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Monobloc distraction

Craniosynostosis

Children with Apert, Crouzon and Pfeiffer syndromes often have functional problems including raised intracranial pressure, severe exorbitism with or without subluxation of the globe, upper airway obstruction with severe obstructive sleep apnoea and feeding problems. Monobloc frontofacial advancement allows correction of all these problems in a single procedure.

The operation combines transcranial frontal advance and extracranial Le Fort III midfacial advance with the frontal bones and maxilla being brought forward in one piece either immediately at surgery or more slowly by distraction using a rigid external distractor (RED frame). The RED frame comprises a halo device which is attached to the mobilised facial skeleton through a combination of cranial pins, rods and wires. Distraction at a rate of ~1.5 mm per day is achieved post-operatively by progressively shortening the wires. Once the midface has advanced the required distance and following a consolidation period of 6 weeks the distractor is removed under general anaesthesia.

Since monobloc frontofacial advancement may be associated with high morbidity especially in young infants and children, timing of surgery is crucial. Ideally the procedure should be delayed until skeletal maturity has been achieved at around 12 years of age. However, it may be considered in infants less than 1 year of age if the severity of the functional problems is such that surgery can no longer be delayed.

Anaes concerns

  1. Patient position: supine ‘head-up’ tilt;
  2. Surgical approach: combined intra-oral and transcranial (coronal) incisions;
  3. Surgical duration: 6–8 hours;
  4. Reinforced oral tracheal tube secured with a circum-mandibular wire (a nasotracheal tube sutured to the septum may also be used). In patients with a tracheostomy, a reinforced tracheal tube is placed via the tracheostome and sutured to the anterior chest wall;
  5. A throat pack not only protects the airway from blood and bony fragments but also assists in securing the tracheal tube;
  6. Lacrilube ointment followed by temporary tarsorrhaphies are used to protect the eyes intra-operatively. These are replaced with Frost sutures for 48 h post-operatively;
  7. At least two large peripheral venous cannulae;
  8. Femoral central venous line recommended especially in the younger child;
  9. Arterial line essential;
  10. Urinary catheter;
  11. Intra-operative cell salvage routinely used;
  12. A rapid infusor may be useful in older patients;
  13. Particular care should be taken to ensure that all pressure points are padded;
  14. Antiembolism compression stockings (TEDS) for older teenagers;
  15. Bilateral nasopharyngeal airways and a nasogastric tube are inserted at the end of surgery;
  16. While some centres electively ventilate patients for a few days post-operatively, it is common practice at the author's institution to extubate all patients at the end of surgery provided that they are haemodynamically stable and have no respiratory compromise;
  17. As the external distractor is a bulky device it may impede access to the airway making reintubation very difficult. If there are any post-operative airway concerns the halo may be placed with the suspension frame left until later.

Removal of RED frame

In the older child, removal of a rigid external distractor is relatively simple, involving disconnection of the halo device followed by removal of the cranial pins. In infants, however, insertion of titanium mesh sheets to prevent penetration of the skull by the cranial pins necessitates removal of the distractor and sheets via a coronal incision. As the presence of a RED frame may make airway management difficult it is important to ensure that the necessary tools and expertise required to remove the frame are readily available before induction of anaesthesia. In cooperative children the suspension frame may be removed prior to induction of anaesthesia. If this is not feasible, the facemask may have to be inverted and then changed for a laryngeal mask airway once the patient is adequately anaesthetised as the frame's wires and bars makes conventional placement of a facemask impossible. Laryngoscopy and intubation may also be difficult if not impossible, and for procedures other than removal of the frame where intubation is deemed necessary, it is advisable that the surgeon removes the wires and bars.

References

Chapter 25 - Anaesthesia for Craniofacial Surgery in Children