A Noelle Larson1, Carl-Eric Aubin2, David W Polly3, Charles G T Ledonio3, Baron S Lonner4, Suken A Shah5, B Stephens Richards6, Mark A Erickson7, John B Emans8, Stuart L Weinstein9. 1. Department of Orthopaedic Surgery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA. Electronic address: larson.noelle@gmail.com. 2. Department of Mechanical Engineering, Polytechnique Montreal, P.O. Box 6079, Downtown Station, Montreal, Quebec H3T1C5, Canada. 3. Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Ave South, Suite R200, Minneapolis, MN 55454, USA. 4. Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, 820 2nd Avenue, Suite 7A, New York, NY 10017, USA. 5. Department of Orthopedics, Nemours/Alfred I. DuPont Hospital for Children, 1600 Rockland Road, P.O. Box 269, Wilmington, DE 19899, USA. 6. Department of Orthopedics, Texas Scottish Rite Hospital for Children, 2222 Welborn Street, Dallas, TX 75219, USA. 7. Department of Orthopedic Surgery, The Children's Hospital, 13123 E. 16th Avenue, B060, Aurora, CO 80045, USA. 8. Department of Orthopaedic Surgery, Hunnewell 2, Boston Children's Hospital, Boston, MA 02115, USA. 9. Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 01026 JPP, Iowa City, IA 55242, USA.
Abstract
STUDY DESIGN: Systematic review of clinical studies. OBJECTIVES: To critically evaluate existing literature to determine whether increased anchor or implant density (screws, wires, and hooks per level fused) results in improved curve correction for adolescent idiopathic scoliosis (AIS) surgery. SUMMARY OF BACKGROUND DATA: Wide variability exists in the number of screws used for AIS surgery. High numbers of pedicle screws are increasingly used, but there is limited evidence to support this as best practice. METHODS: Online English-language databases were searched to identify articles addressing anchor density. Articles were reviewed for anchor type/number, radiographic measures, and patient-reported outcomes. RESULTS: Of 196 references identified, 10 studies totaling 929 patients met the inclusion criteria. Reported mean anchor density varied from 1.06 to 2.0 implants per level fused. Mean percent coronal curve correction varied from 64% to 70%. Two studies (463 patients) analyzed hook, hybrid (combined hooks and screws), and screw constructs as a single cohort. Both found increased correction with high-density constructs (p = .01, p < .001), perhaps as a result of the hooks and hybrid constructs. Eight retrospective studies and 1 prospective randomized, controlled trial had predominantly screw constructs (466 patients). Increased anchor density was not associated with improved curve correction. The studies evaluating screw density are significantly underpowered to detect a difference in curve correction. CONCLUSIONS: Wide heterogeneity in anchor density exists in the surgical treatment of AIS. Reports evaluating the effects of increased anchor density are mostly retrospective and significantly underpowered to detect a difference in curve correction and patient outcomes. At this time, there is insufficient evidence to show that anchor density affects clinical outcomes in AIS.
STUDY DESIGN: Systematic review of clinical studies. OBJECTIVES: To critically evaluate existing literature to determine whether increased anchor or implant density (screws, wires, and hooks per level fused) results in improved curve correction for adolescent idiopathic scoliosis (AIS) surgery. SUMMARY OF BACKGROUND DATA: Wide variability exists in the number of screws used for AIS surgery. High numbers of pedicle screws are increasingly used, but there is limited evidence to support this as best practice. METHODS: Online English-language databases were searched to identify articles addressing anchor density. Articles were reviewed for anchor type/number, radiographic measures, and patient-reported outcomes. RESULTS: Of 196 references identified, 10 studies totaling 929 patients met the inclusion criteria. Reported mean anchor density varied from 1.06 to 2.0 implants per level fused. Mean percent coronal curve correction varied from 64% to 70%. Two studies (463 patients) analyzed hook, hybrid (combined hooks and screws), and screw constructs as a single cohort. Both found increased correction with high-density constructs (p = .01, p < .001), perhaps as a result of the hooks and hybrid constructs. Eight retrospective studies and 1 prospective randomized, controlled trial had predominantly screw constructs (466 patients). Increased anchor density was not associated with improved curve correction. The studies evaluating screw density are significantly underpowered to detect a difference in curve correction. CONCLUSIONS: Wide heterogeneity in anchor density exists in the surgical treatment of AIS. Reports evaluating the effects of increased anchor density are mostly retrospective and significantly underpowered to detect a difference in curve correction and patient outcomes. At this time, there is insufficient evidence to show that anchor density affects clinical outcomes in AIS.
Authors: Xiaoyu Wang; A Noelle Larson; Dennis G Crandall; Stefan Parent; Hubert Labelle; Charles G T Ledonio; Carl-Eric Aubin Journal: Scoliosis Spinal Disord Date: 2017-04-17
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