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Okuwaki S, Kotani T, Taniguchi Y, Suzuki T, Yamaguchi T, Demura S, Wada K, Sugawara R, Takeshita K, Watanabe K, Akazawa T, Kawakami N. Evaluation of crankshaft phenomenon after posterior fusion for early onset scoliosis using an inverse trigonometric function: a multicenter retrospective cohort study. Spine Deform 2024:10.1007/s43390-024-00900-4. [PMID: 38805146 DOI: 10.1007/s43390-024-00900-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 05/17/2024] [Indexed: 05/29/2024]
Abstract
PURPOSE The crankshaft phenomenon (CSP) is a corrective loss after posterior surgery for early onset scoliosis (EOS). However, an accurate method for CSP evaluation has yet to be developed. In this study, we evaluated pedicle screw (PS) length and rotation angle using an inverse trigonometric function and investigated the prevalence of the CSP. METHODS Fifty patients from nine institutions (mean age 10.6 years, male/female ratio 4:46) who underwent early definitive fusion surgery at ≤ 11 years of age were included. The rotation angle was calculated as arctan (lateral/frontal PS length) using radiography. Measurements were taken at the apex and lower instrumented vertebra (LIV) immediate, 2-, and 5-year postoperatively. CSP was defined as a rotation angle progression ≥ 5°. We divided patients into CSP and non-CSP groups and measured the demographic parameters, Risser grade, state of the triradiate cartilage, major coronal Cobb angle, T1-T12 length, T1-S1 length, and presence of distal adding-on (DAO). We compared these variables between groups and investigated the correlation between the measured variables and vertebral rotation. Logistic regression analysis investigated factors associated with CSP. RESULTS The rotation angle progressed by 2.4 and 1.3° over 5 years for the apex and LIV, respectively. CSP occurred in 15 cases (30%), DAO in 11 cases (22%), and CSP and DAO overlapped in 4 cases (8%). In the CSP group, the T1-T12 length was low immediate postoperatively. The rotation angle was negatively correlated with preoperative height (r = - 0.33), T1-T12 length (r = - 0.35), and T1-S1 length (r = - 0.30). A lower preoperative T1-T12 length was associated with CSP (odds ratio: 0.996, p = 0.048). CONCLUSIONS CSP occurred in 30% of patients with EOS who underwent definitive fusion. The presence of CSP was associated with a lower preoperative T1-T12 length. LEVEL OF EVIDENCE Diagnosis, level IV.
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Affiliation(s)
- Shun Okuwaki
- Department of Orthopaedic Surgery, Institute of Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, Japan.
- Department of Orthopaedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan.
- Japan Spinal Deformity Institute, Aichi, Japan.
| | - Toshiaki Kotani
- Department of Orthopaedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Yuki Taniguchi
- Department of Orthopaedic Surgery, The University of Tokyo Hospital, Tokyo, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Teppei Suzuki
- Department of Orthopaedic Surgery, National Hospital Organization, Kobe Medical Center, Hyogo, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Toru Yamaguchi
- Department of Orthopaedic and Spine Surgery, Fukuoka Children's Hospital, Fukuoka, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Satoru Demura
- Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kanazawa University, Ishikawa, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Kanichiro Wada
- Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine, Aomori, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Ryo Sugawara
- Department of Orthopaedic Surgery, School of Medicine, Jichi Medical University, Tochigi, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Katsushi Takeshita
- Department of Orthopaedic Surgery, School of Medicine, Jichi Medical University, Tochigi, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Kei Watanabe
- Department of Orthopaedic Surgery, School of Medicine, Niigata University, Niigata, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Tsutomu Akazawa
- Department of Orthopaedic Surgery, St. Marianna University School of Medicine, Kanagawa, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
| | - Noriaki Kawakami
- Department of Orthopaedic Surgery, Ichinomiyanishi Hospital, Aichi, Japan
- Japan Spinal Deformity Institute, Aichi, Japan
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Okuwaki S, Kotani T, Ohyama S, Iwata S, Sakuma T, Iijima Y, Akazawa T, Inage K, Shiga Y, Minami S, Ohtori S, Yamazaki M. Measurement of Postoperative Apical Vertebral Rotation Using Radiographic Images in Adolescent Idiopathic Scoliosis-Quantitative Evaluation Using Inverse Trigonometric Functions. Spine Surg Relat Res 2024; 8:203-211. [PMID: 38618215 PMCID: PMC11007252 DOI: 10.22603/ssrr.2023-0108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 09/10/2023] [Indexed: 04/16/2024] Open
Abstract
Introduction Conventional methods for analyzing vertebral rotation are limited to postoperative patients who underwent posterior fusion. A previous methodology calculated vertebral rotation using inverse trigonometric functions based on the length of the pedicle screw (PS). Accordingly, this study evaluates rotational deformity in patients with postoperative adolescent idiopathic scoliosis (AIS) using inverse trigonometric functions. Methods This retrospective single-center study includes patients with AIS who underwent posterior fusion surgery. Postoperative radiography and computed tomography (CT) scans were retrospectively evaluated. The magnification ratio was calculated using the rod diameter (δ=lateral/frontal rod diameter), and the visible screw lengths were measured using radiographs. The rotation angle was calculated using the apex of the main curve and the lower instrumented vertebra (LIV) (rotation angle=tan-1 (lateral PS length/(δ×frontal PS length))) immediately following the surgery as well as two and five years postoperatively. The correlation between the direct CT measurement and postoperative rotation angle progression was investigated. The crankshaft phenomenon (CSP) and distal adding-on (DAO) were evaluated as postoperative deformities. CSP was defined as a 5° increase in rotation angle. Results Seventy-eight patients (age: 15.3±2.0 years, eight boys and seventy girls) were included. The rotation angle was strongly correlated with CT rotation measurements (r=0.87). The mean rotation angle at the apex and LIV did not change within five years postoperatively (mean: 0.5±3.6° and 0.4±3.4°, respectively). CSP and DAO were observed in 6.4% and 3.8% of patients, respectively. Conclusions The inverse trigonometric method is useful to quantitatively evaluate the postoperative rotation angle and identify CSP.
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Affiliation(s)
- Shun Okuwaki
- Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
- Department of Orthopedic Surgery, Institute of Medicine, University of Tsukuba, Ibaraki, Japan
| | - Toshiaki Kotani
- Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
| | - Shuhei Ohyama
- Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
| | - Shuhei Iwata
- Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
| | - Tsuyoshi Sakuma
- Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
| | - Yasushi Iijima
- Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
| | - Tsutomu Akazawa
- Department of Orthopedic Surgery, St. Marianna University School of Medicine, Kanagawa, Japan
| | - Kazuhide Inage
- Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Yasuhiro Shiga
- Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Shohei Minami
- Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, Chiba, Japan
| | - Seiji Ohtori
- Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Masashi Yamazaki
- Department of Orthopedic Surgery, Institute of Medicine, University of Tsukuba, Ibaraki, Japan
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