[Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know]

Prevalence of hip femoroacetabular impingement deformities in high-level (La Liga) male professional football players

BACKGROUND

Femoroacetabular impingement (FAI) is considered one of the main causes of hip osteoarthritis in young adults, especially in athletes. In recent years, morphological changes in FAI in the hip have been linked to early and intense sports participation, but studying top-level athlete samples is not easy. This paper presents the prevalence of FAI radiological markers in 120 active white male professional football players in the Spanish First Division League (La Liga) and compares the morphological changes with those of a control group of healthy individuals without significant sport activity.

METHODS

The precontract medical evaluation hip X-rays of 120 white male professional football players from four different First Division Spanish football teams were prospectively filed and retrospectively reviewed by a dedicated skeletal radiologist. The footballers' hip X-rays were compared with those of a control group of 80 healthy individuals (age-sex matched) without significant sport activity (obtained from routine work medical checks).

RESULTS

The femoral head-neck deformity associated with the Cam type of femoroacetabular impingement was observed in 61.6% of professional football players and only in 11.6% of the control group (p <0.01). The presence of "herniation pit" (11.6%) and os acetabuli (13.3%) also reached statistical significance in the professional football players group. In the other analyzed parameters, no statistically significant differences between the groups were observed.

CONCLUSIONS

White professional top-level football players have an increased incidence of abnormal lateral epiphyseal extension ("pistol grip deformity"), os acetabuli and herniation pits.

Radiographic signs of acetabular retroversion using a low-dose slot-scanning radiographic system (EOS®)

INTRODUCTION

Acetabular retroversion is assessed using pelvic X-ray. Cross-over-sign (COS), posterior-wall-sign (PWS) and ischial-spine-sign (ISS) are important radiographic signs of the condition. The pelvic area is sensitive to radiation and thus, possibilities to reduce dose should be considered. The purpose was to compare radiographic signs of acetabular retroversion on conventional pelvic anteroposterior (AP) X-rays with a low-dose slot-scanning system (EOS) in a sample of patients with retroversion of the acetabulum and to compare the radiation doses.

METHODS

34 participants with radiographic signs of acetabular retroversion in one or both hips on conventional pelvic X-ray were consecutively recruited. Pelvic EOS-images were acquired in each patient and COS, PWS, ISS, COS-ratio and PWS-ratio was assessed. Radiation dose comparison of X-ray vs. EOS was performed using Dose-Area Products.

RESULTS

Retroversion was present in 57 out of 68 hips. The absolute agreement was 91%, 84% and 76% for COS, PWS and ISS, respectively. No statistically significant differences were present between COS-ratio and PWS-ratio in either modality and Bland-Altman limits of agreement were narrow. The mean radiation dose was 1053 mGy*cm² in X-ray and 593 mGy*cm² in EOS (p = 0.003).

CONCLUSION

The results indicate that pelvic EOS provides diagnostic qualities similar to conventional X-ray using 44% less radiation when radiographic signs of acetabular retroversion are assessed.

Does high level youth sports participation increase the risk of femoroacetabular impingement? A review of the current literature

Sports participation can be an integral part of adolescent development with numerous positive short and long-term effects. Despite these potential benefits very high levels of physical activity, during skeletal maturation, have been proposed as a possible cause of cam-type femoroacetabular impingement (FAI). The influence of physical activity on the developing physis has been previously described both in animal studies and epidemiological studies of adolescent athletes. It is therefore important to determine whether the development of FAI is secondary to excessive physical activity or a combination of a vulnerable physis and a set level of physical activity. A review of the current literature suggests that adolescent males participating in ice-hockey, basketball and soccer, training at least three times a week, are at greater risk than their non-athletic counterparts of developing the femoral head-neck deformity associated with femoroacetabular impingement.

Advanced Imaging in Femoroacetabular Impingement: Current State and Future Prospects

Symptomatic femoroacetabular impingement (FAI) is now a known precursor of early osteoarthritis (OA) of the hip. In terms of clinical intervention, the decision between joint preservation and joint replacement hinges on the severity of articular cartilage degeneration. The exact threshold during the course of disease progression when the cartilage damage is irreparable remains elusive. The intention behind radiographic imaging is to accurately identify the morphology of osseous structural abnormalities and to accurately characterize the chondrolabral damage as much as possible. However, both plain radiographs and computed tomography (CT) are insensitive for articular cartilage anatomy and pathology. Advanced magnetic resonance imaging (MRI) techniques include magnetic resonance arthrography and biochemically sensitive techniques of delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T1rho (T1ρ), T2/T2* mapping, and several others. The diagnostic performance of these techniques to evaluate cartilage degeneration could improve the ability to predict an individual patient-specific outcome with non-surgical and surgical care. This review discusses the facts and current applications of biochemical MRI for hip joint cartilage assessment covering the roles of dGEMRIC, T2/T2*, and T1ρ mapping. The basics of each technique and their specific role in FAI assessment are outlined. Current limitations and potential pitfalls as well as future directions of biochemical imaging are also outlined.

Herniation pits as a radiographic indicator of pincer-type femoroacetabular impingement in symptomatic patients

PURPOSE

The role of herniation pits as a radiographic indicator is still debated. This case-control study was to determine (1) the prevalence and sizes of herniation pits and (2) the relationship between herniation pits and femoral and acetabular bony morphology consistent with femoroacetabular impingement.

METHODS

This comparative study was performed on 151 patients (151 hips; median patient age 46 years; range 16-73 years) with mechanical symptoms, who underwent multi-detector computed tomography (MDCT) arthrography (the symptomatic group), and an age-, gender-, site (left or right)-, and time (at diagnosis)-matched group of control patients that underwent multi-detector computed tomography due to an ureter stone (the asymptomatic group). Two orthopaedic surgeons reviewed images to evaluate the prevalence, sizes of herniation pits, and relationship with morphological abnormality.

RESULTS

The prevalences of herniation pits in symptomatic and asymptomatic groups were 23.8 % (36/151) and 3.3 % (5/151), respectively (OR 9.14, 95 % CI 3.47-24.30; p < 0.001). Herniation pits were found to be significantly associated with pincer-type abnormality (p = 0.034), especially central acetabular retroversion (p < 0.001).

CONCLUSIONS

This study shows that the prevalence of herniation pits is higher in symptomatic patients with femoroacetabular impingement, and herniation pits are associated with central acetabular retroversion. Furthermore, herniation pits were also found to be a useful predictor of pincer-type femoroacetabular impingement.

Can radiographic morphometric parameters for the hip be assessed on MRI?

BACKGROUND

Although morphometric hip parameters measured on radiographs are valuable tools guiding diagnosis and therapy in patients with hip disorders, some clinicians use MRI for such measurements, although it is unclear whether the parameters assessed on MRI differ from those assessed on radiographs.

QUESTIONS/PURPOSES

We asked whether the lateral center-edge angle (LCE), Tönnis angle, extrusion index, and anterior center-edge angle (ACE) are similar on MRI and radiography.

METHODS

We retrospectively reviewed the imaging data of 103 hips from 103 patients: 46 with femoroacetabular impingement and 57 with hip dysplasia. We manually measured the LCE, Tönnis angle, extrusion index, and ACE from radiographs and MRI in all 103 hips. Four straight coronal (Ant-10 mm, Ant-5 mm, Center, and Post-5 mm), three straight sagittal (S-Med-5 mm, S-Center, S-Lat-5 mm), and three 25º oblique sagittal (OS-Med-5 mm, OS-Center, OS-Lat-5 mm) reformats were reconstructed from a three-dimensional isotropic morphologic MRI sequence. MRI measurements were compared against the gold standard radiographic measurements.

RESULTS

We found good agreement for the LCE angle, Tönnis angle, and extrusion index between radiographic and coronal slice MRI measurements. The mean differences between radiographic and MRI measurements were 5º or less or 5% or less (for the extrusion index) in all coronal MRI slices. However, the differences between ACE angles on sagittal MRI slices and radiographs ranged from 5° to 28º.

CONCLUSIONS

LCE, Tönnis angle, and extrusion index can be measured on MRI with comparable results to radiography. The ACE angle on radiographs cannot be estimated reliably from MRI.

CLINICAL RELEVANCE

MRI provides similar morphometric measurements as radiography for most hip parameters, except for the ACE angle.

Three-dimensional quantification of femoral head shape in controls and patients with cam-type femoroacetabular impingement

An objective measurement technique to quantify 3D femoral head shape was developed and applied to normal subjects and patients with cam-type femoroacetabular impingement (FAI). 3D reconstructions were made from high-resolution CT images of 15 cam and 15 control femurs. Femoral heads were fit to ideal geometries consisting of rotational conchoids and spheres. Geometric similarity between native femoral heads and ideal shapes was quantified. The maximum distance native femoral heads protruded above ideal shapes and the protrusion area were measured. Conchoids provided a significantly better fit to native femoral head geometry than spheres for both groups. Cam-type FAI femurs had significantly greater maximum deviations (4.99 ± 0.39 mm and 4.08 ± 0.37 mm) than controls (2.41 ± 0.31 mm and 1.75 ± 0.30 mm) when fit to spheres or conchoids, respectively. The area of native femoral heads protruding above ideal shapes was significantly larger in controls when a lower threshold of 0.1 mm (for spheres) and 0.01 mm (for conchoids) was used to define a protrusion. The 3D measurement technique described herein could supplement measurements of radiographs in the diagnosis of cam-type FAI. Deviations up to 2.5 mm from ideal shapes can be expected in normal femurs while deviations of 4-5 mm are characteristic of cam-type FAI.

Evaluation of articular cartilage in patients with femoroacetabular impingement (FAI) using T2* mapping at different time points at 3.0 Tesla MRI: a feasibility study

OBJECTIVES

To define the feasibility of utilizing T2* mapping for assessment of early cartilage degeneration prior to surgery in patients with symptomatic femoroacetabular impingement (FAI), we compared cartilage of the hip joint in patients with FAI and healthy volunteers using T2* mapping at 3.0 Tesla over time.

MATERIALS AND METHODS

Twenty-two patients (13 females and 9 males; mean age 28.1 years) with clinical signs of FAI and Tönnis grade ≤ 1 on anterior-posterior x-ray and 35 healthy age-matched volunteers were examined at a 3 T MRI using a flexible body coil. T2* maps were calculated from sagittal- and coronal-oriented gradient-multi-echo sequences using six echoes (TR 125, TE 4.41/8.49/12.57/16.65/20.73/24.81, scan time 4.02 min), both measured at beginning and end of the scan (45 min time span between measurements). Region of interest analysis was manually performed on four consecutive slices for superior and anterior cartilage. Mean T2* values were compared among patients and volunteers, as well as over time using analysis of variance and Student's t-test.

RESULTS

Whereas quantitative T2* values for the first measurement did not reveal significant differences between patients and volunteers, either for sagittal (p = 0.644) or coronal images (p = 0.987), at the first measurement, a highly significant difference (p ≤ 0.004) was found for both measurements with time after unloading of the joint. Over time we found decreasing mean T2* values for patients, in contrast to increasing mean T2* relaxation times in volunteers.

CONCLUSION

The study proved the feasibility of utilizing T2* mapping for assessment of early cartilage degeneration in the hip joint in FAI patients at 3 Tesla to predict possible success of joint-preserving surgery. However, we suggest the time point for measuring T2* as an MR biomarker for cartilage and the changes in T2* over time to be of crucial importance for designing an MR protocol in patients with FAI.

Automated detection of the osseous acetabular rim using three-dimensional models of the pelvis

An automated algorithm for detection of the acetabular rim was developed. Accuracy of the algorithm was validated in a sawbone study and compared against manually conducted digitization attempts, which were established as the ground truth. The latter proved to be reliable and reproducible, demonstrated by almost perfect intra- and interobserver reliability. Validation of the automated algorithm showed no significant difference compared to the manually acquired data in terms of detected version and inclination. Automated detection of the acetabular rim contour and the spatial orientation of the acetabular opening plane can be accurately achieved with this algorithm.