Book readingROCKWOOD

p.670~674

R3 李偉群

Scintigraphy

• Suspected multiple stress fracture

• Plain film do not surpport

• Sensitivity approaching 100%, specificity not coupled

Stress fracture

Scintigraphy

• Isotopes: radiactive decay

• Tc-99m MDP: Gamma radiation, 6-hour half life

• Whole body dose: 0.13~0.19 rad

• Bladder dose: 2.62~3.90 rads

Stress fracture

Scintigraphy

• Normal: Blood flow• Stress fracture: new bone formation• 3 phases: 2 early 1 delayed

– Immediately: Blood perfusion to bone and soft tissue (contrast angiography)

– 2’~5’: blood pool scan, soft tissues or extravascular space (hyperremia and capillary permeability)

– 2~4 hours: skeleton, 50% diphosphate tracer adsorbed on hydroxyapatite matrix of bone (new bone formation)

Stress fracture

Scintigraphy

• Stress fracture: all three phases, especially third phase

• Periostitis: only on delayed image• Soft tissue: only in the first two phases

• Local uptake: Osteoid osteoma, other bone tumors, osteomyelitis, bone infarc, and bony dysplasias

Stress fracture

Scintigraphy

• Positive within hours of a bone injury

• Acute stress fractures: all three phases

• Bony healing: initial phase perfusion scan normalizes first; few weeks, second-phase normal; 3~6 months, third-phase gradually diminish, may last up to 1 year

Stress fracture

Bone scan grading system

1 Small, ill-defined cortical area of mildly increased activity MRI: Periosteal edema: mild to moderate on fat-suppressed T2 or STIR images; marrow is normal on T1 and fat-suppressed T2 or STIR images

2 Better-defined cortical area of moderately increased activityMRI: Periosteal edema moderate to severe on fat-suppressed T2 or STIR images; marrow edema on fat-suppressed T2 or STIR images

3 Wide to fusiform, cortical-medullary area of highly increased activity MRI: Periosteal edema: moderate to severe on fat-suppressed T2 or STIR images; marrow edema on T1 and fat-suppressed T2 or STIR images

4 Transcortical area of intensely increased activity MRI: Periosteal edema moderate to severe on fat-suppressed T2 or STIR images; marrow edema on T1 and fat-suppressed T2 or STIR images; fracture line clearly visible

Stress fracture

SPECT scanning

• Suspected lumbosacral stress fracture

• 3-D images

• Suspected pars interarticularis and sacral stress fracture

Stress fracture

MRI

• Better specificity: precise anatomic viscualization

• bony tissue, with comparatively few mobile protons, is not represented in significant detail

• accentuates reactive edema in the soft tissues and marrow surrounding a stress injury – fat-suppressed T2-weighted – short tau inversion recovery (STIR) scans

Stress fracture

MRI

• Not involve exposure to ionizing radiation and require much shorter imaging times than bone scintigraphy

• More difficult diagnostic dilemmas or problematic cases may well warrant MRI scanning

Stress fracture

CT

• provide excellent bony anatomic detail• fracture line orientation-> 3-D CT

information, which may improve treatment decisions for certain bones such as the tarsal navicular

• Longitudinal fracture lines in diaphyseal • Pars and sacral stress fractures are

also well characterized with CT scans

Stress fracture

Treatment

• Initial management is modified rest to allow the bone remodeling process to equilibrate

• The inciting strain must be eliminated in order to break the cycle of accelerated resorption, allowing new bone formation to catch up and adequately repair the focus of stress fracture

• Earlier initiation of rest– athletes, alternative training – nonathletes, a brief rest period

Stress fracture

Treatment

• During this first treatment phase, remediable risk factors should be addressed.

• Braces or other forms of immobilization are seldom needed. No controlled study strongly supports adjunctive measures akin to external electrical stimulation or ultrasound

• For high-level athletes, early pool running programs prove highly successful at maintaining baseline fitness during the rest phase

Stress fracture

Treatment

• Second-phase rehabilitation begins when pain is substantially diminished or absent

• Lower-extremity injuries: 2 weeks after painless walking

• The training program – progressive aerobic conditioning with specified

rest times to permit bone compensation for the slowly increasing strains.

– Cross training is advisable to reduce the likelihood of recurrence .

Stress fracture

Femoral neck• Young: inferior or medial neck lesions

(compression-side)• Older: superior fractures (tension-side), more

likely to fail and displace with continued activity • Activity-related diffuse groin or anterior hip pain

and have pain at the limits of hip rotation on examination.

• MRI scans > scintigraphy : provide differential information for other causes of hip pain such as tendonitis, bone cysts, or avascular necrosis of the femoral head

Stress fracture

Femoral neck

• Stage 1 or 2: modified rest protocol beginning with an initial period of non-weight bearing until pain resolves.

• Stage 3 of compression side demonstrating a nondisplaced cortical crack, are still stable and can be managed nonoperatively

Stress fracture

Femoral neck

• Tension-sided stage 3: complete unloading and frequent clinical and radiographic follow-up to document healing. Some investigators support stabilization with cannulated screw fixation for this injury.

• Stage 4 injuries (widening of the cortical crack or even frank displacement of the completed fracture): operative stabilization.– Nondisplaced complete fractures:multiple screws – Young: emergent ORIF (no delay, no varus malreduction)– Older: consider hip arthroplasty

Stress fracture

Femoral shaft

• Most athletes: proximally in the medial or posteromedial cortex

• Vague activity related anterior thigh pain is the typical complaint, and vigorous stressing on physical examination can reproduce the pain.

• These lesions occur in sites of compressive stress, are stable, and heal with modified rest protocols. Only catastrophic complete failures require reamed intramedullary stabilization.

Stress fracture

Tibia

• Most commonly among lower-extremity• Other overuse injuries:

– Inflamation of aponeurotic tenoperiosteal origins of the tibialis posterior

– soleus and fascial attachments to the posterior medial border of the tibia (shin splints)(medial tibial stress syndrome): medial border, improves after warm up, and is worse in the morning.

– Exertional compartment syndromes of the anterior or deep posterior compartments: muscle aching and subjective tightness that increase shortly after exercise begins.

Stress fracture

Tibia

• Progressive, with a gradual onset exacerbated by exercise and worse with impact,Tenderness is localized and bony

• Most posteromedial compression injuries and usually occur in the proximal or distal thirds

• Transverse orientation is typical but longitudinal stress fractures are also reported

Stress fracture

Tibia • Cessation of the repetitive loading activity• Complete leg rest using crutches • Surgery is not required for this condition, but

return to activity can take up to 3 months• Middle-third of the anterior cortex: tension-

side, repetitive stress of jumping– Bone pain & palpable periosteal thickening– frequently progress to nonunion, and complete

fractures – In chronic cases, a transverse, wedge-shaped

defect

Stress fracture

Tibia

• Initial: prolonged modified rest, with or without cast or brace immobilization– however, even over 4 to 6 months, many fractures

with chronic changes and anterior fissures or cracks will remain symptomatic and nonunited.

• Transverse drilling of the nonunion sites• Reamed intramedullary nailing works well for

recalcitrant cases, and now has some support as the initial treatment of choice for the anterior cortical stress fracture nonunion

Stress fracture

Medial malleolus

• Repetitive running and jumping activities• Bony tenderness and ankle effusion • Vertically oriented fracture line originates at

the junction between the malleolus and plafond directly above the medial border of the talus (cyclic force transmitter)

• For grade 1 and 2 injuries, impact avoidance in a cast or pneumatic brace achieves return to function in 6 to 8 weeks.

Stress fracture

Medial malleolus

• For grade 3 and 4, similar conservative measures are appropriate, but healing may take 4 to 5 months.

• More aggressive intervention is also supported depending on the injury chronicity and the demands of the patient.

• Drilling may enhance healing • Screw fixation for displaced fractures, nonunion,

chronic cases, and elite performers allows early motion and may promote earlier return to activity

Stress fracture

Text book reading-Rockwood

Chapter 21

Stress fracture

Tarsal Navicular

• Repetitive running and jumping activity

• medial arch, dorsal navicular tenderness

Tarsal Navicularavascular central third of the bone, originating at the proximal dorsal articular surface and extending in a plantar distal direction

Tarsal NavicularT1-weighted MR image of the right ankle of a collegiate basketball player shows a navicular stress fracture (arrow) originating at the talonavicular joint surface.

Tarsal Navicular

• 6 weeks of non–weight-bearing cast immobilization--high union rates

• weight-bearing immobilization heal-- much higher risk of delayed union and recurrence

• Compression screw with supplemental bone graft

Metatarsals

• distance runners and ballet dancers

• second metatarsal neck is the most likely site

• gradually worsening forefoot pain

Metatarsals

• second metatarsal plantar base-- en pointe position

Metatarsals

• proximal diaphysis of the fifth metatarsal--basketball players

• 6- to 8-week course of non–weight-bearing cast immobilization

• Sliding bone graft procedures and intramedullary compression screw fixation

Metatarsals• Middle-aged recreational

runner with a several-month history of worsening activity-related lateral foot pain. A. Intermediate delayed union fifth metatarsal stress fracture with a complete fracture, some widening of the cortical gap, and moderate medullary sclerosis. B. Radiographic appearance 3 months after medullary drilling, bone grafting, compression screw stabilization, and an initial period of non-weight bearing.

Other Sites

• Patella stress fractures--Runners and jumpers --extension immobilization for 4 weeks

• Fibula stress--runners 1 to 2 inches above the ankle joint line

• Lateral process of the talus, calcaneal tuberosity, cuboid, and cuneiform

Upper Extremity

• non–weight-bearing bones--recurrent loading activities

• upper extremity sports athletes• humerus --baseball pitchers• olecranon-- throwing sports or gymnastics• distal radial --young gymnasts• metacarpals--

Pelvis

• pubic rami-- female distance runners

• sacral-- distance runners

Book reading

Stress fracture

• Introduction: Breithaupt's 1855 initial account describing a syndrome of painful swollen feet among marching Prussian soldiers.

• Stress fracture: substantial numbers noted for participants in gymnastics, ballet, figure skating, basketball, crew, soccer, and lacrosse.

• United States military recruits develop lower-extremity stress fractures at a gender-dependent rate of up to 4% in men and 7% in women

• stress fractures: normal bone subjected to abnormal or unaccustomed stresses.

• Insufficiency fractures: normal stresses applied to abnormal bone produce fracture.

Pathophysiology

• Ground and joint reaction forces as well as muscle forces stress the bone by applying force across unit areas of bone.

• Wolff's law: Normal loads delivered to normal bone produce normal bone remodeling – initial osteoclastic bone resorption– osteoblastic new bone formation within cortical bone, as well as on

the trabeculae of cancellous bone.• Peaks at 3 weeks• Complete the remodeling cycle ( 3 months)• Optimally loaded and enough time:bone becomes stronger • Repetitive loading: Resorption-dominated accelerated

remodeling process that actually weakens the bone resulting in focally increased remodeling space or porosity and decreased bone mass..

Symptom and sign

• History of load-related pain• Gradual onset of vague pain over a period of weeks during

training.• Initially described as mild and present only during the stress or

activity. • The symptoms very often occur during the first few weeks after

an increase in training volume or intensity, a change in technique or surface, or an alteration of footwear.

• For nonathletes, a recent atypical increase in activity may be described.

• History of previous stress fractures or other painful sites, and the presence of eating disorders, leg length discrepancy, or muscle imbalance should be evaluated. In the female patient, age of menarche and presence of menstrual irregularities must be considered.

Symptom and sign

• For athletes, training regimen alterations are usually the root cause of the pain. Focal bone pain with palpation and stressing

• Percussion of the bone typically produces pain, but passive and active range of motion of adjacent joints does not.

• Femoral diaphyseal fractures occur typically in the medial cortex, so lateral thigh pain is not likely to be correlated with a stress fracture.

Risk factor

• Increase in training frequency and intensity • low bone density may be a risk factor for

women • Smaller bone size • Leg length discrepancy • Age • Female athelete triad

– Menstrual disturbance– Eating disorder– osteopenia

X-ray

• Findings rarely appear before 2 to 3 weeks from the onset of symptoms.

• New periosteal bone formation(3 months)• In some patients, radiographic changes never appear for a number of

stress sfractures.• Only 20% of bone scan foci positive for stress fractures correlate with

positive plain film findings. • X-ray finding:

– periosteal bone formation– horizontal or oblique linear patterns of sclerosis– endosteal callus, and a frank fracture– A late-stage stress fracture in cortical bone appears as a radiolucent line

with extension partially or completely across the cortex. – cancellous bone demonstrate a fracture lucency oriented perpendicular to

the trabeculae.

X-ray

• Plain films are most likely to present positive findings in the fibula and metatarsals.

• Some investigators contend that plain films are unlikely to yield positive results when investigating possible tibial stress fractures, and others state the femur, pars, and tarsal bones are least likely to yield remarkable findings on initial plain film investigation.

Scitingraphy• When x-ray findings are conclusive, additional studies are not required. • Imultiple sites of stress fracture are possible based on history and physical

examination, or if plain films do not support the presumptive diagnosis of stress fracture, three-phase bone scintigraphy has been the study of choice. Bone scan has long been considered the most sensitive test for stress fracture, with sensitivity approaching 100% , but the sensitivity is not coupled with high specificity, so clinical features must be correlated.

• Technetium-99m methylene diphosphonate (99mTc MDP) is the usual radioisotope utilized for bone scans. Gamma radiation is emitted, and the whole body dose for a bone scan is about 0.13 to 0.19 rad. The bladder dose, where the radioactivity is concentrated in the urine, is 2.62 to 3.90 rads, hence the need for frequent voiding during and after the scanning period.

• The mechanism of uptake in bone is not precisely elucidated, but blood flow to the bone is a fundamental requirement.

– In normal bone, uptake is in proportion to blood flow to the bone.– In abnormal situations such as stress fractures that are accompanied by high bone

vascularity, factors other than bone blood flow play a larger role in radiotracer uptake. New bone formation proves to be the most important factor in the uptake,

• Given a correlating history and physical examination, the scintigraphic diagnosis of stress fracture is made by focal increased uptake on the third-phase images.

• Stress fractures are positive on all three phases, but• periostitis develops positive foci only on the delayed images • Other soft tissue injuries are positive only in the first two phases, allowing some

differentiation between bony and soft tissue pathology;.• Radionuclide scans can be positive within hours of a bone injury. Acute stress

fractures are positive on all three phases. As bony healing proceeds, the initial phase perfusion scan normalizes first. Within the ensuing few weeks, the blood pool second-phase images return to normal. Because bony remodeling continues for an extended time period, focal uptake on the delayed images resolves last..

• A grading system, based on the scintigraphic appearance, allows classification into milder or more severe stress fractures, recognizing that these stress injuries occur along a continuum of bony involvement

• The minimally symptomatic grade 1 or grade 2 stress fractures typically resolve more quickly and completely. The grading system can assist in prescribing the requisite rest and rehabilitation