Influence of implant rod curvature on sagittal correction of scoliosis deformity

Remel A. Salmingo, Shigeru Tadano, Yuichiro Abe, Manabu Ito

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Abstract

BACKGROUND CONTEXT: Deformation of in vivo–implanted rods could alter the scoliosis sagittal correction. To our knowledge, no previous authors have investigated the influence of implanted-rod deformation on the sagittal deformity correction during scoliosis surgery. PURPOSE: To analyze the changes of the implant rod’s angle of curvature during surgery and establish its influence on sagittal correction of scoliosis deformity. STUDY DESIGN: A retrospective analysis of the preoperative and postoperative implant rod geometry and angle of curvature was conducted. PATIENT SAMPLE: Twenty adolescent idiopathic scoliosis patients underwent surgery. Average age at the time of operation was 14 years.
OUTCOME MEASURES: The preoperative and postoperative implant rod angle of curvature expressed in degrees was obtained for each patient. METHODS: Two implant rods were attached to the concave and convex side of the spinal deformity.
The preoperative implant rod geometry was measured before surgical implantation. The postoperative implant rod geometry after surgery was measured by computed tomography. The implant rod angle of curvature at the sagittal plane was obtained from the implant rod geometry. The angle of curvature between the implant rod extreme ends was measured before implantation and after surgery. The sagittal curvature between the corresponding spinal levels of healthy adolescents obtained by previous studies was compared with the implant rod angle of curvature to evaluate the sagittal curve correction. The difference between the postoperative implant rod angle of curvature and normal spine sagittal curvature of the corresponding instrumented level was used to evaluate over or under correction of the sagittal deformity. RESULTS: The implant rods at the concave side of deformity of all patients were significantly deformed after surgery. The average degree of rod deformation Dq at the concave and convex sides was 15.8 and 1.6, respectively. The average preoperative and postoperative implant rod angle of curvature at the concave side was 33.6 and 17.8, respectively. The average preoperative and postoperative implant rod angle of curvature at the convex side was 25.5 and 23.9, respectively. A significant relationship was found between the degree of rod deformation and preoperative implant rod angle of curvature (r50.60, p!.005). The implant rods at the convex side of all patients
Original languageEnglish
JournalSpine Journal
Volume14
Issue number8
Pages (from-to)1432–1439
Number of pages8
ISSN1529-9430
DOIs
Publication statusPublished - 2014

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