Introduction: The treatment of injuries involving the acetabulum is challenging. Letournel classification system is the most popular and the most widely accepted, but difficult to be applied. The pattern of the fracture depends on the number of the fracture lines identified on the AP and Judet radiographic views.

Materials and Methods: 147 patients were randomly selected from our acetabular fracture database, which includes 615 patients who have been treated in our institution during the last 25 years and were divided into eight subgroups.

Each group represented all types of acetabular fractures and each patient had a radiographic evaluation of an AP view of the pelvis and two 458 oblique views (Judet views). All X-rays were assessed by eight orthopaedic surgeons in two sessions.

In the first session were asked by the orthopedic surgeons to classify the fractures according to the Letournel classification and a diagram showing the six important radiological Lines. During the second session, that followed six weeks after the first session, the same X-ray pack was given to the same surgeons with different ranking and numbering. In addition a table-algorithm was given to the surgeons with the 10 types of fractures according to the Letournel classification divided in three groups in accordance with the integrity of ilioischial and iliopectineal lines that we accept as basic lines and instructions on the integrity/interruption of one or both of the basic lines and the obturator ring.

Results: Comparison of the two sessions or of the two phase’s observation was accomplished by the use of two parameters; Initially, the proportion of agreement of all observers in the first and second observation phase was assessed taking our diagnosis as the ‘gold’ standard. The unweighted kappa coefficient was utilised to estimate the observers’ agreement arising from the examination of the given X-rays. Finally, the agreement of the observers, related to the intraoperative diagnosis was estimated. The main finding of the herein study lies on the improvement of the agreement rate experienced within both groups, in session B over session A. It is reasonable to assume that the main reason behind this result is the provision of the guideline algorithm protocol in the second session. The total agreement rate was increased from 59.9% in session A to 72.1% in session B, (pvalue = 0.0267).

Conclusion: The application of the proposed algorithm to the Letournel classification system in conjunction to surgical experience, improves the ability to classify even the most complex acetabular fractures.