Master Techniques in Orthopedic Surgery Knee CH21

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Managing Bone Loss with Metaphyseal Cones

Matthew P. Abdel, Henry D. Clarke, and Arlen D. Hanssen

INDICATIONS Primary total knee arthroplasty (TKA) has proved reliable, yet failures do occur. 1,2 Contemporary causes of failure include aseptic loosening, deep periprosthetic joint infection (PJI), instability, and osteolysis due to particulate wear debris. 3-6 Each of these etiologies can result in significant bone loss that must be managed at the time of revision TKA. The management of bone loss during revision TKA is based on the size and type of defects that are encountered. Numerous options exist, and in many circumstances, alternative reconstructive

techniques may be considered including the following 6,7 : ●● Polymethylmethacrylate (PMMA) cement ± screws ●● Particulate and structural bone grafts ●● Metal augments (including cones or sleeves) ●● Allograft prosthetic composites (APCs) ●● Segmental replacement prostheses

The strategy used by each surgeon may be influenced by factors including availability of the re- quired items, surgeon experience, operative time, cost, and age and activity level of the patient. As for many surgeons, our preferred choice is primarily dependent on the size of the defect. Numerous classification systems have been previously described to aid in both preoperative planning and intraoperative management of bone loss in revision TKA. We favor the use of the Anderson Orthopaedic Research Institute (AORI) classification, which is relatively simple and has been validated (Table 21-1). 8,9 Practical guidelines have been published, on the basis of theAORI classification, to aid the surgeon in managing the bone loss encountered in revision TKA. 8,10 With the introduction of larger standard augments, sleeves, porous tantalum cones, and porous titanium cones, the spectrum of defects that can be managed with this technique has increased and represents our primary choice in most circum- stances. 11-13 On the basis of the size of the lesion, our preferred techniques are as follows: ●● AORI type I (Figure 21-1) defects of the femur and tibia, including small, contained defects less than or equal to 5 mm in depth can be managed with cement ( ± screws), or traditional metal augments. TABLE 21-1 . Anderson Orthopaedic Research Institute Classification of Bone Defects in Revision Total Knee Arthroplasty Type I Intact metaphyseal bone Good cancellous bone at or near the normal joint line Type II Damaged metaphyseal bone Loss of cancellous bone that requires reconstruction to restore joint line Type III Deficient metaphyseal bone

Deficient bone compromises major portion of either condyle or plateau

Femoral and tibial defects are classified independently

A = One condyle or plateau B = Both condyles or both plateaus

Adapted from Engh GA and Ammeen DJ. Classification and preoperative radiographic evaluation: knee. Orthop Clin North Am . 1998;29(2):205-217.

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FIGURE 21-1. Type I bone loss has intact metaphyseal bone with less than 5 mm of bone loss.

●● AORI type II defects (Figure 21-2), whether unicondylar or bicondylar, including uncontained defects up to 20 mm in depth, can usually be addressed with porous metaphyseal cones (tantalum or titanium). Some type I and smaller type IIA defects may be treated with metal sleeves. ●● AORI type III defects (Figure 21-3) have historically been managed with structural allograft bone, APCs, or segmental replacement prostheses. However, the introduction of porous tantalum and titanium cones, which can be used with a variety of prosthesis systems, has largely replaced our use of structural allografts. 7

FIGURE 21-2. Type II bone loss has damaged metaphyseal bone with loss of cancellous bone. A involves only one condyle or plateau, whereas B involves both condyles or both plateaus.

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FIGURE 21-3. Type III bone loss has deficient metaphyseal bone that compromises a major portion of either condyle or plateau.

Standardmetal augments are augments that, regardless of size, attach directly to the body of the prosthesis with cement, snap or taper fit, or screw fixation. They may be composed of titanium, cobalt chrome, or tantalum. These augments are system specific and available in a variety of sizes and styles. Femoral aug- ments, typically blocks that are 5 to 20 mm thick, attach to the distal or posterior condyles of the prosthesis (Figure 21-4). Tibial augments include blocks, and partial or full wedges that attach to the undersurface of the tibial tray (Figures 21-5 and 21-6). These tibial augments also replace up to 15 to 20 mm of bone loss. In addition, sleeve augments are available in some systems for the tibia and femur (Figure 21-7). These sleeve augments insert over the stem of a revision component and are designed to fill metaphyseal defects. Porous metaphyseal cones do not attach to the prosthesis, but instead are impacted directly into large areas of femoral or tibial metaphyseal bone loss. Currently available options include porous metaphyseal tantalum cones (Trabecular Metal [TM]; Zimmer-Biomet; Warsaw, IN) (Figure 21-8), and porous titanium cones that are either three-dimensional (3D) printed (Tritanium; Stryker; Mahwah, NJ) (Figure 21-9) or produced via a heating process using a mixture of titanium powder that contains other binding agents (Zimmer-Biomet). These cone augments allow the restoration of a stable foundation upon which the prosthesis, with or without additional standard augments, can be supported. It is this ability to use these augments independently of the prosthesis, as a structural bone graft substitute, that differentiates porous metaphyseal cones from other metaphyseal filling metal augments.

FIGURE 21-4. Revision femoral component demonstrating metal augments on the distal and posterior aspects of the femur. The femoral augments are composed of tantalum and are attached via screw fixation.

FIGURE 21-5. Revision tibial component demonstrating metal augments that are cemented to the tray.

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FIGURE 21-6. In each knee system, a variety of trial tibial augments are available including blocks and wedges of varying thicknesses.

FIGURE 21-7. Some type I and smaller type IIA defects may be treated with a system-specific metal sleeve.

Commercially pure tantalum is formed into a porous trabecular geometry that approximates the structure of cancellous bone. 14-16 TM has two to three times the porosity of conventional porous metal coatings, which helps maximize the potential for bone ingrowth. 14-16 In addition, owing to its inherent strength, it may be used without the need for conventional metal backing to create structural augments. Widespread use in many areas of orthopedic reconstruction has demonstrated the rapid manner in which osseous ingrowth into this tantalum substrate occurs. 14-16 Porous titanium cones are currently available from two manufacturers and are produced using different technology. A newly released cone system with 3D printed titanium (Tritanium; Stryker)

FIGURE 21-8. Tantalum cones are used independently of the prosthesis to reconstruct metaphyseal bone loss in the tibia or femur. A stepped tibial cone is demonstrated before implantation.

FIGURE 21-9. Three-dimensional printed titanium cones are also used independently of the prosthesis. However, the recently released system is based on an intramedullary guided milling system.

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has shown early promise with its cost-effective approach. The construct is based on an intramedullary guided milling system that provides very precise bone preparation, and thus bony apposition. Similar to tantalum cones, the 3D printed cones are unlinked to a specific prosthesis and come in a variety of shapes and sizes. The symmetric tibial shapes and sizes are designed for simple type I and IIA defects where sleeves were traditionally utilized. On the other hand, lobe-shaped cones are available for type IIB and III defects. Femoral cones are bilobed in nature with the goal of bottoming out, and preventing longitudinal femoral fractures with preparation and implantation of the metaphyseal cone. An alternative process for creating porous titanium cones involves heating a titanium powder that contains additional compounds to high temperatures; the additives evaporate leaving a highly porous titanium structure (Zimmer-Biomet). Both femoral and tibial cones are fabricated using this process. In this system, preparation of the host bone is accomplished using a high-speed burr and metaphyseal broaches. Potential advantages of the porous tantalum and titanium cones versus structural bone graft include the following: ●● Availability of a wide variety of prefabricated shapes and sizes of augments ●● Quick and easy use ●● Ability to contour to obtain a custom fit ●● Immediate load bearing ●● Rapid bone ingrowth with stable long-term fixation In distinction, although structural grafts and impaction grafting techniques have been reported to have acceptable results in complex revision hip and knee arthroplasty cases, reservations persist. 17-19 Potential problems with large bone grafts include the following: ●● Limited availability ●● Risk of bacterial and viral disease transmission ●● Increased intraoperative time ●● Prolonged weight-bearing restrictions until graft incorporation has occurred ●● Graft resorption in 5% to 20% of cases 17,19 As a result of these ongoing concerns with the use of structural bone grafts, coupled with the in- creasing availability of tantalum and 3D printed titanium cones and good early results in the revision TKA setting, we have increased our use of porous metaphyseal cones in AORI type II and III bone defects, where we would have previously used bone graft material. CONTRAINDICATIONS Absolute contraindications for the use of porous tantalum and titanium metaphyseal cones include standard contraindications for TKAs including deep periprosthetic infection. Relative contraindications for the use of all metal augments regardless of size and composition include absence of host bone support. In cases where massive bicondylar bone loss exists with absence of any rim of cortical bone, allograft prosthetic composites or segmental replacement prostheses should be considered. PREOPERATIVE PREPARATION Accurate preoperative assessment and classification of bone loss is important to ensure that appro- priate augments or bone graft materials are available. However, owing to the potential for iatrogenic bone loss during component removal, the final classification of the bone defects must be based on the intraoperative findings after prosthesis removal and debridement. Therefore, in revision TKA, the surgeon must be prepared for several contingencies. Although not definitive, preoperative studies can provide helpful information about the type of defects that may be encountered intraoperatively. ●● Knee radiographs are low cost, but may fail to allow accurate assessment of the number and size of lesions, especially in the setting of osteolysis. 20,21 ●● Computed tomography (CT) is a more sensitive tool. In a study comparing radiographs to mul- tidetector CT, radiographs only identified 17% of the osteolytic lesions identified on CT scans. 20 ●● Metal artifact reduction suppression (MARS) magnetic resonance imaging (MRI) also appears to provide superior data to radiographs for evaluating osteolysis. 21 However, this capability may not be routinely available in all centers.

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PART IV Revision Total Knee Arthroplasty Therefore, although radiographs remain an important tool for evaluating limb alignment and component positioning in the coronal and sagittal planes, additional studies should be considered for evaluating bone loss, especially when osteolysis is suspected. Evaluation of radiographs and CT or MRI scans preoperatively is especially important if revision surgery is performed in centers where a complete array of porous metaphyseal cones and revision knee prostheses are not immediately available. This allows the surgeon to procure the prosthetic and augment options that may be required. TECHNIQUE In this section, we address in a stepwise manner the use of both tantalum and 3D printed titanium cons for managing AORI type II and III bone defects. Evaluation of Bone Loss ●● After obtaining adequate surgical exposure, the original components are removed. ●● Loose cement and bone is debrided. ●● Classification of femoral and tibial bone loss is performed according to the previously described AORI system. ●● A tentative reconstructive plan is formulated. ●● The tibial surface is freshened with a saw to create a flat surface. ●● The femoral and tibial canals must be opened up and reamed to size the appropriate stem extensions. Preparation for Tantalum Cones ●● In some cases, only a tibial or femoral cone is required. However, when both the femur and tibia have large bone defects that require reconstruction, start with reconstruction of the tibia. ●● A variety of full femoral and tibial tantalum cones, as well as asymmetric stepped tibial designs, are available. ●● A trial augment is used to size the defect. The trial augment that best fits the bone defect and produces the optimal peripheral contact with the remaining host bone is selected. ●● In most cases, the bone defect does not exactly match one of the available sizes. As such, a high-speed burr can be used to contour the host bone or augment itself. New metaphyseal broaches that aid in metaphyseal preparation, especially with smaller, contained defects, are also now available. ●● Once the tibial trial has a good press fit with maximal peripheral contact, the real cone can be selected and impacted in place. ●● The femur can be prepared in a similar manner if required. Preparation for 3D Printed Titanium Cones ●● Similar to tantalum cones, we prefer to reconstruct the tibia first. ●● A variety of symmetric and lobe-shaped 3D printed titanium tibial cones are designed to be used in type I through III bone defect. ●● Symmetric cones are used in type I and IIA bone defects, whereas lobe-shaped cones are designed to be used in type IIB and III bone defects. ●● The tibial cut is freshened either with an intramedullary alignment guide or freehand. ●● An appropriately sized tibial component is selected, as well as stem and metal augments if needed. It is our preference to utilize a mid-length cemented stem. ●● The rotation of the tibial component is established in line with the tibial crest, and corresponding keel and stem preparation is completed. ●● Either a reamer or stem trial (Figure 21-10) is then placed in the intramedullary canal after the canal is reamed to a diameter where the reamer is stable within the canal. ●● A central symmetric reamer is then utilized to a depth that corresponds to the size of the 3D printed titanium cone (Figure 21-11). ●● The trial (Figure 21-12A), and real 3D printed titanium tibial cone (Figure 21-12B), is then inserted with an impactor. The score mark is aligned with the tibial crest. ●● The femoral cones are based on a bilobed design that allows the lobes to bottom out at the junction of the metaphysis and diaphysis (Figure 21-13). This prevents longitudinal fractures of the femur.

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FIGURE 21-10. An intramedullary reamer that is stable within the tibial canal is impacted in preparation for the central symmetric cone reamer.

FIGURE 21-11. The central symmetric cone reamer is inserted to a specific depth that corresponds to the size of the three-dimensional printed titanium cone.

●● Preparation of the femoral cone includes a central symmetric that is placed to a certain depth that corresponds to the size of the femoral cone (Figure 21-14). ●● Next, an intramedullary device is placed in the femur at the corresponding depth and in the ap- propriate amount of external rotation (Figure 21-15). This allows for smaller side reamers to mill out the bone for the bilobe design (Figure 21-16).

FIGURE 21-12. A, The trial cone is impacted into the milled bone, ensuring the score mark is in line with the tibial crest for rotation. B, The real 3D printed titanium tibial cone is similarly impacted. A B

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FIGURE 21-13. The 3D printed titanium femoral cones are bilobed in design to ensure they bottom out, preventing longitudinal fractures of the femur.

FIGURE 21-14. A central symmetric femoral reamer is inserted to a specific depth that corresponds to the size of the three-dimensional printed titanium cone.

Restoration of Flexion and Extension Gaps Prosthesis sizing and positioning is used to recreate balanced flexion and extension gaps. At this stage, appropriate component rotation and alignment must be set; and component sizes, stem extensions, and conventional modular augments are selected and assembled. In most cases where metaphyseal cones are used, standard metal block augments are also required to address distal or posterior femoral bone loss, especially if isolated to one condyle.

FIGURE 21-15. An intramedullary device is placed in the femur at the corresponding depth, and in the appropriate amount of external rotation, to prepare for the smaller side reamers.

FIGURE 21-16. The smaller side reamers are used to mill out the bone for the bilobe design of the femoral cone.

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Prosthesis Selection ●● Beginning on the tibial side, the trial component, sized earlier in the case, that adequately covers the proximal surface is selected and the appropriate rotation set. ●● The appropriate diameter stem extension, sized earlier in the case, is selected and attached to the trial. ●● The trial component with the appropriate diameter and length stem extension is then impacted through the real metaphyseal cone (Figure 21-17). ●● Axial alignment is then verified with a drop rod and adjustments are made as required. ●● Once alignment has been optimized, the extent of any remaining bone defects is assessed and block or wedge augments are selected. The trial is removed, the augments attached and then reimpacted and checked. ●● Preparation of the femur begins by identifying the surgical transepicondylar (TEA) axis. ●● The femoral component size and stem are then selected. As with the tibia, long diaphyseal engaging stem trials are used initially to optimize alignment. ●● The box cut is then performed by inserting the jig attached to the previously determined stem extension. Rotation is set along the surgical TEA, the jig pinned in place, and the cut performed. ●● The trial femoral component is assembled with distal augments to set the preliminary distal joint line approximately 25 to 30 mm distal to the epicondyles. It is impacted through the real femoral cone that has been inserted, and the distal and posterior bone gaps are evaluated (Figure 21-18). ●● The trial is removed and standard augments distally and posteriorly are optimized. ●● A tibial polyethylene trial that tensions the flexion gap is then inserted. ●● The knee is then extended and the extension gap is evaluated. ●● If the knee has a residual flexion contracture, the distal augments are reduced and the femoral component moved more proximally. Alternatively, the next bigger femoral component can be selected to better fill the flexion gap, if it can be accommodated by the medial–lateral dimension of the femur. This will allow a thinner polyethylene insert to be used. ●● If the knee hyperextends, additional distal augments are added onto the distal femur which better fills the extension gap. ●● When either the medial or lateral collateral ligament is nonfunctional, or in cases where a gross mis- match exists between the flexion and extension gap that cannot be managed by adjusting the position or size of the femoral component, a more constrained condylar prosthesis or hinged device must be used.

FIGURE 21-17. The trial tibial component with 5-mm medial and lateral augments and a short cemented stem trial is passed through the already placed real tibial cone.

FIGURE 21-18. The trial femoral component with appropriate augments and a mid-length cemented stem trial is passed through the already placed real femoral cone.

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PART IV Revision Total Knee Arthroplasty ●● The trial components are removed and the final stem selections are determined depending on whether cemented or uncemented stems are to be used. The trials with the final stem trials are reinserted to ensure that component alignment and position is not affected. ●● Intraoperative radiographs may be obtained to verify appropriate sizing and alignment of the components before insertion of the final components. Insertion of the Femoral and Tibial Components ●● The real modular components are assembled with the appropriate stem extensions and standard metal augments. ●● With the new 3D printed titanium cones, bone graft is not needed to fill these voids because an intramedullary milling system is utilized. However, any remaining small gaps between the tantalum cones that have been previously impacted and the host are filled with either morcellized cancel- lous bone graft or demineralized bone matrix putty. This minimizes cement intrusion between the augment and host bone and, furthermore, may promote bone ingrowth around the entire periphery of the tantalum cone. ●● Finally, the real prosthetic components are cemented through the metaphyseal cones (Figure 21-19A and B). PEARLS AND PITFALLS ●● When preparing conical femoral or tibial bone defects with the high-speed burr to accept tantalum cone trials, unnecessary bone removal should be avoided. However, even with the plastic trial augments, rigorous impaction can produce a split in the bone. Therefore, the preparation process is a precision technique and the trials should be used frequently to assess fit. This fracture risk, in the experience of the authors, has been mitigated with the intramedullary reaming and milling system of the 3D printed titanium cones. ●● In most cases, the authors avoid the use of complete or partial wedges because of the shear stress on the interface between the augment and the cement mantle. Instead, we recommend converting a wedge-shaped defect to a step configuration to allow use of a block augment. This preparation can be performed either freehand, using the trial tray and block to mark the bone that must be removed, or with the use of an intramedullary cutting jig.

FIGURE 21-19. Final (A) anteroposterior and (B) lateral radiographs of a revision total knee arthroplasty with femoral and tibial three-dimensional printed titanium cones. A B

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●● Although the debate regarding cemented and uncemented stem extensions in revision TKA per- sists, we favor the use of cemented stem extensions in most circumstances requiring the use of metaphyseal cones. 22-24 However, unless preoperative radiographs demonstrate a significant extra articular deformity, long stem trials (180-220 mm combined length) help optimize alignment by engaging the diaphysis. In most cases, it is not necessary to cement a stem of this length; and, therefore, before opening the real components, selection of a shorter, wider stem is appropriate. A stem that gives a combined length of 80 to 100 mm is usually adequate. ●● When cementing both femoral and tibial stems, it is preferable to cement the tibia first. To prevent malrotation during the cementing process, the tibial cement should be allowed to cure before proceeding with cementation of the femoral component. Use of a canal plug, cement gun, and pressurization for the tibia and femur helps achieve an optimal cement mantle. Antibiotic-impreg- nated cement is used in every revision case. POSTOPERATIVE MANAGEMENT When a stable construct has been created with the use of a metaphyseal cone, in conjunction with a cemented stem extension and cement about the core implant, the patient is allowed to weight-bear as tolerated on the operative extremity. Most patients require the use of a walker or crutches for ap- proximately 3 weeks and may then progress to a cane. The authors do not currently use continuous passive motion machines with any revision TKA, but do allow the majority of patients to participate in range of motion exercises in physical therapy. A brace or knee immobilizer is used when ambulating if a tubercle osteotomy was performed. COMPLICATIONS In revision TKAs, use of metaphyseal cones may be associated with all the usual complications that can occur in these difficult cases. These problems include mechanical failure of the prosthesis, insta- bility, infection, and aseptic loosening. Specific concerns regarding the metaphyseal cones include the potential for failure because of inadequate bone ingrowth or failure due to mechanical overload when the cones are used in uncontained defects where there is no potential for load sharing with surrounding host bone. At midterm follow-up, a deep periprosthetic infection rate of about 11% has been reported. 12,13 RESULTS Successful midterm results following revision total knee replacement have been reported using con- ventional block and wedge augments in cases with AORI type II defects. 25,26 In addition, growing data for tantalum cones has demonstrated reliable and rapid osseointegration with stable long-term fixation. 11-13,27 In an early report (24-38 months) on 15 tantalum tibial cones used in AORI type IIB or III bone defects, Meneghini et al 13 found that all tibial cones demonstrated bone ingrowth without evidence of loosening or migration. A midterm follow-up study completed by Kamath et al 12 at a mean of 70 months found a revision-free survival of the tibial cone component to be greater than 95%. Howard et al 11 also published an early report on 24 tantalum femoral cones used in type IIB or III bone defects. At a mean of 33 months, all reviewed femoral cones demonstrated osseointegration. In 2012, Lachiewicz et al 27 retrospectively reviewed 33 tantalum metaphyseal cones in a multicenter study (9 femoral and 24 tibial). At a mean of 40 months, the authors found that 26 of the 27 reviewed cones demonstrated osseointegration. Data is currently not available on the 3D printed titanium cones given their recent release. 1. Kelly MA, Clarke HD. Long-term results of posterior cruciate-substituting total knee arthroplasty. Clin Orthop Relat Res . 2002;(404):51-57. 2. Sierra RJ, Cooney WP IV, Pagnano MW, Trousdale RT, Rand JA. Reoperations after 3200 revision TKAs: rates, etiology, and lessons learned. Clin Orthop Relat Res . 2004;(425):200-206. 3. Bozic KJ, Kurtz SM, Lau E, et al. The epidemiology of revision total knee arthroplasty in the United States. Clin Orthop Relat Res . 2010;468(1):45-51. 4. Fehring TK, Odum S, Griffin WL, Mason JB, Nadaud M. Early failures in total knee arthroplasty. Clin Orthop Relat Res . 2001;(392):315-318. REFERENCES

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5. Sharkey PF, HozackWJ, Rothman RH, Shastri S, Jacoby SM. Insall Award paper. Why are total knee arthroplasties failing today? Clin Orthop Relat Res . 2002;(404):7-13. 6. Abdel MP, Pulido L, Severson EP, Hanssen AD. Stepwise surgical correction of instability in flexion after total knee replacement. Bone Joint J . 2014;96-B(12):1644-1648. 7. Parratte S, Abdel MP, Lunebourg A, et al. Revision total knee arthroplasty: the end of the allograft era? Eur J Orthop Surg Traumatol . 2015;25(4):621-622. 8. Engh GA, Ammeen DJ. Classification and preoperative radiographic evaluation: knee. Orthop Clin North Am . 1998;29(2):205-217. 9. Mulhall KJ, Ghomrawi HM, Engh GA, Clark CR, Lotke P, Saleh KJ. Radiographic prediction of intraoperative bone loss in knee arthroplasty revision. Clin Orthop Relat Res . 2006;446:51-58. 10. Lucey SD, Scuderi GR, Kelly MA, Insall JN. A practical approach to dealing with bone loss in revision total knee arthro- plasty. Orthopedics . 2000;23(10):1036-1041. 11. Howard JL, Kudera J, Lewallen DG, Hanssen AD. Early results of the use of tantalum femoral cones for revision total knee arthroplasty. J Bone Joint Surg Am . 2011;93(5):478-484. 12. 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;97(3):216-223. 13. Meneghini RM, Lewallen DG, Hanssen AD. Use of porous tantalum metaphyseal cones for severe tibial bone loss during revision total knee replacement. J Bone Joint Surg Am . 2008;90(1):78-84. 14. Bobyn JD, Poggie RA, Krygier JJ, et al. Clinical validation of a structural porous tantalum biomaterial for adult recon- struction. J Bone Joint Surg Am . 2004;86-A(suppl 2):123-129. 15. Meneghini RM, Ford KS, McCollough CH, HanssenAD, Lewallen DG. Bone remodeling around porous metal cementless acetabular components. J Arthroplasty . 2010;25(5):741-747. 16. Radnay CS, Scuderi GR. Management of bone loss: augments, cones, offset stems. Clin Orthop Relat Res . 2006;446:83-92. 17. Backstein D, Safir O, Gross A. Management of bone loss: structural grafts in revision total knee arthroplasty. Clin Orthop Relat Res . 2006;446:104-112. 18. Engh GA, Herzwurm PJ, Parks NL. Treatment of major defects of bone with bulk allografts and stemmed components during total knee arthroplasty. J Bone Joint Surg Am . 1997;79(7):1030-1039. 19. Haddad FS, Spangehl MJ, Masri BA, Garbuz DS, Duncan CP. Circumferential allograft replacement of the proximal femur. A critical analysis. Clin Orthop Relat Res . 2000(371):98-107. 20. Reish TG, Clarke HD, Scuderi GR, Math KR, Scott WN. Use of multi-detector computed tomography for the detection of periprosthetic osteolysis in total knee arthroplasty. J Knee Surg . 2006;19(4):259-264. 21. Vessely MB, Frick MA, Oakes D, Wenger DE, Berry DJ. Magnetic resonance imaging with metal suppression for evaluation of periprosthetic osteolysis after total knee arthroplasty. J Arthroplasty . 2006;21(6):826-831. 22. Fehring TK, Odum S, Olekson C, Griffin WL, Mason JB, McCoy TH. Stem fixation in revision total knee arthroplasty: a comparative analysis. Clin Orthop Relat Res . 2003;(416):217-224. 23. Haas SB, Insall JN, Montgomery W III, Windsor RE. Revision total knee arthroplasty with use of modular components with stems inserted without cement. J Bone Joint Surg Am . 1995;77(11):1700-1707. 24. Shannon BD, Klassen JF, Rand JA, Berry DJ, Trousdale RT. Revision total knee arthroplasty with cemented components and uncemented intramedullary stems. J Arthroplasty . 2003;18(7 suppl 1):27-32. 25. Pagnano MW, Trousdale RT, Rand JA. Tibial wedge augmentation for bone deficiency in total knee arthroplasty. A followup study. Clin Orthop Relat Res . 1995;(321):151-155. 26. Patel JV, Masonis JL, Guerin J, Bourne RB, Rorabeck CH. The fate of augments to treat type-2 bone defects in revision knee arthroplasty. J Bone Joint Surg Br . 2004;86(2):195-199. 27. Lachiewicz PF, Bolognesi MP, Henderson RA, Soileau ES, Vail TP. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res . 2012;470(1):199-204.