Massive bone loss on both the femur and tibia during revision total knee arthroplasty (TKA) remains a challenging problem. Multiple solutions have been proposed for small osseous defects, including morselised cancellous bone grafting, small-fragment structural allograft, thicker polyethylene inserts, and the use of modular augments attached to revision prosthetic designs. Large osseous defects can be treated with structural allografts, impaction bone-grafting with or without mesh augmentation, custom prosthetic components, and specialised hinged knee components. The metaphyseal area of the distal femur and proximal tibia is a particularly attractive option during revision TKA given that it is usually undamaged and well-vascularised. While multiple reconstructive options have been recommended, porous tantalum metaphyseal cones have the advantage of improved biologic fixation because of their high porosity (75–80%), interconnected pore space, and low modulus of elasticity (3 MPa) similar to that of cancellous bone. Such features allow tantalum cones to fill bone defects while tolerating physiological loads. Indications for porous tantalum metaphyseal cones include patients with Anderson Orthopaedic Research Institute Type 2B or greater defects. The surgical technique is simpler than structural allograft reconstructions with decreased preparation time, resulting in a possible decrease in infection rates. The modularity of porous tantalum metaphyseal cones also allows the surgeon to choose a size and position that best fits the individual defect encountered. Moreover, tantalum cones can be used with several revision systems. Short-term clinical follow up indicates that porous tantalum metaphyseal cones effectively provide structural support with the potential for long-term biologic fixation and durable reconstructions

Aim. Femoral or tibial massive bone defects (AORI F2B-F3 / T2B-T3) are common in septic total knee replacement. Different surgical techniques are described in literature. In our study we show clinical and radiological results associated with the use of tantalum metaphyseal cones in the management of cavitary bone defects in two-stage complex knee revision. Method. Since 2010 we have implanted 70 tantalum metaphyseal cones associated with constrained or semiconstrained knee prostheses in 47 patients. The indication for revision was periprosthetic knee infection (43 cases, 91.5%) or septic knee arthritis (4 patients, 8.5%) with massive bone defect. All cases underwent a two-stage procedure. Patients were screened for main demographic and surgical data. Clinical and radiological analysis was performed in the preoperative and at 3,6 months, 1 years and each year thereafter in the postoperative. The mean follow-up was 31.1 months ± 18.8. No dropout was observed. Results. Objective and subjective functional scores (KSS, OKS) showed a statistically significant improvement from the preoperative to last follow-up (p <0.001). All cones but one (98.6%) showed radiological osteointegration. We did not find any cone-related intraoperative or postoperative mechanical complication with a 100% survival rate when we consider aseptic loosening as cause of revision. Six non progressive radiolucencies were observed. Two septic failures (4.3%) with implant and cone removal were reported. Conclusions. The ideal treatment for cavitary bone defects in two-stage TKA septic revision is still unclear. The use of metaphyseal tantalum cones showed excellent clinical and radiographic results with a low rate of related complications. The main finding of our study is the cone-related infection rate (2.9%) in this particular series of patients. This data is comparable or better than other previous report about this topic with unhomogeneous cohort of patients

The amount of bone loss due to implant failure, loosening, or osteolysis can vary greatly and can have a major impact on reconstructive options during revision total knee arthroplasty (TKA). Massive bone loss can threaten ligamentous attachments in the vicinity of the knee and may require use of components with additional constraint to compensate for associated ligamentous instability. Classification of bone defects can be helpful in predicting the complexity of the reconstruction required and in facilitating preoperative planning and implant selection. One very helpful classification of bone loss associated with TKA is the Anderson Orthopaedic Research Institute (AORI) Bone Defect Classification System as it provides the means to compare the location and extent of femoral and tibial bone loss encountered during revision surgery. In general, the higher grade defects (Type IIb or III) on both the femoral and tibial sides are more likely to require stemmed components, and may require the use of either structural graft or large augments to restore support for currently available modular revision components. Custom prostheses were previously utilised for massive defects of this sort, but more recently have been supplanted by revision TKA component systems with or without special metal augments or structural allograft. Options for bone defect management are: 1) Fill with cement; 2) Fill with cement supplemented by screws or K-wires; 3) Morselised bone grafting (for smaller, especially contained cavitary defects); 4) Small segment structural bone graft; 5) Impaction grafting; 6) Porous metal cones or sleeves 7) Massive structural allograft-prosthetic composites; 8) Custom implants. Of these, use of uncemented highly porous metal metaphyseal cones in combination with an initial cemented or partially cemented implant has been shown to provide versatile and highly durable results for a range of bone defects including those previously requiring structural bone graft. The hybrid fixation combination of both cement and cementless fixation of an individual tibial or femoral component has emerged as a frequent and often preferred technique. Initial secure and motionless interfaces are provided by the cemented portions of the construct, while subsequent bone ingrowth to the cementless porous metal portions is the key to long term stable fixation. As bone grows into the porous portions there is off loading and protection of the cemented interfaces from mechanical stresses. While maximizing support on intact host bone has been a longstanding fundamental principle of revision arthroplasty, this is facilitated by the use of metaphyseal cones or sleeves in combination with initial fixation into the adjacent diaphysis. Preoperative planning is facilitated by good quality radiographs, supplemented on occasion by additional imaging such as CT. Fluoroscopically controlled x-ray views may assist in diagnosing the loose implant by better revealing the interface between the implant and bone and can facilitate accurate delineation of the extent of bone deficiency present. Part of the preoperative plan is to ensure adequate range and variety of implant choices and bone graft resources for the planned reconstruction allowing for the potential for unexpected intraoperative findings such as occult fracture through deficient periprosthetic bone. While massive bone loss may compromise ligamentous attachment to bone, in the majority of reconstructions, the degree of revision implant constraint needed for proper balancing and restoration of stability is independent of the bone defect. Thus, some knees with minimal bone deficiency may require increased constraint due to the status of the soft tissues while others involving very large bone defects, especially of the cavitary sort, may be well managed with minimal constraint

The management of bone loss in revision total knee replacement (TKA) remains a challenge. To accomplish the goals of revision TKA, the surgeon needs to choose the appropriate implant design to “fix the problem,” achieve proper component placement and alignment, and obtain robust short- and long-term fixation. Proper identification and classification of the extent of bone loss and deformity will aid in preoperative planning. Extensive bone loss may be due to progressive osteolysis (a mechanism of failure), or as a result of intraoperative component removal. The Anderson Orthopaedic Research Institute (AORI) is a useful classification system that individually describes femoral and tibial defects by the appearance, severity, and location of bone defects. This system provides a guideline to treatment and enables preoperative planning on radiographs. In Type 1 defects, femoral and tibial defects are characterised by minor contained deficiencies at the bone-implant interface. Metaphyseal bone is intact and the integrity of the joint line is not compromised. In this scenario, the best reconstruction option is to increase the thickness of bone resection and to fill the defect with cancellous bone graft or cement. Type 2 defects are characterised by deficient metaphyseal bone involving one or more femoral condyle(s) or tibial plateau(s). The peripheral rim of cortical bone may be intact or partially compromised, and the joint line is abnormal. Reconstruction options for a Type 2A defect include impaction bone grafting, cement, or more commonly, prosthetic augmentation (e.g. sleeves, augments or wedges). In Type 2B defects, metaphyseal bone of both femoral condyles or both tibial plateaus is deficient. The peripheral rim of cortical bone may be intact or partially compromised, and the joint line is abnormal. Options for a Type 2B defect include impaction grafting, bulk structural allograft, prosthetic augmentation, metaphyseal sleeves (in some cases), or metaphyseal cones. Finally, in the presence of a Type 3 deficiency, both metaphyseal and cortical bone is deficient and there is partial or complete disruption of the collateral ligament attachments. In this case, the most commonly used reconstruction options include hinged implants or megaprostheses with or without bulk structural allograft, prosthetic augmentation, and/or metaphyseal/diaphyseal sleeves or cones. Today, we are fortunate to have a wide variety of options available to aid in reconstruction of a revision TKA with massive bone loss. Historically, use of cement, bone grafting, or use of a tumor-type or hinged implant were considered the main options for reconstruction. The development and adoption of highly porous sleeves and cones has given the surgeon a new and potentially more durable option for reconstruction of previously difficult to treat defects. Using radiographs and computed tomography, surgeons are able to preoperatively classify bone loss and anticipate a reconstruction plan based upon the classification; however, it is always important to have several back-up options on hand during revision surgery in the event bone loss is worse than expected

Stems provide short- and long-term stability to the femoral and tibial components. Poorer epiphyseal and metaphyseal bone quality will require sharing or offloading the femoral and tibial component interfaces with a stem. One needs to use stem technique most appropriate for each individual case because of variable anatomy and bone loss situations. The conflict with trying to obtain stability via the stem is that most stems are cylindrical but femoral and tibial metaphyseal/diaphyseal areas are conical in shape. Viable stem options include fully cemented short and long stems, uncemented long stems, offset uncemented stems, and a hybrid application of a cemented proximal end of longer uncemented diaphyseal engaging stems. Stems are not without their risk. The more the load is transferred to the cortex, the greater the risk of proximal interface stress shielding. A long uncemented stem has similar stress shielding as a short cemented stem. Long diaphyseal engaging stems that are cemented or uncemented have the potential to have end of stem pain, especially if more diaphyseal reaming is done to obtain greater cortical contact. A conical shaped long stem can provide more stability than a long cylindrical stem and avoid diaphyseal reaming. Use of long stems may create difficulty in placement of the tibial and femoral components in an optimal position. If the femoral or tibial components do not allow an offset stem insertion, using a long offset stem or short cemented stem is preferred. The amount of metaphyseal bone loss will drive the choice of stem used. Short cemented stems will not have good stability in poor metaphyseal bone without getting the cement out to the cortex. Long cemented stems provide satisfactory survivorship, however, most surgeons avoid cementing long stems due to the difficulty of removal, if a subsequent revision is required. If the metaphyseal bone is excellent, use of a short cemented stem or long uncemented stem can be expected to have good results. Long fully uncemented stems must have independent stability to be effective, or should be proximally cemented as a hybrid technique. Cases with AOI type IIb and III tibial and femoral defects are best managed with use of metaphyseal cones with short cemented stems or long hybrid straight or offset stems. Some studies also suggest that if the cone is very stable, no stem may be required. My preference is to use a short cemented stem or hybrid conical stem in patients with good metaphyseal bone. If significant metaphyseal bone loss is present, I will use a porous cone with either a short cemented stem, hybrid cylindrical or offset stem depending on the primary stability of the cone and whether the femoral or tibial component can be placed in an optimal position in patients with good metaphyseal bone

Metaphyseal bone loss, due to loosening, osteolysis or infection, is common with revision total knee arthroplasty (TKA). Small defects can be treated with screws and cement, bone graft, and non-porous metal wedges or blocks. Large defects can be treated with bulk structural allograft, impaction grafting, or highly porous metal cones. The AORI classification of bone loss in revision TKA is very helpful with pre-operative planning. Type 1 defects do not require augments or graft—use revision components with stems. Type 2A defects should be treated with non-porous metal wedges or blocks. Type 2B and 3 defects require a bulk structural allograft or porous metal cone. Highly-porous metal metaphyseal cones are a unique solution for large bone defects. Both femoral (full or partial) and tibial (full, stepped, or cone+plate) cones are available. These cones substitute for bone loss, improve metaphyseal fixation, help correct malalignment, restore joint line, and permit use of a short cemented stem. The technique for these cones involve preparing the remaining bone with a high speed burr and rasp, followed by press-fit of the cone into the remaining metaphysis. The interface is sealed with bone graft and putty. The fixation and osteoconductive properties of the outer surface allow ingrowth and biologic fixation. The revision knee component is then implanted, with antibiotic-cement, into the porous cone inner surface, which provides superior fixation compared to cementing into deficient metaphyseal bone. There are several manufacturers that provide porous cones for knee revision, but the tantalum-“trabecular metal” cones have the largest and longest clinical follow-up. The advantages of the trabecular metal cone compared to allograft include: technically easier; biologic fixation; no resorption; and lower risk of infection. The disadvantages include: difficult extraction and intermediate-term follow-up. The author has reported the results of 33 trabecular metal cones (9 femoral, 24 tibial) implanted in 27 revision cases at 2–5.7 years follow-up. One knee (2 cones) was removed for infection. All but one cone showed osseointegration. Multiple other studies have confirmed these results. Trabecular metal cones are now the author's preferred method for the reconstruction of large bone defects in revision TKA

Metaphyseal bone loss, due to loosening, osteolysis or infection, is common with revision total knee arthroplasty (TKA). Small defects can be treated with screws and cement, bone graft, and non-porous metal wedges or blocks. Large defects can be treated with bulk structural allograft, impaction grafting, or highly porous metal cones. The AORI classification of bone loss in revision TKA is very helpful with preoperative planning. Type 1 defects do not require augments or graft—use revision components with stems. Type 2A defects should be treated with non-porous metal wedges or blocks. Type 2B and 3 defects require a bulk structural allograft or porous metal cone. Trabecular metal (TM) metaphyseal cones are a unique solution for large bone defects. Both femoral (full or partial) and tibial (full, stepped, or cone+plate) TM cones are available. These cones substitute for bone loss, improve metaphyseal fixation, help correct malalignment, restore joint line, and permit use of a short cemented stem. The technique for these cones involve preparing the remaining bone with a high speed burr and rasp, followed by press-fit of the cone into the remaining metaphysis. The interface is sealed with bone graft and putty. The fixation and osteoconductive properties of the outer surface allow ingrowth and biologic fixation. The revision knee component is then cemented into the porous cone inner surface, which provides superior fixation compared to cementing into deficient metaphyseal bone. The advantages of the TM cone compared to allograft include: technically easier; biologic fixation; no resorption; and lower risk of infection. The disadvantages include: difficult extraction and intermediate-term follow-up. The author has reported the results of 33 TM cones (9 femoral, 24 tibial) implanted in 27 revision cases at 2–5.7 years follow-up. One knee (2 cones) was removed for infection. All but one cone showed osseointegration. TM cones are now the preferred method for the reconstruction of large bone defects in revision TKA

Restoration of bone loss is a major challenge of revision TKA surgery. It is critical to achieve of a stable construct to support implants and achieve successful results. Major bone defects of the femoral and/or tibia (AORI type IIB/III) have been reconstructed using impaction grafting, structural allografts or tumor prostheses. The major concerns with structural allograft are graft resorption, mechanical failure, tissue availability, disease transmission, considerable surgical skill required and prolonged operative time. Porous tantalum metaphyseal cones, are becoming the established method of choice to correct large bone defects with several recent studies demonstrating promising results. The high coefficient of friction of these implants provides structural support for femoral and tibial components. The high degree of porosity has excellent potential for bone ingrowth and long-term biologic fixation. Several published series, although with relatively small cohorts of patients, have reported good short-term results with trabecular metal cones for major femoral and tibial bony defects in revision TKA. In a recent study, 16 femoral and 17 tibial cones were reviewed at an average follow up of 33 months (range, 13 to 73 months) the mean Knee Society Score improved from 42 pre-operatively to 83 at last follow up with an improvement of the functional score from an average of 34 to 66 (p<0.0001). Radiological follow up revealed no evidence of loosening or migration of the constructs. No evidence of complications were noted in correlation with the use of trabecular metal cones

Metaphyseal bone loss is common with revision total knee arthroplasty (TKA). The causes of bone loss include: osteolysis, loosening, infection, iatrogenic or a combination. Small defects can be treated with screws and cement, bone graft, and non-porous metal wedges or blocks. Large defects can be treated with bulk structural allograft, impaction grafting, or highly porous metal cones or augments. The AORI classification of bone loss in revision TKA is very helpful with preoperative planning. Type 1 defects do not require augments or graft—use revision components with stems. Type 2 defects should be treated with non-porous metal augments—wedges or blocks. Type 3 defects require a bulk structural allograft or large highly porous metal cone. Trabecular metal (TM) metaphyseal cones are a unique solution for large bone defects. There are both femoral (full or partial) and tibial (full or stepped) TM cones available. These cones substitute for bone loss, improve metaphyseal fixation, help correct malalignment, restore joint line, and perhaps, permit use of a shorter stem. The technique for these cones involve sculpturing of the remaining bone with a high speed burr and rasp, followed by press-fit of the cone into the remaining metaphyseal bone. The interface is sealed with bone graft and putty. The fixation and osteoconductive properties of the outer surface allow ingrowth and hopefully long term biologic fixation. The revision knee component is then cemented into the porous cone inner surface, which provides superior fixation compared to deficient metaphyseal bone. The advantages of the TM cone compared to allograft include: technically easier; biologic fixation; no resorption; and (?) lower risk of infection. The disadvantages include: difficult extraction and relatively short-term follow-up. The author has reported the results of 33 TM cones (9 femoral, 24 tibial) implanted in 27 revision cases at 2–5.7 years follow-up. One knee (2 cones) was removed for infection. All but one cone showed osseointegration. TM cones are a promising method for the reconstruction of large bone defects in revision TKA

Introduction. The optimal management of severe tibial and/or femoral bone loss in a revision total knee arthroplasty (TKA) has not been established. Reconstructive methods include structural or bulk allografts, impaction bone-grafting with or without mesh augmentation, custum prosthetic components, modular metal augmentations of prosthesis and tumor prosthesis. Recently metaphyseal fixation using porous tantalum cones (Zimmer, Warsaw, IN) has been proposed as alternative strategy for severe bone loss. Objectives. The purposes of this study were to determine the clinical and radiographic outcomes in patients who underwent revision knee arthroplasty with tantalum cones with a minimum of 5-year follow-up. Methods. From November 2005 to August 2008 a total of 26 porous tantalum metaphyseal cones were used to reconstruct severe tibial and/or femoral bone loss in 18 patients during revision TKA at a single institution. There were 12 females and 6 males with an average age of 73 years (range 55–84) at the time of revision. The mean clinical and radiographic follow-up was 6.3 years (range, 5–8). The reasons for revision were aseptic loosening (5 cases) and deep infection (13 cases). A Two stage procedure was used in all septic cases. According to the Anderson Orthopaedic Reseach Institute (AORI) bone defects classification all femoral and tibial defects were rated 2B and 3 (3 T2b, 9 T3, 3 F2b and 10 F3). A femoral cone was inserted in 6 patients, a tibial cone was inserted in 5, a double cone in 6 (femoral and tibial), and a triple cone in 1 (1 femoral and 2 tibial). A constrained condylar implant (LCCK, Zimmer, Warsaw) was inserted in 6 patients and a rotating hinge knee implants (RHK, Zimmer, Warsaw, IN) in 12 pateints. All patients were prospectively followed for clinical and radiographic evaluation preoperatively and postoperatively at 1, 3, 6 months, one year and yearly thereafter. Results. Knee Society knee scores improved from a mean of 31.3 points before surgery to 76.7 points at latest followup (p < 0.001). Knee Society function scores improved from a mean of 21.7 points before surgery to 65.4 points at latest followup (p < 0.001). The average flexion contracture was 6° and the average flection was 88°. At the time of the latest follow-up the average flexion contraction was 3° and the average flexion was 105°. No radiolucent lines were seen between the cones and the adjacent tibial and femoral bone at the latest follow-up. There was no evidence of loosening or migration of any implant at the time of the final follow-up. There have been two reoperations for recurrent infection (11%). Conclusions. Our experience demonstrates excellent clinical and radiographic mid-term outcomes and confirms that metaphyseal fixation with porous tantalum cones can be achieved. Long-term follow up and comparative studies are necessary