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Early Pelvic Fixation Failure in Neuromuscular Scoliosis

Myung, Karen S. MD, PhD*; Lee, Christopher MD*,†; Skaggs, David L. MD, MMM*

Journal of Pediatric Orthopaedics: April/May 2015 - Volume 35 - Issue 3 - p 258–265
doi: 10.1097/BPO.0000000000000254
Spine

Background: To report on early failures of pelvic fixation in posterior spinal fusions for neuromuscular scoliosis.

Methods: A retrospective review of posterior-only spinal instrumentation and fusion to the pelvis with iliac screws was performed. Forty-one patients with a mean age of 14 years and mean 16 levels fused met the inclusion criteria. Diagnoses include cerebral palsy (22), Duchenne muscular dystrophy (7), other neuromuscular (10), and spina bifida (2). Cox proportional hazards regression modeling was used to compare rates of failure.

Results: The mean preoperative primary Cobb angle was 82 degrees (range, 21 to 144 degrees). The pelvic obliquity correction was 76%. The fixation in the pelvis failed in 12/41 patients (29%). Failures include: screw head disengaged from screw shaft (5), iliac screw disengaged from rod (2), iliac connector disengaged from rod (2), iliac connector disengaged from iliac screw (4), and iliac screw loosened from bone (3). No failures occurred if there were at least 6 screws in L5, S1, and pelvis (0/7 patients). The failure rate with <6 screws in L5, S1, and pelvis was higher at 35% (12/34 patients) (P=0.16). When using traditional iliac screws with connectors to rods, all constructs had <6 screws in L5, S1, and pelvis. Only 1 failure occurred when S2-iliac screws were used, but was without clinical consequence. The mean time from surgery to failure was 18 months (range, 1 to 49 mo).

Conclusion: Not placing bilateral pedicle screws at L5 and S1, in addition to 2 iliac screws, was associated with a 35% early failure rate of pelvic fixation.

Level of Evidence: Level IV.

*Children’s Hospital Los Angeles, Children’s Orthopaedic Center

Department of Orthopaedic Surgery, University of California Los Angeles, Los Angeles, CA

None of the authors received financial support for this study.

The authors certify that all the investigations were conducted in conformity with ethical principles of research, and IRB approval was obtained by the Committee on Clinical Investigations at Children’s Hospital Los Angeles.

D.L.S. is a co-investigator for grants funded by POSNA and SRS (paid to Columbia University); is a consultant for Biomet and Medtronic, a board member for the Growing Spine Study Group, Scoliosis Research Society, Growing Spine Foundation and Medtronic Strategic and Advisory Board; provides expert testimony in medical malpractice cases (<5% of income); receives payment for lectures including service on speakers' bureaus for Biomet, Medtronic, and Stryker; patent holder for Medtronic; receives royalties from Wolters Kluwer Health-Lippincott Williams & Wilkins, receives payment for the development of educational presentations for Stryker, Biomet and Medtronic and receives institutional support from Medtronic (fellowship program). The other authors declare no conflicts of interest.

Reprints: David L. Skaggs, MD, MMM, Children’s Hospital Los Angeles, Children’s Orthopaedic Center, 4650 Sunset Boulevard, Mailstop #69, Los Angeles, CA 90027. E-mail: dskaggs@chla.usc.edu.

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