Stress Fractures

1. Stress Fractures Kevin deWeber, MD, FAAFP, FACSM Director, Military Sports Medicine Fellowship USUHS/Ft. Belvoir 2011 (many slides courtesy Dave Haight, MD

2. Outline • Pathophysiology • Risk Factors • Associations • Diagnosis • General Treatment • Treatment of High-Risk Cases

3. Stress fracture [stress frack-chur] • Break in a normal bone after it is subjected to repeated tensile or compressive stresses, none of which would be large enough individually to cause the bone to fail, in a person who is not known to have an underlying disease that would be expected to cause abnormal bone fragility.

4. Insufficiency Fracture[in-suh-fish-n-see frack-chur] • Fracture due to repeated compressive or tensile stresses in a bone whose mechanical strength is reduced due to a condition that is present either throughout the skeleton (osteoporosis, osteomalacia, osteogenesisimperfecta, etc.) or in a bony region (eg, demineralization in a limb due to disuse).

5. Pathologic fracture[path-o-lah-jickfrack-chur] • Fracture due to a localized loss of strength in a bone from a disease process immediately underlying the bone, eg, bone tumors , bone cysts, and infections.

6. PREVALENCE • 1% of general population get ‘em • 1-8% of collegiate team athletes get ‘em • Up to 31% of military recruits get ‘em • 13-52% of runners get ‘em

7. Most Common Sites of Stress Fractures • Tibia - 39.5% • Metatarsals - 21.6% • Fibula - 12.2% • Navicular - 8.0% • Femur - 6.4% • Pelvis - 1.9% • OTHER – 10.4% Weight- bearing

8. CAUSE • Change in load(force on the bone) • Small number of repetitions with large load • Large number of reps, usual load • Intermediate combination of increased load and repetition

9. PATHOPHYSIOLOGY • Stress fracture: imbalance between bone resorption and formation • Wolff’s Law: change in external stress leads to change in shape and strength of bone • bone re-models in response to stress • ABRUPT increase in duration, intensity, frequency without adequate rest (re-modeling) • Microfracture -> continued load -> stress fracture

10. Review of Risk Factor Types • Intrinsic: • Gender, genetics • Anatomical malalignment/ biomechanical • Dietary • Muscle weakness/imbalance • Extrinsic • Training errors • Equipment mismatch • Technique errors • Environmental • Sports-imposed deficiencies

11. INTRINSIC RISK FACTORSfor Stress Fractures • History of prior stress fracture • Low level of physical fitness • Female Gender • Menstrual irregularity • Diet poor in calcium and dairy • Poor bone health • Poor biomechanics

12. INTRINSIC RISK FACTORS cont • Prior stress fracture: • 6 x risk in distance runner and military recruits • 60% of track athletes have hx of prior stress fracture • One year recurrence: 13% • Poor Physical Fitness – [muscles absorb impact] • >1 cm decrease in calf girth • Less lean mass in LE • < 7 months prior strength tng

13. INTRINSIC RISK FACTORS cont • Why female gender? [1.2-10x] • Higher rates of other risk factors • Poorer bone health, Menstrual irregularity, disordered eating • Poor bone health: • Supplementing female military recruits with Ca and Vit D reduced stress fracture incidence • Lappe J, Cullen D, Haynatzki G, et al.. J Bone Miner Res 2008 • FamHx osteoporosis: 3x risk

14. INTRINSIC RISK FACTORS cont • BIOMECHANICAL FACTORS • Shorter duration of foot pronation • Sub-talar joint control • Tibial striking torque • Early hindfooteversion • Pescavus (unproven) • Pesplanus (unproven) Tibial stress Fractures (retrospective)

15. EXTRINSIC FACTORS • Increasing volume and intensity • Footwear • Older shoes • Absence of shock absorbing inserts • Running Surface?: mixed results • Treadmill vs Track • Activity type

16. ACTIVITY TYPE ASSOCIATIONS • Ballet: spine, femur, metatarsal • Runners: tibia, MT • Sprinters: navicular • Long dist runner: femoral neck, pelvis • Baseball, tennis: humerus • Gymnasts: spine, foot, pelvis • Rowers, golfers: ribs • Hurdlers: patella • Rowers, Aerobics: sacrum • Bowling: pelvis

18. Classic Clinical History • Gradual onset of pain over weeks to months • Initially pain only with activity • “can’t run through it” • Progresses to pain after activity • Eventually constant pain with ADLs • Change in training regimen • “too much too soon” • Change in equipment • Shoes, etc.

19. DIAGNOSIS: take a good History • Sports participation • Occupation • Significant change in training • Hills, surface, intensity • Dietary History: adequacy, Vit D, Calcium • Menstrual History • General Health • Past medical history • Medications • Family history (osteoporosis)

20. DIAGNOSIS: Examination “High-Speed Digital Imaging” • Localized tenderness to palpation in a location known to commonly sustain stress fractures • Fulcrum test? • Neither sensitive nor specific • Hop test? • Neither sensitive nor specific • Risky in high risk fractures • Tuning fork? • 43% sensitive, 49% specific

21. DIAGNOSIS: Biomechanical Evaluation • Leg length discrepancy • 70% incidence in patients w/ LE stress fractures • Joint range of motion and ligamentous stability • Muscle strength and flexibility • Limb alignment (eg, genuvarus or valgus) • Foot type (eg, pescavus or planus) • Gait analysis in shoes worn during physical activity • Core muscle strength (eg, abdominal, back, and hip musculature)

22. IMAGING: X-ray • Poor sensitivity • ~ 30% positive on initial examination • 4 Possible findings • Localized periostealelevation • Cortical thickening • Focal sclerosis • Radiolucent line • 10 - 20% never show up on plain films

23. Early Metatarsal Stress Fracture

24. One Week Later…..

25. Imaging: Bone Scan • Extremely sensitive • 95% show up after 1 day • Not very specific • up to 24% false-positive results (stress reaction) • Differentiate between acute and old lesions • Acute stress fracture: all three phases positive • Shin splint: delayed phase only

26. Imaging: CT scan • Excellent fracture line detail • More specific than bone scan • Useful for fracture age/non-union • Pars interarticularis, sesamoids, etc. • DOWNSIDE: high radiation dose

27. Imaging: MRI • Highly sensitive (= bone scan) • More specific than bone scan • still not perfect • Cost may be lower than bone scan some places • Non-invasive, no radiation • Sensitive for soft tissue injury • DOWN: less cortical bony detail than CT

28. Imaging: Ultrasound • Useful if fracture superficial • Shows hematoma, hypervascularity, periosteal elevation, cortical defect • Metatarsal fractures: sensitivity 83%, specificity 76% • Balal F, Gandjbakhch F, Foltz V et al. J Rheumatol 2009

29. MRI vs. bone scan, CJSM 2002 • MRI less invasive, provided more information than bone scan and recommended for initial diagnosis and staging of stress injuries • “Limited” MRI may be cheaper than bone scan at some institutions

30. RADIATION COMPARISON Study mSvrelative radiation Plain film foot <0.01 < 1.5 days Plain film CXR 0.02 2.4 days Plain film pelvis 0.7 3.2 mo Tech-99 bone scan 3 (150 CXR)1.2 yrs CT L-spine 6 (300 CXR) 2.3 yrs CT abd / pelvis 10 (500 CXR) 4.5 yrs

31. Differential Diagnosis • Muscle strains • Tendinopathy • Nerve entrapment • Medial tibial stress syndrome • Neoplasm • Infection

32. HIGH RISK STRESS FRACTURES • Talus • Tarsal navicular • Proximal fifth metatarsal • Great toe sesamoid • Base of second metatarsal • Medial malleolus • Pars interarticularis • Femoral head • Femoral neck (tension side) • Patella • Anterior cortex of tibia (tension side)

33. GENERAL TREATMENT for LOW-RISK STRESS FRACTURES • PROTECTION • Reduce pain • Promote healing • Prevent further bone damage • ACTIVITY MODIFICATION • Rest from painful activities 6-8 weeks (or until pain-free for two to three weeks) • Cross-training (non-painful exercise) • REHABILITATIVE EXERCISE • Flexibility, strength balance • BIOMECHANICAL CORRECTIONS

34. Early Treatment Speeds Recovery! • Evaluation < 3 weeks of sx onset: • 10.4 weeks to RTP • Evaluation > 3 weeks • 18.4 weeks to RPT • Ohta-Fukushima M, Mutoh Y, Takasugi S, et al. J Sports Med Phys Fitness 2002

35. ACTIVITY MODIFICATION • Activity should be pain free • Approximate desired activity • Cycle • Swim • Walk • Elliptical • Deep water running

36. REHAB EXERCISE and BIOMECHANICAL CORRECTIONS • Muscle flexibility • Strength training • Excessive pronation, pescavus, pesplanus • Limb Length Discrepancy • Replace running shoes every… <300 miles

37. Other Treatment Modalities • Ultrasound: unsure • 1 study no benefit, 2 studies + benefit • ECSWT: maybe—consider in high-risk sites • Worked in 1 small retrospective study • Medications: • Iloprost: 1 small retrospective study in subchondral stress fractures of knee • Capicitatively Coupled Electric Fields: • No benefit in recent RCT

38. HIGH RISK STRESS FRACTURES High risk for delayed union , nonunion, refracture • Talus • Tarsal navicular • Proximal fifth metatarsal • Great toe sesamoid • Base of second metatarsal • Medial malleolus • Pars interarticularis • Femoral head • Femoral neck (tension side) • Patella • Anterior cortex of tibia (tension side)

39. High-Risk Tibial Stress Fracture • Anterior, middle-third stress fractures are very concerning • Tension side of bone • May present like shin splints • Seen more commonly in jumpers and leapers • If you see “dreaded black line” on x-ray, poor prognosis

40. Management of High-Risk Tibial Stress Fx • 4-6 months of rest +/- immobilization • ? Therapeutic US or SWT • Surgery if not healing in 4-6 months • Intramedullary rod

41. Proximal 5th metatarsal stress fracture

42. Mgmt. of 5th Metatarsal Stress Fracture • Sxs <3 wks, neg x-rays: • Avoid WB activity; 5th MT unloader orthotic • Sxs > 3 wks or + x-rays • Cast, NWB x 6 wks OR • Screw fixation (faster RTP) • Non-union: Screw-it!

43. Lumbar Spondylolysis • Stress fracture of the pars interarticularis • Caused by repetitive hyper-extension • Often develops in the teenage or pre-teen years • May be bilateral

44. Sports Associated with Spondy • Football (offensive lineman) • Gymnastics • Wrestling • Diving • Tennis • Volleyball

45. Physical Exam- Spondy • Tenderness to palpation over spines > paraspinal muscles • Extension exacerbates pain “Stork test”—not very sensitive • Tight hamstrings- cause or effect?

46. Imaging Suspected Spondy • AP & lateral x-rays • r/o other bony causes • Obliques don’t change management • Also order SPECT bone scan • MRI not as sensitive • CT with fine cuts: prognostic • Acute vs sclerotic

47. Treatment- Spondy • Relative rest from painful activity • Physical Therapy referral • Williams flexion-based exercises: • Spine Surgeon referral • Anti-lordotic bracing • Brace 6 weeks - 6 months (controversial) • Return to activity in brace when pain-free • Surgery if fail treatment

48. Femoral Neck Stress Fracture • Vague anterior or medial groin/hip pain • Early diagnosis critical • Anterior hip tenderness • Log-roll pain • Pain with straight-leg-raise • If x-rays negative, order MRI • Crutches/NWB until ruled out! • MRI diagnostic imaging of choice for femoral neck stress fractures

49. Femoral Neck Palpation Iliopsoas bursa

50. Femoral Neck Stress Fractures • Compression side. • Inferior part of femoral neck • Less likely to become displaced • Complications possible • Treatment: • Fatigue line <50% neck width: Crutches/NWB until asymptomatic, then relative rest 4-6 wks • Fatigue line >50% neck width: surgical fixation