Crossover Sign Research Articles

The Association of Femoral Neck Stress Fractures with Femoral Acetabular Impingement

Objectives:To determine if there is an increased incidence of femoral acetabular impingement (FAI) in patients presenting with stress fractures of the femoral neck.Methods:After IRB approval, the imaging studies of 25 athletes (22 females, 3 males, mean age 26, range 19 - 39 years) with femoral neck stress injuries were assessed for the presence of features suggesting FAI, including acetabular retroversion, coxa profunda, abnormal femoral head-neck junction, fibrocystic change, os acetabulae, labral tear and chondral injury. All subjects had to have an adequate AP Pelvis radiograph, a lateral radiograph of the affected hip, and an MRI of the affected hip. The alpha angle, anterior offset ratio, and center to edge (CE) angle were measured on radiographs. The grade of stress injury was determined on MR images. All images and measurements were made by a musculoskeletal fellowship trained radiologist, a fellowship trained orthopaedic surgeon, an orthopaedic sports medicine fellow and a physical medicine and rehabilitation resident. Charts were reviewed to determine treatment of the stress fracture, outcome and final follow up, as well as to determine if the patient had any further treatment for their hip.Results:Of the 25 hips (18 right, 7 left) with femoral neck stress reactions, 9 were grade 2 (bone marrow edema), 5 were grade 3 (high T2 and low T1 marrow signal), and 11 were grade 4 (stress fracture). Twenty patients (80%) had coxa profunda - where the floor of the cotyloid fossa touches or extends beyond the ilioischial line (incidence in general population is 15.2% of males, and 19.4% of females). Coxa profunda, defined by the floor of the cotyloid fossa touching or extending beyond the ilioischial line and a center edge angle of more than 35o, was present in 28% of subjects. Acetabular retroversion as assessed by the crossover sign was present in 42% (normal incidence is 5% of population). Center edge angle was greater than 35o in 20% and greater than 40 o in 12% of subjects. Any radiographic sign indicating pincer impingement was present in 66% of subjects. An abnormal alpha angle > 50o was seen in 4, and an abnormal anterior offset ratio < 0.18 was seen in 7. There were no cases of combined FAI. Labral tears were seen in 14, an abnormal femoral head/neck junction in 5, fibrocystic change in 2, os acetabuli in 2 and cartilage damage in 3. Four of the patients had surgery for their femoral neck stress fracture, while 5 patients (20%) had surgery for FAI within the 2 years after their hip stress fracture for persistent intra-articular hip pain.Conclusion:Our results suggest that patients with femoral neck stress injuries have a higher incidence of bony abnormalities associated with pincer impingement, such as coxa profunda and acetabular retroversion. Over coverage of the femoral head may place additional stresses on the femoral neck, predisposing an athlete to stress injury as they take their hips through the extremes of motion while running. This may explain why most femoral neck stress fractures occur on the medial, compressive, side of the femoral neck. We hypothesize that leverage of the lateral femoral neck against the over-covered acetabular rim may result in tensile forces on the medial femoral neck resulting in the stress injury. Some of our patients also had features of cam impingement, as evidenced by an increased alpha angle, decreased anterior offset ratio or fibrocystic change, although the incidence is similar to the values expected in the general population.

Symptomatic Femoroacetabular Impingement

Objectives:The purpose of this study was to compare the clinical, radiographic and intraoperative characteristics of symptomatic FAI in males and females, to determine gender-specific differences in FAI presentation.Methods:We retrospectively identified consecutive cohorts of 50 male and 50 female patients treated for symptomatic FAI by a single surgeon. Established clinical and radiographic methods were used for disease characterization. Statistical analysis was performed to identify significant differences in clinical, radiographic, and intraoperative findings between males and females.Results:Statistical differences in age, BMI, and pain chronicity by gender were not detected. Modified Harris hip scores and UCLA activity scores were significantly lower in females (54.4 vs. 63.7, p 0.005 and 6.8 vs. 8.1, p 0.014, respectively). Females were significantly more likely to have a component of lateral hip pain (38% vs. 20%, p 0.047), in addition to anterior/groin pain. Females had significantly more internal rotation range of motion in flexion than males (16.4° vs. 6.9°, p<0.001), with 58.0% and 86.0% having less than 20°, respectively (p 0.002). Males were significantly more likely than females to have elevated alpha angle (>50 in 94% vs. 70%, p 0.002) and decreased head-neck offset (<0.17 in 96% vs. 78%, p 0.007). Elevated alpha angles on the AP pelvis radiographs were more common in males with FAI compared to females (72% vs. 28%, p<0.001). A crossover sign greater than 10 mm from the acetabular sourcil was significantly more likely in males than in females (64.3% vs. 23.5%, p 0.001). Acetabular articular cartilage cleavage or defects were significantly more common in males (56% vs 24%, p 0.001). The distribution of labral lesions was not significantly different (82% vs 80% detachment).Conclusion:Significant differences in disease characteristics exist between males and females with FAI. Female patients have greater disability at presentation and are less active than males with FAI at presentation, despite less advanced acetabular cartilage pathology. Female patients generally had milder cam-type deformities and less acetabular retroversion than males.

Hip Arthroscopy for FAI: Predictors of Patient Satisfaction and Conversion to Total Hip Arthroplasty 5 to 7 years Following Arthroscopy

Objectives:Hip arthroscopy is treatment method for patients with symptomatic femoroacetabular impingement (FAI). It is unclear what factors are associated with mid-term success. The purpose of this study is to report the clinical outcomes and the predictors of successful outcome at a minimum 5 years post-operatively.Methods:Between March 2005 and September 2006, 646 consecutive hip arthroscopies were performed. This study was IRB approved. Patients were included who underwent arthroscopic treatment of symptomatic FAI and chondrolabral dysfunction with radiographic and physical examination findings consistent with FAI. Exclusion criteria included patients < 18 years of age, professional athletes, labral reconstruction, Legg-Calve-Perthes disease, and those with underlying hip disease such as pigmented villonodular synovitis or synovial chondromatosis. All data were prospectively collected and retrospectively reviewed, including physical exam findings, radiographic measurements (alpha angle, the presence of a crossover sign or acetabular dysplasia, and joint space), re-operations or complications, and conversion to THA. Patients were evaluated pre- and post-operatively with a prospective subjective questionnaire. Primary outcome measure included the modified Harris Hip Score (MHHS), and secondary outcome measures included the Western Ontario and McMaster Universities Arthritis Index (WOMAC), Tegner activity scale, patient satisfaction, and conversion to THA.Results:Twenty-four patients were deceased or refused to participate at follow-up, and 284 patients(293 hips) met the inclusion criteria. The average age was 42 years(range, 18 to 77) and there were 140 females and 144 males. Sixty-eight hips (68 patients) required a total hip arthroplasty (THA) (24%). The average age of the THA group was 52 years (range, 32 to 77), with 60 patients (88%) over 40 years of age at the time of arthroscopy. There were 22 females (32%) and 46 males (68%). The average time to THA was 34.6 months post-operatively (range, 7 months to 5 years) and the average pre-operative MHHS was 58 (range, 24 to 100). Of the remaining 216 patients (225 hips), 171 patients (79%, or 178 hips) were available for follow up at a minimum of 5 years. The average follow-up was 6.6 years (range, 5 to 7.2). The MHHS improved from 61 to 80(p<0.001). The average WOMAC at follow-up was 9.0 and the median Tegner activity scale was 4.0. The median patient satisfaction with outcome was 9 (range, 1 to 10). There was no difference in the MHHS between patients who underwent labral debridement or labral repair(p=0.1). The significant multivariate predictors of increased post-operative patient satisfaction at follow-up were higher modified Harris Hip Scores (p=0.003) and not having a microfracture performed(p=0.015)(r2=0.2). Logistic regression modeling identified 2mm or less of joint space (P<0.0001, odds ratio=11.7, 95% CI: 3.6 to 38.1), hip requiring microfracure (o<0.0001, odds ratio=8.6, 95% CI:30. to 26.6) and age at surgery (p<0.0001) as significant independent, multivariate risk factors for conversion to THA.Conclusion:Hip arthroscopy for FAI and chondrolabral dysfunction results in a significant improvement in outcome measures with high patient satisfaction. Predictors of conversion to THA were age, 2mm or less of joint space, and having a microfracture. These results are from early generation hip arthroscopies and these predictors may be managed differently in current practice.

Prevalence of Radiographic Findings Consistent With Femoroacetabular Impingement in Military Personnel With Femoral Neck Stress Fractures

A femoral neck stress fracture is a serious condition that affects military personnel and endurance athletes. There is increasing evidence that femoroacetabular impingement contributes to significant hip pathology. This study investigates the prevalence of radiographic abnormalities associated with impingement in military personnel treated for femoral neck stress fractures. The radiographs of 69 consecutive soldiers being treated for a femoral neck stress fracture identified on magnetic resonance imaging were reviewed for radiographic signs of femoroacetabular impingement. In the cohort, the average incidence of a crossover sign was 51% (27/53). The incidence of a center edge angle greater than 40° was 47% (25/53). The alpha angle was greater than 50° in 55% (29/53). In conclusion, it appears that young patients with femoral neck stress fractures have a high prevalence of radiographic abnormalities suggestive of hip impingement. Hip impingement may lead to abnormal stress across the femoral neck, predisposing individuals to stress fractures.

Risk Factors for Ligamentum Teres Tears

The purpose of this study was to examine the relationship between nontraumatic ligamentum teres (LT) tears and acetabular radiographic architecture. The inclusion criteria for this study were all patients who had anteroposterior pelvis radiographic views and had undergone arthroscopic examination of the LT. The exclusion criteria were Tonnis arthritic grade 3 and traumatic high-energy mechanisms of injury. Radiographic data were measured preoperatively on an anteroposterior pelvis view, including acetabular inclination (AI), lateral center edge (CE) angle, magnitude of cross-over sign, and ischial spine prominence. A Lateral Coverage Index (LCI) was defined as the center edge angle minus acetabular inclination. Hips were divided into 3 groups according to the LCI: (1) high: 34° and above; (2) medium: 19° to 33°; and (3) low: below 19°. Of the 463 hips (430 patients) included in the study, 226 (49%) had a partial- or full-thickness LT tear. Patients with tears were significantly older than patients without tears (P < .0001), with average ages of 38 and 33 years, respectively. Radiographically, patients with tears had less acetabular retroversion, as reflected by lower ischial spine prominence values and lesser cross-over signs (P = .01 and .0005, respectively). Using the LCI, 115 hips (25%) were classified as high, 236 (50%) as medium, and 114 (25%) as low. Hips with low LCI were 1.74 times more likely to have LT tears than high LCI hips. This study found that the presence of LT tears was associated with acetabular bony morphology and age. LT tears were less frequent with high LCI and acetabular retroversion and less frequent in patients younger than 30 years. Further study is needed to establish whether there is a causal relationship between acetabular undercoverage and LT tears and whether LT tears may be a sign of microinstability of the hip. Level IV, therapeutic case series.

The Crossover Sign Overestimates Acetabular Retroversion

The crossover sign is a radiographic finding associated with cranial acetabular retroversion and has been associated with pincer-type femoroacetabular impingement (FAI) in patients with hip pain. Variable morphology, location, and size of the anterior inferior iliac spine (AIIS) may contribute to the crossover sign even in the absence of retroversion. Thus, the sign may overestimate the incidence of acetabular retroversion. We asked: Can the crossover sign appear on standardized, well-positioned AP pelvis radiographs despite the absence of acetabular retroversion? And what is the contribution of variable size and morphology of the AIIS to a crossover sign? We evaluated radiographs of 53 patients with symptomatic FAI in the absence of substantial chondral degenerative changes (< Tönnis Grade 2). Forty-one radiographs met the appropriate criteria of neutral tilt and obliquity. Three independent reviewers determined presence and location of the crossover sign. Acetabular version was defined using high-resolution three-dimensional CT. CT reconstructions were used to define three AIIS types addressing AIIS morphology. Nineteen of 38 radiographs with a crossover sign on AP radiographs had focal or global acetabular retroversion on three-dimensional CT (positive and negative predictive values = 50%). In contrast, the AIIS extended to or below the level of the anterior superior acetabular rim and was partially or completely responsible for the appearance of a radiographic crossover sign in all 19 hips with an anteverted acetabulum. High interobserver reliability (kappa > 0.8) was found for AIIS types. A crossover sign is frequently present on well-positioned AP pelvis radiographs in the absence of acetabular retroversion. Variable AIIS morphology may explain the appearance of this sign in the presence or absence of acetabular retroversion.

Acetabular fracture types vary with different acetabular version

Acetabular fractures typically occur in high energy trauma. Understanding of the various contributing biomechanical factors and trauma mechanisms is still limited. While several investigations figured out what role femoral position during impact plays in distinct fracture patterns, no data exists on the influence of acetabular version on the fracture type. Our study was carried out to clarify this issue. Radiological data sets of 192 patients (145 male, 47 female, age 14-90years) sustaining acetabular fractures were assessed retrospectively. The crossover ratio of the crossover sign and presence or absence of the posterior wall sign and ischial spine sign were used to determine acetabular retroversion on conventional radiographs. Acetabular version in the axial plane was measured on a computed tomography (CT) scan. Statistics were then performed to analyse the relationship between the acetabular fracture type according to the Letournel classification and acetabular version. A significant difference (p = 0.029) in acetabular version was found between fractures of the anterior [mean equatorial edge (EE) angle 19.93°] and posterior (mean EE angle 17.53°) acetabulum in the CT scan. No difference was shown on the measurements on conventional radiographs. Acetabular version in the axial plane has an influence on the acetabular fracture pattern. While more anteverted acetabula were frequently associated with anterior fracture types according to the Letournel classification, retroversion of the acetabulum was associated with posterior fracture types.

Effect of Pelvic Osteotomy in the Skeletally Immature on Acetabular Coverage

Although pelvic osteotomy in children has been effective in re-establishing containment of the hip joint, its impact on hip joint development with respect to acetabular coverage is ill defined. The purpose of this study is to determine the prevalence of acetabular overcoverage in patients who had pelvic osteotomy during childhood and its impact on patient function. Between 1980 and 2008, all patients who had a pelvic osteotomy done at our institution for non-neuropathic hip dysplasia (DDH) or secondary to Legg-Calvé-Perthes disease (LCP) prior to skeletal maturity were reviewed. A clinical assessment and the WOMAC, UCLA Activity Score, Marx activity score, and SF-36 quality-of-life questionnaires were completed. A standardized AP pelvic X-ray was performed to determine the acetabular coverage, signs of retroversion, and degenerative changes. Twenty-eight patients (32 hips) were identified, of which 14 (9 DDH, 5 LCP) agreed to participate. Impingement sign was positive in eight patients (six DDH, two LCP). Crossover and ischial spine signs were each present in ten hips. Tonnis grades were: 0 in 1 hip, 1 in 10 hips, 2 in 2 hips, and 3 in 1 hip. The mean Tonnis angle was 11.6 ± 8.6°. The mean CE angle was 24.0 ± 15.9° with six hips having a CE angle <20° and one hip with a CE angle >40°. There was no correlation between crossover sign or ischial sign and Tonnis grade (p = 0.739), hip pain (p = 0.520), or impingement sign (p = 1.00). Acetabular overcoverage is common in patients who underwent pelvic osteotomy during childhood. No correlation was identified between retroversion and hip pain in our patient cohort.

Hip Internal Rotation Is Correlated to Radiographic Findings of Cam Femoroacetabular Impingement in Collegiate Football Players

The objective of this study was to determine whether physical examinations (flexion-abduction-external rotation [FABER], impingement, range-of-motion profiles) could be used to detect the bony abnormalities of femoroacetabular impingement (FAI) in an athletic population. We performed a prospective study of 65 male collegiate football players. Both hips were evaluated by 2 orthopaedic surgeons for radiographic signs of FAI. The alpha angle and head-neck offset were measured on frog-leg lateral films. The center-edge angle, acetabular index, crossover sign, and alpha angle were measured on anteroposterior films. Measurements were averaged for both observers. Maximum hip range of motion in flexion (supine) and internal/external rotation (supine, sitting, and prone) was measured with a goniometer. Pain provoked by the impingement and FABER tests was also recorded. Examinations were completed at 2 of 4 stations (2 duplicates), each staffed by 2 clinicians (1 examined and 1 measured). The relation between each range-of-motion and radiographic measure was determined. Data from each station were assessed separately. Only those regressions significant (P < .05) for paired stations were considered clinically significant. The alpha angle and head-neck offset measured on the frog-leg lateral films were significantly correlated (all P < .01) to supine, sitting, and prone internal rotation for all stations. Correlation coefficients ranged from -0.59 to -0.35 for alpha angle and 0.42 to 0.57 for head-neck offset. Although 95% of the hips had at least 1 radiographic sign of FAI, pain was reported in only 8.5% and 2.3% during the impingement and FABER tests, respectively. Internal rotation correlates to radiographic measures of cam FAI in this cohort of collegiate football players. Football players with diminished internal rotation in whom hip pain develops should be evaluated for underlying cam FAI abnormalities. Level IV, therapeutic case series.

Coxa Profunda: Is the Deep Acetabulum Overcovered?

Coxa profunda, or a deep acetabular socket, is often used to diagnose pincer femoroacetabular impingement (FAI). Radiographically, coxa profunda is the finding of an acetabular fossa medial to the ilioischial line. However, the relative position of the acetabular fossa to the pelvis may not be indicative of acetabular coverage. We therefore determined the incidence of coxa profunda and evaluated associations between coxa profunda and other radiographic parameters of acetabular coverage commonly used to diagnose pincer FAI and acetabular dysplasia. We evaluated the radiographs of three cohorts for coxa profunda, lateral center edge (LCE) angle, acetabular index, posterior wall sign, and crossover sign. Data from 67 collegiate football players were collected prospectively (Cohort 1). We identified two patient cohorts through retrospective review of all 179 hips undergoing hip preservation surgery from 2002 to 2008 (83 periacetabular osteotomies [Cohort 2] and 96 surgical dislocation and osteochondroplasties [Cohort 3]). In all three cohorts, we detected no difference in the LCE angle or acetabular index between hips with and without coxa profunda. Coxa profunda existed in hips representing the spectrum of acetabular coverage measured by LCE angle (-18° to 60°) and acetabular orientation determined by the crossover sign. Coxa profunda was a common radiographic finding in both symptomatic patients and asymptomatic football players. Coxa profunda existed in hips representing the spectrum of acetabular coverage and was not associated with an overcovered acetabulum. We conclude coxa profunda is unrelated to overcoverage and suggest its use in diagnosis of pincer FAI be abandoned in favor of other determinants of focal or general overcoverage. Level III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

Radius Crossover Sign

Radius shaft greenstick fractures in children can be a challenging injury to treat because angulation and rotational alignment are difficult to assess. In this report, we describe a simple method for analyzing the deformity and identifying rotational and angular malalignment. This technique involves analyzing the forearm radiographs as 2 segments, proximal and distal, and assuring that the rotational position of each matches the other. We present 3 cases of proximal radius greenstick fractures in malalignment to demonstrate the radius crossover sign. Identifying the radius crossover sign, and proceeding with further closed reduction may prevent deformity that could otherwise result in a significant loss of forearm motion. Level V.

High prevalence of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease

BackgroundAcetabular retroversion is observed in hips after various pediatric hip diseases. This study sought to examine the frequency of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease and its correlation with the prominence of the ischial spine. MethodsWe retrospectively investigated the version and morphological features of the acetabulum using pelvic radiographs after Legg-Calvé-Perthes disease (107 affected hips treated non-operatively and 72 unaffected hips from the contralateral side). The diagnosis of acetabular retroversion was made based on the presence of a positive cross-over sign on anteroposterior pelvic radiographs. The correlation between the presence of a positive cross-over sign and modified Stulberg classes, the onset age of Legg-Calvé-Perthes disease, radiographic parameters for acetabular dysplasia and the prominence of the ischial spine were examined. ResultsThe prevalence of a positive cross-over sign was 49.5 % (45 of 91 hips) in affected hips and 45.8 % (33 of 72 hips) in unaffected hips. Hips with a positive cross-over sign were significantly coexistent bilaterally. The prevalence of prominence of the ischial spine in the positive cross-over sign group was 71.4 % in the affected side and 81.8 % in the unaffected side, indicating a significant correlation between the cross-over sign and the prominence of the ischial spine in both affected and unaffected hips. The positive cross-over sign did not have any correlation with the parameters for acetabular dysplasia and the onset age, however, had a significant correlation with the severity of the femoral head deformity. ConclusionsHigh prevalence of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease was demonstrated. Symmetric acetabular deformity and the coexistence of prominence of the ischial spine suggested the effects of the Legg-Calvé-Perthes disease lesions on the skeletal development of the whole pelvis. Further follow-up is needed to clarify the pathological significance of acetabular retroversion after Legg-Calvé-Perthes disease.

Standardized AP radiographs do not provide reliable diagnostic measures for the assessment of acetabular retroversion

Diagnosis of acetabular retroversion is essential in femoroacetabular impingement (FAI), but its assessment from radiographs is complicated by pelvic tilt and the two-dimensional nature of plain films. We performed a study to validate the diagnostic accuracy of the cross-over sign (COS) and the posterior wall sign (PWS) in identifying acetabular retroversion. COS and PWS were evaluated from radiographs and computed tomography (CT) scans as the standard of reference in 50 hips of subjects with symptoms of FAI. A CT-based method using three-dimensional (3D) models was developed to measure the COS, PWS, true acetabular version, and pelvic tilt relative to the anterior pelvic plane. The new CT-based method aimed to eliminate errors resulting from variations in the position and orientation of the pelvis during imaging. A low level of agreement for COS and PWS was found between radiographs and CT scans. A positive COS strongly correlated with pelvic tilt. These results suggest that COS and PWS determined from anteroposterior radiographs are considerably limited by pelvic tilt and inherent limitations of radiographs. Their use as the sole basis for deciding whether or not surgical intervention is indicated seems questionable.

Femoroasetabular Sıkışma Sendromunda Cerrahi Tedavi Sonuçlarının Analizi

Amaç: Femoroasetabular sıkışma sendromu (FASS) olan hastalarda kalça dislokasyonu ile güvenli rekonstrüksiyon uyguladığımız olguların klinik sonuçlarını değerlendirmeyi amaçladık. Gereç ve Yöntemler: 2006-2009 yılları arasında, kalça displazisi saptanmayan, FASS tanısı alan, ön sıkışma testi (anterior impingement sign) pozitif olan 13 erkek hasta çalışmaya dâhil edildi. Beş olguda arka sıkışma testi de pozitif olarak değerlendirildi. Ortalama yaş 39,3 (aralık 32-47) idi. Tüm olguların ameliyattan önce ve sonra kalça antero-posterior ve false profil grafileri çekildi. Ameliyattan önceki dönemde, olguların tümünde femur tipi, birinde ise eşlik eden asetabulum tipi sıkışma mevcuttu. Tüm olguların radyolojik incelemesinde asetabulum arka duvarı yetmezliği ve

Radiographic Prevalence of Femoroacetabular Impingement in Collegiate Football Players

The prevalence of femoroacetabular impingement may be greater in athletes than in the general population because of increased loading of the hip during sports. This study evaluated the radiographs of collegiate football players in order to quantify the prevalence of femoroacetabular impingement in asymptomatic athletes. Sixty-seven male collegiate football players (age, 21 ± 1.9 years) participated in this prospective study. Both hips (n = 134) were evaluated independently by two orthopaedic surgeons for radiographic signs of femoroacetabular impingement. The alpha angle and femoral head-neck offset were measured on frog-leg lateral radiographs. The lateral center-edge angle, acetabular index, crossover sign, and alpha angle were measured on anteroposterior radiographs. Data for continuous variables were averaged between observers prior to assessing prevalence. Cam femoroacetabular impingement was considered to be present if the femoral head-neck offset was &lt;8 mm and/or the alpha angle was &gt;50° on either radiograph. Pincer femoroacetabular impingement was considered to be present if the lateral center-edge angle was &gt;40°, the acetabular index was &lt;0°, and/or a positive crossover sign was detected by both observers. Ninety-five percent of the 134 hips had at least one sign of cam or pincer impingement, and 77% had more than one sign. Twenty-one percent had only one sign of cam femoroacetabular impingement and 57% had both signs. Fifty-two percent had only one sign of pincer femoroacetabular impingement, 10% had two, and 4% had all three signs. Specifically, 72% had an abnormal alpha angle, 64% had a decreased femoral head-neck offset, 61% had a positive crossover sign, 16% had a decreased acetabular index, and 7% had an increased lateral center-edge angle. Fifty percent of all hips had at least one sign of pincer femoroacetabular impingement and at least one sign of cam impingement. Interobserver and intraobserver repeatability was moderate or better for each measure (range, 0.59 to 0.85). Morphologic abnormalities associated with cam and pincer femoroacetabular impingement were common in these collegiate football players. The prevalence of cam and pincer femoroacetabular impingement was substantially higher than the previously reported prevalence in the general population.

Morphologic differences between the hips of Chinese women and white women: Could they account for the ethnic difference in the prevalence of hip osteoarthritis?

Hip osteoarthritis (OA) is a common disabling disease, which has a much higher prevalence in whites than in Asians. The reasons for this ethnic difference in prevalence are unknown. Hip OA is often thought to be secondary to morphologic abnormalities. This study was undertaken to examine whether particular abnormalities predisposing to hip OA occur more frequently in whites and whether these differences in hip shape account for differences in the prevalence of OA. A morphometric study was performed on 400 hips of 200 female participants without OA from 2 studies, the Beijing OA Study and the Study of Osteoporotic Fractures from the US. We focused on measures of hip dysplasia and impingement (lateral center-edge angle, impingement angle, acetabular slope, femoral head-to-femoral neck ratio, and the crossover sign) and compared data from the hips of Chinese and white women. Compared with their Chinese counterparts, white women had a lower mean impingement angle (83.6° versus 87.0°; P=0.03) and were more likely to have center-edge angles suggestive of impingement (>35°; 11% of hips in Chinese versus 23% of hips in whites, P=0.008). In contrast, low center-edge angles suggesting dysplasia (<20°) were found more often in Chinese women (22% of hips in Chinese versus 7% of hips in whites, P=0.005). In a study of elderly women without signs of OA, the morphometry of impingement and asphericity was more common in the hips of white women compared with Chinese women. Our findings suggest that whites may be at higher risk of hip OA than Chinese because of morphologic findings that predispose whites to femoroacetabular impingement.

Prevalence of Femoroacetabular Impingement in Asymptomatic Contralateral Hips in Patients with Unilateral Idiopathic Osteoarthritis

Radiographic findings of femoroace tabular impingement in the contralateral asymptomatic hip of patients who had undergone total hip arthroplasty because of primary osteoarthritis (n = 44) were compared with controls (n = 40). The centre-edge angle and caput-collum-diaphyseal angle were measured and the presence of crossover sign and a prominent ischial spine noted on anteroposterior radiographs of the pelvis. The α-angle and offset ratio were measured on cross-table lateral radiographs of the hip. The centre-edge angle and offset ratio were significantly lower and the α-angle significantly higher in the study group compared with controls. While the number of cases with an abnormal centre-edge angle was similar in both groups, the numbers with an α-angle > 50° and the number with an offset ratio ≤ 15 were significantly higher in the study group. It was concluded that morphological anomalies associated with femoroacetabular impingement are seen more frequently in the asymptomatic contralateral hip of patients who have undergone hip replacement for primary osteoarthritis than in controls.

Prevalence of Radiographic Findings Thought to Be Associated with Femoroacetabular Impingement in a Population-based Cohort of 2081 Healthy Young Adults

To report the prevalence of qualitative radiographic findings for femoroacetabular impingement (FAI) and associations among them and to characterize the inter- and intraobserver variability of these interpretations. This study is part of an institutional review board-approved population-based prospective follow-up of 2081 of 4006 (participation rate, 51.9%) young adults (874 [42.0%] male participants, 1207 [58.0%] female participants; mean age, 18.6 years) who took part in a randomized hip trial on developmental dysplasia of the hip. All participants gave informed consent. Two pelvic radiographs were obtained. Pistol-grip deformity, focal femoral neck prominence, and flattening of the lateral head, all suggestive of cam-type impingement, and the posterior wall sign, excessive acetabular coverage, and crossover sign, all suggestive of pincer-type impingement, were assessed subjectively by an experienced radiologist. To assess inter- and intraobserver agreement, images from 350 examinations were read independently twice by two observers. Cam-type deformities were seen in 868 male and 1192 female participants, respectively, as follows: pistol-grip deformity, 187 (21.5%) and 39 (3.3%); focal femoral neck prominence, 89 (10.3%) and 31 (2.6%); and flattening of the lateral femoral head, 125 (14.4%) and 74 (6.2%). Pincer-type deformities were seen in the same numbers of male and female participants, respectively, as follows: posterior wall sign, 203 (23.4%) and 131 (11.0%); and excessive acetabular coverage, 127 (14.6%) and 58 (4.9%) (all P < .001, according to sex distribution). The crossover sign was seen in 446 (51.4%) and 542 (45.5%) of the male and female participants, respectively (P = .004). There was a high degree of coexistence (odds ratio [OR] > 2) among most FAI findings. Interobserver agreement was good to very good (κ = 0.74-0.84) in rating cam- and pincer-type findings. Intraobserver agreement was moderate or good (κ = 0.49-0.80) for all findings for both observers. Overall, radiographic FAI findings are quite common in a population of healthy young adults, especially in males, with a high degree of coexistence among most findings (OR > 2).

Radiological evidence of femoroacetabular impingement in asymptomatic athletes

BackgroundFemoroacetabular impingement (FAI) has been stated as one of the main causes of early osteoarthritis in the hip. This is particularly important in young athletes. However, there are no data...

Acetabular Morphology in Slipped Capital Femoral Epiphysis

Children with unilateral slipped capital femoral epiphysis (SCFE) often appear to have overcoverage of their contralateral (normal) side. This increased coverage can be a contributing factor to femoroacetabular impingement. The purpose of this study was to quantify the coverage of the normal hip in patients with unilateral SCFE and to compare our results to matched controls. Between 2003 and 2008, we identified 50 patients treated for unilateral, stable SCFE by in-situ screw fixation. Using postoperative anteroposterior and frog radiographs of the pelvis, the lateral center-edge angle (LCEA) and Tönnis angle (TA) were measured on the uninvolved side. Pelvic tilt was evaluated to ensure the quality of the radiographs, and in those patients with appropriate films, the presence or absence of a posterior wall sign and cross-over sign was noted. Results were compared with 50 age and sex-matched controls. Control data was generated from scout views of otherwise healthy patients who underwent an abdominal computed tomography scan to rule out acute appendicitis. The mean LCEA and TA of the contralateral acetabulum were 33 and 5 degrees, respectively (range: 18 to 47; -7 to 13). Seventy-eight percent had a positive cross-over sign and 39% had a posterior wall sign. In comparison, the mean LCEA and TA in our control group were 20 and 8 degrees, respectively (range: 8 to 35; -6 to 23). In this group, 21% had a positive cross-over sign whereas 15% had a positive posterior wall sign. We found a significantly higher LCEA and lower TA in the study population compared with controls (P=1.6E-16, 0.0003), as well as a higher prevalence of retroversion signs (P=5E-7, 0.02). The contralateral acetabulum in patients with treated unilateral SCFE demonstrates significantly more coverage compared with matched controls. In addition, there is a significantly higher prevalence of acetabular retroversion in these patients. Our findings should alert caregivers to the potential of developing femoroacetabular impingement on the contralateral side in patients who have had a unilateral SCFE. III (retrospective case-control).