Effect of surgical experience and spine subspecialty on the reliability of the {AO} Spine Upper Cervical Injury Classification System

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

Chemical accuracy and precision in Rietveld analysis: The crystal structure of cobalt(II) acetate tetrahydrate

The crystal structure of cobalt(II) acetate tetrahydrate, Co(C2H3O2)·4H2O, has been refined using single-crystal, laboratory powder, and synchrotron powder diffraction data, both individually and in various combinations. The compound crystallizes in the monoclinic space group P21/c, with a=4.80688(3), b=11.92012(7), c=8.45992(5) Å, β=94.3416(4)° at 27 °C, and Z=2. The crystal structure consists of discrete centrosymmetric trans-Co(C2H3O2)(H2O)4 complexes, linked by a three-dimensional network of hydrogen bonds. Each complex participates in 14 hydrogen bonds, 12 intermolecular, and 2 intramolecular. Compared to the single-crystal refinement, refinement of laboratory powder data yielded an average difference in bond distances of 0.02 Å, in bond angles of 3°, and in root mean square atomic displacements of 0.07 Å. The standard uncertainties of the bond distances were 0.01 Å, compared to the 0.001–0.002 Å in the single-crystal refinement. Refinement of the synchrotron powder data yielded improved accuracy and precision. It proved impossible to locate or refine hydrogen positions using a single-powder dataset, but the hydrogens could be refined using rigid groups in a joint refinement of the two powder datasets. Even from powder refinements, it is possible to obtain suitable accuracy and precision to distinguish C–O and C=O bonds, and to examine details of chemical bonding.</jats:p