Are rib versus spine anchors protective against breakage of growing rods?

Kent T. Yamaguchi, David L. Skaggs, Shaun Mansour, Karen S. Myung, Muharram Yazici, Charles Johnston, George Thompson, Paul Sponseller, Behrooz A. Akbarnia, Michael G. Vitale

Research output: Contribution to journalArticlepeer-review

Abstract

esults Thirty-four patients had rib-anchored growing rods and 142 had spine-anchored growing rods. This analysis found that proximal rib-anchored growing rods have a 23% risk of lifetime rod breakage compared with spine-anchored growing rods (6% vs. 29%) (p =.041) without a significant increase in risk of anchor complications (38% vs. 33%) (p =.117). The number of implanted rods (p =.839), age (p =.649), and number of instrumented levels (p =.447) were not statistically significant regarding rod breakage risk, although higher preoperative Cobb angles were significant (p =.014).

Conclusions Preoperative Cobb angle appears to be the most influential factor in determining whether growing rods break (p =.014). Univariate analysis found that rib anchors were associated with less than one-fourth the risk of rod breakage than spine anchors (p =.04) but multivariate analysis found no significant association between anchors and rod breakage (p =.07). This trend suggests that rib-anchored growing rod systems may be associated with less rod breakage because the system is less rigid as a result of some "slop" at the hook-rib interface, as well as the normal motion of the costovertebral joint.

Study Design Retrospective multicenter, case-control study.

Objective To compare the risks of rod breakage and anchor complications between distraction-based growing rods with proximal spine versus rib anchors.

Summary of Background Data Rod breakage is a known complication of distraction-based growing rod instrumentation.

Methods A total of 176 patients met inclusion criteria: minimum 2-year follow-up, younger than age 9 years at index surgery, non-Vertical Expandable Prosthetic Titanium Rib distraction-based growing rods, and known anchor locations. Mean follow-up was 56 months (range, 24-152 months). Survival analyses using Cox proportional hazards model (accounting for varying lengths of follow-up) of rod breakage, anchor complications, preoperative Cobb angle, number of growing rods, age, and number of levels instrumented were performed using a significance level of p <.05.

Original languageEnglish (US)
Pages (from-to)489-492
Number of pages4
JournalSpine deformity
Volume2
Issue number6
DOIs
StatePublished - Nov 1 2014

Keywords

  • Anchors
  • Complications
  • Distraction-based growing rods
  • Rod breakage

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine

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