External Fixation of the Humerus: Safe Pin Placement and Techniques

External fixation is a minimally invasive surgical procedure that uses pins or wires inserted into the bone to provide stability and support for a fractured or injured limb. This article discusses the safe pin placement sites for external fixation of the humerus, as well as the techniques involved in this procedure.

DR.MOHAMMAD HUTAIF, EMIAL

External Fixators: Components, Uses, and Pin Placement

External fixators are devices that stabilize fractures by connecting pins or wires inserted into the bone to external bars or rings. There are two types of pins or wires: transfixion pins or wires, which go through the limb and connect at both ends, and half pins, which stop at the far side of the bone. Transfixion pins or wires provide more stability, but they also limit the movement of the joints near the fixator. They are used for procedures that need high stability, such as bone lengthening. Half pins are more common and allow more joint mobility.

Pins or wires are usually inserted through small skin incisions with minimal soft tissue damage. However, care must be taken to avoid injuring nerves and vessels, especially in open fractures where the normal anatomy may be distorted. Only a few safe pin placements are discussed here for each bone. More details can be found in other sources for specialized procedures.

The stability of an external fixator system depends on several factors. More stability can be achieved by using transfixion pins or wires, spreading and increasing the number of pins or wires, using larger or tapered pins or wires, using more bars or rings, and placing them closer to the skin. Pin position may also be influenced by the biomechanics of the system and the extent of soft tissue injury.

Skin incisions should be large enough to prevent skin tightness around the pins or wires, which can cause infection and pin loosening.

External Fixation of the Humerus

• External fixation is a minimally invasive surgical procedure that uses pins or wires inserted into the bone to provide stability and support for a fractured or injured limb. It is often used in cases where open surgery is not possible or where the soft tissues are too damaged to allow for traditional methods of fracture fixation.
• The humerus is one of the most difficult bones in which to apply external fixators safely. This is because the neurovascular bundles are closely associated with the bone. The median nerve runs along the medial side of the humerus, the ulnar nerve runs along the posterior side of the humerus, and the radial nerve runs along the lateral side of the humerus.
• External fixation of the humerus is typically used in cases of severe soft tissue injuries or infections. It may also be used in the emergency management of polytrauma patients with associated severe lung damage.
• The use of external fixation for humerus fractures has been shown to improve patient outcomes in a number of studies. It has been shown to reduce pain, improve range of motion, and shorten the time to healing.
• If you are considering external fixation for a humerus fracture, be sure to talk to your doctor about the risks and benefits of this treatment option.

Safe Pin Placement for External Fixation of the Humerus

Proximal Third

The humerus is a difficult bone to apply external fixators to safely because of the close proximity of the neurovascular bundles. The following are safe pin placement sites for external fixation of the humerus:

• Proximal third: Half pins may be inserted via a lateral route, but they should not protrude very far beyond the medial cortex to avoid damage to the neurovascular bundle.
• Middle third: Anterior half pins may be inserted, but care should be taken that they do not penetrate the far cortex too deeply. The radial nerve runs across the back of the humerus in the middle third of the bone, so pins should not be inserted from the lateral side of the bone in this area.
• Distal third: Half pins may be inserted in a lateral to medial direction, avoiding the neurovascular bundles that lie anterior and posterior to the epicondyles of the humerus.(Fig. 13-1).

Figure 13-1 The placement of skeletal pins in the humerus varies with anatomic site. The variable relationship of the neurovascular bundles to the bone dictates different pin placement for the proximal, middle, and distal thirds. A: Proximal third: Insert a half pin from the lateral side of the bone. Take care not to penetrate the medial cortex too far to avoid damage to the neurovascular bundle (brachial artery and median nerve). B: Middle third: Place a half pin anteriorly. Take care not to penetrate the far cortex too deeply to avoid damage to the radial nerve, which courses in a medial to lateral direction on the posterior aspect of the middle third of the bone. C: Distal third: Insert transfixion pins from the medial to the

lateral point. Take care to avoid the ulnar nerve, as it runs in the groove on the back of the medial humeral epicondyle where the nerve is easily palpable.