The influence of unilateral periacetabular osteotomy on bony birth canal in female patients with DDH using maximum-inscribed-sphere method / 中华骨科杂志

ABSTRACT

Objective:To investigate the influence of unilateral periacetabular osteotomy (PAO) on the bony birth canal (BBC) in female patients with developmental dysplasia of the hip (DDH) by using pelvic 3D-CT maximum-inscribed-sphere (MIS) method.Methods:A total of 62 female DDH patients of childbearing age were included in the present study. The DICOM data of their pre- and post-operative pelvic CT was collected. The diameters of the MIS in 25 layers of the BBC were measured on the Medical Imaging Interaction Toolkit (MITK) platform. Lateral center edge angle (LCE), T?nnis angle and the distance between the medial margin of the femoral head and Kohler's line were measured on standing anteroposterior pelvic radiographs before and after unilateral PAO. Patients were divided into severe (LCE≤0°) and non-severe group (0°<LCE<20°) according to their LCE values.Results:After unilateral PAO, the BBC above the sciatic spine (1-20th layer) narrowed (0.86-5.95 mm, P<0.05). However, there was no change in levels below the sciatic spine (21-25th layer, P>0.05). The anterior margin of acetabular fragment (1-13th layer) narrowed significantly (4.23-5.95 mm) after unilateral PAO with the narrowest part (5.62-5.95 mm) locating at the inferior margin of pubic ramus and the region superior to the lateral margin of obturator foramen (5-10th layer). The narrowest part of BBC before and after the surgery occurred at the level of bilateral sciatic spines (20th layer). The diameter of MIS changed significantly from 105.34±7.16 mm pre-operatively to 104.47±7.06 mm post-operatively ( t=2.198, P=0.032). There was a positive correlation between the inward displacement of the hip center and the narrowing of the 1-20th layer of the BBC. The decrease of T?nnis angle was positively correlated with the narrowing of the 1-10th layer of the BBC. The increase of LCE was negatively correlated with the narrowing of 2-5th layer of the BBC ( P<0.05). The standardized coefficients were with statistical significance when comparing the distance between the Kohler's line and the medial margin of the femoral head to the size of the 1-20th layer of the BBC ( β=0.27-0.50, P<0.05). The height was positively correlated with the size of the narrowest part of the BBC before and after the surgery ( r=0.565, r=0.586, P<0.001). There was no difference between severe group and non-severe group in their extent of BBC narrowing before and after surgery ( t=-0.685-0.655, P>0.05). Conclusion:Unilateral PAO results in mild narrowing of the BBC superior to the sciatic spine. The narrowest part of the BBC is located at the sciatic spine. Unilateral PAO has slight effects on the narrowest position of the BBC. Normal delivery of a healthy fetus in female patients with DDH of childbearing age could not be affected by unilateral PAO in normal BBC settings.