We report on gender-specific reference intervals of the alpha angle and its association with other qualitative cam-type findings in femoroacetabular impingement at the hip, according to a population-based cohort of 2038 19-year-olds, 1186 of which were women (58%). The alpha angle was measured on standardised frog-leg lateral and anteroposterior (AP) views using digital measurement software, and qualitative cam-type findings were assessed subjectively on both views by independent observers. In all, 2005 participants (837 men, 1168 women, mean age 18.6 years (17.2 to 20.1) were included in the analysis. For the frog-leg view, the mean alpha angle (right hip) was 47° (26 to 79) in men and 42° (29 to 76) in women, with 97.5 percentiles of 68° and 56°, respectively. For the AP view, the mean values were 62° (40 to 105) and 52° (36 to 103) for men and women, respectively, with 97.5 percentiles of 93° and 94°. Associations between higher alpha angles and all qualitative cam-type findings were seen for both genders on both views. The reference intervals presented for the alpha angle in this cross-sectional study are wide, especially for the AP view, with higher mean values for men than women on both views. Cite this article: Bone Joint J 2014;96-B:449–54

Aims. Asphericity of the femoral head-neck junction is common in cam-type femoroacetabular impingement (FAI) and usually quantified using the alpha angle on radiographs or MRI. The aim of this study was to determine the natural alpha angle in a large cohort of patients by continuous circumferential analysis with CT. Methods. CT scans of 1312 femurs of 656 patients were analyzed in this cross-sectional study. There were 362 men and 294 women. Their mean age was 61.2 years (18 to 93). All scans had been performed for reasons other than hip disease. Digital circumferential analysis allowed continuous determination of the alpha angle around the entire head-neck junction. All statistical tests were conducted two-sided; a p-value < 0.05 was considered statistically significant. Results. The mean maximum alpha angle for the cohort was 59.0° (. sd. 9.4). The maximum was located anterosuperiorly at 01:36 on the clock face, with two additional maxima of asphericity at the posterior and inferior head-neck junction. The mean alpha angle was significantly larger in men (59.4°, . sd. 8.0) compared with women (53.5°, . sd. 7.4°; p = 0.0005), and in Caucasians (60.7°, . sd. 9.0°) compared with Africans (56.3°, . sd. 8.0; p = 0.007) and Asians (50.8°, . sd. 7.2; p = 0.0005). The alpha angle showed a weak positive correlation with age (p < 0.05). If measured at commonly used planes of the radially reconstructed CT or MRI, the alpha angle was largely underestimated; measurement at the 01:30 and 02:00 positions showed a mean underestimation of 4° and 6°, respectively. Conclusion. This study provides important data on the normal alpha angle dependent on age, gender, and ethnic origin. The normal alpha angle in men is > 55°, and this should be borne in mind when making a diagnosis of cam-type morphology. Cite this article: Bone Joint J 2018;100-B:570–8

The radiological evaluation of the anterolateral femoral head is an essential tool for the assessment of the cam type of femoroacetabular impingement. CT, MRI and frog lateral plain radiographs have all been suggested as imaging options for this type of lesion. The alpha angle is accepted as a reliable indicator of the cam type of impingement and may also be used as an assessment for the successful operative correction of the cam lesion. We studied the alpha angles of 32 consecutive patients with femoroacetabular impingement. The angle measured on frog lateral radiographs using templating tools was compared with that measured on CT scans in order to assess the reliability of the frog lateral view in analysing the alpha angle in cam impingement. A high interobserver reliability was noted for the assessment of the alpha angle on the frog lateral view with an intraclass correlation coefficient of 0.83. The mean alpha angle measured on the frog lateral view was 58.71° (32° to 83.3°) and that by CT was 65.11° (30° to 102°). A poor intraclass correlation coefficient (0.08) was noted between the measurements using the two systems. The frog lateral plain radiograph is not reliable for measuring the alpha angle. Various factors may be responsible for this such as the projection of the radiograph, the positioning of the patient and the quality of the image. CT may be necessary for accurate measurement of the alpha angle

Introduction: The radiographic evaluation of the antero-lateral femoral head is an essential tool for the assessment of cam type of femoroacetabular impingement. Computerised tomography (CT), magnetic resonance imaging and frog lateral plain radiograph views have all been suggested as imaging options for this type of lesion. The alpha angle is accepted as a reliable indicator of cam type of impingement and this may also be used as an assessment tool for successful operative correction of the cam lesion. The aim of our study was to analyse the reliability of The frog lateral view plain radiographs to analyse the alpha angle in cam femoroacetabular impingement. Patients and Methods: Thirty two patients who presented with femoroacetabular impingement were studied. Interobserver reliability for assessment of alpha angles on frog lateral radiographic view was analysed using intraclass correlation coefficient. The alpha angles measured on frog lateral views using digital templating tools were compared to those measured on CT scans. Results: A high interobserver reliability was noted for the assessment of alpha angles on frog lateral views with a correlation coefficient of 0.83. The average alpha angles measured on frog lateral views was 58.71 degrees (range 32 to 83.3). The average alpha angle measured on CT was 65.11 degrees (range 30 to 102). However, a poor correlation (Spearman r of 0.2) was noted between the measurements using the two systems. Conclusions: Frog lateral plain radiographs are not reliable predictors of alpha angle. Various factors may be responsible for this such as the projection of the radiographs, patient positioning and quality of images. CT imaging may be necessary for accurate measurement of the alpha angle

Cam type femoroacetabular impingement (FAI) is due to an aspheric femoral head, which is best quantified by the alpha angle described on MRI and CT-scan. Radiographic measurement of the alpha angle is not well codified and studies from the literature cannot conclude on the best view to measure it. Most authors also describe a mixed type FAI which associates an aspheric femoral head with an excessive anterior acetabular coverage of the femoral head. Anterior center edge (ACE) angle has been described on the false profile view to measure anterior acetabular coverage in hip dysplasia and has never been evaluated in FAI. In this study, we developed a new lateral hip view which associates a lateral view of the femoral neck and a false profile view of the acétabulum, which we called profile view in impingement position (PVIP). Twenty six patients operated for FAI had CT-scan, the PVIP and the false profile view of one or two hips according to pain. A control group of 19 patients who did not suffer from the hip had the PVIP. Alpha angles were measured twice on 17 CT scan of FAI patients by two observers and compared with the alpha angles measured on the corresponding hip PVIP by a correlation analysis. Alpha angles were measured twice on 45 PVIP in FAI patient and on 19 PVIP in the control group by three observers. ACE angles were measured once on 15 PVIP and on 15 false profile views. Means were compared by two tail paired t-tests, intra- and inter-observer reliability were measured by intraclass correlation coefficient. Mean alpha angle on CT scan was 65.8° and 65.6° for observers 1 and 2 respectively (p>0.05). It was 63.6° and 64.3° on the PVIP (p>0.05). No significant difference was found between CT scan and radiographic measurements, and Pearson's correlation coefficients were good at 0.74 and 0.8. ICC was 0.86 for inter-rater reliability, and 0.91 for intra-rater reliability for CT-scan alpha angle measures. ICC for PVIP measures varied from 0.82 to 0.9 for intra-rater reliability and from 0.6 to 0.9 for inter-rater reliability. Mean alpha angle measured on PVIP in FAI patients was 63.3° and was 44.9° in control subjects and the difference was significant (p<0.001) for the three observers. None of the FAI patients and 88% of the control subjects had an alpha angle < 50°. Mean ACE angle was 26.8° on PVIP and 32.8° on the false profile view, the difference was significant (p=0.015), and the Pearson's correlation coefficient was moderate (r=0.58). The PVIP is a reliable radiographic view to measure the alpha angle. It allows a good quantification of the alpha angle comparable to CT-scan measurements and permits to differentiate patients from control subjects. PVIP is not a good view to quantify anterior edge angle probably because of acetabular retroversion due to the hip flexion needed in this view. Mean ACE angle measured on the false profile view in FAI patient was comparable to ACE angle in general population reported in the literature

Radiographic evaluation of the anterolateral femoral head is an essential tool for the assessment of cam type of femoroacetabular impingement. Computerised tomography (CT), magnetic resonance imaging and frog lateral plain radiograph views have all been suggested as imaging options for this type of lesion. Alpha angle is accepted as a reliable indicator of cam type of impingement and this may also be used as an assessment tool for successful operative correction of the cam lesion. The aim of our study was to analyse the reliability of frog lateral view plain radiographs to analyse the alpha angle in cam femoroacetabular impingement. Thirty two patients who presented with femoroac-etabular impingement were studied. Interobserver reliability for assessment of alpha angles on frog lateral radiographic view was analysed using intraclass correlation coefficient. The alpha angles measured on frog lateral views using digital templating tools were compared to those measured on CT scans. A high interobserver reliability was noted for the assessment of alpha angles on frog lateral views with a correlation coefficient of 0.83. The average alpha angles measured on frog lateral views was 58.71 degrees (range 32 to 83.3). The average alpha angle measured on CT was 65.11 degrees (range 30 to 102). However, a poor correlation (Spearman r of 0.2) was noted between the measurements using the two systems. Frog lateral plain radiographs are not reliable predictors of alpha angle. Various factors may be responsible for this such as the projection of the radiographs, patient positioning and quality of images. CT imaging may be necessary for accurate prediction of alpha angle

Introduction. Recurrence after surgical correction of hallux valgus may be related to coronal rotation of the first metatarsal. The scarf osteotomy is a commonly used procedure for correcting hallux valgus but has limited ability to correct rotation. Using weightbearing computed tomography (WBCT), we aimed to measure the coronal rotation of the first metatarsal before and after a scarf osteotomy, and correlate these to clinical outcome scores. Methods. We retrospectively analyzed 16 feet (15 patients) who had a WBCT before and after scarf osteotomy for hallux valgus correction. On both scans, hallux valgus angle (HVA), intermetatarsal angle, and anteroposterior/lateral talus-first metatarsal angle were measured using digitally reconstructed radiographs. Metatarsal pronation (MPA), alpha angle, sesamoid rotation angle and sesamoid position was measured on standardized coronal CT slices. Preoperative and postoperative(12 months) clinical outcome scores(MOxFQ and VAS) were captured. Results. Mean HVA was 28.6±10.1 degrees preoperatively and 12.1±7.7 degrees postoperatively. Mean IMA was 13.7±3.8 degrees preoperatively and 7.5±3.0 degrees postoperatively. Before and after surgery, there were no significant differences in MPA (11.4±7.7 and 11.4±9.9 degrees, respectively; p = 0.75) or alpha angle (10.9±8.0 and 10.7±13.1 degrees, respectively; p = 0.83). There were significant improvements in SRA (26.4±10.2 and 15.7±10.2 degrees, respectively; p = 0.03) and sesamoid position (1.4±1.0 and 0.6±0.6, respectively; p = 0.04) after a scarf osteotomy. There were significant improvements in all outcome scores after surgery. Poorer outcome scores correlated with greater postoperative MPA and alpha angles (r= 0.76 (p = 0.02) and 0.67 (p = 0.03), respectively). Conclusion. A scarf osteotomy does not correct first metatarsal coronal rotation, and worse outcomes are linked to greater metatarsal rotation. Rotation of the metatarsal needs to be measured and considered when planning hallux valgus surgery. Further work is needed to compare postoperative outcomes with rotational osteotomies and modified Lapidus procedures when addressing rotation

Arthroscopic hip procedures have increased dramatically over the last decade as equipment and techniques have improved. Patients who require hip arthroscopy for femoroacetabular impingement on occasion require surgery on the contralateral hip. Previous studies have found that younger age of presentation and lower Charlson comorbidity index have higher risk for requiring surgery on the contralateral hip but have not found correlation to anatomic variables. The purpose of this study is to evaluate the factors that predispose a patient to requiring subsequent hip arthroscopy on the contralateral hip. This is an IRB-approved, single surgeon retrospective cohort study from an academic, tertiary referral centre. A chart review was conducted on 310 primary hip arthroscopy procedures from 2009-2020. We identified 62 cases that went on to have a hip arthroscopy on the contralateral side. The bilateral hip arthroscopy cohort was compared to unilateral cohort for sex, age, BMI, pre-op alpha angle and centre edge angle measured on AP pelvis XRay, femoral torsion, traction time, skin to skin time, Tonnis grade, intra-op labral or chondral defect. A p-value <0.05 was deemed significant. Of the 62 patients that required contralateral hip arthroscopy, the average age was 32.7 compared with 37.8 in the unilateral cohort (p = 0.01) and BMI was lower in the bilateral cohort (26.2) compared to the unilateral cohort (27.6) (p=0.04). The average alpha angle was 76.3. 0. in the bilateral compared to 66. 0. in the unilateral cohort (p = 0.01). Skin to skin time was longer in cases in which a contralateral surgery was performed (106.3 mins vs 86.4 mins) (p=0.01). Interestingly, 50 male patients required contralateral hip arthroscopy compared to 12 female patients (p=0.01). No other variables were statistically significant. In conclusion, this study does re-enforce existing literature by stating that younger patients are more likely to require contralateral hip arthroscopy. This may be due to the fact that these patients require increased range of motion from the hip joint to perform activities such as sports where as older patients may not need the same amount of range of motion to perform their activities. Significantly higher alpha angles were noted in patients requiring contralateral hip arthroscopy, which has not been shown in previous literature. This helps to explain that larger CAM deformities will likely require contralateral hip arthroscopy because these patients likely impinge more during simple activities of daily living. Contralateral hip arthroscopy is also more common in male patients who typically have a larger CAM deformity. In summary, this study will help to risk stratify patients who will likely require contralateral hip arthroscopy and should be a discussion point during pre-operative counseling. That offering early subsequent or simultaneous hip arthroscopy in young male patients with large CAMs should be offered when symptoms are mild

Background. Cam morphology develops during adolescence and predisposes individuals to future hip pain and osteoarthritis. An improved understanding of cam development is required to determine whether the process is modifiable. Hypothesis/Purpose. The aim of this study was to characterise the risk factors, timing, and pathogenesis of cam formation. Study Design. Longitudinal prospective observational cohort study. Methods. Longitudinal observational cohort study over three years of individuals from football club academies and an age-matched control population, aged 9–18 years at baseline. Assessments include questionnaires, clinical examination, and MRI of both hips. Alpha angle and epiphyseal extension were measured on radial images. Results. Cohort comprised male academy footballers (121 at baseline and 78 at follow-up) and male and female controls (107 at baseline and 71 at follow-up). Mean change in cartilage alpha angle was 12.4° (SD 8.4) for footballers, 7.3° (SD 6.0) for male controls and 4.0° (SD 4.1) for female controls. A positive correlation was found between Physical Activity Questionnaire Score and change in cartilage alpha angle (coefficient 0.787, p=<0.001). The greatest change in cartilage alpha angle occurred in individuals aged 11–12 years at baseline, with no significant change after 14 years of age. A positive correlation between mean cartilage alpha angle and lateral epiphyseal extension was observed (r. 2. = 0.294, p=0.029). Conclusions. Males undertaking intense sporting activity during adolescence at greatest risk of developing cam morphology, but there is no significant change in hip morphology after 14 years of age. The findings are consistent with physiological adaptation and epiphyseal extension in response to hip loading during skeletal immaturity

Abstract. Background. Femoroacetabular impingement (FAI) has been extensively investigated and is strongly associated with athletic participation. The aim of this systematic review is to assess: the prevalence of cam-type FAI across various sports, whether kinematic variation between sports influences hip morphology, and whether performance level, duration and frequency of participation or other factors influence hip morphology in a sporting population. Methods. A systematic search of Embase, PubMed and the Cochrane Library was undertaken following PRISMA guidelines. The study was registered on the PROSPERO database (CRD4202018001). Prospective and retrospective case series, case reports and review articles published after 1999 were screened and those which met the inclusion criteria decided a priori were included for analysis. Results. The literature search identified 58 relevant articles involving 5,683 participants. Forty-nine articles described a higher prevalence of FAI across various ‘hip-heavy’ sports, including soccer, basketball, baseball, ice hockey, skiing, golf and ballet. In studies including non-athlete controls, a greater prevalence of FAI was reported in 66.7% of studies (n=8/12). The highest alpha angle was identified at the 1 o'clock position (n=9/9) in football, skiing, golf, ice hockey and basketball. Maximal alpha angle was found to be located in a more lateral position in goalkeepers versus positional players in ice hockey (1 o'clock vs 1.45 o'clock). A positive correlation was also identified between the alpha angle and both age and activity level (n=5/8 and n=2/3, respectively) and also between prevalence of FAI and both age and activity level (n=2/2 and n=4/5), respectively. Conclusions. Hip-heavy sports show an increased prevalence of FAI, with specific sporting activities influencing hip morphology. Both a longer duration and increased level of training also resulted in an increased prevalence of FAI

One-fourth of all ankle trauma involve injury to the syndesmotic ankle complex, which may lead to syndesmotic instability and/or posttraumatic ankle osteoarthritis in the long term if left untreated. The diagnosis of these injuries still poses a deceitful challenge, as MRI scans lack physiologic weightbearing and plain weightbearing radiographs are subject to beam rotation and lack 3D information. Weightbearing cone-beam CT (WBCT) overcomes these challenges by imaging both ankles during bipedal stance, but ongoingdebate remains whether these should be taken under weightbearing conditions and/or during application of external rotation stress. The aim of this study is study therefore to compare both conditions in the assessment of syndesmotic ankle injuries using WBCT imaging combined with 3D measurement techniques. In this retrospective study, 21 patients with an acute ankle injury were analyzed using a WBCT. Patients with confirmed syndesmotic ligament injury on MRI were included, while fracture associated syndesmotic injuries were excluded. WBCT imaging was performed in weightbearing and combined weightbearing-external rotation. In the latter, the patient was asked to internally rotate the shin until pain (VAS>8/10) or a maximal range of motion was encountered. 3D models were developed from the CT slices, whereafter. The following 3D measurements were calculated using a custom-made Matlab® script; Anterior tibiofibular distance (AFTD), Alpha angle, posterior Tibiofibular distance (PFTD) and Talar rotation (TR) in comparison to the contralateral non-injured ankle. The difference in neutral-stressed Alpha angle and AFTD were significant between patients with a syndesmotic ankle lesion and contralateral control (P=0.046 and P=0.039, respectively). There was no significant difference in neutral-stressed PFTD and TR angle. Combined weightbearing-external rotation during CT scanning revealed an increased AFTD in patients with syndesmotic ligament injuries. Based on this study, application of external rotation during WBCT scans could enhance the diagnostic accuracy of subtle syndesmotic instability

Objectives. The purpose of this study was to investigate whether the femoral head–neck contour, characterised by the alpha angle, varies with the stage of physeal maturation using MRI evaluation of an asymptomatic paediatric population. . Methods. Paediatric volunteers with asymptomatic hips were recruited to undergo MRI of both hips. Femoral head physes were graded from 1 (completely open) to 6 (completely fused). The femoral head–neck contour was evaluated using the alpha angle, measured at the 3:00 (anterior) and 1:30 (anterosuperior) positions and correlated with physeal grade, with gender sub-analysis performed. Results. A total of 43 asymptomatic paediatric volunteers (26 male, 17 female) with mean age 13.0 years (eight to 18) were included with review of bilateral hip MRIs. Correlation between the physeal grade and alpha angle was moderate in males at both the 3:00 (r = 0.477, p < 0.001) and 1:30 (r = 0.509, p < 0.001) positions, whereas there was no significant correlation in females. A significant difference was found between the alpha angles of all the physeal grades (3:00, p = 0.030, 1:30, p = 0.005), but only in males, with the angle increasing with higher grades. For physeal grading, the inter-reader reliability was substantial (intraclass correlation coefficient (ICC) = 0.694), and the intra-reader reliability was also substantial (ICC = 0.788). . Conclusion . The femoral head–neck contour varies and correlates with the stage of physeal development, but only in males, with the alpha angle increasing with progressive physeal maturation. This suggests that gender differences exist in the natural physiological growth, development or remodelling of femoral head–neck junction. In males, pre-physeal fusion may be a critical period of vulnerability for development of morphologic abnormalities of the femoral head–neck junction. Cite this article: Bone Joint Res 2015;4:17–22

There is no consensus regarding the optimum frequency of ultrasound for monitoring the response to Pavlik harness (PH) treatment in developmental dysplasia of hip (DDH). The purpose of our study was to determine if a limited-frequency hip ultrasound (USS) assessment in children undergoing PH treatment for DDH had an adverse effect on treatment outcomes when compared to traditional comprehensive ultrasound monitoring. This study was a single-center non-inferiority randomized controlled trial. Children aged less than six months of age with dislocated, dislocatable and stable dysplastic hips undergoing a standardized treatment program with a PH were randomized, once stability had been achieved, to our current standard USS monitoring protocol (every clinic visit) or to a limited-frequency ultrasound protocol (USS only until hip stability and then end of treatment). Groups were compared based on alpha angle at the end of treatment, acetabular indices (AI) and IHDI grade on follow up radiographs at one-year post harness and complication rates. The premise was that if there were no differences in these outcomes, either protocol could be deemed safe and effective. One hundred patients were recruited to the study; after exclusions, 42 patients completed the standard protocol (SP) and 36 completed the limited protocol (LP). There was no significant difference between the mean age between both groups at follow up x-ray (SP: 17.8 months; LP: 16.6 months; p=0.26). There was no difference between the groups in mean alpha angle at the end of treatment (SP: 69°; LP: 68.1°: p=0.25). There was no significant difference in the mean right AI at follow up (SP: 23.1°; LP: 22.0°; p=0.26), nor on the left (SP:23.3°; LP 22.8°; p=0.59). All hips in both groups were IHDI grade 1 at follow up. The only complication was one femoral nerve palsy in the SP group. In addition, the LP group underwent a 60% reduction in USS use once stable. We found that once dysplastic or dislocated hips were reduced and stable on USS, a limited- frequency ultrasound protocol was not associated with an inferior complication or radiographic outcome profile compared to a standardized PH treatment pathway. Our study supports reducing the frequency of ultrasound assessment during PH treatment of hip dysplasia. Minimizing the need for expensive, time-consuming and in-person health care interventions is critical to reducing health care costs, improving patient experience and assists the move to remote care. Removing the need for USS assessment at every PH check will expand care to centers where USS is not routinely available and will facilitate the establishment of virtual care clinics where clinical examination may be performed remotely

Objectives. The spinopelvic relationship (including pelvic incidence) has been shown to influence pelvic orientation, but its potential association with femoroacetabular impingement has not been thoroughly explored. The purpose of this study was to prove the hypothesis that decreasing pelvic incidence is associated with increased risk of cam morphology. Methods. Two matching cohorts were created from a collection of cadaveric specimens with known pelvic incidences: 50 subjects with the highest pelvic incidence (all subjects > 60°) and 50 subjects with the lowest pelvic incidence (all subjects < 35°). Femoral version, acetabular version, and alpha angles were directly measured from each specimen bilaterally. Cam morphology was defined as alpha angle > 55°. Differences between the two cohorts were analysed with a Student’s t-test and the difference in incidence of cam morphology was assessed using a chi-squared test. The significance level for all tests was set at p < 0.05. Results. Cam morphology was identified in 47/100 (47%) femurs in the cohort with pelvic incidence < 35° and in only 25/100 (25%) femurs in the cohort with pelvic incidence > 60° (p = 0.002). The mean alpha angle was also greater in the cohort with pelvic incidence < 35° (mean 53.7°, . sd. 10.7° versus mean 49.7°, . sd. 10.6°; p = 0.008). Conclusions. Decreased pelvic incidence is associated with development of cam morphology. We propose a novel theory wherein subjects with decreased pelvic incidence compensate during gait (to maintain optimal sagittal balance) through anterior pelvic tilt, creating artificial anterior acetabular overcoverage and recurrent impingement that increases risk for cam morphology. Cite this article: W. Z. Morris, C. A. Fowers, R. T. Yuh, J. J. Gebhart, M. J. Salata, R. W. Liu. Decreasing pelvic incidence is associated with greater risk of cam morphology. Bone Joint Res 2016;5:387–392. DOI: 10.1302/2046-3758.59.BJR-2016-0028.R1

Abstract. Objective. A higher prevalence of cam morphology has been reported in the athletic population but the development of the cam morphology is not fully understood. The purpose of this systematic review is to establish the timing of development of the cam morphology in athletes, the proximal femoral morphologies associated with its development, and other associated factors. Methods. Embase, MEDLINE and the Cochrane Library were searched for articles related to development of the cam morphology, and PRISMA guidelines were followed. Data was pooled using random effects meta-analysis. Study quality was assessed using the Downs and Black criteria and evidence quality using the GRADE framework. Results. This search identified 16 articles involving 2,028 participants. In males, alpha angle was higher in athletes with closed physes than open physes (SMD 0.71; 95% CI 0.23, 1.19). Prevalence of cam morphology was associated with age during adolescence when measured per hip (β 0.055; 95% CI 0.020, 0.091) and per individual (β 0.049; 95% CI 0.034, 0.064). Lateral extension of the epiphysis was associated with an increased alpha angle (r 0.68; 95% CI 0.63, 0.73). A dose-response relationship was frequently reported between sporting frequency and cam morphology. There was a paucity of data regarding the development of cam morphology in females. Conclusions. Very low and low quality evidence suggests that in the majority of adolescent male athletes’ osseous cam morphology developed during skeletal immaturity, and that prevalence increases with age. Very low quality evidence suggests that osseous cam morphology development was related to lateral extension of the proximal femoral epiphysis

Introduction. Alpha angles have been used to identify the precise area on the femoral head/neck junction that causes cam-type FAI. Now, computer programs are available to calculate the precise motion pattern of a hip joint and identify areas of FAI, dysplasia and other morphological abnormalities. We hypothesise that one cannot rely on the alpha angle alone to predict the precise area of resection required to remove cam impingement. Methods. We used Clinical Graphics software to analyse a cohort of 142 hips. We recorded the alpha angle at 12, 1, 2 and 3 o'clock and whether resection was recommended by the software at these points. We then removed the patients with acetabular influences on potential FAI (pure cam group). Results. At the points recommended for resection alpha angles were found to be significantly higher than those where resection was not advised (52.88° v 49.29°, p=0.0001). However, of the alpha angles greater than 50°, resection was recommended in only 49%. Of the alpha angles less than 50°, resection was still recommended in 36%. In the pure cam-type FAI patients we found no statistically significant association between alpha angle and whether resection was or wasn't indicated (p=0.0536). We further analysed each point on the femoral head/neck. Alpha angles were highest at the 1 and 2 o'clock position which would fit with the anatomical variation that most surgeons would associate with the area of impingement. However, the most common recommended area for resection was between 3 and 5 o'clock. Conclusion. Alpha angle is a poor predictor of cam resection to remove FAI. The suggested location of osteochondroplasty required to remove impingement appears to be further anterior and inferior on the femoral neck than many surgeons might predict. Motional analysis software is a valuable tool in assisting surgeons to understand the morphological abnormalities that may affect the hip

Introduction and Objective. Slipped Capital Femoral Epiphysis (SCFE) is one of the most common hip disorders in children and is characterized by a proximal femoral deformity, resulting in early osteoarthritis. Several studies have suggested that SCFE patients after in situ fixation show an altered gait pattern. Early identification of gait alterations might lead to earlier intervention programs to prevent osteoarthritis. The aim of this study is to analyse gait alterations in SCFE patients after in situ fixation compared to typically developed children, using the Computer Assisted Rehabilitation Environment (CAREN) system. Materials and Methods. This is a cross-sectional, multi-center case-control study in the Netherlands. Eight SCFE patients and eight age- and sex-matched typically developed were included from two hospitals. Primary outcomes were kinematic parameters (absolute joint angles), studied with gait analysis using statistical parametric mapping (SPM). Secondary outcomes were spatiotemporal parameters, the Notzli alpha angle, muscle activation patterns (EMG), and clinical questionnaires (VAS, Borg CR10, SF-36, and HOOS), analyzed using non-parametric statistical methods. Results. Patients (mean BMI=28±9 kg/m. 2. ) showed altered gait patterns, with significantly increased external hip rotation and decreased downward pelvic obliquity during the pre-swing phase of the gait cycle compared to typically developed (mean BMI=22±3 kg/m. 2. ). Walking speed, cadence, % stance time, and step length were reduced in SCFE patients. Coefficient of variances of cadence, stance time, and step length were increased. Patients had a mean alpha angle of 64, SD=7.9. Clinical questionnaires showed that general health (SF-36) was 80±25, energy/fatigue (SF-36) was 67±15, pain (VAS) was 0±1.5, and total HOOS score was 85±18. Conclusions. SCFE patients after in situ fixation appear to have developed a compensation mechanism, showing slight alterations in gait parameters, good general health, little functional limitations of the hip, and no self-reported pain. Cam deformities, altered joint loading, and this compensation mechanism might influence long-term early osteoarthritis. BMI reduction should be implemented in care plans, as obesity might also play a role in unfavorable long-term outcomes

Purpose. Femoroacetabular impingement (FAI) may contribute to the development of early onset hip osteoarthritis (OA). A cam lesion (or pistol grip deformity) of the proximal femur reduces head-neck offset resulting in cam type FAI. The alpha angle is a radiographic measurement recommended for diagnosis of cam type FAI. The purpose of this study was to determine if patients that develop end stage hip OA prior to 55 years of age have radiographic evidence of cam type FAI. Method. The anteroposterior (AP) pelvis and lateral hip radiographs of 244 patients (261 hips) who presented to our institution for hip arthroplasty or hip fracture fixation between 2006 and 2008 were retrospectively reviewed. Three cohorts were compared: 1) patients with end stage hip OA < 55 years old (N=76); 2) patients with end stage hip OA > 55 years old (N=84); 3) hip fracture patients > 65 years old without radiographic evidence of hip arthritis were used as controls (N=101). Patients with inflammatory arthritis, avascular necrosis and post-traumatic hip OA were excluded. Alpha angles were measured on the AP pelvis and lateral radiographs by three coauthors using ImageJ 1.43 software (National Institutes of Health, USA). For patients with end stage hip OA, AP alpha angles were measured on both the hip with OA and the contralateral hip. Lateral alpha angles were measured only on the hip with OA. For patients with hip fracture, AP alpha angles were measured on the non-fractured hip and lateral alpha angles were measured on the fractured hip. A one-way ANOVA with post hoc Tukeys HSD test was used to compare the AP and lateral alpha angles for the three cohorts. Results. The intraclass correlation coefficient (ICC) for the three coauthors measuring AP and lateral alpha angles was 0.85 and 0.86 respectively, indicating excellent inter-rater agreement. Patients < 55 years old with end stage hip OA had the largest AP and lateral alpha angles (82.711.6 degrees AP and 63.918.5 degrees lateral). These angles were significantly larger (p<0.01 for both comparisons) than patients > 55 years old with end stage hip OA (71.717.8 degrees AP and 55.518.0 degrees lateral) and hip fracture patients without hip OA (52.710.9 degrees AP and 44.411.4 degrees lateral). Comparing AP alpha angles of the contralateral hips, the mean AP alpha angle for patients < 55 years old with hip OA (70.813.2 degrees) was significantly larger (p=0.04) than patients > 55 years old with hip OA (64.516.2 degrees) which in turn was significantly larger (p<0.01) than the hip fracture patients (52.710.9 degrees). Conclusion. Patients < 55 years old with hip OA had the largest mean AP and lateral alpha angles, significantly larger than patients > 55 years old with hip OA and hip fracture patients without hip OA. Thus young patients with end stage hip OA do have radiographic evidence of cam type FAI. Furthermore, this case-controlled study suggests that cam type FAI may contribute to the development of early onset hip OA

Introduction. Geometric variations of the hip joint can give rise to repeated abnormal contact between the femur and acetabular rim, resulting in cartilage and labrum damage. Population-based geometric parameterisation can facilitate the flexible and automated in silico generation of a range of clinically relevant hip geometries, allowing the position and size of cams to be defined precisely in three dimensions. This is advantageous compared to alpha angles, which are unreliable for stratifying populations by cam type. Alpha angles provide an indication of cam size in a single two-dimensional view, and high alpha angles have been observed in asymptomatic individuals. Parametric geometries can be developed into finite element models to assess the potential effects of morphological variations in bone on soft tissue strains. The aim of this study was to demonstrate the capabilities of our parameterisation research tool by assessing impingement severity resulting from a range of parametrically varied femoral and acetabular geometries. Methods. Custom made MATLAB (MathWorks) and Python codes. [1]. were used to generate bone surfaces, which were developed into finite element models in Abaqus (SIMULIA). Parametric femoral surfaces were defined by a spherical proximal head and ellipse sections through the neck/cam region. This method produced surfaces that were well fitted to bone geometry segmented from CT scans of cam patients and capable of producing trends in results similar to those found using segmented models. A simplified spherical geometry, including the labrum and acetabular cartilage, represented the acetabulum. Femoral parameters were adjusted to define relevant variations in cam size and position. Two radii (small and large cams) and two positions (anterior and superior cams) were defined resulting in four models. Alpha angles of these parametric femurs were measured in an anterior-posterior view and a cross-table lateral view using ImageJ (NIH). A further model was developed using a femur with a medium cam size and position, and the level of acetabular coverage and labrum length were varied. Bones were modelled as rigid bodies and soft tissues were modelled as transversely isotropic linearly elastic materials. With the acetabulum fully constrained in all cases, the femurs were constrained in translation and rotated to simulate flexion followed by internal rotation to cause impingement against the labrum. Results and Discussion. Models generated using the parametric approach showed that potential for tissue damage, indicated through local strain, was not predicted by measured alpha angle, but resulted from cam extent and position as defined by the ellipses. When variations were made to the acetabular rim, an increase in bone coverage had the greatest effect on impingement severity, indicated by strain in the cartilage labral-junction. An increase in labral length increased labral displacement, but had less effect on cartilage-labral strain. Patient specific models currently require full image segmentation, but there is potential to further develop these parametric methods to assess likely impingement severity based on a series of measures of the neck and acetabulum when three-dimensional imaging of patients is available

Femoroacetabular impingement is a cause of hip pain in adults and is potentially a precursor of osteoarthritis. Our aim in this study was to determine the prevalence of bilateral deformity in patients with symptomatic cam-type femoroacetabular impingement as well as the presence of associated acetabular abnormalities and hip pain. We included all patients aged 55 years or less seen by the senior author for hip pain, with at least one anteroposterior and lateral pelvic radiograph available. All patients with dysplasia and/or arthritis were excluded. A total of 113 patients with a symptomatic cam-impingement deformity of at least one hip was evaluated. There were 82 men and 31 women with a mean age of 37.9 years (16 to 55). Bilateral cam-type deformity was present in 88 patients (77.8%) while only 23 of those (26.1%) had bilateral hip pain. Painful hips had a statistically significant higher mean alpha angle than asymptomatic hips (69.9° vs 63.1°, p < 0.001). Hips with an alpha angle of more than 60° had an odds ratio of being painful of 2.59 (95% confidence interval 1.32 to 5.08, p = 0.006) compared with those with an alpha angle of less than 60°. Of the 201 hips with a cam-impingement deformity 42% (84) also had a pincer deformity. Most patients with cam-type femoroacetabular impingement had bilateral deformities and there was an associated acetabular deformity in 84 of 201 patients (42%). This information is important in order to define the natural history of these deformities, and to determine treatment