The adding-on phenomenon in Lenke type I adolescent idiopathic scoliosis Текст научной статьи по специальности «Клиническая медицина»

© ayu. sergunin et al., 2018

the adding-on phenomenon in lenke type i adolescent idiopathic scoliosis

A.Yu. Sergunin, A.S. Vasyura, A.N. Sorokin

Novosibirsk Research Institute of Traumatology and Orthopaedics n.a. Ya.L. Tsivyan, Novosibirsk, Russia

Objective. To analyze the incidence of adding-on phenomenon in the surgery of Lenke type 1 idiopathic scoliosis.

Material and Methods. The study included prospective analysis of radiographs of 89 patients (82 females and 7 males) with idiopathic scoliosis who met the criteria for inclusion. The age of patients at the time of surgery ranged from 12 to 25 years (mean: 16.3 ± 4.4 years). The average follow-up period was 2.3 ± 0.4 years. Scoliotic deformity corresponded to grade III according to V.D. Chaklin's classification in 24 patients, and to grade IV in 65. The magnitude of the primary thoracic curve varied from 30° to 103° of Cobb angle (mean: 61.1° ± 17.1°). In all cases, segmental third generation instrumentation (hybrid or laminar) was used in combination with intraoperative skeletal traction with an afford equal to 50 % of the patient's body weight. Laminar fixation was used in 6 patients, and hybrid fixation with different extent of screw installation in 83.

Results. The following parameters showed significant increase: the magnitude of thoracic curve according to Cobb — 16.0° ± 4.3°, the distance from the center of the vertebra located one level distal to the lowest instrumented vertebra, to the central sacral vertical line (LIV+1-CSVL) — 3.6 ± 2.5 mm, the tilt of the lower instrumented vertebra in the coronal plane (LIV tilt angle) — 3.6° ± 2.8°, the tilt of the vertebra located one level distal to the lowest instrumented vertebra (LIV+1 tilt angle) — 4.6° ± 2.5°, and the distance from the center of the apical vertebra of the primary curve to the central sacral vertical line (AV-CSVL) — 17.2 ± 12.0 mm. A significant correlation was found between postoperative magnitude of the scoliotic curve and AV-CSVL distance, postoperative LIV+1-CSVL distance and postoperative LIV+1 tilt angle. An increase in LIV+1 tilt angle in combination with an increase in LIV+1-CSVL distance by more than 4 mm (or degrees) could be a parameter for measuring the adding-on phenomenon.

Conclusion. The indication for reoperation may probably be a significant tilt of the vertebra located below the lowest instrumented vertebra, accompanied by pain syndrome and coronal imbalance. Key Words: adding-on, idiopathic scoliosis, scoliosis surgery.

Please cite this paper as: Sergunin AYu, Vasyura AS, Sorokin AN. The adding-on phenomenon in Lenke type I adolescent idiopathic scoliosis. Hir. Pozvonoc.

2018; 15(1):26—31. In Russian.

DOI: http://dx.doi.org/10.14531/ss2018.1.26-31.

Scoliotic deformity of Lenke type I is one of the most common forms of idiopathic scoliosis in adolescents [3]. This deformity is characterized by the presence of primary thoracic structural curve and upper thoracic or lumbar nonstructural compensatory curve. The use of selective fusion in this type of deformity involves fixation of thoracic curve only, while compensatory curve is left non-instrumented with an eye to spontaneous self-correction [2]. According to published data [1, 4, 5], adding-on phenomenon can be caused by incorrect choice of the lower instrumented vertebra, when area of fusion with metal constructs is too short and compensatory curve cannot balance the achieved correction.

There is no consensus on the definition of adding-on pathological condi-

tion in the literature. Wang et al. [9, 10] define adding-on phenomenon as a progressive increase in the number of vertebrae included distally within the primary curve combined with either an increase of more than 5 mm in deviation of the first vertebra below instrumentation from the central sacral vertical line, or an increase of more than 5° in the angu-lation of the first disc below the instrumentation at 1 year follow-up. Sponseller et al. [8] define adding-on phenomenon as an increase in the number of vertebrae in the measured curve either proxi-mally or distally combined with a curve increase of more than 6° from the first postoperative radiograph. Schlechter et al. [6] defined adding-on as progression of the primary Cobb below the level of instrumentation due to either an increase in the number of vertebra included with-

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in the curve, or an increase in disc angu-lation distal to the instrumentation. In our practice, we use the definition proposed by Wang et al. [9, 10].

The rate of adding-on occurrence is very variable and ranges from 2 to 51 % [6-8, 10]. The development of this complication can lead to an unsatisfactory clinical outcome and the risk of repeated operations. We have not found any papers devoted to this issue in the Russian literature. In routine practice, we do not use selective fusion algorithms [2, 3] and follow the recommendations by Cotrel and Dubousset. These authors identified the lowest instrumented vertebra according to functional spondylogra-phy and used the vertebra located immediately above the disc showing symmetrical wedging on left/right lateral bending

radiographs as the lowest instrumented vertebra.

The aim of the study was to analyze the occurrence rates of adding-on in surgery of Lenke type I idiopathic scoliosis.

Material and Methods

This study retrospectively analyzed radiographs of patients with idiopathic scoliosis operated on at the specialized Spine Surgery Clinic. Selective fusion was not used.

The study group inclusion criteria: Lenke type I deformity, patient age below 25 years, postoperative follow-up period at least 2 years. A total of 89 patients met these criteria: 82 females and 7 males . The age of the patients at the time of surgery ranged from 12 to 25 years, approximately 16.3 ± 4.4 years. The mean postoperative follow-up was 2.3 ± 0.4 years. Scoliotic deformity corresponded to grade III according to V.D. Chaklin's classification in 24 patients and to grade IV in 65. Magnitude of the primary thoracic curve according to Cobb varied from 30 to 103° and was approximately 61.1° ± 17.1°. In all cases, segmental third generation instrumentation (hybrid or laminar) was used in combination with intraoperative skeletal traction with a 50% tractive force of the patient's body weight. Laminar fixation was used in 6 patients, hybrid fixation with different extent of screw installation in 83. Standing coronal and lateral radiographs of the thoracic and lumbar spine, including pelvic crests, as well as supine side-bending views were made.

Preoperative radiographs, 2-weeks post-op final follow-up radiographs were assessed.

Based on the literature data, the following radiographic parameters were evaluated: primary thoracic curve magnitude, compensatory lumbar curve magnitude, fusion length, the lowest instrumented vertebra, the distance from center of the first thoracic vertebra to the central sacral vertical line (T1-CSVL), the

tilt of the lowest instrumented vertebra in the coronal plane (LIV tilt angle), the tilt of the vertebra located one level distal to the lowest instrumented vertebra (LIV+1 tilt angle), the distance from the center of the apical vertebra of the primary curve to the central sacral vertical line (AV-CSVL), the distance from center of the lowest instrumented vertebra to the central sacral vertical line (LIV-CSVL), the distance from the center of the vertebra located one level distal to the lowest instrumented vertebra, to the central sacral vertical line (LIV+1-CSVL; Fig. 1).

Statistical analysis of the data was performed using Microsoft Excel software. The standard error of the mean was indicated in the parameter estimation. Pair comparison was performed using a standard T-test. The Pearson coefficient was estimated in order to identify a correlation between radiographic parameters. The significance level was set at P < 0.05.

Results and Discussion

In 2 (2.25 %) cases, the lowest instrumented level was L5, in 22 (24.70 %) - L4, in 57 (64.04 %) - L3, in 7 (7.87 %) - L2, in 1 (1.14 %) - L1. Only 5 (5.62 %) of 89 patients can be categorized as having adding-on (Fig. 2). They showed a significant increase in 5 radiographic parameters at the last follow-up examination compared to early postoperative radiographs: thoracic curve magnitude according to Cobb, LIV+1-CSVL, LIV tilt angle, LIV+1 tilt angle, and AV-CSVL. The grade of increase in these parameters is presented in Table 1. The rest radiographic parameters did not change significantly (Table 2, Fig. 3). No significant changes in radiographic parameters were found in patients without adding-on signs during the postoperative period (Table 3). In the study, 5 of 7 radiographic parameters showed significant increase in postoperative period and can be potential criteria for detection of adding-on. A significant correlation

was found for some of the parameters under study: between the postoperative scoliotic curve magnitude and AV-CSVL distance, postoperative LIV+1-CSVL distance and postoperative LIV+1 tilt angle; less significant parameters were LIV+1-CSVL and the postoperative angle of the primary curve. Therefore, these parameters can be used for evaluation of adding-on. Other parameters showed the correlation level close to 0.1 and were regarded as insignificant (Table 4).

Several authors described adding-on phenomenon in their research. Suk et al. [7] revealed adding-on in 17 of 203 patients. Schlechter et al. [6] noted this phenomenon in 52 of 407 operated patients. It was found that this pathology often occurs in the presence of thoracic curve with lumbar compensatory curvature in Lenke type IA and IIA deformities. In the literature, there is no consensus on radiological and clinical parameters to measure the grade of adding-on as well as on clear criteria for repeated interventions directed at its elimination.

Conclusion

An increase in the LIV+1 tilt angle in combination with an increase in the LIV+1-CSVL distance by more than 4 mm (or degrees) can be a parameter to measure the adding-on phenomenon. However, the high measurement error is a drawback of this parameter. Significant criteria for repeated surgery in patients with adding-on are difficult to identify. In this study, none of the patients with adding-on phenomenon were reoperated because deviations from the norm were clinically insignificant. Nevertheless, the significant tilt of the vertebra located under the lower instrumented vertebra associated with pain syndrome and frontal imbalance may probably be an indication for repeated surgery.

The study was not sponsored. The authors declare no conflict of interest.

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Fig. 1

Radiographic parameters under study, a female patient A. aged 10 years with grade IV right-sided thoracic idiopathic scoliosis: 1 - thoracic curve according to Cobb; 2 - LIV tilt angle; j - LIV+1 tilt angle; 4 - CSVL; 5 - T1-CSVL distance; 6 - AV-CSVL distance; 7 -LIV-CSVL distance; 8 -LIV+1-CSVL distance

Fig. 2

Radiographs of a female patient A., 10 years, with grade IV right-sided thoracic idiopathic scoliosis: a - before surgery; b - 2 weeks after surgery; c - 2 years after surgery

Table 1

Radiographic parameters in patients with adding-on

Thoracic curve according to Cobb, degrees LIV+1-CSVL, mm LIV tilt angle, degrees LIV+1 tilt angle, degrees AV-CSVL, mm

16.0 ± 4.3 3.6 ± 2.5 3.6 ± 2.8 4.6 ± 2.5 17.2 ± 12.0

Table 2

Changes in radiographic parameters in patients with adding-on

Parameters Preoperative Postoperative In 2 years after surgery P

Thoracic curve according to Cobb, degrees 64.0 ± 9.1 21.2 ± 5.0 37.2 ± 8.7 0.002

LIV-CSVL, mm 16.2 ± 10.6 13.6 ± 5.8 14.2 ± 3.4 0.8

LIV+1-CSVL, mm 9.2 ± 5.6 8.8 ± 3.4 12.4 ± 3.5 0.02

LIV tilt angle, degrees 10.4 ± 5.0 2.0 ± 3.4 5.6 ± 3.1 0.06

LIV+1 tilt angle, degrees 6.6 ± 9.1 3.2 ± 0.0 7.8 ± 4.6 <0.001

T1-CSVL, mm 16.2 ± 19.7 17.2 ± 14.8 9.8 ± 9.2 0.4

AV-CSVL, mm 51.8 ± 26.0 8.0 ± 5.2 25.2 ± 11.7 0.05

Mean and standard error of the mean, significant difference (P < 0,05).

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_hirurgia pozvonochnika 2018;15(1):26-31_

ayu. sergunin et al. the adding-on phenomenon in lenke type i adolescent idiopathic scoliosis

degrees

preoperative^ postoperatively 24 months after surgery

preoperatively postoperatively 24 months

after surgery

degrees

preoperatively postoperatively 24 months after surgery

preoperatively postoperatively 24 months after surgery

preoperatively postoperatively 24 months after surgery

Fig. 3

A change in the studied parameters in patients with adding-on at follow-up: a - thoracic curve according to Cobb; b - LIV+1-CSVL distance; c - LIV tilt angle; d - LIV+1 tilt angle; e -AV-CSVL distance

P = 0.002

P = 0.02

b

a

P = 0.06

P < 0.001

d

c

P = 0.05

e

Table 3

Changes in radiographic parameters in patients without adding-on

Parameters Preoperative Postoperative In 2 years after surgery P

Thoracic curve according to Cobb, degrees 60.9 ± 17.5 21.0 ± 10.6 22.6 ± 10.4 0.01

LIV-CSVL, mm 14.1 ± 9.9 6.6 ± 6.6 6.1 ± 6.2 0.33

LIV+1-CSVL, mm 7.7 ± 6.6 5.1 ± 5.8 4.1 ± 4.9 0.02

LIV tilt ang^, degrees 12.8 ± 8.1 2.5 ± 2.7 3.3 ± 3.8 0.02

LIV+1 tilt ang^, degrees 8.3 ± 6.1 2.1 ± 2.9 3.2 ± 4.2 0.04

T1-CSVL, mm 12.0 ± 8.5 14.9 ± 11.2 10.0 ± 7.8 <0.001

AV-CSVL, mm 43.8 ± 23.0 9.8 ± 7.3 11.3 ± 9.8 0.1

Mean and standard error of the mean, significant difference (P < 0,05).

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Table 4

Correlation of postoperative radiographic parameters in patients with adding-on

Parameters Curve angle LIV+1-CSVL LIV tilt angle LIV+1 tilt angle AV-CSVL

Postoperative curve angle R = 0.23 R = 0.36 R = 0.1 R = 0.4

LIV+1-CSVL R = 0.23 R = 0.1 R = 0.47 R = 0.12

LIV tilt angle R = 0.36 R = 0.1 R = 0.11 R = 0.11

LIV+1 tilt angle R = 0.1 R = 0.47 R = 0.11 R = 0.1

AV-CSVL R = 0.4 R = 0.12 R = 0.11 R = 0.11

R from 0.1 to 0.3 — weak positive correlation; R from 0.3 to 0.7 — moderately positive correlation.

References

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3. Lenke L, Betz R, Harms J, Bridwell KH, Clements DH, Lowe TG, Blanke K. Adolescent idiopathic scoliosis: a new classification to determine extent of spinal arthrodesis. J Bone Joint Surg Am. 2001;83A:1169-1181. DOI: 10.2106/00004623-200108000-00006.

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8. Sponseller PD, Betz R, Newton PO, Lenke LG, Lowe T, Crawford A, Sucato D, Lonner B, Marks M, Bastrom T. Differences in curve behavior after fusion in adolescent idiopathic scoliosis patients with open triradiate cartilages. Spine. 2009;34:827-831. DOI: 10.1097/BRS.0b013e31819139ef.

9. Wang Y, Bunger CE, Zhang Y, Wu C, Li H, Hansen ES. Distal adding-on in Lenke 1A scoliosis: how to more effectively determine the onset of distal adding-on. Spine. 2013;38:490-495. DOI: 10.1097/BRS.0b013e318273ed11.

10. Wang Y, Hansen ES, Hoy K, Wu C, Bunger CE. Distal adding-on phenomenon in Lenke 1A scoliosis: risk factor identification and treatment strategy comparison. Spine. 2011;36:1113-1122. DOI: 10.1097/BRS.0b013e3181f51e95.

Address correspondence to:

Sergunin Aleksandr Yuryevich

Novosibirsk Research Institute of Traumatology and Orthopaedics n.a. Ya.L. Tsivyan, Frunze str., 17, Novosibirsk, 630091, Russia, Saport2010@ngs.ru

Received 02.10.2017 Review completed 08.11.2017 Passed for printing 16.11.2017

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Aleksandr Yuryevich Sergunin, traumatologist-orthopaedist in the Departament of Pediatric (Orthopaedics No. 1, Novosibirsk Research Institute of Traumatology and Orthopaedics n.a. Ya.L. Tsivyan, Frunze str., 17, 630091, Novosibirsk, Russia, Saport2010@ngs.ru;

Aleksandr Sergeyevich Vasyura, MD, PhD, traumatologist-orthopaedist in the Department of Children and Adolescent Spine Surgery, Novosibirsk Research Institute of Traumatology and Orthopaedics n.a. Ya.L. Tsivyan, Frunze str., 17, 630091, Novosibirsk, Russia, niito@niito.ru;

Artem Nikolaevich Sorokin, MD, PhD, traumatologist-orthopaedist in the Departament of Pediatric Orthopaedics No. 1, Novosibirsk Research Institute of Traumatology and Orthopaedics n.a. Ya.L. Tsivyan, Frunze str., 17, 630091, Novosibirsk, Russia, niito@niito.ru.

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