Computer-assisted periacetabular screw placement: Comparison of different fluoroscopy-based navigation procedures with conventional technique

Abstract

The current gold standard for operatively treated acetabular fractures is open reduction and internal fixation. Fractures with minimal displacement may be stabilised by minimally invasive methods such as percutaneous periacetabular screws. However, their placement is a demanding procedure due to the complex pelvic anatomy. The aim of this study was to evaluate the accuracy of periacetabular screw placement assessing pre-defined placement corridors and comparing different fluoroscopy-based navigation procedures and the conventional technique.

For each screw an individual periacetabular placement corridor was preoperatively planned using the planning software iPlan CMF^© 3.0 (BrainLAB). 210 screws (retrograde anterior column screws, retrograde posterior column screws, supraacetabular ilium screws) were placed in an artificial Synbone pelvis model (30 hemipelves) and in human cadaver specimen (30 hemipelves). 2D- and 3D-fluoroscopy-based navigation procedures were compared to the conventional technique. Insertion time and radiation exposure to specimen were also recorded. The achieved screw position was postoperatively assessed by an Iso-C^3D scan. Perforations of bony cortices or articular surfaces were analysed and the screw deviation severity (difference of the operatively achieved screw position and the preoperatively planned screw position in reference to the pre-defined corridors) was determined using image fusion.

Using 3D-fluoroscopy-based navigation, the screw perforation rate (7%) was significantly lower compared to 2D-fluoroscopy-based navigation (20%). For all screws, the deviation severity was significantly lower using a 3D- compared to a 2D-fluoroscopy-based navigation and the conventional technique. Analysing the posterior column screws, the screw deviation severity was significantly lower using 3D- compared to 2D-fluoroscopy-based navigation. However, for the anterior column screw, the screw deviation severity was similar regardless of the imaging method. Despite the advantages of the 3D-fluoroscopy-based navigation, this method led to significantly longer total procedure and fluoroscopic times, and the applied radiation dose was significantly higher.

Percutaneous periacetabular screw placement is demanding. Especially for posterior column screws, due to a lower perforation rate and a higher accuracy in periacetabular screw placement, 3D-fluoroscopy-based navigation procedure appears to be the method of choice for image guidance in acetabular surgery.

Introduction

The operative treatment of acetabular fractures is one of the most challenging techniques for orthopaedic surgeons and was established by the fundamental studies of Judet et al.,²⁴ by continuous improvement of systematic X-ray interpretation, the subsequent classification, and the development of treatment options.5, 12, 19, 20, 27, 59 Open anatomical reduction of the articular surface in combination with a rigid internal fixation and early mobilisation became the standard treatment for these injuries.30, 31, 32 In acetabular surgery, the Kocher-Langenbeck and the ilioinguinal approaches are the standard posterior and anterior approaches.10, 23, 27, 29 Our own data showed that these approaches were used in 79.5% of all fracture types.³⁸ For the treatment of more complicated fracture types (both column- or T-type-fractures), the extended approaches (extended iliofemoral approach or Maryland-modification) were introduced.1, 21, 41, 58, 60 The fixation of these fractures often requires extensive exposure, which may lead to associated complications such as blood loss, neural or vascular injury, postoperative infection, wound healing problems and heterotopic bone formation. Due to a higher peri- and postoperative morbidity, extended approaches are rarely used.15, 33, 52, 60

However, techniques such as fluoroscopy and in particular fluoroscopy-based computer navigation systems offer the possibility of percutaneous screw placement in acetabular fractures as a minimally invasive procedure. Due to the complex three-dimensional pelvic and acetabular anatomy, percutaneous periacetabular screw placement is a demanding procedure because their placement corridors are narrow. Thus, conventional fluoroscopy for periacetabular screw placement requires the acquisition of multiple images in different projections to determine the correct point of entry and the direction of the screw35, 36, 39, 45 leading to a prolonged surgical and radiation time.49, 50 Fluoroscopy-based computer navigation systems may have the potential to significantly reduce radiation exposure and surgical time while allowing maximum accuracy. Recently, for pedicle screw placement2, 3, 13, 26, 40, 46 and percutaneous transiliosacral screw insertion in cases with minimally displaced sacral fractures or sacroiliac joint disruptions,6, 7, 22, 43, 44, 48, 55, 61 the reduction of malposition rates and radiation exposure was shown by the use of computer navigation systems. However, only a few studies examined 2D-fluoroscopy-9, 17, 28, 35, 55 or 3D-fluoroscopy-25, 55 based navigation for periacetabular screw placement. Thus, data pertaining a comparison of the different fluoroscopy-based navigation systems is not available. However such data would be clinically important for the improvement of patient care.

This study evaluated the accuracy of percutaneous periacetabular screw placement in artificial Synbone pelvis models and human cadaver specimen using 2D- and 3D-fluoroscopy-based navigation systems and conventional standard technique. Specifically, we introduced a parameter “screw deviation severity” to assess the accuracy of the screw placement within a pre-defined placement corridor.