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Emerging S-shaped curves in congenital scoliosis after hemivertebra resection and short segmental fusion
ARTICLE IN PRESS
The Spine Journal ■■ (2016) ■■–■■
Clinical Study
Emerging S-shaped curves in congenital scoliosis after hemivertebra resection and short segmental fusion Xi Yang, MD, Yueming Song, MD, Limin Liu, MD*, Chunguang Zhou, MD, Zhongjie Zhou, MD, Lei Wang, MD, Liang Wang, MD Department of Orthopaedics Surgery, West China Hospital, Sichuan University, No. 37 GuoXue Rd, Chengdu, Sichuan, 610041, China Received 2 December 2015; revised 18 May 2016; accepted 21 June 2016
Abstract
BACKGROUND CONTEXT: Posterior hemivertebra resection with short fusion has gradually become the mainstream treatment for the congenital scoliosis due to single fully segmented hemivertebra. A kind of unexpected emerging S-shaped scoliosis was found secondary to this surgery, and that has not been reported yet. PURPOSE: The aim of the present study was to analyze the possible pathogenesis, clinical feature, and treatment of the emerging S-shaped scoliosis after posterior hemivertebra resection and short fusion. STUDY DESIGN: This study is a retrospective case series. PATIENT SAMPLE: A total of 128 patients participated. OUTCOME MEASURES: Preoperative and postoperative whole spine radiographs were used to measure the Cobb angle of main curve, compensatory curve, and emerging curves. And the hemivertebra location, the fused segment, the apical and ending vertebrae of postoperative-emerging curve (and preoperative compensatory curves) were assessed. METHODS: Both the demographics and radiographic data were reviewed. Postoperativeemerging scoliosis was defined as the curve with an increasing angle of 20° and an apical vertebra locating at least two levels away from fusion region. RESULTS: Of the 128 patients, 9 (7%) showed postoperative-emerging S-shaped scoliosis. The mean age was 11.4 years old. The mean main curve was 36.1±14.4° preoperatively and been significantly corrected to 6.9±6.1° (p<.001). No significant difference was found in the main curve, kyphosis, coronal balance, or sagittal balance during follow-up. The emerging scoliosis occurred at 3 months (in four patients) or 6 months (in five patients) after initial surgery with an average angle of 42.6±12.9° at last follow-up. All patients underwent bracing or observation when the S-shaped scoliosis was arising, and four patients underwent a revision surgery because of deformity developing. CONCLUSIONS: The emerging S-shaped scoliosis was an extraordinary complication that may be developing from the preoperative compensatory scoliosis and usually occurred at 3–6 months after hemivertebra resection. The feature of these curves was similar to the adolescent idiopathic scoliosis (AIS) and brace or revision surgeries were suitable for therapy. © 2016 Elsevier Inc. All rights reserved.
Keywords:
Complication; Congenital scoliosis; Hemivertebra resection; Posterior-only approach; Revision surgery; Short fusion
FDA device/drug status: None. Author disclosures: XY: Nothing to disclose. YS: Nothing to disclose. LL: Nothing to disclose. CZ: Nothing to disclose. ZZ: Nothing to disclose. LeiW: Nothing to disclose. LiangW: Nothing to disclose. No funds were received in support of this work. No benefits in any form have been or will be received from any commercial party related directly or indirectly to the subject of this article. http://dx.doi.org/10.1016/j.spinee.2016.06.006 1529-9430/© 2016 Elsevier Inc. All rights reserved.
* Corresponding author. Department of Orthopaedics Surgery, West China Hospital, Sichuan University, No. 37 GuoXue Rd, Chengdu, Sichuan, 610041, China. Tel.: 86-28-85422430; fax: 86-28-85423326. E-mail address: [email protected] (L. Liu).
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Introduction Hemivertebra is the most frequent cause of congenital scoliosis, and it usually creates a local wedge-shaped deformity, which increases during the spinal growth. If not dealt with, it will lead to an imbalance of the spine and aggravated secondary scoliosis. Given the infamous history of this deformity, current hemivertebra resection is recommended in most cases [1–3]. And the operation should, in principle, be performed as early as possible to avoid the development of any further deformities. In addition, during the early stage, a short fusion can be allowed to avoid excessive intervention in spinal mobility or growth [4–7]. In earlier years, hemivertebra resection by a combined anterior and posterior approach had been advocated because of its good visualization of neural structures and less technical requirement [8,9]. Later, with the wide application of the transpedicular screw, compared with the combined approach, one stage posterior approach hemivertebra resection enjoys an almost equal correction rate but with much lower surgery-related morbidity and much shorter postoperative recovery periods [9]. In recent decades, the posterior-only hemivertebra resection has gradually replaced the combined approach and became the preferred correction for this deformity [4,5,10]. The single-stage posterior hemivertebra resection with short segmental pedicle screw fixation has demonstrated satisfactory deformities correction and rigid stabilization even in very young patients [10–13]. Behind these successful results, the potential complications, especially postoperative progressive deformities, have been given more and more attention in recent literatures [8,12,14–16]. In our department, the posterior-only approach has been performed since 2008. For the congenital patients due to single fully segmented hemivertebra without structural compensatory curves, we have routinely maintained the principles of early surgery and short fusion [17,18]. Consistent with previous reports, a satisfactory deformity correction was shown in a majority of these patients. In addition, we have noticed a kind of unexpected idiopathic postoperative-emerging scoliosis in nine patients. These emerging scoliosis were generally S-shaped and have more than a 20° increase of the Cobb angle from its initial value, the apical vertebra were lying at least two levels from the fusion area. This kind of postoperative complication with such surgery has not been reported in any previous literature. The aim of the present study was to analyze the pathogenesis, feature, and treatment of this new postoperative complication. Methods A total of 128 patients with congenital scoliosis due to single fully segmented hemivertebra who underwent posterior correction and fusion in our department between January 2008 and March 2014 were retrospectively reviewed. Approval was obtained by the local Ethics Committee before
data collection and analysis. The inclusive criteria were as follows: (1) no structural secondary scoliosis before surgery, (2) underwent short segment fixation and fusion, (3) more than 1 year of radiographic follow-up after the initial surgery, (4) postoperative-emerging scoliosis with a more than 20° increasing of the Cobb angle, while at the same time the apical vertebra was at least two levels from the lower (or upper) instrument vertebra, and (5) no arthropathy existed in their lower limbs. Patients who had an anterior approach, more than one hemivertebra or combination with other congenital spinal deformity, were not included in the present study. Nine patients matched these criteria. There were seven women and two men. The mean age of the patients at the time of primary surgery was 11.4±3.6 years. The mean followup was 36.0±9.5 months. All patients had a standard posterioronly hemivertebra resection with transpedicular screw fixation [8,19]. The CD HORIZON M8 or Legacy screw-rod system (Medtronic Sofamor, Danek, USA, Inc., Memphis, TN, USA) was used for fixation in all patients. An average of 2.8±1.1 segments were fused in these patients (the resected hemivertebra was included in the calculation). All surgeries were performed by both senior authors. Whole spine anteroposterior and lateral radiographs were reviewed preoperatively, 1 week, 3 months, 6 months, and 9 months postoperatively, and then each year postoperatively to assess deformity correction and development. The parameters measured in the anteroposterior radiographs were the main curve, the compensatory curves, the postoperativeemerging curves, and the coronal balance. The main curve was measured as the Cobb angle between two vertebrae immediately adjacent to the hemivertebra. Both the preoperative compensatory curves (more than 10° at the neutral position) and the postoperative-emerging curves (as above defined) were measured as the Cobb angle between the two most tilted vertebrae on corresponding radiographs. The end vertebrae and the apical vertebrae of all these curves were recorded respectively. And the bending radiographs were reviewed to assess both the flexibility of the preoperative compensatory curves and postoperative-emerging curves. Coronal balance was measured by the deviation of the C7 plumb line from the center sacral vertical line. It was considered significant when the deviation exceeded 20 mm. The parameters measured in the lateral radiographs were the segmental kyphosis, postoperative junctional kyphosis and the sagittal balance. The segmental kyphosis was measured between the two vertebrae adjacent to the hemivertebra. The proximal junctional kyphosis (PJK) had only been recorded when the angle increased more than 10° during the follow-up. The sagittal balance was measured as the horizontal distance from the C7 plumb line to the posterior superior corner of S1. In all of these patients, three-dimensional computed tomography (CT) scans were taken preoperatively to assess the morphology of the hemivertebra, while 3 months and 6 months postoperatively, and annually after surgery to assess the fusion status. Meanwhile, the integrity and position of the internal fixation were evaluated.
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Statistical analysis was performed using the SPSS17 software (IBM, Inc., New York, NY, USA). The preoperative and postoperative follow-up results were analyzed statistically with the use of the paired Student’s t test. p<.05 was considered significant. Result Of 128 patients, 9 (7%) who matched the criteria were included in the present study, with an average age of 11.4 years (range from 7 to 15 years), and an average Risser sign of grade 2 (range from 0 to 4). The location of the hemivertebra was in the thoracolumbar area in six patients (T11 in three patients, T12 in one patient, and L1 in two patients), and in thoracic in three patients (T4, T5, and T7, respectively). The averaged Cobb angle of the preoperative main curve was 36.1±14.4°. Seven of the nine patients had an average compensatory curve of 20.3±4.8°. After primary surgery, the mean follow-up of these patients was 26 months with the range from 18 to 42 months (for the patients who underwent revision surgery, the followup was identified as the time between two operations). There was no patient demonstrated PJK, pseudoarthrosis, or internal fixation failure during the whole follow-up period. The value of the main curve had been significantly decreased to 6.9±6.1° (p<.001) by surgery with the mean rate of correction at 82.5%. And this angle was fairly constant until the final follow-up (7.9±6.6°, p=.08). The mean segmental kyphosis was 20.4±4.1° preoperatively. The kyphosis had been significantly corrected to 9.9±4.2° postoperatively (p<.001) and remained constant at 9.2±4.0° at the final follow-up (p=.53). The coronal balances before correction, after correction, and at the final follow-up were 0.6±0.6, 0.6±0.4, and 0.8±0.6, respectively (preoperation vs. postoperation, p=.63; and postoperation vs. final operation, p=.09). The sagittal
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balance was 1.6±1.0 preoperative, 1.2±0.9 postoperative, and 1.7±0.9 at the final follow-up (preoperation vs. postoperation, p=.13; and postoperation vs. final operation, p=.12). In four patients, the emerging scoliosis occurred at 3 months after the initial operation, whereas in the other five patients, it occurred at 6 months. All these emerging scoliosis appeared in S-shaped curves. It appeared as the main thoracic scoliosis with a lumbar scoliosis in four patients, the main lumbar scoliosis with a thoracic scoliosis in four patients, and double thoracic scoliosis with a lumbar scoliosis in one patient (patient 4, Fig. 1). Details of the end vertebrae, the apical vertebrae, the Cobb angle, and treatment of the emerging scoliosis of all nine patients are listed in the Table. The mean value of the main emerging curve was 42.6±12.9 at the final followup. And the apical vertebra of the main emerging curve was at least 2 levels far from the end instrument vertebra, with an average of 3.2 levels (range from 2 to 6 levels). The region of postoperative-emerging scoliosis was in accord with their preoperative compensatory scoliosis in five patients (Patients 2, 4, 5, 7, and 8). Six of nine patients underwent bracing therapy when the S-shaped scoliosis arose, whereas the remaining three patients underwent closely observation. The emerging scoliosis had developed into the structural curves and beyond 45° in four patients during follow-up. A posterior-only revision surgery was performed in these four patients at 18 months after initial surgery (Patients 1, 2, 4, and 5). The fusion region was extended to cover all structural curves (Fig. 2). During an average of 22.5 months follow-up, no new deformity developed after revision. Discussion In recent years, single-stage posterior hemivertebra resection and short fusion has gradually become the mainstream
Fig. 1. The pre- and postfirst operative radiographs of Patient 4. A 15-year-old man with a fully segmental hemivertebra at T11. The preoperative anteroposterior (AP) and bending films showed three slightly flexible compensatory curves located in T2–T7, T7–T9, and L1–L5, respectively. The posterior hemivertebra resection with T10–T12 fusion was performed. And the postoperative AP film showed that both the main curve and the compensatory curves were obviously corrected. However, an unwonted emerging S-shaped scoliosis appeared 6 months after this operation. These emerging curves were 36.1°, 42.5°, and 21.5° at T2–T7 (PT), T7–T12 (MT), and T12–L5 (L) respectively, exceeded 20° than preoperative same levels. Meanwhile, the apical vertebra of MT was T8, which are located two levels far from the upper instrument vertebra. The trunk balance is always normal.
ARTICLE IN PRESS Preop., preoperative; Postop., postoperative; MC, main curve; CC, compensatory curve; EC, emerging curve; AV, apical vertebra; MT, main thoracic scoliosis; PT, proximal thoracic scoliosis; L, lumbar scoliosis; M, male; F, female.
L2 L3 L4 T9 T7 ML+T ML+T ML+T MT+L MT+L 6 3 3 6 6 10.4 3.8 18.0 8.5 1.5 T9–T12 T10–T12 T12–L2 T11–L1 T11–L3 T11(35.2) T11(21.8) L1(42.1) T12(36.0) L1(31.5) 3 0 0 0 4 F F F F M 5 6 7 8 9
14 5 10 7 15
Therapy
Brace and revision Revision Brace Brace and revision T9 T9 L2 T8
T1–T12(50.5) and T12–L5(28.6) T4–T12(64.2) and T12–L5(32.5) T9–T12(20.2) and T12–L3(25.9) T2–T7(44.3), T7–T12(51.4), and T12–L5(26.1) T5–T12(25.3) and T12–L4(47.5) T4–T12(26.1) and T12–L5(40.3) T8–T11(20.4) and T11–L5(45.0) T6–T11(38.4) and T11–L5(28.1) T5–T11(23.1) and T11–L5(21.0) MT+L MT+L ML+T PT+MT+L 3 3 6 6 13.9 5.3 0 0.5 T1–T6 T4–T6 T5–T8 T10–T12
T12–L4(30.0) T6–T12(24.5) — T2–T7(16.0), T7–T9(20.8) and L1–L5(21.9) T12–L4(18.5) T4–T10(15.9) L2–L5(20.0) T6–T11(15.0) — T4(69.0) T5(34.4) T7(18.2) T11(36.5) 4 3 0 4 F F F M 1 2 3 4
14 13 10 15
AV of main EC EC (levels and °) Type of EC Onset of EC (mo) Postop. MC (°) Fused segment CC (levels and °) Sex Case
Age
Risser
Hemivertebra and preop. MC (°)
Table Patient’s demographic, anatomical, and radiographic characteristics
Revision Brace Brace Brace Observe
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treatment for the congenital scoliosis of fully segmented nonincarcerated hemivertebra [4,10–13,16]. Early or even prophylactic hemivertebra resection was recommended to stop the development of the local deformity and to prevent the longer fusion extending to the advanced secondary structural curves [10–13]. The modern transpedicular instrumentation could provide the short and sufficiently rigid stabilization in such patients, thereby avoiding wider distractions of spinal growth and mobility [11,16]. With the wide application of posterior hemivertebra resection and short fusion, the number of these cases has steadily increased, and the surgical complications have gradually become another prominent problem besides deformity correction by surgery itself [8,12,14–16]. The postoperative new deformity is one of the most common complications in this surgery. Although its incidence is lower than neurologic injuries, deformity progress has usually been given more attention because of its huge impact on initial correction and the potential risk of revision surgery. Wang et al [12] reported that the 18.9% (7/37) of congenital scoliosis patients with posterior hemivertebra resection and short fusion had more than a 10° increase kyphosis developing above the top of instrumentation at an average 4.5 years follow-up period. The authors then analyzed that the possible cause of PJK in these pediatric patients contains following two factors. The first and main point is that the misplaced screws in upper instrumental vertebra may have disturbed the normal growth on the endplate. The second point is the excess damage that may have been caused in the facet capsules or supraspinous ligament above the fusion segments during exposure, which directly related to the occurrence of PJK. Shi et al [14] reported 19 patients with a hemivertebra that underwent revision surgery because of the deformity progression after their first operation. No incomplete resection of the malformed hemivertebra or failure in internal fixation or pseudarthrosis has been recognized as the main cause of their development deformity after hemivertebra resection and fusion. Similar results and reason analysis of these complications have also been reported by Ruf et al [16] in 2009 and Zhang et al [8] in 2011. Although the type and cause of deformity are various, these progressive deformities reported in previous literature have a common ground, that the postoperative deformity develops on the hemivertebra resection level or surgical fusion area [8,12,14,16]. In contrast, the progressive curve developing in present congenital patients actually have little correlation with the initial surgical segment. In our patients, the emerging scoliosis showed an S-shaped appearance, and the apical vertebra of the curves were located at least two levels far from the upper or lower instrumented vertebra, which were remarkably different from adding-on deformity. In addition, there was no developed kyphosis, pseudoarthrosis, or failure of internal fixation occurring over the range of fusion. The hemivertebra, together with the adjacent growth plates have also been completely resected by the initial posterior surgery. With the method of exclusion, it seemed that this emerging scoliosis
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Fig. 2. The pre- and postrevision radiographs of Patient 4. The patient had undergone a brace since the emerging scoliosis was found at 6 months after initial surgery. However, the emerging scoliosis still developed gradually. The films before the revision showed that the proximal and the main thoracic curves were relatively serious and structural at 18 months after the first operation. Then, a posterior revision was performed. The fusion was extended according to the basic laws in patients with adolescent idiopathic scoliosis (AIS). The upper instrumented vertebra was chosen at T2, the upper end vertebra of PT, whereas the lowest instrumented vertebra was chosen at the stable vertebra (L3). A satisfied deformity correction and trunk balance were found during 24 months follow-up after revision.
was a kind of agnogenic postoperative deformity in congenital patients that have not been reported previously. The development of the S-shaped curves in congenital patients who underwent posterior hemivertebra resection and short fusion was surprising and unforeseen. It was hard to find any direct reason to explain the appearance of this complication. The emerging curve in almost all current patients (eight patients) presented double curves which included a thoracic curve and a lumbar one (except one patient who presented with double thoracic curve with a lumbar curve; Fig. 1). This kind of S-shaped curve was conducive in maintaining trunk balance in a standing position. So, there was no coronal imbalance found in any of the present patients. When comparing the coronal spinal curvature before and after primary surgery, we have noticed that the location of postoperative progressive curves had a high consistency with preoperative secondary curves [10]. Secondary curve is the spontaneous deformity that compensates for the local scoliosis due to hemivertebra. And in the early period of congenital scoliosis, the secondary curves usually are limited and unstructured, and do not need specific treatment [4,5,19]. In the present study, the preoperative secondary curves in all our patients were slight and flexible (mean Cobb angle in the neutral position was 20.3°). Based on the general principle, local hemivertebra resection and short fusion was chosen without any intervention in these slight secondary deformities. Anomalously, the compensatory curves quickly developed during the first 6 months after operation. To explain the development of these curves, a potential mechanism was put forward. Secondary curves in congenital patients in theory are accompanied with the biomechanics change of paravertebral muscle or facet joint. With the growth and development of the spine, these biomechanical changes will gradually alter to morphological changes. These microscopic changes may be earlier than the appearance of structural scoliosis. In pa-
tients with congenital scoliosis with good coronal trunk balance, hemivertebra resection and local scoliosis correction in fact will break the original coronal balance. If the morphology of paravertebral muscle and facet joint has already changed irreversibly at this time, the preoperative secondary curves may further develop (in such short term after initial surgery) to reach a new trunk balance. It seems that the emerging S-shaped scoliosis after hemivertebra resection can also be understood as the accelerated development of preoperative secondary scoliosis. Seven out of nine present patients were aged between 10 and 15 years, whereas the other two patients were aged less than 10 years. The result indicated that a higher percentage of this complication occurred in the adolescent patients. Adolescence is the second peak of growth and development. Rapid growth of the body may increase the possibility of this complication. But above all, the teenage years are a relatively late age for operating on patients with congenital scoliosis due to hemivertebra [10–12,19]. From their first time of standing up to their adolescence, the period in fact is long enough for the appearance of morphological changes at their posterior spine complex. The level of the hemivertebra was on T11–L1 in six of nine current patients, whereas it was on T4–T7 in the other three patients. The level was in accordance with the position distribution of the hemivertebra. The thoracolumbar junction had been documented as the predominant sites of hemivertebra [5,16,20]. Isolated hemivertebra in upper thoracic or lumbosacral region usually results in early trunk decompensation [7]. The patients with upper thoracic or lumbosacral hemivertebra used to undergo longer fusion when they were young in our department. Until now, we have not found any posterior emerging scoliosis in these patients. On the other side, thoracolumbar junction as we know was a specific region where the stress concentration was high and postoperative deformities (such as PJK) are prone to develop [12].
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Unfortunately, due to the limitation of the current retrospective study, we could not prove whether the hemivertebra in thoracolumbar junction or the short fusion during adolescence were the risk factors for the emerging S-shaped scoliosis. Despite the preoperative hemivertebra, the characteristics and development of postoperative-emerging S-shaped scoliosis in the present patients were quite similar to the curves in patients with adolescent idiopathic scoliosis (AIS). In fact, we found that the therapeutic strategy for AIS was suitable similarly for current patients. Brace was recommended to control the progression of this postoperative curve when it was relatively slight and flexible at the early stage. When the emerging curve became structural, revision by extending the initial fusion segment was an optional choice to improve the appearance of the trunk. The fusion range could be determined by complying with the general laws in patients with AIS [21]. In the four present patients who underwent reoperation, we have chosen the upper end vertebra to be the upper instrumented vertebra with the stable vertebra to be the lower instructed vertebra. Finally, satisfactory correction and fusion were achieved, and no progressive deformity was found up to the last follow-up. Looking back on these patients with postoperativeemerging S-shaped scoliosis, especially the ones who underwent revision surgery, a serious question is raised and therefore must be considered in depth. Was the short fusion (after hemivertebra resection) really sufficient for these patients, in other words, should we plan to do a long segmental fusion at first surgery? It is hard for this question to be exactly answered by now because the pathogenetic mechanism or predictive factors of the postoperative-emerging scoliosis are still unclear because of the retrospective property and small sample size of the present study. However, given a low rate (about 7%) of this complication, we hold that the short fusion following posterior hemivertebra resection was still the first choice for patients with congenital scoliosis due to hemivertebra. And the postoperative-emerging S-shaped scoliosis should be added into the general complications of such surgery, and patients should be informed before surgery. Conclusions In conclusion, posterior emerging S-shaped curve is an extraordinary and previously unreported complication after posterior hemivertebra resection and short fusion. In the present study, the emerging curve was defined as the postoperative scoliosis with more than 20° of an increase in the Cobb angle from its initial value, whereas the apical vertebra was at least two levels from the lower (or upper) instrument vertebra. This unusual deformity seems to be developing from slight and compensatory secondary scoliosis before surgery. However, the specific cause is still unclear. The majority of patients with posterior emerging scoliosis were teenagers who had a hemivertebra in the thoracolumbar junction area. This S-shaped
curve used to be flexible at the beginning of progression at 3–6 months after the initial surgery. And at this time, brace was recommended. When the deformities developed to structured scoliosis, reoperation with longer fusion should be done, and the fusion segment could be decided as being the same as the posterior correction in AIS. References [1] McMaster MJ, Ohtsuka K. The natural history of congenital scoliosis. A study of two hundred and fifty-one patients. J Bone Joint Surg Am 1982;64:1128–47. [2] Winter RB, Moe JH, Eilers VE. Congenital scoliosis: a study of 234 patients treated and untreated. J Bone Joint Surg Am 1968;50A: 1–15. [3] Yaszay B, O’Brien M, Shufflebarger HL, et al. Efficacy of hemivertebra resection for congenital scoliosis: a multicenter retrospective comparison of three surgical techniques. Spine 2011;36:2052–60. [4] Ruf M, Harms J. Hemivertebrae resection by a posterior approach: innovate operative technique and first results. Spine 2002;27:1116– 23. [5] Wang S, Zhang J, Qiu G, et al. Posterior hemivertebra resection with bisegmental fusion for congenital scoliosis: more than 3 year outcomes and analysis of unanticipated surgeries. Eur Spine J 2013;22:387–93. [6] Nakamura H, Matsuda H, Konishi S, et al. Single-stage excision of hemivertebrae via the posterior approach alone for congenital spine deformity: follow-up period longer than ten years. Spine 2002;27:110– 15. [7] Zhuang Q, Zhang J, Li S, et al. One-stage posterior-only lumbosacral hemivertebra resection with short segmental fusion: a more than 2-year follow-up. Eur Spine J 2015;25:1567–74. Published online. [8] Zhang J, Shengru W, Qiu G, et al. The efficacy and complications of posterior hemivertebra resection. Eur Spine J 2011;20:1692–702. [9] Mladenov K, Kunkel P, Stuecker R. Hemivertebra resection in children, results after single posterior approach and after combined anterior and posterior approach: a comparative study. Eur Spine J 2012;21:506– 13. [10] Chang DG, Suk SI, Kim JH, et al. Surgical outcomes by age at the time of surgery in the treatment of congenital scoliosis in children under age 10 years. Spine J 2015;15:1783–95. [11] Ruf M, Harms J. Posterior hemivertebra resection with transpedicular instrumentation: early correction in children aged 1 to 6 years. Spine 2003;28:2132–8. [12] Wang Y, Kawakami N, Tsuji T, et al. Proximal junctional kyphosis following posterior hemivertebra resection and short fusion in children younger than 10 years. Clin Spine Surg 2016 Jun 20 [Epub ahead of print]. [13] Crostelli M, Mazza O, Mariani M. Posterior approach lumbar and thoracolumbar hemivertebra resection in congenital scoliosis in children under 10 years of age: results with 3 years mean follow up. Eur Spine J 2014;23:209–15. [14] Shi Z, Li Q, Cai B, et al. Causes of the failure and the revision methods for congenital scoliosis due to hemivertebra. Congenit Anom (Kyoto) 2015;55:150–4. [15] Reames DL, Smith JS, Fu KM, Scoliosis Research Society Morbidity and Mortality Committee, et al. Complications in the surgical treatment of 19,360 cases of pediatric scoliosis: a review of the Scoliosis Research Society Morbidity and Mortality database. Spine 2011;36:1484–91. [16] Ruf M, Jensen R, Letko L, et al. Hemivertebra resection and osteotomies in congenital spine deformity. Spine 2009;34:1791–9. [17] Zhou C, Liu L, Song Y, et al. Hemivertebrae resection for unbalanced multiple hemivertebrae: is it worth it? Eur Spine J 2014;23:536– 42.
ARTICLE IN PRESS X. Yang et al. / The Spine Journal ■■ (2016) ■■–■■ [18] Wang L, Song Y, Pei F, et al. Comparison of one-stage anteroposterior and posterior-alone hemivertebrae resection combined with posterior correction for hemivertebrae deformity. Indian J Orthop 2011;45: 492–9. [19] Ruf M, Harms J. Pedicle screws in 1- and 2-year-old children: technique, complications, and effect on further growth. Spine 2002;27:460–6.
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[20] Bollini G, Launay F, Docquier P, et al. Congenital abnormalities associated with hemivertebrae in relation to hemivertebrae location. J Pediatr Orthop B 2010;19:90–4. [21] Mulconrey DS, Lenke LG. Chapter 13 selection of fusion levels. In: Newton PO, editor. Idiopathic scoliosis: the Harms Study Group treatment guide. Stuttgart, Baden-Württemberg: Thieme Medical Publishers Inc; 2010. p. 172–96.
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Clinical Study
Emerging S-shaped curves in congenital scoliosis after hemivertebra resection and short segmental fusion Xi Yang, MD, Yueming Song, MD, Limin Liu, MD*, Chunguang Zhou, MD, Zhongjie Zhou, MD, Lei Wang, MD, Liang Wang, MD Department of Orthopaedics Surgery, West China Hospital, Sichuan University, No. 37 GuoXue Rd, Chengdu, Sichuan, 610041, China Received 2 December 2015; revised 18 May 2016; accepted 21 June 2016
Abstract
BACKGROUND CONTEXT: Posterior hemivertebra resection with short fusion has gradually become the mainstream treatment for the congenital scoliosis due to single fully segmented hemivertebra. A kind of unexpected emerging S-shaped scoliosis was found secondary to this surgery, and that has not been reported yet. PURPOSE: The aim of the present study was to analyze the possible pathogenesis, clinical feature, and treatment of the emerging S-shaped scoliosis after posterior hemivertebra resection and short fusion. STUDY DESIGN: This study is a retrospective case series. PATIENT SAMPLE: A total of 128 patients participated. OUTCOME MEASURES: Preoperative and postoperative whole spine radiographs were used to measure the Cobb angle of main curve, compensatory curve, and emerging curves. And the hemivertebra location, the fused segment, the apical and ending vertebrae of postoperative-emerging curve (and preoperative compensatory curves) were assessed. METHODS: Both the demographics and radiographic data were reviewed. Postoperativeemerging scoliosis was defined as the curve with an increasing angle of 20° and an apical vertebra locating at least two levels away from fusion region. RESULTS: Of the 128 patients, 9 (7%) showed postoperative-emerging S-shaped scoliosis. The mean age was 11.4 years old. The mean main curve was 36.1±14.4° preoperatively and been significantly corrected to 6.9±6.1° (p<.001). No significant difference was found in the main curve, kyphosis, coronal balance, or sagittal balance during follow-up. The emerging scoliosis occurred at 3 months (in four patients) or 6 months (in five patients) after initial surgery with an average angle of 42.6±12.9° at last follow-up. All patients underwent bracing or observation when the S-shaped scoliosis was arising, and four patients underwent a revision surgery because of deformity developing. CONCLUSIONS: The emerging S-shaped scoliosis was an extraordinary complication that may be developing from the preoperative compensatory scoliosis and usually occurred at 3–6 months after hemivertebra resection. The feature of these curves was similar to the adolescent idiopathic scoliosis (AIS) and brace or revision surgeries were suitable for therapy. © 2016 Elsevier Inc. All rights reserved.
Keywords:
Complication; Congenital scoliosis; Hemivertebra resection; Posterior-only approach; Revision surgery; Short fusion
FDA device/drug status: None. Author disclosures: XY: Nothing to disclose. YS: Nothing to disclose. LL: Nothing to disclose. CZ: Nothing to disclose. ZZ: Nothing to disclose. LeiW: Nothing to disclose. LiangW: Nothing to disclose. No funds were received in support of this work. No benefits in any form have been or will be received from any commercial party related directly or indirectly to the subject of this article. http://dx.doi.org/10.1016/j.spinee.2016.06.006 1529-9430/© 2016 Elsevier Inc. All rights reserved.
* Corresponding author. Department of Orthopaedics Surgery, West China Hospital, Sichuan University, No. 37 GuoXue Rd, Chengdu, Sichuan, 610041, China. Tel.: 86-28-85422430; fax: 86-28-85423326. E-mail address: [email protected] (L. Liu).
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Introduction Hemivertebra is the most frequent cause of congenital scoliosis, and it usually creates a local wedge-shaped deformity, which increases during the spinal growth. If not dealt with, it will lead to an imbalance of the spine and aggravated secondary scoliosis. Given the infamous history of this deformity, current hemivertebra resection is recommended in most cases [1–3]. And the operation should, in principle, be performed as early as possible to avoid the development of any further deformities. In addition, during the early stage, a short fusion can be allowed to avoid excessive intervention in spinal mobility or growth [4–7]. In earlier years, hemivertebra resection by a combined anterior and posterior approach had been advocated because of its good visualization of neural structures and less technical requirement [8,9]. Later, with the wide application of the transpedicular screw, compared with the combined approach, one stage posterior approach hemivertebra resection enjoys an almost equal correction rate but with much lower surgery-related morbidity and much shorter postoperative recovery periods [9]. In recent decades, the posterior-only hemivertebra resection has gradually replaced the combined approach and became the preferred correction for this deformity [4,5,10]. The single-stage posterior hemivertebra resection with short segmental pedicle screw fixation has demonstrated satisfactory deformities correction and rigid stabilization even in very young patients [10–13]. Behind these successful results, the potential complications, especially postoperative progressive deformities, have been given more and more attention in recent literatures [8,12,14–16]. In our department, the posterior-only approach has been performed since 2008. For the congenital patients due to single fully segmented hemivertebra without structural compensatory curves, we have routinely maintained the principles of early surgery and short fusion [17,18]. Consistent with previous reports, a satisfactory deformity correction was shown in a majority of these patients. In addition, we have noticed a kind of unexpected idiopathic postoperative-emerging scoliosis in nine patients. These emerging scoliosis were generally S-shaped and have more than a 20° increase of the Cobb angle from its initial value, the apical vertebra were lying at least two levels from the fusion area. This kind of postoperative complication with such surgery has not been reported in any previous literature. The aim of the present study was to analyze the pathogenesis, feature, and treatment of this new postoperative complication. Methods A total of 128 patients with congenital scoliosis due to single fully segmented hemivertebra who underwent posterior correction and fusion in our department between January 2008 and March 2014 were retrospectively reviewed. Approval was obtained by the local Ethics Committee before
data collection and analysis. The inclusive criteria were as follows: (1) no structural secondary scoliosis before surgery, (2) underwent short segment fixation and fusion, (3) more than 1 year of radiographic follow-up after the initial surgery, (4) postoperative-emerging scoliosis with a more than 20° increasing of the Cobb angle, while at the same time the apical vertebra was at least two levels from the lower (or upper) instrument vertebra, and (5) no arthropathy existed in their lower limbs. Patients who had an anterior approach, more than one hemivertebra or combination with other congenital spinal deformity, were not included in the present study. Nine patients matched these criteria. There were seven women and two men. The mean age of the patients at the time of primary surgery was 11.4±3.6 years. The mean followup was 36.0±9.5 months. All patients had a standard posterioronly hemivertebra resection with transpedicular screw fixation [8,19]. The CD HORIZON M8 or Legacy screw-rod system (Medtronic Sofamor, Danek, USA, Inc., Memphis, TN, USA) was used for fixation in all patients. An average of 2.8±1.1 segments were fused in these patients (the resected hemivertebra was included in the calculation). All surgeries were performed by both senior authors. Whole spine anteroposterior and lateral radiographs were reviewed preoperatively, 1 week, 3 months, 6 months, and 9 months postoperatively, and then each year postoperatively to assess deformity correction and development. The parameters measured in the anteroposterior radiographs were the main curve, the compensatory curves, the postoperativeemerging curves, and the coronal balance. The main curve was measured as the Cobb angle between two vertebrae immediately adjacent to the hemivertebra. Both the preoperative compensatory curves (more than 10° at the neutral position) and the postoperative-emerging curves (as above defined) were measured as the Cobb angle between the two most tilted vertebrae on corresponding radiographs. The end vertebrae and the apical vertebrae of all these curves were recorded respectively. And the bending radiographs were reviewed to assess both the flexibility of the preoperative compensatory curves and postoperative-emerging curves. Coronal balance was measured by the deviation of the C7 plumb line from the center sacral vertical line. It was considered significant when the deviation exceeded 20 mm. The parameters measured in the lateral radiographs were the segmental kyphosis, postoperative junctional kyphosis and the sagittal balance. The segmental kyphosis was measured between the two vertebrae adjacent to the hemivertebra. The proximal junctional kyphosis (PJK) had only been recorded when the angle increased more than 10° during the follow-up. The sagittal balance was measured as the horizontal distance from the C7 plumb line to the posterior superior corner of S1. In all of these patients, three-dimensional computed tomography (CT) scans were taken preoperatively to assess the morphology of the hemivertebra, while 3 months and 6 months postoperatively, and annually after surgery to assess the fusion status. Meanwhile, the integrity and position of the internal fixation were evaluated.
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Statistical analysis was performed using the SPSS17 software (IBM, Inc., New York, NY, USA). The preoperative and postoperative follow-up results were analyzed statistically with the use of the paired Student’s t test. p<.05 was considered significant. Result Of 128 patients, 9 (7%) who matched the criteria were included in the present study, with an average age of 11.4 years (range from 7 to 15 years), and an average Risser sign of grade 2 (range from 0 to 4). The location of the hemivertebra was in the thoracolumbar area in six patients (T11 in three patients, T12 in one patient, and L1 in two patients), and in thoracic in three patients (T4, T5, and T7, respectively). The averaged Cobb angle of the preoperative main curve was 36.1±14.4°. Seven of the nine patients had an average compensatory curve of 20.3±4.8°. After primary surgery, the mean follow-up of these patients was 26 months with the range from 18 to 42 months (for the patients who underwent revision surgery, the followup was identified as the time between two operations). There was no patient demonstrated PJK, pseudoarthrosis, or internal fixation failure during the whole follow-up period. The value of the main curve had been significantly decreased to 6.9±6.1° (p<.001) by surgery with the mean rate of correction at 82.5%. And this angle was fairly constant until the final follow-up (7.9±6.6°, p=.08). The mean segmental kyphosis was 20.4±4.1° preoperatively. The kyphosis had been significantly corrected to 9.9±4.2° postoperatively (p<.001) and remained constant at 9.2±4.0° at the final follow-up (p=.53). The coronal balances before correction, after correction, and at the final follow-up were 0.6±0.6, 0.6±0.4, and 0.8±0.6, respectively (preoperation vs. postoperation, p=.63; and postoperation vs. final operation, p=.09). The sagittal
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balance was 1.6±1.0 preoperative, 1.2±0.9 postoperative, and 1.7±0.9 at the final follow-up (preoperation vs. postoperation, p=.13; and postoperation vs. final operation, p=.12). In four patients, the emerging scoliosis occurred at 3 months after the initial operation, whereas in the other five patients, it occurred at 6 months. All these emerging scoliosis appeared in S-shaped curves. It appeared as the main thoracic scoliosis with a lumbar scoliosis in four patients, the main lumbar scoliosis with a thoracic scoliosis in four patients, and double thoracic scoliosis with a lumbar scoliosis in one patient (patient 4, Fig. 1). Details of the end vertebrae, the apical vertebrae, the Cobb angle, and treatment of the emerging scoliosis of all nine patients are listed in the Table. The mean value of the main emerging curve was 42.6±12.9 at the final followup. And the apical vertebra of the main emerging curve was at least 2 levels far from the end instrument vertebra, with an average of 3.2 levels (range from 2 to 6 levels). The region of postoperative-emerging scoliosis was in accord with their preoperative compensatory scoliosis in five patients (Patients 2, 4, 5, 7, and 8). Six of nine patients underwent bracing therapy when the S-shaped scoliosis arose, whereas the remaining three patients underwent closely observation. The emerging scoliosis had developed into the structural curves and beyond 45° in four patients during follow-up. A posterior-only revision surgery was performed in these four patients at 18 months after initial surgery (Patients 1, 2, 4, and 5). The fusion region was extended to cover all structural curves (Fig. 2). During an average of 22.5 months follow-up, no new deformity developed after revision. Discussion In recent years, single-stage posterior hemivertebra resection and short fusion has gradually become the mainstream
Fig. 1. The pre- and postfirst operative radiographs of Patient 4. A 15-year-old man with a fully segmental hemivertebra at T11. The preoperative anteroposterior (AP) and bending films showed three slightly flexible compensatory curves located in T2–T7, T7–T9, and L1–L5, respectively. The posterior hemivertebra resection with T10–T12 fusion was performed. And the postoperative AP film showed that both the main curve and the compensatory curves were obviously corrected. However, an unwonted emerging S-shaped scoliosis appeared 6 months after this operation. These emerging curves were 36.1°, 42.5°, and 21.5° at T2–T7 (PT), T7–T12 (MT), and T12–L5 (L) respectively, exceeded 20° than preoperative same levels. Meanwhile, the apical vertebra of MT was T8, which are located two levels far from the upper instrument vertebra. The trunk balance is always normal.
ARTICLE IN PRESS Preop., preoperative; Postop., postoperative; MC, main curve; CC, compensatory curve; EC, emerging curve; AV, apical vertebra; MT, main thoracic scoliosis; PT, proximal thoracic scoliosis; L, lumbar scoliosis; M, male; F, female.
L2 L3 L4 T9 T7 ML+T ML+T ML+T MT+L MT+L 6 3 3 6 6 10.4 3.8 18.0 8.5 1.5 T9–T12 T10–T12 T12–L2 T11–L1 T11–L3 T11(35.2) T11(21.8) L1(42.1) T12(36.0) L1(31.5) 3 0 0 0 4 F F F F M 5 6 7 8 9
14 5 10 7 15
Therapy
Brace and revision Revision Brace Brace and revision T9 T9 L2 T8
T1–T12(50.5) and T12–L5(28.6) T4–T12(64.2) and T12–L5(32.5) T9–T12(20.2) and T12–L3(25.9) T2–T7(44.3), T7–T12(51.4), and T12–L5(26.1) T5–T12(25.3) and T12–L4(47.5) T4–T12(26.1) and T12–L5(40.3) T8–T11(20.4) and T11–L5(45.0) T6–T11(38.4) and T11–L5(28.1) T5–T11(23.1) and T11–L5(21.0) MT+L MT+L ML+T PT+MT+L 3 3 6 6 13.9 5.3 0 0.5 T1–T6 T4–T6 T5–T8 T10–T12
T12–L4(30.0) T6–T12(24.5) — T2–T7(16.0), T7–T9(20.8) and L1–L5(21.9) T12–L4(18.5) T4–T10(15.9) L2–L5(20.0) T6–T11(15.0) — T4(69.0) T5(34.4) T7(18.2) T11(36.5) 4 3 0 4 F F F M 1 2 3 4
14 13 10 15
AV of main EC EC (levels and °) Type of EC Onset of EC (mo) Postop. MC (°) Fused segment CC (levels and °) Sex Case
Age
Risser
Hemivertebra and preop. MC (°)
Table Patient’s demographic, anatomical, and radiographic characteristics
Revision Brace Brace Brace Observe
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treatment for the congenital scoliosis of fully segmented nonincarcerated hemivertebra [4,10–13,16]. Early or even prophylactic hemivertebra resection was recommended to stop the development of the local deformity and to prevent the longer fusion extending to the advanced secondary structural curves [10–13]. The modern transpedicular instrumentation could provide the short and sufficiently rigid stabilization in such patients, thereby avoiding wider distractions of spinal growth and mobility [11,16]. With the wide application of posterior hemivertebra resection and short fusion, the number of these cases has steadily increased, and the surgical complications have gradually become another prominent problem besides deformity correction by surgery itself [8,12,14–16]. The postoperative new deformity is one of the most common complications in this surgery. Although its incidence is lower than neurologic injuries, deformity progress has usually been given more attention because of its huge impact on initial correction and the potential risk of revision surgery. Wang et al [12] reported that the 18.9% (7/37) of congenital scoliosis patients with posterior hemivertebra resection and short fusion had more than a 10° increase kyphosis developing above the top of instrumentation at an average 4.5 years follow-up period. The authors then analyzed that the possible cause of PJK in these pediatric patients contains following two factors. The first and main point is that the misplaced screws in upper instrumental vertebra may have disturbed the normal growth on the endplate. The second point is the excess damage that may have been caused in the facet capsules or supraspinous ligament above the fusion segments during exposure, which directly related to the occurrence of PJK. Shi et al [14] reported 19 patients with a hemivertebra that underwent revision surgery because of the deformity progression after their first operation. No incomplete resection of the malformed hemivertebra or failure in internal fixation or pseudarthrosis has been recognized as the main cause of their development deformity after hemivertebra resection and fusion. Similar results and reason analysis of these complications have also been reported by Ruf et al [16] in 2009 and Zhang et al [8] in 2011. Although the type and cause of deformity are various, these progressive deformities reported in previous literature have a common ground, that the postoperative deformity develops on the hemivertebra resection level or surgical fusion area [8,12,14,16]. In contrast, the progressive curve developing in present congenital patients actually have little correlation with the initial surgical segment. In our patients, the emerging scoliosis showed an S-shaped appearance, and the apical vertebra of the curves were located at least two levels far from the upper or lower instrumented vertebra, which were remarkably different from adding-on deformity. In addition, there was no developed kyphosis, pseudoarthrosis, or failure of internal fixation occurring over the range of fusion. The hemivertebra, together with the adjacent growth plates have also been completely resected by the initial posterior surgery. With the method of exclusion, it seemed that this emerging scoliosis
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Fig. 2. The pre- and postrevision radiographs of Patient 4. The patient had undergone a brace since the emerging scoliosis was found at 6 months after initial surgery. However, the emerging scoliosis still developed gradually. The films before the revision showed that the proximal and the main thoracic curves were relatively serious and structural at 18 months after the first operation. Then, a posterior revision was performed. The fusion was extended according to the basic laws in patients with adolescent idiopathic scoliosis (AIS). The upper instrumented vertebra was chosen at T2, the upper end vertebra of PT, whereas the lowest instrumented vertebra was chosen at the stable vertebra (L3). A satisfied deformity correction and trunk balance were found during 24 months follow-up after revision.
was a kind of agnogenic postoperative deformity in congenital patients that have not been reported previously. The development of the S-shaped curves in congenital patients who underwent posterior hemivertebra resection and short fusion was surprising and unforeseen. It was hard to find any direct reason to explain the appearance of this complication. The emerging curve in almost all current patients (eight patients) presented double curves which included a thoracic curve and a lumbar one (except one patient who presented with double thoracic curve with a lumbar curve; Fig. 1). This kind of S-shaped curve was conducive in maintaining trunk balance in a standing position. So, there was no coronal imbalance found in any of the present patients. When comparing the coronal spinal curvature before and after primary surgery, we have noticed that the location of postoperative progressive curves had a high consistency with preoperative secondary curves [10]. Secondary curve is the spontaneous deformity that compensates for the local scoliosis due to hemivertebra. And in the early period of congenital scoliosis, the secondary curves usually are limited and unstructured, and do not need specific treatment [4,5,19]. In the present study, the preoperative secondary curves in all our patients were slight and flexible (mean Cobb angle in the neutral position was 20.3°). Based on the general principle, local hemivertebra resection and short fusion was chosen without any intervention in these slight secondary deformities. Anomalously, the compensatory curves quickly developed during the first 6 months after operation. To explain the development of these curves, a potential mechanism was put forward. Secondary curves in congenital patients in theory are accompanied with the biomechanics change of paravertebral muscle or facet joint. With the growth and development of the spine, these biomechanical changes will gradually alter to morphological changes. These microscopic changes may be earlier than the appearance of structural scoliosis. In pa-
tients with congenital scoliosis with good coronal trunk balance, hemivertebra resection and local scoliosis correction in fact will break the original coronal balance. If the morphology of paravertebral muscle and facet joint has already changed irreversibly at this time, the preoperative secondary curves may further develop (in such short term after initial surgery) to reach a new trunk balance. It seems that the emerging S-shaped scoliosis after hemivertebra resection can also be understood as the accelerated development of preoperative secondary scoliosis. Seven out of nine present patients were aged between 10 and 15 years, whereas the other two patients were aged less than 10 years. The result indicated that a higher percentage of this complication occurred in the adolescent patients. Adolescence is the second peak of growth and development. Rapid growth of the body may increase the possibility of this complication. But above all, the teenage years are a relatively late age for operating on patients with congenital scoliosis due to hemivertebra [10–12,19]. From their first time of standing up to their adolescence, the period in fact is long enough for the appearance of morphological changes at their posterior spine complex. The level of the hemivertebra was on T11–L1 in six of nine current patients, whereas it was on T4–T7 in the other three patients. The level was in accordance with the position distribution of the hemivertebra. The thoracolumbar junction had been documented as the predominant sites of hemivertebra [5,16,20]. Isolated hemivertebra in upper thoracic or lumbosacral region usually results in early trunk decompensation [7]. The patients with upper thoracic or lumbosacral hemivertebra used to undergo longer fusion when they were young in our department. Until now, we have not found any posterior emerging scoliosis in these patients. On the other side, thoracolumbar junction as we know was a specific region where the stress concentration was high and postoperative deformities (such as PJK) are prone to develop [12].
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Unfortunately, due to the limitation of the current retrospective study, we could not prove whether the hemivertebra in thoracolumbar junction or the short fusion during adolescence were the risk factors for the emerging S-shaped scoliosis. Despite the preoperative hemivertebra, the characteristics and development of postoperative-emerging S-shaped scoliosis in the present patients were quite similar to the curves in patients with adolescent idiopathic scoliosis (AIS). In fact, we found that the therapeutic strategy for AIS was suitable similarly for current patients. Brace was recommended to control the progression of this postoperative curve when it was relatively slight and flexible at the early stage. When the emerging curve became structural, revision by extending the initial fusion segment was an optional choice to improve the appearance of the trunk. The fusion range could be determined by complying with the general laws in patients with AIS [21]. In the four present patients who underwent reoperation, we have chosen the upper end vertebra to be the upper instrumented vertebra with the stable vertebra to be the lower instructed vertebra. Finally, satisfactory correction and fusion were achieved, and no progressive deformity was found up to the last follow-up. Looking back on these patients with postoperativeemerging S-shaped scoliosis, especially the ones who underwent revision surgery, a serious question is raised and therefore must be considered in depth. Was the short fusion (after hemivertebra resection) really sufficient for these patients, in other words, should we plan to do a long segmental fusion at first surgery? It is hard for this question to be exactly answered by now because the pathogenetic mechanism or predictive factors of the postoperative-emerging scoliosis are still unclear because of the retrospective property and small sample size of the present study. However, given a low rate (about 7%) of this complication, we hold that the short fusion following posterior hemivertebra resection was still the first choice for patients with congenital scoliosis due to hemivertebra. And the postoperative-emerging S-shaped scoliosis should be added into the general complications of such surgery, and patients should be informed before surgery. Conclusions In conclusion, posterior emerging S-shaped curve is an extraordinary and previously unreported complication after posterior hemivertebra resection and short fusion. In the present study, the emerging curve was defined as the postoperative scoliosis with more than 20° of an increase in the Cobb angle from its initial value, whereas the apical vertebra was at least two levels from the lower (or upper) instrument vertebra. This unusual deformity seems to be developing from slight and compensatory secondary scoliosis before surgery. However, the specific cause is still unclear. The majority of patients with posterior emerging scoliosis were teenagers who had a hemivertebra in the thoracolumbar junction area. This S-shaped
curve used to be flexible at the beginning of progression at 3–6 months after the initial surgery. And at this time, brace was recommended. When the deformities developed to structured scoliosis, reoperation with longer fusion should be done, and the fusion segment could be decided as being the same as the posterior correction in AIS. References [1] McMaster MJ, Ohtsuka K. The natural history of congenital scoliosis. A study of two hundred and fifty-one patients. J Bone Joint Surg Am 1982;64:1128–47. [2] Winter RB, Moe JH, Eilers VE. Congenital scoliosis: a study of 234 patients treated and untreated. J Bone Joint Surg Am 1968;50A: 1–15. [3] Yaszay B, O’Brien M, Shufflebarger HL, et al. Efficacy of hemivertebra resection for congenital scoliosis: a multicenter retrospective comparison of three surgical techniques. Spine 2011;36:2052–60. [4] Ruf M, Harms J. Hemivertebrae resection by a posterior approach: innovate operative technique and first results. Spine 2002;27:1116– 23. [5] Wang S, Zhang J, Qiu G, et al. Posterior hemivertebra resection with bisegmental fusion for congenital scoliosis: more than 3 year outcomes and analysis of unanticipated surgeries. Eur Spine J 2013;22:387–93. [6] Nakamura H, Matsuda H, Konishi S, et al. Single-stage excision of hemivertebrae via the posterior approach alone for congenital spine deformity: follow-up period longer than ten years. Spine 2002;27:110– 15. [7] Zhuang Q, Zhang J, Li S, et al. One-stage posterior-only lumbosacral hemivertebra resection with short segmental fusion: a more than 2-year follow-up. Eur Spine J 2015;25:1567–74. Published online. [8] Zhang J, Shengru W, Qiu G, et al. The efficacy and complications of posterior hemivertebra resection. Eur Spine J 2011;20:1692–702. [9] Mladenov K, Kunkel P, Stuecker R. Hemivertebra resection in children, results after single posterior approach and after combined anterior and posterior approach: a comparative study. Eur Spine J 2012;21:506– 13. [10] Chang DG, Suk SI, Kim JH, et al. Surgical outcomes by age at the time of surgery in the treatment of congenital scoliosis in children under age 10 years. Spine J 2015;15:1783–95. [11] Ruf M, Harms J. Posterior hemivertebra resection with transpedicular instrumentation: early correction in children aged 1 to 6 years. Spine 2003;28:2132–8. [12] Wang Y, Kawakami N, Tsuji T, et al. Proximal junctional kyphosis following posterior hemivertebra resection and short fusion in children younger than 10 years. Clin Spine Surg 2016 Jun 20 [Epub ahead of print]. [13] Crostelli M, Mazza O, Mariani M. Posterior approach lumbar and thoracolumbar hemivertebra resection in congenital scoliosis in children under 10 years of age: results with 3 years mean follow up. Eur Spine J 2014;23:209–15. [14] Shi Z, Li Q, Cai B, et al. Causes of the failure and the revision methods for congenital scoliosis due to hemivertebra. Congenit Anom (Kyoto) 2015;55:150–4. [15] Reames DL, Smith JS, Fu KM, Scoliosis Research Society Morbidity and Mortality Committee, et al. Complications in the surgical treatment of 19,360 cases of pediatric scoliosis: a review of the Scoliosis Research Society Morbidity and Mortality database. Spine 2011;36:1484–91. [16] Ruf M, Jensen R, Letko L, et al. Hemivertebra resection and osteotomies in congenital spine deformity. Spine 2009;34:1791–9. [17] Zhou C, Liu L, Song Y, et al. Hemivertebrae resection for unbalanced multiple hemivertebrae: is it worth it? Eur Spine J 2014;23:536– 42.
ARTICLE IN PRESS X. Yang et al. / The Spine Journal ■■ (2016) ■■–■■ [18] Wang L, Song Y, Pei F, et al. Comparison of one-stage anteroposterior and posterior-alone hemivertebrae resection combined with posterior correction for hemivertebrae deformity. Indian J Orthop 2011;45: 492–9. [19] Ruf M, Harms J. Pedicle screws in 1- and 2-year-old children: technique, complications, and effect on further growth. Spine 2002;27:460–6.
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[20] Bollini G, Launay F, Docquier P, et al. Congenital abnormalities associated with hemivertebrae in relation to hemivertebrae location. J Pediatr Orthop B 2010;19:90–4. [21] Mulconrey DS, Lenke LG. Chapter 13 selection of fusion levels. In: Newton PO, editor. Idiopathic scoliosis: the Harms Study Group treatment guide. Stuttgart, Baden-Württemberg: Thieme Medical Publishers Inc; 2010. p. 172–96.