Safety of screw placement on the medial iliosciatic plate for acetabular posterior column: a comparison between males and females by 3D reconstruction technique / 中华创伤骨科杂志

ABSTRACT

Objective To compare the safe zone and safe angles between males and females for screw placement on the medial iliosciatic plate for acetabular posterior column using 3D reconstruction technique.Methods Normal pelvic CT scans of 52 adults (27 males and 25 females;aged from 18 to 74 years,averaging 47.2 years) were obtained to create pelvic 3D models.After the acetabulum was thickened by 5 mm,the width (d) of the safe zone for placement of the medial iliosciatic plate was measured.After the vertical distance (w) between the vertex of the obturator canal and the greater sciatic notch was measured,the ratio (r) of d/w was calculated.The recombined innominatum model was cut through the center of the acetabulum with a plane perpendicular to the quadrilateral plate and the greater sciatic notch.The cross-section was marked as M.In males,4 points at distances of 1.0 cm,1.5 cm,2.0 cm and 2.5 cm anterior to the greater sciatic notch were marked.At the 4 points,the angulations (∠ a,∠b,∠ c and ∠ d) between the quadrilateral plate and the tangent line of the outer edge of the thickened acetabulum model were measured on the cross-section M.In females,3 points at distances of 1.0 cm,1.5 cm and 2.0 cm anterior to the greater sciatic notch were marked before ∠a,∠b,and ∠c were measured.The differences in the above parameters were compared between males and females.Results The width (d) of the safe zone for placement of the medial iliosciatic plate was 28.56 ±2.44 mm in males and 24.36 ±2.47 mm in females;the ratio (r) was 0.61 ± 0.07 in males and 0.54 ± 0.05 in females.The safe angulations for screw placement in males,∠ a,∠b,∠cand ∠d,were 88.04°±3.18°,77.81°±3.85°,68.01°±4.11°and56.81°±4.81° while those in females,∠a,∠b and ∠c,were 91.29°±4.52°,76.23°±3.82° and 62.79°±3.51°,respectively.There were statistically significant differences between males and females in values of d,r,∠ a and ∠ c (P ＜ 0.05).Conclusions In fixation of acetabular posterior column fractures using medial iliosciatic plate,the differences between males and females should be taken into account.Besides,specific safe angles should be chosen according to the position of the plate.