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Updated: 6/7/2022

Femoral Neck Stress Fractures

Review Topic
Images compression side.jpg fn stress compression side .jpg scan stress.jpg
  • summary
    • A Femoral Neck Stress Fracture (FNSF) is caused by repetitive loading of the femoral neck that leads to either compression side (inferior-medial neck) or tension side (superior-lateral neck) stress fractures. 
    • Diagnosis can be be made with radiographs but findings often lag behind often resulting in negative radiographs early on. MRI is the diagnostic study of choice in the presence of normal radiographs. 
    • Nonoperative treatment is indicated for compression sided fractures with < 50% femoral neck width. Cannulated screw fixation is indicated for tension sided stress fractures or compression sided fractures with > 50% width or hip effusion.
  • Epidemiology
    • Incidence
      • 0.04% of military personnel
        • 20 per 10,000 recruits per year
      • 3-5% of sports-related stress fractures 
      • 9% of lower extremity stress fractures 
    • Demographics
      • age range
        • 16-56 years of age
      • male: female ratio
        • female > male 
      • race
        • most commonly caucasian
    • Risk factors 
      • demographic 
        • female
        • caucasian
        • older age
      • activity-related
        • military personnel 
        • track and field or cross-country athlete
        • high training volume and intensity 
      • medical
        • lower BMI 
        • decreased bone mineral density
        • energy deficiency (energy expenditure > caloric intake) 
        • tobacco use
      • anatomical
        • femoroacetabular impingement (FAI)
        • coxa vara
        • abnormal running gait pattern
  • Etiology
    • Pathophysiology
      • mechanism
        • repetitive loading of femoral neck exceeds elastic properties of bone causing microscopic fracture 
        • continuous microscopic fractures exceed osteoblastic activity resulting in stress fracture 
    • Genetics 
      • 3x higher risk with absent gene
        • calcitonin receptor C allele
        • vitamin D recepter C-A haplotype
    • Associated conditions
      • "female athlete triad"
        • amenorrhea, eating disorder, and osteoporosis
        • must be considered in any female athlete with stress fracture
        • 2-4x increased risk 
          • hormonal dysregulation of hypothalamic-pituitary-gonadal (HPG) axis
          • decrease in estrogen levels which is necessary for osteoblast maturation 
          • increased osteoclast activity relative to osteoblast activity
        • oral-contraceptives use increases bone mineral density 
      • FAI
        • associated with 50% of FNF stress fractures
        • 42% CAM lesion
        • 78% pincer lesion
  • Anatomy
    • Osteology
      • neck-shaft angle 130 +/- 7 deg
      • anteversion 10 +/- 7 deg
      • calcar region
        • strongest part of femoral neck with dense bone along posteromedial neck 
    • Ligaments
      • hip capsule reinforced by 3 ligaments
        • iliofemoral ligament 
          • composed of lateral (superior) and medial (inferior) fibrous branches
          • insert onto AIIS and extends out to IT line forming Y-shaped ligament of Bigelow 
          • reinforce capsule during ER and extension
        • ischiofemoral ligament
          • inserts on ischium posteroinferior to acetabular rim and attaches to posterior IT line
          • reinforce capsule during IR in neutral and flexion-adduction positions 
        • pubofemoral ligament
          • inserts on superior pubic ramus and insert onto femur (with medial iliofemoral and inferior ischiofemoral ligaments)
          • reinforcing inferior capsule to restrict excessive abduction and ER during hip extension
    • Muscles 
      • hip extensors 
        • induce highest tensile strain in proximal-posterior neck cortex and compressive strain in anterior neck
        • primary hip extensors 
          • gluteus maximus
          • hamstring muscles
            • semitendinosus
            • semimembranosus 
            • bicep femoris long head
            • biceps femoris short head 
      • knee extensors
        • lowest potential to load femoral neck due to low hip reaction force generated by rectus
        • rectus femoris
          • only hip-spanning muscle of knee extensor muscle group
      • hip flexors
        • highest compressive strain in proximal-posterior neck cortex and tensile strain in anterior neck
        • primary hip flexors
          • iliopsoas
          • sartorius
          • rectus femoris 
      • hip abductors 
        • induced highest compressive strain in distal and superolateral neck 
        • primary abductors 
          • gluteus medius
          • gluteus minimus
          • tensor fascia lata 
    • Blood supply of femoral head
      • provided by three main branches 
        • medial femoral circumflex artery
          • predominant blood supply to femoral head
        • lateral femoral circumflex artery
        • artery of ligamentum teres
          • small contribution (~10%)
      • greater displacement of fracture leads to greater risk of disruption of vascular supply
    • Biomechanics 
      • 3-5x body weight across femoral neck with jogging
        • 8.4x body weight with running 
      • compression-sided fractures
        • compressive forces occur primarily along inferior femoral neck near calcar region
        • microfracture propagates at 45 deg of applied forces leading to more stable oblique pattern
      • tension-sided fractures
        • bending forces along superolateral neck are stabilized by abductor forces 
        • adbuctors fatigue and fracture propagates at 90 deg of cortex 
        • unstable transverse pattern
      • Femoral Neck Stress Fracture Classifications 
      • Fullerton-Snowdy 
      • Shin
      • Rohen-Quinquilla 
      • Steele
      • Modality
      • Radiographs and Bone scan 
      • Radiographs and MRI 
      • MRI
      • Radiographs and MRI 
      • Categories 
      • Compression-sided
      • Compression-sided edema + no fracture
      • Fracture line <50%
      • Fracture line > 50%
      •  Low grade I : Endosteal edema ‚ȧ 6 mm
      • Low grade II: Endosteal edema >6 mm + no fracture
      • Compression-sided edema no fracture
      • Fracture <50% without hip effusion 
      • Fracture <50% with hip effusion 
      • Fracture >50% with hip effusion 
      • Tension-sided 
      • Tension-sided
      • High grade III: fracture <50% neck width
      • High grade IV: fracture >50% neck width 
      • Tension-sided 
      • Displaced
      • Displaced
      • Displaced
  • Presentation
    • History
      • history of overuse running activities 
      • recent increase in training 
      • high impact activities 
    • Symptoms
      • insidious onset of thigh or groin pain
        • may radiate to knee
      • pain increases with repetitive weight-bearing activities
      • pain improves with cessation of activity
      • completion of fracture may be associated with cracking or popping and inability to bear weight
    • Physical exam
      • palpation
        • tenderness directly over groin region (62%)
      • motion
        • pain with extremes of hip motion (79%)
        • antalgic gait
      • provocative tests
        • pain with straight leg raise, log roll, or axial load
  • Imaging
    • Radiographs
      • recommended views
        • AP pelvis
        • AP hip
        • cross-table lateral of hip
      • findings
        • early findings
          • usually normal
            • 90% of initial radiographs normal
            • 50% of repeat radiographs at 4-6 weeks
        • late findings
          • may take 6-8 weeks to see radiographic changes
            • "grey cortex sign"
            • linear lucency
            • endosteal callous formation
            • sclerotic line traversing trabeculae
      • indications
        • modality of choice when radiographs are negative
      • findings
        • periosteal or bone marrow edema on STIR or fat-suppressed T2
        • line of decrease of intensity on T1 coronal corresponding with signal on T2 and STIR
        • hip effusion
          • 8x higher risk of propagation
      • utility
        • sensitivity 100% 
        • specificity 100%
    • Bone scan
      • indication 
        • negative radiographs with contraindication to MRI
          • largely replaced by MRI
      • findings
        •  increased uptake in femoral neck
          • uptake due to increased metabolic activity secondary to bone remodeling
      • utility
        • sensitivity 93-100%
        • specificity 76-95%
        • false-positive rate 32%
    • Early osteoarthritis
      • generally older patients with limited motion, particularly IR
      • radiographs with joint space narrowing and subchondral sclerosis 
    • Hip labral tears
      • hip pain and snapping in young active patient commonly with FAI
      • MRI arthrogram study of choice
    • Chondral defects of hip 
      • significant clinical overlap with labral tears, FAI, and hip dysplasia 
      • MRI can detect chondral defect and loose bodies
    • Rectus strain 
      • athlete with more sudden onset of hip pain and tenderness over rectus near AIIS
      • pain with resisted hip flexion or extension
    • Hip Osteonecrosis  
      • history of irradiation, trauma, sickle-cell, steroids, alcoholism, lupus, and other risk factors
      • radiographic findings showing sclerotic changes, crescent sign, or flattening of femoral head
    • Osteoid osteoma
      • insidious onset with night time pain worse with EtOH and improves with NSAIDs
      • radiographs with reactive bone around central nidus
      • other neoplasms should be considered
    • Lumbar disc herniation
      • pain is more positional than activity-related
      • may be associated with back pain, paresthesias and positive SLR
  • Treatment
    • Nonoperative
      • non-weight bearing and activity restriction
        • indications
          • compression side stress fractures + fracture line <50% width
          • tension side stress changes with no fracture line (MRI)
        • outcomes
          • 75-100% heal and can return to activity if correct indications met
    • Operative
      • cannulated screw fixation
        • indications
          • tension side stress fractures
          • compression side stress fractures with fatigue line >50% femoral neck width
          • compression side stress fracture with hip effusion
            • 8x increase risk of progression with presence of hip effusion 
          • progression of compression side stress fractures
        • technique
          • inverted triangle using three cannulated screws (7.0 or 7.3 mm) 
        • outcomes
          • similar outcomes versus lower-risk FNSF treated nonoperative
            • effectively prevent progression to displaced fracture
          • more likely to result in military seperation 
      • open reduction internal fixation 
        • indications 
          • displaced femoral neck stress fracture
        •  technique
          • cannulated screws
          • sliding hip screw
        • outcome
          • lower return to activity following ORIF for displaced FNSF than nondisplaced
    • Non-weight bearing and activity restriction for 6 weeks
      • technique
        • increase 25% body weight per week until full painless full weight-bearing
        • gradual return to full weight-bearing 
        • unrestricted activity at 3-4 months 
      • pros
        • avoid hardware-related complication
      • cons
        • risk of refracture (case reports)
        • progression of fracture  
    • Cannulated screw fixation
      • pros
        • reduce risk of progression of fracture
        • potential for earlier weight-bearing 
      • cons
        • hardware-related complications
      • approach
        • percutaneous
        • mini-open direct lateral 
      • technique
        • three cannulated screws in inverted triangle generally preferred over two
          • inferior calcar
            • inferior calcar provides higher load to failure 
          • posterosuperior 
          • anterosuperior 
        • starting point should be at or above lesser trochanter to avoid stress riser
        • screws should be parallel with maximal spread
        • threads should be in head fragment and not crossing fracture line
        • washer may be used to stop the screw head from penetrating  greater trochanter
      • complications
        • screw cutout 
        • varus collapse
        • implant failure
        • shortening of femoral neck
        • nonunion
    • Open reduction internal fixation
      • approach
        • anterior Smith-Peterson
          • internervous plane is femoral and superior gluteal nerve (SGN)
            • superficial 
              • tensor fascia lata (SGN) and sartorius (femoral)
            • deep
              • gluteus medius (SGN) and rectus femoris (femoral)
          • reduction via anterior approach followed by separate lateral incision for implant insertion
            • anterior approach allow for better direct visualization of entire femoral neck 
        • Watson-Jones
          • intermuscular plane
            • tensor fascia lata (SGN) and gluteus medius (SGN)
          • reduction and insertion of implant performed through same approach
            • limited visualization of subcapital neck region 
      • technique 
        • anatomic reduction is paramount to mitigate risk of osteonecrosis
          • early surgical intervention also reduces risk of AVN 
        • reduction tools
          • joysticks with k-wires or Shantz pin
          • pointed reduction clamps
          • medial buttress plate
        • cannulated screws or dynamic hip screw
        • consider autologous bone graft to mitigate nonunion risk 
      • complications
        • surgical site infection
        • avascular necrosis
        • nonunion
        • screw cutout
        • malreduction
        • implant failure
  • Complications
    • Fracture progression or completion
      • incidence 
        • 14%
      • associated with disabling complications 
        • avascular necrosis  
        • nonunion
        • malunion
      • risk factors 
        • hip effusion associated with 8x risk of progression
          • size of fracture not associated with progression 
        • delayed diagnosis 
      • treatment
        • cannulated screw fixation
    • Avascular necrosis
      • incidence
        • unlikely with incomplete stress fracture
        • more common with displaced FNSFs (5-42%)
      • factors associated with AVN in displaced FNSFs
        • delay in surgical treatment
        • initial displacement
        • varus malreduction
      • treatment 
        • precollapse
          • core decompression or vascularize free-fibula graft
        • collapse
          • hip arthroplasty 
    • Delayed union or nonunion
      • incidence
        • unlikely with incomplete stress fracture
        • more common with displaced FNSFs (9-44%)
      • risk factors
        • delay in treatment
        • noncompliance 
      • treatment
        • valgus intertrochanteric osteotomy
    • Varus malunion
      • incidence
        • 5-33%
      • treatment
        • revision ORIF with bone grafting 
        • hip arthroplasty 
    • Refracture
      • case reports following nonoperative treatment
  • Prognosis
    • Lacking high-quality studies
      • natural history
        • likely for fracture to progress and displace
      • negative predictors of return
        • fracture displacement
        • high athletic ability or demand (versus recreational athletes) 
        • delayed treatment 
      • survival with treatment
        • return to military 
          • ~75% with nonoperative treatment 
          • ~40-45% with operative treatment 
        • return to sports
          • 30-100% with nonoperative treatment
          • 48-56% with operative treatment

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Questions (6)
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(OBQ17.143.1) An 18-year-old female Marine Corps recruit has had increasing left hip pain since starting basic training. She states that the pain was originally a dull ache, but it has become much sharper as the running and rucking distances have increased. She now has pain at rest and finds it difficult to bear weight. She notes that she has lost 10% of her body weight since starting basic training. Radiographs are obtained, which do not demonstrate any osseous abnormalities. You obtain a left hip MRI, and select cuts are shown below. You measure the fatigue line to represent 60% of the diameter of the femoral neck. What is the diagnosis and preferred treatment of this patient's pathology?

QID: 214803

Complete femoral neck fracture; surgical fixation



Compression-sided femoral neck fracture; surgical fixation



Compression-sided femoral neck fracture; weight bearing restriction with crutches



Tension-sided femoral neck fracture; surgical fixation



Tension-sided femoral neck fracture; weight bearing restriction with crutches



L 2 E

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(OBQ13.39) A 22 year-old college cross-country runner developed hip and groin pain that initially started while running, but is now painful when walking across campus. Radiographs show no evidence of a stress fracture, an alpha angle of 45 degrees, and a lateral center edge angle of 30 degrees. An MRI shows focal, intense marrow edema in the superior-lateral femoral neck. What is the most appropriate treatment?

QID: 4674

Operative treatment with percutaneous screw placement



Hip arthroscopy with cam resection



Hip arthroscopy to treat both cam and pincer impingment



Non-operative treatment with NSAIDs and reduction in mileage



Non-operative treatment with partial weight-bearing



L 4 C

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(OBQ11.184) A 24-year-old female marathon runner experiences gradual onset of right groin pain. Initially it was only painful during running, but now it is painful with walking. She has no mechanical symptoms and denies back or lower leg symptoms. On exam, she has pain when attempting a straight leg raise and with passive internal rotation of the hip. Pelvis and hip radiographs demonstrate normal acetabular version and normal femoral head-neck offset. What is the next most appropriate step in her care?

QID: 3607

Intra-articular hip corticosteroid injection



Tapered oral corticosteroid dosing regimen for one week



EMG and nerve conduction studies



MR imaging of the hip



CT abdomen and pelvis to evaluate for sports hernia



L 1 C

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(OBQ04.272) A 20-year-old male marathoner has had left sided groin pain for the past 4 weeks. He has continued to maintain his routine running regimen despite the discomfort. Radiograph, bone scan, and MR images are shown in Figures A-D. What is the most appropriate next step in management?

QID: 1377

Referral to orthopaedic oncologist



Valgus intertrochanteric osteotomy



Hip arthroscopic evaluation and labral repair



Percutaneous screw fixation



Irrigation and debridement with course of intravenous antibiotics



L 1 D

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Evidence (31)
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