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Research Article | DOI: https://doi.org/10.31579/2694-0248/132
Institute of Musculoskeletal Disorders and Orthopaedics Medanta- The Medicity Hospital Gurugram, Haryana, India.
*Corresponding Author: Ashok Rajgopal, Institute of Musculoskeletal Disorders and Orthopaedics Medanta- The Medicity Hospital Sector 38 Gurugram 122002, Haryana India.
Citation: Rasiq Rashid, Kalpana Aggarwal, Ashok Rajgopal (2025), Long Term Outcomes Using Global Modular Replacement System for Massive Bone Loss Around the Knee, J. Clinical Orthopedics and Trauma Care, 7(2); DOI:10.31579/2694-0248/132
Copyright: © 2025, Ashok Rajgopal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received: 09 July 2025 | Accepted: 17 July 2025 | Published: 25 July 2025
Keywords: global modular replacement system; complex knee pathology; massive bone loss; limb salvage surgery; functional outcomes; revision knee surgery
Background/ Aims:
This study investigates long-term clinical and functional outcomes of the Global Modular Replacement System (GMRS) in patients with complex knee pathologies and massive bone loss.
Materials and Methods:
A cohort of 36 knees in 35 patients who underwent limb salvage using GMRS between 2007 and 2020 was retrospectively reviewed. The study assessed outcomes using the Knee Society Score (KSS), Oxford Knee Score (OKS), Musculoskeletal Tumor Society (MSTS) score, range of motion (ROM), and radiographic evaluations.
Results:
Significant improvement was observed across all measures at a mean follow up of 10.6 ±4.4 years. The KSS improved from 40.1 ± 21.6 preoperatively to 88.1 ± 6.4 postoperatively. Similarly, the OKS increased from 10.9 ±4.1 preoperatively to 39.7 ± 3.9 postoperatively, and the MSTS score rose from 9.9 ± 3.0 to 27.6 ± 3.3, indicating significant functional gains. The mean ROM improved from 62.8° ± 33.6° preoperatively to 96.1° ± 18.4° postoperatively. The overall complication rate was 14.28%, with no instances of aseptic loosening or mechanical failure.
Conclusion:
GMRS is a reliable and effective option for limb-salvage procedures in complex knee cases, offering substantial improvement in pain relief, knee function and mobility. It has low complication rates in the long-term follow-up.
GMRS- Global Modular Replacement System
KSS- Knee Society Score
OKS- Oxford Knee Score
MSTS- Musculoskeletal Tumor Society Score
TKA- Total Knee Arthroplasty
ROM- Range of Motion
DAIR- Debridement Antibiotic and Implant Retention
ORIF- Open Reduction and Internal Fixation
GCT- Giant Cell Tumor
Advancements in medical oncology, surgical techniques, and reconstruction options have made limb-salvage surgery the preferred treatment over amputation [1,2]. Several reconstructive strategies are available for managing bone defects, including autografts, allogeneic bone grafting, bone transport, and the use of standard or megaprostheses. While modular megaprostheses are commonly used following bone tumor resection, they also provide an effective limb-salvage solution in complex cases following trauma and revision total knee arthroplasty (TKA) [3]. A key advantage of megaprostheses is their intraoperative flexibility, allowing surgeons to reconstruct large bone defects [3,4,5]. Early knee megaprostheses, featuring either fixed or rotating hinge articulation, were custom-made and primarily used for limb salvage after distal femoral or proximal tibial tumor resections [6,7,8]. However, technological advancements and growing expertise in limb salvage procedures have increased the demand for modular revision implants. Systems like Global Modular Replacement System (GMRS), Mu-tars, Compress, Stanmore, and Exactech modular implants are integral to limb salvage surgeries, offering tailored solutions to address a wide range of bone deficiencies and ensuring effective treatments for patients with complex bone conditions [9].These implants are now used for metastatic disease, comminuted periarticular fractures, knee non-union following failed open reduction and internal fixation (ORIF), and salvage revision TKA [10,11,12,13]. The GMRS features a dual-axis rotating hinge, which better replicates physiological knee motion and minimizes torsional stress at the implant–bone interface, unlike fixed-hinge systems, which are associated with higher rates of aseptic loosening and mechanical complications [6, 7, 14]. It additionally offers extensive modularity and incorporates a hydroxyapatite-coated collar to promote biological fixation, contributing to its durability and favourable long-term outcomes in both oncologic and non-oncologic reconstructions [9, 15, 16]. A key strength of the present study lies in its inclusion of a heterogeneous cohort with diverse and complex indications ranging from oncologic resections to peri articular comminuted fractures, non- union and failed arthroplasties, all characterized by massive bone loss around the knee joint. This clinical diversity underscores the versatility and adaptability of the GMRS system in addressing extensive skeletal defects where conventional reconstructive options are insufficient.
The aim of this study was to evaluate the long-term clinical and functional outcomes of the GMRS in patients with complex knee pathology, not amenable to standard TKA implants.
Hypothesis: The use of the Global Modular Replacement System in complex knee pathologies with massive bone loss is a promising option and offers good outcomes that are sustained over a long term follow up.
Following institutional review board (IRB) approval, we conducted a retrospective study of 36 knees in 35 patients who underwent limb salvage surgery using the GMRS between 2007 and 2020. The study was conducted in accordance with the Helsinki Declaration. One patient underwent bilateral reconstruction. Data was collected from institutional records. The average follow-up was 10.6 ± 4.4 years (Range: 4 – 17).
Patient Demographics:
The mean age at surgery was 51.1 years (range: 15–75), with a median age of 55 years (IQR: 45–65).The cohort consisted of 29 females (82.9%) and 6 males (17.1%). Patient demographics are tabulated in Table 1.
| Age | No. of patients | % |
| ≤21 years | 3 patients | 8.6% |
| 21–30 years | 3 patients | 8.6% |
| 31–40 years | 2 patients | 5.7% |
| 41–50 years | 3 patients | 8.6% |
| 51–60 years | 12 patients | 34.3% |
| 61–70 years | 10 patients | 28.6% |
| 70 years | 2 patients | 5.7% |
Table 1: Patient Demographics
Inclusion Criteria:
Patients with complex knee pathology unsuitable for conventional TKA, including:
Exclusion Criteria:
Patients underwent preoperative clinical evaluation, radiographic imaging, and oncologic staging when applicable. All procedures were performed by a single surgeon. The selection of GMRS components was individualized intra-operatively, tailored to anatomical and defect-specific considerations. Indications for using the GMRS components in this study included revision TKA, malignancies and Giant Cell Tumors (GCT) of the distal femur and proximal tibia, and peri- articular trauma around the knee. These indications are tabulated in Table 2.
| S. No | Condition | Cases |
| 1 | Revision TKA | 10 |
| 2 | Distal Femur Osteosarcoma | 8 |
| 3 | Osteoblastoma Distal Femur | 1 |
| 4 | Chondrosarcoma Proximal Tibia | 1 |
| 5 | Distal Femur Metastases | 3 |
| 6 | Distal Femur Giant Cell Tumor (GCT) | 4 |
| 7 | Proximal Tibia GCT | 1 |
| 8 | Comminuted Distal Femur Fracture | 3 |
| 9 | Distal Femur Non Union | 5 |
Table 2: Indications for GMRS
All patients operated for malignancies underwent intraoperative marrow biopsy and frozen section to confirm disease free margins.
Postoperative care followed a standardized rehabilitation protocol, with early mobilization based on intraoperative stability and patient-specific factors. Patients were evaluated at 3 months, 6 months, 12 months, and annually thereafter.
Outcome Measures:
Statistical analysis was conducted using SPSS version 24.0 (IBM Corp., Armonk, NY). The analysis included demographic profiling of patients, along with clinical and functional measures. Quantitative data were summarized as means with standard deviations, while categorical data were presented as absolute numbers and percentages. Preoperative and postoperative scores for the Knee Society Score (KSS), Oxford Knee Score (OKS), Musculoskeletal Tumor Society (MSTS) score, and range of motion (ROM) were compared using paired t-tests to assess significant changes over time. Cross-tabulation was performed, and Chi-square tests were used to evaluate associations between categorical variables. A p-value of less than 0.05 was considered statistically significant. The clinical relevance of improvements in functional scores (KSS, OKS, MSTS) and ROM was assessed using 95% confidence intervals (CIs) and mean differences. Additionally, complication rates were calculated as proportions.
Statistical analysis was conducted using SPSS version 24.0 (IBM Corp., Armonk, NY). The analysis included demographic profiling of patients, along with clinical and functional measures. Quantitative data were summarized as means with standard deviations, while categorical data were presented as absolute numbers and percentages. Preoperative and postoperative scores for the Knee Society Score (KSS), Oxford Knee Score (OKS), Musculoskeletal Tumor Society (MSTS) score, and range of motion (ROM) were compared using paired t-tests to assess significant changes over time. Cross-tabulation was performed, and Chi-square tests were used to evaluate associations between categorical variables. A p-value of less than 0.05 was considered statistically significant. The clinical relevance of improvements in functional scores (KSS, OKS, MSTS) and ROM was assessed using 95% confidence intervals (CIs) and mean differences. Additionally, complication rates were calculated as proportions.
Results:
Mean follow-up in years was 10.6 ± 4.4 years (Range: 4 – 17), and favourable clinical and functional outcomes were achieved in the majority of patients. The KSS, OKS and MSTS scores were further categorised into Excellent, Good, Fair and Poor based on classifications by Miralles-Muñoset al. [22], Edmondson et al. [23] and Enneking et al. [20] respectively.
KSS improved from preoperative values of 40.1 ± 21.6 to 88.1 ± 6.4 at the last follow up. This improvement was statistically significant with p<0>
The OKS improved from 10.9 ± 4.1 preoperatively to 39.7 ± 3.9 at the last follow up (95% CI: −30.3 to −27.2; t = −38.000; p < 0>
The MSTS score improved significantly from 9.9 ± 3.0 preoperatively to 27.6 ± 3.3 at the last follow-up (p < 0>t = –33.968). The MSTS scoring system evaluates six parameters (pain, function, emotional acceptance, supports, walking, and gait), each graded 0–5, for a total maximum score of 30 [20].
The mean ROM improved from 62.8° ± 33.6° preoperatively to 96.1° ± 18.4° at last follow up. (mean difference −33.3° ± 4.8°, 95% CI: −43.0 to −23.7; t = −6.997; p < 0>
All functional scores demonstrated statistically significant improvement from baseline, confirming the efficacy of GMRS in complex knee reconstruction across a spectrum of challenging indications.
The improvement in outcome scores is shown in Figure 1
Figure 1: Improvement in Outcome Scores
The overall complication rate in our study was 14.28 %.
No cases of aseptic loosening, mechanical prosthetic failure, or periprosthetic fractures occurred during the follow-up period. Figure 2 shows pre and post-operative X-Ray images of a patient with osteosarcoma right distal femur at ten years follow up.
Figure 2: Pre- and Post-Operative X-Rays at 10 years
One patient, who underwent distal femoral replacement for osteosarcoma, required hip disarticulation for an aggressive recurrence.
One patient, with a distal femoral replacement for post traumatic bone loss, sustained a patellar tendon rupture following a fall eight years postoperatively which was successfully managed with surgical reconstruction using a Tendo Achilles allograft. One patient developed postoperative stiffness due to non-compliance to physiotherapy protocols. A
deep surgical site infection occurred in one case and was treated with early debridement, antibiotics and implant retention (DAIR procedure). Intravenous antibiotics were administered for 6 weeks, followed by oral antibiotics for a further 6 weeks. One patient sustained an intraoperative popliteal artery injury during revision TKA, which was managed successfully with immediate vascular repair. Complications are tabulated in Table 3.
| Complications | Treatment | No. of patients | |
| 1. | Recurrence | Disarticulation | 1 patient |
| 2. | Patellar tendon rupture | Reconstruction of patellar tendon | 1 patient |
| 3. | Stiff knee | Refused intervention | 1 patient |
| 4. | Infection | DAIR and antibiotics | 1 patient |
| 5. | Popliteal artery injury intra-operatively | Vascular repair | 1 patient |
Table 3: Complications
The results of this study demonstrate that the GMRS offers favourable mid to long-term outcomes in patients with complex knee pathologies that are not amenable to standard TKA. Significant improvements were observed across multiple functional scores, including the KSS, OKS, MSTS score, and ROM, which were sustained over the study period. These favourable outcomes warrant further discussion in terms of their clinical relevance, particularly in comparison with existing literature. Our findings are similar to those of Capanna et al. [5], who reported excellent functional outcomes and high implant survival rates in patients undergoing lower limb reconstructions using modular megaprostheses. Bernthal et al. [4] reported high MSTS scores and acceptable complication rates for endoprosthetic reconstructions following tumor resection, consistent with our results, where 31.4% of patients achieved excellent and 57.1
Given the promising results of this study, the GMRS should be considered an effective solution for complex knee reconstructions, particularly in cases where standard TKA is unsuitable. This study demonstrates good functional outcomes, with significant improvement in movements, pain relief and independent ambulation. However, future research with larger cohorts, multi centric randomized controlled trials and longer follow ups are needed to evaluate long- term outcomes and survivorship of this option.
None of the authors have any potential conflict of interest.
This study did not require any funding
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