Abstract
Background:
There is a lack of evidence regarding long-term outcomes of rotating-hinge knee prostheses with distal femoral replacement in a large oncologic patient series. In this study, we investigated the proportion of patients experiencing complications requiring surgery in the long term, as well as the cumulative incidence of implant removal/revision and amputation at 5, 10, 15, and 20 years through competing risk analyses.
Methods:
We retrospectively studied 214 patients treated with a Finn/Orthopaedic Salvage System (OSS) knee prosthesis (Zimmer Biomet) after distal femoral resection from 1991 to 2017. The study end points were postoperative complications requiring surgery. Reoperations were classified as major when there was (1) removal of the metal-body femoral component, the tibial component, or the bone-implant fixation; (2) major revision (exchange of the metal-body femoral component, the tibial component, or the bone-implant fixation); or (3) amputation. Minor reoperations were defined as all other reoperations. Competing risk analysis was used to estimate the cumulative incidence of implant removal/revision or amputation.
Results:
There were 312 reoperations in 113 patients (98 major reoperations in 68 patients and 214 minor reoperations). Seventeen patients (8%) required ≥5 additional operations, and 21 patients (10%) required >1 major reoperation. Although the number of reoperations decreased over time, major and minor reoperations continuously accrued after 10 years. The cumulative incidences of implant removal or revision for any reason at 5, 10, 15, and 20 years were 22.6%, 30.1%, 34.3%, and 42.5%, respectively. Although most implant removals/revisions occurred in the first 10 years, the risk persisted after 10 years, at a mean of 1.24%/year, mainly due to deep infection (1.06%/year).
Conclusions:
The long-term outcomes of treatment with a Finn/OSS distal femoral rotating-hinge knee prosthesis showed it to be a durable reconstruction technique. The rate of implant removal/revisions after 10 years was gradual (1.24%/year). Deep infection remains a major late-failure mechanism, and lifetime surveillance for prosthetic problems is needed.
Level of Evidence:
Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Endoprosthetic reconstruction is the most common method of reconstruction after distal femoral resection for bone tumors1-17; advantages include widespread availability, technical simplicity, and immediate stability after surgery.
The rotating-hinge knee prosthesis has become popular for use in distal femoral reconstruction. These prostheses have been reported to provide better early outcomes compared with fixed-hinge knee prostheses, but this remains controversial12,18-23. The Finn/Orthopaedic Salvage System (OSS) rotating-hinge knee prosthesis (Zimmer Biomet) is one such design. However, to our knowledge, evidence regarding the long-term outcomes associated with this prosthesis is lacking; in particular, we are not aware of any studies of large numbers of patients followed for 10 years after surgery.
Therefore, we aimed to document the long-term outcomes after distal femoral replacement with a rotating-hinge megaprosthesis, focusing specifically on (1) the proportion of patients who experienced complications requiring surgery and (2) the cumulative incidence of implant removal or revision and amputation at 5, 10, 15, and 20 years as shown by competing risk analyses.
Materials and Methods
The institutional review board at Memorial Sloan Kettering Cancer Center approved this study (#16-582). Institutional databases were searched to identify patients in whom a Finn/OSS rotating-hinge knee prosthesis had been implanted after distal femoral resection of a malignant or aggressive benign tumor. Patients were eligible for the study if they underwent the rotating-hinge replacement for primary reconstruction after tumor resection or as a revision of a failed oncologic treatment. Patients who received total femoral replacement or an extensible implant for their primary reconstruction were ineligible.
We identified 275 eligible patients treated from 1991 to 2017. Thirty-two patients treated with an extensible prosthesis and 29 lost to follow-up after <2 years of follow-up without meeting any end points or having a competing event (death) were excluded. Two hundred and fourteen patients were analyzed (Fig. 1).
Fig. 1.
Flow diagram showing how patients were identified as eligible for analysis.
Patient demographics and therapy details are summarized in Table I. The mean age (and standard deviation) was 38.1 ± 20.2 years. The most common histologic diagnosis was osteosarcoma (n = 115; 53.7%). One hundred and eighty-four patients (86.0%) underwent primary reconstruction after tumor resection, and 26 (12.1%) underwent revision reconstruction (Tables I and II). One hundred and fifteen patients (62.5%) received chemotherapy, and 5 patients (2.3%) received radiation therapy.
TABLE I.
Patient Demographics and Adjuvant Therapy Data
| Characteristic | No. (%) of Patients* |
|---|---|
| Overall | 214 (100) |
| Age (yr) | 38.1 ± 20.2 |
| Sex | |
| Male | 109 (50.9) |
| Female | 105 (49.1) |
| Histologic diagnosis | |
| Osteosarcoma | 115 (53.7) |
| Chondrosarcoma | 22 (10.3) |
| Bone-involving soft-tissue sarcoma | 11 (5.1) |
| Malignant fibrous histiocytoma of bone | 10 (4.7) |
| Giant-cell tumor of bone | 9 (4.2) |
| Ewing sarcoma | 5 (2.3) |
| Cancer metastasis | 22 (10.3) |
| Post-radiation-therapy fracture | 4 (1.9) |
| Others† | 16 (7.5) |
| Indication | |
| After tumor resection | 184 (86.0) |
| Post-radiation-therapy fracture | 4 (1.9) |
| Failure of previous reconstruction | 26 (12.1) |
| Chemotherapy‡ | 115 (62.5) |
| Radiation therapy | 5 (2.3) |
Except for age, which is given as the mean and standard deviation.
Others include plasmacytoma/lymphoma (n = 5), recurrent tenosynovial giant-cell tumor (n = 4), leiomyosarcoma of bone (n = 4), hemangioma of the knee joint (n = 1), radiation sarcoma (n = 1), and angiosarcoma (n = 1).
The percentage was calculated by dividing the number of patients with chemotherapy by the number (184) for whom the indication was “after tumor resection.”
TABLE II.
Procedures Performed Before Implantation of the Primary Finn/OSS Rotating-Hinge Knee Prosthesis and Reasons for Failure
| Procedure | Reconstruction* | Reason for Revision | No. |
|---|---|---|---|
| Wide resection | Allograft or other prosthesis | Infection | 11 |
| Wide resection | Other prosthesis | Broken implant, aseptic loosening | 8 |
| Wide resection | Other prosthesis | Periprosthetic fracture | 3 |
| Wide resection | Allograft | Nonunion | 3 |
| Curettage of giant-cell tumor | Cement | Osteoarthritis | 1 |
“Allograft” means a massive allograft to reconstruct the bone defect, and “other prosthesis” includes several prostheses other than the Finn/OSS, such as Lane-Burstein, Stanmore, Global Modular Replacement System, and GUEPAR devices.
Distal femoral resection was performed through a medial or lateral parapatellar approach, including excision of the previous biopsy site. Uninvolved vastus muscle was spared. The Finn/OSS rotating-hinge knee prosthesis has a constrained hinge mechanism that also permits axial rotation and distraction movements between the undersurface of the polyethylene bearing and the fixed tibial tray. Because it has a weight-bearing rotating tibial articulation, weight-bearing is shared throughout the prosthesis—i.e., it is not borne by the axle alone. The femoral component has an anatomic center of rotation and a deep patellar tracking groove to enhance patellar biomechanics. Over the time period of the study, there were 2 design changes—the modular taper and the length of the articular component (7 versus 8 cm)—but neither contributed to any of the failure modes. The Finn knee and the OSS have the same rotating-hinge design with an axle-and-yoke mechanism. Fixation of the stem is designed to be uncemented if a good press-fit can be obtained intraoperatively. An uncemented Compress (compliant compression fixation) device (Zimmer Biomet) was inserted with 400, 600, or 800 lb (181.4, 272.2, or 362.9 kg) of force depending on the cortical thickness at the junction site.
Young patients with localized disease who did not undergo radiation therapy received press-fit stem fixation of the femur until 2002, after which the Compress device was used for all such patients. Elderly patients, those with metastatic cancer, and those requiring local radiation therapy received a cemented femoral component. The tibial component was uncemented whenever the surgeon could achieve a tight fit of the implant in the tibial bone.
Surgical details and outcomes are summarized in Table III. The percentage of femoral resection was categorized as <40% and ≥40% according to the literature11. The fixation of the femoral component was categorized as cement, press-fit, or Compress. The type of joint resection was categorized as intra-articular or extra-articular, and extra-articular resection was categorized as (1) classic extra-articular resection (en bloc resection of the extensor mechanism), (2) modified extra-articular resection (continuity of the extensor mechanism retained by coronal osteotomy of the patella) as first described and illustrated by Healey24 and reported by Capanna et al.25, and (3) periarticular excision (circumferential arthrotomy around the patella, joint closure, and en bloc extracapsular resection).
TABLE III.
Surgical Details and Outcomes
| Characteristic | No. (%) of Patients |
|---|---|
| Overall | 214 (100) |
| Surgical details | |
| Percentage of femoral resection | |
| <40% | 138 (64.5) |
| ≥40% | 76 (35.5) |
| No. of resected quadriceps muscles | |
| 0, 1, or 2 | 178 (83.2) |
| 3 or 4 | 36 (16.8) |
| Type of joint resection | |
| Intra-articular | 167 (78.0) |
| Extra-articular | 47 (22.0) |
| Classic | 7 (3.3) |
| Modified | 18 (8.4) |
| Peri-articular | 22 (10.3) |
| Fixation of femoral component | |
| Cement | 76 (35.5) |
| Press-fit | 64 (29.9) |
| Compress | 74 (34.6) |
| Patellar resurfacing | 53 (24.8) |
| Flap reconstruction | 6 (2.8) |
| Surgical outcomes | |
| Patients requiring reoperation(s) | 113 (52.8) |
| Patients requiring major reoperation(s) | 68 (31.8) |
| Limb status at final follow-up | |
| First prosthesis still present | 146 (68.2) |
| Revised prosthesis | 59 (27.6) |
| No prosthesis | 9 (4.2) |
| Amputation | 7 (3.3) |
| Rotationplasty | 1 (0.5) |
| Spacer | 1 (0.5) |
| Oncologic status at final follow-up | |
| Alive | 136 (63.6) |
| Dead | 78 (36.4) |
The study end points were postoperative complications requiring any unplanned surgery. Reoperations were classified as major if they involved (1) removal of the metal-body femoral component, the tibial component, or the bone-implant fixation; (2) major revision (exchange of the metal-body femoral component, the tibial component, or the bone-implant fixation); or (3) amputation. Minor reoperations were defined as those other than major reoperations. Postoperative complications were recorded according to the definitions suggested by Henderson et al. (see Appendix Table 1)26.
Since 78 (36.4%) of the 214 patients died, and death is a competing event of implant removal/revision, the Kaplan-Meier method overestimates the cumulative incidence of implant removal/revision27,28. Therefore, we performed a competing risk method to estimate the incidence of implant removal/revision and amputation accurately28,29, with death as a competing event30.
Statistical analyses were conducted using SPSS version 23.0 (IBM) and R version 3.0.1 (R Foundation for Statistical Computing).
Results
Proportion of Patients Experiencing Complications Requiring Surgery
There were 312 reoperations in 113 patients (Fig. 2-A, left panel, and Table III). Of these, 98 were major reoperations in 68 patients and 214 were minor (Table IV). Seventeen patients (8%) required ≥5 additional operations, whereas only 101 patients (47%) did not require any additional operations (Fig. 2-B, left panel). Twenty-one patients (10%) required >1 major reoperation, whereas 146 patients (68%) did not require any major reoperation (Fig. 2-B, right panel). Although the number of reoperations decreased over time, major and minor reoperations continuously accrued after 10 years, with the number of reoperations (major and minor) performed after 10 years accounting for 76 (24.4%) of the 312 reoperations performed overall: 54 (25.2%) of the 214 minor reoperations and 22 (22.4%) of the 98 major reoperations were performed after 10 years (Table IV). According to the classification described by Henderson et al.26, types 1 and 2 (soft-tissue failure and aseptic loosening) were the most common types of early complications (within 2 years after surgery) requiring reoperations whereas type-4 complications (infections) persisted throughout the life of the prosthesis, occurring even >10 years following the initial surgery (Fig. 2-A). Of 112 type-4 complications, 84 were early infections (within 2 years after surgery) and 28 were late infections (≥2 years after surgery. Other than type-4 complications, minor complications including patellar or polyethylene-related complications were the main causes of minor reoperations after 5 years postoperatively (Fig. 2-A, right panel). Patellar complications were the cause of 7.1% (13) of the 183 overall reoperations performed at <5 years and 17.8% (23) of the 129 performed at ≥5 years, whereas polyethylene-related complications led to 4.4% (8 of 183) and 8.5% (11 of 129), respectively (Table IV).
Fig. 2-A.
Distribution of the numbers of overall reoperations, major reoperations, and minor reoperations according to their causes at each time point. Type = type of complication according to the classification of Henderson et al.26.
TABLE IV.
Types and Reasons for Reoperations According to Postoperative Timing
| Type/Timing of Reoperations |
No. (%) of Reoperations |
Complication Causing Reoperation | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Type 1 |
Type 2 |
Type 3 | Type 4 |
Type 5 | Stiff Knee |
Polyethylene | Patellar | Other | |||
| Implant | Fracture | ||||||||||
| Overall reoperations | |||||||||||
| <5 yr | 183 (58.7) | 27 | 22 | 14 | 10 | 62 | 5 | 14 | 8 | 13 | 8 |
| 5-10 yr | 53 (17.0) | 0 | 11 | 3 | 1 | 15 | 3 | 0 | 6 | 11 | 3 |
| >10 yr | 76 (24.4) | 2 | 8 | 1 | 5 | 35 | 0 | 2 | 5 | 12 | 6 |
| Total | 312 (100) | 29 | 41 | 18 | 16 | 112 | 8 | 16 | 19 | 36 | 17 |
| Minor reoperations | |||||||||||
| <5 yr | 128 (59.8) | 27 | 2 | 0 | 5 | 48 | 4 | 14 | 8 | 13 | 7 |
| 5-10 yr | 32 (15.0) | 0 | 1 | 0 | 0 | 11 | 1 | 0 | 6 | 11 | 2 |
| >10 yr | 54 (25.2) | 2 | 1 | 0 | 2 | 25 | 0 | 2 | 5 | 12 | 5 |
| Total | 214 (100) | 29 | 4 | 0 | 7 | 84 | 5 | 16 | 19 | 36 | 14 |
| Major reoperations | |||||||||||
| <5 yr | 55 (56.1) | 0 | 20 | 14 | 5 | 14 | 1 | 0 | 0 | 0 | 1 |
| 5-10 yr | 21 (21.4) | 0 | 10 | 3 | 1 | 4 | 2 | 0 | 0 | 0 | 1 |
| >10 yr | 22 (22.4) | 0 | 7 | 1 | 3 | 10 | 0 | 0 | 0 | 0 | 1 |
| Total | 98 (100) | 0 | 37 | 18 | 9 | 28 | 3 | 0 | 0 | 0 | 3 |
Fig. 2-B.
Distribution according to the number of overall reoperations and major reoperations undergone by the individual patients.
Long-Term Cumulative Incidence of Implant Removal/Revision and Amputation Demonstrated by Competing Risk Analyses
The cumulative incidences of implant removal/revision for any reason at 5, 10, 15, and 20 years were 22.6%, 30.1%, 34.3%, and 42.5%, respectively (Fig. 3-A). Although most implant removal/revision operations (56.1%; 55 of 98) were performed in the first 5 years (Table IV), the risk of implant failure persisted after 10 years at a mean of 1.24%/year.
Fig. 3-A.
Competing risk analysis showing the cumulative incidence of removal/revision for any reason. The horizontal blue line indicates baseline.
None of the Henderson type-1 complications were associated with major reoperations (Table IV), but the cumulative incidence of type-1-associated complications was high (Fig. 3-B). The cumulative incidence of implant removal/revision for each cause is summarized in Figures 3-C through 3-F and Table V. Tumor recurrence (type-5 complication) was the rarest cause of implant removal/revision at each time point. Aseptic loosening (type 2) and structural failure (type 3) were the most common causes; however, these became less frequent in the long term, especially after 15 years. Meanwhile, implant removal/revision procedures due to deep infection (type 4) became more frequent after 15 years, with the largest mean increase in cumulative incidence after 10 years (1.06%/year). We also analyzed the relationship of aseptic loosening (type 2) and structural failure (type 3) with fixation of the femoral stem. Although the associations were not statistically significant, press-fit fixation had a higher frequency of aseptic loosening (type 2) (p = 0.496) while Compress fixation had a higher frequency of structural failure (type 3) (p = 0.150) (see Appendix Fig. 1). Given the heterogeneous nature of the patient population, which comprised several major categories, we categorized the patients into 5 subgroups and compared implant removal/revision among them. These subgroups included (1) patients ≤40 years of age with bone sarcoma (mainly osteosarcoma or Ewing sarcoma), (2) patients >40 years of age with bone sarcoma (mainly malignant fibrous histiocytoma of bone or chondrosarcoma), (3) patients with metastatic bone disease, (4) patients with another type of tumor (bone-involving soft-tissue sarcoma or a benign tumor, including giant-cell tumor of bone, tenosynovial giant-cell tumor, etc.), and (5) patients who underwent distal femoral replacement for failure of a previous reconstruction (Table II) or a post-radiation-therapy fracture. Although we could not show statistical significance (p = 0.065), likely because of low statistical power, there was a clear tendency for better prosthetic survival in patients with metastatic bone disease and those who were >40 years of age and had bone sarcoma (see Appendix Fig. 2).
Fig. 3-B.
Competing risk analysis showing the cumulative incidence of soft-tissue failure (Henderson type-126 complication). The horizontal blue line indicates baseline.
Fig. 3-C.
Figs. 3-C through 3-F Competing risk analyses showing the cumulative incidences of removal/revision for Henderson types 2 through 526. The horizontal blue line indicates baseline. Fig. 3-C Removal/revision due to aseptic loosening (type 2).
Fig. 3-F.
Removal/revision due to tumor progression (type 5).
TABLE V.
Cause and Timing of Implant Removal/Revision
| Complication Type26 Causing Implant Removal/Revision | Cumulative Incidence (%) | Implant Removal/Revision Rate After 10 Yr (%/yr) | |||
|---|---|---|---|---|---|
| 5 Yr | 10 Yr | 15 Yr | 20 Yr | ||
| Any type | 22.6 | 30.1 | 34.3 | 42.5 | 1.24 |
| Type 2 | 9.5 | 14.0 | 18.5 | 18.5 | 0.45 |
| Type 3 | 8.5 | 9.6 | 10.8 | 12.2 | 0.26 |
| Type 4 | 7.1 | 8.3 | 9.1 | 18.9 | 1.06 |
| Type 5 | 0.5 | 1.6 | 1.6 | 1.6 | 0.00 |
Amputations were performed in 7 patients (3.3%). Five were a result of uncontrolled deep infection, and 2 were a result of local recurrence. Competing risk analyses with amputation as the end point demonstrated that the cumulative incidences of amputation at 5, 10, 15, and 20 years were 0.5%, 1.2%, 3.7%, and 10.6%, respectively (Fig. 3-G).
Fig. 3-G.
Competing risk analysis showing the cumulative incidence of amputation as the end point.
Discussion
The non-rotating-hinge knee prosthesis was shown to produce acceptable results after distal femoral resection8,11,14-17. However, in a report focusing on very long-term outcomes, Grimer et al. demonstrated a <10% implant survival rate for 102 fixed-hinge distal femoral replacements at 20 years postoperatively13. These results suggested the inevitable need for additional surgery as well as the importance of long-term follow-up11.
Although improved moderate-term surgical outcomes have been reported in studies of rotating-hinge knee prostheses from various manufacturers1,2,4,5,7-10, there is a lack of evidence regarding the long-term outcomes of these prostheses in large numbers of patients. We undertook this study to obtain this evidence.
In our long-term follow-up series, 24.4% (76) of 312 reoperations and 22.4% (22) of 98 major operations were done after 10 years postoperatively (Table IV), although most (56.1%) of the major reoperations were performed in the first 5 years. Based on our competing risk analyses, the risk of implant failure persisted after 10 years at a mean of 1.24%/year (Fig. 3-A and Table V). These results suggested that additional surgery ≥10 years following primary reconstruction may be inevitable, highlighting the importance of long-term follow-up. Aseptic loosening and structural failure were still the most common complications despite the risk diminishing over time. In distinction, the risk of deep infection persisted throughout the life of the prosthesis, even after 10 years. New strategies are needed to prevent and treat deep infections associated with megaprostheses. Also, careful attention should be paid to complications such as patellar or polyethylene-related complications since they continue to occur over the long term (Table IV). Since the cumulative incidence of amputation increased after 15 years (Fig. 3-G), patients should be cautioned initially and at the time of later revision surgery regarding the possibility of amputation in the long term.
Major previous reports on outcomes of rotating-hinge knee replacement are summarized in Table VI1,2,4,5,7-10,18. The mean follow-up period was 12.4 years for survivors in our study (standard deviation, 6 years), and the median was 9.6 years; 88 patients were followed for ≥10 years, and 44 were followed for ≥15 years. It is difficult to adequately compare implant failure rates among studies because of different follow-up periods (5 to 8 years in most studies), different methods of estimating failure rate (the authors of only 1 report considered competing risk1; others used Kaplan-Meier estimate regardless of competing risk), different sites for the prostheses (distal femoral and proximal tibial), and different classifications and definitions of failures. However, the long-term cumulative incidence of failure in our study appears to be at least as good as those in the other oncology reports. The cumulative incidence of implant failure is higher in oncologic cases compared with non-oncologic cases treated with rotating-hinge knee replacement31,32. In what we believe to be the largest series of rotating-hinge knee prostheses (n = 408) in non-oncologic cases32, Cottino et al. emphasized the importance of preserving quadriceps muscle to avoid aseptic loosening. In contrast, Kostuj et al. found no difference in outcome or function, despite a higher infection rate, between revision reconstructions and primary oncologic reconstructions33. Similarly, Heyberger et al. and Zimel et al. reported no difference in revision rates (p = 0.77) between revision and primary reconstructions34,35.
TABLE VI.
Summary of Major Previous Reports on Rotating-Hinge Knee Replacement in Bone Tumor Surgery*
| Revision Rate Per Failure Type | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Report | Institution | No. of DFR Cases |
Prosthesis | Follow-up (yr) | Type 1 | Type 2 | Type 3 | Type 4 | Type 5 | Implant Survival/Cumulative Incidence of Failure |
Analysis |
| Pala et al.9, CORR, 2015 | Instituto Rizzoli | 187 | GMRS (Stryker) | Mean, 4 (range, 2-8) | 8.5% | 5.7% | NR | 9.3% | 5.7% | Implant survival, 73% and 60% at 4 and 8 yr | Kaplan-Meier; RH followed max. 8 yr |
| Pala et al.18, Int Orthop, 2016 | Instituto Rizzoli | RH, 196 | GMRS (Stryker) | Mean, 7.9 (range, 0-27) | 6.1% | 2.0% | NR | 6.6% | 4.6% | Kaplan-Meier; mixture of femoral/tibial cases; mixture of RH/FH; RH followed max. 7 yr | |
| Myers et al.8, JBJS Br, 2007 | Royal Orthopaedic Hospital | RH, 174; FH, 161 | Custom (Stanmore) | Unknown for RH; mean, 12 (range, 5-30) for RH and FH survivors | NR | NR | NR | NR | NR | Cumulative incidence of failure for RH, 17% and 22% at 5 and 10 yr | Kaplan-Meier; mixture of RH/FH; RH followed max. 12 yr |
| Bickels et al.4, CORR, 2002 | George Washington University and Tel-Aviv University | 102 | Custom and modular (Howmedica) | Median, 7.8 (range, 2-16.5) | NR | 5.4% | NR | 5.4% | NR | Implant survival, 93% and 88% at 5 and 10 yr | Kaplan-Meier; most cases censored at <5 yr |
| Morgan et al.7, CORR, 2006 | University of Washington | 76 | Modular (several manufacturers) | Median 4.8 (range, 0.1-19.6) | NR | 17.1% | NR | 41.9% | NR | Implant survival, 73% and 59% at 5 and 10 yr | Kaplan-Meier; most cases censored at <5 yr |
| Coathup et al.5, JBJS, 2013 | Royal National Orthopaedic Hospital | 61 | Custom (Stanmore) | Mean, 8.5 (range, 2-16) | NR | 8.0% | 3.0% | 3.0% | 5.0% | Implant survival, 75%, 84%, and 89% at 5, 10, and 15 yr | Kaplan-Meier; most cases censored at <5 yr |
| Batta et al.2, BJJ, 2014 | Royal National Orthopaedic Hospital | 69 | Custom (Stanmore) | Mean, 10.4 (range, 0.3-17.7) | 7.0% | 13.0% | 10.0% | 7.0% | 4.0% | Implant survival, 73%, 65%, and 55% at 5, 10, and 15 yr | Kaplan-Meier; most cases censored at <5 yr |
| Schwartz et al.10, CORR, 2010 | UCLA | 186 | Custom, 54; GMRS, 46% (several manufacturers) | Mean, 8.0 (range, 0.1-28.0) | NR | 29.0% | NR | 3.2% | NR | Implant survival, 77% at 10 yr (survival without revision) | Kaplan-Meier; several different prostheses; most cases censored at <5 yr |
| Bus et al.1, CORR, 2017 | Leiden University | 89 | MUTARS (implantcast) | Mean, 7.2 (range, 0.4-18) | 6.0% | 16.0% | 14.0% | 13.0% | 10.0% | Cumulative incidence of failure, 30%, 37%, and 54% at 5, 10, and 15 yr | Competing risk analysis; several different prostheses; most cases censored at <5 yr |
| Current study | MSK | 214 | Finn/OSS (Biomet) | Mean, 12.4 for survivors (9.1 overall) | 0% | 15.0% | 10.7% | 10.3% | 1.4% | Cumulative incidence of failure, 22.6%, 30.1%, 34.4%, and 42.5% at 5, 10, 15, and 20 yr | Competing risk analysis; no mixture of RH/FH; no mixture of femoral/tibial cases; used single prosthesis (Finn/OSS) |
DFR = distal femoral replacement, GMRS = Global Modular Replacement System, NR = not reported, RH = rotating hinge, FH = fixed hinge, UCLA = University of California Los Angeles, MUTARS = Modular Universal Tumor And Revision System, MSK = Memorial Sloan Kettering Cancer Center, and OSS = Orthopaedic Salvage System.
Our study has several limitations. First, it was a retrospective observational study and lacked a control group since other methods of reconstruction were rarely used at our institution. Second, the heterogeneity of the patient population might have affected the surgical outcomes even though the defects were reconstructed with the same implant design. There were also different fixation methods, which could affect the risk of aseptic loosening or structural failure. However, we included all patients with distal femoral reconstruction using the Finn/OSS rotating-hinge knee prosthesis to address important questions regarding the long-term outcome of this procedure, as most of these variables are uncontrollable in the clinical setting. The variation was minimized because the kinematics of the knee articulation were identical and independent of the femoral fixation. Third, the procedures were conducted by a limited number of oncologic surgeons at a single high-volume center. Decisions regarding the types of procedures to perform as well as determinations regarding the outcomes of interest (need for revision, failure, etc.) may be parochial to the practitioners, care teams, and institutional experience represented in this group. There is the potential for selection, indication, and expertise bias confounding our findings. We caution that our results and outcomes may not necessarily be generalizable to other health-care environments and institutional settings.
In conclusion, we reported durable long-term outcomes of distal femoral replacement with the Finn/OSS rotating-hinge knee prosthesis. The failure rate after 10 years is gradual (1.24%/year) and not as frequent as those reported after fixed-hinge knee replacement12,13,18-23. Despite the decreased cumulative incidence of aseptic loosening and structural failure after 10 years, a substantial number of patients still developed failure in the long term, especially due to deep infection. Attempts to overcome infection such as the use of antimicrobial (silver- or iodine-coated) megaprostheses will be the next challenge to improve the long-term outcomes of distal femoral replacement. While the long-term follow-up schedule is individualized, we recommend lifetime evaluation by a surgeon familiar with, and able to treat, late problems that continue to occur with the specific implant. Notably, design changes make it imperative that appropriate sizes with which to exchange older components are available. Our results may help clinicians plan the surveillance schedule and explain the exact long-term burden of reoperations to patients who remain disease-free.
Supplementary Material
Fig. 3-D.
Removal/revision due to structural failure (type 3).
Fig. 3-E.
Removal/revision due to deep infection (type 4).
Disclosure:
This research was funded in part by the NIH/NCI Cancer Center Support Grant P30 CA008748, The Limb Preservation Fund, and The Perlman Research Fund. The funding body had no role in the study’s design nor the data collection, analysis, and interpretation, and was not involved in the writing of the manuscript. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work.
The authors thank Professor Hideo Yasunaga, MD, PhD, Department of Health Economics and Epidemiology Research, School of Public Health, The University of Tokyo, for biostatistical support, and Jessica Massler, MSW, for editorial assistance.
Footnotes
Appendix
Supporting material provided by the authors is posted with the online version of this article as a data supplement at jbjs.org.
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