ABSTRACT
Objective:To compare the biomechanical performance between 5 internal fixation methods for fracture of the acetabular posterior column using finite element analysis.Methods:One healthy female volunteer (50 years old, 160 cm in height and 63 kg in weight with a body mass index of 24.6 kg/m 2) was recruited for this study to undergo CT scan. Her CT scan data were imported into software Mimics15.0 in the format of DICOM to generate a 3D model of the pelvis. After pre-processing and accessory ligament structures added, a 3D finite element model of the pelvis was established and verified by software ANSYS. Next, software ANSYS was used to generate a model of acetabular posterior column fracture, on which models of 5 internal fixation methods (internal iliac-ischial plating, conventional posterior column plating, anterograde tensile screwing, lesser sciatic notch screwing and ischial tuberosity screwing) were established. Then stress was loaded onto the 5 internal fixation models to compare stress displacements of the fracture line on the articular surface and sites of stress concentration between the 5 internal fixation models. Results:The average stress displacement of the fracture line at the standing position was 6.13 μm for conventional posterior column plating, <6.85 μm for ischial tuberosity screwing, <7.07 μm for lesser sciatic notch screwing, <7.08 μm for internal iliac-ischial plating, and <7.85 μm for anterograde tensile screwing; the average stress displacement of the fracture line at the sitting position was 7.77 μm for conventional posterior column plating, <9.65 μm for internal iliac-ischial plating, <9.69 μm for anterograde tensile screwing,<10.1 μm for lesser sciatic notch screwing, and<10.20 μm for ischial tuberosity screwing. In all the 5 internal fixation models, the stress was chiefly concentrated at fracture ends.Conclusion:Internal iliac-ischial plating and conventional posterior column plating provide better stability than the hollow screws (anterograde tensile screwing, ischial tuberosity screwing and lesser sciatic notch screwing) for fracture of the acetabular posterior column.
ABSTRACT
Objective To explore the clinical efficacy of medial iliosciatic plating via the Stoppa approach for complex acetabular fractures involving the posterior column.Methods Between February 2015 and February 2016,a total of 16 complex acetabular facture cases treated by the medial iliosciatic plate via the Stoppa approach were retrospectively analyzed in this study.This approach provided good exposure to a large region of the pelvis and acetabulum including pubis symphysis,pubic ramus,anterior and inner wall of acetabulum,quadrilateral surface,inner surface of posterior column,true pelvic margin,greater sciatic notch and sacroiliac articulation.The anterior and column was reduced and fixed by the anterior column plate and the medial ilioseiatie plate.The screw direction and angle were adjusted according to the intraoperative X-ray.Surgical time,amount of bleeding,and relevant complications were recorded.The reduction of the posterior column fracture was evaluated by Matta scoring system on the plain X-ray of the pelvic post-surgery,and functional outcomes of the hip joint affected were evaluated one year post-surgery by the Merle d'Aubigne-Postel scoring system.All the cases were followed for at least 12 months.Results The reduction and fixation of the posterior column was accomplished in all the 1 6 patients.The average surgical time was 165.5 min (range,130-270 min).The average blood loss was 1 245.6 ml (range,600-5 600 ml).Thc intraoperative infusionof concentrated red blood cells averaged 6 units.According to the Matta scoring system,anatomical reduction was achieved in 12 cases,satisfactory reduction in 3,and poor reduction in one.The patients were followed from 12 to 22 months.According to the Merle d'Aubigne-Postel scoring system,there were 11 cases of excellent and 3 cases of good,yielding a good or excellent rate of 87.5％.The average Merle d'Aubigne-Postel score was 15.8 (range,8-18).There were 1 case of external iiiac vein rupture and 1 case of bladder rupture.Both were repaired during surgery.Superior gluteal artery rupture was found in 1 case and surgical ligation of the artery was performed during surgery.Conclusion In the treatment of complicated acetabular fractures involving the posterior column,the medial iliosciatic plating via the Stoppa approach is safe and effective,because it can provide a safe and sufficient operative field for surgeons to reduce and fix the posterior column fractures,and it leads to satisfactory recovery of the patients with limited complications.
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.