Abstract
BackgroundDue to complex pelvic geometry, percutaneous screw placement in the posterior acetabular column can pose a major challenge even for experienced surgeons.MethodsThe present study examined the preformed bone stock of the posterior acetabular column in 260 hemipelvises. Retrograde posterior column screws were virtually implanted using iPlan® CMF (BrainLAB AG, Feldkirchen, Germany); maximal implant length, maximal implant diameter and angles between the screw trajectories and the reference planes anterior pelvic plane as well as the midsagittal plane were assessed for gender-specific differences.ResultsThe virtual analysis of the preformed bone stock column showed two constrictions of crucial clinical importance. These were located 49.6 ± 3.4 (41.0–60.2) mm (inferior margin of acetabulum) and 77.0 ± 5.6 (66.5–95.3) mm (centre of acetabulum) from the entry point of the implant in men and respectively 43.7 ± 2.3 (38.3–49.3) mm as well as 71.2 ± 3.5 (63.5–79.99) mm in women (men vs. women: p < 0.001). The entry point of the retrograde posterior column screw was located dorsal from the transition of the lower margin of the ischial tuberosity to ramus inferior pointing to the medial margin of the ischial tuberosity. In female patients, the entry point was located significantly closer to the medial margin of the ischial tuberosity. However, 7.3 mm screws can generally be used in men and women. The angle between the screw trajectory and the anterior pelvic plane in sagittal section was 14.0 ± 4.9 (2.5–28.6) °, the angle between the screw trajectory and the midsagittal plane in axial section was 31.1 ± 12.8 (1.5–77.9) ° and the angle between the screw trajectory and the midsagittal plane in coronal section was 8.4 ± 3.8 (1.5–20.0) °. For all angles, significant gender-specific differences were found (p < 0.001).ConclusionTherefore, the anterior pelvic plane as well as the midsagittal plane can facilitate intraoperative orientation for retrograde posterior column screw placement considering gender-specific differences in preformed bone corridor, implant length as well as angles formed between screw trajectory and these reference planes.
Highlights
Due to complex pelvic geometry, percutaneous screw placement in the posterior acetabular column can pose a major challenge even for experienced surgeons
Fluoroscopy-assisted percutaneous screw osteosynthesis of the acetabulum may require several trials for correct screw placement which leads to high radiation doses [2]
The analysis of the anatomically preformed periacetabular screw corridor of the posterior column showed two sites of constriction which are important in daily clinical routine. These constrictions can be found at the inferior margin of acetabulum and at the centre of acetabulum In average, they were located 49.6 ± 3.4 (41.0–60.2) mm and 77.0 ± 5.6 (66.5–95.3) mm from the entry point of the implant in men and respectively 43.7 ± 2.3 (38.3–49.3) mm as well as 71.2 ± 3.5 (63.5–79.9) mm in women
Summary
Due to complex pelvic geometry, percutaneous screw placement in the posterior acetabular column can pose a major challenge even for experienced surgeons. Minimally-invasive osteosynthesis approaches are limited due to the demanding reduction, which cannot always be completely achieved, and because of the complex threedimensional geometry of the pelvis with limited bone corridors for screw placement. Based on previous findings [3, 4] suggesting that there are gender-specific differences regarding the best implant position, we first defined an optimal screw position for the retrograde placed posterior column screw and analysed the surrounding preformed bone corridor. We examined 260 hemipelvises virtually using data from CT scans of 130 uninjured European pelvises which were collected during clinical routine exams at our trauma centre. Our first hypothesis was that there are gender-specific differences considering the optimal implant position
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