Severe metaphyseal deformities may require osteotomy, but osteotomy should be considered with care in this region. Osteotomy of the metaphysis (unlike a subtrochanteric osteotomy) leads to a small proximal bony fragment. A small proximal fragment can be difficult to fix adequately, and is at risk for fracture or devascularization (Fig 6).
Finally, some severe deformities of the upper metaphysis and femoral neck may be treated by resection of part of the involved segment of medial bone and placement of a calcar replacement implant.
Diaphyseal Level Deformities
Deformities in the diaphysis of the femur can have a profound effect on implant alignment. For the purposes of hip arthroplasty, some distal diaphyseal femoral deformities can be ignored, and sometimes choosing a shorter femoral implant allows the surgeon to avoid the deformity. However, if the deformity is in the region encompassed by the femoral implant, it often mandates a change in technique. Moderate deformities can be treated using cemented implants positioned to compensate for the deformity. To ensure an adequate circumferential cement mantle, smaller than expected implants may be needed. Osteotomy is needed for more severe deformities at this level (Fig 7). When osteotomy is performed, the surgeon can use either a cemented or uncemented implant. Because preventing cement from extruding into the osteotomy site is difficult, most surgeons prefer uncemented implants when possible. Extensively porous-coated implants or proximally porous-coated implants with distal flutes work well for this purpose. Ideally, stable fixation of the osteotomy is achieved with the femoral implant alone. Long-stemmed implants are needed for osteotomies below the subtrochanteric level. The shape of the osteotomy can be transverse, oblique, or a step-cut.9,14,15,17,19 When excellent fixation of the proximal and distal fragments with the implant can be achieved, a transverse osteotomy usually is sufficient and is technically easiest to perform, although it provides less inherent rotational stability. Adjunctive fixation of the osteotomy often is not necessary but can be provided with plates or strut grafts if needed. On occasion, a diaphyseal deformity is best treated in two stages; that is, correction of the deformity followed by total hip arthroplasty after osteotomy healing.
To the author's knowledge, there are few articles that discuss total hip arthroplasty in association with proximal femoral deformity in a comprehensive, yet generic, manner.16 Studies are available on total hip arthroplasty for specific diagnoses that often are associated with deformity, but they include all patients with specific diagnoses-those with and those without deformity.1,6,7,10-13 Studies regarding femoral osteotomy in association with total hip arthroplasty also are available.8,9,14,15,17,19 Those studies selectively provide information on patients with deformities severe enough to warrant osteotomy.
Clinical results of total hip arthroplasty are compromised if femoral deformity leads to (1) poorer pain relief; (2) poorer hip mechanics and limp; (3) poorer implant durability; or (4) increased complications. Studies on total hip arthroplasty for failed fixation of intertrochanteric hip fractures have shown lower hip scores than the hip scores typically associated with primary total hip arthroplasty.10,12 However, it is uncertain whether the poorer scores in this patient population are attributable to residual femoral deformity associated with the fracture or attributable to age or other factors in this specific patient population.10 Patients treated with total hip arthroplasty after intertrochanteric osteotomy have mostly favorable clinical results.1,7 A number of studies have reported results of total hip arthroplasty for developmental dysplasia2: most show total hip arthroplasty markedly improves hip function but that some patients have a residual limp. From the current literature, it is not possible to delineate the reason(s) some patients have a recurrent limp: probably residual femoral deformity, associated acetabular abnormalities, and associated muscle abnormalities all play a role.
Effect on Durability of Fixation
Proximal femoral deformity can compromise implant fixation, whether cemented or uncemented implants are used. Cemented implant fixation can be compromised if deformity leads to poor implant alignment, a poor cement mantle, poor cement technique or a poor bone-cement interface. Patients with femoral deformity also may have sclerotic bone (that can lead to poorer cement interdigitation with bone) caused by previous fracture, osteotomy, or disease processes like Paget's disease. The literature suggests, but does not prove, that deformity can compromise long-term cemented implant durability.7,11,13 In 305 hips treated with cemented total hip arthroplasty after intertrochanteric osteotomy at the Mayo Clinic, Ferguson et al7 found a higher rate of revision surgery than in a comparable series of cemented total hip arthroplasty in the general patient population from the same institution. McDonald and Sim11 compared the long-term results of 80 cemented hip replacements in patients with Paget's disease (48 with femoral involvement) and found a higher rate of revision surgery for aseptic loosening at 10 years than in 7,222 total hip arthroplasties in patients without Paget's disease. Merkow et al13 also identified a higher rate of femoral loosening in patients with Paget's disease than reported in most other series and thought that problems with femoral implant alignment and cement technique might have contributed. In each of these series, residual femoral deformity is only one of several factors including patient demographics and underlying disease processes that may have affected implant durability.
Uncemented implants also may be at risk for loosening in patients with femoral deformity primarily because deformity can compromise the initial fit and fixation of the prosthesis to bone. There are as yet insufficient data to evaluate the effect femoral deformity has on reliability and durability of uncemented femoral fixation.
Most series of total hip arthroplasty in patient populations with femoral deformity report a higher incidence of complications. The most frequent complications related specifically to femoral deformity are femoral fracture and femoral perforation during canal preparation. For cemented total hip arthroplasty after intertrochanteric osteotomy, Ferguson et al7 reported femoral fracture or perforation in seven of 307 hips and Benke et al1 reported a fracture in three of 105 hips. In a series of total hip arthroplasties for failed fixation of an intertrochanteric hip fracture, Mehlhoff et al12 reported one canal perforation and one fracture; the authors thought both complications were related to residual femoral deformity. Paavilainen et al15 reported one perforation and one fracture in 54 uncemented hip replacements in patients with developmental dysplasia of the hip who were not treated with osteotomy.
Patients with proximal femoral deformity also may be at increased risk for dislocation because of bony impingement of the femur against the pelvis. Mehlhoff et al12 reported dislocation in three of 13 hips after total hip arthroplasty for treatment of a failed intertrochanteric hip fracture. Other factors such as patient age and abductor problems also may have contributed to dislocations in this group of patients.
Osteotomy in Association With Total Hip Arthroplasty
Several studies report on total hip arthroplasty with concomitant osteotomy for femoral deformity.4,9,15,17 In a series of 20 primary total hip arthroplasties done for patients with various diagnoses who were treated with total hip arthroplasty and concomitant femoral osteotomy, Papagelopoulos et al17 reported Harris hip scores improved from 51 to 77 points in unrevised hips. Complications included intraoperative fracture in four hips and osteotomy nonunion in three. Paavilainen et al15 reported on 46 shortening osteotomies of different types used during total hip arthroplasty for patients with developmental hip dysplasia: there were two femoral fractures, one femoral fragment nonunion, and two postoperative dislocations. Holtgrewe and Hungerford9 reported three osteotomies in patients undergoing primary total hip arthroplasty. After surgery the mean Harris hip score was 94 points and all osteotomies healed. DeCoster et al4 reported on three biplanar osteotomies done during total hip arthroplasty after previous femoral osteotomy; all osteotomies healed.
The purposes of the current study are to: (1) review the technical challenges posed by femoral deformity during total hip arthroplasty; (2) develop a useful method of classifying femoral deformities; (3) examine methods available to perform total hip arthroplasty in the presence of deformity; and (4) discuss results of total hip arthroplasty in patient populations with femoral deformity.
Femoral deformities encountered during total hip arthroplasty range from mild to severe, can occur at any level of the femur, and arise from numerous diagnoses. A classification scheme was developed that divides femoral deformities according to anatomic level and subcategorizes them by deformity geometry and etiology. The classification is designed to be rational, practical, and user friendly. The anatomic site of deformity most influences technical challenges posed by the deformity and the geometry and etiology of the deformity have an effect on treatment methods. The classification scheme proposed in this paper is designed to be applicable to a broad spectrum of femoral deformities. Other femoral classifications also are available but have a different emphasis. The American Academy of Orthopaedic Surgeons system focuses on bone loss rather than deformity and is designed especially for patients undergoing revision hip surgery.3 Other classification schemes are designed to subcategorize patients with a specific diagnosis such as developmental hip dysplasia2,5 and are less applicable to the generic subject of femoral deformity.
The classification method proposed in this article is designed specifically to aid in analyzing the technical problems posed by specific deformities and to provide a framework for possible solutions. Thus, greater trochanteric deformities typically cause problems with exposure and hip biomechanics and can be treated with trochanteric osteotomy. Femoral neck deformities can affect implant alignment and rotation and usually can be treated by using implants that compensate for altered femoral neck anatomy. Metaphyseal deformities have a marked effect on implant and fixation options. Metaphyseal deformities can be treated with femoral implants that bypass the deformity, require resection of the deformity or with special modular or nonmodular implants tailored to fit the deformity. Diaphyseal defects can have an important impact on implant alignment. At times a short implant can be used that ends proximal to the deformity; however, many patients with major diaphyseal deformities require femoral osteotomy.
Femoral deformity is recognized to increase the technical difficulty of an arthroplasty and to increase risk of many intraoperative complications, including femoral fracture and femoral perforation. There are few studies regarding the generic subject of hip arthroplasty in patients with femoral deformity,16 but series on patients with Paget's disease,11,13 or previous femoral osteotomies7-patient groups with a higher number of patients with femoral deformity-suggest deformities may compromise the quality of femoral reconstruction in some cases and result in poorer functional results and poorer long-term arthroplasty durability.
Treatment of the patient with a femoral deformity requires judgment. Efforts to normalize hip anatomy with osteotomy or special implants are esthetically appealing and major residual, uncorrected deformities may have adverse biomechanical consequences. At the same time, the surgeon must take into account the significant risks associated with elaborate reconstructions of the femur. As a general guideline, older, sicker, patients with lower physical demands may be better treated with simpler operations that restore hip anatomy less completely, whereas younger more active patients may be better treated by more complete and anatomic reconstruction at the time of the primary total hip arthroplasty. Improved implants and improved operative techniques hopefully will improve the surgeon's ability to treat these complex problems successfully and with a minimum of complications.
The author thanks Miguel E. Cabanela, MD for contributing some case examples used as figures in this article.
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© 1999 Lippincott Williams & Wilkins, Inc.
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