Rotational Osteotomies

Rotational osteotomies attain femoral head coverage by cutting one to three of the pelvic bones, with the acetabulum being rotated on the intact structures. These osteotomies cover the femoral head with acetabular cartilage, and they intuitively are the first choice for femoral head coverage procedures. They all require a concentrically reduced femoral head.

The innominate osteotomy of Salter is the most widely used of the rotational osteotomies for the pediatric population. It divides the ilium just above the acetabulum, which allows the acetabulum to be rotated through the symphysis pubis. Neither the contour nor the volume of the acetabulum is changed. This procedure can obtain 20 degrees of improvement in the center-edge angle and 10 degrees of improvement in the acetabular index.

The patient is placed in the supine position with a sandbag under the ipsilateral thorax, and the affected limb is draped free. Adductor contracture is released with a subcutaneous or open tenotomy. Incision and exposure are provided via a Smith-Peterson approach to the hip. A so-called bikini incision starts 2 cm distal to the center of the iliac crest, extends 1 cm distal to the anterosuperior iliac spine, and ends below the middle of the inguinal ligament. The interval between the tensor fascia latae and the sartorius is developed to expose the rectus femoris and the anteroinferior iliac spine. The iliac apophysis is incised down to bone along the iliac crest from the posterior end of the skin incision to the anteroinferior iliac spine. The lateral portion of the apophysis and the periosteum of the outer table are carefully stripped in a continuous sheet to the lateral edge of the acetabulum and posteriorly to the greater sciatic notch; this space is then packed. Adhesions of the joint capsule to the lateral aspect of the ilium can be freed with a periosteal elevator. The medial half of the apophysis and the periosteum of the inner wall are carefully stripped in a continuous sheet to expose the sciatic notch. Care is taken to remain subperiosteal to avoid injury to the sciatic nerve and the superior gluteal artery. The tendinous portion of the iliopsoas is exposed on its deep surface at the level of the pelvic brim and rolled over to visualize the musculotendinous junction. A scissors is passed between the tendon and the musculotendinous junction, and the tendon is cut sharply with a scalpel. The tip of a curved forceps is passed subperiosteally from the medial side and through the sciatic notch to grasp the end of the Gigli saw. The index finger of the opposite hand is used to guide the forceps. The skin and the soft tissues are retracted widely. The osteotomy extends in a straight line from the sciatic notch to the anteroinferior iliac spine, with care taken to remain at right angles to the vertical axis of the ilium. The hands are kept far apart, and continuous tension is placed on each end of the saw to keep it from binding (Figure 37-1). A triangular-shaped bone graft is then taken from the iliac crest with large bone cutters. (A saw may be used in older children.) The base of the graft extends from the anterosuperior iliac spine to the anteroinferior iliac spine. A towel clip is placed on each fragment. The proximal fragment should only be steadied. The towel clip on the distal fragment should be placed well posterior to avoid fracture. The distal fragment is then rotated downward and forward in line with the ilium, which opens the osteotomy anterolaterally. Avoid the posterior or medial displacement of the distal fragment. If the hip capsule has not been opened, the leg can be used to attain the desired correction by placing it in a figure-four position. Downward pressure on the knee as the heel is moved toward the child’s chin produces the desired rotation. The wedge-shaped bone graft is then inserted into the osteotomy site, and the traction is released from the distal fragment. The posterior aspect of the osteotomy should remain closed. Two heavy, threaded K-wires are inserted across the osteotomy site, through the graft, and into the distal segment that lies medial and posterior to the acetabulum (Figure 37-2). Care is taken to avoid penetrating the hip joint. The hip is carefully moved so that crepitus can be heard and felt for; this may indicate that a pin has penetrated the joint. The two halves of the iliac apophysis are sutured together. The K-wires are cut so that their ends lie in subcutaneous fat. A drain is usually not necessary if only an innominate osteotomy has been performed. The wound is then closed. A 1½ hip spica cast is applied with the hip in slight abduction, flexion, and internal rotation and with the knee in flexion. In older, reliable children, three-point partial weight bearing with crutches may be permitted with no immobilization.

Figure 37–1 The inner and outer tables of the ilium are exposed. The periosteum is elevated carefully from the sciatic notch with a curved periosteal elevator, such as a Crego elevator. A right-angled forceps is passed medial to lateral while the finger of the other hand is used to push the periosteum down and away from the sciatic notch on the outer table. A Gigli saw is grasped in the forceps and pulled through the sciatic notch. Retractors are placed in the sciatic notch on each side of the ilium to provide wide retraction and to protect the soft tissues. The osteotomy is performed with the Gigli saw, which emerges at or just above the anterior inferior iliac spine. While using the Gigli saw, the hands should be spread as far apart as possible. Constant tension should be kept on each end of the Gigli saw, because it has a tendency to bind. The bone graft that is used to hold the osteotomy site open is taken from the anterior iliac crest. This can be done with bone-biting forceps in young children, but it is facilitated by the use of a power saw in older children. At this point, it is imperative to perform an intramuscular tenotomy of the iliopsoas as decribed for the anterior approach to the congenitally dislocated hip.

Figure 37–2 Although the graft should be secure, it is not secure enough at this point to be left alone without fixation. Smooth or thin wires should not be used. Two heavy threaded Kirchner wires should be used and passed from the proximal fragment into the distal fragment. In the distal fragment, these should lie medial and posterior to the acetabulum; this determines their starting point in the proximal fragment. There is a danger of passing one of the wires into the hip joint when the capsule has not been opened, as may occur during the treatment of acetabular dysplasia. This danger and the fact that properly placed pins appear on the postoperative radiograph to be penetrating the hip joint make it imperative that the surgeon has a good grasp of the pelvic anatomy and that he or she carefully moves the hip to feel and listen for crepitus. After this, the wound is closed. A drain is usually not necessary when only an innominate osteotomy has been performed.

Osteotomies in which all three pelvic bones (e.g., Steel, Tönnis, Carlioz) are cut offer greater rotational advantages. The Ganz periacetabular osteotomy may be performed for patients with a closed triradiate cartilage. This procedure is discussed in detail in Chapter 26, and it will not be discussed here. Variations of the triple osteotomy exist for patients with open triradiate cartilage.

Volume-Reducing Osteotomies

Volume-reducing osteotomies involve the use of incomplete cuts and hinge on different aspects of the triradiate cartilage; thus, these procedures are limited to patients with open triradiate cartilage.

The Pemberton osteotomy addresses a size “mismatch” between the acetabulum and the femoral head. By hinging on the posterior limb of the triradiate cartilage, the shape of the acetabulum can be changed to provide improved coverage for the femoral head.

The patient is positioned supine, with a bump placed under the involved hip. Exposure is via a Smith-Peterson approach to the hip. Just as with the Salter osteotomy, the iliac apophysis is split, and both the inner and outer tables of the ilium are exposed subperiosteally. Exposure is carried out to the sciatic notch, and the rectus insertion is left alone. Although it was not recommended by Pemberton in his original article, the division of the psoas tendon (as in the Salter osteotomy) may facilitate correction. Two flat-blade retractors are inserted into the sciatic notch on either side of the ilium. The osteotomy is performed with a narrow curved osteotome through the outer table, starting 1 cm above the anteroinferior iliac spine and extending posteriorly, keeping 1 cm to 1.5 cm from the attachment of the hip capsule. Because the osteotomy is carried posteriorly and then inferiorly through the outer table, it will disappear into the soft-tissue attachments behind the capsule. Visualization can be facilitated by the rotation of the retractor in the sciatic notch. Care must be taken to avoid cutting into the sciatic notch. Direct the osteotomy to the ilioischial limb of the triradiate cartilage. With the use of the same osteotome, a corresponding cut is made on the inner table. As with the outer table, avoid cutting into the sciatic notch. The plane of the osteotomy may be adjusted on the basis of the type of coverage that is necessary. A more transverse cut will provide more anterior coverage, whereas a laterally inclined osteotomy will provide more lateral coverage. After both cortices of the ilium have been cut, a wide curved osteotomy is used to connect the two cuts. As the osteotome proceeds posteriorly, it will become apparent that it cannot make the sharp turn inferiorly into the posterior column. A special Pemberton right-angled curved osteotome is used to complete this cut into the triradiate cartilage (Figure 37-3). A small lamina spreader can hold the osteotomy apart and facilitate this cut. The acetabulum can now be directed into the desired position. A groove is cut into each surface of the osteotomy with a narrow gouge or curette. A triangular wedge of bone is removed from the anterior iliac crest and placed in the osteotomy site (Figure 37-4). Because the graft will be recessed in the osteotomy site, the graft should be larger than the gap created by the osteotomy. This osteotomy is quite secure, and it does not require additional fixation. The iliac apophysis is reapproximated, and the wound is closed. The patient is placed in a 1½ hip spica cast.

Figure 37–3 After the inner and outer cortices of the ilium are divided as far as can be seen, a wider curved osteotome is used to connect these two cuts. As the osteotome proceeds posteriorly, it becomes apparent that it is not able to make the sharp turn inferiorly to avoid cutting into the sciatic notch. At this point, an osteotome with a right-angled curve (available via special order from Zimmer Co., Warsaw, IN) is inserted into the osteotomy. This can be made easier by prying down on the acetabular roof with an osteotome and then inserting a small lamina spreader to hold the osteotomy apart. The special osteotome is used to complete the cut into the triradiate cartilage. It is not possible to see the tip of the osteotome as it completes the osteotomy. It is not necessary and usually not possible to see the triradiate cartilage unless the acetabulum is levered down excessively. When the osteotomy is complete, the acetabular roof can be levered down into the desired position and held there with a lamina spreader.

Figure 37–4 Grooves are prepared in the cancellous surface on each side of the osteotomy to provide the secure fixation of the bone graft. This can be done with a curette. A triangular wedge of bone is cut from the anterior iliac crest. It should be larger than the gap that it is designed to span, because it will be recessed into the cancellous bone. When in place, the bone graft should be secure and stable; this can be verified by attempting to dislodge the graft. The wound is then closed in a routine manner.

The San Diego acetabuloplasty was developed to address the problems with dislocated hips in children with spastic cerebral palsy. Specifically, these issues are an elongated acetabulum and a superolateral acetabular deficiency. As with other acetabuloplasties, soft-tissue releases, open reduction, and femoral osteotomy may also be performed in conjunction with this procedure.

The patient is positioned supine, with a bump placed under the involved hip. Exposure is via a Smith-Peterson approach to the hip. Unlike the previously described procedures, only the outer table of the ilium is exposed subperiosteally. Exposure is carried out to the sciatic notch. The iliac apophysis is not split but instead elevated as a unit. A 1.5-cm-wide straight osteotome is used to make an osteotomy 0.5 cm to 1 cm above the edge of the acetabulum on a line drawn from the anteroinferior iliac spine to the sciatic notch. A preliminary notch is made at the extreme ends of the intended osteotomy, at the sciatic notch and the anteroinferior iliac spine, to prevent inadvertent fracture. The lateral cortex is cut, but the medial wall is kept intact; this will allow the fragment to bend freely. A 2-cm-wide curved osteotome is used to deepen the osteotomy in a medial and caudal direction behind the acetabulum to the horizontal limb of the triradiate cartilage (Figure 37-5). The osteotome should be directed halfway between the medial wall of the ilium and the medial wall of the acetabulum; this can be monitored with image intensification. Bicortical bone graft is obtained from the anterosuperior iliac spine and shaped into three or four small triangles with a base of 1 cm. The osteotomy site is opened with an osteotome or a lamina spreader. The grafts are placed into the osteotomy site, with the largest graft placed in the area in which maximum coverage is needed (Figure 37-6). This osteotomy is stable and does not require further fixation. The wound is closed. A 1½ hip spica cast is placed on the patient, with the hip in 45 degrees of flexion and 30 degrees of abduction.

Figure 37–5 With the use of a combination of straight and curved osteotomes, the osteotomy is deepened by heading medially and caudally behind the acetabulum. This cut must proceed between the medial wall of the ilium and the medial wall of the acetabulum; this can be monitored with an image intensifier. Mubarak and colleagues describe the osteotomy as going to—but not through—the triradiate cartilage. In our experience, the osteotomy does not have to be carried to the triradiate cartilage, as illustrated here. In the soft bone of the usual child with paralytic hip disease, there is sufficient mobility without the use of the triradiate cartilage; in fact, the osteotomy can be used in some cases in which the triradiate cartilage has closed. Next, a Kerrison rongeur is used to remove the cortex anteriorly and posteriorly as it extends around to the medial iliac wall. This is essential to allow the fragment to bend freely. In contradistinction to the Dega osteotomy, which involves the cutting of a considerable portion of the medial iliac cortex, these two areas that are removed with the Kerrison rongeur are the only cuts made into the medial wall.

Figure 37–6 A piece of the ilium in the region of the anterosuperior iliac spine is removed, and three tricortical triangular pieces of bone are fashioned. These are wedged securely into the osteotomy site, which is held open with a lamina spreader. The amount of correction and where it occurs vary slightly with the size of the grafts and the site of placement of the largest and smallest grafts. The largest graft is usually placed anteriorly. It has generally been difficult to attempt to get more posterior coverage by placing the largest graft posteriorly. The amount of coverage should be verified, and the surgeon should be certain that the grafts are secure. No internal fixation is necessary. The wound is then closed.

Salvage Procedures

These procedures are usually reserved for hips that lack significant femoral head coverage because of an inability to acquire such coverage with articular cartilage by other osteotomies (i.e., rotational or volume reducing). These procedures place bone over the hip joint capsule on the uncovered portion of the femoral head. However, there are data that document the good long-term results of these procedures.

The medial displacement osteotomy of Chiari consists of the construction of a congruent shelf above the femoral head. It is primarily indicated for older patients with painful subluxated hips. The concentric reduction of the hip is not a prerequisite. This procedure medializes the hip joint, thereby reducing the forces. However, it is unable to provide much anterior coverage, and it may cause a prolonged limp by shortening the abductor lever arm.

Position the patient supine, with a bump placed under the involved hip. Exposure is via a Smith-Peterson approach. As with the Salter osteotomy, the inner and outer tables of the ilium are exposed. The superior aspect of the hip capsule needs to be well exposed anteroposteriorly to facilitate the correct placement of the osteotomy. A guidewire should be drilled lateral to medial, with a 10-degree to 15-degree cephalad incline just above the acetabular roof. The osteotomy should be between the capsular insertion and the reflected rectus head, it should head in a curvilinear fashion along the capsular insertion, and it should end anteriorly under the anteroinferior iliac spine and posteriorly in the sciatic notch (Figure 37-7). Pass a Gigli saw through the sciatic notch (i.e., like the initiation of the Salter osteotomy) to score the anterior cortex of the sciatic notch to ensure that the osteotomy fractures through that point in the notch. The lateral cortex is cut first, and this is followed by the medial cortex. Ensure that there are no posterior tethers. The distal fragment is displaced medially by abducting the leg. Further displacement can be achieved by placing direct pressure over the greater trochanter. After the desired displacement is achieved, fixation is obtained with two or three screws or large threaded Steinmann pins. Coverage can be augmented anteriorly by obtaining corticocancellous bone from the inner table of the ilium and placing it in the osteotomy site before fixation (Figure 37-8). Additional cancellous bone graft is added and held in place by the periosteum when the wound is closed.

Figure 37–7 The placement of the osteotomy is crucial to the success of the operation. If it is too high, it does not provide coverage for the hip; if it is too low, there is not a sufficient capsule between the femoral head and the ilium. Therefore, it is important that the superior aspect of the hip capsule be well exposed anteroposteriorly. In addition, it is necessary to know where the roof of the acetabulum lies. This may be difficult in many subluxated hips because of a markedly thickened capsule. In some cases, it may be necessary to thin thiscapsule.

Conceptualizing how the distal fragment is displaced medially in relation to the proximal fragment (despite the fact that the pelvic ring is divided in only one place) is important to the understanding of the osteotomy. The displacement occurs as the distal fragment rotates on the symphysis pubis; this is the reason why the direction of the osteotomy is important for obtaining “displacement.” Proceeding lateral to medial, the osteotomy should incline cephalad by about 10 degrees. This permits the inferior fragment that contains the hip joint to displace medially.

These two crucial points—the location of the acetabular roof and the direction of the osteotomy—can be verified by drilling a small guidewire or by driving an osteotome lateral to medial in the estimated direction of the osteotomy at the proposed site of the osteotomy while viewing this with a radiograph or an image intensifier. The osteotomy should incline cephalad 10 degrees to 15 degrees from lateral to medial to facilitate the displacement (or, more correctly, the rotation).

Figure 37–8 As mentioned previously, it is often necessary to augment the coverage obtained with the Chiari osteotomy. This is especially true anteriorly, where the ilium is thin. An excellent method for accomplishing this coverage has been described. An appropriately sized piece of corticocancellous bone is removed from the inner table of the ilium and then placed in the osteotomy site before fixation. The screws or pins that are used for fixation will then transfix this graft. Additional cancellous bone graft is added over this graft and held in place by the periosteum and the muscles when the wound is closed.

Several variations of the shelf procedure exist. The goals of this procedure are to increase the load-bearing area of the hip and to increase the stability of the hip. The procedure is indicated for patients with asymmetric incongruity in whom redirectional osteotomies would not be appropriate.

The patient is positioned supine, with a bump placed under the involved hip. Exposure is via a Smith-Peterson approach. Only the outer table of the ilium is exposed subperiosteally. The reflected head of the rectus femoris is sectioned at the junction of the conjoint tendon; it is reflected to expose the entire hip capsule, and it will be used to secure the bone graft. The location of the slot should be at the edge of the acetabulum; the correct location can be verified with image intensification. When the correct location is identified, a -inch drill or a burr is used to make a series of 1-cm-deep holes that incline 20 degrees cephalad at the edge of the acetabulum (Figure 37-9). A narrow rongeur or burr is used to connect the holes and to produce a slot; the floor of the slot should be the subchondral bone of the acetabulum. Corticocancellous and cancellous strips of bone graft are obtained from the outer table of the ilium. The cancellous grafts are cut into 1-cm-wide strips that are long enough to provide adequate lateral femoral head coverage. They are placed in the slot so that they extend out over the capsule. A second layer of cancellous strips is placed perpendicular to the first layer (Figure 37-10). Extending the graft too anterior or lateral may result in impingement, so this should be avoided. The reflected head of the rectus is sutured back to the conjoint tendon, which holds the grafts in place. The remaining bone is cut into small pieces and placed over the graft. The wound is closed, and the patient’s hip is placed in a 1½ hip spica cast in 20 degrees of flexion and 15 degrees of abduction.

Figure 37–9 During the exposure, the reflected head of the rectus tendon should be identified, dissected free of the capsule, and divided somewhere between its mid portion and its junction with the conjoined tendon; this procedure is used to secure the grafts in place. The most important part of the surgery is identifying the correct location for the slot: it should be placed at the exact acetabular edge. The surgeon must determine whether this is the true or false acetabulum; this is done by determining which of the two affords greater stability and congruity. The acetabulum is identified by creating a small incision in the capsule or by inserting a probe. In the subluxated and dysplastic hip, the capsule is usually thickened and adherent to the ilium, which may cause the surgeon to place the slot and therefore the graft too high. The correct location should be verified radiographically by placing a guide pin into the ilium at the presumed acetabular edge. In some cases, it may necessary to thin the capsule to permit the graft to be placed in the proper location.

After the correct location is verified, a -inch drill bit is used to make a series of holes at the edge of the acetabulum. These holes should be drilled to a depth of about 1 cm, and they should incline about 20 degrees, as illustrated. They should extend far enough anteriorly and posteriorly to provide the necessary coverage.

Figure 37–10 The cancellous grafts are cut into strips that are 1 cm wide and of appropriate length to provide the desired amount of lateral coverage. These are placed into the slot so that they extend out over the capsule. A second layer of cancellous strips are placed at 90 degrees to the first layer of strips of graft. The grafts must not extend too far laterally or anteriorly in the quest for spectacular radiographic coverage of the hip, because this could lead to a loss of motion as a result of impingement.