Orthopaedic Research Institute Research Articles

Tibial component with and without stem extension in a trabecular metal cone construct

PurposeThe purpose of this study was to investigate stability and strain distribution of a tibial plateau reconstruction with a trabecular metal cone while the tibial component is implanted with and without a stem, and whether prosthetic stability was influenced by bone mineral density. Trabecular metal cones are designed to fill up major bone defects in total knee arthroplasty. Tibial components can be implanted in combination with a stem, but it is unclear whether this is necessary after reconstruction with a trabecular metal cone. Implanting a stem can give extra stability, but may have negative side effects.MethodsTibial revision arthroplasties with trabecular metal cones were performed after reconstruction of a 2B bone defect according to the Anderson Orthopedic Research Institute classification. Components were implanted in seven pairs of cadaveric tibiae; one tibia of each pair was implanted with stem and the other without. All specimens were loaded to one bodyweight alternating between the medial and lateral tibial component. Implant-bone micro-motions, bone strains, bone mineral density and correlations were measured and/or calculated.ResultsTibial components without a stem showed only more varus tilt [difference in median 0.14° (P < 0.05)], but this was not considered clinically relevant. Strain distribution did not differ. Bone mineral density only had an effect on the anterior/posterior tilt [ρ: −0.72 (P < 0.01)].ConclusionTibial components, with or without a stem, which are implanted after reconstruction of major bone defects using trabecular metal cones produce very similar biomechanical conditions in terms of stability and strain distribution. If in vivo studies confirm that a stem extension is not mandatory, orthopaedic surgeons can decide not to implant a stem.Level of evidenceII.

CORR Insights®: No Difference between Trabecular Metal Cones and Femoral Head Allograft in Revision TKA: Minimum 5-year Followup.

Where Are We Now? A substantial increase in the volume of primary TKA in conjunction with increases in patient lifespan has resulted in an increased need for revision TKA. An analysis of revision TKA volume in Medicare beneficiaries showed revision volume increased 105.9% from 1991 to 2010 [2]. There is some degree of bone loss associated with each revision procedure because of initial bone resection at the time of primary TKA, osteolysis from wear debris or other causes, and bone loss associated with component removal. Minor bone defects (Anderson Orthopaedic Research Institute [AORI] Types 1 and 2 [4]) are usually managed simply with cancellous cavitary bone grafting, bone cement with or without screws, or peripheral metal augments. Larger defects (AORI Types 2B and 3 [2]) make it more difficult to achieve durable implant fixation because of the loss of bone support. Historically, structural allografts have been used to reconstruct these defects, with 91% demonstrating satisfactory function in a report of 46 subjects at a mean followup duration of 97 months [5], although problems with nonunion, late graft collapse, and the potential for disease transmission have been identified [1]. These problems have resulted in the development of metaphyseal sleeves and trabecular metal cones to enhance long-term fixation [3, 6, 7]. Short-term results with these devices have been favorable but have analyzed only a single method of defect management rather than comparative studies of multiple techniques. The current report is the first to compare different techniques (structural allograft versus trabecular metal cones). The authors observed no differences in pain relief, function, or repeat revision TKA rates between patients treated with the two approaches. Where Do We Need To Go? Numerous questions remain regarding management of large bone defects in revision TKA. Will the findings of this small study, which includes a combined total of only 45 patients (30 femoral had allografts versus 15 trabecular metal cones), be confirmed in larger and more diverse revision TKA populations? Will the clinical results remain similar with longer followup duration since some reports of use of structural allografts have demonstrated failure due to graft resorption at followup intervals longer than 10 years? Should a revision TKA utilizing either of these techniques fail, what are the results of a repeat revision procedure? Does one technique result in a simpler or more complex re-revision procedure? For example, will use of a structural allograft provide restored bone stock for future revisions? Should infection occur, does an incorporated structural allograft or trabecular metal cone require total removal? How difficult is removal of a well-fixed trabecular metal cone and what are the technical tips for safe removal? Does removal of a well-fixed trabecular metal cone result in a substantial amount of retained third-body metallic debris particulate that may accelerate polyethylene wear in repeat revision procedures? Allografts can be sterilized using multiple methods; to what degree are there clinically important tradeoffs among these approaches? Will irradiation of frozen grafts to reduce disease transmission result in unacceptable reductions in mechanical strength compared to fresh-frozen allografts? Lastly, is use of modular stem extensions necessary for all revision TKA operations utilizing one or both of the techniques studied in the current evaluation? If so, how long should the stems be? Are short cemented stem extensions adequate or will longer stem extensions engaging diaphyseal bone prove more durable? How Do We Get There? Randomized comparative analyses of the two techniques with followup duration of a minimum of 10 years are necessary. While difficult to accomplish, a multicenter effort would likely be required to create a case volume adequate to draw firm conclusions. In such a study, it would be beneficial to include a third technique of using porous coated metaphyseal sleeves [3] as these are commonly used for Types 2B and 3 [2] bone defects. All Type 2B and 3 bone defects [4] are not the same. Some have more loss of cortical rim support than others. The amount of bone loss using the AORI bone defect classification [4] is variable. A more-critical evaluation of defect size and shape is necessary to better discern whether structural bone allografts or trabecular metal cones are superior in the management of specific bone defect geometries. Of course, bone defects also occur on the femur; are results different when dealing with femoral versus tibial defects? For example, Type 3 femoral defects have the potential for loss of collateral ligament support; does this influence which approach might be better? These questions and others call for larger, longer-term, randomized and likely multicenter studies. To accomplish this, economic support from national organizations such as the Knee Society and the American Association of Hip and Knee Surgeons would be helpful as their memberships contain leaders in TKA with competent databases necessary to provide the required meaningful data.

No Difference Between Trabecular Metal Cones and Femoral Head Allografts in Revision TKA: Minimum 5-year Followup.

Encouraging clinical results have been reported with the use of femoral head structural allografts and, more recently, trabecular metal cones for the management of large structural defects of the femur and tibia during revision total knee arthroplasty (TKA). However, to our knowledge, there are no published studies comparing these two techniques. Compared with bulk allografts, do trabecular metal cones result in (1) better validated outcomes scores; (2) a lower risk of loosening or revision at 5 years; and (3) fewer surgical complications when used for the management of bone loss in revision TKA? Between 2002 and 2008, three surgeons performed 450 TKA revisions, 45 (10%) of which were performed using augmentation of host bone; in those, femoral head allograft was used in 30 (75%) and trabecular metal cones in 15 (25%). From 2002 to 2007, femoral head allografts were used in all patients (28 patients); from 2007 to 2008, trabecular metal augments were used in all patients. There was a period of 1 year (16 knees) in which there was some overlap; during that time, femoral head structural allografts were used in cases in which we were unable to fit the defect or achieve adequate stability with trabecular metal cones. Followup was at a mean of 9 years (range, 5-12 years). No patients were lost to followup. Knee function and quality of life were assessed using the Oxford Knee Score, WOMAC, SF-12, and the UCLA activity score. Radiographs were assessed for signs of loosening. Surgical complications included superficial or deep infections, iatrogenic fractures, symptomatic deep venous thromboses or pulmonary emboli, and blood loss requiring transfusion; these were obtained from our database and from review of patients' charts. The mean Oxford Knee Score in the allograft and trabecular metal cone groups was 91 (SD 10) and 91 (SD 14), respectively (95% confidence interval [CI], 88-94; p = 0.29). Mean WOMAC scores were 94 (SD 10) and 92 (SD 14), respectively (95% CI, 80-105; p = 0.52) and mean UCLA scores were 6 (SD 1.2) and 6 (SD 1.5), respectively (95% CI, 4-8; p = 0.49). Five- and 10-year survivorship of the allografts was 93% (95% CI, 77-98) and 93% (95% CI, 77-99), respectively. Survivorship at a mean of 5 years in the trabecular metal cones group was 91% (95% CI, 56-98). With the numbers available, there were no differences between the groups in terms of the frequency of surgical complications (3% [one of 30] versus 7% [one of 15]; odds ratio, 0.5; p = 0.632). With the numbers available, we found no difference in pain, function, or repeat revision when comparing femoral head allografts and trabecular metal cones for severe bone defects during revision TKA. However, we used allografts for the larger bone defects. Based on these results, we believe that femoral head allografts and trabecular metal cones can both be used for the management of Anderson Orthopaedic Research Institute Types 2 and 3 defects. Future multicenter studies are required with larger numbers, cost analyses, and a longer duration of followup. Level III, therapeutic study.

Radiological Stability after Revision of Infected Total Knee Arthroplasty Using Modular Metal Augments.

PurposeTo evaluate the radiological stability according to the number of modular augments after revision of infected total knee arthroplasty (TKA).Materials and MethodsBetween February 2006 and September 2013, 37 patients (39 knees) followed ≥2 years after revision of infected TKA using modular metal augments for bone defects were reviewed retrospectively. We divided the patients into 3 groups according to the number of augments into group A (≤2 augments, 14 knees), group B (3–4 augments, 18 knees), and group C (5≥ augments, 7 knees) and evaluated the width of radiolucent zones around the implant at the last follow-up.ResultsThere were 3 Anderson Orthopedic Research Institute type I, 33 type II, and 3 type III bone defects. The mean number of radiolucent zones of group A was 3 and the sum of width averaged 4.4 mm. In group B, the values were 4.8 and 6.2 mm, respectively. In group C, the values were 8.1 and 12.9 mm, respectively. The differences between the three groups were statistically significant.ConclusionsIn revision TKA with modular metal augmentation caused by infected TKA, increased modularity can result in radiological instability.

Porous Tantalum Metaphyseal Cones for Severe Tibial Bone Loss in Revision Knee Arthroplasty

Severe metaphyseal and meta-diaphyseal bone loss poses important challenges in revision total knee arthroplasty. The best strategy for addressing massive tibial bone loss has not been determined. The purpose of this study was to assess the intermediate-term clinical and radiographic results of porous tibial cone implantation. Sixty-six porous tantalum tibial cones (sixty-three patients) were reviewed at a mean follow-up time of seventy months (range, sixty to 106 months). According to the Anderson Orthopaedic Research Institute bone defect classification, twenty-four knees had a Type-3 defect, twenty-five knees had a Type-2B defect, and seventeen knees had a Type-2A defect. The mean age at the time of the index revision was sixty-seven years (range, forty-one to eighty-three years), and 57% of patients were female. The mean American Society of Anesthesiologists Physical Status was 2.4 (range, 2 to 3), and the mean body mass index was 33 kg/m(2) (range, 25 to 53 kg/m(2)). Fifteen patients (24%) were on immunosuppressant medications, and eight patients (13%) were current smokers. The patients underwent a mean number of 3.4 prior knee surgical procedures (range, one to twenty procedures), and 49% of patients (thirty-one patients) had a history of periprosthetic infection. The mean Knee Society Scores improved significantly from 55 points preoperatively (range, 4 to 97 points) to 80 points (range, 28 to 100 points) at the time of the latest follow-up (p < 0.0001). One patient had progressive radiolucencies about the tibial stem and cone on radiographs. One patient had complete radiolucencies about the tibial cone, concerning for fibrous ingrowth. Three other cones were revised: one for infection, one for aseptic loosening, and one for periprosthetic fracture. Revision-free survival of the tibial cone component was >95% at the time of the latest follow-up. Porous tantalum tibial cones offer a promising management option for severe tibial bone loss. At the intermediate-term follow-up (five to nine years), porous tantalum tibial cones had durable clinical results and radiographic fixation. The biologic ingrowth of these implants offers the potential for successful long-term structural support in complex knee reconstruction.

Porous metal metaphyseal cones for severe bone loss: when only metal will do.

Metaphyseal bone loss is common with revision total knee replacement (RTKR). Using the Anderson Orthopaedic Research Institute (AORI) classification, type 2-B and type 3 defects usually require large metal blocks, bulk structural allograft or highly porous metal cones. Tibial and femoral trabecular metal metaphyseal cones are a unique solution for large bone defects. These cones substitute for bone loss, improve metaphyseal fixation, help correct malalignment, restore the joint line and may permit use of a shorter stem. The technique for insertion involves sculpturing of the remaining bone with a high speed burr and rasp, followed by press-fit of the cone into the metaphysis. The fixation and osteoconductive properties of the porous cone outer surface allow ingrowth and encourage long-term biological fixation. The revision knee component is then cemented into the porous cone inner surface, which provides superior fixation compared with cementing into native but deficient metaphyseal bone. The advantages of the cone compared with allograft include: technical ease, biological fixation, no resorption, and possibly a lower risk of infection. The disadvantages include: difficult extraction and relatively short-term follow-up. Several studies using cones report promising short-term results for the reconstruction of large bone defects in RTKR.

Revision total knee arthroplasty using metaphyseal sleeves at short-term follow-up.

The treatment of bone loss in revision total knee arthroplasty (TKA) has involved using revision implants in association with cement, augments, particulate, and structural allograft. Newer metaphyseal augments were introduced to allow for metaphyseal fixation of the prosthesis while managing significant bone loss. The purpose of the current study was to evaluate the outcome of revision TKA using metaphyseal sleeves. The authors prospectively followed 96 knees that underwent revision TKA with metaphyseal sleeves. Eighty-three knees met the minimum 2-year criteria for follow-up. Thirty-six sleeves were used in femoral revisions and 83 sleeves were used in tibial revisions. The defects were classified according to the Anderson Orthopaedic Research Institute classification. Femoral defects were classified as type I in 4 knees, type IIb in 25 knees, and type III in 7 knees. Tibial defects were classified as type I in 9 knees, type IIa in 1 knee, type IIb in 68 knees, and type III in 5 knees. The patients were followed for an average of 2.4 years (range, 2.0-3.7 years). Mean Knee Society function score improved from 47.9 to 61.1 points. Mean Short Form 36 physical score improved from 43.3 to 56.3 points. Mean Western Ontario and McMaster Universities Arthritis Index improved from 55.3 to 25.9 points. None of the implants demonstrated progressive radiolucent lines around the metaphyseal sleeves. At final follow-up, only 2 (2.7%) tibial components required revision for aseptic loosening. At short-term follow-up, revision TKA with metaphyseal sleeves provided reliable fixation. This is especially encouraging given the severe nature of bone loss in the majority of patients in whom a metaphyseal sleeve was used. Long-term follow-up is needed to demonstrate the true effectiveness of these devices.

A 30-mm cemented stem extension provides adequate fixation of the tibial component in revision knee arthroplasty.

The optimal stem length and method of fixation for the tibial component in revision knee arthroplasty remains controversial. The use of a cemented 30-mm stem extension provides certain advantages compared with other methods of fixation, but there are few published results. We therefore asked (1) what is the survivorship (with respect to loosening and repeat revision) of tibial component revisions when a 30-mm stem extension is used; and (2) what factors are associated with the appearance tibial radiolucent lines? We retrospectively reviewed 54 patients (58 knees) with fixation of the revision tibial component with a 30-mm cemented stem extension; another seven patients died and 11 patients had these components but were lost to followup. These implants represented 74% of our tibial revisions during the period in question (76 of 103); general indications for using them were need for a varus-valgus constrained liner or proximal bone loss requiring a metaphyseal cone or metal augment with an intact diaphysis. The Anderson Orthopaedic Research Institute tibial defect was Grade 1 in 37, 2A in 10, 2B in four, and Grade 3 in seven knees; constrained liners were used in 34% (20 of 58 knees). Patients were evaluated and followed for a mean of 5 years (range, 2-12 years). There were no revisions for tibial component loosening. One patient had débridement and liner exchange for late infection. Radiolucent lines were seen in 25 tibial components but only eight knees had radiolucencies in four or more zones. There were significantly fewer radiolucencies in revisions that used metaphyseal cones (20 in eight knees with cones compared with 53 in 17 without, p=0.013). The cemented 30-mm tibial stem extension provided excellent fixation in knee revision arthroplasty, even with metaphyseal defects and constrained polyethylene liners, although this series included relatively few patients with severe tibial defects. Longer followup is required for patients with radiolucent lines to confirm that the fixation will remain durable. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Use of Stepped Porous Titanium Metaphyseal Sleeves for Tibial Defects in Revision Total Knee Arthroplasty: Short Term Results

Stepped porous titanium metaphyseal sleeves may provide an option for enhanced fixation in managing challenging tibial defects in revision total knee arthroplasty (TKA). We retrospectively reviewed data on 51 patients who underwent revision TKA utilizing a metaphyseal sleeve for Anderson Orthopaedic Research Institute (AORI) Type II and III tibial defects between June 2007 and July 2011. Of these 51 patients, 36 patients had complete clinical and radiographic data. At final follow-up (mean: 38months) significant improvements in knee range of motion and Knee Society scores were observed postoperatively (P<0.001). Four revision procedures were necessary, but none for aseptic implant fixation failure. Radiographic review at final follow-up revealed stable, osteointegrated components without component migration or clinically significant osteolysis. Metaphyseal sleeve use in the management of moderate to severe tibial defects in revision TKA resulted in satisfactory clinical outcomes and is a versatile option for achieving stable fixation.

Failure Analysis of Knee Arthrodesis With the Wichita Fusion Nail

Arthrodesis is a salvage procedure for failed total knee arthroplasty with the intent to create a stable, pain-free limb on which to ambulate or transfer. For many patients, the alternative to arthrodesis may be an above-knee amputation. Available techniques for knee arthrodesis include compression plating, external fixators, and intramedullary fixation. The purpose of this study was to report the knee fusion rate of consecutive patients at 1 institution using an intramedullary fusion nail and to identify patient risk factors for fusion failure. Between November 1998 and November 2008, twenty-eight patients undergoing knee arthrodesis with an average follow-up of 18 months (range, 3-64 months) were retrospectively studied. Demographic information, presence of fusion, clinical function, pain level, and bone defect data were collected and analyzed. Eighty-two percent (23/28) of patients had radiographic evidence of successful fusion with an average time to fusion of 21 weeks (range, 10-58 weeks). When examining patient variables that could correlate with fusion rates, patients with an Anderson Orthopaedic Research Institute type 3 femoral or type 3 tibial defect had a statistically significant lower fusion rate. The intramedullary fusion nail is an effective device for knee arthrodesis that offers ease of insertion through the knee wound with the advantages of initial bone compression and rigid fixation. Although the use of intramedullary fusion nails leads to a high fusion rate, significant bone deficiency limits successful fusion.

Tantalum cones for major osteolysis in revision knee replacement

We report the results of revision total knee replacement (TKR) in 26 patients with major metaphyseal osteolytic defects using 29 trabecular metal cones in conjunction with a rotating hinged total knee prosthesis. The osteolytic defects were types II and III (A or B) according to the Anderson Orthopaedic Research Institute (AORI) classification. The mean age of the patients was 72 years (62 to 84) and there were 15 men and 11 women. In this series patients had undergone a mean of 2.34 previous total knee arthroplasties. The main objective was to restore anatomy along with stability and function of the knee joint to allow immediate full weight-bearing and active knee movement. Outcomes were measured using Knee Society scores, Oxford knee scores, range of movement of the knee and serial radiographs. Patients were followed for a mean of 36 months (24 to 49). The mean Oxford knee clinical scores improved from 12.83 (10 to 15) to 35.20 (32 to 38) (p < 0.001) and mean American Knee Society scores improved from 33.24 (13 to 36) to 81.12 (78 to 86) (p < 0.001). No radiolucent lines suggestive of loosening were seen around the trabecular metal cones, and by one year all the radiographs showed good osteo-integration. There was no evidence of any collapse or implant migration. Our early results confirm the findings of others that trabecular metal cones offer a useful way of managing severe bone loss in revision TKR.

Are Cementless Stems More Durable Than Cemented Stems in Two-stage Revisions of Infected Total Knee Arthroplasties?

The routine use of stems in revision TKA improves survival rates by enhancing the stability of the prosthesis. The ideal method of stem fixation (cemented or uncemented) in two-stage reimplantation remains controversial. The purpose of this study was to answer the following questions: (1) Are rerevision rates for aseptic loosening comparable between cemented stems and uncemented stems in two-stage reimplantation? (2) Is the reinfection rate comparable between antibiotic-impregnated cemented stems and uncemented stems for two-stage reimplantation? (3) Are there any differences in Knee Society radiographic scores between stem techniques? A retrospective analysis was performed in all patients who underwent two-stage reimplantation between 1990 and 2010 at Anderson Orthopaedic Research Institute (AORI) and OrthoCarolina (OC). One hundred fourteen patients with 228 stems met the inclusion criteria. Of these 228 stems, 102 stems were cemented and 126 stems were uncemented. The indication for stem fixation was largely institution specific; AORI used cementless stems 92% (118) of the time, whereas OC used a cemented stem 92% (92) of the time. A 2-year minimum radiographic and clinical followup was required for inclusion into the study. Radiographic evaluations were performed using a modification of the Knee Society radiographic score. Rerevision rates for aseptic loosening were comparable with three cemented and three cementless stem constructs. The reinfection rate was also comparable between cemented and cementless stems (p = 0.86). Using post hoc analysis, 32% of cemented stems were radiographically classified as loose or closely observe (33 of 102) compared with 17% of the cementless stem group (21 of 126; p = 0.006). Patients with good bone quality had a significantly lower rate of radiographic loosening compared with patients with poor bone quality (p = 0.01). There was no significant correlation with radiographic loosening and level of constraint (p = 0.90) or use of articulating versus static antibiotic spacer (p = 0.06). In this retrospective study, cementless diaphyseal-engaging stems had a lower rate of radiographic failure than did cemented stems in two-stage reimplantation. Reinfection rates remain similar despite the absence of antibiotic cement in the cementless constructs. At this time we believe the use of hybrid, cementless diaphyseal-engaging stems should be considered as a possible option at the time of reimplantation.

Constraint choice in revision knee arthroplasty

Along with the increase in primary total knee arthroplasty, there has been an increase in the number of revisions. The aim of this study was to propose a selection algorithm for the knee revision constraint according to the state of ligaments and to the bone defects Anderson Orthopaedic Research Institute Classification [AORI] classification. The hypothesis was that this algorithm would facilitate the appropriate choice of prosthesis constraint, thus providing stable components and a good long-term survivorship of the knee revisions. Sixty consecutive revision knee arthroplasties in 57 patients were prospectively evaluated. Prostheses implanted at revision included postero-stabilised, condylar constrained and rotating hinged, relative to the state of the ligaments and of the bone loss around the knee. The median follow-up was nine years (range, 4-12). The median IKS knee and function scores and HSS score were 41 (15-62), 21.5 (12-43) and 34 (23-65) points, respectively, before the operation, and 81 (48-97), 79 (56-92) and 83.5 (62-98) points (p < 0.001) at the latest follow-up evaluation. The median ROM increased from 74° (29-110°) preoperatively to 121° (98-132°) (p < 0.01) at the final follow-up. Re-revision was necessary in five (8.3%) patients. A selection algorithm for the revision implant constraint based on the state of ligaments and the bone loss AORI classification could provide stable knee reconstructions and long-term success of knee revisions.

Treatment of Large Bone Defects With Trabecular Metal Cones in Revision Total Knee Arthroplasty

The early term results of 29 cases of revision total knee arthroplasty using highly porous trabecular metal cone implants for femoral and tibial major bone deficit reconstruction (Anderson Orthopedic Research Institute classification type 2B and 3) have been prospectively analyzed. Indications for revision surgery included: aseptic loosening/wear, staged reimplantation after infection, as well as periprosthetic fracture. At an average follow-up of 33 months (range, 13-73 months) the mean Knee Society Score and functional score statistically improved. Radiological follow-up revealed no evidence of loosening or migration of the constructs. No evidence of complications was noted in correlation with the use of trabecular metal cones. This study supports evidence that trabecular metal cones are an efficient and effective option for dealing with significant bone deficits and obtaining stable biological fixation in revision total knee arthroplasty.

Reconstruction using femoral head allograft in revision total knee replacement

Structural allografts may be used to manage uncontained bone defects in revision total knee replacement (TKR). However, the availability of cadaver grafts is limited in some areas of Asia. The aim of this study was to evaluate the mid-term outcome of the use of femoral head allografts for the reconstruction of uncontained defects in revision TKR, focusing on complications related to the graft. We retrospectively reviewed 28 patients (30 TKRs) with Anderson Orthopaedic Research Institute (AORI) type 3 bone defects, who underwent revision using femoral head allografts and stemmed components. The mean number of femoral heads used was 1.7 (1 to 3). The allograft-host junctions were packed with cancellous autograft. At a mean follow-up of 76 months (38 to 136) the mean American Knee Society knee score improved from 37.2 (17 to 60) pre-operatively to 90 (83 to 100) (p < 0.001). The mean function score improved from 26.5 (0 to 50) pre-operatively to 81 (60 to 100) (p < 0.001). All the grafts healed to the host bone. The mean time to healing of the graft was 6.6 months (4 to 16). There have been no complications of collapse of the graft, nonunion, infection or implant loosening. No revision surgery was required. The use of femoral head allografts in conjunction with a stemmed component and autogenous bone graft in revision TKR in patients with uncontained bone defects resulted in a high rate of healing of the graft with minimal complications and a satisfactory outcome. Longer follow-up is needed to observe the evolution of the graft.

Tantalum Cones in Revision Total Knee Arthroplasty. A Promising Short-Term Result With 29 Cones in 21 Patients

Twenty-nine porous tantalum metaphyseal cones were implanted in 21 patients (14 women and 7 men) during revision TKA. The average age at the time of the procedure was 73.3years. Sixteen revisions were considered aseptic and 5 were reimplantations after sepsis. Eight patients had stemmed revision implants and thirteen primary designs. According to the Anderson Orthopaedic Research Institute bone defect classification, femoral defects were rated as F3 in 14 knees and F2B in 3 knees. Tibial defects were rated as T2A in 3 cases, T2B in 3 cases and T3 in 5 cases. A femoral cone was inserted in 10 patients, a double cone (femur and tibia) in 8, and a single tibial cone in 3. A rotating hinge knee prosthesis (RHK, Zimmer) was inserted in 10 patients and a constrained condylar prosthesis (LCCK, Zimmer) in 11 patients. The diaphysis was cemented in 9 cases and, in 11 cases, just the metaphysis. At an average follow up of 36months only one reconstruction was removed due to persistent infection. All metaphyseal cones showed evidence of stable osseointegration. According to the Knee Society Score the results were rated as excellent in 12 cases, good in 5 cases, fair in 3 and poor in 1 case. In the short term, porous tantalum metaphyseal cones provided structural support for large femoral and tibial defects. They also provided the environment for bone graft osseointegration, repair of femoral fractures and effective interdigitation of cement mantle into the trabecular metal cone.

Reconstruction of Complex Distal Femur and Proximal Tibia Defects Using Tantalum Cones

As the number of primary total knee arthroplasties increase, revision procedures with massive bone defects will also increase. Although multiple reconstructive options have been recommended, porous tantalum metaphyseal cones have the advantage of improved biological fixation because of their high porosity, interconnected pore space, and a modulus of elasticity 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 large contained or uncontained osseous defects that are typically categorized as Anderson Orthopaedic Research Institute type 2B or greater. 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 allows the surgeon to choose a size and position that best fits the individual defect encountered. Moreover, tantalum cones can be used with any revision system. Short-term clinical follow-up indicates that porous tantalum metaphyseal cones effectively provide structural support with the potential for long-term biological fixation and durable reconstructions.

Cementless Metaphyseal Sleeves Used for Large Tibial Defects in Revision Total Knee Arthroplasty

Revision arthroplasty of large tibial defects remains a challenge. Thirty revision knee arthroplasties using a porous titanium tibial sleeve for Anderson Orthopaedic Research Institute (AORI) Type 2B and Type 3 defects with minimum 2year follow up were retrospectively reviewed. The average Knee Society Score increased from 55 pre-operatively to 92 post-operatively. Six patients had a repeat operation though none were sleeve related. All radiographs at final follow-up showed well fixed components with osseous in-growth. Seven patients had end-of-stem pain, four of which resolved. Our short-term results show that porous titanium sleeves are a promising option when managing large areas of metaphyseal bone loss by filling defects and providing stable construct with biologic fixation.

Revision Total Knee Arthroplasty With the Use of Trabecular Metal Cones: A Randomized Radiostereometric Analysis With 2 Years of Follow-Up

“Trabecular Metal Cone” (TM Cone) (Zimmer, Inc, Warsaw, Ind) for reconstruction of bone loss in the proximal tibia during revision total knee arthroplasty is now optional. Forty patients were randomized to receive revision total knee arthroplasty with or without TM Cone (No TM Cone). The Anderson Orthopaedic Research Institute bone loss classification and NexGen revision system were used. Radiostereometric analysis was performed with 24 months of follow-up. Maximum total point motion: stable migration was seen in the TM Cone group. No statistically significant difference was found. Segment motion analysis at 24 months showed the same net direction of rotation for the groups around the y-, z-axis and around the x-, y-axis for translation. Tibial revision implants with TM Cone result in an early stable situation with less irregular migration pattern than revision without TM Cone.

Bone mineral density changes of the proximal tibia after revision total knee arthroplasty. A randomised study with the use of porous tantalum metaphyseal cones

Forty patients were enrolled in a prospective randomised study using conventional method or "Trabecular Metal Cone" (TM Cone) (Zimmer inc., Warsaw, USA) for reconstruction of bone loss of the proximal tibia during revision total knee arthroplasty (rTKA). The aim was to evaluate changes in bone mineral density (BMD) at the proximal tibia. Thirty-six patients [median 67 years (range: 40-85 years)] received rTKA with NexGen® (Zimmer Warsaw, USA) revision system. Knee Society´s Knee Scoring System and the Anderson Orthopaedic Research Institute (AORI) bone classification was used. Changes in BMD were measured by dual energy X-ray absorptiometry (DEXA). Knee and function score improved in both groups. No significant changes between the groups were found. Changes in BMD within the two groups were quite similar. Overall decreases in BMD of 0.1 - 5.4 % were found in both groups (ROI 1-6) postoperative to 12 months of follow-up, except that ROI 7 showed an increase in BMD (0.8 - 1.3 %). After 24 months of follow-up, an increase in BMD was found along the stem (ROI 2-5) of 1.9 - 6.3 % , with significant changes in the TM Cone Group (ROI 3, 4, 5) . No significant changes in BMD between the groups were found. The bone remodelling pattern was almost the same in the two groups after two years.