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postoperative spinal alignment remodeling


The Spine Journal

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(2011)

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Clinical Study

Postoperative spinal alignment remodeling in Lenke 1C scoliosis treated with selective thoracic fusion
Yu Wang, MDa,b,*, Cody E. Bnger, MD, DMSca, Yanqun Zhang, MDa, u Chunsen Wu, MDc, Ebbe S. Hansen, MD, DMSca
Department of Orthopaedics E, Aarhus University Hospital, Norrebrogade 44, Aarhus 8000, Denmark Department of Orthopaedics, Peking University First Hospital, Xishiku street 8, Beijing 100034, China c Department of Epidemiology, School of Public Health, Aarhus University, Nordre Ringgade 1, Aarhus 8000, Denmark
b a

Received 3 February 2011; revised 24 July 2011; accepted 22 October 2011

Abstract

BACKGROUND CONTEXT: Selective thoracic fusion may cause spinal imbalance in certain patients; how the spinal alignment changes over time after surgery is highly correlated with the ?nal spinal balance. PURPOSE: To investigate how spinal alignment changes over time after selective thoracic fusion and how spinal alignment remodeling affects spinal balance. METHODS: All adolescent idiopathic scoliosis (AIS) cases surgically treated in our institution between 2002 and 2008 were reviewed. Inclusion criteria were as follows: Lenke 1C scoliosis patients treated with posterior pedicle screw–only constructs; the lowest instrumented vertebra (LIV) ended at L1 level or above; and 2-year radiographic follow-up. Standing anteroposterior and lateral digital radiographs from four different time points (preoperatively, immediately, 3 months, and 2 years postoperatively) were reviewed. In each standing anteroposterior radiograph, the center sacral vertical line (CSVL, the vertical line that bisects the proximal sacrum) was ?rst drawn, and the translation (deviation from the CSVL) of some key vertebrae was measured, such as the LIV, LIV?1 (the ?rst vertebra below LIV), LIV?2 (the second vertebra below LIV), LIV?3 (the third vertebra below LIV), lumbar apical vertebra (AV), thoracic AV, and T1. Additionally, the Cobb angles of the major thoracic and lumbar curves were measured at different time points, and the correction rates were calculated. Furthermore, clinical photographs of the patients from the back were taken preoperatively and postoperatively. RESULTS: Of 278 AIS patients reviewed, 29 met the inclusion criteria. The continuous follow-up of our present study revealed an interesting phenomenon: postoperative spinal alignment remodeling. A hypothetical criterion was established to determine the onset of the phenomenon. By means of a series of analyses, the criterion was validated. The results of our present study showed that selective thoracic fusion tended to cause leftward spinal imbalance in these Lenke 1C AIS patients. Twenty of the 29 patients had leftward spinal imbalance immediately after surgery. Although some patients regained spinal balance through postoperative spinal alignment remodeling, 11 patients remained imbalanced at 2-year follow-up. CONCLUSIONS: Selective thoracic fusion is prone to cause leftward spinal imbalance in Lenke 1C scoliosis patients. Postoperative spinal alignment remodeling can facilitate recovery of spinal balance in some patients. Postoperative spinal imbalance in Lenke 1C scoliosis patients could be prevented by selecting stable vertebra or the vertebrae above as LIV, checking the balance condition during surgery, or considering ratio criteria when selecting candidates for selective thoracic fusion. ? 2011 Elsevier Inc. All rights reserved.
Idiopathic scoliosis; Lenke 1C; Imbalance; Decompensation; Spinal alignment remodeling

Keywords:

FDA device/drug status: Not applicable. Author disclosures: YW: Nothing to disclose. CEB: Nothing to disclose. YZ: Nothing to disclose. CW: Nothing to disclose. ESH: Nothing to disclose. 1529-9430/$ - see front matter ? 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2011.10.024

* Corresponding author. Department of Orthopaedics E, Aarhus University Hospital, Norrebrogade 44, Aarhus 8000, Denmark. Tel.: (45) 52220123; fax: (45) 78464150. E-mail address: yu.wang@ki.au.dk (Y. Wang)

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Y. Wang et al. / The Spine Journal

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(2011)

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Introduction Selective thoracic fusion is a treatment option for patients who have adolescent idiopathic scoliosis (AIS). King et al. [1] recommended that patients with Type II (major thoracic/compensatory lumbar) curves be treated with selective thoracic fusion. According to the surgical classi?cation developed in 2001 by Lenke et al. [2], selective thoracic fusion can be chosen when the lumbar curve is nonstructural. Selective thoracic fusion may cause leftward spinal imbalance in certain patients [3–7]. How the spinal alignment changes over time after surgery is highly correlated with the ?nal balance of the spine. We have observed that spinal alignment sometimes changes substantially in the few years after surgery. This change, a phenomenon that we refer to as ‘‘postoperative spinal alignment remodeling,’’ can enable some patients to regain spinal balance. How spinal alignment changes over time after selective thoracic fusion and how postoperative spinal alignment remodeling affects spinal balance have not been well investigated. In addition, one of the drawbacks of some previous studies is that different curve patterns were included or different surgical approaches were undertaken, which may obscure ?ndings speci?c to a certain group of patients. Postoperative curve behavior could vary if the curve pattern or construct type differs. Furthermore, many previous studies were not based on posterior pedicle screw–only constructs, an approach that is becoming increasingly used for the treatment of AIS. It remains unclear how posterior pedicle screw–only constructs affect postoperative spinal balance. The purposes of this study were, therefore, to investigate changes in spinal alignment after selective thoracic fusion in Lenke 1C type AIS treated with posterior pedicle screw–only constructs and evaluate the effect of postoperative spinal alignment remodeling on spinal balance.

radiographs were reviewed at four times (preoperatively, immediately, 3 months, and 2 years postoperatively). In each standing anteroposterior radiograph, the center sacral vertical line (CSVL, the vertical line that bisects the proximal sacrum) was ?rst drawn. The translation (deviation from the CSVL) of some key vertebrae was then measured, such as the LIV, LIV?1 (the ?rst vertebra below LIV), LIV?2 (the second vertebra below LIV), LIV?3 (the third vertebra below LIV), lumbar AV, thoracic AV, and T1 (Fig. 1). These measurements allowed us to depict how the translation of different parts of the spine changed over time. Additionally, the Cobb angles of major thoracic and lumbar curves were measured at the four times, and then the correction rate was calculated: correction rate5(preoperative Cobb angle?postoperative Cobb angle)O(preoperative Cobb angle)?100%. All measurements were performed by one of the two authors and repeated by the other. The mean values of the measurements made by the two authors were used for the ?nal analyses, and measurement errors were calculated. Back appearance evaluation Clinical photographs of the patients from the back were taken before and 1 week after surgery. Surgical maneuvers Several surgical maneuvers were used intraoperatively, including rod rotation, distraction on the concave side, compression on the convex side, and sometimes in situ contouring. Statistical analysis Mean values are reported with the range in parentheses. The t test was used to detect the difference in each parameter between every two times. A secondary (post hoc) analysis categorized the patients into two groups: the remodeling group in which thoracic AV shifted toward the right side by more than 5 mm at 2-year follow-up and the noremodeling group. Repeated-measures analysis of variance was used to test the difference in the translation trend between the two groups. The Fisher exact test was used to compare the proportion of improvement in 3-month translation between the two groups. The signi?cance level was de?ned as 0.05. The data were analyzed by means of STATA 10.1 software (Stata Corp., College Station, TX, USA).

Materials and methods Inclusion criteria We reviewed all the AIS cases surgically treated in our institution from 2002 to 2008. Collection and analysis of radiographic and clinical data were performed by two authors who were not directly involved in the patients’ surgery. Inclusion criteria were as follows: Lenke 1C scoliosis patients treated with posterior pedicle screw–only constructs; the lowest instrumented vertebra (LIV) ended at L1 level or above; and 2-year radiographic follow-up. Radiographic measurements All image data were available, and all measurements were performed in our picture archiving and communication systems. Standing anteroposterior and lateral digital

Results Of 278 AIS patients reviewed, 29 met the inclusion criteria. Median age at surgery was 16 years, ranging from 13 to 23.7 years. The LIV was T11 in one patient, T12 in 21 patients, and L1 in the remaining seven patients.

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Fig. 1. De?nitions of the radiographic parameters: CSVL, center sacral vertical line, the vertical line that bisects proximal sacrum [2]; AV, apical vertebra; LIV, lowest instrumented vertebra; LIV?1, the ?rst vertebra below LIV; LIV?2, the second vertebra below LIV; LIV?3, the third vertebra below LIV; AVT, apical vertebra translation, distance in millimeters from the CSVL to the midpoint of the apical body. The midpoint of a vertebral body is determined by drawing a cross (?) in the body: a line is drawn from the upper left corner to the lower right of the body/disc and from the upper right to the lower left of the body/disc. The intersection is the midpoint; when the midpoint is on the right side of the CSVL, the value of the deviation of the vertebra is de?ned as a positive value; when on the left side, it is de?ned as a negative value. T1 translation, distance in millimeters from the CSVL to the midpoint of the T1.

In our picture archiving and communication systems, the precision of the length measurement was 0.1 mm and the precision of the angle measurement was 0.1 . The mean error in the length measurement was 1.9 mm (range, 0 to 4.8 mm), and the mean error in angle measurement was 2.7 (range, 0 to 5.7 ). Lateral radiographs revealed no significant change in sagittal spinal alignment in the postoperative period. Postoperative lumbar curve behavior The Cobb angle measurements at the four times (preoperatively, immediately, 3 months, and 2 years postoperatively) are shown in Table 1. The average correction rates for the thoracic and lumbar curves at the 2-year followup were 0.61 and 0.41, respectively. On the other hand, before surgery, the T1, LIV, LIV?1, LIV?2, and LIV?3 were generally on the left side of the CSVL; after surgery they shifted signi?cantly even further toward the left side (p!.05). As for the thoracic AV, it was generally on the right side of the CSVL before surgery but was found to shift to the left side of the CSVL postoperatively. In summary, the entire spine generally became leftward imbalanced after surgery. However, during the following 2 years, all these key vertebrae progressively returned toward the right side (Figs. 2 and 3). At 2-year follow-up, the translation of T1, LIV?2, and LIV?3 already showed no significant differences from their preoperative translation.

Although the translation, on average, showed signi?cant improvement in the 2 years after surgery, postoperative spine alignment remodeling did not occur in every patient. To determine the onset of postoperative spinal alignment remodeling, criteria are needed. However, we are unaware of any existing criteria. Therefore, we performed a secondary (post hoc) analysis to validate a hypothetical criterion. According to the hypothetical criterion, postoperative spinal alignment remodeling was determined in 13 of 29 patients. Secondary (post hoc) analysis We hypothesized that postoperative spinal alignment remodeling could be de?ned as when the thoracic AV shifted toward the right side by more than 5 mm at 2 years postoperatively. To validate this hypothetical criterion, the patients were categorized into two groups according to the criterion. Thirteen patients were included in the remodeling group, the remaining 16 in the no-remodeling group. Repeatedmeasures analysis of variance was used to test the difference in vertebral translation trend between the two groups. For each key vertebra, the remodeling group showed significant improvement in vertebral translation during the postoperative period (Fig. 4, Table 2). Additionally, 10 of 13 patients in the remodeling group had already shown an improvement of more than 5 mm in thoracic apical vertebra translation (AVT) at the 3-month follow-up, whereas in the no-remodeling group, only 1 of

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Table 1 Mean (range) of Cobb angle or translation preoperatively and postoperatively (n529) Time Measurement Thoracic Cobb (  ) Lumbar Cobb (  ) T1 translation (mm) Thoracic AVT (mm) LIV translation (mm) LIV?1 translation (mm) LIV?2 translation (mm) LIV?3 translation (mm) Preoperative 55.3 43.0 ?14.0 33.7 ?8.5 ?18.1 ?22.1 ?18.7 (39.5, 76.4) (28.6, 57.8) (?34.6, 7.0) (0.6, 77.6) (?51, 36) (?43.2, 13.4) (?36.6, ?2.9) (?36, ?3.6) Immediate postoperative 19.5 23.3 ?20.0 ?7.1 ?24.5 ?27.8 ?26.9 ?21.8 (6.8, 35.5)* (3.3, 38.4)* (?40.8, 0.0)* (?28.6, 24.6)* (?43.1, 1.2)* (?40, ?10.9)* (?37.8, ?10.4)* (?34.2, ?6.4)* 3-mo postoperative 21.0 26.6 ?20.1 ?6.0 ?23.7 ?26.7 ?26.3 ?20.7 (5.5, 35.5)* (12.1, 43.3)* (?35.3, ?4.9)* (?26.6, 22.8)* (?45, 4.0)* (?42.1, ?2.1)* (?42.6, ?11.5)* (?39.4, ?5.5)* 2-y postoperative 22.0 25.3 ?16.7 ?1.4 ?19.9 ?23.7 ?23.8 ?19.4 (2.6, 39.9)* (7.2, 43.0)* (?37.8, ?4.0)y (?29.2, 22.8)*,y (?44.2, 10.4)*,y (?37.7, 4.4)*,y (?36.6, ?2.5)y (?32.1, ?7.9)y

AV, apical vertebra; LIV, lowest instrumented vertebra; LIV?1, the ?rst vertebra below LIV; LIV?2, the second vertebra below LIV; LIV?3, the third vertebra below LIV. Mean value reported with the range in parentheses. Translation is deviation from the center sacral vertical line. * Signi?cantly different from the preoperative value, p!.05. y Signi?cantly different from the immediate postoperative value, p!.05.

16 patients demonstrated a comparable improvement at the 3-month follow-up. This difference between the two groups was signi?cant (p!.001, by the Fisher exact test). These results indicate that we could predict the onset of postoperative spinal alignment remodeling on the results of the 3-month follow-up. Postoperative spinal balance The parameter of T1 translation represented global coronal balance of the spine. The parameters of thoracic and lumbar AVT de?ned the lateral borders of the spine. At the 2-year follow-up, both the T1 and lumbar AVT had not improved compared with their preoperative translation (Table 3). Thoracic AV was on the right side of the CSVL

in all patients before surgery. Immediately after surgery, however, the thoracic AVT was more than 5 mm on the left side in 20 of 29 patients, that is, the bulk of the thoracic spine was on the left side of the CSVL in 20 of 29 patients. Postoperative clinical photographs showed that leftward spinal imbalance could be seen in many patients, varying only in magnitude from patient to patient (Fig. 5). At the 2-year follow-up, there were still 11 patients whose thoracic AVT was more than 5 mm on the left side.

Discussion Selective thoracic fusion, a widely accepted procedure for the treatment of AIS, has the advantages of preserving

Fig. 2. The T1, thoracic AV, LIV, LIV?1, LIV?2, and LIV?3 all shifted signi?cantly toward the left side immediately after surgery (p!.05). However, in the course of the following 2 years, they all moved progressively back toward the right side. AV, apical vertebra; LIV, lowest instrumented vertebra; LIV?1, the ?rst vertebra below LIV; LIV?2, the second vertebra below LIV; LIV?3, the third vertebra below LIV.

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Fig. 3. Radiographs of a patient’s spine show a typical example of postoperative spinal alignment remodeling: immediately after selective thoracic fusion, the lumbar Cobb angle decreased, demonstrating improvement, whereas translation of the thoracic and lumbar vertebrae deteriorated; the T1, thoracic AV, lumbar AV, LIV, LIV?1, LIV?2, and LIV?3 all shifted to the left side. However, in the following 4 years, all of them moved progressively back toward the right side. At 4-year follow-up, the lumbar spine translation was even less than the preoperative translation, and the thoracic spine was almost completely balanced. AV, apical vertebra; LIV, lowest instrumented vertebra; LIV?1, the ?rst vertebra below LIV; LIV?2, the second vertebra below LIV; LIV?3, the third vertebra below LIV.

lumbar motion and growth potential. However, in certain cases, it may result in postoperative coronal imbalance [8–10]. Therefore, measurement of the Cobb angle alone is not suf?ciently comprehensive for the evaluation of selective thoracic fusion [11–15]; vertebral translation should also be taken into consideration, especially the translation of such key vertebrae as T1, thoracic and lumbar AVs. How spinal alignment changes over time after selective thoracic fusion and how postoperative spinal alignment remodeling affects spinal balance have not been well investigated [16,17]. The aim of the present study was to partly answer these questions.

Postoperative spinal alignment remodeling The continual follow-up of our present study revealed an interesting phenomenon: postoperative spinal alignment remodeling. Brie?y, immediately after selective thoracic fusion, both the thoracic and lumbar spine shifted toward the left side as a result of surgery, resulting in a leftward spinal imbalance. However, in some patients, this spinal imbalance improved gradually in the following 2 years; that is, the thoracic and lumbar spine moved progressively back toward the right side. Some patients even eventually

Fig. 4. For each key vertebra, the change in vertebral translation in the postoperative period was compared between the two groups. The remodeling group showed signi?cant improvement compared with the no-remodeling group.

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Table 2 Comparison of change in vertebral translation between the remodeling and no-remodeling groups Mean (range) change (mm) in translation (2-y to immediate postoperative) Vertebra T1 Thoracic AV LIV LIV?1 LIV?2 LIV?3 Remodeling group (n513) 14.2 16.8 11.5 10 8 5.5 (8.9, 19.6) (12.6, 20) (6.1, 17) (4.8, 15.3) (3, 12.9) (1.9, 9.1) No-remodeling group (n516) ?5.7 ?2.8 ?1.1 ?0.7 ?0.9 ?0.2 (?9.4, (?6.4, (?3.7, (?3.3, (?2.4, (?1.5, ?2) 0.8) 1.5) 1.9) 0.6) 1.2)

p value between differences* !.001 !.001 !.001 !.001 !.001 !.001

AV, apical vertebra; LIV, lowest instrumented vertebra; LIV?1, the ?rst vertebra below LIV; LIV?2, the second vertebra below LIV; LIV?3, the third vertebra below LIV. Mean value reported with the range in parentheses. Translation is deviation from the center sacral vertical line. * Paired t test.

the spine, statore?ex, and physiotherapy may all contribute to postoperative spinal alignment remodeling. Risk factor analysis studies are needed to investigate the causes of the phenomenon and more extensive follow-ups are desirable to observe how spinal alignment remodeling continues in the long run. At present, the presence of postoperative spinal alignment remodeling cannot be predicted before surgery. But our analyses indicate that we could predict on the results of the 3-month follow-up. That is, if patients do not exhibit postoperative spinal alignment remodeling at the 3-month follow-up, then they are unlikely to present with it at the 2-year follow-up. On the other hand, if a patient shows remodeling at the 3-month follow-up, then this remodeling is very likely to continue throughout the following 2 years. Postoperative spinal balance The results of our present study show that selective thoracic fusion tends to cause leftward spinal imbalance in Lenke 1C AIS patients. Of the 29 patients, 20 presented with leftward spinal imbalance immediately after surgery. Although nine patients regained spinal balance through postoperative spinal alignment remodeling, there were still 11 patients who remained imbalanced at the 2-year follow-up. These results are in accordance with the ?ndings in the literature, which show that postoperative spinal imbalance occurs primarily in patients with Lenke 1C or King Type II curves [4,12,18]. The causes of postoperative spinal imbalance remain inconclusive. Three factors are most commonly cited: excessive correction of the thoracic curve [19], inappropriate selection of the LIV [20–23], and a smaller ratio of MT:TL/L curve, that is, the main thoracic:thoracolumbar/lumbar curve [24,25]. Systematic risk factor analysis studies are needed to identify the risk factors for postoperative spinal imbalance in Lenke 1C scoliosis. Treatment strategy for Lenke 1C scoliosis As the results show, postoperative spinal imbalance can be iatrogenic. It could be prevented by checking balance condition during surgery. We found that the thoracic spine shifted further toward the left side in only three of 29 patients at 2 years postoperatively; that is, the leftward spinal

showed complete restoration of spinal balance at the 2-year follow-up. But the phenomenon of postoperative spinal alignment remodeling did not present in every patient, and there are as yet no criteria for determining the onset of this phenomenon. Hence, we hypothesized that the presence of postoperative spinal alignment remodeling could be determined when the thoracic AV shifted toward the right side by more than 5 mm at 2 years after surgery. We chose the parameter of thoracic AVT mainly because, among the available parameters, thoracic AVT best represents translation of the entire thoracic spine. In addition, we considered the cutoff value in the criterion. The lower the cutoff value, the more sensitive but less speci?c the criterion becomes. We set the cutoff value at 5 mm mainly because 5 mm was higher than the mean measuring error, which was 1.9 mm in the present study. Therefore, when a postoperative spinal alignment remodeling is determined by the criterion, it is unlikely to be a false-positive. Furthermore, we validated this criterion by a series of comparative analyses. The results showed that the two groups were accurately differentiated by means of the criterion. Studies with larger cohorts are needed to further validate this criterion. The mechanism of postoperative spinal alignment remodeling is still unclear. The biomechanical property of
Table 3 Postoperative spinal balance evaluation Time Measurements T1 translation (mm) Thoracic AVT (mm) Lumbar AVT translation (mm) Preoperative ?14.0 (?34.6, 7) 33.7 (0.6, 77.6) ?25.8 (?51, ?10.3)

Immediate postoperative ?20 (?40.8, 0)* ?7.1 (?28.6, 24.6)* ?29.8 (?43.1, ?13.6)*

3-mo postoperative ?20.1 (?35.3, ?4.9)* ?6 (?26.6, 22.8)* ?29.6 (?45, ?12.6)*

2-y postoperative ?16.7 (?37.8, ?4)y ?1.4 (?29.2, 22.8)*,y ?26.8 (?44.2, ?7.9)y

AV, apical vertebra; AVT, apical vertebra translation. Mean value reported with the range in parentheses. Translation is deviation from the center sacral vertical line. * Signi?cantly different from the preoperative value, p!.05. y Signi?cantly different from the immediate postoperative value, p!.05.

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Fig. 5. A 16-year-old girl with Lenke 1C scoliosis underwent selective thoracic fusion. Immediately after surgery, both the radiographs and clinical photos showed leftward spinal imbalance.

imbalance rarely deteriorated in the 2 years after surgery. Thus, after corrective manipulation during surgery, we can check whether the thoracic AV has crossed the CSVL to the left side. If it has, we should decrease the correction to avoid overcorrection and, therefore, prevent postoperative leftward spinal imbalance. In other words, making sure that the thoracic AV does not cross the CSVL to the left side during surgery probably prevents postoperative spinal imbalance. Postoperative spinal imbalance could also be prevented by proper selection of the LIV. When selecting the LIV, choosing stable vertebra (SV) or the vertebrae above SV could be better than choosing the vertebrae below the SV because the vertebrae below the SV are more distal and more deviated toward the left side. Regarding the ratio of MT:TL/L curve, it has been noted to cause postoperative spinal imbalance in the literature. Lenke et al. [25] recommend that the ratio criteria should be assessed when considering the potential to perform a selective thoracic fusion. When the ratios are greater than or equal to 1.2, selective fusion should be possible. McCall and Bronson [26] found that lumbar curves greater than 45 associated with a low ?exibility index were signi?cantly more likely to develop postoperative progression of the uninstrumented lumbar curve with resultant spinal decompensation. Patel et al. [24] believe that the greater the difference between the magnitudes of the thoracic and lumbar curves, the greater the thoracic correction that can safely be achieved. Hence, the ratio of MT:TL/L Cobb angle could be a major causative factor for the onset of postoperative spinal imbalance. Thus, when selecting candidates for

selective thoracic fusion, the ratio criteria should be considered.

Conclusions Selective thoracic fusion is prone to cause leftward spinal imbalance in Lenke 1C scoliosis patients. Postoperative spinal alignment remodeling can facilitate recovery of spinal balance in some patients. Postoperative spinal imbalance in Lenke 1C scoliosis patients could be prevented by selecting a stable vertebra or the vertebra above as the LIV, checking balance condition during surgery, or considering the ratio criteria when selecting candidates for selective thoracic fusion.

Acknowledgments The authors thank the Danish Strategic Research Council for ?nancial support. The authors thank Linda Marie Nygaard for her revisions of the manuscript and Astrid Hedegaard Konradsen for her excellent work on the radiographic follow-up. The authors also thank Michael S. Altus, PhD, ELS, of Intensive Care Communications, Inc., Baltimore, MD, USA, for his excellent services. References
[1] King H, Moe J, Bradford D, et al. The selection of fusion levels in thoracic idiopathic scoliosis. J Bone Joint Surg Am 1983;65: 1302–13.

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[2] Lenke L, Betz R, Harms J, et al. Adolescent idiopathic scoliosis: a new classi?cation to determine extent of spinal arthrodesis. J Bone Joint Surg Am 2001;83:1169–81. [3] Bridwell KH. Surgical treatment of adolescent idiopathic scoliosis: the basics and the controversies. Spine 1994;19:1095–100. [4] Frez R, Cheng JC, Wong EM. Longitudinal changes in truncal balance after selective fusion of King II curves in adolescent idiopathic scoliosis. Spine 2000;25:1352–9. [5] Large DF, Doig WG, Dickens DR, et al. Surgical treatment of double major scoliosis. Improvement of the lumbar curve after fusion of the thoracic curve. J Bone Joint Surg Br 1991;73:121–4. [6] Lenke LG, Betz RR, Bridwell KH, et al. Spontaneous lumbar curve coronal correction after selective anterior or posterior thoracic fusion in adolescent idiopathic scoliosis. Spine 1999;24:1663–71. [7] Richards S. Lumbar curve response in type II idiopathic scoliosis after posterior instrumentation of the thoracic spine. Spine 1992; 17(8 Suppl):S282–6. [8] McCance S, Denis F, Lonstein J, et al. Coronal and sagittal balance in surgically treated adolescent idiopathic scoliosis with the King II curve pattern. Spine 1998;23:2063–73. [9] Bridwell K, McAllister J, Betz R, et al. Coronal decompensation produced by Cotrel-Dubousset ‘‘derotation’’ maneuver for idiopathic right thoracic scoliosis. Spine 1991;16:769–77. [10] Lenke L, Bridwell K, Baldus C, et al. Preventing decompensation in King type II curves treated with Cotrel-Dubousset instrumentation: strict guidelines for selective fusion. Spine 1992;17(8 Suppl):274–81. [11] Jansen RC, van Rhijn LW, Duinkerke E, et al. Predictability of the spontaneous lumbar curve correction after selective thoracic fusion in idiopathic scoliosis. Eur Spine J 2007;16:1335–42. [12] Edwards CC 2nd, Lenke LG, Peelle M, et al. Selective thoracic fusion for adolescent idiopathic scoliosis with C modi?er lumbar curves: 2to 16-year radiographic and clinical results. Spine 2004;29:536–46. [13] Newton PO, Upasani VV, Bastrom TP, et al. The deformity-?exibility quotient predicts both patient satisfaction and surgeon preference in the treatment of Lenke 1B or 1C curves for adolescent idiopathic scoliosis. Spine 2009;34:1032–9. [14] Parisini P, Di Silvestre M, Lolli F, et al. Selective thoracic surgery in the Lenke type 1A: King III and King IV type curves. Eur Spine J 2009;18(Suppl 1):82–8.

[15] Fu G, Kawakami N, Goto M, et al. Comparison of vertebral rotation corrected by different techniques and anchors in surgical treatment of adolescent thoracic idiopathic scoliosis. J Spinal Disord Tech 2009;22:182–9. [16] Sponseller PD, Betz R, Newton PO, et al. Differences in curve behavior after fusion in adolescent idiopathic scoliosis patients with open triradiate cartilages. Spine 2009;34:827–31. [17] Lonner BS, Auerbach JD, Levin R, et al. Thoracoscopic anterior instrumented fusion for adolescent idiopathic scoliosis with emphasis on the sagittal plane. Spine J 2009;9:523–9. [18] Newton PO, Faro FD, Lenke LG, et al. Factors involved in the decision to perform a selective versus nonselective fusion of Lenke 1B and 1C (King-Moe II) curves in adolescent idiopathic scoliosis. Spine 2003;28:S217–23. [19] Thompson JP, Transfeldt EE, Bradford DS, et al. Decompensation after Cotrel-Dubousset instrumentation of idiopathic scoliosis. Spine 1990;15:927–31. [20] Suk SI, Lee SM, Chung ER, et al. Determination of distal fusion level with segmental pedicle screw ?xation in single thoracic idiopathic scoliosis. Spine 2003;28:484–91. [21] Arlet V, Marchesi D, Papin P, et al. Decompensation following scoliosis surgery: treatment by decreasing the correction of the main thoracic curve of ‘‘letting the spine go’’. Eur Spine J 2000;9:156–60. [22] Benli IT, Tuzuner M, Akaline S, et al. Spinal imbalance and decompensation problems in patients treated with Cotrel-Dubousset instrumentation. Eur Spine J 1996;5:380–6. [23] Margulies JY, Floman Y, Robin GC, et al. An algorithm for selection of instrumentation levels in scoliosis. Eur Spine J 1998;7:88–94. [24] Patel PN, Upasani VV, Bastrom TP, et al. Spontaneous lumbar curve correction in selective thoracic fusions of idiopathic scoliosis: a comparison of anterior and posterior approaches. Spine 2008;3: 1068–73. [25] Lenke LG, Edwards CC 2nd, Bridwell KH. The Lenke classi?cation of adolescent idiopathic scoliosis: how it organizes curve patterns as a template to perform selective fusions of the spine. Spine 2003;28: S199–207. [26] McCall RE, Bronson W. Criteria for selective fusion in idiopathic scoliosis using Cotrel-Dubousset instrumentation. J Pediatr Orthop 1992;12:475–9.


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Total knee arthroplasty (TKA) is associated with significant postoperative ... mechanical advantage for deformity correction and maintain spinal alignment. ...
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remodeling of the transplanted cancellous bone graft...Spinal alignment in the sagittal plane was ...postoperative survey; therefore, results of the ...
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10.4061/2011/415946 Clinical Study Acute Reciprocal Changes Distant from the Site of Spinal Osteotomies Affect Global Postoperative Alignment Eric Klineberg,1...
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10.4061/2011/415946 Clinical Study Acute Reciprocal Changes Distant from the Site of Spinal Osteotomies Affect Global Postoperative Alignment Eric Klineberg,1...
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10.4061/2011/415946 Clinical Study Acute Reciprocal Changes Distant from the Site of Spinal Osteotomies Affect Global Postoperative Alignment Eric Klineberg,1...
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10.4061/2011/415946 Clinical Study Acute Reciprocal Changes Distant from the Site of Spinal Osteotomies Affect Global Postoperative Alignment Eric Klineberg,1...
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10.4061/2011/415946 Clinical Study Acute Reciprocal Changes Distant from the Site of Spinal Osteotomies Affect Global Postoperative Alignment Eric Klineberg,1...
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