Updated: 3/30/2021

Femoral Neck Fx Nonunion

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Summary
  • Femoral neck fracture nonunion represents a failure of bony healing after fixation of an intracapsular femoral neck fracture.
  • Diagnosis is generally confirmed by radiographs demonstrating residual fracture lines, interval displacement +/-hardware failure.
  • Treatment is operative ranging from valgus intertrochanteric femoral osteotomy to total hip arthroplasty. 
Etiology
  • Epidemiology
    • incidence
      • occur after 10-30% of femoral neck ORIF
    • demographics
      • increasing age at higher risk for nonunion
    • risk factors
      • fracture morphology
        • significant initial displacement
        • vertically oriented fracture pattern (Pauwels type III)      
        • posterior comminution
      • fracture malreduction, particularly with varus malalignment
      • older age
      • delay of fracture fixation >24 hours
  • Pathophysiology
    • mechanism of injury
      • initial femoral neck fracture occurs due to high energy trauma in the younger population, and ground-level falls in the elderly
      • nonunion occurs after fracture displacement and/or hardware failure before bony consolidation
    • pathoanatomy
      • femoral neck fractures are intracapsular, placing them at higher risk for nonunion than other hip fractures
        • lack periosteal or extraosseous blood supply
        • bathed in synovial fluid which deters fracture healing
        • healing is intra-osseous only (no callus formation)
          • achieving and maintaining anatomic reduction is essential
  • Associated conditions
    • orthopaedic conditions
      • avascular necrosis (AVN)
      • femoral neck malunion
      • hardware failure
      • surgical site infection leading to septic nonunion
    • medical conditions or comorbidities
      • low bone mineral density
  • Prognosis
    • natural history
      • typically, patients present with pain and difficulty with ambulation months after fixation
        • persistent pain with radiographic lack of healing at 3 months signifies likely nonunion
          • revision surgery should be considered at this point. 
    • prognostic variables 
      • unfavorable fracture patterns, malreduction, poor bone quality all poor prognostic factors with ORIF
    • survival with treatment                                         
      • valgus intertrochanteric osteotomy
        • eventual union rates of 80-90%
      • hip arthroplasty
        • approximately 90% implant survivorship at 10 years, 75% at 20 years.
        • higher rate of dislocation (up to 10-20%), compared to primary hip arthroplasty
Anatomy
  • Osteology
    • normal proximal femur neck shaft-angle 130 +/- 7°
    • normal proximal femur anteversion 10 +/- 7°
    • proximal femur consists of tensile and compressive trabecular groups 
  • Muscles
    • hip abductors 
      • important to preserve neurovascular supply and attachments of abductors to avoid abductor lurch and Trendelenburg gait
  • Ligaments
    • iliofemoral, ischiofemoral and pubofemoral ligaments attach to outer hip capsule and help to prevent excessive hip motion 
  • Blood Supply 
    • a confluence of arteries forms an extracapsular arterial ring that divides into the ascending cervical arteries which supply the femoral neck via perforators 
      • main blood supply in adults is the medial femoral circumflex artery (lateral epiphyseal artery)
      • lateral femoral circumflex contributes to anterior arterial ring
      • superior and inferior gluteal arteries give small contributions to arterial ring
      • artery of ligamentum teres comes from obturator or medial femoral circumflex
        • plays insignificant role in blood supply
    • femoral neck fracture with displacement is thought to disrupt the blood supply to the femoral neck
  • Biomechanics
    • in double-leg stance, force vector through hip is vertical
    • in single-leg stance, force vector through hip is parallel to femoral neck
      • compressive load through hip is 4x bodyweight
      • repetitive loading can increase tensile forces and lead to superior femoral neck fracture
Classification
  • Primarily descriptive

Leighton's classification

Type 1  • Inadequate fixation or non-anatomic reduction
Type 2  • Loss of fixation with fracture displacement
Type 3  • Fibrous nonunion with no displacement and intact fixation  
 
Presentation
  • History
    • prior femoral neck fracture
    • evaluation of medical history
      • low bone density
      • metabolic disease
      • nutritional deficiencies
      • tobacco use
  • Symptoms
    • persistent groin/buttock pain
    • pain with weight bearing
    • pain with hip extension
    • pain may radiate down medial thigh/knee
  • Physical exam
    • inspection
      • important to evaluate prior incision for drainage, erythema and to verify approach of prior surgery
    • motion
      • discomfort with active or passive range of motion at hip
        • decreased internal rotation
      • antalgic gait
    • neurovascular
      • evaluate sciatic and femoral nerve function
    • provacative tests
      • pain with log-roll
      • pain with straight leg raise
Imaging
  • Radiographs      
    • recommended views
      • AP pelvis and hip
      • cross-table lateral hip
      • full length femur 
    • optional views
      • traction/internal rotation hip view
      • contralateral hip films for intraoperative templating
    • findings
      • radiolucent fracture lines
      • fracture settling
      • failure of hardware (backing out)
      • perforation of femoral head with hardware
      • change in fracture position by >10mm
      • femoral head collapse (AVN)
      • calcar comminution
      • varus malalignment
  • CT   
    • indications
      • most definitive way to diagnose femoral neck nonunion
      • useful if diagnosis uncertain or for surgical planning 
  • MRI
    • indications
      • concern for diagnosis of femoral head AVN in the setting of nonunion
  • Bone scan
    • indications
      • may help rule out concomitant femoral head AVN
    • findings
      • equivocal radiographs may show increased uptake in area of the nonunion
Studies
  • Labs
    • indications
      • must rule out infection
    • inflammatory markers
      • CBC with manual diff, ESR, CRP
  • Hip aspiration
    • indications
      • if high suspicion for infection in the setting of elevated inflammatory markers
  • Intraoperative tissue sample
    • if concerned for infection, can send frozen-section for histology before proceeding with further fixation
      • if positive for infection, staged approach preferred
Treatment
  • Nonoperative
    • observation
      • indications
        • only indicated in non-ambulatory patients with comorbid conditions
      • outcomes
        • poor functional outcomes with non-operative management
  • Operative
    • revision ORIF
      • indications
        • not recommended due to proximal bone loss, residual leg length discrepancy and high residual failure rates
    • proximal femoral osteotomy
      • indications
        • failure of fracture fixation
        • nonunion >3 months postoperatively
        • varus collapse
        • considerations
          • femoral head viability
          • remaining femoral neck bone quality
          • patient age     
            • in younger patients, arthroplasty may be less desirable
          • duration of nonunion
            • longer duration may cause contractures, fibrosis and acetabular wear
      • techniques
        • valgus intertrochanteric osteotomy       
          • most commonly used salvage procedure
            • primary issue is mechanical orientation of fracture in this group
            • technique reorients vertical fracture to a horizontal fracture to achieve compression at the nonunion site
            • improves abductor function by restoring femoral length and abductor lever arm
              • patients may still describe persistent limp due to abductor weakness
          • contraindications
            • significant bone loss
            • joint incongruity
            • age > 65 (relative)
      • outcomes
        • 80-90% union rates
        • high percentage of associated femoral head AVN but only small percentage remain symptomatic after osteotomy
    • bone grafting   
      • indications
        • failed prior fixation attempts
        • nonunion remains well aligned with loss of posterior bone stock
      • techniques
        • quadratus femoris-vascularized pedicle graft
        • free vascularized fibular grafting
      • outcomes
        • not be as beneficial when fracture malalignment is primary cause of nonunion
        • union rates up to 90%
    • hip hemiarthroplasty
      • indications
        • low physical demand and more comorbidities
        • cognitive decline
      • techniques
        • cemented vs. uncemented
      • outcomes
        • less extensile than THA
        • lower dislocation rate compared with THA
        • contraindications
          •  significant acetabular erosion
    • total hip arthroplasty  
      • indications
        • salvage operation of choice in older patients with femoral neck fracture nonunion  
          • prior femoral bony defects
          • poor acetabular bone quality
      • outcomes
        • excellent 10-year survivorship (~90%)
          • improved for patients greater than 65
        • complications
          • dislocation
            • rates may be decreasing with advent of new implant technologies
          • trochanteric nonunion
          • thromboembolic complication
          • loosening
          • infection
    • hip arthrodesis
      • indications
        • young patients with nonviable femoral heads
        • heavy manual laborers
      • outcomes
        • arthroplasty becoming favored over arthrodesis, even at young age
Technique
  • Observation
    • bedrest, non-weightbearing on affected extremity
    • complications
      • may increase risk for other systemic complications
  • Revision ORIF
    • approach
      • through initial incision when appropriate
    • technique
      • removal of hardware, adequate reduction of fracture
      • new stable bony fixation with bone grafting
    • complications
      • very high failure rates
      • residual leg length discrepancy
  • Valgus intertrochanteric osteotomy          
    • approach
      • direct lateral approach to proximal femur 
    • technique
      • goal is to convert vertically oriented fracture to about 30 degrees in order to create compression
      • can use blade plate or sliding hip screw for ultimate fixation
    • complications
      • femoral malrotation
      • excessive medialization of femoral shaft can decrease offset 
        • cause abductor efficiency
        • a longer blade can avoid medialization of shaft
  • Bone grafting
    • approach
      • lateral incision just anterior to greater trochanter between 10-15cm long
    • technique
      • quadratus femoris-vascularized pedicle graft   
        • insertion of quadratus taken down off the greater trochanter with a bony flap that is transplanted to the posterior femoral neck and sutured or fixed into place with screws
      • free vascularized fibular grafting
    • complications
      • donor site morbidity
      • may need to be combined with mechanical realignment
  • Hip hemiarthroplasty
    • approach
      • posterior 
      • anterolateral 
      • direct anterior 
    • technique
      • unipolar vs. bipolar
        • recent studies have not shown bipolar femoral heads to provide any benefit over unipolar heads
      • cemented shows superior outcomes, fewer complications than uncemented
    • complications
      • results of failed hip hemiarthroplasty when converted to THA are worse than primary THA. 
  • Total hip arthroplasty
    • approach 
      • similar to hip hemiarthroplasty 
    • technique
      • there may be esidual bony defects in proximal femur from old hardware     
        • may have to bypass this area with longer stems     
        • may increase risk for intraoperative fracture while reaming the canal
      • poor acetabular bone quality can make cup placement difficult and increase risk for fracture
        • avoid overly aggressive acetabular component impaction
        • augment cup with screws
    • complications
      • dislocation
        • use of larger diameter heads and new implant technology (i.e dual mobility) may be helpful in decreasing dislocation rates
      • increased rates of aseptic loosening 
        • risks include patient age < 65 and BMI >30. 
  • Hip arthrodesis
    • approach
      • lateral approach with trochanteric osteotomy
    • technique
      • optimal positioning of hip joint:
        • 20-35° hip flexion
        • 0-5° adduction
        • 5-10° external rotation
    • complications
      • adjacent joint arthrosis/pain
      • low back pain
Complications
  • Concomitant femoral head AVN
    • incidence
      • up to 40% in setting of nonunion
      • around 15% appear to be symptomatic
    • risk factors
      • initial fracture displacement
      • poor reduction
    • treatment
      • hip arthroplasty 
  • Acetabular cartilage degeneration
    • risk factors
      • associated femoral head AVN or chondral wear
    • treatment
      • total hip arthroplasty
  • Trendelenburg gait
    • risk factors
      • loss of femoral offset secondary to abductor inefficiency in nonunion/malunion or valgus producing osteotomy
    • treatment
      • avoiding loss of femoral offset or damage to abductors during salvage operations
  • Prosthetic dislocation
    • incidence
      • 10-20% in salvage total hip arthroplasty group compared to <10% in primary arthroplasty group after femoral neck fracture
    • risk factors
      • abductor insufficiency
      • abnormal hip joint kinematics after nonunion
      • posterior hip approach
    • treatment
      • larger femoral heads, dual mobility implants may decrease risk
      • choose surgical approach to optimize stability
 

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