Percutaneous Femoral Derotational Osteotomy in the Skeletally Immature Patient

Background:

Percutaneous femoral derotational osteotomies are performed in both adult and pediatric patients for excessive symptomatic femoral anteversion or retroversion^1,2. The aim of the procedure is to correct version abnormalities with use of a minimally invasive technique³.

Description:

This is a percutaneous procedure that involves creation of femoral drill holes at the osteotomy site prior to reaming the canal⁴. External fixator pins are placed proximal and distal to the osteotomy site prior to completing the osteotomy. These pins are derotational markers for the surgeon and act to hold the correction with use of an external fixator while the interlocking screws are being placed. The pins are placed at a degree of divergence that is equal to the degree of intended derotation so that the pins will become parallel in the axial plane following derotation of the femur. The percutaneous osteotomy is then completed with use of an osteotome, and the trochanteric entry nail is passed across the osteotomy site while correcting rotation. Once rotation is fully corrected and the pins are parallel, the external fixator is placed to hold the rotation and interlocking screws are placed.

Alternatives:

Nonoperative alternatives to this procedure include physical therapy for gait training and strengthening as well as modalities to address hip and knee pain that may be associated with version abnormalities. Although physical therapy is often prescribed, it must be noted that excess version is a fixed osseous structural pathology that therapy cannot address. Additionally, compensatory mechanisms that may be taught to improve gait and walk with a neutral foot progression angle may exacerbate hip or knee pathology as a result of the underlying version abnormality. Surgical alternatives include derotational osteotomies of the proximal or distal aspects of the femur with use of an open technique with plate fixation, as opposed to an intramedullary nail following percutaneous diaphyseal osteotomy as presented here¹. Additionally, an open technique with intramedullary nail fixation may be performed⁵.

Rationale:

Excessive anteversion can cause both hip and knee symptoms, including hip pain, instability, labral and psoas pathology, and patellofemoral instability⁶. Excessive retroversion can cause impingement between the femoral neck and acetabulum, which results in pathology of the labrum and articular cartilage⁷. Additionally, abnormalities of version often lead to gait disturbances with frequent tripping and difficulty running⁸. Children with femoral version abnormalities have limited remodeling potential after age 8³. A derotational osteotomy may be performed to correct symptomatic excess femoral version in an older child or adolescent.

Expected Outcomes:

The patient may be weight-bearing as tolerated with upper-extremity assistance immediately following the procedure. The osteotomy typically heals between 6 and 12 weeks, and the patient may return to activities as tolerated once the osteotomy is healed. Gordon et al. described the outcomes of a similar technique for femoral derotational osteotomy in skeletally immature patients with excessive femoral anteversion³. The study retrospectively reviewed the results of the technique in 13 patients and 21 limbs at a minimum follow-up of 1 year. All patients complained of tripping and gait abnormalities preoperatively. All patients noted gait improvement, and no intraoperative or postoperative complications were reported. Healing of the osteotomy occurred at a mean of 6 weeks postoperatively. No patient developed osteonecrosis. We routinely remove hardware in skeletally immature patients approximately 1 year postoperatively. Complications are rare and include hardware irritation, infection, nonunion, and neurovascular injury.

Important Tips:

• Preoperative planning is critical for this procedure, and the surgeon should know the intended degree of derotation, the location of the osteotomy relative to the greater trochanter, the length of the nail, and the approximate diameter of the nail prior to entering the operating room.

• Percutaneous bicortical femoral drill holes are created at the site of the osteotomy prior to reaming to allow for egress of reamings and bone marrow elements at the osteotomy site, which serve as autograft and stimulate bone healing. Additionally, the drill holes provide ventilation to prevent excessive intramedullary pressure during reaming^9-11.

• External fixator pins are placed proximal and distal to the osteotomy prior to completion of the osteotomy to allow for rotational assessment after completion of the osteotomy. Placing these pins bicortically so that they are secure in the bone and ensuring that the divergence is correct for the intended amount of derotation is critical in this procedure because once the osteotomy is complete, the pins are the only markers of rotation the surgeon has to guide the correction.

• An external fixator is helpful in holding the femur at the intended degree of derotation during placement of the interlocking screws.

Acronyms & Abbreviations:

• ROM = range of motion

• CT = computed tomography

• MRI = magnetic resonance imaging

• AP = anteroposterior

• GT = greater trochanter

• AV = anteversion

• ER = external rotation

• IR = internal rotation

• A = anterior

• P = posterior

• M = medial

• L = lateral

• XR = X-ray

• Prox = proximal

• Ex fix = external fixator

• WBAT = weight-bearing as tolerated

• BLE = bilateral lower extremities

• DVT = deep venous thrombosis

• PT = physical therapy

• ppx = prophylaxis

• AVN = avascular necrosis (osteonecrosis)

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