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).