Proximal Femoral Osteotomy

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CHAPTER SYNOPSIS

Abnormal morphology of the proximal femur can compromise hip joint mechanics and result in pathologic contact pressures and progressive joint degeneration. Correction of the primary deformity with a proximal femoral osteotomy can improve load transmission patterns across the hip joint and prevent or substantially delay the need for future total hip arthroplasty in appropriate patients. Proper patient selection is critical for successful outcomes after proximal femoral osteotomy, and many patient factors must be considered. Formulation of a detailed preoperative plan will help ensure proper execution of this technically demanding procedure.

IMPORTANT POINTS:

1

The ideal candidate for a reconstructive proximal femoral osteotomy has a symptomatic structural abnormality of the proximal femur but little or no radiographic signs of secondary hip arthritis.
2

Many developmental and acquired conditions result in femoral deformities amenable to proximal femoral osteotomy; the proximal femoral deformity must be accurately characterized to plan the proper correction.
3

Correction of the deformity must be achievable and must normalize hip mechanics by decreasing impingement and increasing joint stability, congruence, and contact area.
4

Avoid overcorrection, which can produce mechanical consequences worse than the original deformity.
5

Achieving rigid internal fixation intraoperatively is an absolute necessity.

SURGICAL PEARLS/PITFALLS:

1

The intertrochanteric osteotomy should always be performed transversely at the upper border of the lesser trochanter.
2

The proper site of chisel insertion is almost always located at or just proximal to the vastus ridge on the lateral femur, at least 1.5 to 2 cm proximal to the osteotomy.
3

A distance of at least 1.5 to 2 cm must be preserved between the osteotomy and the site of chisel/blade insertion to avoid fracture of the proximal femoral fragment through the lateral cortical bridge and subsequent loss of fixation.
4

The greater trochanter is a posterior structure on the proximal femur, and the proper chisel insertion site is in the anterior third of the greater trochanter to avoid cortical perforation of the posterior femoral neck.
5

Exposure of the anterior cortex of the femoral neck is simple and facilitates triangulation of the center of the femoral neck during chisel insertion.
6

Frequent fluoroscopic checks during chisel insertion help with proper position and minimize the risk of femoral head or neck perforation; frequent checks during blade insertion also ensure the blade follows the chisel tract.
7

Backing the chisel out a few millimeters at regular intervals during insertion prevents incarceration of the chisel in bone.
8

When performing a valgus-producing osteotomy, choose a blade 1 cm longer than the desired depth of insertion to help facilitate lateral shaft displacement.
9

Wedge or block resection at a valgus osteotomy often is necessary to avoid overlengthening of the involved extremity.
10

A no-wedge technique when producing a varus osteotomy minimizes limb shortening.
11

Easy access for palpating the contralateral foot and ankle through the surgical drapes helps facilitate leg-length assessment intraoperatively.
12

Varus correction of more than 15 to 20 degrees will result in elevation of the greater trochanter. Care must be taken that the tip of the trochanter ends up no higher than the mid-point between the center of the femoral head and the proximal weight-bearing subchondral bone of the head. Distal transfer of the greater trochanter may be necessary to avoid severe abductor dysfunction.
13

Increasing flexion or extension correction through the osteotomy imposes a progressive varus influence on the neck-shaft angle; care must be taken to avoid inadvertent excessive varus correction.

INTRODUCTION

Total hip arthroplasty (THA) is a highly successful procedure and remains the treatment of choice for the elderly patient with end-stage degenerative joint disease of the hip. Long-term results demonstrate excellent durability with a high rate of patient satisfaction attributable to prolonged, predictable pain relief and functional improvement. However, extension of THA indications to younger, more active patients has produced inferior mid- and long-term results with relatively high failure rates attributable to bearing surface wear and associated periprosthetic osteolysis and aseptic loosening. Alternative bearing surfaces were introduced to reduce wear and decrease the incidence and severity of osteolysis after THA. However, these modern bearing surfaces have limitations of their own, and no long-term clinical data exist yet to support their routine use in hip arthroplasty for young, active patients. By functioning to delay or altogether avoid the need for THA, joint-preserving procedures such as proximal femoral osteotomy should continue to play an important role in the treatment of pathologic hip conditions in the young adult.

The rationale for osteotomies about the hip is based on the established notion that osteoarthritis of the hip is almost exclusively a secondary diagnosis. Few, if any, cases of osteoarthritis can be attributed to primary degeneration of the hip joint. After exclusion of all metabolic and inflammatory conditions known to result in degeneration of articular cartilage in the hip, all cases of hip arthritis essentially are associated with an underlying structural abnormality. The most common structural abnormalities associated with secondary osteoarthritis of the hip are the sequelae of pediatric and developmental hip disease: developmental dysplasia of the hip (DDH), slipped capital femoral epiphysis (SCFE), and Legg-Calvé-Perthes disease (LCPD). An analysis of 474 patients with advanced osteoarthritis of the hip from five different series identified one of these three underlying deformities in 76% of patients, the most common being hip dysplasia (43%), followed by LCPD (22%) and SCFE (11%). In addition, the natural history of hips affected by these developmental disorders has been well documented by long-term follow-up studies, with a high prevalence of hip osteoarthritis in these patients at a relatively young age. By age 50 years, significant osteoarthritis will develop in 43% to 50% of hips with dysplasia, 50% of hips with LCPD, and 20% of hips with SCFE.

The association of abnormal hip morphology with osteoarthritis is easily understood from a biomechanical perspective. Hyaline cartilage and subchondral bone of the hip joint function within a normal physiologic range of mechanical load. The abnormal structure of at-risk hips alters mechanics along a spectrum of instability, incongruity, and impingement and exposes the joint to pathologic contact and sheer stresses. Left uncorrected, the unit load in the hip exceeds the endurance limit of articular cartilage, cartilage function and viability are compromised, and progressive degeneration of the joint soon follows. Proximal femoral osteotomy is an attempt to stop this process by correcting the primary deformity, improving joint congruity and load transmission patterns, relieving impingement, and reestablishing a functional range of motion. The procedure has a role in both the prevention and treatment of secondary hip arthritis.

INDICATIONS AND PATIENT SELECTION

The ideal candidate for a reconstructive proximal femoral osteotomy has a symptomatic structural abnormality of the proximal femur but little or no radiographic signs of secondary hip arthritis. In this setting of prevention, restoration of normal anatomy and mechanics in a joint with viable articular cartilage can prevent further joint degeneration and avoid or considerably delay the need for future THA. Proximal femoral osteotomy is performed less commonly today as a salvage procedure in hips with established degenerative arthritis. The short-term goals of a salvage osteotomy are similar to those of a reconstructive osteotomy. Optimizing hip mechanics can relieve pain and improve function, but in the presence of nonviable articular cartilage the extent and duration are unpredictable. A salvage osteotomy must be approached with the expectation of pain relief for a limited duration and the understanding that THA will definitely be required in the future.

Multiple developmental and acquired conditions of the hip result in abnormalities that can be treated with a proximal femoral osteotomy ( Table 7-1 ). Although the final common pathway culminates with degeneration of the hip joint, each of these conditions presents with variable architecture along a continuum of severity. Regardless of the etiology, successful reconstruction requires that the patient’s pathoanatomy be accurately characterized so an achievable, patient-specific plan can be devised for adequate deformity correction.

Table 7-1

Indications for Reconstructive Proximal Femoral Osteotomy: Developmental and Acquired Conditions of the Hip

Condition	Pathoanatomy	Osteotomy Type
DDH/coxa valga	Coxa valga and excessive femoral anteversion	Combined varus, extension, derotation
	Decreased joint contact area with high contact and sheer stresses
	Overload of acetabular dome and anterolateral rim
LCPD	Coxa magna, coxa plana, or coxa breva; relative trochanteric overgrowth	Valgus
	Poor congruency, impingement, abductor dysfunction, leg-length discrepancy
SCFE	Relative varus, retroversion, and extension of proximal femur	Combined flexion, valgus, derotation
	Poor congruency, decreased arc of motion, impingement
Osteonecrosis	Necrotic segment of bone in weight bearing area of femoral head	Variable
Posttraumatic nonunion	Nonunion of femoral neck fracture with viable femoral head	Valgus
	Nonunion of intertrochanteric region of the femur	Variable
Malunion	Uniplanar or multiplanar deformity of proximal femur	Variable
	Altered mechanics, impingement, leg-length inequality

Patients with DDH may have a variety of deformities of both the acetabulum and proximal femur. Classically, a shallow, excessively anteverted acetabulum with a lateralized hip center of rotation and an upsloping sourcil results in decreased joint contact area and concentration of forces on the anterolateral margin of the acetabulum. The most common associated femoral deformities are coxa valga and excessive femoral anteversion, which can both contribute to femoral head extrusion and further concentration of forces on the anterolateral rim. A varus intertrochanteric osteotomy of the proximal femur improves forces across the hip joint by increasing the abductor lever arm (decreasing the abductor’s contribution to total joint reaction forces) and simultaneously improving congruity (increasing joint contact area). Derotation of the proximal femur also increases joint contact area by redirecting the femoral head posteriorly into the excessively anteverted acetabulum. Although the acetabulum usually is the dominant site of pathology, some cases of severe dysplasia require a proximal femoral osteotomy in conjunction with acetabular reorientation to achieve adequate congruence of the joint and restore proper mechanics. Isolated varus intertrochanteric osteotomy is now rarely indicated but can adequately reconstruct a hip with coxa valga and mild or absent dysplasia (lateral center-edge angle greater than 15 to 20 degrees and normal sloped sourcil).

The most common residual deformities of childhood LCPD are coxa magna, coxa breva, and coxa plana, all of which can produce joint incongruence. Capital physeal growth arrest results in trochanteric overgrowth and leg-length inequality with associated abductor dysfunction and fatigue. Valgus intertrochanteric osteotomy can be used to improve congruity and redistribute contact forces within the joint ( Fig. 7-1 ). Distal movement of the trochanter results in increased abductor forces and function, and reorientation of the femoral neck to a more valgus position can increase overall leg length.

Posteromedial displacement of the epiphysis in SCFE produces a complex deformity of the proximal femur with varying degrees of varus, retroversion, and extension, with extension typically being the dominant component of the deformity. The net result is femoroacetabular impingement and obligatory external rotation when the hip is flexed, and in severe cases joint congruity may be compromised with the hip in neutral position. An intertrochanteric osteotomy can be tailored to address this multiplanar deformity ( Fig. 7-2 ). The largest degree of correction typically is required in the sagittal plane with flexion of the femur at the osteotomy site. This sagittal plane correction affects alignment in the coronal plane as well, and as the proximal fragment rotates anteriorly a component of valgus may be reintroduced. Additional valgus and femoral anteversion can be incorporated at the osteotomy site as needed.

Select patients with osteonecrosis of the femoral head can be successfully treated with intertrochanteric osteotomy to rotate the necrotic segment of bone into a non-weight-bearing region of the hip joint. A valgus flexion osteotomy rotates an anterolateral femoral head lesion out of the weight-bearing area of the joint and advances healthy articular cartilage and supporting subchondral bone from the posteromedial head into the weight-bearing zone. Alternatively, lesions localized in the superomedial femoral head are best addressed with a varus osteotomy combined with flexion or extension as needed to optimize rotation of the necrotic segment out of the weight-bearing zone. Ideal candidates for osteotomy should have no signs of systemic disease and not be receiving ongoing high-dose corticosteroid therapy. They must have preserved hip range of motion, a relatively small necrotic lesion, and little or no subchondral collapse. Lesion size determined by combined radiographic necrotic arc angles correlates with outcome after osteotomy. The necrotic arc angle is subtended by lines drawn from the center of the femoral head to the margins of the necrotic lesion. Favorable candidates should have a combined necrotic arc angle of 200 degrees or less on anteroposterior and lateral radiographs.

The most common posttraumatic indication for proximal femoral osteotomy is nonunion of a femoral neck fracture. A valgus intertrochanteric osteotomy can be used to convert shear forces to compressive forces at the site of the nonunion ( Fig. 7-3 ). The presence of osteonecrosis is not a contraindication to osteotomy but does decrease the long-term success rate of the procedure. Preoperative radiographs must be scrutinized for signs of osteonecrosis so the patient can be counseled appropriately. If lateral radiographs demonstrate posterior angulation of the nonunion, consideration should be given to adding a flexion component to the valgus osteotomy to avoid anterior femoroacetabular impingement after healing. Proximal femoral osteotomy also may be used to address nonunion of the intertrochanteric region of the femur as well as impingement, leg-length discrepancy, and contractures associated with malunion. The osteotomy must be carefully planned to address completely the pathoanatomy specific to each posttraumatic case.

A salvage osteotomy may be appropriate for treatment of established hip arthritis in select patients, such as young, active patients with unilateral hip disease. Salvage procedures can be successful in delaying the need for THA for several years, but patient satisfaction postoperatively depends on a clear understanding of the limited goals of the procedure. A salvage procedure can be performed for any of the specific diagnoses outlined above when preoperative radiographs demonstrate more than mild secondary adaptive or degenerative changes in the hip joint. The principles of reconstructive osteotomy also apply in the setting of joint salvage, and for any chance at a successful outcome the procedure must still address the underlying abnormality and improve the mechanical environment of the joint. The classic salvage osteotomy is performed in dysplastic hips with an aspherical femoral head and established arthritis. The procedure uses the large inferior-medial osteophyte on the femoral head (capital drop osteophyte, as described by Bombelli ) to increase joint contact area in the hip. Valgus realignment of the proximal femur rotates the capital drop osteophyte into contact with the medial osteophytes of the acetabulum. The center of hip rotation is shifted medially, reducing the lever arm of the hip joint, and the contact of the inferior osteophytes serves as a fulcrum to open the superolateral joint space. Similar to reconstructive osteotomies for DDH, adding a component of extension at the osteotomy site helps further contain the femoral head and improve joint contact area and congruity. Extension at the osteotomy site also can be used to improve a preoperative hip flexion contracture.

Like other reconstructive and salvage orthopedic procedures, careful and proper patient selection is paramount for successful outcomes after proximal femoral osteotomy. Many complex subjective and objective patient variables must be considered concurrently when determining whether osteotomy is an appropriate course of treatment. The patient’s functional deficits should be evaluated in the context of his or her baseline level of physical activity, including activities of daily living, occupational and work-related activities, and leisure activities. Some patients tolerate significant lifestyle changes more effectively than others; perceptions regarding level of dysfunction and disability may vary greatly between patients of different age groups, occupations, and cultural backgrounds. The surgeon must have a clear understanding of the patient’s goals and expectations after surgery, and the patient must be able to comprehend the risks, benefits, and limitations of the anticipated procedure. Although intangible, unreasonable expectations on the part of the patient are a strong contraindication to proceeding with a reconstructive or salvage osteotomy. Motivation is a key factor in the patient’s recovery postoperatively, and the patient must be committed to active participation in an extended rehabilitation program.

Absolute contraindications to osteotomy include active infection, inflammatory arthritis, neuropathic arthropathy, and severe osteopenia ( Box 7-1 ). Osteotomy is contraindicated in morbidly obese patients (body mass index greater than 40), and most surgeons consider obesity (body mass index of 30 to 40) a contraindication as well. Osteotomy in these patients is technically more difficult and, like THA, is associated with a much higher rate of infection and complications. Active smokers must agree to stop tobacco use before surgery and abstain until radiographic union of the osteotomy postoperatively.

Box 7-1

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