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 Table of Contents  
SPINE CLINIC
Year : 2020  |  Volume : 3  |  Issue : 2  |  Page : 216-230

The spine clinics: Adolescent idiopathic scoliosis


1 Department of Orthopaedics, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi, India
2 Department of Spine Surgery, Kothari Medical Centre, Kolkata, West Bengal, India
3 Department of Spine Surgery, Ganga Hospital, Coimbatore, Tamil Nadu, India
4 Department of Spine Surgery, Chirayu Hospital, Ahmedabad, Gujarat, India
5 Department of Orthopaedic Spine Surgery, Lilavati Hospital and Research Centre, Mumbai, Maharashtra, India

Date of Submission09-Jun-2020
Date of Decision12-Jun-2020
Date of Acceptance23-Jun-2020
Date of Web Publication13-Jul-2020

Correspondence Address:
Dr. Tarun Suri
Department of Orthopaedics, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi.
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/isj.isj_49_20

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  Abstract 

This section of the symposium brings to the reader seven case scenarios with regard to adolescent idiopathic scoliosis (AIS). These are the common curve patterns which a spine surgeon encounters in his practice. They have been contributed by different spine surgeons and highlight the varied approaches taken by them to achieve a satisfactory outcome. Each scenario highlights the proper workup required for such cases along with planning of the levels of fusion.

Keywords: Adding-on, adolescent idiopathic scoliosis, Lenke curves, selective thoracic fusion


How to cite this article:
Suri T, Basu S, Shetty TA, Jhala A, Nene A, Aggarwal N, Jakkepally S, Gajjar S, Shah MS. The spine clinics: Adolescent idiopathic scoliosis. Indian Spine J 2020;3:216-30

How to cite this URL:
Suri T, Basu S, Shetty TA, Jhala A, Nene A, Aggarwal N, Jakkepally S, Gajjar S, Shah MS. The spine clinics: Adolescent idiopathic scoliosis. Indian Spine J [serial online] 2020 [cited 2020 Oct 25];3:216-30. Available from: https://www.isjonline.com/text.asp?2020/3/2/216/289654




  Introduction Top


Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional deformity which affects the cosmesis and self-image domains of a large number of children. There are numerous classification systems and curve patterns described in literature, but the one most commonly used is the Lenke classification.[1] It describes essentially six curve types, with criteria for structural curves and consideration to sagittal profile. The Lenke classification shows higher inter- and intra-reliability compared to the earlier used King classification. It also provided a better and more reliable tool to assist surgeons in choosing the best method of treatment for each curve pattern.[2] It gives broad guidelines for selecting fusion levels and selective thoracic fusion (STF). Apart from above, other factors such as rib/loin hump, preoperative level of shoulders, and sometimes activity demands play a role in decision making.

This manuscript takes us through different curve patterns with typical examples and highlights planning and decision-making used in their management. This will help the readers understand the basic concepts for choosing fusion levels. A case of a specific complication “adding-on” is also discussed to showcase how an error in choosing fusion level can lead to recurrence of deformity and coronal imbalance.


  Clinical Scenario 1. Lenke Type 1 Curve Top


A 14-year-old girl presented with deformity in back with a progressive curve noticed since 2 years. She was 2 years post menarche with no previous medical history. There was no history of back pain. She was a school student and doing all activities of daily living. On examination, right thoracic scoliosis was noted and right shoulder was slightly higher compared to the left [Figure 1]A. There was no spinal decompensation or truncal shift. There was right thoracic hump and left lumbar hump, which was more prominent on Adam’s test. The skin of the back was normal with no stigmata. The findings of neurological examination were normal.
Figure 1: (A) 14-year-old girl with right thoracic scoliosis and higher right shoulder. (B and C) Preoperative whole spine standing AP/lateral films show a Lenke type 1CN curve right main thoracic curve (structural) and nonstructural proximal thoracic and lumbar curves. (C and D) Supine bending films

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  Imaging Top


Whole spine standing anteroposterior (AP), lateral and supine bending films [Figure 1B]–[E] showed a right thoracic scoliosis with the main thoracic curve from T5 to T11(apex at T8, Cobb’s angle 78.5°, correcting to 41.2° on bending films), a left proximal thoracic curve from T1 to T5 (apex at T3, Cobb’s angle 37.2°, correcting to 15.6° on bending films making it a nonstructural), and left lumbar curve from T11 to L4 (apex at L2, Cobb’s angle 54.6° correcting to 1.2° on bending; making it nonstructural). As the proximal thoracic and lumbar curves are < 25o on bending X-rays and T10 to L2 kyphosis is < 20o; hence, this curve is classified as Lenke 1. Adding the coronal lumbar modifier, because the lumbar apex L2 crosses the midline and the central sacral vertebral line (CSVL) did not touch the apex and goes outside the pedicle of L2 vertebra the curve is classified as 1C. In lateral view, T5–T12 thoracic kyphosis is 19.9°. The thoracolumbar (TL) junction from T10 to L2 is 0.6° and lumbar lordosis is 50.5°. According to sagittal thoracic modifier, the curve becomes Lenke 1CN. The Riser grade is “0”.


  Planning for Levels of Fusion Top


As far as selection of upper-instrumented vertebra (UIV), the end vertebra of main thoracic curve is T5 and the proximal thoracic curve from T1 to T5 is of 37.2° but corrects to 15.6° making it nonstructural. The CSVL touches the T4 vertebra. Hence, we selected T4, which is one level above the end vertebra as the UIV. This will also allow sufficient vertebral levels above T4 to compensate for the shoulder balance.

Selection of lower instrumented vertebra (LIV) is more controversial as this curve is Lenke 1C. The big controversy lies whether to do an STF or to include the lumbar curve in the fusion. Lenke 1C curve is known as the “false double major” pattern, because the lumbar curve shows less magnitude and more flexibility on side-bending films which suggests that it is a compensatory curve present only to maintain coronal balance of a fixed thoracic curve.[3] Doing the STF and leaving a large magnitude lumbar curve may increase the chance of junctional kyphosis, progression of the lumbar curve with adding-on, and revision surgery.[4] On the other hand, fusing the lumbar curve up to middle or lower lumbar spine increases the chance of early degeneration of the unfused lumbar spine below the fusion mass.[5] Therefore, the surgical strategy should aim for maximal three-dimensional spinal deformity correction while maintaining coronal and sagittal balance, sparing as many mobile segments as possible, and avoiding complications.

There are many clinical and radiographic criteria defined by different authors regarding when to do STF.[6] Even after following strict criteria the rate of STF ranges from 50% to 75% by different authors as there is risk of postoperative coronal decompensation (11.4%–39.8%)[7],[8],[9] and unpredicted spontaneous lumbar curve correction.[7],[10],[11] Factors that are thought to cause decompensation include skeletal immaturity, over correction of the thoracic curve, incorrect choice of the fusion levels, incorrect identification of curve patterns, excessive lumbar curve magnitude or stiffness and the relative position and magnitude of the apical vertebra.[12] Patient lifestyle including activity level and preference to sports may also be taken into consideration while doing STF. Some patients such as professional dancers or athletes require more lumbar flexibility for their activity and thus require STF. But if the patient undergoes STF, the patient and family need to understand the potential for lumbar curve progression, junctional problems, and revision surgery to extend the fusion.[4]

In the above case, the main thoracic curve is 78.3° and lumbar curve is 54.6°, which is of large magnitude, but less than the main thoracic curve but on bending film it is quite flexible and gets corrected to 1.2°. Applying STF criteria to our patient the thoracic curve magnitude is more than 20% than the lumbar curve magnitude. The ratio of apical vertebral translation of thoracic to lumbar vertebra is more than 1.2 and Nash Moe vertebral rotation is grade 2 and there is no TL kyphosis. This curve falls into the criteria of STF. However, the lumbar curve was taken into fusion because (a) the magnitude of the lumbar curve was far higher than 45°, (b) patient was skeletally immature with riser sign “0,” (c) lumbar hump was clinically prominent (d) patient was reluctant for a possible second surgery at a later date if need arises due to excessive progression of the lumbar curve, and (f) patient had no requirement of excessive lumbar flexibility like a dancer or indulgence in sports.

Once it was decided to fuse the lumbar curve, the next step was to determine the last instrumented vertebra (LIV). The goal is to preserve as much lumbar mobile segments as possible in order to preserve the movement of the patient and decrease the chances of adjacent level degeneration. Here L4 is the stable vertebra but fusion up to L4 will spare only two mobile segments distally. Moreover, L3 vertebra is the last touched vertebra and is also beyond the apex of the lumbar curve. Hence, we chose L3 as LIV, which will preserve three mobile segments below the fusion.


  Management Top


The patient was operated by posterior approach with fusion from T4 to L3. Multiple facetectomies were carried out. As it was a flexible curve pedicle screws were inserted at strategic vertebrae to decrease the implant density but not compromising the correction at the same time. Correction was achieved by multiple techniques of rod rotation, cantilever and compression and distraction maneuvers. Immediate postoperative radiographs showed good deformity correction with good sagittal alignment [Figure 2]A and B. The correction of main thoracic curve was from 78.3° to 20.7° (74% correction) and of proximal thoracic curve was from 37.2° to 22.9° (38% correction). The shoulder on left side was seen slightly elevated and with T1 tilt of 6.3° and clavicle tilt of 0.9°.
Figure 2: (A) Immediate postoperative clinical picture showing good curve correction, but a postoperative shoulder imbalance (left high). Right hip is also at a higher level. (B) X-rays showing satisfactory curve correction and sagittal balance, with high left shoulder. (C) 5-year follow-up clinical photograph showing good maintenance of correction and balanced shoulders and hips. (D) 5-year follow-up X-ray with excellent maintenance of main thoracic curve and balanced out proximal thoracic and lumbar curves

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At 5-year follow-up [Figure 2C] and [D], the proximal thoracic curve further decreased to 12.8°. The left shoulder, which was higher in immediate postoperative period, got balanced along with radiological parameters of shoulder balance. Similarly, the lumbar curve got further corrected from 10.9° to 7° at 5-year follow-up, with balancing of the hips.


  Clinical Scenario 2: Lenke Type 2AN Curve Top


An 11-year old girl presented with gradually progressive deformity of the back for the past 1 year. She was premenarchal. She had normal birth and developmental history. On examination [Figure 3]A and B, head was central and right shoulder was elevated. Right thoracic curve was noted with corresponding rib hump which were prominent on Adam’s forward bending test. There were no neurocutaneous markers and no signs of ligamentous laxity. Neurology was normal.
Figure 3: 11/female with right thoracic scoliosis, high right shoulder, and a prominent rib hump (A and B). Radiographs reveal main thoracic (major) and proximal thoracic curves both as structural. Type 2AN curve

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  Imaging Top


Whole spine standing AP/lateral and supine bending radiographs [Figure 3C]–[F] showed right thoracic scoliosis with the main thoracic curve extending from T6–T12 (apex at T8 and Cobb’s angle of 84º) and proximal thoracic curve extending from T1 to T5 (apex at T3 and Cobb’s angle of 40°). The Cobb’s angles in bending radiographs were 58° and 30° for main thoracic and proximal thoracic curves, indicating that both the curves were structural. Thoracic kyphosis was 16º and lumbar lordosis was 41º. The Risser grade was 0.


  Planning for Levels of Fusion Top


The patient was diagnosed as Type 2 AN AIS. Clinically patient had prominent rib hump and elevated right shoulder. Also, her bending films indicated that both main thoracic and proximal thoracic curve were structural, but lumbar curve was nonstructural; hence, it was decided to fuse both proximal and main thoracic curve. UIV was decided to be T2 as proximal thoracic curve was structural. For choosing the LIV, the stable vertebra, L2 in this case was selected.


  Management Top


T2-L2 posterior instrumented deformity correction and fusion was performed under neuromonitoring control. Techniques used were concave side rod rotation, differential rod contouring (for better correction of rib hump), and cantilever capturing. Minor adjustments of shoulder balance and LIV tilt were done by compression and distraction maneuvers. Both shoulders were level with good correction of deformity [Figure 4]A. Postoperative radiograph was well balanced with good position of implants [Figure 4]B and C. Postoperative Cobb’s angle of thoracic and lumbar curves was 18º and 10º, respectively. Postoperative thoracic kyphosis and lumbar lordosis was 10º and 31º, respectively. Though we achieved a good coronal balance and curve correction, the authors would have desired a better thoracic kyphosis for a good sagittal profile. As this is often reported, surgeons constantly need to be aware of the loss of thoracic kyphosis while doing a posterior pedicle screw instrumented correction of a thoracic curve.
Figure 4: (A) Postoperative clinical photograph and (B,C) postoperative radiographs good deformity correction with balanced shoulders

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At 2 years the correction was well maintained. Postoperative Cobb’s angle at 2 years was 18º and 10º for thoracic and lumbar curves, respectively.


  Clinical Scenario 3. Lenke Type 3 Curve Top


A 14-year-old boy presented with progressive deformity in mid and lower back. On examination [Figure 5]A, there was right thoracic scoliosis with right shoulder higher compared to left. Right sided flank crease was noticed. Limb lengths were equal. No pelvic tilt was noticed. Neurology was normal.
Figure 5: (A) 14-year-old boy with right thoracic scoliosis with right shoulder high. (B) Radiographs revealing a Lenke type 3CN curve (double major type) with major main thoracic and structural lumbar curves and nonstructural proximal thoracic curve

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  Imaging Top


X-ray of whole spine (standing antero-posterior, lateral, and bending views) were done [Figure 5B–E]. Cobb’s angle from T5 to T10 was 76° correcting to 57° and T11 to L4 was 59° correcting to 26°. Kyphosis angle from T5 to T12 was 20°. CSVL did not touch the lumbar apex (L1–L2 disc). According to Lenke classification, it was type 3 C N. Risser grade was 3.


  Planning of Levels of Fusion Top


As proximal thoracic curve was nonstructural and right shoulder was higher, T4 was selected as UIV to balance the shoulders. As the boy was 14 years with Risser 3 and the lumbar curve was correcting to 26° on bending, we did think of an STF. However, the presence of significant flank asymmetry, just borderline values of Cobb’s ratio, and poor lumbar curve flexibility tilted the balance in favor of fusion of both curves. As L4 was the last touched vertebrae by CSVL, it was selected as LIV, with an aim to horizontalize it.


  Management Top


T4-L4 posterior instrumented deformity correction and fusion was done under intra-operative neuromonitoring. By cantilever maneuver convex side rod was inserted. Direct vertebral rotation was done at apex to achieve rotatory correction. Compression was done on rod over convex side of curve to achieve lordosis. There was good correction of the deformity with balanced shoulders and loin in the postoperative period [Figure 6]. Postoperative Cobb’s angle from T4 to 12 was 46° and T12 to L4 was 24°.
Figure 6: Postoperative clinical photograph showing good deformity correction with balanced shoulders and minimal loin asymmetry. Radiographs showing good curve correction, balanced shoulders, and horizontalized LIV (L4)

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  Clinical Scenario 4. Lenke Type 5C Managed by Posterior Approach Top


A 13-year-old girl presented with gradually progressive deformity of the back for the past 6 months. Onset of menarche was at the age of 11.5 years. She had normal birth and developmental history. On examination [Figure 7]E and F, head was slightly shifted toward left with truncal shift to left with right shoulder elevation. Left-sided TL curve was noted with corresponding hump which were prominent on Adam’s forward bending test. There were no neurocutaneous markers and no signs of ligamentous laxity. Neurology was normal.
Figure 7: (A, B, C, and D) Preoperative radiographs revealing a Lenke type 5CN curve with a T11-L4 left lumbar major curve and nonstructural main thoracic curve. (E and F) Preoperative clinical photograph showing left thoracolumbar curve with left loin hump, with left truncal shift and right shoulder elevation. (G, H, I, and J) Postoperative radiographs and clinical photographs

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  Imaging Top


Whole spine standing AP/lateral and supine bending radiographs [Figure 7]A–D showed left TL scoliosis. The TL curve was extending from T11 to L3 with apex at L2 and Cobb’s angle of 46º. The Cobb’s angle on bending radiographs was 24º. Lumbar lordosis was 50º. The Risser grade was 2. Lumbar spine modifier was C, with CSVL intersecting L4 vertebra. A diagnosis of Lenke Type 5 C (N) curve was made.


  Planning for the Levels of Fusion Top


As only TL curve was structural (being the major curve) and there was a prominent left-side loin hump, it was decided to fuse only the TL curve. The upper end vertebra of this major curve was chosen as the UIV. Selection of L3 or L4 as LIV in Lenke type 5C curves has been debated for long. While ending the fusion at L3 saves a mobile segment of the lumbar spine, it carries the risk of loss of deformity correction, spinal imbalance, and excessive loss of mobile lumbar segments due to “adding-on.”[13] Harrington suggested that the most distal vertebra to be included in the fusion that is the LIV should be within the Stable Zone of Harrington.[14] On the contrary, King et al.[15] considered the vertebra bisected by the CSVL as the “stable vertebra” and proposed that the stable vertebra should be included in the fusion. With the advent of pedicle screws, flexibility radiographs (supine bending/ fulcrum bending) gained importance to decide the levels of fusion.[16],[17],[18],[19],[20] Based on their experience and study of literature, Shu et al. proposed criteria for the determination of the LIV in Lenke 5C patients with large curves: the presumed LIV should be stable on bending films; the vertebra below the presumed LIV should be horizontalized on bending films; the disc below the presumed LIV should be bilaterally open on convex and concave bending films as a flexible segment is a good compensation for potential imbalance; and the postoperative LIV tilt and LIV translation should be less than 8° and 2cm, respectively.[21],[22],[23]

In our case, L4 met most of the criteria mentioned above––it is stable vertebra, L5 is getting horizontalized on bending films, and L4–L5 disc is opening bilaterally on bending films [Figure 7C and D]. Hence, L4 was selected as LIV.


  Management Top


T11-L4 posterior instrumented deformity correction and fusion was performed under neuromonitoring control. Clinical result was satisfactory with deformity correction and decrease in loin hump [Figure 7I and J]. Postoperative radiograph was well balanced and with good position of implants [Figure 7G and H]. Postoperative Cobb’s angle of TL curve was 7º. Postoperative lumbar lordosis was 45º. At 5 years the correction was well maintained (Cobb’s angle 8º).


  Clinical Scenario 5. Lenke Type 5 Curve Managed by Anterior Approach Top


A 16-year-old girl presented with painless, gradually progressive deformity of the back for the past 18 months. She attained menarche at the age of 14.5 years. She was only child from nonconsanguineous marriage, with normal birth and developmental history. On examination, head was shifted toward left with truncal shift to left and right shoulder was slightly elevated [Figure 8]A and B. Left-sided TL curve was noted with corresponding hump which was prominent on Adam’s forward bending test. There were no neurocutaneous markers and no signs of ligamentous laxity. Neurology was normal.
Figure 8: (A and B). Preoperative clinical photographs showing a left thoracolumbar scoliosis, with left-sided truncal shift and left loin hump. (C–F) Whole spine standing AP/lateral and supine bending AP films revealing a type 5CN curve (major curve: left T10-L3, 65°)

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  Imaging Top


Plain radiographs showed scoliosis with the left TL curve [Figure 8C]–[F]. The major TL curve was extending from T10 to L3 with apex at L1 and Cobb’s angle of 65º (reducing to 50° on bending). Main Thoracic curve measured 24o and reduced to 22° on bending films. So, TL curve was structural and MT was nonstructural. Thoracic kyphosis of 35o and lumbar lordosis was 54º. Lumbar modifier was C. The Risser grade was 4.


  Planning of Levels of Fusion Top


The patient was diagnosed as Type 5 C (N) AIS. As only TL curve was structural, it was decided to fuse only that segment. Patient was planned for anterior surgery to save fusion levels (from UEV to LEV in case of anterior). The UIV was decided as T10 (UEV) and LIV was decided to be L3 (LEV). In posterior surgery, LIV would be LEV +1 (L4) as shown in the case above.


  Management Top


T10-L3 anterior instrumented deformity correction and fusion was performed under neuromonitoring control [Figure 9]. Discectomy and anterior releases were done at all levels; anterior instrumentation was done from T10 to L3 on convex side using screws with angle and simple washers. Contoured cobalt chrome rod was captured using cantilever mechanism and deformity correction was done with rod rotation and intersegmental periapical compression. Anterior spinal fusion was done from T10 to L3 using autogenous morselized rib graft and by mesh cage at L2–L3. Postoperative radiograph showed well balanced spine (TL curve 17º) and with good position of implants [Figure 10]B–E. There was appreciable correction of deformity with minimal loin hump and balanced spine [Figure 10]A and F. Postoperative lumbar lordosis was 38º. At 2 years [Figure 11], the correction was well maintained (TL curve: 18º). The disc-wedge angle below LIV did not increase suggesting no adding-on.
Figure 9: Intraoperative photographs of anterior scoliosis correction. (A) Exposure of vertebral bodies (curved arrows) and discs (arrow heads) through anterior approach. (B) Multiple discectomies done (arrow heads). (C) Screw fixation at all the levels. (D) Rod capturing and deformity correction

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Figure 10: Postoperative clinical photograph and radiographs (C, E, and F) show good deformity correction and restoration of truncal balance as compared to preoperative state (A, B, and D)

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Figure 11: 2-year follow-up radiographs showing maintained correction, with no increase in disc-wedge angle, no adding-on

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  Clinical Scenario 6.:Lenke Type 6 Curve Top


A 17-year-old girl presented with deformity of the back for the past 6 years. She noticed deformity at the age of 11 years, which was rapidly progressing till onset of menarche at the age of 13 years. On examination, head was central and right shoulder was elevated. Right thoracic and left lumbar curve were noted with corresponding rib hump and loin hump which were prominent on Adam’s forward bending test. There were no neurocutaneous markers and no signs of ligamentous laxity. Neurology was normal.


  Imaging Top


Whole spine standing AP/lateral and side-bending radiographs showed the scoliosis with right thoracic and left lumbar curve [Figure 12]. The thoracic curve was extending from T4 to T9 with apex at T7 and Cobb’s angle of 40.8º and the lumbar curve was extending from T10 to L3 with apex at L1 and Cobb’s angle of 53.5º. The Cobb’s angle in bending radiographs was 32.1º and 37.8º for thoracic and lumbar curves, respectively, indicating that both curves were structural. Thoracic kyphosis was 25.9º and lumbar lordosis was 36.2º. Risser grade was 5. Lumbar modifier was C.
Figure 12: 17-year-old girl with Lenke type 6CN curve (A and B). TL/L curve (T10-L3): 53.5°, MT curve: 40.8°, PT curve: 13°. Both TL/L and MT curves are structural on bending films (C and D)

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  Planning of Levels of Fusion Top


The patient was diagnosed as Type 6CN AIS. Her major concern was cosmetic disfigurement. Clinically patient had prominent rib hump, elevated right shoulder, and significant loin hump. Bending films indicated that both the curves were structural; hence, it was decided to include both the curves in fusion. The main thoracic curve was extending to T4 and proximal thoracic curve was nonstructural; hence, the UIV was decided as T4. The lower substantially touched vertebra by CSVL was L4; hence, L4 was decided as the LIV.[24],[25] L3 was not considered as lower level as it was not touching CSVL and LIV tilt was 35.3º.


  Management Top


T4-L4 posterior instrumented deformity correction and fusion was performed under neuromonitoring control. Pedicle screws were applied strategically. As the lumbar curve was more tilted, all the levels were instrumented in lumbar spine. Uniaxial screws were used in L3 and L4 to correct the lumbar rotation. Facetectomy was done from T4–T5 to L3–L4 bilaterally. Pontes osteotomy was performed at three levels around thoracic and lumbar apex. Contoured cobalt chrome rod was applied on the left side from distal to proximal using the combination of cantilever forces and rod rotation maneuver. On the contrary, under contoured rod (differential rod contouring) was applied for better correction of thoracic rib hump along with rotational correction of lumbar hump. Minor adjustments of shoulder balance and LIV tilt were done by compression and distraction maneuvers. Decortication was done and fusion bed was packed with auto and allograft. Postoperative radiograph showed well-balanced spine with good position of implants [Figure 13]A and B. Postoperative Cobb’s angle of thoracic and lumbar curves was 17.2º and 18.3º, respectively. At 2 years and 5 years the correction was well maintained. Postoperative Cobb’s angle at 5 years was 20.2º and 21.3º for thoracic and lumbar curves, respectively [Figure 13]C and D.
Figure 13: (A and B) Immediate postoperative radiographs showing good curve correction in both coronal and sagittal planes. Both shoulders are balanced radiologically. (C and D) 5-year follow-up radiographs showing excellent maintenance of correction

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  Clinical Scenario 7: “Adding-on” After Type 1AN Adolescent Idiopathic Scoliosis Top


A 13-year-old girl presented with progressively increasing deformity for the past 2 years. On examination, head was centered over the pelvis and right shoulder elevated. She had a right thoracic curve with a corresponding rib hump which was prominent on Adam’s forward bending test. There were no neurocutaneous markers and no signs of ligamentous laxity. Neurology was normal.


  Imaging Top


Whole spine standing AP/lateral and side-bending films [Figure 14]A–D revealed scoliosis with right thoracic and left lumbar curve. The thoracic curve was extending from T4-T12 with apex at T9 and Cobb’s angle of 53.8º and the lumbar curve was extending from L1-L5 with apex at L3 and Cobb’s angle of 24.2º. The Cobb’s angle in bending radiographs was 30.1º and 2.2º for thoracic and lumbar curves, respectively, indicating that only thoracic curve was structural. The translation was measured as 74.04 mm and 3.3 mm for thoracic and lumbar curve, respectively. Thoracic kyphosis was 22.9º and lumbar lordosis was 48.2º. The Risser grade was 2 and triradiate cartilage was fused. Lumbar modifier was A.
Figure 14: 13/female with type 1AN curve (main thoracic) managed by selective thoracic fusion (T4–T12) with good curve correction in the postoperative radiographs

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  Planning of Fusion Levels Top


The patient was diagnosed as Type 1AN AIS. Clinically patient had a prominent rib hump and elevated right shoulder. Bending films indicated that the thoracic curve was structural; hence, it was decided to do STF from T4-T12. Other criteria that were in favor of STF were more prominent rib hump than loin hump, curve type, ratio of apical vertebral translation of thoracic and lumbar curve >1.2, ratio thoracic curve magnitude to lumbar curve magnitude >1.2, ratio of apical vertebral rotation of thoracic to lumbar curve >1.2, TL kyphosis of 3º, and closed triradiate cartilage.[4]


  Management Top


T4-T12 posterior instrumented deformity correction and fusion was performed under neuromonitoring control. Correction was achieved using multiple facetectomies periapical Ponte’s osteotomies (2 levels) concave side rod rotation differential rod contouring and segmental compression–-distraction. Deformity was under-corrected to maintain the spinal balance. Postoperative radiograph was well balanced and with good position of implants [Figure 14E] and [F]. Postoperative Cobb’s angle was 22.8º.

At the follow-up disc wedge angle (DWA) was noted to be increasing; it was 9.6º at 2 months and 10.8º at months 13.6º at 1 year and 14.6º at 18 months [Figure 15].
Figure 15: Adding on phenomenon. There is progressive increase in distal wedge angles, DWA (angulation of first disc space below LIV) from (A) immediate postoperative, to the follow-up at (A) 2 months, (B) 6 months, (C) 12 months, and (D) 18 months

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  Cause for adding on Top


Adding phenomenon was defined as progression or extension of primary curve.[26] There is a progressive increase in the number of vertebrae included within the primary curve distally in combination with either an increase of >5mm in the deviation of the first vertebra below the instrumentation from the CSVL or an increase of >5° in angulation of the first disc below the instrumentation.[27] In this case, cause of adding-on phenomenon was improper selection of LIV. We have chosen LIV as T12 which was lower end vertebra of thoracic curve. However, LIV should have been neutral and proximal stable vertebra which was L1 in this case.[5]

Depending on the direction of the L4 vertebra tilt, Miyanji et al.[28] described two subtypes of Lenke type 1A curve––1A-L: L4 tilted toward left and 1A-R: L4 tilted toward right [Figure 16]. Our case shown here is Lenke type 1A-R. The 1A-L curve shared radiographic features with the 1B curve and were both found to have a lumbar apex translated to the left and a similar stable vertebrae and distal fusion level. In essence, the1A-L curve could be thought of as a smaller version of the 1B curve. The 1A-R curve, on the other hand, had a more distal stable vertebra, and therefore a more distal LIV when compared to the 1A-L and 1B curves. The 1A-L curve type has a small compensatory lumbar curve and can be fused to the stable vertebra sparing the lumbar spine. On the contrary, the 1A-R curve type describes an overhanging curve pattern similar to the King IV curve type that requires a more distal fusion, generally two levels more than the 1A-L curve. Cho et al.[29] found that Lenke 1A-R curves are two times more likely to experience adding-on than Lenke 1A-L curves. They found that type 1A-R curve, by its nature, tempts surgeons to fuse shorter than may be optimal for stability and hence predisposes to adding-on, as happened in our case.
Figure 16: Two patterns of Lenke type 1A curves

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Due to progressive increase in deformity, revision surgery and extension of fusion was done up to L3 [Figure 17]A and B. The result was a balanced and corrected spine, which was maintained at 5-year follow-up [Figure 17]C and D.
Figure 17: (A) 18-month postoperative X-ray after index surgery, showing adding-on with recurrence of deformity. (B and C) Extension of fusion to L3 results in a balanced spine with deformity correction. (D) Maintenance of correction at 5-year follow-up

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  Conclusion Top


Above seven cases highlight the importance of clinical factors and diligent radiological planning required for successful outcome of various types of curve patterns in AIS. The thought process involved in planning of fusion levels in each of these cases is discussed separately. Specific cases also highlight the problems which can arise such as postoperative shoulder imbalance and adding-on, in case the levels are erroneous.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17]



 

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Introduction
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Planning for Lev...
Management
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Imaging
Planning for Lev...
Management
Clinical Scenari...
Imaging
Planning of Leve...
Management
Clinical Scenari...
Imaging
Planning for the...
Management
Clinical Scenari...
Imaging
Planning of Leve...
Management
Clinical Scenari...
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Planning of Leve...
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Clinical Scenari...
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