Effects of degree of translation or rotation of acetabular fragment of periacetabular osteotomy procedure on pelvic X-ray parameters.

The present study aims to investigate the effect of amount of lateralization and/or anteversion of the point where the iliac cut meets with the posterior column cut of periacetabular osteotomy (PAO), on X-ray parameters such as Center of edge (CE) angle, retroversion index (RVI) and sharp angle. Fourteen patients with symptomatic hip dysplasia (CE° < 20°) were included. Pelvis Computerized tomography (CT) sections were used for 3D printing. PAO was then performed on these models. The point (A), 1 cm lateral to the pelvic brim, is marked where the iliac cut intersects the posterior column cut. In Group I (1.5-0), point A is lateralized parallel to the osteotomy line for 1.5 cm. In Group II (1.5-0.5), it is additionally anteverted for 0.5 cm. In Group III (3-0), point A is lateralized for 3 cm and then additionally anteverted for 1 cm (Group IV: 3-1). Radiographs were taken in each stage. The lateral CE angle, RVI and sharp angle were measured. All had an increase in the CE angle and RVI and a decrease in the sharp angle compared to the control group (P < 0.05). The amount of CE angle (ΔCE) or RVI increase (ΔRV) was as follows: 3-1(38°, 0.3) > 3-0(27°, 0.2) and 1.5-0.5(25°, 0.1) > 1.5-0(17°, 0.07) (P < 0.05) (with no difference between groups 1.5-0.5 and 3-0, P = 0.7). The amount of sharp angle decrease was as follows: 3-1(20°), 3-0(18°) < 1.5-0.5(11°) < 1.5-0(8°) (P < 0.05). The lateralization of the intersection point where the iliac wing cut meets with the posterior column cut along the cut surface led to an increase of lateral cover and focal retroversion. Additional anteversion leads to further increases in those parameters, while groups 1.5-0.5 and 3-0 did not differ between.