Purpose: A classification system for fractures is an important communication tool for surgeons allowing the development of management schemes as well as an estimation of the prognosis. The purpose of our work was to evaluate the inter- and intra-observer reproducibility of the Letournel classification system for acetabular fractures.

Material methods and results: Sixty-five x-rays (AP and Judet views) and computed tomography (CT) series were chosen at random from a data base containing 800 fractures. The distribution of the fracture types followed data in the literature. Three groups of observers were formed, each composed of three orthopaedic surgeons. Group 1 included surgeons who had studied with Letournel, group 2 surgeons specialised in acetabular fractures, and group 3 surgeons qualified for general traumatology surgery. The kappa coefficient was determined to assess agreement between observers. Each observer read the images twice without knowledge of the treatment. The observers first classed the fractures using the x-rays alone then with the x-rays in combination with the CT. Two sessions were organised, two months apart to avoid any possible memorisation. Reproducibility without then with CT for the first session were: group 1: 0.07 and 0.74; group 2: 0.71 and 0.69; group 3: 0.51 and 0.512. Results were similar in the second session. Intra-observer reproducibility without then with CT was: group 1: 0.80 and 0.83; group 2 0.80 and 0.80; group 3: 0.64 and 0.69. Among the six more experimented observers (groups 1 and 2), 100% agreement was found for 66% of the x-rays compared with 22% for the new observers.

Discussion and conclusion: The Letournel classification system using x-rays in combination or not with CT is reliable (kappa > 7) for properly trained surgeons with regular experience in treating acetabular fractures. The value of the CT in the assessment of acetabular fractures is well established for identifying detached elements and joint crush. Conversely, CT does not appear to be essential to class ace-tabular fractures. The Letournel classification can be used as a reliable tool for the description of acetabular fractures and taught to surgeons desiring to undertake regular treatment of these fractures.