Sterile Field Kit Components

Commercially available sterile field kits allow for placement of an external fixator by hand and typically consist of the following components:

1. Scalpel
2. Mosquito clamp
3. Pins
4. Bars
5. Manual drill-brace: Serves dual function as hand drill as well as tightener for clamps; each end is labeled for reference (“pin end” and “clamp).
6. Bar-to-bar and/or Pin-to-bar clamps
7. Pin connectors: Not available in every kit. May come pre-assembled with angel wing.

Basic principles:

1. Two pins (at least) are required on each end of the fractured bone.
2. Pins should avoid immediate proximity to the fracture site (at least 2-3 fingerbreadths away).
3. The external fixator is a tool to reduce fractured bone. Try to restore length and gross alignment.

Minimum Supplies: 4 threaded pins, 2 pin connectors, 2 bars, 2 angel wings (4 suggested), 4 bar-to-bar clamps. Note: Fluoroscopy is beneficial but not essential.

Step-By-Step Instructions (Associated photos for a knee spanning external fixator)

Pin Placement

1. Identify external fixator pin sites as described above, taking care to remain in safe zones.
   - Femur: Anterior or anterolateral
   - Tibia: Just medial to anterior tibial crest (ridge)
   - Calcaneus (heel): 1-2 fingerbreadths in front of (anterior) and above (proximal) to the posterior corner of the heel. Drill centrally-threaded pin from medial to lateral to avoid posterior tibial artery.
2. Start either proximal or distal to fracture.
3. Identify 1st pin site, use scalpel to make stab incision (7-10mm).
4. Use a blunt hemostat to dissect down to bone (keep tips of hemostat closed).
5. Insert pin perpendicular to bone (Figure 1).
   - **Pearl: To drill the tibial pins, it can be helpful to start drilling perpendicular to the bone and create a divot without going all the way through the cortex, then redirect your hand so it is pointing toward the floor. This may help avoid slippage of the drill.
6. Place pin bicortically—when using a power drill to insert pins be wary of excessive depth of the pin that can damage deep structures. If inserting by hand and/or without power, once the far cortex is engaged (when increased resistance is felt as the pin is turned), advance the pin an additional 6-8 full turns to reach a safe depth. When fluoroscopic imaging is available, placing pins with power is safe and effective. Hand-inserted pins can be adjusted at follow on facilities when needed.
7. If the pin clamps are going to be used, slide pin connector over 1st pin to template location of 2nd pin and mark skin with pin or knife (Figure 2). If clamps are not available or desired, placing the pins in any safe location is possible followed by connection to bars with pin-bar or combination clamps.
8. Repeat steps 3-6 for 2nd pin. Placing the pin parallel to the first can reduce the complexity of the fixator, but off-plane pins can increase stability. Pin placement should be decided based on the associated anatomy, fracture and soft tissue injury patterns and fixator stability (Figure 3).
9. Move to proximal (or distal) pin site and repeat steps 1-8 (Figure 4).
10. Tighten down the screws securing the pins of the proximal and distal pin connectors, ensuring there are 2-3 finger-breaths between the pin connectors and the skin. This is important because swelling will often occur and may lead to skin compromise if the skin is too close to the pin connector. Putting the pin connector too far from the skin, however, will decrease the stability of the construct (Figure 5).
11. If fluoroscopy is available, confirm safe, bicortical position of all pins. The drill tip of the pin should be advanced to a depth allowing full engagement of the cortex with the threaded portion of the pin. A few of the threads of the pin should be penetrating through the second cortex.

External fixator Assembly

1. Place angel wings onto pin connectors and tighten all components into place with the hand tightener; this includes tightening all screws of the pin connector so that both the pins and the angel wings are secured. (Figure 5)