Supraacetabular osseous corridor: defining dimensions, sex differences, and alternatives

Evaluation of the superior pubic ramus and supra acetabular corridors using statistical shape modelling

INTRODUCTION

The incidence of osteoporotic pelvic fractures is increasing. The broken anterior pelvic ring is preferentially fixed with long intramedullary screws, which require a good understanding of the patient-specific anatomy to prevent joint perforation. The aim of this study was to assess the variability of the superior pubic ramus and the supra acetabular corridors' length and width using statistical shape modelling.

MATERIALS AND METHODS

A male and female statistical shape model was made based on 59 forensic CT scans. For the superior pubic ramus and the supra acetabular corridor the longest and widest completely fitting cylinder was created for the first 5 principal components (PC) of both models, male and female pelvises separately.

RESULTS

A total of 59 pelvises were included in this study of which 36 male and 23 female. The first 5 principal components explained 75% and 79% of the pelvic variation in males and females, respectively. Within 3 PCs of the female statistical shape model (SSM) a superior pubic ramus corridor of < 7.3 mm was found, 5.5 mm being the narrowest linear corridor measured. Both corridors in all PCs of the male SSM measured > 7.3 mm.

CONCLUSION

Within females a 7.3 mm and 6.5 mm screw won't always fit in the superior pubic ramus corridor, especially if a flat sacrum, a small pelvis or a wide subpubic angle are present. The supra acetabular corridor did not seem to have sex-specific differences. In the supra-acetabular corridor there was always enough space to accommodate a 7.3 mm screw, both in males and females.

Fluroscopy-assisted transiliac antegrade lag screw placement technique in both columns of acetabulum: A novel procedure

The use of pelvic osseous fixation corridors and lag screw fixation in acetabular and pelvic surgery has gained popularity, especially with the recent development of intraoperative imaging and navigation techniques. However, advanced intraoperative imaging and navigation techniques require technical equipment and are costly. Therefore, traditional fluoroscopic techniques still maintain their importance. In this article, we describe a novel pelvic osseous fixation corridor that traverses both columns of the acetabulum, along with the detailed methodology of its fluoroscopic imaging and the techniques for fluoroscopy-assisted screw placement. The technique of placing screws in this current fixation corridor is only under fluoroscopy assistance, without using any specially produced guide or navigation device. LEVEL OF PROOF: IV.

Iliac dysmorphism: defining radiographic characteristics and association with pelvic osseous corridor size

INTRODUCTION

Insertion of iliac wing implants requires understanding of the curvilinear shape of the ilium. This study serves to quantitatively identify the area of iliac inner-outer table convergence (IOTC), characterize the iliac wing osseous corridor, and define the gluteal pillar osseous corridor.

METHODS

Computed tomography scans of 100 male and 100 female hemipelves were evaluated. The iliac wing was studied using manual best-fit analysis of the bounds of the inner and outer cortices. The IOTC was defined as the location of the iliac wing with an intercortical width less than 5 mm. The shortest distance from the apex of the iliac crest to the superior border of the IOTC was defined as the iliac wing osseous corridor. Finally, the width of the gluteal pillar corridor from the gluteus medius tubercle to the ischial tuberosity was measured.

RESULTS

The IOTC is an elliptical area measuring 22.3 cm². All ilia had an area where the inner and outer cortices converged to an intercortical width of less than 5 mm; 48% converged to a single cortex. The shortest mean distance from the superior edge of the iliac crest to the beginning of the IOTC was 20.3 mm in men and 13.8 mm in women (p < 0.001). The gluteal pillar diameter averaged 5.3 mm in men and 4.3 mm in women (p < 0.001).

DISCUSSION

All ilia converge to a thin and frequently unicortical central region. A 4.5 mm iliac wing lag screw will not breach the cortex if it remains within 20 mm or 14 mm distal to the cranial aspect of the iliac crest in males and females, respectively. Not only is the gluteal pillar smaller than previously thought, in 41% of males and 73% of females, it is not be large enough for 5 mm implants.

CONCLUSION

This study quantitatively assesses the dimensions of the IOTC, the iliac crest osseous corridor, and the gluteal pillar. Overall, our findings provide improved understanding of the limits for implant use in the iliac wing as well as better appreciation of the complex osteology of the ilium. This will help surgeons to identify safe areas for implant placement and avoid inadvertent cortical penetration.