Indications for the use of metaphyseal fixation in revision total knee replacement
In total knee arthroplasty (TKA) revision surgery, surgeons are often faced with periprosthetic bone loss. Bone loss may even be the ultimate reason for the revision, eg, in patients with aseptic loosening. Additionally, removing a prosthetic component may create further defects. The quantity and quality of bone ultimately drives the decision which type of anchorage to choose for the revision prosthesis. Part 1 of the newsletter will explain the different types of bone defects and the treatment modalities available to address them, with a special focus on metaphyseal anchorage.
Bone defect classification
Bone defects are an important challenge faced by surgeons when revising a TKA, because they make it difficult to securely anchor an implant. The level of difficulty depends on the severity and location of the defect. Various techniques have been devised to overcome the problem. A wide range of classifications have been developed to classify bone defects based on size, severity, and location of the defects. Some of them may be used for preoperative planning and to guide treatment.
Glen Purnomo, Orthopaedic and Traumatology Specialist at St. Vincentius a Paulo Catholic Hospital, Surabaya, Indonesia, points out: “There is no perfect classification system that would allow to accurately evaluate bone loss for preoperative planning, provide guidelines for management, have proven intra- and interobserver reliability, and predict outcome. Take the Anderson Orthopaedic Research Institute (AORI) classification, which is currently the most widely used: it does not unequivocally prescribe the method to measure defect sizes, so the evaluation remains somewhat subjective. It also misses to include the patella in the evaluation. While some other classifications clearly define the size of the defect, in practice, the radioopaqueness of the implants pose great difficulties to determine the true size of the defect.”
Table 1 provides an overview about the most important classification systems with regard to the type of assessment, ie, preoperative or intraoperative, the features taken into account, ie, dimensions, morphology, and implant stability, as well as the possibility to act as guide for treatment .
Table 1. Bone defect classifications compiled by Mancuso F, Beltrame A, Colombo E, et al. Management of metaphyseal bone loss in revision knee arthroplasty. Acta Biomed. 2017 Jun 7;88(2s):98–111.
The different classification systems all use similar assessment criteria. For instance, the minimal type in the Rand classification, the small type in the Slooff and Malefijt classification, the type 1 defect in the AORI classification, the uncontained minor type in the Massachusetts General Hospital classification, the type 1 in the Clatworthey and Gross classification, the cystic type in the Huff and Sculco classification, and the cavitary type in the Bargar and Gross classification—all describe a defect that is small and contained, not requiring complex reconstruction. The massive type in the Rand classification, the discontinuity type in the Bargar and Gross classification, the type 3 defect in the AORI classification, the peripheral type in the Dorr classification, the segmental type in the Huff and Sculco classification, the ice-cream type in the Insall classification—all describe severe defects that reach into the condyles and may even affect the integrity of collateral ligaments .
Currently, the most frequently used classification is the AORI classification. It uses the same categories to describe femoral as well as tibial bone loss . In the AORI classification, bone defects are initially assessed on the preoperative radiographs. Type 1 defects include simple cystic lesions around the femoral condyles or the proximal tibia, but have essentially healthy cancellous bone at or near the joint line level, so that the revision component's stability is not compromised. This means that there is no component subsidence or osteolysis, and that in the tibia, the metaphyseal bone is intact above the tibial tubercle, and in the femur, the metaphyseal bone is intact below the epicondyles.
Type 2 defects are characterized by a shortened metaphyseal flare and component subsidence or, referring to the femur, joint line elevation of the failed component and, referring to the tibia, a component position up to or below the tip of the fibular head. Type 2a defects have metaphyseal bone damage and cancellous bone loss in one femoral condyle or one side of the tibial plateau, whereas type 2b defects involve metaphyseal bone loss in both femoral condyles, or across the entire tibial plateau.
Type 3 defects involve a completely deficient metaphyseal segment. On the femoral side, this means that the bone is damaged to or above the level of the epicondyles, with component subsidence to the epicondyles. On the tibial side, this means that the bone is damaged, or the prosthetic component has subsided to the level of the tibial tubercle.
Figure 1. Anderson Orthopaedic Research Institute (AORI) bone defect classification: (a) type 1 (intact metaphyseal bone with minor defects not compromising the stability of a revision component), (b) type IIA (damaged metaphyseal bone with defects in one femoral condyle or tibial plateau), (c) type IIB (more than one damaged metaphyseal bone), and (d) type III (deficient metaphyseal bone with bone loss compromising a major portion of the condyle or plateau). The latter defects are occasionally associated with collateral or patellar ligament detachment and usually require bone grafting or custom implants. Redrawn from Qiu YY, Yan CH, Chiu KY, et al. Review article: bone defect classifications in revision total knee arthroplasty. J Orthop Surg (Hong Kong). 2011 Aug;19(2):238–243.
Because assessment of bone defects is complicated through the radioopaqueness of the prosthetic components, their severity is often underestimated on preoperative x-rays and then found to be much more extensive during the actual revision surgery . Additionally, removal of the previous prosthesis may further damage the bone. Therefore, the authors of the AORI classification suggest refining the preoperative assessment intraoperatively. In addition, the method of reconstruction may require removing further bone. For instance, if a major structural allograft or a hinged or a custom component is needed to reconstruct the knee, the bone defect is classified as a type 3 .
Different defect types require different treatment modalities
The management of bone defects in patients undergoing revision TKA has been described in many publications [1, 4–6].
According to the zonal fixation concept, established by Morgan-Jones et al  in 2015, implant anchorage can be achieved in the epiphyseal, metaphyseal, or diaphyseal zones (Figure 2).
Figure 2. Zonal fixation concept according to Morgan-Jones R, Oussedik SI, Graichen H, et al. Zonal fixation in revision total knee arthroplasty. Bone Joint J. 2015 Feb;97-b(2):147–149.
Glen Purnomo explains: “Apart from the size of the defect, considerations are also based on the type of defect, whether it is contained or uncontained, the location of the defect, and the quality of the bone. Metaphyseal anchorage is used in the presence of significant metaphyseal defect (AORI types 2 or 3), when we want an immediately stable construct with axial and rotational stability. Our considerations for the type of fixation are primarily based on bone quality rather than patient age. However, in younger patients, anticipation of possible future revisions requires to choose more bone-preserving options.”
Treatment of AORI type 1 defects is usually regarded as uncomplicated . They may be filled with cement or morselized cancellous bone graft. Sculco et al  recommended that in defects between 5 and 10 mm, the structural integrity of the cement mantle could be augmented with screws inserted into the condyle or plateau with the screwheads just below the intended level of the implant. However, they caution that the durability of this technique is not as high as that of modular metal augments and should thus be reserved for older patients with lower physical demands.
In AORI type 2 defects, the extent of the bone loss dictates that some form of augmentation has to be used to (a) provide the prosthesis with adequate support for secure anchorage, and (b) enable restoration of the joint line at a physiological level. Secure anchorage may be achieved with structural augmentation (autograft, allograft, or prosthetic) or longer stems that bypass the defect and offload the joint line [4, 8].
Type 2A defects, particularly those with peripheral cortical involvement, can be treated with modular metal augments. Lombardi et al  recommended the use of modular augments when more than 50% of the femoral condyle and/or tibial plateau were compromised with a defect greater than 5 mm in depth . Augments for the tibia come in wedge or block shapes and can fill a defect of up to 20 mm. Augments for the distal femur can be placed either distally or posteriorly and are up to 8–10 mm in length depending on the revision system. Distal femoral augments help reconstitute the joint line and posterior augments help with rotational alignment and improve overall bone-implant contact and stability .
Type 2B defects have variable amounts of metaphyseal bone loss in both femoral condyles, or both compartments of the tibial plateau. They are treated in a similar manner as type 3 defects.
Type 3 defects are the most severe defects encountered in revision TKA with extensive metaphyseal bone loss and structural impairment of both femoral condyles and/or both medial and lateral tibial compartments. Reconstruction options include metaphyseal structural support in the form of structural allograft, highly porous metaphyseal cones, stepped titanium sleeves, megaprostheses, or customized prostheses.
Lei et al  created a comprehensive overview of the most common currently available treatment modalities for the different defect types, including their major advantages and disadvantages (Table 2).
Table 2. Management of bone defects in revision TKA.
Source: Lei PF, Hu RY, Hu YH. Bone Defects in Revision Total Knee Arthroplasty and Management. Orthop Surg. 2019 Feb;11(1):15–24.
Treatment modalities for metaphyseal fixation
Metaphyseal fixation can be achieved with structural allograft or porous metal devices, ie, metal cones and metaphyseal sleeves .
Structural bone allograft
Structural bone allograft is a biological option in the treatment of significant bone defects, ie, in AORI types 2 and 3 . Since it can be manually sculpted to exactly match the defect , unnecessary removal of healthy host bone can be avoided . For the purpose of treating bone defects in revision TKA, it is most commonly derived from the femoral head, bulk distal femur, or proximal tibia [1, 4, 8].
Its advantages are most evident in young patients, since they are more likely to face further revision surgeries . Moreover, structural allograft allows for reattachment of ligaments and tendons . It has been recommended to attach the allograft directly to the host bone to encourage biological incorporation and protect it from excessive stress by securing it with a long-cemented stem [4, 10]. However, preparation of structural allografts to fit the native defect can be technically demanding and time consuming [11, 12].
Unfortunately, structural allograft is also associated with several important drawbacks, eg, the risk of disease transmission, deep infection, graft nonunion, resorption, fracture, or collapse [10, 11]. Additionally, in many geographical regions its availability is limited.
We asked Seng-Jin Yeo, Professor of Duke NUS Medical School and Senior Consultant of Orthopaedic Surgery at Singapore General Hospital how he rates the use of allograft—should it be used at all? He advised that structural allograft could well be considered for young patients, where the aim was to restore bone stock and there was a high risk of future revision surgeries. At the same time, he cautioned that the advantages of a less complicated potential future revision should be carefully weighed against the known drawbacks of allograft. Personally, he never uses allografts. In his practice, sleeves and revision implants including megaprosthesis are readily available and provide predictable and good long-term outcomes."
This is probably representative for the majority of practices nowadays, with a clear preference of metal implants over allograft due to the aforementioned drawbacks. Therefore, this newsletter will also focus on metal implants.
Metal implants: sleeves and cones
The major technical difference between sleeves and cones is the interface between the metaphyseal fixation device and the implant. While cones are cemented to the implant, sleeves are fixed to the tibial and femoral implants via a morse taper, removing a possible source of failure at the cement-implant interface [13, 14]. Sleeved implants are assembled and implanted en bloc. So far, no offset stems are available. In contrast to that, cones are press-fitted into the host bone in the metaphysis without cement before the tibial or femoral components are positioned and cemented into the cone . In this way, sleeves transfer stress to the metaphysis with primary fixation and cones reconstruct the plateau for the base plate to load through .
While it is important to consider these differences during preoperative planning for revision TKA, there is no consensus in the medical community regarding the superiority of one implant type over the other for a given defect type . Also, a direct comparison of results is hampered because in spite of the overlap of indications, there are also important differences in the application of sleeves and cones.
Even though both cones and sleeves can be used to address bone defects of a multitude of sizes and locations, the design of each type of implant bears some limitations.
Sleeves were designed to fill large contained cavitary and combined cavitary-segmental metaphyseal defects in the femur and tibia . They are shaped as a stepped taper and have a porous titanium surface. This makes them most suitable for situations of central bone loss with a limited capacity to alter the joint line [17, 18]. They must be used with the manufacturer's articulating components because they are constructed with precise morse taper junctions. The morse connection usually allows some degree of rotation of the tibial or femoral component to fit the individual anatomy . Femoral sleeves are especially advantageous when there is significant posterior femoral condyle bone loss, as they can add rotational stability to the implant . However, placement of the sleeves is somewhat restricted by the lack of offset stems, and the size of the stem is restricted by the maximum diameter of the sleeve .
We asked Seng-Jin Yeo about the advantages and disadvantages he saw in his daily practice for sleeves. He explained: “The reaming and broaching instrumentation used to fashion the bone to accept sleeves is very easy and quick to use. The morse taper junction that fixes the sleeve to the tibial and femoral components creates a very stable construct which achieves both fixation and bone defect management at the same time. One minor drawback is that using sleeves for an eccentric bone defect may require removing healthy bone during preparation as there is no option for offset stems. Although it is possible to use cones with different manufacturers for example in single component revision, practically this is rarely done. Revision of both components is more commonly performed as it is easier, so to balance the gaps and restore the joint line. Therefore, cones are usually used in conjunction with the same implant manufacturer.”
Currently, there is no consensus whether to use diaphyseal stems with metaphyseal sleeves . At the time of their market introduction, sleeves were recommended to be used only in conjunction with stems. Recently, many authors have questioned this technique . The clinical results achieved with sleeve-only constructs (Figure 5) [17, 21–24] appear to be on a par with the results published on sleeves used in conjunction with stems (Figure 3 and Figure 4).
Figure 3. Type 2B defect in the tibia and femur treated with a stemmed sleeve construct.
Preoperative x-rays showing severe tibial component migration with bone loss on the medial condyle of the tibia, osteolysis of the lateral condyle of the tibia, and fracture line at the metaphyseal-diaphyseal junction of the proximal tibia (shown by arrows) (a). Intraoperative findings after removal of implants demonstrate AORI F2B and AORI T2B defects (b). Postoperative x-rays show metaphyseal sleeve with stem construct on both femur and tibia. Note the fracture line at the metaphyseal-diaphyseal junction of the proximal tibia (shown by arrows) (c). Follow-up x-rays 6 months after surgery show the well-fixed implant and fracture union (d).
Images courtesy of Seng-Jin Yeo.
Figure 4. Type 3 defect in the femur and type 2B defect in the tibia treated with a stemmed sleeve construct. Preoperative x-rays show severe femoral component migration to the level of the epicondyles, indicating AORI F3 defect (a). Intraoperative findings after removal of implants demonstrate massive bone loss of both femoral condyles, indicating AORI F3 defect and bone loss on both condyles of the tibia, indicating AORI T2B defect (b). Postoperative x-rays after reconstruction with metaphyseal sleeve and stem construct (c).
Images courtesy of Seng-Jin Yeo.
While the implantation of sleeves with stems is a well-established and successful procedure, there are also reasons against stemmed implants. One of their disadvantages is that in rare cases, pain can develop around the tip of the stem—we describe this phenomenon in more detail in part 3 of this newsletter. Moreover, a procedure that does not use a stem may contribute to simplify the bone preparation, thereby reducing operating time and reducing the revision cost . But most importantly, in patients with a bowed intramedullary canal, the use of a stem can be impracticable  and bears the risk of malalignment . As the bowing may guide longer constructs into malalignment, shorter constructs, which stay proximal to the bowing, are less at risk. On the other hand, in patients with straight bones, a stemmed construct is very useful to guide the implant in the right position. In these patients, the risk of malalignment is higher with a much shorter sleeve-only construct . Some surgeons have therefore advocated using stems for preparation and trial implants, but a stemless final implant. Nevertheless, the fixation area of a sleeve-only implant compared with a sleeve and stem construct is much smaller, which has the potential to affect implant fixation. Some authors have therefore proposed using the concept of zonal fixation  to guide the decision on whether to use a stem. In patients where zones 1 and 2, ie, epiphyseal and metaphyseal, fixation are deemed sufficient, a sleeve-only fixation should be chosen, and a sleeve and stem construct would be appropriate in patients with uncontained defects, ie, AORI types 2B and 3 .
Figure 5. Type 2A defects in tibia and femur treated with a sleeve only construct on the tibial side.
Preoperative x-rays show migration of tibial component of unicompartmental knee arthroplasty with bone loss, indicating AORI type T2A (a). Postoperative x-rays after conversion to TKA. A metaphyseal sleeve without stem was used to reconstruct the tibia due to bone loss. Cement was used to fill the minor bone defect in the medial condyle of the tibia (b).
X-rays courtesy of Seng-Jin Yeo.
Seng-Jin Yeo also has practical concerns. Particularly large diameter stems become extremely well fixed to the sleeve and are often impossible to disengage in the case of a revision surgery. This makes removal of a well ingrowth stem and sleeve construct extremely difficult. In addition, the use of stem may cause stress shielding and increase the risk of cortex bone resorption. Therefore, his preference is to use sleeves without stems in type 2 AORI defects, particularly on the femoral side, because the femoral sleeves are relatively long and the femoral sagittal bow can be accommodated. However, if the defect is so large that diaphyseal fixation is needed for stable fixation, he would instead use a stemmed implant. In Yeo's practice, this is more often the case in the tibia than in the femur.
From a biomechanical perspective, several in vitro models have shown that a sleeved construct primarily achieves its stability through the sleeve, with little contribution of the stem, independent of the type of defect [20, 25, 27–29].
Cones (Figure 6), on the other hand, can be used in larger cavitary defects, which may be central or eccentric [30, 31]. As the articulating component is cemented into the cone, surgeons can use their preferred articulating implant, independent of its manufacturer, which greatly increases the permutations that can be used to recreate the joint line .
Figure 6. Type 3 defect in tibia treated with a cone construct. The femoral component was left in situ.
Preoperative x-rays show loosening and migration of the tibial component. Note the tip of the stem is pointing laterally (a). Postoperative x-rays after reconstruction of the bone defect with a cone (b).
X-rays courtesy of Seng-Jin Yeo.
Cones are available from different manufacturers with a surface of porous titanium (“tritanium” or “Stiktite”) or made from bulk porous tantalum (“trabecular metal”). They come in many different shapes and sizes to fit a wide range of defects in the tibia and femur. The high variability makes them suitable for nearly all types of metaphyseal bone deficiencies, in particular for cavities in which a reliable cortical shell is present . The reconstruction of segmental defects is facilitated through the option to use offset stems, along with symmetrical or asymmetrical cones . Peripheral defects can be addressed by only fitting the distal part of the cone . Adjustment of the joint line to its original position is enabled through the wide variety of shapes and sizes along with cement augmentation and can be further titrated with augments and base plates in different heights. Cementing the prosthetic component into the cone allows for a relatively wide range of implant rotation and alignment, independent of the cone location.
Axial stability is provided by stems, while rotational stability is improved by keel and box together with the cone for tibial and femoral component respectively . Some authors have emphasized the need for a cemented stem, arguing that only a cemented stem could provide sufficient primary stability to the construct to enable osseointegration of the cones .
We asked Seng-Jin Yeo how he rated the advantages and disadvantages of cones. He explained: “Cones act more like a bone graft filler that receives the tibial or femoral component, which is then cemented to the cone. It is good for eccentric defects and can be used with offset stems. In theory, it can be used with any revision implant design. However, a big disadvantage is that, in spite of the recent improvements in instrumentation, shaping the bone to receive the cone takes considerably longer than the reaming and broaching for sleeves. Moreover, additional augments may still be needed, which adds to time and cost.”
This series of articles was created with the support of the following specialists (in alphabetical order):
This article was compiled by Elke Rometsch, Project Manager Medical Writing, AO Foundation, Switzerland.
Additional AO resources
Access videos, tools, and other assets to learn more about this topic.
- AO Surgery Reference
- Video: Tips and Tricks to Improve Total Knee Arthroplasty Outcomes
- Video: The Difficult Primary Total Knee Arthroplasty
- Upcoming events: AO Recon Course finder
- Mancuso F, Beltrame A, Colombo E, et al. Management of metaphyseal bone loss in revision knee arthroplasty. Acta Biomed. 2017 Jun 7;88(2s):98–111.
- Qiu YY, Yan CH, Chiu KY, et al. Review article: bone defect classifications in revision total knee arthroplasty. J Orthop Surg (Hong Kong). 2011 Aug;19(2):238–243.
- Engh GA, Ammeen DJ. Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. Instr Course Lect. 1999;48:167–175.
- Sculco PK, Abdel MP. Contemporary bone loss options: Rebuild, reinforce, and augment. Seminars in Arthroplasty. 2015;26(2):108–111.
- Panegrossi G, Ceretti M, Papalia M, et al. Bone loss management in total knee revision surgery. Int Orthop. 2014 Feb;38(2):419–427.
- Lee YS, Chen AF. Managing bone loss in revision total knee arthroplasty. Annals of Joint. 2016;1:17–17.
- Morgan-Jones R, Oussedik SI, Graichen H, et al. Zonal fixation in revision total knee arthroplasty. Bone Joint J. 2015 Feb;97-b(2):147–149.
- Lei PF, Hu RY, Hu YH. Bone Defects in Revision Total Knee Arthroplasty and Management. Orthop Surg. 2019 Feb;11(1):15–24.
- Lombardi AV, Berend KR, Adams JB. Management of bone loss in revision TKA: it's a changing world. Orthopedics. 2010 Sep 7;33(9):662.
- Bauman RD, Lewallen DG, Hanssen AD. Limitations of Structural Allograft in Revision Total Knee Arthroplasty. Clinical Orthopaedics and Related Research®. 2009;467(3):818–824.
- Clatworthy MG, Ballance J, Brick GW, et al. The use of structural allograft for uncontained defects in revision total knee arthroplasty. A minimum five-year review. J Bone Joint Surg Am. 2001 Mar;83(3):404–411.
- Backstein D, Safir O, Gross A. Management of Bone Loss: Structural Grafts in Revision Total Knee Arthroplasty. Clinical Orthopaedics and Related Research®. 2006;446:104–112.
- Haidukewych GJ, Hanssen A, Jones RD. Metaphyseal fixation in revision total knee arthroplasty: indications and techniques. J Am Acad Orthop Surg. 2011 Jun;19(6):311–318.
- Alexander GE, Bernasek TL, Crank RL, et al. Cementless metaphyseal sleeves used for large tibial defects in revision total knee arthroplasty. J Arthroplasty. 2013 Apr;28(4):604–607.
- Salim X, Lopez DJ, Jeys L, et al. Cones and sleeves in knee arthroplasty: a narrative review. Current Orthopaedic Practice. 2019 09/01;30:1.
- Roach RP, Clair AJ, Behery OA, et al. Aseptic Loosening of Porous Metaphyseal Sleeves and Tantalum Cones in Revision Total Knee Arthroplasty: A Systematic Review. J Knee Surg. 2020 Feb 19.
- Graichen H, Scior W, Strauch M. Direct, Cementless, Metaphyseal Fixation in Knee Revision Arthroplasty With Sleeves-Short-Term Results. J Arthroplasty. 2015 Dec;30(12):2256–2259.
- Martin-Hernandez C, Floria-Arnal LJ, Muniesa-Herrero MP, et al. Mid-term results for metaphyseal sleeves in revision knee surgery. Knee Surg Sports Traumatol Arthrosc. 2017 Dec;25(12):3779–3785.
- Ihekweazu UN, Weitzler L, Wright TM, et al. Distribution of Bone Ongrowth in Metaphyseal Sleeves for Revision Total Knee Arthroplasty: A Retrieval Analysis. J Arthroplasty. 2019 Apr;34(4):760–765.
- Graichen H, Scior W. Is stemless implant fixation a valid option in total knee revision arthroplasty - Review of in vitro and in vivo studies. J Orthop. 2021 Jan-Feb;23:113–117.
- Bugler KE, Maheshwari R, Ahmed I, et al. Metaphyseal Sleeves for Revision Total Knee Arthroplasty: Good Short-Term Outcomes. J Arthroplasty. 2015 Nov;30(11):1990–1994.
- Agarwal S, Azam A, Morgan-Jones R. Metal metaphyseal sleeves in revision total knee replacement. Bone Joint J. 2013 Dec;95-b(12):1640–1644.
- Thorsell M, Hedström M, Wick MC, et al. Good clinical and radiographic outcome of cementless metal metaphyseal sleeves in total knee arthroplasty. Acta Orthop. 2018 Feb;89(1):84–88.
- Agarwal S, Neogi DS, Morgan-Jones R. Metaphyseal sleeves in revision total knee arthroplasty: Minimum seven-year follow-up study. Knee. 2018 Dec;25(6):1299–1307.
- Fonseca F, Sousa A, Completo A. Femoral revision knee Arthroplasty with Metaphyseal sleeves: the use of a stem is not mandatory of a structural point of view. J Exp Orthop. 2020 Apr 26;7(1):24.
- Scior W, Chanda D, Graichen H. Are Stems Redundant in Times of Metaphyseal Sleeve Fixation? J Arthroplasty. 2019 Oct;34(10):2444–2448.
- Awadalla M, Al-Dirini RMA, O'Rourke D, et al. Influence of varying stem and metaphyseal sleeve size on the primary stability of cementless revision tibial trays used to reconstruct AORI IIA defects. A simulation study. J Orthop Res. 2018 Jul;36(7):1876–1886.
- Nadorf J, Gantz S, Kohl K, et al. Tibial revision knee arthroplasty: influence of modular stems on implant fixation and bone flexibility in AORI Type T2a defects. Int J Artif Organs. 2016 Nov 29;39(10):534–540.
- Nadorf J, Kinkel S, Gantz S, et al. Tibial revision knee arthroplasty with metaphyseal sleeves: The effect of stems on implant fixation and bone flexibility. PLoS One. 2017;12(5):e0177285.
- Kamath AF, Lewallen DG, Hanssen AD. Porous tantalum metaphyseal cones for severe tibial bone loss in revision knee arthroplasty: a five to nine-year follow-up. J Bone Joint Surg Am. 2015 Feb 4;97(3):216–223.
- Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty: a minimum 2-year follow-up. J Arthroplasty. 2009 Oct;24(7):1086–1092.
- Huten D. Femorotibial bone loss during revision total knee arthroplasty. Orthop Traumatol Surg Res. 2013 Feb;99(1 Suppl):S22–33.