Abstract
Purpose of the study
Percutanous acetabular surgery is a new and developing technique in fixation of acetabulum fractures. The most common screw used is the anterior column screw that traverses anterograde or retrograde through the anterior column of the acetabulum. Standard height and width calculations derived from CT scans do not take the trajectory of the screw into consideration. They have been shown to exaggerate the available safe bone corridor for screw passage. Posterior column screws can be placed in a retrograde fashion via the ischial tuberosity to fixate posterior column. Limited international data is available and no studies to date have been conducted on the South African population. This study assesses the anterior and posterior acetabular columns of South African individuals and ascertains the safe bone corridor sizes.
Methods
Pelvic CT-scans of 100 randomly selected patients were reviewed. Specific computer software was used to virtually place anterior screws through the anterior acetabular column, in its clinical trajectory. Specific entry points inferior to the pubic tubercles significantly changed the relation of the screw trajectory to the mid- column isthmus and were incorporated in the measurement of the anterior column. All the available lengths and diameters were measured and averages were calculated for males and females.
Results
On average, males have longer and larger diameter anterior columns. The entry point on the pubic tubercle has a significant impact on the relative diameter at the mid- column. Not all commercially available cannulated screw diameters are safe to place into the anterior column.
Conclusion
Although the international literature shows that percutaneous anterior column fixation is of value for early mobilisation after fractures, intimate knowledge of the local data regarding the available safe corridors for screw passage is limited. This study shows the safe bone corridors that can be used to avoid breaching the cortex during screw insertion. It also recommends safe screw diameters.
NO DISCLOSURES
