Thamrong Lertudomphonwanit1, Michael P Kelly2, Keith H Bridwell2, Lawrence G Lenke3, Steven J McAnany2, Prachya Punyarat4, Timothy P Bryan2, Jacob M Buchowski2, Lukas P Zebala2, Brenda A Sides2, Karen Steger-May5, Munish C Gupta6. 1. Department of Orthopaedic Surgery, Faculty of Medicine Ramathibodi Hospital, Mahidol University, 270 Rama VI Rd, Ratchathewi, Bangkok 10400, Thailand. 2. Department of Orthopedic Surgery, Barnes-Jewish Institute of Health, Washington University in St. Louis, 660 S. Euclid Ave, Campus Box 8233, St. Louis, MO 63110, USA. 3. Department of Orthopedic Surgery, The Spine Hospital at New York-Presbyterian/Allen, Columbia University, 5141 Broadway 3 Field West-029, New York, NY 10034, USA. 4. Division of Neurosurgery, Department of Surgery, Faculty of Medicine, Thammasat University, 95 Paholyotin Rd, Khlongnueng, Pathumthani 12120, Thailand. 5. Division of Biostatistics, Washington University School of Medicine, 660 S. Euclid Ave, St. Louis, MO 63110, USA. 6. Department of Orthopedic Surgery, Barnes-Jewish Institute of Health, Washington University in St. Louis, 660 S. Euclid Ave, Campus Box 8233, St. Louis, MO 63110, USA. Electronic address: munishgupta@wustl.edu.
Abstract
BACKGROUND CONTEXT: Risk factors associated with rod fracture (RF) following adult spinal deformity (ASD) surgery fused to the sacrum remain debatable, and the impact of RF on patient-reported outcomes (PROs) after ASD surgery has not been investigated. PURPOSE: We aimed to evaluate the prevalence of and risk factors for RF and determine PROs changes associated with RF after ASD surgery fused to the sacrum. STUDY DESIGN/ SETTING: A retrospective single-center cohort study was performed. PATIENT SAMPLE: Patients undergoing long-construct posterior spinal fusions to the sacrum performed at a single institution by two senior spine surgeons from 2004 to 2014 were included. OUTCOME MEASURES: Patient demographics, radiographic parameters, and surgical factors were assessed for risk factors associated with RF. Oswestry Disability Index (ODI) and Scoliosis Research Society-30 (SRS-30) scores were assessed at baseline, 1 year postoperatively, and latest follow-up. METHODS: Inclusion criteria were ASD patients age >18 who had ≥5 vertebrae instrumented and fused posteriorly to the sacrum and either development of RF or no development of RF with minimum 2-year follow-up. Patient characteristics, operative data, radiographic parameters, and PROs were analyzed at baseline and follow-up. Separate Cox proportional hazard models based on rod material and diameter were used to determine factors associated with RF. RESULTS: Five hundred twenty-six patients (80%) were available for analysis. RF occurred in 97 (18.4%) patients (unilateral RF n=61 [63%]; bilateral RF n=36 [37%]). Risk factors for fracture of 5.5 mm cobalt chromium (CC) instrumentation (CC 5.5 model) included preoperative sagittal vertical axis (hazard ratio [HR] 1.07, 95% confidence interval [95% CI] 1.02-1.14 per 1-cm increase), preoperative thoracolumbar kyphosis (HR 1.02, 95% CI 1.01-1.04 per 1-degree increase), and number of levels fused for patients who received rhBMP-2 <12 mg per level fused (HR 1.48, 95% CI 1.20-1.82 per 1-level increase). Implants that were 5.5-mm CC constructs were at a higher risk for fracture than 6.35-mm stainless steel (SS) constructs (HR 8.49, 95% CI 4.26-16.89). The RF group had less overall improvement in SRS Satisfaction (0.93 vs. 1.32; p=.007) and SRS Self-image domain scores (0.72 vs. 1.02; p=.01). The bilateral RF group had less overall improvement in ODI (8.1 vs. 15.8; p=.02), SRS Subscore (0.51 vs. 0.85; p=.03), and SRS Pain domain scores (0.48 vs. 0.95; p=.02) compared with the non-RF group at final follow-up. CONCLUSIONS: The prevalence of all RF after index procedures was 18.4%, 37% for bilateral RF. Greater preoperative sagittal vertical axis, greater preoperative thoracolumbar kyphosis, increased number of vertebrae fused for patients who received rhBMP-2 <12 mg per level fused, and CC 5.5-mm rod were associated with RF. Less improvement in patient satisfaction and self-image was noted in the RF group. Furthermore, bilateral RF significantly affected PROs as measured by ODI and SRS Subscore at final follow-up.
BACKGROUND CONTEXT: Risk factors associated with rod fracture (RF) following adult spinal deformity (ASD) surgery fused to the sacrum remain debatable, and the impact of RF on patient-reported outcomes (PROs) after ASD surgery has not been investigated. PURPOSE: We aimed to evaluate the prevalence of and risk factors for RF and determine PROs changes associated with RF after ASD surgery fused to the sacrum. STUDY DESIGN/ SETTING: A retrospective single-center cohort study was performed. PATIENT SAMPLE: Patients undergoing long-construct posterior spinal fusions to the sacrum performed at a single institution by two senior spine surgeons from 2004 to 2014 were included. OUTCOME MEASURES: Patient demographics, radiographic parameters, and surgical factors were assessed for risk factors associated with RF. Oswestry Disability Index (ODI) and Scoliosis Research Society-30 (SRS-30) scores were assessed at baseline, 1 year postoperatively, and latest follow-up. METHODS: Inclusion criteria were ASDpatients age >18 who had ≥5 vertebrae instrumented and fused posteriorly to the sacrum and either development of RF or no development of RF with minimum 2-year follow-up. Patient characteristics, operative data, radiographic parameters, and PROs were analyzed at baseline and follow-up. Separate Cox proportional hazard models based on rod material and diameter were used to determine factors associated with RF. RESULTS: Five hundred twenty-six patients (80%) were available for analysis. RF occurred in 97 (18.4%) patients (unilateral RF n=61 [63%]; bilateral RF n=36 [37%]). Risk factors for fracture of 5.5 mm cobalt chromium (CC) instrumentation (CC 5.5 model) included preoperative sagittal vertical axis (hazard ratio [HR] 1.07, 95% confidence interval [95% CI] 1.02-1.14 per 1-cm increase), preoperative thoracolumbar kyphosis (HR 1.02, 95% CI 1.01-1.04 per 1-degree increase), and number of levels fused for patients who received rhBMP-2 <12 mg per level fused (HR 1.48, 95% CI 1.20-1.82 per 1-level increase). Implants that were 5.5-mm CC constructs were at a higher risk for fracture than 6.35-mm stainless steel (SS) constructs (HR 8.49, 95% CI 4.26-16.89). The RF group had less overall improvement in SRS Satisfaction (0.93 vs. 1.32; p=.007) and SRS Self-image domain scores (0.72 vs. 1.02; p=.01). The bilateral RF group had less overall improvement in ODI (8.1 vs. 15.8; p=.02), SRS Subscore (0.51 vs. 0.85; p=.03), and SRS Pain domain scores (0.48 vs. 0.95; p=.02) compared with the non-RF group at final follow-up. CONCLUSIONS: The prevalence of all RF after index procedures was 18.4%, 37% for bilateral RF. Greater preoperative sagittal vertical axis, greater preoperative thoracolumbar kyphosis, increased number of vertebrae fused for patients who received rhBMP-2 <12 mg per level fused, and CC 5.5-mm rod were associated with RF. Less improvement in patient satisfaction and self-image was noted in the RF group. Furthermore, bilateral RF significantly affected PROs as measured by ODI and SRS Subscore at final follow-up.