Proximal femoral valgus osteotomy has been utilized for a wide variety of orthopedic conditions. It is applied to coxa vara of various origins such as congenital/developmental coxa vara, septic hip sequelae, or slipped capital femoral epiphysis to improve hip mechanics. It is also performed in conditions such as Legg-Calvè-Perthes disease (LCPD) or secondary osteonecrosis of the femoral head (ONFH) to reorient abnormally shaped femoral head and achieve better joint congruity. Many techniques of proximal femur valgus osteotomy have been described; however, none have confirmed superiority over the other. Commonly used techniques involve removal of a lateral wedge of the proximal femur,1–3 which may result in further shortening of a pathologic limb. The center of rotation of angulation of a coxa vara deformity is very proximal and usually at the level of the center of the femoral head.4 An osteotomy that is not performed at the same level with the center of rotation of angulation will result in secondary translational deformity.5 To avoid this, lateralization of the distal fragment when performing intertrochanteric or subtrochanteric valgus osteotomy has been recommended.4,6,7 However, previously described techniques did not put much emphasis on this concept. In addition, it is usually difficult to maintain the desired correction of multiplanar deformity intraoperatively, mainly due to tension of the soft tissues across the osteotomy site. Herein, we introduced a surgical technique of proximal femoral valgus osteotomy using step-cut design and report its early outcome.

SURGICAL TECHNIQUE

In supine position, the operated limb was prepared and draped up to iliac crest. The proximal femur was exposed through the lateral approach. The fascia lata was incised longitudinally in line with the skin incision. Vastus lateralis was elevated from the proximal femur through an L-shaped periosteal incision along the vastus lateralis ridge proximally and posterior margin of its femoral origin. To ensure the rotation of the osteotomy was maintained, a guide pin was inserted parallel to the femoral neck and another was inserted at the distal femoral metaphysis, parallel to the knee rotation axis. These wires serve as a mark for rotational alignment before the osteotomy. A Schanz pin (for pediatric hip locking plate fixation) or a chisel (for angled blade plate) was inserted to the proximal fragment, and subsequently a transverse osteotomy was made at the level of the lesser trochanter. The Schanz pin or chisel controlled the proximal osteotomy fragment, and could be used to estimate the amount of valgization required and later, to guide the proximal fragment into the step-cut. The osteotomy surface of the distal fragment was exposed and the step-cut was formed by excising a triangular bone fragment using a small pneumatic saw (Fig. 1). The fragment was designed to make angle α, the amount of valgization to be made and angle β, the angle formed by lateral corner of the proximal fragment, which was measured with a goniometer after the transverse osteotomy was performed (Fig. 2). The accuracy of the angle on the osteotomy site was confirmed using a triangular template made out of small piece of plastic which were cut according to the desired α and β angles. Bony configuration was achieved by engaging the proximal fragment into the step-cut of the distal fragment. Lateralization of the distal fragment was controlled by the mediolateral placement of the apex of wedge excised from the distal fragment. Flexion or extension component of the correction was imposed by size differential between the wedge excised from anterior and posterior cortices. If the anterior wedge was bigger than the posterior wedge, the fragments engaged better in a flexed position, and vice versa. In children who were obese, cases with proximal thigh scarring due to multiple surgery, or cases requiring significant correction, an external fixator-assisted technique was applied, according to surgeons’ choice, using a unilateral hybrid external fixator (Dyna-extor II, JoyM, Seoul, Korea) to facilitate and maintain correction until plate fixation. After visual and fluoroscope confirmation, the osteotomy was fixed with either an angled blade plate (Stryker, MI) or a pediatric locking hip plate (Depuy Synthes, Oberdorf, Switzerland). As the correction of deformity was done by the angles, the role of the implant was to maintain the correction achieved. Bilateral short leg casts with a connecting bar to prevent the child from weight-bearing, while allowing motion of the knee and hip, was applied for 4 weeks postoperatively.

FIGURE 1:

Intraoperative photographs show the angles α and β on the osteotomy surface of the distal fragment.

FIGURE 2:

Illustrative diagram indicating the position of the angles α and β (A), and showing the configuration of the osteotomy once the proximal fragment is engaged in the step-cut (B).

Patients

This surgical technique was applied to 24 hips (21 patients) from October 2005 to October 2014. They were 16 male and 5 female patients, with an average age of 9.8 years (range, 6.0 to 15.6 y) at the time of index operation. The procedure was performed to improve hip joint congruency in 14 ONFH, which consisted of 10 LCPD, 2 posttraumatic, a slipped capital femoral epiphyses-associated, and a postinfectious ONFH. In another 10 hips, the procedure was performed to reorient the proximal femur and correct coxa vara. They consisted of coxa vara secondary to varization osteotomy for LCPD (3 hips), associated with osteogenesis imperfecta (3 hips) (Fig. 3), spondyloepyphyseal dysplasia (2 hips), septic hip sequelae (1 hip), and the juvenile Paget disease (1 hip). Implants used for fixation consisted of 16 locking compression plates and 8 blade plates.

FIGURE 3:

A, A 4-year-old mutation-confirmed osteogenesis imperfecta patient presented with progressive coxa vara deformity of the left hip. B, Step-cut valgization osteotomy of the proximal femur was performed, fixed with a pediatric locking plate.

RESULTS

Mean duration of follow-up was 4.3 years, ranging from 1.5 to 10.5 years. All cases successfully achieved valgization of the proximal femur, with an average of 24.7 degrees (range, 15.3 to 38.0 degrees), measured based on intraoperative fluoroscopy images. There was an average of 4.0 mm increase in length on the operated limb, based on pelvic anteroposterior radiographs or teleradiogram films. All osteotomies united uneventfully and no perioperative complications were noted.

DISCUSSION

Valgus osteotomy of the proximal femur has been widely used to address hip joint incongruity due to primary or secondary ONFH, and acquired or congenital coxa vara. In ONFH, proximal femoral valgization aims to redirect the head to achieve optimal congruency, thus maximizing surface contact and reducing peak contact pressure between the head and acetabulum.8 Furthermore, by reducing the head-shaft offset, there is reduction on the joint reactive forces acting across the hip joint. This delays the onset of developing degenerative arthritis.9 In the skeletally immature, optimal joint congruency has been shown to induce favorable remodeling of the femoral head.10 In coxa vara, proximal femoral valgization restores the function of the hip abductors.11 This has been shown to reduce pain and improve Trendelenberg gait.12

Findings in our series were comparable with previous reports in terms of mean age at index procedure,13,14 disease heterogenicity13–15, and follow-up duration.2,3 Various implant are used for fixation in proximal valgus osteotomy including dynamic compression plates, tension bend wires, pediatric locking hip plates, angled blade plates, and compression hip screws.2,14,16,17 In our institution, both pediatric locking hip plates and angled blade plates were used based on patient factors and at the discretion of the attending surgeon. All hips achieved valgization and there was lengthening of the operated limb, comparable with previous reports.2,14,17 No complications were noted in our series as compared with the 5.7% to 9% complication rate reported previously.13,17,18 This includes nonunion, loss of fixation, infection, and peri-implant fractures.

The step-cut technique has several advantages. Intraoperatively, the desired degree of valgization can be achieved by controlling the amount of angle α at the distal fragment. Compared with our previous experiences with valgus osteotomy without the triangular cut, the step-cut technique provides temporary intraoperative stability with minimal risk of loss of correction, making internal fixation in target configuration much easier. External fixator-assisted correction was used in selected cases in obese children, severe deformity or proximal thigh scarring due to previous surgery.19 The step-cut provides stability even after definitive fixation, without the need for postoperative hip spica immobilization. It also allows lateralization of the distal fragment, which is important in valgization of the proximal femur, as to prevent the knee from secondary deformity. In addition, the amount of the bone resected in a triangular form is relatively small, as compared with the bone resected during lateral closing wedge osteotomy, thus avoiding risk of shortening of the limb.

CONCLUSION

In conclusion, the step-cut valgus osteotomy technique was efficacious, replicable, and safe in achieving femoral head reorientation and correcting multiplanar deformity of a proximal femur.

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