AO Spine-DGOU Osteoporotic Fracture Classification System: Internal Validation by the AO Spine Knowledge Forum Trauma

Abstract

Study DesignCross-sectional survey.ObjectivesInjury classifications are important tools to identify fracture patterns, guide treatment-decisions and aid to identify optimal treatment plans. The AO Spine-DGOU Osteoporotic Fracture (OF) classification system was developed, and the aim of this study was to assess the reliability of this new classification system.Methods23 Members of the AO Spine Knowledge Forum Trauma participated in the validation process. Participants were asked to rate 33 cases according to the OF classification at 2 time points, 4 weeks apart (assessment 1 and 2). The kappa statistic (κ) was calculated to assess inter-observer reliability and intra-rater reproducibility. The gold master key for each case was determined by approval of at least 5 out of 7 members of the DGOU.ResultsA total of 1386 ratings (21 raters) were performed. The overall inter-rater agreement was moderate with a combined kappa statistic for the OF classification of 0.496 in assessment 1 and 0.482 in assessment 2. The combined percentage of correct ratings (compared to gold-standard) in assessment 1 was 71.4% and 67.4% in assessment 2. The average intra-rater reproducibility was substantial (κ = 0.74, median 0.76, range 0.55 to 1.00, SD 0.13) for the assessed fracture types.ConclusionsThe assessed overall inter-rater reliability was moderate and substantial in some instances. The average intra-rater reproducibility is substantial. It seems that appropriate training of the classification system can enhance inter- and intra-rater reliability.

Keywords: fracture classification; osteoporosis; spinal fracture; validation study.

Figure 1.

Development of the OF classification system. OF 1: No vertebral deformation (vertebral body edema in MRI-STIR only). X-rays do not show vertebral deformation. OF 2: Deformation of 1 endplate without or with only minor posterior wall involvement (<1/5). OF 3: Deformation of 1 endplate with distinct posterior wall involvement (>1/5). OF 4: Deformation of both endplates with or without posterior wall involvement. This type can lead to the loss of integrity of the vertebral frame structure (complete burst), or vertebral body collapse, or pincer-type fracture. OF 5: Injuries with anterior or posterior tension band failure. These injuries have signs of distraction, rotation, or translation.