Iliac Crest Bone Harvest

Article

Iliac Crest Grafting for Mandibular Reconstruction

Marginal VS Segmental Resection

• Marginal Resection: involves the alveolar portion of the bone with an intact inferior or posterior mandibular border, maintaining continuity.
  • Goal is to restore the morphology of the alveolar process to facilitate placement of dental implants or provide an anatomic foundation for a dental prosthesis.
• Segmental Resection: defined by the presence of mandibular discontinuity
  • Anterior mandibular segmental defects are not well tolerated and often cause significant loss of support for the tongue musculature (glossoptosis), which leads to potential airway compromise if not reconstructed
  • Small segmental lateral defects may be well tolerated without reconstruction

Iliohypogastric nerve (L1, L2): The lateral cutaneous branch of the iliohypogastric nerve is located overlying the ilium tubercle and is the most commonly injured nerve during an anterior iliac crest bone graft (AICBG). The iliohypogastric nerve provides sensory innervation to the skin of the pubis and lateral aspect of the buttock.

Lateral branch of the subcostal nerve (T12, L1): Located overlying the anterior superior iliac spine. The subcostal nerve is located medial to the iliohypogastric nerve and provides sensory innervation to the lateral buttock.

Lateral femoral cutaneous nerve: Located between the psoas major and the iliacus muscle, medial to the subcostal nerve. In 2.5% of the population, the lateral femoral cutaneous nerve can be found within 1 cm of the anterior superior iliac spine. The lateral femoral cutaneous nerve provides sensory innervation to the skin of the anterior and lateral thigh. Damage to this nerve may result in a meralgia paresthetica.

Nerves & Innervation

• Sensory cutaneous nerves in the region of the iliac crest may be typically transverse the pelvis in a superior-medial to inferior-lateral direction.
• The most commonly affected nerve is the lateral cutaneous branch of the iliohypogastric nerve (L1, L2), which runs over the tubercle of the ilium.
• The lateral cutaneous branch of the subcostal nerve (T12, L1) runs over the tip of the anterior superior spine and is slightly inferior to the iliohypogastric nerve.
• The lateral femoral cutaneous nerve is the most inferior nerve of interest and courses medially between the psoas major and the iliacus muscle, deep to the inguinal ligament to perforate the tensor fascia lata and innervate the skin of the lateral thigh. In 2.5% of the population the lateral femoral cutaneous nerve courses within 1 cm of the anterior superior spine and may be transected accidentally if the dissection plane is extended inferiorly. When this nerve is injured, a condition known as meralgia paresthetica may present, with persistent dysesthesia and anesthesia to the lateral thigh (Fig. 2).

Blood Supply

• The blood supply to the AIS is based on the perforating branches of the deep circumflex iliac artery and vein, which are located on the medial ilium.
• The gluteal artery is the most common source of bleeding during harvest of the AIS.

Surgical Technique

• The skin overlying the AIS is retracted medially and a 4- to 6-cm incision is placed 1- to 2-cm posterior to the tubercle of the ilium and 1 cm inferior to the anterior superior iliac spine. This placement avoid the course of the iliohypogastic and subcostal nerves superiorly and the lateral femoral cutaneous nerve inferomedially.
• Layers of dissection:
  • Skin
  • Subcutaneous tissue
  • Scarpa’s fascia
• A dissection plane is established between the tensor fascia lata laterally and the external and transverse abdominal muscles medially to identify the dense fibrous periosteum of the iliac crest.
• Once the crest is identified, the periosteum is sharply transected and with blunt dissection the iliacus muscle is reflected medially to expose the medial  iliac crest.
• The musculoperiosteal layer provides protection to the intra-abdominal contents during bone graft harvesting.

Harvesting Technique from the Anterior Iliac Crest

1. Clamshell approach expands the medial and lateral cortices to gain access to the underlying cancellous bone.
2. Tschopp approach pedicles the anterior iliac crest osteotomy on the external oblique muscle.
3. Trap door approach provides a similar but broader access than the clamshell approach by pedicling the medial and lateral cortices on the external oblique and tensor fascia lata,  respectively.
4. Tessier approach creates oblique osteotomies to pedicle the medial and lateral walls of the anterior iliac crest to access the cancellous bone.

Anatomy

• Anterior iliac crest is located between the anterior iliac spine (AIS) and tubercle of the ilium, which is 6cm posterior to the AIS.
• Most cancellous bone is located between the AIS and tubercle of the ilium. A maximum of 50cc of uncompressed cancellous bone can be harvested from the anterior iliac crest.
• The AIS serves as an attachment for the external abdominal oblique muscle medially and tensor fascia lata laterally. The tensor fascia lata originates from the anterior iliac crest, attaching laterally it fans out inferiorly to attach to the hip and knee joints to insert on the lateral tibia. The tensor fascia lata is the most important structure related to gait disturbance.
• Inferior to the crest, the gluteus medius and minimus muscles attach to the lateral cortex. The iliacus muscle attaches to the medial surface of the iliac crest.
• The inguinal ligament attaches to the anterior superior iliac spine and inserts onto the pubic tubercle.
• The sartorius muscle attaches to the anterior inferior iliac spine and inserts onto the medial aspect of the tibia.

Nerves & Innervation

• Sensory cutaneous nerves in the region of the iliac crest may be typically transverse the pelvis in a superior-medial to inferior-lateral direction.
• The most commonly affected nerve is the lateral cutaneous branch of the iliohypogastric nerve (L1, L2), which runs over the tubercle of the ilium.
• The lateral cutaneous branch of the subcostal nerve (T12, L1) runs over the tip of the anterior superior spine and is slightly inferior to the iliohypogastric nerve.
• The lateral femoral cutaneous nerve is the most inferior nerve of interest and courses medially between the psoas major and the iliacus muscle, deep to the inguinal ligament to perforate the tensor fascia lata and innervate the skin of the lateral thigh. In 2.5% of the population the lateral femoral cutaneous nerve courses within 1 cm of the anterior superior spine and may be transected accidentally if the dissection plane is extended inferiorly. When this nerve is injured, a condition known as meralgia paresthetica may present, with persistent dysesthesia and anesthesia to the lateral thigh (Fig. 2).

Blood Supply

• The blood supply to the AIS is based on the perforating branches of the deep circumflex iliac artery and vein, which are located on the medial ilium.
• The gluteal artery is the most common source of bleeding during harvest of the AIS.

Surgical Technique

• The skin overlying the AIS is retracted medially and a 4- to 6-cm incision is placed 1- to 2-cm posterior to the tubercle of the ilium and 1 cm inferior to the anterior superior iliac spine. This placement avoid the course of the iliohypogastic and subcostal nerves superiorly and the lateral femoral cutaneous nerve inferomedially.
• Layers of dissection:
  • Skin
  • Subcutaneous tissue
  • Scarpa’s fascia
• A dissection plane is established between the tensor fascia lata laterally and the external and transverse abdominal muscles medially to identify the dense fibrous periosteum of the iliac crest.
• Once the crest is identified, the periosteum is sharply transected and with blunt dissection the iliacus muscle is reflected medially to expose the medial  iliac crest.
• The musculoperiosteal layer provides protection to the intra-abdominal contents during bone graft harvesting.

Harvesting Technique from the Anterior Iliac Crest

1. Clamshell approach expands the medial and lateral cortices to gain access to the underlying cancellous bone.
2. Tschopp approach pedicles the anterior iliac crest osteotomy on the external oblique muscle.
3. Trap door approach provides a similar but broader access than the clamshell approach by pedicling the medial and lateral cortices on the external oblique and tensor fascia lata,  respectively.
4. Tessier approach creates oblique osteotomies to pedicle the medial and lateral walls of the anterior iliac crest to access the cancellous bone.

Anatomy

• The posterior iliac crest provides up to 100 cc of uncompressed bone. Most bone is located beneath the insertion of the gluteus maximus muscle adjacent to the sacroiliac joint.
• The insertion of the gluteus maximus is defined by the presence of a well-defined and palpable triangular fossa. The insertion of the gluteus maximus is between the superior and middle cluneal nerves.
• The gluteus medius attaches to the posterior ilium inferior to the gluteus maximus insertion.

Nerves & Innervation

• The superior cluneal nerve (L1-3) pierces the lumbodorsal fascia superior to the posterior iliac crest and innervates the skin over the posterior medial buttocks.
• The middle cluneal nerves (S1-3) emerge from the sacra foramina course laterally and innervate the medial buttocks.
• The sciatic notch and nerve, which supplies the motor innervation to the lower extremity, is 6- to 8-cm inferior the posterior iliac cfrst and should not be encountered during routine dissection.

Blood Supply

• The subgluteal artery is the major blood supply of the posterior iliac crest and is the terminal branch of the deep circumflex artery

Surgical Technique

• A hip roll may be used to define the bony landmarks of the posterior iliac crest
• A 6- to 8cm curvilinear incision is placed over the bony prominence of the posterior iliac crest. The inferior extension of the incision is typically paramedian and 3cm lateral to the gluteal crease.
• Layers of dissection:
  • Skin
  • Subcutaneous tissue.
  • Lumbodorsal fascia
• A thick white lumbodorsal fascial layer separating the abdominal and gluteal muscles can be sharply transected to expose the posterior iliac crest.
• The gluteus medius, which is not intimately attached to the bone, can be reflected gently to expose the posterior iliac crest further and facilitate appropriate retraction for bone harvest.

• 1cc of cancellous bone is required for each mm of segmental defect that is to be reconstructed
• Anterior ilium: 50cc
• Tibial plateau: 10-15cc
• Posterior ilium: 100 cc