Garden City Hospital James M. Steinberg, DO

1. FRACTURES OF THE POSTERIOR WALL OF THE ACETABULUMMichael R. Baumgaertner, MDJAOS January/February 1999 Garden City Hospital James M. Steinberg, DO

2. Introduction • Most common acetabular fracture • Frequently have poor outcomes, often worse than more complex fractures • Epstein’s study of 150 posterior wall fractures; • 88% treated closed did poorly • 37% of those treated open did poorly • Matta and Letournel demonstrated that > 1mm of displacement led to serious joint deterioration

3. Etiology • Most fractures are result of sudden deceleration of an unrestrained occupant of a MVA • Force is transmitted from the floorboard to the foot or dashboard to knee • As the femoral head dislocates it fractures the posterior wall • Sciatic nerve function should be assessed before and after closed reduction • Neurologic injury occurs in 18-22% of posterior wall fracture dislocations

4. Classification • Letournel’s Classification: • Type I: fracture line that creates a single posterior fragment • Type II: multi-fragment posterior wall fracture • Type III: single fragment or multi-fragment wall fx with some of the articular surface medial to the primary fracture line impacted into the cancellous bone of the posterior column • Type III fractures are similar to split depression fractures of the tibial plateau

5. Radiographs • Most acetabular fractures can be recognized on an AP of the pelvis • Radiographic landmarks: posterior rim, anterior rim, tear drop, acetabular roof, iliopectineal line and ilioischial line • Obturator oblique view (rotate pt 45 degrees onto the unaffected side) displays the posterior aspect of the acetabulum • Iliac oblique view ( rotate pt 45 degrees onto the affected side) assesses the posterior column

6. Computed Tomography • Most valuable tool in assessing posterior acetabular wall fractures • 3mm overlapping sections are required to exclude incarcerated fragments and joint incongruity • Ideal study for identifying posteromedial marginal impaction • Utilized to quantify the amount of posterior wall that remains by comparing to the intact contralateral side

7. Management • Urgent closed reduction with adequate sedation and muscle relaxation • Assess stability by flexing and adducting the hip • Evaluate sciatic nerve function • Absolute indications for ORIF: • failure of closed reduction • deteriorating sciatic nerve function • incarcerated fragments • femoral neck fractures

8. Management • Fractures involving 50% or more of the posterior wall are unstable and require ORIF • Fractures involving 20% or less can be managed by close observation and activity restriction • No consensus on fractures that are clinically stable but involve 20-50% of the posterior wall • Closed Management: • hip dislocation precautions until capsular healing • limited wt bearing until evidence of fracture healing • X-rays at 1, 3 ,6, and 12 weeks • CT if evidence of instability

9. Surgical Treatment • Surgical intervention should be within 72 hours • Maintain hip in mild abduction and external rotation instead of skeletal traction • Kocher-Langenbeck approach is always used for isolated posterior wall acetabular fxs • Approach differs from that of a THA: • anatomic planes are blurred due to hematoma • landmarks may be absent or distorted • viability of the femoral head and wall fragments must be maintained • Sciatic nerve should always be visualized

10. Kocher-Langenbeck Approach • Skin and fascial incisions are centered at the posterosuperior aspect of the greater troch and extends just distal to the PSIS • Gluteus maximus is split proximally until the inf gluteal nerve and released from its osseous insertion 1 cm from its attachment • Careful dissection of the superficial surface of the quadratus femoris allows identification of the sciatic nerve

11. Kocher-Langenbeck Approach • Interval between the inferior gemellus and quadratus femoris is identified to avoid injury to the med femoral circumflex artery • Tendons of the piriformis and obturator internus are carefully elevated off the joint capsule • allows for fractured wall fragments to maintain blood supply • retraction of these muscles allows exposure of the retroacetabular surface

12. Kocher-Langenbeck Approach • Obturator internus tendon can be sutured to the gluteus fascia to create a soft tissue sling to protect the sciatic nerve • Origin of the hamstrings and quadratus femoris can be taken down off the ischium for better inferior exposure • Gluteus minimus is elevated off the capsule and ilium as needed • care must be taken near the superior border of the sciatic notch to avoid injury to the superior gluteal nerve, artery and vein

13. Kocher-Langenbeck Approach • Anterior and superior exposure is fascilitated by hip abduction • Field can be maintained by Stienmann pin placement into the superolateral ilium

14. Reduction • Inspect the joint • Wall fragments are rotated back on their capsular attachments • Fracture surfaces are debrided of clot and callus • Schanz screw can be placed in the troch to allow for distraction of the femoral head • Free osteochondral fragments of significant size are marked for orientation for later reconstruction

15. Reduction • Joint is irrigated and femoral head is reduced • Anatomic reduction is achieved: • if the edge of the intact acetabular articular surface is seen through the fracture plane • articular surface is concentric and perfectly satisfied by the femoral head • Fragments that are marginally impacted must be elevated and supported with bone graft • Concentrically reduced femoral head acts as a template to guide the reduction

16. Fixation • Typically requires buttress plating • Large single fragments can be stabilized with 3 - 5 lag screws • Helpful to contour the plate on a pelvic model prior to surgery • Leaving the buttress plate slightly underbent aids in reduction • Screws must be directed away from the joint to avoid penetration

17. Screw Positioning • Bosse: screws placed in any position on the acetabular rim would not violate the joint as long as they are placed in the coronal plane perpendicular to the body • Letournel: Kirschner wires placed tangential to the articular surface under direct vision at the proximal and distal extent of the intact acetabular rim allows a fixed plane of reference • Most recommend placing the buttress plate at least 6-9 mm from the rim and directing screws parallel or posterior to the coronal plane

18. Postoperative Care • IV antibiotics and DVT prophylaxis • Complete set of pelvic x-rays • CT if any question of quality of reduction • AP of the pelvis 6 and 12 weeks and 12 and 24 months after surgery • Motion restriction for 4-6 weeks (adduction, int rotation, and excessive flexion) • Touch down weight bearing for 6 -8 weeks • Strengthening exercises should start at 6 weeks and continue for at least 6 months

19. Complications • Hematoma • Infection • Thromboembolism • Sciatic nerve injury • Osteonecrosis • Heterotopic bone formation • Posttraumatic arthrosis

20. Summary • Posterior hip dislocation with minimal acetabular fractures do well if reduction is prompt and atraumatic • Delay in reduction is usually catastrophic to the joint • Anatomic reduction is achievable in most cases • Displacement as little as 1mm can lead to significant posttraumatic arthrosis