Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis

Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis

THEKNE-02346; No of Pages 9 The Knee xxx (2016) xxx–xxx Contents lists available at ScienceDirect The Knee Radiographic assessment of knee–ankle al...

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THEKNE-02346; No of Pages 9 The Knee xxx (2016) xxx–xxx

Contents lists available at ScienceDirect

The Knee

Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis Fuqiang Gao a,1, Jinhui Ma b,1, Wei Sun a,⁎, Wanshou Guo a, Zirong Li a, Weiguo Wang a a

Center for Osteonecrosis and Joint Preserving & Reconstruction, Department of Orthopaedic Surgery, China–Japan Friendship Hospital, Yinghuadong Road, Chaoyang District, Beijing, China b Peking University China–Japan Friendship School of Clinical Medicine, Yinghuadong Road, Chaoyang District, Beijing, China

a r t i c l e

i n f o

Article history: Received 25 October 2015 Received in revised form 27 June 2016 Accepted 29 September 2016 Available online xxxx Keywords: Radiographs Alignment Ankle Knee Osteoarthritis Total knee arthroplasty

a b s t r a c t Background: There are unanswered questions about knee–ankle alignment after total knee arthroplasty (TKA) for varus and valgus osteoarthritis (OA) of the knee. The aim of this retrospective study was to assess knee–ankle alignment after TKA. Methods: The study consisted of 149 patients who had undergone TKA due to varus and valgus knee OA. The alignment and angles in the selected knees and ankles were measured on fulllength standing anteroposterior radiographs, both pre-operatively and post-operatively. The paired t-test and Pearson's correlation tests were used for statistical analysis. Results: The results showed that ankle alignment correlated with knee alignment both preoperatively and postoperatively (P b 0.05). The pre-operative malalignment of the knee was corrected (P b 0.05), and the ankle tilt angle was accordingly improved in the operative side after TKA (P b 0.05). In addition, TKA had little effect on knee–ankle alignment on the non-operative side (P N 0.05). Conclusion: These findings indicated that routine TKA could correct the varus or valgus deformity of a knee, and improve the tilt of the ankle. Ankle alignment correlated with knee alignment both pre-operatively and postoperatively. Both pre-operative knee and ankle malalignment can be simultaneously corrected following TKA. Level of evidence: Level III. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Total knee arthroplasty (TKA) is a very successful surgical procedure used to treat end-stage osteoarthritis (OA) of the knee so that pain can be relieved and joint function can be restored due to the correction of lower extremity malalignment [1,2]. It is also known that TKA surgery can achieve normal Saxial alignment of the lower extremity in the coronal, sagittal and rotational planes by implanting the prosthesis precisely, contributing to improve long-term survival of the prosthesis [3]. Postoperative lower extremity alignment, measured on anteroposterior radiographs, is an important determinant of long-term outcomes following TKA [4,5]. Several factors such as soft tissue laxity, tibial bone loss, inappropriate bone resection, improper cementation, preoperative varus deformity of N20°, and femoral bowing of N5° could contribute to malalignment after TKA [6]. Malalignment

⁎ Corresponding author at: Center for Osteonecrosis and Joint Preserving & Reconstruction, Department of Orthopaedic Surgery, China–Japan Friendship Hospital, 2 Yinghuadong Road, Chaoyang District, Beijing 100029, China. E-mail addresses: [email protected] (F. Gao), [email protected] (J. Ma), [email protected] (W. Sun). 1 Joint first authors.

http://dx.doi.org/10.1016/j.knee.2016.09.023 0968-0160/© 2016 Elsevier B.V. All rights reserved.

Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023

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F. Gao et al. / The Knee xxx (2016) xxx–xxx

after TKA could cause overloading of the implant bearing and the bone itself, leading to osteolysis, instability and early loosening [7,8], which is one of the major mechanisms leading to early clinical failure and may result in revision surgery [4,9–12]. Moreland pointed out that prosthetic alignment is the most crucial factor affecting the survival of the implant [9]. Other studies have also thought that prosthesis survival following TKA depends on restoration of the mechanical alignment of the operated leg [11,13,14]. Patients with OA knee and requiring TKA commonly present with ankle OA and abnormal ankle alignment; [15] however, whether ankle malalignment is affected after TKA, and/or correlates with knee malalignment pre-operatively and postoperatively, remains uncertain. Few reports are available that assess the association of the abnormal alignment and degenerative changes in the ankle joint with the varus or valgus deformity in the knee. Two studies from different institutions reported inconsistent findings regarding the relationship between ankle and knee malalignment in TKA [15,16]. Indeed, Chandler and Moskal did not find a relationship between knee and hindfoot malalignment before or after TKA [16]. Meanwhile, Tallroth et al. demonstrated that the ankle tilt is pre-operatively associated with deviation in the tibiofemoral angle and mechanical axis [15]. However, few studies have actually used full-length standing anteroposterior radiographs of both lower extremities to assess this issue, and there is no consensus concerning the change of knee–ankle alignment after TKA for varus or valgus OA knee. The aim of this study was to compare pre-operative and postoperative knee–ankle alignment and angles, using both hip-toankle radiographs in the standing position, and assess knee–ankle alignment after primary TKA. 2. Materials and methods 2.1. Patient information A retrospective study was conducted of patients with symptomatic varus or valgus OA knee who had undergone primary TKA between January and October 2013 in China–Japan Friendship Hospital. During this period, all patients were submitted to routine pre-operative and postoperative full-length standing anteroposterior radiographs of both lower extremities. Exclusion criteria were patients that: lacked full-length pre-operative or postoperative standing anteroposterior radiographs; had unclear radiographs; underwent uni-compartmental knee arthroplasty (UKA), revision TKA or other knee surgeries; had a history of ankle injury and received any type of ankle surgery. A total of 149 patients were included, with 32 men and 117 women aged 67.2 ± 8.7 years (range: 43 to 86). Mean body mass index (BMI) values of 26.2 ± 12.4 kg/m2 (range: 18.7 to 35.3) were obtained. From the 149 knees, 24 patients had pre-operative unilateral valgus deformity (range: − 30 to − one degree), as measured by the mechanical axis; 82 individuals showed preoperative unilateral varus deformity (range: one to 24°) and 43 patients had bilateral varus gonarthrosis (range: left one to 30°; right one to 25°). To assess the relationship between knee and ankle alignment before and after TKA, the patients were grouped into two categories: unilateral and simultaneous-bilateral arthroplasty. The correlation between pre-operative and postoperative knee and ankle alignment was then analyzed on unilateral operative and non-operative sides, as well as bilateral left and right sides. After dividing the patients into the unilateral varus, unilateral valgus, and bilateral varus groups, pre-operative and postoperative knee and ankle alignment were compared within each of the three groups. The perioperative demographic characteristics of the patients are listed in Table 1. The pre-operative and postoperative radiographs that were used in this study were routinely taken before and after TKA, and there were no other experimentations on humans, so ethics was not involved in the study. 2.2. Measurement of alignment and angles The same surgical technique was performed in all patients. The alignment and angles in the knees and ankles were preoperatively and postoperatively assessed on full-length standing anteroposterior radiographs. Two experienced orthopedic surgeons (FG and JM) independently measured the selected angles by using the same instrumentation for all radiographs. The images from the included patients were evaluated with Picture Archiving and Communication Systems (PACS) (Carestream Health. Inc., Canada) and were randomly presented to one of the two surgeons by an independent investigator who was unaware of the study design, in order to enhance measurement accuracy. The two surgeons had the same professional qualifications and were trained before the initial measurement. The data extraction and quality assessment were independently performed by two Table 1 Demographics and baseline characteristics. Demographics

Unilateral valgus gonarthrosis

Unilateral varus gonarthrosis

Bilateral varus gonarthrosis

n

24

82

43

Gender (male/female) Age (years) Height (cm) Weight (kg) BMI (kg/m2) Anesthesia (ESA/GA) Anticoagulants (LMWH/R)

3/21 67.5 ± 8.9 162.5 ± 6.7 71.4 ± 10.6 27.0 ± 5.2 9/15 19/5

18/64 65.8 ± 13.7 162.5 ± 6.2 65.5 ± 15.2 25.1 ± 4.5 31/51 71/11

11/32 68.3 ± 12.5 165.1 ± 5.9 72.4 ± 11.3 26.5 ± 7.3 14/29 40/3

BMI, body mass index; ESA, epidural spinal anesthesia; GA, general anesthesia; LMWH, low molecular weight heparin; R, rivaroxaban.

Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023

F. Gao et al. / The Knee xxx (2016) xxx–xxx

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of the authors (WS and ZL). If there were any disagreements, all of the authors discussed until consensus could be reached. This presupposed a standardized technique, and consistent positioning and orientation of the lower extremity to minimize possible errors in the measurements. The center of the femoral head was defined by using Moses circles; [7] the midpoint of the knee was considered to be the center of the femoral condyle at the level of the top of the intercondylar notch, and the center of the ankle was represented by the midpoint of the talus joint surface [8]. A line drawn from the center of the femoral head to that of the knee represented the mechanical axis of the femur. A line drawn from the center of the tibial plateau to that of the talus represented the mechanical axis of the tibia. Normal alignment of the lower extremity is achieved when the mechanical axis passes through the midpoints of the hip, knee and ankle in a straight line. The femoral valgus angle (FVA) is formed by the intersection of the lines along the femur mechanical and anatomical axes. The varus (+)/valgus (−) angle of the knee (hip-knee-ankle angle, HKA) is formed by a line from the center of the femoral head to that of the knee, and a line from the knee center to the ankle center. The femoral angle (FA) is the intersection of the lines along the anatomical and trans-condylar axes of the femur. The tibial angle (TA) is the intersection of the lines along the anatomical and trans-condylar axes of the tibia. The tilt angle of the ankle (TAA) is that between the horizontal line and a line drawn through the joint surface of the talus. The TAA had negative and positive values, respectively, below and above the horizontal line. The tibiotalar angle (TTA) is the angle between the anatomical axis of the tibia and a line drawn through the joint surface of the talus (Figure 1).

Figure 1. Measurements of pre-operative lower limb alignment and angles on full-length standing anteroposterior radiographs. The FVA is formed by the intersection of the lines along the mechanical and anatomical femur axes. The HKA is formed by a line from the center of the femoral head to that of the knee, and a line from the knee center to the ankle center. The FA is the intersection of the lines along the anatomical and transcondylar axes of the femur. The TA is the intersection of the lines along the anatomical and transcondylar axes of the tibia. The TAA is drawn between the horizontal line and a line through the joint surface of the talus. The TTA is the angle between the anatomical axis of the tibia and a line drawn through the joint surface of the talus.

Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023

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2.3. Statistical analysis Quantitative variables are mean ± standard deviation (SD). Statistical evaluation included Pearson correlation and paired ttest. Scatter plots and Pearson's correlation coefficients were used to identify the correlations between the HKA (knee) and TAA (ankle joint). Changes in FVA, HKA, FA, TA, TAA and TTA were compared using paired t-test. All statistical analyses were performed using SPSS version 19.0 (SPSS Inc., USA). P N 0.05 was considered statistically significant. 3. Results 3.1. Correlation between the knee and ankle alignment Abnormal knee alignment significantly correlated with ankle malalignment in unilateral varus or valgus gonarthrosis pre-operatively and postoperatively. The HKA had a significant positive correlation with the TAA angle on the unilateral operative side before (P b 0.001) (Figure 2A, Table 2) and after TKA (P = 0.032) (Figure 2B, Table 2). There was also a significant positive correlation between the HKA and the TAA angle on the unilateral non-operative side before (P b 0.001) (Figure 2C, Table 2) and after TKA (P b 0.001) (Figure 2D, Table 2). A significant relationship was found between knee and ankle malalignment in bilateral varus gonarthrosis before and after TKA. The HKA was associated with the TAA on the bilateral left side before (P b 0.001) (Figure 3A, Table 2) and after TKA (P = 0.007) (Figure 3B, Table 2). The HKA significantly correlated with the TAA on the bilateral right side before (P b 0.001) (Figure 3C, Table 2) and after TKA (P = 0.004) (Figure 3D, Table 2). Scatter plots were generated to identify the correlations between the HKA (knee) and TAA (ankle joint) in the unilateral and simultaneous-bilateral arthroplasty groups (Figures 2, 3). Interestingly, there were significant correlations between knee and ankle alignment in both the unilateral arthroplasty and simultaneous-bilateral arthroplasty groups before and after TKA. 3.2. Knee alignment Following TKA, the HKA decreased from pre-operative 9.3 ± 5.9° varus to postoperative 2.4 ± 2.8° varus on the operative side for unilateral varus gonarthrosis (P b 0.001); on the non-operative side, the HKA decreased from 5.4 ± 5.0° varus to 3.5 ± 4.0° varus (P = 0.009) (Table 3). For unilateral valgus gonarthrosis, the HKA on the operative side was −7.8 ± 6.7° of valgus pre-operatively and 3.3 ± 2.9° of varus postoperatively (P b 0.001) (Table 3). The HKA on the non-operative side was 5.2 ± 5.8° of varus preoperatively and 7.3 ± 4.1° of varus postoperatively (P = 0.587) (Table 3). Knee malalignment on bilateral varus gonarthrosis were corrected simultaneously in both left (P b 0.001) and right (P b 0.001) sides after simultaneous-bilateral TKA (Table 4).

Figure 2. There was a significant correlation between the HKA and TAA in unilateral operative and non-operative sides before and after TKA. The HKA had a positive correlation with the TAA angle in unilateral operative side before (A) and after TKA (B). There was also a positive correlation with the HKA and TAA angles in the unilateral non-operative side before (C) and after TKA (D).

Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023

F. Gao et al. / The Knee xxx (2016) xxx–xxx

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Table 2 Correlation between the varus (+)/valgus (−) angle of the knee (HKA) and the tilt angle of the ankle (TAA) before and after TKA measured on full-length standing A–P radiographs. Side/time

HKA

Unilateral operative side before TKA Unilateral operative side after TKA Unilateral non-operative side before TKA Unilateral non-operative side after TKA Bilateral left side before TKA Bilateral left side after TKA Bilateral right side before TKA Bilateral right side after TKA

5.5 2.2 4.6 4.6 8.5 1.6 8.4 3.2

± ± ± ± ± ± ± ±

9.3 3.8 9.9 9.8 5.6 2.0 5.1 2.9

TAA

Correlation coefficients

P

1.2 ± 8.1 −2.3 ± 5.5 2.5 ± 5.9 2.9 ± 5.3 3.4 ± 5.7 −0.7 ± 3.7 3.0 ± 6.4 0.0 ± 4.0

0.664 0.208 0.387 0.426 0.540 0.403 0.676 0.430

b0.001 0.032 b0.001 b0.001 b0.001 0.007 b0.001 0.004

3.3. Ankle alignment Comparing the TAA of pre-operative and postoperative ankles for unilateral varus and valgus gonarthroses on full-length standing anteroposterior radiographs, significantly improved ankle tilt was found for the operative side after TKA, unlike the non-operative counterpart (Table 5). In bilateral varus gonarthrosis, abnormal ankle alignment was corrected simultaneously in both left (P b 0.001) and right (P b 0.001) sides after simultaneous-bilateral TKA (Figure 4, Table 6). 4. Discussion The present findings indicated that ankle alignment correlates with knee alignment both pre-operatively and postoperatively. The pre-operative malalignment of the knee was corrected, and the ankle tilt angle was accordingly improved on the operative side after TKA. In addition, both pre-operative knee and ankle malalignment could be simultaneously corrected following TKA. Osteoarthritis is the most common form of arthritis; it often occurs in the knee, and can induce pain and physical disability [17]. Although knee OA incidence is higher than that of ankle OA, the latter is usually observed on X-ray radiographs for some patients with symptomatic knee OA. Tallroth et al. reported that one-third of patients with knee OA also suffer from ankle OA [15]. However, studies assessing the relationship between the knee and ankle deformities caused by OA are scarce. Several studies have described an apparent association between hindfoot and knee deformities; [18–20] however, these reports evaluating the correlation between knee and ankle malalignment have lacked accurate measurements and had small sample

Figure 3. Correlation of the HKA versus the TAA angle in bilateral varus gonarthrosis before and after TKA. The HKA had a positive correlation with the TAA angle in bilateral left side before (A) and after TKA (B). There were positive correlations between the HKA and TAA angles in bilateral right side before (C) and after TKA (D).

Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023

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F. Gao et al. / The Knee xxx (2016) xxx–xxx

Table 3 t-Test comparison of knee alignment after TKA for unilateral varus and valgus gonarthroses. Parameters

Operative side FA

Non-operative side HKA

TA

FA

FVA

HKA

TA

Unilateral varus gonarthrosis (n = 82, mean ± SD) Pre-operative 89.3 ± 4.2 4.8 ± 0.6 Postoperative 91.0 ± 2.3 4.6 ± 0.6 t-Value −3.351 2.499 P 0.001 0.013

FVA

9.3 ± 5.9 2.4 ± 2.8 9.497 b0.001

85.0 ± 3.6 89.5 ± 2.3 −9.523 b0.001

88.8 ± 3.1 89.4 ± 3.5 −1.221 0.224

4.7 ± 0.6 4.7 ± 0.6 0.000 1.000

5.4 ± 5.0 3.5 ± 4.0 2.658 0.009

86.6 ± 2.9 87.7 ± 2.9 −2.496 0.014

Unilateral valgus gonarthrosis (n = 24, mean ± SD) Pre-operative 81.8 ± 4.3 4.5 ± 0.5 Postoperative 91.6 ± 2.8 4.7 ± 0.5 t-Value −9.399 −1.054 P b0.001 0.298

−7.8 ± 6.7 3.3 ± 2.9 −7.477 b0.001

88.2 ± 2.7 89.0 ± 2.0 −1.206 0.234

88.4 ± 2.4 82.7 ± 2.8 1.202 0.241

4.8 ± 0.8 4.7 ± 0.4 0.214 0.832

5.2 ± 5.8 7.3 ± 4.1 −0.548 0.587

87.3 ± 3.1 87.6 ± 17.0 −0.374 0.710

FA, femoral angle; FVA, femoral valgus angle; HKA, varus (+)/valgus (−) angle of knee; TA, tibial angle; SD, standard deviation.

sizes. The present results revealed that knee alignment is significantly associated with ankle alignment in patients with knee OA before TKA (P b 0.001), which is consistent with findings by Tallroth et al. [15] These authors showed that the ankle tilt significantly correlates with tibiofemoral angle and mechanical axis deviations before knee surgery (P b 0.0001, r = 0.766 and 0.777, respectively). In addition, Norton et al. demonstrated that a varus knee deformity is associated with a valgus hindfoot alignment (P b 0.0001, r = −0.347), and a valgus knee deformity with a varus hindfoot alignment in patients undergoing TKA (P = 0.0012, r = −0.302) [21]. These findings indicate that knee deformity can induce compensatory changes in the ankle; conversely, the ankle can compensate for a varus or valgus deformity of the knee in order to restore normal lower extremity alignment in the coronal plane by going into the valgus or varus position. The present conclusions corroborate these findings [15,21]. However, another study reported no correlation between pre-operative knee alignment and foot alignment [16]. These discrepant results can be explained as follows. First, their methods were different from the present study. Indeed, Chandler and Moskal evaluated the femorotibial (anatomic) axis angle and calcaneotibial alignment by performing hindfoot weight-bearing alignment radiographs or Cobey's views [16]. The present study measured the mechanical axis angle, tilt angle of the ankle and tibiotalar angle using full-length standing anteroposterior radiographs, with the PACS system enhancing measurement accuracy. Coronal alignment is the most important of all limb alignments [3], and was selected for knee deformity evaluation in the present study. Indeed, coronal alignment of the lower limb is of great significance for planning and assessing outcome after TKA [18,19]. Moreover, Sheehy et al. suggested that limb malalignment is better described using the mechanical axis than the anatomic one [22]. Fang et al. also indicated that standing full-length lower extremity radiographs have become the gold standard for assessing overall limb alignment, providing a concurrent and superior conception of the real ankle malalignment [5,15]. Secondly, the present study had a larger sample size (149 patients) compared with the study by Chandler and Moskal, which assessed 86 patients [16]. Thus, the present results may be more convincing. Knee OA is the most common reason for TKA, which can correct the varus or valgus deformity of the knee OA, so as to relieve symptoms and improve the quality of life by resuming normal limb alignment [17]. Multiple studies have shown that correct postoperative limb alignment after TKA is a key factor in obtaining a higher survival rate of the prosthesis [1–5,9]. Recently, some reports have challenged the premise that restoring limb alignment in the coronal plane improves long-term survival of the prosthesis [5,23]. Fang et al. suggested that TKA should aim to restore alignment within 2.4 to 7.2° of valgus [5]. However, limb alignment that deviates within a neutral mechanical axis ± 3° is still considered acceptable [24]. In the present study, postoperative lower extremity alignment of all operative legs averaged 2.3 ± 3.3° varus (i.e. reduced compared with pre-operative values of 6.8 ± 7.9° varus (P b 0.001)). Improved limb alignment of implants after TKA is forcefully associated with better function, greater stability, a lower rate of loosening, higher clinical scores and increased longevity [1–5,25]. On the contrary, poor lower extremity alignment in TKA could cause instability, wear, and aseptic loosening of the prostheses [24,25]. This illustrates that normal limb alignment following TKA is highly important to the long-term prognosis of a prosthesis. However, whether normal ankle alignment can be simultaneously restored after TKA remains unclear.

Table 4 t-Test comparison of knee alignment after TKA for bilateral varus gonarthrosis. Parameters

Left side FA

Right side FVA

Bilateral varus gonarthrosis (n = 43, mean ± SD) Pre-operative 89.5 ± 3.5 4.6 ± 0.6 Postoperative 91.1 ± 1.8 4.5 ± 0.5 t-Value −2.727 1.000 P 0.009 0.323

HKA

TA

FA

FVA

HKA

TA

8.5 ± 5.6 1.6 ± 2.0 8.671 b0.001

85.7 ± 4.1 90.1 ± 1.6 −6.781 b0.001

89.7 ± 3.0 91.4 ± 2.3 −3.535 0.001

4.8 ± 0.6 4.8 ± 0.5 −0.330 0.743

8.4 ± 5.1 3.2 ± 2.9 6.744 b0.001

86.1 ± 3.5 89.0 ± 1.9 −5.143 b0.001

FA, femoral angle; FVA, femoral valgus angle; HKA, varus (+)/valgus (−) angle of knee; TA, tibial angle; SD, standard deviation.

Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023

F. Gao et al. / The Knee xxx (2016) xxx–xxx

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Table 5 t-Test comparison of ankle alignment after TKA for unilateral varus and valgus gonarthroses. Parameters

Operative side TTA

Non-operative side TAA

TTA

TAA

Unilateral varus gonarthrosis (n = 82, mean ± SD) Pre-operative 87.9 ± 4.8 Postoperative 87.5 ± 4.4 t-Value −0.459 P 0.647

3.6 ± 6.7 −1.4 ± 5.0 5.460 b0.001

88.7 ± 4.9 88.7 ± 3.9 0.044 0.965

2.5 ± 5.5 1.8 ± 5.1 0.861 0.391

Unilateral valgus gonarthrosis (n = 24, mean ± SD) Pre-operative 89.5 ± 5.1 Postoperative 87.3 ± 5.8 t-Value −1.383 P 0.173

−6.9 ± 7.3 −1.1 ± 5.7 −3.053 0.004

90.1 ± 4.4 87.4 ± 4.7 0.749 0.458

4.3 ± 6.7 2.9 ± 5.2 0.821 0.416

TTA, tibiotalar angle; TAA, tilt angle of ankle; SD, standard deviation.

As shown above, the pre-operative ankle tilt could be improved simultaneously with knee realignment following TKA, and there is a significant correlation between knee and ankle alignment after TKA (P b 0.05). This indirectly illustrates that ankle deformity can be reversed along with knee realignment. Tallroth et al. and Chandler and Moskal have demonstrated that ankle joint malalignment is improved significantly after TKA, which is in agreement with the present conclusion [15,16]. Chandler and Moskal and Norton et al. recommended that knee surgery or TKA should be performed prior to ankle surgery so that ankle OA development can be delayed in some patients [16,21]. The present authors are in agreement with these ideas. The main etiologies of ankle OA are secondary (e.g. trauma), and primary OA is rare [26]. Abnormal lower-limb alignment is a risk factor for ankle OA development and progression. The correction of ankle malalignment could retard or interfere with the degenerative process of ankle OA [15]. Nevertheless, in the present study it was observed that ankle OA in some patients was not alleviated, because the ankle began to show irreversible degenerative changes with the progression of knee OA. Norton et al. also revealed that the ankle symptoms may persist or even worsen in patients undergoing TKA who also suffer from stiff subtalar joints due to inability of the ankle joint to realign after TKA [21]. Further studies are needed to investigate the factors affecting ankle OA prognosis in patients with knee OA after TKA. The present study had some limitations. Firstly, the degrees of OA in the knee and ankle were not recorded; how alignment changes in knee OA affect the degree of OA in the ankle remains to be explored in the future. Secondly, the observations were limited to inpatients with no long-term follow-up. Thirdly, variability in the lower-extremity rotation of the radiographs may

Figure 4. Pre-operative full-length standing anteroposterior radiograph of a 58-year-old woman with bilateral symptomatic varus knee OA. The ankle joint tilts laterally and the medial joint space is moderately narrowed. There is severe subchondral sclerosis at the knee and ankle joint surfaces (A). The knee deformities were corrected to a normal valgus, and the ankle joints showed normal alignment following simultaneous-bilateral TKA (B).

Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023

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F. Gao et al. / The Knee xxx (2016) xxx–xxx Table 6 t-Test comparison of ankle alignment after TKA for bilateral varus gonarthrosis. Parameters

Left side TTA

Bilateral varus gonarthrosis (n = 43, mean ± SD) Pre-operative 91.3 ± 4.2 Postoperative 91.9 ± 3.0 t-Value −0.893 P 0.377

Right side TAA

TTA

TAA

3.4 ± 5.7 −0.7 ± 3.7 5.288 b0.001

92.0 ± 5.4 92.1 ± 3.0 −0.215 0.831

3.0 ± 6.4 0.0 ± 4.0 4.044 b0.001

TTA, tibiotalar angle; TAA, tilt angle of ankle; SD, standard deviation.

have had an influence on the radiographic measurements that were performed. It could be considered that the use of a threedimensional imaging study would provide more accurate results; however, concerns regarding increased radiation exposure and imaging costs make this more difficult to implement. Furthermore, full-length standing anteroposterior radiographs can easily be obtained in the routine clinical setting. Last, there was no control group of patients with normal alignments of the knee. As the main purpose of this study was to assess the change of knee-ankle malalignment before and after TKA, it is believed that a separate normal control group was not essential in the present study. Therefore, further studies are needed to clarify the effects of the changes in knee alignment after TKA on the alignment and degenerative changes of the ankle. In conclusion, the present findings indicate that routine TKA can correct the varus or valgus deformity of the knee in patients with symptomatic knee OA, improve the tilt of the ankle, and delay ankle degeneration. A relationship exists between knee and ankle alignment before and after TKA. Both pre-operative knee and ankle malalignment can be simultaneously corrected following TKA, which has marginal effects on knee-ankle alignment on the non-operative side. Source of funding No disclosures of funding were received for this work. Conflict of interest This study was supported by the National Natural Science Foundation of China (81372013) and the Research Fund of China– Japan Friendship Hospital (2013-MS-27, 2014-4-QN-29). China–Japan Friendship Hospital Youth Science and Technology Excellence Project (2014-QNYC-A-06). The authors declare that they have no conflict of interest. Acknowledgments We are grateful to all the participating patients of this study. We thank the staff members of this trial, our colleagues, and all the study staff for their enormous efforts in collecting and ensuring the accuracy and completeness of all the data. References [1] Kim SJ, MacDonald M, Hernandez J, Wixson RL. Computer assisted navigation in total knee arthroplasty: improved coronal alignment. J Arthroplasty 2005;20: 123–31. [2] Tew M, Waugh W. Tibiofemoral alignment and the results of knee replacement. J Bone Joint Surg Am 1985;67B:551. [3] Keene G, Simpson D, Kalairajah Y. Limb alignment in computer-assisted minimally-invasive unicompartmental knee replacement. J Bone Joint Surg Br 2006; 88(1):44–8. [4] Rosenberger RE, Hoser C, Quirbach S, Attal R, Hennerbichler A, Fink C. Improved accuracy of component alignment with the implementation of image-free navigation in total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2008;16(3):249–57. [5] Fang DM, Ritter MA, Davis KE. Coronal alignment in total knee arthroplasty: just how important is it? J Arthroplasty 2009;24(6):39–43. [6] Mullaji AB, Shetty GM, Lingaraju AP, Bhayde S. Which factors increase risk of malalignment of the hip–knee–ankle axis in TKA? Clin Orthop Relat Res 2013; 471(1):134–41. [7] Bargren JH, Blaha JD, Freeman MAR. Alignment in total knee arthroplasty: correlated biomechanical and clinical observations. Clin Orthop Relat Res 1983;173: 178–83. [8] Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. J Bone Joint Surg Br 1991;73(5):709–14. [9] Moreland JR. Mechanisms of failure in total knee arthroplasty. Clin Orthop Relat Res 1988;226:49–64. [10] Hofmann S, Romero J, Roth-Schiffl E, Albrecht T. Rotational malalignment of the components may cause chronic pain or early failure in total knee arthroplasty. Orthopade 2003;32(6):469–76. [11] Lombardi Jr AV, Berend KR, Ng VY. Neutral mechanical alignment: a requirement for successful TKA: affirms. Orthopedics 2011;34(9):e504–6. [12] Ritter MA, Faris PM, Keating EM, Meding JB. Postoperative alignment of total knee replacement. Its effect on survival. Clin Orthop Relat Res 1994;299:153–6. [13] Nouta KA, Pijls BG, Nelissen RG. All-polyethylene tibial components in TKA in rheumatoid arthritis: a 25-year follow-up study. Int Orthop 2012;36(3):565–70. [14] O'Connor MI. Implant survival, knee function, and pain relief after TKA: are there differences between men and women? Clin Orthop Relat Res 2011;469(7): 1846–51. [15] Tallroth K, Harilainen A, Kerttula L, Sayed R. Ankle osteoarthritis is associated with knee osteoarthritis. Conclusions based on mechanical axis radiographs. Arch Orthop Trauma Surg 2008;128(6):555–60. [16] Chandler JT, Moskal JT. Evaluation of knee and hindfoot alignment before and after total knee arthroplasty: a prospective analysis. J Arthroplasty 2004;19(2): 211–6.

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Please cite this article as: Gao F, et al, Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.023