SUMMARY

• Hip dislocations are traumatic hip injuries that result in femoral head dislocation from the acetabular socket.

• Diagnosis can be made with hip radiographs to determine the direction of dislocation and CT scan studies to assess for associated injuries. 

• Treatment is urgent reduction to minimize risk of avascular necrosis followed by CT scan to assess for associated injuries that may require surgical treatment (loose bodies, femoral head fractures, acetabular fractures).

EPIDEMIOLOGY

• Incidence

  • rare, but high incidence of associated injuries

ETIOLOGY

• Pathophysiology

  • mechanism is usually young patients with high energy trauma

• Pathoanatomy

  • Hip joint inherently stable due to

    • bony anatomy

    • soft tissue constraints including

      • labrum

      • capsule

      • ligamentum teres

CLASSIFICATION

• Simple vs. Complex

  • simple

    • pure dislocation without associated fracture

  • complex

    • dislocation associated with fracture of acetabulum or proximal femur

• Anatomic classification

  • posterior dislocation (90%)

    • occur with axial load on femur, typically with hip flexed and adducted

      • axial load through flexed knee (dashboard injury) 

    • position of hip determines associated acetabular injury

      • increasing flexion and adduction favors simple dislocation

    • associated with

      • osteonecrosis

      • posterior wall acetabular fracture

      • femoral head fractures 

         

      • sciatic nerve injuries

      • ipsilateral knee injuries (up to 25%) 

         

  • anterior dislocation

    • associated with femoral head impaction or chondral injury

    • occurs with the hip in abduction and external rotation

    • inferior ("obturator") vs. superior ("pubic")

      • hip extension results in a superior (pubic) dislocation

        • Clinically hip appears in extension and external rotation

      • flexion results in inferior (obturator) dislocation

        • Clinically hip appears in flexion, abduction, and external rotation 

           

PRESENTATION

• Symptoms

  • acute pain, inability to bear weight, deformity

• Physical exam

  • ATLS

    • 95% of dislocations with associated injuries

  • posterior dislocation (90%)

    • most common

    • associated with posterior wall and anterior femoral head fracture

    • hip and leg in slight flexion, adduction, and internal rotation 

    • detailed neurovascular exam (10-20% sciatic nerve injury)

    • examine knee for associated injury or instability

    • chest X-ray ATLS workup for aortic injury 

       

  • anterior dislocation

    • hip and leg in extension, abduction, and external rotation 

IMAGING

• Radiographs

  • recommended views

    • AP

    • cross-table lateral

      • used to differentiate between anterior vs. posterior dislocation

      • scrutinize femoral neck to rule out fracture prior to attempting closed reduction

    • obtain AP, inlet/outlet, judet views after reduction

  • findings

    • loss of congruence of femoral head with acetabulum

    • disruption of shenton's line 

      • arc along inferior femoral neck + superior obturator foramen

    • anterior dislocation

      • femoral head appears larger than contralateral femoral head

      • femoral head is medial or inferior to acetabulum

    • posterior dislocation 

      • femoral head appears smaller than contralateral femoral head

      • femoral head superimposes roof of acetabulum

      • decreased visualization of lesser trochanter due to internal rotation of femur

• CT

  • helps to determine direction of dislocation, loose bodies, and associated fractures

    • anterior dislocation 

    • posterior dislocation 

  • post reduction CT must be performed for all traumatic hip dislocations to look for 

     

    • femoral head fractures 

    • loose bodies 

    • acetabular fractures 

• MRI

  • controversial and routine use is not currently supported

  • useful to evaluate labrum, cartilage and femoral head vascularity

TREATMENT

• Nonoperative

  • emergent closed reduction within 12 hours 

     

    • indications

      • acute anterior and posterior dislocations

    • contraindications

      • ipsilateral displaced or non-displaced femoral neck fracture

• Operative

  • open reduction and/or removal of incarcerated fragments

    • indications

      • irreducible dislocation 

         

      • radiographic evidence of incarcerated fragment

      • delayed presentation

      • non-concentric reduction

      • should be performed on urgent basis

  • ORIF

    • indications

      • associated fractures of

        • acetabulum

        • femoral head

        • femoral neck

          • should be stabilized prior to reduction

  • arthroscopy

    • indications

      • no current established indications

      • potential for removal of intra-articular fragments

      • evaluate intra-articular injuries to cartilage, capsule, and labrum

TECHNIQUES

• Closed reduction 

  • perform with patient supine and apply traction in line with deformity regardless of direction of dislocation

  • must have adequate sedation and muscular relaxation to perform reduction

  • assess hip stability after reduction

  • post reduction CT scan required to rule out

    • femoral head fractures

    • intra-articular loose bodies/incarcerated fragments

      • may be present even with concentric reduction on plain films

      • acetabular fractures

  • post-reduction

    • for simple dislocation, follow with protected weight bearing for 4-6 weeks

• Open reduction

  • approach

    • posterior dislocation

      • posterior (Kocher-Langenbeck) approach

    • anterior dislocation

      • anterior (Smith-Petersen) approach

  • technique

    • may place patient in traction to reduce forces on cartilage due to incarcerated fragment or in setting of unstable dislocation

    • repair of labral or other injuries should be done at the same time

COMPLICATIONS

• Post-traumatic arthritis

  • up to 20% for simple dislocation, markedly increased for complex dislocation

• Femoral head osteonecrosis

  • 5-40% incidence

  • Increased risk with increased time to reduction

• Sciatic nerve injury

  • 8-20% incidence

  • associated with longer time to reduction

• Recurrent dislocations

  • less than 2%