Femoral diaphyseal stress fractures: results of a systematic bone scan and magnetic resonance imaging evaluation in 25 runners

Abstract Objective : The purpose of this study was to evaluate femoral diaphyseal stress injuries in runners and to document the results of a systematic grading system based on magnetic resonance imaging (MRI) and radionuclide bone study. Design : A retrospective review of medical records and radiologic findings on patients seen between 1992–2002. Grading was preformed of triple phase bone scan and MRI results. Setting : Stanford University Medical Center, Sports Medicine Clinic. Patients : Twenty-five track and field varsity team members and recreational runners subsequently diagnosed with 31 femoral diaphyseal stress injuries. Outcome measures : Sixteen MRI's and 19 bone scans were evaluated with previously established grading systems. Results : Injury location in 31 femoral diaphyseal stress fractures included the proximal femur in 18 (58.1%), the midfemur in 11 (35.5%), and the distal femur in two legs (6.5%). MRI grading revealed grade I in two of 16 (12.5%), grade II in seven of 16 (43.8%), and grade III in seven of 16 (43.8%) runners. Radionuclide bone study grading revealed grade I in four of 19 (21.1%), grade II in nine of 19 (47.4%), and grade III in six of 19 (31.6%) runners. There was close correlation between grade of MRI and radionuclide bone study in the 12 athletes who had both exams, with 91.7% coincidence. Conclusion : These data of 25 femoral diaphyseal stress fractures show that women were more frequently affected than men and nearly half of these injuries occurred in first-year collegiate runners. The location was mainly in the proximal femur, on the compressive side of bone. If routine radiographs are negative, a radionuclide bone study or MRI with fat-suppression technique can be used to detect and grade bony changes in the femoral diaphyses and to help plan an appropriate rehabilitation program.