As in all locations of long bones safe zones for pin placement can be defined. In the typical emergency situation, the patient is supine. Therefore, the safe zone of the distal third of the humerus is not practical.
3. Pin insertion (humeral shaft)
For bridging the humerus two pins are placed proximal and distal to the fracture. Proximally, the pins are placed anterolaterally. Take care not to injure the axillary nerve or the long head of the biceps.
Distally the pins can be placed laterally. Doing so, the radial nerve is at high risk. To reduce radial nerve injuries, it is recommended to use incisions large enough to ensure palpation and/or direct visualization of the radial nerve (no stab incisions). It may be better to use a single incision for the insertion of both pins.
Pearl: To minimize the size of the incision, yet still obtain adequate hold in the distal fragment it is useful to insert pins in divergent directions.
After stab incision of the skin perform a blunt dissection of the soft tissues with scissors down to the bone. Use of drill sleeves with trocar prevents damage to muscular, vascular and neurological structures.
Proper pin insertion
To prevent postoperative complications, pin-insertion technique is more important than any pin-care protocol:
Correct placement of pins (see safe zones) avoiding ligaments and tendons, eg tibia anterior
Correct insertion of pins (eg trajectory, depth) avoiding heat necrosis
Extending skin incisions to release soft-tissue tension around the pin insertion (see inspection and treatment of skin incisions)
Various aftercare protocols to prevent pin-track infection have been advocated by experts worldwide, so no standard protocol for pin-site care is given here. Nevertheless, the following points are recommended:
The aftercare should follow the same protocol until removal of the external fixator.
The pin-insertion sites should be kept clean. Any crusts or exudates should be removed. The pins may be cleaned with saline and/or disinfectant solution/alcohol. The frequency of cleaning depends on the circumstances and may vary from daily to weekly but should be done in moderation.
No ointments or antibiotic solutions are recommended for routine pin-site care.
Dressings are not usually necessary once wound drainage has ceased.
Pin-insertion sites need not be protected for showering or bathing with clean water.
The patient or the carer should learn and apply the cleaning routine.
Pin loosening or pin-track infection
If a pin loosens or there is pin-track infection, the following steps need to be taken:
Remove all involved pins and place new pins in a healthy location.
Debride the pin sites in the operating theater, using curettage and irrigation.
Take specimens for microbiology to guide appropriate antibiotic treatment if necessary.
Allow infected pin tracks to heal before changing to definitive internal fixation, otherwise infection will result.
Gentle use of the hand and forearm should start as soon as the patient is able to tolerate this, with some caution if pins are near the elbow. Pendulum exercises or assisted shoulder motion should be considered as soon as tolerable.
Check the wound 7-10 days after surgery. X-rays are taken to check the reduction.
The patient should be seen every 3 or 4 weeks with examination and x-rays until union is secure, and range of motion and strength have returned.
If the fixator is used for definitive fixation, it should be left until callus is visible and the fracture site is stable and non-tender. Remember the risk of delayed union or nonunion, so monitor the patient and if necessary consider alternative treatment.