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Primary posterior stabilized total knee arthroplasty: analysis of different instrumentation

Primary posterior stabilized total knee arthroplasty: analysis of different instrumentation Background: Intercondylar femoral bone removal during posterior stabilized (PS) total knee arthroplasty (TKA) makes many cruciate substituting implant designs less appealing than cruciate retaining implants. Bone stock conservation is considered fundamental in the prevision of future revision surgeries. The purpose of this study was to compare the quantity of intercondylar bone removable during PS housing preparation using three contemporary PS TKA instrumentations. Method: We compared different box cutting jigs which were utilized for the PS housing of three popular PS knee prostheses. The bone removal area from every PS box cutting jig was three-dimensionally measured. Results: Independently from the implant size, the cutting jig for a specific PS TKA always resected significantly less bone than the others: this difference was statistically significant, especially for small- to medium-sized total knee femoral components. Conclusion: This study does not establish a clinical relevance of removing more or less bone at primary TKA, but suggests that if a PS design is indicated, it is preferable to select a model which possibly resects less distal femoral bone. Keywords: TKA, Total knee arthroplasty, Posterior stabilized, Cruciate substituting total knee arthroplasty Introduction [3]. There are several potential disadvantages in the use of The use of posterior stabilized (PS) implants in total knee PS designs with respect to other CR implants, including arthroplasty (TKA) is becoming increasingly popular. tibial post wear and breakage [4], increased incidence of Many designs, which are modifications of the original anterior knee pain [5], and implant instability especially Insall-Burstein prosthesis (Zimmer, Warsaw, IN, USA) during the midflexion phase [6]. [1], have inherited the classical cam and post mechan- One of the major disadvantages of PS designs is also ism to guide anteroposterior knee motion in lieu of the linked to the amount of bone removed during femoral posterior cruciate ligament. Potential advantages of PS ‘box osteotomy’ for the PS mechanism housing compared TKA include the possibility of easier balancing of severe to posterior cruciate retaining implants. Theoretically, a coronal and sagittal deformities (i.e., varus/valgus or major preservation of bone stock would be useful in the recurvatum), better controlled flexion kinematics, less case of future revision of the implant: in fact, the amount polyethylene sliding wear, greater weight-bearing max- and location of bone loss determine which reconstructive imal flexion, and greater posterior femoral rollback than method (cones, methaphyseal sleeves, and/or stems) will cruciate retaining (CR) high-flexion TKA [2]. A decrement be necessary to achieve implant stability [7]. In a recent in patello-femoral contact pressure in PS TKA designs review, Huten defined previous bone resections as the first when compared to CR designs is another potential advantage cause of bone loss in revision total knee arthroplasty [8]. The current study was performed to examine the max- imum volumetric bone resection area required for the PS * Correspondence: pindelli@stanford.edu Centro Eccellenza Sostituzioni Articolari Toscana (CESAT), Clinica Ortopedica housing of three worldwide highly utilized posterior stabi- Universita’ di Firenze, Florence 50134, Italy lized TKA designs: Sigma PS (De Puy, Johnson & Johnson, Fondazione Onlus “In Cammino”, Piazza Lavagnini 1, Fucecchio, Florence Warsaw, IN, USA), Persona (Zimmer, Warsaw, IN, USA) 50054, Italy Full list of author information is available at the end of the article © 2014 Indelli et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 2 of 5 http://www.josr-online.com/content/9/1/54 and Vanguard (Biomet Orthopedics Inc., Warsaw, IN, caliber (Figures 2, 3, and 4). Data was collected on an USA). The authors compared the manufacturer’sinstru- Excel spreadsheet as an average in the small, medium, ments (PS box cutting jigs) in order to highlight their and large size groups. The size of the saw blade (1 mm) design differences. was considered in the measurement process, as shown in Figures2,3,and 4. Material and method The goal of each measurement was to evaluate the tri- The authors acquired the complete surgical instrumental dimensional box size of each femoral jig, not the amount set of three different PS TKA devices Sigma PS (De Puy, of bone actually removed during the surgical procedure. Johnson & Johnson, Warsaw, IN, USA), Persona (Zim- Statistical analysis was performed using analysis of vari- mer, Warsaw, IN, USA), and Vanguard (Biomet Inc, ance (ANOVA) test with box volume as the dependent Warsaw, IN, USA): analysis of very small (‘micro’) and variable. very large (‘macro’) size implants were excluded for this study. The Sigma PS TKA surgical instrumentation in- Results cluded two cutting jigs for small femoral sizes (sizes 2 and For all implant sizes (Figure 5), the Zimmer Persona jig 2.5), two jigs for medium femoral sizes (sizes 3 and 4), and showed a significantly inferior tridimensional box area one jig for large sizes (size 5). The Vanguard TKA surgical than the Biomet Vanguard and Sigma PS (P <0.003). The instrumentation included three cutting jigs for small difference between the ZimmerPersona and the SigmaPS femoral sizes (sizes 55, 57.5, 60), three jigs for medium was even more statistically significant in small and medium femoral sizes (sizes 62.5, 65, 67.5), and three jigs for large size implants (P < 0.008). sizes (sizes 70, 72.5, 75). The Persona TKA surgical instru- For the small size implant, Biomet Vanguard average mentation included one cutting jig for small femoral sizes tridimensional box area was 11.04 cm compared to 3 3 (sizes 3 to 5), one jig for medium femoral sizes (sizes 6 to 24.03 cm for Sigma PS and to 6.18 cm forZimmerPersona 9), and one jig for large sizes (sizes 10 to 12). In an in vivo (P <0.002). situation, the surgical step necessary for femoral box For the medium size implant, Biomet Vanguard average osteotomy requires application of a cutting jig to the distal tridimensional box area was 13.59 cm compared to 3 3 part of the femur (Figure 1). 28.91 cm for Sigma PS and 7.69 cm for Zimmer Persona An in vitro tridimensional evaluation (anteroposterior (P <0.003). length, mediolateral length, and thickness) of the max- For the large size implant, Biomet Vanguard average imum bone removal area was performed for each of the tridimensional box area was 16.05 cm compared to 3 3 three groups of cutting jigs (small sizes, medium sizes, 36.66 cm for Sigma PS and 13.32 cm forZimmerPersona large sizes) through direct measurement with a millimeter (P < 0.006). Figure 1 Right knee. Intraoperative image of a femoral jig before Figure 2 The De Puy Sigma PS femoral cutting jig (large sizes) ‘box osteotomy.’ is shown. An osteotome defines the bone removable area. Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 3 of 5 http://www.josr-online.com/content/9/1/54 The difference between the Biomet Vanguard and the Sigma PS was statistically significant (P < 0.01), while the difference between the Biomet Vanguard and the Zimmer Persona was not (P > 0.1). The difference between the Sigma PS and the Zimmer Persona was statistically significant (P <0.008). The volumetric bone resection for the PS housing does not include resection volume for the femoral lugs, typ- ical of the Zimmer Persona design. In fact, an additional 0.59 cm of bone was calculated from each of the two lugs of this PS TKA design. Discussion Preservation or substitution of the posterior cruciate ligament in primary TKA is still a controversial issue [9]. Gait analysis [10] and in vivo [11] and in vitro [12] studies showed reproduction of a close to normal knee kinematic using either solution. A clinical comparative study between different types of TKA (cruciate retain- ing or posterior stabilized) with identical femoral geom- etry showed similar midterm outcomes with regards to the range of motion, functional outcomes, and survival rate [13]. The purpose of this study was to compare the max- Figure 3 The Vanguard femoral cutting jig (large sizes) is imum quantity of intercondylar bone removable in three shown. An osteotome defines the bone removable area. highly used contemporary PS TKA designs. The implants tested in the current study have the characteristic of pro- ducing similar kinematics in the PS mechanism, including flexion angle for cam and post interaction. The PFC Sigma (DePuy Orthopaedics Inc., Warsaw, IN, USA) TKA was introduced in 1996 as an improvement of the Press-Fit Condylar (PFC) implant (Johnson & Johnson, Raynham, MA, USA). Design features regard- ing the PS housing included an updated femoral coronal geometry and a deeper and more prolonged trochlear groove to improve patellar tracking. Recently, few stud- ies have investigated the functional outcome of the PFC and PFC Sigma knee systems [14], showing satisfactory midterm results. Few authors reported minor issues on extensor mechanism complications following the use of this implant [15]. Because of these patello-femoral issues, the PFC Sigma femoral component was redesigned, be- coming available in 2009 under the name PFC Sigma PS (DePuy Orthopaedics Inc., Warsaw, IN, USA). The new principal modifications regarding the PS housing design included a ‘Jcurve’ femoral design, a new femoral box, and smoother trochlear groove edges: these design changes provided a better patellar route during ROM [5]. The Sigma PS implant shows an in vivo posterior cam-post engagement at an average of 93° [16]. A new specific TKA instrumentation (high performance, HP; DePuy Orthopae- dics Inc., Warsaw, IN, USA) was introduced as well, Figure 4 The Persona femoral cutting jig (large sizes) is shown. including a new PS box cutting jig which was evaluated in An osteotome defines the bone removable area. the current study (Figure 2). Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 4 of 5 http://www.josr-online.com/content/9/1/54 Figure 5 Bar diagram showing the maximum volumetric bone resection (cm ) for each PS cutting jigs of the tested designs. The Biomet Vanguard PS TKA (Biomet Inc, Warsaw, cam and peg mechanisms for these designs also have IN, USA) was first introduced in 2003. The femoral com- many differences with regards to size, position, and articu- ponent has a rounded sagittal profile and a wide, deep, lating geometries. and long trochlear groove. The standard box resection cut Very few studies compared bone loss between different is parallel to the distal femoral resection (Figure 3). This types of PS implant devices. In 2000, Haas et al. [20] implant rolls and slides anteriorly until engaging the post showed significant differences in bone loss between differ- and cam mechanism at 78° of flexion. Midterm clinical ent PS designs. Unfortunately, none of them were modern, results of this design are very promising too [17]. patella ‘friendly’ implants. Recently, Wragg et al. [2] com- The Zimmer Persona (Zimmer, Warsaw, IN, USA) pared the amount of sawbone excised between PS and design was born following the experience of the Insall- cruciate retaining designs, showing that significantly more Burstein PS knee, which had a cam and post articulation bone is excised using PS devices. at 60° of knee flexion and the NexGen Legacy (Zimmer, This study had several limitations. First, our measure- Warsaw, IN, USA), which showed initial cam-post engage- ments were performed in an in vitro environment: we ment at 100° [18]. Both of these implants showed satisfac- compared the tridimensional box area required for the tory long-term clinical results [1,19]. The Zimmer Persona PS housing using different PS box cutting jigs and not TKA is characterized by side-specific implants, an in- the real quantity of bone removed during an in vivo box crease in size selection having gender specific measures, osteotomy. This area does not necessarily correspond anatomical asymmetric tibial plates, and a femur-shaped with actual intraoperative bone resection. The amount cutting jig (Figure 4). of bone removable in an in vivo situation is variable and The authors of the current study compared the PS box also dependent upon femoral condyles conformation cutting jigs, divided in small, medium, and large, which and the level of distal femoral resection. Many intramedul- are part of the surgical instrumentation of these knee lary femoral resection guides provide a standard 10-mm systems. All measurements showed that all implants re- distal femur osteotomy. Secondarily, the clinical value of quire some bone resection: few studies correlated quan- removing more or less bone during primary TKA has to be fully established. Our hypothesis, unfortunately not fully tity of bone resection to implant selection in case of revision [7,8]. Our results indicate that some cutting jigs provable by this study, is that resection of a larger segment tested might remove over twice as much bone from the of intercondylar notch might have an influence on in vivo knee kinematics, polyethylene wear, stability of the implant, intercondylar notch; this is especially true in small and medium sizes. and overall survivorship. On the other side, we agree with Other than saving bone stock in prevision of a possible the previous studies reporting on the need of more invasive revision fixation devices (cones, methaphyseal sleeves, and/ implant revision, resection of intercondylar bone may create a potential stress riser in the distal femur, predis- or stems) in the case of extensive bone loss [7]. posing to intercondylar fracture. In this study, we are not attempting to point out a better design at the Conclusions expense of another, but simply to identify a less invasive This study shows that once a PS total knee arthroplasty surgical instrumentation if a PS solution is needed. The design is chosen, some extra bone resection must to be Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 5 of 5 http://www.josr-online.com/content/9/1/54 taken in account. Differences exist in the tridimensional 13. Lee SM, Seong SC, Lee S, Choi WC, Lee MC: Outcomes of the different types of total knee arthroplasty with the identical femoral geometry. PS mechanism housing area of different PS TKA designs. Knee Surg Relat Res 2012, 24(4):214–220. Surgeons still have various options when they select a 14. Hanusch B, Lou TN, Warriner G, Hui A, Gregg P: Functional outcome of PFC TKA design: CR or ultra-congruent implants, which do Sigma fixed and rotating-platform total knee arthroplasty. A prospective randomized controlled trial. Int Orthop 2010, 34:349–354. not need accessory bone resection for the PS mechanism 15. Ranawat AS, Ranawat CS, Slamin JE, Dennis DA: Patellar crepitation in the housing, have shown excellent long-term clinical results. P.F.C. sigma total knee system. Orthopedics 2006, 29(9 Suppl):68–70. 16. Stiehl JB, Dennis DA, Komistek RD, Keblish PA: In vivo kinematic comparison of posterior cruciate ligament retention or sacrifice with a Competing interests mobile bearing total knee arthroplasty. Am J Knee Surg 2000, 13(1):13–18. The authors declare that they have no competing interests. 17. Kievit AJ, Schafroth MU, Blankevoort L, Sierevelt IN, van Dijk CN, van Geenen RC: Early experience with the Vanguard complete total knee system: 2-7 years Authors’ contributions of follow-up and risk factors for revision. J Arthroplasty 2013, 29:348–354 PFI conceived the study, participated in its design and coordination, and [Epub ahead of print]. originally drafted the manuscript. LL participated in the design of the study 18. Moynihan A, Varadarajan K, Hanson GR, Park S, Nha KW, Suggs JF, and performed the statistical analysis. SC performed the instrumentation Johnson T, Li G: In vivo knee kinematics during high flexion after a measurements. AG participated in the design of the study and was posterior-substituting total knee arthroplasty. Int Orthop 2010, responsible for the images section. MM selected the references and 34(4):497–503. reviewed the final manuscript. All authors read and approved the final 19. Seon JK, Park JK, Shin YJ, Seo HY, Lee KB, Song EK: Comparisons of manuscript. kinematics and range of motion in high-flexion total knee arthroplasty: cruciate retaining vs. substituting designs. Knee Surg Sports Traumatol Author details Arthrosc 2011, 19(12):2016–2022. Centro Eccellenza Sostituzioni Articolari Toscana (CESAT), Clinica Ortopedica 20. Haas SB, Nelson CL, Laskin RS: Posterior stabilized knee arthroplasty: an Universita’ di Firenze, Florence 50134, Italy. Fondazione Onlus “In Cammino”, assessment of bone resection. Knee 2000, 7:25–29. Piazza Lavagnini 1, Fucecchio, Florence 50054, Italy. Breyer Center for Overseas Study, Stanford University in Florence, Florence 50100, Italy. Clinica doi:10.1186/s13018-014-0054-y Ortopedica Universita’ di Catania, Catania 95121, Italy. L.U.de.S. Libera Cite this article as: Indelli et al.: Primary posterior stabilized total knee Universita’ degli Studi di Scienze Umane e Tecnologiche, Lugano 6900, arthroplasty: analysis of different instrumentation. Journal of Orthopaedic Surgery and Research 2014 9:54. Switzerland. Received: 9 January 2014 Accepted: 16 June 2014 Published: 19 July 2014 References 1. Indelli PF, Aglietti P, Buzzi R, Baldini A: The Insall-Burstein II prosthesis: a 5- to 9-year follow-up study in osteoarthritic knees. J Arthroplasty 2002, 17(5):544–549. 2. Wragg R, Khan RJZ, Damasena ITW: A comparison of bone loss at total knee replacement: posterior stabilized versus cruciate retaining. J Orthopaedics 2012, 9(1):e1. 3. Becher C, Heyse TJ, Kron N, Ostermeier S, Hurschler C, Schofer MD, Fuchs-Winkelmann S, Tibesku CO: Posterior stabilized TKA reduce patellofemoral contact pressure compared with cruciate retaining TKA in vitro. Knee Surg Sports Traumatol Arthrosc 2009, 17(10):1159–1165. 4. Puloski SK, McCalden RW, MacDonald SJ, Rorabeck CH, Bourne RB: Tibial post wear in posterior stabilized total knee arthroplasty. An unrecognized source of polyethylene debris. J Bone Joint Surg Am 2001, 83-A(3):390–397. 5. Indelli PF, Marcucci M, Pipino G, Charlton S, Carulli C, Innocenti M: The effects of femoral component design on the patello-femoral joint in a PS total knee arthroplasty. Arch Orthop Trauma Surg 2013, 134:59–64 [Epub ahead of print]. 6. Rodriguez-Merchan EC: Instability following total knee arthroplasty. HSS J 2011, 7(3):273–278. 7. Bono JV, Scott RD (Eds): Revision total knee arthroplasty. New York: Springer; Submit your next manuscript to BioMed Central 8. Huten D: Femorotibial bone loss during revision total knee arthroplasty. Orthop Traumatol Surg Res 2013, 99S:S22–S33. and take full advantage of: 9. Pagnano MW, Cushner FD, Scott WN: The role of the posterior cruciate ligament in total knee arthroplasty. J Am Acad Orthop Surg 1998, 6:176–187. • Convenient online submission 10. Joglekar S, Gioe TJ, Yoon P, Schwartz MH: Gait analysis comparison of • Thorough peer review cruciate retaining and substituting TKA following PCL sacrifice. Knee 2012, 19(4):279–285. • No space constraints or color figure charges 11. Zimlitski M, Bhokray KK, Rajan BM, Nachkebia L, Loria G: Total knee • Immediate publication on acceptance arthroplasty with NexGen legacy posterior stabilized. Georgian Med News • Inclusion in PubMed, CAS, Scopus and Google Scholar 2011, 199:14–20. 12. Li G, Zayontz S, Most E, Otterberg E, Sabbag K, Rubash HE: Cruciate-retaining • Research which is freely available for redistribution and cruciate-substituting total knee arthroplasty: an in vitro comparison of the kinematics under muscle loads. J Arthroplasty 2001, Submit your manuscript at 16(8 Suppl 1):150–156. www.biomedcentral.com/submit http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Orthopaedic Surgery and Research Springer Journals

Primary posterior stabilized total knee arthroplasty: analysis of different instrumentation

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Copyright © 2014 by Indelli et al.; licensee BioMed Central Ltd.
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Medicine & Public Health; Orthopedics; Surgical Orthopedics
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Abstract

Background: Intercondylar femoral bone removal during posterior stabilized (PS) total knee arthroplasty (TKA) makes many cruciate substituting implant designs less appealing than cruciate retaining implants. Bone stock conservation is considered fundamental in the prevision of future revision surgeries. The purpose of this study was to compare the quantity of intercondylar bone removable during PS housing preparation using three contemporary PS TKA instrumentations. Method: We compared different box cutting jigs which were utilized for the PS housing of three popular PS knee prostheses. The bone removal area from every PS box cutting jig was three-dimensionally measured. Results: Independently from the implant size, the cutting jig for a specific PS TKA always resected significantly less bone than the others: this difference was statistically significant, especially for small- to medium-sized total knee femoral components. Conclusion: This study does not establish a clinical relevance of removing more or less bone at primary TKA, but suggests that if a PS design is indicated, it is preferable to select a model which possibly resects less distal femoral bone. Keywords: TKA, Total knee arthroplasty, Posterior stabilized, Cruciate substituting total knee arthroplasty Introduction [3]. There are several potential disadvantages in the use of The use of posterior stabilized (PS) implants in total knee PS designs with respect to other CR implants, including arthroplasty (TKA) is becoming increasingly popular. tibial post wear and breakage [4], increased incidence of Many designs, which are modifications of the original anterior knee pain [5], and implant instability especially Insall-Burstein prosthesis (Zimmer, Warsaw, IN, USA) during the midflexion phase [6]. [1], have inherited the classical cam and post mechan- One of the major disadvantages of PS designs is also ism to guide anteroposterior knee motion in lieu of the linked to the amount of bone removed during femoral posterior cruciate ligament. Potential advantages of PS ‘box osteotomy’ for the PS mechanism housing compared TKA include the possibility of easier balancing of severe to posterior cruciate retaining implants. Theoretically, a coronal and sagittal deformities (i.e., varus/valgus or major preservation of bone stock would be useful in the recurvatum), better controlled flexion kinematics, less case of future revision of the implant: in fact, the amount polyethylene sliding wear, greater weight-bearing max- and location of bone loss determine which reconstructive imal flexion, and greater posterior femoral rollback than method (cones, methaphyseal sleeves, and/or stems) will cruciate retaining (CR) high-flexion TKA [2]. A decrement be necessary to achieve implant stability [7]. In a recent in patello-femoral contact pressure in PS TKA designs review, Huten defined previous bone resections as the first when compared to CR designs is another potential advantage cause of bone loss in revision total knee arthroplasty [8]. The current study was performed to examine the max- imum volumetric bone resection area required for the PS * Correspondence: pindelli@stanford.edu Centro Eccellenza Sostituzioni Articolari Toscana (CESAT), Clinica Ortopedica housing of three worldwide highly utilized posterior stabi- Universita’ di Firenze, Florence 50134, Italy lized TKA designs: Sigma PS (De Puy, Johnson & Johnson, Fondazione Onlus “In Cammino”, Piazza Lavagnini 1, Fucecchio, Florence Warsaw, IN, USA), Persona (Zimmer, Warsaw, IN, USA) 50054, Italy Full list of author information is available at the end of the article © 2014 Indelli et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 2 of 5 http://www.josr-online.com/content/9/1/54 and Vanguard (Biomet Orthopedics Inc., Warsaw, IN, caliber (Figures 2, 3, and 4). Data was collected on an USA). The authors compared the manufacturer’sinstru- Excel spreadsheet as an average in the small, medium, ments (PS box cutting jigs) in order to highlight their and large size groups. The size of the saw blade (1 mm) design differences. was considered in the measurement process, as shown in Figures2,3,and 4. Material and method The goal of each measurement was to evaluate the tri- The authors acquired the complete surgical instrumental dimensional box size of each femoral jig, not the amount set of three different PS TKA devices Sigma PS (De Puy, of bone actually removed during the surgical procedure. Johnson & Johnson, Warsaw, IN, USA), Persona (Zim- Statistical analysis was performed using analysis of vari- mer, Warsaw, IN, USA), and Vanguard (Biomet Inc, ance (ANOVA) test with box volume as the dependent Warsaw, IN, USA): analysis of very small (‘micro’) and variable. very large (‘macro’) size implants were excluded for this study. The Sigma PS TKA surgical instrumentation in- Results cluded two cutting jigs for small femoral sizes (sizes 2 and For all implant sizes (Figure 5), the Zimmer Persona jig 2.5), two jigs for medium femoral sizes (sizes 3 and 4), and showed a significantly inferior tridimensional box area one jig for large sizes (size 5). The Vanguard TKA surgical than the Biomet Vanguard and Sigma PS (P <0.003). The instrumentation included three cutting jigs for small difference between the ZimmerPersona and the SigmaPS femoral sizes (sizes 55, 57.5, 60), three jigs for medium was even more statistically significant in small and medium femoral sizes (sizes 62.5, 65, 67.5), and three jigs for large size implants (P < 0.008). sizes (sizes 70, 72.5, 75). The Persona TKA surgical instru- For the small size implant, Biomet Vanguard average mentation included one cutting jig for small femoral sizes tridimensional box area was 11.04 cm compared to 3 3 (sizes 3 to 5), one jig for medium femoral sizes (sizes 6 to 24.03 cm for Sigma PS and to 6.18 cm forZimmerPersona 9), and one jig for large sizes (sizes 10 to 12). In an in vivo (P <0.002). situation, the surgical step necessary for femoral box For the medium size implant, Biomet Vanguard average osteotomy requires application of a cutting jig to the distal tridimensional box area was 13.59 cm compared to 3 3 part of the femur (Figure 1). 28.91 cm for Sigma PS and 7.69 cm for Zimmer Persona An in vitro tridimensional evaluation (anteroposterior (P <0.003). length, mediolateral length, and thickness) of the max- For the large size implant, Biomet Vanguard average imum bone removal area was performed for each of the tridimensional box area was 16.05 cm compared to 3 3 three groups of cutting jigs (small sizes, medium sizes, 36.66 cm for Sigma PS and 13.32 cm forZimmerPersona large sizes) through direct measurement with a millimeter (P < 0.006). Figure 1 Right knee. Intraoperative image of a femoral jig before Figure 2 The De Puy Sigma PS femoral cutting jig (large sizes) ‘box osteotomy.’ is shown. An osteotome defines the bone removable area. Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 3 of 5 http://www.josr-online.com/content/9/1/54 The difference between the Biomet Vanguard and the Sigma PS was statistically significant (P < 0.01), while the difference between the Biomet Vanguard and the Zimmer Persona was not (P > 0.1). The difference between the Sigma PS and the Zimmer Persona was statistically significant (P <0.008). The volumetric bone resection for the PS housing does not include resection volume for the femoral lugs, typ- ical of the Zimmer Persona design. In fact, an additional 0.59 cm of bone was calculated from each of the two lugs of this PS TKA design. Discussion Preservation or substitution of the posterior cruciate ligament in primary TKA is still a controversial issue [9]. Gait analysis [10] and in vivo [11] and in vitro [12] studies showed reproduction of a close to normal knee kinematic using either solution. A clinical comparative study between different types of TKA (cruciate retain- ing or posterior stabilized) with identical femoral geom- etry showed similar midterm outcomes with regards to the range of motion, functional outcomes, and survival rate [13]. The purpose of this study was to compare the max- Figure 3 The Vanguard femoral cutting jig (large sizes) is imum quantity of intercondylar bone removable in three shown. An osteotome defines the bone removable area. highly used contemporary PS TKA designs. The implants tested in the current study have the characteristic of pro- ducing similar kinematics in the PS mechanism, including flexion angle for cam and post interaction. The PFC Sigma (DePuy Orthopaedics Inc., Warsaw, IN, USA) TKA was introduced in 1996 as an improvement of the Press-Fit Condylar (PFC) implant (Johnson & Johnson, Raynham, MA, USA). Design features regard- ing the PS housing included an updated femoral coronal geometry and a deeper and more prolonged trochlear groove to improve patellar tracking. Recently, few stud- ies have investigated the functional outcome of the PFC and PFC Sigma knee systems [14], showing satisfactory midterm results. Few authors reported minor issues on extensor mechanism complications following the use of this implant [15]. Because of these patello-femoral issues, the PFC Sigma femoral component was redesigned, be- coming available in 2009 under the name PFC Sigma PS (DePuy Orthopaedics Inc., Warsaw, IN, USA). The new principal modifications regarding the PS housing design included a ‘Jcurve’ femoral design, a new femoral box, and smoother trochlear groove edges: these design changes provided a better patellar route during ROM [5]. The Sigma PS implant shows an in vivo posterior cam-post engagement at an average of 93° [16]. A new specific TKA instrumentation (high performance, HP; DePuy Orthopae- dics Inc., Warsaw, IN, USA) was introduced as well, Figure 4 The Persona femoral cutting jig (large sizes) is shown. including a new PS box cutting jig which was evaluated in An osteotome defines the bone removable area. the current study (Figure 2). Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 4 of 5 http://www.josr-online.com/content/9/1/54 Figure 5 Bar diagram showing the maximum volumetric bone resection (cm ) for each PS cutting jigs of the tested designs. The Biomet Vanguard PS TKA (Biomet Inc, Warsaw, cam and peg mechanisms for these designs also have IN, USA) was first introduced in 2003. The femoral com- many differences with regards to size, position, and articu- ponent has a rounded sagittal profile and a wide, deep, lating geometries. and long trochlear groove. The standard box resection cut Very few studies compared bone loss between different is parallel to the distal femoral resection (Figure 3). This types of PS implant devices. In 2000, Haas et al. [20] implant rolls and slides anteriorly until engaging the post showed significant differences in bone loss between differ- and cam mechanism at 78° of flexion. Midterm clinical ent PS designs. Unfortunately, none of them were modern, results of this design are very promising too [17]. patella ‘friendly’ implants. Recently, Wragg et al. [2] com- The Zimmer Persona (Zimmer, Warsaw, IN, USA) pared the amount of sawbone excised between PS and design was born following the experience of the Insall- cruciate retaining designs, showing that significantly more Burstein PS knee, which had a cam and post articulation bone is excised using PS devices. at 60° of knee flexion and the NexGen Legacy (Zimmer, This study had several limitations. First, our measure- Warsaw, IN, USA), which showed initial cam-post engage- ments were performed in an in vitro environment: we ment at 100° [18]. Both of these implants showed satisfac- compared the tridimensional box area required for the tory long-term clinical results [1,19]. The Zimmer Persona PS housing using different PS box cutting jigs and not TKA is characterized by side-specific implants, an in- the real quantity of bone removed during an in vivo box crease in size selection having gender specific measures, osteotomy. This area does not necessarily correspond anatomical asymmetric tibial plates, and a femur-shaped with actual intraoperative bone resection. The amount cutting jig (Figure 4). of bone removable in an in vivo situation is variable and The authors of the current study compared the PS box also dependent upon femoral condyles conformation cutting jigs, divided in small, medium, and large, which and the level of distal femoral resection. Many intramedul- are part of the surgical instrumentation of these knee lary femoral resection guides provide a standard 10-mm systems. All measurements showed that all implants re- distal femur osteotomy. Secondarily, the clinical value of quire some bone resection: few studies correlated quan- removing more or less bone during primary TKA has to be fully established. Our hypothesis, unfortunately not fully tity of bone resection to implant selection in case of revision [7,8]. Our results indicate that some cutting jigs provable by this study, is that resection of a larger segment tested might remove over twice as much bone from the of intercondylar notch might have an influence on in vivo knee kinematics, polyethylene wear, stability of the implant, intercondylar notch; this is especially true in small and medium sizes. and overall survivorship. On the other side, we agree with Other than saving bone stock in prevision of a possible the previous studies reporting on the need of more invasive revision fixation devices (cones, methaphyseal sleeves, and/ implant revision, resection of intercondylar bone may create a potential stress riser in the distal femur, predis- or stems) in the case of extensive bone loss [7]. posing to intercondylar fracture. In this study, we are not attempting to point out a better design at the Conclusions expense of another, but simply to identify a less invasive This study shows that once a PS total knee arthroplasty surgical instrumentation if a PS solution is needed. The design is chosen, some extra bone resection must to be Indelli et al. Journal of Orthopaedic Surgery and Research 2014, 9:54 Page 5 of 5 http://www.josr-online.com/content/9/1/54 taken in account. Differences exist in the tridimensional 13. Lee SM, Seong SC, Lee S, Choi WC, Lee MC: Outcomes of the different types of total knee arthroplasty with the identical femoral geometry. PS mechanism housing area of different PS TKA designs. Knee Surg Relat Res 2012, 24(4):214–220. Surgeons still have various options when they select a 14. Hanusch B, Lou TN, Warriner G, Hui A, Gregg P: Functional outcome of PFC TKA design: CR or ultra-congruent implants, which do Sigma fixed and rotating-platform total knee arthroplasty. A prospective randomized controlled trial. Int Orthop 2010, 34:349–354. not need accessory bone resection for the PS mechanism 15. Ranawat AS, Ranawat CS, Slamin JE, Dennis DA: Patellar crepitation in the housing, have shown excellent long-term clinical results. P.F.C. sigma total knee system. Orthopedics 2006, 29(9 Suppl):68–70. 16. Stiehl JB, Dennis DA, Komistek RD, Keblish PA: In vivo kinematic comparison of posterior cruciate ligament retention or sacrifice with a Competing interests mobile bearing total knee arthroplasty. Am J Knee Surg 2000, 13(1):13–18. The authors declare that they have no competing interests. 17. Kievit AJ, Schafroth MU, Blankevoort L, Sierevelt IN, van Dijk CN, van Geenen RC: Early experience with the Vanguard complete total knee system: 2-7 years Authors’ contributions of follow-up and risk factors for revision. J Arthroplasty 2013, 29:348–354 PFI conceived the study, participated in its design and coordination, and [Epub ahead of print]. originally drafted the manuscript. LL participated in the design of the study 18. Moynihan A, Varadarajan K, Hanson GR, Park S, Nha KW, Suggs JF, and performed the statistical analysis. SC performed the instrumentation Johnson T, Li G: In vivo knee kinematics during high flexion after a measurements. AG participated in the design of the study and was posterior-substituting total knee arthroplasty. Int Orthop 2010, responsible for the images section. MM selected the references and 34(4):497–503. reviewed the final manuscript. All authors read and approved the final 19. Seon JK, Park JK, Shin YJ, Seo HY, Lee KB, Song EK: Comparisons of manuscript. kinematics and range of motion in high-flexion total knee arthroplasty: cruciate retaining vs. substituting designs. Knee Surg Sports Traumatol Author details Arthrosc 2011, 19(12):2016–2022. Centro Eccellenza Sostituzioni Articolari Toscana (CESAT), Clinica Ortopedica 20. Haas SB, Nelson CL, Laskin RS: Posterior stabilized knee arthroplasty: an Universita’ di Firenze, Florence 50134, Italy. Fondazione Onlus “In Cammino”, assessment of bone resection. Knee 2000, 7:25–29. Piazza Lavagnini 1, Fucecchio, Florence 50054, Italy. Breyer Center for Overseas Study, Stanford University in Florence, Florence 50100, Italy. Clinica doi:10.1186/s13018-014-0054-y Ortopedica Universita’ di Catania, Catania 95121, Italy. L.U.de.S. Libera Cite this article as: Indelli et al.: Primary posterior stabilized total knee Universita’ degli Studi di Scienze Umane e Tecnologiche, Lugano 6900, arthroplasty: analysis of different instrumentation. Journal of Orthopaedic Surgery and Research 2014 9:54. Switzerland. Received: 9 January 2014 Accepted: 16 June 2014 Published: 19 July 2014 References 1. Indelli PF, Aglietti P, Buzzi R, Baldini A: The Insall-Burstein II prosthesis: a 5- to 9-year follow-up study in osteoarthritic knees. J Arthroplasty 2002, 17(5):544–549. 2. Wragg R, Khan RJZ, Damasena ITW: A comparison of bone loss at total knee replacement: posterior stabilized versus cruciate retaining. J Orthopaedics 2012, 9(1):e1. 3. 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Journal of Orthopaedic Surgery and Research – Springer Journals

Published: Jul 19, 2014

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