Intraoperative Use of 3-D Fluoroscopy in the Treatment of Developmental Dislocation of the Hip in an Infant

Abstract not available. Introduction provided instead.

Confirming reduction of a developmental dislocation of the hip (DDH) through a spica cast is an imaging challenge. Computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound have been advocated.^1-11 Each of these modalities has its benefits and drawbacks. Ultrasound allows the hip to be visualized in the operating room but is operator-dependent and requires cutting a window in the posterolateral aspect of the cast—thereby weakening an area that is crucial in holding the reduction. MRI is useful for visualizing the hip, acetabulum, and soft-tissue structures through a spica cast, but MRI availability and cost, and the prolonged sedation required, make this modality prohibitive for routine use at many centers. CT provides excellent visualization of bony details and anatomical relationships but subjects patients to ionizing radiation. In addition, both MRI and CT require waiting for the patient to recover from general anesthesia before moving him or her from the operating room to the scanner. When the reduction is suboptimal, the patient must be returned to the operating room for repeat anesthesia and corrective action.

At our institution, we have begun using a 3-dimensional (3-D) fluoroscope (Siremobil Iso-C^3D; Siemens Medical Solutions, Erlangen, Germany) in the operating room to confirm reductions after application of spica casts. Similar to a conventional C-arm, this instrument is portable and can provide 2-D images useful for intraoperative arthrography. Unlike a standard fluoroscope, the 3-D fluoroscope automatically rotates 190° around an isocentric point on the patient. It obtains either 50 fluoroscopic images in 1 minute or 100 images in 2 minutes, depending on the desired level of anatomical detail. Specialized software then processes the images and reconstructs them to provide axial, coronal, and sagittal views of the anatomy. These images are of high quality and are comparable to those obtained with a CT scanner. The radiation dose for the 50- image cycle is equivalent to 20 seconds of standard fluoroscopy or approximately 0.77 mGy (77 mrad).¹² The radiation dose for the 100-image cycle is equivalent to 40 seconds of standard fluoroscopy or approximately 1.57 mGy (157 mrad).¹² We have found that the 50-image cycle provides adequate visualization of anatomical detail. To put the radiation dose in perspective, natural background radiation from the atmosphere is approximately 1 mrad per day.

The primary benefit of this instrument in the treatment of an infant with DDH is that it allows the surgeon to assess the reduction without taking the patient off the operating table, and corrective action can be taken without the risks associated with repeat anesthesia or the cost and inconvenience of a return trip to the operating room.

We present the case of an infant with DDH to illustrate the use of 3-D fluoroscopy in reduction imaging. We obtained informed consent from the patient’s family to perform the procedure and publish the case data.