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Calvarial Bone Graft

last modified on: Thu, 09/21/2023 - 14:34

see also: Case Example Calvarial Bone Graft Harvest

return to: Reconstructive Procedures Protocols

GENERAL CONSIDERATIONS

  1. Indications
    1. Bone grafts are used for a variety of purposes in facial skeletal surgery including trauma, oncologic, and congenital reconstructive cases. Calvarial bone grafts serve as an excellent means of recontouring the nasal and periorbital areas where bony definition and acute angles require sturdy and precisely-shaped bone grafts.
  2. Contraindications
    1. Outer table bone graft harvest may not be safe in young children due to the thinness of the skull and poorly-developed diploe space.
    2. In patients who have had numerous reconstructive procedures requiring bone grafts, it may be difficult to locate a safe area from which to harvest further grafts. This should be considered in preoperative planning.
  3. Pertinent Anatomy
    1. The skull is composed of membranous bone. This type of bone demonstrates less resorption compared to bone from other sources.
    2. The skull is comprised of the paired parietal and temporal bones and the single frontal and occipital bones. Of these bones, the parietal bone consistently has the greatest thickness and should be the first choice as a harvest site.
    3. Two danger areas to be avoided are the midline over the sagittal sinus and the area lateral to the temporal line that may be quite thin.
    4. In general, grafts should also not be harvested from the area of suture lines that may be somewhat thinner than the surrounding bone and have a poorly-defined diploe space.
    5. The skull in an adult consists of an inner and outer table of membranous bone separated by a diploe space. The majority of bone grafts are harvested from the outer table. The bone thickness of the skull stops increasing by the age of 20 years.

PREOPERATIVE PREPARATION

  1. Evaluation
    1. If a coronal flap is planned, it provides access for harvesting of the bone grafts.
    2. In the balding patient or patient at risk for male pattern baldness, an incision approximately 3 cm medial to the palpable temporal line paralleling the squamosal suture centered behind the ear will provide access to the parietal bone in an area which will be hidden despite hair loss.
    3. If there is a question regarding the integrity of the skull, a bone window CT scan should be obtained. The CT scan is also beneficial if a patient has had previous bone grafts or skull surgery performed to define the areas accessible for graft harvest.
  2. Potential Complications
    1. The most concerning complication of outer table graft harvest is intracranial penetration. Although this infrequently causes significant sequelae, the potential exists for sagittal sinus injury, brain injury, cerebrospinal fluid leak, and meningitis. If intracranial extension of the defect is identified as emergent, an intraoperative neurosurgery consultation to evaluate the wound is mandatory.
    2. Contour abnormalities of the skull bothersome to the patient may also complicate this procedure. Care should be taken to smooth the contour of the harvest site.
    3. Some degree of bone resorption of free bone grafts is to be anticipated. Over years, this resorption may be substantial. In many cases, the bone is replaced with fibrous tissue, and the structural integrity of the reconstruction remains. However, patients should be aware that bone resorption does occur and may result in contour changes with time. 
    4. Hematoma is a potential and it's recommended a surgical drain be used appropriately.  Generally this just remains overnight and can be removed the next day.

NURSING CONSIDERATIONS

  1. Room Setup
    1. See Basic Soft Tissue Room Setup
    2. Mayfield headrest (available only)
    3. Mayo stand x 2 (for the extra power equipment)
  2. Instrumentation and Equipment
    1. Standard
      1. Fracture Tray
      2. Minor Instrument Tray, Otolaryngology
      3. Bipolar Forceps Trays
    2. Special
      1. Smith-Pete osteotome tray. Need Reuben osteotomes.
      2. Nasal Sharp Tray
      3. Bien Otologic Electric Drill Tray
      4. Midas Rex Drill Tray
      5. Hall Micro Sagittal Saw Tray (Pneumatic)
      6. Irrigation pouch, 19 x 24 in with additional suction
      7. Cummings retractor, medium x 2, and large x 2
      8. Raney scalp hemostasis clips x 5
      9. Syringe, Luer Lock, 30 cc x 2 with blunt 18-gauge needle x 2 for irrigation while drilling
      10. Bone wax
      11. Colorado microtip monopolar cautery
      12. Bone Pate suction collector-collect bone pate for filling in contour defect at end.
  3. Medications (specific to nursing)
    1. Balance salt solution (BSS), 15 ml dropper x 2
    2. Antibiotic ointment
    3. 1% lidocaine with 1:100,000 epinephrine, may dilute epinephrine in children
  4. Prep and Drape
    1. Standard prep, 10% providone iodine: part hair and comb hair away from the incision line and prep entire head
    2. Drape
      1. Drape under the head
      2. Towels to square off head
      3. Split sheet
  5. Drains and Dressings
    1. Varidyne vacuum suction, or Penrose drain, 1/2 in
    2. Antibiotic ointment along suture line
    3. Fluffs, Kerlix roll 4 in
  6. Special Considerations
    1. Surgeon may place tarsorrhaphy sutures (4-0 silk G-3) to protect the cornea.
    2. Coronal incision requires panther bands, 1/4 in and 1/8 in, used to secure hair before prepping and Raney clips used for hemostasis.
    3. Cleanup after procedure requires sterile water/saline, hydrogen peroxide/saline, and an irrigation basin to clean the head.

ANESTHESIA CONSIDERATIONS

  1. Specific
    1. The patient should be supine on a Mayfield headrest.
    2. The table will be turned 180° from the anesthesiologist.

OPERATIVE PROCEDURE

  1. The incision site may depend on the type of graft required. Grafts taken from the anterior parietal bone tend to be more curved than those taken from the posterior parietal bone. If a coronal incision is to be used, the grafts will be harvested through that incision.
  2. Maximum single graft size should not exceed 5 to 6 cm long and 1.5 to 2 cm wide. Wider grafts are more difficult to harvest, and longer grafts increase the possibility of entering the inner table bone.  Ideal size for nasal recon is 4"x1".
  3. Outer table partial thickness "potato chip graft"
    1. Elevated with sharp small osteotome
    2. A thin layer of bone is elevated. The periosteum is often left intact and attached to the underlying bone to hold pieces together as they fragment.
    3. These grafts are particularly useful in orbital wall and floor grafting.
  4. Outer table full thickness (most common approach)
    1. Graft is outlined with a Midas B-1 or C-1 bit. Feather down until bleeding bone; this is the diploic layer. A small cutting burr will serve this purpose as well. Along a long edge of the bone, relieve the adjacent calvarium to the diploic layer with a Midas acorn bit, or a large cutting burr. This allows insertion of the 90° oscillating saw. If only one graft is needed, relieving both sides of the graft will allow for a graft of twice the width.
    2. The right-angled oscillating saw is used to free the graft. Alternatively, a curved wide osteotome used circumferentially from trough to graft center will free the graft. Care must be taken so the osteotome or saw blade is kept parallel to the diploic layer.
  5. Inner table or full thickness graft
    1. If the patient has had a craniotomy, the bone flap will be available for harvest of the inner table while the neurosurgical component of the procedure is taking place.
    2. Using an oscillating saw and osteotomes, grafts from the inner table of the bone flap may be harvested using the technique described for outer table full thickness grafts. This work is done on the back table.
    3. Either the inner or outer cortex may be utilized; however, contour of the skull is best maintained when the inner table is harvested.
    4. The remaining bone flap is replaced and secured with miniplates.
    5. If excessive bleeding is encountered on drilling, a venous lake in the diploic space may have been encountered. Seal it with bone wax. Another graft site may need to be selected. Bone wax is used to stop bleeding at the bony edge of the harvest site.
    6. Scalp closure
      1. Ideally, three planes are closed: periosteum, galea, and skin. Galea and skin are key.
      2. A Penrose or suction drain is used and a craniotomy-type pressure dressing is placed
  6. Nasal dorsum reconstruction
    1. If using for recon of saddle nose deformity.  May use intracartilagenous incision(s) to access dorsum.  Create pocket in nose and elevate periosteum off of nasal bones.  Course rasp used to roughen bone on dorsum.  Bone graft shaped into ellipse and sized and thinned appropriately and tested in pocket until completely satisfied.  Bone then placed and left in place without fixation to allow bony adherence.
    2. Nasal cast to remain on for 2 weeks to help bone stay in place and heal appropriately.

POSTOPERATIVE CARE

  1. Suction drains remain until drainage is less than 30 cc per 24 hours.
  2. The craniotomy dressing may be removed after 24 hours.
  3. Patient may wash hair carefully on postoperative day 3 and apply antibiotic ointment to incision line.

REFERENCES

Cutting CB, McCarthy JG. Comparison of residual osseous mass between vascularized and nonvascularized onlay bone transfers. Plast Reconst Surg. 1983;72:672-675.

Frodel JL, Marentette LJ, Quatela VC, Weinstein GS. Calvarial bone graft harvest techniques, considerations, and morbidity. Arch Otolaryngol Head Neck Surg. 1993;119: 17-23.

Young VL, Schuster RH, Harris LW. Intracerebral hematoma complicating split calvarial bone-graft harvesting. Plast Reconst Surg. 1990;86:763-765.

Emerick KS, Hadlock TA, Cheney ML.  Nasofacial reconstruction with calvarial bone grafts in compromised defects. Laryngoscope. 2008 Sep;118(9):1534-8.

Cheney ML, Gliklich RE.  The use of calvarial bone in nasal reconstruction. Arch Otolaryngol Head Neck Surg. 1995 Jun;121(6):643-8

Jeyaraj P. Split Calvarial Grafting for Closure of Large Cranial Defects: The Ideal Option?. J Maxillofac Oral Surg. 2019;18(4):518-530. doi:10.1007/s12663-019-01198-w

Smolka W. Calvarial grafts for alveolar ridge reconstruction prior to dental implant placement: an update. Oral Maxillofac Surg. 2014;18(4):381-385. doi:10.1007/s10006-014-0464-3

Lee HJ, Choi JW, Chung IW. Secondary skull reconstruction with autogenous split calvarial bone grafts versus nonautogenous materials. J Craniofac Surg. 2014;25(4):1337-1340. doi:10.1097/SCS.0000000000000806