Congenital (Infantile) Coxa Vara Treatment & Management

A large percentage of patients with congenital coxa vara (CCV) will require surgical intervention (see Indications for and Goals of Surgical Intervention).

Treatment of CCV is contraindicated in children who demonstrate any of the following:

• Lack of symptoms on clinical assessment
• Radiographs showing a Hilgenreiner epiphyseal angle (HEA) of less than 45°
• Radiographs showing an HEA of 45-60° with no documented progression

In such situations, close clinical and radiographic follow-up is warranted.

Many forms of nonoperative treatment have been proposed for CCV, including spica cast immobilization and skeletal pin traction with bed rest, with generally unsatisfactory results. It is generally accepted that no place remains for conservative nonoperative measures for individuals who require treatment of either symptomatic or progressive CCV.

Surgical indications

Weinstein et al proposed a radiologic means of quantifying CCV. ^[10] This measure, the HEA, is the angle subtended by the horizontal Hilgenreiner line through the triradiate cartilages and an oblique line through the proximal femoral capital physes (see the image below). A study of normal values of the HEA found that the angle in children younger than 7 years averages 20°, with a wide variation of 4-35°. The mean value for those aged 8 years to maturity is 23°.

Congenital coxa vara. Determination of Hilgenreiner epiphyseal angle, using Hilgenreiner line as horizontal axis and line through defect adjacent to metaphysis as diagonal axis.

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On the basis of this measurement, patients in whom surgery is indicated include the following:

• A child with a clinical limp and an HEA greater than 60°
• A child with a clinical limp and an HEA of 45-60° with documented progression of varus deformity

Historically, CCV, if left untreated, was believed to be a relentless and progressive deformity leading to pain and a loss of hip function with the development of premature degenerative changes (see the image below).

Congenital coxa vara. Natural history of untreated progressive developmental coxa vara with premature degeneration of hip joint.

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Some authors have shown, however, that not all patients with the diagnosis of CCV necessarily follow this course. On the basis of the HEA, three relatively distinct groups have emerged, as follows:

• In those with an HEA smaller than 45°, the CCV is more commonly found to halt progression spontaneously and to heal without intervention
• In patients with an HEA greater than 60°, the CCV follows a more traditional course of progressive deformity that can be aided only by surgical intervention
• An intermediate group, comprising patients with angle measurements of 45-60°, represents a so-called gray zone; these patients require observation for either healing or progression, the latter of which necessitates surgical intervention

Goals of treatment

As noted previously, surgical intervention is required in a large percentage of those with CCV. Accordingly, remembering the indications for surgery and clearly defining the goals of treatment are important for ensuring the best possible outcome and minimizing the number of surgical procedures the patient must undergo.

The goals of surgical intervention are as follows:

• Correction of the neck-shaft angle to a more physiologic angle and the HEA to less than 35-40° ^[12]
• Correction of femoral anteversion (or retroversion) to more normal values
• Ossification and healing of the defective inferomedial femoral neck fragment
• Reconstitution of the abductor mechanism through replacement of its normal length-tension relationship

Surgical options

The treatment of choice for CCV has followed the recommendations of early work by Amstutz, Freiberger, and Wilson in the use of either subtrochanteric or intertrochanteric osteotomies (see the image below). ^{[13, 14]}

Congenital coxa vara. Surgical methods of valgus-producing proximal femoral osteotomies. (A) Pauwels Y-shaped osteotomy. (B) Langenskiöld intertrochanteric osteotomy. (C) Borden subtrochanteric osteotomy.

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Of the intertrochanteric osteotomies, the Pauwels Y-shaped and Langenskiöld valgus-producing osteotomies have yielded good results. It should be kept in mind, however, that these osteotomies have a somewhat limited ability to correct the associated femoral neck retroversion. The subtrochanteric valgus-producing osteotomies used by many authors also have provided good and lasting clinical results (see the image below). In the end, the actual type of osteotomy performed may be less important than ensuring that the goals of surgical correction, as outlined above, are achieved. ^{[15, 16, 17, 18, 19, 20]}

Surgical treatment of congenital coxa vara. Progression from preoperative radiographs at ages 2 and 5 years, with characteristic bony changes. Postoperative radiographs at ages 6 and 12 years, with early and late follow-up results.

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Many issues have been raised surrounding surgical intervention, including the following:

• Amount of correction needed
• Associated procedures at the time of surgery to aid in the osteotomy and decrease hip joint forces
• Optimal age for operation

Postoperatively, good results have been achieved consistently when the HEA has been corrected to less than 35-40°. Although some have suggested the need to correct the neck-shaft angle to more than 130-135°, Carroll et al found no strong correlation between the postoperative neck-shaft angle and lasting good clinical outcomes. ^[21] They suggested that the most consistent and reliable predictor of outcome was the HEA.

Weighill emphasized the use of an adductor tenotomy in association with osteotomy, with adductor release removing the deforming force during reduction of the femoral bone fragments and aiding in postoperative stability of the osteotomy. ^[22] If required, a segment of proximal femur may be removed to facilitate reduction and reduce joint reactive forces at the hip joint. Unfortunately, this may further shorten an already short limb.

With regard to the optimal age for surgical intervention. Weighill suggested that the best time for correction may be as early as 18 months. Weinstein et al found that patients treated when older than 5 years maintained correction better than those treated when younger than 5 years. ^[10] Serafin et al suggested that correction in children younger than 9 years maximizes the remodeling potential of both the proximal femur and the acetabulum. ^[8]

Most patients seem to present for evaluation and are considered for treatment when aged 5-10 years. Femoral osteotomy procedures are technically easier in the older child because more bone stock is present. Earlier surgical intervention may allow the hip, including the acetabulum, to remodel more completely. However, this remodeling potential in very young children has been suggested to lead to higher recurrence rates after surgical correction. In young surgical patients, the incidence of greater trochanteric overgrowth is also higher. Most agree, however, that the milder the deformity, the easier the correction.

It is generally accepted that the age at correction is less important than the ability to correct the hip to meet the goals of surgery. Once the diagnosis is clear and progression is evident, few reasons remain to delay surgery beyond an age at which stable fixation can be achieved reliably. Long-term outcomes have supported the view that adequate realignment of the deformity is most important. The authors tend to operate as soon as patients meet radiographic and clinical criteria, regardless of their age or size.

Preparation for surgery

As with many surgical procedures, preoperative planning is essential to achieve a favorable outcome. Up-to-date imaging is necessary to determine the amount of bone to be resected and the size of implants to be used. Templating the operative plan is often invaluable to ensure that the proposed result will meet the surgical goals. Having hardware of various angles available is helpful if intraoperative measurements lead to alteration in the amount of bone resected.

Operative details

Position the patient supine on a radiolucent table, and ensure that adequate-quality images are available before beginning surgery. Rotate the affected hip under fluoroscopy to compensate for hip (femoral head) version, defining the maximal varus deformity. From this view, determine the size of the bone wedge to be resected. Use clinical rotation of the hip to decide whether derotation will be combined with wedge resection.

Free draping of the hip allows better intraoperative control. The proximal lateral femur is routinely exposed. Image intensification is used in implant insertion and bone resection. Confirm correct positioning once provisional fixation is achieved.

After skin closure in the usual fashion, with the use of wound suction as required, apply a 1.5 hip spica cast. Obtain postoperative radiographs through the spica cast for later comparison. Maintain a nonweightbearing status for the patient until early bone healing is demonstrated radiographically, at approximately 6-10 weeks after surgery.

Premature closure of the proximal femoral physis has been consistently noted, occurring along with or shortly after healing of the inferomedial fragment of metaphyseal bone. Carroll et al ^[21] reported that all of their patients had premature closure of the proximal femoral physis, as did Desai et al. ^[9] Closure occurred at an average of 3 years after surgical correction. Pylkkanen reported a 90% rate of premature closure. ^[7] This, along with any residual shortening due to the osteotomy, necessitates follow-up with the aim of contralateral physeal arrest or ipsilateral lengthening at the appropriate time, should a clinically significant limb-length discrepancy exist near maturity.

Associated with premature closure of the proximal femoral physis is the often-encountered overgrowth of the greater trochanter (see the image below). Desai et al found this to occur in 60% of their series, with just under 50% of these patients having abductor weakness at final follow-up. ^[9] There was  no overgrowth in cases where successful greater trochanteric apophysiodesis was achieved. All of these patents had a good clinical outcome. Undertake surgical epiphysiodesis or distal transfer if overgrowth of the greater trochanter is noted both radiographically and clinically on follow-up.

Greater trochanteric overgrowth in treated congenital coxa vara.

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Perform an initial postoperative check 1 week after surgery, with radiographs to ensure maintenance of position and integrity of fixation. The patient should be seen every 2 weeks until early healing is present (~6-8 weeks after surgery). At that time, the spica cast is removed, and physiotherapy is begun for mobilization and range-of-motion instruction.

Close follow-up every 3-6 months is required to ensure that the deformity is resolving. Assess for greater trochanteric overgrowth and commonly encountered proximal femoral physeal closure. Carry out trochanteric apophysiodesis if indicated (see Complications). Perform a careful serial examination for a relative limb-length discrepancy, and treat as appropriate.