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Effect of individual distal femoral valgus resection in total knee arthroplasty for patients with valgus knee: A retrospective cohort study
Accepted Manuscript Effect of individual distal femoral valgus resection in total knee arthroplasty for patients with valgus knee: A retrospective cohort study Kai Zhou, Zongke Zhou, Xiaojun Shi, Bin Shen, Pengde Kang, Jing Yang, Fuxing Pei PII:
S1743-9191(18)30579-X
DOI:
10.1016/j.ijsu.2018.02.048
Reference:
IJSU 4467
To appear in:
International Journal of Surgery
Received Date: 7 November 2017 Revised Date:
19 February 2018
Accepted Date: 21 February 2018
Please cite this article as: Zhou K, Zhou Z, Shi X, Shen B, Kang P, Yang J, Pei F, Effect of individual distal femoral valgus resection in total knee arthroplasty for patients with valgus knee: A retrospective cohort study, International Journal of Surgery (2018), doi: 10.1016/j.ijsu.2018.02.048. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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International Journal of Surgery Author Disclosure Form
Please state any conflicts of interest None
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Please state any sources of funding for your research
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The following additional information is required for submission. Please note that failure to respond to these questions/statements will mean your submission will be returned. If you have nothing to declare in any of these categories then this should be stated.
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This work was supported by Health Industry Special Scientific Research Projects of China-The safety and effectiveness evaluation of arthroplasty [grant number: 201302007] the National Natural Science Foundation of China (grant number. 81672135).
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Please state whether Ethical Approval was given, by whom and the relevant Judgement’s reference number
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This study was approved by the Ethics Committee and Institutional Review Board of West China Hospital, Sichuan University (2012-268)
Research Registration Unique Identifying Number (UIN) Please enter the name of the registry and the unique identifying number of the study. You can register your research at http://www.researchregistry.com to obtain your UIN if you have not already registered your study. This is mandatory for human studies only.
UIN: researchregistry2964
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Study design: Z.Z.K and F.X.P Data collections: K.Z , X.J.S, B.S and J.Y Data analysis: P.D.K and X.J.S Writing: K.Z
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Author contribution Please specify the contribution of each author to the paper, e.g. study design, data collections, data analysis, writing. Others, who have contributed in other ways should be listed as contributors.
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Zongke Zhou
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Guarantor The Guarantor is the one or more people who accept full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish.
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Effect of individual distal femoral valgus resection in total knee arthroplasty for
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patients with valgus knee: A retrospective cohort study
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ACCEPTED MANUSCRIPT Abstract Background: Proper limb alignment and implant positioning are important for successful total knee arthroplasty (TKA). It remains unknown whether any
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differences exist in the restoration of limb alignment for valgus knees between fixed and individual femoral valgus correction angle (VCA) for distal femoral resection.
Methods: A total of 63 patients (66 knees) had fixed 4° VCA (fixed group), and 55
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patients (59 knees) had individual VCA (individual group). We compared the VCA,
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mechanical femorotibial (MFT) angle, femoral component angle (α), and tibial component angle (β) between the two groups.
Results: There were statistically significant differences in postoperative MFT angle between the two groups (2.0° ± 1.2° versus 2.8° ± 1.6°, p < 0.002). A total of 51
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(77.3%) patients in the individual group had postoperative alignment deviation within ±3° as compared with that of 32 (54.2%) patients in the fixed group (p = 0.006). We found better postoperative alignment accuracies in the individual group for grade II
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knee valgus deformities (1.8° ± 1.2° versus 2.8° ± 1.5°, p = 0.00). There was a
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significant difference in α angle deviations between the two groups (1.7° ± 1.3° versus 2.5° ± 1.8°, p = 0.00). The number of patients with postoperative femoral coronal component alignment deviations within ±3° in the individual group was higher compared to that in the control group (87.8% versus 67.8%, p = 0.006). Conclusions: This radiological study showed that individual VCA for distal femoral resection could achieve better postoperative alignment accuracy and fewer outliers of limb and femoral component malalignment in the coronal plane. 2
ACCEPTED MANUSCRIPT Keywords: Total knee arthroplasty; valgus correction angle; mechanical alignment;
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valgus knee
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1. Introduction
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Valgus knee deformity accounts for approximately 10% of patients undergoing primary total knee arthroplasty (TKA). It could be caused by rheumatoid arthritis, post-traumatic arthritis, osteoarthritis, or metabolic bone disease [1]. Proper limb
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alignment and implant positioning are important for successful TKA and to avoid
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valgus deformity [2]. Failing to restore a neutral mechanical axis correlates with increased loosening and shorter long-term survival of the prosthesis [3, 4]. The proposed aim for restoring coronal alignment, as measured at the mechanical femorotibial (MFT) angle, is that the ideal MFT angle should be within ±3° of 0° [5,
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6]. To achieve this, the femur and tibia should be cut perpendicular to their respective mechanical axes in the coronal plane [7, 8]. The femoral valgus correction angle (VCA), which is considered to be equal to
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the femoral mechanical anatomic angle, determines the resection of the distal femur
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and the axial alignment of the lower limb in TKA [2]. Owing to morphological and gender differences, the mechanical and anatomic axes of the femur vary between 2° and 9° [9, 10]. In practice, most surgeons use a fixed resection angle for patients based on the average value in the nonarthritic population [11, 12]. For varum knee deformities, many studies have compared the difference between fixed and individual VCAs for distal femoral resection in lower limb alignment restoration [2, 13-16]. An increasing number of studies have indicated that individual VCA improves the 4
ACCEPTED MANUSCRIPT accuracy of postoperative limb alignment restoration, and the fixed VCA may lead to malalignment [2, 13, 15, 16]. However, some clinicians argued that a fixed VCA is safe for an uncomplicated primary TKA [17, 18].
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We have previously performed TKA with fixed VCA, but it remains unknown whether fixed VCA is appropriate for patients with valgus deformity. Hence, this study aimed to assess the distribution of VCA and any potential difference in
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postoperative alignment between the fixed VCA and individual VCA groups. We
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hypothesized that an individual VCA could reduce the postoperative mechanical axis and component alignment outliers and enhance the accuracy of postoperative limb
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alignment to neutral.
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2. Materials and Methods
Patients
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This study was designed as a retrospective cohort study, and the work has been
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reported in line with the Strengthening the Reporting of Cohort Studies in Surgery (STROCSS) criteria [19]. This work was approved by the Ethics Committee and Institutional Review Board of ***** and was registered in the Research Registry (UIN: *****). Informed patient consent was also obtained. All patients were
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consecutively enrolled by one surgical team in the department of orthopedics. A total of 63 patients (66 knees) in the fixed group were recruited between March 2013 and December 2014, when our standard practice was to use a fixed VCA of 4° in patients
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with valgus deformity. Another 55 patients (59 knees) in the individual group were
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recruited between January 2015 and October 2016, when the standard practice was to adjust the angle to the measured VCA, which was the angle between the femoral mechanical axis and mid-medullary axis of the distal diaphysis of the femur passing through the center of the femoral intercondylar notch before the surgery. The inclusion criteria were patients suffering from unilateral end-stage osteoarthritis or rheumatoid arthritis with genu valgus deformity and who planned to for a primary TKA. The exclusion criteria were patients with prior surgery involving the femur or 6
ACCEPTED MANUSCRIPT tibia, prior lower extremity fracture, preoperative fixed flexion deformity more than 30°, and spine and hip joint disorder.
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Operation technique All operations were performed by the same team led by an experienced senior surgeon (Z.K.Z.); the procedure and technology were similar to those performed by
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Ranawat [1] and Rossi [20]. An anterior midline skin incision was made by the medial
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parapatellar approach, using intramedullary guides for the femur and extramedullary guides for the tibia. Cemented, posterior, stabilized TKAs were performed on all subjects, and a Sigma fixed-bearing or rotating-platform, posterior-stabilized total knee prosthesis (P.F.C.; Johnson & Johnson/DePuy, Warsaw, IN, USA) was implanted.
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The consistency of actual and planned VCA was judged by an intraoperative intramedullary guide. The entry point of the femoral intramedullary alignment rod was also determined according to the preoperative measurement. The femoral
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intramedullary alignment rod was inserted in the center of the femoral intercondylar
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notch, 10 mm anterior to the femoral insertion of the posterior cruciate ligament. Preoperative and postoperative full-length, standing hip-to-ankle (HTA)
radiographs were taken for all patients, using a standardized radiographic technique [2, 15]. Postoperative radiographs were not taken up to the full extension of the knee (≤5° flexion contracture) to avoid measurement errors. The lower extremities were fully extended and positioned so that the patella and tibial tuberosities were facing toward the X-ray source and the lateral malleoli were at a distance of 30 cm. This standard 7
ACCEPTED MANUSCRIPT position ensured that the tibia was in the vertical position and facing toward to the X-ray source with minimal rotation. The lesser trochanter and the fibular head profiles were important indices to assess the quality of the radiograph. When the overlap of
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the proximal tibia and the fibula did not exceed 60% of the fibula and the lesser trochanter was clearly shown, this meant that the limb was neither externally nor
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internally rotated; then these radiographs were being taken at that time.
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Radiographic measurement
The following anatomical points and measurements were identified on the radiographs with Philips Extended Brilliance™ Workspace as previously described [2, 15, 18] (Fig.1). Hip joint center H was identified using Moses circle. Kf, the distal
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endpoint of the femur, was defined as the center of the femoral intercondylar notch before the surgery and as the midpoint between the medial and lateral condyles after the surgery. Kt, the upper end of the tibia, was defined as the midpoint between the
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tips of the tibial spines before the surgery and as the midpoint of the tibial component
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base after the surgery. The ankle center (A) was the midpoint between the inner edges of the malleoli and one-half of the height of the talus. Fm was the midpoint of the medullary canal at the center of the femoral shaft. The femoral anatomic axis FmKf was defined as a line drawn from Fm to the center of the knee. The femoral mechanical axis HKf was defined as a line joining the center of the hip and knee. The tibial mechanical axis AKt was defined by a line joining the center of the knee and the ankle. Line 1 was drawn tangential to the prosthetic femoral condyles, and Line 2 was 8
ACCEPTED MANUSCRIPT drawn parallel to the tibial tray. Five angles were defined. The VCA was defined as the angle between the femoral mechanical and anatomic axes. The MFT angle was defined as the angle
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between the femoral and tibial mechanical axes (HKf–KtA). The anatomic femorotibial (AFT) angle was defined as the angle between the femoral anatomic and tibial mechanical axes (FmKf–KtA). The α angle was defined as the medial angle
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between the femoral mechanical axis and Line 1, with an ideal value of 90°. The β
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angle was defined as the medial angle between the tibial mechanical axis and Line 2, with an ideal value of 90°. On the coronal radiograph, deviation from the ideal value was the alignment error in which the varus was assigned a negative value and the valgus was assigned a positive value. The outliers were defined as more than ±3°
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deviation from the ideal value. For the assessment of interobserver variability, a randomly generated set of 20 patients was tracked by two investigators (K.Z. and X.J.S.). Investigator 1 (K.Z.) repeated this process 1 month later to assess the
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intraobserver agreement.
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We divided the data into three subgroups according to three grades of valgus deformity [1, 20]. In grade I, the lateral soft tissues are contracted, but the medial collateral ligament is not elongated, and the deviation is <10°. In grade II, the axial deviation is between 10° and 20°, with contracture of the lateral structures and elongation of the MCL, but functional. In grade III, the axial deformity is >20°, the lateral structures are tight, and the medial stabilizers are nonfunctional.
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ACCEPTED MANUSCRIPT Statistical analysis The sample size was estimated to be 110 participants before the study. The two-sided test was used to assess the difference between two means (α = 0.05, β =
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0.10), and a mean difference of 1.3° in the mechanical axis deviation with a standard deviation (SD) of 1.6° and 2.1° for individual and fixed VCAs, respectively, was observed [2]. Quantitative data were represented as mean ± SD; qualitative data were
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represented as number and percentage (%). Differences in continuous variables
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between the two groups were evaluated using the Student’s t-test or Mann–Whitney U test, depending on the distribution characteristics of the data. The chi-square test or Fisher exact test was used to estimate the differences between groups in categorical variables. Interobserver reliability was assessed using the intraclass correlation
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coefficient (ICC) (ICC <0.40, poor; ICC >0.40–0.75, fair to good; and ICC >0.75, excellent agreement). Statistical analysis was performed using SPSS 17.0 (SPSS Inc.,
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Chicago, USA). Statistical significance was set at p <0.05.
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3. Results
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Preoperative demographic and radiographic data are presented in Table 1. There were no significant differences in the baseline data between the two groups. All parameters showed excellent interobserver reproducibility (ICC: 0.81–0.90, p <0.001) without significant systematic bias. Similarly, the parameters showed excellent
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intraobserver reproducibility (ICC: 0.88–0.93, p < 0.001). The distribution of VCAs in the two groups is shown in Fig. 2. The VCAs in valgus knees ranged from 2° to 7°, and 59.2% had a VCA <4°.
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The individual group had a mean postoperative MFT angle deviation of 2.0° ±
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1.2°, and the fixed group had a mean angle deviation of 2.8° ± 1.6°; the difference was significant (p = 0.002; Table 2). There were statistically significant increases in the proportion of patients with a postoperative MFT angle deviation within 2° and 3° in the individual group as compared with that in the fixed group (2°: 56.1% vs. 37.2%, p = 0.035, and 3°: 77.3% vs. 54.2%, p = 0.006; Table 2). The postoperative mechanical alignment distributions are shown in Fig. 3. Subgroup analysis showed better postoperative alignment accuracy in the individual group than that in the fixed 11
ACCEPTED MANUSCRIPT group for knee valgus deformities grade II (1.8° ± 1.2° vs. 2.8° ± 1.5°, p = 0.00), whereas for knee valgus deformities grade I (1.4° ± 0.5° vs. 0.8° ± 0.8°) or grade III (3.0° ± 0.9° vs. 4.1° ± 2.0°), the differences were not significant between the two
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groups (p = 0.20, p = 0.24, respectively; Table 2). The mean α angle deviations were 1.7° ± 1.3° and 2.5° ± 1.8° in the individual group and the fixed group, respectively, which showed significant difference (p = 0.00;
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Table 3). In the individual group, there were46 patients (69.6%) with had femoral
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coronal component alignment deviations <2° and 58 patients (87.8%) with had deviations <3°, which were significantly higher than those in the control group (2°: 26 patients [44%], p = 0.003; 3°: 40 patients [67.8%], p = 0.006). There were no significant differences between the two groups in the mean β angles (90.4° ± 1.5° vs.
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90.6° ± 1.3°, p = 0.445; Table 3).
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4. Discussion
The effect of fixed and individual VCAs for distal femoral resection on the restoration of limb alignment in genu valgum deformity was unclear. This study showed that individual VCA in TKA had better accuracy in postoperative coronal mechanical
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alignment and femoral component alignment as compared to than that of fixed VCA. The distal femoral resection plays an important role in restoring a neutral limb alignment. It is a common practice among surgeons to use the same VCA for distal
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femoral resection and assume that there is minimal variation in the angle between the
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mechanical and anatomical axes [17]. Previous studies [9, 21] suggest that varus deformities in the coronal plane were more likely to have larger VCA angles, and valgus deformities were more likely to have smaller VCA angles. Elkus recommended using a smaller than normal angle (5°–6°) in order to avoid undercorrection of the valgus deformity [22]. In a retrospective study, Davis [18] reported that utilizing using a fixed 4° VCA for valgus knees led to acceptable postoperative alignment (individual: 2.6°; fixed: 1.3°; p = 0.08). Similar to previous reports, we empirically used 4° VCA 13
ACCEPTED MANUSCRIPT in our previous practice. However, several recent studies found VCAs with great variations and a wide distribution in varus or normal knees [9, 10]. Mullaji et al. showed that the percentage
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of limbs with a VCA >7° was 44.9% and the percentage of limbs with a VCA <5° was 10.9% among 503 Indian patients [23]. Bardakos et al. measured the VCA in 174 knees and found that 51% of patients required a VCA <5° or >6° to achieve neutral
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alignment [14]. Nam et al. reviewed radiographs of 493 patients undergoing primary
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TKA and found that 28.6% of patients them had a VCA >5° ± 2° [24]. In valgus knees, we found a wide distribution (2–7°) of VCAs, and 59.2% were <4°. The average VCAs in the two groups were 4.0° ± 1.1° and 4.1° ± 0.9°. The findings also indicated that a routine fixed VCA may be unsuitable for all valgus knees and may lead to
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inaccurate limb alignments.
Many researchers, including us, claimed that an individual VCA can significantly improve postoperative limb alignment. According to a retrospective study of 211
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TKAs by Deakin [15], 85% of knees in the variable group had postoperative
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alignment within ±3° of neutral as compared to 69% in the fixed-angle group (p = 0.006). The authors concluded that a fixed VCA is inappropriate and that tailoring the VCA to the patient’s specific anatomy can improve postoperative alignment. In addition, we had shown that individual VCA could enhance the accuracy of postoperative limb alignment restoration after analyzing 546 varus knees [2]. Notably, almost all the previous studies mainly focused on varus knees, perhaps because valgus knee deformity is observed in only 10% of patients undergoing TKAs [1]. 14
ACCEPTED MANUSCRIPT The present study found that individual VCA could enhance the accuracy of postoperative limb alignment in valgus knees and decrease the >3° outliers’ proportion. Especially in moderate deformity, the individual VCA improved
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alignment accuracy by one degree (1.8° ± 1.2° vs. 2.8° ± 1.5°, p = 0.00), which was similar in severe deformity; this difference was not statistically significant (3.0° ± 0.9° vs. 4.1° ± 2.0°, p = 0.24) perhaps due to fewer patients in the grade III deformity
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subgroup (11 patients vs. 6 patients), which increases the probability of type-I error.
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Our finding is similar with that of a previous report on varus knees [16], which indicated that individual VCA is preferable in patients with moderate-to-severe varus deformity. Wang found a correlation between MFT angle and VCA (r = –0.58) in healthy adults [10], implying that more deformities in the varus tended to have a
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larger VCA [9] and more deformities in the valgus tended to have a smaller VCA; hence, the potential explanation for our result is that individual VCA is more anatomically suitable and superior for improving the postoperative limb alignment in
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severe deformity.
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Although the concept of anatomical alignment has been suggested recently suggested by some researchers, achieving a neutral mechanical alignment after TKA remains the central scope of most surgeons [2]. The acceptable deviation in limb alignment was 0° ± 3° [5, 6, 25]. Long-term survival analysis has shown that the longevity of the implants and optimal long-term outcomes depend on the accuracy of bone cuts and proper restoration of the mechanical axis of the leg [9, 26, 27]. In this study, patients in both groups had slight residual valgus because of insufficient distal 15
ACCEPTED MANUSCRIPT femoral valgus resection. Matsuda et al. investigated 375 patients (500 TKAs) and found that postoperative varus malalignment reduced the patient's satisfaction [28]. Other studies reported that postoperative varus malalignment had a higher component
that slight residual valgus was safer than overcorrection.
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failure rate than neutral and valgus malalignments [29, 30]. Therefore, we thought
This study had some limitations. First, only the coronal alignments were
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considered in this study, although the rotational alignment is also important for the
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success of TKA. But However, this study focused on different VCA methods, which mainly influence coronal alignment; it is reasonable to discussing discuss the coronal alignment in this study. Future research with three-dimensional CT would be helpful in studying rotational alignment. Second, only East Asian patients were recruited in
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this study. There is a great variation in femoral anatomy between races; hence, the results should be interpreted with caution when applying them to other ethnicities owing to different anatomic parameters. Third, the major objective of this study was
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to compare the radiographic effect of fixed VCA and individual VCA for distal
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femoral resection on the restoration of limb alignment, and no clinical follow-up data of functional scores or survival were available. Future studies focusing on the association between clinical outcome and limb alignment deviation would be meaningful.
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5. Conclusions
This radiological study showed that individual VCA for distal femoral resection could achieve better postoperative alignment accuracy and fewer outliers of limb and
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femoral component malalignment in the coronal plane. However, whether different
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VCA methods result in discrepancy in prosthetic survivorship survival requires further evaluation.
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Reference
Ranawat AS, Ranawat CS, Elkus M, et al, Total knee arthroplasty for severe valgus deformity, J.
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1.
Bone Joint Surg. Am. 87 Suppl 1 (2005) 271-284. 2.
Shi X, Li H, Zhou Z, et al,, Individual valgus correction angle improves accuracy of postoperative
limb alignment restoration after total knee arthroplasty, Knee Surg. Sports Traumatol. Arthrosc. 25 (2015) 277-283.
Gioe TJ, Killeen KK, Grimm K, Mehle S, Scheltema K, Why are total knee replacements revised?:
EP
3.
analysis of early revision in a community knee implant registry, Clin. Orthop. Relat. Res. 428 (2004) 100-106.
Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM, Insall Award paper. Why are total
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4.
knee arthroplasties failing today?, Clin. Orthop. Relat. Res. 404 (2002) 7-13. 5.
Mahaluxmivala J, Bankes MJ, Nicolai P, Aldam CH, Allen PW, The effect of surgeon experience
on component positioning in 673 Press Fit Condylar posterior cruciate-sacrificing total knee arthroplasties, J. Arthroplasty 16 (2001) 635-640. 6.
Ritter MA, Faris PM, Keating EM, Meding JB, Postoperative alignment of total knee replacement.
Its effect on survival, Clin. Orthop. Relat. Res. 299 (1994) 153-156. 7.
Longstaff LM, Sloan K, Stamp N, Scaddan M, Beaver R, Good alignment after total knee
arthroplasty leads to faster rehabilitation and better function, J. Arthroplasty 24 (2009) 570-578. 8.
Choong PF, Dowsey MM, Stoney JD, Does accurate anatomical alignment result in better
function and quality of life? Comparing conventional and computer-assisted total knee arthroplasty, J. Arthroplasty 24 (2009) 560-569. 9.
Deakin AH, Basanagoudar PL, Nunag P, Johnston AT, Sarungi M, Natural distribution of the 18
ACCEPTED MANUSCRIPT femoral mechanical-anatomical angle in an osteoarthritic population and its relevance to total knee arthroplasty, The Knee 19 (2012) 120-123. 10. Wang Y, Zeng Y, Dai K, Zhu Z, Xie L, Normal lower-extremity alignment parameters in healthy Southern Chinese adults as a guide in total knee arthroplasty, J. Arthroplasty 25 (2010) 563-570. 11. Huang TW, Kuo LT, Peng KT, Lee MS, Hsu RW, Computed tomography evaluation in total knee arthroplasty: computer-assisted navigation versus conventional instrumentation in patients with advanced valgus arthritic knees, J. Arthroplasty 29 (2014) 2363-2368.
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12. Huang TW, Hsu WH, Peng KT, et al,, Total knee arthroplasty with use of computer-assisted navigation compared with conventional guiding systems in the same patient: radiographic results in Asian patients, J. Bone Joint Surg. Am. 93 (2011) 1197-1202.
13. Meric G, Gracitelli GC, Aram LJ, Swank ML, Bugbee WD, Variability in Distal Femoral Anatomy in Patients Undergoing Total Knee Arthroplasty: Measurements on 13,546 Computed
SC
Tomography Scans, J. Arthroplasty 30 (2015) 1835-1838.
14. Bardakos N, Cil A, Thompson B, Stocks G, Mechanical axis cannot be restored in total knee arthroplasty with a fixed valgus resection angle: a radiographic study, J. Arthroplasty 22 (2007) 85-89. 15. Deakin AH, Sarungi M, A comparison of variable angle versus fixed angle distal femoral
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resection in primary total knee arthroplasty, J. Arthroplasty 29 (2014) 1133-1137.
16. Palanisami D, Iyyampillai G, Shanmugam S, Natesan R, S R, Individualised distal femoral cut improves femoral component placement and limb alignment during total knee replacement in knees with moderate and severe varus deformity, Int. Orthop. 40 (2016) 2049-2054. 17. Kharwadkar N, Kent RE, Sharara KH, Naique S, 5 degrees to 6 degrees of distal femoral cut for uncomplicated primary total knee arthroplasty: is it safe?, The Knee 13 (2006) 57-60. 18. Davis JA, Hogan C, Dayton M, Postoperative Coronal Alignment After Total Knee Arthroplasty:
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Does Tailoring the Femoral Valgus Cut Angle Really Matter? J. Arthroplasty 30 (2015) 1444-1448. 19. Agha RA, Borrelli MR, Vella-Baldacchino M, Thavayogan R and Orgill DP, for the STROCSS Group. The STROCSS Statement: Strengthening the Reporting of Cohort Studies in Surgery, Inter. J. Surg. 46 (2017) 198-202.
20. Rossi R, Rosso F, Cottino U, et al, Total knee arthroplasty in the valgus knee, Int. Orthop. 38
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(2014) 273-283.
21. Tang WM, Zhu YH, Chiu KY, Axial alignment of the lower extremity in Chinese adults, J. Bone Joint Surg. Am. 82-A (2000) 1603-1608.
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22. Elkus M, Ranawat CS, Rasquinha VJ, et al, Total knee arthroplasty for severe valgus deformity. Five to fourteen-year follow-up, J. Bone Joint Surg. Am. 86-A (2004) 2671-2676. 23. Mullaji AB, Shetty GM, Kanna R, Vadapalli RC, The influence of preoperative deformity on valgus correction angle: an analysis of 503 total knee arthroplasties, J. Arthroplasty 28 (2013) 20-27. 24. Nam D, Maher PA, Robles A, McLawhorn AS, Mayman DJ, Variability in the relationship between the distal femoral mechanical and anatomical axes in patients undergoing primary total knee arthroplasty, J. Arthroplasty 28 (2013) 798-801. 25. Thienpont E, Cornu O, Bellemans J, Victor J, Current opinions about coronal plane alignment in total knee arthroplasty: A survey article, Acta Orthop. Belg. 81 (2015) 471-477. 26. Parratte S, Pagnano MW, Trousdale RT, Berry DJ, Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern, cemented total knee replacements, J. Bone Joint Surg. Am. 92 (2010) 2143-2149. 27. Fang DM, Ritter MA, Davis KE, Coronal alignment in total knee arthroplasty: just how important 19
ACCEPTED MANUSCRIPT is it?, J. Arthroplasty 24 (2009) 39-43. 28. Matsuda S, Kawahara S, Okazaki K, Tashiro Y, Iwamoto Y, Postoperative alignment and ROM affect patient satisfaction after TKA, Clin. Orthop. Relat. Res. 471 (2013) 127-133. 29. Liu HX, Shang P, Ying XZ, Zhang Y, Shorter survival rate in varus-aligned knees after total knee arthroplasty, Knee Surg. Sports Traumatol. Arthrosc. 24 (2016) 2663-2671. 30
.
Kim YH, Park JW, Kim JS, Park SD, The relationship between the survival of total knee
arthroplasty and postoperative coronal, sagittal and rotational alignment of knee prosthesis, Int. Orthop.
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SC
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38 (2014) 379-385.
Table 1 Baseline data of the two groups Parameters Individual group
Fixed group
p
66 49/17 36/30 64.4 ± 5.5 153.3 ± 9.8 28.3 ± 3.3
59 43/16 31/28 65.3 ± 7.1 154.1 ± 11.2 28.6 ± 4.1
0.863 0.822 0.435 0.672 0.654
194.9 ± 5.5 4.0 ± 1.1 191 ± 5.8 8 (12.1) 185.2 ± 1.0 47 (71.2) 189.5 ± 3.5 11 (16.7) 201 ± 4.3
194.2 ± 4.1 4.1 ± 0.9 190.1 ± 4.6 5 (8.5) 184.8 ± 0.4 48 (81.3) 189.7 ± 3.7 6 (10.2) 198.4 ± 2.2
0.427 0.845 0.445 0.504 0.66 0.185 0.79 0.29 0.2
Demographic variables
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No. of knees Female/male Right/left Age (yrs) Height (cm) BMI (kg/m2) Radiographic measurements AFT (°) VCA (°) MFT (°) No.† Grade I* Degree‡ No. Grade II Degree No. Grade III Degree
BMI, body mass index; HSS, hospital for special surgery; ROM, range of motion; VAS, visual analog scale; AFT, anatomic femorotibial angle; VCA, valgus correction angle; MFT, mechanical femorotibial angle The values are represented as the mean ±SD or n (%). *subgroup by preoperative valgus deformity †patient number 20
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‡MFT angle
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Table 2 Comparison of the mechanical femorotibial angle between the two groups Parameters Individual group Fixed group p Postop MFT angle deviation (°) 2.0 ± 1.2 2.8 ± 1.6 0.002 Deviation within 1° 20 (30.3) 12 (20.3) 0.202 Deviation within 2° 37 (56.1) 22 (37.2) 0.035 Deviation within 3° 51 (77.3) 32 (54.2) 0.006 Alignment deviation (°) Grade I 1.4 ± 0.5 0.8 ± 0.8 0.20 Grade II 1.8 ± 1.2 2.8 ± 1.5 0.00 Grade III 3.0 ± 0.9 4.1 ± 2.0 0.24
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The values are represented as the mean ±SD or n (%).
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Table 3 Radiological outcomes of component alignment in the two groups Radiological Individual group Fixed group p outcome Postoperative angle deviation (°)
α β
2.5 ± 1.8 0.6 ± 1.3
0.006 0.445
58 (87.8) 57 (86.3)
40 (76.8) 49 (83.1)
0.006 0.606
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Deviation within ±3°
1.7 ± 1.3 0.4 ± 1.5
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α β
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The values are represented as the mean ±SD or n (%).
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Figure legends
Fig.1 Identification of the hip (H), knee (Kf, Kt), and ankle centers (A) and construction of axes (mechanical femoral axis, anatomic femoral axis, and mechanical
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tibial axis) and angles (VCA, MFT angle, α angle, and β angle)
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Fig.2 The distribution of VCAs in study patients Fig.3 The distribution of postoperative mechanical axis alignment between the two groups
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ACCEPTED MANUSCRIPT Effect of individual distal femoral valgus resection in total knee arthroplasty for patients with valgus knee: A retrospective cohort study
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Kai Zhou a, Zongke Zhou a,*, Xiaojun Shi a, Bin Shen a, Pengde Kang a, Jing Yang a, Fuxing Pei a
Department of Orthopaedics, West China Hospital of Sichuan University, Chengdu,
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a
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Corresponding author:
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610041, China
Prof. Zong-ke Zhou, PhD. Tel: 0086-028-85422570; Fax:
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0086-028-85423438; E-mail: [email protected]
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Background: Proper limb alignment and implant positioning are important for successful total knee arthroplasty (TKA). Whether any differences exist in the
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restoration of limb alignment for valgus knees between fixed and individual femoral valgus correction angle (VCA) for distal femoral resection remains unknown.
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Methods: A total of 63 patients (66 knees) had fixed 4° VCA (fixed group) and 55 patients (59 knees) had individual VCA (individual group). We compared the VCA,
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mechanical femorotibial (MFT) angle, femoral component angle (α) and tibial component angle (β) in the two groups.
Results: There were statistically significant differences in postoperative MFT angle between the two groups (2.0° ± 1.2° versus 2.8° ± 1.6°, p < 0.002). A total of 51
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(77.3%) patients in the individual group had postoperative alignment deviation within ± 3° as compared to 32 (54.2%) in the fixed group (p = 0.006). We found better
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postoperative alignment accuracies in the individual group when divided into knee valgus deformities grade II (1.8° ± 1.2° versus 2.8° ± 1.5°, p = 0.00). There was a
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significant difference in the α angle between the two groups (1.7° ± 1.3° versus 2.5° ± 1.8°, p = 0.00). More patients had postoperative femoral component alignment deviation within ± 3° (87.8% versus 67.8%, p = 0.006). Conclusions: This radiological study showed that individual VCA for distal femoral resection could achieve better postoperative accuracy and fewer outliers of limb and femoral component alignment in the coronal plane.
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ACCEPTED MANUSCRIPT Keywords: Total knee arthroplasty; valgus correction angle; mechanical alignment; valgus knee
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Ethical approval The Ethics Committee and Institutional Review Board of West China Hospital,
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Sichuan University, approved this study.
Funding
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This work was supported by Health Industry Special Scientific Research Projects of China – The safety and effectiveness evaluation of arthroplasty [grant number: 201302007] – and the National Natural Science Foundation of China (grant number:
Conflicts of interest
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81672135).
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None of the authors report conflict of interest.
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Acknowledgments
We acknowledge the help offered by the Department of Radiology, West China
Hospital, Sichuan University. We also thank the Elsevier Support for providing assistance in language.
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ACCEPTED MANUSCRIPT Highlights 1. Valgus knee deformity only accounts for 10% of patients undergoing TKA. 2. The femoral VCA determines the axial alignment of the lower limb in TKA.
restoring valgus knee alignment.
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3. It remains unclear whether the fixed VCA or the individual VCA is better in
4. The individual VCA decreased the limb alignment outliers and enhanced the limb
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alignment accuracy.
S1743-9191(18)30579-X
DOI:
10.1016/j.ijsu.2018.02.048
Reference:
IJSU 4467
To appear in:
International Journal of Surgery
Received Date: 7 November 2017 Revised Date:
19 February 2018
Accepted Date: 21 February 2018
Please cite this article as: Zhou K, Zhou Z, Shi X, Shen B, Kang P, Yang J, Pei F, Effect of individual distal femoral valgus resection in total knee arthroplasty for patients with valgus knee: A retrospective cohort study, International Journal of Surgery (2018), doi: 10.1016/j.ijsu.2018.02.048. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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International Journal of Surgery Author Disclosure Form
Please state any conflicts of interest None
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Please state any sources of funding for your research
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The following additional information is required for submission. Please note that failure to respond to these questions/statements will mean your submission will be returned. If you have nothing to declare in any of these categories then this should be stated.
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This work was supported by Health Industry Special Scientific Research Projects of China-The safety and effectiveness evaluation of arthroplasty [grant number: 201302007] the National Natural Science Foundation of China (grant number. 81672135).
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Please state whether Ethical Approval was given, by whom and the relevant Judgement’s reference number
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This study was approved by the Ethics Committee and Institutional Review Board of West China Hospital, Sichuan University (2012-268)
Research Registration Unique Identifying Number (UIN) Please enter the name of the registry and the unique identifying number of the study. You can register your research at http://www.researchregistry.com to obtain your UIN if you have not already registered your study. This is mandatory for human studies only.
UIN: researchregistry2964
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Study design: Z.Z.K and F.X.P Data collections: K.Z , X.J.S, B.S and J.Y Data analysis: P.D.K and X.J.S Writing: K.Z
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Author contribution Please specify the contribution of each author to the paper, e.g. study design, data collections, data analysis, writing. Others, who have contributed in other ways should be listed as contributors.
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Zongke Zhou
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Guarantor The Guarantor is the one or more people who accept full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish.
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Effect of individual distal femoral valgus resection in total knee arthroplasty for
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patients with valgus knee: A retrospective cohort study
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ACCEPTED MANUSCRIPT Abstract Background: Proper limb alignment and implant positioning are important for successful total knee arthroplasty (TKA). It remains unknown whether any
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differences exist in the restoration of limb alignment for valgus knees between fixed and individual femoral valgus correction angle (VCA) for distal femoral resection.
Methods: A total of 63 patients (66 knees) had fixed 4° VCA (fixed group), and 55
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patients (59 knees) had individual VCA (individual group). We compared the VCA,
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mechanical femorotibial (MFT) angle, femoral component angle (α), and tibial component angle (β) between the two groups.
Results: There were statistically significant differences in postoperative MFT angle between the two groups (2.0° ± 1.2° versus 2.8° ± 1.6°, p < 0.002). A total of 51
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(77.3%) patients in the individual group had postoperative alignment deviation within ±3° as compared with that of 32 (54.2%) patients in the fixed group (p = 0.006). We found better postoperative alignment accuracies in the individual group for grade II
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knee valgus deformities (1.8° ± 1.2° versus 2.8° ± 1.5°, p = 0.00). There was a
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significant difference in α angle deviations between the two groups (1.7° ± 1.3° versus 2.5° ± 1.8°, p = 0.00). The number of patients with postoperative femoral coronal component alignment deviations within ±3° in the individual group was higher compared to that in the control group (87.8% versus 67.8%, p = 0.006). Conclusions: This radiological study showed that individual VCA for distal femoral resection could achieve better postoperative alignment accuracy and fewer outliers of limb and femoral component malalignment in the coronal plane. 2
ACCEPTED MANUSCRIPT Keywords: Total knee arthroplasty; valgus correction angle; mechanical alignment;
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valgus knee
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1. Introduction
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Valgus knee deformity accounts for approximately 10% of patients undergoing primary total knee arthroplasty (TKA). It could be caused by rheumatoid arthritis, post-traumatic arthritis, osteoarthritis, or metabolic bone disease [1]. Proper limb
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alignment and implant positioning are important for successful TKA and to avoid
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valgus deformity [2]. Failing to restore a neutral mechanical axis correlates with increased loosening and shorter long-term survival of the prosthesis [3, 4]. The proposed aim for restoring coronal alignment, as measured at the mechanical femorotibial (MFT) angle, is that the ideal MFT angle should be within ±3° of 0° [5,
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6]. To achieve this, the femur and tibia should be cut perpendicular to their respective mechanical axes in the coronal plane [7, 8]. The femoral valgus correction angle (VCA), which is considered to be equal to
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the femoral mechanical anatomic angle, determines the resection of the distal femur
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and the axial alignment of the lower limb in TKA [2]. Owing to morphological and gender differences, the mechanical and anatomic axes of the femur vary between 2° and 9° [9, 10]. In practice, most surgeons use a fixed resection angle for patients based on the average value in the nonarthritic population [11, 12]. For varum knee deformities, many studies have compared the difference between fixed and individual VCAs for distal femoral resection in lower limb alignment restoration [2, 13-16]. An increasing number of studies have indicated that individual VCA improves the 4
ACCEPTED MANUSCRIPT accuracy of postoperative limb alignment restoration, and the fixed VCA may lead to malalignment [2, 13, 15, 16]. However, some clinicians argued that a fixed VCA is safe for an uncomplicated primary TKA [17, 18].
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We have previously performed TKA with fixed VCA, but it remains unknown whether fixed VCA is appropriate for patients with valgus deformity. Hence, this study aimed to assess the distribution of VCA and any potential difference in
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postoperative alignment between the fixed VCA and individual VCA groups. We
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hypothesized that an individual VCA could reduce the postoperative mechanical axis and component alignment outliers and enhance the accuracy of postoperative limb
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alignment to neutral.
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2. Materials and Methods
Patients
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This study was designed as a retrospective cohort study, and the work has been
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reported in line with the Strengthening the Reporting of Cohort Studies in Surgery (STROCSS) criteria [19]. This work was approved by the Ethics Committee and Institutional Review Board of ***** and was registered in the Research Registry (UIN: *****). Informed patient consent was also obtained. All patients were
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consecutively enrolled by one surgical team in the department of orthopedics. A total of 63 patients (66 knees) in the fixed group were recruited between March 2013 and December 2014, when our standard practice was to use a fixed VCA of 4° in patients
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with valgus deformity. Another 55 patients (59 knees) in the individual group were
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recruited between January 2015 and October 2016, when the standard practice was to adjust the angle to the measured VCA, which was the angle between the femoral mechanical axis and mid-medullary axis of the distal diaphysis of the femur passing through the center of the femoral intercondylar notch before the surgery. The inclusion criteria were patients suffering from unilateral end-stage osteoarthritis or rheumatoid arthritis with genu valgus deformity and who planned to for a primary TKA. The exclusion criteria were patients with prior surgery involving the femur or 6
ACCEPTED MANUSCRIPT tibia, prior lower extremity fracture, preoperative fixed flexion deformity more than 30°, and spine and hip joint disorder.
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Operation technique All operations were performed by the same team led by an experienced senior surgeon (Z.K.Z.); the procedure and technology were similar to those performed by
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Ranawat [1] and Rossi [20]. An anterior midline skin incision was made by the medial
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parapatellar approach, using intramedullary guides for the femur and extramedullary guides for the tibia. Cemented, posterior, stabilized TKAs were performed on all subjects, and a Sigma fixed-bearing or rotating-platform, posterior-stabilized total knee prosthesis (P.F.C.; Johnson & Johnson/DePuy, Warsaw, IN, USA) was implanted.
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The consistency of actual and planned VCA was judged by an intraoperative intramedullary guide. The entry point of the femoral intramedullary alignment rod was also determined according to the preoperative measurement. The femoral
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intramedullary alignment rod was inserted in the center of the femoral intercondylar
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notch, 10 mm anterior to the femoral insertion of the posterior cruciate ligament. Preoperative and postoperative full-length, standing hip-to-ankle (HTA)
radiographs were taken for all patients, using a standardized radiographic technique [2, 15]. Postoperative radiographs were not taken up to the full extension of the knee (≤5° flexion contracture) to avoid measurement errors. The lower extremities were fully extended and positioned so that the patella and tibial tuberosities were facing toward the X-ray source and the lateral malleoli were at a distance of 30 cm. This standard 7
ACCEPTED MANUSCRIPT position ensured that the tibia was in the vertical position and facing toward to the X-ray source with minimal rotation. The lesser trochanter and the fibular head profiles were important indices to assess the quality of the radiograph. When the overlap of
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the proximal tibia and the fibula did not exceed 60% of the fibula and the lesser trochanter was clearly shown, this meant that the limb was neither externally nor
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internally rotated; then these radiographs were being taken at that time.
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Radiographic measurement
The following anatomical points and measurements were identified on the radiographs with Philips Extended Brilliance™ Workspace as previously described [2, 15, 18] (Fig.1). Hip joint center H was identified using Moses circle. Kf, the distal
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endpoint of the femur, was defined as the center of the femoral intercondylar notch before the surgery and as the midpoint between the medial and lateral condyles after the surgery. Kt, the upper end of the tibia, was defined as the midpoint between the
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tips of the tibial spines before the surgery and as the midpoint of the tibial component
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base after the surgery. The ankle center (A) was the midpoint between the inner edges of the malleoli and one-half of the height of the talus. Fm was the midpoint of the medullary canal at the center of the femoral shaft. The femoral anatomic axis FmKf was defined as a line drawn from Fm to the center of the knee. The femoral mechanical axis HKf was defined as a line joining the center of the hip and knee. The tibial mechanical axis AKt was defined by a line joining the center of the knee and the ankle. Line 1 was drawn tangential to the prosthetic femoral condyles, and Line 2 was 8
ACCEPTED MANUSCRIPT drawn parallel to the tibial tray. Five angles were defined. The VCA was defined as the angle between the femoral mechanical and anatomic axes. The MFT angle was defined as the angle
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between the femoral and tibial mechanical axes (HKf–KtA). The anatomic femorotibial (AFT) angle was defined as the angle between the femoral anatomic and tibial mechanical axes (FmKf–KtA). The α angle was defined as the medial angle
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between the femoral mechanical axis and Line 1, with an ideal value of 90°. The β
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angle was defined as the medial angle between the tibial mechanical axis and Line 2, with an ideal value of 90°. On the coronal radiograph, deviation from the ideal value was the alignment error in which the varus was assigned a negative value and the valgus was assigned a positive value. The outliers were defined as more than ±3°
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deviation from the ideal value. For the assessment of interobserver variability, a randomly generated set of 20 patients was tracked by two investigators (K.Z. and X.J.S.). Investigator 1 (K.Z.) repeated this process 1 month later to assess the
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intraobserver agreement.
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We divided the data into three subgroups according to three grades of valgus deformity [1, 20]. In grade I, the lateral soft tissues are contracted, but the medial collateral ligament is not elongated, and the deviation is <10°. In grade II, the axial deviation is between 10° and 20°, with contracture of the lateral structures and elongation of the MCL, but functional. In grade III, the axial deformity is >20°, the lateral structures are tight, and the medial stabilizers are nonfunctional.
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ACCEPTED MANUSCRIPT Statistical analysis The sample size was estimated to be 110 participants before the study. The two-sided test was used to assess the difference between two means (α = 0.05, β =
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0.10), and a mean difference of 1.3° in the mechanical axis deviation with a standard deviation (SD) of 1.6° and 2.1° for individual and fixed VCAs, respectively, was observed [2]. Quantitative data were represented as mean ± SD; qualitative data were
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represented as number and percentage (%). Differences in continuous variables
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between the two groups were evaluated using the Student’s t-test or Mann–Whitney U test, depending on the distribution characteristics of the data. The chi-square test or Fisher exact test was used to estimate the differences between groups in categorical variables. Interobserver reliability was assessed using the intraclass correlation
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coefficient (ICC) (ICC <0.40, poor; ICC >0.40–0.75, fair to good; and ICC >0.75, excellent agreement). Statistical analysis was performed using SPSS 17.0 (SPSS Inc.,
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Chicago, USA). Statistical significance was set at p <0.05.
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3. Results
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Preoperative demographic and radiographic data are presented in Table 1. There were no significant differences in the baseline data between the two groups. All parameters showed excellent interobserver reproducibility (ICC: 0.81–0.90, p <0.001) without significant systematic bias. Similarly, the parameters showed excellent
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intraobserver reproducibility (ICC: 0.88–0.93, p < 0.001). The distribution of VCAs in the two groups is shown in Fig. 2. The VCAs in valgus knees ranged from 2° to 7°, and 59.2% had a VCA <4°.
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The individual group had a mean postoperative MFT angle deviation of 2.0° ±
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1.2°, and the fixed group had a mean angle deviation of 2.8° ± 1.6°; the difference was significant (p = 0.002; Table 2). There were statistically significant increases in the proportion of patients with a postoperative MFT angle deviation within 2° and 3° in the individual group as compared with that in the fixed group (2°: 56.1% vs. 37.2%, p = 0.035, and 3°: 77.3% vs. 54.2%, p = 0.006; Table 2). The postoperative mechanical alignment distributions are shown in Fig. 3. Subgroup analysis showed better postoperative alignment accuracy in the individual group than that in the fixed 11
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groups (p = 0.20, p = 0.24, respectively; Table 2). The mean α angle deviations were 1.7° ± 1.3° and 2.5° ± 1.8° in the individual group and the fixed group, respectively, which showed significant difference (p = 0.00;
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Table 3). In the individual group, there were46 patients (69.6%) with had femoral
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coronal component alignment deviations <2° and 58 patients (87.8%) with had deviations <3°, which were significantly higher than those in the control group (2°: 26 patients [44%], p = 0.003; 3°: 40 patients [67.8%], p = 0.006). There were no significant differences between the two groups in the mean β angles (90.4° ± 1.5° vs.
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90.6° ± 1.3°, p = 0.445; Table 3).
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4. Discussion
The effect of fixed and individual VCAs for distal femoral resection on the restoration of limb alignment in genu valgum deformity was unclear. This study showed that individual VCA in TKA had better accuracy in postoperative coronal mechanical
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alignment and femoral component alignment as compared to than that of fixed VCA. The distal femoral resection plays an important role in restoring a neutral limb alignment. It is a common practice among surgeons to use the same VCA for distal
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femoral resection and assume that there is minimal variation in the angle between the
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mechanical and anatomical axes [17]. Previous studies [9, 21] suggest that varus deformities in the coronal plane were more likely to have larger VCA angles, and valgus deformities were more likely to have smaller VCA angles. Elkus recommended using a smaller than normal angle (5°–6°) in order to avoid undercorrection of the valgus deformity [22]. In a retrospective study, Davis [18] reported that utilizing using a fixed 4° VCA for valgus knees led to acceptable postoperative alignment (individual: 2.6°; fixed: 1.3°; p = 0.08). Similar to previous reports, we empirically used 4° VCA 13
ACCEPTED MANUSCRIPT in our previous practice. However, several recent studies found VCAs with great variations and a wide distribution in varus or normal knees [9, 10]. Mullaji et al. showed that the percentage
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of limbs with a VCA >7° was 44.9% and the percentage of limbs with a VCA <5° was 10.9% among 503 Indian patients [23]. Bardakos et al. measured the VCA in 174 knees and found that 51% of patients required a VCA <5° or >6° to achieve neutral
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alignment [14]. Nam et al. reviewed radiographs of 493 patients undergoing primary
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TKA and found that 28.6% of patients them had a VCA >5° ± 2° [24]. In valgus knees, we found a wide distribution (2–7°) of VCAs, and 59.2% were <4°. The average VCAs in the two groups were 4.0° ± 1.1° and 4.1° ± 0.9°. The findings also indicated that a routine fixed VCA may be unsuitable for all valgus knees and may lead to
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inaccurate limb alignments.
Many researchers, including us, claimed that an individual VCA can significantly improve postoperative limb alignment. According to a retrospective study of 211
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TKAs by Deakin [15], 85% of knees in the variable group had postoperative
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alignment within ±3° of neutral as compared to 69% in the fixed-angle group (p = 0.006). The authors concluded that a fixed VCA is inappropriate and that tailoring the VCA to the patient’s specific anatomy can improve postoperative alignment. In addition, we had shown that individual VCA could enhance the accuracy of postoperative limb alignment restoration after analyzing 546 varus knees [2]. Notably, almost all the previous studies mainly focused on varus knees, perhaps because valgus knee deformity is observed in only 10% of patients undergoing TKAs [1]. 14
ACCEPTED MANUSCRIPT The present study found that individual VCA could enhance the accuracy of postoperative limb alignment in valgus knees and decrease the >3° outliers’ proportion. Especially in moderate deformity, the individual VCA improved
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alignment accuracy by one degree (1.8° ± 1.2° vs. 2.8° ± 1.5°, p = 0.00), which was similar in severe deformity; this difference was not statistically significant (3.0° ± 0.9° vs. 4.1° ± 2.0°, p = 0.24) perhaps due to fewer patients in the grade III deformity
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subgroup (11 patients vs. 6 patients), which increases the probability of type-I error.
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Our finding is similar with that of a previous report on varus knees [16], which indicated that individual VCA is preferable in patients with moderate-to-severe varus deformity. Wang found a correlation between MFT angle and VCA (r = –0.58) in healthy adults [10], implying that more deformities in the varus tended to have a
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larger VCA [9] and more deformities in the valgus tended to have a smaller VCA; hence, the potential explanation for our result is that individual VCA is more anatomically suitable and superior for improving the postoperative limb alignment in
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severe deformity.
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Although the concept of anatomical alignment has been suggested recently suggested by some researchers, achieving a neutral mechanical alignment after TKA remains the central scope of most surgeons [2]. The acceptable deviation in limb alignment was 0° ± 3° [5, 6, 25]. Long-term survival analysis has shown that the longevity of the implants and optimal long-term outcomes depend on the accuracy of bone cuts and proper restoration of the mechanical axis of the leg [9, 26, 27]. In this study, patients in both groups had slight residual valgus because of insufficient distal 15
ACCEPTED MANUSCRIPT femoral valgus resection. Matsuda et al. investigated 375 patients (500 TKAs) and found that postoperative varus malalignment reduced the patient's satisfaction [28]. Other studies reported that postoperative varus malalignment had a higher component
that slight residual valgus was safer than overcorrection.
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failure rate than neutral and valgus malalignments [29, 30]. Therefore, we thought
This study had some limitations. First, only the coronal alignments were
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considered in this study, although the rotational alignment is also important for the
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success of TKA. But However, this study focused on different VCA methods, which mainly influence coronal alignment; it is reasonable to discussing discuss the coronal alignment in this study. Future research with three-dimensional CT would be helpful in studying rotational alignment. Second, only East Asian patients were recruited in
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this study. There is a great variation in femoral anatomy between races; hence, the results should be interpreted with caution when applying them to other ethnicities owing to different anatomic parameters. Third, the major objective of this study was
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to compare the radiographic effect of fixed VCA and individual VCA for distal
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femoral resection on the restoration of limb alignment, and no clinical follow-up data of functional scores or survival were available. Future studies focusing on the association between clinical outcome and limb alignment deviation would be meaningful.
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5. Conclusions
This radiological study showed that individual VCA for distal femoral resection could achieve better postoperative alignment accuracy and fewer outliers of limb and
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femoral component malalignment in the coronal plane. However, whether different
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VCA methods result in discrepancy in prosthetic survivorship survival requires further evaluation.
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Reference
Ranawat AS, Ranawat CS, Elkus M, et al, Total knee arthroplasty for severe valgus deformity, J.
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1.
Bone Joint Surg. Am. 87 Suppl 1 (2005) 271-284. 2.
Shi X, Li H, Zhou Z, et al,, Individual valgus correction angle improves accuracy of postoperative
limb alignment restoration after total knee arthroplasty, Knee Surg. Sports Traumatol. Arthrosc. 25 (2015) 277-283.
Gioe TJ, Killeen KK, Grimm K, Mehle S, Scheltema K, Why are total knee replacements revised?:
EP
3.
analysis of early revision in a community knee implant registry, Clin. Orthop. Relat. Res. 428 (2004) 100-106.
Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM, Insall Award paper. Why are total
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4.
knee arthroplasties failing today?, Clin. Orthop. Relat. Res. 404 (2002) 7-13. 5.
Mahaluxmivala J, Bankes MJ, Nicolai P, Aldam CH, Allen PW, The effect of surgeon experience
on component positioning in 673 Press Fit Condylar posterior cruciate-sacrificing total knee arthroplasties, J. Arthroplasty 16 (2001) 635-640. 6.
Ritter MA, Faris PM, Keating EM, Meding JB, Postoperative alignment of total knee replacement.
Its effect on survival, Clin. Orthop. Relat. Res. 299 (1994) 153-156. 7.
Longstaff LM, Sloan K, Stamp N, Scaddan M, Beaver R, Good alignment after total knee
arthroplasty leads to faster rehabilitation and better function, J. Arthroplasty 24 (2009) 570-578. 8.
Choong PF, Dowsey MM, Stoney JD, Does accurate anatomical alignment result in better
function and quality of life? Comparing conventional and computer-assisted total knee arthroplasty, J. Arthroplasty 24 (2009) 560-569. 9.
Deakin AH, Basanagoudar PL, Nunag P, Johnston AT, Sarungi M, Natural distribution of the 18
ACCEPTED MANUSCRIPT femoral mechanical-anatomical angle in an osteoarthritic population and its relevance to total knee arthroplasty, The Knee 19 (2012) 120-123. 10. Wang Y, Zeng Y, Dai K, Zhu Z, Xie L, Normal lower-extremity alignment parameters in healthy Southern Chinese adults as a guide in total knee arthroplasty, J. Arthroplasty 25 (2010) 563-570. 11. Huang TW, Kuo LT, Peng KT, Lee MS, Hsu RW, Computed tomography evaluation in total knee arthroplasty: computer-assisted navigation versus conventional instrumentation in patients with advanced valgus arthritic knees, J. Arthroplasty 29 (2014) 2363-2368.
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12. Huang TW, Hsu WH, Peng KT, et al,, Total knee arthroplasty with use of computer-assisted navigation compared with conventional guiding systems in the same patient: radiographic results in Asian patients, J. Bone Joint Surg. Am. 93 (2011) 1197-1202.
13. Meric G, Gracitelli GC, Aram LJ, Swank ML, Bugbee WD, Variability in Distal Femoral Anatomy in Patients Undergoing Total Knee Arthroplasty: Measurements on 13,546 Computed
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Tomography Scans, J. Arthroplasty 30 (2015) 1835-1838.
14. Bardakos N, Cil A, Thompson B, Stocks G, Mechanical axis cannot be restored in total knee arthroplasty with a fixed valgus resection angle: a radiographic study, J. Arthroplasty 22 (2007) 85-89. 15. Deakin AH, Sarungi M, A comparison of variable angle versus fixed angle distal femoral
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resection in primary total knee arthroplasty, J. Arthroplasty 29 (2014) 1133-1137.
16. Palanisami D, Iyyampillai G, Shanmugam S, Natesan R, S R, Individualised distal femoral cut improves femoral component placement and limb alignment during total knee replacement in knees with moderate and severe varus deformity, Int. Orthop. 40 (2016) 2049-2054. 17. Kharwadkar N, Kent RE, Sharara KH, Naique S, 5 degrees to 6 degrees of distal femoral cut for uncomplicated primary total knee arthroplasty: is it safe?, The Knee 13 (2006) 57-60. 18. Davis JA, Hogan C, Dayton M, Postoperative Coronal Alignment After Total Knee Arthroplasty:
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Does Tailoring the Femoral Valgus Cut Angle Really Matter? J. Arthroplasty 30 (2015) 1444-1448. 19. Agha RA, Borrelli MR, Vella-Baldacchino M, Thavayogan R and Orgill DP, for the STROCSS Group. The STROCSS Statement: Strengthening the Reporting of Cohort Studies in Surgery, Inter. J. Surg. 46 (2017) 198-202.
20. Rossi R, Rosso F, Cottino U, et al, Total knee arthroplasty in the valgus knee, Int. Orthop. 38
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(2014) 273-283.
21. Tang WM, Zhu YH, Chiu KY, Axial alignment of the lower extremity in Chinese adults, J. Bone Joint Surg. Am. 82-A (2000) 1603-1608.
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22. Elkus M, Ranawat CS, Rasquinha VJ, et al, Total knee arthroplasty for severe valgus deformity. Five to fourteen-year follow-up, J. Bone Joint Surg. Am. 86-A (2004) 2671-2676. 23. Mullaji AB, Shetty GM, Kanna R, Vadapalli RC, The influence of preoperative deformity on valgus correction angle: an analysis of 503 total knee arthroplasties, J. Arthroplasty 28 (2013) 20-27. 24. Nam D, Maher PA, Robles A, McLawhorn AS, Mayman DJ, Variability in the relationship between the distal femoral mechanical and anatomical axes in patients undergoing primary total knee arthroplasty, J. Arthroplasty 28 (2013) 798-801. 25. Thienpont E, Cornu O, Bellemans J, Victor J, Current opinions about coronal plane alignment in total knee arthroplasty: A survey article, Acta Orthop. Belg. 81 (2015) 471-477. 26. Parratte S, Pagnano MW, Trousdale RT, Berry DJ, Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern, cemented total knee replacements, J. Bone Joint Surg. Am. 92 (2010) 2143-2149. 27. Fang DM, Ritter MA, Davis KE, Coronal alignment in total knee arthroplasty: just how important 19
ACCEPTED MANUSCRIPT is it?, J. Arthroplasty 24 (2009) 39-43. 28. Matsuda S, Kawahara S, Okazaki K, Tashiro Y, Iwamoto Y, Postoperative alignment and ROM affect patient satisfaction after TKA, Clin. Orthop. Relat. Res. 471 (2013) 127-133. 29. Liu HX, Shang P, Ying XZ, Zhang Y, Shorter survival rate in varus-aligned knees after total knee arthroplasty, Knee Surg. Sports Traumatol. Arthrosc. 24 (2016) 2663-2671. 30
.
Kim YH, Park JW, Kim JS, Park SD, The relationship between the survival of total knee
arthroplasty and postoperative coronal, sagittal and rotational alignment of knee prosthesis, Int. Orthop.
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38 (2014) 379-385.
Table 1 Baseline data of the two groups Parameters Individual group
Fixed group
p
66 49/17 36/30 64.4 ± 5.5 153.3 ± 9.8 28.3 ± 3.3
59 43/16 31/28 65.3 ± 7.1 154.1 ± 11.2 28.6 ± 4.1
0.863 0.822 0.435 0.672 0.654
194.9 ± 5.5 4.0 ± 1.1 191 ± 5.8 8 (12.1) 185.2 ± 1.0 47 (71.2) 189.5 ± 3.5 11 (16.7) 201 ± 4.3
194.2 ± 4.1 4.1 ± 0.9 190.1 ± 4.6 5 (8.5) 184.8 ± 0.4 48 (81.3) 189.7 ± 3.7 6 (10.2) 198.4 ± 2.2
0.427 0.845 0.445 0.504 0.66 0.185 0.79 0.29 0.2
Demographic variables
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No. of knees Female/male Right/left Age (yrs) Height (cm) BMI (kg/m2) Radiographic measurements AFT (°) VCA (°) MFT (°) No.† Grade I* Degree‡ No. Grade II Degree No. Grade III Degree
BMI, body mass index; HSS, hospital for special surgery; ROM, range of motion; VAS, visual analog scale; AFT, anatomic femorotibial angle; VCA, valgus correction angle; MFT, mechanical femorotibial angle The values are represented as the mean ±SD or n (%). *subgroup by preoperative valgus deformity †patient number 20
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‡MFT angle
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Table 2 Comparison of the mechanical femorotibial angle between the two groups Parameters Individual group Fixed group p Postop MFT angle deviation (°) 2.0 ± 1.2 2.8 ± 1.6 0.002 Deviation within 1° 20 (30.3) 12 (20.3) 0.202 Deviation within 2° 37 (56.1) 22 (37.2) 0.035 Deviation within 3° 51 (77.3) 32 (54.2) 0.006 Alignment deviation (°) Grade I 1.4 ± 0.5 0.8 ± 0.8 0.20 Grade II 1.8 ± 1.2 2.8 ± 1.5 0.00 Grade III 3.0 ± 0.9 4.1 ± 2.0 0.24
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Table 3 Radiological outcomes of component alignment in the two groups Radiological Individual group Fixed group p outcome Postoperative angle deviation (°)
α β
2.5 ± 1.8 0.6 ± 1.3
0.006 0.445
58 (87.8) 57 (86.3)
40 (76.8) 49 (83.1)
0.006 0.606
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Deviation within ±3°
1.7 ± 1.3 0.4 ± 1.5
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α β
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Figure legends
Fig.1 Identification of the hip (H), knee (Kf, Kt), and ankle centers (A) and construction of axes (mechanical femoral axis, anatomic femoral axis, and mechanical
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Fig.2 The distribution of VCAs in study patients Fig.3 The distribution of postoperative mechanical axis alignment between the two groups
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ACCEPTED MANUSCRIPT Effect of individual distal femoral valgus resection in total knee arthroplasty for patients with valgus knee: A retrospective cohort study
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Kai Zhou a, Zongke Zhou a,*, Xiaojun Shi a, Bin Shen a, Pengde Kang a, Jing Yang a, Fuxing Pei a
Department of Orthopaedics, West China Hospital of Sichuan University, Chengdu,
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Corresponding author:
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610041, China
Prof. Zong-ke Zhou, PhD. Tel: 0086-028-85422570; Fax:
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0086-028-85423438; E-mail: [email protected]
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Background: Proper limb alignment and implant positioning are important for successful total knee arthroplasty (TKA). Whether any differences exist in the
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restoration of limb alignment for valgus knees between fixed and individual femoral valgus correction angle (VCA) for distal femoral resection remains unknown.
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Methods: A total of 63 patients (66 knees) had fixed 4° VCA (fixed group) and 55 patients (59 knees) had individual VCA (individual group). We compared the VCA,
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mechanical femorotibial (MFT) angle, femoral component angle (α) and tibial component angle (β) in the two groups.
Results: There were statistically significant differences in postoperative MFT angle between the two groups (2.0° ± 1.2° versus 2.8° ± 1.6°, p < 0.002). A total of 51
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(77.3%) patients in the individual group had postoperative alignment deviation within ± 3° as compared to 32 (54.2%) in the fixed group (p = 0.006). We found better
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postoperative alignment accuracies in the individual group when divided into knee valgus deformities grade II (1.8° ± 1.2° versus 2.8° ± 1.5°, p = 0.00). There was a
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significant difference in the α angle between the two groups (1.7° ± 1.3° versus 2.5° ± 1.8°, p = 0.00). More patients had postoperative femoral component alignment deviation within ± 3° (87.8% versus 67.8%, p = 0.006). Conclusions: This radiological study showed that individual VCA for distal femoral resection could achieve better postoperative accuracy and fewer outliers of limb and femoral component alignment in the coronal plane.
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ACCEPTED MANUSCRIPT Keywords: Total knee arthroplasty; valgus correction angle; mechanical alignment; valgus knee
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Ethical approval The Ethics Committee and Institutional Review Board of West China Hospital,
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Sichuan University, approved this study.
Funding
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This work was supported by Health Industry Special Scientific Research Projects of China – The safety and effectiveness evaluation of arthroplasty [grant number: 201302007] – and the National Natural Science Foundation of China (grant number:
Conflicts of interest
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81672135).
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None of the authors report conflict of interest.
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Acknowledgments
We acknowledge the help offered by the Department of Radiology, West China
Hospital, Sichuan University. We also thank the Elsevier Support for providing assistance in language.
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ACCEPTED MANUSCRIPT Highlights 1. Valgus knee deformity only accounts for 10% of patients undergoing TKA. 2. The femoral VCA determines the axial alignment of the lower limb in TKA.
restoring valgus knee alignment.
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3. It remains unclear whether the fixed VCA or the individual VCA is better in
4. The individual VCA decreased the limb alignment outliers and enhanced the limb
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alignment accuracy.