The Hip: Preservation, Replacement and Revision Tracking Pixel
Duke Orthopaedics
presents
Wheeless' Textbook of Orthopaedics

Posterior Acetabular Wall Fractures


  - See:
      - Associated Transverse and Posterior Wall Frx 
      - Classification and Column Theory 

- Discussion:
    - most common type of acetabular frx (up to 50% of acetabular fractures will contain a posterior wall fragment);
    - posterior wall frxs involve the posterior articular surfaces, often w/ retroacetabular surface and sometimes entire surface;
    - frx of posterior rim & posterior column may be seen in MVA from posteriorly directed dashboard impact;
    - hips w/ > 40-50% involvement of posterior wall (as per CT scan) or w/ posterior subluxation are unstable and require ORIF to restore acetabular wall; 
    - posterior wall and posterior dislocation of hip;
             - reduction needs to be within 6 hours of injury;
             - CT only need be performed following closed hip reduction;
    - work up of acetabular frx and associated injuries:
             - inspection of soft tissues:
             - GYN / urinary / rectal injuries: RUG vs. suprapubic catheter placement;
             - neurologic injury:
                    - w/ this injury, the sciatic nerve may be injured about 30% of patients;
                    - be sure to document even subtle signs of injury;
                    - ref: Somatosensory evoked potential monitoring in the surgical treatment of acute, displaced acetabular fractures. Results of a prospective study.
             - transverse frx (most common);
             - posterior dislocation of hip;
             - posterior dislocation with femoral head fracture:
                    - if femoral head fragment is above the fovea, then attached ligamentum teres prevents reduction of the femoral head fracture;
                    - with small infrafoveal fragments, a posterior approach may allow fixation or debridement of the femoral head fragment;
             - anteroposterior compression fractures;
             - PCL rupture (may occur along w/ posterior wall frx when dashboard injury is the mechanism of injury);


- Radiographic Studies:
    - internal (obturator) oblique view:
             - visualizes iliopubic (anterior) column of pelvis & posterior rim;
             - demostrates the fracture fragment, acetabular defects and degree of displacement;
    - note whether there are intra-articular frx fragments;
    - note degree of comminution:
             - most posterior wall fractures will have some degree of posterior comminution;
             - w/ isolated posterior wall frx, ilioischial line remains intact;
             - note that comminution of the posterior wall fragment is a poor predictor of outcome (3 or more fragments indicates poor prognosis);
             - posterior wall fracture extending into the acetabular roof also indicates negative prognosis;

                ***

- CT Scan:
    - hips w/ less than 34% of the remaining posterior wall are generally unstable;
    - hips w/ more than 55% of the remaining posteiror wall are generally stable;
    - note degree of comminution;
           - single posterior fragment is present in 30%;
           - multiple fragment fractures occur in about 30%;
           - osteochondral depression fractures of the posterior wall;
    - references:
           - Computed tomography evaluation of stability in posterior fracture dislocation of the hip.
           - Stability of posterior fracture-dislocations of hip. Quantitative assessment using computed tomography

            **



- Non Operative Treatment:
    - indications:
          - stable fractures (less than 30-50%) which are demonstrated to be stable under flouroscopic evaluation;
          - congruent reduction w/ assurance that incarcerated fracture fragments are not present (as determined from fine cut CT scan); 
          - references:
                  - Computed tomography as a predictor of hip stability status in posterior wall fractures of the acetabulum.
                  - Outcomes of Post Wall Fractures of Acetabulum Treated Nonoperatively After Diagnostic Screening with Dynamic Stress Exam Under Anesthesia
                  - Can Experts in Acetabular Fracture Care Determine Hip Stability after Posterior Wall Fractures using Plain Radiographs and Computed Tomography?

- Surgical Considerations:
    - indications for ORIF:
           - irreducible fracture dislocation;
           - incarcerated osteochondral fragments:
                  - in some cases, small fragments which lie in the lower half of the acetabulum do not require removal; 
                  - ref: Intra-articular Fragments in Acetabular Fracture–Dislocation
           - hip instability;
           - defect in the posterior wall of more than 50% (associated w/ instability even if instability is not apparent on static radiographs);
                  - defects of between 30-50% may or may not be stable;
                  - often the status of the posterior capsule determines whether the hip is stable; 
          - elderly patients:
                  - fractures in elderly patients and those with extensive comminution are more likely to have a poor clinical result;
                  - ref: Results of Operative Treatment of Fractures of the Posterior Wall of the Acetabulum 

- Surgical Technique:
   - prone positioning:
           - posterior wall fractures that extend from the greater and or lesser sciatic notch are usually best operated on w/ prone positioning;
           - w/ posterior instability, prone position ensures hip reduction;
           - prone position keeps the hip in extension which reduces sciatic nerve tension;
           - be sure that the patient is placed on a flouro table and be sure to run through all of the important flouroscopic views prior to prepping the patient; 
     - implants and tools for posterior wall fracture:
           - 3.5 mm cortical screws4.0 mm cancellous bone screws3.5 mm reconstructed plate, curved,
           - spiked ball pusher, T handle chuck and schanz half pin, flouro OR table; 
           - synthes spring plates
    - bone grafting: indicated for comminuted posterior wall fractures; 

- Surgical Exposure:
    - Kocher Langenback incision:
           - a sliding trochanteric osteotomy may be required if there is cranial extension of the wall fragment;
           - releasing 1 cm of the gluteus insertion onto the femur widens the posterior exposure; 
           - knee should be flexed to protect the sciatic nerve;
    - deep exposure:
           - schanz screw (w/ T chuck handle) can be inserted into the greater trochanter, inorder to distract the femoral head for improved exposure;
           - joint is debrided & irrigated to remove all loose fragments;
           - articular surfaces are inspected & impactions of articular surface are elevated;
           - in some cases, the posterior wall fragment may be displaced anteriorly and held tethered by the anterior capsule (ligament of Bigelow); 
           - small fragments may be discarded, but save & reduce all fragments since significant posterior wall defects may lead to hip instability; 
           - capsular attachment to the posterior wall fragment should be preserved to maintain circulation;  
           - superior fracture extension of the posterior wall:
                   - consider trochanteric slide osteotomy in order to
                            - avoid stretch on the superior gluteal neurovascular bundle;
                            - avoid direct damage to the medius and minimus muscles; 
           - references:
                   - Modified Kocher-Langenbeck approach for the stabilization of posterior wall fractures of the acetabulum.
                   - Modified "2-portal" kocher-langenbeck approach: a minimally-invasive procedure protecting the short external rotator muscles

    - fixation w/ lag screws:
           - fixation w/ lag screws is inferior to fixation w/ lag screws and a contoured plate;
           - best indication for lag screw fixation is large non comminuted posterior wall fragment;
           - two synthes 3.5 mm cortical screws are inserted after the outer cortex has been over-drilled w/ a 3.5 mm drill bit;
           - it is important to aim the drill bit perpendicular to the fracture site (rather than perpendicular to the cortex site);

                   

           - hazards:
                   - danger zone of the acetabulum (screw penetration of joint): 
                   - consider role of hip arthroscopy;
                   - note: its easy for screws inserted into retroacetabular space to enter joint;
                   - screws are normally directed away from the joint, oblique to the retroacetabular surface;
                   - retrograde drilling of frx frag may avoid joint penetration, however, requires stripping fragment from hip capsule, (removing its blood supply);
                   - radiographic methods to determine articular penetration:
                          - multiple flourscopic views including cross table lateral view and the Judet iliac view are often the most useful views;
                          - flouroscopy w/ intra-articular contrast dye and moving the hip w/o crepitus are other methods to avoid joint penetration;
                          - using flouroscopy to achieve "end on" view of lag screws;
                   - reference:
                          - Radiographic diagnosis of screw penetration of the hip joint in acetabular fracture reconstruction
                          - Danger Zone of the Acetabulum.    

    - fixation w/ reconstruction plate (and lag screws or sping plate):
            - most indicated for comminuted posterior wall frx;
            - butress plate (8 hole 3.5 mm recon plate) is placed along posterior rim of acetabulum (placed from superior pole of ischium to inferior iliac wing);
                   - plate is curved so that it roughly parallels rim of acetabulum (it should be precontoured on a model preoperatively);
                   - undercontouring of the plate helps butress the fragment;
                   - generally two screws are placed above and below acetabulum;
            - generally two lag screws are inserted midway between the reconstruction plate and the edge of the posterior wall;
            - note: its easy for screws inserted into retroacetabular space to enter joint;
            - see: danger zone of the acetabulum:
            - screws are normally directed away from the joint, oblique to the retroacetabular surface; 
            - referencs:
                   - Fixation of marginal posterior acetabular wall fractures using locking reconstruction plates and monocortical screws.
                   - The Use of Cervical Vertebrae Plates for Cortical Substitution in Posterior Wall Acetabular Fractures




            - spring plate: (synthes spring plates)
                   - indicated for comminution;
                   - use a four hole one third tubular plate;
                   - one end of the plate holes is cut out and bent 90 deg;
                   - the plates are contoured to fit the bone;
                   - the two prongs are inserted into the acetabulum 5 mm from its edge;
                   - the plates are secured to the pelvis at the most posterior hole;
                   - following application of the plate, the 3.5 recon plate is placed over the spring plate;
                   - there is some controversy as to whether spring plates offer any significant stability; 
                   - spring plates create a special risk of intra-articular compromise of the joint surface;
                   - if the "hooks" of the plate are too long or malpositioned, the femoral head may be at risk for damage;
                  - ref: The Use of a T-Plate as "Spring Plates" for Small Comminuted Posterior Wall Fragments.
            - bone grafting:
                   - bone grafting is often required to support impacted articular fragments; 
                   - articular impaction is managed with elevation and application cancellous bone graft;
                   - large free fragments are reattached and small fragments removed;
                   - avoid fracture gaps;

- Post Op: 
    - postoperative CT scan allows optimal evaluation of surgical reconstruction;
    - need to limit postoperative hip flexion inorder to limit stress on the posterior wall fragment;

- Complications:
    - this fracture type is associated w/ a high complication rate;
    - iatrogenic sciatic nerve injury may occur and may be prevented by constant knee flexion during the case and by intraoperative SSEP monitoring;
    - loss of fracture fixation is a common complication;
    - after ORIF of posterior wall frx, post traumatic osteoarthitis may occur in up to 20% of patients



Biomechanical consequences of fracture and repair of the posterior wall of the acetabulum.

Comminuted Fractures of the Posterior Wall of the Acetabulum. A biomechanical evaluation of fixation methods

Posterior Acetabular Wall Fractures: a technique for screw placement.    

Hip Arthroscopy to Remove Loose Bodies After Traumatic Dislocation. 

Outcomes of Posterior Wall Fractures of the Acetabulum Treated Nonoperatively After Diagnostic Screening with Dynamic Stress Examination under Anesthesia.

Does Early Fixation of Posterior Wall Acetabular Fractures Lead to Increased Blood Loss?

Surgical techniques-How do I do it? Open reduction and internal fixation of posterior wall fractures of the acetabulum



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

Last updated by Data Trace Staff on Monday, February 24, 2014 9:16 am