Can computed tomography predict hip stability in posterior wall acetabular fractures?

Background: In a pilot study, two-dimensional (2-D) CT assessment of posterior wall fracture fragments predicted hip stability with small fracture fragments and instability for large fracture fragments.

Questions/purposes: To confirm the previous findings, we determined whether there is sufficient observer consistency and accuracy to predict hip stability in posterior wall acetabular fractures for this CT assessment method and assessed its ease of clinical use.

Methods: We selected 10 fractures having variable characteristics with known clinical outcome and created three study participant groups, based on level of training, for evaluation. Each observer reviewed the CT scans from the 10 fractures and applied the method in two separate sessions, the second after at least a 1-month washout period.

Results: Participants reported subjective ease in using the method, averaging 5 minutes (range, 3-11 minutes) for each assessment. Intraobserver and interobserver reliability were both greater than 0.80 regardless of the level of experience. Although sensitivity was 90%, specificity was only 61% after comparison with examination under anesthesia (EUA). Inappropriate nonoperative treatment would have occurred in 6% of cases and inappropriate operative treatment in 16%.

Conclusions: This method for assessing hip instability is reliable, reproducible, and easy to learn and use. However, as a diagnostic tool in the clinical setting, it is useful only for fractures involving greater than 50% of the posterior wall owing to limited accuracy. For fractures less than 50%, EUA should be performed to determine hip stability.