Parietal bone may be harvested (Fig. 3) through a horizontal incision (typically, 4 cm to 6 cm) superior to the temporal line. Typically the nondominant side is chosen. Incision to and through the periosteum, followed by subperiosteal undermining, provides proper exposure. A drill is used to outline the proposed graft (typical graft size, 1 cm to 1.5 cm by 4 cm to 4.5 cm). A trough is drilled through the outer table to the diploe; this allows the proper angle for application of a chisel or powered oscillating saw to harvest the grafts care -fully. Short controlled taps on a sharp osteotome allow increased precision and help de-crease the risk of inner-table penetration and dural tear.
Patients must be cautioned preoperatively of the risk of possible dural tear and possible brain injury. Any dural entry should elicit an immediate neurosurgical consultation.
The donor site can be contoured with hydroxyapatite cement or any other biocompatible bone substitute material. The incision is typically closed in a multilayer fashion.
Figure 3. Calvarial bone harvest. Parietal bone may be harvested through a horizontal incision (typically, 4 cm to 6 cm) superior to the temporal line. Typically the nondominant side is chosen (A). A drill is used to outline the proposed graft (typical graft size, 1 cm to 1.5 cm by 4 cm to 4.5 cm). A trough is drilled through the outer table to the diploe (B, D, E). A chisel or powered oscillating saw may be used to harvest the grafts carefully (C, F—I). Narrower grafts are safer and easier to harvest.
When harvesting auricular cartilage, the surgeon can simplify the dissection by performing local anesthetic injections in the subperichondrial plane. This will act to hydrodissect the flap and allow blunt dissection to elevate the flap.
Special care must be taken to evert the skin edges when performing the skin closure. There will be a tendency for the dissected flap to overlap the skin on the side that was not dissected. Vertical mattress sutures are most effective for aligning the skin edges.
If lateral ear position is a concern, the radix helicis can be left intact to support the auricle and preserve lateral ear position.
Perichondrium can be dissected off the posterior surface of the cartilage and used as tissue for camouflage or to cushion a tip graft.
If small cartilage grafts are needed, the posterior approach can be used to harvest ear cartilage.
If the patient has one ear that protrudes more than the other, then the cartilage should be harvested from that side. If the patient sleeps on one side of the head, then the cartilage should be removed from the contralateral side.
Palpate appropriate-shaped cartilage, and place the incision over the rib to be harvested. In female patients, the incision should be placed in the proximity of the inframammary crease.
Postoperative pain can be minimized by cutting as little muscle as possible when dissecting over the costal cartilage. The muscle fibers can be bluntly dissected to expose the costal cartilage and then retracted to perform the dissection.
Postoperative pain can be significantly decreased by keeping the inferior ribs intact to support the rib cage. With the inferior ribs intact, the patient will have much less pain on inspiration.
Dissect perichondrium off cartilage, taking special care to elevate perichondrium off the inferior surface of the costal cartilage. By leaving the perichondrium intact over the pleura, there will be minimal chance of pneumothorax.
The incision should be closed in multiple layers. After closing the muscle, fascia, and subcutaneous tissues, evert the dermal sutures [4-0 polydioxanone suture (PDS)] to provide prolonged support to the skin edges. The wound will remain everted for several months; however, the scar camouflage will be excellent. Patients should be informed of the temporary excess eversion of the skin edges.
With costal cartilage for grafting, symmetric carving is essential to avoid postoperative warping.
Harvesting Et/inlaid Bone
Avoid resecting ethmoid bone high near the cribriform plate to prevent cerebrospinal fluid leak. Use atraumatic instruments and techniques when removing the bone.
The bone graft can be shaped with a burr.
Harvesting Calvarial Bone
Examine the curvature of the skull to determine the most favorable shape to the bone to harvest the bone graft. The parietal or occipital areas are the most common areas where calvarial bone grafts are harvested.
Create a bone trough down to the diploic layer to allow a curved osteotome to elevate the external table gently off an intact inner table. Generous irrigation is necessary to avoid damage to the bone.
Narrower 1 cm to 2 cm strips of bone are easier to elevate off the inner table.
The bone defect can be filled with a bone substitute material.
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