Posterior Approach to the Iliac Crest for Bone Graft
Posterior iliac crest bone grafts usually are taken during any posterior spine surgery that requires additional autogenous bone to supplement the area to be fused. The grafts also may be used as corticocancellous grafts for any part of the skeleton that needs fusion or refusion.
Position of the Patient
Place the patient prone on the operating table, with bolsters running
longitudinally to support the chest wall and pelvis, allowing the chest wall and abdomen to expand without touching the table. Place drapes distally enough so that the beginning of the gluteal cleft and the posterior superior iliac spine can be seen (see Fig. 6-101).
Landmarks and Incision
Landmarks
Palpate the posterior superior iliac spine under the dimpling of the skin above the buttock. The subcutaneous posterior part of the iliac crest also is palpable.
Incision
Make an 8-cm oblique incision centered over the posterior superior iliac spine and in line with the iliac crest (Fig. 7-5, inset).
If scoliosis surgery or lumbar surgery is being performed, the midline incision can be extended distally to the sacrum. Then, the skin and a thick, fatty, subcutaneous layer can be retracted laterally. Using a Hibbs retractor dissect the flap free from the underlying lumbodorsal fascia until the posterior superior iliac spine and crest can be palpated and seen (see Fig. 7-5).
Internervous Plane
Muscles insert into or take origin from the iliac crest, but do not cross it. Therefore, the outer border of the iliac crest is truly an internervous plane. The gluteus medius, minimus, and maximus muscles take their origins from the outer surface of the ilium (the gluteus medius and minimus are supplied by the superior gluteal nerve and the gluteus maximus is supplied by the inferior gluteal nerve). The segmentally supplied paraspinal muscles take their origin from the iliac crest itself, as does the latissimus dorsi, which is supplied proximally by the long thoracic nerve. Thus, an incision into the iliac crest does not denervate muscles, even if it is not placed exactly on the outer lip of the crest.
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Figure 7-5 If lumbar spine surgery is being performed, extend the midline incision distally, retracting the skin laterally until the posterior superior iliac spine and crest can be palpated and seen. Incise the soft tissues overlying the crest down to bone. Make an 8-cm oblique incision, centered over the posterior superior iliac spine and in line with the iliac crest (inset).
Superficial Surgical Dissection
Incise the subcutaneous tissues in the line of the skin incision until the iliac crest is reached. In children, the iliac apophysis is white and quite visible; it may be incised or split in line with the iliac crest, using it as an avascular plane. In adults, the apophysis is ossified and fused to the crest; the incision lands directly on the crest itself.
Use a Cobb elevator to remove the apophysis or muscles from the iliac
crest both medially and laterally, to bare the surface of the posterior portion of the crest.
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Nerves
The cluneal nerves cross the iliac crest. They can be avoided by placing the incision no more than 8 cm anterolateral to the posterior superior iliac spine. The nerves supply sensation to the skin over the cluneal (gluteal) area. They are composed of the posterior primary rami of L1, L2, and L3. Their loss does not cause problems for the patient.
Deep Surgical Dissection
Strip the musculature completely off the posterior portion of the lateral surface of the ilium so that a large enough graft can be obtained. Take care to stay in a subperiosteal plane while passing from the iliac crest to the outer cortex of the ilium. Proceeding 1.5 cm down the ilium in the area of the posterior superior spine, the elevated posterior gluteal line can be seen and felt; pass subperiosteally up over the line and then down its other side. Do not err by letting the line direct the incision outward from bone into muscle. A Taylor retractor will help the exposure by holding the muscles laterally. Note that the posterior gluteal line separates the origins of the gluteus maximus (posterior) from the gluteus medius (anterior; Fig. 7-6).
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Nerves
It is remotely possible that an osteotome will hit the sciatic nerve, which runs close to the distal end of the wound deep to the sciatic notch; however, if an imaginary line is drawn from the posterior superior iliac spine perpendicular to the operating table, and all work is performed cephalad to it, both the notch and the nerve will be avoided completely. If a larger graft is necessary, palpate the sciatic notch itself before taking the graft (see Fig. 7-6B).
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Figure 7-6 A: Subperiosteally strip the musculature off the posterior portion of the lateral surface of the ilium. B: Proceeding down the outer surface of the ilium in the area of the posterior superior spine, the elevated posterior gluteal line can be seen and felt; pass subperiosteally up and over the line and then down its other side. Do not err by letting the line direct you outward from bone to muscle. If you draw an imaginary line from the posterior superior iliac spine perpendicular to the operating table and stay cephalad to it, you will avoid the sciatic notch and its contents.
Vessels
The superior gluteal vessel, a branch of the internal iliac (hypogastric) artery, leaves the pelvis via the sciatic notch, staying against the bone and proximal to the piriformis muscle. If a graft is taken too close to the sciatic notch, the vessel may be cut and may retract into the pelvis. Nutrient vessels from the artery supply the iliac crest bone along the midportion of the anterior gluteal line, and the vessel may become an osseous bleeder as it enters bone via the nutrient foramen. To control bone bleeding, use bone wax on the raw cancellous surface of the pelvis after the graft has been removed.
Bone
Avoid the sciatic notch. Breaking through the thick portion of the bone that forms the notch disrupts the stability of the pelvis. Removal of bone from the false pelvis proximal to the notch does not cause loss of stability (see Fig. 7-6B).
How to Enlarge the Approach
Local Measures
Place a sharp-tipped, right-angled Taylor retractor into the bone to retract the gluteal muscles away from the bone and increase the exposure. To increase the exposure further, lengthen the iliac crest incision and strip more of the gluteal muscles from the outer cortex to avoid working through a “keyhole.”
Extensile Measures
This incision cannot be extended. It is designed specifically for removing bone for graft material from the posterior outer cortex of the ilium. Inner cortex also may be taken, but soft tissues should not be stripped off the anterior (deep) aspect of the ilium.
Anterior Approach to the Pubic Symphysis
The anterior approach to the pubic symphysis is an approach that is used almost exclusively for the open reduction and internal fixation of a ruptured symphysis or internal fixation of displaced fractures of the superior pubic ramus. Other uses include biopsy of tumors and treatment of chronic osteomyelitis.
Because widely displaced symphysis injuries often are associated with urologic damage, obtaining a urologic assessment is advisable before undertaking open surgery, which often includes a retrograde urethrogram. A urethral catheter must be inserted before surgery. A full bladder will seriously interfere with the surgical approach.
Position of the Patient
Place the patient supine on the operating table.
Landmarks and Incision
Landmarks
The superior pubic ramus and pubic tubercles are easily palpable in all but the most obese patients. The pubic symphysis will be palpable (as a gap) only in cases of rupture.
Incision
Make a 15-cm curved incision in the line of the skin crease, centering it about 1 cm above the pubic symphysis (Fig. 7-7).
Internervous Plane
An internervous plane is not available for use in this approach. Because the rectus abdominis muscles receive a segmental nerve supply, they are not denervated, even though they are divided by this approach.
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Figure 7-7 Palpate the pubic tubercles. Make a curved incision in the line of the skin crease, centering it 1 cm above the pubic symphysis.
Superficial Surgical Dissection
Incise the subcutaneous fat in the line of the skin incision, deepening the incision down to the anterior portion of the rectus sheath (Fig. 7-8). Identify, ligate, and divide the superficial epigastric arteries and veins that run up from below across the operative field. Then, divide the rectus sheath transversely, about 1 cm above the symphysis pubis. The two rectus abdominal muscles now are visible (Fig. 7-9). In most cases of rupture of
the symphysis pubis, one of these muscles will have been detached from its insertion into the pubic symphysis. Divide the remaining muscle a few millimeters above its insertion into the bone.
Deep Surgical Dissection
Retract the cut edges of the rectus abdominal muscles superiorly to reveal the symphysis and pubic crest (Fig. 7-10). If access to the back of the symphysis is required, use the fingers or a swab to push the bladder gently off the back of the bone. Palpation of the posterior surface of the body of the pubis is useful to identify the correct direction for the insertion of screws. This dissection is very easy to perform unless adhesions have formed due to damage to the bladder. Such adhesions make it difficult to open up this potential space (the preperitoneal space of Retzius) (Fig. 7-11). The pubic symphysis and superior pubic rami now are exposed adequately for internal fixation.
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Bladder
The bladder may have been damaged during the trauma. If so, adhesions will have developed between the damaged bladder and the back of the pubis. Mobilization of the space of Retzius, therefore, may lead to inadvertent bladder rupture. If fixation is considered in the presence of urologic damage, it is best to operate in conjunction with an experienced urologic surgeon.
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Figure 7-8 Incise the fat in the line of the skin incision and retract the skin edges to reveal the anterior portion of the rectus sheath.
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Figure 7-9 Divide the rectus sheath transversely 1 cm above the symphysis pubis to reveal the rectus abdominis muscles and pyramidalis.
How to Enlarge the Approach
Local Measures
Because of the considerable amount of subcutaneous fat in this area, it may be necessary to extend the skin incision and superficial dissection in both directions to allow better visualization of the deep structures in obese patients.
Extensile Measures
The approach can be extended laterally to expose the entire anterior column of the acetabulum and the inner wall of the ilium. (See ilioinguinal approach to acetabulum, page 378.)
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Figure 7-10 Divide the rectus muscles 1 cm above their insertion and retract their cut edges superiorly to reveal the superior ramus of the pubis.
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Figure 7-11 A: Open the plane behind the symphysis pubis, using your finger as a blunt dissector. B: The pubic symphysis and superior pubic rami now are exposed.
Anterior Approach to the Sacroiliac Joint
The anterior approach to the sacroiliac joint offers safe, reliable access to that structure and allows anterior plates to be positioned accurately across the joint. It also permits the exposure of the inner wall of the ala of the ilium, allowing fixation of associated iliac fractures. Paradoxically, although the sacroiliac joint is one of the most posterior structures in the entire pelvic ring, the anterior approach allows greater exposure and
control than does the seemingly more logical posterior approach, because of the shape of the joint. Anteriorly, the joint is flat and directly available, whereas posteriorly it is overhung by the posterior iliac crest.
Position of the Patient
Place the patient in a supine position on the operating table and put a large sandbag under the buttock. This will push the iliac crest up toward the surgeon. Support the opposite iliac wing with a support attached to the operating table and then tilt the table 20 degrees away, allowing the mobile contents of the pelvis to fall away.
Landmarks and Incision
Landmarks
The anterior superior iliac spine and the anterior third of the iliac crest are subcutaneous and easy to palpate.
Incision
Make a long, curved incision over the iliac crest, beginning 7 cm posterior to the anterior superior iliac spine (at about the level of the iliac tubercle). Curve the incision forward until the anterior superior iliac spine is reached. Continue the incision anteriorly and medially along the line of the inguinal ligament for an additional 4 to 5 cm (Fig. 7-12).
Internervous Plane
No true internervous plane is available for use. The approach consists simply of stripping muscles off the inner side of the pelvis; because the bone is being approached via its subcutaneous surface, no muscle is denervated.
Superficial Surgical Dissection
Deepen the skin incision through the subcutaneous fat onto the subcutaneous surface of the iliac crest. Two techniques can be used to detach the iliacus from the deep surface of the iliac wing.
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Bone block technique. Expose the deep fascia overlying the glutei and tensor fasciae latae muscles at the point where it attaches to the outer lip of the iliac crest. Incise the periosteum of the entire anterior third of the
iliac crest and gently strip the muscles off the outer wall of the pelvis to expose about 1 cm of the outer surface below the crest of the ilium.
Predrill the iliac crest for easy reattachment. Using an oscillating saw, transect the wing of the ilium at this level, cutting only the outer cortex and the cancellous bone underneath (Fig. 7-13). Next, crack the inner cortex with an osteotome. This allows the anterior superior iliac spine to be detached along with the transected portion of the iliac wing (Fig. 7-14).
Figure 7-12 Make a curved incision over the iliac crest, beginning 7 cm posterior to the anterior superior iliac spine.
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Soft tissue release only. Start just posterior to the anterior superior iliac spine and detach the iliacus muscle and its overlying fascia from the
deep surface of the iliac wing. Begin by using sharp dissection and then develop the plane using a swab used as a tissue expander.
Deep Surgical Dissection
The iliacus muscle arises from the inner wall of the ilium; detach it by blunt dissection. If the bone block technique is used as the dissection is deepened, the detached anterior superior iliac spine, which still is attached to the lateral end of the inguinal ligament, must be mobilized. This block of bone and muscle must be moved medially; to accomplish this, divide some fibers of both the tensor fasciae latae and sartorius muscles (Fig. 7-15). Note that the lateral cutaneous nerve of the thigh is about 1 cm distal and medial to the anterior superior iliac spine, and may have to be divided to permit this mobilization.
Remaining strictly in a subperiosteal plane, strip the iliacus muscle off the inner wall of the pelvis to expose the underlying sacroiliac joint (see Fig. 7-15). The distance is surprisingly short. As the muscle is stripped off, some nutrient vessels will have to be detached from the inner wall of the pelvis. Bleeding usually can be controlled by bone wax.
The L4, L5 nerve roots and the lumbosacral trunk run along the anterior surface of the sacrum approximately 1.5 cm medial to the sacroiliac joint. Therefore do not continue the dissection more than 1.5 cm medial to the sacroiliac joint. If a standard 3.5 mm plate is used to stabilise the joint place the plate so that only one screw hole is placed medial to the joint. Using two holes of the same plate will endanger the nerve root (see Fig. 7-15, inset).
Mobilizing the iliacus muscle off the inside of the pelvis with a large bone block allows the muscles to be reattached securely with screws during closure. The muscle then resumes its anatomic position, and the dead space beneath it is obliterated. If the bone block technique is used, failure to securely reattach the iliac crest will produce impaired function, a poor cosmetic result, possible chronic pain, and a high risk of hematoma formation.
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Figure 7-13 Strip the muscles from the outer wall of the pelvis. Predrill the iliac crest. Divide the outer cortex 1 cm below the crest using an oscillating saw.
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Nerves
The lateral cutaneous nerve of the thigh may have to be divided during the mobilization of the anterior superior iliac spine. This will cause some
numbness of the lateral aspect of the thigh. Even if the nerve is not transected a neurapraxia due to retraction is common and patients should be warned that an area of numbness on the lateral aspect of the thigh may occur following surgery that in some cases may be permanent.
The L4, L5 nerve roots and the lumbosacral trunk crosses the anterior surface of the sacrum approximately 1.5 cm medial to the sacroiliac joint. If plates are applied too far medially on the sacrum the nerve will be damaged. This nerve root marks the medial limit of the approach.
Sacral Nerve Roots
The sacral nerve roots can be damaged at the point where they arise from the sacral foramina. For this reason, the dissection cannot be carried further medially than the sacral foramina. The sacral nerve roots are not usually exposed during this approach. They can be at risk at two stages of the operation. If sharp pointed retractors such as Hohmann are used medially, great care should be taken that the point of these retractors is not inadvertently inserted into a sacral foramen. Sacral nerve roots can also be entrapped under the medial end of plates applied to the anterior surface of the sacroiliac joint. Meticulous preoperative planning will allow you to know exactly how many screw holes can be inserted safely into the sacrum without endangering the sacral nerve roots. In most cases, only one screw can be inserted.
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Figure 7-14 Crack the inner cortex using an osteotome to complete the iliac osteotomy.
Vessels
Relatively large nutrient vessels often are avulsed from the inner wall of the ilium. Bleeding from these vessels can be controlled by pressure or bone wax.
How to Enlarge the Approach
Local Measures
Paradoxically, the key to adequate exposure of the posteriorly placed sacroiliac joint is adequate anterior dissection. The lateral end of the inguinal ligament and its attached anterior superior iliac spine must be mobilized to visualize the sacroiliac joint adequately.
Extensile Measures
The approach may be enlarged into an extended ilioinguinal approach that provides access to the entire anterior column of the acetabulum. This approach is discussed later in this chapter (page 378).
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Figure 7-15 Strip the iliacus from the inner wall of the pelvis to expose the underlying sacroiliac joint.
