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Posterior Column of Acetabulum

- See:
     - Classification and Column Theory
     - Posterior Wall Fractures
     - AO Foundation Posterior Column Frx

- Discussion:
    - posterior column extends from obturator foramen thru posterior aspect of the wt bearing dome
             of acetabulum & then obliquely through greater sciatic notch;
    - frx of posterior rim & posterior column arise from MVA, most likely as  result of dashboard impact;
    - associated injuries:
             - posterior dislocation of the femur
             - AP compression frx

- Radiographs:
    - posterior column fractures involve not only posterior articular surfaces, but also the ilioischial line;
    - AP view:
            - medial displacement of the femoral head and sciatic buttress;
            - ilioishial line is disrupted;
    - external (iliac) oblique view:
             - visualizes ilioischial (posterior) column & anterior acetabular rim;
             - often reveals the internal and superior boundaries of the displaced fragment;
             - radiographic technique: pt is supine w/ uninvolved side rotated anteriorly 45 deg and central beam directed
                       vertically toward the affected hip
    - assesment of stability:
             - in the study by Vrahas, et al (1999), a cadaveric biomechanical study was performed to determine the relative stability of
                      anterior column, posterior column, and transverse fractures;
                      - they noted that posterior column frx w/ posterior roof-arc angle (iliac oblique radiograph) of 70 degrees or less were
                                unstable and required ORIF;
                      - references:
                              - The effects of simulated transverse, anterior column, and posterior column fractures of the acetabulum on the stability of the hip joint.
- PreOp Planning:
    - work up of acetabular frx:
          - w/ posterior injury, the sciatic nerve may be injured in 40% of patients;

- Surigical Approach:
    - Kocher-Langenback incision is used w/ pt in prone position;
    - dislocation of femoral head:
            - Surgical Hip Dislocation for Exposure of the Posterior Column

 - Reduction:
    - sciatic notch is useful landmark to help reconstruct posteror column;
           - posterior column is strong & triangular, w/ extremely thick bone at greater trochanter sciatic notch;
           - medial surface forms posterior aspect of quadrilateral plate;
    - reduction may achieved w/ direct visualization of quadrilateral surface thru distraction of femur if needed, & thru palpation
           of quadrilateral surface through greater sciatic notch (through posterior approach);
    - insertion of Schanz screw:
           - w/posterior approach, reduction is by inserting a Schanz screw into the ischium just inferior to the subcotyloid gutter;
           - T chuck is applied over Schanz screw, which is then used to rotate a displaced posterior column frx into a reduced position;
                - the surgeon's other hand can guide the reduction by palpating the quadrilateral surface;
                - additionally a Schanz screw may be placed into the greater trochanter for additional traction;
    - frx lines may be distracted using lamina spreader or AO femoral distractor;
    - frx lines may be compressed using Farabeuf clamps;
    - blood clot & granulation tissue are removed, as are any free fragments that might impede reduction;
    - identify & reduce marginally  impacted frx of posterior wall;

- Reconstruction:
    - posterior column is reconstructed using lag screws or pelvic recon plates;
    - initial fixation is w/ lag screw, placed from posterior to anterior & followed by a curved plate on the retroacetabular surface;
    - small reconstruction plate applied from the ischial tuberosity to the lateral ilium along the retroacetabular surfaces.

- Screw Placement in the Ischial Tuberosity:
    - anatomical hazards:
            - internal pudendal bundle usually lies 1.5 cm from the medial posterior margin of
                      ischial  tuberosity;
            - internal pudendal bundle passes out of greater sciatic foramen, passes around
                      sacrospinous ligament, over the internal obturator muscle (just medial to the
                      tuberosity) and then into lesser foramen;
            - excessively medially angulated screws may injure the internal pudendal;
            - at 2 cm below the inferior acetabular margin, hamstring origin is encountered (and therefore
                   dissection below this point is avoided);
    - technique of insertion:
            - maximal purchase is achieved w/ entry into the tuberosity 5 or 10 mm medial to the lateral margin
                        of the tuberosity and are directed inferiorly;
            - at the level of the inferior acetabular margin, direct the screw 35-40 deg caudally;
            - at 1 cm below the inferior acetabular margin, direct screws 45-50 deg caudally;
            - at 2 cm below the inferior acetabular margin, direct screws 50-55 deg caudally

Modified technique of percutaneous posterior columnar screw insertion and neutralization plate for complex acetabular fractures
Transgluteal Posterior Column Screw Stabilization for Fractures of the Acetabulum: A Technical Trick

Custom-made Locked Plating for Acetabular Fracture: A Pilot Study in 24 Consecutive Cases

Percutaneous Fixation of Anterior and Posterior Column Acetabular Fractures

Percutaneous retrograde posterior column acetabular fixation: is the sciatic nerve safe? A cadaveric study.