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Hoernschemeyer DG, Hawkins SD, Tweedy NM, Boeyer ME. Anterior Vertebral Body Tethering: A Single-Center Cohort with 4.3 to 7.4 Years of Follow-up. J Bone Joint Surg Am 2024:00004623-990000000-01152. [PMID: 38968364 DOI: 10.2106/jbjs.23.01229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/07/2024]
Abstract
BACKGROUND Vertebral body tethering (VBT) is a well-recognized, non-fusion alternative for idiopathic scoliosis in children with growth remaining. To date, there have been almost no published outcome studies with postoperative follow-up of >2 years. We aimed to fill this gap by evaluating mid-term outcomes in our first 31 consecutive patients. METHODS We retrospectively assessed additional clinical and radiographic data (mean, 5.7 ± 0.7 years) from our first 31 consecutive patients. Assessments included standard deformity measures, skeletal maturity status, and any additional complications (e.g., suspected broken tethers or surgical revisions). Using the same definition of success (i.e., all residual deformities, instrumented or uninstrumented, ≤30° at maturity; no posterior spinal fusion), we revisited the success rate, revision rate, and suspected broken tether rate. RESULTS Of our first 31 patients treated with VBT, 29 (of whom 28 were non-Hispanic White and 1 was non-Hispanic Asian; 27 were female and 2 were male) returned for additional follow-up. The success rate dropped to 64% with longer follow-up as deformity measures increased, and the revision rate increased to 24% following 2 additional surgical revisions. Four additional suspected broken tethers were identified, for a rate of 55%, with only 1 occurring beyond 4 years. No additional patients had conversion to a posterior spinal fusion. We observed a mean increase of 4° (range, 2° to 8°) in main thoracic deformity measures and 8° (range, 6° to 12°) in thoracolumbar deformity measures. CONCLUSIONS With >5 years of follow-up, we observed a decrease in postoperative success, as progression of the deformity was observed in most subgroups, and an increase in the revision and suspected broken tether rates. No additional patients had conversion to a posterior spinal fusion, which may indicate long-term survivorship. LEVEL OF EVIDENCE Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
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Affiliation(s)
| | | | - Nicole M Tweedy
- Department of Orthopaedic Surgery, University of Missouri, Columbia, Missouri
| | - Melanie E Boeyer
- Department of Orthopaedic Surgery, University of Missouri, Columbia, Missouri
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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] [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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Nicolini LF, Oliveira RC, Ribeiro M, Stoffel M, Markert B, Kobbe P, Hildebrand F, Trobisch P, Simões MS, de Mello Roesler CR, Fancello EA. Tether pre-tension within vertebral body tethering reduces motion of the spine and influences coupled motion: a finite element analysis. Comput Biol Med 2024; 169:107851. [PMID: 38113683 DOI: 10.1016/j.compbiomed.2023.107851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 11/30/2023] [Accepted: 12/11/2023] [Indexed: 12/21/2023]
Abstract
Anterior Vertebral Body Tethering (VBT) is a novel fusionless treatment option for selected adolescent idiopathic scoliosis patients which is gaining widespread interest. The primary objective of this study is to investigate the effects of tether pre-tension within VBT on the biomechanics of the spine including sagittal and transverse parameters as well as primary motion, coupled motion, and stresses acting on the L2 superior endplate. For that purpose, we used a calibrated and validated Finite Element model of the L1-L2 spine. The VBT instrumentation was inserted on the left side of the L1-L2 segment with different cord pre-tensions and submitted to an external pure moment of 6 Nm in different directions. The range of motion (ROM) for the instrumented spine was measured from the initial post-VBT position. The magnitudes of the ROM of the native spine and VBT-instrumented with pre-tensions of 100 N, 200 N, and 300 N were, respectively, 3.29°, 2.35°, 1.90° and 1.61° in extension, 3.30°, 3.46°, 2.79°, and 2.17° in flexion, 2.11°, 1.67°, 1.33° and 1.06° in right axial rotation, and 2.10°, 1.88°, 1.48° and 1.16° in left axial rotation. During flexion-extension, an insignificant coupled lateral bending motion was observed in the native spine. However, VBT instrumentation with pre-tensions of 100 N, 200 N, and 300 N generated coupled right lateral bending of 0.85°, 0.81°, and 0.71° during extension and coupled left lateral bending of 0.32°, 0.24°, and 0.19° during flexion, respectively. During lateral bending, a coupled extension motion of 0.33-0.40° is observed in the native spine, but VBT instrumentation with pre-tensions of 100 N, 200 N, and 300 N generates coupled flexion of 0.67°, 0.58°, and 0.42° during left (side of the implant) lateral bending and coupled extension of 1.28°, 1.07°, and 0.87° during right lateral bending, respectively. Therefore, vertebral body tethering generates coupled motion. Tether pre-tension within vertebral body tethering reduces the motion of the spine.
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Affiliation(s)
- Luis Fernando Nicolini
- Group of Analysis and Mechanical Design - GRANTE, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil; Mechanical and Aerospace Technology Laboratory (NUMAE), Dep. of Mechanical Engineering, Federal University of Santa Maria, Brazil.
| | - Rafael Carreira Oliveira
- Group of Analysis and Mechanical Design - GRANTE, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil
| | - Marx Ribeiro
- Group of Analysis and Mechanical Design - GRANTE, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil; Department of Orthopedics, Trauma and Reconstructive Surgery, RWTH Aachen University Hospital, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Marcus Stoffel
- Institute of General Mechanics (IAM), RWTH Aachen University, Germany
| | - Bernd Markert
- Institute of General Mechanics (IAM), RWTH Aachen University, Germany
| | - Philipp Kobbe
- Department of Orthopedics, Trauma and Reconstructive Surgery, RWTH Aachen University Hospital, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Frank Hildebrand
- Department of Orthopedics, Trauma and Reconstructive Surgery, RWTH Aachen University Hospital, Pauwelsstr. 30, 52074, Aachen, Germany
| | | | - Marcelo Simoni Simões
- Biomechanical Engineering Laboratory - LEBm, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil
| | - Carlos Rodrigo de Mello Roesler
- Group of Analysis and Mechanical Design - GRANTE, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil; Biomechanical Engineering Laboratory - LEBm, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil
| | - Eduardo Alberto Fancello
- Group of Analysis and Mechanical Design - GRANTE, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil; Biomechanical Engineering Laboratory - LEBm, Dep. of Mechanical Engineering, Federal University of Santa Catarina, Brazil
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Froehlich S, Mittelmeier W, Desai B, Pandey SJ, Raddatz H, Lembcke B, Klinder A, Osmanski-Zenk K. Surgical Treatment of Adolescent Idiopathic Scoliosis with the ApiFix Minimal Invasive Dynamic Correction System-A Preliminary Report of a 24-Month Follow-Up. Life (Basel) 2023; 13:2032. [PMID: 37895414 PMCID: PMC10608253 DOI: 10.3390/life13102032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 09/28/2023] [Accepted: 10/06/2023] [Indexed: 10/29/2023] Open
Abstract
Adolescent idiopathic scoliosis (AIS) is a three-dimensional growth disorder. Corrective surgical procedures are the recommended treatment option for a thoracic angle exceeding 50° and a lumbar major curve of 40°. Over the past few years, dynamic growth modulation implants have been developed as alternatives to permanent fusion. The ApiFix system was designed as a 2D "posterior dynamic device" for curve correction. After implantation in a minimally invasive procedure, it uses polyaxial joints and a self-adjusting rod to preserve the degree of motion and to accommodate the patient's growth. It provides an effective method of controlling deformity and fills the gap between the conservative treatment of major curves that are >35° and the fusion procedure. The objective of the two-center cohort study was the analysis of the correction results of patients, who underwent surgical intervention with the ApiFix system. The inclusion criteria were AIS, Lenke type 1 or type 5, a major curve on bending films of ≤30°, and an angle of the major curve of between 35° and 60°. Postoperative radiograph data were obtained longitudinally for up to 24 months of follow-up and compared to preoperative (preop) values. For comparisons of the different time points, non-parametric tests (Wilcoxon) or paired t-tests for normally distributed values were used to analyze repeated measures. Overall, 36 patients (25 female and 11 male) were treated with the ApiFix system from April 2018 to October 2020. Lenke type 1 was identified in 21 (58%) cases and Lenke type 5 was identified in 15 (42%) cases. The average angle of the thoracic major curve for Lenke 1 was 43°. The preoperative lumbar major curve (Lenke 5) was determined to be 43°. Over a follow-up of 24 months, a correction of the major curve to an average of 20° was observed for Lenke 1 and that to an average of 15° was observed for Lenke 5. Lenke type 1 and type 5 showed significant changes in the major curve over the individual test intervals in the paired comparisons compared to the starting angle (Lenke 1: preop-24 months, 0.002; Lenke 5: preop-24 months, 0.043). Overall, 11 events were recorded in the follow-up period, that required revision surgery. We distinguished between repeated interventions required after reaching the maximum distraction length of the implant due to the continued growth of the patient (n = 4) and complications, such as infections or problems associated with the anchorage of the implant (n = 7). The results from the present cohort revealed a statistically significant improvement in the postoperatively measured angles of the major and minor curves in the follow-up after 24 months. Consequently, the results were comparable to those of the already established vertebral body tethering method. Alignment in AIS via dynamic correction systems in combination with a possible growth modulation has been a treatment alternative to surgical fusing procedures for more than a decade. However, the long-term corrective effect has to be validated in further studies.
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Affiliation(s)
- Susanne Froehlich
- Orthopedic Clinic and Policlinic, University Rostock Medical Center, 18057 Rostock, Germany; (W.M.); (B.L.); (A.K.); (K.O.-Z.)
| | - Wolfram Mittelmeier
- Orthopedic Clinic and Policlinic, University Rostock Medical Center, 18057 Rostock, Germany; (W.M.); (B.L.); (A.K.); (K.O.-Z.)
| | - Biren Desai
- Sana Dreifaltigkeits-Hospital Cologne, 50933 Köln, Germany
| | | | - Herbert Raddatz
- Orthopedic Clinic and Policlinic, University Rostock Medical Center, 18057 Rostock, Germany; (W.M.); (B.L.); (A.K.); (K.O.-Z.)
| | - Bjoern Lembcke
- Orthopedic Clinic and Policlinic, University Rostock Medical Center, 18057 Rostock, Germany; (W.M.); (B.L.); (A.K.); (K.O.-Z.)
| | - Annett Klinder
- Orthopedic Clinic and Policlinic, University Rostock Medical Center, 18057 Rostock, Germany; (W.M.); (B.L.); (A.K.); (K.O.-Z.)
| | - Katrin Osmanski-Zenk
- Orthopedic Clinic and Policlinic, University Rostock Medical Center, 18057 Rostock, Germany; (W.M.); (B.L.); (A.K.); (K.O.-Z.)
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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] [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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