AO).
Hexapod (spatial) frames: six oblique struts calculated by software to correct multiplanar deformity simultaneously (Campbell, AO).
Hinged fixators: maintain reduction of unstable elbow injuries while allowing controlled motion (AO).
Spanning (joint-bridging) frames: damage control of complex articular fractures and fracture-dislocations; allow CT and planning while soft tissues recover (AO, Rockwood).
AO component systems (AO)
System | Tube/rod | Schanz screws |
|---|---|---|
Large | 11 mm | 4-6 mm |
Medium | 8 mm | 3-6 mm |
Small | 4 mm | 1.8-4 mm |
Mini (fingers) | 2 mm | K-wires and 2-mm Schanz screws |
Biomechanics: Factors Increasing Frame Stability
Factor | Effect |
|---|---|
Pin distance from the fracture | Closer = stiffer (AO) |
Pin spread within each main fragment | Wider = stiffer (AO) |
Bar (rod) distance from bone | Closer = stiffer (AO, Campbell) |
Number of bars | Two bars stiffer than one; double bars mainly resist AP bending (AO, Rockwood) |
Configuration | Uniplanar < A-frame < biplanar (AO); a unilateral biplanar delta frame has overall stiffness similar to a bilateral transfixion frame (Rockwood) |
Pin diameter | 5-6 mm in large bones; bending stiffness rises with the fourth power of pin radius, so a 5-mm pin is about 144% stiffer than a 4-mm pin (Rockwood) |
Number of pins | At least two pins in each main fragment (AO); additional half-pins increase stability (Campbell) |
Surgeon-controlled factors listed by Campbell: appropriate reduction, larger-diameter half-pins, decreased bone-to-rod distance, additional half-pins, increased pin spacing, pins in different planes and additional rods; these are balanced against keeping pins out of the zone of future internal fixation.
A pin hole larger than about 20-30% of the bone diameter markedly increases the risk of fracture through the pin hole; about 6 mm is the maximum pin size in adult bone without creating a stress fracture risk (Rockwood).
An unstable frame delays healing, and an overly rigid frame can also cause delayed union (AO).
Technique 58.6: Half-Pin Fixators, General Method (Campbell)
Handle the skin and soft tissues with care.
Make short longitudinal skin incisions along safe zones and reach bone by gentle blunt dissection.
Insert the appropriate drill sleeve and trocar. The pin should be no larger than one-third of the bone diameter.
Drill with a low-speed power drill, with pauses, irrigating the drill sleeve with saline.
Insert the pins by power through the soft-tissue sleeves, or by hand while avoiding toggling.
Thermal necrosis may initiate pin loosening and infection; predrilling reduces bone temperature by approximately 50%.
Clean pin sites daily with antibacterial soap and water or dilute peroxide and saline.
Cover with a light pressure dressing to minimize pin-skin motion.
Pin insertion details (Rockwood, AO)
Place the trocar and drill sleeve in the center of the bone under fluoroscopy, so the pin passes through the near cortex, the medullary canal and the far cortex; an eccentric (transcortical) pin is a stress riser and can cause fracture after frame removal (Rockwood).
The pilot hole should equal, or be slightly smaller than, the pin core diameter; a mismatch greater than about 0.4 mm can damage surrounding bone (Rockwood).
With self-drilling pins, advance until the threads engage the far cortex; the tip may protrude 2-3 mm beyond the far cortex, which matters where neurovascular structures lie on the bone (Rockwood).
Temperatures above about 50°C cause bone cell death; use cooling irrigation, low insertion speed and low force with either pin type (Rockwood).
A correctly placed pin sits fully in the far cortex without protruding beyond it (AO).
In metaphyseal bone self-drilling screws are safer because the drill hole may be hard to find again (AO).
Avoid nerves, vessels and tendons; never place pins into the joint or within capsular reflections; avoid the fracture hematoma and contused or degloved skin; measure Schanz screws for the planned frame (AO).
Release any skin tension around the pin with a small knife after insertion (Campbell, Rockwood).
Safe zones (Campbell, AO)
Structures at risk: the radial nerve in the distal half of the arm and proximal half of the forearm, the dorsal sensory radial nerve just above the wrist, and the anterior tibial artery and deep peroneal nerve at the junction of the third and fourth quarters of the leg (Campbell).
Meticulous use of fluoroscopy during pin insertion halves the risk of neurovascular injury; avoid pin penetration more than 2-3 mm beyond the cortex (Campbell).
In the tibia, pins need not be placed in the anterior crest; the anteromedial surface is a safe zone with adequate cortical thickness and low infection risk, whereas drilling the thick crest generates heat and the drill can slip. Distally, tibialis anterior and extensor digitorum tendons are at risk (AO).
Unilateral frames are usually applied anteromedially or medially in the tibia and anterolaterally or laterally in the femur (AO).
Technique 58.7: Circular Wire Fixators, General Method (Campbell)
In general, 1.5- and 1.8-mm wires need no incision or drill sheath; olive wires require a small skin incision only. Self-drilling-tip wires need no predrilling.
Use a low-speed power drill with frequent pauses (preferably an oscillating drill) or a hand drill.
Determine the safe angle for the transfixion wire at each cross-sectional level.
Stab the wire through skin and muscle to bone.
Drill the wire across both cortices with a low-speed drill.
When the wire emerges from the far cortex, drive it through the remaining soft tissues with a mallet, traversing tissue exactly as it lies; release the skin with a small incision if needed.
Fix the wires to the frame without bending them to meet the frame; small spacers may be needed.
Large fragments generally need two levels of fixation with two wires at each level.
Fix short fragments with one ring and a drop wire, or a wire offset from the main ring by a few centimeters.
Increase stability by increasing the angle between wires at each level, within anatomic constraints.
Modular Reduction Technique (AO, Rockwood)
Insert two Schanz screws in each main fragment, near the fracture but outside the zone of injury, at slightly different angles.
Connect the screws of each fragment to a separate tube or rod, creating a partial frame on each fragment; these act as reduction handles.
Connect the two partial frames with tube-to-tube clamps left loose.
Reduce the fracture in all planes, check clinically and fluoroscopically, then tighten the tube-to-tube clamps.
Damage Control Spanning Frames (Rockwood, AO)
Early spanning restores length by ligamentotaxis and reduces swelling; a delay of more than a few days may make displaced metaphyseal fragments irreducible and require larger incisions at definitive surgery (Rockwood).
Knee: a quadrilateral frame or simple monolateral frame across the knee for dislocations, distal femoral and tibial plateau fractures (Rockwood).
Ankle: a triangular construct with two or three mid-distal tibial pins and a centrally threaded calcaneal pin; add forefoot pins or a blocking bar to prevent rotation around the calcaneal pin, posterior subluxation and forefoot equinus (Rockwood).
Place pins outside the zone of injury and away from future incisions (AO).
Postoperative Management
Pin care: there is no universal standard. Saline with dilute hydrogen peroxide is commonly recommended for initial care; remove crusts, which stiffen the pin-skin interface. Ointments are not recommended. Apply compressive dressings immediately to limit pin-skin motion; these can be removed after 10 days to 2 weeks once pin sites have healed, after which showering is sufficient. If drainage develops, perform pin care three times a day (Rockwood).
Pin track infection occurs in up to 30% of patients (Campbell); a meta-analysis reported an overall risk of 27.4% for at least one pin-site infection (Rockwood). A persistently infected pin usually loosens; remove it and reinsert at another site (AO).
Weight bearing and dynamization: except for spanning and some special frames, partial weight bearing is allowed from the start and increased as healing progresses; partial or full weight bearing is the best and most effective method of dynamization (AO). Late gradual frame "build-down" with axial dynamization may stimulate healing, with careful radiographic monitoring (Campbell).
Prolonged rigid immobilization of adjacent joints (over 6-8 weeks) should be avoided because of ankylosis (Campbell).
Conversion to Internal Fixation (AO)
If conversion is planned, do it early, ideally within the first 10 days to 2 weeks, when complication risk is lower.
All pin sites must be clean if internal fixation will be placed near them; pin tracks older than 10-14 days are considered contaminated and need sterile cleaning and debridement.
If pin tracks are infected or sterility is doubtful, debride and allow a "pin holiday" of at least 10 days (splint immobilization) before internal fixation, with appropriate antibiotics.
Monitor closely for 6 weeks after conversion.
Complications (Campbell)
Pin track infection; neurovascular, muscle or tendon impalement; compartment syndrome.
Delayed union in 20-30% (up to 80%) with prolonged rigid definitive fixation because the frame unloads the fracture; dynamize over time.
Refracture after removal, because union is largely endosteal and the cortex becomes cancellized.
Adjacent joint stiffness; ankle osteoarthritis in 50-70% after tibial external fixation (risk factors: age over 45, BMI over 25, osteoporosis, fixation longer than 50 days, double-level transport).
Wire or ring breakage.
References
Whittle AP, Azar FM. General principles of fracture treatment. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Philadelphia: Elsevier; 2026. Chapter 58, Techniques 58.6-58.7.
Höntzsch D. External fixator. In: Buckley RE, Moran CG, Apivatthakakul T, eds. AO Principles of Fracture Management. 3rd ed. Stuttgart: Thieme; 2017. Chapter 3.3.3. (Turkish edition: AO Kırık Tedavisinin Prensipleri.)
External fixation. In: Tornetta P III, Ricci WM, Ostrum RF, McKee MD, Ollivere BJ, de Ridder VA, eds. Rockwood and Green's Fractures in Adults. 10th ed. Philadelphia: Wolters Kluwer; 2024. Chapter 11. (Turkish edition: Erişkin Kırıkları.)