Atypical Fractures Do Not Have a Thicker Cortex

Unlabelled: An association between atypical fractures and general cortical thickness of the femoral shaft is often suggested in the literature. Our radiographic measurements of 59 atypical and 218 ordinary fractures now exclude a difference larger than 10 % in mean femoral cortical thickness (sum of lateral and medial) with 95 % confidence.

Introduction: An increased general cortical thickness in patients with fatigue fracture of the femoral shaft (atypical fractures) is commonly suggested. However, there are scarce data to support this.

Methods: In a published nationwide Swedish study, we identified by radiographic review 59 women with an atypical fracture during 2008. The femoral cortical thickness index (thickness/femoral diameter) of these women was now compared with the 218 ordinary fractures that occurred in the same region of the femur in a case-control design. The cortical thickness index 5 cm below the lesser trochanter was the primary variable.

Results: Patients with atypical fractures were younger. Without correction for age, they had a thicker cortex (i.e., higher index). However, the difference in cortical thickness disappeared after age correction. The 95 % CI excludes a group mean difference exceeding 10 % of total mean thickness. Similarly, there was no significant difference in cortical thickness between patients with or without bisphosphonate treatment or between the ipsi- and contralateral femurs in patients with an atypical fracture.

Conclusion: The concept of a generally increased cortical thickness in patients with atypical fractures should be reconsidered.