Trochanteric Distalization (Relative Femoral Neck Lengthening) for Legg-Calvé-Perthes Disease and Coxa Vara

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CHAPTER 27 Trochanteric Distalization (Relative Femoral Neck Lengthening) for Legg-Calvé-Perthes Disease and Coxa Vara

Karl F. Schultz

Introduction

Isolated distalization of the greater trochanter of the femur has been a relatively uncommonly used salvage procedure for various pediatric hip diseases. The procedure was first described in 1969 by Jani for the relative overgrowth of the greater trochanter, and since then there have been several publications that have discussed the functional results with the use of either a distalization technique, a lateralization technique, or combined techniques. Most commonly, the distalization is performed concomitantly with an intertrochanteric osteotomy and the functional lengthening of the femoral neck.

The relief of the Trendelenburg gait, a lessening of pain, and an improvement in the range of motion are common goals for all trochanteric distalization procedures. In the setting of total hip replacement, distalization procedures have been extensively studied. Although this technique falls outside of the scope of this chapter, some of the related conclusions can be helpful for surgical decision making for hip preservation.

Indications

The distalization procedure is indicated for coxa brevis with minimal degeneration of the hip as a result of the following:

• Osteonecrosis as a complication of developmental dysplasia of the hip (DDH) treatment

• Legg-Calvé-Perthes disease

• Congenital coxa vara

• Bacterial coxitis

Basic science

The purpose of the procedure is twofold: 1) to alleviate any bony impingement of the greater trochanter on the lateral ilium, thereby increasing the range of motion (particularly abduction in full extension); and 2) to increase the moment arm of the abductors as a result of the distal or lateral placement of the trochanter in addition to increasing the baseline tension.

In 1977, Gore and colleagues postulated that the distalization of the trochanter would be beneficial to hip biomechanics by increasing the abductor moment arm and by increasing the resting muscle tension. This was partially confirmed by Free and Delp in a computer model in the presence of a total hip replacement; the authors examined the effect of the distalization and lateralization of the greater trochanter on the moment arm of the abductors as well as the force-generating capacity of this procedure. The study showed a maximum increase of 11% for anterolateral transfer in a patient with normal anatomy. However, when the hip was shortened by the superior displacement of the hip center, which somewhat replicated the shortening of the abductors in the presence of coxa brevis, there was a 43% decrease in the force-generation capacity of the abductors. Although the moment arm of the abductors was not significantly changed with distalization in this setting, the force-generating capacity was restored via the restoration of the resting muscle length.

History and physical examination

The history is dependent on the presenting diagnosis, its severity, and how long the deformity has been present. Patients will usually present with a limp, varying degrees of pain with abduction, and substantially limited abduction of the hip. There is nearly always an accompanying diagnosis that has led to the coxa brevis, as mentioned previously. Presentation can be at any time during childhood or adulthood.

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