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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

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

Percutaneous Fixation of Anterior and Posterior Column Acetabular Fractures



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

Last updated by Data Trace Staff on Friday, January 2, 2015 2:13 pm