STEFANO ZANASI VILLA ERBOSA HOSPITAL GRUPPO SAN DONATO ORTHOPAEDICS DEPARTMENT

1. USO DEI CONI METAFISARI IN TANTALIO POROSO PER LE GRAVI PERDITE DI SOSTANZA OSSEA TIBIO-FEMORALE NELLE REVISIONI COMPLESSE DI PTG SIOT 2012 STEFANO ZANASI VILLA ERBOSA HOSPITAL GRUPPO SAN DONATO ORTHOPAEDICS DEPARTMENT IIIRD DIVISION – JOINT ARTHROPLASTY OPERATIVE CENTER CHIEF: PROF. DR. STEFANO ZANASI 1

2. RECONSTRUCTION OF BONE DEFICIENCIES IS OFTEN REQUIRED TO ACHIEVE A SUCCESSFUL RESULT IN PATIENTS MANAGED WITH REVISION TOTAL KNEE ARTHROPLASTY. REESTABLISHMENTOF A STABLE WELL-ALIGNED AND SUPPORTED FEMUR OR TIBIAL BASE IS NECESSARY FOR SUCCESSFUL RECONSTRUCTION For small contained defects, classified as Anderson Orthopaedic Research Institute AORI type I, cement and/or morselized allograft is often sufficient to treat the defect. For larger defectsAORI type IIthe use of metal augmentation or allograft is often required. RECONSTRUCTION OF MASSIVE DEFECTS AORI TYPE IIIREMAINS A CHALLENGING PROBLEM FOR ORTHOPAEDIC SURGEONS.

3. RECONSTRUCTION OF MASSIVE DEFECTS (AORI TYPE III ) REMAINS A CHALLENGING PROBLEM FOR ORTHOPAEDIC SURGEONS. Options for the surgical reconstruction of large bone defects include impaction grafting, large structural allografts, and the use of a tumor prosthesis. Recently, novel metaphyseal filling implants fabricated from porous tantalum have become available; THESE IMPLANTS PROVIDE AN ALTERNATIVE FOR THE RECONSTRUCTION OF MASSIVE BONE DEFECTS DURING REVISION TOTAL KNEE ARTHROPLASTY.

4. CHARACTERISTICS OF TRABECULAR METAL MATERIALTHE POROUS METAL TANTALUM PROVIDES A NEW TOOLFOR MODULAR RECONSTRUCTION IN THESE CASES.Importantcharacteristics of tantalum include 1. its NEGATIVE CHARGE AND INTERCONNECTIVE PORES, which form a scaffolding and surface for osteoblast-mediated bone ingrowth (Osteoconductive porous scaffold). 2. LOWER MODULUS OF ELASTICITY (3MPA) and HIGH (70%-80%) POROSITY -SIMILAR TO BONE- allowing for a more uniform stress transfer and the potential fordiminished stress shielding. Physiological load-bearing High friction and stability with bone

5. 3. Basic science research has also demonstrated A LOWER BACTERIAL ADHERENCE,and INCREASED LEUKOCYTE ACTIVATION, when compared to other orthopedic metal implant materials. 4. The UNEVEN TEXTURE provides an initial scratch fit after insertion.

6. TANTALUM CONES : CLINICAL RATIONALE & OPTIONS • The modular nature of the cones allows the surgeon to choose a size and position that best fits the insertion • Reliable, structural alternative to bone graft • Distal and posterior femoral options • Full and half block tibial options • Multiple thickness options

7. Trabecular Metal Tibial Cones • Compressive forces load surrounding bone • 14o M/L angles for clearance of lateral wall • 12o posterior angle for clearance of cortical wall • 15 and 30 mm height options 14° 12°

9. TRABECULAR METAL FEMORAL CONES 30, 40, & 50 mm height options Small, Medium & Large

11. SURGICAL TECHNIQUEThis technique included a careful intraoperative assessment of the bone defect Next, a variety of trial sizes were used to guide careful contouring of prominent areas of femoral bone with a high-speed burr. Finally, the porous tantalum cone was placedwith size-specific impactors.Once the tantalum cone had been impacted into a stable position, the porous internal surface of the cone provided a receptive surface for cementation of the femoralor/and tibialimplant. Rotational and axial stability was confirmed by means of the application of manual force to the implant in its final resting position.

12. Exemplificativefemoralcone case

13. Any areas or voids between the periphery of the porous tantalum cone and the adjacent bone of the distal part of the femur are filled with morselizedcancellous bone graft or demineralized bone matrix or both to prevent any egress of bone cement between the cone and the host bone during cementation of the stemmed component. The revision femoral/tibial component are inserted through the cone with use of cemented stem extensions in all cases. Cement therefore is used in the metaphyseal region in the femoral cone and the remaining metaphyseal portion of the distal part of the femur in order to join the stemmed femoral implant mechanically to the porous cone

14. Exemplificativefemoralcone case 2

15. Exemplificativetibialcone case

16. Because of their porous nature, these implants may provide a better environment for biologic fixation, particularly when limited host bone is available.The purpose of the present study was to determine the early outcomes obtained with the use of porous tantalum metaphyseal cones, designed as an alternative treatment for severe femoral AND TIBIAL bone loss at the time of revision total knee arthroplasty

17. 20 Patients (11 females and 9 males) with a mean age of 72 years (range, 54 to 91 yrs) at the time of surgery had porous tantalum metaphyseal femoral (14) or/ and tibial (12) cones (Trabecular Metal; Zimmer, Warsaw, Indiana) implanted at the time of revision total knee arthroplastyduring the period from June 2009 to December 2011LCCK or RHK hinge was cemented: straight or offset tibial and femoral stem extension were always associated (8 cases uncemented and 12 cemented) The mean duration of clinical follow-up for the cohort was 18 ms (range 35 to 9 ms); Revision surgery included aseptic loosening of the femoral component (11 patients), second-stage reimplantation for the treatment of deep infection ( 6 patients),severe osteolysis around a well-fixed femoral component (1 patient), periprostheticfemoral fracture (1 patient), and severe knee instability (1 patient). .

18. In all cases, substantial bone loss was identified at the time of revision, necessitating the use of a tantalum femoral/tibial cone and stem extension. FEMORAL BONE LOSS AT THE TIME OF REVISION TOTAL KNEE ARTHROPLASTY WAS CATEGORIZED AS AORI TYPE IIBOR GREATER IN ALL TWENTY PATIENTS.KNEE SOCIETY SCORES AND IKDC SCORES were calculated on the basis of data gathered during the preoperative and last f.up clinic visit.RADIOGRAPHIC EVALUATION CONSISTED OF COMPARISON OF IMMEDIATE POSTOPERATIVE ANTEROPOSTERIOR AND LATERAL KNEE RADIOGRAPHS WITH SUBSEQUENT FOLLOW-UP RADIOGRAPHS. Follow-up radiographs were reviewed to evaluate for evidence of osseointegration and complications associated with the use of these implants

19. *

20. RESULTSThe results of revision total knee arthroplasty with use of femoral cones are summarized in TablePreoperatively, the average preoperative flexion contracture was 3° (range, -4° to 10°) and the average maximum flexion was 96° (range, 40° to 130°).At the latest follow-up, there was an average residual flexion contracture of 0.5° (range, 0° to 6°) and the mean maximum flexion was 114° (range, 65° to 130°).The mean Knee Society score improved from 52 points (range, 21 to 81) preoperatively to 83 points (range, 59 to 91 points) at the latest follow-up.8/20 pts were able to walk without any canes supportAfter a mean duration of clinical follow-up of thirty-three months,19/20 of the femoral and or tibial cones were still in situ.Radiographic evaluation of the twenty patients showed evidence of osseointegration with reactive trabeculation at points of implant-to-host bone contact. There was no evidence of loosening or migration of any of the femoral cones.No complications were identified that were related to the use of the cone. There were no postoperative infections in this cohort.

21. RADIOGRAPHIC OUTCOMESSerial x-rays were examined preoperatively, postoperatively, and at each subsequent visit. Review of the 18 non revised X-rays cases revealed signs of stable bony ingrowthat the bone-trabecular metal interface, andstreaming trabeculations into the trabecular surface. Average tibiofemoral alignment was 5.4° of valgus(range, 4°-7°). No cases of progressive osteolysis,loosening, or subsidence were noted.

22. No osteolysis,loosening, or subsidence Case 16: infection F, 74 YRs3rd revision 34ms F.UP ROM 0-125 KS 86

23. Two (10 %) out of twenty patients required subsequent surgery. One patient sustained a periprosthetic femoral fracture following a fall at six months following revision total knee arthroplasty. In this case, the fracture occurred proximal to the revision total knee construct. At the time of open reduction and internal fixation of the fracture, the arthroplasty components, including the femoral cones, were found to be stable. One patient required extensor mechanism reconstruction for the treatment of disruption.

25. DISCUSSIONTHE OPTIMUM TREATMENT METHOD FOR LARGE FEMORAL BONE DEFECTS DURING REVISION KNEE REPLACEMENT HAS NOT BEEN ESTABLISHED. STUDIES EVALUATING THE RESULTS OF REVISION TOTAL KNEE ARTHROPLASTY WITH EITHER STRUCTURAL ALLOGRAFTS OR IMPACTION GRAFTING LARGELY HAVE HAD ONLY SHORT TO INTERMEDIATE FOLLOW-UP INTERVALS. Clatworthyet al. reported a 72% allograft survival rate in a study of fifty-two revision total knee arthroplasties involving sixty-six structural grafts that were performed at three institutions. Twelve knees had repeat revision at a mean of 70.7 months, with only two of those knees having retention of the allograft. Enghet al. reported an 87% rate of good to excellent results after a mean duration of follow-up of 4.2 years in a study of thirty-five knees with AORI type-3 bone loss treated with bulk allograft. Lonneret al. reported on seventeen revision total knee arthroplasties in patients with uncontained defects that were treated with impaction grafting. No failures were reported, but only two knees had more than twenty-four months of follow-up.

26. ALTHOUGH THERE HAVE BEEN FEW PUBLISHED REPORTS ON THE USE OF POROUS TANTALUM METAPHYSEAL CONES FOR REVISION TOTAL KNEE ARTHROPLASTY, EARLY RESULTS HAVE BEEN FAVORABLE. PROVIDING EXCELLENT INITIAL MECHANICAL STABILITY, which is advantageous in situations in which implant-to-host bone contact is reduced. Meneghini et al.evaluated fifteen revision total knee replacements in which tibial cones had been used for the reconstruction of AORI type-IIB or III proximal tibial defects. After an average duration of follow-up of thirty-four months, all cones showed good evidence of osseointegration, with no evidence of loosening or migration. Radnay and Scuderi, in a study of ten patients with large proximal tibial defects, reported no evidence of loosening or migration of the tantalum implants after ten months of follow-up. One potential disadvantage of the use tantalum cones may be the extreme difficulty of removing these implants if required for the treatment of recalcitrant deep periprosthetic infection. Although implant removal was not required in the current series of patients, it should be considered as a potential complication when choosing this reconstructive option.

27. CONCLUSIONS CONE AUGMENT implants offer some potential advantages over traditional techniques for the treatment of large femoral and or tibial defects at the time of revision total knee arthroplasty. The surgical technique is relatively simple when compared with that associated with the use of a structural bone allograft. 2. The preparation time associated with the use of these implants Is much less than that associated with the use of a structural allograft This potentially could translate into SHORTER OPERATIVE TIMES AND A decreased relative risk of infection 3. Eliminating the allograft removes the potential for disease transmission that exists in association with the use of that reconstructive option.

28. 4. The use of structural allograft carries a risk of graft collapse or resorption, complications that are unlikely in association with the use of tantalum cones. 5.provided structural support for the stem/hinge implants that were inserted at the time of revision total knee arthroplasty in this series. cones are used in a modular nonlinked fashion, can be inserted at multiple angles and positions, can be used with any revision system, and come in a number of sizes, to address the specific dimensions of the lesion encountered. 6. The potential for long-term biologic fixation may provide durability for reconstructions

29. Long-term follow-up and comparison with alternative reconstructive techniques will be required to evaluate whether this technique will provide durable long-term outcomes.