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Updated: Mar 7 2024

Subtrochanteric Fractures

Images fracture_moved.jpg refx 13yo ii_moved.jpg hip.jpg 0 AP - subtrochanteric fx_moved.gif taylor type i.jpg taylor type ii.jpg
  • Summary
    • Subtrochanteric fractures are proximal femur fractures located within 5 cm of the lesser trochanter that may occur in low energy (elderly) or high energy (young patients) mechanisms.
    • Diagnosis is made with orthogonal radiographs of the hip in patients that present with inability to bear weight.
    • Treatment is generally operative with cephalomedullary nail fixation. 
  • Epidemiology
    • Incidence
      • common
        • 7 to 34% of femur fractures
  • Etiology
    • Pathophysiology
      • young patients
        • high-energy mechanism (MVC)
      • elderly patients
        • low-energy mechanism (ground level falls)
      • rule out pathologic or atypical femur fracture
        • denosumab or bisphosphonate use, particularly alendronate, can be risk factor
    • Pathoanatomy
      • deforming forces on the proximal fragment are
        • abduction
          • gluteus medius and gluteus minimus
        • flexion
          • iliopsoas
        • external rotation
          • short external rotators
      • deforming forces on distal fragment
        • adduction & shortening
          • adductors
  • Anatomy
    • Biomechanics
      • weight bearing leads to net compressive forces on medial cortex and tensile forces on lateral cortex
  • Classification
    • Russel-Taylor classification
      • Historically used to differentiate between fractures that would amenable to an intramedullary nail (type I) and those that required some form of a lateral fixed angle device (type II)
      • Current interlocking options with both trochanteric and piriformis entry nails allow for treatment of type II fractures with intramedullary implants
        • Russel-Taylor Classification
        • Type I
        • No extension into piriformis fossa
        • Type II
        • Extension into greater trochanter with involvement of piriformis fossa
        • Look on lateral xray to identify piriformis fossa extension
    • AO/OTA classification 
        • AO/OTA Classification Examples
        • 32-A3.1
        • Simple (A), Transverse (3), Subtrochanteric fracture (0.1)
        • 32-B3.1
        • Wedge (B), Fragmented (3), Subtrochanteric fracture (0.1)
        • 32-C1.1
        • Complex (C), Spiral (1), Subtrochanteric fracture (0.1)
    • ASBMR Task Force Case Definition of Atypical Femur Fractures (AFFs), Revised criteria
        • ASBMR Task Force Case Definition of Atypical Femur Fractures (AFFs), Revised criteria
        • Four of five major features should be present to designate a fracture as atypical; minor features may or may not be present in individual cases
        • Major criteria
        • Associated with no trauma or minimal trauma, as in a fall from a standing height or less
        • Fracture originates at the lateral cortex and is substantially transverse in its orientation, although it may become oblique as it crosses the medial femur
        • Noncomminuted
        • Complete fractures extend through both cortices and may be associated with a medial spike; incomplete fractures involve only the lateral cortex
        • Localized periosteal or endosteal thickening of the lateral cortex is present at the fracture site
        • Minor criteria
        • Generalized increase in cortical thickness of the femoral diaphyses
        • Prodromal symptoms such as dull or aching pain in the groin or thigh
        • Bilateral incomplete or complete femoral diaphysis fractures
        • Delayed fracture healing
        • Specifically excluded are fractures of the femoral neck, intertrochanteric fractures with spiral subtrochanteric extension, pathological fractures associated with primary or metastatic bone tumors, and periprosthetic fractures
  • Presentation
    • History
      • long history of bisphosphonate or denosumab
      • history of thigh pain before trauma occurred
    • Symptoms
      • hip and thigh pain
      • inability to bear weight
    • Physical exam
      • pain with motion
      • typically associated with obvious deformity (shortening and varus alignment)
      • flexion of proximal fragment may threaten overlying skin
  • Imaging
    • Radiographs
      • recommended views
        • AP and lateral of the hip
        • AP pelvis
        • full length femur films including the knee
      • optional views
        • traction views may assist with defining fragments in comminuted patterns but is not required 
      • findings
        • proximal fragment flexed and abducted
        • distal fragment adducted and ER
        • bisphosphonate-related fractures have
          • lateral cortical thickening
          • increased diaphyseal cortical thickness
          • transverse vs. short oblique fracture orientation
          • medial spike (if complete fracture)
          • lack of comminution
  • Treatment
    • Nonoperative
      • observation with pain management
        • indications
          • non-ambulatory patients with medical co-morbidities that would not allow them to tolerate surgery
          • limited role due to strong muscular forces displacing fracture and inability to mobilize patients without surgical intervention
    • Operative
      • intramedullary nailing (usually cephalomedullary)
        • indications
          • historically Russel-Taylor type I fractures
          • newer design of intramedullary nails has expanded indications
          • most subtrochanteric fractures treated with IM nail
          • patients on bisphosphonate therapy with pain and radiographic evidence of stress fracture
      • fixed angle plate
        • indications
          • surgeon preference
          • associated femoral neck fracture
          • narrow medullary canal
          • pre-existing femoral shaft deformity
  • Techniques
    • Intramedullary Nailing
      • position
        • lateral positioning
          • advantages
            • allows for easier reduction of the distal fragment to the flexed proximal fragment
            • allows for easier access to entry portal, especially for piriformis nail
        • supine positioning
          • advantages
            • protective to the injured spine
            • address other injuries in polytrauma patients
            • easier to assess rotation
      • techniques
        • 1st generation nail (rarely used)
        • 2nd generation reconstruction nail
        • cephalomedullary nail
        • trochanteric or piriformis entry portal
          • piriformis nail may mitigate risk of iatrogenic malreduction from proximal valgus bend of trochanteric entry nail
      • pros
        • preserves vascularity
        • load-sharing implant
        • stronger construct in unstable fracture patterns
      • cons
        • reduction technically difficult
          • nail can not be used to aid reduction
          • fracture must be reduced prior to and during passage of nail
          • may require percutaneous reduction aids or open clamp placement to achieve and maintain reduction
        • mismatch of the radius of curvature
          • nails with a larger radius of curvature (straighter) can lead to perforation of the anterior cortex of the distal femur
      • complications
        • varus malreduction (see complications below)
    • Fixed angle plate
      • approach
        • lateral approach to proximal femur
          • may split or elevate vastus lateralis off later intermuscular septum
          • dangers include perforating branches of profunda femoris
      • technique
        • 95 degree blade plate or condylar screw
        • sliding hip screw is contraindicated due to high rate of malunion and failure
        • blade plate may function as a tension band construct
          • femur eccentrically loaded with tensile force on the lateral cortex converted to compressive force on medial cortex
      • cons
        • compromise vascularity of fragments
        • inferior strength in unstable fracture patterns
  • Complications
    • Varus/ procurvatum malunion
      • the most frequent intraoperative complication with antegrade nailing of a subtrochanteric femur fracture is varus and procurvatum (or flexion) malreduction
    • Nonunion
      • rates of nonunion lowest when using reamed, statically locked IMN 
      • can be treated with plating
        • allows correction of varus malalignment
    • Bisphosphonate fractures
      • nail fixation
        • increased risk of iatrogenic fracture
          • because of brittle bone and cortical thickening
        • increased risk of nonunion with nail fixation resulting in increased need for revision surgery
        • bisphosphonates must be discontinued 
          • high rate of progression to fracture of contralateral femur
      • plate fixation
        • increased risk of plate hardware failure
          • because of varus collapse and dependence on intramembranous healing inhibited by bisphosphonates
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