Stress Fractures

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Stress Fractures

• Rochelle Nolte, MD
• CDR USPHS/USCG

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Objectives

• Participants will understand the risk factors
  that contribute to the development of stress
  fractures
• Participants will increase their comfort in
  diagnosing stress fractures
• Participants will increase their comfort in
  treating stress fractures

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Stress Fractures

• Definition
• Pathophysiology
• Risk factors
• Epidemiology
• Diagnosis
• Treatment
• Prevention

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Definition

• Partial or complete fracture of bone that results
  from the repeated application of a stress lower
  than that required to fracture the bone in a
  single loading situation

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Pathophysiology

• Bone loading
• Stress
• Load or force per unit area that develops on a
  plane surface
• Strain
• Deformation (change in dimension)

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Pathophysiology

• Factors that influence bones response to loading
• Load direction
• Bone geometry
• Bone microarchitecture
• Bone density
• Muscle contraction

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Pathophysiology

• Bone remodeling
• Adapts to mechanical loading
• Prevents accumulation of microfractures
• Maintains blood calcium levels

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Pathophysiology

• Stages of remodeling
• Quiescence
• Activation
• Hormonal, chemical, or physical stimulus
• Resorption (osteoclasts)
• Reversal
• 1-2 weeks during which the bone is weak
• Formation (osteoblasts)
• Matrix synthesis, then mineralization

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Pathophysiology

• Accelerated remodeling leads to stress fracture
  development by
• Coalescence of resorbed cavities
• Microfractures extend to cortex
• Physiological and clinical continuum
• Early intervention is associated with more rapid
  healing

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Risk factors

• Training errors
• Too much too soon
• Total load
• Intensity
• Pace
• Muscle fatigue
• Attenuation of GRF is through eccentric
  contraction of muscle

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Risk factors

• Lower extremity alignment
• Pes cavus
• Pes planus
• Genu varum
• Genu valgum
• Abnormal Q angle
• Leg length discrepancies
• Femoral neck anteversion

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Risk factors

• Terrain
• Equipment and footgear
• Intrinsic mechanical factors
• Bone mineral density
• Bone geometry
• Skeletal alignment
• Body size and composition

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Risk factors

• Physiologic factors
• Bone turnover
• Muscle flexibility
• Joint range of motion
• Muscular strength and endurance
• Nutritional factors
• Caloric intake
• Calcium intake
• Nutrient deficiencies

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Risk factors

• Hormonal factors
• Estrogen
• Age at menarche
• Amenorrhea
• Oligomenorrhea
• Luteal phase defect
• Female Athlete Triad
• Physical training
• Volume, pace, intensity of training
• Recovery periods

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Risk factors

• Extrinsic mechanical factors
• Surface
• Footwear, insoles, orthotics
• External loading
• Other factors
• Genetic predisposition
• Physical fitness
• Psychological traits

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Epidemiology

• Most studies done in military
• US incidence lt10
• Most studies indicate 1-3
• Females from 1.1-21.0
• Distribution
• Male
• 66 MT, 20 calcaneus, 13 lower leg
• Female
• 39 calcaneus, 31 MT, 27 lower leg

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Epidemiology
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Diagnosis

• History
• Localized pain that typically begins after or
  toward the end of physical activity
• Pain may start earlier and earlier during
  activity and progress to pain with ADLs
• Detailed history of preceding 2-6 weeks to
  evaluate for risk factors

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Diagnosis

• Physical exam
• Localized tenderness
• Spinal extension test (pars)
• Fulcrum test (femur)
• Hop test (tibia)
• Evaluate for underlying risk factors
• LE alignment, biomechanics, etc

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Diagnosis

• Imaging
• Plain film x-rays
• Poor sensitivity, especially in first 2-3 weeks
• More helpful in long bones (tib/fib/MTs)
• CT scan
• Can differentiate between stress fracture and
  stress reaction as well as identify other
  conditions that can mimic stress fracture such as
  osteomyelitis, osteoid osteoma, or malignancy

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Diagnosis

• Imaging
• Triple phase bone scan
• Phase I flow images immediately after tracer
  injected
• Evaluates perfusion to bone and soft tissue
• Phase II blood pool image at 1 minute
• Reflects extent of hyperemia
• Phase III delayed image at 3-4 hours
• 50 of tracer absorbed into bone matrix
• Proportional to rate of osteoblastic activity

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Diagnosis

• Triple phase bone scan
• Stress fractures shows uptake in all 3 phases
• Phases I II help define age and severity and
  differentiate bony from soft tissue injury (no
  Phase III uptake)
• Phase I normalizes first, then stage II, Phase
  III can have residual uptake for many months

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Diagnosis

• Imaging MRI
• Becoming increasingly popular as secondary
  imaging after plain films
• Less time than Triple Phase Bone Scan
• Less radiation than CT scan
• Increase specificity over Bone Scan
• Better at evaluating edema and soft tissue injury
  than CT scan

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Metatarsal Stress Fractures

• Second most common site of stress fractures after
  the tibia
• Neck of 2nd MT is most common site
• Forefoot pain that gradually worsens
• Focal tenderness
• Diagnosis is clinical (x-ray optional)
• Treatment is rest and correction of biomechanical
  abnormalities

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Proximal 5th MT Stress fractures

• Proximal diaphyseal stress fractures may present
  before or after completion of fracture
• Imaging helps differentiate from soft tissue
  injury
• Accurate diagnosis important
• Treatment starts with 4-8 wk NWB
• OR early screw fixation

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Navicular Stress Fractures

• Vague activity-associated midfoot pain
• Tenderness at the N-spot
• Bone scan and CT may have low sensitivity
  depending on technique
• Plain films rarely helpful
• At risk of non-union
• Treatment starts with NWB 6-8 week

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Calcaneus Stress Fractures

• Localized heel pain
• Squeeze test can help differentiate from
  bursitis, tendonitis, fasciitis
• Plain films positive at 2-4 weeks
• Treatment is relative rest and correction of risk
  factors
• Generally back to activity at 6 weeks

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Tibial Stress Fractures

• Differential Diagnosis
• Shin splints
• Partial tearing of the musculotendinous unit
  secondary to muscle fatigue because of repetitive
  stress
• Location is diffuse and in 1 of 2 areas
• Anterior compartment lateral to tibia
• Posteromedial border of the middle to lower third
  of the tibia

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Tibial Stress Fractures

• Differential diagnosis
• Medial tibial stress syndrome (MTSS)
• Exercise-induced pain usually along a 3-6 cm area
  over the posteriomedial edge of the distal
  one-third of the tibia
• Bone scan will be normal in Phase I and II, but
  may show mild uptake in Phase III, but the uptake
  is more diffuse than the focal uptake seen in a
  stress fracture
• Delayed films may show cortex hypertrophy

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Tibial Stress Fractures

• Differential Diagnosis
• Tendinitis
• Effort-related compartment syndrome
• Popliteal Artery Entrapment
• Bony or soft tissue neoplasms
• Radiculopathy
• Peroneal Nerve entrapment
• Saphenous nerve entrapment
• Venous thrombosis

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Tibial Stress Fractures

• Area of medial malleolus
• Tenderness over medial malleolus
• May have effusion if prolonged injury
• Radiograph may be helpful
• Treatment is immobilization 6 weeks
• Long Air Cast
• Walking cast
• Displaced fractures referred to surgery

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Tibial Stress Fractures

• Posterior-medial (most common)
• Focal tenderness along medial tibia
• Single leg hop test (up to 10 hops)
• Is tibial pain localized? (think stress fx)
• Or is it diffuse? (think MTSS/shin splints)
• Plain films not usually positive initially
• Treatment is relative rest until pain free
• May mean no running for 1-12 weeks depending on
  severity at presentation

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Tibial Stress Fractures

• Anterior Mid-Tibia
• Dreaded Black Line
• Prone to delayed/non-union and complete fracture
• Is the tension side, not the compression side
  of the tibia
• NWB for 6-8 weeks initially
• IM rod is indicated after 3-6 months of failed
  conservative therapy

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Tibial Stress Fractures

• Tibial plateau
• Less frequent than shaft/diaphysis fx
• Plain films may show 2-3 mm linear area of
  sclerosis
• MRI will show bone marrow edema of the medial
  tibial plateau before radiographic signs appear

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Fibular Stress Fractures

• Focal tenderness
• Usually in distal third of fibula
• MRI will show bone marrow edema
• Plain film may or may not be diagnostic
• Treatment is relative rest
• Return to activity is usually 6 wk

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Femoral Shaft Stress Fractures

• DDX includes muscle/tendon injury
• Hop test
• Fulcrum test downward pressure on distal femur
  while patient is sitting on edge of table will
  elicit pain
• Initial treatment is NWB with crutches,
  progressing to PWB
• Typically 12 weeks to full activity

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Femoral Neck Stress Fractures

• High-risk of displacement or AVN
• Vague hip or groin pain
• May have limited internal rotation
• Plain film followed by MRI if suspect
• Refer displaced fractures to surgery
• NWB with crutches or bed rest until able to
  tolerate WB without pain then progressive WB for
  2-3 months

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Pars interarticularis Stress Fx

• Most common at L5, but also at L4,3
• Localized unilateral LBP
• Worsened with extension or rotation
• Usually insidious onset with dull ache
• Scotty dog defect on oblique films
• Acute fractures may show on x-rays
• Single photon emission CT (SPECT)
• Treatment recommendations vary

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Treatment

• Phase I
• Pain control
• Relative rest or NBW as appropriate
• Modification of risk factors
• Investigation of bone health
• Maintain muscular strength and endurance without
  painful weight-bearing
• Referral to surgery for high-risk fxs

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Treatment

• Phase II
• Gradual return to regular activity
• Generally begin about a week after resolution of
  focal bony tenderness
• Continue strengthening program
• Continue modification of underlying risk factors
• Monitor for delayed healing or indication that
  surgery may be needed

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Treatment

• Long AirCast
• Immobilization for tibial stress fractures
• Probably reduces time to return to full activity
• Level of Evidence B

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Prevention

• The use of shock absorbing inserts in footwear
  probably reduces the incidence of stress
  fractures in military personnel, but there is
  insufficient evidence to determine the best
  design for the inserts
• Level of evidence B meta-anaylsis of 16 trials,
  most done on military trainees

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Prevention

• Modification of known risk factors prior to
  injury
• Review training schedule
• Review types of training
• Assessment of fitness, body composition,
  biomechanics, nutrition, and hormonal status
• Education about footwear
• Education about early symptoms

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Summary

• Risk factors for stress fractures
• Intrinsic factors
• Extrinsic factors
• Diagnosis
• HP and appropriate imaging
• Treatment
• Relative rest for most routine fractures
• NWB and/or referral for surgery for high risk
  fractures

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Summary

• Prevention by modification of known modifiable
  risk factors before injury occurs and education
  of athletes and those responsible for training is
  key
• Earlier treatment is associated with less
  morbidity and time lost from training

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Questions?

• Thanks for coming!