Re:과사용증후군 - 스트레스 골절

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운동선수의 스트레스 골절에 대한 모든 자료

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 Stress fractures

A stress fracture can be defined as a partial or complete bone fracture that results

from repeated application of a stress lower than the stress required to fracture the

bone in a single loading [75,76].   Stress fractures develop when bone fails to adapt adequately to the mechanical

load experienced during physical activity. Ground reaction forces and muscular

contraction result in bone strain. Bone normally responds to strain by increasing the

rate of remodeling. In this process, lamellar bone is resorbed by osteoclasts,

creating resorption cavities, which are subsequently replaced with denser bone by

osteoblasts. Because there is a lag between increased activity of the osteoclasts and

osteoblasts, bone is weakened during this time. If sufficient recovery time is

allowed, bone mass eventually increases. If loading continues, however, microdamage

may accumulate at the weakened region. Remodeling is thought to repair

normally occurring microdamage. The process of microdamage accumulation and

bone remodeling, both resulting from bone strain, plays an important part in the

development of stress fractures. If microdamage accumulates, repetitive loading

continues, and remodeling cannot maintain the integrity of the bone; a stress

fracture may result [77] .

Stress fractures account for 0.7% to 20% of all injuries presenting to sports

medicine clinics [78] . Track and field athletes have the highest incidence of stress

fractures when compared with athletes in other sports such as football, basketball,

soccer, and rowing [79] . Great variation exists in the absolute percentage of stress

fractures reported at each bony site, but the most common sites seem to be the tibia,

followed by the metatarsals and fibula [75] . The site of stress fractures also appears

to vary from sport to sport. Among track athletes, navicular stress fractures

predominate; tibial stress fractures are most common in distance runners; and

metatarsal stress fractures predominate in dancers [75] .

Although numerous risk factors for stress fractures have been proposed,

research is needed to confirm‎ anecdotal observations. Presently, most studies in

athletes are case series, and are confined to injured groups only, or are crosssectional

designs that do not allow the temporal relationship between risk factor

and injury to be assessed. Results from large military epidemiological studies

cannot be readily generalized to athletes, given important differences in training,

fitness level, footwear, and services. These results may provide additional insight,

however, especially given the deficiencies in the athletic literature [77] .

One important risk factor is that of a history of a previous stress fracture. Low

bone density is an identified risk factor in women, although this has not been as

clearly studied in men [77,80] .Women in the military appear predisposed to stress

fractures compared with their male counterparts, but this has not necessarily been

confirmed in athletes. Overall training levels may influence this result [75] .

Menstrual irregularity, in particular amenorrhea of longer than 6 months duration,

is a risk factor [77,81] . A family history of osteoporosis is considered to be a risk

factor for low bone density and osteoporosis in both females and males, but it is not

clear that this necessarily predisposes to stress fractures in athletes [77,82,83] .

Nutritional status, in particular low calcium intake, may contribute to stress

fracture. Other dietary factors such as fiber, protein, alcohol, and caffeine intake

may play a role but have not been as well studied [77] .

Biomechanical factors may predispose to stress fractures by creating areas of

stress concentration in bone or promoting muscle fatigue. High arches may  predispose to increased risk for femoral and tibial stress fractures, whereas pes

planus may predispose to metatarsal stress fractures [77,84–86] . Leg length

inequality has been postulated as a risk factor. Friberg reported a higher incidence

of tibial, metatarsal, and femoral fractures in the longer leg and a higher incidence

of fibular stress fractures in the shorter leg in military recruits [87] . A leg-length

discrepancy has also been reported to be associated with a higher incidence of stress

fractures in athletes [77,88,89] . In particular, a leg-length inequality of greater than

0.5 cm was reported in 70% of women with stress fractures, compared with only

36% of women without stress fractures [89] . Other biomechanical variables linked

to increase stress fracture risk have included hip external rotation of greater than

65 [90] , greater forefoot varus, restricted ankle joint dorsiflexion, narrow transverse

diameter of the tibial diaphysis, and smaller calf circumference measurement

[79,90,91] . No studies have reported the effects of such physiological factors of

muscle mass or muscle strength on predisposition to stress fracture [77] . Additionally,

no consistent relationships have been observed between body size or composition

and stress fracture risk.

Anecdotal observation and clinical case series suggest that a transition in

training, in particular increasing mileage, as well as a higher absolute volume of

training can predispose to stress fractures in athletes, although little controlled

research has examined this aspect [77] . Additionally, although no data exist on how

stress fracture risk is specifically affected by training surface, it may be prudent

to advise athletes to minimize the time they spend training on hard, uneven surfaces

[75] .

A higher incidence of stress fracture was reported in military recruits using older

or worn running shoes [92] . It is unclear if this is a direct result of decreased shock

absorption or perhaps decreased mechanical support [75] . Reports are conflicting

about whether or not insoles can prevent stress fractures. From a practical

standpoint it is important for individuals to train in shoes appropriate for their foot

type. Athletes with high arched rigid feet should select cushioned shoes. Athletes

with low arches should select shoes providing stability and motion control [75] .

A patient with a stress fracture typically presents with a history of insidious

onset of activity-related pain that progressively worsens over time. The most

obvious physical examination feature is localized bony tenderness. Special clinical

tests, such as the ‘‘hop test’’ for femoral stress fracture and spinal and hip extension

used in diagnosis of pars stress fractures, may be helpful. Clinical reports have

suggested that the application of ultrasound or a vibrating tuning fork may be

helpful in the diagnosis of stress fractures by increasing pain at the fracture site;

however, current literature neither supports nor refutes these commonly used

clinical tools.

Commonly used imaging studies include radiographs, bone scans, and MRIs. In

approximately two thirds of symptomatic patients, radiographs are initially

negative and only half ever develop positive radiograph findings [93] . The most

common sign in early stress fracture is a region of focal periosteal bone formation.

The gray cortex sign (a cortical area of decreased density) may also be seen [94,95] .

In those cases where clinically indicated, advanced imaging such as a bone scan or   MRI should be employed to confirm‎ the diagnosis. Bone scans will confirm‎ the

diagnosis as early 2 to 8 days after the onset of symptoms [96] . MRI has shown

promise in grading progressive stages of stress fractures severity. A four-stage

grading system has been developed: grade 1 injuries demonstrate periosteal edema

on the fat-suppressed images, grade 2 injuries demonstrate abnormal increased

signal intensity on fat-suppressed T-2 weighted images, and in grade 3 injuries

decreased signal intensity is seen on T-1 weighted images. In grade 4 injuries, an

actual fracture line is present, typically visualized on both T-1 and T-2 weighted

images [94,96] .

Stress fractures can be generally classified as noncritical and critical. Noncritical

stress fractures in the lower leg, foot, and ankle include the medial tibia, fibula, and

metatarsals 2, 3, and 4. Treatment of these stress fractures requires relative rest.

Athletes may benefit from a short period of immobilization in a walking boot (ie,

3 weeks), or in the case of metatarsal stress fractures, from a stiff sole shoe or steel

insert. Return to full sport activity is generally achieved within 6 to 8 weeks.

Critical stress fractures require special attention due to a higher rate of nonunion,

and include the anterior tibia, medial malleolus, talus, navicular, fifth metatarsal,

and sesamoids [75,77] .

Medial tibia

 Stress fracture of the medial tibia present with medial shin pain aggravated by

exercise. Tenderness is most commonly localized in the posteromedial border of

the lower third, which is the most common site. Biomechanic examination may

reveal either a rigid, high-arched foot that is incapable of absorbing load, or an

excessively flat foot that causes muscle fatigue. Treatment involves relative rest

until the pain resolves. Athletes may benefit from a short period use of either a

walking boot or pneumatic brace (an air cast), which may be removed for

nonimpact cross training. The air cast brace is believed to unload the tibia by

compressing the lower leg, thus redistributing forces and decreasing the amount of

tibial bowing [75,97–99] . Bony tenderness typically disappears between 4 to

8 weeks, after which the athlete may begin a gradual return to activity.Although the

time to return to full activity varies considerably, the average period for full release

to sport activity is 8 to 12 weeks.

Anterior cortex of the tibia

 Stress fractures of the anterior cortex of the midshaft of the tibia are among the

critical stress fractures because they are prone to delayed union, nonunion, and

complete fracture. As with other stress fractures, in the acute phase plain radiographs

are often normal and diagnosis may require bone scanning or MRI. In later

stages, plain radiographs may demonstrate the ‘‘dreaded black line.’’ This

appearance is due to bony resorption, and indicates nonunion. At this late stage,

bone scanning will often be normal and patients may only have minimal symptoms

and thus may be fully participating in sports. It is believed that the mid anterior

cortex of the tibia is vulnerable to nonunion due to poor vascularity and increased  tension because of morphologic bowing of the tibia [75] . Treatment programs have

included prolonged periods of rest and immobilization (up to 4 to 6 months), bone

stimulation, and surgery. Brukner recommends the use of a long pneumatic leg

brace combined with electric stimulation for 10 hours per day for both the acute

stress fracture and the established nonunion, as denoted by the presence of the

dreaded black line on plain radiographs. Fracture healing is monitored both

clinically and radiographically. Athletes do not return to activity until evidence

exists of cortical bridging on radiography. If after 4 to 6 months there is no evidence

of healing either clinically or radiologically, surgical intervention is indicated

(drilling at the fracture site, bone grafting, or insertion of an intramedullary

rod) [75] .

Fibular stress fractures

 Because the fibula has a minimal role in weight bearing, it is believed that fibular

stress fractures result from muscle traction and torsional forces. Although most

stress fractures are in the distal third of the fibula, proximal stress fractures have

been described. Patients are treated with weight bearing rest until bony tenderness

resolves (usually 4 to 6 weeks). Athletes may benefit from a short period (ie,

3 weeks) in a walking boot. Sport activity is then gradually commenced. Soft tissue

tightness should be corrected, as should biomechanical abnormalities such as

excessive pronation or excessive supnation [75] .

Medial malleolus

 Medial malleolar stress fractures generally present with a several-week history

of mild discomfort followed by an acute episode that results in seeking medical

attention. Although the fracture line is frequently vertical from the junction of the

tibial plafond and the medial malleolus, it may run obliquely from the junction to

the distal tibial metaphysis [75] . Excessive pronation and accompanying tibial

rotation distributes excessive forces to the medial malleolus.

Undisplaced or minimally displaced stress fractures of the medial malleolus are

treated conservatively in a pneumatic leg brace for 6 weeks. A displaced fracture or

a fracture that progresses to nonunion should be treated operatively.

The talus

 Talar stress fractures most commonly involve the lateral body near the junction

of the body with the lateral process of the talus. Talar neck stress fractures have

been reported but are considered rare. Athletes may present with prolonged pain

(for several months) following an ankle sprain despite rehabilitation. Excessive

subtalar pronation is felt to predispose to talar stress fractures by allowing

impingement of the lateral process of the calcaneus on the concave posterolateral

corner of the talus. Treatment involves non-weight–bearing rest for 6 weeks

followed by rehabilitation. Orthotic control of pronation is recommended if present.

Nonunion fractures respond well to surgical excision of the lateral process [75] . 

 The calcaneus

Calcaneal stress fractures present with localized tenderness over the medial or

lateral aspects of the calcaneus. The most common site is the upper posterior

margin, just anterior to the apophyseal plate and at a right angle to the normal

trabecular pattern. Plain radiographs may show a sclerotic appearance on lateral

radiograph parallel to the posterior margin of the calcaneus. Bone scanning and

MRI are more sensitive. Treatment is achieved with 6 to 8 weeks of weight-bearing

rest with the use of a soft heel cushion. Joint mobilization and flexibility of the calf

muscles are indicated when appropriate. Orthotics may be prescribed to control

excessive pronation. Running is usually resumed after 6 weeks.

 The cuboid and cuneiforms

Stress fractures of cuboid and cuneiform bones are rare. These are generally

considered noncritical stress fractures that may be treated with weight-bearing rest

until bony tenderness resolves, after which a gradual return to sport activity is

commenced. As for other noncritical stress fractures, a short period in a walking

boot may provide comfort. One report did propose a period of non-weight–bearing

on crutches for 4 weeks for a cuboid stress fracture, followed by progressive weight

bearing and return to sport activity at 8 weeks [75,100].

 The navicular

Navicular stress fractures occur most commonly in the central third, which is

believed to be susceptible to stress fracture and subsequent delayed union or

nonunion because of relative avascularity and the presence of shear forces in this

region. Pain is typically insidious in onset and somewhat nonspecific in location.

Critical to clinical examination is palpation of the ‘‘N’’ spot in the proximal dorsal

portion of the navicular. Plain radiography has low sensitivity and advanced

imaging such as bone scan, computed tomography (CT), and MRI should be

pursued early in suspected cases. Initial treatment requires 6 weeks of non-weight–

bearing immobilization. If at this point clinical tenderness remains, another 2 weeks

may be required. Patient should then undergo a gradual return to activity coupled

with physical therapy for joint mobilization, soft tissue work, muscle strengthening,

and biomechanical correction. Patients that do not respond to the conservative

treatment regimen undergo surgery (screw fixation with or without bone grafting of

the established nonunion) [75,77,101].

 Metatarsals

Metatarsal stress fractures involving metatarsals 1, 3, 4, and the distal aspect of

metatarsal 2 are usually uncomplicated and can be treated with relative rest.

Patients may benefit from a walking boot or the use of a steel plate insert or

counterforce arch brace. Once tenderness to palpation and pain with ambulation

has resolved, a gradual return to running program is commenced. Fractures  of the base of the second metatarsal and proximal fifth metatarsal require special

consideration.

Stress fractures at the base of the second metatarsal are most common among

ballet dancers. Most of these fractures can be treated with weight-bearing rest but

patients must refrain from training activity for 6 weeks.

Three types of proximal fifth metatarsal stress fractures have been described:

(1) the tuberosity avulsion fracture, (2) the Jones fracture at the junction of the

metaphysis and diaphysis, and (3) the diaphysial stress fracture [75] .

The most common fracture seen is a simple avulsion fracture of the tuberosity,

usually caused by the contraction of the peroneus brevis tendon as a result of an

acute inversion injury or the lateral band of the plantar aponeursis. This is usually

an uncomplicated type of fracture that will respond to a short period of immobilization

for pain relief, followed by progressive activity. The Jones and more distal

diaphyseal stress fractures are critical stress fractures prone to nonunion and require

6 to 10 weeks of non-weight–bearing rest. Athletes that fail to heal conservatively

or those who require more rapid treatment undergo surgical fixation with placement

of a fixation screw. Displaced fractures may require open reduction internal

fixation. After screw fixation, progressive weight bearing is initiated at 2 weeks,

with return to running in 7 weeks. When bone grafting is used, running activities

are delayed for 12 weeks to allow for bony healing.

The sesamoids

 The medial and lateral sesamoid bones at the first metatarsal phalangeal (MTP)

joints act to increase mechanical advantage of the flexor hallucis brevis tendon and

stabilize the first MTP joint in association with the plantar plate capsule. They also

protect the flexor hallucis longus tendon and absorb weight-bearing stress on the

medial forefoot. The medial sesamoid bone is more commonly affected. Radiographs

are often negative and diagnosis may require advanced imaging. A bone

scan or MRI is also useful in differentiating a bipartite sesamoid from a true stress

fracture. Stress fractures of the sesamoid bones are prone to nonunion. Treatment

involves non-weight–bearing rest for 6 weeks. Weight bearing is commenced

when bony tenderness is no longer present. Padding is used to distribute weight

away from the sesamoid bones in the form of a sesamoid or dancer pad. If nonunion

occurs, or if the bone is splintered, excision is recommended [75] .