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.

The physical examination will reveal a positive Trendelenburg sign. A positive “gear stick test” as described by MacNicol is a limitation of abduction in extension with an improvement of abduction in flexion, because the high-riding trochanter is allowed to slip posteriorly in flexion. A positive impingement sign may also be present. With the proximal femoral growth disturbance, there will usually be a limb-length discrepancy present.

Imaging and diagnostic studies

An anteroposterior pelvic view and frog-leg lateral view of the affected hip are required. In addition, an abduction view may be obtained if there is a question of bony impingement after looking at the radiographs (Figure 27-1). For the purposes of isolated distalization or lateralization of the trochanter, these studies will usually suffice.

image

Figure 27–1 A and B, Case example: Anterior-posterior radiograph of the pelvis of a 24 year old showing a preserved hip joint, short femoral neck, trochanteric overgrowth and leg-length discrepancy. On physical exam, he has a vaulting gait due to leg length discrepancy and a positive Trendelenburg sign and positive trochanteric impingement sign on the right side with mild trochanteric tenderness and a positive gear stick test. C, An axial computed tomography image depicting the posterior position of the trochanter. D, Post-operative anterior-posterior radiograph after trochanteric distalization procedure with augmented fixation with claw plate due to the patients smoking history. At one year out, the osteotomy healed, Trendelenburg and gear stick sign were negative, and the patient was able to return to work with a shoe lift. R, Right.

Surgical technique

The patient is placed in the lateral decubitus position. A bumper is placed between the patient’s legs such that the leg is held in slight abduction. Great care should be taken to adequately pad all bony prominences, and an axillary roll should be placed. The surgical extremity is then prepped and draped free.

An 8-cm to 10-cm incision is made longitudinally over the lateral aspect of the trochanter and taken down to the fascia lata in line with the incision. Any bursal tissue is taken down to reveal the proximal border of the vastus lateralis at the vastus tubercle and the posterior border of the gluteus medius.

An osteotomy is performed with an oscillating saw from immediately proximal to the insertion of the vastus lateralis to just above the trochanteric (piriformis) fossa. The osteotomy is gently elevated with broad osteotomes superiorly. A bone hook can be used to retract the osteotomized fragment superiorly. Any remaining medial trochanter can be excised carefully and in a subperiosteal manner to protect the blood supply to the femoral head. After adequate mobilization of the fragment is achieved, a bone hook is used to distalize the fragment. During the distalization, some rotation of the trochanteric fragment can occur, which can be alleviated by releasing the tendinous insertion of the gluteus minimus on the anterior border of the trochanteric fragment. Additional bumps under the extremity are used to gain approximately 15 degrees of additional abduction.

The use of an image intensifier may help with the optimal final position of the fragment. The optimal placement of the trochanter is achieved when the tip of the trochanter is level with the center of rotation of the femoral head.

After adequate distalization is achieved, the reduction is held with a bone hook (and, if necessary, a smooth Kirschner wire), and two 3.5-mm screws with or without washers are placed perpendicular to the osteotomy plane. The hip should be ranged to ensure a secure fixation.

The fascia is then closed, usually without great difficulty, with the hip in abduction. The subcutaneous tissue and skin are also closed, with or without a suction drain, as needed.

Postoperative treatment

The patient is allowed to perform toe-touch weight bearing with a strict avoidance of active abduction or passive adduction. If necessary, a spica cast can be used for younger pediatric patients, or a hip abduction brace can be used for adults. In general, neither of these measures is necessary if the patient can be relied on to follow the weight-bearing precautions. These precautions can be eased at 8 weeks, at which point active abduction can be started.

Results and outcomes

The results of the related studies are summarized in Table 27-1.

Table 27–1 Results Summary

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Complications

Complications are rare in the pediatric age group, but they include infection and deep venous thrombosis with the possibility of embolic events. As such, some form of anticoagulation should be used, particularly in the adult group.

Nonunion of the trochanter is also a possible complication, but it is very rare in the reported series. One trochanteric fragment fracture was reported.

In addition, it is possible to interrupt the vascular supply to the femoral head during the procedure (if osteonecrosis is not already present). Again, this was not reported as a complication in any of the case series in the literature.

Annotated references and suggested readings

Eilert R.E., Hill K., Back J. Greater trochanteric transfer for the treatment of coxa brevis. Clin Orthop Relat Res. 2005;434:92-101.

Free S.A., Delp S.L. Trochanteric transfer in total hip replacement: effects on the moment arms and force-generating capacities of the hip abductors. J Orthop Res. 1996;14:245-250.

Garrido I.M., Molto F.J.L., Lluch D.B. Distal transfer of the greater trochanter in acquired coxa vara. Clinical and radiographic results. J Pediatr Orthop B. 2003;12:38-43.

Gore D.R., Murray M.P., Gardner G.M., Sepic S.B. Roentgenographic measurements after Muller total hip replacement: correlations among roentgenographic measurements and hip strength and mobility. J Bone Joint Sur Am. 1977;59:948-953.

Jani L. Die entwicklung des Schenkelhalses nach der trochanterversetsung. Arch orthop Unfallchirurgie. 1969;66:127-132.

Lloyd-Roberts G.C., Wetherill M.H., Fraser M. Trochanteric advancement for premature arrest of the femoral capital growth plate. J Bone Joint Surg (B). 1985;67–B:21-24.

MacNicol M.F., Makris D. Distal transfer of the greater trochanter. J Bone Joint Surg Br. 1991;73–B:838-841.

Pucher A., Ruszkowski K., Nowicki J., et al. Distal greater trochanteric transfer in the treatment of deformity of the proximal femur caused by avascular necrosis. Orthop Traumatol Rehabilitation. 2006;8:41-47.

The authors reevaluated their distal greater trochanteric transfers at a mean of 15 years after the procedure. They found an increase of 22% in abductor torque as measured with strain gauges, and they concluded that transfer did improve hip function and delayed osteoarthritis of the hip..

Pucher A., Ruszkowski K., Bernardczyk K., Nowicki J. The value of distal greater trochanteric transfer in the treatment of deformity of the proximal femur owing to avascular necrosis. J Pediatr Orthop. 2000;20:311-316.

Schneidmueller D., Carstens C., Thomsen M. Surgical treatment of overgrowth of the greater trochanter in children and adolescents. J Pediatr Orthop. 2006;26:486-490.

Takata K., Maniwa S., Ochi M. Surgical treatment of high-standing greater trochanter. Arch Orthop Trauma Surg. 1999;119:461-463.

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