Kent T Yamaguchi1, David L Skaggs2, Shaun Mansour3, Karen S Myung3, Muharram Yazici4, Charles Johnston5, George Thompson6, Paul Sponseller7, Behrooz A Akbarnia8, Michael G Vitale9. 1. Department of Orthopaedic Surgery, University of California-Los Angeles, Los Angeles, CA, USA. 2. Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 W Sunset Boulevard, Mailstop #69, Los Angeles, CA 90027, USA. Electronic address: dskaggs@chla.usc.edu. 3. Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 W Sunset Boulevard, Mailstop #69, Los Angeles, CA 90027, USA. 4. Department of Orthopaedic Surgery, Hacettepe University Faculty of Medicine, 06100 Sihhiye-Ankara/Turkey. 5. Department of Orthopaedic Surgery, Texas Scottish Rite Hospital for Children, 2222 Welborn St, Dallas, TX 75219, USA. 6. Department of Orthopaedic Surgery, Rainbow Babies and Children's Hospital, Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH 44106, USA. 7. Department of Orthopaedic Surgery, Johns Hopkins University, 601 North Caroline Street JHOC #5215, Baltimore, Maryland 21287-0882, USA. 8. San Diego Center for Spinal Disorders, 4130 La Jolla Village Dr, La Jolla, CA 92037, USA. 9. Department of Orthopaedic Surgery, New YorkePresbyterian Morgan Stanley Children's Hospital, Columbia University Medical Center, 3959 Broadway, New York, NY 10032, USA.
Abstract
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. RESULTS: 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. RESULTS: 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.
Authors: Lawrence G Lenke; Adam N Fano; Rajiv R Iyer; Hiroko Matsumoto; Daniel J Sucato; Amer F Samdani; Justin S Smith; Munish C Gupta; Michael P Kelly; Han Jo Kim; Daniel M Sciubba; Samuel K Cho; David W Polly; Oheneba Boachie-Adjei; Stephen J Lewis; Peter D Angevine; Michael G Vitale Journal: Spine Deform Date: 2022-03-15
Authors: Hiroko Matsumoto; Michael W Fields; Benjamin D Roye; David P Roye; David Skaggs; Behrooz A Akbarnia; Michael G Vitale Journal: Spine Deform Date: 2020-09-21