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Kevin deWeber, MD, FAAFP, FACSM Director, Military Sports Medicine Fellowship USUHS/Ft. Belvoir 2011 (many slides courtesy Dave Haight, MD Slide 2 Outline Pathophysiology Risk Factors Associations Diagnosis General Treatment Treatment of High-Risk Cases Slide 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. Slide 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, osteogenesis imperfecta, etc.) or in a bony region (eg, demineralization in a limb due to disuse). Slide 5 Pathologic fracture [path-o-lah-jick frack-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. Slide 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 Slide 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% Slide 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 Slide 9 PATHOPHYSIOLOGY Stress fracture: imbalance between bone resorption and formation Wolffs 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 Slide 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 Slide 11 INTRINSIC RISK FACTORS for 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 Slide 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 Slide 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 Slide 14 INTRINSIC RISK FACTORS cont BIOMECHANICAL FACTORS Shorter duration of foot pronation Sub-talar joint control Tibial striking torque Early hindfoot eversion Pes cavus (unproven) Pes planus (unproven) Slide 15 EXTRINSIC FACTORS Increasing volume and intensity Footwear Older shoes Absence of shock absorbing inserts Running Surface?: mixed results Treadmill vs Track Activity type Slide 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 Slide 17 Slide 18 Classic Clinical History Gradual onset of pain over weeks to months Initially pain only with activity cant 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. Slide 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) Slide 20 DIAGNOSIS: Examination 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 High-Speed Digital Imaging Slide 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, genu varus or valgus) Foot type (eg, pes cavus or planus) Gait analysis in shoes worn during physical activity Core muscle strength (eg, abdominal, back, and hip musculature) Slide 22 IMAGING: X-ray Poor sensitivity ~ 30% positive on initial examination 4 Possible findings Localized periosteal elevation Cortical thickening Focal sclerosis Radiolucent line 10 - 20% never show up on plain films Slide 23 Early Metatarsal Stress Fracture Slide 24 One Week Later.. Slide 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 Slide 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 Slide 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 Slide 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 Slide 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 Slide 30 RADIATION COMPARISON Study mSv relative radiation Plain film foot 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 Slide 35 ACTIVITY MODIFICATION Activity should be pain free Approximate desired activity Cycle Swim Walk Elliptical Deep water running Slide 36 REHAB EXERCISE and BIOMECHANICAL CORRECTIONS Muscle flexibility Strength training Excessive pronation, pes cavus, pes planus Limb Length Discrepancy Replace running shoes every Slide 37 Other Treatment Modalities Ultrasound: unsure 1 study no benefit, 2 studies + benefit ECSWT: maybeconsider 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 Slide 38 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) High risk for delayed union, nonunion, refracture Slide 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 Slide 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 Slide 41 Proximal 5th metatarsal stress fracture Slide 42 Mgmt. of 5 th Metatarsal Stress Fracture Sxs3 wks or + x-rays Cast, NWB x 6 wks OR Screw fixation (faster RTP) Non-union: Screw-it! Slide 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 Slide 44 Sports Associated with Spondy Football (offensive lineman) Gymnastics Wrestling Diving Tennis Volleyball Slide 45 Physical Exam- Spondy Tenderness to palpation over spines > paraspinal muscles Extension exacerbates pain Stork testnot very sensitive Tight hamstrings- cause or effect? Slide 46 Imaging Suspected Spondy AP & lateral x-rays r/o other bony causes Obliques dont change management Also order SPECT bone scan MRI not as sensitive CT with fine cuts: prognostic Acute vs sclerotic Slide 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 Slide 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 Slide 49 Femoral Neck Palpation Iliopsoas bursa Slide 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: surgical fixation Slide 51 Femoral Neck Stress Fx Tension side: HIGH-RISK Superior cortex or tension side of neck High propensity to become displaced Frequent complications Treated acutely with internal fixation Slide 52 Tarsal Navicular Stress Fx: HIGH-RISK Consider in: Sprinters, Jumpers, Hurdlers, Basketball, Football Mean interval of 7 -12 months before diagnosis DONT BE THAT GUY WHO MISSES IT Vague mid-foot medial arch pain Foot cramping Slide 53 Slide 54 Tarsal Navicular Stress Fx X-rays usually negative MRI or thin-cut CT better than bone scan Slide 55 Tarsal Navicular Stress Fracture Meta-analysis 2010: NWB cast better than WB 6-8 weeks Semirigid orthotic during subsequent ambulation NWB trend better than surgery Torg JS, Moyer J, Gaughan JP, Boden BP. Am J Sports Med 2010. Nonunion/displacement: surgery Slide 56 Navicular Stress Fx Return to Play After casting, if no tenderness at the N spot, then can gradually return Reassess every 1-2 weeks, gradual return at 6 weeks if no symptoms AFTER 6 weeks of protection, 6 weeks of PT for strength and flexibility prior to return to run! Average return to play is 4-6 months Follow up radiography not helpful for return to activity Slide 57 Sesamoid Stress Fracture Risk: Sudden start-stop sports Repetitive forced dorsiflexion Slide 58 Sesamoid Stress Fracture Tx: NWB x 6 weeks with cast to tip of great toe to prevent DF Failure: Surgery (excision or grafting) Slide 59 Talus Stress Fracture Chronic pain after ankle sprain Location of fx: body near lateral process MRI or CT for best imaging Tx: 6-8 wks NWB in cast Failure to heal: Excision of lateral process Slide 60 Patella Stress Fracture Risk factors: cerebral palsy, hurdlers ACL reconstruction w/ BTB Tx if x-rays neg: Non-painful activity Tx if x-rays + or high-demand athlete K-wire fixation Slide 61 Femoral Head Stress Fracture Tx: NWB Ortho referral; high rate of arthroplasty Slide 62 Medial Malleolus Stress Fracture Seen in runners and jumpers Risk of non-union Tx if x-rays neg and MRI w/o fx line: SLWC or ankle brace; takes 4-5 MONTHS High-level athlete: surgery (FASTER RTP) Tx if x-rays + or non-union: Surgery Slide 63 Orthopedic Consultation High Risk Fracture sites High Level Athlete/Laborer Failed conservative therapy Slide 64 PREVENTION of STRESS FRACTURES Small incremental increases in training FITT Shock absorbing shoe/boot inserts Calcium 2000mg, Vit D 800 IU (27% decr.) Increased dairy products 62% decreased risk SF for each cup of skim milk Modification of female recruit training: Lower march speed Softer surface Individual step length/speed Interval training instead of longer runs ??: OCPs (sig increase in bone mineral density, no impact on stress fracture rate) NO: HCP selection of military recruits running shoes based on foot morphology 3 prospective studies by Knapik et al Slide 65 Israeli Army Prevention Study Shoe modifications, orthoses, and pharmacological treatment with risedronate not effective in lowering the incidence of stress fractures in Israeli army recruits Greater than 60% decrease in stress fractures was achieved by enforcing a minimum sleep regimen and lowering the cumulative marching during infantry training. FINESTONE, A., and C. MILGROM. How Stress Fracture Incidence WasLowered in the Israeli Army: A 25-yr Struggle. Med. Sci. Sports Exerc.2008. 40(11S):S623 S629 Slide 66 QUESTIONS?