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Mulford KL, Regan C, Nolte CP, Pinter ZW, Milbrandt TA, Larson AN. Automated measurements of interscrew angles in vertebral body tethering patients with deep learning. Spine J 2024; 24:333-339. [PMID: 37774982 DOI: 10.1016/j.spinee.2023.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 09/10/2023] [Accepted: 09/16/2023] [Indexed: 10/01/2023]
Abstract
BACKGROUND CONTEXT Vertebral body tethering is the most popular nonfusion treatment for adolescent idiopathic scoliosis. The effect of the tether cord on the spine can be segmentally assessed by comparing the angle between two adjacent screws (interscrew angle) over time. Tether breakage has historically been assessed radiographically by a change in adjacent interscrew angle by greater than 5° between two sets of imaging. A threshold for growth modulation has not yet been established in the literature. These angle measurements are time consuming and prone to interobserver variability. PURPOSE The purpose of this study was to develop an automated deep learning algorithm for measuring the interscrew angle following VBT surgery. STUDY DESIGN/SETTING Single institution analysis of medical images. PATIENT SAMPLE We analyzed 229 standing or bending AP or PA radiographs from 100 patients who had undergone VBT at our institution. OUTCOME MEASURES Physiologic Measures: An image processing algorithm was used to measure interscrew angles. METHODS A total of 229 standing or bending AP or PA radiographs from 100 VBT patients with vertebral body tethers were identified. Vertebral body screws were segmented by hand for all images and interscrew angles measured manually for 60 of the included images. A U-Net deep learning model was developed to automatically segment the vertebral body screws. Screw label maps were used to develop and tune an image processing algorithm which measures interscrew angles. Finally, the completed model and algorithm pipeline was tested on a 30-image test set. Dice score and absolute error were used to measure performance. RESULTS Inter- and Intra-rater reliability for manual angle measurements were assessed with ICC and were both 0.99. The segmentation model Dice score against manually segmented ground truth across the 30-image test set was 0.96. The average interscrew angle absolute error between the algorithm and manually measured ground truth was 0.66° and ranged from 0° to 2.67° in non-overlapping screws (N=206). The primary modes of failure for the model were overlapping screws on a right thoracic/left lumbar construct with two screws in one vertebra and overexposed images. An algorithm step which determines whether an overlapping screw was present correctly identified all overlapping screws, with no false positives. CONCLUSION We developed and validated an algorithm which measures interscrew angles for radiographs of vertebral body tether patients with an accuracy of within 1° for the majority of interscrew angles. The algorithm can process five images per second on a standard computer, leading to substantial time savings. This algorithm may be used for rapid processing of large radiographic databases of tether patients and could enable more rigorous definitions of growth modulation and cord breakage to be established.
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Affiliation(s)
- Kellen L Mulford
- Orthopedic Surgery Artificial Intelligence Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA; Mayo Clinic Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA
| | - Christina Regan
- Orthopedic Surgery Artificial Intelligence Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA; Mayo Clinic Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA
| | - Charles P Nolte
- Orthopedic Surgery Artificial Intelligence Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA; Mayo Clinic Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA
| | - Zachariah W Pinter
- Orthopedic Surgery Artificial Intelligence Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA; Mayo Clinic Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA
| | - Todd A Milbrandt
- Mayo Clinic Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA
| | - A Noelle Larson
- Orthopedic Surgery Artificial Intelligence Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA; Mayo Clinic Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA.
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Vatkar A, Najjar E, Patel M, Quraishi NA. Vertebral body tethering in adolescent idiopathic scoliosis with more than 2 years of follow-up- systematic review and meta-analysis. Eur Spine J 2023; 32:3047-3057. [PMID: 37306799 DOI: 10.1007/s00586-023-07724-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 04/01/2022] [Accepted: 04/17/2023] [Indexed: 06/13/2023]
Abstract
BACKGROUND CONTEXT Whilst spinal fusion remains the gold standard in the treatment of adolescent idiopathic scoliosis (AIS), anterior vertebral body tethering (AVBT) is gaining momentum with relatively few studies on its efficacy thus far. PURPOSE To conduct a systematic review reporting on the early results of AVBT for patients undergoing surgery for AIS. We aimed to systematically evaluate the relevant literature pertaining to the efficacy of AVBT with respect to degree of correction of the major curve Cobb angle, complications and revision rates. STUDY DESIGN/SETTING Systematic review. PATIENT SAMPLE Of a total of 259 articles, 9 studies met the inclusion criteria and were analysed. Overall, 196 patients of (mean age 12.08 years) underwent an AVBT procedure for correction of AIS with a mean follow-up of 34 months. OUTCOME MEASURES Degree of Cobb angle correction, complications and revision rates were used as outcome measures. METHODS A systematic review of the literature on AVBT was performed for studies published between Jan 1999-March 2021 applying the PRISMA guidelines. Isolated case reports were excluded. RESULTS Overall, 196 patients of (mean age 12.08 years) underwent an AVBT procedure for correction of AIS with a mean follow-up of 34 months. There was a significant correction of the main thoracic curve of scoliosis (mean preoperative Cobb angle 48.5°, post-operative Cobb angle at final follow-up of 20.1°, P = 0.01). Overcorrection and mechanical complications were seen in 14.3% and 27.5% of cases, respectively. Pulmonary complications including atelectasis and pleural effusion were seen in 9.7% of patients. Tether revision was performed in 7.85%, and revision to a spinal fusion in 7.88%. CONCLUSION This systematic review incorporated 9 studies of AVBT and 196 patients with AIS. The complication and revision to spinal fusion rates were 27.5% and 7.88%, respectively. The current literature on AVBT is restricted largely to retrospective studies with non-randomised data. We would recommend a prospective, multi-centre trial of AVBT with strict inclusion criteria and standardised outcome measures.
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Affiliation(s)
- Arvind Vatkar
- The Centre for Spinal Studies and Surgery (CSSS), Queen's Medical Centre, Nottingham University Hospitals, Derby Rd, Lenton, Nottingham, NG7 2UH, UK.
| | - Elie Najjar
- The Centre for Spinal Studies and Surgery (CSSS), Queen's Medical Centre, Nottingham University Hospitals, Derby Rd, Lenton, Nottingham, NG7 2UH, UK
| | - Mohammed Patel
- The Centre for Spinal Studies and Surgery (CSSS), Queen's Medical Centre, Nottingham University Hospitals, Derby Rd, Lenton, Nottingham, NG7 2UH, UK
| | - Nasir A Quraishi
- The Centre for Spinal Studies and Surgery (CSSS), Queen's Medical Centre, Nottingham University Hospitals, Derby Rd, Lenton, Nottingham, NG7 2UH, UK
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Guldeniz O, Yip CCH, Nafo W, Cheung KMC. Biomechanics of the tether breakage: tensile behaviour of a single-unit vertebral body tethering construct. Spine Deform 2023; 11:825-831. [PMID: 36763247 PMCID: PMC10261170 DOI: 10.1007/s43390-023-00657-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 01/29/2023] [Indexed: 02/11/2023]
Abstract
PURPOSE Tether breakage was reported as the most common complication of vertebral body tethering. However, as the literature suggests the physiological loads do not have the potential to cause the failure of the tether. Currently, the biomechanical reason behind the tether breakage is unknown. The current study aims to elucidate the effects of the tension forces on the failure mechanisms of the VBT and provide mechanical justification for how it can be identified radiographically. METHODS Tensile tests (20%/min strain rate) were performed on single-unit VBT samples. Failure modes and mechanical characteristics were reported. RESULTS The failure took place prematurely due to the slippage of the tether at the screw-tether junction where the tether is damaged significantly by the locking cap. Slippage was initiated at 10-13% tensile strain level where the tensile stress and tension force were 50.4 ± 1.5 MPa and 582.2 ± 30.8 N, respectively. CONCLUSION The failure occurs because of high-stress concentrations generated within the locking region which damages the tether surface and leads to the slippage of the tether. We observed that the loads leading to failure are within the physiological limits and may indicate the high likelihood of the tether breakage. The failure mode observed in our study is shown to be the dominant failure mode, and a design improvement on the gripping mechanism is suggested to avoid failure at the screw-tether junction. We observed that the tether elongates 10-13% prior to the breakage, which can be employed as a diagnostic criterion to screen for tether breakages radiographically.
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Affiliation(s)
- Ogulcan Guldeniz
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Christopher C H Yip
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Wanis Nafo
- Department of Mechanical System Engineering, Jeonbuk National University, Jeonju, Republic of Korea
| | - Kenneth M C Cheung
- Department of Orthopaedic Surgery, HKU-Shenzhen Hospital, Shenzhen, China.
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
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Wan SHT, Guldeniz O, Yeung MHY, Cheung JPY, Kwan KYH, Cheung KMC. Inter-screw index as a novel diagnostic indicator of tether breakage. Spine Deform 2023; 11:887-895. [PMID: 37014574 PMCID: PMC10261206 DOI: 10.1007/s43390-023-00679-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 03/11/2023] [Indexed: 04/05/2023]
Abstract
PURPOSE Tether breakage is the most common complication of Vertebral Body Tethering (VBT) occurring in up to 52% of Adolescent Idiopathic Scoliosis (AIS) patients and risks continued progression and revision. Radiographical diagnosis of tether breakage is commonly defined by a 5° increase in inter-screw angle and associates breakage with loss of correction. However, the sensitivity of this method was 56% only, suggesting that tethers can break without an increase in angulation, which was supported by other studies. To our knowledge, current literature lacks a method merely focusing on the diagnosis of tether breakage radiographically that does not associate the breakages with loss of correction. METHODS This was a retrospective review of prospectively collected data of AIS patients who underwent VBT. The "inter-screw index" is defined as the percentage increase in inter-screw distance since post-op, with ≥ 13% increase defined as tether breakage as suggested by our mechanical tests. CTs were reviewed to identify the breakages and compared with inter-screw angle and inter-screw index. RESULTS 94 segments from 13 CTs were reviewed, and 15 tether breakages were identified. Use of inter-screw index correctly identified 14 breakages (93%), whereas ≥ 5° increase in inter-screw angle only identified 12 breakages (80%). CONCLUSION Use of inter-screw index is proven to be more sensitive than inter-screw angle in identifying tether breakages. Therefore, we propose the use of inter-screw index to diagnose tether breakages radiographically. Tether breakages were not necessarily accompanied by a loss of segmental correction leading to an increase in inter-screw angle, especially after skeletal maturity. LEVEL OF EVIDENCE Level 3.
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Affiliation(s)
- Sandra H T Wan
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Ogulcan Guldeniz
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Matthew H Y Yeung
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Jason P Y Cheung
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Kenny Y H Kwan
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Kenneth M C Cheung
- Department of Orthopaedic Surgery, HKU-Shenzhen Hospital, Shenzhen, China.
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
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Baroncini A, Migliorini F, Eschweiler J, Hildebrand F, Trobisch P. The timing of tether breakage influences clinical results after VBT. Eur Spine J 2022; 31:2362-2367. [PMID: 35864248 DOI: 10.1007/s00586-022-07321-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 07/01/2022] [Accepted: 07/06/2022] [Indexed: 05/20/2023]
Abstract
INTRODUCTION Tether breakage is a frequent mechanical complications after vertebral body tethering (VBT), but not all patients with a breakage show loss of correction. The reason of this clinical finding has not yet been clarified. We hypothesized that the integrity of the tether is relevant only in the early stages after VBT, when it drives growth modulation and tissue remodelling. After these mechanisms have taken place, the tether loses its function and a breakage will not alter the new shape of the spine. Thus, tether breakage would have a greater clinical relevance when occurring shortly after surgery. METHODS All consecutive patients who underwent VBT and had a min. 2-year follow-up were included. The difference in curve magnitude between the 1st standing x-ray and the last follow-up was calculated (ΔCobb). For each curve, the presence and timing of tether breakage were recorded. The curves were grouped according to if and when the breakage was observed (no breakage, breakage at 0-6 months, 6-12 months, > 12 months). The ΔCobb was compared among these groups with the analysis of variance (ANOVA). RESULTS Data from 152 curves were available: 68 with no breakage, 12 with a breakage at 0-6 months, 37 at 6-12 months and 35 > 12 months. The ANOVA found significant difference in the ΔCobb among the groups (Sum of square 2553.59; degree of freedom 3; mean of square 851.1; Fisher test 13.8; P < 0.0001). Patients with no breakage or breakage at > 12 months had similar ΔCobb (mean 4.8° and 7.8°, respectively, P = 0.3), smaller than the 0-6 or 6-12 groups (15.8° and 13.8°, respectively). CONCLUSION Tether breakage leads to a consistent loss of correction when occurring within the first 12 months, while it has limited clinical relevance when occurring later on.
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Affiliation(s)
- A Baroncini
- Department of Orthopaedic Surgery, RWTH Aachen University Clinic, Pauwelsstrasse 30, 52074, Aachen, Germany.
- Department of Spine Surgery, Eifelklinik St. Brigida, Simmerath, Germany.
| | - F Migliorini
- Department of Orthopaedic Surgery, RWTH Aachen University Clinic, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - J Eschweiler
- Department of Orthopaedic Surgery, RWTH Aachen University Clinic, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - F Hildebrand
- Department of Orthopaedic Surgery, RWTH Aachen University Clinic, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - P Trobisch
- Department of Spine Surgery, Eifelklinik St. Brigida, Simmerath, Germany
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Shankar D, Eaker L, von Treuheim TDP, Tishelman J, Silk Z, Lonner BS. Anterior vertebral body tethering for idiopathic scoliosis: how well does the tether hold up? Spine Deform 2022; 10:799-809. [PMID: 35258844 DOI: 10.1007/s43390-022-00490-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 02/19/2022] [Indexed: 10/18/2022]
Abstract
PURPOSE Durability of outcomes following vertebral body tethering (VBT) is a concern and may be impacted by tether breakage (TB), which has been unstudied in a large cohort. We characterized TB rates and their impact on clinical outcomes in the largest single-surgeon series to date. METHODS Inclusion criteria were VBT patients with AIS, major Cobb angle ≤ 75°, and minimum 2-year follow-up (FU). TBs were identified on 1- and 2-year FU X-rays. TB rates between single-cord and double-cord tethers were evaluated using two-proportion z test. Curve correction rates and SRS-22 scores between patients with and without TB at 2 years were evaluated using Mann-Whitney U test. RESULTS 69 patients were included. By 2-year FU, 18 (27%) had experienced TB. TB primarily occurred in major (70%) versus minor curves and thoracolumbar tethers (75%) versus thoracic. TB rates between thoracolumbar single (32%) and double-cord tethers (30%) were not significantly different (p = 0.88). Mean major curve correction at 2-year FU was lower (p = 0.02) in patients with major curve TB (48° to 24°, 50%) versus those without (53°-21°, 60%). 2 patients (3%) required reoperation, 1 due to foraminal encroachment from a screw tip and 1 for curve progression with TB. CONCLUSION TB rate was 27% at 2 years following VBT. Broken major curve tethers are associated with minor loss of correction that may not be clinically significant. TB rates are higher for thoracolumbar curvatures and double cords may not be protective against TB. Further study of long-term TB rates is imperative. LEVEL OF EVIDENCE IV.
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Baroncini A, Trobisch P, Eschweiler J, Migliorini F. Analysis of the risk factors for early tether breakage following vertebral body tethering in adolescent idiopathic scoliosis. Eur Spine J 2022; 31:2348-2354. [PMID: 35507127 DOI: 10.1007/s00586-022-07231-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 03/17/2022] [Accepted: 04/14/2022] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Tether breakage is a common mechanical complication after VBT. When this occurs shortly after surgery, patients may be at higher risk for loss of correction. Aim of this study was to analyze demographic and radiographic parameters that may potentially be risk factors for early tether breakage, as no data are yet available on this topic. MATERIALS AND METHODS All skeletally immature patients who underwent VBT and for whom a 1-year follow-up was available were included in the study. Demographic, intraoperative and coronal and sagittal parameters from the preoperative and 1st standing X-rays were collected. Patients were divided in two groups according to the presence or absence of a breakage and the outcomes of interest were compared. RESULTS Data from 105 patients were available (age 14.2 ± 1.5, 153 curves). Lumbar curves showed a higher risk of breakage than thoracic ones (71% vs. 29%, P < 0.0001). Overall, preoperative risk factors were a high curve magnitude (MD, mean difference - 4.1°, P = 0.03) and a limited flexibility (MD 8.9%, P = 0.006); postoperative risk factors were a large residual curve (MD - 6.4°, P = 0.0005) and a limited correction (MD 8.4%, P = 0.0005). The same risk factors were identified in thoracic curves, while in lumbar instrumentation only a higher preoperative Cobb angle represented a risk factor for breakage. Age and skeletal maturity did not represent risk factors. CONCLUSION The main preoperative risk factors for early tether breakage after VBT are a high curve magnitude and a limited flexibility. A limited curve correction also represents a risk factor for this complication.
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Affiliation(s)
- A Baroncini
- Department of Orthopaedics and Trauma Surgery, RWTH Aachen University Clinic, Pauwelsstrasse 30, 52074, Aachen, Germany. .,Department of Spine Surgery, Eifelklinik St. Brigida, Simmerath, Germany.
| | - P Trobisch
- Department of Spine Surgery, Eifelklinik St. Brigida, Simmerath, Germany
| | - J Eschweiler
- Department of Orthopaedics and Trauma Surgery, RWTH Aachen University Clinic, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - F Migliorini
- Department of Orthopaedics and Trauma Surgery, RWTH Aachen University Clinic, Pauwelsstrasse 30, 52074, Aachen, Germany
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