Surgical Technique for the Lateral Approach to the Proximal Femur

The lateral surgical approach is similar for all age groups. A straight lateral incision that extends from the tip of the trochanter to a point several centimeters distal to the greater trochanter is used for exposure. The length of the incision varies with the size of the implant to be used for fixation and with the size of the child. Sharp dissection is carried down to the fascia lata with the scalpel and electrocautery. The skin and subcutaneous tissue are elevated together off of the fascia lata for a few centimeters in both the anterior and posterior directions. The fascia lata is divided in line with the skin incision. Just deep to the fascia lata lies the fascia of the vastus lateralis, which is longitudinally incised directly over the vastus lateralis muscle.

With lateral traction on the posterior edge of the vastus lateralis fascia and counter (medial) traction on the vastus lateralis muscle mass, the electrocautery is used to mobilize and reflect the vastus muscle from lateral to medial off of the lateral intermuscular septum. Care is taken to avoid dissecting through the septum and into the posterior muscle compartment of the thigh. Proximally, the vastus release extends anteriorly over the shaft of the femur. The lateral-to-medial reflection of the vastus lateralis muscle mass is completed from proximal to distal. Within the distal vastus muscle, care should be taken to identify and coagulate the vessels that distally perforate through the lateral intermuscular septum from the posterior to the anterior compartment.

As the vastus lateralis is retracted medially, the periosteum of the femur is visualized. The lateral periosteum is incised, and the femur is subperiosteally exposed just distal to the lesser trochanter. A curved retractor is carefully placed subperiosteally around the anterior shaft of the femur. Posteriorly, the periosteum and the soft tissues are more securely attached to the bone; they are best elevated off of the bone with the electrocautery and the elevator. With blunt dissection, the subperiosteal exposure can be extended distally. With an adequate exposure, the femur should be visible and accessible from the proximal aspect of the greater trochanter to a point distal to the lesser trochanter, which is sufficient for the application of the fixation plate (Box 36-1).

Surgical Technique for Correcting Proximal Femoral Valgus Deformity in Young Children

For children who are less than 5 years old, a small fragment, a semi-tubular straight plate, a Wagner forked plate (Aesculap, San Francisco, CA), or a small blade plate (Synthes, Paoli, PA) can be used for fixation. The appropriate implant is temporarily inserted into the incision to assess the adequacy of the exposure. If necessary, the skin and fascial incisions are extended distally to facilitate the insertion of the plate. C-arm imaging is used to confirm the optimum position of hip abduction, flexion, and internal rotation needed to reduce or satisfactorily position the femoral head into the acetabulum. A four- or five-hole small-fragment straight semi-tubular plate is the best choice for a femoral shortening osteotomy in conjunction with the open reduction of a developmentally dislocated hip. The anterior iliofemoral approach and open reduction are performed first through an oblique incision that parallels the lateral edge of the iliac crest. For the shortening osteotomy, the lateral proximal femur is approached as previously described. The osteotomy (Figure 36-1) is performed just distal to the lesser trochanter. The plate is placed just distal to the inferior edge of the greater trochanter physis as assessed with the C-arm. The plate is provisionally fixed by inserting a screw in the most proximal screw hole. A drill hole is also made in the bone that corresponds with the second most proximal hole. The proximal screw is loosened, and the plate is rotated anteriorly. The femoral osteotomy is performed just distal to the predrilled second proximal hole.

Figure 36–1 A, Anteroposterior pelvic radiograph of a 6-year-old girl that shows dislocation of the left hip (developmental dysplasia of the hip) with proximal displacement of the femur. Anteroposterior intraoperative C-arm radiographs, B, before and, C, after the open reduction of the left femoral head into the true acetabulum facilitated by a 2.5-cm proximal femoral shortening osteotomy fixated with a five-hole semi-tubular small fragment plate and, D, after left pelvic (Pemberton-type) osteotomy.

With the femoral head reduced, the amount of fragment overlap is directly measured; it is typically 1 cm to 2 cm. This determines how much shortening is required. A second osteotomy that is parallel to the first is completed. The fragments are reduced and fixed to each other with the correction of excess anteversion as appropriate. The femoral head is reduced, and the position and stability are assessed. If additional shortening or a change in the rotational alignment is needed, the distal screws are removed, the distal fragment is further shortened or rotated, and the plate is reapplied with the use of new holes.

A Wagner forked plate works well for younger, smaller patients as fixation if angular correction is desired beyond shortening or rotation, as in a varus osteotomy to correct coxa valga associated with residual DDH or with static encephalopathy. If the Wagner plate is to be used, a smooth K-wire is inserted just proximal to the intended site of plate insertion (Figure 36-2). The K-wire is inserted from lateral to medial and placed superiorly in the neck on the anteroposterior view to provide enough space for the subsequent insertion of the Wagner plate. It is centered in the femoral neck on the lateral view. Subperiosteal retractors are circumferentially placed around the femur to protect the soft tissues. A femoral osteotomy is performed at the midpoint of the lesser trochanter, and this is confirmed with the use of C-arm imaging. The femur is transversely cut with an oscillating power saw under direct vision. After completing the osteotomy, consideration should be given to shortening the distal fragment 1 cm to 2 cm, because growth stimulation and secondary limb-length discrepancy often occur in these young patients. A Wagner forked plate of appropriate size is inserted into the proximal femoral fragment with the use of the previously inserted K-wire as a guide. The forked tips of the plate are inserted through the distal lateral cortex and carefully advanced medially and proximally into the femoral neck; the correct position is confirmed with the C-arm. After the prongs of the plate are fully inserted, the distal femoral fragment is reduced and secured to the proximal fragment with a self-centering bone-holding clamp. When performing a varus-producing osteotomy, the distal fragment should be slightly medialized relative to the proximal fragment. The proportion of medialization will vary slightly, depending on the entry point of the plate in the proximal fragment. Excessive medialization can produce an unstable construct as a result of a loss of contact between the fragments.

Figure 36–2 A, Anteroposterior radiograph of the pelvis of a 6-year-old boy with hip dysplasia (subluxation, coxa valga, and acetabular deficiency as a result of static encephalopathy). B, A guide pin has been inserted into the femoral neck. The osteotomy was performed at the lower half of the lesser trochanter, and a Wagner forked plate was introduced. C, Lateral C-arm image confirming the placement of the forked plate. D, An anteroposterior radiograph that shows the proximal femoral osteotomy fixated with a Wagner plate and noted acetabular dysplasia. E, Anteroposterior radiograph that shows a laminar spreader opening a periacetabular (Pemberton-type) osteotomy. F, Final C-arm image after the insertion of a bone graft that was obtained as the femur was intentionally shortened during a femoral osteotomy.

The reduction of the femoral head in the acetabulum and the neck shaft angle is assessed with the use of C-arm imaging. If necessary, the varus/valgus alignment can be adjusted by removing the bone-reduction clamp and bending the side plate in situ. In small children (i.e., those less than 3 years old) a varus neck shaft angle of 105 degrees to 110 degrees will typically remodel into an acceptable neck shaft angle at maturity. Obtaining an excessive neck shaft angle (i.e., more than 90 degrees) is undesirable. Remodeling occurs slowly, and a near-normal neck shaft angle may never be achieved. A neck shaft angle of 110 degrees to 115 degrees is used in older children, who have less remodeling potential. The rotational alignment of the two fragments is adjusted to help optimize the reduction of the femoral head into the acetabulum. By doing so, excess external rotation of the distal fragment should be avoided, because this may lead to an out-toeing gait. It may be desirable to slightly extend the distal fragment to create flexion of the proximal fragment, which provides anterior femoral head coverage by the acetabulum in the weight-bearing position. The extension of the distal fragment is achieved by tilting the plate posteriorly as the prongs are inserted into the proximal fragment.

The hip range of motion should be assessed, with flexion and extension, abduction and adduction, and internal and external rotation being noted; passive abduction should be at least 30 degrees. If passive hip abduction motion is limited by an adductor muscle contracture, which is likely with neuromuscular hip dysplasia, an adductor tenotomy may be indicated; this is typically performed at the beginning of the surgical procedure. Hip rotation motion should be assessed, and external and internal rotation should be approximately equal. After a satisfactory reduction of the fragments is achieved, the plate is secured to the distal femur with two bicortical screws. The most proximal hole on the plate should be filled with one long screw directed into the femoral neck to securely engage the proximal fragment.

The final neck shaft angle, the plate fixation, and the hip reduction should be evaluated using the C-arm. A deep suction drain is placed, and the wound is closed in separate fascial layers. For young children (i.e., those less than 6 years old), a 1½ hip spica cast holding the thigh in a slightly abducted and flexed position is applied for 5 to 6 weeks (Box 36-2).

Surgical Technique for Correcting Femoral Valgus Deformity in Older Children, Preadolescents, and Adolescents

Among 5- to 12-year-old children, the varus osteotomy is usually secured with an intermediate 90-degree angled blade plate with a 10-mm offset and a 35- to 40-mm blade length (Synthes, Paoli, PA). The correction needed in this patient population is determined from functional radiographic images, noting the position of flexion, abduction, and internal rotation that optimally reduces the femoral head into the acetabulum. Alternatively, recently developed relatively low-profile locking plates of appropriate size for children (Synthes, Paoli, PA) have become available. The locking plate provides secure fixation, and, during insertion, it allows for some adjustment with regard to the degree of correction that can be obtained. The locking plate technique can be particularly advantageous when performing osteotomies on bones with relative osteomalacia. To insert a blade plate, a channel that corresponds with the size of the blade must be cut into the bone.

A special chisel is used to cut the channel from lateral to medial in the proximal femur. The chisel insertion site must be proximal enough in the proximal femur so that there will be sufficient femoral neck length to allow for the insertion of the entire blade (i.e., approximately 35 mm to 40 mm). The desired direction of the proximal and distal site of chisel entry into the proximal fragment is determined with the use of both of the K-wires as reference points as well as with C-arm imaging. With the use of a 90-degree template, the first reference wire is placed in a lateral to medial direction perpendicular to the shaft of the proximal diaphysis. While monitoring with a C-arm that provides anteroposterior and lateral views, the second wire is inserted proximal to the first wire into the femoral neck. This wire will serve as a directional guide for subsequent chisel placement. The chisel is advanced into the proximal femur parallel to the proximally placed guide pin to a depth equal to the length of the blade selected with the use of preoperative templating. The chisel insertion is carefully monitored with frequent anteroposterior and lateral C-arm images. If increased anterior coverage of the femoral head is desired, this can be accomplished by tilting the chisel posteriorly in the sagittal plane. When the blade plate is inserted into the posteriorly angulated chisel slot, the side plate will be extended. After the completion of the osteotomy and the reduction of the proximal and distal fragments to the blade plate, desired flexion will occur at the osteotomy site. The proximal fragment will be tilted posteriorly into the acetabulum, which will result in an improvement in the anterior coverage of the femoral head.

With the use of C-arm guidance, an osteotomy site is selected approximately 1.5 cm to 2 cm distal to the chisel channel. Subperiosteal retractors are placed circumferentially around the osteotomy site to protect the soft tissues, including the medial circumflex artery, from injury. A transverse intertrochanteric osteotomy is performed with a power saw, and the distal fragment is mobilized. The chisel is removed from the proximal fragment, and the blade plate is inserted. C-arm imaging is used to ensure that the blade is advanced into the same channel developed by the chisel. Next, the distal femoral fragment is reduced to the side plate and secured with a bone-reduction clamp. C-arm imaging is used to evaluate the neck shaft angle, to assess the adequacy of the varus correction, and to ensure that the femoral head will be optimally seated within the acetabulum. If less varus is desired, the 90-degree blade plate can be exchanged for a 100-degree blade plate. Alternatively, the blade plate can be removed and the side plate bent with plate benders to increase or decrease the blade-plate angle and to achieve the appropriate varus/valgus correction. Rotational correction can be adjusted by rotating the distal fragment as needed. Minor changes in flexion and extension (i.e., 10 degrees or less) can be obtained by altering the anterior and posterior angulation of the distal femoral fragment as it is secured on the side plate. This adjustment is limited by the necessity of achieving the bicortical fixation of all three distal screws that are used to secure the side plate.

After the optimal correction has been achieved, the side plate is secured to the distal fragment with three bicortical screws with the use of the standard compression plating technique. After osteotomy fixation, hip range of motion is assessed to ensure that adequate flexion and extension, abduction and adduction, and approximately equal internal and external rotation have been obtained. Final C-arm images are taken to assess that both an appropriate redirection of the proximal femur and a stable osteotomy construct have been achieved (Figure 36-3). If the PFO is performed in conjunction with a pelvic osteotomy for the treatment of residual DDH, the pelvic osteotomy is performed first, followed by the PFO. If these procedures are performed in conjunction with a pelvic osteotomy to treat severe neuromuscular hip dysplasia, the PFO and any accompanying soft-tissue releases are done first, followed by the pelvic osteotomy. A deep suction drain is inserted into the fascial layers. The fascia of the vastus lateralis and the tensor fascia lata are repaired separately.

Figure 36–3 A, Anteroposterior bilateral hip radiograph of a 7-year-old child with evolving Legg-Calvé-Perthes disease of the left hip. B and C, Anteroposterior and lateral intraoperative C-arm radiographs of the left hip after a varus proximal femoral osteotomy fixated with a 100-degree adolescent-size blade plate.

Fixation achieved with a blade-plate construct is typically rigid enough to maintain osteotomy correction without the need for supplemental spica casting. Despite this, we still recommend applying a 1½ hip spica cast for children 7 years old or younger to ensure patient comfort and to assist with transfers. For children who are 7 to 10 years old who are being treated for residual hip dysplasia, a removable abduction foam pillow can be used as an alternative to hip spica casting. Patients are allowed to be up with crutches and to have touch-down weight bearing on the involved extremity if they can comply with limited weight bearing. Patients who are undergoing proximal femoral varus osteotomy for the treatment of Legg-Calvé-Perthes disease benefit from abduction cast splinting (i.e., a bilateral cylinder cast connected with an abducting bar) to ensure femoral head containment during the acute stages of the healing of the osteotomy.

A proximal femoral varus-producing osteotomy is similarly performed for both preadolescents and adolescents. The same lateral approach and subperiosteal femoral exposure as described previously are used. The osteotomy site is typically located just proximal to the lesser trochanter in the intertrochanteric region. The osteotomy is fixated with either an adolescent-size (i.e., 90-degree angled, 40-mm blade length, and 10-mm offset) or an adult-size (i.e., 90-degree angled, 40-mm blade plate, and 10-mm offset) blade plate (Synthes, Paoli, PA). The radiographically monitored techniques for chisel and plate insertion are the same as those that were previously described. However, it is often considerably more difficult to insert both the chisel and the blade plate into the relatively denser bone of the adolescent. The chisel is gradually driven into the femur to a depth that is equal to the length of the blade plate that has been selected during preoperative planning (Figure 36-4).

Figure 36–5 A, Anteroposterior bilateral hip radiograph of a 13-year-old adolescent after a varus osteotomy for the containment treatment of Legg-Calvé-Perthes disease at the age of 9 years. Residual pathologic varus deformity persists. The neck shaft angles of the proximal femurs are 105 degrees on the left and 125 degrees on the right. B, Anteroposterior and, C, lateral intraoperative C-arm radiographs of the left proximal femur after a valgus osteotomy fixated with a 120-degree adult-size blade plate. The neck shaft angle has been restored to 125 degrees. Note that the center of the medullary canal of the distal fragment is aligned with the piriformis fossa.

Postoperatively, older patients are mobilized with protective weight bearing equal to the weight of the lower extremity for 6 weeks. When early bone consolidation callus formation appears on plain radiographs, progressive weight bearing is allowed. Most patients can perform full weight bearing without crutch protection by 8 to 10 weeks. Elective hardware removal is advised before excessive lateral bone overgrowth (Box 36-3).

Surgical Technique for Correcting Proximal Femoral Varus Deformity

Valgus osteotomy of the proximal femur in younger patients is indicated for the treatment of varus deformities of the proximal femur. Clinical problems that are commonly treated with a proximal femoral valgus-producing osteotomy include congenital (developmental) coxa vara, growth disturbance from avascular necrosis associated with previous treatment for DDH, and residual varus after a proximal femoral varus-producing osteotomy for Legg-Calvé-Perthes disease. Patients with coxa vara have limited hip abduction and more external rotation than internal rotation. The goals of a valgus-producing osteotomy are to increase the neck shaft angle, and to improve hip mechanics by increasing hip abduction and normalizing the abductor function that reduces gait deviations. Preoperatively, the desired correction can be determined from functional radiographic images with the hip in adduction and internal rotation.

A proximal femoral valgus osteotomy is performed through the same lateral approach as previously described for performing a varus osteotomy. The proximal femoral valgus osteotomy in young children is fixated with an intermediate blade plate that is 130-degree angled with a 35-mm to 45-mm blade length and a three- or four-hole side plate (Synthes, Paoli, PA). K-wires are inserted under C-arm guidance and used as a reference when inserting the chisel. To accomplish this, the first K-wire is inserted perpendicular into the proximal femoral diaphysis from a lateral to medial direction, which simulates the position of a side plate parallel to the shaft of the femur after the blade is inserted. A second and more proximal guidewire is placed into the proximal femoral neck at an angle predetermined with the use of preoperative templates to obtain the desired varus deformity correction.

Next, the bone-cutting chisel is inserted into the proximal fragment parallel to the second, proximal K-wire. With the use of C-arm guidance, the cutting chisel is advanced into the femoral neck to a depth that is equal to the length of the blade on the preselected blade plate. Later, after the osteotomy has been completed and the 130-degree blade plate has been inserted and fixed to the distal fragment, a 30-degree valgus correction will have been achieved. If flexion or extension correction is also desirable, the chisel should be tilted either anteriorly or posteriorly; anterior tilt flexes the distal fragment and functionally increases hip joint flexion, thus potentially decreasing anterior head coverage. Similarly, if the chisel is tilted posteriorly, the distal fragment is extended, which in turn increases femoral head coverage during weight bearing.

When using the 130-degree blade plate to fix a valgus osteotomy, it is desirable and possible to remove the chisel and insert the blade plate before the osteotomy is performed. When it is positioned in valgus, the blade plate will not be in the way of the performance of the osteotomy. The osteotomy is performed at the intertrochanteric area with the power saw. Subperiosteal retractors are placed circumferentially around the osteotomy site to protect the soft tissues, including the medial circumflex artery, from injury.

When the osteotomy is complete, the distal fragment is mobilized and secured to the side plate with a bone clamp. If additional lengthening of the extremity is not desired, then one or both osteotomy fragments should be appropriately shortened to avoid the overlengthening of the extremity. After the blade plate has been inserted, a more normal neck shaft angle will be noted when the varus deformity is corrected as assessed with the C-arm (Figure 36-5). If necessary, it is possible to alter the relative degree of varus and valgus by changing to a different angle blade plate or bending the blade plate with a plate bender. Passive hip abduction will be notably increased. Patients with the coxa vara deformity often have inherent shortening of the adductor muscles. If after the correction of the varus deformity it appears that the shortening of the adductor muscle is limiting passive abduction, an adductor tenotomy should be performed, typically of the adductor longus tendon. Internal and external hip rotation is assessed. It may be necessary to internally rotate the distal fragment to correct an out-toeing gait deformity. The medial and lateral relationship of the two fragments is assessed. The fixation screws are inserted into the distal fragment with the use of a compression technique. Final C-arm images are taken to confirm that the desired correction has been achieved.

Figure 36–4 A, Anteroposterior pelvic radiograph of a 15-year-old girl with hip dysplasia: acetabular dysplasia, coxa valga (i.e., a neck shaft angle of 150 degrees), and subluxation. B, Anteroposterior pelvic radiograph 5 weeks after combined Bernese periacetabular and proximal femoral varus osteotomies. The latter was fixated with a 90-degree adult-size blade plate. The neck shaft angle was restored to 130 degrees.

A suction drain is placed deep to the vastus lateralis muscle; it exits through the skin proximally and laterally. The fascial layers (i.e., the vastus lateralis fascia and the fascia lata) are securely closed in separate layers, and the subcutaneous tissue and skin are closed. To protect the osteotomy and to minimize discomfort in a young child (i.e., those 6 years old or younger), a spica cast or an abduction cast is used for 5 to 6 weeks. Alternatively, for older children (i.e., those 6 years old and older), the use of a soft abduction foam pillow often provides sufficient comfort when correcting a varus deformity. Typically, for older children, protective early weight bearing is permitted. Healing readily occurs without a loss of correction in these patients.

Very severe varus deformities can occur among younger children as a result of either congenital (developmental) coxa vara or coxa vara that occurs as a result of the treatment of DDH. The trochanter in these patients is often very high riding, the femoral neck is shortened, and the neck shaft angle is less than 90 degrees. When correcting this severe deformity, consideration must be given to restoring a more normal neck shaft angle, distal and lateral repositioning of the greater trochanter, and restoring a more normal femoral neck length. Both Wagner and Morscher have used a three-part osteotomy when attempting to correct all aspects of this often severe deformity. When performing either of these two relatively complex femoral osteotomies, the surgeon should be aware of the circulatory pathways of the medial femoral circumflex artery as it courses into the femoral capital epiphysis. There is an inherent risk of injury to the critical terminal branches of the medial circumflex artery as well as a risk for the subsequent occurrence of femoral capital epiphysis avascular necrosis that occurs with any osteotomy that cuts through the lateral femoral base of the trochanter or the femoral neck. Similarly, Cech and colleagues reported about the use of a two-part osteotomy to obtain correction, specifically of the typically severe coxa vara deformity that can occur after marked growth disturbance associated with the closed treatment of DDH. The 100-degree blade plate is inserted directly through the lateral aspect of the trochanter, and the osteotomy cut is a two-part triangle that is centered along the newly elongated inferior neck of the proximal femur. This osteotomy is theoretically less likely to injure the circulation of the proximal femur than the Wagner and Morscher osteotomies. When correcting relatively severe coxa vara deformities with any of the previously described valgus osteotomies, the trochanter is moved distally. This places the abductor muscles under increased tension, and a relative abductor contracture may be noted intraoperatively. With time, the functional abduction muscle tightness will resolve (Box 36-4).

Surgical Technique for Proximal Femoral Osteotomy for Slipped Capital Femoral Epiphysis

A proximal femoral osteotomy is frequently performed to correct the chronic and often severe proximal femoral deformity that results from an SCFE. The slip deformity is characterized by the posterior displacement of the epiphysis on the metaphysis. This exposed femoral neck impinges on the anterior acetabulum during flexion. Patients with this condition present with some of the most challenging of all problems related to joint-preservation surgery. The surgical approach that is necessary to correct complex SCFE deformities often includes both a proximal femoral redirectional osteotomy and a femoral head–neck osteochondroplasty. The proximal femoral redirectional osteotomy flexes and internally rotates the distal fragment (i.e., the lower extremity) relative to the displaced epiphysis. The proximal femur osteochondroplasty further reduces or eliminates anterolateral cam hip joint impingement. The surgical correction of the slip deformity with PFO and osteochondroplasty is indicated for healed slip deformities and chronic stable deformities; it is not indicated for slip deformities that are unstable.

The two current surgical techniques that provide the comprehensive correction of an SCFE deformity include the anterolateral (Watson-Jones) approach and the more recently described surgical hip dislocation. The extensive reconstructive procedures that are needed to adequately correct this deformity can be facilitated with a surgical hip dislocation. In North America, many patients with SCFE deformity have associated morbid obesity. For those patients with severe obesity, the surgical correction of a problematic slip deformity should be deferred until the patient has achieved an appropriate weight loss.

The anterolateral (Watson-Jones) hip approach provides sufficient exposure for performing a proximal intertrochanteric femoral osteotomy, a capsulotomy, and an anterolateral osteochondroplasty. The patient is positioned supine with a bump under the ipsilateral buttock. The incision starts at a point approximately 4 cm to 5 cm posterior and 3 cm distal to the anterosuperior iliac spine, extends to and then gradually curves anteriorly around the posterior edge of greater trochanter, and extending distally for several centimeters parallel with the shaft of the femur. The skin and the subcutaneous tissue are reflected together to anteriorly and posteriorly expose the fascia lata. Distal to the trochanter, the fascia lata is incised in a longitudinal direction parallel to the shaft of the femur. This is extended proximally across the greater trochanter, along the posterior edge of the gluteus maximus muscle. The posterior border of the tensor is separated from the anterior border of the gluteus medius muscle. The surgeon should further develop this interval proximally, being careful to avoid injury to the branches of the superior gluteal nerve, which courses in an anteromedial direction and innervates the tensor fascia lata muscle.

Deep to the anterior border of the gluteus medius, the greater trochanter and the anterolateral base of the femoral neck can be identified. Just distal to the anterolateral base of the femoral neck are the origins of the vastus lateralis and the vastus intermedius muscles. The vastus fascia is longitudinally incised in line with the femur, and the vastus muscle is reflected off of the lateral intramuscular septum in a proximal-to-distal and lateral-to-medial direction. The reflection of the vastus lateralis is extended proximally and medially to include the vastus intermedius muscle, which completes the exposure of the base of the proximal femur.

Starting laterally at the base of the neck, the hip capsule is exposed medially up to the anterolateral edge of the acetabulum. Narrow, deep-type retractors are helpful for exposing the capsule. An arthrotomy is made in the direction of the femoral neck; care should be taken when incising the capsule proximally to avoid cutting the labrum. Further exposure of the femoral neck is achieved by proximally extending the capsulotomy medially and laterally. After the labrum has been visualized, the anterior rim of the acetabulum can be palpated. A cobra-type retractor is inserted on the anterolateral acetabulum rim and placed around the medial femoral neck to optimize the exposure. This type of retractor should not be placed around the superior/posterior femoral neck because of the risk of injury to the terminal branches of the medial femoral circumflex artery as it enters the posterior lateral femoral neck. The normal bony anatomy will be distorted by a prominent anterolateral metaphyseal bump of bone. The size of the prominence varies with the severity of the slip. If the slipped epiphysis had previously been stabilized, the screw heads may protrude on the anterior neck of the femur. The epiphysis, which has been displaced posteriorly on the metaphysis, will not be visible at this time. The screws should be removed if the physis is closed. If the physis is still open and the slip has not been previously stabilized with screw fixation, then consideration should be given to inserting a 6.5-mm cannulated screw into the epiphysis before performing the redirectional osteotomy.

The intertrochanteric osteotomy can be fixed with either a 120-degree or a 90-degree angled blade plate. The 120-degree blade plate is inserted through the lateral cortex of the femur beginning at the level of the greater trochanter and is directed proximally into the femoral neck, whereas the 90-degree blade plate is inserted through the lateral femoral cortex and transversely across the proximal femur at the base of the femoral neck and is perpendicular to the femoral shaft (Figure 36-6).

Figure 36–6 A, Anteroposterior pelvic radiograph of a 14-year-old girl with a previous in situ pinning of bilateral slipped capital femoral epiphyses; she walks with an external rotation deformity which is greater on the left side than on the right. B, Frog-leg lateral radiograph of the left hip that demonstrates the posterior tilt of the femoral head and femoroacetabular impingement. There is noted anterolateral hip pain with flexion and obligatory external rotation in flexion. C, Anteroposterior intraoperative C-arm radiographs that show the screw removal, the insertion of reference wires, and the initial chisel placement to be used for cutting a tract for inserting the blade plate. D, Anteroposterior and, E, lateral intraoperative C-arm radiographs that show the advancement of the chisel. Note the large bony ridge along the anterolateral proximal femur that pathologically impinges on the acetabulum. F, Lateral intraoperative C-arm radiographs after the fixation of the flexion osteotomy (i.e., the posterior tilt of the femoral head as seen in image B has been corrected) and after the large anterolateral bump has been resected. G, Anteroposterior and, H, lateral radiographs of the left hip 6 weeks postoperatively showing proximal femoral flexion and rotational osteotomy fixated with a 120-degree adult-size blade plate. Note that the center of the femoral shaft is aligned with the piriformis fossa on both views. Also note the resection of a previously existing anterolateral head–neck bony “bump” (as seen in image D); the hip now flexes to 95 degrees with 15 degrees of internal rotation in flexion.

The exact slope of the chisel channel that is used to cut the channel in the proximal femur is determined with the use of two K-wires for reference. The first reference K-wire is placed perpendicular to the proximal lateral femoral cortex under C-arm guidance. If the 120-degree angled blade plate is used, the second wire is inserted from lateral to medial into the femoral neck but sloping 30 degrees proximally. If the 90-degree blade plate is to be inserted, the second wire is inserted into the proximal femur parallel to the first K-wire and just proximal to the desired entry site of the blade plate in a lateral-to-medial direction.

Whichever blade plate is to be used (i.e., 120 degree or 90 degree), the chisel is inserted just distal and parallel to the proximal reference K-wire. To facilitate the insertion of the chisel, three parallel drill holes are made at the preselected chisel entry site. On the sagittal plane, the chisel entry site must be anteriorly inclined equal to the degree of desired correction of the pathologically posteriorly angulated epiphysis; the amount of correction may be as much as 60 degrees. Accordingly, the parallel drills are similarly inclined proximal to distal in the anteroposterior plane. The cutting chisel is inserted with critical C-arm guidance; two views made at 90 degrees to each other are essential (these are typically anteroposterior and frog-leg lateral views). The chisel is slowly advanced into the proximal femur medially to a depth that equals the length of the blade of the blade plate that has been selected.

The intertrochanteric osteotomy is performed just proximal to the lesser trochanter with a power saw at a site that is 2 cm or less distal to the blade plate insertion.

When performing the osteotomy, subperiosteal retractors are placed circumferentially around the osteotomy to protect the soft tissues, most importantly, the medial circumflex artery, from injury. After the completion of the osteotomy, the soft tissues are further stripped from the proximal aspect of the distal fragment, which allows the fragment to be flexed and reduced to the blade plate; the blade plate is in a flexed position and securely fixed in the proximal fragment. The distal fragment is firmly secured to the blade plate with a bone clamp. As the hip is carefully extended, the previously posteriorly displaced epiphysis will reduce anteriorly back into the acetabulum. The preliminary reduction is assessed with the C-arm.

The varus deformity noted on the preoperative anteroposterior x-ray is more apparent than real as a result of the external rotation of the posteriorly displaced or tilted epiphysis. If the condition does not appear to have been corrected, which is uncommon, additional varus correction can be achieved by exchanging the 120-degree blade plate for a 130-degree blade plate or by exchanging the 90-degree blade plate for a 100-degree blade plate. More medialization of the distal fragment can be achieved by driving the 120-degree blade plate farther into the femoral neck or by using a blade plate with a shorter blade. When using the 90-degree blade plate, further medialization can be achieved by driving the nail more medially or, more likely, by exchanging the 10-mm offset blade plate for a 15-mm offset 90-degree blade plate. More lateralization is achieved with either the 120-degree or the 90-degree blade plate by partially extracting the previously placed blade plate or exchanging it with a blade plate with a longer blade. Optimal positioning of the femoral shaft relative to the head aligns the piriformis fossa with the medullary canal of the distal fragment. A long cortical screw is used to fix the proximal fragment to the blade plate. Next, two screws are inserted in a compression mode to secure the distal fragment to the side plate. The bone clamp is removed, and the range of hip motion is assessed. Passive flexion and abduction motion should be notably improved with the hip flexed 45 degrees. Internal rotation should be equal to external rotation. The reduction is assessed with the C-arm and the final two screws are inserted.

Despite the flexion-correcting osteotomy, a prominent anterolateral metaphyseal bump may still impinge on the acetabulum during hip flexion and internal rotation in flexion and abduction. This abnormal bony prominence can also be visualized radiographically on the frog-leg lateral view. Through this anterolateral approach, it is possible to perform an osteochondroplasty to excise the bony prominence for an approximately 100-degree to 110-degree arc at the head–neck junction. After the completion of the osteochondroplasty, the range of hip motion is assessed. The goal is to achieve equal internal and external rotation as measured with the hip in approximately 45 degrees of flexion, 90 degrees or more of flexion, 15 degrees of internal rotation in 90 degrees of flexion, and more than 30 degrees of abduction. The capsule is loosely reapproximated. A deep drain is placed and brought out laterally through the soft tissue. The vastus lateralis and the intermedius fascia are reapproximated. If the anterior edge of the gluteus medius tendon was incised during the exposure, it should be securely repaired with a heavy permanent suture. The fascia lata and the gluteus maximus fascia are approximated with No. 1 interrupted absorbable suture. The subcutaneous and skin tissues are closed.

Patients ambulate on postoperative day 1 or 2, as previously described. Large corrections have often been made at the osteotomy site. Weight bearing should not be progressed until there is radiologic evidence of progressive consolidation, which may take several weeks. With this approach, bone overgrowth on the implant often occurs. Implant removal is advised within 1 to 1.5 years (Box 36-5).