The Journal of Arthroplasty 30 (2015) 1995–1998
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
The Effect of Porous Tantalum Cones on Mechanical Alignment and Canal-Fill Ratio in Revision Total Knee Arthroplasty Performed with Uncemented Stems Martin Bédard, MD, FRCSC a, Katherine Cabrejo-Jones, MD b, Michèle Angers, MD, FRCSC c, Rémi Pelletier-Roy b, Stéphane Pelet, MD, PhD, FRCSC a a b c
Department of Orthopaedic Surgery, CHU de Québec, Hôpital de l’Enfant Jésus, Québec City, QC, Canada Université Laval, Québec City, QC, Canada Department of Orthopaedic Surgery, CHU de Québec, Hôpital Saint-François d’Assise, Québec City, QC, Canada
a r t i c l e
i n f o
Article history: Received 29 January 2015 Accepted 7 May 2015 Keywords: revision total knee arthroplasty trabecular metal cones mechanical alignment canal fill ratio uncemented stems
a b s t r a c t In revision total knee arthroplasty (TKA), the internal diameter of metal cones may limit the ability of the stem to properly fill the medullary canal. We prospectively studied 115 patients who underwent revision TKA with uncemented stems to evaluate the effect of metal cones on mechanical alignment and stem positioning. Correction on the mechanical alignment was well achieved in all patients, regardless of whether a metal cone was used. The proportion of patients achieving restoration of neutral mechanical alignment was similar between groups, as were the mean canal fill ratio (CFR) and the proportion of patients achieving CFR ≥85%. The use of porous tantalum cones in revision TKA with uncemented stems is not an obstacle in achieving optimal mechanical alignment and stem positioning. © 2015 Elsevier Inc. All rights reserved.
Primary total knee arthroplasty (TKA) rates have increased dramatically in recent years, and more TKAs are being performed in younger patients. This situation will presumably increase the incidence of revision TKA in the decades to come [1–3]. One of the greatest challenges for orthopaedic surgeons is the reconstruction of Anderson Orthopaedic Research Institute (AORI) [4] Type III defects in which the metaphyseal bone is deficient and compromises a major portion of condyle or plateau, and, occasionally, disrupts ligaments and/or the patellar tendon [5]. Conventional treatment options for these large bone defects include impaction grafting [6–8], large structural allografts [9–12], and the use of tumor prosthesis [12,13]. More recently, Trabecular Metal (TM; Zimmer, Warsaw, IN) cones have been shown to be a promising option. Studies have demonstrated good short term results with excellent osteointegration [14–18]. Regardless of the treatment option, intramedullary stems must be used in revision TKA to offload and reduce interface stress on damaged bone, and to maximize fixation since bone defects compromise durable fixation of the components. Currently, there is no consensus on whether cemented stems or press-fit stems should be used. Both have given
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.05.016. Reprint requests: Martin Bédard, MD, FRCSC, Department of Orthopaedic Surgery, CHU de Québec, Hôpital de l’Enfant Jésus, 1401, 18e Rue, Québec, QC, Canada, G1J 1Z4. http://dx.doi.org/10.1016/j.arth.2015.05.016 0883-5403/© 2015 Elsevier Inc. All rights reserved.
satisfactory results with N90% survival after 10 years [19–21] and have unique advantages and disadvantages. When press-fit stems are used in conjunction with TM cones, the internal diameter of the cone may limit the ability of the stem to fill the medullary canal, possibly resulting in a suboptimal canal fill ratio (CFR). A CFR ≥ 85% (defined as the diameter of the stem/diameter of the canal × 100), is a good predictor of proper mechanical alignment and therefore a good indicator of prosthesis survival [22]. The primary aim of our study was to evaluate whether a CFR ≥85% and good mechanical alignment could be achieved when using simultaneous uncemented stems and TM cones in revision TKA. Our secondary goal was to compare the ability to obtain good CFR and mechanical alignment between uncemented stems used with or without cones. Materials and Methods Study Design The study involved a prospective analysis of 115 patients who underwent complete revision TKA from September 2008 to February 2014 by a single surgeon (M.B.). A total of 21 patients (12 women and 9 men, mean age 74.8 years at time of surgery) received 25 TM cones (8 femoral and 17 tibial). All cones were implanted in association with an uncemented diaphyseal-engaging stem. The remaining 94 patients (60 women and 34 men, mean age 68.9 years at time of surgery) underwent revision TKA without TM cones. Cemented stems were excluded. A total of 96 femoral and 80 tibial stems were installed without
1996
M. Bédard et al. / The Journal of Arthroplasty 30 (2015) 1995–1998
Table 1 Patient Characteristics. All Revisions Revisions with Revisions without N = 115 TM Cones N = 21 TM Cones N = 94 Age (years) Mean Range Gender Male Female Number of uncemented stems Femur Tibia Total number of cones Femur Tibia Diagnosis for Revision TKA Aseptic Loosening Infection Instability Stiffness Implant Breakage Periprosthetic Fracture Extensor Mechanism Rupture Patella & Malrotation
70.0 50–93
74.8 58–91
68.7 50–93
47 68
12 9
35 59
104 97 25 8 17
8 17 25 8 17
96 80 – – –
32 29 27 16 2 6 2
13 3 2 2 1 – –
19 26 25 14 1 6 2
1
–
1
cones using an uncemented press-fit technique. The indications for revision TKA included aseptic loosening, deep infection, instability, stiffness, implant fracture, periprosthetic fracture, extensor mechanism disruption, and patellar instability with component malrotation [23]. Patient characteristics are summarized in Table 1. All measurements of CFR and mechanical alignment of the knee were performed by an independent fellowship-trained arthroplasty surgeon (M.A.). CFR was measured at 1.5 cm proximal to stem tip on post-operative anteroposterior (AP) and lateral radiographs for all stems. Mechanical alignment was measured on preoperative and postoperative 3-ft standing radiographs. Routine clinical follow-up and radiographic measurements were prospectively obtained for all patients at 6 weeks, 3 months, 6 months, 12 months, and then on a yearly basis. All post-operative radiographic measurements in this study were done at the 6-week follow-up. Operative Procedure The surgical technique used in this study was similar to that previously published by others [14,17,23]. After the removal of the old implants, assessment of the bone defects was carried out according to the AORI classification system to identify patients who required a TM cone for revision TKA. According to the AORI classification, TM cones were used in 6 type 2B defects and 19 type 3 defects. Careful contouring of metaphyseal bone was carried out using a high-speed burr to allow insertion of the cone. Trial components were tested to determine the appropriate cone size. Size-specific impactors were used for the final impaction of the TM cones. Bone allograft was used to fill any areas or voids between the periphery of the TM cone and the adjacent bone. Once the cone was impacted into a stable position, the final prosthetic components were cemented to the TM cone, making sure the diaphyseal part of the stem was free of cement. This was done by first introducing the tip of the stem in the medullary canal and then using a cement gun in order to fill the cone with cement. Since the inner diameter of the TM cone may limit stem size, it is important to report that the largest femoral and tibial stems used with cones had a diameter of 17 mm and 16 mm, respectively. All stems larger than 17 mm were implanted without a cone in this series. The decision regarding the use of a porous metal cone was solely based on intra-operative assessment of metaphyseal bone defect. In all cases, reaming of the medullary canal and selection of the final stem diameter were done before assessment of any possible bone
defect. Therefore, a possible bias concerning a change in surgical technique, i.e. limited canal reaming knowing that a cone will later be required, is excluded. In the scenario where a cone was required based on the intra-operative bone defect and that a stem larger than 17 mm was already reamed, the surgeon was willing to cement a 17-mm stem in the diaphysis to ensure proper fixation, avoid undersizing of a press-fit stem, and be able to simultaneously use a porous metal cone. This latter scenario did not occur in this cohort since no cones were used with cemented stems. Minimal length was 145 mm for all stems, making sure the diaphysis was engaged. Surgical data can be found in Tables 2 and 3. Type 2B bone defects in the group who did not receive a cone (12 patients) were treated with metal augments and cement. Six patients with type 3 femoral defects did not receive a cone and underwent revision with distal femoral arthroplasty for periprosthetic fracture around a loose femoral implant. Statistical Analysis An independent expert carried out all statistical analyses (S.P.). Descriptive statistics were performed using paired Student t-tests to compare correction of the mechanical alignment, and two-tailed Fisher exact test for CFR and non-continuous data. A measurement error of 1 mm was adjusted prior to calculations. An alpha error of 5% was arbitrarily set. Source of Funding No external source of funding was used for this study. Results Mechanical Alignment The mean mechanical alignment for the cohort was significantly improved after the surgery (3.6° varus pre-operative to 1.0° varus postoperative, P = 0.01). Mean pre-operative mechanical alignment for patients who received TM cones was 8.33° varus (range, 20.8 o varus–7.2° valgus). Post-operatively, mechanical alignment was significantly improved to 1.87° varus (range, 5.9°varus–2.8° valgus, P b 0.05). Mechanical alignment in the group without cones improved from 2.39° varus Table 2 Surgical Data for Types of Bone Defects and Diameter of Uncemented Stems. Femur with Uncemented Stems
Bone defects None Type 1 Type 2A Type 2B Type 3 Stem diameter 10 mm 11 mm 12 mm 13 mm 14 mm 15 mm 16 mm 17 mm 18 mm 20 mm 22 mm 24 mm
Tibia with Uncemented Stems
With Cone N=8
Without Cone N = 96
With Cone N = 17
Without Cone N = 80
– – – 2 6
36 24 21 9 6
– – – 4 13
45 20 12 3 –
– – – 1 1 2 3 1 – – – –
– – 6 10 12 13 22 16 12 4 1 –
– 1 2 5 3 4 2 – – – – –
3 8 11 19 21 10 4 2 2 – – –
M. Bédard et al. / The Journal of Arthroplasty 30 (2015) 1995–1998 Table 3 Type of Constraint Used During the Revision Procedure for Both Groups.
Type of constraint Posterior-stabilized Varus–valgus constrained Hinge
All Revisions N = 115
Revisions with TM Cones N = 21
Revisions Without TM Cones N = 94
39 63 13
3 17 1
36 46 12
(range, 17.4° varus–22.4° valgus) pre-operatively to 0.78° varus (range, 7.0° varus–6.2° valgus) post-operatively (P = 0.16). Post-operatively, 18 patients (85.7%) in the TM cone group and 76 patients (80.9%) without cones achieved a neutral (3° varus to 3° valgus) mechanical alignment (P = 0.23). Femoral CFR Mean CFR measured by AP radiographs for femoral stems used with TM cones was 81.0% (95% CI, 69.9%–92.1%), and 83.9% (95% CI, 82.0%–85.8%) for femoral stems used without TM cones. Mean CFR measured on lateral radiographs was 83.9% (95% CI, 76.7%–91.1%) for femoral stems used with TM cones, and 84.6% (95% CI, 83.0%– 86.2%) for femoral stems used without TM cones. The proportion of femoral stems that showed ≥ 85% CFR on AP radiographs was 50% for stems used with TM cones and 54% for stems used without TM cones. On the lateral view, the proportion of femoral stems that showed ≥ 85% CFR was 50% for stems used with TM cones and 47% for stems used without TM cones. When analyzed for femoral stems that showed ≥ 85% CFR on either the AP or lateral view, 75% of stems used with TM cones and 71% of stems used without TM cones achieved this CFR. None of these differences were statistically significant (P = 1.0). Table 4 details these results. Tibial CFR For tibial stems used with TM cones, mean CFR on AP radiographs was 85.8% (95% CI, 82.6%–89.0%), compared to 86.1% (95% CI, 84.6%– 87.6%) for tibial stems used without TM cones. Mean CFR measured on lateral radiographs for tibial stems used with TM cones was 78.9% (95% CI, 73.8%–84.0%) and 80.0% (95% CI, 78.1%–81.9%) for stems used without TM cones. Fifty-nine percent of tibial stems used with TM cones, and 60% of tibial stems used without TM cones, showed ≥ 85% CFR on AP radiographs. Lateral radiographs showed that 24% of tibial stems used with TM cones had ≥85% CFR, and 28% of tibial stems used without TM cones had ≥85% CFR. When analyzed for tibial stems that showed ≥85% CFR on either the AP or lateral view, 70% of stems used with TM cones and 75% of stems used without TM cones achieved this CFR. None of these differences were statistically significant (P = 0.76). Table 5 details these results. Complications In the TM cone group, one intra-operative fracture of the distal femur occurred following impaction of a TM cone. Simultaneous open reduction and internal fixation with metal plate and screws were performed at the time of revision. Protected weight-bearing was allowed
1997
for 6 weeks post-operatively and the fracture healed uneventfully at 3 months. CFR and mechanical alignment were not compromised. Two undisplaced metaphyseal fractures of the tibia were diagnosed on the same-day post-operative radiograph in the group without TM cones. They were treated with toe touch weight-bearing for 6 weeks and healed without further intervention. None of the 115 revisions performed in this series required another revision, but one patient from the non-TM cone group underwent knee arthrodesis following recurrent deep infection. Discussion We conclude from these results that the inner diameter of the TM cone did not limit the optimal placement of uncemented tibial and femoral stems in these patients undergoing revision TKA. The position of the cone must be in the same axis as the medullary canal to obtain proper placement of the stem so as to obtain optimal CFR and restore mechanical alignment. To our knowledge, no study to date has evaluated the impact of TM cones with long uncemented stems on the ability to achieve optimal CFR and adequate mechanical alignment in revision TKA. Uncemented stems provide mechanical support for the prosthetic component, are much easier to remove, and decrease the complexity due to cement use [20,24]. Press-fit stems have also been shown to help in restoring a neutral mechanical axis when CFR ≥85% is obtained [23]. Disadvantages of diaphyseal press-fit stems include end-of-stem pain, need for offset when diaphyseal engagement results in implant malposition, and iatrogenic fracture. On the other hand, cemented stems offer the benefits of solid, durable fixation for patients with large, osteopenic canals; and patients who require extension of cement into the canal to provide adequate fixation in damaged or sclerotic metaphyseal bone [24]. In addition, cemented stems allow for the delivery of antibiotic cement. Because they are shorter and do not need to engage the diaphysis, they allow for placement inside the medullary canal without influencing the position of the implant [19,20]. However, cemented stems are difficult to remove and there is higher risk of malalignment [20].Thus, both cemented and press-fit stems have good outcome data, and are useful in specific patients. When CFR is 85% or greater, it is predictive of proper mechanical alignment and therefore a good indicator of prosthesis survival [25]. In our study, we demonstrated that the proportion of patients who had CFR ≥ 85% was not different between those who received a femoral stem with a TM cone and those who received a femoral stem without a TM cone (75% vs 71%). Similarly, there was no difference in the proportion of patients who had CFR ≥85% between those who received a tibial stem with a TM cone and those who received a tibial stem without a TM cone (70% vs 75%). Since the largest stems used with TM cones in this series have a diameter of 17 mm in the femur and 16 mm in the tibia, the ability to obtain a CFR ≥ 85% with larger stems remains uncertain and may possibly require burring on the inner part of the TM cone in order to permit stem introduction. Wide intramedullary canals requiring simultaneous TM cone and stems larger than 17 mm require full cementation of a narrower stem to obtain adequate fixation. The proportion of patients who achieved CFR ≥85% in our study was similar to or better than that previously published by others. Parsley et al [22] reported that 58% of uncemented femoral stems and 58% of
Table 4 CFR Values in Revision TKA for Femoral Uncemented Stems. With TM Cone N = 8 Mean CFR (%) Anteroposterior Lateral Anteroposterior or lateral
81.0 (69.9–92.1) 83.9 (76.7–91.1) –
CFR N85% (% Patients) 50% 50% 75%
Without TM Cone N = 96 Mean CFR (%) 83.9 (82.0–85.8) 84.6 (83.0–86.2) –
CFR N85% (% Patients)
P Value
54% 47% 71%
1.0
1998
M. Bédard et al. / The Journal of Arthroplasty 30 (2015) 1995–1998
Table 5 CFR Values in Revision TKA for Tibial Uncemented Stems. With TM Cone N = 17 Mean CFR (%) Anteroposterior Lateral Anteroposterior or lateral
85.8 (82.6–89.0) 78.9 (73.8–84.0) –
CFR N85% (% patients) 59% 24% 70%
uncemented tibial stems had CFR ≥85% following revision TKA. These rates are somewhat lower than ours. Nakasone et al [25] reported rates that were closer to those observed in our study, with 73% of femoral stems and 76% of tibial stems achieving CFR ≥85% postoperatively. There are several strengths and limitations to our study. The strengths include the systematic follow-up of all the patients included in this study, as well as the use of independent experts: one to perform the radiographic analysis, and the other to carry out statistical analysis. One limitation is the small number of patients who received TM cones in revision TKA. This procedure is limited to the most complex cases where there are significant bone defects that require the use of a TM cone to provide support for the femoral or tibial component. However, the patient population in the study by Nakasone et al [25] was also small and gave similar results to ours. Another limitation is the short follow-up of the patients in this study. Postoperative radiographic measurements were taken 6 weeks following revision TKA. As this was a timely analysis, no long-term data are available. Conclusion TM cones do not have a negative influence in the ability to achieve optimal mechanical alignment when using an uncemented stem technique in revision TKA. Achieving maximal CFR remains a difficult task in all revisions, however, the majority of our patients who received TM cones had CFR ≥85%. Therefore, the use of TM cones is not an obstacle to obtaining optimal mechanical alignment and optimal CFR in patients undergoing revision TKA. References 1. Harkess JW, Murphy RF, Mihalko WM. The progression of total knee arthroplasty from 1993–2003. Curr Orthop Pract 2014;25:136. 2. Kurtz SM, Lau E, Ong K, et al. Future young patient demand for primary and revision joint replacement: national projections from 2010 to 2030. Clin Orthop Relat Res 2009;467:2606. http://dx.doi.org/10.1007/s11999-009-0834-6. 3. Losina E, Thornhill TS, Rome BN, et al. The dramatic increase in total knee replacement utilization rates in the United States cannot be fully explained by growth in population size and the obesity epidemic. J Bone Joint Surg Am 2012;94:201. http://dx.doi.org/10.2106/JBJS.J.01958. 4. Engh GA, Ammeen DJ. Classification and preoperative radiographic evaluation: knee. Orthop Clin North Am 1998;29:205. 5. Glynn A, Austin MS. Revision total knee arthroplasty in patients with massive bone loss. Available at www.boneandjoint.org.uk/content/focus/revision-total-kneearthroplasty-patients-massive-bone-loss. [Accessed December 18, 2014].
Without TM Cone N = 80 Mean CFR (%) 86.1 (84.6–87.6) 80.0 (78.1–81.9) –
CFR N85% (% Patients)
P Value
60% 28% 75%
0.76
6. Garino JP. The use of impaction grafting in revision total knee arthroplasty. J Arthroplasty 2002;17:94 [DOI: aarth01704b0094 [pii]]. 7. Lotke PA, Carolan GF, Puri N. Impaction grafting for bone defects in revision total knee arthroplasty. Clin Orthop Relat Res 2006;446:99. http://dx.doi.org/10.1097/01.blo. 0000214414.06464.00 [[doi];00003086-200605000-00018 [pii]]. 8. Lotke PA, Carolan GF, Puri N. Technique for impaction bone grafting of large bone defects in revision total knee arthroplasty. J Arthroplasty 2006;21:57 [DOI: S08835403(06)00060-X [pii]]. 9. Clatworthy MG, Ballance J, Brick GW, et al. The use of structural allograft for uncontained defects in revision total knee arthroplasty. A minimum five-year review. J Bone Joint Surg Am 2001;83-A:404. 10. Dennis DA, Little LR. The structural allograft composite in revision total knee arthroplasty. Orthopedics 2005;28:1005. 11. Engh GA, Ammeen DJ. Use of structural allograft in revision total knee arthroplasty in knees with severe tibial bone loss. J Bone Joint Surg Am 2007;89:2640 [DOI: 89/12/ 2640 [pii]]. 12. Kuchinad RA, Garbedian S, Rogers BA, et al. The use of structural allograft in primary and revision knee arthroplasty with bone loss. Adv Orthop 2011;2011:578952. 13. Ramappa M, McMurtry I, Port A. Direct exchange endoprosthetic reconstruction with tumour prosthesis for periprosthetic knee infection associated with segmental bone defects. Strateg Trauma Limb Reconstr 2010;5:31. 14. Howard JL, Kudera J, Lewallen DG, et al. Early results of the use of tantalum femoral cones for revision total knee arthroplasty. J Bone Joint Surg Am 2011;93:478 [DOI: 93/5/478 [pii]]. 15. Lachiewicz PF, Bolognesi MP, Henderson RA, et al. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res 2012;470:199. 16. Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty: a minimum 2-year follow-up. J Arthroplasty 2009;24: 1086 [DOI: S0883-5403(08)00702-X [pii]]. 17. 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;90:78 [DOI: 90/1/78 [pii]]. 18. Derome P, Sternheim A, Backstein D, et al. Treatment of large bone defects with trabecular metal cones in revision total knee arthroplasty: short term clinical and radiographic outcomes. J Arthroplasty 2014;29:122 [DOI: S0883-5403(13)00337-9 [pii]]. 19. Haidukewych GJ, Hanssen A, Jones RD. Metaphyseal fixation in revision total knee arthroplasty: indications and techniques. J Am Acad Orthop Surg 2011;19:311 [DOI: 19/6/311 [pii]]. 20. Haidukewych GJ, Service B. Contemporary bone loss management options for revision total knee arthroplasty. Semin Arthroplast 2012;23:39. 21. Winemaker MJ, Beingessner DM, Rorabeck CH. Revision total knee arthroplasty: should tibial stems be cemented or uncemented? Knee 1998;5:175. 22. Parsley BS, Sugano N, Bertolusso R, et al. Mechanical alignment of tibial stems in revision total knee arthroplasty. J Arthroplasty 2003;18:33 [DOI: S0883540303003024 [pii]]. 23. Vince KG, Bedard M. Implanting the revision total knee arthroplasty. In: Lotke PA, Lonner JH, editors. Master techniques in orthopaedic surgery: knee arthroplasty. Philadelphia, PA: Lippincott Williams & Wilkins; 2008. p. 203. 24. Mabry TM, Hanssen AD. The role of stems and augments for bone loss in revision knee arthroplasty. J Arthroplasty 2007;22:56 [DOI: S0883-5403(07)00119-2 [pii]]. 25. Nakasone CK, Abdeen A, Khachatourians AG, et al. Component alignment in revision total knee arthroplasty using diaphyseal engaging modular offset press-fit stems. J Arthroplasty 2008;23:1178 [DOI: S0883-5403(07)00597-9 [pii]].
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
The Effect of Porous Tantalum Cones on Mechanical Alignment and Canal-Fill Ratio in Revision Total Knee Arthroplasty Performed with Uncemented Stems Martin Bédard, MD, FRCSC a, Katherine Cabrejo-Jones, MD b, Michèle Angers, MD, FRCSC c, Rémi Pelletier-Roy b, Stéphane Pelet, MD, PhD, FRCSC a a b c
Department of Orthopaedic Surgery, CHU de Québec, Hôpital de l’Enfant Jésus, Québec City, QC, Canada Université Laval, Québec City, QC, Canada Department of Orthopaedic Surgery, CHU de Québec, Hôpital Saint-François d’Assise, Québec City, QC, Canada
a r t i c l e
i n f o
Article history: Received 29 January 2015 Accepted 7 May 2015 Keywords: revision total knee arthroplasty trabecular metal cones mechanical alignment canal fill ratio uncemented stems
a b s t r a c t In revision total knee arthroplasty (TKA), the internal diameter of metal cones may limit the ability of the stem to properly fill the medullary canal. We prospectively studied 115 patients who underwent revision TKA with uncemented stems to evaluate the effect of metal cones on mechanical alignment and stem positioning. Correction on the mechanical alignment was well achieved in all patients, regardless of whether a metal cone was used. The proportion of patients achieving restoration of neutral mechanical alignment was similar between groups, as were the mean canal fill ratio (CFR) and the proportion of patients achieving CFR ≥85%. The use of porous tantalum cones in revision TKA with uncemented stems is not an obstacle in achieving optimal mechanical alignment and stem positioning. © 2015 Elsevier Inc. All rights reserved.
Primary total knee arthroplasty (TKA) rates have increased dramatically in recent years, and more TKAs are being performed in younger patients. This situation will presumably increase the incidence of revision TKA in the decades to come [1–3]. One of the greatest challenges for orthopaedic surgeons is the reconstruction of Anderson Orthopaedic Research Institute (AORI) [4] Type III defects in which the metaphyseal bone is deficient and compromises a major portion of condyle or plateau, and, occasionally, disrupts ligaments and/or the patellar tendon [5]. Conventional treatment options for these large bone defects include impaction grafting [6–8], large structural allografts [9–12], and the use of tumor prosthesis [12,13]. More recently, Trabecular Metal (TM; Zimmer, Warsaw, IN) cones have been shown to be a promising option. Studies have demonstrated good short term results with excellent osteointegration [14–18]. Regardless of the treatment option, intramedullary stems must be used in revision TKA to offload and reduce interface stress on damaged bone, and to maximize fixation since bone defects compromise durable fixation of the components. Currently, there is no consensus on whether cemented stems or press-fit stems should be used. Both have given
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.05.016. Reprint requests: Martin Bédard, MD, FRCSC, Department of Orthopaedic Surgery, CHU de Québec, Hôpital de l’Enfant Jésus, 1401, 18e Rue, Québec, QC, Canada, G1J 1Z4. http://dx.doi.org/10.1016/j.arth.2015.05.016 0883-5403/© 2015 Elsevier Inc. All rights reserved.
satisfactory results with N90% survival after 10 years [19–21] and have unique advantages and disadvantages. When press-fit stems are used in conjunction with TM cones, the internal diameter of the cone may limit the ability of the stem to fill the medullary canal, possibly resulting in a suboptimal canal fill ratio (CFR). A CFR ≥ 85% (defined as the diameter of the stem/diameter of the canal × 100), is a good predictor of proper mechanical alignment and therefore a good indicator of prosthesis survival [22]. The primary aim of our study was to evaluate whether a CFR ≥85% and good mechanical alignment could be achieved when using simultaneous uncemented stems and TM cones in revision TKA. Our secondary goal was to compare the ability to obtain good CFR and mechanical alignment between uncemented stems used with or without cones. Materials and Methods Study Design The study involved a prospective analysis of 115 patients who underwent complete revision TKA from September 2008 to February 2014 by a single surgeon (M.B.). A total of 21 patients (12 women and 9 men, mean age 74.8 years at time of surgery) received 25 TM cones (8 femoral and 17 tibial). All cones were implanted in association with an uncemented diaphyseal-engaging stem. The remaining 94 patients (60 women and 34 men, mean age 68.9 years at time of surgery) underwent revision TKA without TM cones. Cemented stems were excluded. A total of 96 femoral and 80 tibial stems were installed without
1996
M. Bédard et al. / The Journal of Arthroplasty 30 (2015) 1995–1998
Table 1 Patient Characteristics. All Revisions Revisions with Revisions without N = 115 TM Cones N = 21 TM Cones N = 94 Age (years) Mean Range Gender Male Female Number of uncemented stems Femur Tibia Total number of cones Femur Tibia Diagnosis for Revision TKA Aseptic Loosening Infection Instability Stiffness Implant Breakage Periprosthetic Fracture Extensor Mechanism Rupture Patella & Malrotation
70.0 50–93
74.8 58–91
68.7 50–93
47 68
12 9
35 59
104 97 25 8 17
8 17 25 8 17
96 80 – – –
32 29 27 16 2 6 2
13 3 2 2 1 – –
19 26 25 14 1 6 2
1
–
1
cones using an uncemented press-fit technique. The indications for revision TKA included aseptic loosening, deep infection, instability, stiffness, implant fracture, periprosthetic fracture, extensor mechanism disruption, and patellar instability with component malrotation [23]. Patient characteristics are summarized in Table 1. All measurements of CFR and mechanical alignment of the knee were performed by an independent fellowship-trained arthroplasty surgeon (M.A.). CFR was measured at 1.5 cm proximal to stem tip on post-operative anteroposterior (AP) and lateral radiographs for all stems. Mechanical alignment was measured on preoperative and postoperative 3-ft standing radiographs. Routine clinical follow-up and radiographic measurements were prospectively obtained for all patients at 6 weeks, 3 months, 6 months, 12 months, and then on a yearly basis. All post-operative radiographic measurements in this study were done at the 6-week follow-up. Operative Procedure The surgical technique used in this study was similar to that previously published by others [14,17,23]. After the removal of the old implants, assessment of the bone defects was carried out according to the AORI classification system to identify patients who required a TM cone for revision TKA. According to the AORI classification, TM cones were used in 6 type 2B defects and 19 type 3 defects. Careful contouring of metaphyseal bone was carried out using a high-speed burr to allow insertion of the cone. Trial components were tested to determine the appropriate cone size. Size-specific impactors were used for the final impaction of the TM cones. Bone allograft was used to fill any areas or voids between the periphery of the TM cone and the adjacent bone. Once the cone was impacted into a stable position, the final prosthetic components were cemented to the TM cone, making sure the diaphyseal part of the stem was free of cement. This was done by first introducing the tip of the stem in the medullary canal and then using a cement gun in order to fill the cone with cement. Since the inner diameter of the TM cone may limit stem size, it is important to report that the largest femoral and tibial stems used with cones had a diameter of 17 mm and 16 mm, respectively. All stems larger than 17 mm were implanted without a cone in this series. The decision regarding the use of a porous metal cone was solely based on intra-operative assessment of metaphyseal bone defect. In all cases, reaming of the medullary canal and selection of the final stem diameter were done before assessment of any possible bone
defect. Therefore, a possible bias concerning a change in surgical technique, i.e. limited canal reaming knowing that a cone will later be required, is excluded. In the scenario where a cone was required based on the intra-operative bone defect and that a stem larger than 17 mm was already reamed, the surgeon was willing to cement a 17-mm stem in the diaphysis to ensure proper fixation, avoid undersizing of a press-fit stem, and be able to simultaneously use a porous metal cone. This latter scenario did not occur in this cohort since no cones were used with cemented stems. Minimal length was 145 mm for all stems, making sure the diaphysis was engaged. Surgical data can be found in Tables 2 and 3. Type 2B bone defects in the group who did not receive a cone (12 patients) were treated with metal augments and cement. Six patients with type 3 femoral defects did not receive a cone and underwent revision with distal femoral arthroplasty for periprosthetic fracture around a loose femoral implant. Statistical Analysis An independent expert carried out all statistical analyses (S.P.). Descriptive statistics were performed using paired Student t-tests to compare correction of the mechanical alignment, and two-tailed Fisher exact test for CFR and non-continuous data. A measurement error of 1 mm was adjusted prior to calculations. An alpha error of 5% was arbitrarily set. Source of Funding No external source of funding was used for this study. Results Mechanical Alignment The mean mechanical alignment for the cohort was significantly improved after the surgery (3.6° varus pre-operative to 1.0° varus postoperative, P = 0.01). Mean pre-operative mechanical alignment for patients who received TM cones was 8.33° varus (range, 20.8 o varus–7.2° valgus). Post-operatively, mechanical alignment was significantly improved to 1.87° varus (range, 5.9°varus–2.8° valgus, P b 0.05). Mechanical alignment in the group without cones improved from 2.39° varus Table 2 Surgical Data for Types of Bone Defects and Diameter of Uncemented Stems. Femur with Uncemented Stems
Bone defects None Type 1 Type 2A Type 2B Type 3 Stem diameter 10 mm 11 mm 12 mm 13 mm 14 mm 15 mm 16 mm 17 mm 18 mm 20 mm 22 mm 24 mm
Tibia with Uncemented Stems
With Cone N=8
Without Cone N = 96
With Cone N = 17
Without Cone N = 80
– – – 2 6
36 24 21 9 6
– – – 4 13
45 20 12 3 –
– – – 1 1 2 3 1 – – – –
– – 6 10 12 13 22 16 12 4 1 –
– 1 2 5 3 4 2 – – – – –
3 8 11 19 21 10 4 2 2 – – –
M. Bédard et al. / The Journal of Arthroplasty 30 (2015) 1995–1998 Table 3 Type of Constraint Used During the Revision Procedure for Both Groups.
Type of constraint Posterior-stabilized Varus–valgus constrained Hinge
All Revisions N = 115
Revisions with TM Cones N = 21
Revisions Without TM Cones N = 94
39 63 13
3 17 1
36 46 12
(range, 17.4° varus–22.4° valgus) pre-operatively to 0.78° varus (range, 7.0° varus–6.2° valgus) post-operatively (P = 0.16). Post-operatively, 18 patients (85.7%) in the TM cone group and 76 patients (80.9%) without cones achieved a neutral (3° varus to 3° valgus) mechanical alignment (P = 0.23). Femoral CFR Mean CFR measured by AP radiographs for femoral stems used with TM cones was 81.0% (95% CI, 69.9%–92.1%), and 83.9% (95% CI, 82.0%–85.8%) for femoral stems used without TM cones. Mean CFR measured on lateral radiographs was 83.9% (95% CI, 76.7%–91.1%) for femoral stems used with TM cones, and 84.6% (95% CI, 83.0%– 86.2%) for femoral stems used without TM cones. The proportion of femoral stems that showed ≥ 85% CFR on AP radiographs was 50% for stems used with TM cones and 54% for stems used without TM cones. On the lateral view, the proportion of femoral stems that showed ≥ 85% CFR was 50% for stems used with TM cones and 47% for stems used without TM cones. When analyzed for femoral stems that showed ≥ 85% CFR on either the AP or lateral view, 75% of stems used with TM cones and 71% of stems used without TM cones achieved this CFR. None of these differences were statistically significant (P = 1.0). Table 4 details these results. Tibial CFR For tibial stems used with TM cones, mean CFR on AP radiographs was 85.8% (95% CI, 82.6%–89.0%), compared to 86.1% (95% CI, 84.6%– 87.6%) for tibial stems used without TM cones. Mean CFR measured on lateral radiographs for tibial stems used with TM cones was 78.9% (95% CI, 73.8%–84.0%) and 80.0% (95% CI, 78.1%–81.9%) for stems used without TM cones. Fifty-nine percent of tibial stems used with TM cones, and 60% of tibial stems used without TM cones, showed ≥ 85% CFR on AP radiographs. Lateral radiographs showed that 24% of tibial stems used with TM cones had ≥85% CFR, and 28% of tibial stems used without TM cones had ≥85% CFR. When analyzed for tibial stems that showed ≥85% CFR on either the AP or lateral view, 70% of stems used with TM cones and 75% of stems used without TM cones achieved this CFR. None of these differences were statistically significant (P = 0.76). Table 5 details these results. Complications In the TM cone group, one intra-operative fracture of the distal femur occurred following impaction of a TM cone. Simultaneous open reduction and internal fixation with metal plate and screws were performed at the time of revision. Protected weight-bearing was allowed
1997
for 6 weeks post-operatively and the fracture healed uneventfully at 3 months. CFR and mechanical alignment were not compromised. Two undisplaced metaphyseal fractures of the tibia were diagnosed on the same-day post-operative radiograph in the group without TM cones. They were treated with toe touch weight-bearing for 6 weeks and healed without further intervention. None of the 115 revisions performed in this series required another revision, but one patient from the non-TM cone group underwent knee arthrodesis following recurrent deep infection. Discussion We conclude from these results that the inner diameter of the TM cone did not limit the optimal placement of uncemented tibial and femoral stems in these patients undergoing revision TKA. The position of the cone must be in the same axis as the medullary canal to obtain proper placement of the stem so as to obtain optimal CFR and restore mechanical alignment. To our knowledge, no study to date has evaluated the impact of TM cones with long uncemented stems on the ability to achieve optimal CFR and adequate mechanical alignment in revision TKA. Uncemented stems provide mechanical support for the prosthetic component, are much easier to remove, and decrease the complexity due to cement use [20,24]. Press-fit stems have also been shown to help in restoring a neutral mechanical axis when CFR ≥85% is obtained [23]. Disadvantages of diaphyseal press-fit stems include end-of-stem pain, need for offset when diaphyseal engagement results in implant malposition, and iatrogenic fracture. On the other hand, cemented stems offer the benefits of solid, durable fixation for patients with large, osteopenic canals; and patients who require extension of cement into the canal to provide adequate fixation in damaged or sclerotic metaphyseal bone [24]. In addition, cemented stems allow for the delivery of antibiotic cement. Because they are shorter and do not need to engage the diaphysis, they allow for placement inside the medullary canal without influencing the position of the implant [19,20]. However, cemented stems are difficult to remove and there is higher risk of malalignment [20].Thus, both cemented and press-fit stems have good outcome data, and are useful in specific patients. When CFR is 85% or greater, it is predictive of proper mechanical alignment and therefore a good indicator of prosthesis survival [25]. In our study, we demonstrated that the proportion of patients who had CFR ≥ 85% was not different between those who received a femoral stem with a TM cone and those who received a femoral stem without a TM cone (75% vs 71%). Similarly, there was no difference in the proportion of patients who had CFR ≥85% between those who received a tibial stem with a TM cone and those who received a tibial stem without a TM cone (70% vs 75%). Since the largest stems used with TM cones in this series have a diameter of 17 mm in the femur and 16 mm in the tibia, the ability to obtain a CFR ≥ 85% with larger stems remains uncertain and may possibly require burring on the inner part of the TM cone in order to permit stem introduction. Wide intramedullary canals requiring simultaneous TM cone and stems larger than 17 mm require full cementation of a narrower stem to obtain adequate fixation. The proportion of patients who achieved CFR ≥85% in our study was similar to or better than that previously published by others. Parsley et al [22] reported that 58% of uncemented femoral stems and 58% of
Table 4 CFR Values in Revision TKA for Femoral Uncemented Stems. With TM Cone N = 8 Mean CFR (%) Anteroposterior Lateral Anteroposterior or lateral
81.0 (69.9–92.1) 83.9 (76.7–91.1) –
CFR N85% (% Patients) 50% 50% 75%
Without TM Cone N = 96 Mean CFR (%) 83.9 (82.0–85.8) 84.6 (83.0–86.2) –
CFR N85% (% Patients)
P Value
54% 47% 71%
1.0
1998
M. Bédard et al. / The Journal of Arthroplasty 30 (2015) 1995–1998
Table 5 CFR Values in Revision TKA for Tibial Uncemented Stems. With TM Cone N = 17 Mean CFR (%) Anteroposterior Lateral Anteroposterior or lateral
85.8 (82.6–89.0) 78.9 (73.8–84.0) –
CFR N85% (% patients) 59% 24% 70%
uncemented tibial stems had CFR ≥85% following revision TKA. These rates are somewhat lower than ours. Nakasone et al [25] reported rates that were closer to those observed in our study, with 73% of femoral stems and 76% of tibial stems achieving CFR ≥85% postoperatively. There are several strengths and limitations to our study. The strengths include the systematic follow-up of all the patients included in this study, as well as the use of independent experts: one to perform the radiographic analysis, and the other to carry out statistical analysis. One limitation is the small number of patients who received TM cones in revision TKA. This procedure is limited to the most complex cases where there are significant bone defects that require the use of a TM cone to provide support for the femoral or tibial component. However, the patient population in the study by Nakasone et al [25] was also small and gave similar results to ours. Another limitation is the short follow-up of the patients in this study. Postoperative radiographic measurements were taken 6 weeks following revision TKA. As this was a timely analysis, no long-term data are available. Conclusion TM cones do not have a negative influence in the ability to achieve optimal mechanical alignment when using an uncemented stem technique in revision TKA. Achieving maximal CFR remains a difficult task in all revisions, however, the majority of our patients who received TM cones had CFR ≥85%. Therefore, the use of TM cones is not an obstacle to obtaining optimal mechanical alignment and optimal CFR in patients undergoing revision TKA. References 1. Harkess JW, Murphy RF, Mihalko WM. The progression of total knee arthroplasty from 1993–2003. Curr Orthop Pract 2014;25:136. 2. Kurtz SM, Lau E, Ong K, et al. Future young patient demand for primary and revision joint replacement: national projections from 2010 to 2030. Clin Orthop Relat Res 2009;467:2606. http://dx.doi.org/10.1007/s11999-009-0834-6. 3. Losina E, Thornhill TS, Rome BN, et al. The dramatic increase in total knee replacement utilization rates in the United States cannot be fully explained by growth in population size and the obesity epidemic. J Bone Joint Surg Am 2012;94:201. http://dx.doi.org/10.2106/JBJS.J.01958. 4. Engh GA, Ammeen DJ. Classification and preoperative radiographic evaluation: knee. Orthop Clin North Am 1998;29:205. 5. Glynn A, Austin MS. Revision total knee arthroplasty in patients with massive bone loss. Available at www.boneandjoint.org.uk/content/focus/revision-total-kneearthroplasty-patients-massive-bone-loss. [Accessed December 18, 2014].
Without TM Cone N = 80 Mean CFR (%) 86.1 (84.6–87.6) 80.0 (78.1–81.9) –
CFR N85% (% Patients)
P Value
60% 28% 75%
0.76
6. Garino JP. The use of impaction grafting in revision total knee arthroplasty. J Arthroplasty 2002;17:94 [DOI: aarth01704b0094 [pii]]. 7. Lotke PA, Carolan GF, Puri N. Impaction grafting for bone defects in revision total knee arthroplasty. Clin Orthop Relat Res 2006;446:99. http://dx.doi.org/10.1097/01.blo. 0000214414.06464.00 [[doi];00003086-200605000-00018 [pii]]. 8. Lotke PA, Carolan GF, Puri N. Technique for impaction bone grafting of large bone defects in revision total knee arthroplasty. J Arthroplasty 2006;21:57 [DOI: S08835403(06)00060-X [pii]]. 9. Clatworthy MG, Ballance J, Brick GW, et al. The use of structural allograft for uncontained defects in revision total knee arthroplasty. A minimum five-year review. J Bone Joint Surg Am 2001;83-A:404. 10. Dennis DA, Little LR. The structural allograft composite in revision total knee arthroplasty. Orthopedics 2005;28:1005. 11. Engh GA, Ammeen DJ. Use of structural allograft in revision total knee arthroplasty in knees with severe tibial bone loss. J Bone Joint Surg Am 2007;89:2640 [DOI: 89/12/ 2640 [pii]]. 12. Kuchinad RA, Garbedian S, Rogers BA, et al. The use of structural allograft in primary and revision knee arthroplasty with bone loss. Adv Orthop 2011;2011:578952. 13. Ramappa M, McMurtry I, Port A. Direct exchange endoprosthetic reconstruction with tumour prosthesis for periprosthetic knee infection associated with segmental bone defects. Strateg Trauma Limb Reconstr 2010;5:31. 14. Howard JL, Kudera J, Lewallen DG, et al. Early results of the use of tantalum femoral cones for revision total knee arthroplasty. J Bone Joint Surg Am 2011;93:478 [DOI: 93/5/478 [pii]]. 15. Lachiewicz PF, Bolognesi MP, Henderson RA, et al. Can tantalum cones provide fixation in complex revision knee arthroplasty? Clin Orthop Relat Res 2012;470:199. 16. Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty: a minimum 2-year follow-up. J Arthroplasty 2009;24: 1086 [DOI: S0883-5403(08)00702-X [pii]]. 17. 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;90:78 [DOI: 90/1/78 [pii]]. 18. Derome P, Sternheim A, Backstein D, et al. Treatment of large bone defects with trabecular metal cones in revision total knee arthroplasty: short term clinical and radiographic outcomes. J Arthroplasty 2014;29:122 [DOI: S0883-5403(13)00337-9 [pii]]. 19. Haidukewych GJ, Hanssen A, Jones RD. Metaphyseal fixation in revision total knee arthroplasty: indications and techniques. J Am Acad Orthop Surg 2011;19:311 [DOI: 19/6/311 [pii]]. 20. Haidukewych GJ, Service B. Contemporary bone loss management options for revision total knee arthroplasty. Semin Arthroplast 2012;23:39. 21. Winemaker MJ, Beingessner DM, Rorabeck CH. Revision total knee arthroplasty: should tibial stems be cemented or uncemented? Knee 1998;5:175. 22. Parsley BS, Sugano N, Bertolusso R, et al. Mechanical alignment of tibial stems in revision total knee arthroplasty. J Arthroplasty 2003;18:33 [DOI: S0883540303003024 [pii]]. 23. Vince KG, Bedard M. Implanting the revision total knee arthroplasty. In: Lotke PA, Lonner JH, editors. Master techniques in orthopaedic surgery: knee arthroplasty. Philadelphia, PA: Lippincott Williams & Wilkins; 2008. p. 203. 24. Mabry TM, Hanssen AD. The role of stems and augments for bone loss in revision knee arthroplasty. J Arthroplasty 2007;22:56 [DOI: S0883-5403(07)00119-2 [pii]]. 25. Nakasone CK, Abdeen A, Khachatourians AG, et al. Component alignment in revision total knee arthroplasty using diaphyseal engaging modular offset press-fit stems. J Arthroplasty 2008;23:1178 [DOI: S0883-5403(07)00597-9 [pii]].
