The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 82, Issue 1

Instructional Course Lecture | January 01, 2000

Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Operative Treatment for Metastatic Disease of the Pelvis and the Proximal End of the Femur*†

TIMOTHY A. DAMRON, M.D.‡, SYRACUSE, NEW YORK; FRANKLIN H. SIM, M.D.§, ROCHESTER, MINNESOTA

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An Instructional Course Lecture, American Academy of Orthopaedic Surgeons

J Bone Joint Surg Am, 2000 Jan 01;82(1):114-26

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The prognosis for patients who have invasive cancer continues to improve. According to the statistics of the American Cancer Society³ for 1988 through 1992, the five-year survival rate for patients who have prostate cancer is 90 percent for whites and 75 percent for blacks and the five-year survival rate for patients who have breast cancer is 86 percent for whites and 70 percent for blacks. However, estimates suggest that 50 percent of the 1,228,600 new cases of invasive cancer diagnosed each year will eventually metastasize to bone³.

Figures in this Article

Introduction

Introduction | Proximal Femoral Lesions | Periacetabular Lesions | Overview | References

Many of these metastatic lesions involve the pelvis and the proximal end of the femur. In fact, the pelvis is second only to the spine in terms of the frequency of osseous involvement by metastatic disease, and the proximal end of the femur is the most common site of long-bone involvement by metastatic disease. While the recent introduction of bisphosphonates, which counteract the destruction of bone in patients who have metastatic cancer, has resulted in substantial delays in the development of initial skeletal complications and in a reduced prevalence of such complications over the short-term in patients who have breast cancer or multiple myeloma, the long-term efficacy of bisphosphonates has not been proved. Therefore, the appropriate orthopaedic treatment of skeletal metastases to the pelvis and the proximal end of the femur remains vital to the care of patients who have invasive cancer.

A number of technological advances during the last decade have simplified the treatment of metastases to the pelvis and the proximal end of the femur. With regard to the acetabulum, new off-the-shelf protrusio ring devices are available for challenging acetabular reconstructions. Superior fixation of these devices is achieved either through several types of superior flanges, with or without screw-holes, or through dual narrow plates. Inferior fixation is achieved with either an obturator hook or an ischial flange, which is designed to allow screw placement. Every possible combination of superior and inferior fixation is now manufactured.

With regard to the femur, numerous modular calcar-replacement prostheses as well as modular proximal femoral replacement megaprostheses are now available off the shelf. While the reconstruction intramedullary nail remains the standard for intramedullary fixation of a femur that is involved by metastatic disease, several third-generation reconstruction-type intramedullary nails are now on the market. All of these third-generation devices have the capacity for distal interlocking, and the options for proximal fixation range from a spiral blade to assorted hip-screw devices. In addition, hybrid so-called endo-reconstruction nails are now available. These unique devices consist of a proximal femoral prosthesis, the distal end of which is a reconstruction nail with interlocking capability.

Advances in preoperative planning and radiographic techniques have also allowed better treatment of patients who have metastatic lesions in the pelvis or the proximal end of the femur. The importance of evaluation of the entire pelvis and femur with plain radiographs is widely recognized, as is the value of total-skeleton technetium-99 nuclear bone-scanning in the assessment of occult disease that may affect operative planning. Computerized tomography scans of the periacetabular region are recommended for the preoperative evaluation of metastatic lesions in this area and may be complemented by three-dimensional reconstructions. In the setting of highly vascular lesions, such as renal cancer and myeloma, preoperative arteriographic evaluation and embolization may reduce intraoperative bleeding.

The operative treatment of metastatic lesions in the pelvis and the proximal end of the femur presents unique challenges, but the principles of treatment are the same as those for metastatic lesions at any site. First, appropriate patient selection is critical so that the time needed to recover from the operation is not longer than the estimated survival. The time to recovery after insertion of an intramedullary femoral nail is much shorter than that after a complex acetabular reconstruction. Survival depends on multiple factors and is best estimated by the medical oncologist. Primary lung carcinoma other than small-cell carcinoma, a short time from the diagnosis of the primary lesion to the development of metastatic disease, presentation with metastatic disease, and concurrent visceral metastatic involvement generally suggest a shorter expected duration of survival.

The second principle of treatment is that ideally the construct should be stable enough to allow the patient to walk with full weight-bearing immediately after the operation as well as durable enough to last the expected lifetime of the patient. Healing of pathological fractures cannot be relied on because healing generally proceeds more slowly than normal, is impeded both by the metastatic tumor and by the effects of radiation treatment⁶, and depends on the type of primary tumor. Gainor and Buchert¹⁷ calculated an overall rate of union of pathological fractures of 35 percent (forty-five of 129 fractures), with disease-specific rates of union ranging from zero of seventeen fractures associated with lung carcinoma to ten of fifteen fractures associated with myeloma. For lesions about the hip, where as much as six times body weight may be borne by the bone¹⁶, the need for immediate stability and prolonged durability strongly favors prosthetic replacement rather than internal fixation. As it can for metastatic lesions elsewhere, methylmethacrylate may play an important role in any attempt at internal fixation in this region; the addition of methylmethacrylate to internal fixation has been demonstrated to provide better relief of pain and an improved ability to walk and is unaffected by radiation therapy^{4,5,12,19,21,24,25,43}. Methylmethacrylate is also strongly recommended for use with prosthetic reconstruction in this setting.

The third operative principle for the treatment of metastatic disease is that any planned reconstruction should address all areas of weakened bone that are present at the time of the operation as well as all areas that are likely to be weakened subsequently. In the setting of a pathological fracture of the proximal end of the femur, the main issues are whether to perform a hemiarthroplasty or a total hip arthroplasty as well as the appropriate length of the stem for the femoral prosthesis. These issues will be discussed in the section on prosthetic replacement.

Finally, postoperative radiation therapy is very important to minimize progression of the disease and the risk of failure of the implant. The rate of failure of the fixation increases with time, in part because of progression of the disease. Townsend et al.⁴⁷ retrospectively reviewed the results of sixty-four orthopaedic stabilization procedures in sixty patients in whom cancer had metastasized to previously nonirradiated bone. Thirty-five of the stabilization procedures had been followed by radiation therapy at the operative site, and the other twenty-nine had not. The patients who had received postoperative radiation therapy had improved function at each time-interval that was assessed and a lower rate of reoperation than the patients who had not received radiation therapy. The entire femur should be irradiated after any procedure that involves reaming of the bone.

*Printed with permission of the American Academy of Orthopaedic Surgeons. This article, as well as other lectures presented at the Academy's Annual Meeting, will be available in March 2000 in Instructional Course Lectures, Volume 49. The complete volume can be ordered online at www.aaos.org, or by calling 800-626-6726 (8 A.M.-5 P.M. Central time).

†Although none of the authors has received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article, benefits have been or will be received but are directed solely to a research fund, foundation, educational institution, or other nonprofit organization with which one or more of the authors is associated. No funds were received in support of this study.

‡Department of Orthopedic Surgery, State University of New York Health Science Center at Syracuse, 550 Harrison Center, Syracuse, New York 13202. E-mail address: damront@vax.cs.hscsyr.edu.§Department of Orthopedic Surgery, Mayo Clinic and Mayo Foundation, 200 First Street S.W., Rochester, Minnesota 55905.

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FIG1-A:: Fig. 1-A: Preoperative anteroposterior radiograph of a right hip, showing a fracture of the femoral neck secondary to metastatic prostate cancer.

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FIG1-B:: Fig. 1-B: Anteroposterior radiograph made after bipolar hemiarthroplasty with use of a long-stem femoral component.

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FIG2-A:: Fig. 2-A: Preoperative anteroposterior radiograph of the proximal end of a left femur, showing a laterally based area of intertrochanteric destruction (arrows) secondary to metastatic breast cancer.

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FIG2-B:: Fig. 2-B: Anteroposterior radiograph made after prophylactic intertrochanteric fixation with a dynamic hip-screw augmented with methylmethacrylate and a supplementary screw.

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FIG3-A:: Fig. 3-A: Anteroposterior radiograph of the proximal end of a right femur, showing a pathological intertrochanteric fracture secondary to metastatic breast cancer.

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FIG3-B:: Fig. 3-B: Anteroposterior radiograph made after bipolar hemiarthroplasty with insertion of a long-stem calcar-replacement prosthesis with cement.

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FIG4-A:: Fig. 4-A: Anteroposterior radiograph of the proximal end of a left femur, showing a large lytic destructive area in the subtrochanteric region (arrows) that was representative of an impending pathological fracture secondary to metastatic hypernephroma.

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FIG4-B:: Fig. 4-B: Anteroposterior radiograph made after prophylactic fixation with a reconstruction intramedullary nail.

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FIG5-A:: Fig. 5-A Anteroposterior radiograph of a left femur, showing extensive destruction and a subtrochanteric pathological fracture.

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FIG5-B:: Fig. 5-B Anteroposterior radiograph made after resection of the diseased proximal femoral bone and reconstruction with an early type of nonmodular proximal femoral replacement hemiarthroplasty performed with cement.

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FIG6-A:: Fig. 6-A Anteroposterior radiograph of the left side of a pelvis, showing a class-II defect²³ of the acetabular wall (arrow) secondary to metastatic breast cancer.

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FIG6-B:: Fig. 6-B Anteroposterior radiograph made after total hip arthroplasty with acetabular reconstruction with a Ganz antiprotrusio ring, screws, and cement.

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FIG7-A:: Fig. 7-A Anteroposterior radiograph of the pelvis, showing a solitary metastasis from hypernephroma involving the right ischium (arrows) and extending to the acetabulum. (Reproduced, with modification, from: Sim, F. H.; Frassica, F. J.; and Chao, E. Y. S.: Orthopaedic management using new devices and prostheses. Clin. Orthop., 312: 163, 1995. Reprinted with permission of the Mayo Foundation.)

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FIG7-B:: Fig. 7-B Anteroposterior radiograph made after excision of the involved bone segment and reconstruction with a saddle prosthesis. (Reprinted, with permission of the Mayo Foundation, from: Sim, F. H.; Frassica, F. J.; and Chao, E. Y. S.: Orthopaedic management using new devices and prostheses. Clin. Orthop., 312: 163, 1995.)

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FIG8:: Fig. 8 Conceptual illustration showing the typical complex reconstruction of a class-III defect²³ in the acetabulum with flexible Steinmann pins and an antiprotrusio device. (Reprinted with permission of the Mayo Foundation.)

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FIG9-A:: Fig. 9-A Anteroposterior radiograph of the pelvis, showing a class-III defect²³ of the left acetabular dome and the peripheral rim due to metastatic renal cancer.

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FIG9-B:: Fig. 9-B Anteroposterior radiograph of the left side of the pelvis, made after reconstruction with Steinmann pins and an antiprotrusio device as part of a total hip arthroplasty performed with cement.

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TABLE I: SCORING SYSTEM FOR RISK OF PATHOLOGICAL FRACTURE IN LONG BONES³⁷

Variable	1 Point	2 Points	3 Points
Site of lesion	Upper limb	Lower limb	Peritrochanteric
Degree of pain	Mild	Moderate	Aggravated by function
Type of lesion	Blastic	Mixed	Lytic
Size of lesion	<1/3 diameter of bone	1/3—2/3 diameter of bone	>2/3 diameter of bone

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TABLE I: SCORING SYSTEM FOR RISK OF PATHOLOGICAL FRACTURE IN LONG BONES³⁷

Variable	1 Point	2 Points	3 Points
Site of lesion	Upper limb	Lower limb	Peritrochanteric
Degree of pain	Mild	Moderate	Aggravated by function
Type of lesion	Blastic	Mixed	Lytic
Size of lesion	<1/3 diameter of bone	1/3—2/3 diameter of bone	>2/3 diameter of bone

Proximal Femoral Lesions

Introduction | Proximal Femoral Lesions | Periacetabular Lesions | Overview | References

Impending Pathological Fractures

Operative treatment of the proximal end of the femur may be indicated because of an actual or impending pathological fracture. The definition of an impending pathological fracture remains controversial. According to Harrington et al.²², a lesion in the proximal end of the femur that measures 2.5 centimeters, occupies at least 50 percent of the diameter of the bone, is accompanied by an adjacent fracture of the lesser trochanter, or for which treatment with radiation therapy has failed is considered at high risk for fracture. These criteria were questioned by Keene et al.³⁰ on the basis of a retrospective review of metastases from the breast to the proximal end of the femur. Those authors³⁰ suggested that there is no reliable relationship between the risk of fracture and the size of the area involved, the degree of pain, or the nature of the lesion (lytic, blastic, or mixed).

More recently, Mirels³⁷ developed a scoring system for the prediction of fracture risk. This system was validated within his institution; however, its widespread use has been questioned because of suspected variability in its application and the subjective nature of some of the scoring components. With this system, each lesion is evaluated on the basis of four factors: site, size, type, and pain (Table I). Each factor is assigned 1, 2, or 3 points, according to increasing risk, and a total point score is calculated. A total score of 9 points indicates a 33 percent risk of fracture, and it is thought that a lesion should have a score of at least 9 points to warrant prophylactic fixation. A score of 8 points indicates a lower risk (15 percent) and is considered a borderline indication for prophylactic fixation. Ultimately, the application of engineering principles and of more advanced radiographic techniques, such as computerized tomography, to the assessment of fracture risk, as described in the pioneering work of Hipp et al.²⁷, may prove more reliable.

Femoral Head and Neck

Internal fixation of pathological fractures and impending pathological fractures that are due to metastatic involvement of the femoral head and neck region is associated with an unacceptably high risk of subsequent pathological fracture. Thus, prosthetic replacement is the treatment of choice. When the involvement does not extend more proximally than the level of the femoral neck, a collared prosthesis inserted with cement, without calcar replacement, may suffice (Figs. 1-A and 1-B). Such prostheses are now available with long straight or curved femoral stems. A calcar-replacement prosthesis is recommended for more distal lesions or fractures in the base of the neck.

Two main issues relative to the use of arthroplasty in hips with metastatic involvement remain controversial. The first issue is the length of the femoral stem. From a biomechanical standpoint, the tip of the intramedullary femoral stem should bypass the most distal area of weakness by two bone diameters. Even in the absence of known distal metastases, the use of a long intramedullary stem inserted with cement may be indicated prophylactically if it is believed that the patient is at substantial risk for such lesions. One argument against the routine use of long-stem prostheses inserted with cement is the associated increased risk of embolization and cardiac arrest³⁹.

The second issue relative to the use of arthroplasty for patients who have a proximal femoral lesion is the treatment of the acetabulum. Habermann et al.²⁰ reported that previously unrecognized acetabular involvement was discovered through biopsy of the acetabulum in nineteen (83 percent) of twenty-three patients with metastatic disease who were having a hip arthroplasty. Those authors recommended total hip arthroplasty on a routine basis whenever a femoral stem is implanted to treat metastatic involvement. As unrecognized involvement has not clearly been shown to lead to problems or persistent pain, many authors still recommend hemiarthroplasty in this setting^9,38,40,44. One of the disadvantages of insertion of an acetabular component is the added potential for instability, particularly when a calcar or proximal femoral replacement prosthesis is used. The additional exposure necessary for insertion of an acetabular component and the consequent increased blood loss have discouraged the use of routine total hip arthroplasty in the treatment of metastatic involvement of the femoral head and neck.

Lane et al.³² reported on 167 patients who had had endoprosthetic replacement as treatment for a pathological or impending pathological fracture about the hip. The median survival time was 5.6 months. None of the patients had dislocation, loosening, or failure of the prosthesis, and most of the patients regained or had improvement in the ability to walk.

Intertrochanteric Fractures

The operative treatment of pathological intertrochanteric fractures remains controversial. Many surgeons prefer prosthetic replacement to standard internal fixation supplemented with bone cement. There are advantages and disadvantages to each option.

Classically, a dynamic hip-screw combined with curettage and complete packing of the defect with bone cement is used for internal fixation (Figs. 2-A and 2-B). The main advantages of this technique are that it preserves the hip joint and that most orthopaedic surgeons are very comfortable using a dynamic hip-screw device. One of the disadvantages is that orthopaedic surgeons may not have experience with packing of a bone defect, particularly around a fixation device. Consequently, stable fixation in this region may be difficult to achieve, as it relies largely on the technique of cementing to compensate for medial bone loss, which often occurs, as well as on the integrity of the femoral head and neck region for purchase of the hip screw. In addition, placement of a plate-and-screw device does not allow prophylactic protection of the entire bone from failure due to distal metastatic disease. As a result of these limitations, the fixation may fail because of a combination of the high stresses placed on the proximal end of the femur and progression of the disease.

Intramedullary fixation devices have also been used to treat pathological intertrochanteric fractures of the femur. The most useful device has been the intramedullary hip-screw, the most popular of which is the Gamma nail (Howmedica, Rutherford, New Jersey). From a theoretical viewpoint, these devices derive a biomechanical advantage from their placement closer to the medial side of the femur, where there are compressive forces, and away from the lateral side, where there are tensile forces. However, short intramedullary hip-screws have been associated with complications such as fracture at the tip of the nail in the diaphysis. Long intramedullary hip-screws are now preferred and have the added advantage of protecting the entire bone^11,33. However, few reports on their usage have been published.

Calcar-replacement femoral stems are the prostheses of choice in the setting of pathological intertrochanteric fracture (Figs. 3-A and 3-B). The main advantage of these prostheses is that they require removal of much of the diseased bone, which greatly decreases the reliance on that bone for stability and consequently decreases the likelihood of failure due to progression of the disease. In addition, fixation of the prosthesis with cement allows immediate full weight-bearing, the availability of different neck lengths due to the modularity of the implant allows improved equalization of limb lengths and stability of the hip joint, long stems are available to treat distal disease, and the survival of these prostheses is excellent over the shortened life span of these patients.

The disadvantage of arthroplasty, as cited by proponents of internal fixation, is that it is a more extensive procedure¹⁵. It is certainly true that arthroplasty introduces a different set of complications than those seen with internal fixation. These complications include instability, fracture of the greater trochanter, and loosening of the prosthesis. Infection may occur after either arthroplasty or internal fixation, but the risk is highest in patients who have an arthroplasty after internal fixation has failed. The rate of infection in one study of hips with a pathological fracture that had been treated with arthroplasty was 1 percent (two of 167 hips)³².

In a report from the Mayo Clinic, the overall survival rate of calcar-replacement prostheses inserted to treat pathological bone lesions was 93 percent (twenty-six of twenty-eight prostheses)⁹. Eight patients (29 percent) had at least one complication; three of them had an infection. There was only one case of instability in the series, which consisted predominantly of hemiarthroplasties. In contrast, the rate of dislocation of similar calcar-replacement prostheses that had been inserted together with an acetabular component as a hip revision in a study by McLaughlin and Harris³⁵ was 21 percent (eight of thirty-eight hips).

Subtrochanteric Fractures

Forces in the subtrochanteric region may reach six times body weight¹⁶, which places extreme demands on fixation devices. Nail-plate devices have an unacceptably high prevalence of failure when used to fix subtrochanteric pathological fractures, and their use has been abandoned by most surgeons. Viable options include reconstruction-type intramedullary nails or prosthetic replacement. Because of the high cost and increased instability inherent to the large proximal femoral replacement megaprostheses needed to replace the amount of bone loss associated with these fractures, intramedullary fixation is preferred whenever adequate fixation can be achieved in the remaining proximal bone.

The first widely used reconstruction intramedullary nail was the Zickel nail (Howmedica), a rigid intramedullary device with a proximal hip-bolt placed through it into the region of the femoral neck. The Zickel nail has been very successful, particularly when used with methylmethacrylate. However, it has been associated with shortening and loss of rotational control when it has been used without methylmethacrylate, partly because of the lack of distal interlocking capability. Cortical penetration, comminution of the proximal end of the femur, malrotation, and malposition of the proximal locking device also have been reported^36,41,51.

The prototype second-generation reconstruction nail was the Russell-Taylor nail (Smith and Nephew, Memphis, Tennessee) with proximal fixation with dual interlocking screws in the femoral neck and the capacity for distal interlocking (Figs. 4-A and 4-B)¹⁸. Typically, the femoral canal is overreamed by one to two millimeters and a nail with the appropriate diameter is inserted. This device has been associated with fewer complications and it is easier to insert compared with the Zickel nail, to the extent that it has essentially become the standard of treatment of subtrochanteric pathological fractures. In the laboratory, Russell-Taylor nails fail by screw cutout in the femoral head^13,31, suggesting that the proximal fixation may be inadequate, particularly when the proximal bone stock is not ideal. As reported by Weikert and Schwartz⁴⁹, who studied patients with impending pathological fractures, and by Karachalios et al.²⁹, who studied those with pathological subtrochanteric fractures, these nails may be used successfully without methylmethacrylate in some patients but care should be taken to ensure that the proximal fixation is adequate. Indications for the use of methylmethacrylate with these devices have not been well established, but the addition of methylmethacrylate should be considered when a separate incision for an open biopsy is used to approach the lesion, for large segmentally destructive lesions, or when bone apposition cannot be restored.

More recently, so-called third-generation variations of the reconstruction nail have become available. The common features of these third-generation nails are the capacity for distal locking and the use of a device proximally for secure fixation in the femoral neck. The nails differ primarily on the basis of the type of proximal interlocking device that is used. The spiral-blade nail utilizes a single low-profile spiral-blade device to secure the proximal fixation while decreasing bone loss in the femoral neck⁴². These nails have often been inserted without reaming, thus diminishing blood loss. Both in biomechanical laboratory testing and in clinical usage, these devices have been reported to fail by cutout of the spiral blade, migration, and breakage of the blade device^7,46,50. Thus, their use as treatment for pathological subtrochanteric fractures is questionable. Direct biomechanical comparison of reconstruction nails in two studies^13,50 favored the second-generation Russell-Taylor nail, which allows proximal fixation with two screws in the femoral neck. However, Hecht et al.²⁶ reported good results with twenty-seven spiral blades implanted in twenty-four patients to treat a pathological lesion. None of the devices failed, although one spiral blade cut out of the anterior aspect of the bone during placement.

The other type of third-generation reconstruction nail, the long intramedullary hip-screw device, utilizes a single large-bore hip-screw proximally, similar to the dynamic hip-screw. These devices are inserted by reaming proximally or proximally and distally. Generally, very good fixation is achieved in the femoral neck. Although early reports on the use of two types of long intramedullary hip-screws have been favorable^10,14, biomechanical laboratory testing³¹ demonstrated that at least one of these types of devices was inferior to the Russell-Taylor reconstruction nail because of failure through bending of the proximal aspect of the nail. The need for methylmethacrylate with these nails, as with the Russell-Taylor reconstruction nail, has not been established.

A proximal femoral replacement prosthesis should be considered when the proximal femoral bone has been so weakened by metastatic disease that a reconstruction nail is unlikely to provide stable fixation (Figs. 5-A and 5-B), even with methylmethacrylate, or when previous fixation of a pathological fracture has failed. These prostheses provide excellent relief of pain and allow the surgeon to replace most, if not all, of the weakened proximal femoral bone. Distal lesions should be bypassed with the intramedullary stem. Before a proximal femoral prosthesis is used, however, a number of other factors should be considered. First, their much greater cost may not be justified in patients who have a very limited life expectancy, such as those who have metastatic lung carcinoma. Second, the exposure needed for resection of bone for implantation of these devices is much more extensive than that needed for either intramedullary nailing or standard prosthetic replacement. Consequently, there is a proportionately higher risk of bleeding and neurological injury during insertion of a megaprosthesis as well as problems with wound-healing and infection postoperatively. The rate of dislocation is also prohibitively high when a proximal femoral replacement prosthesis is combined with an acetabular component, making hemiarthroplasty the construct of choice. Finally, reconstruction of the abductor mechanism is difficult at best. If the trochanteric attachment can be preserved, the bone is secured to the prosthesis with cables, wires, or heavy nonabsorbable suture. If the trochanteric bone is removed, the remaining abductor muscles are reefed down to the vastus lateralis⁴⁵. Most patients need to use a cane to compensate for loss of the abductor mechanism.

The Mayo Clinic experience with proximal femoral replacement prostheses in the setting of metastatic disease and myeloma consists of thirty-four hips that were treated between 1971 and 1984⁴⁵. These hips are part of a larger series of 140 patients (143 hips) who had insertion of a proximal femoral replacement prosthesis for several indications. The overall result was excellent or good for seventy-seven (55 percent) of the 140 patients. The unsatisfactory results were due to instability and the need for a cane, both of which are related to weak abductor muscles. The overall rate of complications for eighty-two patients who had either a metastatic or primary malignant tumor was 46 percent (thirty-eight patients); there were twenty-two major complications (27 percent) and sixteen minor complications (20 percent). Instability was observed in ten (12 percent) of the eighty-two patients and infection, in four (5 percent).

Periacetabular Lesions

Introduction | Proximal Femoral Lesions | Periacetabular Lesions | Overview | References

Classification Systems

Three systems can be used to classify pathological metastatic lesions of the acetabulum. The systems of Levy et al. ³⁴ and Harrington²³ apply specifically to periacetabular lesions resulting from metastatic disease, while that of the American Academy of Orthopaedic Surgeons⁷ applies to lesions resulting from all etiologies and is more widely used to classify those resulting from failed total hip arthroplasty. Plain radiographs of the entire pelvis with Judet radiographs and computerized tomography are recommended in order to assess the extent of bone destruction accurately in patients who have metastatic disease or myeloma.

Levy et al.³⁴ classified acetabular defects due to metastatic disease or myeloma as minor, major, or massive. These three categories are similar to the three classes developed by Harrington²³ on the basis of his review of the cases of fifty-eight patients. Since the classification proposed by Harrington provides guidelines for treatment, it has been the most widely used. With class-I defects in the system of Harrington, which correspond to minor defects in the system of Levy et al., the lateral cortices, superior walls, and medial walls are all intact. Thus, these defects are cavitary and contained. With class-II (major) defects, there is a deficit in the medial wall but the rim is intact. With class-III (massive) defects, there are deficits in both the lateral wall and the superior cortices.

The classification system of the American Academy of Orthopaedic Surgeons⁷ categorizes lesions into five types. Type 1 indicates segmental bone loss; type 2, cavitary defects; type 3, combined segmental and cavitary defects; type 4, pelvic discontinuity; and type 5, massive bone loss. Because the treatment of metastatic defects differs from the treatment of nonmetastatic defects due to acetabular dysplasia or aseptic loosening of a previous acetabular prosthesis, it is difficult to use the Academy's classification as a guide for treatment in the setting of metastatic disease or myeloma. However, the system is detailed, is useful for reporting purposes and for comparisons between series, and provides categories that are sometimes encountered in the setting of metastatic disease and are not as well defined in the other two classifications.

Operative Treatment

Because class-I defects²³ are contained, they may be treated with conventional placement of an acetabular component with cement. The use of porous cups is discouraged because of the inhibitory effects on bone ingrowth by the underlying disease deposits and the damaging effects of radiation therapy. Hemiarthroplasty is an option when the primary problem is a proximal femoral lesion or fracture and the acetabular defect is class I.

Patients who have a class-II defect²³ are at risk for central acetabular fracture-dislocation. Operative treatment of these defects should include medial wire mesh to contain the methylmethacrylate, a protrusio ring to distribute the stresses to the remaining intact rim of bone, and methylmethacrylate to fill the void. An Oh-Harris ring (Zimmer, Warsaw, Indiana) is the prototypical ring for treatment of these defects, although other styles are now available (Figs. 6-A and 6-B).

Class-III defects²³ are the most challenging to treat because there is so little remaining bone on which to rebuild the acetabulum. Resection arthroplasty may be considered for these patients for relief of pain but it should be noted that the prognosis for regaining the ability to walk independently is poor. Resection arthroplasty is best reserved for patients who have an extremely limited life expectancy or for whom a more involved procedure is medically contraindicated. Operations that have a better chance of restoring function include reconstruction with a saddle prosthesis or complex acetabular reconstruction as a component of total hip arthroplasty.

Saddle prostheses (Link America, Denville, New Jersey) extend from the proximal end of the femur to a rotating saddle that articulates in a saddle-joint fashion at 90 degrees to an operatively created notch in the remaining intact superior iliac bone ( Figs. 7-A and 7-B). Aboulafia et al.¹ reported on seventeen patients with a periacetabular tumor who had reconstruction with a saddle prosthesis; nine of them had a metastatic or systemic tumor. Overall, twelve of the seventeen patients had an excellent or good result, one had a fair result, and four had a poor result. All nine of the patients who were alive at the time of the latest follow-up (fifteen to sixty-two months postoperatively), including three of the patients who had had metastatic involvement, had an excellent or good result.

The acetabular reconstruction that is most frequently used to salvage a class-III defect redistributes the weight-bearing force onto intact bone by way of multiple large-diameter threaded Steinmann pins that extend either to intact bone in the superior aspect of the ilium or across the sacroiliac joint into the sacrum (Fig. 8)²⁸. Pins inserted from the anterior aspect of the ilium into a superior dome defect or across a defect in the anterior column into intact bone in the superior aspect of the pubic ramus should be inserted in an antegrade fashion, beginning at the iliac crest and directed distally. Pins inserted to reconstruct the posterior column and to redistribute forces either to the more posterior aspect of the ilium or to the sacrum should be inserted in a retrograde fashion, beginning in the periacetabular defect and advanced proximally. During placement of the latter pins, palpation of the sciatic notch through the posterior aspect of the wound and palpation of the sacroiliac joint from the inner aspect of the superior part of the ilium is recommended. Wire mesh is sometimes necessary, either medially or superolaterally, to contain the bone cement. Once the pins and mesh are in place, a large antiprotrusio cage is fixed in position with cement and is sometimes supplemented with bone-screw fixation through holes in the dome or flanges of the protrusio device. The prototypical antiprotrusio cage used for these defects is the Burch-Schneider cage (Sulzer Medica, Baar, Switzerland), but numerous newer devices that employ a variety of combinations of superior plates or flanges and inferior hooks or flanges are now available (Figs. 9-A and 9-B). When the polyethylene socket is fixed into the protrusio ring with cement, care should be taken to orient it on the basis of the anatomy of the patient rather than on the protrusio ring. A femoral stem that spans the femoral defects should then be inserted with cement. If a standard femoral implant is used, a long neck that necessitates slightly more resection of bone is preferable to a short neck that necessitates less resection of bone. The longer neck is less likely to result in impingement of the proximal end of the femur on the protrusio ring, which may result in levering and dislocation.

As far as we know, the most comprehensive study of acetabular reconstruction in the setting of metastatic disease is the one by Harrington²³, who reported on fifty-eight patients. His patients who had class-I, II, or III defects all had pain preoperatively, and eighteen were unable to walk because of severe pain. The patients survived for a mean of twenty-nine months postoperatively, with twenty patients surviving for at least four years. After total hip arthroplasty, performed with the guidelines that Harrington subsequently recommended, the patients had tremendous relief of pain. Forty-three (74 percent) of the fifty-eight patients had only minimum pain, and only five (9 percent) had severe pain. Fifty-four (93 percent) of the fifty-eight patients regained the ability to walk. Of the fifty-one patients who were alive at the time of the six-month follow-up examination, twenty (39 percent) walked without aids, nineteen (37 percent) used one crutch or cane, six (12 percent) used crutches or a walker, and six were unable to walk. Of the thirty patients who were alive at the time of the two-year follow-up, sixteen (53 percent) remained able to walk without aids. Five patients had loosening as a result of progression of the tumor. Similar results with regard to good relief of pain and an improved ability to walk were subsequently reported by Algan and Horowitz² and by Walker⁴⁸ in small series of patients after procedures performed with similar techniques.

Overview

Introduction | Proximal Femoral Lesions | Periacetabular Lesions | Overview | References

Advances in the treatment of invasive cancers continue to improve the longevity of patients who have these diseases; thus, the care of patients who have bone metastases is an issue of the utmost importance to the orthopaedic surgeon. In terms of maintaining the ability to walk, no site of potential metastatic involvement is more crucial than the proximal end of the femur and the acetabulum. Advances in femoral and acetabular implants, imaging modalities, and operative techniques now allow reconstruction of even the most complex acetabular and proximal femoral defects. However, the orthopaedic surgeon must recognize the need to approach management of these patients from a multidisciplinary perspective. The oncologist, radiotherapist, rehabilitation medicine specialist, radiologist, and pathologist each have a role to play. Only through cooperation among all members of the team will a patient who has metastatic disease or a myeloma be given the best possible care.

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Topics

fracture ; femur ; pathological fracture ; neoplasm metastasis ; prosthesis implantation ; reconstructive surgical procedures ; pelvis ; intertrochanteric fracture ; proximal femur

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TIMOTHY A. DAMRON, FRANKLIN H. SIM; Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Operative Treatment for Metastatic Disease of the Pelvis and the Proximal End of the Femur*†. The Journal of Bone & Joint Surgery. 2000 Jan;82(1):114-26.

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