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Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient
Journal of Orthopaedic Science xxx (2018) 1e6
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Original Article
Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient Jian Zhao 1, Mingyuan Yang 1, Yiling Yang 1, Ziqiang Chen**, Ming Li* Department of Orthopedics, Changhai Hospital, Second Military Medical University, Shanghai, People's Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 January 2018 Received in revised form 4 May 2018 Accepted 29 May 2018 Available online xxx
Background: To investigate the risk factors of proximal junctional kyphosis (PJK) in Lenke 5 AIS patients after all-pedicle instrumentation and correction, and to compare the difference of radiographic and clinical outcome between PJK and Non-PJK populations. Method: Medical records of Lenke 5 AIS patients were reviewed from January 2008 to January 2013, included posteroanterior and lateral full spine X-ray films preoperatively, postoperatively (4e7 days after surgery), and at final follow-up. Demographic data and radiologic parameters were evaluated. Based on the proximal junctional angle (PJA) at final follow-up, those patients were divided into 2 groups: PJK group (n ¼ 35, PJAS10 ), and Non-PJK group (n ¼ 52, PJA<10 ). Comparisons analyses between PJK and Non-PJK groups were carried out. Binary logistic Regression analysis was performed to detect the risk factors of PJK at follow-up. Results: The current study recruited 87 Lenke 5 AIS patients with average follow-up of 4.67 ± 1.17 years. Significant differences between PJK and Non-PJK groups were observed as follows: UIV(P ¼ 0.010), the disruption of junctional ligaments (P < 0.001); preoperative variables [MTC (P ¼ 0.001), TK(P < 0.001), LL (P ¼ 0.017), SVA (P ¼ 0.036), and PJA (P ¼ 0.014)], postoperative variables [TLK(P ¼ 0.004), and PJA (P < 0.001)], and follow-up [SVA (P ¼ 0.014), C-SVA (P < 0.001), and PJA (P0.001). Binary logistic regression showed that the disruption of junctional ligaments, postoperative PJA and UIV (upper instrumented vertebra) at proximal or lower thoracic levels were the main risk factors of PJK [Odds Ratio (OR) ¼ 5.114, 2.345, and 6.212, respectively]. However, the SRS-22 scores did not change significantly in PJK and Non-PJK groups. Conclusion: Greater postoperative PJA, disruption of junctional ligaments, UIV at lower thoracic levels were the main risk factors for PJK in Lenke 5 AIS patients. Recommedation: Preserve junctional ligaments in those individuals with UIV located in the lower thoracic region. © 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
1. Introduction For those severe adolescent idiopathic scoliosis (AIS) patients, corrective surgery can be used to reconstruct the coronal and sagittal alignment [1]. With the use of all-pedicle technique, surgeons can efficiently correct the coronal deviation [2]. However,
* Corresponding author. Department of Orthopaedics, Changhai Hospital, 168 Changhai Street, Shanghai 200433, China. Fax: þ86 21-51190920. ** Corresponding author. Department of Orthopaedics, Changhai Hospital, 168 Changhai Street, Shanghai 200433, China. E-mail addresses: [email protected] (Z. Chen), [email protected] (M. Li). 1 These authors contributed equally to this work.
strong correction of all-pedicle instrumentation also resulted in a series of issues such as the decrease of thoracic kyphosis (TK) [3]. Moreover, the phenomenon of proximal junctional kyphosis (PJK) has drawn the attention of many spine surgeons, because PJK was associated with the clinical outcome in elderly populations [4]. Based on different diagnostic criteria of PJK, a series of studies reported the prevalence ranging from 9.2% to 46% [5e7], but only a few PJK caused symptoms. Correspondingly, several studies have focused on the risk factor of PJK in AIS patients after corrective surgery. The cause of PJK may be related to the difference in scoliosis types, surgical techniques and in fusion selections. Helgeson et al. [8] found that all-pedicle screw constructs led to higher PJK prevalence compared with hook-only and hybrid instrumentation.
https://doi.org/10.1016/j.jos.2018.05.010 0949-2658/© 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
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J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
Kim et al. [9] reported risk factors which included preoperative thoracic hyperkyphosis (TKS40 ), TK decline by 5 , and male gender. However, in another study of 208 consecutive AIS patients, Helgeson et al. [6] did not report any risk factors. When referring to clinical outcome, previous studies indicated that PJK did not significantly affect the Health-Related Quality of Life (HRQOL) [10]. In terms of Lenke 5 AIS patients, Yang et al. [11] reported the prevalence of 43% of PJK after posterior selective lumbar fusion. Correspondingly, Hollenbeck et al. [6] reported that 1 out of 13 Lenke 5 AIS patients suffered from PJK. There are few articles focused on PJK in Lenke 5 AIS patients. The purpose of this study is to investigate the risk factors of proximal junctional kyphosis (PJK) in Lenke 5 AIS patients after all-pedicle instrumentation and correction, and to compare the difference of radiographic and clinical outcome between PJK and Non-PJK populations. 2. Methods and materials 2.1. Patient population This study was approved by the Institutional Review Board of Changhai hospital, and all patients were informed of the contents of the study. Lenke 5 AIS patients treated by posterior corrective surgery in our hospital from January 2008 to January 2013 were assessed retrospectively. Each patient had to meet these criteria for inclusion in this study: (1) Lenke 5 AIS patients ages of 11e18 years; (2) TL/LC(Thoracolumbar/lumbar curve) > 40 ; (3) Onestage posterior pedicle screw instrumentation and corrective surgery performed by the same group; (4) minimal followed-up for 2 years.
2.2. Data collection Surgeries were planned and carried out by the same group according to Lenke's suggestion for fusion levels [12]. If selective fusion was performed, the upper-instrumented vertebra (UIV) always stopped at proximal end vertebra. Otherwise, the fusion segments included both thoracolumbar/lumbar curve and major thoracic curve, which meant the UIV frequently existed at the upper thoracic region. The lower instrumented vertebra (LIV) always stopped at neutral vertebrae on standing films. The following demographic data were recorded: Age (years), Gender (Female/Male), Risser sign, the time of final follow up (years), UIV, LIV, status of junctional ligaments (Disrupted/Preserved). The disrupted supraspinous and interspinous ligaments between the UIV and the supra-adjacent vertebra were defined as disrupted junctional ligaments. UIV stopped at proximal thoracic region (at T9 and upper vertebras) or lower thoracic region (at T10 and lower vertebras) was analyzed, separately. The standing posteroanterior and lateral X-ray films before surgery, postoperatively (4e7 days after surgery), and at final follow-up were collected. On the posteroanterior X-ray film, MTC (major thoracic curve), and TL/LC (thoracolumbar/lumbar curve) were measured for further analysis. On the lateral film, the following parameters were measured: C2eC7 lordosis (CL), C2eC7 sagittal vertical axis (CSVA), T5-T12 kyphosis (TK), T10-L2 kyphosis (TLK), lumbar lordosis (LL), sagittal vertical axis (SVA), and proximal junctional angle (PJA). The CL was the angle between the inferior endplate of C2 and the inferior endplate of C7. PJA referred to the angle between the lower end plate of the UIV and the upper end plate of the second supra adjacent vertebrae [13]. When PJA 10 or increased by 10 greater than the preoperative measurement, PJK was diagnosed (Fig. 1).
Fig. 1. An example of proximal junctional kyphosis (PJK) following corrective surgery. Corrective surgery was performed at the age of 13. PJA was 24 at 10 years' follow-up.
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
Moreover, the pelvic sagittal radiographic parameters, including pelvic tilt (PT), pelvic incidence (PI), and sacral slope (SS), were measured. The Scoliosis Research Society (SRS)-22 questionnaire was used to assess the clinical outcome of those individuals. The questionnaire survey was performed before the surgery, and at final follow-up.
2.3. Statistical analysis The statistical analyses were conducted by SPSS 18.0. Descriptive statistics were presented in the form of mean with standard deviation (SD), and count data were presented in numbers. Repeated Measure Design Within-Subject Factors was used to assess the effect of surgical correction on aforementioned parameters. If normal distribution was guaranteed, independent twosample t test was used to compare the differences of variables between PJK and Non-PJK groups. Alternatively, ManneWhitney U test was performed. Chi-square test was used to investigate the distribution differences of categorical data. To reveal independent risk factors of PJK at final follow-up, binary logistic regression models were constructed using variables that were of significance in univariate analysis.
3. Results 3.1. General information Initially, 126 Lenke 5 AIS patients were identified from the database. After the inclusion and exclusion process, there were 87 (69.05%) Lenke 5 AIS patients (female/male: 66/21) recruited for this study. The average age, Risser sign, and follow-up time were 13.51 ± 1.27 years, 3.7 ± 0.83, 4.67 ± 1.17years, respectively. The detailed demographic parameters are demonstrated in Table 1.
Table 1 Demographic and radiological parameters based on 87 Lenke 5 AIS patients. Variables Demographic details
Mean ± SD
Age (years) Gender (Female/Male) Risser Follow up time (years) UIV at upper/lower thoracic UIV(T3/T4/T5/T6/T8/T9/T10/T11/T12) LIV(L3/L4/L5) JL (Disrupted/Preserved)
13.85 ± 1.49 66/21 3.70 ± 0.83 4.67 ± 1.17 51/36 1/11/9/4/7/19/19/14/3 29/51/7 39/48
Radiologic parameters MTC TL/LC TK TLK LL PT PI SS SVA C-SVA CL PJA Clinical Outcome SRS-22 (n ¼ 39)
Mean ± SD Preoperative
Postoperativeerative Follow-up
19.89 ± 7.76 44.78 ± 5.72 23.54 ± 9.42 5.89 ± 3.24 45.94 ± 10.47 10.79 ± 6.05 45.86 ± 7.25 35.00 ± 6.83 10.03 ± 25.96 14.83 ± 5.96 14.95 ± 8.88 5.38 ± 2.13
9.82 ± 3.91 12.02 ± 4.12 20.25 ± 8.69 7.13 ± 2.85 44.78 ± 8.91 7.93 ± 5.36 45.97 ± 6.81 37.98 ± 6.23 9.40 ± 21.50 16.05 ± 5.99 15.15 ± 7.83 6.61 ± 2.57
3.98 ± 0.26
Value of P
10.11 ± 3.71 12.41 ± 3.83 24.01 ± 9.08 8.41 ± 2.59 45.49 ± 8.93 11.79 ± 6.32 45.38 ± 5.68 33.60 ± 6.63 8.83 ± 22.73 18.85 ± 7.46 16.87 ± 8.19 9.31 ± 4.73
<0.001 <0.001 0.523 <0.001 0.693 0.098 0.371 0.060 0.591 <0.001 0.001 <0.001
3.94 ± 0.14
0.393*
JL meant junctional ligaments comprised of the supraspinous and interspinous ligaments between the uppermost instrumented the supra-adjacent vertebra. “*” mean the value P was calculated by ManneWhitney U test.
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Preoperatively, the Mean ± SD of MTC, TL/LC, TK, TLK, LL, PT, PI, SS, SVA, C-SVA, CL, PJA, was 19.89 ±7.76 , 44.78 ±5.72 , 23.54 ±9.42 , 5.89 ±3.24 , 45.94 ±10.47, 10.79 ±6.05 , 45.86 ±7.25 , 35.00 ±6.83 , 10.03 mm ± 25.96 mm, 16.15 mm ± 7.02 mm, 14.95 ±8.88 , 5.38 ±2.13 , respectively. Postoperatively (3e7 days after surgery), the corresponding value was 9.82 ±3.91, 12.02 ±4.12 , 20.25 ±8.69 , 7.13 ±2.85 , 44.78 ±8.91, 7.93 ±5.36 , 45.97 ±6.81, 37.98 ±6.23 , 9.40 mm ± 21.50 mm, 16.05 mm ± 5.99 mm, 15.15 ±7.83 , and 6.61 ±2.57, respectively. At final follow-up, the corresponding figure was 10.11 ±3.71, 12.41 ±3.83 , 24.01 ±9.08 , 8.41 ±2.59 , 45.49 ±8.93 , 11.79 ±6.32 , 45.38 ±5.68 , 33.60 ±6.63 , 8.83 mm ± 22.73 mm, 18.85 mm ± 7.46 mm, 16.87 ±8.19 , 9.31 ±4.73 , respectively. Table 1 presents the details of these parameters. As was demonstrated in Table 1, surgical correction had significantly changed MTC(P < 0.001), TL/LC(P < 0.001), TLK(P < 0.001), C-SVA (P < 0.001), CL (P ¼ 0.001) and PJA (P < 0.001). However, there was no difference in terms of TK, LL, PT, PI, SS, and SVA. Additionally, surgical correction did not significantly change the SRS-score (Table 1). 3.2. Comparison analysis between PJK and Non-PJK groups At final follow-up, there were 35 patients (40.23%) out of 87 Lenke 5 AIS patients) who had PJK (PJK group) at follow-up, while the rest of 52 patients demonstrated no significant PJK (Non-PJK group). Between PJK and Non-PJK groups, significant differences of parameters were observed in the following variables: UIV(P ¼ 0.010), the disrupteion of junctional ligaments (P < 0.001); preoperative data including MTC (P ¼ 0.001), TK(P < 0.001), LL (P ¼ 0.017), SVA (P ¼ 0.036), and PJA (P ¼ 0.014), postoperative data including TLK(P ¼ 0.004), and PJA (P < 0.001), and final follow-up data including SVA (P ¼ 0.014), C-SVA (P < 0.001), and PJA (P < 0.001) (Tables 2 and 3). However, no significant difference were found in age, Risser sign, gender distribution, follow-up time, or LIV between the two groups (Table 2). Additionally, no difference were observed in those preoperative radiological parameters (TL/LC, CL, TLK, C-SVA, PT, PI, and SS), postoperative radiological parameters (MTC, TL/LC, TK, CL, C-SVA, LL, PT, PI, SS and SVA) and radiological parameters at followup (MTC, TL/LC, TK, TLK, LL, PT, PI, CL, and SS) (Table 3). Comparison analysis detected no significant differences in SRS22 scores preoperatively (P ¼ 0.375), and at final follow-up (P ¼ 0.654) (Table 2). 3.3. Binary logistic regression analysis To investigate the main risk factors of PJK, binary logistic regression was conducted. Initially, univariate analysis was performed to reveal confounding variables, which showed risk factors were as follows: preoperative MTC, JL (Disrupted/Preserved), preoperative TK, postoperative TLK, preoperative LL, preoperative SVA, preoperative PJA, UIV at proximal or lower thoracic region, and postoperative PJA (Table 4). Then, binary logistic regression based on the aforementioned paramaters showed that the disruption of junctional ligaments, postoperative PJA and UIV at proximal or lower thoracic levels were the main risk factors of PJK [Odds Ratio (OR) ¼ 5.114, 2.345, and 6.212, respectively] (Table 5). 4. Discussion For AIS patients, PJK was a common phenomenon after corrective surgery. Previously, several studies had reported its prevalence ranging from 9.2% to 46% based on different cut-offs of PJA [6,7,14]. Despite several reports about the rate of PJK in AIS patients, there
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
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J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
Table 2 Comparison analysis between two groups in terms of demographic data. Variables
PJK(N ¼ 35)
Non-PJK(N ¼ 52)
P
Age (years) Gender (Female/Male) Risser Follow up time (years) UIV(T3/T4/T5/T6/T8/T9/T10/T11/T12) UIV at upper/lower thoracic LIV(L3/L4/L5) JL (Disrupted/Preserved) Preoperative SRS-22 score Follow-up SRS-22 score
13.26 ± 1.18 26/9 3.74 ± 0.86 4.43 ± 1.14 1/1/0/1/5/7/12/7/1 15/20 7/19/1 24/11 3.92 ± 0.34 3.94 ± 0.18
13.62 ± 1.30 40/12 3.62 ± 0.83 4.83 ± 1.17 0/10/9/3/2/12/7/7/2 36/16 19/28/5 15/37 4.02 ± 0.17 3.93 ± 0.10
0.225 0.486 0.269* 0.188* 0.010 0.016 0.523 <0.001 0.375* 0.654*
JL meant junctional ligaments comprised of the supraspinous and interspinous ligaments between the UIV and the supra-adjacent vertebra. “*” mean the value P was calculated by ManneWhitney U test.
Table 3 Comparison analysis between two groups in terms of radiological parameters. Variables
MTC TL/LL TK TLK LL PT PI SS SVA C-SVA CL PJA
group
PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK
Preoperative
Postoperative
Follow-up
Mean ± SD
P
Mean ± SD
P
Mean ± SD
P
16.43 ± 5.68 22.21 ± 8.15 43.46 ± 3.87 45.67 ± 6.57 28.31 ± 7.80 20.33 ± 9.10 6.40 ± 3.28 5.54 ± 3.19 49.17 ± 9.61 43.77 ± 10.55 10.09 ± 5.88 11.26 ± 6.17 45.54 ± 5.88 46.07 ± 8.10 35.46 ± 5.40 34.69 ± 7.68 2.94 ± 30.30 14.80 ± 21.61 17.71 ± 7.90 15.04 ± 6.21 15.38 ± 7.63 14.66 ± 9.69 6.09 ± 2.17 4.90 ± 1.99
0.001*
9.60 ± 4.74 9.96 ± 3.28 11.63 ± 4.15 12.29 ± 4.10 21.43 ± 8.68 19.46 ± 8.69 8.17 ± 2.58 6.42 ± 2.83 46.29 ± 9.30 43.77 ± 8.58 7.26 ± 5.52 8.38 ± 5.25 45.80 ± 5.76 46.08 ± 7.49 38.40 ± 6.87 37.69 ± 5.78 4.91 ± 19.26 12.42 ± 22.56 16.60 ± 7.24 15.67 ± 5.03 15.49 ± 6.76 14.92 ± 8.53 8.63 ± 2.12 5.25 ± 1.87
0.831*
9.51 ± 3.89 10.52 ± 3.56 11.69 ± 4.12 12.90 ± 3.58 25.40±±9.46 23.08 ± 8.77 9.00 ± 2.63 8.01 ± 2.50 46.37 ± 9.65 44.90 ± 8.45 10.89 ± 4.78 12.38 ± 7.16 45.11 ± 5.03 45.56 ± 6.11 34.23 ± 6.42 33.18 ± 6.80 1.59 ± 20.97 13.70 ± 22.76 22.97 ± 7.57 16.08 ± 6.01 19.17 ± 6.71 15.33 ± 8.78 14.20 ± 3.30 6.02 ± 1.78
0.217
0.145* <0.001 0.225 0.017 0.355* 0.743 0.611 0.036 0.081 0.859* 0.014*
0.466 0.303 0.004 0.198 0.320* 0.854 0.300* 0.111 0.388 0.862* <0.001
0.180* 0.247* 0.081 0.455 0.211* 0.723 0.471 0.014 <0.001 0.059* <0.001*
“*” mean the value P was calculated by ManneWhitney U test. Independent Samples Test. Calculated the rest of values of P.
Table 4 Univariate analysis for risk factors of PJK. Variable
Preoperative MTC JL (Disrupted/Preserved) Preoperative TK Postoperative TLK Preoperative LL Preoperative SVA Preoperative PJA Postoperative PJA UIV at proximal or lower thoracic
B
0.109 1.683 0.107 0.238 0.052 0.019 0.280 0.918 1.099
S.E.
0.034 0.476 0.030 0.088 0.023 0.009 0.112 0.201 0.455
Wald
10.555 12.519 13.049 7.281 5.289 4.163 6.198 20.816 5.832
was insufficient information on the PJK phenomenon in Lenke 5 AIS patients. Yang et al. [11] reported the prevalence of 43% after short posterior spinal fusion in a group of 14 thoracolumbar idiopathic scoliosis patients. Correspondingly, Hollenbeck et al. [6] reported that 1 out of 13 Lenke 5 AIS patients developed PJK. Our study included 87 Lenke 5 AIS patients following one-stage posterior allpedicle instrumentation and correction. With the PJK cut-off of
df
1 1 1 1 1 1 1 1 1
Sig.
0.001 0.000 0.000 0.007 0.021 0.041 0.013 0.000 0.016
Exp(B)
0.90 5.38 1.11 1.27 1.05 1.02 1.32 2.50 3.00
95%CI.for EXP(B) Lower
Upper
0.84 2.12 1.05 1.07 1.01 1.00 1.06 1.69 1.23
0.96 13.67 1.18 1.51 1.10 1.04 1.65 3.71 7.32
10 , the study showed the prevalence of PJK was 40.23% (35 out of 87) with the average follow-up of 4.67 ± 1.17 years. At final followup, surgical correction significantly corrected the TL/LC(P < 0.001), and MTC(P < 0.001), and both TLK and cervical lordosis increased. However, TK, LL and pelvic parameters did not changed significantly. Comparison analyses were performed between PJK and non-PJK groups. They showed that a greater frequency of disrupted
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
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Table 5 Binary logistic regression analysis (Forward Wald method) for risk factors of PJK. Variables
Disruption of junctional ligaments Postoperative PJA UIV at proximal or lower thoracic Constant
B
1.632 0.852 1.827 7.954
S.E.
0.706 0.200 0.706 1.665
Wald
5.339 18.137 6.695 22.824
junctional ligaments (P < 0.001) in the PJK group. In a group of Scheuermann kyphosis cases, Denis et al. [15] also reported the positive association between disrupted junctional ligaments with PJK. In addition, there were more patients with UIV stopped at lower thoracic levels in the PJK group. Lonner et al. [16] had identified the UIV at or cephalad to the UEV (upper end vertebrea) as an independent risk factor of PJK in Lenke 5 AIS patients. In terms of smaller preoperative MTC in PJK groups, we inferred that those individuals of smaller MTC were more frequently corrected by selected fusion, and not the long fusion of both curves. So, the UIV always tended to stop at the lower thoracic region, which increased the risk for PJK [16]. However, greater preoperative parameters [TK (P < 0.001), LL (P ¼ 0.017), and PJA (P ¼ 0.014)], and greater postoperative TLK (P ¼ 0.004), as well as greater postoperative PJA (P < 0.001) were detected in PJK groups (Tables 2 and 3). Previously, Lonner et al. [16] also detected higher PJA in the PJK group than the Non-PJK group. In addition, in the whole group, PJA increased in the follow-up compared to preoperative (Table 1). Given the fact that our study showed greater postoperative TLK (P ¼ 0.004) in PJK group, we suggest carefully contouring of the rod should be taken to moderately decrease the TLK in order to reduce the risk of PJK postoperative. On the other hand, greater C-SVA was observed in PJK group at final follow-up. Previously, it was assumed that a postoperative TK decrease led to kyphotic change in cervical sagittal alignment [17,18]. Additionally, the extent of the kyphotic change in cervical spine related to the extent of the extent of the decrease TK [19,20]. Wang et al. [21] also reported that cervical sagittal alignment was correlated with the whole thoracic sagittal alignment in a study of 30 Lenke 5C AIS patients. Correspondingly, Yagi et al. [22] founded that the cervical sagittal alignment was associated with the global sagittal balance. Our finding showed that cervical sagittal alignment was associated with PJK. In adult scoliosis, similar results also showed that the PJK patients had higher values of C-SVA [23]. Furthermore, the current study also detected smaller SVA in PJK group (1.59 ± 20.97) than in Non-PJK (13.70 ± 22.76) at follow-up. Although, a meta-analysis proposed that SVA difference>5 cm is risk factors for PJK(OR ¼ 2.53, 95 %CI 1.24e5.18, p ¼ 0.01) [24]. However, there are no relevant reports in AIS patients. We inferred that the smaller follow-up SVA in PJK groups might result from small preoperative SVA (2.94 ± 30.30) and postoperative SVA (4.91 ± 19.26). Even though there was no difference in pelvic parameters (PT: pelvic tilt, PI: pelvic incidence, and SS: sacrum slope), we cannot ignore the association between pelvic parameters and PJK in the long-term follow-up. For the elderly, PT and LL were important in compensating for the sagittal spinal misalignment. In adult scoliosis, increased PT and LL were observed for the PJK patients [23]. In the Lenke 5 AIS population, no young-to-adult long-term follow-up was obtained. However, we inferred that PJK occurred more frequently when osteoporosis or osteopenia happened with age. In that time, PT may change to compensate for the misalignment of the spine in Lenke 5 AIS patients following corrective surgery.
df
1 1 1 1
Sig.
0.021 0.000 0.010 0.000
Exp(B)
5.114 2.345 6.212 0.000
95%CI.for EXP(B) Lower
Upper
1.281 1.584 1.557
20.419 3.471 24.782
This study did not detect any differences in terms of SRS-22 score between PJK and Non-PJK groups. This finding was similar to Kim's report [25]. We inferred that the increased PJA did not influence the self-image and satisfaction [25], at least in a shortterm follow-up. Nevertheless, adequate attention should be given to the long-term clinical outcome of PJK in AIS, especially as these patients become older. Several risk factors of PJK had already been reported by previous studies. Based on a group of 193 AIS patients, Kim et al. [25] observed 3 related risk factors for PJK, including hybrid instrumentation, thoracoplasty, and greater preoperative TK (T5T12 > 40 ), with a mean follow-up of 7.3 years. In another study of 410 cases, Kim et al. [9] proposed that greater immediate postoperative TK angle decrease, and male sex correlated with PJK, and reported a higher prevalence of PJK in all-pedicle groups (35%) than the all hook (22%) and hybrid (29%) groups. Furthermore, Helgeson et al. [8] also reported a relatively higher prevalence of PJK in the all-screw group than the hybrid or the hook-only groups. The current study focused mainly on the risk factors for PJK in Lenke 5 AIS patients. Binary logistic regression based on aforementioned parameters showed that the disruption of junctional ligaments, postoperative PJA, and UIV at proximal or lower thoracic levels were the main risk factors of PJK. The disrupted posterior ligament at UIV/UIVþ1 resulted in a significant increase in range of motion at this level, which could be a risk factor for PJK, so the disruption should definitely be avoided during surgery [26]. Therefore, we recommend that the junctional ligaments should be protected, particularly in those individuals with UIV located in the lower thoracic region. In addition, the surgeon should use caution while working with the range of rod contouring at proximal fusion segments. Some limitations need to be considered in this study. First, it was a single-center study with a relatively small sample size. Second, even though there was no significant association between the PJK and SRS-22 score in this young population, it has been reported that PJK could influence the clinical outcome in the elderly, so the further long-term follow-up studies is necessary. Third, concerning lack of the full data related X-ray films at different time points, this study did not discuss whether the PJA is likely to increase with time.
5. Conclusion Greater postoperative PJA, disruption of junctional ligaments, and UIV at lower thoracic region were the main risk factors for PJK in Lenke 5 AIS patients. Therefore, we recommend that junctional ligaments should be preserved during surgery, especially in the individuals with UIV located in the lower thoracic region.
Conflict of interest None.
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
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J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
Acknowledgement This study was supported by Natural Science Fund of Shanghai (17441900500). We are very grateful for the help of Charlotte Isler in polishing the English text in this article. References [1] Mimura T, Takahashi J, Ikegami S, Kuraishi S, Shimizu M, Futatsugi T, Uehara M, Oba H, Koseki M, Kato H. Can surgery for adolescent idiopathic scoliosis of less than 50 degrees of main thoracic curve achieve good results? J Orthop Sci 2018 Jan;23(1):14e9. [2] Suk SI, Lee CK, Kim WJ, Chung YJ, Park YB. Segmental pedicle screw fixation in the treatment of thoracic idiopathic scoliosis. Spine 1995 Jun 15;20(12): 1399e405. [3] Ozkunt O, Karademir G, Sariyilmaz K, Gemalmaz HC, Dikici F, Domanic U. Analysing the change of sagittal balance in patients with Lenke 5 idiopathic scoliosis. Acta Orthop Traumatol Turcica 2017 Oct;51(5):377e80. [4] Raman T, Miller E, Martin CT, Kebaish KM. The effect of prophylactic vertebroplasty on the incidence of proximal junctional kyphosis and proximal junctional failure following posterior spinal fusion in adult spinal deformity: a 5-year follow-up study. Spine J 2017 Oct;17(10):1489e98. [5] Cho SK, Kim YJ, Lenke LG. Proximal junctional kyphosis following spinal deformity surgery in the pediatric patient. J Am Acad Orthop Surg 2015 Jul;23(7):408e14. [6] Hollenbeck SM, Glattes RC, Asher MA, Lai SM, Burton DC. The prevalence of increased proximal junctional flexion following posterior instrumentation and arthrodesis for adolescent idiopathic scoliosis. Spine 2008 Jul 01;33(15): 1675e81. [7] Lee GA, Betz RR, Clements 3rd DH, Huss GK. Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis. Spine 1999 Apr 15;24(8): 795e9. [8] Helgeson MD, Shah SA, Newton PO, Clements 3rd DH, Betz RR, Marks MC, Bastrom T. Evaluation of proximal junctional kyphosis in adolescent idiopathic scoliosis following pedicle screw, hook, or hybrid instrumentation. Spine 2010 Jan 15;35(2):177e81. [9] Kim YJ, Lenke LG, Bridwell KH, Kim J, Cho SK, Cheh G, Yoon J. Proximal junctional kyphosis in adolescent idiopathic scoliosis after 3 different types of posterior segmental spinal instrumentation and fusions: incidence and risk factor analysis of 410 cases. Spine 2007 Nov 15;32(24):2731e8. [10] Rhee JM, Bridwell KH, Won DS, Lenke LG, Chotigavanichaya C, Hanson DS. Sagittal plane analysis of adolescent idiopathic scoliosis: the effect of anterior versus posterior instrumentation. Spine 2002 Nov 01;27(21):2350e6. [11] Yang SH, Chen PQ. Proximal kyphosis after short posterior fusion for thoracolumbar scoliosis. Clin Orthop Relat Res 2003 Jun;(411):152e8. [12] Lenke LG, Betz RR, Haher TR, Lapp MA, Merola AA, Harms J, Shufflebarger HL. Multisurgeon assessment of surgical decision-making in adolescent idiopathic scoliosis: curve classification, operative approach, and fusion levels. Spine 2001 Nov 1;26(21):2347e53.
[13] Glattes RC, Bridwell KH, Lenke LG, Kim YJ, Rinella A, Edwards 2nd C. Proximal junctional kyphosis in adult spinal deformity following long instrumented posterior spinal fusion: incidence, outcomes, and risk factor analysis. Spine 2005 Jul 15;30(14):1643e9. [14] Wang J, Zhao Y, Shen B, Wang C, Li M. Risk factor analysis of proximal junctional kyphosis after posterior fusion in patients with idiopathic scoliosis. Injury 2010 Apr;41(4):415e20. [15] Denis F, Sun EC, Winter RB. Incidence and risk factors for proximal and distal junctional kyphosis following surgical treatment for Scheuermann kyphosis: minimum five-year follow-up. Spine 2009 Sep 15;34(20):E729e34. [16] Lonner BS, Ren Y, Newton PO, Shah SA, Samdani AF, Shufflebarger HL, Asghar J, Sponseller P, Betz RR, Yaszay B. Risk factors of proximal junctional kyphosis in adolescent idiopathic scoliosis-the pelvis and other considerations. Spine Deform 2017 May;5(3):181e8. [17] Ilharreborde B, Vidal C, Skalli W, Mazda K. Sagittal alignment of the cervical spine in adolescent idiopathic scoliosis treated by posteromedial translation. Eur Spine J 2013 Feb;22(2):330e7. [18] Hilibrand AS, Tannenbaum DA, Graziano GP, Loder RT, Hensinger RN. The sagittal alignment of the cervical spine in adolescent idiopathic scoliosis. J Pediatr Orthoped 1995;15(5):627e32. [19] Hwang SW, Samdani AF, Tantorski M, Cahill P, Nydick J, Fine A, Betz RR, Antonacci MD. Cervical sagittal plane decompensation after surgery for adolescent idiopathic scoliosis: an effect imparted by postoperative thoracic hypokyphosis. J Neurosurg Spine 2011 Nov;15(5):491e6. [20] Trobisch PD, Ducoffe AR, Lonner BS, Errico TJ. Choosing fusion levels in adolescent idiopathic scoliosis. J Am Acad Orthop Surg 2013 Sep;21(9): 519e28. [21] Wang F, Zhou XY, Xu XM, Yang YL, Zhu XD, Bai YS, Wei XZ, Li M. Cervical sagittal alignment limited adjustment after selective posterior thoracolumbar/ lumbar curve correction in patients with Lenke type 5C adolescent idiopathic scoliosis. Spine 2017 May;42(9):E539e46. [22] Yagi M, Iizuka S, Hasegawa A, Nagoshi N, Fujiyoshi K, Kaneko S, Takemitsu M, Shioda M, Machida M. Sagittal cervical alignment in adolescent idiopathic scoliosis. Spine Deform 2014-Mar;2(2):122e30. [23] Zhao J, Yang M, Yang Y, Yin X, Yang C, Li L, Li M. Proximal junctional kyphosis in adult spinal deformity: a novel predictive index. Eur Spine J 2018 Mar 5 [Epub ahead of print]. [24] Liu FY, Wang T, Yang SD, Wang H, Yang DL, Ding WY. Incidence and risk factors for proximal junctional kyphosis: a meta-analysis. Eur Spine J 2016 Aug;25(8):2376e83. [25] Kim YJ, Bridwell KH, Lenke LG, Kim J, Cho SK. Proximal junctional kyphosis in adolescent idiopathic scoliosis following segmental posterior spinal instrumentation and fusion: minimum 5-year follow-up. Spine 2005 Sep 15;30(18): 2045e50. [26] Lange T, Schulte TL, Gosheger G, Schulze Boevingloh A, Mayr R, Schmoelz W. Effects of multilevel posterior ligament dissection after spinal instrumentation on adjacent segment biomechanics as a potential risk factor for proximal junctional kyphosis: a biomechanical study. BMC Muscoskel Disord 2018 Feb 14;19(1):57.
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
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Original Article
Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient Jian Zhao 1, Mingyuan Yang 1, Yiling Yang 1, Ziqiang Chen**, Ming Li* Department of Orthopedics, Changhai Hospital, Second Military Medical University, Shanghai, People's Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 January 2018 Received in revised form 4 May 2018 Accepted 29 May 2018 Available online xxx
Background: To investigate the risk factors of proximal junctional kyphosis (PJK) in Lenke 5 AIS patients after all-pedicle instrumentation and correction, and to compare the difference of radiographic and clinical outcome between PJK and Non-PJK populations. Method: Medical records of Lenke 5 AIS patients were reviewed from January 2008 to January 2013, included posteroanterior and lateral full spine X-ray films preoperatively, postoperatively (4e7 days after surgery), and at final follow-up. Demographic data and radiologic parameters were evaluated. Based on the proximal junctional angle (PJA) at final follow-up, those patients were divided into 2 groups: PJK group (n ¼ 35, PJAS10 ), and Non-PJK group (n ¼ 52, PJA<10 ). Comparisons analyses between PJK and Non-PJK groups were carried out. Binary logistic Regression analysis was performed to detect the risk factors of PJK at follow-up. Results: The current study recruited 87 Lenke 5 AIS patients with average follow-up of 4.67 ± 1.17 years. Significant differences between PJK and Non-PJK groups were observed as follows: UIV(P ¼ 0.010), the disruption of junctional ligaments (P < 0.001); preoperative variables [MTC (P ¼ 0.001), TK(P < 0.001), LL (P ¼ 0.017), SVA (P ¼ 0.036), and PJA (P ¼ 0.014)], postoperative variables [TLK(P ¼ 0.004), and PJA (P < 0.001)], and follow-up [SVA (P ¼ 0.014), C-SVA (P < 0.001), and PJA (P0.001). Binary logistic regression showed that the disruption of junctional ligaments, postoperative PJA and UIV (upper instrumented vertebra) at proximal or lower thoracic levels were the main risk factors of PJK [Odds Ratio (OR) ¼ 5.114, 2.345, and 6.212, respectively]. However, the SRS-22 scores did not change significantly in PJK and Non-PJK groups. Conclusion: Greater postoperative PJA, disruption of junctional ligaments, UIV at lower thoracic levels were the main risk factors for PJK in Lenke 5 AIS patients. Recommedation: Preserve junctional ligaments in those individuals with UIV located in the lower thoracic region. © 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
1. Introduction For those severe adolescent idiopathic scoliosis (AIS) patients, corrective surgery can be used to reconstruct the coronal and sagittal alignment [1]. With the use of all-pedicle technique, surgeons can efficiently correct the coronal deviation [2]. However,
* Corresponding author. Department of Orthopaedics, Changhai Hospital, 168 Changhai Street, Shanghai 200433, China. Fax: þ86 21-51190920. ** Corresponding author. Department of Orthopaedics, Changhai Hospital, 168 Changhai Street, Shanghai 200433, China. E-mail addresses: [email protected] (Z. Chen), [email protected] (M. Li). 1 These authors contributed equally to this work.
strong correction of all-pedicle instrumentation also resulted in a series of issues such as the decrease of thoracic kyphosis (TK) [3]. Moreover, the phenomenon of proximal junctional kyphosis (PJK) has drawn the attention of many spine surgeons, because PJK was associated with the clinical outcome in elderly populations [4]. Based on different diagnostic criteria of PJK, a series of studies reported the prevalence ranging from 9.2% to 46% [5e7], but only a few PJK caused symptoms. Correspondingly, several studies have focused on the risk factor of PJK in AIS patients after corrective surgery. The cause of PJK may be related to the difference in scoliosis types, surgical techniques and in fusion selections. Helgeson et al. [8] found that all-pedicle screw constructs led to higher PJK prevalence compared with hook-only and hybrid instrumentation.
https://doi.org/10.1016/j.jos.2018.05.010 0949-2658/© 2018 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
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J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
Kim et al. [9] reported risk factors which included preoperative thoracic hyperkyphosis (TKS40 ), TK decline by 5 , and male gender. However, in another study of 208 consecutive AIS patients, Helgeson et al. [6] did not report any risk factors. When referring to clinical outcome, previous studies indicated that PJK did not significantly affect the Health-Related Quality of Life (HRQOL) [10]. In terms of Lenke 5 AIS patients, Yang et al. [11] reported the prevalence of 43% of PJK after posterior selective lumbar fusion. Correspondingly, Hollenbeck et al. [6] reported that 1 out of 13 Lenke 5 AIS patients suffered from PJK. There are few articles focused on PJK in Lenke 5 AIS patients. The purpose of this study is to investigate the risk factors of proximal junctional kyphosis (PJK) in Lenke 5 AIS patients after all-pedicle instrumentation and correction, and to compare the difference of radiographic and clinical outcome between PJK and Non-PJK populations. 2. Methods and materials 2.1. Patient population This study was approved by the Institutional Review Board of Changhai hospital, and all patients were informed of the contents of the study. Lenke 5 AIS patients treated by posterior corrective surgery in our hospital from January 2008 to January 2013 were assessed retrospectively. Each patient had to meet these criteria for inclusion in this study: (1) Lenke 5 AIS patients ages of 11e18 years; (2) TL/LC(Thoracolumbar/lumbar curve) > 40 ; (3) Onestage posterior pedicle screw instrumentation and corrective surgery performed by the same group; (4) minimal followed-up for 2 years.
2.2. Data collection Surgeries were planned and carried out by the same group according to Lenke's suggestion for fusion levels [12]. If selective fusion was performed, the upper-instrumented vertebra (UIV) always stopped at proximal end vertebra. Otherwise, the fusion segments included both thoracolumbar/lumbar curve and major thoracic curve, which meant the UIV frequently existed at the upper thoracic region. The lower instrumented vertebra (LIV) always stopped at neutral vertebrae on standing films. The following demographic data were recorded: Age (years), Gender (Female/Male), Risser sign, the time of final follow up (years), UIV, LIV, status of junctional ligaments (Disrupted/Preserved). The disrupted supraspinous and interspinous ligaments between the UIV and the supra-adjacent vertebra were defined as disrupted junctional ligaments. UIV stopped at proximal thoracic region (at T9 and upper vertebras) or lower thoracic region (at T10 and lower vertebras) was analyzed, separately. The standing posteroanterior and lateral X-ray films before surgery, postoperatively (4e7 days after surgery), and at final follow-up were collected. On the posteroanterior X-ray film, MTC (major thoracic curve), and TL/LC (thoracolumbar/lumbar curve) were measured for further analysis. On the lateral film, the following parameters were measured: C2eC7 lordosis (CL), C2eC7 sagittal vertical axis (CSVA), T5-T12 kyphosis (TK), T10-L2 kyphosis (TLK), lumbar lordosis (LL), sagittal vertical axis (SVA), and proximal junctional angle (PJA). The CL was the angle between the inferior endplate of C2 and the inferior endplate of C7. PJA referred to the angle between the lower end plate of the UIV and the upper end plate of the second supra adjacent vertebrae [13]. When PJA 10 or increased by 10 greater than the preoperative measurement, PJK was diagnosed (Fig. 1).
Fig. 1. An example of proximal junctional kyphosis (PJK) following corrective surgery. Corrective surgery was performed at the age of 13. PJA was 24 at 10 years' follow-up.
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
Moreover, the pelvic sagittal radiographic parameters, including pelvic tilt (PT), pelvic incidence (PI), and sacral slope (SS), were measured. The Scoliosis Research Society (SRS)-22 questionnaire was used to assess the clinical outcome of those individuals. The questionnaire survey was performed before the surgery, and at final follow-up.
2.3. Statistical analysis The statistical analyses were conducted by SPSS 18.0. Descriptive statistics were presented in the form of mean with standard deviation (SD), and count data were presented in numbers. Repeated Measure Design Within-Subject Factors was used to assess the effect of surgical correction on aforementioned parameters. If normal distribution was guaranteed, independent twosample t test was used to compare the differences of variables between PJK and Non-PJK groups. Alternatively, ManneWhitney U test was performed. Chi-square test was used to investigate the distribution differences of categorical data. To reveal independent risk factors of PJK at final follow-up, binary logistic regression models were constructed using variables that were of significance in univariate analysis.
3. Results 3.1. General information Initially, 126 Lenke 5 AIS patients were identified from the database. After the inclusion and exclusion process, there were 87 (69.05%) Lenke 5 AIS patients (female/male: 66/21) recruited for this study. The average age, Risser sign, and follow-up time were 13.51 ± 1.27 years, 3.7 ± 0.83, 4.67 ± 1.17years, respectively. The detailed demographic parameters are demonstrated in Table 1.
Table 1 Demographic and radiological parameters based on 87 Lenke 5 AIS patients. Variables Demographic details
Mean ± SD
Age (years) Gender (Female/Male) Risser Follow up time (years) UIV at upper/lower thoracic UIV(T3/T4/T5/T6/T8/T9/T10/T11/T12) LIV(L3/L4/L5) JL (Disrupted/Preserved)
13.85 ± 1.49 66/21 3.70 ± 0.83 4.67 ± 1.17 51/36 1/11/9/4/7/19/19/14/3 29/51/7 39/48
Radiologic parameters MTC TL/LC TK TLK LL PT PI SS SVA C-SVA CL PJA Clinical Outcome SRS-22 (n ¼ 39)
Mean ± SD Preoperative
Postoperativeerative Follow-up
19.89 ± 7.76 44.78 ± 5.72 23.54 ± 9.42 5.89 ± 3.24 45.94 ± 10.47 10.79 ± 6.05 45.86 ± 7.25 35.00 ± 6.83 10.03 ± 25.96 14.83 ± 5.96 14.95 ± 8.88 5.38 ± 2.13
9.82 ± 3.91 12.02 ± 4.12 20.25 ± 8.69 7.13 ± 2.85 44.78 ± 8.91 7.93 ± 5.36 45.97 ± 6.81 37.98 ± 6.23 9.40 ± 21.50 16.05 ± 5.99 15.15 ± 7.83 6.61 ± 2.57
3.98 ± 0.26
Value of P
10.11 ± 3.71 12.41 ± 3.83 24.01 ± 9.08 8.41 ± 2.59 45.49 ± 8.93 11.79 ± 6.32 45.38 ± 5.68 33.60 ± 6.63 8.83 ± 22.73 18.85 ± 7.46 16.87 ± 8.19 9.31 ± 4.73
<0.001 <0.001 0.523 <0.001 0.693 0.098 0.371 0.060 0.591 <0.001 0.001 <0.001
3.94 ± 0.14
0.393*
JL meant junctional ligaments comprised of the supraspinous and interspinous ligaments between the uppermost instrumented the supra-adjacent vertebra. “*” mean the value P was calculated by ManneWhitney U test.
3
Preoperatively, the Mean ± SD of MTC, TL/LC, TK, TLK, LL, PT, PI, SS, SVA, C-SVA, CL, PJA, was 19.89 ±7.76 , 44.78 ±5.72 , 23.54 ±9.42 , 5.89 ±3.24 , 45.94 ±10.47, 10.79 ±6.05 , 45.86 ±7.25 , 35.00 ±6.83 , 10.03 mm ± 25.96 mm, 16.15 mm ± 7.02 mm, 14.95 ±8.88 , 5.38 ±2.13 , respectively. Postoperatively (3e7 days after surgery), the corresponding value was 9.82 ±3.91, 12.02 ±4.12 , 20.25 ±8.69 , 7.13 ±2.85 , 44.78 ±8.91, 7.93 ±5.36 , 45.97 ±6.81, 37.98 ±6.23 , 9.40 mm ± 21.50 mm, 16.05 mm ± 5.99 mm, 15.15 ±7.83 , and 6.61 ±2.57, respectively. At final follow-up, the corresponding figure was 10.11 ±3.71, 12.41 ±3.83 , 24.01 ±9.08 , 8.41 ±2.59 , 45.49 ±8.93 , 11.79 ±6.32 , 45.38 ±5.68 , 33.60 ±6.63 , 8.83 mm ± 22.73 mm, 18.85 mm ± 7.46 mm, 16.87 ±8.19 , 9.31 ±4.73 , respectively. Table 1 presents the details of these parameters. As was demonstrated in Table 1, surgical correction had significantly changed MTC(P < 0.001), TL/LC(P < 0.001), TLK(P < 0.001), C-SVA (P < 0.001), CL (P ¼ 0.001) and PJA (P < 0.001). However, there was no difference in terms of TK, LL, PT, PI, SS, and SVA. Additionally, surgical correction did not significantly change the SRS-score (Table 1). 3.2. Comparison analysis between PJK and Non-PJK groups At final follow-up, there were 35 patients (40.23%) out of 87 Lenke 5 AIS patients) who had PJK (PJK group) at follow-up, while the rest of 52 patients demonstrated no significant PJK (Non-PJK group). Between PJK and Non-PJK groups, significant differences of parameters were observed in the following variables: UIV(P ¼ 0.010), the disrupteion of junctional ligaments (P < 0.001); preoperative data including MTC (P ¼ 0.001), TK(P < 0.001), LL (P ¼ 0.017), SVA (P ¼ 0.036), and PJA (P ¼ 0.014), postoperative data including TLK(P ¼ 0.004), and PJA (P < 0.001), and final follow-up data including SVA (P ¼ 0.014), C-SVA (P < 0.001), and PJA (P < 0.001) (Tables 2 and 3). However, no significant difference were found in age, Risser sign, gender distribution, follow-up time, or LIV between the two groups (Table 2). Additionally, no difference were observed in those preoperative radiological parameters (TL/LC, CL, TLK, C-SVA, PT, PI, and SS), postoperative radiological parameters (MTC, TL/LC, TK, CL, C-SVA, LL, PT, PI, SS and SVA) and radiological parameters at followup (MTC, TL/LC, TK, TLK, LL, PT, PI, CL, and SS) (Table 3). Comparison analysis detected no significant differences in SRS22 scores preoperatively (P ¼ 0.375), and at final follow-up (P ¼ 0.654) (Table 2). 3.3. Binary logistic regression analysis To investigate the main risk factors of PJK, binary logistic regression was conducted. Initially, univariate analysis was performed to reveal confounding variables, which showed risk factors were as follows: preoperative MTC, JL (Disrupted/Preserved), preoperative TK, postoperative TLK, preoperative LL, preoperative SVA, preoperative PJA, UIV at proximal or lower thoracic region, and postoperative PJA (Table 4). Then, binary logistic regression based on the aforementioned paramaters showed that the disruption of junctional ligaments, postoperative PJA and UIV at proximal or lower thoracic levels were the main risk factors of PJK [Odds Ratio (OR) ¼ 5.114, 2.345, and 6.212, respectively] (Table 5). 4. Discussion For AIS patients, PJK was a common phenomenon after corrective surgery. Previously, several studies had reported its prevalence ranging from 9.2% to 46% based on different cut-offs of PJA [6,7,14]. Despite several reports about the rate of PJK in AIS patients, there
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
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J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
Table 2 Comparison analysis between two groups in terms of demographic data. Variables
PJK(N ¼ 35)
Non-PJK(N ¼ 52)
P
Age (years) Gender (Female/Male) Risser Follow up time (years) UIV(T3/T4/T5/T6/T8/T9/T10/T11/T12) UIV at upper/lower thoracic LIV(L3/L4/L5) JL (Disrupted/Preserved) Preoperative SRS-22 score Follow-up SRS-22 score
13.26 ± 1.18 26/9 3.74 ± 0.86 4.43 ± 1.14 1/1/0/1/5/7/12/7/1 15/20 7/19/1 24/11 3.92 ± 0.34 3.94 ± 0.18
13.62 ± 1.30 40/12 3.62 ± 0.83 4.83 ± 1.17 0/10/9/3/2/12/7/7/2 36/16 19/28/5 15/37 4.02 ± 0.17 3.93 ± 0.10
0.225 0.486 0.269* 0.188* 0.010 0.016 0.523 <0.001 0.375* 0.654*
JL meant junctional ligaments comprised of the supraspinous and interspinous ligaments between the UIV and the supra-adjacent vertebra. “*” mean the value P was calculated by ManneWhitney U test.
Table 3 Comparison analysis between two groups in terms of radiological parameters. Variables
MTC TL/LL TK TLK LL PT PI SS SVA C-SVA CL PJA
group
PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK PJK Non-PJK
Preoperative
Postoperative
Follow-up
Mean ± SD
P
Mean ± SD
P
Mean ± SD
P
16.43 ± 5.68 22.21 ± 8.15 43.46 ± 3.87 45.67 ± 6.57 28.31 ± 7.80 20.33 ± 9.10 6.40 ± 3.28 5.54 ± 3.19 49.17 ± 9.61 43.77 ± 10.55 10.09 ± 5.88 11.26 ± 6.17 45.54 ± 5.88 46.07 ± 8.10 35.46 ± 5.40 34.69 ± 7.68 2.94 ± 30.30 14.80 ± 21.61 17.71 ± 7.90 15.04 ± 6.21 15.38 ± 7.63 14.66 ± 9.69 6.09 ± 2.17 4.90 ± 1.99
0.001*
9.60 ± 4.74 9.96 ± 3.28 11.63 ± 4.15 12.29 ± 4.10 21.43 ± 8.68 19.46 ± 8.69 8.17 ± 2.58 6.42 ± 2.83 46.29 ± 9.30 43.77 ± 8.58 7.26 ± 5.52 8.38 ± 5.25 45.80 ± 5.76 46.08 ± 7.49 38.40 ± 6.87 37.69 ± 5.78 4.91 ± 19.26 12.42 ± 22.56 16.60 ± 7.24 15.67 ± 5.03 15.49 ± 6.76 14.92 ± 8.53 8.63 ± 2.12 5.25 ± 1.87
0.831*
9.51 ± 3.89 10.52 ± 3.56 11.69 ± 4.12 12.90 ± 3.58 25.40±±9.46 23.08 ± 8.77 9.00 ± 2.63 8.01 ± 2.50 46.37 ± 9.65 44.90 ± 8.45 10.89 ± 4.78 12.38 ± 7.16 45.11 ± 5.03 45.56 ± 6.11 34.23 ± 6.42 33.18 ± 6.80 1.59 ± 20.97 13.70 ± 22.76 22.97 ± 7.57 16.08 ± 6.01 19.17 ± 6.71 15.33 ± 8.78 14.20 ± 3.30 6.02 ± 1.78
0.217
0.145* <0.001 0.225 0.017 0.355* 0.743 0.611 0.036 0.081 0.859* 0.014*
0.466 0.303 0.004 0.198 0.320* 0.854 0.300* 0.111 0.388 0.862* <0.001
0.180* 0.247* 0.081 0.455 0.211* 0.723 0.471 0.014 <0.001 0.059* <0.001*
“*” mean the value P was calculated by ManneWhitney U test. Independent Samples Test. Calculated the rest of values of P.
Table 4 Univariate analysis for risk factors of PJK. Variable
Preoperative MTC JL (Disrupted/Preserved) Preoperative TK Postoperative TLK Preoperative LL Preoperative SVA Preoperative PJA Postoperative PJA UIV at proximal or lower thoracic
B
0.109 1.683 0.107 0.238 0.052 0.019 0.280 0.918 1.099
S.E.
0.034 0.476 0.030 0.088 0.023 0.009 0.112 0.201 0.455
Wald
10.555 12.519 13.049 7.281 5.289 4.163 6.198 20.816 5.832
was insufficient information on the PJK phenomenon in Lenke 5 AIS patients. Yang et al. [11] reported the prevalence of 43% after short posterior spinal fusion in a group of 14 thoracolumbar idiopathic scoliosis patients. Correspondingly, Hollenbeck et al. [6] reported that 1 out of 13 Lenke 5 AIS patients developed PJK. Our study included 87 Lenke 5 AIS patients following one-stage posterior allpedicle instrumentation and correction. With the PJK cut-off of
df
1 1 1 1 1 1 1 1 1
Sig.
0.001 0.000 0.000 0.007 0.021 0.041 0.013 0.000 0.016
Exp(B)
0.90 5.38 1.11 1.27 1.05 1.02 1.32 2.50 3.00
95%CI.for EXP(B) Lower
Upper
0.84 2.12 1.05 1.07 1.01 1.00 1.06 1.69 1.23
0.96 13.67 1.18 1.51 1.10 1.04 1.65 3.71 7.32
10 , the study showed the prevalence of PJK was 40.23% (35 out of 87) with the average follow-up of 4.67 ± 1.17 years. At final followup, surgical correction significantly corrected the TL/LC(P < 0.001), and MTC(P < 0.001), and both TLK and cervical lordosis increased. However, TK, LL and pelvic parameters did not changed significantly. Comparison analyses were performed between PJK and non-PJK groups. They showed that a greater frequency of disrupted
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
J. Zhao et al. / Journal of Orthopaedic Science xxx (2018) 1e6
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Table 5 Binary logistic regression analysis (Forward Wald method) for risk factors of PJK. Variables
Disruption of junctional ligaments Postoperative PJA UIV at proximal or lower thoracic Constant
B
1.632 0.852 1.827 7.954
S.E.
0.706 0.200 0.706 1.665
Wald
5.339 18.137 6.695 22.824
junctional ligaments (P < 0.001) in the PJK group. In a group of Scheuermann kyphosis cases, Denis et al. [15] also reported the positive association between disrupted junctional ligaments with PJK. In addition, there were more patients with UIV stopped at lower thoracic levels in the PJK group. Lonner et al. [16] had identified the UIV at or cephalad to the UEV (upper end vertebrea) as an independent risk factor of PJK in Lenke 5 AIS patients. In terms of smaller preoperative MTC in PJK groups, we inferred that those individuals of smaller MTC were more frequently corrected by selected fusion, and not the long fusion of both curves. So, the UIV always tended to stop at the lower thoracic region, which increased the risk for PJK [16]. However, greater preoperative parameters [TK (P < 0.001), LL (P ¼ 0.017), and PJA (P ¼ 0.014)], and greater postoperative TLK (P ¼ 0.004), as well as greater postoperative PJA (P < 0.001) were detected in PJK groups (Tables 2 and 3). Previously, Lonner et al. [16] also detected higher PJA in the PJK group than the Non-PJK group. In addition, in the whole group, PJA increased in the follow-up compared to preoperative (Table 1). Given the fact that our study showed greater postoperative TLK (P ¼ 0.004) in PJK group, we suggest carefully contouring of the rod should be taken to moderately decrease the TLK in order to reduce the risk of PJK postoperative. On the other hand, greater C-SVA was observed in PJK group at final follow-up. Previously, it was assumed that a postoperative TK decrease led to kyphotic change in cervical sagittal alignment [17,18]. Additionally, the extent of the kyphotic change in cervical spine related to the extent of the extent of the decrease TK [19,20]. Wang et al. [21] also reported that cervical sagittal alignment was correlated with the whole thoracic sagittal alignment in a study of 30 Lenke 5C AIS patients. Correspondingly, Yagi et al. [22] founded that the cervical sagittal alignment was associated with the global sagittal balance. Our finding showed that cervical sagittal alignment was associated with PJK. In adult scoliosis, similar results also showed that the PJK patients had higher values of C-SVA [23]. Furthermore, the current study also detected smaller SVA in PJK group (1.59 ± 20.97) than in Non-PJK (13.70 ± 22.76) at follow-up. Although, a meta-analysis proposed that SVA difference>5 cm is risk factors for PJK(OR ¼ 2.53, 95 %CI 1.24e5.18, p ¼ 0.01) [24]. However, there are no relevant reports in AIS patients. We inferred that the smaller follow-up SVA in PJK groups might result from small preoperative SVA (2.94 ± 30.30) and postoperative SVA (4.91 ± 19.26). Even though there was no difference in pelvic parameters (PT: pelvic tilt, PI: pelvic incidence, and SS: sacrum slope), we cannot ignore the association between pelvic parameters and PJK in the long-term follow-up. For the elderly, PT and LL were important in compensating for the sagittal spinal misalignment. In adult scoliosis, increased PT and LL were observed for the PJK patients [23]. In the Lenke 5 AIS population, no young-to-adult long-term follow-up was obtained. However, we inferred that PJK occurred more frequently when osteoporosis or osteopenia happened with age. In that time, PT may change to compensate for the misalignment of the spine in Lenke 5 AIS patients following corrective surgery.
df
1 1 1 1
Sig.
0.021 0.000 0.010 0.000
Exp(B)
5.114 2.345 6.212 0.000
95%CI.for EXP(B) Lower
Upper
1.281 1.584 1.557
20.419 3.471 24.782
This study did not detect any differences in terms of SRS-22 score between PJK and Non-PJK groups. This finding was similar to Kim's report [25]. We inferred that the increased PJA did not influence the self-image and satisfaction [25], at least in a shortterm follow-up. Nevertheless, adequate attention should be given to the long-term clinical outcome of PJK in AIS, especially as these patients become older. Several risk factors of PJK had already been reported by previous studies. Based on a group of 193 AIS patients, Kim et al. [25] observed 3 related risk factors for PJK, including hybrid instrumentation, thoracoplasty, and greater preoperative TK (T5T12 > 40 ), with a mean follow-up of 7.3 years. In another study of 410 cases, Kim et al. [9] proposed that greater immediate postoperative TK angle decrease, and male sex correlated with PJK, and reported a higher prevalence of PJK in all-pedicle groups (35%) than the all hook (22%) and hybrid (29%) groups. Furthermore, Helgeson et al. [8] also reported a relatively higher prevalence of PJK in the all-screw group than the hybrid or the hook-only groups. The current study focused mainly on the risk factors for PJK in Lenke 5 AIS patients. Binary logistic regression based on aforementioned parameters showed that the disruption of junctional ligaments, postoperative PJA, and UIV at proximal or lower thoracic levels were the main risk factors of PJK. The disrupted posterior ligament at UIV/UIVþ1 resulted in a significant increase in range of motion at this level, which could be a risk factor for PJK, so the disruption should definitely be avoided during surgery [26]. Therefore, we recommend that the junctional ligaments should be protected, particularly in those individuals with UIV located in the lower thoracic region. In addition, the surgeon should use caution while working with the range of rod contouring at proximal fusion segments. Some limitations need to be considered in this study. First, it was a single-center study with a relatively small sample size. Second, even though there was no significant association between the PJK and SRS-22 score in this young population, it has been reported that PJK could influence the clinical outcome in the elderly, so the further long-term follow-up studies is necessary. Third, concerning lack of the full data related X-ray films at different time points, this study did not discuss whether the PJA is likely to increase with time.
5. Conclusion Greater postoperative PJA, disruption of junctional ligaments, and UIV at lower thoracic region were the main risk factors for PJK in Lenke 5 AIS patients. Therefore, we recommend that junctional ligaments should be preserved during surgery, especially in the individuals with UIV located in the lower thoracic region.
Conflict of interest None.
Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010
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Please cite this article in press as: Zhao J, et al., Proximal junctional kyphosis following correction surgery in the Lenke 5 adolescent idiopathic scoliosis patient, Journal of Orthopaedic Science (2018), https://doi.org/10.1016/j.jos.2018.05.010