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Duke Orthopaedics
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Wheeless' Textbook of Orthopaedics

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;
 - 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/ the posterior approach, reduction can be facilitated by inserting a Schanz screw into the ischium just inferior to the subcotyloid gutter;
           - a T chuck is applied over the the 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:
          - the internal pudendal bundle usually lies 1.5 cm from the medial posterior margin of the 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






Transgluteal Posterior Column Screw Stabilization for Fractures of the Acetabulum: A Technical Trick



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Clifford R. Wheeless, III, MD on Sunday, July 21, 2013 9:25 pm