Effect of surgical experience and spine subspecialty on the reliability of the AO Spine Upper Cervical Injury Classification System
Authors: Lambrechts Mark J. , Schroeder Gregory D. , Karamian Brian A. , Canseco Jose A. , Oner F. Cumhur , Benneker Lorin M. , Bransford Richard J. , Kandziora Frank , Rajasekaran Shanmuganathan , El-Sharkawi Mohammad , Kanna Rishi , Joaquim Andrei Fernandes , Schnake Klaus , Kepler Christopher K. , Vaccaro Alexander R. , _ _ , _ _ , Asif Dewan , Borkar Sachin , Bakar Joseph , Zagorac Slavisa , Wimalachandra Welege , Garashchuk Oleksandr , Verdu-Lopez Francisco , Lofrese Giorgio , Bhatt Pragnesh , Obadaseraye Oke , Partenheimer Axel , Riehle Marion , Popescu Eugen Cesar , Konrads Christian , Senan Nur Aida Faruk , Toluse Adetunji , Neves Nuno , Sunami Takahiro , Kuipers Bart , Subbiah Jayakumar , Dyab Anas , Loughenbury Peter , Cawley Derek , Schmidt René , Kumar Loya , Karim Farhan , Silk Zacharia , Parolin Michele , Robijn Hisco , Kalbani Al , Rasschaert Ricky , Müller Christian , Nieuwenhuijse Marc , Ayhan Selim , Menachem Shay , Dhatt Sarvdeep , Khan Nasser , Haribabu Subramaniam , Kimani Moses , Alarcon Olger , Alor Nnaemeka , Iyer Dinesh , Ziga Michal , Gousias Konstantinos , Murray Gisela , Triffaux Michel , Hartmann Sebastian , Yuh Sung-Joo , Lang Siegmund , Linn Kyaw , Dhillon Charanjit Singh , Hamouda Waeel , Carnesecchi Stefano , Kumar Vishal , Cari Lady Lozano , Shah Gyanendra , Takeo Furuya , Sartor Federico , Gonzalez Fernando , Dabasia Hitesh , Liawrungrueang Wongthawat , Liu Lincoln , El Moudni Younes , Yurak Ratko , Aceituno Héctor , Karthigeyan Madhivanan , Demetriades Andreas , Muthu Sathish , Scholz Matti , Alsammak Wael , Chandrachari Komal , Shan Khoh Phaik , Trungu Sokol , Dejaegher Joost , Marroquin Omar , Alexandru Moisa Horatiu , Diez-Ulloa Máximo-Alberto , Pereira Paulo , Bernucci Claudio , Hohaus Christian , Georgiopoulos Miltiadis , Heuer Annika , Atan Ahmed Arieff , Murerwa Mark , Lindtner Richard , Tripathi Manjul , Kim Huynh Hieu , Hassan Ahmed , Foster Norah , O’Halloran Amanda , Kabir Koroush , Ganau Mario , Cruz Daniel , Henine Amin , Milano Jeronimo , Mbarak Abeid , Sousa Arnaldo , Munjal Satyashiva , Alkharsawi Mahmoud , Mirza Muhammad , Tsitsopoulos Parmenion , Tsuang Fon-Yih , Risenbeck Oliver , Viswanadha Arun-Kumar , Samy Samer , Orosco David , Zambito-Brondo Gerardo , Chaudhry Nauman , Marquez Luis , Lepard Jacob , Muñoz Juan , Corluka Stipe , Reuben Soh , Kaen Ariel , Ampar Nishanth , Bigdon Sebastien , Caba Damián , De Miranda Francisco , Lay Loren , Marintschev Ivan , Imran Mohammed , Mohindra Sandeep , Reddycherla Naga Raju , Bazán Pedro , Alhammoud Abduljabbar , Feeley Iain , Margetis Konstantinos , Durst Alexander , Jani Ashok Kumar , Vieira Rian Souza , Santos Felipe , Karlin Joshua , Montemurro Nicola , Mlyavykh Sergey , Sonkwe Brian , Perovic Darko , Lourido Juan , Ramieri Alessandro , Laos Eduardo , Hadesberg Uri , Iencean Andrei-Stefan , Neves Pedro , Bertolini Eduardo , Kumar Naresh , Bancel Philippe , Sharma Bishnu , Koerner John , Neto Eloy Rusafa , Ostadrahimi Nima , Morillo Olga , Rakesh Kumar , Morakis Andreas , Godinho Amauri , Keerthivasan P. , Menger Richard , Carius Louis , Lakhey Rajesh Bahadur , Shiban Ehab , Borse Vishal , Boudreau Elizabeth , Lacerda Gabriel , Konstantinos Paterakis , Saeed Mubder Mohammed , Hasheela Toivo , Pereira Susana Núñez , Reidler Jay , Rahamimov Nimrod , Zimny Mikolaj , Tokala Devi Prakash , Elgafy Hossein , Badani Ketan , Ng Bing Wui , Juarez Cesar Sosa , Repantis Thomas , Fernández-Bances Ignacio , Kleimeyer John , Lauper Nicolas , Romero-Muñoz Luis María , Yusuf Ayodeji , Klez Zdenek , Afolayan John , Rutges Joost , Grundshtein Alon , Zaluski Rafal , Stavridis Stavros I. , Aoyama Takeshi , Vachata Petr , Urbanski Wiktor , Tejeda Martin , Muñiz Luis , Karanja Susan , Martín-Benlloch Antonio , Torres Heiller , Pan Chee-Huan , Duchén Luis , Fujioka Yuki , Enercan Meric , Pluderi Mauro , Majer Catalin , Kamath Vijay 
Published: August 2022

OBJECTIVE
The objective of this paper was to determine the interobserver reliability and intraobserver reproducibility of the AO Spine Upper Cervical Injury Classification System based on surgeon experience (< 5 years, 5–10 years, 10–20 years, and > 20 years) and surgical subspecialty (orthopedic spine surgery, neurosurgery, and "other" surgery).

METHODS
A total of 11,601 assessments of upper cervical spine injuries were evaluated based on the AO Spine Upper Cervical Injury Classification System. Reliability and reproducibility scores were obtained twice, with a 3-week time interval. Descriptive statistics were utilized to examine the percentage of accurately classified injuries, and Pearson’s chi-square or Fisher’s exact test was used to screen for potentially relevant differences between study participants. Kappa coefficients (κ) determined the interobserver reliability and intraobserver reproducibility.

RESULTS
The intraobserver reproducibility was substantial for surgeon experience level (< 5 years: 0.74 vs 5–10 years: 0.69 vs 10–20 years: 0.69 vs > 20 years: 0.70) and surgical subspecialty (orthopedic spine: 0.71 vs neurosurgery: 0.69 vs other: 0.68). Furthermore, the interobserver reliability was substantial for all surgical experience groups on assessment 1 (< 5 years: 0.67 vs 5–10 years: 0.62 vs 10–20 years: 0.61 vs > 20 years: 0.62), and only surgeons with > 20 years of experience did not have substantial reliability on assessment 2 (< 5 years: 0.62 vs 5–10 years: 0.61 vs 10–20 years: 0.61 vs > 20 years: 0.59). Orthopedic spine surgeons and neurosurgeons had substantial intraobserver reproducibility on both assessment 1 (0.64 vs 0.63) and assessment 2 (0.62 vs 0.63), while other surgeons had moderate reliability on assessment 1 (0.43) and fair reliability on assessment 2 (0.36).

CONCLUSIONS
The international reliability and reproducibility scores for the AO Spine Upper Cervical Injury Classification System demonstrated substantial intraobserver reproducibility and interobserver reliability regardless of surgical experience and spine subspecialty. These results support the global application of this classification system.