Abstract
We evaluated the medium to long-term results of treatment with a custom prosthetic knee replacement after wide resection of a primary malignant tumor of the distal part of the femur in forty consecutive patients. The duration of follow-up ranged from five to seventeen years (median, eight years). At the time of the latest follow-up, thirty-five (88 per cent) of the forty patients were free of disease and five (13 per cent) were alive with metastatic disease. No local recurrence was observed. Twenty early complications occurred in eighteen patients (45 per cent). Aseptic loosening of the femoral component, which necessitated a revision in eleven patients at an average of fifty-one months, was the most frequent mode of failure. The rate of prosthetic survival, as estimated with use of the Kaplan-Meier method, was 85, 67, and 48 per cent at three, five, and ten years. Univariate analysis demonstrated that the rate of prosthetic survival was significantly worse for male patients, for those in whom at least 40 per cent of the femur had been resected, for those who had had total resection of the quadriceps muscles or subtotal resection (preservation of only the rectus femoris muscle), and for those in whom a straight femoral stem had been used (p < 0.05 for all comparisons). Multivariate analysis showed that the independent adverse prognostic factors for prosthetic survival were male gender, resection of at least 40 per cent of the femur, and fixation of the femoral stem with cement. The rate of limb salvage was calculated, with use of the Kaplan-Meier method, to be 93 per cent at three years and 90 per cent at five and ten years.At the latest follow-up examination, the functional scores according to the classification system of the Musculoskeletal Tumor Society ranged from 14 to 29 points; the mean was 24 points, which represents function that is 80 per cent that of normal. The mean scores in the categories of walking supports and gait were better for the patients in whom the quadriceps muscles had been preserved than for those who had had total or subtotal resection of those muscles.Although advances in imaging and local therapy narrow the indications for an extra-articular resection of a tumor, the implant that was used in the present study continues to be used in approximately 15 per cent of patients who have a fracture or an intra-articular extension of the tumor that necessitates extensive extra-articular resection.
Extensive resection about the knee to treat a primary bone tumor makes limb salvage difficult24. Wide resection of a sarcoma leaves a very large osseous defect, and soft-tissue coverage frequently is inadequate. The reconstructed joint is subjected to large mechanical stresses that may compromise function of the limb and long-term fixation at the bone-implant interface. Compared with the various reconstructive methods that are available1,4,13-15,17,18, prosthetic replacement offers several advantages, such as early stability, mobilization, and weight-bearing.
Although satisfactory short-term results have been documented after prosthetic knee replacement for a malignant bone tumor1,27, there have been few studies of the long-term results.
The objective of the present study was to assess the medium to long-term results of reconstruction of a large defect with a custom-designed constrained knee prosthesis after wide resection of a primary malignant tumor of the distal end of the femur. Specifically, we analyzed the rate of prosthetic survival, the early and late complications, and the functional outcome after use of the Lane-Burstein knee replacement. Although there are fewer indications for wide extra-articular resection of the knee than there were in the past, this prosthesis remains one of the few implants specifically designed for such reconstructions.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Orthopaedic Surgery Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, N.Y. 10021. E-mail address: healeyj@.mskcc.org.
‡Department of Orthopaedic Surgery, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195.
§Departments of Orthopaedic Surgery (J. M. L.) and Biomechanics and Biomaterials (J. C. O.), The Hospital for Special Surgery, 535 East 70th Street, New York, N.Y. 10021.
Patients
We retrospectively reviewed the records of fifty-five consecutive patients in whom a Lane-Burstein knee prosthesis had been implanted after the excision of a primary malignant tumor of the distal end of the femur between 1979 and 1990. The preliminary results, operative technique, complications, rate of local recurrence, and performance of the prosthesis were reported previously18. Fifteen of the fifty-five patients died of metastatic disease at a median of twenty-four months (range, three to forty-eight months). Thus, the overall five-year rate of survival was 73 per cent. We evaluated the surviving forty patients after a minimum duration of follow-up of five years (maximum, seventeen years; mean, 8.3 years; median, eight years) (Table I). Eleven patients were followed for more than ten years.
Twenty patients were male and twenty were female. The ages of the patients at the time of the operation ranged from twelve to sixty-eight years (mean, 25.6 years). There were thirty osteosarcomas, four chondrosarcomas, four malignant fibrous histiocytomas, and two Ewing sarcomas. Thirty-five tumors were classified as stage IIB; three, as stage IB; and two, as stage IIIB according to the surgical staging system described by Enneking3. Imaging studies consisted of computed tomography, bone scanning, and plain radiography. Magnetic resonance imaging was available during only the last two years of the study, and the scans were not adequate, by current clinical standards, for assessment of possible intra-articular extension of the tumor. Thirty-four patients had chemotherapy before and after the operation. No patient had local radiation therapy or cryosurgery. Of the fifteen patients who died of metastatic disease, two had local recurrence of an osteosarcoma and one had disseminated metastatic disease as well as local recurrence of an Ewing sarcoma.
During the time-period of the study, we performed an operation on 150 patients who had a primary malignant bone tumor involving the distal end of the femur. Twenty-eight patients (19 per cent) had an amputation, twenty (13 per cent) had a reconstruction with an osteoarticular allograft or intercalary graft, fifteen (10 per cent) had a Van Nes rotationplasty, two (1 per cent) had an arthrodesis, and thirty (20 per cent) had implantation of another kind of prosthesis or of an allograft-prosthesis composite. An amputation was performed when there was an infected tumor, uncontrollable hemorrhage or pain after fracture, progression of the tumor during preoperative chemotherapy, or anticipated unmanageable limb-length discrepancy in a child who was six years old or less. Reconstruction with an intercalary graft or allograft was done when the tumor did not involve the epiphysis, joint capsule, ligaments, or patella. A Van Nes rotationplasty was done when a major limb-length discrepancy was anticipated in a patient who wished to participate in vigorous sports activities. Only two patients chose to have an arthrodesis even though it was offered routinely. The Lane-Burstein knee replacement was used in the remaining patients. Thus, the present report addresses the results of the reconstructions that we used for fifty-five (37 per cent) of the 150 patients who had a malignant bone tumor of the distal end of the femur.
Operative Treatment
Excision was performed through a medial or lateral parapatellar approach. The previous biopsy site was included in the resected specimen. A wide resection was carried out in all patients. The wide margin was confirmed histologically for thirty-eight patients. Two patients had a positive margin at the level of the femoral resection on histological examination, even though the margins had been negative on evaluation of intraoperative frozen sections. These two patients were found to be free of disease at more than ten years after the operation.
The resection was entirely extra-articular in twenty-eight patients and was intra-articular in twelve. A knee effusion (before or after chemotherapy), a fracture, or ligamentous involvement was considered to be an indication for extra-articular resection. During the time of the study, our practice was to include a five-centimeter margin of normal bone in the resection. A total of 12.5 to 27.0 centimeters (mean, 20.4 centimeters) of the femur was resected, which represented 29 to 63 per cent (mean, 43 per cent) of the total length of the femur as calculated from measurements made on anteroposterior radiographs. The quadriceps muscles were resected with a two-centimeter margin when they had been invaded by tumor or violated by the biopsy track. The rectus femoris muscle was removed when the tumor involved the muscle itself or the suprapatellar pouch. Twenty-five patients had total resection of the quadriceps muscles or subtotal resection (only the rectus femoris muscle saved). In nine patients, an attempt was made to provide active extension by anterior transfer of the sartorius muscle to the patella or the remaining patellar ligament. The patella was attached with a compression screw to a porous titanium-alloy plate on the proximal aspect of the tibial component in fourteen patients6. One patient had resection of the common peroneal nerve because of involvement by tumor. Ten patients had a muscle transfer to facilitate closure of the wound: eight patients had a rotational gastrocnemius flap, and two had a free latissimus dorsi flap7,8.
The patients who had patellar advancement wore an extension brace for three months postoperatively to promote fixation of the patella to the prosthesis. The remaining patients used the brace until they had mastered the technique of hyperextending the knee during the stance phase of gait. Thereafter, most patients walked without the use of a brace or walking aids.
Prosthesis
The prosthesis was designed in the Department of Biomechanics at The Hospital for Special Surgery, and it was manufactured there until 1988. Beginning in 1989, the prosthesis was manufactured by Biomet (Warsaw, Indiana). The basic design and several developmental modifications have been reported previously11,20. The semiconstrained-hinge prosthesis consists of a twenty-eight-millimeter titanium-alloy femoral sphere articulating against an ultra-high molecular weight polyethylene spherical tibial socket and a transverse medial-lateral axle. It permits 130 degrees of flexion, 3.5 degrees of hyperextension, and minimum rotational and varus-valgus motions. Hyperextension enhances stability of the knee in the stance phase of gait even in the absence of quadriceps function. The rotatory and lateral laxity is designed to absorb forces out of the line of extension-flexion.
The tibial component was designed to be fixed with cement. The femoral stem was also designed to be inserted with cement, but it can be implanted without cement if a good press-fit can be obtained intraoperatively. Second-generation cementing techniques were used. The femoral component was press-fit in twenty-seven patients and was inserted with cement in thirteen. The five-centimeter portion adjacent to the femur is coated with an extramedullary porous surface. Local bone was used as a graft to bridge the host bone and the porous surface.
The length of the intramedullary portion of the femoral stem ranged from 7.0 to 19.0 centimeters (mean, 12.0 centimeters). A curved femoral stem with a 50-degree radius was used in the last nineteen patients so as to provide a better match with the anterolateral bow of the femoral diaphysis.
Assessment of Results
The functional evaluation of the patients was performed with use of the revised 30-point functional classification system established by the International Society of Limb Salvage and the Musculoskeletal Tumor Society5. According to this system, six parameters—pain, function, use of walking supports, walking ability, gait, and emotional acceptance—are each evaluated on a scale of 0 to 5 points. The individual scores are added together to obtain an overall functional score, which then is expressed as a percentage of normal (30 points).
The procedure was considered to be a failure when replacement of any of the components of the prosthesis was necessary. Survival of the prosthesis (from the date of the operation to the date of revision or the time of the latest follow-up) was estimated with use of the Kaplan-Meier method. The log-rank (Cox-Mantel) test was used to compare the survivorship curves. The chi-square test and the Student t test were used to assess the potential prognostic factors. Multivariate analysis was performed with use of the Cox proportional-hazards model. To arrive at a parsimonious multivariate model, covariates were selected with a stepwise regression model with use of backward elimination. A p value of less than 0.05 was considered to be significant.
Thirty-five (88 per cent) of the forty patients were free of disease and five patients (13 per cent) were alive with metastatic disease at the time of the latest follow-up (Table I). No local recurrence was observed. Salvage of the limb was successful in thirty-five patients, although fifteen (43 per cent) of them had had revision of the prosthesis. Three of the fifteen revisions might not have been necessary if early wound complications could have been avoided. Of the five patients who did not have salvage of the limb, three had an amputation and two had a rotationplasty. An amputation was done when there was intractable infection or soft-tissue deficiency. A rotationplasty was done when the patient was willing to have such a procedure and an aseptic site, at which cement had not been used, could be obtained for osteosynthesis.
Twenty early complications occurred in eighteen patients (45 per cent), before chemotherapy was resumed (Table II). The most frequent complication was skin necrosis, which occurred in ten patients who had had an extra-articular resection and in two who had had an intra-articular resection. Three patients had complete exchange of all of the prosthetic components because of the skin necrosis. Three other patients had a complication that was related to the design of the prosthesis. A patellar fracture occurred in two patients; both had had an extra-articular resection with a coronal osteotomy of the patella, leaving a thin patellar fragment. One of them was managed with a patellectomy, with the soft-tissue extensor mechanism retained. The other patient refused a patellectomy and had chronic pain. The third patient had a loose patellar compression screw, which was replaced. At the time of the latest follow-up, the prosthesis was intact in nine of the eighteen patients who had an early complication and eleven of the twenty-two patients who did not.
Thirty late complications occurred in twenty-six patients (65 per cent), after chemotherapy had been resumed (Table II). Aseptic loosening was the most frequent mode of prosthetic failure (sixteen patients; 40 per cent), necessitating revision of the prosthesis in eleven patients at a mean of fifty-one months (range, nine to ninety-six months) postoperatively (Figs. 1 and 2). A revision was recommended when the patient had progressive pain or when there was radiographic evidence of bone loss. All instances of aseptic loosening involved the femoral component, and loosening was defined as progressive radiolucency around the stem or unexplained pain in the thigh. Aseptic loosening developed in twelve of the twenty-eight patients who had had an extra-articular resection and in four of the twelve who had had an intra-articular resection. Although this difference was not found to be significant, there was only 9 per cent power to identify a difference in the rates of aseptic loosening between these two groups of patients. Eleven of the twenty-five patients who had had total or subtotal resection of the quadriceps muscles and five of the fifteen in whom those muscles had been preserved had aseptic loosening.
There were six periprosthetic fractures. Two femoral fractures that occurred proximal to the tip of the intramedullary portion of the stem were treated with open reduction and insertion of a longer-stemmed component. One patellar fracture was treated with open reduction. Two additional femoral fractures and one tibial fracture with minimum displacement healed successfully in a cast-brace. The femoral fractures were due to the use of a straight stem and reamers early in the study period. This technical complication has been prevented with use of more anatomically curved stems and flexible reamers.
Late infection developed in four patients who had osteosarcoma. The infections were evident at thirty-eight, forty-four, forty-six, and ninety-three months. Three of the patients had removal of the prosthesis and implantation of an antibiotic-permeated methylmethacrylate spacer, followed by a staged reimplantation of another prosthesis. This treatment was successful for two patients, with no sign of infection twenty-seven and fifty-two months later. However, one patient, who had infection with Staphylococcus epidermidis and Streptococcus faecalis, had an amputation because of recurrent symptomatic infection. The fourth patient had a soft-tissue abscess, as a result of a penetrating injury, that did not involve the prosthesis and was managed with irrigation, débridement, and patellectomy.
The polyethylene axle bushing failed at 140 months in one patient, and the polyethylene anterior extension-stop bumper failed at 192 months in another. Both the worn-out and the deformed components were replaced by new ones without difficulty. One femoral component fractured through the modular, distal diaphyseal segment, at twenty-six months postoperatively. The failed component was replaced by an identical segmental prosthesis.
Prosthetic Survival
The rate of prosthetic survival without replacement of any component was 85, 67, and 48 per cent at three, five, and ten years (Fig. 3). The rate of prosthetic survival without aseptic loosening was 72 per cent at five years and 58 per cent at ten years (Fig. 4). The rate of limb preservation was 92 per cent at three years and 90 per cent at five and ten years after the primary implantation (Fig. 5). Univariate analysis demonstrated that the rate of prosthetic survival was significantly worse for male patients (p = 0.0013), after resection of at least 40 per cent of the femur (p = 0.0065), after total or subtotal resection of the quadriceps (p = 0.032), and after use of a straight femoral stem (p = 0.045) (Figs. 6, 7, 8 and 9). With the numbers available, we could not detect a significant association between the rate of prosthetic survival and age (p = 0.37), chemotherapy (p = 0.25), the type of joint resection (extra-articular or intra-articular) (p = 0.16), or the method of fixation of the femoral stem (cemented or press-fit) (p = 0.49). Multivariate analysis showed that the significant negative prognostic factors were male gender (p = 0.0047), resection of at least 40 per cent of the femur (p = 0.023), and fixation of the femoral stem with cement (p = 0.025) (Table III).
Function
At the latest follow-up examination, the mean active flexion of the knee was 88 degrees for the fourteen patients in whom the patella was attached to the tibial component and 95 degrees for the twenty-six patients in whom it was not. The amount of extensor lag in the patients who had patellar advancement was related to the success of the patellar attachment: the mean lag was 70 degrees in the two patients in whom the attachment failed and 3 degrees in the twelve patients in whom it was successful. The mean extensor lag was 13 degrees (range, 0 to 90 degrees) for the fifteen patients in whom the quadriceps muscles had been preserved.
The overall functional scores ranged from 11 to 29 points (mean, 24 points) at thirty-six months and from 14 to 29 points (mean, 24 points) at the most recent follow-up examination. Of the thirty-five patients who had an intact prosthesis at the time of the latest follow-up, nineteen (54 per cent) had no pain in the involved limb, fourteen (40 per cent) had modest pain, and two (6 per cent) had moderate pain. One patient (3 per cent) had no functional restrictions, thirty (86 per cent) had restrictions in recreational activities, and four (11 per cent) had partial disability. Nineteen (54 per cent) of the thirty-five patients were enthusiastic about the result, fourteen (40 per cent) were satisfied, and two (6 per cent) accepted the result. Twenty-two patients (63 per cent) walked without the use of supports, five (14 per cent) wore a knee brace, and eight (23 per cent) walked with one cane. Twenty-three (66 per cent) of the thirty-five patients could walk an unlimited distance, eleven (31 per cent) had some limitations in walking, and one (3 per cent) could walk inside only. Seven patients (20 per cent) had no discernible limp, twenty-two (63 per cent) had a minor cosmetic limp (cosmetic alteration only5), and six (17 per cent) had a major cosmetic limp (minor functional deficit5).
At the time of the latest follow-up, the mean functional scores in the categories of walking supports and gait were better for the patients in whom the quadriceps had been preserved (4.7 and 3.9 points) than for the patients who had had total or subtotal resection of those muscles (4.1 and 3.4 points). The mean score for pain was worse for the patients who had had an intra-articular resection (3.9 points) than for the patients who had had an extra-articular resection (4.4 points). This unexpected result was due to the fact that some patients who had had an intra-articular resection had patelloprosthetic pain, which was not present in the patients who had had a patellectomy with the extra-articular resection.
Resection with limb salvage is now widely accepted as a treatment option for most malignant bone tumors of the extremities25. Considering the advantages with respect to function19, appearance, and emotional acceptance, limb salvage seems preferable to an ablative procedure. However, a durable reconstruction is elusive. At present, there is no single generally satisfactory method for reconstruction of massive osseous and soft-tissue defects after wide resection of a malignant bone tumor4,12,15,17. Although prosthetic reconstruction is criticized because it is virtually certain to fail in young patients, it offers maintenance of motion and immediate functional restoration. This is especially important for patients who have metastatic tumors and may have a limited life expectancy. Since 1979, we have utilized a custom-designed Lane-Burstein knee prosthesis for reconstruction after the resection of a bone tumor around the knee joint11. Since 1990, we have used this prosthesis for the nearly 15 per cent of patients who have needed extensive resection, and we have employed a rotating-hinge knee prosthesis most often. A Van Nes rotationplasty is done for children who are less than ten years old, and allografts are used for children who have a substantial amount of growth remaining in the proximal tibial physis. Patients rarely choose to have an arthrodesis of the knee, even though it is an excellent option after extra-articular resection.
In the present study, we reviewed the medium to long-term results of reconstruction with the Lane-Burstein knee prosthesis after wide resection of a primary malignant bone tumor of the distal end of the femur. The oncological results were encouraging: there was no local recurrence in forty patients. However, the prosthetic survival rates9 of 67 per cent at five years and 48 per cent at ten years are of concern.
Survival analysis showed that the percentage of femoral bone that was resected distally was related to the risk of prosthetic failure. Recently, Unwin et al. demonstrated that the risk of aseptic loosening of a Stanmore prosthesis was related to the percentage of femoral bone that was resected. Those authors assumed that the offset distance between the tip of the intramedullary stem and the line of force contributed to aseptic loosening.
The extent of soft-tissue resection is another important factor. We found that total or subtotal resection of the quadriceps muscles was associated with poor prosthetic survival. Even though many patients could walk well with hyperextension of the knee during the weight-bearing phase of gait, impaired function of the quadriceps may increase the stresses on the stem and the bone-implant interface and contribute to long-term failure. The prevalence of aseptic loosening was greater for the patients who had had extensive resection of the quadriceps muscles. In a study of the Kotz modular reconstruction system, Capanna et al. reported that most broken stems were associated with more extensive excision of the quadriceps muscles.
The indications for extra-articular or intra-articular resection of a malignant bone tumor of the distal end of the femur are controversial. Although intra-articular resection allows for better function and a greater variety of reconstructive options, it is not always appropriate. In the present study, most (twenty-eight) of the forty malignant tumors in the distal end of the femur were excised extra-articularly in order to enhance the operative margin. This may have contributed to the excellent oncological result in the current series. We currently reserve extra-articular resection for the 15 to 20 per cent of patients in whom intra-articular extension of the tumor is in question. If better imaging modalities, such as magnetic resonance imaging, had been available during the study period, we might have been able to avoid extra-articular resection in twenty of the twenty-eight patients who were so managed in the present study. Extra-articular resection would still have been indicated for eight patients. Improvements in imaging and local therapy will further narrow the indications for extra-articular resection. However, although it may be needed less frequently in the future, the Lane-Burstein prosthesis remains a suitable choice to maintain a mobile knee after extra-articular resection of the knee.
Some surgeons prefer to perform an arthrodesis after an extra-articular resection of the knee joint because of difficulties with reconstructing the extensor mechanism10. We do not think that this difficulty excludes the possibility of a mobile prosthetic knee reconstruction, as evidenced by the satisfactory functional results achieved for our patients who had had resection of the quadriceps muscles. An arthrodesis of the knee was offered to all patients and all chose to keep a mobile knee joint, which indicates the premium that patients place on motion of the knee.
It is important to avoid early complications, which may delay the resumption of chemotherapy postoperatively16. We found that ten of the twelve patients who had skin necrosis had had an extra-articular resection. During the period when these operations were performed, we usually dissected outside of the fascia of involved muscle. This practice may have improved the margin of resection qualitatively and quantitatively, but it undoubtedly contributed to the high rate of wound complications. Every effort should be made to cover the prosthesis with vascularized tissue deep to the skin. The liberal use of rotational muscle flaps or vascularized free-tissue transfers should be considered when extrafascial dissection has been done7. When preoperative chemotherapy is effective, we now narrow the operative margins and dissect deep to the fascia. This approach has reduced the rate of complications, but the long-term control of disease has not yet been proved. More comparative studies of radiographic findings and of macroscopic and microscopic examination of extension of the tumor are necessary to provide scientific underpinnings for operative practices22.
The functional results were encouraging, particularly in the categories of pain, use of walking supports, and walking ability. At the time of the latest follow-up, 94 per cent (thirty-three) of thirty-five patients who had salvage of the limb had no or modest pain and 67 per cent (twenty-two) of the patients who had no or modest pain walked without supports. The patients in whom the quadriceps muscles had been preserved had better scores for gait. The high percentage (94 per cent) of patients who were enthusiastic about or satisfied with the result despite the high percentage (46 per cent) who had disability or pain, or both, reflects the patients' expectations, effective pain management by the medical team, and the patients' gratitude for having survived cancer.
To our knowledge, we have described one of the longest follow-up studies of prosthetic knee replacement and resection of a malignant tumor of the distal end of the femur. We found that salvage of the limb yielded satisfactory overall results and relatively good functional results at the time of the most recent follow-up, although revision was necessary in 43 per cent (fifteen) of these thirty-five patients. The results are similar to those found after replacement with the Walldius 2.22 prosthesis23 and worse than the short-term results after replacement with a currently used rotating-hinge prosthesis2. However, direct comparison of our results with those of others is not appropriate, as the operative management and the prognostic factors for prosthetic survival were different for each of the prostheses that have been evaluated1,2,13,21,23,27 (Table IV). Paradoxically, the long-term oncological success contributed to the high rate of failure of the implant and subsequent revision—that is, more patients lived long enough for the prosthesis to fail. Long-term studies of the clinical results of prosthetic replacements will be valuable to clarify the indications and limitations of each procedure and prosthetic design.
NOTE: The authors thank Dr. Andrew G. Huvos for performing the histological examinations.
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Simon, M. A.; Aschliman, M. A.; Thomas, N.; and Mankin, H. J.: Limb-salvage treatment versus amputation for osteosarcoma of the distal end of the femur. J. Bone and Joint Surg.,68-A: 1331-1337, Dec. 1986.68-A1331
1986
Unwin, P. S.; Cannon, S. R.; Grimer, R. J.; Kemp, H. B. S.; Sneath, R. S.; and Walker, P. S.: Aseptic loosening in cemented custom-made prosthetic replacements for bone tumours of the lower limb. J. Bone and Joint Surg.,78-B(1): 5-13, 1996.78-B(1)5
1996
Ward, W. G.; Eckardt, J. J.; Johnston-Jones, K. S.; Eilber, F. R.; Namba, R.; Dorey, F. J.; Mirra, J.; and Kabo, J. M.: Five to ten year results of custom endoprosthetic replacement for tumors of the distal femur. In Complications of Limb Salvage. Prevention, Management and Outcome, pp. 483-491. Edited by K. L. B. Brown. Montreal, International Symposium on Limb Salvage, 1991.