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How low can you go? Implant density in posterior spinal fusion converted from growing constructs for early onset scoliosis

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Abstract

Study design

Retrospective, multicenter comparative.

Objectives

Our purpose was to compare early onset scoliosis (EOS) patients treated with ultra-low, low, and high implant density constructs when undergoing conversion to definitive fusion.

Summary of background data

Larson et al. demonstrated that implant density (ID) at fusion does not correlate with outcomes in the treatment of adolescent idiopathic scoliosis, but did not address growth-friendly graduates.

Methods

EOS patients treated with growth-friendly constructs converted to fusion between 2000 and 2017 were reviewed from a multicenter database. ID was defined as number of pedicle screws, hooks, and sublaminar/bands per level fused. Patients were divided into ultra-low ID (< 1.3), low (≥ 1.3 and < 1.6), and high ID (≥ 1.6). Exclusion criteria: < 2 years follow-up from fusion or inadequate radiographs.

Results

A total of 152 patients met inclusion criteria with 39 (26%) patients in the high ID group, 33 (22%) patients in the low ID group, and 80 (52%) in the ultra-low ID group. Groups were similar in operative time (p = 0.61), pre-fusion major curve (p = 0.71), mean number of levels fused (p = 0.58), clinical follow-up (p = 0.30), and radiographic follow-up (p = 0.90). Patients in the low ID group (11.6 ± 1.5 years) were slightly younger at the time of definitive fusion than patients in the ultra-low ID group (12.9 ± 2.2 years) and high ID group (12.5 ± 1.7 years) (p = 0.009). There was significantly more blood loss in the high ID group than the other two groups (high ID: 946.8 ± 606.0 mL vs. low ID: 733.9 ± 434.5 mL and ultra-low ID: 617.4 ± 517.2 mL; p = 0.01), but there was no significant difference with regard to percent of total blood volume lost (high ID: 59.3 ± 48.7% vs. low ID: 54.5 ± 37.5% vs. ultra-low ID: 51.7 ± 54.9%; p = 0.78). There was a difference in initial improvement in major curve between the groups (high ID: 21.6° vs. low ID: 18.0° vs. ultra-low ID: 12.6°; p = 0.01). However, during post-fusion follow-up, correction decreased 7.1° in the high ID group, 2.6 in the low ID group, and 2.8 in the ultra-low ID group (p = 0.19). At final follow-up, major curve correction from pre-fusion was similar between groups (high ID: 14.5° vs. low ID: 15.5° vs. ultra-low ID: 9.7°, p = 0.14). At final follow-up, there was no difference in T1–T12 length gain (p = 0.85), T1–S1 length gain (p = 0.68), coronal balance (p = 0.56), or sagittal balance (p = 0.71). The revision rate was significantly higher in the ultra-low ID group (13.8%; 11/80) versus the high ID group (2/39; 5.1%) and low ID group (0/33; 0%) (p = 0.04).

Conclusions

Although an ID < 1.3 in growth-friendly graduates produces similar outcomes with regard to curve correction and spinal length gain as low and high ID, this study suggests that an ID < 1.3 is associated with an increased revision rate.

Level of evidence

III.

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Funding

No external funding was secured for this study. This study has been carried out with approval from the Committee on Clinical Investigations at Children’s Hospital Los Angeles.

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Authors

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Contributions

EC: data collection, data analysis, manuscript writing, manuscript approval. PG: study idea, study design, manuscript review, manuscript approval. JAG: study idea, study design, manuscript review, manuscript approval. KDI: study idea, study design, manuscript review, manuscript approval. DLS: study idea, study design, manuscript review, manuscript approval. PDS: study idea, study design, manuscript review, manuscript approval. AFS: study idea, study design, manuscript review, manuscript approval. SWH: study idea, study design, manuscript review, manuscript approval. MEO: study idea, study design, manuscript review, manuscript approval. JS: study idea, study design, manuscript review, manuscript approval. GHT: study idea, study design, manuscript review, manuscript approval. MGV: study idea, study design, manuscript review, manuscript approval. JTS: study idea, study design, manuscript review, manuscript approval. LMA: study idea, study design, manuscript review, manuscript approval. Pediatric Spine Study Group: data collection, manuscript review, manuscript approval.

Corresponding author

Correspondence to Lindsay M. Andras.

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Conflict of interests

Edward Compton/Kenneth D. Illingworth/Jennifer Schottler: No conflicts of interest to disclose. Purnendu Gupta: DePuy, A Johnson & Johnson Company: Paid consultant. Jaime A. Gomez: Stryker: Research support. David L. Skaggs: CHLA Foundation: Board or committee member; Grand Rounds: Paid consultant; Green Sun Medical: Stock or stock Options; Growing Spine Foundation: Board or committee member; Growing Spine Study Group: Board or committee member; Journal of Children’s Orthopaedics: Editorial or governing board; Medtronic: Other financial or material support; Nuvasive (Co-PI, Paid to Growing Spine Foundation): Research support; Orthobullets: Editorial or governing board; Paid consultant; Stock or stock Options; Orthopedics Today: Editorial or governing board; Spine Deformity: Editorial or governing board; Wolters Kluwer Health: Publishing royalties, financial or material support; Zimmer Biomet: IP royalties; Other financial or material support; Paid consultant; Paid presenter or speaker; Zipline Medical, Inc.: Stock or stock Options. Paul D. Sponseller: DePuy, A Johnson & Johnson Company: IP royalties; Paid consultant; Research support; Globus Medical: IP royalties; Journal of Bone and Joint Surgery: Editorial or governing board; Journal of Bone and Joint Surgery—American: Publishing royalties, financial or material support; Orthopediatrics: Other financial or material support; Scoliosis Research Society: Board or committee member. Amer F. Samdani: Children’s Spine Study Group: Board or committee member; DePuy, A Johnson & Johnson Company: Paid consultant; Ethicon: Paid consultant; Globus Medical: Paid consultant; Nuvasive: IP royalties; Paid consultant; Setting Scoliosis Straight Foundation: Board or committee member; Stryker: Paid consultant; Zimmer Biomet: IP royalties; Paid consultant. Steven W. Hwang: Auctus: Stock or stock Options; Nuvasive: Paid consultant; Paid presenter or speaker; Zimmer: Paid presenter or speaker. Matthew E. Oetgen: AAOS: Board or committee member; Journal of the American Academy of Orthopaedic Surgeons: Editorial or governing board; Pediatric Orthopaedic Society of North America: Board or committee member; Scoliosis Research Society: Board or committee member. George H. Thompson: Executive Committee Growing Spine Foundation: Board or committee member; Journal of Pediatric Orthopedics: Editorial or governing board; Nuvasive: Other financial or material support; Orthopediatrics: IP royalties; Paid consultant; Stock or stock Options; Orthopediatrics—travel expenses and per diem: Other financial or material support; Scoliosis Research Society: Board or committee member; Shriner’s Hospital for Children—travel expenses and per diem: Other financial or material support; Shriner’s Hospital for Children Medical Advisory Board: Board or committee member; Societe Internationale de Chirurgie Orthopedique et de Traumatologie: Board or committee member; Son–owner JBT Medical Technologies: Employee; Wolters Kluwer Health—Lippincott Williams & Wilkins: Publishing royalties, financial or material support. Michael G. Vitale: Biomet: IP royalties; Paid consultant; Children’s Spine Foundation: Board or committee member; Research support; FOX, Children’s Spine Foundation: Other financial or material support; IPOS: Board or committee member; OREF: Research support; Pediatric Orthopaedic Society of North America: Board or committee member; Project for Safety in Spine Surgery: Board or committee member; SRS, POSNA, OSRF: Research support; Stryker: Paid consultant. John T. Smith: Biomet: Paid consultant; Board of Directors, Children’s Spine Foundation: Editorial or governing board; Children’s Spine Foundation: Board or committee member; DePuy, A Johnson & Johnson Company: Paid consultant; Globus Medical: IP royalties; Paid consultant; Missonix: Paid presenter or speaker; Nuvasive: Paid consultant; Scoliosis Research Society: Board or committee member; Spineguard: Paid consultant; Wishbone Medical: Paid consultant. Lindsay M. Andras: Biomet: Paid consultant; Paid presenter or speaker; Eli Lilly: Stock or stock Options; Journal of Pediatric Orthopedics: Editorial or governing board; Medtronic: Paid consultant; Paid presenter or speaker.

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Compton, E., Gupta, P., Gomez, J.A. et al. How low can you go? Implant density in posterior spinal fusion converted from growing constructs for early onset scoliosis. Spine Deform 9, 1479–1488 (2021). https://doi.org/10.1007/s43390-021-00321-7

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  • DOI: https://doi.org/10.1007/s43390-021-00321-7

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