Stress Fracture

Aka: Stress Fracture, Fatigue Fracture

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II. Epidemiology: General

  1. Accounts for up to 20% of sports medicine injuries (varies by sport and cohort)
    1. Stress Fracture represents 10-15% of all Running Injury (esp. cross country)
    2. Stress Fracture represents up to 20% of injuries in women who are runners or military recruits

III. Epidemiology: Relative Risks

  1. Women > Men
    1. Relative Risk = 3.5
  2. White males > Black males
    1. Relative Risk = 4.7
  3. White females > Black females
    1. Relative Risk = 8.5

IV. Mechanisms

  1. Bone remodeling is triggered by microinjury
    1. Osteoclasts remove damaged bone and Osteoblasts lay down new bone in its place
    2. Repeated microinjury results in an imbalance between load-induced microinjury and repair
      1. Microdamage accumulates when rate of damage exceeds rate of repair
      2. Osteoclast removal of bone is not matched by sufficient Osteoblast activity
    3. Injuries progress from bone stress reaction, to Stress Fracture and to complete Fracture
      1. Stress reactions have increased bone turnover (marrow edema on MRI)
      2. Stress Fractures demonstrate a Fracture line
  2. Contributing Factors
    1. Weight bearing
    2. Muscle forces
      1. Muscle Strength increases faster than bone strength
    3. Muscle Fatigue

V. Risk factors

  1. Repetitive activity
    1. Military recruits
    2. Sports (e.g. distance Running, track and field sport)
      1. Running
        1. Mileage >25 miles per week (esp. >40 miles/week)
        2. Running on irregular or banked surfaces
      2. Track and Field
      3. Basketball
      4. Soccer
      5. Dance
  2. Increases in intensity, frequency, and loading
    1. Too fast
    2. Too far
      1. Increased duration of high impact activity is correlated with an increased Stress Fracture risk
        1. Field (2011) Arch Pediatr Adolesc Med 165(8): 723-8 [PubMed]
    3. Too soon
      1. Stress Fracture risk increases in the first 2 weeks of increasing training intensity
  3. Biomechanical forces (esp. Running)
    1. Over pronators or Supinators
    2. Rear foot eversion during stance phase
    3. Excessive hip adduction
    4. Hallux Valgus
    5. Genu Varum or genu valgus
    6. Increased Q Angle of the Knee
    7. High Longitudinal Arch
    8. Leg Length Discrepancy
    9. External hip rotation
    10. Changes in foot gear or training surface
    11. Decreased lower extremity Muscle mass
    12. Muscle Fatigue
    13. Cowan (1996) Med Sci Sports Exerc 28(8): 945-52 [PubMed]
    14. McCormick (2012) Clin Sports Med 31:291-306 [PubMed]
    15. Gallo (2012) Sports Health 4(6): 485-95 [PubMed]
  4. Systemic Diseases that weaken bone
    1. Rheumatoid Arthritis
    2. Systemic Lupus Erythematosus
    3. Osteoarthritis
    4. Pyrophosphate Arthropathy
    5. Renal Disease
    6. Osteoporosis (Female Athlete Triad)
    7. Joint Replacement
    8. Nutritional deficiency (e.g. dieting)
      1. Vitamin D Deficiency
  5. Other Associated risk factors
    1. Tobacco Abuse
    2. Alcohol >10 drinks per week
    3. Female Athlete Triad
    4. Female Gender
      1. Female runners are twice as likely as male runners to sustain Stress Fractures
      2. Highest risk among female runners with lower BMI, increased foot pronation and wider Pelvis
      3. Pujalte (2014) Med Clin North Am 98(3): 851-68 [PubMed]
    5. Nutritional deficiency
      1. Inadequate Dietary Calcium
      2. Inadequate Vitamin D
      3. Low Fat Diet
      4. Nieves (2010) PM R 2(8): 740-50 [PubMed]

VI. Pathophysiology: Common Stress Fracture Sites

  1. Tibia Stress Fracture (23-50% of Stress Fractures among athletes)
  2. Metatarsal Stress Fracture (16% of Stress Fractures)
  3. Fibula Stress Fracture (15% of Stress Fractures)
  4. Tarsal Navicular Stress Fracture
  5. Calcaneal Stress Fracture
  6. Medial Malleolus Stress Fracture
  7. Femoral Neck Stress Fracture (6%)
  8. Femoral Shaft Stress Fracture
  9. Pubic Ramus Stress Fracture
  10. Pelvic Stress Fracture (1-2%)
    1. Seen almost exclusively in women
  11. Lumbar Stress Fracture
  12. Coracoid process Stress Fracture
  13. Humerus Stress Fracture
  14. Olecranon Stress Fracture

VII. Symptoms

  1. Deep ache following rapid training change
  2. Pain progression
    1. Start: Pain after activity
    2. Next: Pain with activity
    3. Next: Pain with walking (at presentation in 81% of patients)
    4. Last: Pain at rest
  3. Night pain rarely occurs
    1. Consider another diagnosis

VIII. Signs

  1. Fracture site intense localized pain
    1. Tenderness to palpation (present in most cases)
    2. Edema at Fracture site may be present
    3. Compression induces pain
    4. Percussion of bone distant from symptomatic site
    5. Vibrating tuning fork (128 Hz) at suspected site
      1. Mediocre Test Sensitivity and Specificity
      2. Lesho (1997) Mil Med 162(12): 802-3 [PubMed]
  2. Specific Tests for leg or pelvis Stress Fracture
    1. Fulcrum Test
    2. Hop Test
      1. Poor Specificity (common finding in Shin Splints)
      2. Batt (1998) Med Sci Sports Exerc 30(11): 1564-71 [PubMed]

IX. Differential Diagnosis

  1. Primary benign Bone Neoplasm
    1. Osteoid Osteoma
    2. Osteoblastoma
    3. Eosinophilic Granuloma
  2. Infections
    1. Chronic or Subacute Osteomyelitis
  3. Chronic Musculoskeletal Soft Tissue Injury
    1. Tendonitis
    2. Muscle Strain
    3. Chronic Compartment Syndrome
  4. Metastatic Neoplasm to bone
    1. Breast Cancer
    2. Prostate Cancer
  5. Primary Malignant Bone Neoplasms
    1. Osteosarcoma
    2. Ewing Sarcoma
  6. Nerve Compression Syndromes
    1. Tarsal Tunnel Syndrome
    2. Carpal Tunnel Syndrome
    3. Ulnar Tunnel Syndrome
  7. Herniated Intervertebral Disc
  8. Osteoarthritis
  9. Hypertrophic Pulmonary Osteoarthropathy

X. Imaging

  1. Overall imaging approach (preferred)
    1. Step 1: XRay negative and Stress Fracture suspicion persists
    2. Step 2: Repeat XRay in 2-3 weeks is negative and Stress Fracture suspicion persists
    3. Step 3: Obtain MRI (preferred) or bone scan
  2. Imaging modalities
    1. Stress Fracture XRay
    2. Stress Fracture Bone Scan
    3. Stress Fracture CT
    4. Stress Fracture MRI
      1. Preferred second-line study after XRay
      2. Identifies marrow edema (stress reaction) and subtle Fracture lines
      3. Evaluates regional soft tissue
    5. Ultrasound is being investigated for specific Stress Fracture sites (e.g. Metatarsal Stress Fracture)
      1. Banal (2009) J Rheumatol 36(8): 1715-9 [PubMed]

XI. Management

  1. Rest for 4-7 weeks (may require up to 3 months)
    1. Activity should be pain-free only (starting with pain free ambulation)
    2. Reduce Stress Fracture risk Fractures
    3. Non-weight bearing until pain free while walking
      1. Tibia Stress Fracture
      2. Femoral Stress Fracture
  2. Analgesia
    1. Acetaminophen is preferred over NSAIDS
      1. NSAIDS may delay healing
  3. Immobilization
    1. Short-leg Casting or CAM-Walker Indications
      1. Non-compliance
      2. High-risk for non-union
        1. Navicular Stress Fracture
        2. Metatarsal Stress Fracture
    2. Pneumatic brace (Air cast)
      1. Support results in quicker recovery and less pain
      2. Indicated in tibial and fibular Stress Fractures
  4. Active rest (cross training)
    1. Consider formal rehabilitation program with physical therapy for strength and Stretching
    2. Goals
      1. Cardiovascular conditioning
      2. Flexibility
      3. Proprioception
      4. Strength
    3. Activities
      1. Swimming
      2. Pool Running with float vest or antigravity treadmill Running
      3. Biking
      4. Stair climbing machines (later stages)
    4. Progressive return to primary activity (e.g. Running)
      1. Many low risk Stress Fractures (e.g. tibia, fibula) require 4-8 weeks of rest prior to resuming Running
        1. Some Stress Fractures (e.g. posteromedial tibia, Sacrum or Pelvis) require 12 weeks of rest
      2. Pain free ambulation and cross training for at least 2 weeks, before reinitiating Running
        1. Start at 30-50% of preinjury intensity and duration
        2. Gradually increase intensity and duration by no more than 10% per week
        3. Pain with activity or after activity should signal need to rest or back-off intensity and duration
  5. Surgery
    1. Indications
      1. High Risk Fractures for non-union
      2. Non-healing Fractures
    2. Specific high risk sites
      1. Tarsal Navicular Stress Fracture
      2. Proximal anterior Tibia Stress Fracture
      3. Base of fifth Metatarsal Stress Fracture (proximal diaphysis)
      4. Base of second Metatarsal Stress Fracture
      5. Femoral Neck Stress Fracture
      6. Medial Malleolus Stress Fracture
      7. Talus Stress Fracture
      8. Great toe Sesamoid Fracture
    3. Modifying factors
      1. High risk Stress Fracture sites have high complication rates
        1. Malunion
        2. Progression to complete Fracture
        3. Avascular necrosis
        4. Arthritic changes
      2. High risk Stress Fracture sites with non-displaced, low-grade MRI may respond to conservative therapy
        1. Consider 6-8 weeks of immobilization and non-weight bearing
  6. Experimental: Electromagnetic field devices
    1. Questionable efficacy
    2. High cost

XII. Prevention

  1. Do not increase Exercise intensity >10% per week
  2. Stretch and warm-up before Exercise
  3. Choose level Running surfaces
  4. Shoes should be light weight and in good condition
  5. Consider Orthotics for biomechanical factor correction
  6. Shock-absorbing insoles may be beneficial
  7. Osteoporosis Prevention (unclear efficacy)
    1. Consider Calcium supplement 1000 mg orally daily
    2. Consider Vitamin D 800 IU orally daily

XIII. Reference

  1. Simmons (1997) AAFP Sports Med Review
  2. Titchner, Morris and Davenport (2021) Crit Dec Emerg Med 35(5): 17-23
  3. Buckwalter (1997) Am Fam Physician, 56(1):175-182 [PubMed]
  4. Patel (2011) Am Fam Physician 83(1): 39-46 [PubMed]
  5. Sanderlin (2003) Am Fam Physician 68:1527-32 [PubMed]
  6. Warden (2014) J Orthop Sports Phys Ther 44(10): 749-65 [PubMed]

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