Abstract
-
Acetabular revision arthroplasty, a demanding field of reconstructive hip surgery, calls for innovative strategies to deal with challenging bone defects and implant failure seen in revision cases.
-
Conventional implant solutions might fall short of adequately addressing severe bone loss and ensuring stable fixation, highlighting the necessity of customized strategies.
-
Personalized megaimplants, distinguished by their tailor-made design and large-scale construction, present a viable option to overcome these challenges.
-
The present article provides an elaborate analysis of custom-made megaimplants in acetabular revision arthroplasty, shedding light on the underlying principles, design complexities, manufacturing methods, applications in the clinical setting, and outcome assessment.
-
The aim of this review is to present a comprehensive insight into personalized megaimplants and their contribution to the advancement of orthopedic surgery.
Introduction
Revision arthroplasty of the acetabulum poses a significant challenge for orthopedic surgeons, especially when faced with severe bone loss and failure of previous implants (1, 2). The strategy for revising the acetabulum is extremely complex and demands extensive expertise, especially in treating high-risk groups such as women, individuals with rheumatoid arthritis, and patients with a history of radiation therapy to the pelvis (3, 4). Due to the continuously increasing number of revision total hip arthroplasties (THAs) performed, the incidence of severe acetabular defects and related pelvic discontinuity (PD) has also been on the rise (5, 6). The proper treatment strategy for challenging acetabular revision cases, seen at an incidence of 1–5%, requires establishing stable continuity between the ischium and ilium in addition to restoring the anatomical hip center (7). Conventional acetabular implants might fail to suffice in handling such complex scenarios, requiring state-of-the-art solutions to ensure stable fixation and restore hip function (8, 9). Developments in implant technology have introduced novel solutions in revision THA, leading to an improvement in patients’ quality of life. On the other hand, the rate of failure is high in surgery, and the outcomes are widely variable (10). In addition, successful acetabular revision surgery essentially requires bone stock and an anatomical implant structure that is compatible with biological recovery (11, 12). There is a lack of readily available information on the short- and long-term outcomes of the commonly employed materials in acetabular revision procedures, including revision antiprotrusio cages, cup–cage constructs, custom triflange implants, and porous metals, in terms of complications and mechanical failure (13, 14, 15).
Customized megaimplants offer an innovative strategy by tailoring the implant design to meet the specific anatomical needs of the patient, providing a personalized solution for complex acetabular revision cases (16, 17, 18). This article delivers an extensive review of the design principles, manufacturing methods, clinical uses, evaluation of outcomes, and prospective development of customized megaimplants in the context of acetabular revision arthroplasty.
Rationale for individualized megaimplants
Opting for individualized megaimplants in acetabular revision arthroplasty is driven by the innate limitations associated with traditional implant solutions in adequately addressing extensive bone defects and achieving stable fixation (19, 20). Many patients face the risk of severe bone loss or PD due to repeated acetabular revision surgeries (Fig. 1) (4). However, it is possible to achieve successful outcomes through customized planning in such a difficult-to-manage and difficult-to-treat situation. In challenging revision surgeries, custom- made megaimplants, featuring large-scale construction and personalized geometry, aim to address these drawbacks by offering robust support, restoring the anatomy of the acetabulum, and promoting osteointegration (21). The combination of cutting-edge imaging modalities, computational modeling, and additive production techniques has facilitated the creation of personalized megaimplants, representing a notable advancement in the realm of orthopedic surgery. In this respect, particularly 3D printing technology provides a significant contribution to anatomical–biological recovery (22).
Patient with severe bone defects and pelvis discontinuity in left hip.
Citation: EFORT Open Reviews 9, 5; 10.1530/EOR-24-0064
Preoperative planning and development of individualized megaimplants
Assessment of the acetabulum during revision hip arthroplasty is usually performed with direct radiographs. Yet, assessments based on radiographs may prove insufficient, particularly in cases involving existing components or cement in patients with prior THA or revision THA. In such scenarios, the inclusion of CT with 3D reconstruction becomes imperative for patient evaluation (Fig. 2) (23, 24). It is possible to create an individualized implant design simultaneously with the CT scan. However, this requires conducting a CT scan with proper methods. Patients should be placed in the supine position with their legs naturally aligned and in neutral rotation. For a complete pelvic exam, encompassing the region between the uppermost point of the ilium and the lowest point of the ischium, a slice thickness of 1.5 mm is utilized. These imaging methods offer in-depth anatomical insights, empowering surgeons to correctly identify bone defects, assess implant placement, and visualize the inherent acetabular anatomy. With the aid of dedicated software, orthopedic surgeons collaborate closely with biomedical engineers to create custom-made megaimplant designs, taking into consideration patient-specific anatomical alterations, bone deficiencies, and surgical aims (25).
At this stage, deficient acetabular anterosuperior and posteroinferior columns are measured using the Paprosky classification. A specialized software, as proposed by Gelaude et al., is employed to evaluate the total bone loss from the radial acetabular bone (26). Gelaude's method incorporates 3D image processing and an efficient anatomical 3D reconstruction derived from CT images (Fig. 3). This technique generates a ratio and a graph, allowing for a direct comparison of specimens. The ratio serves to quantify the extent of the initial acetabular bone loss, while the graph visually depicts the remaining bone stock in the radial direction. In addition, bone quality is assessed with the software, providing a detailed evaluation ranging from excellent to bad bone quality using the color scale. This is followed by the completion of the individualized megaimplant design that covers the acetabular bone defect and restores the center of rotation of the hip joint using the data collected (Fig. 4). The software is instrumental in planning the trajectories of screws, determining screw lengths through the cup, and precisely positioning delineated flanges over the pubis, ilium, and ischium host bones (Fig. 5). Ultimately, it is imperative to receive feedback from the surgeon to optimize the implant's anteversion, inclination, and center of rotation before the final 3D implant is generated.
Gelaude’s method incorporates 3D image processing.
Citation: EFORT Open Reviews 9, 5; 10.1530/EOR-24-0064
The individualized megaimplant design that covers the acetabular bone defect and restores the center of rotation of the hip joint using the data collected.
Citation: EFORT Open Reviews 9, 5; 10.1530/EOR-24-0064
Final position of the individualized megaimplant and screws on the software.
Citation: EFORT Open Reviews 9, 5; 10.1530/EOR-24-0064
Employing additive manufacturing techniques, such as selective laser melting or electron beam melting, the megaimplant is constructed from biocompatible materials like titanium alloys or cobalt–chromium alloys (27, 28). These additive manufacturing processes ensure exceptional precision in forming intricate implant geometries, incorporating porous structures to boost osteointegration and mechanical stability (29). Post-processing stages, encompassing surface finishing, sterilization, and quality control, are diligently implemented to make sure that the implant not only adheres to regulatory standards but is also primed for surgical implantation.
Clinical applications and outcomes
The 3D printing process is followed by the clinical application of individualized megaimplants. The proper surgical incision is selected based on the surgeon’s experience in accessing the hip joint within the largest field possible. In case of aseptic acetabular revision arthroplasty, all existing acetabular components, screws, cement, and/or fragmented bone tissue should be removed completely after proper tissue release. On the other hand, surgeries secondary to septic revision require thorough debridement to remove all membrane tissue covering the joint surface. Curetting and reaming procedures are conducted on the sclerotic base and defects. In order to facilitate surgery, the individualized acetabular megaimplant comes with a plastic 3D-printed model of the patient’s hemipelvis in addition to the 3D-printed trial implant model. The 3D-printed model serves as a guide to identify the defect calculated during the CT scan analysis. Subsequent to the impaction of trial implants, assessments for functionality and stability are carried out. It is essential to handle the 3D-printed drill guides with care due to their fragility. Failing to do so may hinder the implementation of preoperatively planned screw directions in the event of impairment or breakage in the guide structure. It is also essential to adhere to the screw order planned preoperatively. Numbering of the screws, carried out by the implant manufacturer, signifies the sequence of screw placement and length. Finally, after removing the trial implants, the actual implant is positioned in the defect and secured using drill guides with the flange and cup screws. A standard/revision or dual mobility cup/liner component is cemented into position after securely placing the acetabular component (1).
Personalized megaimplants have exhibited promising outcomes in various clinical scenarios in acetabular revision arthroplasty. Particularly in cases of severe acetabular bone loss, megaimplants offer structural support and restoration of acetabular anatomy in addition to promoting stable implant fixation (2). Clinical studies have also reported successful outcomes with megaimplants in terms of increased implant survivorship, lower rates of re-revision, and improved functional outcomes compared to conventional implant alternatives (3, 10, 30, 31).
In addition, personalized megaimplants bring versatility to the management of complex acetabular defects, encompassing conditions like PD, acetabular protrusion, and severe osteolysis. By tailoring the implant geometry to address the patient's unique bone deficiencies and anatomical variations, it would be possible for surgeons to ensure optimal stability of the implant, minimizing the risk of complications such as infection, dislocation, and loosening.
Postoperative protocol and common complications
Postoperative stability evaluation starts with an anteroposterior pelvic radiograph. Individualized megaimplants provide substantial joint stability after a surgery that has been duly completed by properly following each step in the preoperative plan. However, a partial weight-bearing protocol should still be implemented to ensure a controlled osteointegration process and allow for the healing of bone defects due to the cementless individualized 3D structure of the implant. In the postoperative period, patients are allowed partial weight-bearing, limited to 30 kg, for the first 6 weeks. Those who can tolerate this load may gradually increase their weight, transitioning to full weight-bearing between weeks 8 and 12. Abductor muscle strength may require some time to recover, especially in patients who experience prolonged immobility before the surgery. In such cases, protocols for strengthening the abductor and quadriceps muscles should be implemented, and supervised by a competent rehabilitation team. The range of motion of the hip joint should also be restored in a controlled manner during the postoperative period. The risk of postoperative dislocation is highest within the first month in such advanced revision cases, and these patients should be carefully instructed on movements they can perform.
The most common complication is the challenges encountered during the removal of the previous acetabular implants in the course of revision (1, 32). An aggressive debridement or long-term immobility of the joint may result in uncontrolled growth of the acetabular bone defect as a consequence of poor bone quality due to osteopenia (4). There is no need to use a bone graft to support individualized megaimplants that provide stable fixation, and the use of excess grafts in some cases may lead to an increased risk of infection. The screw guide used during implant fixation is also 3D printed, and improper use thereof may cause breakage or faulty alignment of screw directions. In such cases, screws that were placed with precision may lead to inadequate fixation or neurovascular tissue damage.
Conclusion
The adoption of individualized megaimplants marks an evolutionary approach to acetabular revision arthroplasty, delivering customized solutions for challenging bone defects and implant failures. Through the integration of advanced imaging technologies, computational modeling, and additive fabrication methods, megaimplants lead to optimal implant stability, restored hip biomechanics, and better patient outcomes. On the other hand, given the fact that screw trajectory and fit are highly sensitive to component position, even minor changes in positioning may lead to an unintended neurovascular injury. Although screw mapping and preoperative planning are still in their early stages, they limit the surgeon’s ability to customize and unitize a modular structure during surgery. Therefore, a custom-made implant minimizes the problems that can be encountered in intraoperative fixation. Sustained innovation and collaborative efforts are imperative to achieve the entire potential of personalized megaimplants and to further improve the quality of care for patients undergoing acetabular revision surgery.
ICMJE Conflict of Interest Statement
The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of this review.
Funding Statement
This work did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sector.
References
- 1↑
Citak M, Kochsiek L, Gehrke T, Haasper C, Suero EM, & Mau H. Preliminary results of a 3D-printed acetabular component in the management of extensive defects. Hip International 2018 28 266–271. (https://doi.org/10.5301/hipint.5000561)
- 2↑
Romagnoli M, Zaffagnini M, Carillo E, Raggi F, Casali M, Leardini A, Marcheggiani Muccioli GM, Grassi A, & Zaffagnini S. Custom-made implants for mass ive acetabular bone loss: accuracy with CT assessment. Journal of Orthopaedic Surgery and Research 2023 18 742. (https://doi.org/10.1186/s13018-023-04230-5)
- 3↑
Tack P, Victor J, Gemmel P, & Annemans L. Do custom 3D-printed revision acetabular implants provide enough value to justify the additional costs? The health-economic comparison of a new porous 3D-printed hip implant for revision arthroplasty of Paprosky type 3B acetabular defects and its closest alternative. Orthopaedics & Traumatology, Surgery & Research 2021 107 102600. (https://doi.org/10.1016/j.otsr.2020.03.012)
- 4↑
Sculco PK, Wright T, Malahias M-A, Gu A, Bostrom M, Haddad F, Jerabek S, Bolognesi M, Fehring T, Gonzalez DellaValle A, et al. The diagnosis and treatment of acetabular bone loss in revision hip arthroplasty: an international consensus symposium. HSS Journal®: the Musculoskeletal Journal of Hospital for Special Surgery 2021 18 8–41. (https://doi.org/10.1177/15563316211034850)
- 5↑
Babis GC, & Nikolaou VS. Pelvic discontinuity: a challenge to overcome. EFORT Open Reviews 2021 6 459–471. (https://doi.org/10.1302/2058-5241.6.210022)
- 6↑
Faraj S, de Windt TS, van Hooff ML, van Hellemondt GG, & Spruit M. Custom-made acetabular revision arthroplasty for pelvic discontinuity: can we handle the challenge? Bone and Joint Open 2023 4 53–61. (https://doi.org/10.1302/2633-1462.42.BJO-2022-0159.R1)
- 7↑
Vega CA, Moruno F, Garavano E, Sued M, & Palomino Prado E. Tratamiento de defectos acetabulares tipo IIIA-B de Paprosky y discontinuidad pélvica con implantes 3D a medida: resultados a mediano plazo. Revista de la Asociación Argentina de Ortopedia y Traumatología 2023 88 511–519. (https://doi.org/10.15417/issn.1852-7434.2023.88.5.1760)
- 8↑
Coden G, Matzko C, Hushmendy S, Macaulay W, & Hepinstall M. Impact of acetabular implant design on aseptic failure in total hip arthroplasty. Arthroplasty Today 2021 7 60–68. (https://doi.org/10.1016/j.artd.2020.11.017)
- 9↑
Madanipour S, Lemanu D, Jayadev C, Aston W, Donaldson J, Miles J, Carrington R, McCulloch R, & Skinner J. Ischial screw fixation can prevent cup migration in 3D-printed custom acetabular components for complex hip reconstruction. Arthroplasty 2022 4 52. (https://doi.org/10.1186/s42836-022-00154-3)
- 10↑
Fang S, Wang Y, Xu P, Zhu J, Liu J, Li H, & Sun X. Three-dimensional-printed titanium implants for severe acetabular bone defects in revision hip arthroplasty: short- and mid-term results. International Orthopaedics 2022 46 1289–1297. (https://doi.org/10.1007/s00264-022-05390-5)
- 11↑
Shon WY, Santhanam SS, & Choi JW. Acetabular reconstruction in total hip arthroplasty. Hip & Pelvis 2016 28 1–14. (https://doi.org/10.5371/hp.2016.28.1.1)
- 12↑
Kim Y-H. Acetabular cup revision. Hip & Pelvis 2017 29 155–158. (https://doi.org/10.5371/hp.2017.29.3.155)
- 13↑
Wang C-X, Huang ZD, Wu B-J, Li W-B, Fang X-Y, & Zhang W-M. Cup-cage solution for massive acetabular defects: a systematic review and meta-analysis. Orthopaedic Surgery 2020 12 701–707. (https://doi.org/10.1111/os.12710)
- 14↑
Baauw M, van Hooff ML, & Spruit M. Current construct options for revision of large acetabular defects: a systematic review. JBJS Reviews 2016 4 e2. (https://doi.org/10.2106/JBJS.RVW.15.00119)
- 15↑
Xiao Q, Wang H, Zhou K, Wang D, Ling T, Pei F, & Zhou Z. The mid-long term results of reconstructional cage and morselized allografts combined application for the Paprosky type III acetabular bone defects in revision hip arthroplasty. BMC Musculoskeletal Disorders 2019 20 517. (https://doi.org/10.1186/s12891-019-2915-3)
- 16↑
von Hertzberg-Boelch SP, Wagenbrenner M, Arnholdt J, Frenzel S, Holzapfel BM, & Rudert M. Custom made monoflange acetabular components for the treatment of Paprosky type III defects. Journal of Personalized Medicine 2021 11 283. (https://doi.org/10.3390/jpm11040283)
- 17↑
Merema BJ, Kraeima J, ten Duis K, Wendt KW, Warta R, Vos E, Schepers RH, Witjes MJH, & IJpma FFA. The design, production and clinical application of 3D patient-specific implants with drilling guides for acetabular surgery. Injury 2017 48 2540–2547. (https://doi.org/10.1016/j.injury.2017.08.059)
- 18↑
Soloviev D, Maslov L, & Zhmaylo M. Acetabular implant finite element simulation with customised estimate of bone properties. Materials 2023 16 398. (https://doi.org/10.3390/ma16010398)
- 19↑
Cursaru A, Iordache S, Costache M, Serban B, Popa M, Cretu B, & Cirstoiu C. Management of acetabular bone loss in hip revision arthroplasty: case series presentation. Cureus 2023 15 e45432. (https://doi.org/10.7759/cureus.45432)
- 20↑
D’Apolito R, & Zagra L. Uncemented cups and impaction bone grafting for acetabular bone loss in revision hip arthroplasty: a review of rationale, indications, and outcomes. Materials 2022 15 3728. (https://doi.org/10.3390/ma15103728)
- 21↑
Meng M, Wang J, Huang H, Liu X, Zhang J, & Li Z. 3D printing metal implants in orthopedic surgery: methods, applications and future prospects. Journal of Orthopaedic Translation 2023 42 94–112. (https://doi.org/10.1016/j.jot.2023.08.004)
- 22↑
Bozkurt Y, & Karayel E. 3D printing technology; methods, biomedical applications, future opportunities and trends. Journal of Materials Research and Technology 2021 14 1430–1450. (https://doi.org/10.1016/j.jmrt.2021.07.050)
- 23↑
Ma Z, Tang H, Zhou Y, Wang S, Yang D, & Guo S. Assessing component orientation of total hip arthroplasty using the low-dose bi-planar radiographs. BMC Musculoskeletal Disorders 2022 23 886. (https://doi.org/10.1186/s12891-022-05835-3)
- 24↑
Baauw M, van Hellemondt GG, van Hooff ML, & Spruit M. The accuracy of positioning of a custom-made implant within a large acetabular defect at revision arthroplasty of the hip. The Bone and Joint Journal 2015 97–B 780–785. (https://doi.org/10.1302/0301-620X.97B6.35129)
- 25↑
Wong KC. 3D-printed patient-specific applications in orthopedics. Orthopedic Research and Reviews 2016 8 57–66. (https://doi.org/10.2147/ORR.S99614)
- 26↑
Gelaude F, Clijmans T, & Delport H. Quantitative computerized assessment of the degree of acetabular bone deficiency: total radial acetabular bone loss (TrABL). Advances in Orthopedics 2011 2011 494382. (https://doi.org/10.4061/2011/494382)
- 27↑
Tamayo JA, Riascos M, Vargas CA, & Baena LM. Additive manufacturing of Ti6Al4V alloy via electron beam melting for the development of implants for the biomedical industry. Heliyon 2021 7 e06892. (https://doi.org/10.1016/j.heliyon.2021.e06892)
- 28↑
Trevisan F, Calignano F, Aversa A, Marchese G, Lombardi M, Biamino S, Ugues D, & Manfredi D. Additive manufacturing of titanium alloys in the biomedical field: processes, properties and applications. Journal of Applied Biomaterials and Functional Materials 2018 16 57–67. (https://doi.org/10.5301/jabfm.5000371)
- 29↑
Mobarak MH, Islam MA, Hossain N, Al Mahmud MZ, Rayhan MT, Nishi NJ, & Chowdhury MA. Recent advances of additive manufacturing in implant fabrication: a review. Applied Surface Science Advances 2023 18 100462. (https://doi.org/10.1016/j.apsadv.2023.100462)
- 30↑
Di Laura A, Henckel J, & Hart A. Custom 3D-printed implants for acetabular reconstruction. JBJS Open Access 2023 8 e22.00120. (https://doi.org/10.2106/JBJS.OA.22.00120)
- 31↑
Macak D, Dzupa V, & Krbec M. Custom-made 3D printed titanium acetabular component: advantages and limits of use. Acta Chirurgiae Orthopaedicae et Traumatologiae Cechoslovaca 2021 88 69–74. (https://doi.org/10.55095/achot2021/012)
- 32↑
Winter P, Kurz K, Jung A, Roch J, Wolf M, & Siebel T. The clinical outcome of custom-made implants in primary and revision hip arthroplasty. Acta Chirurgiae Orthopaedicae et Traumatologiae Cechoslovaca 2022 89 423–428. (https://doi.org/10.55095/achot2022/067)
