Abstract
Purpose
Patients frequently present with bilateral symptomatic knee osteoarthritis and request simultaneous total knee arthroplasties (TKAs). Technical differences between simultaneous and staged TKAs could affect clinical and radiographic outcomes. We hypothesized staged TKAs would have fewer mechanical alignment outliers than simultaneous TKAs.
Methods
We reviewed 87 simultaneous and 72 staged TKAs with at least 2 years of follow-up. Radiographic assessment was done using standing long leg and lateral radiographs of the knee. Coronal and sagittal measurements were performed by four blinded observers on two separate occasions with an intra-observer agreement of 0.95 and inter-observer of 0.92.
Results
The first simultaneous knee had no difference in the probability of establishing the mechanical axis outside 3° of neutral (45%) compared to the first staged knee (54%, p = 0.337). However, the second simultaneous knee (49%) was more likely to establish the axis outside mechanical neutral compared to the second staged knee (28%; Odds Ratio (OR): 2.54, Confidence Interval (CI): 1.31 – 4.94, p = 0.006). There was an increased risk of deep venous thrombosis with staged TKA (OR: 2.96, CI: 1.28 – 6.84, p = 0.011), but other perioperative complication rates were not significantly different. There were no clinically significant differences in range of motion or Knee Society Score.
Conclusion
There is a significantly increased risk of establishing the second knee outside mechanical neutral during a simultaneous TKA compared to staged bilateral TKAs, possibly related to a number of surgeon- and system-related factors. The impact on clinical outcomes and radiographic loosening may become significant in long-term follow up.
Keywords: Staged Total Knee Arthroplasty, Simultaneous Total Knee Arthroplasty, Mechanical Alignment, Total Knee Arthroplasty Alignment Outliers, Total Knee Arthroplasty Outcomes
Introduction
The prevalence of obesity, an aging population, and expanding surgical indications contribute to the increasing demand for total knee arthroplasty (TKA) [1]. Moreover, patients frequently present with bilateral symptomatic disease and may request simultaneous bilateral TKAs rather than staged bilateral TKAs [2]. There is no consensus regarding the efficacy of simultaneous bilateral TKA. Advocates of simultaneous bilateral TKAs commonly cite reduced cost of care [3, 4, 5], length of hospitalization, isolated anesthesia risk under a single anesthetic, a single rehabilitation with reduced overall rehabilitation times, increased patient satisfaction [2], and better functional outcomes [3, 6, 7]. Critics of simultaneous bilateral TKAs point to analyses that reveal increased peri-operative morbidity, including thromboembolic events, deep vein thrombosis, cardiac and neurologic events, wound complications, and blood loss [1, 8–14]. Additionally, large scale retrospective analyses and meta-analyses provide no strong consensus [1, 3, 15–18].
Suboptimal component alignment is a potential technical error that can occur during TKA [19, 20]. Surgeon fatigue, different operative teams, different techniques, and even surgeon handedness may factor into technical differences that could emerge during bilateral TKAs [21]. We hypothesized that 1) the coronal alignment of the second knee would improve when TKAs were staged, and 2) there would be more coronal alignment outliers when TKAs were performed simultaneously. Additional secondary outcomes included perioperative complications, knee range of motion, knee society scores, and aseptic loosening.
Methods
After institutional review board approval, 159 patients, who underwent simultaneous bilateral or staged bilateral TKAs with a minimum of 2-years of clinical and radiographic follow-up, were retrospectively reviewed (Table 1). Consecutive patients were identified from an institutional database if they had bilateral TKAs done at our institution, and surgeries were performed between 1995 and 2013. Seventy-two patients (45%) underwent staged bilateral TKA, defined as the contralateral TKA being performed on a separate hospitalization by the same surgeon, and 87 patients (55%) underwent simultaneous bilateral TKA by the same surgeon under the same anesthetic. All TKAs were performed by arthroplasty fellowship-trained, board-certified orthopaedic surgeons. A standardized rehabilitation protocol was followed for all patients. The decision to perform staged or simultaneous TKAs was decided based on surgeon and patient preference. However, patient age and medical co-morbidities that are routinely factored into surgical decision making were also considered in the decision for staged or simultaneous TKAs.
Table 1.
Patient Characteristics for Staged and Simultaneous Total Knees
| Characteristic | Staged | Simultaneous | P 1 | P 2 | P 3 | |
|---|---|---|---|---|---|---|
| First Knee | Second Knee | |||||
| Age (year) ± SD | 64.3 ± 12.1 | 65.8 ± 12.2 | 65.8 ± 9.5 | 0.382 | 0.976 | 0.437 |
| Sex (female) | 54 (75%) | 58 (67%) | 0.252 | |||
| Ethnicity | 0.087 | |||||
| Black | 10 (14%) | 3 (3%) | ||||
| White | 41 (57%) | 51 (59%) | ||||
| Asian | 9 (13%) | 6 (7%) | ||||
| Hispanic | 8 (11%) | 5 (6%) | ||||
| Undisclosed | 4 (6%) | 22 (25%) | ||||
| Etiology | 0.431 | |||||
| Osteoarthritis | 65 (90%) | 75 (86%) | ||||
| Inflammatory | 7 (10%) | 12 (14%) | ||||
| First Side (left) | 35 (51%) | 22 (25%) | 0.002 | |||
| BMI (kg/m 2 ) ± SD | 29.9 ± 6.9 | 29.9 ± 6.7 | 31.0 ± 7.5 | 0.364 | 0.358 | 0.995 |
| ASA Classification | 0.277 | 0.079 | 0.750 | |||
| I | 2 (%) | 1 (%) | 3 (%) | |||
| II | 49 (%) | 47 (%) | 68 (%) | |||
| III | 21 (%) | 24 (%) | 16 (%) | |||
| Implant | 1.000 | 0.819 | 0.410 | |||
| Cruciate Retaining | 0 (0.0%) | 1 (1%) | 1 (1%) | |||
| Posterior Stabilized | 63 (88%) | 66 (92%) | 82 (94%) | |||
| Cruciate Stabilized | 4 (6%) | 2 (3%) | 4 (5%) | |||
| Condylar Constraint | 5 (7%) | 2 (3%) | 0 (0%) | |||
| Liner Thickness (mm) ± SD | 10.8 ± 1.4 | 10.6 ± 1.5 | 10.7 ± 1.5 | 0.549 | 0.675 | 0.184 |
| Length of Stay (days) ± SD | 3.7 ± 1.2 | 3.6 ± 0.8 | 4.5 ± 1.7 | <0.001 | <0.001 | 0.795 |
| Disposition | <0.001 | <0.001 | 0.468 | |||
| Nursing Facility | 34 (47%) | 35 (49%) | 76 (87%) | |||
| Home, no Home Health | 15 (21%) | 10 (14%) | 3 (3%) | |||
| Home, with Home Health | 22 (31%) | 27 (38%) | 6 (7%) | |||
| Not Documented | 1 (1%) | 0 (0%) | 2 (2%) | |||
| Follow-up (years) ± SD | 7.1 ± 3.5 | 5.7 ± 3.1 | 7.1 ± 3.9 | 0.941 | <0.001 | <0.001 |
Abbreviations: SD, standard deviation; ASA, American Society of Anesthesiologist; BMI, body mass index; P1 is a test of significance is between simultaneous TKA and staged TKA first knee, P2 is a test of significance is between simultaneous TKA and staged TKA second knee, P3 is a test of significance is between the staged first and second TKAs
Radiographic assessment was done using postoperative full-length standing 36-inch hip-to-ankle and lateral radiographs of the knee. Coronal and sagittal alignment was measured by four blinded resident and attending physician observers on two separate occasions. Inter- and intra-observer agreement was determined using kappa coefficient analysis. The anatomic axis as well as the distal femoral and proximal tibial angles, tibial slope, femoral flexion, and patellar tilt were measured by four observers on two separate occasions separated by at least two weeks to establish intra-observer agreement. A coronal alignment side-to-side difference between staged or simultaneous knees of 3° or greater was considered to be a clinically significant component outlier, given prior data suggesting these knees may have worse long-term survival [23–25]. All digital images were analyzed using a picture archiving and communication system (General Electric, Milwaukee, WI, USA) which permitted angular measurements to the level of 0.1°. A two-tailed power analysis determined we had 99% power to detect a difference of 0.5° in any of the angular measurement assuming a measurement error of 0.6°. Statistical analyses were performed using Stata 12 statistical software (College Station, TX). Continuous data were analyzed and compared with two-tailed independent Student t-test and Mann-Whitney U test for variables with non-normal distributions. Categorical data were analyzed using a Chi square test, the Freeman-Halton extension of the Fisher’s exact test was used when an individual data point was less than 5. McNemar’s test was used for matched pairs. Significance was set at p < 0.05.
Results
Demographic comparisons yielded no significant differences in age, sex, ethnicity, disease etiology, body mass index, or American Society of Anesthesiologists score between the simultaneous and staged cohorts (p > 0.05, table 1). A higher number of patients undergoing simultaneous bilateral TKAs had the surgeon start (e.g., the first knee) on the right knee (75%) when compared to staged bilateral TKAs (51%, p = 0.002). In simultaneous TKAs, the right knee was more often chosen as the first side given that the surgeons in this study are right-handed. Staged TKA patients had an even distribution of left versus right knee first, as the surgeon chose to begin with the more symptomatic side. Choice of implant and liner thickness did not vary between the cohorts (p > 0.05). Patients undergoing simultaneous TKAs were likely to have 3 fewer cumulative inpatient days in the hospital (p < 0.001), but 87% of patients undergoing simultaneous bilateral TKAs were discharged to a rehabilitation facility when compared to 47% of the patients undergoing staged TKAs (p < 0.001, Table 1).
Radiographically, the mean measurement difference between observers was 0.5 ± 0.6° and the intra-observer agreement was 0.95 and inter-observer agreement of 0.92. Staged first versus second TKAs had differences in the mean femoral flexion and lateral patellar tilt, as well as the probability of establishing the mechanical axis outside 3° of neutral (54% versus 28%, p = 0.004, Table 2). Simultaneous TKAs had no difference in the mean mechanical alignment (p = 0.646) nor the probability of establishing the mechanical axis outside 3° of neutral for the first (45%) and second knee (49%, p = 0.649, Table 2).
Table 2.
Radiographic Alignment and Outliers after Staged or Simultaneous TKA
| Staged | P 1 | Simultaneous | P 2 | P 3 | P 4 | |||
|---|---|---|---|---|---|---|---|---|
| First Knee | Second Knee | First Knee | Second Knee | |||||
| Coronal Outliers (>3°) | 38 (54%) | 20 (28%) | 0.004 | 39 (45%) | 43 (49%) | 0.649 | 0.337 | 0.009 |
| Mechanical Varus | 1.4° ± 4.1° | −1.1° ± 3.6° | 0.375 | 1.4° ± 3.6° | 1.2 ± 4.7 | 0.646 | 0.834 | 0.889 |
| Distal Femoral Valgus | 85.6° ± 2.3° | 85.6° ± 2.4° | 0.968 | 83.2° ± 8.3° | 84.1 ± 3.0 | 0.905 | <0.001 | 0.001 |
| Proximal Tibial Varus | 87.8° ± 2.3° | 87.8° ± 2.3° | 0.818 | 88.6° ± 2.8° | 88.9 ± 2.9 | 0.542 | 0.030 | 0.002 |
| Femoral Flexion | 3.0° ± 3.7° | 1.7° ± 3.8° | 0.020 | 3.3° ± 4.2° | 3.1 ± 3.5 | 0.337 | 0.352 | 0.004 |
| Tibial Slope | 7.9° ± 3.2° | 8.4° ± 3.0° | 0.322 | 8.2° ± 3.5° | 8.1 ± 4.1 | 0.960 | 0.617 | 0.660 |
| Lateral Patellar Tilt | −1.1° ± 5.5° | 0.7° ± 4.9° | 0.046 | −0.9° ± 5.2° | −1.2 ± 6.3 | 0.653 | 0.719 | 0.040 |
Abbreviations: P1 is a test of significance is between staged TKA first and second knees, P2 is a test of significance is between simultaneous TKA first and second knees, P3 is a test of significance is between simultaneous TKA and staged TKA first knee, P4 is a test of significance is between simultaneous TKA and staged TKA second knee
There were differences observed between the first staged and first simultaneous TKAs in mean distal femoral valgus and proximal tibial varus (Table 2). The first knee of a staged TKA had no difference in the probability of establishing the mechanical axis outside 3° of neutral (54%) when compared to the first knee of a simultaneous TKA (45%, p = 0.337, Table 2). The second staged TKA and second simultaneous TKA knees likewise had small differences mean distal femoral valgus and proximal tibial varus, angles as well as femoral flexion and lateral patellar tilt (Table 2). The second knee during a simultaneous TKA (49%) had higher odds of establishing the mechanical axis outside 3° of neutral when compared to the second knee after staged TKA (28%, Odds Ratio: 2.54, Confidence interval: 1.31 – 4.94, p = 0.009, Table 2). There was no significant difference in the rate of revision for aseptic loosening between staged or simultaneous knees over the duration of our study with a minimum of 2 years of follow up. There was also no significant difference in the rate of coronal alignment outside 3° of neutral comparing left versus right TKAs.
There was a three-fold increase in the odds of a deep venous thrombosis with staged TKAs (Odds Ratio: 2.96, Confidence Interval: 1.28 – 6.84, p = 0.014, Table 3), but there was no other significant difference in other perioperative complications between groups. There was no significant difference in knee range of motion with either side after staged or simultaneous TKA (Table 4). However, there was a statistically significant three-point improvement in KSS between the first and second staged TKA (89 ± 13, p = 0.024, Table 4). Beyond the minimum two year follow up, the rate of patients lost to follow up was 67% in simultaneous TKAs and 72% in staged TKAs.
Table 3.
Incidence of Postoperative Complications at Final Follow-up after Staged and Simultaneous TKA
| Complication | Staged | Simultaneous | P |
|---|---|---|---|
| cellulitis | 2 (3%) | 0 (0%) | 0.203 |
| deep vein thrombosis | 20 (28%) | 10 (11%) | 0.014 |
| peroneal nerve palsy | 2 (3%) | 0 (0%) | 0.204 |
| quadriceps rupture | 0 (0%) | 1 (1%) | 1.000 |
| aseptic loosening | 5 (7%) | 5 (6%) | 1.000 |
| laxity | 1 (1%) | 2 (2%) | 1.000 |
| deep infection | 2 (3%) | 1 (1%) | 0.590 |
| arthrofibrosis | 1 (1%) | 2 (3%) | 1.000 |
| reoperation | 9 (13%) | 10 (11%) | 1.000 |
Table 4.
Clinical Outcomes after Staged and Simultaneous TKA
| Staged TKA | P 1 | Simultaneous TKA | P 2 | P 3 | P 4 | |||
|---|---|---|---|---|---|---|---|---|
| First Knee | Second Knee | First Knee | Second Knee | |||||
| Extension | 0.0 ± 1.0° | 0.2 ± 1.0° | 0.327 | 0.6 ± 1.6° | 0.6 ± 2.1° | 0.666 | 0.079 | 0.329 |
| Flexion | 118.4 ± 12.1° | 115.6 ± 13.3 | 0.114 | 119.1 ± 13.0 | 119.1 ± 12.5 | 0.802 | 0.819 | 0.215 |
| Knee Society Score | 86 ± 14 | 89 ± 13 | 0.024 | 85 ± 15 | 85 ± 13 | 1.000 | 0.649 | 0.070 |
Abbreviations: P1 is a test of significance is between staged TKA first and second knees, P2 is a test of significance is between simultaneous TKA first and second knees, P3 is a test of significance is between simultaneous TKA and staged TKA first knee, P4 is a test of significance is between simultaneous TKA and staged TKA second knee
Discussion
In patients with symptomatic osteoarthritis of both knees, patients may prefer both knees to be done under a single anesthetic [2]. Additionally, there are economic benefits to performing TKAs simultaneously [4, 5, 17, 26–28], as well as evidence for improved functional outcomes [2, 29, 30, 32]. However, several studies show an increase in the risks of a major perioperative complication with simultaneous TKA [3, 15, 29, 31–36], while other studies have failed to demonstrate significant outcome-related differences [37–40]. Despite this, there is little information regarding component alignment and outliers during staged and simultaneous TKAs. We found that, in general, peri-operative complications and clinical outcomes were not significantly different whether TKAs were done in a staged or simultaneous fashion, except for deep venous thrombosis having a higher incidence in staged TKAs, which may be related to more medical complex patients receiving staged rather than simultaneous surgeries. However, simultaneous TKAs had a longer cumulative length of inpatient stay, and a higher rate of patients requiring skilled nursing facility placement at discharge.
Instability after TKA is often accentuated by errors in component positioning or improper restoration of alignment, and any difference in these parameters may lead to future extension or flexion instability [41] that may reduce the lifespan of the TKA [48]. This is particularly true for coronal alignment. It is recommended that femoral and tibial components be positioned in less than 3° from mechanical neutral in the coronal plane to improve functional outcomes and avoid alignment associated complications [23–25], and most arthroplasty surgeons aim for this goal. Optimal sagittal positioning, according to many authors, include the femoral component positioned between 0 to 3° of flexion and the tibial component between 0 to 7° of posterior slope [25].
Radiographic analysis of our patients demonstrated that our inter- and intra-observer agreement and error margin of TKA alignment measurements is similar to published standards [46]. Outlier analysis identified that the second TKA after staged arthroplasty was more than twice as likely to establish the mechanical axis within 3° of mechanical neutral when compared to the second TKA during simultaneous arthroplasty.
Astonishingly, performing as few as five TKAs in a staged fashion prevents one second TKA component outlier generated by simultaneous bilateral TKAs. Additionally, the second staged TKA had a statistically significant but possibly not clinically significant increase in knee society score compared to the first TKA (table 4), given prior data indicating the minimal clinically important difference being greater than our mean score increase [49]. The ability to correct and reduce the number of outliers in staged knees may lead to improved long-term TKA survival and knee function.
The reduction in coronal outliers with staged TKAs may be due to a number of factors, including surgeon fatigue, different operative teams, different techniques, and the ability to radiographically and clinically examine the first TKA after staged arthroplasty and make necessary adjustments for the second TKA. The operative time for simultaneous TKAs can lead to surgeon fatigue that may affect the accuracy of TKA alignment. Additionally, this operative time may lead to changes in the scrub and circulator teams that can bring individuals less familiar with the procedure that makes the surgery less efficient and potentially introduce error into the process. It is unclear why these factors may affect coronal alignment more than other parameters. There were small but likely not clinically significant differences in femoral flexion and patellar tilt, while other parameters did not show significant differences. Performing staged bilateral TKAs does allow the surgeon to evaluate the patient’s radiographic and clinical outcomes after the first TKA and make any necessary adjustments prior to performing the second TKA, for example if a patient is not completely satisfied with their first TKA and alignment is outside 3° of mechanical neutral. This can allow the surgeon to fine tune alignment to meet the patients’ needs and correct errors made during the first TKA. The combination of these factors during staged TKAs could lead to reduced likelihood of placement of the components outside of the recommended coronal alignment parameters.
One potential way to minimize the alignment errors that can be introduced during simultaneous TKAs would be the use of surgical navigation or robotic assistance. These allow the surgeon to more precisely align TKA components and may help to reduce outliers in TKA mechanical alignment. A recent randomized control trial by Gøthesen et al. examined the functional outcomes and radiographic alignment of conventionally placed TKAs versus computer navigated TKAs. The group of navigated knees had statistically significant fewer outliers in mechanical axis and tibial slope, where outliers were similarly defined as being greater than 3° off from neutral alignment. The clinical outcomes of patients with navigated knees were statistically marginally better in this study, but the clinical relevance of this finding is debated over their one year follow up period [45]. The limited follow up of both this study may preclude the discovery of differences in implant survival with accurate component placement. Patients undergoing simultaneous bilateral TKAs may be a useful future research population in examining the clinical and radiographic outcomes of navigated or robotic total knees.
This study is not without limitations. Firstly, this is a non-randomized study that may include selection bias in the decision of which patients were chosen to receive staged versus simultaneous TKAs. As previously mentioned, patient preference as well as medical comorbidities were included in the decision of whether to proceed with staged versus simultaneous surgery. The retrospective nature of the study and smaller cohort sizes also may lead to potential inclusion bias. Secondly, our power analysis determined that we examined enough patients to detect potentially significant differences in technical measurements, however this may not translate to being able to detect a small clinical difference. Thirdly, the wide time span of our study may not accurately reflect modern surgical practice due to its evolution over the span of our study. Finally, we did have a relatively high number of patients lost to follow up beyond our minimum of 2 years in both treatment groups (67% in simultaneous TKAs, 72% in staged TKAs), which will affect our ability to detect differences in long-term clinical outcomes; however, this does not affect our ability to determine the presence of coronal alignment outside mechanical neutral at the time of surgery.
In conclusion, staged and simultaneous bilateral TKAs do not significantly differ in many clinical outcomes and complication rates. However, staged knees have a lower rate of alignment outliers, as staging TKAs allows the surgeon to radiographically and clinically examine the effects of component position from the first knee prior to implantation of the second knee. Staging TKAs also reduces the risk of surgeon fatigue and different operative teams compared to simultaneous TKAs that can contribute to errors in component positioning. This results in fewer outliers in terms of coronal component positioning, which suggests tracking the long-term survival of staged and simultaneous bilateral TKAs in registry data may be warranted. Over the life of the implant, accurate component positioning with a staged second TKA or a simultaneous second TKA with navigation or robotic assistance may improve the survival of the implant.
Supplementary Material
Acknowledgements
We would like to acknowledge Rikesh A. Gandhi and Melvin G. Joice for their help with data collection, analysis, and original manuscript preparation. DFA was supported, in part by NIH NCATS (KL2TR003143). The content is solely the responsibility of the authors and does not reflect the official views of the NIH. These funding sources had no role in the study design, data collection, analysis, interpretation of data, writing the report, or the decision to submit the findings for publication.
Funding
D.F.A. was supported, in part by NIH NCATS (KL2TR003143). The content is solely the responsibility of the authors and does not reflect the official views of the NIH. These funding sources had no role in the study design, data collection, analysis, interpretation of data, writing the report, or the decision to submit the findings for publication.
Footnotes
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Conflict of Interest
The authors report no conflicts of interest.
Level of Evidence: IV
References
- 1.Restrepo C, Parvizi J, Dietrich T, Einhorn TA. (2007) Safety of simultaneous bilateral total knee arthroplasty. A meta-analysis. J Bone Joint Surg Am. 89(6):1220–1226. DOI: 10.2106/JBJS.F.01353. [DOI] [PubMed] [Google Scholar]
- 2.Ritter MA, Harty LD, Davis KE, Meding JB, Berend M. (2003) Simultaneous bilateral, staged bilateral, and unilateral total knee arthroplasty. A survival analysis. J Bone Joint Surg Am. 85-A(8):1532–1537. [DOI] [PubMed] [Google Scholar]
- 3.Memtsoudis SG, González Della Valle A, Besculides MC, Gaber L, Sculco TP. (2008) In-hospital complications and mortality of unilateral, bilateral, and revision TKA: based on an estimate of 4,159,661 discharges. Clin Orthop. 466(11):2617–2627. DOI: 10.1007/s11999-008-0402-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Odum SM, Troyer JL, Kelly MP, Dedini RD, Bozic KJ. (2013) A cost-utility analysis comparing the cost-effectiveness of simultaneous and staged bilateral total knee arthroplasty. J Bone Joint Surg Am. 95(16):1441–1449. DOI: 10.2106/JBJS.L.00373. [DOI] [PubMed] [Google Scholar]
- 5.Reuben JD, Meyers SJ, Cox DD, Elliott M, Watson M, Shim SD. (1998) Cost comparison between bilateral simultaneous, staged, and unilateral total joint arthroplasty. J Arthroplasty. 13(2):172–179. DOI: 10.1016/S0883-5403(98)90095-X. [DOI] [PubMed] [Google Scholar]
- 6.Bagsby D, Pierson JL. (2015) Functional outcomes of simultaneous bilateral versus unilateral total knee arthroplasty. Orthopedics. 38(1):e43–47. DOI: 10.3928/01477447-20150105-59. [DOI] [PubMed] [Google Scholar]
- 7.Stanley D, Stockley I, Getty CJ. (1990) Simultaneous or staged bilateral total knee replacements in rheumatoid arthritis. A prospective study. J Bone Joint Surg Br. 72(5):772–774. DOI: 10.1302/0301-620X.72B5.2211753. [DOI] [PubMed] [Google Scholar]
- 8.Adili A, Bhandari M, Petruccelli D, De Beer J. (2001) Sequential bilateral total knee arthroplasty under 1 anesthetic in patients > or = 75 years old: complications and functional outcomes. J Arthroplasty. 16(3):271–278. DOI: 10.1054/arth.2001.21495. [DOI] [PubMed] [Google Scholar]
- 9.Bederman SS, Betsy M, Winiarsky R, Seldes RM, Sharrock NE, Sculco TP. (2001) Postoperative ileus in the lower extremity arthroplasty patient. J Arthroplasty. 16(8):1066–1070. doi: 10.1054/arth.2001.27675 [DOI] [PubMed] [Google Scholar]
- 10.Dorr LD, Merkel C, Mellman MF, Klein I. (1989) Fat emboli in bilateral total knee arthroplasty. Predictive factors for neurologic manifestations. Clin Orthop. (248):112–119. DOI: 10.1097/00003086-198911000-00019. [DOI] [PubMed] [Google Scholar]
- 11.Jankiewicz JJ, Sculco TP, Ranawat CS, Behr C, Tarrentino S. (1994) One-stage versus 2-stage bilateral total knee arthroplasty. Clin Orthop. (309):94–101. [PubMed] [Google Scholar]
- 12.Lombardi AV, Mallory TH, Fada RA, et al. (2001) Simultaneous bilateral total knee arthroplasties: who decides? Clin Orthop. (392):319–329. DOI: 0.1097/00003086–200111000-00042. [DOI] [PubMed] [Google Scholar]
- 13.Ritter MA, Meding JB. Bilateral simultaneous total knee arthroplasty. (1987) J Arthroplasty. 2(3):185–189. DOI: 10.1016/S0883-5403(87)80036-0. [DOI] [PubMed] [Google Scholar]
- 14.Mantilla CB, Horlocker TT, Schroeder DR, Berry DJ, Brown DL. (2002) Frequency of myocardial infarction, pulmonary embolism, deep venous thrombosis, and death following primary hip or knee arthroplasty. Anesthesiology. 96(5):1140–1146. DOI: 10.1097/00000542-200205000-00017. [DOI] [PubMed] [Google Scholar]
- 15.Fu D, Li G, Chen K, Zeng H, Zhang X, Cai Z. (2013) Comparison of clinical outcome between simultaneous-bilateral and staged-bilateral total knee arthroplasty: a systematic review of retrospective studies. J Arthroplasty. 28(7):1141–1147. DOI: 10.1016/j.arth.2012.09.023. [DOI] [PubMed] [Google Scholar]
- 16.Hart A, Antoniou J, Brin YS, Huk OL, Zukor DJ, Bergeron SG. (2016) Simultaneous Bilateral Versus Unilateral Total Knee Arthroplasty: A Comparison of 30-Day Readmission Rates and Major Complications. J Arthroplasty. 31(1):31–35. DOI: 10.1016/j.arth.2015.07.031. [DOI] [PubMed] [Google Scholar]
- 17.Hu J, Liu Y, Lv Z, Li X, Qin X, Fan W. (2011) Mortality and morbidity associated with simultaneous bilateral or staged bilateral total knee arthroplasty: a meta-analysis. Arch Orthop Trauma Surg. 131(9):1291–1298. DOI: 10.1007/s00402-011-1287-4. [DOI] [PubMed] [Google Scholar]
- 18.Meehan JP, Danielsen B, Tancredi DJ, Kim S, Jamali AA, White RH. (2011) A population-based comparison of the incidence of adverse outcomes after simultaneous-bilateral and staged-bilateral total knee arthroplasty. J Bone Joint Surg Am. 93(23):2203–2213. DOI: 10.2106/JBJS.J.01350. [DOI] [PubMed] [Google Scholar]
- 19.Heyse TJ, Decking R, Davis J, Boettner F, Laskin RS. (2005) Varus gonarthrosis predisposes to varus malalignment in TKA. HSS J Musculoskelet J Hosp Spec Surg. 5(2):143–148. DOI: 10.1007/s11420-009-9118-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Incavo SJ, Wild JJ, Coughlin KM, Beynnon BD. (2007) Early revision for component malrotation in total knee arthroplasty. Clin Orthop. 458:131–136. DOI: 10.1097/BLO.0b013e3180332d97. [DOI] [PubMed] [Google Scholar]
- 21.Seo JG, Lee BH, Moon Y-W, Chang MJ, Park SH. (2014) Disparate postoperative results in the first and second knees on simultaneous bilateral total knee arthroplasty. J Arthroplasty. 29(12):2331–2336. DOI: 10.1016/j.arth.2014.07.025. [DOI] [PubMed] [Google Scholar]
- 22.Capeci CM, Brown EC, Scuderi GR, Scott WN. (2006) Component asymmetry in simultaneous bilateral total knee arthroplasty. J Arthroplasty. 21(5):749–753. DOI: 10.1016/j.arth.2005.09.010. [DOI] [PubMed] [Google Scholar]
- 23.Barrett WP, Mason JB, Moskal JT, Dalury DF, Oliashirazi A, Fisher DA. (2011) Comparison of radiographic alignment of imageless computer-assisted surgery vs conventional instrumentation in primary total knee arthroplasty. J Arthroplasty. 26(8):1273–1284.e1. DOI: 10.1016/j.arth.2011.04.037. [DOI] [PubMed] [Google Scholar]
- 24.Jeffery RS, Morris RW, Denham RA. (1991) Coronal alignment after total knee replacement. J Bone Joint Surg Br. 73(5):709–714. DOI: 10.1302/0301-620X.73B5.1894655. [DOI] [PubMed] [Google Scholar]
- 25.Kim Y-H, Park J-W, Kim J-S, Park S-D. (2014) The relationship between the survival of total knee arthroplasty and postoperative coronal, sagittal and rotational alignment of knee prosthesis. Int Orthop. 38(2):379–385. DOI: 10.1007/s00264-013-2097-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Husted H, Troelsen A, Otte KS, Kristensen BB, Holm G, Kehlet H. (2011) Fast-track surgery for bilateral total knee replacement. J Bone Joint Surg Br. 93(3):351–356. DOI: 10.1302/0301-620X.93B3.25296. [DOI] [PubMed] [Google Scholar]
- 27.Lane GJ, Hozack WJ, Shah S, et al. (1997) Simultaneous bilateral versus unilateral total knee arthroplasty. Outcomes analysis. Clin Orthop. (345):106–112. [PubMed] [Google Scholar]
- 28.Macario A, Schilling P, Rubio R, Goodman S. (2003) Economics of one-stage versus two-stage bilateral total knee arthroplasties. Clin Orthop. (414):149–156. DOI: 10.1097/01.blo.0000079265.91782.ca. [DOI] [PubMed] [Google Scholar]
- 29.Leonard L, Williamson DM, Ivory JP, Jennison C. (2003) An evaluation of the safety and efficacy of simultaneous bilateral total knee arthroplasty. J Arthroplasty. 2003;18(8):972–978. DOI: 10.1016/S0883-5403(03)00282-1. [DOI] [PubMed] [Google Scholar]
- 30.Sheth DS, Cafri G, Paxton EW, Namba RS. (2016) Bilateral Simultaneous vs Staged Total Knee Arthroplasty: A Comparison of Complications and Mortality. J Arthroplasty. 31(9 Suppl):212–216. DOI: 10.1016/j.arth.2016.03.018. [DOI] [PubMed] [Google Scholar]
- 31.Bolognesi MP, Watters TS, Attarian DE, Wellman SS, Setoguchi S. (2013) Simultaneous vs staged bilateral total knee arthroplasty among Medicare beneficiaries, 2000–2009. J Arthroplasty. 28(8 Suppl):87–91. DOI: 10.1016/j.arth.2013.05.039. [DOI] [PubMed] [Google Scholar]
- 32.March LM, Cross M, Tribe KL, et al. (2004) Two knees or not two knees? Patient costs and outcomes following bilateral and unilateral total knee joint replacement surgery for OA. Osteoarthritis Cartilage. 12(5):400–408. DOI: 10.1016/j.joca.2004.02.002. [DOI] [PubMed] [Google Scholar]
- 33.Memtsoudis SG, Ma Y, Chiu Y-L, Poultsides L, Gonzalez Della Valle A, Mazumdar M. (2011) Bilateral total knee arthroplasty: risk factors for major morbidity and mortality. Anesth Analg. 113(4):784–790. DOI: 10.1213/ANE.0b013e3182282953. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Memtsoudis SG, Ma Y, González Della Valle A, et al. (2009) Perioperative outcomes after unilateral and bilateral total knee arthroplasty. Anesthesiology. 111(6):1206–1216. DOI: 10.1097/ALN.0b013e3181bfab7d. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Niki Y, Katsuyama E, Takeda Y, Enomoto H, Toyama Y, Suda Y. (2014) Comparison of postoperative morbidity between simultaneous bilateral and staged bilateral total knee arthroplasties: serological perspective and clinical consequences. J Arthroplasty. 29(3):504–509. DOI: 10.1016/j.arth.2013.07.019. [DOI] [PubMed] [Google Scholar]
- 36.Stefánsdóttir A, Lidgren L, Robertsson O. (2008) Higher early mortality with simultaneous rather than staged bilateral TKAs: results from the Swedish Knee Arthroplasty Register. Clin Orthop. 466(12):3066–3070. DOI: 10.1007/s11999-008-0404-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37.Hooper GJ, Hooper NM, Rothwell AG, Hobbs T. (2009) Bilateral total joint arthroplasty: the early results from the New Zealand National Joint Registry. J Arthroplasty. 24(8):1174–1177. DOI: 10.1016/j.arth.2008.09.022. [DOI] [PubMed] [Google Scholar]
- 38.Jain S, Wasnik S, Mittal A, Sohoni S, Kasture S. (2013) Simultaneous bilateral total knee replacement: a prospective study of 150 patients. J Orthop Surg Hong Kong. 21(1):19–22. DOI: 10.1177/230949901302100107. [DOI] [PubMed] [Google Scholar]
- 39.Kim Y-H, Choi Y-W, Kim J-S. (2009) Simultaneous bilateral sequential total knee replacement is as safe as unilateral total knee replacement. J Bone Joint Surg Br. 91(1):64–68. DOI: 10.1302/0301-620X.91B1.21320. [DOI] [PubMed] [Google Scholar]
- 40.Spicer E, Thomas GR, Rumble EJ. (2013) Comparison of the major intraoperative and postoperative complications between unilateral and sequential bilateral total knee arthroplasty in a high-volume community hospital. Can J Surg J Can Chir. 56(5):311–317. DOI: 10.1503/cjs.012912. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 41.Parratte S, Pagnano MW. (2008) Instability after total knee arthroplasty. J Bone Joint Surg Am. 90(1):184–194. [PubMed] [Google Scholar]
- 42.Seol J-H, Seon J-K, Song E-K. (2016) Comparison of postoperative complications and clinical outcomes between simultaneous and staged bilateral total knee arthroplasty. J Orthop Sci Off J Jpn Orthop Assoc. 21(6):766–769. DOI: 10.1016/j.jos.2016.07.023. [DOI] [PubMed] [Google Scholar]
- 43.Hardaker WT, Ogden WS, Musgrave RE, Goldner JL. (1978) Simultaneous and staged bilateral total knee arthroplasty. J Bone Joint Surg Am. 60(2):247–250. [PubMed] [Google Scholar]
- 44.Morrey BF, Adams RA, Ilstrup DM, Bryan RS. (1987) Complications and mortality associated with bilateral or unilateral total knee arthroplasty. J Bone Joint Surg Am. 69(4):484–488. [PubMed] [Google Scholar]
- 45.Gøthesen Ø, Espehaug B, Havelin LI, Petursson G, Hallan G, Strøm E, Dyrhovden G, Furnes O. (2014) Functional outcome and alignment in computer-assisted and conventionally operated total knee replacements: A multicentre parallel-group randomised controlled trial. Bone Joint J. 96-B:609–18 [DOI] [PubMed] [Google Scholar]
- 46.Meneghini RM, Mont MA, Backstein DB, Bourne RB, Dennis DA, Scuderi GR. Development of a Modern Knee Society Radiographic Evaluation System and Methodology for Total Knee Arthroplasty. J Arthroplasty. 2015. Dec;30(12):2311–4. [DOI] [PubMed] [Google Scholar]
- 47.Boonen B, Kerens B, Schotanus MGM, Emans P, Jong B, Kort NP. Inter-observer reliability of measurements performed on digital long-leg standing radiographs and assessment of validity compared to 3D CT-scan. The Knee. 2016. Jan;21(1):20–24. [DOI] [PubMed] [Google Scholar]
- 48.Berend ME, Ritter MA, Meding JB, Faris PM, Keating EMm, Redelman R, Faris GW, Davis KE. The Chetranjan Ranawat Award: Tibial Component Failure Mechanisms in Total Knee Arthroplasty. Clinical Orthopaedics and Related Research. 2004. Nov;428:26–34. [DOI] [PubMed] [Google Scholar]
- 49.Lee WC, Kwan YH, Chong HC, Yeo SJ. The minimal clinically important difference for Knee Society Clinical Rating System after total knee arthroplasty for primary osteoarthritis. Knee Surg Sports Traumatol Arthrosc. 2017. Nov;25(11):3354–3359. [DOI] [PubMed] [Google Scholar]
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