Radiographic signs associated with femoroacetabular impingement occur with high prevalence at all ages in a hospital population

Prevalence of Morphological Variations Associated With Femoroacetabular Impingement According to Age and Sex: A Study of 1878 Asymptomatic Hips in Nonprofessional Athletes

Background:

Radiographic findings related to the cam and pincer variants of femoroacetabular impingement (FAI) include measurements of the alpha angle and lateral center-edge angle (LCEA). The function of these radiographic findings has been put into question because of high heterogeneity in reported studies.

Purpose:

The aim of this study was 3-fold: (1) to determine the prevalence of cam and pincer variants according to sex and age on anteroposterior (AP) pelvic radiographs from an asymptomatic nonathletic population, (2) to identify the most common radiographic signs of cam- and pincer-type variants, and (3) to determine if there are variations in the prevalence of these radiographic signs according to sex and age.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

There were 3 independent observers who retrospectively analyzed the 939 AP pelvic radiographs (1878 hips) of patients aged 18 to 50 years who did not have hip symptoms and who were not professional athletes. The prevalence of the cam and pincer variants according to the alpha angle and LCEA, respectively, and the presence of other radiographic signs commonly associated with these variables were determined in the overall population and by subgroup according to sex and age group (18-30, 31-40, and 41-50 years). Descriptive and inferential statistics were used to analyze the study sample.

Results:

The mean age of the included population was 31.0 ± 9.2 years, and 68.2% were male. The prevalence of the cam-type variant was 29.7% (558/1878), and that of the pincer-type variant was 24.3% (456/1878). The radiographic signs that were most associated with the cam and pincer variants were a pistol-grip deformity and the crossover sign, respectively. Significant differences (P < .001) in the prevalence of these variants were identified between men and women in both variants. No differences were observed in the alpha angle or LCEA according to sex or age.

Conclusion:

Radiographic findings suggestive of FAI had significant variations with respect to sex and age in this study sample. This study provides information to determine the prevalence of these anatomic variants in the general population.

The Prevalence of Radiographic Findings of Structural Hip Deformities for Femoroacetabular Impingement in Patients With Hip Pain

BACKGROUND

Radiography is the initial imaging modality used to evaluate femoroacetabular impingement (FAI), and diagnostic radiographic findings are well-established. However, the prevalence of these radiographic findings in patients with hip pain is unknown.

PURPOSE

The purpose was 3-fold: (1) to determine the overall prevalence of radiographic FAI deformities in young patients presenting with hip pain, (2) to identify the most common radiographic findings in patients with cam-type FAI, and (3) to identify the most common radiographic findings in patients with pincer-type FAI.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A geographic database was used to identify patients aged 14 to 50 years with hip pain between the years 2000 to 2016. The following were evaluated on radiographs: cam type: typical pistol grip deformity, alpha angle >55°; pincer type: crossover sign (COS), coxa profunda or protrusio acetabuli, lateral center edge angle (LCEA) ≥40°, Tönnis angle <0°; and mixed type: both cam- and pincer-type features. Posterior wall sign (PWS) and ischial spine sign (ISS) were also evaluated. The prevalence of each was determined. Descriptive statistics were performed on all radiographic variables.

RESULTS

There were 1893 patients evaluated, and 1145 patients (60.5%; 1371 hips; 374 male and 771 female; mean age, 28.8 ± 8.4 years) had radiographic findings consistent with FAI. Of these hips, 139 (10.1%) had cam type, 245 (17.9%) had pincer type, and 987 (72.0%) had mixed type. The prevalence of a pistol grip deformity and an alpha angle >55° was 577 (42.1%) and 1069 (78.0%), respectively. The mean alpha angle was 66.9°± 10.5°. The prevalence of pincer-type radiographic findings was the following: COS, 1062 (77.5%); coxa profunda, 844 (61.6%); ISS, 765 (55.8%); PWS, 764 (55.7%); Tönnis angle <0°, 312 (22.8%); LCEA ≥40°, 170 (12.4%); and protrusio acetabuli, 7 (0.5%).

CONCLUSION

The overall prevalence of radiographic findings consistent with FAI in young patients with hip pain was 60.5%. Radiographic findings for mixed-type FAI were the most prevalent. The most common radiographic finding for cam-type FAI was an alpha angle >55°. The most common radiographic finding for pincer-type FAI was the COS.

Prevalence of Femoroacetabular Impingement Syndrome among Young and Middle-aged White Adults

Objective.

The purpose of the study was to determine the prevalence of femoroacetabular impingement syndrome (FAIS) in white adults 20 to 49 years of age.

Methods.

Participants were white men and women aged 20–49 years, recruited through random digit dialing from the population of Metro Vancouver, British Columbia, Canada. Participants filled out a self-administered questionnaire and underwent a physical examination and radiographs of both hips. FAIS was defined as a combination of hip symptoms, physical signs of impingement, and radiological findings of cam or pincer morphology as recommended by the Warwick Agreement. All analyses were weighted to reflect the population from which the sample was drawn.

Results.

Data were obtained for 500 participants. In the study population, 48.9% were males and the age distribution was 32.2%, 31.4%, and 36.4% in the groups 20–29, 30–39, and 40–49 years, respectively. The physical signs of impingement correlated significantly with symptoms, but there was no significant association between either symptoms or physical examination with radiographic findings. FAIS on either side was found in 3.0% (95% CI 1.5–4.5) of the population.

Conclusion.

In this study, FAIS was present in 3% of whites aged 20–49 years. Further research is needed to develop consistent criteria for assessing hip symptoms, physical signs, and hip joint morphology, and to better understand the relationships between them.

Pincer-type MRI morphology seen in over a third of asymptomatic healthy volunteers without femoroacetabular impingement

BACKGROUND

In daily routine, pincer femoroacetabular impingement (FAI) findings are often seen without a clinical diagnosis of pincer FAI.

PURPOSE

To assess the presence of pincer FAI MRI findings in asymptomatic volunteers with negative impingement test versus patients with clinically confirmed FAI.

STUDY TYPE

Case-control study.

POPULATION

Sixty-three asymptomatic volunteers and 63 matched patients with FAI were included.

FIELD STRENGTH/ SEQUENCE

A coronal T₁ -weighted turbo spin-echo sequence as well as a 3D oblique transverse water-excitation true fast imaging sequence at 1.5T.

ASSESSMENT

The volunteers underwent standard MRI of the hip, and patients underwent MR arthrography of the symptomatic hip using the same MR sequences. Measurements of cranial acetabular version, acetabular depth, and lateral center-edge angle were performed independently by three fellowship-trained musculoskeletal radiologists.

STATISTICAL TESTS

Descriptive statistics, Mann-Whitney U-test, Unpaired t-test, receiver operating characteristics (ROC), Intraclass correlation coefficient (ICC).

RESULTS

Forty-one percent (26/63, reader 1), 32% and 37% (20 and 23/63, reader 2/3) of asymptomatic volunteers had at least one positive MR finding for pincer-FAI. Patients with pincer or mixed-type FAI had cranial retroversion of the acetabulum of -0.2° ± 7.1 (mean ± standard deviation) for reader 1 and -0.3° ± 5.5/-0.2° ± 4.8 for reader 2 / reader 3, while asymptomatic volunteers had an anteversion of 6.2° ± 6.4 (reader 1) and 3.2° ± 4.9/3.1° ± 6.5 (readers 2/3): This difference was statistically significant (P ≤ 0.002), but there was a large overlap between the groups. Acetabular depth measurements were very similar for patients with either pincer or mixed-type FAI (5.1-5.3 mm ± 3.1) and volunteers (5.2-6.1 mm ± 2.6), without a statistically significant difference (P ≤ 0.50). Lateral center-edge angle was also similar in patients with either pincer or mixed-type FAI (32.1-35.1° ± 9.1) and volunteers (30.7-33.2° ± 6.5), without a statistically significant difference (P ≤ 0.28).

DATA CONCLUSION

There is a large overlap in pincer-type MRI findings between patients with symptomatic FAI and asymptomatic volunteers. More than a third of volunteers exhibited at least one positive pincer-type MRI finding.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1296-1303.

The Prevalence of Cam and Pincer Morphology and Its Association With Development of Hip Osteoarthritis

Synopsis Our understanding of femoroacetabular impingement syndrome is slowly improving. The number of studies on all aspects (etiology, prevalence, pathophysiology, natural history, treatment, and preventive measures) of femoroacetabular impingement syndrome has grown exponentially over the past few years. This commentary provides the latest updates on the prevalence of cam and pincer hip morphology and its relationship with development of hip osteoarthritis (OA). Cam and pincer morphology is highly prevalent in the general population and in this paper is presented for different subgroups based on age, sex, ethnicity, and athletic activity. Methodological issues in determining prevalence of abnormal hip morphology are also discussed. Cam morphology has been associated with development of hip OA, but the association between pincer morphology and hip OA is much less clear. Results from reviewed studies, as well as remaining gaps in literature on this topic, are critically discussed and put into perspective for the clinician. J Orthop Sports Phys Ther 2018;48(4):230-238. doi:10.2519/jospt.2018.7816.

INFLUENCE OF AGE ON PARAMETERS FOR FEMOROACETABULAR IMPINGEMENT AND HIP DYSPLASIA IN X-RAYS

Objective:

While several radiographic parameters have been established to describe the geometry and pathology of the hip, their reference values and clinical significance remain a matter of dispute. The present study tests the hypothesis that age has a relevant impact on radiographic hip parameters.

Method:

Pelvic antero-posterior views were measured for CE angle, Sharp’s angle, acetabular depth-to-width ratio, femoral head extrusion index, roof obliquity, caput-collum-diaphyseal (CCD) angle, and Murray’s femoral head ratio, and the values obtained were correlated with age.

Results:

Significant weak and moderate linear correlations (all Ps<0.001) were observed between age and CE angle (ρ=0.31), Sharp’s angle (ρ=-0.38), extrusion index (ρ=-0.22), CCD angle (ρ=-0.15), depth-to-width ratio (ρ=-0.38), and roof obliquity (ρ=-0.19), while Murray’s femoral head ratio (ρ=0.05; P=0.274) was not associated with age. Interestingly, the parameters describing the acetabulum all showed a relevant increase in coverage with age, leading to CE-angles well beyond 40° and a Sharp’s angle below 35° in a large portion of asymptomatic older adults.

Conclusion:

While a decrease in CCD angle with age is described in most orthopedic textbooks, the changes observed with age in acetabular geometry far exceed those measured at the femoral head-neck junction. We recommend considering these alterations that may be attributable to age when formulating a radiographic diagnosis. Level of Evidence III, Diagnostic Studies - Investigating a Diagnostic Test.

Radiographic Diagnosis of Pincer-Type Femoroacetabular Impingement: A Systematic Review

Background:

Femoroacetabular impingement (FAI) is a well-recognized condition that causes hip pain and can lead to early osteoarthritis if not managed properly. With the increasing awareness and efficacy of operative treatments for pincer-type FAI, there is a need for consensus on the standardized radiographic diagnosis.

Purpose:

To perform a systematic review of the evidence regarding imaging modalities and radiographic signs for diagnosing pincer-type FAI.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A literature review was performed in 2016 using the Cochrane, PubMed, and Embase search engines. All articles focusing on a radiographic diagnosis of pincer-type FAI were reviewed. Each of the included 44 articles was assigned the appropriate level of evidence, and the particular radiographic marker and/or type of imaging were also summarized.

Results:

There were 44 studies included in the final review. Most of the articles were level 4 evidence (26 articles), and there were 12 level 3 and 6 level 2 articles. The crossover sign was the most commonly used radiographic sign (27/44) followed by the lateral center-edge angle (22/44). Anteroposterior (AP) pelvis plain radiographs were the most commonly used imaging modality (33 studies). Poor-quality evidence exists in support of most currently used radiographic markers, including the crossover sign, lateral center-edge angle, posterior wall sign, ischial spine sign, coxa profunda, acetabular protrusion, and acetabular index. There is poor-quality conflicting evidence regarding the use of the herniation pit to diagnose pincer-type FAI. Some novel measurements, such as β-angle, acetabular roof ratio, and acetabular retroversion index, have been proposed, but they also lack support from the literature.

Conclusion:

No strong evidence exists to support a single best set of current radiographic markers for the diagnosis of pincer-type FAI, largely due to the lack of better quality trials (levels 1 and 2) that compare conventional radiographic findings with the gold standard, which is the intraoperative findings. More sophisticated imaging modalities such as computed tomography and magnetic resonance arthrography are often needed to diagnose pincer-type FAI, and these investigations are relatively accurate in assessing labral pathology or cartilage damage.

Prevalence of cam hip shape morphology: a systematic review

OBJECTIVE

Cam hip shape morphology is a recognised cause of femoroacetabular impingement (FAI) and is associated with hip osteoarthritis. Our aim was to systematically review the available epidemiological evidence assessing the prevalence of cam hip shape morphology in the general population and any studied subgroups including subjects with and without hip pain.

DESIGN

All studies that reported the prevalence of cam morphology, measured by alpha angles, in subjects aged 18 and over, irrespective of study population or presence of hip symptoms were considered for inclusion. We searched AMED, MEDLINE, EMBASE, CINAHL and CENTRAL in October 2015. Two authors independently identified eligible studies and assessed risk of bias. We planned to pool data of studies considered clinically homogenous.

RESULTS

Thirty studies met inclusion criteria. None of the included studies were truly population-based: three included non-representative subgroups of the general population, 19 included differing clinical populations, while eight included professional athletes. All studies were judged to be at high risk of bias. Due to substantial clinical heterogeneity meta analysis was not possible. Across all studies, the prevalence estimates of cam morphology ranged from 5 to 75% of participants affected. We were unable to demonstrate a higher prevalence in selected subgroups such as athletes or those with hip pain.

CONCLUSIONS

There is currently insufficient high quality data to determine the true prevalence of cam morphology in the general population or selected subgroups. Well-designed population-based epidemiological studies that use homogenous case definitions are required to determine the prevalence of cam morphology and its relationship to hip pain.

Etiology of Femoroacetabular Impingement in Athletes: A Review of Recent Findings

The relationship between hip deformities and osteoarthritis has recently received a lot of attention. In particular, it has been shown that both osteoarthritis and its precursors, such as the hip deformities that lead to femoroacetabular impingement (FAI), are more prevalent in elite athletes compared with the general population. However, the etiology of the above-mentioned types of hip deformity is not currently well understood. Many recent studies have attempted to shed light on the etiology of this disease. In this article, the main clinical, radiological, mechanobiological, and biomechanical findings of relevance to understanding the etiology of hip deformities leading to FAI are reviewed. Based on these findings, a consistent biomechanical theory explaining the development of hip deformities in athletes is then presented. According to the presented theory, the repetitive, impact-like musculoskeletal loads that athletes experience, particularly when they undertake extreme ranges of hip motion, cause the development of hip deformities. According to this theory, these musculoskeletal loads trigger abnormal growth patterns during the years of skeletal development and cause the formation of hip deformities. A number of hypotheses based on the proposed theory are then formulated that could be tested in future studies to ascertain whether the proposed theory could sufficiently describe the development of hip deformities in athletes.

Open and Arthroscopic Surgical Treatment of Femoroacetabular Impingement

Femoroacetabular impingement (FAI) is a common cause of hip pain, and when indicated, can be successfully managed through open surgery or hip arthroscopy. The goal of this review is to describe the different approaches to the surgical treatment of FAI. We present the indications, surgical technique, rehabilitation, and complications associated with (1) open hip dislocation, (2) reverse periacetabular osteotomy, (3) the direct anterior “mini-open” approach, and (4) arthroscopic surgery for FAI.

Treatment of cam-type femoroacetabular impingement

PURPOSE

the aim of this study was to evaluate preliminary clinical and radiographic results of arthroscopic treatment of cam-type femoroacetabular impingement (FAI).

METHODS

thirty-eight patients underwent hip arthroscopy for cam-type FAI between 2009 and 2012. Preoperative assessment was based on clinical examination, modified Harris Hip Score (mHHS) and radiographic examination with anteroposterior pelvis, frog-leg and Lequesne views. The patients' clinical conditions at follow-up were assessed using the mHHS administered as a telephone survey. Radiographic outcome measurements evaluated pre and postoperatively were the alpha angle and femoral head-neck offset.

RESULTS

the patients were clinically evaluated at a mean follow-up of 36 months. Radiographic follow-up was performed at an average of 12.7 months. Thirty of the 38 patients (79%) were satisfied with the results of the arthroscopic procedure. A total of nine patients subsequently underwent a total hip replacement. All 30 patients who declared themselves satisfied recorded an mHHS increase; in particular, the mHHS increased from a mean of 52.9 preoperatively (range: 27.5-82.5) to a mean of 85.6 postoperatively (range: 45.1-100.1). Three significant differences between the two groups of patients (satisfied and not satisfied) were recorded: mean age, alpha angle and BMI were all significantly greater in the patients who were not satisfied with the treatment.

CONCLUSIONS

a crucial aspect in order to obtain good clinical outcomes of arthroscopic treatment of cam-type impingement is correct selection of patients who are likely to benefit from this kind of surgery. Hip arthroscopy should be avoided in patients aged over 50 years with risk factors for early osteoarthritis (high BMI and a significantly increased alpha angle).

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Imaging prevalence of femoroacetabular impingement in symptomatic patients, athletes, and asymptomatic individuals: A systematic review

BACKGROUND

There is a wide discrepancy in reported prevalence rates for cam, pincer, and mixed femoroacetabular impingement (FAI), particularly among distinct populations, namely asymptomatic or symptomatic subjects and athletes. No systematic analysis to date has yet compared studies among these groups to determine differences in radiographic signs of FAI.

METHODS

A systematic review of existing literature was performed to determine the prevalence of radiographic signs of FAI among athletes, asymptomatic subjects, and symptomatic patients. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied to systematically search PubMed, MEDLINE, CINAHL, and Cochrane databases.

RESULTS

We identified 361 studies in our literature search. After considering the exclusion criteria, 60 were included in this systematic review: 15 in athletes, 10 in purely asymptomatic patients, and 35 in symptomatic, non-athlete populations. Cam impingement was significantly (p=0.0003) more common in athletes versus asymptomatic subjects but not compared to symptomatic patients (p=0.107). In addition, cam FAI was significantly more common in symptomatic versus asymptomatic cases (p=0.009). The percentage of patients with cam-type FAI showed significant differences across groups (p=0.006). No significant differences were found between pincer-type FAI morphology prevalence when comparing athletes to symptomatic patients. However, mixed-type FAI was significantly more common in athletes versus asymptomatic subjects (p=0.03) and in asymptomatic versus symptomatic subjects (p=0.015). The percentage of patients with mixed-type FAI showed significant differences across groups (p=0.041). The mean alpha angle was significantly greater in the symptomatic group versus either the asymptomatic or athlete group (p<0.001). Significant differences in mean alpha angles were noted across groups (p=0.0000).

CONCLUSIONS

Imaging suspicion of FAI is common among athletes, asymptomatic, and symptomatic populations. However, significant differences in type and imaging signs of FAI exist among these groups that need to be considered in patients' decision making.

Prevalence of Imaging Features on CT Thought to Be Associated With Femoroacetabular Impingement: A Retrospective Analysis of 473 Asymptomatic Adult Hip Joints

OBJECTIVE

The objective of our study was to investigate the prevalence of imaging features on CT thought to be associated with femoroacetabular impingement (FAI) and the associations among them.

MATERIALS AND METHODS

Of 430 consecutive adult patients (age range, 18-40 years) who underwent hip CT at our institution for hip symptoms or trauma surveillance, the asymptomatic hips were selected for the study, which resulted in the inclusion of 473 hip joints in the study group. Images were obtained using an MDCT scanner and were reformatted using a bone algorithm. The CT images were retrospectively evaluated by two radiologists for features indicative of FAI such as the alpha angle, femoral head-neck offset, acetabular version angle, and center-edge angle. The intraclass correlation coefficient was used to evaluate intra- and interobserver variabilities. Associations among these parameters were evaluated by calculating the odds ratio between each of the parameters separately.

RESULTS

Of the 473 asymptomatic hip joints we studied, 190 (40%) joints showed at least one of the following features on CT: alpha angle greater than 55°, head-neck offset less than 8 mm, acetabular version angle less than 15°, or center-edge angle greater than 40°. At least one feature was found in the hips of male patients (43.2%), which is more frequently than in the hips of female patients (35.4%). There was a high degree of coexistence (odds ratio > 2) among these CT findings.

CONCLUSION

Imaging features on CT that are known to be associated with FAI are common in asymptomatic adult hip joints, especially in men, with a high degree of coexistence among the findings.

A quantitative non-invasive assessment of femoroacetabular impingement with CT-based dynamic simulation--cadaveric validation study

Background

Femoroacetabular impingement (FAI) is caused by an anatomic deviation of the acetabular rim or proximal femur, which causes chronic groin pain. Radiological identification of FAI can be challenging. Advances in imaging techniques with the use of computed tomography (CT) scan enable 3D simulation of FAI. We made an experimental cadaveric validation study to validate the 3D simulation imaging software.

Methods

The range of motion (ROM) of five cadaveric hips was measured using an electromagnetic tracking system (EMTS). Specific marked spots in the femur and pelvis were created as reproducible EMTS registration points. Reproducible motions were measured. Hips were subsequently imaged using high-resolution CT after introduction of artificial cam deformities. A proprietary software tool was used, Articulis (Clinical Graphics) to simulate the ROM during the presence and absence of the induced cam deformities.

Results

According to the EMTS, 13 of the 30 measured ROM end-points were restricted by > 5° due to the induced cam deformities. Using Articulis, with the same 5° threshold, we correctly detected 12 of these 13 end point limitations and detected no false positives. The median error of the measured limitations was 1.9° (interquartile range 1.1° - 4.4°). The maximum absolute error was 5.4°.

Conclusions

The use of this dynamic simulation software to determine the presence of motion limiting deformities of the femoroacetabular is validated. The simulation software is able to non-invasively detect a reduction in achievable ROM, caused by a cam type deformity.

Femoroacetabular impingement: normal values of the quantitative morphometric parameters in asymptomatic hips

OBJECTIVE

To determine the means and the reference intervals of the quantitative morphometric parameters of femoroacetabular impingement (FAI) in normal hips with high-resolution computed tomography (CT).

METHODS

We prospectively included 94 adult individuals who underwent CT for thoracic, abdominal or urologic pathologies. Patients with a clinical history of hip pathology and/or with osteoarthritis on CT were excluded. We calculated means and 95% reference intervals for imaging signs of cam-type (alpha angle at 90° and 45° and femoral head-neck offset) and pincer-type impingement (acetabular version angle, lateral centre-edge angle and acetabular index).

RESULTS

The 95 % reference interval limits were all far beyond the abnormal thresholds found in the literature for cam-type and to a lesser extent for pincer-type FAI. The upper limits of the reference intervals for the alpha angles (at 90°/45°) were 68°/83° (men) and 69°/84° (women), compared to thresholds from the literature (50°, 55° or 60°). Reference intervals were similar between genders for cam-type parameters, and slightly differed for pincer-type.

CONCLUSION

The 95% reference intervals of morphometric measurements of FAI in asymptomatic hips were beyond the abnormal thresholds, which was especially true for cam-type FAI. Our results suggest the need for redefining the current morphometric parameters used in the diagnosis of FAI.

KEY POINTS

• 95% reference intervals limits of FAI morphotype were beyond currently defined thresholds. • Reference intervals of pincer-type morphotype measurements were close to current definitions. • Reference intervals of cam-type morphotype measurements were far beyond the current definitions. • Current morphometric definitions of cam-type morphotype should be used with care.