Introduction
  • Subtrochanteric typically defined as area from lesser trochanter to 5cm distal
    • fractures with an associated intertrochanteric component may be called
      • intertrochanteric fracture with subtrochanteric extension
      • peritrochanteric fracture
  • Epidemiology
    • usually in younger patients with a high-energy mechanism
    • may occur in elderly patients from a low-energy mechanism 
      • 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
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		  
 • 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
 
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)
 Facture Location 
 • Femur (3) , Diaphysis (2), Subtrochanteric region (0.1)
Fracture Pattern
 •  Simple (A), Wedge (B), Complex (C)
 
 

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 
    • fixed angle plate 
      • indications
        • surgeon preference
        • associated femoral neck fracture
        • narrow medullary canal
        • pre-existing femoral shaft deformity
Techniques
  • Intramedullary Nailing
    • position
      • lateral positioning post
        • 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 
    • 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
    • plate fixation
      • increased risk of plate hardware failure
        • because of varus collapse and dependence on intramembranous healing inhibited by bisphosphonates