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Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees
THEKNE-02326; No of Pages 7 The Knee xxx (2016) xxx–xxx
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The Knee
Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees☆ Young Gon Na a, Moon Jong Chang b, Sang Hwa Eom c, Seok Jin Kim c, Seong Cheol Park c, Tae Kyun Kim c,⁎ a b c
Department of Orthopaedic Surgery, CM Hospital, Seoul, Republic of Korea Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul National University Boramae Hospital, Seoul, Republic of Korea Joint Reconstruction Center, Seoul National University Bundang Hospital, 82 Gumi-ro, 173 Beon-gil Bundang-gu, Seongnam-si, Gyeonggi-do 13620, Republic of Korea
a r t i c l e
i n f o
Article history: Received 25 December 2015 Received in revised form 15 July 2016 Accepted 1 September 2016 Available online xxxx Keywords: Posterolateral rotatory instability Osteoarthritis Dynamic alignment Single-limb stance Double-limb stance
a b s t r a c t Background: We aimed to determine whether coronal alignment measured on the single-limb stance (SLS) radiographs differs from those on the double-limb stance (DLS) images. We also investigated whether the size of such differences was affected by the knee pathology, lower limb alignment, and geometry of the tibia or femur. Methods: We measured coronal alignment with mechanical tibiofemoral angle (MTFA) on the DLS and SLS radiographs in patients with posterolateral rotatory instability (PLRI, 30 knees), osteoarthritis (OA) with varus deformity who were scheduled for high tibial osteotomy (HTO) (60 knees), and in normal control (60 knees). The measurements on the SLS radiographs were compared with those on DLS images and the size of the differences were compared between the three groups. The correlation between the radiograph-related differences of coronal alignment and the limb alignment or geometry of tibia/femur was investigated. In the OA group, the size of the radiograph-related differences before HTO were compared with those after surgery. Results: The coronal alignment on the SLS radiographs indicated varus accentuation compared to those on the DLS radiographs in the PLRI and OA groups (1.6 and 2.4°, respectively), while it was negligible in the normal group. Greater varus inclination of the tibial plateau was related to greater varus accentuation (r = 0.249). The HTO decreased the extent of varus accentuation in the OA group (reduction of varus accentuation = 1.5°). Conclusions: Coronal alignment on the SLS radiograph is different from static alignment measured on the DLS radiograph, which may reflect dynamic alignment. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Accurate measurements of coronal alignment of the lower extremities are crucial for appropriate management of knee disorders related to ligament laxity or osteoarthritis, combined with malalignment. Concurrent alignment correction is sometimes ☆ No financial support was provided for this study.Each author certifies that his or her institution has approved the human protocol for this investigation, and that all investigations were conducted in conformity with ethical principles of research.This work was performed at the Joint Reconstruction Center, Seoul National UniversityBundang Hospital. ⁎ Corresponding author at: Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, Republic of Korea. E-mail addresses: [email protected] (Y.G. Na), [email protected] (M.J. Chang), [email protected] (S.H. Eom), [email protected] (S.J. Kim), [email protected] (S.C. Park), [email protected] (T.K. Kim).
http://dx.doi.org/10.1016/j.knee.2016.09.003 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
required for patients undergoing anterior cruciate ligament reconstruction with varus malalignment [1–3]. High tibial osteotomy can be an initial surgical treatment in posterolateral rotatory instability with varus deformity [4]. Inaccurate preoperative alignment information may cause under- or overcorrection after osteotomy. Traditionally, a full-length standing anteroposterior (AP) radiography taken with patients in double-limb stance (DLS) has been used as a gold standard to measure the coronal alignment [5,6]. DLS radiographs can only reflect static alignment; however, dynamic alignment may provide different information [7–9]. Dynamic alignment can be measured better on the gait analysis rather than on the static radiographic measurement, but it requires special equipment and facility [10–12]. The coronal alignment on the single-limb stance (SLS) full-length standing AP radiograph may be different from the static alignment measured on the DLS radiograph as the entire body weight is transmitted through the single limb [13]. Previous reports revealed that the differences in weight bearing on the knee joint could result in differences in coronal alignment [8,14]. In addition, the SLS radiograph theoretically simulates the stance phase of a gait cycle so the SLS radiograph might reflect the dynamic alignment of the lower limb despite its inherent static nature. [6–8,13]. Several previous studies reported increasing varus deformity on the SLS radiographs than on the DLS images in patients with arthritic knees with varus deformity [8,14,15]. However, whether such differences in coronal alignment between SLS and DLS radiographs are observed in other knee conditions, such as posterolateral rotatory instability (PLRI) or normal knee, are not reported in the literature. Furthermore, factors which are associated with increased differences in the coronal alignment measurement between SLS and DLS radiographs are not thoroughly investigated yet. Magnitude of malalignment and geometry of the knee joint may be plausible candidate, as they can affect the moment across the knee joint [16–18]. Because high tibial osteotomy (HTO) alters lower limb alignment and proximal tibial geometry, the changes after HTO may give some insight about the effect of magnitude of malalignment and the geometry of proximal tibia. Therefore, we sought to determine whether the coronal alignments measured on the SLS radiograph differ from those on the DLS images in patients with various knee conditions such as normal, PLRI and OA with varus deformity. We also aimed to determine whether these resultant differences were affected by the alignment of the lower limbs and geometry of the knee joint. Finally, we also wanted to determine whether these radiograph-related differences in the coronal alignment changed after correction of the malalignment in the patients with medial OA who underwent HTO.
2. Materials and methods 2.1. Study design This retrospective study was conducted using the following three patient groups with different knee conditions from the consecutive patient cohort of our institute: 1) normal group (n = 60), 2) PLRI group (n = 30) and 3) OA with varus deformity group who underwent HTO (n = 60). The patients were excluded in this study if the accurately-taken whole-limb standing radiographs were not available, e.g. the patella was not 'facing forwards' or the flexion contracture of the knee was greater than 10° (n = 14). The PLRI group included 30 consecutive patients who underwent posterolateral complex reconstruction for knee joint laxity and/ or high tibial osteotomy for combined malalignment from 2005 through 2013. All the patients had prior traumatic injury but the patients with acute injury within three months were not included in this study. The diagnosis of PLRI was done by physical examination (external rotation recurvatum test, varus stress test at 30°, dial test at 30° and 90°, posterolateral drawer test) and magnetic resonance image (MRI) findings (injury of lateral collateral ligament and/or popliteofibular ligament and/or popliteus tendon). For the normal group, we selected 60 patients with non-symptomatic opposite knees from the 280 patients (247 men and 33 women) who underwent primary anterior cruciate ligament (ACL) reconstruction between August 2008 and March 2012. The normal controls were age- and sex-matched 2:1 with the PLRI group, with selecting the closest match among the available candidates. The OA with varus deformity group consisted of 60 consecutive patients who underwent medial opening-wedge HTO for primary OA in the medial compartment (Kellgren-Lawrence classification III) using TomoFix® system (Synthes GmbH; Solothurn, Switzerland) from August 2005 through March 2012. The patients in OA group were typically elderly females, so we could not match age or gender with other two groups. Compared to the other two groups, the OA group was more frequently female and older and consequently had lower mean weight and height (Table 1). This study was approved by institutional review board of authors' hospital and the written informed consent was waived by the board. Table 1 Demographic features of the patients in the three study groups Parameter
Normal (n = 60)
PLRI (n = 30)
OA (n = 60)
p Value
Male (%) Age (years) Height (cm) Weight (kg) BMI (kg/m2)
52 (87%) 33.8 (12.1) 171.1 (7.2) 74.5 (12.9) 25.4 (3.6)
26 (87%) 33.8 (13.3) 171.9 (8.0) 73.4 (14.5) 24.8 (4.4)
6 (10%) 55.5 (5.0) 156.5 (6.5) 65.7 (9.4) 26.8 (2.8)
b0.001 b0.001 b0.001 b0.001 0.023
Data are presented as mean and (standard deviation). Abbreviations: BMI, body mass index; PLRI, posterolateral rotatory instability; OA, osteoarthritis. Significant (p b0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
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2.2. Radiographic evaluation Radiographic evaluations were performed using full-limb standing AP radiographs with patients in both DLS and SLS position. Pre- and postoperative images were used in the OA group while only preoperative radiographs were used in the PLRI and normal groups. In the OA group, the best quality-images without significant rotation were selected for the radiographic measurement among consecutive images taken at three, six, and 12 months after HTO. All the radiographs were taken on 14 × 51 inch-grid cassettes to ensure that the patella was facing directly anterior. We tried to set the foot orientation and the width between both feet consistent in all patients using a footplate while taking the images. The footplate had the standardized feet-shape on it so that the patients could stand on it with standardized position and foot orientation, following the foot shape. When taking SLS radiograph, patients were required to maintain their balance and keep still without any support (or minimal support if it's impossible). The trunk position was allowed to be in comfortable status during SLS. All radiographic images were digitally acquired using a picture archiving communication system (PACS). Radiographic measurements were conducted using PACS software (Infinite, Seoul, Korea) with the minimum detectable differences 0.1° in angle and 0.1 mm in length measurements. In the DLS AP radiograph, five radiographic parameters were measured: three parameters relating to coronal limb alignment, namely the mechanical tibiofemoral angle (MTFA), the joint space tilt angle (JSTA) and weight loading line (WLL) coordinate, and two bone geometric parameters including the femoral condylar orientation (FCO), and the tibial plateau inclination (TPI). The MTFA was defined as the angle formed between the mechanical axes of the femur (the line from the femoral head center to the center of the femoral intercondylar notch) and the tibia (the line from the center between both tibial spine tips to the center of the tibial plafond, distally). A negative value was given to knees in varus alignment. The JSTA was defined as the angle between the tangential line to the subchondral plates of both femoral condyles and the tangential line to the subchondral plate of the proximal tibia, and a negative value was given to the knee with lateral space opening (Fig. 1). The WLL coordinate of the knee (%) was defined as the portion of the mechanical axis of the limb (the line from the femoral head center to the ankle talus center) passing through the knee from the edge of the medial tibial plateau (0%) to the edge of the lateral tibial plateau (100%). A negative value was given in severe varus with the WLL passing through the medial side of the medial edge of the tibial plateau. The FCO was defined as the angle between the mechanical axis of the femur and the tangential line to the subchondral plates of both femoral condyles, and a negative value was given in varus orientation [19]. The TPI was defined as the angle between the mechanical axis of the tibia and the tangential line to the subchondral plate of the proximal tibia, and a negative value was given in varus orientation [19]. In the SLS AP radiograph, the MTFA, JSTA, and WLL coordinate were measured in same manner. To determine intra- and inter-observer reliabilities of radiographic assessments, two orthopedic surgeons (two of the authors) performed radiographic assessments in 20 randomly selected knees twice within a three-week interval. The intra- and inter-
JSTA
Fig. 1. Definition of the joint space tilt angle (JSTA). The joint space tilt angle (JSTA) was defined as the angle between the tangential line to the subchondral plates of both femoral condyles and the tangential line to the subchondral plate of the proximal tibia. Negative value indicates that the lateral joint space is wider than the medial side.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
observer reliabilities of assessments of all radiographic measurements were evaluated using intraclass correlation coefficients (ICCs). The ICCs of intra- and inter-observer reliabilities of all measurement were N0.9 (range, 0.903 to 0.996). Thus, measurements taken by a single investigator (one of the authors) were used in the analyses. 2.3. Statistical analysis Statistical analyses were carried out with SPSS for Windows version 20.0 (SPSS Inc., Chicago, Illinois), and p-values b0.05 were considered significant. We compared three measures; the MTFA, JSTA and WLL coordinate, between SLS and DLS radiographs in each study group using the paired t-test. The radiograph-related difference, Δ, (difference between SLS and DLS radiographs) was compared among three groups using analysis of variance (ANOVA) test with Bonferroni post hoc test. The proportions of the patients with radiographrelated difference over two or three degrees of MTFA in the three groups were compared using the Chi-square test. To determine the effect of the alignment of lower limbs and the bone geometry (FCO and TPI) on the radiograph-related differences, we performed partial correlation analysis. The knee conditions, age, gender and BMI were adjusted as covariates. To determine whether the correction of the malalignment can reduce coronal alignment changes, the changes of the MTFA, JSTA and WLL coordinate between before and after HTO were compared using the paired t-test in the OA with varus deformity group. 3. Results 3.1. Difference of the coronal alignment between SLS and DLS in three knee conditions The coronal alignment measured on the SLS radiographs showed varus accentuation compared to those on the DLS radiographs in the PLRI and OA groups: 1.6° for MTFA, 1.0° for JSTA and 7.4% for WLL coordinate in PLRI group; 2.4° for MTFA, 1.2° for JSTA and 9.8% for WLL coordinate in OA group (Table 2 and Fig. 2). In the normal group, although MTFA and WLL also presented changes into varus direction on the SLS radiograph compared to those on the DLS images, the extent of the varus accentuation was only 0.4° for MTFA and 2.5% for WLL coordinate. The radiograph-related differences of coronal alignment in the PLRI and OA groups were greater than those in the normal group (Table 3). However, the radiograph-related difference of the PLRI and OA groups did not differ on the post hoc test. The patients with the MTFA difference between SLS and DLS over two degrees (23%, 30%, 62% in normal, PLRI and OA group respectively, p b 0.001) or three degrees (5%, 20%, 37% in normal, PLRI and OA group respectively, p b 0.001) were more frequent in PLRI and OA group than normal group. 3.2. Effect of the limb alignment, bone geometry on the difference of the coronal alignment between SLS and DLS Greater varus inclination in the proximal tibia plateau was related to greater radiograph-related differences in coronal alignment, whereas the FCO and the magnitude of malalignment did not affect the differences (Table 4). There was positive correlation between tibial plateau inclination and the amount of changes in the three coronal alignment parameters in the partial correlation analysis. On the other hand, no significant relationship was found between the radiograph-related differences in coronal alignment and the femoral condylar orientation or mechanical tibiofemoral angle. 3.3. Effect of the high tibial osteotomy on the difference of the coronal alignment between SLS and DLS in the OA group In the OA group, correction of malalignment with high tibial osteotomy decreased varus accentuation of the coronal alignment on the SLS radiograph compared to those on the DLS radiographs (pre-HTO vs. post-HTO: Δ MTFA, − 2.4° vs. − 0.9°; Δ JSTA, −1.2° vs. −0.4°; Δ WLL, −9.7% vs. −4.1%, all p b 0.001, Table 5). The extent of varus accentuation measured by the changes of MTFA, JSTA and WLL coordinate on the SLS and DLS radiograph was decreased postoperatively by 1.5°, 0.7° and 5.6%, respectively. Table 2 The differences in measures of coronal limb alignment between the SLS and DLS radiographs Group
Measures
Normal
MTFA (°) JSTA (°) WLL (%) MTFA (°) JSTA (°) WLL (%) MTFA (°) JSTA (°) WLL (%)
PLRI
OA
SLS −2.4 (2.9) −1.6 (1.6) 35.9 (13.3) −6.2 (5.0) −2.7 (1.7) 18.3 (23.8) −11.1 (3.4) −5.7 (2.1) −0.5 (14.4)
DLS
Difference
p Value
−1.9 (2.5) −1.4 (1.4) 38.4 (11.9) −4.6 (4.3) −1.7 (1.5) 25.7 (19.6) −8.8 (2.8) −4.5 (2.1) 9.3 (12.5)
−0.4 (1.5) −0.2 (1.3) −2.5 (6.4) −1.6 (1.4) −1.0 (0.8) −7.4 (7.4) −2.4 (1.6) −1.2 (1.2) −9.8 (7.1)
0.028 0.302 0.003 b0.001 b0.001 b0.001 b0.001 b0.001 b0.001
Data are presented as means and (standard deviations). Abbreviations: PLRI, posterolateral rotatory instability; OA, osteoarthritis; SLS, single limb stance; DLS, double limb stance; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle, WLL, weight loading line coordinate. Significant (p b0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
Normal DLS
SLS
Δ=-0.4° -2.5%
5
OA
PLRI DLS
SLS
Δ=-1.6° -7.4%
DLS
SLS
Δ=-2.4° -9.8%
Fig. 2. The differences in coronal limb alignment between SLS and DLS radiographs. The difference in mechanical tibiofemoral angle and the weight loading line coordinate between SLS and DLS radiographs (Δ) were shown on the typical three cases of the each group. Negative value means varus accentuation of the coronal alignment on the SLS radiograph compared to those on the DLS image. Red lines indicate the mechanical axis of the limb (the line from the femoral head center to the ankle talus center). Yellow lines indicate the mechanical axis of the femur (the line from the femoral head center to the center of the femoral intercondylar notch) and the tibia (the line from the center between both tibial spine tips to the center of the tibial plafond, distally). Blue lines indicate the width of the tibial plateau. Abbreviations: DLS, double-limb stance; SLS, single-limb stance; PLRI, posterolateral rotatory instability; OA, osteoarthritis. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
4. Discussion This study demonstrated that the coronal alignments shifted varus on the SLS radiograph compared to the DLS radiographs in PLRI and OA groups and the greater varus inclination of the tibia plateau was related to greater varus accentuation. In addition, high tibial osteotomy decreased the extent of varus accentuation in the OA group. Our findings give some insight to the difference of dynamic alignment compared to the static alignment, and the clinical usability of SLS radiograph to simply estimate the dynamic coronal alignment. The coronal alignments measured on the SLS radiograph was different from those on the DLS images in patients with PLRI and OA, but negligible in normal group. The adduction moment is placed on the lower limbs in standing position because body weight
Table 3 Comparison of the radiograph-related differences of coronal alignment between the three study groups Alignment measures
Normal (n = 60)
PLRI (n = 30)
OA (n = 60)
p Value
ΔMTFA (°) ΔJSTA (°) ΔWLL (%)
−0.4 (1.5) −0.2 (1.3) −2.5 (6.4)
−1.6 (1.4) −1.0 (0.8) −7.4 (7.5)
−2.4 (1.6) −1.2 (1.2) −9.8 (7.1)
b0.001 b0.001 b0.001
Data are presented as means and (standard deviations) in the parenthesis. Abbreviations: Δ, the differences of measurements between the single-limb stance and double-limb stance radiographs; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle, WLL, weight loading line coordinate; PLRI, posterolateral rotatory instability; OA, osteoarthritis. Significant (p b0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
Table 4 The effect of lower limb alignment and bone geometry on radiograph-related differences of coronal alignment. Alignment & bone geometry
Partial correlation coefficient (p Value)
MTFA* (°) FCO (°) TPI (°)
ΔMTFA
ΔJSTA
ΔWLL
0.127 (0.126) −0.041 (0.624) 0.249 (0.002)
0.060 (0.474) 0.030 (0.723) 0.226 (0.006)
0.156 (0.059) −0.086 (0.299) 0.288 (b0.001)
Abbreviations: Δ, the differences of measurements between the single-limb stance and double-limb stance radiographs; MFTA*, mechanical tibiofemoral angle on the double limb stance radiograph; FCO, femoral condylar orientation on the double limb stance radiograph; TPI, tibial plateau inclination on the double limb stance radiograph; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle; WLL, weight loading line coordinate. Significant (p b0.05) values are presented in bold.
passes through the medial side of the knee joint [8,20]. Furthermore, this adduction moment can increase when the patient stands on a single limb because most of body weight passes through that limb [13]. The varus accentuation of the coronal alignment of lower limb seen in the SLS radiographs in the OA patients agreed with previously reported studies [8,14,15]. In addition, we found a similar radiograph-related difference in the patterns of coronal alignment in the patients with laxity of lateral ligament complex. On the other hand, we confirmed that the varus accentuation on SLS radiographs in the normal control group was smaller than PLRI and OA groups: 0.4° for MTFA and 2.5% for WLL coordinate. The adduction moment created by the ground reaction force is offset primarily by the lateral collateral ligament (LCL) and secondarily by the iliotibial band. The varus accentuation found in the PLRI group can be interpreted by the effect of the diminished function of the LCL, while that in the OA group is explained by the chronic attenuation of the LCL due to the varus deformity, and the age-related relative inability of the iliotibial band to dynamically stabilize the joint [9,21–23]. Although the mean difference of the coronal alignment (MTFA) was 1.6° in PLRI group and 2.4° in OA group, 20% and 37% of PLRI and OA group patients presented radiograph-related difference over three degrees. Moreover, the maximum difference was 6.1° in PLRI group and 6.5° in OA group. Our findings suggest that the dynamic alignment needs to be considered in OA or PLRI patients, whereas it may not be a significant issue in normal group. Furthermore, substantial varus accentuation in SLS radiographs may be possibly a pathognomic finding of laxity of the lateral ligament complex of the knee joint or pathologic varus malalignment of the lower extremities, although further investigations are warranted to reveal the clinical implication of these findings. The varus accentuation of the coronal alignment of lower limb seen in the SLS radiographs, compared to DLS radiographs was related with the varus inclination of proximal tibia, whereas not associated with the distal femoral geometry or magnitude of malalignment of lower limb. To our surprise, alignment of the lower limb was not related to size of the radiograph-related difference in varus alignment, and this finding was discordant with the previous study that reported correlation of the knee adduction moment and the mechanical axis [16]. In contrast, we found that greater varus inclination of the proximal tibia plateau was related to greater accentuation of varus alignment by SLS radiographs. The authors speculate that the tibial plateau could act as a base supporting the superjacent femoral condyles. The greater varus geometry of the proximal tibia could result in medial tilting of the tibial plateau, compared to the ground level, which would subsequently cause greater response of the knee to the adduction moment when in SLS. The extent of the varus accentuation of the coronal alignment on the SLS radiograph compared to those on the DLS radiographs was reduced after HTO. The changes of varus accentuation on the SLS radiographs may be interpreted as the effect of the magnitude of malalignment or the geometry of the proximal tibia. However, the association between the magnitude of malalignment and the varus accentuation on the SLS radiographs was not obvious in our study, as described above. So, we thought that these findings can be explained better by the fact that the HTO procedure changes the proximal tibial geometry from varus to valgus. As we mentioned above, the varus tibial plateau inclination was positively related to the size of the differences in coronal alignment between SLS and DLS radiographs. Alteration of the proximal tibial geometry after HTO resulted in the lateral tilting of the tibial plateau compared to the ground level, in contrast to the usual preoperative geometry of medial tilting of the tibial plateau that caused greater varus accentuation of the coronal alignment on SLS. Considering the findings of this study, SLS radiography may be applicable in assessing knee pathology. For example, it may be use as a tool for screening or diagnosing PLRI. Posterolateral corner injury and PLRI are often underdiagnosed because MRI findings are not always typical. If a patient presents with significant varus accentuation of coronal alignment on the SLS compared to DLS radiograph, a diagnosis of PLRI should be suspected clinical suspicion about the presence of PLRI. SLS may also be useful to Table 5 The effect of the high tibial osteotomy on the radiograph-related differences of coronal alignment in the patients with osteoarthritis and varus deformity. Alignment measures
Preoperative
Postoperative
Difference
p Value
ΔMTFA (°) ΔJSTA (°) ΔWLL (%)
−2.4 (1.6) −1.2 (1.0) −9.7 (7.4)
−0.9 (1.2) −0.4 (0.8) −4.1 (5.4)
−1.5 (1.6) −0.7 (1.2) −5.6 (7.6)
b0.001 b0.001 b0.001
Data are presented as mean and (standard deviation). Abbreviations: Δ, the differences of measurements between the single-limb stance and double-limb stance radiographs; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle, WLL, weight loading line coordinate. Significant (p b 0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
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enable evaluation of dynamic alignment without a gait lab, which is not commonly available in the daily practice. Dynamic alignment should be considered in the planning of osteotomies around the knee. Current knowledge is mainly based on the static alignment which reflects only the static position. In order to improve our understanding of the human kinematics and enhance the surgical outcome, consideration of dynamic condition is needed using a relevant tool. SLS radiograph can be a simple and convenient option for this purpose. Further research is warranted and should include validation of SLS with gait lab and its clinical usefulness in diagnosis and surgical planning. This study has several limitations. First, the baseline demographic characteristics of the three groups differed. The normal group was matched on age and gender with the PLRI group whereas the demographics of the OA groups were too different from other two groups to match. However, we adjusted the age, gender and BMI during the statistical analyses to minimize the effect of the differences in the demographics. Second, radiographic measurements can be affected by measurement errors or the process of taking the radiograph. We tried to select the most appropriate radiographs among the available images of each patient, which were taken with the patella facing forward. Furthermore, we confirmed that the intra- and inter-observer reliabilities were N 0.9 for all parameters. Third, whether the whole-limb radiographs were taken with SLS or DLS position could not be blinded to the radiographic evaluator. It may bias the results of radiographic measurements. Fourth, we did not compare the radiographically-measured coronal alignment with those measured by gait analysis, which may reflect the dynamic condition. Fifth, we did not directly explore the clinical relevance of the SLS radiograph in this study, although we proposed some possible usefulness in the practice. More detailed clinical meaning of these findings should be revealed by succeeding researches. This study demonstrates that coronal alignments measured on SLS radiographs differ from static alignment measured on DLS, showing varus accentuated on SLS radiographs in PLRI and OA groups. Our findings suggest that DLS radiograph, a gold standard for measuring coronal limb alignment, is limited in representing dynamic weight bearing limb alignment. SLS whole leg standing AP radiograph may be a simple and convenient method to estimate dynamic alignment during stance phase of gait. Information from SLS radiograph may be helpful in diagnosing PLRI and making surgical plans for patients with varus knee osteoarthritis.
Conflict of interest Dr. Kim received research funding from Smith & Nephew and BBraun Aesculap, and is a design consultant for Smith & Nephew and BBraun Aesculap. None of the other authors (YGN, MJC, SHE, SJK, SCP) have relevant conflicts of interest to declare.
References [1] Won HH, Chang CB, Je MS, Chang MJ, Kim TK. Coronal limb alignment and indications for high tibial osteotomy in patients undergoing revision ACL reconstruction. Clin Orthop Relat Res 2013;471:3504–11. [2] Badhe NP, Forster IW. High tibial osteotomy in knee instability: the rationale of treatment and early results. Knee Surg Sports Traumatol Arthrosc 2002;10:38–43. [3] Noyes FR, Barber-Westin SD, Hewett TE. High tibial osteotomy and ligament reconstruction for varus angulated anterior cruciate ligament-deficient knees. Am J Sports Med 2000;28:282–96. [4] Arthur A, LaPrade RF, Agel J. Proximal tibial opening wedge osteotomy as the initial treatment for chronic posterolateral corner deficiency in the varus knee: a prospective clinical study. Am J Sports Med 2007;35:1844–50. [5] Murphy SB. Tibial osteotomy for genu varum. Indications, preoperative planning, and technique. Orthop Clin North Am 1994;25:477–82. [6] Brown GA, Amendola A. Radiographic evaluation and preoperative planning for high tibial osteotomies. Oper Tech Sports Med 2012;20:93–102. [7] Harrington IJ. Static and dynamic loading patterns in knee joints with deformities. J Bone Joint Surg Am 1983;65:247–59. [8] Specogna AV, Birmingham TB, Hunt MA, Jones IC, Jenkyn TR, Fowler PJ, et al. Radiographic measures of knee alignment in patients with varus gonarthrosis: effect of weightbearing status and associations with dynamic joint load. Am J Sports Med 2007;35:65–70. [9] Johnson F, Leitl S, Waugh W. The distribution of load across the knee. A comparison of static and dynamic measurements. J Bone Joint Surg 1980;62:346–9. [10] Foroughi N, Smith RM, Lange AK, Baker MK, Singh MAF, Vanwanseele B. Dynamic alignment and its association with knee adduction moment in medial knee osteoarthritis. Knee 2010;17:210–6. [11] Hunt MA, Birmingham TB, Jenkyn TR, Giffin JR, Jones IC. Measures of frontal plane lower limb alignment obtained from static radiographs and dynamic gait analysis. Gait Posture 2008;27:635–40. [12] Kawakami H, Sugano N, Yonenobu K, Yoshikawa H, Ochi T, Hattori A, et al. Gait analysis system for assessment of dynamic loading axis of the knee. Gait Posture 2005;21:125–30. [13] Paley D. Principles of Deformity Correction. New York, NY: Springer; 2002. [14] Chen A, Rich V, Bain E, Sterett WI. Variability of single-leg versus double-leg stance radiographs in the varus knee. J Knee Surg 2009;22:213–7. [15] Desai SS, Shetty GM, Song H-R, Lee SH, Kim TY, Hur CY. Effect of foot deformity on conventional mechanical axis deviation and ground mechanical axis deviation during single leg stance and two leg stance in genu varum. Knee 2007;14:452–7. [16] Andrews M, Noyes FR, Hewett TE, Andriacchi TP. Lower limb alignment and foot angle are related to stance phase knee adduction in normal subjects: a critical analysis of the reliability of gait analysis data. J Orthop Res 1996;14:289–95. [17] Wada M, Maezawa Y, Baba H, Shimada S, Sasaki S, Nose Y. Relationships among bone mineral densities, static alignment and dynamic load in patients with medial compartment knee osteoarthritis. Rheumatology 2001;40:499–505. [18] Hurwitz DE, Ryals AB, Case JP, Block JA, Andriacchi TP. The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain. J Orthop Res 2002;20:101–7. [19] Lasam MP, Lee KJ, Chang CB, Kang YG, Kim TK. Femoral lateral bowing and varus condylar orientation are prevalent and affect axial alignment of TKA in Koreans. Clin Orthop Relat Res 2013;471:1472–83. [20] Amis AA. Biomechanics of high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2013;21:197–205. [21] Andriacchi TP. Dynamics of knee malalignment. Orthop Clin North Am 1994;25:395–403. [22] Hsu RW, Himeno S, Coventry MB, Chao EY. Normal axial alignment of the lower extremity and load-bearing distribution at the knee. Clin Orthop Relat Res 1990; 255:215–27. [23] Maquet P. Valgus osteotomy for osteoarthritis of the knee. Clin Orthop Relat Res 1976;120:143–8.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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The Knee
Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees☆ Young Gon Na a, Moon Jong Chang b, Sang Hwa Eom c, Seok Jin Kim c, Seong Cheol Park c, Tae Kyun Kim c,⁎ a b c
Department of Orthopaedic Surgery, CM Hospital, Seoul, Republic of Korea Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul National University Boramae Hospital, Seoul, Republic of Korea Joint Reconstruction Center, Seoul National University Bundang Hospital, 82 Gumi-ro, 173 Beon-gil Bundang-gu, Seongnam-si, Gyeonggi-do 13620, Republic of Korea
a r t i c l e
i n f o
Article history: Received 25 December 2015 Received in revised form 15 July 2016 Accepted 1 September 2016 Available online xxxx Keywords: Posterolateral rotatory instability Osteoarthritis Dynamic alignment Single-limb stance Double-limb stance
a b s t r a c t Background: We aimed to determine whether coronal alignment measured on the single-limb stance (SLS) radiographs differs from those on the double-limb stance (DLS) images. We also investigated whether the size of such differences was affected by the knee pathology, lower limb alignment, and geometry of the tibia or femur. Methods: We measured coronal alignment with mechanical tibiofemoral angle (MTFA) on the DLS and SLS radiographs in patients with posterolateral rotatory instability (PLRI, 30 knees), osteoarthritis (OA) with varus deformity who were scheduled for high tibial osteotomy (HTO) (60 knees), and in normal control (60 knees). The measurements on the SLS radiographs were compared with those on DLS images and the size of the differences were compared between the three groups. The correlation between the radiograph-related differences of coronal alignment and the limb alignment or geometry of tibia/femur was investigated. In the OA group, the size of the radiograph-related differences before HTO were compared with those after surgery. Results: The coronal alignment on the SLS radiographs indicated varus accentuation compared to those on the DLS radiographs in the PLRI and OA groups (1.6 and 2.4°, respectively), while it was negligible in the normal group. Greater varus inclination of the tibial plateau was related to greater varus accentuation (r = 0.249). The HTO decreased the extent of varus accentuation in the OA group (reduction of varus accentuation = 1.5°). Conclusions: Coronal alignment on the SLS radiograph is different from static alignment measured on the DLS radiograph, which may reflect dynamic alignment. © 2016 Elsevier B.V. All rights reserved.
1. Introduction Accurate measurements of coronal alignment of the lower extremities are crucial for appropriate management of knee disorders related to ligament laxity or osteoarthritis, combined with malalignment. Concurrent alignment correction is sometimes ☆ No financial support was provided for this study.Each author certifies that his or her institution has approved the human protocol for this investigation, and that all investigations were conducted in conformity with ethical principles of research.This work was performed at the Joint Reconstruction Center, Seoul National UniversityBundang Hospital. ⁎ Corresponding author at: Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, Republic of Korea. E-mail addresses: [email protected] (Y.G. Na), [email protected] (M.J. Chang), [email protected] (S.H. Eom), [email protected] (S.J. Kim), [email protected] (S.C. Park), [email protected] (T.K. Kim).
http://dx.doi.org/10.1016/j.knee.2016.09.003 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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required for patients undergoing anterior cruciate ligament reconstruction with varus malalignment [1–3]. High tibial osteotomy can be an initial surgical treatment in posterolateral rotatory instability with varus deformity [4]. Inaccurate preoperative alignment information may cause under- or overcorrection after osteotomy. Traditionally, a full-length standing anteroposterior (AP) radiography taken with patients in double-limb stance (DLS) has been used as a gold standard to measure the coronal alignment [5,6]. DLS radiographs can only reflect static alignment; however, dynamic alignment may provide different information [7–9]. Dynamic alignment can be measured better on the gait analysis rather than on the static radiographic measurement, but it requires special equipment and facility [10–12]. The coronal alignment on the single-limb stance (SLS) full-length standing AP radiograph may be different from the static alignment measured on the DLS radiograph as the entire body weight is transmitted through the single limb [13]. Previous reports revealed that the differences in weight bearing on the knee joint could result in differences in coronal alignment [8,14]. In addition, the SLS radiograph theoretically simulates the stance phase of a gait cycle so the SLS radiograph might reflect the dynamic alignment of the lower limb despite its inherent static nature. [6–8,13]. Several previous studies reported increasing varus deformity on the SLS radiographs than on the DLS images in patients with arthritic knees with varus deformity [8,14,15]. However, whether such differences in coronal alignment between SLS and DLS radiographs are observed in other knee conditions, such as posterolateral rotatory instability (PLRI) or normal knee, are not reported in the literature. Furthermore, factors which are associated with increased differences in the coronal alignment measurement between SLS and DLS radiographs are not thoroughly investigated yet. Magnitude of malalignment and geometry of the knee joint may be plausible candidate, as they can affect the moment across the knee joint [16–18]. Because high tibial osteotomy (HTO) alters lower limb alignment and proximal tibial geometry, the changes after HTO may give some insight about the effect of magnitude of malalignment and the geometry of proximal tibia. Therefore, we sought to determine whether the coronal alignments measured on the SLS radiograph differ from those on the DLS images in patients with various knee conditions such as normal, PLRI and OA with varus deformity. We also aimed to determine whether these resultant differences were affected by the alignment of the lower limbs and geometry of the knee joint. Finally, we also wanted to determine whether these radiograph-related differences in the coronal alignment changed after correction of the malalignment in the patients with medial OA who underwent HTO.
2. Materials and methods 2.1. Study design This retrospective study was conducted using the following three patient groups with different knee conditions from the consecutive patient cohort of our institute: 1) normal group (n = 60), 2) PLRI group (n = 30) and 3) OA with varus deformity group who underwent HTO (n = 60). The patients were excluded in this study if the accurately-taken whole-limb standing radiographs were not available, e.g. the patella was not 'facing forwards' or the flexion contracture of the knee was greater than 10° (n = 14). The PLRI group included 30 consecutive patients who underwent posterolateral complex reconstruction for knee joint laxity and/ or high tibial osteotomy for combined malalignment from 2005 through 2013. All the patients had prior traumatic injury but the patients with acute injury within three months were not included in this study. The diagnosis of PLRI was done by physical examination (external rotation recurvatum test, varus stress test at 30°, dial test at 30° and 90°, posterolateral drawer test) and magnetic resonance image (MRI) findings (injury of lateral collateral ligament and/or popliteofibular ligament and/or popliteus tendon). For the normal group, we selected 60 patients with non-symptomatic opposite knees from the 280 patients (247 men and 33 women) who underwent primary anterior cruciate ligament (ACL) reconstruction between August 2008 and March 2012. The normal controls were age- and sex-matched 2:1 with the PLRI group, with selecting the closest match among the available candidates. The OA with varus deformity group consisted of 60 consecutive patients who underwent medial opening-wedge HTO for primary OA in the medial compartment (Kellgren-Lawrence classification III) using TomoFix® system (Synthes GmbH; Solothurn, Switzerland) from August 2005 through March 2012. The patients in OA group were typically elderly females, so we could not match age or gender with other two groups. Compared to the other two groups, the OA group was more frequently female and older and consequently had lower mean weight and height (Table 1). This study was approved by institutional review board of authors' hospital and the written informed consent was waived by the board. Table 1 Demographic features of the patients in the three study groups Parameter
Normal (n = 60)
PLRI (n = 30)
OA (n = 60)
p Value
Male (%) Age (years) Height (cm) Weight (kg) BMI (kg/m2)
52 (87%) 33.8 (12.1) 171.1 (7.2) 74.5 (12.9) 25.4 (3.6)
26 (87%) 33.8 (13.3) 171.9 (8.0) 73.4 (14.5) 24.8 (4.4)
6 (10%) 55.5 (5.0) 156.5 (6.5) 65.7 (9.4) 26.8 (2.8)
b0.001 b0.001 b0.001 b0.001 0.023
Data are presented as mean and (standard deviation). Abbreviations: BMI, body mass index; PLRI, posterolateral rotatory instability; OA, osteoarthritis. Significant (p b0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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2.2. Radiographic evaluation Radiographic evaluations were performed using full-limb standing AP radiographs with patients in both DLS and SLS position. Pre- and postoperative images were used in the OA group while only preoperative radiographs were used in the PLRI and normal groups. In the OA group, the best quality-images without significant rotation were selected for the radiographic measurement among consecutive images taken at three, six, and 12 months after HTO. All the radiographs were taken on 14 × 51 inch-grid cassettes to ensure that the patella was facing directly anterior. We tried to set the foot orientation and the width between both feet consistent in all patients using a footplate while taking the images. The footplate had the standardized feet-shape on it so that the patients could stand on it with standardized position and foot orientation, following the foot shape. When taking SLS radiograph, patients were required to maintain their balance and keep still without any support (or minimal support if it's impossible). The trunk position was allowed to be in comfortable status during SLS. All radiographic images were digitally acquired using a picture archiving communication system (PACS). Radiographic measurements were conducted using PACS software (Infinite, Seoul, Korea) with the minimum detectable differences 0.1° in angle and 0.1 mm in length measurements. In the DLS AP radiograph, five radiographic parameters were measured: three parameters relating to coronal limb alignment, namely the mechanical tibiofemoral angle (MTFA), the joint space tilt angle (JSTA) and weight loading line (WLL) coordinate, and two bone geometric parameters including the femoral condylar orientation (FCO), and the tibial plateau inclination (TPI). The MTFA was defined as the angle formed between the mechanical axes of the femur (the line from the femoral head center to the center of the femoral intercondylar notch) and the tibia (the line from the center between both tibial spine tips to the center of the tibial plafond, distally). A negative value was given to knees in varus alignment. The JSTA was defined as the angle between the tangential line to the subchondral plates of both femoral condyles and the tangential line to the subchondral plate of the proximal tibia, and a negative value was given to the knee with lateral space opening (Fig. 1). The WLL coordinate of the knee (%) was defined as the portion of the mechanical axis of the limb (the line from the femoral head center to the ankle talus center) passing through the knee from the edge of the medial tibial plateau (0%) to the edge of the lateral tibial plateau (100%). A negative value was given in severe varus with the WLL passing through the medial side of the medial edge of the tibial plateau. The FCO was defined as the angle between the mechanical axis of the femur and the tangential line to the subchondral plates of both femoral condyles, and a negative value was given in varus orientation [19]. The TPI was defined as the angle between the mechanical axis of the tibia and the tangential line to the subchondral plate of the proximal tibia, and a negative value was given in varus orientation [19]. In the SLS AP radiograph, the MTFA, JSTA, and WLL coordinate were measured in same manner. To determine intra- and inter-observer reliabilities of radiographic assessments, two orthopedic surgeons (two of the authors) performed radiographic assessments in 20 randomly selected knees twice within a three-week interval. The intra- and inter-
JSTA
Fig. 1. Definition of the joint space tilt angle (JSTA). The joint space tilt angle (JSTA) was defined as the angle between the tangential line to the subchondral plates of both femoral condyles and the tangential line to the subchondral plate of the proximal tibia. Negative value indicates that the lateral joint space is wider than the medial side.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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observer reliabilities of assessments of all radiographic measurements were evaluated using intraclass correlation coefficients (ICCs). The ICCs of intra- and inter-observer reliabilities of all measurement were N0.9 (range, 0.903 to 0.996). Thus, measurements taken by a single investigator (one of the authors) were used in the analyses. 2.3. Statistical analysis Statistical analyses were carried out with SPSS for Windows version 20.0 (SPSS Inc., Chicago, Illinois), and p-values b0.05 were considered significant. We compared three measures; the MTFA, JSTA and WLL coordinate, between SLS and DLS radiographs in each study group using the paired t-test. The radiograph-related difference, Δ, (difference between SLS and DLS radiographs) was compared among three groups using analysis of variance (ANOVA) test with Bonferroni post hoc test. The proportions of the patients with radiographrelated difference over two or three degrees of MTFA in the three groups were compared using the Chi-square test. To determine the effect of the alignment of lower limbs and the bone geometry (FCO and TPI) on the radiograph-related differences, we performed partial correlation analysis. The knee conditions, age, gender and BMI were adjusted as covariates. To determine whether the correction of the malalignment can reduce coronal alignment changes, the changes of the MTFA, JSTA and WLL coordinate between before and after HTO were compared using the paired t-test in the OA with varus deformity group. 3. Results 3.1. Difference of the coronal alignment between SLS and DLS in three knee conditions The coronal alignment measured on the SLS radiographs showed varus accentuation compared to those on the DLS radiographs in the PLRI and OA groups: 1.6° for MTFA, 1.0° for JSTA and 7.4% for WLL coordinate in PLRI group; 2.4° for MTFA, 1.2° for JSTA and 9.8% for WLL coordinate in OA group (Table 2 and Fig. 2). In the normal group, although MTFA and WLL also presented changes into varus direction on the SLS radiograph compared to those on the DLS images, the extent of the varus accentuation was only 0.4° for MTFA and 2.5% for WLL coordinate. The radiograph-related differences of coronal alignment in the PLRI and OA groups were greater than those in the normal group (Table 3). However, the radiograph-related difference of the PLRI and OA groups did not differ on the post hoc test. The patients with the MTFA difference between SLS and DLS over two degrees (23%, 30%, 62% in normal, PLRI and OA group respectively, p b 0.001) or three degrees (5%, 20%, 37% in normal, PLRI and OA group respectively, p b 0.001) were more frequent in PLRI and OA group than normal group. 3.2. Effect of the limb alignment, bone geometry on the difference of the coronal alignment between SLS and DLS Greater varus inclination in the proximal tibia plateau was related to greater radiograph-related differences in coronal alignment, whereas the FCO and the magnitude of malalignment did not affect the differences (Table 4). There was positive correlation between tibial plateau inclination and the amount of changes in the three coronal alignment parameters in the partial correlation analysis. On the other hand, no significant relationship was found between the radiograph-related differences in coronal alignment and the femoral condylar orientation or mechanical tibiofemoral angle. 3.3. Effect of the high tibial osteotomy on the difference of the coronal alignment between SLS and DLS in the OA group In the OA group, correction of malalignment with high tibial osteotomy decreased varus accentuation of the coronal alignment on the SLS radiograph compared to those on the DLS radiographs (pre-HTO vs. post-HTO: Δ MTFA, − 2.4° vs. − 0.9°; Δ JSTA, −1.2° vs. −0.4°; Δ WLL, −9.7% vs. −4.1%, all p b 0.001, Table 5). The extent of varus accentuation measured by the changes of MTFA, JSTA and WLL coordinate on the SLS and DLS radiograph was decreased postoperatively by 1.5°, 0.7° and 5.6%, respectively. Table 2 The differences in measures of coronal limb alignment between the SLS and DLS radiographs Group
Measures
Normal
MTFA (°) JSTA (°) WLL (%) MTFA (°) JSTA (°) WLL (%) MTFA (°) JSTA (°) WLL (%)
PLRI
OA
SLS −2.4 (2.9) −1.6 (1.6) 35.9 (13.3) −6.2 (5.0) −2.7 (1.7) 18.3 (23.8) −11.1 (3.4) −5.7 (2.1) −0.5 (14.4)
DLS
Difference
p Value
−1.9 (2.5) −1.4 (1.4) 38.4 (11.9) −4.6 (4.3) −1.7 (1.5) 25.7 (19.6) −8.8 (2.8) −4.5 (2.1) 9.3 (12.5)
−0.4 (1.5) −0.2 (1.3) −2.5 (6.4) −1.6 (1.4) −1.0 (0.8) −7.4 (7.4) −2.4 (1.6) −1.2 (1.2) −9.8 (7.1)
0.028 0.302 0.003 b0.001 b0.001 b0.001 b0.001 b0.001 b0.001
Data are presented as means and (standard deviations). Abbreviations: PLRI, posterolateral rotatory instability; OA, osteoarthritis; SLS, single limb stance; DLS, double limb stance; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle, WLL, weight loading line coordinate. Significant (p b0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
Normal DLS
SLS
Δ=-0.4° -2.5%
5
OA
PLRI DLS
SLS
Δ=-1.6° -7.4%
DLS
SLS
Δ=-2.4° -9.8%
Fig. 2. The differences in coronal limb alignment between SLS and DLS radiographs. The difference in mechanical tibiofemoral angle and the weight loading line coordinate between SLS and DLS radiographs (Δ) were shown on the typical three cases of the each group. Negative value means varus accentuation of the coronal alignment on the SLS radiograph compared to those on the DLS image. Red lines indicate the mechanical axis of the limb (the line from the femoral head center to the ankle talus center). Yellow lines indicate the mechanical axis of the femur (the line from the femoral head center to the center of the femoral intercondylar notch) and the tibia (the line from the center between both tibial spine tips to the center of the tibial plafond, distally). Blue lines indicate the width of the tibial plateau. Abbreviations: DLS, double-limb stance; SLS, single-limb stance; PLRI, posterolateral rotatory instability; OA, osteoarthritis. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
4. Discussion This study demonstrated that the coronal alignments shifted varus on the SLS radiograph compared to the DLS radiographs in PLRI and OA groups and the greater varus inclination of the tibia plateau was related to greater varus accentuation. In addition, high tibial osteotomy decreased the extent of varus accentuation in the OA group. Our findings give some insight to the difference of dynamic alignment compared to the static alignment, and the clinical usability of SLS radiograph to simply estimate the dynamic coronal alignment. The coronal alignments measured on the SLS radiograph was different from those on the DLS images in patients with PLRI and OA, but negligible in normal group. The adduction moment is placed on the lower limbs in standing position because body weight
Table 3 Comparison of the radiograph-related differences of coronal alignment between the three study groups Alignment measures
Normal (n = 60)
PLRI (n = 30)
OA (n = 60)
p Value
ΔMTFA (°) ΔJSTA (°) ΔWLL (%)
−0.4 (1.5) −0.2 (1.3) −2.5 (6.4)
−1.6 (1.4) −1.0 (0.8) −7.4 (7.5)
−2.4 (1.6) −1.2 (1.2) −9.8 (7.1)
b0.001 b0.001 b0.001
Data are presented as means and (standard deviations) in the parenthesis. Abbreviations: Δ, the differences of measurements between the single-limb stance and double-limb stance radiographs; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle, WLL, weight loading line coordinate; PLRI, posterolateral rotatory instability; OA, osteoarthritis. Significant (p b0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
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Table 4 The effect of lower limb alignment and bone geometry on radiograph-related differences of coronal alignment. Alignment & bone geometry
Partial correlation coefficient (p Value)
MTFA* (°) FCO (°) TPI (°)
ΔMTFA
ΔJSTA
ΔWLL
0.127 (0.126) −0.041 (0.624) 0.249 (0.002)
0.060 (0.474) 0.030 (0.723) 0.226 (0.006)
0.156 (0.059) −0.086 (0.299) 0.288 (b0.001)
Abbreviations: Δ, the differences of measurements between the single-limb stance and double-limb stance radiographs; MFTA*, mechanical tibiofemoral angle on the double limb stance radiograph; FCO, femoral condylar orientation on the double limb stance radiograph; TPI, tibial plateau inclination on the double limb stance radiograph; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle; WLL, weight loading line coordinate. Significant (p b0.05) values are presented in bold.
passes through the medial side of the knee joint [8,20]. Furthermore, this adduction moment can increase when the patient stands on a single limb because most of body weight passes through that limb [13]. The varus accentuation of the coronal alignment of lower limb seen in the SLS radiographs in the OA patients agreed with previously reported studies [8,14,15]. In addition, we found a similar radiograph-related difference in the patterns of coronal alignment in the patients with laxity of lateral ligament complex. On the other hand, we confirmed that the varus accentuation on SLS radiographs in the normal control group was smaller than PLRI and OA groups: 0.4° for MTFA and 2.5% for WLL coordinate. The adduction moment created by the ground reaction force is offset primarily by the lateral collateral ligament (LCL) and secondarily by the iliotibial band. The varus accentuation found in the PLRI group can be interpreted by the effect of the diminished function of the LCL, while that in the OA group is explained by the chronic attenuation of the LCL due to the varus deformity, and the age-related relative inability of the iliotibial band to dynamically stabilize the joint [9,21–23]. Although the mean difference of the coronal alignment (MTFA) was 1.6° in PLRI group and 2.4° in OA group, 20% and 37% of PLRI and OA group patients presented radiograph-related difference over three degrees. Moreover, the maximum difference was 6.1° in PLRI group and 6.5° in OA group. Our findings suggest that the dynamic alignment needs to be considered in OA or PLRI patients, whereas it may not be a significant issue in normal group. Furthermore, substantial varus accentuation in SLS radiographs may be possibly a pathognomic finding of laxity of the lateral ligament complex of the knee joint or pathologic varus malalignment of the lower extremities, although further investigations are warranted to reveal the clinical implication of these findings. The varus accentuation of the coronal alignment of lower limb seen in the SLS radiographs, compared to DLS radiographs was related with the varus inclination of proximal tibia, whereas not associated with the distal femoral geometry or magnitude of malalignment of lower limb. To our surprise, alignment of the lower limb was not related to size of the radiograph-related difference in varus alignment, and this finding was discordant with the previous study that reported correlation of the knee adduction moment and the mechanical axis [16]. In contrast, we found that greater varus inclination of the proximal tibia plateau was related to greater accentuation of varus alignment by SLS radiographs. The authors speculate that the tibial plateau could act as a base supporting the superjacent femoral condyles. The greater varus geometry of the proximal tibia could result in medial tilting of the tibial plateau, compared to the ground level, which would subsequently cause greater response of the knee to the adduction moment when in SLS. The extent of the varus accentuation of the coronal alignment on the SLS radiograph compared to those on the DLS radiographs was reduced after HTO. The changes of varus accentuation on the SLS radiographs may be interpreted as the effect of the magnitude of malalignment or the geometry of the proximal tibia. However, the association between the magnitude of malalignment and the varus accentuation on the SLS radiographs was not obvious in our study, as described above. So, we thought that these findings can be explained better by the fact that the HTO procedure changes the proximal tibial geometry from varus to valgus. As we mentioned above, the varus tibial plateau inclination was positively related to the size of the differences in coronal alignment between SLS and DLS radiographs. Alteration of the proximal tibial geometry after HTO resulted in the lateral tilting of the tibial plateau compared to the ground level, in contrast to the usual preoperative geometry of medial tilting of the tibial plateau that caused greater varus accentuation of the coronal alignment on SLS. Considering the findings of this study, SLS radiography may be applicable in assessing knee pathology. For example, it may be use as a tool for screening or diagnosing PLRI. Posterolateral corner injury and PLRI are often underdiagnosed because MRI findings are not always typical. If a patient presents with significant varus accentuation of coronal alignment on the SLS compared to DLS radiograph, a diagnosis of PLRI should be suspected clinical suspicion about the presence of PLRI. SLS may also be useful to Table 5 The effect of the high tibial osteotomy on the radiograph-related differences of coronal alignment in the patients with osteoarthritis and varus deformity. Alignment measures
Preoperative
Postoperative
Difference
p Value
ΔMTFA (°) ΔJSTA (°) ΔWLL (%)
−2.4 (1.6) −1.2 (1.0) −9.7 (7.4)
−0.9 (1.2) −0.4 (0.8) −4.1 (5.4)
−1.5 (1.6) −0.7 (1.2) −5.6 (7.6)
b0.001 b0.001 b0.001
Data are presented as mean and (standard deviation). Abbreviations: Δ, the differences of measurements between the single-limb stance and double-limb stance radiographs; MTFA, mechanical tibiofemoral angle; JSTA, joint space tilt angle, WLL, weight loading line coordinate. Significant (p b 0.05) values are presented in bold.
Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003
Y.G. Na et al. / The Knee xxx (2016) xxx–xxx
7
enable evaluation of dynamic alignment without a gait lab, which is not commonly available in the daily practice. Dynamic alignment should be considered in the planning of osteotomies around the knee. Current knowledge is mainly based on the static alignment which reflects only the static position. In order to improve our understanding of the human kinematics and enhance the surgical outcome, consideration of dynamic condition is needed using a relevant tool. SLS radiograph can be a simple and convenient option for this purpose. Further research is warranted and should include validation of SLS with gait lab and its clinical usefulness in diagnosis and surgical planning. This study has several limitations. First, the baseline demographic characteristics of the three groups differed. The normal group was matched on age and gender with the PLRI group whereas the demographics of the OA groups were too different from other two groups to match. However, we adjusted the age, gender and BMI during the statistical analyses to minimize the effect of the differences in the demographics. Second, radiographic measurements can be affected by measurement errors or the process of taking the radiograph. We tried to select the most appropriate radiographs among the available images of each patient, which were taken with the patella facing forward. Furthermore, we confirmed that the intra- and inter-observer reliabilities were N 0.9 for all parameters. Third, whether the whole-limb radiographs were taken with SLS or DLS position could not be blinded to the radiographic evaluator. It may bias the results of radiographic measurements. Fourth, we did not compare the radiographically-measured coronal alignment with those measured by gait analysis, which may reflect the dynamic condition. Fifth, we did not directly explore the clinical relevance of the SLS radiograph in this study, although we proposed some possible usefulness in the practice. More detailed clinical meaning of these findings should be revealed by succeeding researches. This study demonstrates that coronal alignments measured on SLS radiographs differ from static alignment measured on DLS, showing varus accentuated on SLS radiographs in PLRI and OA groups. Our findings suggest that DLS radiograph, a gold standard for measuring coronal limb alignment, is limited in representing dynamic weight bearing limb alignment. SLS whole leg standing AP radiograph may be a simple and convenient method to estimate dynamic alignment during stance phase of gait. Information from SLS radiograph may be helpful in diagnosing PLRI and making surgical plans for patients with varus knee osteoarthritis.
Conflict of interest Dr. Kim received research funding from Smith & Nephew and BBraun Aesculap, and is a design consultant for Smith & Nephew and BBraun Aesculap. None of the other authors (YGN, MJC, SHE, SJK, SCP) have relevant conflicts of interest to declare.
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Please cite this article as: Na YG, et al, Coronal alignment on the single-limb stance radiograph in posterolateral rotatory instability, osteoarthritis and healthy knees, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.09.003