Stress Fracture

Stress Fracture is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • Overuse injuries caused by cumulative microdamage from repetitive bone loading
  • Stress fractures occur in different situations:
    • Fatigue fracture: abnormal repetitive stress applied to normal bone (e.g., young college athletes or new military recruits with increased physical activity demands and inadequate conditioning). Common sites include tibia, fibula, metatarsals, femoral neck, and navicular.
    • Insufficiency fracture: normal stress applied to structurally abnormal bone (e.g., femoral neck fracture in osteopenic bone, metabolic bone disease). Common sites include spine, sacrum, femoral head, and medial femoral condyle.
    • Combination fracture: abnormal stress applied to abnormal bone (e.g., female long-distance runners with premature osteoporosis from female athletic triad)
  • Weight-bearing bones of the lower extremity are most commonly affected at the following sites:
    • Tibia/fibula
    • Metatarsal bones
    • Navicular
    • Femoral neck
    • Pars interarticularis
  • Less commonly affected sites:
    • Pelvis
    • Calcaneus
    • Ribs
    • Ulna
  • High-risk stress fractures occur in zones of tension or areas with poor blood supply and are more likely to result in fracture displacement and/or nonunion. High-risk sites include the following:
    • Tension side of femoral neck
    • Anterior tibial diaphysis
    • Sesamoids
    • Pars interarticularis of lumbar spine (L4, L5)
    • 5th metatarsal at metaphyseal–diaphyseal junction
    • Proximal 2nd metatarsal
    • Medial malleolus
    • Tarsal navicular
    • Patella
    • Talar neck
  • Synonym(s): march fracture; fatigue fracture

Epidemiology

Incidence
  • Greatest incidence in 15- to 27-year-olds
  • Females more commonly affected than males
  • Females have higher incidence of fatigue fractures as compared to males (attributed to female athlete triad) (1).
  • Affects 9–21% of track and field athletes annually
  • Accounts for up to 20% of visits to sports medicine and orthopedic clinics
  • Across all sports, the most commonly injured body sites are the lower leg, foot, and lower back/lumbar spine/pelvis.
  • Occurs in <1% of general population

Prevalence
  • Affects up to 6.9% of male and 21.0% of female military members (2)
  • Affects 1–3% of college athletes

Etiology and Pathophysiology

  • Bone is dynamic and constantly remodeling in response to applied physiologic stress.
  • Repetitive loading or overuse causes microfractures that don’t heal due to imbalance between bone resorption and bone formation.
  • If microdamage accumulates in excess of reparation, bony fatigue leads to stress fracture.

Risk Factors

  • Intrinsic (3)[A]
    • Females are at 2.3 times higher risk than males.
    • Female athlete triad (low energy availability with or without disordered eating, menstrual dysfunction, and low bone mineral density)
    • Females with disrupted menstrual cycles are 2 to 4 times for more likely to sustain stress injury (1)[C].
    • History of previous stress fracture—increases risk of future stress fracture by 5 times
    • History of osteoporosis, osteomalacia, rheumatoid arthritis, prolonged corticosteroid therapy
    • Body composition—increased risk of stress fractures with BMI <19
    • Skeletal malalignment: pes cavus, pes planus, leg length discrepancies, excessive forefoot varus, tarsal coalitions, prominent posterior calcaneal process, tight heel cords
    • Biomechanical factors such as increased vertical loading rate (e.g., heel-to-toe running instead of forefoot striking)
    • Muscle fatigue and decreased lean muscle mass
    • Extremes of body size and composition
    • Previous inactivity or low aerobic fitness
  • Extrinsic (3)[A]
    • Type of exercise—both male and female athletes who participate in running, track and field, cross country, and gymnastics are at highest risk
    • Training regimen—running >32 km/week increases risk by 2 times in all athletes and by 3 times in female athletes
    • Nutritional/dietary habits—history of a diagnosed eating disorder
    • Rapid increase in mileage, running pace, or training volume
    • Inappropriate footwear
    • Hard training surface
    • Inadequate recovery or rest and training with fatigued muscle
    • There is no evidence that use of oral contraceptives is related to stress fracture risk.

General Prevention

  • Avoid abrupt increases in physical activity (no more than 10% increase in load per week).
  • Reduce intensity and duration of activity if new-onset pain.
  • Proper footwear
  • Increasing dynamic physical activity (jumping; plyometric training) increases bone density and resistance to mechanical stress.
  • Decrease vertical loading rate either by switching to forefoot strike running or (if continuing with heel-to-toe strike) by using a heel pad insert.
  • Shock-absorbing foot inserts may help.
  • Increased calcium and vitamin D intake may reduce stress fractures in female runners and military recruits.
  • Vitamin D supplementation (800 IU/day) in combination with calcium (2,000 mg/day) is effective in reducing fracture risk (2)[C].

Commonly Associated Conditions

  • Osteoporosis/osteopenia
  • Female athlete triad
  • Metabolic bone disorders

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