P0840 - No Difference in Outcomes with High vs Low Implant Density in Growing Construct Conversion to Posterior Spinal Fusion for Early Onset Scoliosis

Purpose: Larson et al. demonstrated that implant density (ID) at fusion does not correlate with surgical outcomes in the treatment of adolescent idiopathic scoliosis, but did not address growth-friendly graduates. Our purpose was to determine if Early Onset Scoliosis (EOS) patients treated with low implant density constructs have similar outcomes as patients treated with high density constructs when undergoing conversion to definitive fusion.

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

Results: 152 patients met inclusion criteria with 39 (26%) patients in the high ID group and 113 (74%) patients in the low ID group. There was no significant difference in age (p=0.85), pre-fusion major curve (p=0.45), number of levels fused (p=0.34), operative time (p=0.52), radiographic follow up (p=0.73), and clinical follow up (p=0.86) between the high and low ID groups.
The high ID group (946.8 ± 606.0 mL) had significantly higher EBL than the low ID group (650.9 ± 495.6 mL) (p=0.004). There was a significantly greater initial improvement in major curve in the high ID group (21.6º) versus the low ID group (14.2º) (p=0.01). During post-fusion follow-up, there was no significant difference in loss of correction between the high ID group (-7.1º) and the low ID group (-2.8º) (p=0.07). At final follow-up, there was no significant difference in major curve correction from pre-fusion between the groups (high ID:14.5º vs low ID:11.4º, p=0.31). At final follow-up, there was no significant difference in T1-T12 length gain (p=0.57) and T1-S1 length gain (p=0.65) from pre-fusion between the groups. There was no significant difference in coronal balance (p=0.37) and sagittal balance (p=0.87) at final follow-up. There was no significant difference in revision rate between groups (high ID: 5.1% (2/39) and low ID: 9.7% (11/113)) (p=0.52).

Conclusions: In the largest series of growth-friendly construct conversion to definitive fusion reported to date, similar curve correction and spinal length gain were seen with low and high implant density constructs. Although there is a trend towards increased complications in the high ID group, this study suggests that for many growth-friendly graduates, a low ID strategy can produce similar outcomes.

Presenting Author(s)

Lindsay M. Andras

Assistant Professor of Orthopaedic Surgery
Children's Hospital Los Angeles
Los Angeles, California
Disclosure: Eli Lilly (Stockholder/Ownership Interest (excluding diversified mutual funds))Medtronic (Consultant, Speaker's Bureau)Nuvasive (Consultant, Speaker's Bureau)Orthobullets (Royalties, Financial/Material Support)ZimmerBiomet (Consultant, Speaker's Bureau)

Co-Author(s)

EC

Edward Compton

Medical Student
Children's Hospital Los Angeles
Los Angeles, California
Disclosure: No Financial Relationships Disclosed
Purnendu Gupta

Chief of Staff
Shriners Hospital for Children
Chicago, Illinois
Disclosure: Depuy Synthes (Consultant)
JG

Jaime A. Gomez

Assistant Professor, Department of Orthopaedic Surgery
Children's Hospital at Montefiore Medical Center
The Bronx, New York
Disclosure: Stryker (Consultant)
KI

Kenneth D. Illingworth

Assistant Professor of Orthopaedic Surgery
Children's Hospital Los Angeles
Los Angeles, California
Disclosure: No Financial Relationships Disclosed
DS

David L. Skaggs

Chief of Orthopaedic Surgery Director of Spine Surgery Endowed Chair of Pediatric Spinal Disorders
Children's Hospital Los Angeles
Los Angeles, California
Disclosure: No Financial Relationships Disclosed
PS

Paul D. Sponseller

Chief, Division of Pediatric Orthopaedics Professor of Orthopaedic Surgery
Johns Hopkins School of Medicine
Baltimore, Maryland
Disclosure: depuy synthes spne (Consultant)globus (Royalties)
AS

Amer F. Samdani

Chief of Surgery
Shriners Hospital for Children-Philadelphia
Philadelphia, Pennsylvania
Disclosure: DePuy, A Johnson & Johnson Company (Consultant)Ethicon (Consultant)Globus Medical (Consultant)Nuvasive (Consultant, Royalties)Stryker (Consultant)Zimmer Biomet (Consultant, Royalties)
SH

Steven W. Hwang

Pediatric Neurosurgeon
Shriners Hospital for Children-Philadelphia
Philadelphia, Pennsylvania
Disclosure: No Financial Relationships Disclosed
Matthew E. Oetgen

Division Chief, Orthopaedic Surgery and Sports Medicine
Children's National
Washington, District of Columbia
Disclosure: No Financial Relationships Disclosed
Jennifer Schottler

Clinical Research Coordinator
Shriners Hospital for Children
Chicago, Illinois
Disclosure: No Financial Relationships Disclosed
GT

George H. Thompson

Director, Pediatric Orthopaedics at Case Western Reserve University
Rainbow Babies and Children's Hospital
Cleveland, Ohio
Disclosure: OrthoPediatrics (Consultant, Royalties, Stockholder/Ownership Interest (excluding diversified mutual funds))
Michael G. Vitale

Ana Lucia Professor of Orthopaedic Surgery at CUMC
Columbia University Medical Center
New York, New York
Disclosure: Biomet (Consultant, Royalties)Childrens Spine Foundation (Grant/Research Support)OREF (Grant/Research Support)SRS, POSNA, OSRF (Grant/Research Support)Stryker (Consultant)
JS

John T. Smith

Orthopaedics - Professor (Clinical) Pediatrics - Adjunct Professor
University of Utah
Salt Lake City, Utah
Disclosure: Globus (Consultant, Royalties)Nuvasive (Consultant)Wishhbone (Consultant)
PP

Pediatric Spine Study Group PSSG

Pediatric Orthopedic Spine Study Group
Pediatric Spine Study Group
Valley Forge, Pennsylvania
Disclosure: Children’s Spine Foundation (Grant/Research Support)DePuy Synthes Spine (Grant/Research Support)Food and Drug Administration (Grant/Research Support)Growing Spine Foundation (Grant/Research Support)NuVasive (Grant/Research Support)Pediatric Orthopaedic Society of North America (Grant/Research Support)