Femoral Head Fractures - Trauma

Introduction

Overview
- femoral head fractures are rare traumatic injuries that are usually associated with hip dislocations
  - treatment may be nonoperative or operative depending on the location of the fracture and degree of fracture displacement.
Epidemiology
- incidence
  - rare
  - increasing because of more MVA and better resuscitation
Pathophysiology
- mechanism of injury
  - impaction, avulsion or shear forces involved
    - unrestrained passenger MVA (knee against dashboard)
    - falls from height
    - sports injury
    - industrial accidents
- pathoanatomy
  - the location and size of the fracture fragment and degree of comminution depend on the position of the hip at the time of dislocation
    - 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 are 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
- medial femoral circumflex artery (MFCA)
  - main blood supply to the weightbearing portion of the femoral head
  - MFCA originates from the profunda femoris
- artery to the ligamentum teres
  - lesser blood supply (10-15%)
  - from the obturator artery or MFCA
  - 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
  - ipsilateral knee
    - ligamentous stability
- neurovascular
  - may have signs of sciatic nerve injury

Imaging

Radiographs
- recommended views
  - AP pelvis, hip series
    - both pre-reduction and post-reduction
  - judet views
    - associated acetabular fracture
  - inlet and outlet views
    - associated pelvic ring injury
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 (size, location, comminution)
  - plane of 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
  - outcomes
    - 5-40% incidence of femoral head osteonecrosis
    - increased risk with increased time to reduction
- TDWB x 4-6 weeks, restrict adduction and internal rotation
  - indications
    - Pipkin I
    - nondisplaced Pipkin II with < 1 mm step off
    - no interposed fragments
    - stable hip joint
  - outcomes
    - satisfactory results if <1mm step off, serieal radiographs required
    - development of post-traumatic arthritis based on joint incongruity and initial cartilage damage
Operative
- ORIF
  - indications
    - Pipkin II with > 1 mm 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
  - outcomes
    - best resereved for older patients
    - higher dislocation risk than THA performed for OA
- arthroscopy
  - indications
    - removal of loose bodies
  - outcomes
    - dependent on ability to remove incarcerated fragments and initial cartilage damage

Techniques

hip reduction
- technique
  - adequate sedation and muscular relaxation are vital
  - traction in-line with the thigh, extremity slightly adducted, counterforce on pelvis
  - forceful reduction should be avoided
  - obtain post reduction CT
TDWB x 4-6 weeks, restrict adduction and internal rotation
- technique
  - perform serial radiographs to document maintained reduction

ORIF of femoral head (Pipkin I, II, III)
- approach
  - anterior (Smith-Peterson) approach
    - utilizes internervous plane between the superior gluteal and femoral nerves
    - improved visualization
    - reduced surgical time
    - improved fracture reduction
      - femoral head fracture is commonly anteromedial
    - lower incidence of AVN
    - less blood loss
    - higher rate of functionally significant HO compared to posterior approach
  - 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
    - trochanteric osteotomy allows access to both the femoral head fracture and posterior wall acetabular fracture
    - preserves the medial circumflex artery supply to the femoral head
    - utilizes plane created by splitting of gluteus maximus (no true internervous plane)
  - anterior (Smith-Peterson) approach
    - for fixation of suprafoveal fractures
      - small posterior wall fractures may not need to be addressed surgically
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

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 an associated head injury
AVN
- incidence is 0-23%
  - risk is greater with delayed reduction of dislocated hip
  - anterior approach not associated with increased AVN risk
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