Fatigue fractures are a type of stress fracture, and are due to abnormal stresses on normal bone. They should not be confused with an insufficiency fracture, which occurs due to normal stresses on abnormal bone. Plain films typically demonstrate a linear sclerotic region. MRI is the most sensitive and specific modality. Bone scan is sensitive but not specific.
Some authors 3 use the term stress fracture synonymously with fatigue fractures, and thus some caution with the term is suggested.
The demographics are usually young active patients, with specific locations having different demographics in keeping with the associated activity 2.
The abnormal stresses result in repeated microfractures at sites of structural weakness and incomplete healing results with repeated injury. These are typical in athletes.
In many cases of lower limb fractures, bilateral abnormalities are present, whereas in the upper limb they are more frequently unilateral.
pelvis and lower lower limb (most common)
- medial neck of femur
- compressive forces
- ballet, running, gymnastics
- pubic rami / obturator ring
- bowling, gymnastics, stooping
- medial neck of femur
- proximal in children
- mid to distal in adults 2
calcaneum (case 1)
- bilateral in up to 27% of cases
- jumping/landing on heels/prolonged standing
metatarsals (case 2)
- marching/prolonged standing/ballet
- sesamoid of great toe
- prolonged standing
- upper limb
- spinous processes of C6, C7, T1, T2
- trap shooting
- chronic cough, golf, carrying heavy pack
- coronoid process of ulna
- propelling wheelchair, throwing javelin
- hook of hamate
- racket sports, golf
Early diagnosis is best made with bone scan or MRI, as plain films may appear normal for some time.
- initially normal
- periosteal reaction progressing to callus formation in diaphyseal fractures
- linear sclerosis and cortical thickening more common in metaphyseal and epiphyseal fractures 2
MRI is as sensitive as bone scanning but is of higher specificity, both in isolating the exact anatomic location and in distinguishing fractures from tumours or infection.
- low marrow signal
- enhancement can be prominent
- T2: high marrow signal with extension into adjacent soft tissues
There is increased activity at the site of fracture.
Treatment and prognosis
Treatment depends on the location and whether the fracture is complete or incomplete.
Options therefore include: conservative management, plaster cast, internal fixation. Most importantly change in behaviour to reduce the activity which has lead to the fracture is needed. In some instances altered technique may be sufficient to prevent re-occurrence.
- 1. Kaplan PA, Dussault R, Helms CA et-al. Musculoskeletal MRI. Saunders. (2001) ISBN:0721690270. Read it at Google Books - Find it at Amazon
- 2. Burgener FA, Kormano M, Pudas T. Bone and Joint Disorders. Thieme. (2006) ISBN:1588904458. Read it at Google Books - Find it at Amazon
- 3. Greaney RB, Gerber FH, Laughlin RL et-al. Distribution and natural history of stress fractures in U.S. Marine recruits. Radiology. 1983;146 (2): 339-46. Radiology (abstract) - Pubmed citation