Anatomic Study for Pubic Medullary Screw Insertion

Abstract

Purpose. To study the anatomy of the pubic ramus and adjacent structures in 160 Japanese to establish a safer pubic screw fixation technique. Methods. 80 male and 80 female Japanese aged 16 to 89 (mean, 50) years (10 persons in each decade of age) underwent 3-dimensional computed tomographic scanning of their pelvises. The angle at which the screw should be targeted, the appropriate length of the screw, the size of the canal for screw insertion, and the proximity to the bladder, iliac artery, and iliac vein were determined. Correlations between the canal diameters (of the acetabular, base, and parasymphyseal areas) and body features (age, height, and weight) were analysed. Results. In men and women respectively, the appropriate mean screw length was 124.6 and 123.8 mm; the guide wire should be targeted at a mean of 66º and 67º cephalad and 54.1º and 55.9º laterally for insertion of a retrograde pubic screw; the minimum distances from the pubis to the bladder/iliac artery/ iliac vein were 0 and 0 mm/4.9 and 4.6 mm/0.8 and 0.2 mm. In both men and women, the canal diameters at the base were positively correlated to weight. In women, the canal diameters at the parasymphyseal area were correlated to height and weight. Canal diameters at the acetabulum were not correlated to height and weight. Conclusion. Pubic screw fixation may be potentially disastrous (owing to joint penetration and iliac vein injury) and should be performed with caution. When the canal diameter at the acetabulum is extremely narrow, plate fixation, computer-assisted surgery, or changing to a smaller-diameter screw is recommended.

Biomechanical comparison of three minimally invasive fixations for unilateral pubic rami fractures

“…Although longer screw can provide better stability, the risk of cannulated screw breakage is significantly increased when the screw is too long (length > 100 mm) and too thin (diameter < 6.5 mm). Therefore, the diameter of the superior pubic branch less than 6.5 mm is also a contraindication of intramedullary cannulated screw technique [8]. As the pubis is close to the bladder, iliac artery and iliac vein, retrograde screw placement based on the easily accessible pubic tubercle are safer.…”

Retrograde Transpubic Approach for Percutaneous Radiofrequency Ablation and Cementoplasty of Acetabular Metastasis

“…Preprocedural planning is essential for a successful treatment with good outcome and no complications. Before proceeding to the RTP approach, radiologic assessment of the target region by CT scanning with bone and soft tissue windowing and multiplanar reformation is essential to evaluate the pubic ramus geometry, to identify the neighbouring vital structures, and to determine the entry point and target [ 7 ]. With this approach, it is important to choose a skin entry point controlateral to the pubic symphysis aligned with the long axis of the superior ramus.…”

“…The CT is also useful to prevent injury to adjacent soft tissue and organs structures, not seen on fluoroscopy. Suzuki et al [ 7 ] stated that percutaneous screw fixation in a small area such as a pubic ramus or acetabulum is difficult to perform under fluoroscopy, but computer-assisted surgery can achieve a smaller margin of error [ 7 , 15 ]. However, it is more cumbersome and time-consuming than using C-arm fluoroscopy alone [ 13 ].…”

“…Pelvic bone and particularly the acetabulum are frequently involved by bone metastases. However, their percutaneous treatment is sometimes hampered by technical difficulties related to a complex anatomy and the proximity of critical structures such as nerves, iliac or femoral vessels, and pelvic organs [ 7 ].…”

Experimental study on treatment of acetabular anterior column fractures: applyment of a minimally invasive percutaneous lag screw guide apparatus

“…For traditional treatment of displacement or slightly displacement acetabula anterior column, minimally invasive percutaneous the lag screw technique is generally divided into anterograde and retrograde techniques. A vast majority of domestic and foreign scholars have studied the entry point and puncture angle of the anterograde and retrograde techniques [ 3 – 9 ].…”