Letter to the Editor. Correction of thoracic hypokyphosis in the treatment of scoliosis

View More View Less
  • Hôpitaux pédiatriques de Nice CHU LENVAL, Nice, France
Free access

TO THE EDITOR: We have read with great interest the article about simultaneous translation on two rods (ST2R) by Sakai et al.1 (Sakai D, Schol J, Hiyama A, et al. Simultaneous translation on two rods improves the correction and apex translocation in adolescent patients with hypokyphotic scoliosis. J Neurosurg Spine. 2021;34[4]:597–607). We congratulate the authors for re-emphasizing the correction of thoracic hypokyphosis in the treatment of adolescent idiopathic scoliosis (AIS).

We are pleased to see that Sakai et al. confirm the potential of the ST2R technique to increase thoracic kyphosis (TK) in significant proportions.1 They also highlight the ability to change the position of the apex of TK. Indeed, bending the rods according to the desired sagittal profile allows, on the one hand, the ability to restore TK in accordance with the sagittal contour of the rods and, on the other hand, the ability to place the apex at the level determined by the rods.2,3 However, two issues remain unresolved concerning sagittal targets: where to locate the TK apex, and what angular values should we aim for?

Regarding the apex, we can expect regular TK between T2 and T12 with an apex in the middle at T7 and a proximal kyphosis equal to the distal kyphosis.3 Elsewhere, we can provide two unequal arches with, for example, an apex around T8 or T9 depending on the spinal morphotype according to the Roussouly classification.4 As Sakai et al. reported, this issue is not resolved.1 Personally, for adolescents we prefer a regular kyphosis between T2 and T12 with an apex at T7.2,3

Regarding the TK target value, recent literature is available about normal TK, which is related to pelvic parameters and lumbar lordosis in healthy adolescents.5 The TK is not the same for all patients, but everyone has a specific TK depending on each individual’s lumbopelvic parameters. Therefore, it seems important to give the scoliotic patients the kyphosis they need for a good sagittal alignment. Thus, it is necessary to calculate the target TK preoperatively and to bend the rods to the desired shape either preoperatively2 or intraoperatively.

We strongly encourage the authors to continue their approach in this direction with the aim of further improving sagittal alignment.

Disclosures

Jean-Luc Clément received consultancy fees and royalties from Médicrea International. Federico Solla received financial support for attending symposia from Médicrea International, Euros, and Zimmer.

References

  • 1

    Sakai D, Schol J, Hiyama A, et al. . Simultaneous translation on two rods improves the correction and apex translocation in adolescent patients with hypokyphotic scoliosis. J Neurosurg Spine. 2021;34(4):597607.

    • Search Google Scholar
    • Export Citation
  • 2

    Solla F, Clément JL, Cunin V, et al. . Patient-specific rods for thoracic kyphosis correction in adolescent idiopathic scoliosis surgery: preliminary results. Orthop Traumatol Surg Res. 2020;106(1):159165.

    • Search Google Scholar
    • Export Citation
  • 3

    Clément JL, Pelletier Y, Solla F, Rampal V. Surgical increase of thoracic kyphosis increases unfused lumbar lordosis in selective fusion for thoracic adolescent idiopathic scoliosis. Eur Spine J. 2019;28(3):581589.

    • Search Google Scholar
    • Export Citation
  • 4

    Sebaaly A, Silvestre C, Rizkallah M, et al. . Revisiting thoracic kyphosis: a normative description of the thoracic sagittal curve in an asymptomatic population. Eur Spine J. Published online November 22, 2020. doi: 10.1007/s00586-020-06670-7

    • Search Google Scholar
    • Export Citation
  • 5

    Clément JL, Solla F, Amorese V, et al. . Lumbopelvic parameters can be used to predict thoracic kyphosis in adolescent. Eur Spine J. 2020;29(9):22812286.

    • Search Google Scholar
    • Export Citation
View More View Less
  • Tokai University School of Medicine, Kanagawa, Japan

Response

We sincerely appreciate the letter from Dr. Clément and his colleagues on our recent paper examining the potential of the ST2R technique for curvature corrections in hypokyphotic AIS patients. We are particularly grateful for the response as Dr. Clément is the original surgeon to describe the ST2R technique.1

An interesting point is raised by Clément et al. as to the desired correctional outcome, particularly considering the TK and TK apex. We concur that this largely remains an unresolved aspect of spinal corrections. As suggested by Clément and coworkers, an optimal TK and apex are likely dependent on the “natural” profile tendency of the patient’s specific spine. This is emphasized by the discrepancies reported in sagittal plane parameters in relation to age, sex, and ethnicity;2,3 for example, one study found that Japanese females tend to have fewer pelvic inclinations and lower lordotic angles than those of European ethnicity.4 These aspects should similarly be taken into consideration when comparing study cohorts from across the world. Future investigations examining the effects of apex translocation likely require careful deliberation on the spinal types, relation to pelvic tilts, etc., as proposed by Clément et al.

Alternatively, current reports generally evaluate sagittal parameters only in a static standing position. We strongly believe advancements in dynamic spinal alignment assessment, such as through gait analysis, will become critical tools to further assess functionality and compensation strategies of AIS patients before and following surgery, thereby potentially providing better insights to optimize surgical correction targets.

References

  • 1

    Clement JL, Chau E, Kimkpe C, Vallade MJ. Restoration of thoracic kyphosis by posterior instrumentation in adolescent idiopathic scoliosis: comparative radiographic analysis of two methods of reduction. Spine (Phila Pa 1976). 2008;33(14):15791587.

    • Search Google Scholar
    • Export Citation
  • 2

    Le Huec JC, Hasegawa K. Normative values for the spine shape parameters using 3D standing analysis from a database of 268 asymptomatic Caucasian and Japanese subjects. Eur Spine J. 2016;25(11):36303637.

    • Search Google Scholar
    • Export Citation
  • 3

    Lonner BS, Auerbach JD, Sponseller P, et al. . Variations in pelvic and other sagittal spinal parameters as a function of race in adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2010;35(10):E374E377.

    • Search Google Scholar
    • Export Citation
  • 4

    Endo K, Suzuki H, Nishimura H, et al. . Characteristics of sagittal spino-pelvic alignment in Japanese young adults. Asian Spine J. 2014;8(5):599604.

    • Search Google Scholar
    • Export Citation

Contributor Notes

Correspondence Jean-Luc Clément: clement.jluc@wanadoo.fr.

INCLUDE WHEN CITING Published online May 28, 2021; DOI: 10.3171/2021.3.SPINE21236.

Disclosures Jean-Luc Clément received consultancy fees and royalties from Médicrea International. Federico Solla received financial support for attending symposia from Médicrea International, Euros, and Zimmer.

  • 1

    Sakai D, Schol J, Hiyama A, et al. . Simultaneous translation on two rods improves the correction and apex translocation in adolescent patients with hypokyphotic scoliosis. J Neurosurg Spine. 2021;34(4):597607.

    • Search Google Scholar
    • Export Citation
  • 2

    Solla F, Clément JL, Cunin V, et al. . Patient-specific rods for thoracic kyphosis correction in adolescent idiopathic scoliosis surgery: preliminary results. Orthop Traumatol Surg Res. 2020;106(1):159165.

    • Search Google Scholar
    • Export Citation
  • 3

    Clément JL, Pelletier Y, Solla F, Rampal V. Surgical increase of thoracic kyphosis increases unfused lumbar lordosis in selective fusion for thoracic adolescent idiopathic scoliosis. Eur Spine J. 2019;28(3):581589.

    • Search Google Scholar
    • Export Citation
  • 4

    Sebaaly A, Silvestre C, Rizkallah M, et al. . Revisiting thoracic kyphosis: a normative description of the thoracic sagittal curve in an asymptomatic population. Eur Spine J. Published online November 22, 2020. doi: 10.1007/s00586-020-06670-7

    • Search Google Scholar
    • Export Citation
  • 5

    Clément JL, Solla F, Amorese V, et al. . Lumbopelvic parameters can be used to predict thoracic kyphosis in adolescent. Eur Spine J. 2020;29(9):22812286.

    • Search Google Scholar
    • Export Citation
  • 1

    Clement JL, Chau E, Kimkpe C, Vallade MJ. Restoration of thoracic kyphosis by posterior instrumentation in adolescent idiopathic scoliosis: comparative radiographic analysis of two methods of reduction. Spine (Phila Pa 1976). 2008;33(14):15791587.

    • Search Google Scholar
    • Export Citation
  • 2

    Le Huec JC, Hasegawa K. Normative values for the spine shape parameters using 3D standing analysis from a database of 268 asymptomatic Caucasian and Japanese subjects. Eur Spine J. 2016;25(11):36303637.

    • Search Google Scholar
    • Export Citation
  • 3

    Lonner BS, Auerbach JD, Sponseller P, et al. . Variations in pelvic and other sagittal spinal parameters as a function of race in adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2010;35(10):E374E377.

    • Search Google Scholar
    • Export Citation
  • 4

    Endo K, Suzuki H, Nishimura H, et al. . Characteristics of sagittal spino-pelvic alignment in Japanese young adults. Asian Spine J. 2014;8(5):599604.

    • Search Google Scholar
    • Export Citation

Metrics

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 88 88 88
PDF Downloads 39 39 39
EPUB Downloads 0 0 0