THE USE OF MR IMAGING IN THE ASSESSMENT AND CLINICAL MANAGEMENT OF STRESS REACTIONS OF BONE IN HIGH-PERFORMANCE ATHLETES
Section snippets
HISTOLOGIC GRADING OF STRESS FRACTURES AND THE INTRODUCTION OF AN IMAGING GRADING SYSTEM
As long ago as 1963, Johnson et al8 described the histogenesis of tibial stress fractures of various age. During the first week there was active osteoclastic resorption of the cortex, but decalcification, microfracture, microcallus, and osteocyte death was not apparent. During the second week, endosteal (and occasionally periosteal) callus formation was present. Johnson found that if the inciting activity was discontinued at this time, no actual fracture occurred. On the other hand, if the
THE MR GRADING OF STRESS PHENOMENA AND STRESS FRACTURES
It became obvious that MR imaging was not only just as sensitive in demonstrating early stress changes to bone, but was more specific than scintigraphy. Five years ago the authors proposed a similar MR grading system (Table 2). There are several MR sequences to demonstrate subtle marrow changes, and most of these depend on fat suppression. They go under a number of acronyms, which include FLASH (Fast, Low- Angle SHot), FISP (Fast Imaging Steady-state Precession), and STIR (Short Tau Inversion R
DIFFERENTIAL DIAGNOSIS OF STRESS FRACTURES ON MR IMAGING
Given the correct clinical setting, the diagnosis of stress fracture or stress injury is usually easy to substantiate; however, many different diseases and conditions can give rise to high signal on delayed T2, and, particularly, on fat-suppression sequences. Increased intramedullary signal on these delayed sequences represents early bone hemorrhage, marrow edema, or fluid, and can be seen in such things as early infection and in some early tumours, particularly those involving the marrow, such
EVERYDAY USE OF MR IMAGING IN THE ASSESSMENT OF INJURY IN ATHLETES
With the introduction of MR imaging, attention has begun to focus on abnormalities in the bone marrow signal as well as in the surrounding soft tissues. Initial reports described a broad band of altered signal in the marrow, containing a narrow fracture line and increased signal in the periosteum, which was thought to be characteristic of a stress fracture. A number of isolated case reports and small series have also confirmed these findings, but have also suggested a second, more amorphous
CLINICAL MANAGEMENT
Treatment of stress fractures using a classification system is predicated on the belief that bone follows predictable responses to external stress. If those external stresses increase, the pattern of bone biologic response continues. If the external stress is diminished or removed, a predictable pattern of bone healing will ensue.
A grading system and a standard treatment of lower extremity stress fractures have been used at the University of Minnesota since 1990 (this treatment protocol will be
THE CLINICAL USEFULNESS OF THE MR GRADING SYSTEM
The primary benefit of using the MR classification system as opposed to a bone scintigraphy grading system is its ease of use. It involves less time and no radiation. MR classification categories are more readily defined and understood by the radiologist and the clinician; however, MR imaging has additional usefulness to the clinician and to the athlete.
MR imaging also has the ability to define the duration of the injury to some extent. With bone scanning, it is difficult to determine the age
AT-RISK FRACTURES
The concept of at-risk fractures takes precedence over the aggressive approach to sport reentry as described previously. If the location of the lesion is in a critical anatomic site, consideration for the seriousness of a complete fracture has to be considered in regards to the aggressiveness of the treatment program. These fractures might include a long bone fracture with an intra-articular extension, a femoral neck stress fracture, or a tibial navicular fracture.
SUMMARY
Based on experience, the authors believe that MR imaging is a useful tool in the assessment and management of stress fractures and stress phenomenum of bone. The use of standard, graded MR evaluation aides the assessment of a repetitive stress injury to bone by allowing a more accurate diagnosis of bone injury. This more accurate assessment has predictive value in estimating the duration of disability. The use of a standard, graded MR evaluation aides the management of repetitive stress
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Address reprint requests to Harry J. Griffiths, MD, University of Minnesota Hospital and Clinic, Department of Radiology, 420 Delaware Street S.E., Minneapolis, MN 55455
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Departments of Orthopaedics and Radiology, University of Minnesota Hospital and Clinic, Minneapolis, Minnesota