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Reconstruction of Hip Stability After Proximal and Total Femur Resections

Bickels, Jacob*; Meller, Isaac**; Henshaw, Robert, M.*; Malawer, Martin, M.*

Clinical Orthopaedics and Related Research: June 2000 - Volume 375 - Issue - p 218-230
Section II: Original Articles: Tumor
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Dislocation is the most common complication after proximal and total femur endoprosthetic reconstruction. The current study describes a surgical technique of acetabular preservation and reconstruction of the joint capsule and abductor mechanism that recreates joint stability and avoids dislocation. Between 1980 and 1996, 57 patients underwent proximal or total femur resection with endoprosthetic reconstruction. Forty-six patients had primary sarcoma of bone, nine had other bone tumors, and two had metabolic bone disease. The acetabulum was spared and not resurfaced in all patients. Bipolar hemiarthroplasty was performed in 49 patients, and fixed unipolar hemiarthroplasty was performed in eight. Soft tissue reconstruction included Dacron tape capsulorrhaphy over the prosthetic neck, reattachment of the abductor mechanism to the prosthesis, and extracortical bone fixation. The average followup period was 6.5 years (range, 2-18.2 years). Dislocation occurred in only one (1.7%) patient, and aseptic prosthetic loosening occurred in three (5.3%) patients. Four patients with primary bone sarcoma had local recurrence, of whom one required amputation of the limb. The limb salvage rate was 98%. Eighty-one percent of the patients had a good to excellent functional outcome. Acetabular preservation, capsulorrhaphy, and reconstruction of the abductor mechanism recreate hip stability and avoid dislocation after proximal and total femur endoprosthetic reconstruction.

From the *Department of Orthopedic Oncology, Washington Cancer Institute, Washington Hospital Center, George Washington University, Washington, DC; and **The National Unit of Orthopedic Oncology, Tel-Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.

Reprint requests to Martin M. Malawer, MD, Department of Orthopedic Oncology, Washington Cancer Institute, Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010.

Received: December 14, 1998.

Revised: May 12, 1999; September 28, 1999.

Accepted: October 11, 1999.

The proximal and midfemur are common sites for primary bone sarcomas.26-28 Metastatic tumors are the most common malignant lesion of the proximal femur, with carcinomas being the most common tumor type.7 Patients who were candidates for extensive femoral resection because of malignant tumor long were considered a high risk group for limb sparing procedures because of the extent of soft tissue resection and use of adjuvant chemotherapy and radiation therapy. Improved survival of patients with musculoskeletal malignancies, developments in bioengineering, and refinements in surgical technique have allowed limb sparing procedures to be done in these situations. Local tumor control is good, as is the probability of a functional extremity. Proximal and total femur resection became a reliable surgical option in the treatment of primary bone sarcomas and metastatic bone disease14,17,21 and, more recently, in the treatment of various nononcologic indications. These indications include failure of internal fixation, severe acute fractures with poor bone quality, failed total hip arthroplasty, chronic osteomyelitis, metabolic bone disease, and various congenital skeletal defects.4,11,19

Methods of skeletal reconstruction include resection arthrodesis,9 massive osteoarticular allograft,22 endoprosthetic reconstruction,11 and prosthetic allograft composites.12 Osteoarticular allografts, which were popular in the 1970s and 1980s, attempt to restore the natural anatomy of a joint by matching the donor bone to the recipient's anatomy; however, with time, osteoarticular allografts are associated with increased rates of infection, nonunion, instability, fracture, and subchondral collapse, which lead to failure.20,25,34 Introduced in mid-1980s, modular prostheses revolutionized endoprosthetic reconstruction.2,5 The modular system enables the surgeon to measure the actual bone defect at the time of surgery and select the most appropriate components to use in reconstruction.2,5 Components of these interchangeable systems include articulating segments, bodies, and stems of varying lengths and diameters. Design features include extensive porous coating on the extracortical portion of the prostheses for bone and soft tissue fixation and metallic loops to assist in muscle reattachment.

Dislocation is the most common complication after proximal and total femur resection with endoprosthetic reconstruction, ranging from 11% to 15%.15,16,24,30,34 The current long-term followup study, based on the experience with 57 patients who underwent proximal or total femur resection with endoprosthetic reconstruction, focuses on the surgical technique and emphasizes preservation of the acetabulum (acetabular sparing and avoidance of resurfacing), repair of the joint capsule, and reconstruction of the abductor mechanism as a means of restoring joint stability and avoiding dislocation. As a result, dislocation occurred in only one (1.7%) patient in this series. Proximal and total femur endoprosthetic reconstructions were grouped together because the surgical technique around the proximal femur, concerns of joint stability, and reconstruction techniques are similar in both types of reconstruction.

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MATERIALS AND METHODS

Between 1980 and 1996, 39 proximal femur resections and 18 total femur resections were performed in two institutions. All participating surgeons trained together and used the same surgical technique of resection and reconstruction. Thirty-five male and 22 female patients, ranging in age from 5 to 85 years (average, 41 years) were included. Seven patients were younger than 12 years. Forty-six patients had primary bone sarcomas, six patients had metastatic carcinomas to the femur, three patients had other primary tumors of bone, and two patients had renal osteodystrophy that was associated with excessive bone loss, deformity, and functional impairment. Table 1 summarizes the histopathologic diagnoses and surgical classification of the patients in this series.

TABLE 1

TABLE 1

Proximal femur resection was performed for metaphyseodiaphyseal lesions that extended below the lesser trochanter, caused extensive cortical destruction, and spared at least 1/3 of the distal femoral diaphysis. Total femur resection was performed for diaphyseal lesions that extended proximally to the lesser trochanter and distally to the distal 1/3 of the diaphysis and caused extensive bone destruction. Resection of a metastatic lesion was performed when the tumor was extremely large, had progressed significantly despite radiation or chemotherapy, a previous operative procedure failed, and the lesion was a solitary metastasis.

Complete staging studies were performed before surgery for all patients with a primary bone sarcoma. The imaging studies included plain radiography, computed tomography (CT), and magnetic resonance imaging (MRI) of the whole femur and the hip and knee. Particular attention was given to the anatomic relation of the tumor to the sciatic nerve and femoral vessels; angiography was used to assess patency of the latter and its relation to the tumor. All patients were followed up for a minimum of 2 years (range, 24-418 months; average, 80 months). For the first 2 years after surgery, patients were evaluated every 3 months. On each visit, physical examination, plain radiography, and chest CT were performed. Patients were evaluated semiannually for an additional 3 years and annually thereafter. Functional evaluation was done according to the American Musculoskeletal Tumor Society System8 and results presented here are based on each patient's most recent followup. An orthopaedic oncologist analyzed the clinical records, operative reports, and imaging studies. The histopathologic diagnoses, types of resection, prostheses used for reconstruction, complications, and rates of local tumor recurrence and revisions were determined.

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Surgical Technique

Limb sparing surgery that involves endoprosthetic replacement has three steps: tumor resection, endoprosthetic reconstruction, and soft tissue reconstruction. The techniques of proximal femur resection, endoprosthetic reconstruction, capsular repair, reconstruction of the abductor mechanism, and extracortical bone fixation are described. The additional steps required for total femur resection are described briefly.

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Tumor Resection

The patient is placed in a lateral position and a long posterolateral incision is made (Fig 1). This approach allows exposure of the proximal 1/3 of the femur, the retrogluteal area, and allows for identification of the common femoral artery. An ilioinguinal extension to that incision is added if the tumor has an extensive, medial soft tissue component along the proximal femur. This incision allows safe exposure of the femoral canal, femoral triangle, profundus femoral artery, and sartorial canal. If total femur resection is performed, the incision is brought distally to the anterolateral aspect of the patellar tendon and tibial tuberosity. If the tumor has a medial component along the distal femur, it is approached best through a medially curved incision (Fig 1; insert). Posterior reflection of the gluteus maximus muscle exposes the retrogluteal area, external rotators, sciatic nerve, abductors, and posterior capsule. The abductors are identified. If there is no tumor involvement, the greater trochanter or small bony attachment is osteotomized (Fig 2). Otherwise, the abductors are transected through their tendinous attachments and retracted, exposing the hip and acetabulum. The vastus lateralis is reflected distally from its origin. The vastus lateralis has to be preserved because of its future role in soft tissue coverage of the prosthesis; it will be advanced proximally and sutured to the abductors. Care is taken not to ligate its main pedicle.

Fig 1

Fig 1

Fig 2

Fig 2

Although the major neurovascular bundle usually is not involved by metastatic lesions of the proximal femur, it may be displaced by large medial extraosseous extension of primary bone sarcomas. In that case, the lateral interval of the sartorius muscle is opened, the femoral triangle is identified, and the neurovascular bundle is retracted medially by a blunt cobra retractor below the pectineus muscle. The profundus artery and vein are identified and may be ligated just distal to their takeoff from the common femoral artery.

The hip capsule has a major role in securing and stabilizing the head of the prosthesis within the acetabulum. The capsule rarely is involved by tumors of the proximal femur and thus can be spared and used in reconstruction. All patients in the current series underwent intraarticular resection of the hip with preservation of the acetabulum (the acetabulum was spared and not resurfaced) and the joint capsule. The capsule is opened longitudinally along its anterolateral aspect and detached circumferentially from the femoral neck; the acetabular attachment remains intact (Fig 3). Femur osteotomy is performed at the appropriate location as determined by the preoperative imaging studies. In general, 3 to 4 cm beyond the farthest point is appropriate for primary sarcomas; 1 to 2 cm is sufficient for metastatic carcinomas. After femoral osteotomy, the proximal femur is retracted laterally. If total femur resection is performed, a tibial osteotomy is performed in the same manner as a standard knee arthroplasty. The remaining medial structures now are well visualized; these consist of the psoas and adductor muscles, which should be identified at this point or before the distal femur is osteotomized. Depending on the oncologic margins, the profundus femoral artery is preserved or ligated.

Fig 3

Fig 3

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Endoprosthetic Reconstruction

Modular prostheses (Howmedica, Rutherford, NJ) preferably were used for reconstruction. Since the introduction of the modular proximal and total femur endoprostheses in 1988, the authors used custom made prostheses only in cases requiring an unusual stem length or diameter or in skeletally immature patients. In patients younger than 12 years, the expandable, noncemented Kotz prosthesis (Howmedica, Limerick, Ireland) was used. Forty-nine prostheses had a bipolar head, and eight had a fixed unipolar head. The largest possible stem diameter was chosen. A 1-mm cement mantle is required around the stem; thus, the canal was reamed 2 mm larger than the chosen stem diameter. Trial articulation initially was performed; three parts (neck, body, and head) were assembled to articulate the proximal femoral component. Total femur prostheses were mated to the tibial component via a rotating hinge mechanism.

The definitive modular prosthesis was assembled (Fig 4). The orientation of the prosthesis is critical. With the linea aspera as the only remaining anatomic guideline, the prosthesis was placed with the femoral neck anteverted about 5° to 10° with respect to an imaginary perpendicular line from the prosthesis and a line drawn from the linea aspera through the body of the prosthesis. Cementing technique involved pulsatile lavage, use of an intramedullary cement restrictor, reduction of the cement by centrifugation, use of cement gun, pressurization of the cement, and enhancement of the prosthesis cement interface by precoating the proximal portion of the femoral or tibial stem with bone cement.

Fig 4

Fig 4

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Soft Tissue Reconstruction and Extracortical Bone Fixation

Special attention was given to reestablishing hip stability and providing adequate muscle coverage of the prosthesis. The remaining hip capsule is sutured tightly with 3-mm Dacron tape (Deknatel, Fall River, MA) around the neck of the prosthesis, forming a noose that provides immediate stability (Figs 4, 5). Dacron is a nonabsorbable synthetic polyester (polyethylene-terephthalate) that has a minimum pullout tensile strength of 36.1 N and allows approximation of the cut ends of the joint capsule under significant tension. It provides the initial mechanical support needed for healing and scarring of the capsule. When the capsule is closed adequately, the surgeon cannot dislocate the prosthesis. The capsule is reinforced by rotating the external rotator muscles proximally and suturing them to its posterolateral aspect. The psoas muscle is rotated anteriorly and tenodesed to the anterior capsule as additional reinforcement (Fig 6).

Fig 5A

Fig 5A

Fig 6

Fig 6

The extracortical component of the prosthesis can be used for additional bone and soft tissue fixation in the form of a noose around the prosthesis. Bone struts, either autografts or allografts, are held circumferentially with Dacron tape to the prosthesis host bone interface (Fig 6). Theoretically, this procedure prevents debris from entering the bone cement interface, thereby reducing the possibility of aseptic loosening.18,31

If the greater trochanter was resected en bloc with the surgical specimen, the remaining abductor tendon is attached to the lateral aspect of the prosthesis through a metal loop with Dacron tape. If a fragment of the greater trochanter remains, it is fixed to the prosthesis with a cable grip system. Dynamic reconstruction is obtained by tenodesing the vastus lateralis to overlie the abductor muscle fixation. The remaining muscles are sutured to the vastus lateralis anteriorly and the hamstrings posteriorly (Fig 7).

Fig 7

Fig 7

The wound is closed over a 28-gauge chest tube that is attached to a continuous suction at 20 cm H2O. The patient's extremity is placed in balanced suspension or tibial pin traction with the hip elevated and flexed 20°.

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Postoperative Management

The extremity is kept in balanced suspension for at least 5 days. An abduction brace is customized for the patient. Continuous suction is required for 3 to 5 days, and perioperative intravenous antibiotic therapy is continued until the drainage tubes are removed. Postoperative mobilization with an abduction brace and weightbearing as tolerated are continued for 6 weeks. Active hip abduction is required before the brace is removed and unprotected, full weightbearing allowed.

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RESULTS

Fifty-seven patients with lesions of the proximal femur and midfemur underwent proximal or total femur resection. All had an intraarticular resection of the hip; the acetabulum was preserved and not resurfaced. Reconstruction devices included 38 modular, 12 custom made, and seven expandable prostheses with unipolar or bipolar heads. Table 2 summarizes the prostheses types used for reconstruction in the current series.

TABLE 2

TABLE 2

None of the patients had flap necrosis, nerve palsy, or thromboembolic complications. Deep wound infection necessitating surgical intervention occurred in two (3.5%) patients. Both were treated with repeated wound debridement and irrigations, delayed primary closure, and a regimen of intravenous antibiotics for 12 weeks after wound closure.

Dislocation occurred in one (1.7%) patient. This patient underwent proximal femur resection at 8 years of age, and reconstruction was performed with an expandable prosthesis. Dislocation occurred 58 months after surgery because of developmental acetabular dysplasia. The patient was treated with soft tissue reconstruction, and the prosthesis remained intact. Aseptic loosening occurred in three (5.2%) patients. Two of these patients had undergone proximal femur resection, and one had undergone total femur resection. Loosening occurred after 24 months; in the patient who underwent total femur resection, loosening occurred 14.7 years after surgery after a major trauma. All three loosenings occurred at the bone cement interface and required surgical revision.

Local recurrence developed in four of 46 (8.7%) patients with primary bone sarcomas, all of whom had a Stage IIB tumor at presentation.10 All recurrences occurred in the soft tissues. Three patients were treated with wide local excision with preservation of the prosthesis and adjuvant radiation therapy. Amputation was performed in the fourth. The limb salvage rate in the 46 patients with primary bone sarcomas was 98%. Table 3 summarizes the complications, indications for, and number of revision procedures, local recurrences, and functional outcome of the patients in this series.

TABLE 3

TABLE 3

All patients were ambulatory. None of the patients who underwent proximal femur endoprosthetic reconstruction required a walking aid (crutches, walker, or cane), and only three of the 18 (16%) patients who underwent total femur resection required such assistance. Trendelenburg test was positive in nine (16%) patients. Function was estimated to be good or excellent in 46 (81%) patients and fair in 11 (19%) patients. No difference in function was found between patients who underwent proximal femur replacement and those who underwent total femur replacement.

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DISCUSSION

This article presents the surgical technique and outcome of proximal and total femur endoprosthetic reconstruction with an emphasis on joint stability, which is achieved by preservation of the acetabulum and reconstruction of the joint capsule and abductor mechanism.

The intracapsular location of the femoral neck makes it biologically possible for tumors of the proximal femur to spread into the hip and adjacent synovium, joint capsule, and ligamentum teres. The ligamentum teres provides a mechanism for transarticular skip metastases to the acetabulum. Fortunately, intraarticular involvement is rare and usually occurs after a pathologic fracture. The capsule can be preserved and an intraarticular resection of the femur can be performed in most cases. In the case of capsular or acetabular involvement or both, extraarticular resection of the hip is performed, and a saddle prosthesis may be used for reconstruction.1

All patients in the current series underwent intraarticular resection of the hip with preservation of the acetabulum. Hemiarthroplasty was used because of the increased likelihood of hip dislocation after acetabular resurfacing.32,33 Other major factors in stabilization are preservation of the hip capsule and capsulorrhaphy over the prosthetic neck and reconstruction of the abductor mechanism to the prosthesis.16,25,34

Hip abductors, which are attached to the greater trochanter, may be attenuated by an enlarging mass from the proximal femur but rarely are involved directly. It is important that these muscles be preserved after resection of most proximal femoral sarcomas because they are crucial to the soft tissue reconstruction, stability of the prosthetic replacement, and good functional outcome.24,30 There is a greater tendency for hip dislocation after massive proximal femur resection than after total hip arthroplasty, in which the abductor mechanism is preserved.3,24,25,32,33 Stability of the prosthesis is achieved further by balanced proximal traction by the abductors from the lateral aspect and the psoas muscle from the medial aspect. The psoas muscle is in close proximity to the anteromedial aspect of the hip; if a tumor enlarges anteriorly or posteromedially, a portion of this muscle may have to be resected. It is important that the remaining muscle be preserved for use in soft tissue reconstruction of the hip.24

Dislocation is the most common complication after proximal and total femur resection; rates range from 11% to 15%.15,16,24,30,34 In early series, in which capsular preservation was not emphasized, joint stability was based on muscle reconstruction and scar formation. Patients were placed in a long leg brace with a pelvic band or skeletal traction for 6 weeks to 5 months.3,21 Kabukcuoglu et al16 reported 54 patients who underwent proximal femur endoprosthetic reconstruction. In that series, an attempt was made to preserve the joint capsule, but the acetabulum was resurfaced, and no attempt was made to repair the hip abductors to the prosthesis; instead, they were sutured to the fascia lata.16 Those authors reported six (11%) dislocations, two of which necessitated surgical revision. Rechl et al24 reported 45 patients who underwent proximal femur endoprosthetic reconstruction. In that series, the abductor mechanism was reattached to the prosthesis in 41 of the 45 patients, but the acetabulum was resurfaced in all of them.24 Those authors reported seven (15.5%) dislocations.

In the current series, which emphasizes acetabular preservation, capsular repair, and anatomic reconstruction of the abductor mechanism, only one (1.7%) patient experienced a dislocation; it occurred almost 5 years after surgery and was secondary to acetabular dysplasia. Table 4 reviews the literature of dislocation rate after proximal or total femur endoprosthetic reconstruction; only series that include data on prosthesis type and technique of soft tissue reconstruction were included. The current series, which emphasizes the use of all three elements of hip reconstruction (acetabular preservation, capsulorrhaphy, and reconstruction of the abductor mechanism to the prosthesis), had the lowest dislocation rate.

TABLE 4

TABLE 4

There have been few reports on the longevity of proximal femur replacement prosthesis. Dobbs et al6 reported 81 patients who underwent proximal femur resection and reconstruction with a custom made prostheses. Event free survival rates were 73% and 63% at 5 and 10 years, respectively. Unwin et al29 reported a series of 263 patients who underwent proximal femur resection with endoprosthetic reconstruction. They reported a 93.8% probability that patients would not experience aseptic loosening during the 10 years after surgery.29 The favorable outcome of proximal femur replacements also was reported by Horowitz et al,13 who hypothesized a positive correlation between prosthetic survival and the availability of soft tissue for coverage.

The oncologic objective of proximal and total femur resections is to achieve local tumor control. Patient survival will be determined by the presence of metastatic disease and its response to adjuvant treatment modalities. Thus, the rate of local recurrence is the most appropriate criterion with which to evaluate the oncologic adequacy of proximal and total femur resections. Only four of the 46 (8.7%) patients in the current series who were treated for primary bone sarcomas had local recurrence of their disease, and only one patient required limb amputation. That rate is similar to that reported for tumors at the more common sites, such as the distal femur and proximal tibia, and is within the range expected after limb sparing procedures.23

The technique of acetabular preservation and hemiarthroplasty, Dacron tape capsulorrhaphy, and reconstruction of the abductor mechanism to the prosthesis significantly lowers the dislocation rate, which is the most common complication after proximal and total endoprosthetic reconstruction.

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