Value of 3D fluoroscopic imaging of acetabular fractures comparison to 2D fluoroscopy and CT imaging.

PURPOSE: Intraoperative two-dimensional (2D) fluoroscopy of acetabular fractures is difficult due to the complex three-dimensional (3D) anatomy. Intraoperative 3D fluoroscopy may have particular utility in the evaluation of acetabular fractures. We compared the accuracy of 3D fluoroscopic imaging in evaluating acetabular fracture displacement and implant placement with fluoroscopy and computed tomography (CT) scans.

METHODS: In 24 cadaveric acetabuli, a transverse acetabular fracture was created. First a 2 mm step-off of the articular surface was created and reconstruction plates placed on the anterior and posterior columns. In 12 specimens, two screws were placed intraarticularly, protruded by 2 mm. In the remaining 12 specimens, the same constructs were used but the screws remained extraarticular. Second tests were designed to simulate an impaction injury. After hardware removal, a hollow trephine (diameter of 14.9 mm) was used to core a bone cylinder on the dome of the acetabulum, and impacted until it was recessed into the articular surface by 2 mm. Plates were placed, and screws were placed intraarticularly in 12 specimens, as in the first set of tests. All cadavers were imaged with standard 2D-, 3D fluoroscopy and CT. Three observers randomly evaluated all imaging studies for all specimens.

RESULTS: For detection of intraarticular screws, both the Iso-C3D and the CT scans were significantly more sensitive (96 and 96%, respectively) and specific (96 and 100%, respectively) in detecting the intraarticular position compared to 2D fluoroscopy (75%; P < 0.05). Sensitivity of articular step-off detection was no different between the Iso-C3D (83%), CT (79%), and 2D fluoroscopy (87%). Articular impaction was correctly identified in 79% of specimens with the Iso-C 3 D technique, while the CT was accurate in 92%. 2D fluoroscopy was accurate in 62% for the impactions (P < 0.05 vs. CT).

CONCLUSIONS: 3D-fluoroscopic imaging appears to be extremely accurate in evaluating acetabular fracture constructs. Its sensitivity and specificity for evaluating intraoperative hardware was greater than with 2D fluoroscopy and equivalent to CT scan. Volumetric impactions were also reliably demonstrated on both of the 3D modalities, which were both superior to 2D fluoroscopy. Overall, Iso-C3D multiplanar imaging yields information regarding implant placement and articular reduction that is more detailed and accurate than standard fluoroscopy and is comparable to CT.