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Knee megaprosthesis: Analysis of clinical outcomes, complications, and implant survival across complex indications
, Moulay Omar Lamrani
⁎Corresponding author: Yassine Ben Bouzid. yassine.benbouzid2@gmail.com
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
Knee megaprosthesis are an essential solution for managing complex pathologies, including peri-prosthetic fractures and tumor resections. However, their application is frequently associated with high rates of mechanical and infectious complications, necessitating thorough evaluation of functional outcomes and implant survival rates.
This retrospective study included 28 patients who underwent knee megaprosthesis for complex fractures, pseudarthrosis or tumor-related indications. Functional outcomes were assessed using the Knee Society Score (KSS) and the Knee Society Functional Score (KSKF). Complications were classified according to Henderson's classification, and implant survival rates were calculated based on a mean follow-up of 3.7 years.
The gross survival rate of the implants was 51.5 %, while the adjusted survival rate was 42.9 %. Infectious complications were observed in 17.8 % of cases, and mechanical failures occurred in 7.1 %. Postoperative functional scores demonstrated moderate improvement, although limitations remained common among patients who experienced complications.
Knee megaprosthesis provide a viable solution for complex knee pathologies but carry a significant risk of complications. Rigorous patient selection, implant customization strategies, and optimized follow-up protocols are crucial to improving long-term outcomes.
Keywords
Knee megaprosthesis
Tumor reconstruction
Complex peri-prosthetic fractures
Mechanical and infectious complications
Functional outcomes and implant survival
1 Introduction
Knee megaprosthesis represent a significant advancement in managing complex knee pathologies, including peri-prosthetic fractures, bone tumors, and revisions following the failure of standard prostheses. Initially introduced for the treatment of tumor resections, these devices have been extended to non-oncological indications, such as pseudoarthrosis and complex fractures, due to their ability to provide immediate fixation and rapid functional support.1
Distal femoral and proximal tibial fractures pose significant challenges, particularly in elderly patients with underlying osteoporosis or comorbidities. In such cases, conventional internal fixation, such as plates or intramedullary nails, may be insufficient to ensure stability and promote healing.2 Consequently, megaprosthesis, particularly rotating hinge implants, have emerged as a preferred alternative, enabling early mobilization and reducing complications associated with prolonged immobilization.3
From an oncological perspective, megaprosthesis have become a standard modality for reconstructions following segmental resections in bone sarcomas, such as osteosarcomas and chondrosarcomas.4 However, despite advancements in design and materials, the long-term failure rate of these implants remains high. The primary causes include aseptic loosening, peri-prosthetic infection, and structural failures, which often necessitate complex revisions.5
Previous studies have reported variable survival rates for knee megaprosthesis, ranging from 51 % to 85 % at 10 years, depending on the initial indication and factors such as age, body weight, and the condition of surrounding soft tissues.3 Biau et al.3 demonstrated that implant-related complications were significantly higher in patients treated for peri-prosthetic fractures compared to those with tumor-related indications, underscoring the importance of patient selection.
Despite their clinical utility, megaprosthesis present unique challenges in complication management. Infections remain one of the leading causes of failure, with reported rates reaching up to 17.8 % in some series. The management of these complications, often based on two-stage strategies, highlights the complexity of long-term follow-up for these patients.5
This study provides a comprehensive analysis of 28 patients who underwent knee megaprosthesis for indications ranging from complex fractures to tumor-related pathologies. The aim is to contribute to a better understanding of the indications and outcomes associated with knee megaprosthesis, thereby optimizing therapeutic decisions and tailoring interventions to individual patient needs.
2 Materials and Methods
We conducted a comprehensive study of 33 cases (Fig. 1) involving rotating hinge megaprosthesis (Zimmer, Link, Stanmore) between 2005 and 2022.
2.1 Inclusion and exclusion criteria
The inclusion criteria targeted patients over 18 years of age who underwent rotating hinge megaprosthesis implantation for tumor-related, traumatic, or revision indications, with a minimum follow-up of one and a half years. Conversely, the exclusion criteria excluded patients lost to follow-up, incomplete medical records, and those who died in the immediate postoperative period. The study relied on medical records, operative reports, and outpatient registers, and data were compiled in an Excel spreadsheet.
2.2 Patient selection and characteristics
Among the initial 33 cases, 5 were excluded. Four of these involved distal femur fractures, and the fifth case presented with aseptic pseudoarthrosis of the distal femur, occurring one year after osteosynthesis (Fig. 1). Two of these patients received ZSS prosthesis (Zimmer), while the other three received Link Endo-Model prosthesis (Link). Additionally, four patients were lost to follow-up, and one died from postoperative complications due to medical reasons.
A final cohort of 28 patients met the inclusion criteria, comprising 13 males and 15 females, with a male-to-female ratio of 0.86. The average age of the patients was 62 years (range: 22–86 years), and the mean body mass index (BMI) was 25.7 kg/m2. The right side was affected in 13 patients and the left side in 15 patients. In 18 cases, the indication involved the distal femur, while in 7 cases it involved the proximal tibia. Three cases simultaneously involved both sites.
2.3 Indications
The indications for the use of megaprosthesis were categorized into three primary groups: pseudoarthrosis, fractures, and tumor-related conditions (Fig. 1). Each indication was carefully evaluated using established classification systems to guide surgical decision-making and prosthesis selection.
Pseudoarthrosis cases were classified as either aseptic or septic. Further sub-classification was performed based on the type of bone healing failure: atrophic, oligotrophic, or hypertrophic.
Fracture cases were evaluated using multiple classification systems depending on the context. For peri-prosthetic fractures, the Rorabeck classification was employed, distinguishing between fractures based on stability and displacement. Native knee fractures were assessed using the AO classification for ditals femur fracture and the Schatzker classification for tibial plateau fractures.
For tumor-related indications, cases included primary malignancies, such as osteosarcoma and chondrosarcoma, as well as metastatic lesions and locally aggressive benign tumors like giant cell tumors. The extent of tumor involvement, as well as the condition of surrounding soft tissues, guided the surgical plan. This evaluation also considered oncological margins to minimize the risk of local recurrence and optimize functional outcomes.
By using these well-established classification systems, the surgical team ensured a systematic approach to selecting the appropriate prosthesis and surgical strategy for each patient. This approach aimed to balance the need for immediate stability and functional restoration with the management of underlying pathological conditions.
2.4 Failure analysis
Failures were classified according to Henderson's classification (Table 1) into soft tissue failure (Type I), aseptic loosening (Type II), structural failure (Type III), peri-prosthetic infection (Type IV), and tumor recurrence or extension (Type V).
| Category | Type | Subgroup |
| Mechanical | I.Soft tissue failure | A: instability due to tendon/muscle ruptureB: aseptic wound dehiscence |
| II. Aseptic loosening | A: <2 years after implantationB: >2 years after implantation | |
| III. Structural failure | A: prosthetic failureB: periprosthetic fracture | |
| Non-mechanical | IV. Periprosthetic infection | A: <2 years after implantationB: >2 years after implantation |
| V. Tumor progression with contamination of prosthesis | A: soft tissue tumorB: bone tumor |
2.5 Infection diagnosis and management
Infections were diagnosed using a combination of clinical, biological (white blood cell count and CRP levels), and radiological findings (standard X-rays and CT scans). The Tsukuyama classification was used to determine the indication for implant revision or polyethylene exchange combined with lavage.
3 Results
3.1 Results analysis
The indications for megaprosthesis included conditions involving the distal femur in 19 cases and the proximal tibia in 7 cases. Two patients did not fit this distribution: one presented with a painful and disabling knee arthrodesis, and the other suffered from post-traumatic gonarthrosis.
Pseudoarthrosis was the indication in 9 cases, with 8 classified as aseptic and 1 as septic. Among the aseptic pseudoarthrosis cases, 7 were atrophic, 1 was oligotrophic, and 1 was hypertrophic. The distal femur was involved in 8 cases, while the tibial plateau was affected in 1 case. Prosthesis placement involved the use of Link Endo-Model prosthesis in 7 cases, including 1 managed with a two-stage procedure due to a septic context. The remaining 2 cases were treated with ZSS prosthesis.
Fractures accounted for 7 cases, involving the distal femur in 6 patients and the proximal tibia in 1. Three fractures occurred in native knees, classified as AO type C3 in 2 cases and type A1 in 1 case. The other four cases were peri-prosthetic fractures, with two classified as Rorabeck type II and one as Rorabeck type III. Of these, 4 fractures were closed, and 2 were Gustilo grade 2 open fractures. In the open fracture cases, one patient initially underwent external fixation and was transferred to our center 11 days post-trauma. This case involved a peri-prosthetic fracture managed with a two-stage procedure: the first stage included removal of the external fixator, preparation of bone cuts, bacteriological sampling, and placement of a spacer. After negative bacteriological results, a prosthesis was implanted in the second stage, one month later. The second open fracture case was treated with external fixation and debridement, followed by bacteriological sampling. Once negative results were obtained, a prosthesis was implanted within one week.
Tumor-related conditions were identified in 10 cases, involving 5 cases in the distal femur and 5 in the proximal tibia. Among these, 6 were osteosarcomas, 2 were renal carcinoma metastases, 1 was a recurrent giant cell tumor, and 1 was a chondrosarcoma. Prosthesis placement included Link Endo-Model prosthesis in 4 cases, MegaSystem-C prosthesis in 4 cases, a Stanmore prosthesis in 1 case, and a ZSS prosthesis in another case.
3.2 Implant failures and affected sites
The incidence of complications in our series was 57.14 % (16 patients out of 28), occurring on average 15.4 months after surgery (range: 3 days to 8 years). One case involved a vascular complication characterized by acute ischemia occurring 12 days postoperatively, and two cases involved common peroneal nerve paralysis identified immediately after surgery, leading to a vasculoneural complication rate of 10.7 % (Table 2).
| Failure type | Incidence (n) | Details |
| Tibial Implant Failure | 0 | Non reported |
| Combined component failure | 6 | Loosening and Structural failure |
| Soft tissue failure | 4 | Joint Stiffness (2), Hematoma (1) |
| Vasculoneural complications | 3 | Acute ischemia (1), Peroneal Paralysis (2) |
The failure rate of the femoral implant alone was 10.7 % (n = 3), with no cases of isolated tibial implant failure. Both the femoral and tibial components were involved in 21.4 % (n = 6) of cases. Soft tissues were implicated in 14.2 % of cases (n = 4) (Table 3).
| Age (years) | Indication | Model | Site | Time to revision (month) | Complication | Femoral stem diameter (mm) | Tibial stem diameter (mm) |
| 75 | Fracture | MEGA C | Soft tissue | 24 | Stiffness | 12 | 14 |
| 51 | Metastatic renal cell carcinoma | LINK Endomodel | Femur | 39 | Implant rupture | 8 | 8 |
| 83 | Periprosthetic fracture | LINK Endomodel | Femur and tibia | 48 | Chronic infection | 8 | 8 |
| 69 | Tumor | MEGA C | Femur and tibia | 2 | Acute infection; chronic infection | 16 | 12 |
| 65 | Pseudarthrosis | LINK Endomodel | Femur and tibia | 2 | Acute infection; chronic infection | 8 | 8 |
| 86 | Pseudarthrosis | LINK Endomodel | Femur | 24 | Aseptic loosening | 8 | 8 |
| 28 | Tumor | ZSS | Femur and tibia | 3 | Acute infection | 10 | 10 |
| 34 | Tumor | MEGA C | Soft tissue | 4 | Stiffness | 11 | 11 |
| 22 | Tumor | Stanmore | Soft tissue | 2 | Stiffness | 14 | 14 |
| 30 | Tumor | LINK Endomodel | Soft tissue | 1 | Stiffness | 14 | 12 |
| 38 | Tumor | LINK Endomodel | Femur | 96 | Aseptic loosening | 8 | 11 |
| 71 | Periprosthetic fracture | LINK Endomodel | Femur and tibia | 7 | Aseptic loosening | 8 | 8 |
| 72 | Fracture | RHK | Femur and tibia | 2 | Acute infection | 16 | 10 |
| 59 | Pseudarthrosis | LINK Endomodel | Soft tissue | 0.1 | Hematoma | 8 | 8 |
The reoperation rate was 46.4 % (13 cases out of 28), with 28.5 % of cases requiring implant replacement. Among these, 25 % underwent a single reoperation, 7.14 % underwent two reoperations, and 10.7 % required three surgical revisions (Table 3).
Henderson classification gype 1 complications occurred in 17.8 % of cases. These were primarily dominated by joint stiffness, which had an incidence of 14.28 % and occurred on average 2.25 months post-implantation (range: 1–4 months). The range of motion (ROM) varied between 0/50° and 0/90° but improved after manipulation under general anesthesia to 0/90° and 0/140°. One case involved a hematoma that developed three days after implantation and required surgical evacuation.
Henderson classification type 2 (aseptic loosening) was observed in 10.7 % of cases. The average time to loosening was 2.9 years, ranging from 7 months to 8 years. Loosening affected the femoral component in 7.14 % of cases and involved both components in 3.5 %. The primary indications for prosthesis placement in these cases were pseudoarthrosis of the distal femur and distal femoral fractures.
Henderson classification type 3 was identified in two cases, both involving fractures of the femoral stem. The implants used were Link intramedullary prosthesis. In one case, the femoral stem fracture was associated with aseptic loosening, necessitating massive structural allograft reconstruction of the distal femur followed by revision with a Link prosthesis. In the other case, revision surgery involved a Mega C prosthesis.
Henderson classification type 4 (infections) accounted for 17.8 % of cases. Two patients experienced recurrent infections progressing to chronicity, two cases were classified as acute infections, and one as chronic infection. In acute infections, surgical debridement with replacement of mobile components was performed, accompanied by bacteriological sampling to initiate targeted antibiotic therapy. For chronic infections, a two-stage revision was carried out. Additionally, two patients received suppressive antibiotic therapy.
3.3 Implant diameter
The diameters of the implants varied based on their location. Femoral implants had diameters ranging from 8 to 16 mm, with an average of 10.5 mm, while tibial implants ranged from 8 to 15 mm, with a slightly lower average of 10 mm (Table 3). An analysis of mechanical complications revealed a significant relationship with implant diameter. Loosening was systematically observed in implants with smaller diameters, specifically 8 mm, highlighting potential deficiencies in stability or resistance. Conversely, joint stiffness complications were more frequently associated with larger-diameter implants, ranging from 11 to 14 mm. This could be explained by restricted motion due to increased mechanical constraints. Notably, two cases of femoral implant rupture were identified, and in both instances, the implants had a diameter of 8 mm, confirming the increased vulnerability of smaller diameters to repetitive mechanical loads. These findings suggest that implant diameter selection should be carefully tailored to the specific characteristics of each patient to minimize the risk of mechanical complications (Fig. 2).
3.4 Functional outcomes
The Knee Society Score (KSS) and Knee Society Functional Score (KSKF) revealed contrasting trends between pre- and postoperative periods. Preoperatively, the KSS ranged from 0 to 100, with an average of 58.6, while the KSKF exhibited a similar range with an average of 53.14. Postoperatively, the KSS slightly decreased to an average of 58.4, ranging from 0 to 83. This relative decline suggests that clinical aspects, such as pain or stability, did not significantly improve or were impacted by complications inherent to this complex procedure. However, the postoperative KSKF showed a noticeable improvement, increasing to an average of 61.85, reflecting a perceptible functional enhancement for most patients, albeit moderate (Fig. 2). These findings highlight that while megaprosthesis can achieve functional improvement, clinical limitations remain, necessitating focused efforts on complication management and postoperative rehabilitation to optimize outcomes.
3.5 Prosthesis survival
The evaluation of implant survival yielded mixed results. Of the 33 implanted prostheses, 16 required revision surgery, representing 48.5 % of cases. The reasons for revision primarily included infections, loosening, joint stiffness, and implant rupture, underscoring the complexity of complications in this type of surgery. The average time to revision was 1.75 years, with a range of 3 days–8 years, indicating that mechanical or infectious complications are likely to occur early after implantation (Fig. 3).
The gross survival rate for all patients was 51.5 %, while the adjusted survival rate, excluding patients lost to follow-up (n = 4) and deaths unrelated to the prosthesis (n = 1), was 42.9 %. At the end of the follow-up period, 17 prostheses remained functional, with an average follow-up duration of 3.7 years. These findings suggest that while megaprosthesis can improve joint function for some patients, it is associated with a significant risk of complications requiring revision surgery (Fig. 4).
4 Discussion
The results of this study confirm both the opportunities and challenges associated with using megaprosthesis for varied indications, such as complex fractures and tumor-related pathologies. The observed gross survival rate of 51.5 % aligns with previous studies, reporting survival rates ranging from 50 % to 85 % depending on the indications.3,4,6 In contrast, the adjusted survival rate of 42.9 % highlights the impact of mechanical and infectious complications on long-term outcomes.5,7
Tumor-related indications, particularly osteosarcomas and chondrosarcomas, appear to be associated with higher survival rates compared to peri-prosthetic fractures. Biau et al. reported a 10-year survival rate of 85 % for megaprosthesis used after tumor resection, whereas complex fractures exhibited significantly lower rates.3,8 This disparity may be attributed to the quality of surrounding soft tissues and the presence of bone loss in non-oncological cases.4,9
Peri-prosthetic infections represented a major cause of failure in this study, with an incidence of 17.8 %, comparable to the 15 %–20 % range reported by Meluzio et al.5 The management of acute infections through lavage and component replacement led to functional improvement in 75 % of cases, mirroring the strategies advocated by Tsukuyama et al. to limit complete revisions.10 However, chronic infections, present in two cases, required two-stage revisions, underscoring the complexity of their management.6,11
Mechanical complications, including aseptic loosening and implant fractures, also represented significant causes of failure. Implant fractures accounted for 7.1 % of complications in this study, consistent with Koch et al.’s findings on the fragility of femoral stems, particularly those with smaller diameters (<10 mm).1 Pala et al. emphasized that larger-diameter stems (>12 mm) may reduce fracture risks, a strategy that could be adopted in similar cases.4,12
Additionally, joint stiffness, observed in 14.2 % of cases, represents a common postoperative challenge with these complex prosthesis. Evans et al. reported that rotating hinge implants improve stability but that functional limitations persist without early and intensive rehabilitation.2,13 This observation is corroborated by our study, where moderate functional outcomes, as measured by KSS and KSKF scores, were particularly evident in patients who experienced early complications.9,14
In cases of complex fractures, the use of megaprosthesis should be approached cautiously and limited to well-defined indications. Unlike fractures managed with plates or intramedullary nails, megaprosthesis are reserved for cases involving significant bone loss, soft tissue deficits, or situations where joint stability cannot be achieved otherwise. These prosthesis represent a last resort to ensure acceptable function when other alternatives are insufficient.5,8
However, adopting megaprosthesis in these contexts is not without challenges. Mechanical complications, such as fractures and aseptic loosening, along with peri-prosthetic infections, remain prevalent. Meluzio et al. demonstrated that distal femur fractures managed with these prosthesis exhibit high complication rates, negatively impacting long-term implant survival.5 In our study, these observations are corroborated, with a fracture rate of 7.1 % and a peri-prosthetic infection rate of 17.8 %. These findings underscore the importance of a rigorous patient selection strategy. Detailed fracture analysis, including residual bone quality and soft tissue condition, is essential to identify suitable candidates for this treatment.4,9
Moreover, customizing implants and adopting advanced surgical techniques could help reduce complication rates. Pala et al. highlighted that larger-diameter stems with porous coatings could enhance fixation and prolong implant longevity in similar contexts.4,12 These strategies, combined with intensive postoperative rehabilitation, appear to be key factors for optimizing functional outcomes and avoiding reoperations.
5 Conclusion
Knee megaprosthesis play a crucial role in managing complex pathologies, such as severe peri-prosthetic fractures and tumor resections. However, their use remains restricted to specific indications where conventional alternatives fail to meet the patient's functional and structural needs. The results of this study, consistent with the literature, reveal moderate survival rates but highlight frequent complications, including peri-prosthetic infections, loosening, and mechanical fractures. These findings emphasize the importance of strict patient selection, customized implants, and optimized postoperative management strategies to mitigate risks. Despite their challenges, megaprosthesis offer viable solutions to restore joint function and improve quality of life in highly complex cases, requiring multidisciplinary approaches and continuous research to refine techniques and enhance long-term outcomes.
Patient consent statement
Written informed consent was obtained from all patients involved in this study for the publication of their data and accompanying images. The authors ensured that all personal identifiers were removed to protect patient privacy.
Ethics statement and consent to participate
This study was conducted in accordance with the principles outlined in the Declaration of Helsinki. Ethical approval was deemed unnecessary by our institutional review board due to the retrospective nature of the study. Written informed consent was obtained from all patients for the publication of their data and accompanying images.
Availability of data and materials
The datasets used and analyses during the study are available from the corresponding author.
Author contribution
Yassine Ben Bouzid: writing the paper/data collection Yassine Ben Bouzid and Moulay Omar Lamrani: data analysis and interpretation Moulay Omar Lamrani: stylistic and grammatical revision of the manuscript Moulay Omar Lamrani and Yassine Ben Bouzid: Operating surgeons All authors reviewed the final manuscript.
Guarantor
Ben Bouzid Yassine, M.D.
Email: Yassine.benbouzid2@gmail.com.
Phone number: +212648309466.
Ethical statement
This study was conducted in accordance with the principles outlined in the Declaration of Helsinki. Ethical approval was deemed unnecessary by our institutional review board due to the retrospective nature of the study. Written informed consent was obtained from all patients for the publication of their data and accompanying images.
Funding statement
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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