The advantages of MRI in the detection of occult hip fractures

Abstract

While the displaced hip fracture can be visualized easily by plain radiography, the non-displaced fracture may be radiographically occult and require different imaging modalities, e.g., MRI for proper visualization. The accuracy of readers and cost advantages of utilizing MRI have not been assessed. Therefore, we undertook a study of these factors. The medical records of all patients who had visited the emergency room from June 2002 until May 2003 with a clinically suspected hip fracture, negative or equivocal plain film and subsequent MRI examination were retrospectively reviewed. Two senior and two junior radiologists independently evaluated both the MR images and radiographs of all 33 patients in a blinded study. One of three possible evaluations was described for the images of each modality: absence, presence or possibility of fracture. The economic consequences of using MRI in the detection of occult hip fractures were calculated. For all four doctors participating in this study, MRI proved to be far more sensitive and specific in the detection of occult hip fractures than radiography. Using the MR images, the senior radiologists identified the occult hip fracture patients with 100% accuracy and were in complete agreement. The agreement between junior and senior radiologists was high (average kappa=0.75). MRI also detected soft tissue injuries in 39% of the patients that could not be identified with radiography. Adoption of the new protocol using MRI saves hospitals from Euro 242 to 627 per patient. By shortening the time to diagnosis and permitting a superior visualization of both bone and soft tissue injuries, MR imaging prevents unnecessary hospitalization and delays in definitive treatment. MR images should be assessed by senior radiologists.

Added value of interpreter experience in occult and suspect hip fractures: a retrospective analysis of 254 patients

“…The interobserver agreement for MRI was almost perfect (k=0.99) which shows a high diagnostic reproducibility and is in line with previously reported data [23]. Also, the accuracy for MRI in diagnosing occult and suspect hip fractures is well documented in the literature with figures reported as about 93-100% [3, 19,24,25]. In the current study the clinical follow-up revealed no missed fractures at MRI.…”

“…Perusal of the literature shows no patent distinction between occult fractures with initially negative radiographs from suspect radiographs and several reported series confuse these entities [16][17][18][19]. The prevalence of occult hip fracture varies widely in the literature with an estimated sensitivity of hip radiography between 91 -98% [3,12].…”

Bilateral occult hip fracture

“…Although this distinction might seem selfevident (occult fracture generally refers to fractures that are not visible on plain radiographs but are found later to be present on other imaging modalities 12 ), the failure to appreciate this difference is one of the factors that has led to the misrepresentation in the literature of the incidence of occult fractures of the hip, often quoted in the 2 to 10% range. 9,[13][14][15][16][17][18] Examining the literature that has produced this figure, we focused on the work of Parker, who was searching for missed fractures; his combined missed and occult rate was 1.9%. 19 His true occult fracture rate was only 0.4%.…”

The Role of MRI in the Evaluation of Painful Hip Joint (MRI of Hip Joint)

“…Magnetic resonance imaging (MRI) with its excellent soft tissue contrast and resolution with no operator dependence and no ionizing radiation is the imaging modality of choice for evaluation of hip joint abnormalities (2). MRI offers valuable information regarding occult bony and cartilage injury such as stress fractures, avascular necrosis, and osteoarthritis, as well as soft tissue abnormalities such as muscle tears and bursitis (3). MRI provides a useful assessment of patients in whom a femoroacetabular impingement is clinically suspected.…”