- See:
-
Associated Transverse and Posterior Wall Frx:
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Classification and Column Theory
-
Posterior Column Fractures:
-
Posterior Dislocation of Hip;
- Discussion:
- most common type of acetabular frx (upto 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 with > 40-50% involvement of posterior wall (as determined by CT scan) or with posterior subluxation will be unstable and will require ORIF to restore acetabular wall;
-
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;
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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;
*** 
- 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.
MS Calkins et al. CORR Vol 227. 1988 Feb. p 152-163.
- Stability of posterior fracture-dislocations of the hip: Quantitative assessment using computed tomography.
Keith JE, Brashear R, Guilford WB: J Bone Joint Surg (Am) 70A:711-714, 1988
** 
- 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);
- 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;
- 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;
-
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 screws
-
4.0 mm cancellous bone screws;
-
3.5 mm reconstructed plate, curved;
- spiked ball pusher;
- T handle chuck and schanz half pin;
- flouro OR table;
-
bone grafting:
- indicated for comminuted posterior wall fractures;
-
surgical outcomes:
- 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 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;
-
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 efforts are made to save& reduce all fragments since significant posterior wall defects
may lead to hip instability;
- bone grafting is often required to support impacted articular fragments;
-
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:
- 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 the fractured fragment may help avoid joint penetration, however, this
requires stripping the fragment from the 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 frx reconstruction.
NA Ebraheim et al. J. Orthop. Trauma. Vol 3(3) 1989. p 196-201.
-
fixation w/ reconstruction plate (and lag screws or sping plate):
- most indicated for comminuted posterior wall frx;
- butress plate (8 hole
3.5 mm reconstructed 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;
-
spring plate:
- 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;
- Post Op:
- 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.
J.A. Goulet MD, J.P. Rouleau, D.J. Mason, and S.A. Goldstein PH.D. JBJS Vol 76-A No 10. Oct 1994.
Posterior Acetabular Wall Fractures: a technique for screw placement. Bosse, M.J. J. Orthop. Trauma, 5: 167-172, 1991.
Danger Zone of the Acetabulum. NA Ebraheim, J. Waldrop, RA Yeasting, and WT Jackson. J. Orthop Trauma. Vol 6. No 2. pp 146-151.
Radiological diagnosis of screw penetration of hip joint in acetabular fracture reconstruction. Ebraheim N. J. Orthop. Trauma. 3: 196-201. 1989.
Hip Arthroscopy to Remove Loose Bodies After Traumatic Dislocation.
Outcomes of Posterior Wall Fractures of the Acetabulum
