[Radiological diagnosis of femoroacetabular impingement]

Automated measurement of alpha angle on 3D-magnetic resonance imaging in femoroacetabular impingement hips: a pilot study

BACKGROUND

Femoroacetabular impingement (FAI) syndrome is an established pre-osteoarthritic condition. Diagnosis is based on both clinical and radiographic parameters. An abnormal manually calculated alpha angle in magnetic resonance imaging (MRI) is traditionally utilized to diagnose abnormal femoral head-neck offset. This pilot study aimed to assess the feasibility of automated alpha angle measurements in patients with FAI syndrome, and to compare automated with manual measurements data with regard to the time and effort needed in each method.

METHODS

Alpha angles were measured with manual and automated techniques, using postprocessing software in nineteen hip MRIs of FAI syndrome patients. Two observers conducted manual measurements. Intra- and inter-observer reproducibility and correlation of manual and automated alpha angle measurements were calculated using intra-class correlation (ICC) analysis. Both techniques were compared regarding the time taken (in minutes) and effort required, measured as the amount of mouse button presses performed.

RESULTS

The first observer's intra-observer reproducibility was good (ICC 0.77; p < 0.001) while the second observer's was good-to-excellent (ICC 0.93; p < 0.001). Inter-observer reproducibility between both observers in the first (ICC 0.45; p < 0.001) and second (ICC 0.56; p < 0.001) manual alpha angle assessment was moderate. The intra-class correlation coefficients between manual and automated alpha angle measurements were ICC = 0.24 (p = 0.052; observer 1, 1st measurement), ICC = 0.32 (p = 0.015; observer 1, 2nd measurement), ICC = 0.50 (p < 0.001; observer 2, 1st measurement), and ICC = 0.45 (p < 0.001; observer 2, 2nd measurement). Average runtime for automatic processing of the image data for the automated assessment was 16.6 ± 1.9 min. Automatic alpha angle measurements took longer (time difference: 14.6 ± 3.9 min; p < 0.001) but required less effort (difference in button presses: 231 ± 23; p < 0.001). While the automatic processing is running, the user can perform other tasks.

CONCLUSIONS

This pilot study demonstrates that objective and reliable automated alpha angle measurement of MRIs in FAI syndrome hips is feasible. Trial registration The Ethics Committee of the University of Düsseldorf approved our study (Registry-ID: 2017084398).

Diagnostic Use of Magnetic Resonance Imaging and Magnetic Resonance Arthrography for Intra-Articular Pathologies of the Hip Joint

INTRODUCTION

In no other country magnetic resonance imaging (MRI) is as frequently used as in Germany. The study's aim is to analyse a daily referral procedure for hip MRI in German healthcare and to estimate ineffective costs for the healthcare system.

MATERIAL AND METHODS

Over one year 203 consecutive MRIs of the hip joint were analysed retrospectively. Referrals were reviewed for their indications, e.g. prevalence of MRIs to detect intra-articular pathologies in the German population was estimated with data of three health insurances.

RESULTS

No indication was noted on 21% of the referrals to MRI. On 66% of the referrals a reasonable indications could be identified. There were more uncertainties of the indications for arthrographies. Collecting data concerning the prevalence of MRI for intra-articular hip pathologies is difficult due to the lack of precise diagnosis and procedure coding. The expendable costs caused by MRI of the hip joint amount from 800,000 to 2.4 million € during a one year period.

DISCUSSION

Medical referrals should be used thoroughly for communication between referrers and radiologists. Contribution of the letter of referral to health economics is underestimated. To improve estimation of prevalences in the diagnostics of intra-articular hip pathologies, precise diagnosis and procedure codings are needed.

What MRI Findings Predict Failure 10 Years After Surgery for Femoroacetabular Impingement?

BACKGROUND

Magnetic resonance arthrogram (MRA) with radial cuts is presently the best available preoperative imaging study to evaluate chondrolabral lesions in the setting of femoroacetabular impingement (FAI). Existing followup studies for surgical treatment of FAI have evaluated predictors of treatment failure based on preoperative clinical examination, intraoperative findings, and conventional radiography. However, to our knowledge, no study has examined whether any preoperative findings on MRA images might be associated with failure of surgical treatment of FAI in the long term.

QUESTIONS/PURPOSES

The purposes of this study were (1) to identify the preoperative MRA findings that are associated with conversion to THA, any progression of osteoarthritis, and/or a Harris hip score of < 80 points after acetabuloplasty and/or osteochondroplasty of the femoral head-neck junction through a surgical hip dislocation (SHD) for FAI at a minimum 10-year followup; and (2) identify the age of patients with symptomatic FAI when these secondary degenerative findings were detected on preoperative radial MRAs.

METHODS

We retrospectively studied 121 patients (146 hips) who underwent acetabuloplasty and/or osteochondroplasty of the femoral head-neck junction through SHD for symptomatic anterior FAI between July 2001 and March 2003. We excluded 35 patients (37 hips) with secondary FAI after previous surgery and 11 patients (12 hips) with Legg-Calvé-Perthes disease. All patients underwent preoperative MRA to further specify chondrolabral lesions except in 19 patients (32 hips) including 17 patients (20 hips) who presented with an MRI from an external institution taken with a different protocol, 10 patients with no preoperative MRA because the patients had already been operated on the contralateral side with a similar appearance, and two patients (two hips) refused MRA because of claustrophobia. This resulted in 56 patients (65 hips) with idiopathic FAI and a preoperative MRA. Of those, three patients (three hips) did not have minimal 10-year followup (one patient died; two hips with followup between 5 and 6 years). The remaining patients were evaluated clinically and radiographically at a mean followup of 11 years (range, 10-13 years). Thirteen pathologic radiographic findings on the preoperative MRA were evaluated for an association with the following endpoints using Cox regression analysis: conversion to THA, radiographic evidence of any progression of osteoarthritis, and/or a Harris hip score of < 80. The age of the patient when each degenerative pattern was found on the preoperative MRA was recorded.

RESULTS

The following MRI findings were associated with one or more of our predefined failure endpoints: cartilage damage exceeding 60° of the circumference had a hazard ratio (HR) of 4.6 (95% confidence interval [CI], 3.6-5.6; p = 0.003) compared with a damage of less than 60°, presence of an acetabular rim cyst had a HR of 4.1 (95% CI, 3.1-5.2; p = 0.008) compared with hips without these cysts, and presence of a sabertooth osteophyte had a HR of 3.2 (95% CI, 2.3-4.2; p = 0.013) compared with hips without a sabertooth osteophyte. The degenerative pattern associated with the youngest patient age when detected on preoperative MRA was the sabertooth osteophyte (lower quartile 27 years) followed by cartilage damage exceeding 60° of the circumference (28 years) and the presence of an acetabular rim bone cyst (31 years).

CONCLUSIONS

Preoperative MRAs with radial cuts reveal important findings that may be associated with future failure of surgical treatment for FAI. Most of these factors are not visible on conventional radiographs or standard hip MRIs. Preoperative MRA evaluation is therefore strongly recommended on a routine basis for patients undergoing these procedures. Findings associated with conversion to arthroplasty, radiographic evidence of any progression of osteoarthritis, and/or a Harris hip score of < 80 points should be incorporated into the decision-making process in patients being evaluated for joint-preserving hip surgery.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Ultrasound is as reliable as plain radiographs in the diagnosis of cam-type femoroacetabular impingement

INTRODUCTION

In the diagnosis of femoroacetabular impingement (FAI), plain radiographs are accepted as the initial imaging method. However, there is no consensus regarding the optimal lateral view, and radiographs can underestimate the asphericity of the head-neck junction. Our research question was if ultrasound has at least the same reliability as X-ray and can be used as an alternative or additional method in the initial imaging of FAI.

MATERIALS AND METHODS

Forty patients with a median age of 39 years were consecutively included after diagnosis of cam-type FAI on magnetic resonance imaging (MRI). All patients underwent radiography involving a plain anteroposterior-view, frog-leg lateral view, and ultrasound of the hip joint in the ventral longitudinal section at 20° internal rotation. Parameters measured by MRI, radiographs, and ultrasound were the alpha angle, anterior offset, offset ratio, and anterior femoral distance.

RESULTS

No significant difference between the alpha angle on MRI (64.8°), the frog-leg view (66.3°), or ultrasound (65.6°) could be detected. Comparable correlation was found between the alpha angle on MRI and the frog-leg lateral view (r = 0.73; p < 0.0001) and between the alpha angle on MRI and sonograms (r = 0.77; p < 0.0001). The intra-class correlation coefficient for measurements using ultrasound was 0.81-0.98, and using radiographs was 0.83-0.99, with the exception of measurements involving the anterior offset on the frog-leg lateral view (0.61 and 0.64).

CONCLUSIONS

Ultrasound is as reliable as plain radiographs in the diagnosis of cam-type FAI and can serve as an alternative or additional method in initial imaging.

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.

Ultrasonography can quantify the extent of osteochondroplasty after treatment of Cam-type femoroacetabular impingement

PURPOSE

Surgical resection of femoroacetabular Cam impingement (cam-FAI) is now a generally accepted treatment, producing adequate hip score increases. Insufficient resection at the head-neck junction is the main reason for revision. The anterolateral region of the head-neck junction is visualized only suboptimally by radiography, which can be inadequate for monitoring resection results postoperatively. Our aim was to investigate the extent of Cam resection by ultrasonography (US) and determine if there is any correlation with clinical outcome.

METHODS

Altogether, 40 consecutive patients (mean age 39 years) were enrolled in this prospective study following arthroscopic Cam resection. All patients underwent standardized US examination in the ventral longitudinal section at 20° external rotation, neutral position, and 20° internal rotation the day before arthroscopy and two days afterward. Alpha angle, anterior offset, offset ratio, and anterior femoral distance were measured on sonograms. Hip Disability and Osteoarthritis Outcome Score (HOOS) and Western Ontario and McMaster University Index of Osteoarthritis (WOMAC) were conducted the day before surgery and 6 weeks postoperatively (at the earliest).

RESULTS

Alpha angle was significantly smaller on postoperative US in all hip joint positions. At 20° internal rotation, the alpha angle decreased from 65.6 to 36.9° (p < 0.0001). All but two (5%) patients had alpha angles <50°. Anterior offset increased significantly on US in neutral position and at 20° internal rotation. HOOS and WOMAC increased significantly. No correlation was found between measurements for Cam-FAI and the scores.

CONCLUSIONS

US may be a useful tool for monitoring Cam-FAI resection results postoperatively.

Symptomatic femoroacetabular impingement: does the offset decrease correlate with cartilage damage? A pilot study

BACKGROUND

Current measures of the reduced head-neck offset such as residual deformity of slipped capital femoral epiphysis (SCFE) including the alpha angle, which measures the femoral head-neck sphericity but does not account for acetabular abnormalities, do not represent the true magnitude of the deformity and the mechanical consequences. The beta angle (angle between the femoral head-neck junction and acetabular rim) accounts for the morphology of both the acetabulum and femur and, thus, may be the more appropriate parameter for assessing SCFE deformity.

QUESTIONS/PURPOSES

We determined (1) whether the beta angle could be reliably measured on MRI; and (2) whether the beta angle correlates with the cartilage status.

METHODS

We recruited 10 adult patients (mean age, 28 years) with symptomatic cam femoroacetabular impingement and 15 asymptomatic volunteers (mean age, 24 years) to have three-dimensional MRI including delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) for cartilage status assessment. Corresponding alpha angles, beta angles, and acetabular dGEMRIC indices were obtained in seven radial reformats to assess the hip in seven regions (anterior to superior and posterior).

RESULTS

We noted high reproducibility for both alpha and beta angle measurements. The dGEMRIC indices correlated with beta angles in the superoinferior and superior regions but not the alpha angles.

CONCLUSIONS

Beta angle measurement in radial MR images is reproducible and appears to correspond to cartilage damage in the superior regions of the hip. The beta angle may be a useful parameter to assess hip deformity in the followup of SCFE although further confirmation is warranted.

Evaluation of Cam-type femoroacetabular impingement by ultrasound

PURPOSE

In the diagnosis of femoroacetabular impingement (FAI), magnetic resonance imaging (MRI) and X-ray are widely accepted methods for detection. When evaluating the hip head-neck junction using MRI, oblique axial sequences are required. However, the construction and analysis of these images are restricted to specialist radiologists and surgeons in the field of hip joint MRI. This study sought to investigate whether ultrasound, a simple and inexpensive method, can be used as a reliable tool for diagnosing Cam-type FAI.

METHODS

Forty patients, with a mean age of 39 years (range, 18-61 years), were consecutively included in this prospective study, following a diagnosis of Cam-type FAI on an oblique axial MRI. All patients underwent ultrasound examination in the ventral longitudinal section at 20° external rotation, neutral position and 20° internal rotation. The alpha angle, anterior offset, offset-ratio, and anterior femoral distance (AFD) were measured using MRI and ultrasound.

RESULTS

No significant differences were detected between the alpha angle on MRI and that using ultrasound in the neutral position or in 20° internal rotation, with strong correlations observed between these parameters (r = 0.67 for neutral position, r = 0.77 for 20° internal rotation). The Pearson's correlation coefficient for the alpha angle on MRI and the ratio of AFD/anterior offset on ultrasound in internal rotation was 0.76 (p < 0.0001).

CONCLUSIONS

The results show strong correlations between MRI and ultrasound measurements in patients with Cam-type FAI. Consequently, ultrasound may provide a useful tool for the early diagnosis of Cam-type FAI in daily practice.

A classification-system improves the intra- and interobserver reliability of radiographic diagnosis of "pistol-grip-deformity"

Early detection of pistol-grip-deformity may be beneficial in optimising the outcome and the cost effectiveness of surgery. It is important to identify reliable radiographic parameters in assessing femoro-acetabular impingement (FAI) to develop a treatment algorithm. Radiographs of 47 patients ranging from "pistol grip deformity" to a normal head-neck-junction were measured for alpha angle and head ratio, and then classified by two different observers. The Bland-Altman plot was used for inter- and intraobserver agreement of alpha angle and head ratio. Inter- and intraobserver agreement for classification of "pistol grip deformity" was determined using weighted Cohen's kappa coefficient. Observer I achieved a kappa coefficient of 0.97. Observer II achieved a kappa coefficient of 0.92. An interobserver kappa coefficient between 0.87 and 0.92 was achieved by using a classification system. By testing for interobserver agreement, a bias of -0.004 with an upper limit of 0.461 and a lower limit of -0.47 was seen for the ratio and a bias of -3.7 with an upper limit of 17.2 and a lower limit of -24.6 for the alpha angle. Therefore, poor results were seen for intra- and interobserver reliability by using only a single plane for classification of "pistol grip deformity". The strength of agreement could be improved by using a classification system (based on two planes).

[Arthrosis - update 2012]

Osteoarthritis is the most common joint disease in adults. With higher life expectancy and a growing proportion of elderly people in society, the relevance of osteoarthritis is becoming higher, especially in terms of socioeconomic effects and burdens for the healthcare system. In this review the pathogenesis and risk factors of the disease are presented with the focus on the knee, hip and shoulder, clinical symptoms, diagnosis and especially radiological imaging and therapy options.

Radiographic risk factors for labral lesions in femoroacetabular impingement

BACKGROUND

Tears of the acetabular labrum can lead to pain, disability, and osteoarthritis. Several pathomechanisms have been proposed, including femoroacetabular impingement (FAI). Labral tears have been reported to occur in the presence of even subtle deformities of the acetabulum and femoral head-neck junction.

QUESTIONS/PURPOSES

We analyzed the association of the extent of bony deformity and presence and extent of labral lesions in hips with FAI.

PATIENTS AND METHODS

Radiographs of 123 hips in 116 patients receiving surgical treatment for FAI were analyzed and correlated to the presence and extent of labral lesions. Radiographic parameters of the acetabulum included acetabular index of the weightbearing zone, center-edge angle, inclination of the acetabulum, lateral head extrusion index, and retroversion. On the femoral side, neck-shaft angle, asphericity of the femoral head, superior and anterior alpha angle, offset, and offset ratio were measured. Osteoarthritis was graded according to Tönnis and Kellgren and Lawrence. Labral lesions were graded according to the modified Beck classification. A correlation between labral lesions and age, gender, affected side, type of impingement, and presence and extent of chondromalacia also was tested.

RESULTS

No correlation was found between presence or extent of labral lesions and any radiographic parameter tested, except osteoarthritis classification. The severity of labral lesions correlated to the severity of acetabular chondromalacia as well as patient age (Beck Grade 0 versus Grade 1, Beck Grade 0 versus Grades 1 and 2).

CONCLUSIONS

In the presence of impingement-inducing deformity, the extent of deformation is not associated with the incidence of labral lesions. Labral lesions are associated with early degenerative hip disease in FAI.

LEVEL OF EVIDENCE

Level I, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

[Femoroacetabular impingement: minimally invasive hip surgery]

Minimally invasive hip surgery is an innovative surgical technique mainly used in femoroacetabular impingement (FAI). The purpose of the surgical correction in FAI deformity is to eliminate the etiologic factor in the development of the so-called idiopathic hip osteoarthritis. Decisive for the success of joint preservation is the preoperative assessment of the deformity and the possible damage to the cartilage. The optimal intervention in the presence of substantial cartilage damage is joint replacement. The patient's history and the findings of physical examination with detailed radiographs and magnetic resonance imaging based on a sagittal oblique localizer optionally using intra-articular contrast prevent underestimation of the stage of the disease. Knowledge about the options and techniques of minimally invasive hip surgery helps to identify patients appropriate for other interventions like surgical dislocation of the hip and the periacetabular osteotomy.