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http://upload.orthobullets.com/topic/1036/images/hip position.jpg
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Introduction
  • A rare fracture pattern that is usually associated with hip dislocations
    • the location and size of the fracture fragment and degree of comminution depend on the position of the hip at the time of dislocation  
  • Epidemiology
    • incidence
      • rare
      • increasing because of more MVA and better resuscitation
  • Mechanism
    • impaction, avulsion or shear forces involved
      • unrestrained passenger MVA (knee against dashboard)
      • falls from height
      • sports injury
      • industrial accidents
    • 5-15% of posterior hip dislocations are associated with a femoral head fracture
      • because of contact between femoral head and posterior rim of acetabulum
    • anterior hip dislocations usually associated with impaction/indentation fractures of the femoral head
  • Associated conditions
    • femoral neck fracture (see Pipkin Classification below)
    • acetabular fracture (see Pipkin Classification below)
    • sciatic nerve neuropraxia
    • femoral head AVN
    • ipsilateral knee ligamentous instability (knee vs dashboard)
Anatomy
  • Blood supply
    • the femoral head has 3 sources of arterial supply  
      • extracapsular arterial ring
        • medial circumflex femoral artery (main supply to the head)
          • from profunda femoris
        • lateral circumflex femoral artery
      • ascending cervical branches
      • artery to the ligamentum teres
        • from the obturator artery or MCFA
        • supplies perifoveal area
Classification
 
Pipkin Classification
Type I
Fx below fovea/ligamentum (small)
Does not involve the weightbearing portion of the femoral head
  
Type II Fx above fovea/ ligamentum (larger)
Involves the weightbearing portion of the femoral head 
   
Type III Type I or II with associated femoral neck fx
High incidence of AVN
 
Type IV Type I or II with associated acetabular fx (usually posterior wall fracture)  
 
Presentation
  • History
    • frontal impact MVA with knee striking dashboard
    • fall from height 
  • Symptoms
    • localized hip pain
    • unable to bear weight
    • other symptoms associated with impact
  • Physical exam
    • inspection
      • shortened lower limb
        • with large acetabular wall fractures, little to no rotational asymmetry is seen
      • posterior dislocation
        • limb is flexed, adducted, internally rotated
      • anterior dislocation
        • limb is flexed, abducted, externally rotated
    • neurovascular
      • may have signs of sciatic nerve injury
Imaging
  • Radiographs
    • recommended views
      • AP pelvis, lateral hip and Judet views
        • both pre-reduction and post-reduction
      • inlet and outlet views
        • if acetabular or pelvic ring injury suspected
  • CT scan
    • indications
      • after reduction
      • to evaluate:
        • concentric reduction
        • loose bodies in the joint
        • acetabular fracture
        • femoral head or neck fracture
    • findings
      • femoral head fracture
      • intra-articular fragments
      • posterior pelvic ring injury
      • impaction
      • acetabular fracture
Treatment
  • Nonoperative
    • hip reduction
      • indications
        • acute dislocations
          • reduce hip dislocation within 6 hours
      • technique
        • obtain post reduction CT
    • TDWB x 4-6 weeks, restrict adduction and internal rotation
      • indications
        • Pipkin I
        • undisplaced Pipkin II with < 1mm step off
        • no interposed fragments
        • stable hip joint
      • technique
        • perform serial radiographs to document maintained reduction
  • Operative
    • ORIF
      • indications
        • Pipkin II with > 1mm step off
        • if performing removal of loose bodies in the joint
        • associated neck or acetabular fx (Pipkin type III and IV)
        • polytrauma
        • irreducible fracture-dislocation
        • Pipkin IV
          • treatment dictated by characteristics of acetabular fracture
          • small posterior wall fragments can be treated nonsurgically and suprafoveal fractures can then be treated through an anterior approach
      • outcomes
        • outcomes mimic those of their associated injuries (hip dislocations and femoral neck fractures)
        • poorer outcomes associated with 
          • use of posterior (Kocher-Langenbeck) approach
          • use of 3.0mm cannulated screws with washers
    • arthroplasty
      • indications
        • Pipkin I, II (displaced), III, and IV in older patients
        • fractures that are significantly displaced, osteoporotic or comminuted
Surgical Techniques
  • ORIF of femoral head (Pipkin I, II, III)
    • approach
      • anterior (Smith-Peterson) approach 
        • the anterior (Smith-Peterson) and anterolateral (Watson-Jones) approaches provide the best visualization of the head compared with the posterior approach
        • utilizes internervous plane between the superior gluteal and femoral nerves
        • no increased risk of AVN
        • shorter surgical time 
        • less blood loss 
        • ease of reduction and fixation
          • because femoral head fragment is commonly anteromedial
        • can use surgical hip dislocation if needed
      • anterolateral (Watson-Jones) 
        • utilizes intermuscular plane between the tensor fascia lata and gluteus medius (both superior gluteal nerve)
    • exposure
      • periacetabular capsulotomy to preserve blood supply to femoral head
    • fixation
      • two or more 2.7mm or 3.5mm lag screws    
        • countersink the heads of the screws to avoid screw head prominence
      • headless compression screws
      • bioabsorbable screws
    • postop
      • rehabilitation
        • mobilization
          • immediate early range of motion
        • weightbearing
          • delay weight bearing for 6-8 weeks
        • stress strengthening of the quadriceps and abductors
      • radiographs
        • radiographs after 6 months to evaluate for AVN and osteoarthritis
  • ORIF of femoral head and acetabulum (Pipkin IV)
    • approach
      • posterior (Kocher-Langenbeck) approach with digastric osteotomy 
        • provides the best visualization of femoral head fracture and acetabular posterior wall fracture
        • preserves the medial circumflex artery supply to the femoral head
        • utilizes plane created by splitting of gluteus maximus (no true internervous plane
        • gluteus maximus is not denervated because it receives nerve supply well medial to the split
      • anterior (Smith-Peterson) approach
        • for fixation of suprafoveal fractures (if posterior wall fragments are small, they can be treated nonsurgically)
  • Arthroplasty
    • approach
      • can use any hip approach for arthroplasty
        • posterior (Kocher-Langenbeck) approach provides the best visualization of acetabular posterior wall fracture
    • pros & cons
      • allows immediate postoperative mobilization and weightbearing
      • hemiarthroplasty can be utilized if no acetabular fracture present
      • total hip arthroplasty favored if patient physiologically younger or if acetabular fracture present
Complications
  • Heterotopic ossification  
    • overall incidence is 6-64%
      • anterior approach has increased heterotopic ossification compared with posterior approach
    • treatment
      • administer radiation therapy if there is concern for HO
        • especially if there is associated head injury
  • AVN
    • incidence is 0-23%
      • risk is greater with delayed reduction of dislocated hip
      • the impact of anterior incision on AVN is unknown
  • Sciatic nerve neuropraxia
    • incidence is 10-23%
      • usually peroneal division of sciatic nerve
      • spontaneous recovery of function in 60-70%
  • DJD
    • incidence 8-75%
    • due to joint incongruity or initial cartilage damage
  • Decreased internal rotation
    • may not be clinically problematic or cause disability
 

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