The Journal of Arthroplasty 30 (2015) 587–591
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Condylar-Stabilizing Tibial Inserts Do Not Restore Anteroposterior Stability After Total Knee Arthroplasty Yoo-Joon Sur, MD, In-Jun Koh, MD, Se-Wook Park, MD, Hyung-Jin Kim, MD, Yong In, MD Department of Orthopaedic Surgery, College of Medicine, The Catholic University of Korea
a r t i c l e
i n f o
Article history: Received 15 August 2014 Accepted 8 November 2014 Keywords: total knee arthroplasty posterior cruciate ligament tibial insert stability range of motion
a b s t r a c t The Triathlon condylar-stabilizing (CS) lipped insert is designed to provide anteroposterior (AP) stability of the posterior-stabilized (PS) insert, without a post. The purpose of this study was to compare the AP stability of the knee in patients with Triathlon CS and PS total knee arthroplasty (TKA) with midterm follow-up. Thirtyone patients received a Triathlon PS TKA in one knee and a Triathlon CS TKA in the contralateral knee, and 28 patients were followed up with a minimum duration of 5 years. Although there was no difference in functional outcomes, the posterior displacement was significantly greater in the CS TKA group than in the PS TKA group (P b 0.001). The Triathlon CS lipped insert could not restore posterior stability with PCL sacrifice. © 2014 Elsevier Inc. All rights reserved.
While the debate between posterior cruciate ligament (PCL) retention or sacrifice in total knee arthroplasty (TKA) continues [1–4], clinical evidence suggests that if the PCL is sacrificed, the function of the knee is improved if some form of PCL substitution is performed [5,6]. The geometry of the components and cam-post mechanism are two issues deemed to influence the kinematics of PCL-sacrificing TKA [7]. In posterior-stabilized (PS) TKA, the physiologic rollback of the femur on the tibia is approximated by the secondary articulation of a central polyethylene spine on the tibial component and a transverse cam on the femoral component. Although this design has proved useful, it is not without clinical problems and complications, such as post breakage [8,9], dislocation [10,11], and patellar clunk syndrome [12,13]. These clinical complications suggest that there is room for improvement for posterior stabilization in TKA with PCL-sacrificing designs. Most manufacturers have begun to produce highly conforming polyethylene inserts with an elevated anterior lip. The use of a highly conforming polyethylene in combination with a cruciate-retaining (CR) femoral component has several theoretical advantages over the cam-post mechanism for a PS TKA design, which include: 1) preservation of the femoral bone stock, 2) quick and easy decision for PCL sacrifice depending on the gap balance, and 3) avoidance of complications related to the cam-post mechanism [14,15]. Although favorable clinical results have been reported with the use of a highly conforming
polyethylene insert [16–18], there is a paucity of evidence about knee stability after TKA using a highly conforming polyethylene insert in combination with PCL sacrifice. The Triathlon condylar-stabilizing (CS) lipped insert (Stryker Orthopaedics, Mahwah, NJ) is a high performance insert designed to provide patients with more natural motion and the potential for greater implant longevity without the use of a PS post (Fig. 1). This tibial insert design uses a highly conforming anterior buildup to increase the surface area contact with the femoral component throughout range of motion. The CS insert provides anteroposterior (AP) constraint without the need to perform box cuts and is flexible for use with either PCL retention or sacrifice. Manufacturers claim that this insert can provide great anterior constraint in combination with a single-radius femoral component without sacrificing internal/external rotation, as seen in most ultracongruent designs. We questioned whether a PCL-sacrificing CS TKA could restore AP stability of the knee. The purpose of this study was to compare the AP stability of the knee as well as the clinical and radiographic results in patients receiving either a CS TKA with PCL sacrifice or a PS TKA with midterm follow-up. The hypothesis was that a CS lipped insert would provide adequate AP stability of the knee in the absence of a functioning PCL comparable to that of a PS insert. Materials and Methods
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.11.018. Reprint requests: Yong In, MD, Department of Orthopaedic Surgery, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpodaero, Seocho-Gu, 137-701, Seoul, Korea. http://dx.doi.org/10.1016/j.arth.2014.11.018 0883-5403/© 2014 Elsevier Inc. All rights reserved.
Between September 2008 and February 2009, we carried out a prospective randomized clinical trial to compare the clinical and radiographic results between the Triathlon CS and PS TKA in patients undergoing one-stage bilateral TKA. This study was approved by the hospital Institutional Review Board. The inclusion criterion was patients with degenerative osteoarthritis in both knees who were scheduled for
588
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
Fig. 1. The Triathlon CS insert (A) has a highly conforming anterior buildup to increase the surface area contact with the femoral component, while the PS insert (B) has a post on its center portion.
one-stage bilateral TKA. The primary objective of this study was to compare the AP stability of the knee in patients who had received a CS TKA in one knee and a PS TKA in the other. Based on previous studies [19,20], 22 patients (22 knees in each group) were required to detect a difference of 3 mm of AP displacement with the use of a two-tailed test (α = 0.05, power = 0.80). Patients with rheumatoid arthritis, osteonecrosis, and posttraumatic osteoarthritis were excluded from the study (three patients). TKA candidates who had previous knee surgery on either knee were excluded (three patients). Patients who had knee range of motion less than 90° were also excluded (three patients). All patients gave written consent prior to the study. After taking into account the drop-out rate, 31 consecutive patients undergoing one-stage bilateral TKA were included in the study. One patient died 1 year after the surgery and two patients were lost to follow-up. In total, 28 patients were followed up with a minimum duration of 5 years (mean: 5.2 years, range: 5–5.5 years). There were 26 women and two men with a mean age of 68.4 ± 7.2 years (range: 56–82 years) at the time of TKA. The mean BMI was 29.3 ± 4.5 kg/m 2 (range: 22.5–41 kg/m2). Randomization to perform CS or PS TKA was accomplished with the use of a sealed envelope that was opened in the operating room before performing surgery. TKAs were performed on both knees sequentially during one session of general anesthesia. Each patient received a Triathlon CS TKA on one knee and a PS TKA on the contralateral knee. A tourniquet was used for all knees. All of the operations were performed by the senior author using the subvastus approach without patellar eversion. Before bone cutting, the PCL was sacrificed in both CS and PS TKAs. Femoral preparation was performed without box cutting for the CS TKA, whereas femoral box cutting was performed for the PS TKA. After bone cutting and appropriate soft tissue release for the correction of the deformity, gap balancing was evaluated using a femorotibial distractor device (Aesculap, Tuttlingen, Germany). Mediolateral flexion–extension gaps were considered to be balanced if
the gap differences were within 2 mm. For the CS TKA, the CR femoral component and the CS tibial insert were implanted, while the PS femoral component and the PS tibial insert were implanted for the PS TKA. All of the patellae were resurfaced using the same eyeball technique. All components were cemented. No knee in either group underwent lateral retinacular release. All patients received the same rehabilitation program. On the first postoperative day, all patients began weightbearing walking with the use of a walker. They were encouraged to perform active range of motion exercises. The closed suction drain was removed 48 h after operation. Skin staples were routinely removed at 10 days after the operation. Clinical and radiographic evaluations were done at 3, 6, and 12 months postoperatively, and then yearly thereafter. Each knee was rated preoperatively and postoperatively using the Knee Society score [21] and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [22]. The active range of motion was measured using a standard 60-cm-long goniometer before the operation and at the time of each follow-up visit. The patients were told to bend their knees as much as they could in a sitting position. At each follow-up, lower extremity alignment was evaluated by measuring the femorotibial angle on a standing AP radiograph. Preoperatively, there were no differences in knee alignments, range of motion, Knee Society scores, and WOMAC scores between the groups (Table 1). Evaluation of the postoperative radiolucent lines at the bone-cement interface was performed using the standing AP, lateral, and merchant radiographs. AP stability of the knee was evaluated using the anterior and posterior stress radiographs with the Telos Stress Device (Telos, Hungen, Germany). Patients were in the lateral decubitus position on the table. A 15 kg force was applied anteriorly and posteriorly with the knee in 90° of flexion and in neutral rotation position. Measurements of anterior and posterior displacement were made by tracing lines along the posterior margin of the tibial component and the most posterior edge of the femoral component, which were parallel to the posterior tibial cortex. The displacement was determined by measuring the perpendicular distance between lines. Anterior and posterior displacements were measured three times by one of the authors. The average value of the three measurements was used. Statistical comparison of the clinical results was performed using SPSS version 13.0 software (SPSS Inc., Chicago, Illinois). Means and standard deviations were used to describe the data. The differences between groups were calculated using a parametric test for independent samples (Student’s t-test). A P value of b 0.05 was considered statistically significant. Results At the final follow-up, the mean postoperative knee alignment was valgus 5.8° ± 2.7° (range, vagus 2°–valgus 12°) in the CS TKA group, and vagus 5.0° ± 2.4° (range, valgus 1°–valgus 10°) in the PS group. The mean postoperative posterior slope of the tibial component was 4.7° ± 2.4° (range, − 0.2°–9.2°) in the CS TKA group, and 4.2° ± 2.4° (range, 0°–10.1°) in the PS group. There were no significant differences in the knee alignment and tibial slope at final follow-up (P = 0.273 and P = 0.523, respectively). The mean range of motion of the knee was 135.8° ± 9.0° (range, 120°–145°) in the CS TKA group, and 133.6° ± 12.2° (range, 100°–145°) in the PS group (P = 0.446). The postoperative WOMAC score and detailed Knee Society scores are summarized in Table 2. Although the WOMAC scores did not differ between the two groups (P = 0.340), there were significant differences in the Knee Society scores (P = 0.017). The scores of the AP stability item were worse for knees with the CS TKA than the scores for knees with the PS TKA at final follow-up (P b 0.001). There were no noticeable radiolucent lines on the latest knee AP and lateral radiographs in both groups. The postoperative AP laxity of the knee was calculated by the sum of the anterior and posterior displacements that were measured on stress radiographs. There was no
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
589
Table 1 Preoperative Data of Patients Undergoing One-Stage Bilateral TKA with Randomization to Treatment with a CS or PS Implant.
Knee alignment (°) Flexion contracture (°) Maximum flexion (°) Knee Society score WOMAC score
Condylar-Stabilizing Group (n = 28)
Posterior-Stabilized Group (n = 28)
Varus 4.4 ± 5.1 (valgus 5.3–varus14.1) 8.7 ± 6.3 (0–25) 129.6 ± 12.6 (100–145) 114.8 ± 23.1 (65–145) 62.7 ± 7.4 (46.6–85.6)
Varus 4.2 ± 4.0 (valgus 6.7–varus 13.0) 8.6 ± 7.5 (0–35) 133.7 ± 11.1 (110–145) 113.0 ± 25.6 (25–153) 63.7 ± 8.6 (46.2–82.4)
significant difference in anterior displacement between the two groups (P = 0.474). However, the posterior displacement was significantly greater in the CS TKA group than in the PS TKA group (P b 0.001). Accordingly, the AP laxity was significantly greater in the CS TKA group than in the PS TKA group (P b 0.001) (Table 3) (Fig. 2). At the last follow-up, no knee had loosening of the femoral, tibial, or patellar component. No knee had a subluxation or dislocation of either the femorotibial or patellofemoral joint. Discussion In the current study, we found that PCL-sacrificing CS TKA could not restore AP stability of the knee at midterm follow-up. The anterior buildup of the CS tibial insert, which is the equivalent of the cam-post mechanism of the PS TKA, failed to provide reliable femoral rollback. Because of AP instability, objective scoring of the Knee Society score was worse for knees with the CS TKA than the score for knees with the PS TKA. Proponents of sacrificing the PCL in TKA have suggested that excision of the PCL makes ligament balancing easier and that the cam-post mechanism provides more reliable femoral rollback [23–25]. A highly conforming polyethylene has been introduced as an alternative to the cam-post mechanism to complement the disadvantages of the PS TKA system. A search of the literature yielded few articles on the outcomes of TKAs using highly congruent/dished polyethylene tibial inserts. Laskin et al [17] compared a dished polyethylene tibial polyethylene insert with a PS tibial insert after sacrificing the PCL and reported no statistically significant differences in the range of motion, ability to ascend and descend stairs, or knee scores. Sathappan et al [18] assessed the midterm results of TKA performed with either a recessed or sacrificed PCL with a dished polyethylene insert. There were no statistically significant differences between PCL recession and resection cases with regard
Table 2 Clinical Results at Latest Follow-Up.
WOMAC score Knee Society score Objective scoring Pain Range of motion APa stability MLb stability Flexion contracture Extension lag Alignment Functional scoring Walking Stairs Functional deductions a b
Anteroposterior. Mediolateral.
Condylar-Stabilizing Group (n = 28)
Posterior-Stabilized Group (n = 28)
11.1 ± 2.1 (7.5–36.3) 172.4 ± 14.0 (139–200)
10.5 ± 2.4 (7.1–30.2) 181.5 ± 13.6 (139–190)
48.5 24.7 4.1 14.6
± ± ± ±
2.6 (40–50) 0.4 (20–25) 3.3 (0–10) 1.3 (10–15) 0 0 −2.8 ± 4.2 (−12–0)
40.7 ± 7.6 (20–50) 42.5 ± 7.5 (30–50) 0
48.9 24.5 9.2 14.6
± ± ± ±
2.8 (40–50) 1.2 (24–25) 1.7 (0–10) 1.3 (10–15) 0 0 −2.7 ± 4.0 (−15–0)
42.5 ± 7.5 (30–50) 44.4 ± 7.3 (30–50) 0
P Value 0.340 0.017
0.630 0.263 0.000 1.000
0.923
0.383 0.328
P Value 0.867 0.954 0.204 0.777 0.641
to range of motion, Knee Society scores, or WOMAC scores. Nonetheless, there have been no kinematic reports evaluating knee stability after TKA with the use of a highly congruent/dished polyethylene insert. The design characteristics of the Triathlon CS knee system reportedly allow for better AP stability and PCL substitution due to two advanced features; 1) an increased anterior rise on the insert complements constant tension of the collateral ligaments to further aid in substituting for the PCL, 2) a single AP radius of the femoral component maintains ligamentous isometry throughout range of motion. Theoretically, the CS tibial insert can provide AP stability of the PS insert without a post or box cut. Louisia et al [26] compared the posterior stability of two different designs of TKA with deep-dished mobile-bearing implants using stress X-rays. Interestingly, both designs of the deep-dished mobile-bearing inserts showed significant posterior tibial translation on stress X-rays. Although the authors tested two mobile-bearing inserts, their results are in agreement with our current study. Owing to unique design features, a mobile-bearing TKA theoretically lessens the surface contact stress by decoupling the components. Therefore, the conformity of the femoral component and tibial insert of the mobile-bearing knee system can be maximized for implant stability [27]. On the other hand, in fixed-bearing design TKA, the conformity of the femoral component and tibial insert is limited by the risk of restricted range of motion and component loosening. In our study, no significant difference was detected in the range of motion between the two groups. We initially expected worse range of motion in the CS TKA group than in the PS TKA group if the CS insert could not provide proper femoral rollback. The femoral rollback mechanism provided by the cam-post mechanism in PS TKA is responsible for the controlled posterior shift of the femur on the tibia, and therefore provides greater posterior clearance in flexion [5]. It has been argued that this leads to improved range of knee motion. Paradoxical forward sliding of the femur without PCL function leads to limitations in flexion [28]. However, there exists a controversy regarding the relationship between knee laxity and range of motion. Ishii et al [29] investigated whether AP translation correlated with the maximum knee flexion angle in a TKA with implantation of a PCL-substituting mobile-bearing prosthesis. They found that there was no correlation between postoperative maximum knee flexion and AP translation. Our results support the suggestion of their study. In our study, even the CS TKA showed significant AP laxity as compared to the PS TKA, and the range of motion had no correlation with knee AP stability. Recently, Berend et al [30] assessed 2449 CR TKAs to determine whether different CR-bearing insert designs provided better range of motion. A CR tibial insert with a 3° posterior slope was inserted in 1334 TKAs. An insert with no slope and a small posterior lip was used in 803 knees. In 312 knees, the PCL was either resected or lax and a deep-dish, anterior-stabilized insert was used in these cases. Despite sacrificing or not substituting for the PCL, the range of motion improvement was the highest, and the manipulation under anesthesia rate was the lowest in TKAs with a deep-dish, anterior-stabilized insert. The authors concluded that substitution for the PCL in the form of a PS design might not be necessary even when the PCL is deficient. Although their study was limited to CR TKAs and there was a lack of data on sagittal stability, in agreement with our results, it was suggested that
590
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
Table 3 Anterior and Posterior Displacements on Stress Radiographs at Latest Follow-Up.
Anterior displacement (mm) Posterior displacement (mm) APa laxity (mm) a
Condylar-Stabilizing Group (n = 28)
Posterior-Stabilized Group (n = 28)
P Value
0.24 ± 4.51 (−9.00–7.40) −9.54 ± 3.22 (−14.79–6.90) 9.78 ± 4.96 (1.50–19.38)
0.97 ± 2.83 (−4.47–6.53) −1.69 ± 1.99 (−5.00–4.80) 3.01 ± 2.31 (0–7.61)
0.474 b 0.001 b 0.001
AP; anteroposterior.
the range of motion after PCL-sacrificing TKA with use of a highly congruent/dished polyethylene insert would be comparable to that of CR or PS TKAs. In this study, we found that the midterm functional outcomes for knees with a CS TKA were similar to those for knees with a PS TKA. There were no significant differences in WOMAC scores and functional scorings of Knee Society scores between groups. Our results do not reflect the results of previous reports on PCL substitution in TKA with regards to knee function. It has been known that appropriate PCL substitution allows for better AP stability, increased range of motion, reduced quadriceps force in extension, improved stair-climbing ability, and improved patellofemoral function [31,32]. This probably is because the lack of femoral rollback decreases the moment arm of the extension mechanism so that more quadriceps force is needed for knee extension. Stair climbing is likely to be more difficult, and stress is likely to be greater at the tibial articular surface in knees without appropriate femoral rollback. Although more studies with improved methods are needed to evaluate knee function following TKA, our study showed that substantial posterior laxity of the knee did not affect knee function such as walking or stair ambulation.
In the present study, the results of the CS TKA group raise the question of the consequences of AP laxity on polyethylene wear in the long term. Seon et al [33] suggested that the preservation of the PCL in CR TKA would keep the femoral rollback, reproducing the normal movement of the joint and preventing a posterior translation. It has been theorized that a well-functioning PCL would reduce the aseptic loosening and polyethylene wear after TKA [34]. In our study, with a minimum duration of 5 years, we could not find any radiolucent line around the femoral or tibial components in both groups. However, we believe that long-term followup is needed to determine whether substantial AP laxity of the knee can be a potential cause of catastrophic failure after TKA. Mont et al [35] compared a CS insert with a CR insert in Triathlon CR TKAs. Reasons for the use of a CS insert included flexion instability and failure to obtain equal flexion and extension gaps. They found that the use of a Triathlon CR TKA showed comparable results with both polyethylene inserts at short-term follow-up. Based on our study, we suggest that a CS insert can be used in CR TKA when it comes to PCL recession. The major limitation of the present study is that there is no consensus on optimal AP laxity of the knee following TKA. Although
Fig. 2. A 72-year-old female patient’s stress radiographs of both knees. Anterior (A) and posterior (B) stress radiographs of the right knee with a CS TKA show greater posterior displacement than the anterior (C) and posterior (D) stress radiographs of the left knee with a PS TKA.
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
the distance of translation differs depending on the study, a postoperative AP translation of approximately 5 to 10 mm is believed to be the preferred value for TKA [29,36,37]. Ishii et al reported that proper AP translation facilitates physiologic rollback of the femoral component [29]. In this study, the CS TKA group showed a mean 9.78 mm AP displacement, of which posterior displacement accounted for over 97% of the total laxity. Although the kinetics of the knee after TKA is different from that of the normal knee, it is believed that the amount of the posterior displacement of the CS TKA group is too much to restore normal knee function. Secondly, the sample size might not be sufficiently large to reveal a difference in WOMAC score and functional score between groups. Because our primary objective was to compare the AP stability over the first 5 postoperative years in patients who had received a CS TKA in one knee and a PS TKA in the other, the sample size was calculated for the primary outcomes. In conclusion, our findings revealed that a CS TKA could not restore AP stability with PCL sacrifice. Although the midterm functional outcomes for knees with a CS TKA were similar to those for knees with a PS TKA, we suggest that the CS TKA has no benefits with regards to knee stability after TKA.
15.
16.
17.
18.
19. 20.
21. 22.
23. 24.
References 1. Chaudhary R, Beaupre LA, Johnston DW. Knee range of motion during the first two years after use of posterior cruciate-stabilizing or posterior cruciate-retaining total knee prostheses. A randomized clinical trial. J Bone Joint Surg Am 2008;90(12):2579. 2. Clark CR, Rorabeck CH, MacDonald S, et al. Posterior-stabilized and cruciate-retaining total knee replacement: a randomized study. Clin Orthop Relat Res 2001;392:208. 3. Kim YH, Choi Y, Kwon OR, et al. Functional outcome and range of motion of high-flexion posterior cruciate-retaining and high-flexion posterior cruciate-substituting total knee prostheses. A prospective, randomized study. J Bone Joint Surg Am 2009;91(4):753. 4. Victor J, Banks S, Bellemans J. Kinematics of posterior cruciate ligament-retaining and -substituting total knee arthroplasty: a prospective randomised outcome study. J Bone Joint Surg (Br) 2005;87(5):646. 5. Harato K, Bourne RB, Victor J, et al. Midterm comparison of posterior cruciateretaining versus -substituting total knee arthroplasty using the Genesis II prosthesis. A multicenter prospective randomized clinical trial. Knee 2008;15(3):217. 6. Maruyama S, Yoshiya S, Matsui N, et al. Functional comparison of posterior cruciateretaining versus posterior stabilized total knee arthroplasty. J Arthroplasty 2004;19(3):349. 7. Pandit H, Ward T, Hollinghurst D, et al. Influence of surface geometry and the campost mechanism on the kinematics of total knee replacement. J Bone Joint Surg (Br) 2005;87(7):940. 8. Lee CS, Chen WM, Kou HC, et al. Early nontraumatic fracture of the polyethylene tibial post in a NexGen LPS-Flex posterior stabilized knee prosthesis. J Arthroplasty 2009; 24(8):1292.e5. 9. Lim HC, Bae JH, Hwang JH, et al. Fracture of a polyethylene tibial post in a Scorpio posterior-stabilized knee prosthesis. Clin Orthop Surg 2009;1(2):118. 10. Jung WH, Jeong JH, Ha YC, et al. High early failure rate of the Columbus posterior stabilized high-flexion knee prosthesis. Clin Orthop Relat Res 2012;470(5):1472. 11. Lee SC, Jung KA, Nam CH, et al. Anterior dislocation after a posterior stabilized total knee arthroplasty. J Arthroplasty 2012;27(2):324.e17. 12. Frye BM, Floyd MW, Pham DC, et al. Effect of femoral component design on patellofemoral crepitance and patella clunk syndrome after posterior-stabilized total knee arthroplasty. J Arthroplasty 2012;27(6):1166. 13. Yau WP, Wong JW, Chiu KY, et al. Patellar clunk syndrome after posterior stabilized total knee arthroplasty. J Arthroplasty 2003;18(8):1023. 14. Lutzner J, Firmbach FP, Lutzner C, et al. Similar stability and range of motion between cruciate-retaining and cruciate-substituting ultracongruent insert total knee
25.
26.
27. 28.
29.
30.
31.
32. 33.
34.
35.
36. 37.
591
arthroplasty. Knee Surg Sports Traumatol Arthrosc 2014 [Epub ahead of print, PMID: 24519619]. Peters CL, Mulkey P, Erickson J, et al. Comparison of total knee arthroplasty with highly congruent anterior-stabilized bearings versus a cruciate-retaining design. Clin Orthop Relat Res 2014;472(1):175. Hofmann AA, Tkach TK, Evanich CJ, et al. Posterior stabilization in total knee arthroplasty with use of an ultracongruent polyethylene insert. J Arthroplasty 2000; 15(5):576. Laskin RS, Maruyama Y, Villaneuva M, et al. Deep-dish congruent tibial component use in total knee arthroplasty: a randomized prospective study. Clin Orthop Relat Res 2000;380:36. Sathappan SS, Wasserman B, Jaffe WL, et al. Midterm results of primary total knee arthroplasty using a dished polyethylene insert with a recessed or resected posterior cruciate ligament. J Arthroplasty 2006;21(7):1012. Mizu-Uchi H, Matsuda S, Miura H, et al. Anteroposterior stability in posterior cruciate ligament-retaining total knee arthroplasty. J Arthroplasty 2006;21(4):592. Schuster AJ, von Roll AL, Pfluger D, et al. Anteroposterior stability after posterior cruciate-retaining total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2011;19(7):1113. Insall JN, Dorr LD, Scott RD, et al. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res 1989;248:13. Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15(12):1833. Bercik MJ, Joshi A, Parvizi J. Posterior cruciate-retaining versus posterior-stabilized total knee arthroplasty: a meta-analysis. J Arthroplasty 2013;28(3):439. Straw R, Kulkarni S, Attfield S, et al. Posterior cruciate ligament at total knee replacement. Essential, beneficial or a hindrance? J Bone Joint Surg (Br) 2003; 85(5):671. Verra WC, van den Boom LG, Jacobs W, et al. Retention versus sacrifice of the posterior cruciate ligament in total knee arthroplasty for treating osteoarthritis. Cochrane Database Syst Rev 2013;10:CD004803. Louisia S, Siebold R, Canty J, et al. Assessment of posterior stability in total knee replacement by stress radiographs: prospective comparison of two different types of mobile bearing implants. Knee Surg Sports Traumatol Arthrosc 2005;13(6):476. Dennis DA, Komistek RD. Mobile-bearing total knee arthroplasty: design factors in minimizing wear. Clin Orthop Relat Res 2006;452:70. Stiehl JB, Dennis DA, Komistek RD, et al. In vivo kinematic comparison of posterior cruciate ligament retention or sacrifice with a mobile bearing total knee arthroplasty. Am J Knee Surg 2000;13(1):13. Ishii Y, Noguchi H, Takeda M, et al. Anteroposterior translation does not correlate with knee flexion after total knee arthroplasty. Clin Orthop Relat Res 2014;472(2): 704. Berend KR, Lombardi Jr AV, Adams JB. Which total knee replacement implant should I pick? Correcting the pathology: the role of knee bearing designs. Bone Joint J 2013; 95-B(11 Suppl. A):129. Insall JN, Lachiewicz PF, Burstein AH. The posterior stabilized condylar prosthesis: a modification of the total condylar design. Two to four-year clinical experience. J Bone Joint Surg Am 1982;64(9):1317. Scott WN, Rubinstein M, Scuderi G. Results after knee replacement with a posterior cruciate-substituting prosthesis. J Bone Joint Surg Am 1988;70(8):1163. Seon JK, Park JK, Jeong MS, et al. Correlation between preoperative and postoperative knee kinematics in total knee arthroplasty using cruciate retaining designs. Int Orthop 2011;35(4):515. Carvalho Jr LH, Temponi EF, Soares LF, et al. Relationship between range of motion and femoral rollback in total knee arthroplasty. Acta Orthop Traumatol Turc 2014; 48(1):1. Mont MA, Costa CR, Naiziri Q, et al. Comparison of 2 polyethlene inserts for a new cruciate-retaining total knee arthroplasty prosthesis. Orthopedics 2013; 36(1):33. Jones DP, Locke C, Pennington J, et al. The effect of sagittal laxity on function after posterior cruciate-retaining total knee replacement. J Arthroplasty 2006;21(5):719. Seon JK, Song EK, Yoon TR, et al. In vivo stability of total knee arthroplasty using a navigation system. Int Orthop 2007;31(1):45.
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Condylar-Stabilizing Tibial Inserts Do Not Restore Anteroposterior Stability After Total Knee Arthroplasty Yoo-Joon Sur, MD, In-Jun Koh, MD, Se-Wook Park, MD, Hyung-Jin Kim, MD, Yong In, MD Department of Orthopaedic Surgery, College of Medicine, The Catholic University of Korea
a r t i c l e
i n f o
Article history: Received 15 August 2014 Accepted 8 November 2014 Keywords: total knee arthroplasty posterior cruciate ligament tibial insert stability range of motion
a b s t r a c t The Triathlon condylar-stabilizing (CS) lipped insert is designed to provide anteroposterior (AP) stability of the posterior-stabilized (PS) insert, without a post. The purpose of this study was to compare the AP stability of the knee in patients with Triathlon CS and PS total knee arthroplasty (TKA) with midterm follow-up. Thirtyone patients received a Triathlon PS TKA in one knee and a Triathlon CS TKA in the contralateral knee, and 28 patients were followed up with a minimum duration of 5 years. Although there was no difference in functional outcomes, the posterior displacement was significantly greater in the CS TKA group than in the PS TKA group (P b 0.001). The Triathlon CS lipped insert could not restore posterior stability with PCL sacrifice. © 2014 Elsevier Inc. All rights reserved.
While the debate between posterior cruciate ligament (PCL) retention or sacrifice in total knee arthroplasty (TKA) continues [1–4], clinical evidence suggests that if the PCL is sacrificed, the function of the knee is improved if some form of PCL substitution is performed [5,6]. The geometry of the components and cam-post mechanism are two issues deemed to influence the kinematics of PCL-sacrificing TKA [7]. In posterior-stabilized (PS) TKA, the physiologic rollback of the femur on the tibia is approximated by the secondary articulation of a central polyethylene spine on the tibial component and a transverse cam on the femoral component. Although this design has proved useful, it is not without clinical problems and complications, such as post breakage [8,9], dislocation [10,11], and patellar clunk syndrome [12,13]. These clinical complications suggest that there is room for improvement for posterior stabilization in TKA with PCL-sacrificing designs. Most manufacturers have begun to produce highly conforming polyethylene inserts with an elevated anterior lip. The use of a highly conforming polyethylene in combination with a cruciate-retaining (CR) femoral component has several theoretical advantages over the cam-post mechanism for a PS TKA design, which include: 1) preservation of the femoral bone stock, 2) quick and easy decision for PCL sacrifice depending on the gap balance, and 3) avoidance of complications related to the cam-post mechanism [14,15]. Although favorable clinical results have been reported with the use of a highly conforming
polyethylene insert [16–18], there is a paucity of evidence about knee stability after TKA using a highly conforming polyethylene insert in combination with PCL sacrifice. The Triathlon condylar-stabilizing (CS) lipped insert (Stryker Orthopaedics, Mahwah, NJ) is a high performance insert designed to provide patients with more natural motion and the potential for greater implant longevity without the use of a PS post (Fig. 1). This tibial insert design uses a highly conforming anterior buildup to increase the surface area contact with the femoral component throughout range of motion. The CS insert provides anteroposterior (AP) constraint without the need to perform box cuts and is flexible for use with either PCL retention or sacrifice. Manufacturers claim that this insert can provide great anterior constraint in combination with a single-radius femoral component without sacrificing internal/external rotation, as seen in most ultracongruent designs. We questioned whether a PCL-sacrificing CS TKA could restore AP stability of the knee. The purpose of this study was to compare the AP stability of the knee as well as the clinical and radiographic results in patients receiving either a CS TKA with PCL sacrifice or a PS TKA with midterm follow-up. The hypothesis was that a CS lipped insert would provide adequate AP stability of the knee in the absence of a functioning PCL comparable to that of a PS insert. Materials and Methods
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.11.018. Reprint requests: Yong In, MD, Department of Orthopaedic Surgery, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, 222 Banpodaero, Seocho-Gu, 137-701, Seoul, Korea. http://dx.doi.org/10.1016/j.arth.2014.11.018 0883-5403/© 2014 Elsevier Inc. All rights reserved.
Between September 2008 and February 2009, we carried out a prospective randomized clinical trial to compare the clinical and radiographic results between the Triathlon CS and PS TKA in patients undergoing one-stage bilateral TKA. This study was approved by the hospital Institutional Review Board. The inclusion criterion was patients with degenerative osteoarthritis in both knees who were scheduled for
588
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
Fig. 1. The Triathlon CS insert (A) has a highly conforming anterior buildup to increase the surface area contact with the femoral component, while the PS insert (B) has a post on its center portion.
one-stage bilateral TKA. The primary objective of this study was to compare the AP stability of the knee in patients who had received a CS TKA in one knee and a PS TKA in the other. Based on previous studies [19,20], 22 patients (22 knees in each group) were required to detect a difference of 3 mm of AP displacement with the use of a two-tailed test (α = 0.05, power = 0.80). Patients with rheumatoid arthritis, osteonecrosis, and posttraumatic osteoarthritis were excluded from the study (three patients). TKA candidates who had previous knee surgery on either knee were excluded (three patients). Patients who had knee range of motion less than 90° were also excluded (three patients). All patients gave written consent prior to the study. After taking into account the drop-out rate, 31 consecutive patients undergoing one-stage bilateral TKA were included in the study. One patient died 1 year after the surgery and two patients were lost to follow-up. In total, 28 patients were followed up with a minimum duration of 5 years (mean: 5.2 years, range: 5–5.5 years). There were 26 women and two men with a mean age of 68.4 ± 7.2 years (range: 56–82 years) at the time of TKA. The mean BMI was 29.3 ± 4.5 kg/m 2 (range: 22.5–41 kg/m2). Randomization to perform CS or PS TKA was accomplished with the use of a sealed envelope that was opened in the operating room before performing surgery. TKAs were performed on both knees sequentially during one session of general anesthesia. Each patient received a Triathlon CS TKA on one knee and a PS TKA on the contralateral knee. A tourniquet was used for all knees. All of the operations were performed by the senior author using the subvastus approach without patellar eversion. Before bone cutting, the PCL was sacrificed in both CS and PS TKAs. Femoral preparation was performed without box cutting for the CS TKA, whereas femoral box cutting was performed for the PS TKA. After bone cutting and appropriate soft tissue release for the correction of the deformity, gap balancing was evaluated using a femorotibial distractor device (Aesculap, Tuttlingen, Germany). Mediolateral flexion–extension gaps were considered to be balanced if
the gap differences were within 2 mm. For the CS TKA, the CR femoral component and the CS tibial insert were implanted, while the PS femoral component and the PS tibial insert were implanted for the PS TKA. All of the patellae were resurfaced using the same eyeball technique. All components were cemented. No knee in either group underwent lateral retinacular release. All patients received the same rehabilitation program. On the first postoperative day, all patients began weightbearing walking with the use of a walker. They were encouraged to perform active range of motion exercises. The closed suction drain was removed 48 h after operation. Skin staples were routinely removed at 10 days after the operation. Clinical and radiographic evaluations were done at 3, 6, and 12 months postoperatively, and then yearly thereafter. Each knee was rated preoperatively and postoperatively using the Knee Society score [21] and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [22]. The active range of motion was measured using a standard 60-cm-long goniometer before the operation and at the time of each follow-up visit. The patients were told to bend their knees as much as they could in a sitting position. At each follow-up, lower extremity alignment was evaluated by measuring the femorotibial angle on a standing AP radiograph. Preoperatively, there were no differences in knee alignments, range of motion, Knee Society scores, and WOMAC scores between the groups (Table 1). Evaluation of the postoperative radiolucent lines at the bone-cement interface was performed using the standing AP, lateral, and merchant radiographs. AP stability of the knee was evaluated using the anterior and posterior stress radiographs with the Telos Stress Device (Telos, Hungen, Germany). Patients were in the lateral decubitus position on the table. A 15 kg force was applied anteriorly and posteriorly with the knee in 90° of flexion and in neutral rotation position. Measurements of anterior and posterior displacement were made by tracing lines along the posterior margin of the tibial component and the most posterior edge of the femoral component, which were parallel to the posterior tibial cortex. The displacement was determined by measuring the perpendicular distance between lines. Anterior and posterior displacements were measured three times by one of the authors. The average value of the three measurements was used. Statistical comparison of the clinical results was performed using SPSS version 13.0 software (SPSS Inc., Chicago, Illinois). Means and standard deviations were used to describe the data. The differences between groups were calculated using a parametric test for independent samples (Student’s t-test). A P value of b 0.05 was considered statistically significant. Results At the final follow-up, the mean postoperative knee alignment was valgus 5.8° ± 2.7° (range, vagus 2°–valgus 12°) in the CS TKA group, and vagus 5.0° ± 2.4° (range, valgus 1°–valgus 10°) in the PS group. The mean postoperative posterior slope of the tibial component was 4.7° ± 2.4° (range, − 0.2°–9.2°) in the CS TKA group, and 4.2° ± 2.4° (range, 0°–10.1°) in the PS group. There were no significant differences in the knee alignment and tibial slope at final follow-up (P = 0.273 and P = 0.523, respectively). The mean range of motion of the knee was 135.8° ± 9.0° (range, 120°–145°) in the CS TKA group, and 133.6° ± 12.2° (range, 100°–145°) in the PS group (P = 0.446). The postoperative WOMAC score and detailed Knee Society scores are summarized in Table 2. Although the WOMAC scores did not differ between the two groups (P = 0.340), there were significant differences in the Knee Society scores (P = 0.017). The scores of the AP stability item were worse for knees with the CS TKA than the scores for knees with the PS TKA at final follow-up (P b 0.001). There were no noticeable radiolucent lines on the latest knee AP and lateral radiographs in both groups. The postoperative AP laxity of the knee was calculated by the sum of the anterior and posterior displacements that were measured on stress radiographs. There was no
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
589
Table 1 Preoperative Data of Patients Undergoing One-Stage Bilateral TKA with Randomization to Treatment with a CS or PS Implant.
Knee alignment (°) Flexion contracture (°) Maximum flexion (°) Knee Society score WOMAC score
Condylar-Stabilizing Group (n = 28)
Posterior-Stabilized Group (n = 28)
Varus 4.4 ± 5.1 (valgus 5.3–varus14.1) 8.7 ± 6.3 (0–25) 129.6 ± 12.6 (100–145) 114.8 ± 23.1 (65–145) 62.7 ± 7.4 (46.6–85.6)
Varus 4.2 ± 4.0 (valgus 6.7–varus 13.0) 8.6 ± 7.5 (0–35) 133.7 ± 11.1 (110–145) 113.0 ± 25.6 (25–153) 63.7 ± 8.6 (46.2–82.4)
significant difference in anterior displacement between the two groups (P = 0.474). However, the posterior displacement was significantly greater in the CS TKA group than in the PS TKA group (P b 0.001). Accordingly, the AP laxity was significantly greater in the CS TKA group than in the PS TKA group (P b 0.001) (Table 3) (Fig. 2). At the last follow-up, no knee had loosening of the femoral, tibial, or patellar component. No knee had a subluxation or dislocation of either the femorotibial or patellofemoral joint. Discussion In the current study, we found that PCL-sacrificing CS TKA could not restore AP stability of the knee at midterm follow-up. The anterior buildup of the CS tibial insert, which is the equivalent of the cam-post mechanism of the PS TKA, failed to provide reliable femoral rollback. Because of AP instability, objective scoring of the Knee Society score was worse for knees with the CS TKA than the score for knees with the PS TKA. Proponents of sacrificing the PCL in TKA have suggested that excision of the PCL makes ligament balancing easier and that the cam-post mechanism provides more reliable femoral rollback [23–25]. A highly conforming polyethylene has been introduced as an alternative to the cam-post mechanism to complement the disadvantages of the PS TKA system. A search of the literature yielded few articles on the outcomes of TKAs using highly congruent/dished polyethylene tibial inserts. Laskin et al [17] compared a dished polyethylene tibial polyethylene insert with a PS tibial insert after sacrificing the PCL and reported no statistically significant differences in the range of motion, ability to ascend and descend stairs, or knee scores. Sathappan et al [18] assessed the midterm results of TKA performed with either a recessed or sacrificed PCL with a dished polyethylene insert. There were no statistically significant differences between PCL recession and resection cases with regard
Table 2 Clinical Results at Latest Follow-Up.
WOMAC score Knee Society score Objective scoring Pain Range of motion APa stability MLb stability Flexion contracture Extension lag Alignment Functional scoring Walking Stairs Functional deductions a b
Anteroposterior. Mediolateral.
Condylar-Stabilizing Group (n = 28)
Posterior-Stabilized Group (n = 28)
11.1 ± 2.1 (7.5–36.3) 172.4 ± 14.0 (139–200)
10.5 ± 2.4 (7.1–30.2) 181.5 ± 13.6 (139–190)
48.5 24.7 4.1 14.6
± ± ± ±
2.6 (40–50) 0.4 (20–25) 3.3 (0–10) 1.3 (10–15) 0 0 −2.8 ± 4.2 (−12–0)
40.7 ± 7.6 (20–50) 42.5 ± 7.5 (30–50) 0
48.9 24.5 9.2 14.6
± ± ± ±
2.8 (40–50) 1.2 (24–25) 1.7 (0–10) 1.3 (10–15) 0 0 −2.7 ± 4.0 (−15–0)
42.5 ± 7.5 (30–50) 44.4 ± 7.3 (30–50) 0
P Value 0.340 0.017
0.630 0.263 0.000 1.000
0.923
0.383 0.328
P Value 0.867 0.954 0.204 0.777 0.641
to range of motion, Knee Society scores, or WOMAC scores. Nonetheless, there have been no kinematic reports evaluating knee stability after TKA with the use of a highly congruent/dished polyethylene insert. The design characteristics of the Triathlon CS knee system reportedly allow for better AP stability and PCL substitution due to two advanced features; 1) an increased anterior rise on the insert complements constant tension of the collateral ligaments to further aid in substituting for the PCL, 2) a single AP radius of the femoral component maintains ligamentous isometry throughout range of motion. Theoretically, the CS tibial insert can provide AP stability of the PS insert without a post or box cut. Louisia et al [26] compared the posterior stability of two different designs of TKA with deep-dished mobile-bearing implants using stress X-rays. Interestingly, both designs of the deep-dished mobile-bearing inserts showed significant posterior tibial translation on stress X-rays. Although the authors tested two mobile-bearing inserts, their results are in agreement with our current study. Owing to unique design features, a mobile-bearing TKA theoretically lessens the surface contact stress by decoupling the components. Therefore, the conformity of the femoral component and tibial insert of the mobile-bearing knee system can be maximized for implant stability [27]. On the other hand, in fixed-bearing design TKA, the conformity of the femoral component and tibial insert is limited by the risk of restricted range of motion and component loosening. In our study, no significant difference was detected in the range of motion between the two groups. We initially expected worse range of motion in the CS TKA group than in the PS TKA group if the CS insert could not provide proper femoral rollback. The femoral rollback mechanism provided by the cam-post mechanism in PS TKA is responsible for the controlled posterior shift of the femur on the tibia, and therefore provides greater posterior clearance in flexion [5]. It has been argued that this leads to improved range of knee motion. Paradoxical forward sliding of the femur without PCL function leads to limitations in flexion [28]. However, there exists a controversy regarding the relationship between knee laxity and range of motion. Ishii et al [29] investigated whether AP translation correlated with the maximum knee flexion angle in a TKA with implantation of a PCL-substituting mobile-bearing prosthesis. They found that there was no correlation between postoperative maximum knee flexion and AP translation. Our results support the suggestion of their study. In our study, even the CS TKA showed significant AP laxity as compared to the PS TKA, and the range of motion had no correlation with knee AP stability. Recently, Berend et al [30] assessed 2449 CR TKAs to determine whether different CR-bearing insert designs provided better range of motion. A CR tibial insert with a 3° posterior slope was inserted in 1334 TKAs. An insert with no slope and a small posterior lip was used in 803 knees. In 312 knees, the PCL was either resected or lax and a deep-dish, anterior-stabilized insert was used in these cases. Despite sacrificing or not substituting for the PCL, the range of motion improvement was the highest, and the manipulation under anesthesia rate was the lowest in TKAs with a deep-dish, anterior-stabilized insert. The authors concluded that substitution for the PCL in the form of a PS design might not be necessary even when the PCL is deficient. Although their study was limited to CR TKAs and there was a lack of data on sagittal stability, in agreement with our results, it was suggested that
590
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
Table 3 Anterior and Posterior Displacements on Stress Radiographs at Latest Follow-Up.
Anterior displacement (mm) Posterior displacement (mm) APa laxity (mm) a
Condylar-Stabilizing Group (n = 28)
Posterior-Stabilized Group (n = 28)
P Value
0.24 ± 4.51 (−9.00–7.40) −9.54 ± 3.22 (−14.79–6.90) 9.78 ± 4.96 (1.50–19.38)
0.97 ± 2.83 (−4.47–6.53) −1.69 ± 1.99 (−5.00–4.80) 3.01 ± 2.31 (0–7.61)
0.474 b 0.001 b 0.001
AP; anteroposterior.
the range of motion after PCL-sacrificing TKA with use of a highly congruent/dished polyethylene insert would be comparable to that of CR or PS TKAs. In this study, we found that the midterm functional outcomes for knees with a CS TKA were similar to those for knees with a PS TKA. There were no significant differences in WOMAC scores and functional scorings of Knee Society scores between groups. Our results do not reflect the results of previous reports on PCL substitution in TKA with regards to knee function. It has been known that appropriate PCL substitution allows for better AP stability, increased range of motion, reduced quadriceps force in extension, improved stair-climbing ability, and improved patellofemoral function [31,32]. This probably is because the lack of femoral rollback decreases the moment arm of the extension mechanism so that more quadriceps force is needed for knee extension. Stair climbing is likely to be more difficult, and stress is likely to be greater at the tibial articular surface in knees without appropriate femoral rollback. Although more studies with improved methods are needed to evaluate knee function following TKA, our study showed that substantial posterior laxity of the knee did not affect knee function such as walking or stair ambulation.
In the present study, the results of the CS TKA group raise the question of the consequences of AP laxity on polyethylene wear in the long term. Seon et al [33] suggested that the preservation of the PCL in CR TKA would keep the femoral rollback, reproducing the normal movement of the joint and preventing a posterior translation. It has been theorized that a well-functioning PCL would reduce the aseptic loosening and polyethylene wear after TKA [34]. In our study, with a minimum duration of 5 years, we could not find any radiolucent line around the femoral or tibial components in both groups. However, we believe that long-term followup is needed to determine whether substantial AP laxity of the knee can be a potential cause of catastrophic failure after TKA. Mont et al [35] compared a CS insert with a CR insert in Triathlon CR TKAs. Reasons for the use of a CS insert included flexion instability and failure to obtain equal flexion and extension gaps. They found that the use of a Triathlon CR TKA showed comparable results with both polyethylene inserts at short-term follow-up. Based on our study, we suggest that a CS insert can be used in CR TKA when it comes to PCL recession. The major limitation of the present study is that there is no consensus on optimal AP laxity of the knee following TKA. Although
Fig. 2. A 72-year-old female patient’s stress radiographs of both knees. Anterior (A) and posterior (B) stress radiographs of the right knee with a CS TKA show greater posterior displacement than the anterior (C) and posterior (D) stress radiographs of the left knee with a PS TKA.
Y.-J. Sur et al. / The Journal of Arthroplasty 30 (2015) 587–591
the distance of translation differs depending on the study, a postoperative AP translation of approximately 5 to 10 mm is believed to be the preferred value for TKA [29,36,37]. Ishii et al reported that proper AP translation facilitates physiologic rollback of the femoral component [29]. In this study, the CS TKA group showed a mean 9.78 mm AP displacement, of which posterior displacement accounted for over 97% of the total laxity. Although the kinetics of the knee after TKA is different from that of the normal knee, it is believed that the amount of the posterior displacement of the CS TKA group is too much to restore normal knee function. Secondly, the sample size might not be sufficiently large to reveal a difference in WOMAC score and functional score between groups. Because our primary objective was to compare the AP stability over the first 5 postoperative years in patients who had received a CS TKA in one knee and a PS TKA in the other, the sample size was calculated for the primary outcomes. In conclusion, our findings revealed that a CS TKA could not restore AP stability with PCL sacrifice. Although the midterm functional outcomes for knees with a CS TKA were similar to those for knees with a PS TKA, we suggest that the CS TKA has no benefits with regards to knee stability after TKA.
15.
16.
17.
18.
19. 20.
21. 22.
23. 24.
References 1. Chaudhary R, Beaupre LA, Johnston DW. Knee range of motion during the first two years after use of posterior cruciate-stabilizing or posterior cruciate-retaining total knee prostheses. A randomized clinical trial. J Bone Joint Surg Am 2008;90(12):2579. 2. Clark CR, Rorabeck CH, MacDonald S, et al. Posterior-stabilized and cruciate-retaining total knee replacement: a randomized study. Clin Orthop Relat Res 2001;392:208. 3. Kim YH, Choi Y, Kwon OR, et al. Functional outcome and range of motion of high-flexion posterior cruciate-retaining and high-flexion posterior cruciate-substituting total knee prostheses. A prospective, randomized study. J Bone Joint Surg Am 2009;91(4):753. 4. Victor J, Banks S, Bellemans J. Kinematics of posterior cruciate ligament-retaining and -substituting total knee arthroplasty: a prospective randomised outcome study. J Bone Joint Surg (Br) 2005;87(5):646. 5. Harato K, Bourne RB, Victor J, et al. Midterm comparison of posterior cruciateretaining versus -substituting total knee arthroplasty using the Genesis II prosthesis. A multicenter prospective randomized clinical trial. Knee 2008;15(3):217. 6. Maruyama S, Yoshiya S, Matsui N, et al. Functional comparison of posterior cruciateretaining versus posterior stabilized total knee arthroplasty. J Arthroplasty 2004;19(3):349. 7. Pandit H, Ward T, Hollinghurst D, et al. Influence of surface geometry and the campost mechanism on the kinematics of total knee replacement. J Bone Joint Surg (Br) 2005;87(7):940. 8. Lee CS, Chen WM, Kou HC, et al. Early nontraumatic fracture of the polyethylene tibial post in a NexGen LPS-Flex posterior stabilized knee prosthesis. J Arthroplasty 2009; 24(8):1292.e5. 9. Lim HC, Bae JH, Hwang JH, et al. Fracture of a polyethylene tibial post in a Scorpio posterior-stabilized knee prosthesis. Clin Orthop Surg 2009;1(2):118. 10. Jung WH, Jeong JH, Ha YC, et al. High early failure rate of the Columbus posterior stabilized high-flexion knee prosthesis. Clin Orthop Relat Res 2012;470(5):1472. 11. Lee SC, Jung KA, Nam CH, et al. Anterior dislocation after a posterior stabilized total knee arthroplasty. J Arthroplasty 2012;27(2):324.e17. 12. Frye BM, Floyd MW, Pham DC, et al. Effect of femoral component design on patellofemoral crepitance and patella clunk syndrome after posterior-stabilized total knee arthroplasty. J Arthroplasty 2012;27(6):1166. 13. Yau WP, Wong JW, Chiu KY, et al. Patellar clunk syndrome after posterior stabilized total knee arthroplasty. J Arthroplasty 2003;18(8):1023. 14. Lutzner J, Firmbach FP, Lutzner C, et al. Similar stability and range of motion between cruciate-retaining and cruciate-substituting ultracongruent insert total knee
25.
26.
27. 28.
29.
30.
31.
32. 33.
34.
35.
36. 37.
591
arthroplasty. Knee Surg Sports Traumatol Arthrosc 2014 [Epub ahead of print, PMID: 24519619]. Peters CL, Mulkey P, Erickson J, et al. Comparison of total knee arthroplasty with highly congruent anterior-stabilized bearings versus a cruciate-retaining design. Clin Orthop Relat Res 2014;472(1):175. Hofmann AA, Tkach TK, Evanich CJ, et al. Posterior stabilization in total knee arthroplasty with use of an ultracongruent polyethylene insert. J Arthroplasty 2000; 15(5):576. Laskin RS, Maruyama Y, Villaneuva M, et al. Deep-dish congruent tibial component use in total knee arthroplasty: a randomized prospective study. Clin Orthop Relat Res 2000;380:36. Sathappan SS, Wasserman B, Jaffe WL, et al. Midterm results of primary total knee arthroplasty using a dished polyethylene insert with a recessed or resected posterior cruciate ligament. J Arthroplasty 2006;21(7):1012. Mizu-Uchi H, Matsuda S, Miura H, et al. Anteroposterior stability in posterior cruciate ligament-retaining total knee arthroplasty. J Arthroplasty 2006;21(4):592. Schuster AJ, von Roll AL, Pfluger D, et al. Anteroposterior stability after posterior cruciate-retaining total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2011;19(7):1113. Insall JN, Dorr LD, Scott RD, et al. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res 1989;248:13. Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15(12):1833. Bercik MJ, Joshi A, Parvizi J. Posterior cruciate-retaining versus posterior-stabilized total knee arthroplasty: a meta-analysis. J Arthroplasty 2013;28(3):439. Straw R, Kulkarni S, Attfield S, et al. Posterior cruciate ligament at total knee replacement. Essential, beneficial or a hindrance? J Bone Joint Surg (Br) 2003; 85(5):671. Verra WC, van den Boom LG, Jacobs W, et al. Retention versus sacrifice of the posterior cruciate ligament in total knee arthroplasty for treating osteoarthritis. Cochrane Database Syst Rev 2013;10:CD004803. Louisia S, Siebold R, Canty J, et al. Assessment of posterior stability in total knee replacement by stress radiographs: prospective comparison of two different types of mobile bearing implants. Knee Surg Sports Traumatol Arthrosc 2005;13(6):476. Dennis DA, Komistek RD. Mobile-bearing total knee arthroplasty: design factors in minimizing wear. Clin Orthop Relat Res 2006;452:70. Stiehl JB, Dennis DA, Komistek RD, et al. In vivo kinematic comparison of posterior cruciate ligament retention or sacrifice with a mobile bearing total knee arthroplasty. Am J Knee Surg 2000;13(1):13. Ishii Y, Noguchi H, Takeda M, et al. Anteroposterior translation does not correlate with knee flexion after total knee arthroplasty. Clin Orthop Relat Res 2014;472(2): 704. Berend KR, Lombardi Jr AV, Adams JB. Which total knee replacement implant should I pick? Correcting the pathology: the role of knee bearing designs. Bone Joint J 2013; 95-B(11 Suppl. A):129. Insall JN, Lachiewicz PF, Burstein AH. The posterior stabilized condylar prosthesis: a modification of the total condylar design. Two to four-year clinical experience. J Bone Joint Surg Am 1982;64(9):1317. Scott WN, Rubinstein M, Scuderi G. Results after knee replacement with a posterior cruciate-substituting prosthesis. J Bone Joint Surg Am 1988;70(8):1163. Seon JK, Park JK, Jeong MS, et al. Correlation between preoperative and postoperative knee kinematics in total knee arthroplasty using cruciate retaining designs. Int Orthop 2011;35(4):515. Carvalho Jr LH, Temponi EF, Soares LF, et al. Relationship between range of motion and femoral rollback in total knee arthroplasty. Acta Orthop Traumatol Turc 2014; 48(1):1. Mont MA, Costa CR, Naiziri Q, et al. Comparison of 2 polyethlene inserts for a new cruciate-retaining total knee arthroplasty prosthesis. Orthopedics 2013; 36(1):33. Jones DP, Locke C, Pennington J, et al. The effect of sagittal laxity on function after posterior cruciate-retaining total knee replacement. J Arthroplasty 2006;21(5):719. Seon JK, Song EK, Yoon TR, et al. In vivo stability of total knee arthroplasty using a navigation system. Int Orthop 2007;31(1):45.
