Clinical Quiz Answer

A Unique Leg Injury in a Dancer

Deborah Cudnowski, MD
Peter J. Carek, MD, MS

THE PHYSICIAN AND SPORTSMEDICINE - VOL 30 - NO. 12 - DECEMBER 2002

Diagnosis

The MRI (figure 3) revealed a longitudinally oriented stress fracture in the metadiaphyseal region of the distal left femur. As the fracture was believed to be stable, conservative care was instituted. Since the patient was experiencing pain with activities of daily living, she was provided crutches and instructed to refrain from weight-bearing activity for several days. Once the pain had eased, she was instructed to progress to weight bearing as tolerated (ie, active rest).

Discussion

Stress fractures of the lower extremity, especially involving the tibia, are very common.^1,2 Most stress fractures in the long bones of the legs have a horizontal or oblique orientation, aligning themselves perpendicular to the main axis of the bone.³ In the femur, stress fractures are usually located in the femoral neck and appear as horizontal fractures. Longitudinal stress fractures are uncommon and are very rare in the femoral shaft.⁴

Injury mechanism. The mechanism for a longitudinal stress fracture of the femur is unclear. The fracture line appears to be related to local biomechanical conditions such as intensity and direction of the weight-bearing forces and muscle traction.⁵ Several muscles of the medial thigh (eg, pectineal, iliopsoas, and adductor) exert important traction on the medial cortex of the upper femoral shaft. Their action on cortical bone weakened by stress-induced remodeling may explain intracortical orientation of the fracture line.

Presenting complaints. Clinically, an athlete with a stress fracture typically describes pain or ache associated with a specific activity.⁶ Continuing the activity increases pain to a point at which the patient ceases the offending activity.

While mild-to-moderate swelling and point tenderness at the site of pain is frequently present on physical examination, the soft tissue surrounding the femur precludes detecting these physical findings. Percussion distal or proximal to the fracture may cause transmission of pain.⁷ Having the patient hop on the affected extremity may also provoke pain at the fracture site.

Diagnostic techniques. The plain radiograph is the initial diagnostic imaging study, but at most only 50% of stress fractures are detectable on plain films.⁶ If the initial radiographs are negative and a stress fracture is suspected, further diagnostic options include repeating the radiographs in 2 to 3 weeks, radionuclide bone scintigraphy, MRI, and computed tomography.^6,8 Currently, the technetium-99 diphosphate three-phase or single-phase bone scan is the "gold standard" of diagnosis, although MRI is preferable for distinguishing fractures from tumor, infection, or an overlying soft-tissue injury.^6-8

MRI, which is emerging as the premier technique for evaluating musculoskeletal injuries, is capable of depicting the full range of stress injury involving bone.⁶ A combination of T1-weighted sequences, which optimize anatomic detail, and a sequence that depicts bone "edema" are required for the assessment of stress injuries. A variety of edema-sensitive sequences are available and employ a form of fat suppression to further enhance contrast.

Treatment. As most stress fractures of the femur are uncomplicated, they can successfully be treated with conservative measures. Cessation of the offending activity is the foundation of therapy. Brief courses of non-weight bearing, cryotherapy, and analgesics may be implemented. Most stress fractures heal with 6 to 12 weeks of conservative treatment. When athletes have been pain-free for 10 to 14 days, they may gradually resume training. Athletes must be pain-free before they resume full activity. Implementation of partial activity and other treatment measures should be instituted if pain recurs, as was the case with this patient.

References

1. Matheson GO, Clement DB, McKenzie DC, et al: Stress fractures in athletes: a study of 320 cases. Am J Sports Med 1987;15(1):46-58
2. McBryde AM Jr: Stress fractures in athletes. J Sports Med 1975;3(5):212-217
3. Devas MB: Stress fractures of the femoral neck. J Bone Joint Surg Br 1965;47(4):728-738
4. O'Kane JW, Matsen LJ: Mid-third femoral stress fracture with hip pain. J Am Board Fam Pract 2001;14(1):64-67
5. Anderson MW, Greenspan A: Stress fractures. Radiology 1996;199(1):1-12
6. Callahan LR: Stress fractures in women. Clin Sports Med 2000;19(2):303-314
7. Knapp TP, Garrett WE Jr: Stress fractures: general concepts. Clin Sports Med 1997;16(2):339-356
8. Deutsch AL, Coel MN, Mink JH: Imaging of stress injuries to bone: radiography, scintigraphy, and MR imaging. Clin Sports Med 1997:16(2):275-290

Dr Cudnowski is a family physician in Duluth, Minnesota. Dr Carek is associate professor and residency program director in the department of family medicine at the Medical University of South Carolina in Charleston. Address correspondence to Peter J. Carek, MD, MS, 9298 Medical Plaza Dr, Charleston, SC 29406; e-mail to carekpj@musc.edu.

Disclosure information: Drs Cudnowski and Carek disclose no significant relationship with any manufacturer of any commercial product mentioned in this article. No drug is mentioned in this article for an unlabeled use.