A 3D CT morphometric analysis of the medial pelvic terrain: New insights into quadrilateral plate and medial acetabular surface.

BACKGROUND

The medial bony hemipelvis has been defined as quadrilateral plate (QP). Any isolated or combined injuries to QP, often lead to early degenerative arthritis of hip joint. Conventionally defined QP and its delineation of fixation zones from non-fixation zone or medial acetabular surface (MAS) will lead to novel Pentagonal Plate (PP).

METHODOLOGY: 3D reconstructions of the pelvic CT scans were created, focusing on right hemipelvis for all patients. The dimensions of the QP and novel PP in the right hemipelvis were defined and measured using RadiAnt DICOM Viewer software. Statistical analysis was conducted using latest version of SPSS software.

RESULTS

This study included 100 adults (42 females and 58 males) who underwent CT scans of pelvis for non traumatic non orthopedic reasons like gynaecological, general surgical and urological reasons between July 2019 and December 2020. Average dimensions of the sides of conventional QP were found to be 4.95 ± 0.85 cm, 3.98 ± 0.73 cm, 4.03 ± 0.78 cm, and 5.48 ± 0.91 cm. The study identifies 3 triangular fixation zones within conventional QP, corresponding to the sciatic buttress, part of anterior column, and part of the posterior column. These zones were excluded from conventional QP, resulting in definition of a novel pentagonal plate (PP) with a 34 % smaller surface area, precisely delineating true medial surface of acetabular socket.

CONCLUSION

Novel PP identifies MAS with more precision and delineates 3 triangular fixation zones across sciatic buttress, anterior and posterior columns. This knowledge enables better understanding of fixation zones and force concentration due to antecedent injury which opens doors to newer plate designs, explaining why certain fractures involving the MAS undergo early degenerative arthritis and rationalizing alternative treatment strategies like fix and replace for even younger patients with adverse fracture configurations.