The Journal of Arthroplasty xxx (2015) xxx–xxx
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Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients Ashir Ejaz, MD, PhD a,b,c, Anders C. Laursen, MD a,b,c, Thomas Jakobsen, MD, PhD a,c, Sten Rasmussen, MD a,b,c, Poul Torben Nielsen, MD a, Mogens B. Laursen, MD, PhD a,b,c a b c
Department of Orthopaedic Surgery, Aalborg University Hospital, Aalborg, Denmark Orthopaedic Surgery Research Unit, Aalborg University Hospital, Aalborg, Denmark Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
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Article history: Received 13 February 2015 Accepted 29 May 2015 Available online xxxx Keywords: implant fixation tourniquet RSA TKA RCT
a b s t r a c t We aimed to determine whether not using a tourniquet in cemented TKA would affect migration of the tibial component measured by radiosterometric analysis (RSA). Seventy patients were randomized into a tourniquet group and a non-tourniquet group and using model-based RSA, the migration of the tibial component was analyzed. Primary and secondary outcome measures were maximum total point motion (MTPM) and translations and rotations. Follow-up period was 2 years. The tibial component was well fixated in both groups and no significant difference in migration between the two groups was detected (P = 0.632). Mean MTPM (SD) was 0.47 mm (0.16) in the tourniquet group and 0.45 mm (0.21) in the non-tourniquet group. Absence of tourniquet indicates that stable fixation of the tibial component can be achieved in cemented TKA. © 2015 Elsevier Inc. All rights reserved.
A pneumatic tourniquet in elective total knee arthroplasty (TKA) is still commonly used to provide a bloodless field and reduce blood loss. Furthermore, the diminished bleeding should in combination with careful pulse lavage provide a better cementation and fixation of the implant [1]. This is because a dry cement–bone interface allows proper cement penetration and bone cement interdigitation [2]. Although many studies have been carried out to settle the question of whether or not to use tourniquet, they have primarily focused on clinical outcomes such as operation time, intraoperative bleeding, pain and knee flexion [3–5]. Systematic reviews and meta-analysis regarding the problems of tourniquet use in TKA have not reached a definitive consensus, but encourage further investigation of implant fixation [6–8]. Radiostereometric analysis (RSA) was developed by Selvik [9] in 1974 and is an accurate 3-dimensional measurement technique, that can be used to evaluate migration and fixation of implants with reference to 1 mm tantalum markers implanted in the surrounding bone. Early micromotion between implant and bone is associated with early need for revision [10]. Model-based RSA (MBRSA) is a further developed method to determine migration and unlike marker-based RSA it does not require markers attached to the implant. Instead MBRSA uses a digital image-processing technique based on Cad models to determine the location and orientation of the implant. MBRSA has been compared with
No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.05.058. Reprint requests: Ashir Ejaz, MD, PhD, Ny Kastetvej 30-06, DK-9000 Aalborg, Denmark.
marker-based RSA and been shown to be a valid technique to determine the accuracy of implantation [11,12]. To our knowledge, RSA-evaluation of tourniquet effects on implant fixation has been carried out in only two other studies, both of which used marker-based RSA [13,14]. Other studies have used plain radiographs to assess whether loosening took place without tourniquet use [3,5]. This present study is the first using model-based RSA to detect possible migration when a tourniquet was not used. We assumed that if no difference in migration was detected between the two groups, it was acceptable to conclude that tourniquet use did not influence the quality of implant fixation. There are no clinical studies indicating that tourniquet use improves fixation. The aim of this RCT study was to determine whether implant fixation was influenced by the absence of a tourniquet and the presence of active bleeding. We hypothesized that not using a tourniquet during TKA would not affect implant fixation. Materials and methods This prospective randomized clinical trial was conducted at Aalborg University Hospital, Aalborg, Denmark. A total of 70 primary TKAs were performed between January 2011 and January 2012. Approval from the local ethics committee (approval no. N20090045) and registration at ClinicalTrials.gov (NCT01309035) were obtained. All patients gave written consent and were enrolled in this study in accordance with the Consolidated Standards of Reporting Trials (CONSORT) and The Helsinki Declaration (Fig. 1). This study was part of a larger randomized controlled trial where 2 other main aims were investigated: tourniquets effect on clinical
http://dx.doi.org/10.1016/j.arth.2015.05.058 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
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A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
Fig. 1. Flowchart of included participants.
outcomes [16] and ischemic conditions. The results of implant fixation are presented in this publication. Patients aged 50–85 years were included if inclusion criteria were met and an elective unilateral TKA because of gonarthrosis stages 3–5 according to Ahlbäck [15] was planned. Exclusion criteria included rheumatoid arthritis, peripheral vascular disease, diabetes, prior knee surgery and use of anticoagulation medicine. Patients in both groups were comparable with regard to demographics (Table 1). Patients were block randomized using sealed envelopes and were allocated into two groups: 33 patients had surgery using a tourniquet (Tq group) and 31 patients had surgery without the use of a tourniquet (non-Tq group). The envelopes were opened when the surgeon was present in the operating theatre before surgery. Patients were unaware of the group to which they had been allocated. Surgical technique All procedures were standardized with regard to preoperative tranexamic acid, spinal anesthesia, postoperative pain and rehabilitation regimen. Before surgery, tranexamic acid (1 g) was administered orally, and immediately prior to skin incision, cefuroxime (1.5 g) was administered
intravenously. In addition, tranexamic acid (0.5 g) was given 3 hours after surgery, and cefuroxime (750 mg) was given 6 and 12 hours postoperatively. Thrombosis prophylaxis was achieved with use of rivaroxaban (10 mg per day) throughout hospitalization. Both groups had an appropriately sized thigh tourniquet applied, but it was only inflated in the Tq group. In non-Tq group, it was placed on the thigh but not inflated, thereby serving as safety device in case of uncontrollable bleeding. In the Tq group, limb exsanguination was done by elevation for 2 min, and the cuff was inflated to 250 mmHg just prior to skin incision. All knee implants were the NexGen CR-Flex Fixed Bearing Knee (Zimmer, Warsaw, Indiana, USA) with use of high viscosity bone cement, Refobacin Bone Cement R (Biomet, Warsaw, Indiana, USA). In all cases, the patella was resurfaced. Surgical procedures were all performed by one single surgeon. A midline skin incision and medial parapatellar arthrotomy were applied. An intramedullary guide system was used for the femur and external guides for the tibia. The distal femur guide hole was plugged with autogenous bone grafts. Cement was applied on the tibia plateau surface, beneath the tibial tray and along the stem. Anchorage holes were drilled into the tibia plateau to increase the contact area between bone and cement. The proximal tibia bone was prepared for RSA with the insertion of 14–16 tantalum beads of 1.0-mm. Modern cementing technique was used that involved
Table 1 Demographics.
Sex M/F, N Age (years), mean ± SD Height (cm), mean ± SD Weight (kg), mean ± SD BMI, mean ± SD
Total Sample (N = 57)
Tourniquet (N = 29)
Non-tourniquet (N = 28)
57 68.3 ± 8.0 168.1 ± 7.5 69.7 ± 9.3 25.1 ± 2.3
13/16 68.3 ± 8.4 168.0 ± 6.7 69.7 ± 7.3 25.1 ± 2.0
15/13 68.2 ± 7.8 168.2 ± 8.2 69.7 ± 10.9 25.2 ± 2.5
SD: standard deviation.
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
meticulous pulse lavage of the exposed cut-bony surface before cement application. A two-stage cementation procedure was performed. The tibia and patella were implanted first, and then another batch of cement was used to fixate the femoral component. This was done to secure enough time to obtain a careful cementation with proper pressurization. After cementation, further pulse lavage debridement was performed to eliminate cement debris from the wound [17]. Immediately after wound closure, dressings were applied, and the cuff was deflated in the Tq group and removed. Postoperative rehabilitation and pain management were standardized for both groups and followed a standard protocol including full weight bearing.
RSA Outcomes RSAs were all obtained on the first postoperative day. This was used as reference examination. Subsequent follow-up examinations were performed on outpatient controls at 2, 6, 12 and 24 months. The RSA setup was as recommended by Valstar et al [18], with two ceilingfixed automatically synchronised roentgen tubes, which were angled 90° relative to each other. A biplanar calibration box (RSA Biomedical, Sweden) was placed in the midsection of the roentgen focus. All radiographs were fully digitalized. Precision was evaluated at 1year follow-up at which time double examinations were performed, with total repositioning of the patient and the radiographic equipment. All stereoradiographs were analyzed using model-based RSA software (MBRSA v3.3.2, Medis Specials, Leiden, the Netherlands) (Fig. 2). The upper limit for mean error of rigid body fitting (stability of markers) was 0.14. The mean condition number (CN), which indicates the distribution of bone markers and thereby the quality of the rigid body formed by the markers, was 21. This low CN indicates that the distribution and quality were good. A CN lower than 90–100 is suggested as being appropriate [18]. The main outcome measurement was based on maximum total point motion (MTPM), which represents the vector length of a marker in the rigid body that has the longest translational motion, not considering direction, and always has a positive value. In addition, translations and rotations were calculated accordingly to the standards suggested by Valstar et al [18] as secondary RSA outcome variables. Rigid-body translations and rotations of the implant were calculated about a coordinate system centered at the center of the implant, and the axes were aligned with the anatomical directions. Translations along the axes were given as x-translation (medial–lateral movement), y-translations (superior/lift-off and inferior/subsidence movement) and z-translations (anterior and posterior movements). Rotations around the axes were expressed as x-rotation,
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y-rotation and z-rotation, which represent anterior-posterior tilt, internal-external rotation and varus–valgus tilt, respectively. Statistical Analysis Sample size was based on earlier studies [13,19]. Using a SD 0.2 mm with α = 5 and β = 80, the sample size of each group was 25. Because of possible risk of patient drop-out, the number was increased to 35 per group. In a systematic review, it was suggested that an MTPM migration threshold of less than 0.54 mm was acceptable [20]. We chose migration ≥0.5 mm in magnitude at 2-year follow-up to be “clinically relevant” based on previous clinical studies [10,12,21]. This means the 2SD would have to be within ± 0.5 mm. Data were analyzed by ANOVA and Mann–Whitney U-test to compare mean difference in migration (signed values) where appropriate. The level of significance was set at the 95% confidence limit, and P-values less than 0.05 were considered significant. Data are presented as mean and standard deviation (SD). Statistical analysis was performed by using STATA 11.0 Results Seventy patients were enrolled in the trial and 57 (28 male and 29 female) completed the study (Fig. 1). Patients were similar concerning preoperative demographics (Table 1). There were no differences regarding age, weight, gender or radiographic osteoarthritis grade. During 2-years' follow-up no statistically significant difference was detected in the mean values of MTPM between the two groups (P = 0.63) (Fig. 3). No statistically significant difference was detected in mean values of translations or rotations along the sagittal, transverse and longitudinal axes after 2 years (Table 2). In both groups, all of the patients analyzed with RSA showed excellent and stable fixation throughout the follow-ups, and no significant migration was detected. There was no statistical difference detected in mean values of translation or rotation, along or around the x-, y- and z-axes at any time during follow-up, P N 0.05. All mean values were below 0.5 mm and 0.5 degrees for both groups. We registered one case of early tibial component loosening in the Tq group. The patient was initially without symptoms and well mobilized, but on plain radiographs the loosening was detected at week 8. Implant loosening had occurred due to impaired subchondral tibia bone quality caused by a cyst not recognized before or during surgery. This patient was not included in RSA analysis.
Fig. 2. Model-based RSA: in the midsection of the two roentgen foci a model of the implant is matched on the radiostereometric picture of the patient's implant. The migration of the implant is determined in relation to tantalum bone markers (red dots).
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
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A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
Fig. 3. Maximum total point motion during a 2-year follow-up.
Discussion The reason for applying a tourniquet is to ensure less intraoperative bleeding and concurrently optimize surgical visibility and thereby potentially reducing duration of surgery time. Another important argument for tourniquet application is to achieve better implant fixation because blood may impair bone–cement interdigitation [2]. It is known that tibial components migrate after surgery, most marked in the first 6 weeks; later, migration diminishes and stabilizes approximately 1 year after surgery [10,22,23]. Obtaining a good and secure initial fixation is of utter importance. Implant fixation and survival are endpoints that reveal the success of a TKA operation. Therefore it was important to contribute to answering the question of whether using a tourniquet secures better cementation and especially fixation of the tibial component, which seems to be the main site of loosening. The aim of this present RCT study was to investigate whether absence of a tourniquet would worsen implant fixation during the first 2 years after TKA surgery using RSA, expressed by MTPM, as primary outcome. Our study showed no significant difference in mean values of MTPM between patients in whom a tourniquet was used and those in whom a tourniquet was not used. Also, no significant difference in mean values was detected in the translations and rotations. In our study condition number and mean error of rigid body fitting were low, and the overall quality of RSA examinations was good. To our knowledge this is the first study to investigate the effect of a tourniquet on implant migration and long-term survival using modelbased RSA. Only two other studies regarding implant fixation have been conducted; both used marker-based RSA and involved 50 patients and 60 patients, respectively [13,14]. Their results support our findings. MTPM and translations and rotations after 2 years showed no difference. Ryd et al [10] categorized implants movements to be stable if MTPM was b 0.2 mm between 1 and 2 years or as being at risk of loosening if MTPM was N 0.2 mm, thus giving an accuracy of 0.2 mm for translation and 0.5 degrees for rotations. Other studies have reported
accuracy that ranges from 0.05 to 0.5 mm for translation and 0.15° to 1.15° for rotations [21,24]. In accordance with this, our findings showed implant fixation and long-term implant survival was not compromised. One shortcoming of this study was the use of model-based RSA from CAD models. The precision relies on obtaining an exact contour detection of the tibial tray geometry. The method has been proven to be a highly accurate method to evaluate fixation of tibial components [25,26]. Other factors such as osteoporosis that can cause motion were not considered in the present study, but randomization should equalize these parameters. The corner stones of modern cementing technique are surface preparation including comprehensive high pressure pulse lavage that enhances the mechanical bone–cement interdigitation by removing blood and causing a better cement penetration [27]. Furthermore a careful cleaning of remaining cement debris is crucial because it may prevent “third body wear” responsible for implant loosening and polyethylene wear [17]. These steps are some of the key elements to secure a high quality implant fixation so that the risk of long-term survival failure is reduced. Common practice is to cement the components in one phase, whereas we divided the cementation process into two phases. This prolonged the time necessary to complete surgery, but was carried out to secure an optimal and careful cementation of each component. All patients in this study received tranexamic acid, because TKA surgery can lead to substantial blood loss and increased blood transfusion requirements. One method to reduce perioperative blood loss and blood transfusion requirements is with the use of tranexamic acid. In an RCT study where TKA was performed without the use of tourniquet, it was concluded that tranexamic acid was an effective way of reducing blood loss and transfusions requirements [28]. The use of tranexamic acid in TKA is supported by several metaanalysis studies stating that tranexamic acid is safe and effective in minimizing perioperative and postoperative blood loss and is not associated with increased risk of venous thromboembolic events [29–31]. The use of tranexamic acid in this study may have minimized the impact of not using a tourniquet on the quality of cement fixation. MTPM between the two groups showed no difference in migration or rigid body motion pattern, indicating that the absence of a tourniquet did not worsen the fixation of the tibial component and increase the risk of long-term loosening. MTPM can easily be affected by movements from all directions, but it is appropriate for detecting differences between two similar groups. Translations and rotations are more precise variables of the rigid body's center of gravity. These variables did also support that there was no differences in migration between the two groups. The MTPM reported in our study is close to the limit for acceptable migration. This limit varies for implant types, because some have more migration than others [32]. The translations and rotations presented good values. In the randomized study by Vandenbussche et al [5] plain radiographs analysis was performed at 3 months, looking for early signs of aseptic implant loosening with special attention to radiolucent lines, and no significance difference was seen in relation to tourniquet use
Table 2 RSA Results Expressed as Mean Translation and Rotation of the Tibial Component. N = 57
X translation (mm ± SD) Y translation (mm ± SD) Z translation (mm ± SD) X rotation (degrees ± SD) Y rotation (degrees ± SD) Z rotation (degrees ± SD) MTPM mean (mm ± SD)
8 weeks
6 months
12 months
24 months
Tq (n = 29)
Non-Tq (n = 28)
Tq (n = 29)
Non-Tq (n = 28)
Tq (n = 29)
Non-Tq (n = 28)
Tq (n = 29)
Non-Tq (n = 28)
0.07 −0.02 −0.01 −0.09 −0.08 −0.16 0.43
0.01 −0.01 0.04 0.01 0.07 −0,04 0.53
0.02 −0.04 0.05 0.02 −0.05 0.07 0.55
−0.01 −0.02 0.03 −0.04 0.11 0.03 0.51
0.04 0.02 −0.03 −0.02 −0.09 0.02 0.57
−0.03 −0.01 0.01 −0.13 −0.30 −0.10 0.53
0.03 −0.03 −0.02 −0.03 −0.12 0.04 0.47
−0.04 −0.02 0.02 −0.03 −0.08 −0.05 0.45
± ± ± ± ± ± ±
0.39 0.15 0.17 0.41 0.98 0.45 0.22
± ± ± ± ± ± ±
0.14 0.11 0.20 0.34 0.75 0.34 0.32
± ± ± ± ± ± ±
0.33 0.15 0.12 0.35 0.95 0.30 0.42
± ± ± ± ± ± ±
0.22 0.13 0.32 0.50 0.83 0.62 0.34
± ± ± ± ± ± ±
0.30 0.23 0.50 0.57 0.96 0.28 0.40
± ± ± ± ± ± ±
.030 0.11 0.35 0.50 0.81 0.54 0.43
± ± ± ± ± ± ±
0.28 0.18 0.22 0.47 0.88 0.41 0.16
± ± ± ± ± ± ±
.31 0.27 0.28 0.31 0.93 0.58 0.21
Positive directions for translation along orthogonal axis were X (medial–lateral), Y (caudal–cranial), and Z (posterior–anterior). Positive directions for rotation around the coordinate axes were X (anterior posterior tilt), Y (internal–external rotation), and Z (varus–valgus tilt).
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
or non-use. Abdel-Salam and Eyres [3] also reported that no difference was detected between the two groups based on evaluation of plain radiographs during a 2-year follow-up. Alternative methods of using the tourniquet in TKA have been investigated in RCT studies [33,34]. Here a limited use of tourniquet has been favored, suggesting that tourniquet be applied in only shorter periods and released after the cementation phase. This provides the benefit of decreased limb swelling, pain and recovery period without increasing operation time or blood loss. These findings were consistent with the study regarding TKA surgery where tourniquet is absent throughout the operation [16]. Since very little is known about implant fixation and long-term survival or cement interdigitation in relation to tourniquet use, we suggest that further RCT studies be conducted to investigate the long-term revision rates of the tibial component. In conclusion, we found that performing cemented TKA surgery without use of tourniquet is safe in terms of obtaining a good cementation and implant fixation, when tranexamic acid is used intraoperatively, indicating that long-term implant survival is not compromised. Acknowledgements The authors would like to thank Dr. Andreas Kappel for participating in this study and performing all the surgical procedures. References 1. Schlegel UJ, Siewe J, Delank KS, et al. Pulsed lavage improves fixation strength of cemented tibial components. Int Orthop 2011;35(8):1165. 2. Juliusson R, Arve J, Ryd L. Cementation pressure in arthroplasty. In vitro study of cement penetration into femoral heads. Acta Orthop Scand 1994;65(2):131. 3. Abdel-Salam A, Eyres KS. Effects of tourniquet during total knee arthroplasty. A prospective randomized study. J Bone Joint Surg (Br) 1995;77(2):250. 4. Tetro AM, Rudan JF. The effects of a pneumatic tourniquet on blood loss in total knee arthroplasty. Can J Surg 2001;44(1):33. 5. Vandenbussche E, Duranthon LD, Couturier M, et al. The effect of tourniquet use in total knee arthroplasty. Int Orthop 2002;26(5):306. 6. Smith TO, Hing CB. Is a tourniquet beneficial in total knee replacement surgery? A meta-analysis and systematic review. Knee 2010;17(2):141. 7. Tai TW, Lin CJ, Jou IM, et al. Tourniquet use in total knee arthroplasty: a meta-analysis. Knee Surg Sports Traumatol Arthrosc 2011;19(7):1121. 8. Alcelik I, Pollock RD, Sukeik M, et al. A comparison of outcomes with and without a tourniquet in total knee arthroplasty: a systematic review and metaanalysis of randomized controlled trials. J Arthroplasty 2012;27(3):331. 9. Selvik G. Roentgen stereophotogrammetry. A method for the study of the kinematics of the skeletal system. Acta Orthop Scand Suppl 1989;232:1 [Review]. 10. Ryd L, Albrektsson BE, Carlsson L, et al. Roentgen stereophotogrammetric analysis as a predictor of mechanical loosening of knee prostheses. J Bone Joint Surg (Br) 1995; 77(3):377. 11. Trozzi C, Kaptein BL, Garling EH, et al. Precision assessment of model-based RSA for a total knee prosthesis in a biplanar set-up. Knee 2008;15(5):396.
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12. Hurschler C, Seehaus F, Emmerich J, et al. Accuracy of model-based RSA contour reduction in a typical clinical application. Clin Orthop Relat Res 2008;466(8):1978. 13. Ledin H, Aspenberg P, Good L. Tourniquet use in total knee replacement does not improve fixation, but appears to reduce final range of motion. Acta Orthop 2012; 83(5):499. 14. Molt M, Harsten A, Toksvig-Larsen S. The effect of tourniquet use on fixation quality in cemented total knee arthroplasty a prospective randomized clinical controlled RSA trial. Knee 2014;21(2):396. 15. Ahlbäck S. Osteoarthrosis of the knee. A radiographic investigation. Acta Radiol Diagn (Stockh) 1968(Suppl. 277):7. 16. Ejaz A, Laursen AC, Kappel A, et al. Faster recovery without the use of a tourniquet in total knee arthroplasty. Acta Orthop 2014;85(4):422. 17. Niki Y, Matsumoto H, Otani T, et al. How much sterile saline should be used for efficient lavage during total knee arthroplasty? Effects of pulse lavage irrigation on removal of bone and cement debris. J Arthroplasty 2007;22(1):95. 18. Valstar ER, Gill R, Ryd L, et al. Guidelines for standardization of radiostereometry (RSA) of implants. Acta Orthop 2005;76(4):563. 19. Hilding M, Ryd L, Toksvig-Larsen S, et al. Clodronate prevents prosthetic migration: a randomized radiostereometric study of 50 total knee patients. Acta Orthop Scand 2000;71(6):553. 20. Pijls BG, Valstar ER, Nouta KA, et al. Early migration of tibial components is associated with late revision: a systematic review and meta-analysis of 21,000 knee arthroplasties. Acta Orthop 2012;83(6):614. 21. Kärrholm J. Roentgen stereophotogrammetry. Review of orthopedic applications. Acta Orthop Scand 1989;60(4):491. 22. Nilsson KG, Kärrholm J, Ekelund L, et al. Evaluation of micromotion in cemented vs uncemented knee arthroplasty in osteoarthrosis and rheumatoid arthritis. Randomized study using roentgen stereophotogrammetric analysis. J Arthroplasty 1991; 6(3):265. 23. Hilding MB, Yuan X, Ryd L. The stability of three different cementless tibial components. A randomized radiostereometric study in 45 knee arthroplasty patients. Acta Orthop Scand 1995;66(1):21. 24. Valstar ER, Vrooman HA, Toksvig-Larsen S, et al. Digital automated RSA compared to manually operated RSA. J Biomech 2000;33(12):1593. 25. Kaptein BL, Valstar ER, Stoel BC, et al. A new model-based RSA method validated using CAD models and models from reversed engineering. J Biomech 2003;36(6): 873. 26. Valstar ER, de Jong FW, Vrooman HA, et al. Model-based Roentgen stereophotogrammetry of orthopaedic implants. J Biomech 2001;34(6):715. 27. Jaeger S, Seeger JB, Schuld C, et al. Tibial cementing in UKA: a three-dimensional analysis of the bone cement implant interface and the effect of bone lavage. J Arthroplasty 2013;28(9 Suppl.):191. 28. Bidolegui F, Arce G, Lugones A, et al. Tranexamic acid reduces blood loss and transfusion in patients undergoing total knee arthroplasty without tourniquet: a prospective randomized controlled trial. Open Orthop J 2014;11(8):250. 29. Gandhi R, Evans HM, Mahomed SR, et al. Tranexamic acid and the reduction of blood loss in total knee and hip arthroplasty: a meta-analysis. BMC Res Notes 2013;6:184. 30. Tan J, Chen H, Liu Q, et al. A meta-analysis of the effectiveness and safety of using tranexamic acid in primary unilateral total knee arthroplasty. J Surg Res 2013; 184(2):880. 31. Zhang H, Chen J, Chen F, et al. The effect of tranexamic acid on blood loss and use of blood products in total knee arthroplasty: a meta-analysis. Knee Surg Sports Traumatol Arthrosc 2012;20(9):1742. 32. Kärrholm J. Radiostereometric analysis of early implant migration—a valuable tool to ensure proper introduction of new implants. Acta Orthop 2012;83(6):551. 33. Kvederas G, Porvaneckas N, Andrijauskas A, et al. A randomized double-blind clinical trial of tourniquet application strategies for total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2013;21(12):2790. 34. Fan Y, Jin J, Sun Z, et al. The limited use of a tourniquet during total knee arthroplasty: a randomized controlled trial. Knee 2014;21(6):1263.
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
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Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients Ashir Ejaz, MD, PhD a,b,c, Anders C. Laursen, MD a,b,c, Thomas Jakobsen, MD, PhD a,c, Sten Rasmussen, MD a,b,c, Poul Torben Nielsen, MD a, Mogens B. Laursen, MD, PhD a,b,c a b c
Department of Orthopaedic Surgery, Aalborg University Hospital, Aalborg, Denmark Orthopaedic Surgery Research Unit, Aalborg University Hospital, Aalborg, Denmark Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
a r t i c l e
i n f o
Article history: Received 13 February 2015 Accepted 29 May 2015 Available online xxxx Keywords: implant fixation tourniquet RSA TKA RCT
a b s t r a c t We aimed to determine whether not using a tourniquet in cemented TKA would affect migration of the tibial component measured by radiosterometric analysis (RSA). Seventy patients were randomized into a tourniquet group and a non-tourniquet group and using model-based RSA, the migration of the tibial component was analyzed. Primary and secondary outcome measures were maximum total point motion (MTPM) and translations and rotations. Follow-up period was 2 years. The tibial component was well fixated in both groups and no significant difference in migration between the two groups was detected (P = 0.632). Mean MTPM (SD) was 0.47 mm (0.16) in the tourniquet group and 0.45 mm (0.21) in the non-tourniquet group. Absence of tourniquet indicates that stable fixation of the tibial component can be achieved in cemented TKA. © 2015 Elsevier Inc. All rights reserved.
A pneumatic tourniquet in elective total knee arthroplasty (TKA) is still commonly used to provide a bloodless field and reduce blood loss. Furthermore, the diminished bleeding should in combination with careful pulse lavage provide a better cementation and fixation of the implant [1]. This is because a dry cement–bone interface allows proper cement penetration and bone cement interdigitation [2]. Although many studies have been carried out to settle the question of whether or not to use tourniquet, they have primarily focused on clinical outcomes such as operation time, intraoperative bleeding, pain and knee flexion [3–5]. Systematic reviews and meta-analysis regarding the problems of tourniquet use in TKA have not reached a definitive consensus, but encourage further investigation of implant fixation [6–8]. Radiostereometric analysis (RSA) was developed by Selvik [9] in 1974 and is an accurate 3-dimensional measurement technique, that can be used to evaluate migration and fixation of implants with reference to 1 mm tantalum markers implanted in the surrounding bone. Early micromotion between implant and bone is associated with early need for revision [10]. Model-based RSA (MBRSA) is a further developed method to determine migration and unlike marker-based RSA it does not require markers attached to the implant. Instead MBRSA uses a digital image-processing technique based on Cad models to determine the location and orientation of the implant. MBRSA has been compared with
No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.05.058. Reprint requests: Ashir Ejaz, MD, PhD, Ny Kastetvej 30-06, DK-9000 Aalborg, Denmark.
marker-based RSA and been shown to be a valid technique to determine the accuracy of implantation [11,12]. To our knowledge, RSA-evaluation of tourniquet effects on implant fixation has been carried out in only two other studies, both of which used marker-based RSA [13,14]. Other studies have used plain radiographs to assess whether loosening took place without tourniquet use [3,5]. This present study is the first using model-based RSA to detect possible migration when a tourniquet was not used. We assumed that if no difference in migration was detected between the two groups, it was acceptable to conclude that tourniquet use did not influence the quality of implant fixation. There are no clinical studies indicating that tourniquet use improves fixation. The aim of this RCT study was to determine whether implant fixation was influenced by the absence of a tourniquet and the presence of active bleeding. We hypothesized that not using a tourniquet during TKA would not affect implant fixation. Materials and methods This prospective randomized clinical trial was conducted at Aalborg University Hospital, Aalborg, Denmark. A total of 70 primary TKAs were performed between January 2011 and January 2012. Approval from the local ethics committee (approval no. N20090045) and registration at ClinicalTrials.gov (NCT01309035) were obtained. All patients gave written consent and were enrolled in this study in accordance with the Consolidated Standards of Reporting Trials (CONSORT) and The Helsinki Declaration (Fig. 1). This study was part of a larger randomized controlled trial where 2 other main aims were investigated: tourniquets effect on clinical
http://dx.doi.org/10.1016/j.arth.2015.05.058 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
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A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
Fig. 1. Flowchart of included participants.
outcomes [16] and ischemic conditions. The results of implant fixation are presented in this publication. Patients aged 50–85 years were included if inclusion criteria were met and an elective unilateral TKA because of gonarthrosis stages 3–5 according to Ahlbäck [15] was planned. Exclusion criteria included rheumatoid arthritis, peripheral vascular disease, diabetes, prior knee surgery and use of anticoagulation medicine. Patients in both groups were comparable with regard to demographics (Table 1). Patients were block randomized using sealed envelopes and were allocated into two groups: 33 patients had surgery using a tourniquet (Tq group) and 31 patients had surgery without the use of a tourniquet (non-Tq group). The envelopes were opened when the surgeon was present in the operating theatre before surgery. Patients were unaware of the group to which they had been allocated. Surgical technique All procedures were standardized with regard to preoperative tranexamic acid, spinal anesthesia, postoperative pain and rehabilitation regimen. Before surgery, tranexamic acid (1 g) was administered orally, and immediately prior to skin incision, cefuroxime (1.5 g) was administered
intravenously. In addition, tranexamic acid (0.5 g) was given 3 hours after surgery, and cefuroxime (750 mg) was given 6 and 12 hours postoperatively. Thrombosis prophylaxis was achieved with use of rivaroxaban (10 mg per day) throughout hospitalization. Both groups had an appropriately sized thigh tourniquet applied, but it was only inflated in the Tq group. In non-Tq group, it was placed on the thigh but not inflated, thereby serving as safety device in case of uncontrollable bleeding. In the Tq group, limb exsanguination was done by elevation for 2 min, and the cuff was inflated to 250 mmHg just prior to skin incision. All knee implants were the NexGen CR-Flex Fixed Bearing Knee (Zimmer, Warsaw, Indiana, USA) with use of high viscosity bone cement, Refobacin Bone Cement R (Biomet, Warsaw, Indiana, USA). In all cases, the patella was resurfaced. Surgical procedures were all performed by one single surgeon. A midline skin incision and medial parapatellar arthrotomy were applied. An intramedullary guide system was used for the femur and external guides for the tibia. The distal femur guide hole was plugged with autogenous bone grafts. Cement was applied on the tibia plateau surface, beneath the tibial tray and along the stem. Anchorage holes were drilled into the tibia plateau to increase the contact area between bone and cement. The proximal tibia bone was prepared for RSA with the insertion of 14–16 tantalum beads of 1.0-mm. Modern cementing technique was used that involved
Table 1 Demographics.
Sex M/F, N Age (years), mean ± SD Height (cm), mean ± SD Weight (kg), mean ± SD BMI, mean ± SD
Total Sample (N = 57)
Tourniquet (N = 29)
Non-tourniquet (N = 28)
57 68.3 ± 8.0 168.1 ± 7.5 69.7 ± 9.3 25.1 ± 2.3
13/16 68.3 ± 8.4 168.0 ± 6.7 69.7 ± 7.3 25.1 ± 2.0
15/13 68.2 ± 7.8 168.2 ± 8.2 69.7 ± 10.9 25.2 ± 2.5
SD: standard deviation.
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
meticulous pulse lavage of the exposed cut-bony surface before cement application. A two-stage cementation procedure was performed. The tibia and patella were implanted first, and then another batch of cement was used to fixate the femoral component. This was done to secure enough time to obtain a careful cementation with proper pressurization. After cementation, further pulse lavage debridement was performed to eliminate cement debris from the wound [17]. Immediately after wound closure, dressings were applied, and the cuff was deflated in the Tq group and removed. Postoperative rehabilitation and pain management were standardized for both groups and followed a standard protocol including full weight bearing.
RSA Outcomes RSAs were all obtained on the first postoperative day. This was used as reference examination. Subsequent follow-up examinations were performed on outpatient controls at 2, 6, 12 and 24 months. The RSA setup was as recommended by Valstar et al [18], with two ceilingfixed automatically synchronised roentgen tubes, which were angled 90° relative to each other. A biplanar calibration box (RSA Biomedical, Sweden) was placed in the midsection of the roentgen focus. All radiographs were fully digitalized. Precision was evaluated at 1year follow-up at which time double examinations were performed, with total repositioning of the patient and the radiographic equipment. All stereoradiographs were analyzed using model-based RSA software (MBRSA v3.3.2, Medis Specials, Leiden, the Netherlands) (Fig. 2). The upper limit for mean error of rigid body fitting (stability of markers) was 0.14. The mean condition number (CN), which indicates the distribution of bone markers and thereby the quality of the rigid body formed by the markers, was 21. This low CN indicates that the distribution and quality were good. A CN lower than 90–100 is suggested as being appropriate [18]. The main outcome measurement was based on maximum total point motion (MTPM), which represents the vector length of a marker in the rigid body that has the longest translational motion, not considering direction, and always has a positive value. In addition, translations and rotations were calculated accordingly to the standards suggested by Valstar et al [18] as secondary RSA outcome variables. Rigid-body translations and rotations of the implant were calculated about a coordinate system centered at the center of the implant, and the axes were aligned with the anatomical directions. Translations along the axes were given as x-translation (medial–lateral movement), y-translations (superior/lift-off and inferior/subsidence movement) and z-translations (anterior and posterior movements). Rotations around the axes were expressed as x-rotation,
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y-rotation and z-rotation, which represent anterior-posterior tilt, internal-external rotation and varus–valgus tilt, respectively. Statistical Analysis Sample size was based on earlier studies [13,19]. Using a SD 0.2 mm with α = 5 and β = 80, the sample size of each group was 25. Because of possible risk of patient drop-out, the number was increased to 35 per group. In a systematic review, it was suggested that an MTPM migration threshold of less than 0.54 mm was acceptable [20]. We chose migration ≥0.5 mm in magnitude at 2-year follow-up to be “clinically relevant” based on previous clinical studies [10,12,21]. This means the 2SD would have to be within ± 0.5 mm. Data were analyzed by ANOVA and Mann–Whitney U-test to compare mean difference in migration (signed values) where appropriate. The level of significance was set at the 95% confidence limit, and P-values less than 0.05 were considered significant. Data are presented as mean and standard deviation (SD). Statistical analysis was performed by using STATA 11.0 Results Seventy patients were enrolled in the trial and 57 (28 male and 29 female) completed the study (Fig. 1). Patients were similar concerning preoperative demographics (Table 1). There were no differences regarding age, weight, gender or radiographic osteoarthritis grade. During 2-years' follow-up no statistically significant difference was detected in the mean values of MTPM between the two groups (P = 0.63) (Fig. 3). No statistically significant difference was detected in mean values of translations or rotations along the sagittal, transverse and longitudinal axes after 2 years (Table 2). In both groups, all of the patients analyzed with RSA showed excellent and stable fixation throughout the follow-ups, and no significant migration was detected. There was no statistical difference detected in mean values of translation or rotation, along or around the x-, y- and z-axes at any time during follow-up, P N 0.05. All mean values were below 0.5 mm and 0.5 degrees for both groups. We registered one case of early tibial component loosening in the Tq group. The patient was initially without symptoms and well mobilized, but on plain radiographs the loosening was detected at week 8. Implant loosening had occurred due to impaired subchondral tibia bone quality caused by a cyst not recognized before or during surgery. This patient was not included in RSA analysis.
Fig. 2. Model-based RSA: in the midsection of the two roentgen foci a model of the implant is matched on the radiostereometric picture of the patient's implant. The migration of the implant is determined in relation to tantalum bone markers (red dots).
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
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A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
Fig. 3. Maximum total point motion during a 2-year follow-up.
Discussion The reason for applying a tourniquet is to ensure less intraoperative bleeding and concurrently optimize surgical visibility and thereby potentially reducing duration of surgery time. Another important argument for tourniquet application is to achieve better implant fixation because blood may impair bone–cement interdigitation [2]. It is known that tibial components migrate after surgery, most marked in the first 6 weeks; later, migration diminishes and stabilizes approximately 1 year after surgery [10,22,23]. Obtaining a good and secure initial fixation is of utter importance. Implant fixation and survival are endpoints that reveal the success of a TKA operation. Therefore it was important to contribute to answering the question of whether using a tourniquet secures better cementation and especially fixation of the tibial component, which seems to be the main site of loosening. The aim of this present RCT study was to investigate whether absence of a tourniquet would worsen implant fixation during the first 2 years after TKA surgery using RSA, expressed by MTPM, as primary outcome. Our study showed no significant difference in mean values of MTPM between patients in whom a tourniquet was used and those in whom a tourniquet was not used. Also, no significant difference in mean values was detected in the translations and rotations. In our study condition number and mean error of rigid body fitting were low, and the overall quality of RSA examinations was good. To our knowledge this is the first study to investigate the effect of a tourniquet on implant migration and long-term survival using modelbased RSA. Only two other studies regarding implant fixation have been conducted; both used marker-based RSA and involved 50 patients and 60 patients, respectively [13,14]. Their results support our findings. MTPM and translations and rotations after 2 years showed no difference. Ryd et al [10] categorized implants movements to be stable if MTPM was b 0.2 mm between 1 and 2 years or as being at risk of loosening if MTPM was N 0.2 mm, thus giving an accuracy of 0.2 mm for translation and 0.5 degrees for rotations. Other studies have reported
accuracy that ranges from 0.05 to 0.5 mm for translation and 0.15° to 1.15° for rotations [21,24]. In accordance with this, our findings showed implant fixation and long-term implant survival was not compromised. One shortcoming of this study was the use of model-based RSA from CAD models. The precision relies on obtaining an exact contour detection of the tibial tray geometry. The method has been proven to be a highly accurate method to evaluate fixation of tibial components [25,26]. Other factors such as osteoporosis that can cause motion were not considered in the present study, but randomization should equalize these parameters. The corner stones of modern cementing technique are surface preparation including comprehensive high pressure pulse lavage that enhances the mechanical bone–cement interdigitation by removing blood and causing a better cement penetration [27]. Furthermore a careful cleaning of remaining cement debris is crucial because it may prevent “third body wear” responsible for implant loosening and polyethylene wear [17]. These steps are some of the key elements to secure a high quality implant fixation so that the risk of long-term survival failure is reduced. Common practice is to cement the components in one phase, whereas we divided the cementation process into two phases. This prolonged the time necessary to complete surgery, but was carried out to secure an optimal and careful cementation of each component. All patients in this study received tranexamic acid, because TKA surgery can lead to substantial blood loss and increased blood transfusion requirements. One method to reduce perioperative blood loss and blood transfusion requirements is with the use of tranexamic acid. In an RCT study where TKA was performed without the use of tourniquet, it was concluded that tranexamic acid was an effective way of reducing blood loss and transfusions requirements [28]. The use of tranexamic acid in TKA is supported by several metaanalysis studies stating that tranexamic acid is safe and effective in minimizing perioperative and postoperative blood loss and is not associated with increased risk of venous thromboembolic events [29–31]. The use of tranexamic acid in this study may have minimized the impact of not using a tourniquet on the quality of cement fixation. MTPM between the two groups showed no difference in migration or rigid body motion pattern, indicating that the absence of a tourniquet did not worsen the fixation of the tibial component and increase the risk of long-term loosening. MTPM can easily be affected by movements from all directions, but it is appropriate for detecting differences between two similar groups. Translations and rotations are more precise variables of the rigid body's center of gravity. These variables did also support that there was no differences in migration between the two groups. The MTPM reported in our study is close to the limit for acceptable migration. This limit varies for implant types, because some have more migration than others [32]. The translations and rotations presented good values. In the randomized study by Vandenbussche et al [5] plain radiographs analysis was performed at 3 months, looking for early signs of aseptic implant loosening with special attention to radiolucent lines, and no significance difference was seen in relation to tourniquet use
Table 2 RSA Results Expressed as Mean Translation and Rotation of the Tibial Component. N = 57
X translation (mm ± SD) Y translation (mm ± SD) Z translation (mm ± SD) X rotation (degrees ± SD) Y rotation (degrees ± SD) Z rotation (degrees ± SD) MTPM mean (mm ± SD)
8 weeks
6 months
12 months
24 months
Tq (n = 29)
Non-Tq (n = 28)
Tq (n = 29)
Non-Tq (n = 28)
Tq (n = 29)
Non-Tq (n = 28)
Tq (n = 29)
Non-Tq (n = 28)
0.07 −0.02 −0.01 −0.09 −0.08 −0.16 0.43
0.01 −0.01 0.04 0.01 0.07 −0,04 0.53
0.02 −0.04 0.05 0.02 −0.05 0.07 0.55
−0.01 −0.02 0.03 −0.04 0.11 0.03 0.51
0.04 0.02 −0.03 −0.02 −0.09 0.02 0.57
−0.03 −0.01 0.01 −0.13 −0.30 −0.10 0.53
0.03 −0.03 −0.02 −0.03 −0.12 0.04 0.47
−0.04 −0.02 0.02 −0.03 −0.08 −0.05 0.45
± ± ± ± ± ± ±
0.39 0.15 0.17 0.41 0.98 0.45 0.22
± ± ± ± ± ± ±
0.14 0.11 0.20 0.34 0.75 0.34 0.32
± ± ± ± ± ± ±
0.33 0.15 0.12 0.35 0.95 0.30 0.42
± ± ± ± ± ± ±
0.22 0.13 0.32 0.50 0.83 0.62 0.34
± ± ± ± ± ± ±
0.30 0.23 0.50 0.57 0.96 0.28 0.40
± ± ± ± ± ± ±
.030 0.11 0.35 0.50 0.81 0.54 0.43
± ± ± ± ± ± ±
0.28 0.18 0.22 0.47 0.88 0.41 0.16
± ± ± ± ± ± ±
.31 0.27 0.28 0.31 0.93 0.58 0.21
Positive directions for translation along orthogonal axis were X (medial–lateral), Y (caudal–cranial), and Z (posterior–anterior). Positive directions for rotation around the coordinate axes were X (anterior posterior tilt), Y (internal–external rotation), and Z (varus–valgus tilt).
Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
A. Ejaz et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
or non-use. Abdel-Salam and Eyres [3] also reported that no difference was detected between the two groups based on evaluation of plain radiographs during a 2-year follow-up. Alternative methods of using the tourniquet in TKA have been investigated in RCT studies [33,34]. Here a limited use of tourniquet has been favored, suggesting that tourniquet be applied in only shorter periods and released after the cementation phase. This provides the benefit of decreased limb swelling, pain and recovery period without increasing operation time or blood loss. These findings were consistent with the study regarding TKA surgery where tourniquet is absent throughout the operation [16]. Since very little is known about implant fixation and long-term survival or cement interdigitation in relation to tourniquet use, we suggest that further RCT studies be conducted to investigate the long-term revision rates of the tibial component. In conclusion, we found that performing cemented TKA surgery without use of tourniquet is safe in terms of obtaining a good cementation and implant fixation, when tranexamic acid is used intraoperatively, indicating that long-term implant survival is not compromised. Acknowledgements The authors would like to thank Dr. Andreas Kappel for participating in this study and performing all the surgical procedures. References 1. Schlegel UJ, Siewe J, Delank KS, et al. Pulsed lavage improves fixation strength of cemented tibial components. Int Orthop 2011;35(8):1165. 2. Juliusson R, Arve J, Ryd L. Cementation pressure in arthroplasty. In vitro study of cement penetration into femoral heads. Acta Orthop Scand 1994;65(2):131. 3. Abdel-Salam A, Eyres KS. Effects of tourniquet during total knee arthroplasty. A prospective randomized study. J Bone Joint Surg (Br) 1995;77(2):250. 4. Tetro AM, Rudan JF. The effects of a pneumatic tourniquet on blood loss in total knee arthroplasty. Can J Surg 2001;44(1):33. 5. Vandenbussche E, Duranthon LD, Couturier M, et al. The effect of tourniquet use in total knee arthroplasty. Int Orthop 2002;26(5):306. 6. Smith TO, Hing CB. Is a tourniquet beneficial in total knee replacement surgery? A meta-analysis and systematic review. Knee 2010;17(2):141. 7. Tai TW, Lin CJ, Jou IM, et al. Tourniquet use in total knee arthroplasty: a meta-analysis. Knee Surg Sports Traumatol Arthrosc 2011;19(7):1121. 8. Alcelik I, Pollock RD, Sukeik M, et al. A comparison of outcomes with and without a tourniquet in total knee arthroplasty: a systematic review and metaanalysis of randomized controlled trials. J Arthroplasty 2012;27(3):331. 9. Selvik G. Roentgen stereophotogrammetry. A method for the study of the kinematics of the skeletal system. Acta Orthop Scand Suppl 1989;232:1 [Review]. 10. Ryd L, Albrektsson BE, Carlsson L, et al. Roentgen stereophotogrammetric analysis as a predictor of mechanical loosening of knee prostheses. J Bone Joint Surg (Br) 1995; 77(3):377. 11. Trozzi C, Kaptein BL, Garling EH, et al. Precision assessment of model-based RSA for a total knee prosthesis in a biplanar set-up. Knee 2008;15(5):396.
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Please cite this article as: Ejaz A, et al, Absence of a Tourniquet Does Not Affect Fixation of Cemented TKA: A Randomized RSA Study of 70 Patients, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.05.058
