Prevalence of cam-type femoroacetabular impingement morphology in asymptomatic volunteers

The prevalence of cam hip morphology in a general population sample

OBJECTIVE

Cam hip morphology is associated with femoroacetabular impingement (FAI) syndrome and causes hip osteoarthritis (OA). We aimed to assess the prevalence of cam hip morphology in a sample representative of the general population, using a measure with a predefined diagnostic accuracy.

DESIGN

Patients aged 16-65, who were admitted to a major trauma centre and received a computed tomography (CT) pelvis were retrospectively screened for eligibility. Subjects with proximal femoral, acetabular or pelvic fractures and those who were deceased were excluded. Eligible subjects were divided into 10 groups based on gender and age. 20 subjects from each group were included. Subjects' index of multiple deprivation (IMD) and ethnicity were recorded. CT imaging was assessed and alpha angles (a measure of cam morphology) measured in the anterosuperior aspect of the femoral head neck junction. An alpha angle greater than 60° was considered to represent cam morphology. This measure and technique has a predefined sensitivity of 80% and specificity of 73% to detect cam morphology associated with FAI syndrome. The prevalence of cam morphology was reported as a proportion of subjects affected with 95% confidence intervals.

RESULTS

200 subjects were included. The sample was broadly representative of the UK general population in terms of IMD. 155 subjects (86%) identified as white. Cam morphology was present in 47% (95% CI 42,51) of subjects.

CONCLUSIONS

In this sample, broadly representative of the UK general population 47% of subjects had cam hip morphology; a hip shape associated with FAI syndrome and OA.

Prevalence of CAM deformity and its influence on therapy success in patients with osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) and CAM-type femoroacetabular impingement (FAI) present two different pathologies of the hip joint. The aim of this study is to describe the prevalence of CAM-FAI in a collective of ONFH hips and to evaluate its influence on ONFH therapy outcome. A cohort of 86 ONFH hips with a mean follow-up of 46.7 months (±20.5) after advanced core decompression (ACD) was evaluated regarding CAM deformity by measuring the alpha angle (α) and head-neck offset. The influence of CAM-type FAI was investigated using the Kaplan-Meier estimator and the Cox regression model. The mean α was 60.4° (±13.8) with 41 hips (47.7%) being ≥60°. The mean head-neck offset was 4.5 mm (±3.2), with 78 hips (90.7%) being ≤9 mm. Survival analysis indicated noticeably better ACD results for α < 60° versus α ≥ 60° (p = 0.07). Treatment failure within the first 2 years was statistically estimated as 27.7% for α < 60° versus 40.7% for α ≥ 60°: The hazard ratio for α ≥ 60° was 1.94. Head-neck offset-dependent survival showed better, though not significant, results for offset >9 mm (p = 0.38, hazard ratio 1.89 for offsets ≤9 mm). The prevalence of CAM-type deformity is greatly increased in patients with concomitant ONFH. There is a strong indication that CAM-type FAI has a negative influence on ONFH therapy outcome. The risk that ONFH treatment will fail seems to be twice as high for α ≥ 60° as for α < 60°. We recommend cotreatment of pathological head-neck offset in patients with ONFH.

Hip Joint Torsional Loading Before and After Cam Femoroacetabular Impingement Surgery

BACKGROUND

Surgical management of cam femoroacetabular impingement (FAI) aims to preserve the native hip and restore joint function, although it is unclear how the capsulotomy, cam deformity, and capsular repair influence joint mechanics to balance functional mobility.

PURPOSE

To examine the contributions of the capsule and cam deformity to hip joint mechanics. Using in vitro, cadaveric methods, we examined the individual effects of the surgical capsulotomy, cam resection, and capsular repair on passive range of motion and resistance of applied torque.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twelve cadaveric hips with cam deformities were skeletonized to the capsule and mounted onto a robotic testing platform. The robot positioned each intact hip in multiple testing positions: (1) extension, (2) neutral 0°, (3) flexion 30°, (4) flexion 90°, (5) flexion-adduction and internal rotation (FADIR), and (6) flexion-abduction and external rotation. Then the robot performed applicable internal and external rotations, recording the neutral path of motion until a 5-N·m of torque was reached in each rotational direction. Each hip then underwent a series of surgical stages (T-capsulotomy, cam resection, capsular repair) and was retested to reach 5 N·m of internal and external torque again after each stage. During the capsulotomy and cam resection stages, the initial intact hip's recorded path of motion was replayed to measure changes in resisted torque.

RESULTS

Regarding changes in motion, external rotation increased substantially after capsulotomies, but internal rotation only further increased at flexion 90° (change +32%, P = .001, d = 0.58) and FADIR (change +33%, P < .001, d = 0.51) after cam resections. Capsular repair provided marginal restraint for internal rotation but restrained the external rotation compared with the capsulotomy stage. Regarding changes in torque, both internal and external torque resistance decreased after capsulotomy. Compared with the capsulotomy stage, cam resection further reduced internal torque resistance during flexion 90° (change -45%, P < .001, d = 0.98) and FADIR (change -37%, P = .003, d = 1.0), where the cam deformity accounted for 21% of the intact hip's torsional resistance in flexion 90° and 27% in FADIR.

CONCLUSION

Although the capsule played a predominant role in joint constraint, the cam deformity provided 21% to 27% of the intact hip's resistance to torsional load in flexion and internal rotation. Resecting the cam deformity would remove this loading on the chondrolabral junction.

CLINICAL RELEVANCE

These findings are the first to quantify the contribution of the cam deformity to resisting hip joint torsional loads and thus quantify the reduced loading on the chondrolabral complex that can be achieved after cam resection.

Connected orthopedics and trauma surgery: New perspectives

Information is everywhere in the surgeon's life. It can improve medical practice and allow for personalized care. To answer the question, "How should the surgeon be connected?" we must assess the role and limitations of digital information in daily practice, particularly through mobile applications or mHealth. These tools and their scope must be defined in order to measure their impact on our clinical practice. New regulations on medical data have been introduced imposing that privacy be maintained. Connected applications can assist the surgeon in making the diagnosis and deciding on the treatment. These tools are already being used widely. Decision algorithms based on machine learning are also a promising way to optimize patient care. Connected applications make the clinical follow-up easier by allowing more reliable, relevant and frequent data transmission. They also provide access to information and training, either early academic learning or continuing medical education. We must adapt to these new modes of learning. Thus, smartphones, tablets and digital applications now have a central role in modern orthopedic surgery. Surgeons have information, technical resources and storage for research data at their disposal, while patients can establish a link with their doctor (current or future) and find lay information about their condition.

Adolescent elite skiers with and without cam morphology did change their hip joint range of motion with 2 years follow-up

PURPOSE

To investigate how range of motion of the hips and the lumbar spine are affected by continued elite, alpine skiing in young subjects, with and without a magnetic resonance imaging verified cam morphology, in a 2-year follow-up study. The hypothesis is that skiers with cam morphology will show a decrease in hip joint range of motion as compared with skiers without cam, after a 2-year follow-up.

METHOD

Thirty adolescent elite alpine skiers were examined at the baseline (mean age 17.3 ± 0.7 years) and after 2 years. All skiers were examined for the presence of cam morphology (α-angle > 55°) using magnetic resonance imaging at the baseline. Clinical examinations of range of motion in standing lumbar flexion and extension, supine hip flexion, internal rotation, FABER test and sitting internal rotation and external rotation were performed both at the baseline and after 2 years.

RESULTS

Skiers with and without cam morphology showed a significant decrease from baseline to follow-up in both hips for supine internal rotation (right: mean - 13.3° and - 10.9° [P < 0.001]; left: mean - 7.6° [P = 0.004] and - 7.9° [P = 0.02]), sitting internal rotation (right: mean - 9.6° and - 6.3° [P < 0.001]; left: mean - 7.6° [P = 0.02] and - 3.3° [P = 0.008]) and sitting external rotation (right: mean - 16.9° and - 11.4° and left: mean - 17.9° and - 14.5° [P < 0.001]) and were shown to have an increased left hip flexion (mean + 8.4° and + 4.6° [P = 0.004]). Skiers with cam were also shown to have an increased right hip flexion (mean + 6.4° [P = 0.037]). Differences were found between cam and no-cam skiers from baseline to follow-up in the sitting internal rotation in both hips (right: mean 3.25°, left: mean 4.27° [P < 0.001]), the right hip flexion (mean 6.02° [P = 0.045]) and lumbar flexion (mean - 1.21°, [P = 0.009]).

CONCLUSION

Young, elite alpine skiers with cam morphology decreased their internal rotation in sitting position as compared with skiers without the cam morphology after 2 years of continued elite skiing.

LEVEL OF EVIDENCE

II.

Unravelling the hip pistol grip/cam deformity: Origins to joint degeneration

This article reviews a body of work performed by the investigators over 9 years that has addressed the significance of cam morphology in the development of hip osteoarthritis (OA). Early hip joint degeneration is a common clinical presentation and preexisting abnormal joint morphology is a risk factor for its development. Interrogating Hill's criteria, we tested whether cam-type femoroacetabular impingement leads to hip OA. Strength of association was identified between cam morphology, reduced range-of-movement, hip pain, and cartilage degeneration. By studying a pediatric population, we were able to characterize the temporality between cam morphology (occurring 1st) and joint degeneration. Using in silico (finite element) and in vivo (imaging biomarkers) studies, we demonstrated the biological plausibility of how a cam deformity can lead to joint degeneration. Furthermore, we were able to show a biological gradient between degree of cam deformity and extent of articular damage. However, not all patients develop joint degeneration and we were able to characterize which factors contribute to this (specificity). Lastly, we were able to show that by removing the cam morphology, one could positively influence the degenerative process (experiment). The findings of this body of work show consistency and coherence with the literature. Furthermore, they illustrate how cam morphology can lead to early joint degeneration analogous to SCFE, dysplasia, and joint mal-reduction post-injury. The findings of this study open new avenues on the association between cam morphology and OA including recommendations for the study, screening, follow-up, and assessment (patient-specific) of individuals with cam morphology in order to prevent early joint degeneration. Statement of significance: By satisfying Hill's criteria, one can deduct that in some individuals, cam morphology is a cause of OA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3125-3135, 2018.

What Are the Reference Values and Associated Factors for Center-edge Angle and Alpha Angle? A Population-based Study

BACKGROUND

The available evidence regarding normal ranges for the center-edge angle and the alpha angle derives from a few small studies, and associated factors such as sex and anthropometric factors have not been well evaluated. Knowing more about normal values for these parameters is critical, because this can inform decisions about when to perform elective hip preservation surgery. Population-level studies would provide considerable clarity on these issues, but to our knowledge, no such studies are available.

QUESTIONS/PURPOSES

The purposes of this study were (1) to use MRI in patients of a population-based study to establish normal values for the alpha and center-edge angles in the normal adult hip; and (2) to determine whether age, sex, or anthropometric variables were associated with differences in these values.

METHODS

We used MRI images (1.5 T) of 3226 participants of the Study of Health in Pomerania (SHIP). SHIP is a population-based study that started with 4308 participants in 1997. Participants were recruited randomly from official inhabitant data files as a stratified cluster sample of the population from a defined region in northeastern Germany. To ensure a representative epidemiologic cohort, stratification variables were sex, age, and city of residence. Between 2008 and 2012, 1094 of these participants underwent whole-body MRI with pelvic sequences in the second followup. In parallel, the next cohort, SHIP-Trend, started with the same protocol in which 2132 participants underwent MRI examination. Reference values were calculated by quantile regressions for the 2.5 and 97.5 percentiles. Associations with the demographic features sex, age, weight, height, body mass index (BMI), and waist circumference were analyzed by bivariate linear regression models.

RESULTS

The mean center-edge angle was 31° (± 7°) with a corresponding calculated normal range of 17° to 45°. The mean alpha angle was 55° (± 8°) with a corresponding calculated normal range between 39° and 71°. Men (30° ± 7°) had a lower center-edge angle than women (32° ± 8°) (p < 0.001, β = 1.4°; 95% confidence interval [CI], 0.9°-1.9°) and a higher alpha angle (57° ± 8° versus 52° ± 7°, p < 0.001, β = 5.7°; 95% CI, 5.2°-6.3°). Moreover, a higher center-edge angle for the left side was found (33° ± 8° versus 30° ± 8°, p < 0.001, β =3.2°; 95% CI, 3.0°-3.4°). In addition to sex, we found that age, height, waist circumference, and BMI affected both center-edge angle and alpha angle. Weight was associated with the alpha angle as well. Because of these associations, age- and sex-adjusted reference values with belonging formulas were calculated.

CONCLUSIONS

The range of normal center-edge and alpha angles is quite wide. Therefore, only markedly abnormal angles may be associated with pathology. Moreover, center-edge angle and alpha angle are associated with age, sex, and anthropometric factors, which have to be taken into account for better interpretation.

CLINICAL RELEVANCE

The association of abnormal radiographic values with true clinical hip pathology is tenuous at best. Assuming that a patient with an abnormal radiograph requires treatment is unwise. The clinical picture has to be substantial for therapeutic decisions.

Can We Discriminate Symptomatic Hip Patients From Asymptomatic Volunteers Based on Anatomic Predictors? A 3-Dimensional Magnetic Resonance Study on Cam, Pincer, and Spinopelvic Parameters

BACKGROUND

Given the high prevalence of patients with hip deformities and no ongoing hip dysfunction, understanding the anatomic factors predicting the symptomatic state is critical. One such variable is how the spinopelvic parameters (SPPs) may interplay with hip anatomic factors.

HYPOTHESIS/PURPOSE

SPPs and femoral- and acetabular-specific parameters may predict which patients will become symptomatic. The purpose was to determine which anatomic characteristics with specific cutoffs were associated with hip symptom development and how these parameters relate to each other.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 2.

METHODS

548 participants were designated either symptomatic patients (n = 176, scheduled for surgery with hip pain and/or functional limitation) or asymptomatic volunteers (n = 372, no pain) and underwent 3-dimensional magnetic resonance imaging. Multiple femoral (α angle, Ω angle, neck angle, torsion), acetabular (version, coverage), and spinopelvic (pelvic tilt, sacral slope [SS], pelvic incidence) parameters were measured semiautomatically. Normative values, optimal differentiating thresholds, and a logistic regression analysis were computed.

RESULTS

Symptomatic patients had larger cam deformities (defined by increased Ω angle and α angle), smaller acetabular coverage, and larger pelvic incidence and SS angles compared with the asymptomatic volunteers. Discriminant receiver operating characteristic analysis confirmed that radial 2-o'clock α angle (threshold 58°-60°, sensitivity 75%-60%, specificity 80%-84%; area under the curve [AUC] = 0.831), Ω angle (threshold 43°, sensitivity 72%, specificity 70%; AUC = 0.830), acetabular inclination (threshold 6°, sensitivity 65%, specificity 70%; AUC = 0.709), and SS (threshold 44°, sensitivity 72%, specificity 75%; AUC = 0.801) ( P < .005) were the best parameters to classify participants. When parameters were entered into a logistic regression, significant positive predictors for the symptomatic patients were achieved for SS, acetabular inclination, Ω angle, and α angle at 2-o'clock, correctly classifying 85% of cases (model sensitivity 72%, specificity 91%; AUC = 0.919).

CONCLUSION

Complex dynamic interplay exists between the hip and SPPs. A cam deformity, acetabular undercoverage, and increased SPP angles are predictive of a hip symptomatic state. SPPs were significant to discriminate between participants and were important in combination with other hip deformities. Symptomatic patients can be effectively differentiated from asymptomatic volunteers based on predictive anatomic factors.

Bilateral femoroacetabular impingement syndrome managed with different approaches: a case report

Purpose

The purpose of this case report is to present the successful management of symptomatic bilateral femoroacetabular impingement (FAI) syndrome in a patient who underwent surgical treatment on one side and non-surgical treatment on the other side.

Methods

We evaluated the treatment outcome of a young female presenting with bilateral FAI syndrome of cam morphology. A follow-up was performed at 5 years following surgical treatment on the right hip and 2 years following non-surgical treatment on the left hip. The evaluation included a clinical examination, patient-reported outcome measurements (PROM), plain radiographs, and magnetic resonance imaging (MRI).

Results

The patient experienced subjective improvements bilaterally. The clinical examination revealed differences in range of motion between the surgically treated and the non-surgically treated sides, with internal rotation differing the most (20° vs almost 0°). Flexion was, however, the same on both sides (125°). The PROM results were satisfactory on both sides, with slightly better results for the surgically treated side (the short version of the International Hip Outcome Tool [iHOT-12]: 96.9 vs 90, the Copenhagen Hip and Groin Outcome Score [HAGOS]: 90–100 vs 65–100). On the surgically treated side, the alpha angle decreased by 19° postoperatively. An MRI did not reveal any injury to the cartilage or labrum on either side.

Conclusion

This patient with bilateral FAI syndrome treated with arthroscopic surgery on one side and physiotherapy together with reduced physical activity on the other side, presented with good results bilaterally at follow-up.

The role of lumbar lordosis and pelvic sagittal balance in femoroacetabular impingement

Aims

The purpose of this study was to evaluate spinopelvic mechanics from standing and sitting positions in subjects with and without femoroacetabular impingement (FAI). We hypothesize that FAI patients will experience less flexion at the lumbar spine and more flexion at the hip whilst changing from standing to sitting positions than subjects without FAI. This increase in hip flexion may contribute to symptomatology in FAI.

Patients and Methods

Male subjects were prospectively enrolled to the study (n = 20). Mean age was 31 years old (22 to 41). All underwent clinical examination, plain radiographs, and dynamic imaging using EOS. Subjects were categorized into three groups: non-FAI (no radiographic or clinical FAI or pain), asymptomatic FAI (radiographic and clinical FAI but no pain), and symptomatic FAI (patients with both pain and radiographic FAI). FAI was defined as internal rotation less than 15° and alpha angle greater than 60°. Subjects underwent standing and sitting radiographs in order to measure spine and femoroacetabular flexion.

Results

Compared with non-FAI controls, symptomatic patients with FAI had less flexion at the spine (mean 22°, sd 12°, vs mean 35°, sd 8°; p = 0.04) and more at the hip (mean 72°, sd 6°, vs mean 62°, sd 8°; p = 0.047). Subjects with asymptomatic FAI had more spine flexion and similar hip flexion when compared to symptomatic FAI patients. Both FAI groups also sat with more anterior pelvic tilt than control patients. There were no differences in standing alignment among groups.

Conclusion

Symptomatic patients with FAI require more flexion at the hip to achieve sitting position due to their inability to compensate through the lumbar spine. With limited spine flexion, FAI patients sit with more anterior pelvic tilt, which may lead to impingement between the acetabulum and proximal femur. Differences in spinopelvic mechanics between FAI and non-FAI patients may contribute to the progression of FAI symptoms. Cite this article: Bone Joint J 2018;100-B:1275–9.

Prevalence of Radiographic Morphology of Femoroacetabular Impingement in Indian Population: A Multicenter Study

BACKGROUND

Femoroacetabular impingement (FAI) is an overlooked entity in India, as primary osteoarthritis of hip is uncommon in Indian population. The purpose of this study is to find out the prevalence of radiographic morphology of FAI in young asymptomatic population in India.

METHODS

This is a multicenter, cross-sectional study. Radiographs of 500 young asymptomatic volunteers were taken from 10 centers across India. Suboptimal imaging lead to exclusion of 48 radiographs. Crossover sign, ischial spine sign, and posterior wall sign were included in "acetabular rotation abnormalities (R)," lateral center-edge angle and acetabular index were included in "acetabular overcoverage abnormalities (O)" while pistol grip deformity and alpha angle in "femoral abnormalities (F)." Furthermore, all the hips were divided into 4 types: normal hips (N); type I hip with single abnormality (R/O/F); type II with combination of any 2 (RO/RF/OF), and type III with all 3 abnormalities.

RESULTS

Sixty-eight percent of 904 hips had at least 1 type of abnormality with 47.5% hips having signs of pincer impingement, 7.9% with signs of cam impingement, and 10.8% with mixed signs. Type I.R hips (32%) were the most common hips followed by type I.O hips (18%) and type I.F (8%). Males had higher percentage of abnormalities (1.5 times) compared to females. Interobserver reliability was 0.55 to 0.81 for all the parameters. Power of study was 0.98.

CONCLUSION

Radiographic morphology of FAI exists with high prevalence in young asymptomatic Indian population similar to other ethnicities except for low prevalence of cam morphology. Long-term follow-up of this cohort will reveal the natural history of these morphologies.

Altered Walking and Muscle Patterns Reduce Hip Contact Forces in Individuals With Symptomatic Cam Femoroacetabular Impingement

BACKGROUND

Cam-type femoroacetabular impingement (FAI) is a causative factor for hip pain and early hip osteoarthritis. Although cam FAI can alter hip joint biomechanics, it is unclear what role muscle forces play and how they affect the hip joint loading. Purpose/Hypothesis: The purpose was to examine the muscle contributions and hip contact forces in individuals with symptomatic cam FAI during level walking. Patients with symptomatic cam FAI would demonstrate different muscle and hip contact forces during gait.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eighteen patients with symptomatic cam FAI were matched for age and body mass index with 18 control participants. Each participant's walking kinematics and kinetics were recorded throughout a gait cycle (ipsilateral foot-strike to ipsilateral foot-off) by use of a motion capture system and force plates. Muscle and hip contact forces were subsequently computed by use of a musculoskeletal modeling program and static optimization methods.

RESULTS

The FAI group walked slower and with shorter steps, demonstrating reduced joint motions and moments during contralateral foot-strike, compared with the control group. The FAI group showed reduced psoas major (median, 1.1 newtons per bodyweight [N/BW]; interquartile range [IQR], 1.0-1.5 N/BW) and iliacus forces (median, 1.2 N/BW; IQR, 1.0-1.6 N/BW), during contralateral foot-strike, compared with the control group (median, 1.6 N/BW; IQR, 1.3-1.6 N/BW, P = .004; and median, 1.5 N/BW; IQR, 1.3-1.6 N/BW, P = .03, respectively), which resulted in lower hip contact forces in the anterior ( P = .026), superior ( P = .02), and medial directions ( P = .038). The 3 vectors produced a resultant peak force at the anterosuperior aspect of the acetabulum for both groups, with the FAI group demonstrating a substantially lower magnitude.

CONCLUSION

FAI participants altered their walking kinematics and kinetics, especially during contralateral foot-strike, as a protective mechanism, which resulted in reduced psoas major and iliacus muscle force and anterosuperior hip contact force estimations.

CLINICAL RELEVANCE

Limited hip mobility not only is attributed to bone-on-bone impingement, caused by cam morphology, but could be attributed to musculature as well. Not only would the psoas major and iliacus be able to protect the hip joint during flexion-extension, athletic conditioning could further strengthen core muscles for improved hip mobility and pelvic balance.

A Prospective Analysis of the Contralateral Hip Among Patients With Femoroacetabular Impingement: What Are the Risk Factors for Disease Progression?

BACKGROUND

The pathophysiology of femoroacetabular impingement (FAI) remains to be better understood, including factors affecting symptom development and disease progression.

PURPOSE

(1) To determine rates of initial and subsequent symptom development in the contralateral hip of patients with symptomatic FAI and (2) to identify predictors of the development of symptomatic contralateral FAI.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

This prospective study cohort included the contralateral hip of 179 consecutive patients undergoing primary surgical treatment of FAI. At presentation and follow-up time points, patients recorded the presence of symptoms in the contralateral hip. Patients with a minimum 1-year follow-up were included in the final cohort. Univariate analysis compared the patient characteristics and FAI imaging characteristics (cam and pincer) of initially asymptomatic patients who developed symptoms and those who remained asymptomatic. Kaplan-Meier survival curves were calculated to demonstrate symptom development over time.

RESULTS

A total of 148 patients (83%) were followed for at least 1 year (mean, 2.9 years). Thirty-four (23%) patients had symptoms in the contralateral hip at the time of the initial presentation. An additional 27 hips (24% of the initially asymptomatic) developed symptoms during the follow-up period at a mean 2.0 years from presentation. Head-neck offset ratio on the anteroposterior pelvis radiograph was significantly lower among hips that developed symptoms (0.153 vs 0.163 asymptomatic group, P = .027). Maximum alpha angle ( P = .503), lateral center edge angle ( P = .975), and crossover sign ( P = .865) were not predictive of the development of symptoms. Patients developing contralateral hip symptoms were less likely to have a UCLA (University of California, Los Angeles) activity score of 9 or 10 at presentation (18.2% vs 43.8%, P = .032). The total arc of rotation in flexion (internal rotation in 90° of flexion + external rotation in flexion) was significantly decreased in hips developing symptoms (39.4º vs 50.4º, P = .012). Kaplan-Meier survival analysis demonstrated that 72%, 67%, 56%, and 48% of all patients remained asymptomatic at 1, 2, 3, and 4 years, respectively.

CONCLUSION

Approximately 1 in 4 patients with FAI presents with symptoms in the contralateral hip, and an additional 1 in 4 patients develops significant symptoms in the following 4 years. Several factors, including low activity level, less hip rotational motion, and decreased head-neck offset ratio, were significantly associated with the development of symptoms, while the alpha angle and crossover sign were not.

Asymptomatic Participants With a Femoroacetabular Deformity Demonstrate Stronger Hip Extensors and Greater Pelvis Mobility During the Deep Squat Task

Background:

Cam-type femoroacetabular impingement (FAI) is a femoral head-neck deformity that causes abnormal contact between the femoral head and acetabular rim, leading to pain. However, some individuals with the deformity do not experience pain and are referred to as having a femoroacetabular deformity (FAD). To date, only a few studies have examined muscle activity in patients with FAI, which were limited to gait, isometric and isokinetic hip flexion, and extension tasks.

Purpose:

To compare (1) hip muscle strength during isometric contraction and (2) lower limb kinematics and muscle activity of patients with FAI and FAD participants with body mass index–matched healthy controls during a deep squat task.

Study Design:

Controlled laboratory study.

Methods:

Three groups of participants were recruited: 16 patients with FAI (14 male, 2 female; mean age, 38.5 ± 8.0 years), 18 participants with FAD (15 male, 3 female; mean age, 32.5 ± 7.1 years), and 18 control participants (16 male, 2 female; mean age, 32.8 ± 7.0 years). Participants were outfitted with electromyography electrodes on 6 muscles and reflective markers for motion capture. The participants completed maximal strength tests and performed 5 deep squat trials. Muscle activity and biomechanical variables were extrapolated and compared between the 3 groups using 1-way analysis of variance.

Results:

The FAD group was significantly stronger than the FAI and control groups during hip extension, and the FAD group had greater sagittal pelvic range of motion and could squat to a greater depth than the FAI group. The FAI group activated their hip extensors to a greater extent and for a longer period of time compared with the FAD group to achieve the squat task.

Conclusion:

The stronger hip extensors of the FAD group are associated with greater pelvic range of motion, allowing for greater posterior pelvic tilt, possibly reducing the risk of impingement while performing the squat, and resulting in a greater squat depth compared with those with symptomatic FAI.

Clinical Relevance:

The increased strength of the hip extensors in the FAD group allowed these participants to achieve greater pelvic mobility and a greater squat depth by preventing the painful impingement position. Improving hip extensor strength and pelvic mobility may affect symptoms for patients with FAI.

Acetabular and spino-pelvic morphologies are different in subjects with symptomatic cam femoro-acetabular impingement

Acetabular and spino-pelvic (SP) morphological parameters are important determinants of hip joint dynamics. This prospective study aimed to determine whether acetabular and SP morphological differences exist between hips with and without cam morphology and between symptomatic and asymptomatic hips with cam morphology. A cohort of 67 patients/hips was studied. Hips were either asymptomatic with no cam (Controls, n = 18), symptomatic with cam (n = 26) or asymptomatic with cam (n = 23). CT-based quantitative assessments of femoral, acetabular, pelvic, and spino-pelvic parameters were performed. Measurements were compared between controls and those with a cam deformity, as well as between the three groups. Morphological parameters that were independent predictors of a symptomatic cam were determined using a regression analysis. Hips with cam deformity had slightly smaller subtended angles superior-anteriorly (87° vs. 84°, p = 0.04) and greater pelvic incidence (53° vs. 48°, p = 0.003) compared to controls. Symptomatic cams had greater acetabular version (p < 0.01), greater subtended angles superiorly and superior-posteriorly (p = 0.01), higher pelvic incidence (p = 0.02), greater alpha angles and lower femoral neck-shaft angles compared to asymptomatic cams (p < 0.01) and controls (p < 0.01). The four predictors of symptomatic cam included antero-superior alpha angle, femoral neck-shaft angle, acetabular depth, and pelvic incidence. In conclusion, this study illustrates that symptomatic hips had a greater amount of supero-posterior coverage; which would be the contact area between a radial cam and the acetabulum, when the hip is flexed to 90°. Furthermore, individuals with symptomatic cam morphology had greater PI. Acetabular- and SP parameters should be part of the radiological assessment of femoro-acetabular impingement. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1840-1848, 2018.

In Search of the Spherical Femoroplasty: Cam Overresection Leads to Inferior Functional Scores Before and After Revision Hip Arthroscopic Surgery

BACKGROUND

Femoroplasty performed for the treatment of cam-type femoroacetabular impingement (FAI) has become a common procedure. Underresection may result in residual FAI. Conversely, overresection may disrupt the labral seal, which is responsible for chondroprotective fluid dynamics of the hip. Hypothesis/Purpose: It was hypothesized that cam overresection negatively affects hip function. The purpose was to examine the effect of the accuracy of previous femoroplasty on hips presenting for revision hip arthroscopic surgery.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Data were prospectively collected for patients presenting for revision hip arthroscopic surgery between June 2010 and August 2014. On the basis of measurements on Dunn view radiographs, cases were divided into 3 groups: overresection (OR group) in which overresection measured over 5% of the diameter of the femoral head, underresection (UR group) in which there was a residual cam lesion (alpha angle >60°), and neutral resection (neutral group). Data collection included the modified Harris Hip Score (mHHS), Nonarthritic Hip Score (NAHS), Hip Outcome Score-Sports-Specific Subscale, and visual analog scale at presentation and at a minimum 2-year follow-up after revision hip arthroscopic surgery and rates of conversion to total hip arthroplasty (THA).

RESULTS

One hundred thirty hips (120 patients) were included. Twenty hips (15.4%) were classified as the OR group, 16 (12.3%) as the UR group, and 94 (72.3%) as the neutral group. The mean follow-up was 39.6 ± 15.9 months. The mHHS and NAHS values at presentation were lower in the OR group compared with the UR group (50.2 ± 15.5 vs 64.7 ± 19.4 [ P = .033] and 48.5 ± 18.6 vs 63.0 ± 19.1 [ P = .044], respectively). The mHHS value at a minimum 2-year follow-up after revision was lower for the OR group (66.7 ± 19.8) than for the UR group (81.0 ± 14.5) ( P = .031). Conversion to THA was more common in the OR group than in the UR group (30% vs 0%, respectively; P = .024). Fifty percent of cases in the OR group, 69.9% in the neutral group, and 75% in the UR group met the minimal clinically important difference for the mHHS (Δ). The latest mHHS value reached the patient acceptable symptomatic state (PASS) in 35% of the cases in the OR group, 53.2% in the neutral group, and 75% in the UR group. Hips in the OR group had a significantly lower chance of reaching the PASS than the UR group (odds ratio, 0.1795 [95% CI, 0.0418-0.7711]; P = .0209).

CONCLUSION

Cam overresection of more than 5% of the diameter of the femoral head on the Dunn view predicts inferior clinical outcomes compared with cam underresection in this population. Furthermore, overresection predicts inferior outcomes after revision hip arthroscopic surgery and higher rates of conversion to THA.

Editorial Commentary: Hip Arthroscopy in a Military Population: Are the Results Comparable to an Athletic Population?

Hip pain is common in the military population and has led to an increase in hip arthroscopy as a means of therapeutic treatment. Return to duty (RTD) is the measure by which military surgeons tend to judge their outcomes; could the servicemember "get back in the fight?" Return to play (RTP) is a common metric in sports medicine for assessing the effectiveness of a surgical intervention. The results of prior studies of RTD hip arthroscopy in the US military population have been underwhelming when compared with RTP in athletic cohorts. This discrepancy in outcomes likely has more to do with the differences in RTD and RTP as outcome measures than any surgeon, pathology, or demographic factors.

Age- and Sex-Specific Morphologic Variations of Capital Femoral Epiphysis Growth in Children and Adolescents Without Hip Disorders

Background:

Understanding the development of the capital femoral epiphysis is essential to identify pathologic variations that may lead to cam morphology.

Purpose/Hypothesis:

The purpose of this study was to investigate the development of the capital femoral epiphysis during childhood and adolescence, with specific morphologic analysis of the peripheral growth and the metaphyseal surface of the growth plate. We hypothesized that age- and sex-dependent morphologic variations of the peripheral growth (cupping) and surface anatomy (epiphyseal tubercle) of the epiphysis would be evident with increasing age.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Pelvic computed tomography scans of 80 children and adolescents (range, 8-15 years; n = 10 per age group; 50% male), imaged because of suspected appendicitis, were used to reformat the proximal femur. All patients had asymptomatic hips with no signs or history of hip disorder. We measured the peripheral cupping of the epiphysis and the epiphyseal tubercle dimensions from 3-dimensional models. All measurements were normalized to the epiphyseal diameter. The effect of age on these parameters was evaluated by use of linear regression analysis. A 2-way analysis of variance (ANOVA) was used to compare these parameters between males and females.

Results:

The mean epiphyseal cupping increased with increasing age (R² = 0.54; P < .001). The mean normalized epiphyseal cupping was consistently higher in the anterior and posterior directions compared with the inferior and superior locations. Male patients aged 10 and 11 years had lower (P = .002) mean epiphyseal cupping compared with female patients of the same age. We observed no difference between male and female participants after 12 years of age (P > .3). The normalized epiphyseal tubercle height (R² = 0.08; P = .009), width (R² = 0.13; P = .001), and length (R² = 0.45; P < .001) decreased with increasing age, with no differences between male and female patients. On average, a 2.6-fold increase was found in epiphyseal cupping from 8 to 15 years of age, whereas normalized tubercle height decreased by 0.4-fold.

Conclusion:

Peripheral cupping of the epiphysis over the metaphysis increases with age, while the relative epiphyseal tubercle dimensions decrease. Females have an earlier onset of rapid increase in the peripheral cupping compared with males; however, no differences in epiphyseal tubercle dimensions were found between male and female patients. These findings may guide future studies investigating the development of cam morphology, which should consider the surface morphologic characteristics of the capital femoral epiphysis, the growth plate, and the differences in morphologic characteristics according to age and sex.

Are femoroacetabular impingement tomographic angles associated with the histological assessment of labral tears? A cadaveric study

Purpose

This study sought to investigate the association between tomographic femoroacetabular impingement (FAI) angles and histologically evaluated labral tears. The authors hypothesized that cadavers presenting with cam and pincer morphologies would present a higher prevalence of acetabular labral tears.

Methods

Twenty fresh cadavers were submitted to computed tomography. Standard FAI angles were measured, including the alpha angle, femoral version, acetabular version, Tonnis angle and center-edge angle. A cam lesion was defined as an alpha angle greater than 50^o. A pincer lesion was defined as a center-edge angle greater than 40^o, a Tonnis angle less than 0^o or acetabular version less than 0^o. After dissection, three fragments of each acetabulum, corresponding to the antero-superior, superior and postero-superior acetabular rim, were obtained. These fragments were submitted to routine histological preparation. Each slide was evaluated for possible labral tears. Tears were classified according to their Seldes type.

Results

The mean age of the cadavers was 50.2 years (SD: 7.4; 13 males). Sixteen (80%) of the cadavers had a cam lesion, and eight cadavers (40%) had a pincer lesion. Histologically, 16 (80%) of the cadavers had a labral tear in at least one region. According to the Seldes classification, 60.7% and 28.6% of these labral tears were type 1 and type 2, respectively. A mixed type of labral tear (10.7%), which represented a new form of Seldes tear, was described. Cadavers with a labral tear had significantly higher alpha angles than other cadavers (53.29^ovs 49.33^o, p = 0.01). Pincer lesions were not associated with labral tears. We found no association between pincer or cam lesions and Seldes classification.

Conclusion

Cadavers presenting with higher alpha angles had a higher incidence of labral tears. No association was found between FAI and Seldes classification.

Clinical relevance

This study demonstrated a high prevalence of FAI abnormalities associated with histological alterations in a cadaveric sample. Joint damage may be present in the early stages of FAI.

Correlation of Patient Symptoms With Labral and Articular Cartilage Damage in Femoroacetabular Impingement

Background:

Femoroacetabular impingement (FAI) can lead to labral and articular cartilage injuries as well as early osteoarthritis of the hip. Currently, the association of patient symptoms with the progression of labral and articular cartilage injuries due to FAI is poorly understood.

Purpose:

To evaluate the correlation between patient-reported outcome (PRO) scores and cartilage compositional changes seen on quantitative magnetic resonance imaging (MRI) as well as cartilage and labral damage seen during arthroscopic surgery in patients with FAI.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients were prospectively enrolled before hip arthroscopic surgery for symptomatic FAI. Patients were included if they had cam-type FAI without radiographic arthritis. All patients completed PRO scores, including the Hip disability and Osteoarthritis Outcome Score (HOOS) and a visual analog scale for pain. MRI with mapping sequences (T_1ρ and T₂) on both the acetabular and femoral regions was performed before surgery to quantitatively assess the cartilage composition. During arthroscopic surgery, cartilage and labral injury grades were recorded using the Beck classification. Pearson and Spearman correlation coefficients were then obtained to evaluate the association between chondrolabral changes and PRO scores.

Results:

A total of 46 patients (46 hips) were included for analysis (mean age, 35.5 years; mean body mass index [BMI], 23.9 kg/m²; 59% male). Increasing BMI was correlated with a more severe acetabular cartilage grade (ρ = 0.37; 95% CI, 0.08-0.65). A greater alpha angle was correlated with an increased labral tear grade (ρ = 0.59; 95% CI, 0.37-0.82) and acetabular cartilage injuries (ρ = 0.61; 95% CI, 0.42-0.80). With respect to PRO scores, increasing femoral cartilage damage in the anterosuperior femoral head region, as measured on quantitative MRI using T_1ρ and T₂ mapping, correlated with lower (worse) scores on the HOOS Activities of Daily Living (r = 0.35; 95% CI, 0.06-0.64), Symptoms (r = 0.32; 95% CI, 0.06-0.57), and Pain (r = 0.31; 95% CI, 0.06-0.55) subscales. There was no correlation between PRO scores and acetabular cartilage damage or labral tearing found on quantitative MRI or during arthroscopic surgery.

Conclusion:

Femoral cartilage damage, as measured on T_1ρ and T₂ mapping, appears to have a greater correlation with clinical symptoms than acetabular cartilage damage or labral tears in patients with symptomatic FAI.

Epidemiology of Hip and Groin Injuries in Collegiate Athletes in the United States

Background:

Hip and groin pain is a common complaint among athletes. Few studies have examined the epidemiology of hip and groin injuries in collegiate athletes across multiple sports.

Purpose:

To describe the rates, mechanisms, sex-based differences, and severity of hip/groin injuries across 25 collegiate sports.

Study Design:

Descriptive epidemiology study.

Methods:

Data from the 2009-2010 through 2013-2014 academic years were obtained from the National Collegiate Athletic Association Injury Surveillance Program (NCAA ISP). The rate of hip/groin injuries, mechanism of injury, time lost from competition, and need for surgery were calculated. Differences between sex-comparable sports were quantified using rate ratios (RRs) and injury proportion ratios (IPRs).

Results:

In total, 1984 hip/groin injuries were reported, giving an overall injury rate of 53.06 per 100,000 athlete-exposures (AEs). An adductor/groin tear was the most common injury, comprising 24.5% of all injuries. The sports with the highest rates of injuries per 100,000 AEs were men’s soccer (110.84), men’s ice hockey (104.90), and women’s ice hockey (76.88). In sex-comparable sports, men had a higher rate of injuries per 100,000 AEs compared with women (59.53 vs 42.27, respectively; RR, 1.41 [95% CI, 1.28-1.55]). The most common injury mechanisms were noncontact (48.4% of all injuries) and overuse/gradual (20.4%). In sex-comparable sports, men had a greater proportion of injuries due to player contact than women (17.0% vs 3.6%, respectively; IPR, 4.80 [95% CI, 3.10-7.42]), while women had a greater proportion of injuries due to overuse/gradual than men (29.1% vs 16.7%, respectively; IPR, 1.74 [95% CI, 1.46-2.06]). Overall, 39.3% of hip/groin injuries resulted in time lost from competition. Only 1.3% of injuries required surgery.

Conclusion:

Hip/groin injuries are most common in sports that involve kicking or skating and sudden changes in direction and speed. Most hip/groin injuries in collegiate athletes are noncontact and do not result in time lost from competition, and few require surgery. This information can help guide treatment and prevention measures to limit such injuries in male and female collegiate athletes.

Hip Arthroscopy: Common Problems and Solutions

The use of hip arthroscopy continues to expand. Understanding potential pitfalls and complications associated with hip arthroscopy is paramount to optimizing clinical outcomes and minimizing unfavorable results. Potential pitfalls and complications are associated with preoperative factors such as patient selection, intraoperative factors such as iatrogenic damage, traction-related complications, inadequate correction of deformity, and nerve injury, or postoperative factors such as poor rehabilitation. This article outlines common factors that contribute to less-than-favorable outcomes.

Differences in Hip Joint Biomechanics and Muscle Activation in Individuals With Femoroacetabular Impingement Compared With Healthy, Asymptomatic Individuals: Is Level-Ground Gait Analysis Enough?

Background:

Femoroacetabular impingement (FAI) is a recognized cause of hip and groin pain and a significant factor in hip joint function during sport. Objective tests for understanding hip function are lacking in this population.

Purpose:

To determine whether biomechanical and electromyographic features of hip function during level-ground walking differ between a group diagnosed with FAI and those with no symptoms of FAI.

Study Design:

Controlled laboratory study.

Methods:

A total of 20 asymptomatic individuals and 20 individuals with FAI walked on a dual-belt instrumented treadmill at self-selected walking velocities. Sagittal and frontal plane joint motions, moments, and muscle activation for the gluteus medius, gluteus maximus, rectus femoris, and medial and lateral hamstrings were analyzed. Discrete measures were extracted from each biomechanical waveform, and principal component analysis was used to determine hip joint muscle activation and hip adduction moment patterns. Statistical significance was determined by use of Student t tests with Bonferroni adjustments for multiple comparisons (α = .05).

Results:

Individuals with FAI walked more slowly (P = .015) and had lower self-reported function (P < .001). No differences in muscle strength were found between the symptomatic and contralateral legs in the FAI group (P > .017), but those with FAI had lower strength in the knee extensors and flexors and the hip extensors, flexors, and adductors compared with the asymptomatic group (P < .017). Individuals with unilateral symptomatic FAI walked with similar biomechanical and hip muscle electromyographic results bilaterally. The only differences found were a greater amplitude of gluteus maximus activation in the FAI symptomatic leg compared with the asymptomatic group and greater medial hamstring activation than lateral hamstring activation in the FAI group in both limbs compared with the asymptomatic group.

Conclusion:

Individuals with FAI were generally deconditioned and reported significantly more functional limitations. No biomechanical differences existed between groups during level walking, yet hamstring and gluteus maximus activation differed when the symptomatic group was compared with the asymptomatic group.

Clinical Relevance:

The field lacks objective testing of hip joint function to understand implications of FAI for dynamic movements, particularly with applications to biomechanics and electromyography. Level walking was of limited value for understanding FAI hip function, and the development of a more challenging gait assessment is warranted.

The natural alpha angle of the femoral head-neck junction

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.

Anatomic Predictors of Sagittal Hip and Pelvic Motions in Patients With a Cam Deformity

BACKGROUND

As there is a high prevalence of patients with cam deformities and no ongoing hip dysfunction, understanding the biomechanical factors predicting the onset of symptoms and degenerative changes is critical. One such variable is how the spinopelvic parameters may influence hip and pelvic sagittal mobility. Hypothesis/Purpose: Pelvic incidence may predict sagittal hip and pelvic motions during walking and squatting. The purpose was to determine which anatomic characteristics were associated with symptoms and how they influenced functional hip and pelvic ranges of motion (ROMs) during walking and squatting.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifty-seven participants underwent computed tomography and were designated either symptomatic (n = 19, cam deformity with pain), asymptomatic (n = 19, cam deformity with no pain), or control (n = 19, no cam deformity or pain). Multiple femoral (cam deformity, neck angle, torsion), acetabular (version, coverage), and spinopelvic (pelvic tilt, sacral slope, pelvic incidence) parameters were measured from each participant's imaging data, and sagittal hip and pelvic ROMs during walking and squatting were recorded using a motion capture system.

RESULTS

Symptomatic participants had large cam deformities, smaller femoral neck-shaft angles, and larger pelvic incidence angles compared with the asymptomatic and control participants. Discriminant function analyses confirmed that radial 1:30 alpha angle (λ₁ = 0.386), femoral neck-shaft angle (λ₂ = 0.262), and pelvic incidence (λ₃ = 0.213) ( P < .001) were the best anatomic parameters to classify participants with their groups. Entering these 3 parameters into a hierarchical linear regression, significant regressions were achieved for hip ROM only when pelvic incidence was included for walking ( R² = 0.20, P = .01) and squatting ( R² = 0.14, P = .04). A higher pelvic incidence decreased walking hip ROM ( r = -0.402, P = .004). Although symptomatic participants indicated a trend of reduced squatting hip and pelvic ROMs, there were no significant regressions with the anatomic parameters.

CONCLUSION

A cam deformity alone may not indicate early clinical signs or decreased ROM. Not only was pelvic incidence a significant parameter to classify the participants, but it was also an important parameter to predict functional ROM. Symptomatic patients with a higher pelvic incidence may experience limited sagittal hip mobility.

CLINICAL RELEVANCE

Patients with symptomatic femoroacetabular impingement showed a higher pelvic incidence and, combined with a cam deformity and varus neck, can perhaps alter the musculature of their iliopsoas, contributing to a reduced sagittal ROM. With an early and accurate clinical diagnosis, athletes could benefit from a muscle training strategy to protect their hips.

Musculoskeletal Screening Tests and Bony Hip Morphology Cannot Identify Male Professional Soccer Players at Risk of Groin Injuries: A 2-Year Prospective Cohort Study

BACKGROUND

Musculoskeletal hip/groin screening tests are commonly performed to detect at-risk individuals. Bony hip morphology is considered a potential intrinsic risk factor but has not been examined prospectively.

PURPOSE

To evaluate the association between intrinsic risk factors identified from musculoskeletal and radiographic screening tests and hip/groin injuries leading to time loss from training and/or match play in professional male soccer players.

STUDY DESIGN

Prospective cohort study; Level of evidence, 2.

METHODS

Male professional soccer players, aged ≥18 years, underwent screening specific for hip/groin pain during 2 consecutive seasons of the Qatar Stars League. The screening battery included pain provocation, range of motion, and strength tests as well as a hip radiographic examination. The radiographic examination included an anteroposterior pelvic view and 45° Dunn view, with bony hip morphology determined using quantitative methods. Time-loss (≥1 day) hip/groin injuries and individual player exposure (training and match play) were recorded prospectively, and injuries were categorized as adductor-related, inguinal-related, iliopsoas-related, pubic-related, or hip-related groin pain, or "other," as recommended in the Doha agreement. We calculated hazard ratios (HRs) from univariate and multivariate Cox regression models to assess the relationship between potential risk factors and hip/groin injuries.

RESULTS

There were 438 players, completing 609 player seasons, and 113 hip/groin injuries that met the criteria for inclusion, with 85 injuries categorized as adductor-related. The proportion of players with bony morphological variants was the following: cam, 71%; pincer, 5%; and acetabular dysplasia, 13%. Previous hip/groin injuries (HR, 1.8; 95% CI, 1.2-2.7) and eccentric adduction strength were associated with the risk of hip/groin injuries. Higher (>1 SD above the mean) than normal eccentric adduction strength was associated with an increased risk for all hip/groin injuries (HR, 1.6; 95% CI, 1.0-2.5). Lower (<1 SD below the mean) than normal eccentric adduction strength was associated with an increased risk for adductor-related injuries (HR, 1.7; 95% CI, 1.0-3.0). No other musculoskeletal screening test or bony hip morphology variables were associated with the injury risk.

CONCLUSION

Previous groin injuries and eccentric adduction strength were associated with the risk of groin injuries. However, these associations were not strong enough to identify an "at-risk" individual, and therefore, musculoskeletal screening tests were not useful to dictate individualized prevention strategies. Bony hip morphology was not associated with the risk of groin injuries.

Characterization of proximal femoral anatomy in the skeletally-immature patient

PURPOSE

The morphology of the proximal femur has been extensively studied in the adult population. However, no literature providing a comprehensive evaluation of the anatomy in paediatric patients exists. The current study aims to characterize such anatomy in skeletally-immature patients, examine potential differences between genders, and analyze how these anatomical parameters change with age.

METHODS

Cadaveric femurs from the Hamann-Todd Osteological Collection were examined. Specimens with open physes and no skeletal disease or deformity were included for analysis. Age and gender were recorded for each specimen. Each femur was photographed in standardized modified axial and anteroposterior views. In all, 14 proximal femoral anatomical parameters were measured from these photographs. Comparisons between genders and age were calculated.

RESULTS

A total of 43 femurs from ages four to 17 years met inclusion criteria. The majority were female (56%); no difference existed in age between genders (p = 0.62). The specimens had a neutral mean neck-shaft angle (130.7º) and anteversion (12.8º), and the sphericity of the ossified femoral heads was symmetrical. Male specimens had significantly higher alpha angles (p = 0.01), posterior offset (p = 0.02), neck width (p = 0.04) and head-neck length ratio (p = 0.02) values than female specimens. Strong positive correlations exist between length/size parameters and age, while negligible correlations were noted for angular measurements.

CONCLUSIONS

This study establishes reference values for a comprehensive list of anatomical parameters for the skeletally-immature ossified proximal femur. It highlights gender differences in morphology and demonstrates that angular characteristics remain relatively stable while length parameters generally increase with age.

LEVEL OF EVIDENCE

Level III Diagnostic.

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.

The Relationship Between the Location of Uptake on Positron Emission Tomography/Computed Tomography and the Impingement Point by Computer Simulation in Femoroacetabular Impingement Syndrome With Cam Morphology

PURPOSE

To clarify the concordance rate of the location of uptake on positron emission tomography/computed tomography (PET/CT) and the impingement point demonstrated in computer simulation in femoroacetabular impingement (FAI) syndrome with cam morphology.

METHODS

We included hip joints with FAI syndrome that underwent ¹⁸F-fluoride PET/CT. We also excluded hips with SUV_max <6. Each hip was evaluated for the region of the SUV_max point on PET/CT as well as the impingement point by computer simulation. We used ZedHip software (Lexi, Tokyo, Japan) for impingement simulation analysis based on CT data. Bony impingement is identified if there is a mesh in acetabular and femoral side contact in at least one unit. We investigated the rate of concordance between these 2 regions for each 10° flexion angle of the hip, ranging from 0° to 90°.

RESULTS

Twenty-two hips of 22 patients were evaluated. The SUV_max region was most frequently distributed in the proximal middle region in 12 hips. In 18 of 22 hips (81.8%), the SUV_max region was concordant with the impingement region for at least one flexion angle. The concordance rates in 50° (P = .034), 60° (P = .007), 70° (P = .011), and 80° (P = .046) of flexion were significantly higher than in 90° of flexion.

CONCLUSIONS

It was possible to visualize and clarify the detailed location of abnormal uptake in FAI syndrome patients with cam morphology by applying ¹⁸F-fluoride PET/CT. The concordance rates in 50°, 60°, 70°, and 80° of flexion were significantly higher than in 90° of flexion, which suggested that impingement may more frequently occur at less than 90° of flexion in FAI syndrome with cam morphology.

LEVEL OF EVIDENCE

Level III, cross-sectional diagnostic study.

UK FASHIoN: feasibility study of a randomised controlled trial of arthroscopic surgery for hip impingement compared with best conservative care

BACKGROUND

Femoroacetabular impingement (FAI) is a syndrome of hip or groin pain associated with shape abnormalities of the hip joint. Treatments include arthroscopic surgery and conservative care. This study explored the feasibility of a randomised controlled trial to compare these treatments.

OBJECTIVES

The objectives of this study were to estimate the number of patients available for a full randomised controlled trial (RCT); to explore clinician and patient willingness to participate in such a RCT; to develop consensus on eligibility criteria, surgical and best conservative care protocols; to examine possible outcome measures and estimate the sample size for a full RCT; and to develop trial procedures and estimate recruitment and follow-up rates.

METHODS

Pre-pilot work: we surveyed all UK NHS hospital trusts (n = 197) to identify all FAI surgeons and to estimate how much arthroscopic FAI surgery they performed. We interviewed a purposive sample of 18 patients, 36 physiotherapists, 18 surgeons and two sports physicians to explore attitudes towards a RCT and used consensus-building methods among them to develop treatment protocols and patient information. Pilot RCT: we performed a pilot RCT in 10 hospital trusts. Patients were randomised to receive either hip arthroscopy or best conservative care and then followed up at 3, 6 and 12 months using patient-reported questionnaires for hip pain and function, activity level, quality of life, and a resource-use questionnaire. Qualitative recruitment intervention: we performed semistructured interviews with all researchers and clinicians involved in the pilot RCT in eight hospital trusts and recorded and analysed diagnostic and recruitment consultations with eligible patients.

RESULTS

We identified 120 surgeons who reported treating at least 1908 patients with FAI by hip arthroscopy in the NHS in the financial year 2011/12. There were 34 hospital trusts that performed ≥ 20 arthroscopic FAI operations in the year. We found that clinicians were positive about a RCT: only half reported equipoise, but most said that they would be prepared to randomise patients. Patients strongly supported a RCT, but expressed concerns about its design; these were used to develop patient information for the pilot RCT. We developed a surgical protocol and showed that this could be used in a RCT. We developed a physiotherapy-led exercise-based package of best conservative care called 'personalised hip therapy' and showed that this was practicable. In the pilot RCT, we recruited 42 out of 60 eligible patients (70%) across nine sites. The mean duration and recruitment rate across all sites were 4.5 months and one patient per site per month, respectively. The lead site recruited for the longest period (9.3 months) and accrued the largest number of patients (2.1 patients per month). We recorded and analysed 84 diagnostic and recruitment consultations in 60 patients and used these to develop a model for an optimal recruitment consultation. We identified the International Hip Outcome Tool at 12 months as an appropriate outcome measure and estimated the sample size for a full trial as 344 participants: a number that could be recruited in 25 centres over 18 months.

CONCLUSION

We have demonstrated that it is feasible to perform a RCT to establish the clinical effectiveness of hip arthroscopy compared with best conservative care for FAI. We have designed a full trial and developed and tested procedures for it, including an innovative approach to recruitment. We propose that a full trial be implemented.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Prevalence of Cam Deformity with Associated Femoroacetabular Impingement Syndrome in Hip Joint Computed Tomography of Asymptomatic Adults

Purpose

Femoroacetabular impingement (FAI) is considered an important cause of early degenerative arthritis development. Although three-dimensional (3D) imaging such as computed tomography (CT) and magnetic resonance imaging are considered precise imaging modalities for 3D morphology of FAI, they are associated with several limitations when used in out-patient clinics. The paucity of FAI morphologic data in Koreans makes it difficult to select the most effective radiographical method when screening for general orthopedic problems. We postulate that there might be an individual variation in the distribution of cam deformity in the asymptomatic Korean population.

Materials and Methods

From January 2011 to December 2015, CT images of the hips of 100 subjects without any history of hip joint ailments were evaluated. A computer program which generates 3D models from CT scans was used to provide sectional images which cross the central axis of the femoral head and neck. Alpha angles were measured in each sectional images. Alpha angles above 55° were regarded as cam deformity.

Results

The mean alpha angle was 43.5°, range 34.7–56.1°(3 o'clock); 51.24°, range 39.5–58.8°(2 o'clock); 52.45°, range 43.3–65.5°(1 o'clock); 44.09°, range 36.8–49.8°(12 o'clock); 40.71, range 33.5–45.8°(11 o'clock); and 39.21°, range 34.1–44.6°(10 o'clock). Alpha angle in 1 and 2 o'clock was significantly larger than other locations (P<0.01). The prevalence of cam deformity was 18.0% and 19.0% in 1 and 2 o'clock, respectively.

Conclusion

Cam deformity of FAI was observed in 31% of asymptomatic hips. The most common region of cam deformity was antero-superior area of femoral head-neck junction (1 and 2 o'clock).

Predictors of Clinically Suspected Intra-articular Hip Symptoms and Prevalence of Hip Pathomorphologies Presenting to Sports Medicine and Hip Preservation Orthopaedic Surgeons

PURPOSE

The first purpose of the study was to evaluate the prevalence of various radiographic parameters and pathomorphologies for patients presenting with the diagnosis of hip pain. The second purpose of this study was to identify those pathomorphologies and radiographic parameters that were predictive of clinically suspected intra-articular and hip joint-related symptoms.

METHODS

A total of 998 hips (499 patients, 228 males, 271 females, mean age 38 years) presented to 2 orthopaedic surgeons with the diagnosis of hip pain. Patients were retrospectively identified as intra-articular and hip joint-related symptoms or extra-articular and non-hip joint-related symptoms based on history, examination, injection response, and diagnosis listed on clinical notes. A detailed morphologic evaluation of anteroposterior and 45° modified Dunn lateral radiographs of both hips was performed for all patients.

RESULTS

The presence of at least 1 finding consistent with femoroacetabular impingement (FAI) was noted in 96.6% of patients (89.9% of hips) and was bilateral in 83%. The prevalence of dysplasia was 10.6% in patients (6.7% of hips) and was bilateral in 2.8%. Cam-type morphology was more common in males (P < .001). Profunda and protrusio were more common in females (P < .001). Acetabular retroversion was more common in males (P = .02). Fifty-seven percent of hips (564/998) were diagnosed clinically with intra-articular and hip joint related symptoms. Cam-type FAI, mixed-type FAI, increasing alpha angle, and increasing Tönnis grade were independent predictors of clinically suspected intra-articular and hip joint symptoms (P < .001), whereas isolated Pincer-type morphology was not.

CONCLUSIONS

FAI is highly prevalent (96.6%) and frequently bilateral (83%) in patients presenting to an orthopaedic clinic with hip pain. Cam-type morphology and acetabular retroversion are more frequent in men, whereas profunda and protrusio are more frequent in women. Cam-type morphology, increasing alpha angle (larger cam morphology), and increasing Tönnis grade were highly predictive of clinically suspected intra-articular symptoms, whereas isolated pincer-type morphology was not.

LEVEL OF EVIDENCE

Level III, case-control study.

Outcomes of intra-articular corticosteroid injections for adolescents with hip pain

Intra-articular injection of corticosteroid and anesthetic (CSI) is a useful diagnostic tool for hip pain secondary to labral tears or femoroacetabular impingement (FAI). However, the effectiveness of CSI as a stand-alone treatment for hip pain in adolescents is unknown. The purpose of this study is to evaluate the use of CSI for the treatment of hip pain and determine factors that may affect outcomes after injection. Retrospective analysis of 18 patients and 19 hips that underwent fluoroscopic guided hip injection for the treatment of pain at a single institution from 2012 to 2015 was carried out in this study. Mean age at the time of injection was 15.1 years (range 13–17) with mean follow-up of 29.4 months. Fifty-two percent (10/19 hips) went on to surgery after the injection. Average time to surgical conversion was 12.8 months after CSI. Cam or pincer morphologies were present in 90% (9/10 hips) of the operative group. Patients with FAI were more likely to need surgery than patients without bony abnormalities (RR= 10, 95% CI 1.6–64.2, P = 0.0001). There was no difference in the presence of labral tears in the operative and non-operative groups (100% versus 89%, P = 0.47). For adolescents without bony abnormalities, 90% improved with CSI alone and did not require further treatment within 2.4 years. Fluoroscopic guided corticosteroid hip injection may have limited efficacy for the treatment of hip pain secondary to FAI in adolescents. However, for patients without osseous deformity, CSI may offer prolonged improvement of symptoms even in the presence of labral tears.

Origin of Cam Morphology in Femoroacetabular Impingement

Cam morphology of the proximal femur is an abnormal contour of the femoral head-neck junction present in approximately 15% to 25% of the asymptomatic population, predominantly in males. Alpha angle and femoral head-neck offset ratio are 2 objective measurement tools that define cam morphology. Both primary (idiopathic) and secondary cam deformity develops through distinct mechanisms. The cause of primary (idiopathic) cam morphology remains incompletely understood. Mounting evidence suggests that idiopathic cam morphology develops during adolescence through alterations in the capital femoral epiphysis in response to participation in vigorous sporting activity. While the exact cause of epiphyseal extension has not yet been determined, preliminary evidence suggests that epiphyseal extension may reflect a short-term adaptive response to provide stability to the physis at the long-term cost of the development of cam morphology. Commonly recognized causes of secondary cam deformity include frank slipped capital femoral epiphysis, Legg-Calve-Perthes disease, and deformity after fracture of the proximal femur. Recent studies also support subtle slipped capital femoral epiphysis as a unique and silent cause of a small percentage of subjects previously thought to have idiopathic cam deformity.

Acetabular overcoverage in the horizontal plane: an underdiagnosed trigger of early hip arthritis. A CT scan study in young adults

INTRODUCTION

Acetabular overcoverage promotes hip osteoarthritis causing a pincer-type femoroacetabular impingement. Acetabular coverage in the horizontal plane is usually poorly defined in imaging studies and may be misdiagnosed. The goal of this study was to analyze the role of acetabular overcoverage measured in the frontal plane and in the horizontal plane by CT scan and to determine its relationship with other anatomic features in the onset of hip arthritis in young adults.

MATERIALS AND METHODS

We compared prospectively CT scans from two groups of adults of 55 years or younger: the patient group (n = 30) consisted of subjects with diagnosis of early hip arthritis (Tönnis Grade I or II) and the control group (n = 31) consisted of subjects with healthy hips. Two independent observers analyzed centre edge angle (CEA), acetabular anteversion angle (AAA), anterior sector acetabular angle (AASA), posterior sector acetabular angle (PASA), horizontal acetabular sector angle (HASA), femoral anteversion angle (FAVA), alpha angle (AA), and Mckibbin Instability Index (MI).

RESULTS

Angles measuring the acetabular coverage on the horizontal plane (AASA, PASA and, HASA) were significantly higher in the patient group (p < 0.001, p = 0.03 and p < 0.001, respectively). Pearson's correlation coefficient showed a positive correlation between CEA and HASA in patients (r = 0.628) and in controls (r = 0.660). However, a high CEA (> 35º) was strongly associated with a high HASA (> 160º) in patients (p = 0.024) but not in controls (p = 0.21), suggesting that pincer should be simultaneously present in the horizontal and frontal plane to trigger hip degeneration. No significant association was detected between a high alpha angle (> 60º) and a high CEA (> 35º suggesting that a mixed pincer-cam aetiology was not prevalent in our series. Multivariate regression analysis showed the most significant predictors of degenerative joint disease were HASA (p = 0.008), AA (p = 0.048) and ASAA (p = 0.004).

CONCLUSIONS

Acetabular overcoverage in the horizontal plane plays an important role in the onset of early hip arthritis. Considering that this condition is usually underdiagnosed, we suggest the anterior sector acetabular angle, the posterior sector acetabular angle, and the horizontal acetabular sector angles be routinely included in decision-making algorithms in hip conservative surgery to better define hips-at-risk of developing early hip osteoarthritis.

Prevalence of Cam and Pincer Deformities in the X-Rays of Asymptomatic Individuals

Objective

The presence of radiological signs of femoroacetabular impingement (FAI) is not necessarily associated with symptoms. Hence, the prevalence of cam and pincer deformities in the overall population may be underestimated. The purpose of this study was to screen an unselected cohort of people without hip symptoms for native radiological signs of cam and pincer deformities to determine their actual prevalence.

Materials and Methods

110 asymptomatic patients had AP pelvis X-rays and cross-table hip X-rays performed. We evaluated the images for the presence of cross-over signs and measured lateral center edge (LCE) angles, alpha angles (α-angles), and femoral offset ratios.

Results

Positive cross-over signs were seen in 34%; LCE angles > 40° in 13%; and femoral offset ratios < 0.18 in 43%. In 41% of the patients, α-angles were >50°. Male patients showed significantly higher α-angles, lower offset ratios, and a higher prevalence of cross-over signs. In contrast, female patients had significantly higher LCE angles.

Conclusion

According to our data, radiological signs of cam and pincer deformities are common in asymptomatic people. In clinical practice, patients presenting with hip pain and radiological signs of FAI should undergo further diagnostic evaluation. However, in asymptomatic patients, no further evaluation is recommended.

The failing medial compartment in the varus knee and its association with CAM deformity of the hip

BACKGROUND

Since 2011, the knee service at the Nuffield Orthopaedic Centre has been offering a neutralising medial opening wedge high tibial osteotomy (HTO) to a specific group of patients with genu varum and early knee osteoarthritis. An observation was made concerning this group of patients and the presence of CAM deformity at the hip. The aim of this study is to establish whether or not any association exists between the OA phenotype shared by our HTO group and the incidence of CAM deformity at the hip.

METHODS

A cross-sectional study was designed to estimate the prevalence of CAM-type lesions across different groups of individuals. Our HTO group (n=30) was compared to a pre-arthroplasty group (n=20) and control group (n=20). A total of 70 subjects were identified across the different groups all of whom had long-leg radiographs (LLRs) available for analysis. LLRs were analysed using an in house developed Matlab®-based (Matlab R2009b; MathWorks) software package for hip measurements and MediCAD® (Hectec GmbH, Germany) for lower limb alignment measurements.

RESULTS

The HTO group had a significantly higher prevalence of CAM lesions (57%) than both the pre-arthroplasty (40%) and control (30%) groups. This difference was maintained when results were adjusted for potential confounding factors (age, gender and laterality). Across the groups, individuals with tibia vara were more likely to have CAM-deformity of the hip (p=0.021).

CONCLUSION

Patients with symptomatic early knee OA and varus deformity of the knee have a high prevalence of CAM deformity in the hip.

Hip shape is symmetric, non-dependent on limb dominance and gender-specific: implications for femoroacetabular impingement. A 3D CT analysis in asymptomatic subjects

OBJECTIVE

To determine the reference intervals (RefInt) of the quantitative morphometric parameters of femoroacetabular impingement (FAI) in asymptomatic hips with computed tomography (CT) and determine their dependence on age, side, limb dominance and sex.

METHODS

We prospectively included 590 patients and evaluated 1111 hips with semi-automated CT analysis. We calculated overall, side- and sex-specific parameters for imaging signs of cam [omega and alpha angle (α°)] and pincer-type morphology [acetabular version (ACvers), lateral centre-edge angle (LCEA) and cranio-caudal coverage].

RESULTS

Hip shape was symmetrical and did not depend on limb dominance. The 95% RefInt limits were sex-different for all cam-type parameters and extended beyond current abnormal thresholds. Specifically, the upper limits of RefInt for α° at 12:00, 1:30 and 3:00 o'clock positions were 56°, 70° and 58°, respectively, and 45° for LCEA. Acetabular morphology varied between age groups, with a trend toward an LCEA/ACvers increase over time.

CONCLUSION

Our morphometric measurements can be used to estimate normal hip morphology in asymptomatic individuals. Notably they extended beyond current thresholds used for FAI imaging diagnosis, which was most pronounced for cam-type parameters. We suggest the need to reassess α° RefInt and consider a 60° threshold for the 12:00/3:00 positions and 65-70° for other antero-superior positions.

KEY POINTS

• Hip shape is symmetrical regardless of limb dominance. • Pincer/cam morphology is frequent in asymptomatic subjects (20 and 71%, respectively). • LCEA and acetabular version increases with age (5-7° between opposite age groups). • Femoral morphology is stable after physeal closure (in the absence of pathology). • Alpha and omega angle thresholds should be set according to sex.

A sex-specific association between incident radiographic osteoarthritis of hip or knee and incident peripheral arterial calcifications: 8-year prospective data from Cohort Hip and Cohort Knee (CHECK)

OBJECTIVES

There is sparse evidence for a relationship between cardiovascular disease (CVD) and osteoarthritis (OA). We investigated the association between incidence of arterial calcifications and incidence of radiographic knee and/or hip OA.

DESIGN

We used baseline and 8-year follow-up data of Cohort Hip and Cohort Knee (CHECK). Knees and hips were either Kellgren-Lawrence (KL) grade 0 or 1 at baseline. Arterial calcifications were scored on hip and knee radiographs using a four-grade scale. Scores were summed for patient-level analyses. To investigate incidence, participants with arterial calcifications at baseline or missing follow-up were excluded. Incident OA was defined per joint as KL ≥ 2 or prosthesis at year eight. The association between incidenct of arterial calcifications and incident OA was studied using mixed-effects logistic regression.

RESULTS

Of 763 participants included, 623 (82%) were women. Mean (sd) age was 56 (5.1) years, mean (sd) body mass index (BMI) 26.2 (4.1) kg/m². Arterial calcifications developed in 174 participants (283 joints). OA developed in 456 participants (778 joints). Sex modified the association between arterial calcification and OA. In women, incident arterial calcification around a joint was positively associated with incident OA in that joint (adjusted OR 2.51 (95% CI 1.57-4.03)). In men, no association was observed on joint-level, but at patient-level the arterial calcification sum score was negatively associated with incident OA (adjusted OR per point increase 0.70 (95% CI 0.54-0.90)) indicating a systemic effect.

CONCLUSIONS

We observed sex-dependent associations between incident arterial calcification and incident radiographic knee and/or hip OA, which differs between joint- and patient-level.

Female Sex Is a Risk Factor for Failure of Hip Arthroscopy Performed for Acetabular Retroversion

BACKGROUND

The success of hip surgery in treating acetabular retroversion depends on the severity of the structural deformity and on selecting the correct patient for open or arthroscopic procedures.

PURPOSE

To compare a group of patients with retroverted hips treated successfully with hip arthroscopy with a group of patients with retroverted hips that failed arthroscopic surgery, with special emphasis on (1) patient characteristics, (2) perioperative radiographic parameters, (3) intraoperative findings and concomitant procedures, and (4) patient sex.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

We retrospectively reviewed the charts of 47 adult patients (47 hips) with acetabular retroversion who had undergone hip arthroscopy. Retroversion was based on the presence of an ischial spine sign in addition to either a crossover or posterior wall sign on a well-positioned anteroposterior pelvic radiograph. A total of 24 hips (50%) (16 females, 8 males; mean patient age, 31 years) had failed arthroscopy, defined as modified Harris Hip Score (mHHS) <80 or need for subsequent procedure. Twenty-three hips (8 females, 15 males; mean patient age, 29 years) were considered successful, defined as having no subsequent procedures and an mHHS >80 at the time of most recent follow-up. Perioperative variables, radiographic characteristics, and intraoperative findings were compared between the groups, in addition to a subgroup analysis based on sex.

RESULTS

The mean follow-up for successful hips was 30 months (SD, 11 months), with a mean mHHS of 95. In the failure group, 6 patients required subsequent procedures (4 anteverting periacetabular osteotomies and 2 total hip arthroplasties). The mean overall time to failure was 21 months, and the mean time to a second procedure was 24 months (total hip arthroplasty, 29.5 months; periacetabular osteotomy, 21.2 months); 18 hips failed on the basis of a low mHHS (mean, 65; range, 27-79) at last follow-up. Factors significantly different between the success and failure groups included patient sex, with males being more likely than females to have a successful outcome (P < .02), as well as undergoing femoral osteoplasty (P < .02). Intraoperative variables that were associated with worse outcome included isolated labral debridement (P < .002). In a subgroup analysis, males were more likely than their female counterparts to have a successful outcome with both isolated cam and combined cam-pincer resection (P < .05). Level of crossover correction on postoperative radiographs had no correlation with outcome.

CONCLUSION

Acetabular retroversion remains a challenging pathoanatomy to treat arthroscopically. If hip arthroscopy is to be considered in select cases, we recommend labral preservation when possible. Male patients with correction of cam deformities did well, while females with significant retroversion appeared to be at greater risk for failure of arthroscopic treatment.

The Influence of Squat Kinematics and Cam Morphology on Acetabular Stress

PURPOSE

To evaluate the effect of varying degrees of simulated cam morphology on acetabular stress magnitude and location using a finite element model with 1 subject that incorporates population-specific hip/pelvis kinematics during a squat task.

METHODS

A reference model of the hip joint was created from magnetic resonance images obtained from 1 asymptomatic 28-year-old man without femoroacetabular impingement (FAI) morphology or hip dysplasia (alpha angle 41.9°, lateral center edge angle 34.0°, neck-shaft angle 137°, and no visible articular cartilage lesions or bone marrow edema on magnetic resonance). The femoral head/neck geometry was manipulated to mimic different cam morphology severities as reported in a previous study (minimum, moderate, and large). Peak hip and pelvis squat kinematics from healthy individuals (hip flexion 112.6°, abduction 10.5°, internal rotation 14.8°) and persons with FAI (hip flexion 106.3°, abduction 10.5°, internal rotation 8.9°) were applied to the control and cam models. Relative acetabular joint stress values and location of contact were the variables of interest.

RESULTS

Average von Mises stress values for control, minimum, moderate, and large cam models were 9.64, 9.27, 11.36, and 28.43 MPa, respectively. Contact in the control and minimum cam models occurred within the acetabular cup. In the moderate and large cam models, contact shifted anterosuperiorly within the acetabular cup and to anterosuperior acetabular rim, respectively.

CONCLUSIONS

Despite simulating lower degrees of hip flexion and internal rotation, increased stress and a shift in contact location were observed in the simulated models of FAI. This finding suggests that decreased hip internal rotation in this population during functional tasks may be the result of bony abutment.

CLINICAL RELEVANCE

Clinicians should be cautious about prescribing deep squats for persons with cam morphology. Performing squat exercises with neutral or external hip rotation may limit bony abutment at high hip flexion angles.

Cam morphology and inguinal pathologies: is there a possible connection?

Background

To analyse the prevalences of the cam and pincer morphologies in a cohort of patients with groin pain syndrome caused by inguinal pathologies.

Materials and methods

Forty-four patients (40 men and 4 women) who suffered from groin pain syndrome were enrolled in the study. All the patients were radiographically and clinically evaluated following a standardised protocol established by the First Groin Pain Syndrome Italian Consensus Conference on Terminology, Clinical Evaluation and Imaging Assessment in Groin Pain in Athlete. Subsequently, all of the subjects underwent a laparoscopic repair of the posterior inguinal wall.

Results

The study demonstrated an association between the cam morphology and inguinal pathologies in 88.6% of the cases (39 subjects). This relationship may be explained by noting that the cam morphology leads to biomechanical stress at the posterior inguinal wall level.

Conclusions

Athletic subjects who present the cam morphology may be considered a population at risk of developing inguinal pathologies.

Level of evidence

Level IV, Observational cross-sectional study.

Surgical Correction of Cam Deformity in Association with Femoroacetabular Impingement and Its Impact on the Degenerative Process within the Hip Joint

BACKGROUND

Cam morphology in association with femoroacetabular impingement (FAI) is a recognized cause of hip pain and cartilage damage and proposed as a leading cause of arthritis. The purpose of this study was to analyze the functional and biomechanical effects of the surgical correction of the cam deformity on the degenerative process associated with FAI.

METHODS

Ten male patients with a mean age of 34.3 years (range, 23.1 to 46.5 years) and a mean body mass index (and standard deviation) of 26.66 ± 4.79 kg/m underwent corrective surgery for cam deformity in association with FAI. Each patient underwent a computed tomography (CT) scan to assess acetabular bone mineral density (BMD), high-resolution T1ρ magnetic resonance imaging (MRI) of the hips to assess proteoglycan content, and squatting motion analysis as well as completed self-administered functional questionnaires (Hip disability and Osteoarthritis Outcome Score [HOOS]) both preoperatively and 2 years postoperatively.

RESULTS

At a mean follow-up of 24.5 months, improvements in functional scores and squat performance were seen. Regarding the zone of impingement in the anterosuperior quadrant of the acetabular rim, the mean change in BMD at the time of follow-up was -31.8 mg/cc (95% confidence interval [CI], -11 to -53 mg/cc) (p = 0.008), representing a 5% decrease in BMD. The anterosuperior quadrant also demonstrated a significant decrease in T1ρ values, reflecting a stabilization of the cartilage degeneration. Significant correlations were noted between changes in clinical functional scores and changes in T1ρ values (r = -0.86; p = 0.003) as well as between the BMD and maximum vertical force (r = 0.878; p = 0.021).

CONCLUSIONS

Surgical correction of a cam deformity in patients with symptomatic FAI not only improved clinical function but was also associated with decreases in T1ρ values and BMD. These findings are the first, to our knowledge, to show that alteration of the hip biomechanics through surgical intervention improves the overall health of the hip joint.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Quantitative comparison of cortical bone thickness using correspondence-based shape modeling in patients with cam femoroacetabular impingement

The proximal femur is abnormally shaped in patients with cam-type femoroacetabular impingement (FAI). Impingement may elicit bone remodeling at the proximal femur, causing increases in cortical bone thickness. We used correspondence-based shape modeling to quantify and compare cortical thickness between cam patients and controls for the location of the cam lesion and the proximal femur. Computed tomography images were segmented for 45 controls and 28 cam-type FAI patients. The segmentations were input to a correspondence-based shape model to identify the region of the cam lesion. Median cortical thickness data over the region of the cam lesion and the proximal femur were compared between mixed-gender and gender-specific groups. Median [interquartile range] thickness was significantly greater in FAI patients than controls in the cam lesion (1.47 [0.64] vs. 1.13 [0.22] mm, respectively; p < 0.001) and proximal femur (1.28 [0.30] vs. 0.97 [0.22] mm, respectively; p < 0.001). Maximum thickness in the region of the cam lesion was more anterior and less lateral (p < 0.001) in FAI patients. Male FAI patients had increased thickness compared to male controls in the cam lesion (1.47 [0.72] vs. 1.10 [0.19] mm, respectively; p < 0.001) and proximal femur (1.25 [0.29] vs. 0.94 [0.17] mm, respectively; p < 0.001). Thickness was not significantly different between male and female controls.

CLINICAL SIGNIFICANCE

Studies of non-pathologic cadavers have provided guidelines regarding safe surgical resection depth for FAI patients. However, our results suggest impingement induces cortical thickening in cam patients, which may strengthen the proximal femur. Thus, these previously established guidelines may be too conservative. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1743-1753, 2017.

Femoro-acetabular impingement: anatomic study of reliability and accuracy of alpha angle and offset ratio on fifty consecutive peri-operatively resected femoral heads

PURPOSE

The purpose of this study was to determine whether X-ray attributes of the femoro-acetabular impingement (FAI) - alpha angle (AA) and offset ratio (OR) reflect real measurements on resected femoral heads.

METHODS

FAI AA and OR were assessed on 50 consecutively-resected femoral heads. The parameters were measured on heads cut through the maximum range of the deformity and compared to the same parameters on standardized X-ray projections (anterior-posterior [AP] and axial views).

RESULTS

Mean AA was 76.47° on dissected heads vs. 75.81° on axial X-ray (p = 0.688). Mean OR was 0.132 on dissected heads vs. 0.220 on axial X-ray (p < 0.001). Mean AA on ideal AP X-ray was 79.46° vs. 81.51° on AP standing plain X-ray view (p = 0.431). AA measurements on plain X-ray AP and axial view of halved femoral heads correlated highly.

CONCLUSIONS

AA on axial X-ray view reflected the real AA in our series, but the risk of cartilage damage cannot be predicted.

Imaging of impingement syndromes around the hip joint

Impingement syndromes are increasingly recognised as significant causes of hip pain and dysfunction. A broad spectrum of intraarticular and extraarticular conditions has been implicated in their pathophysiology. Physical examination is often inconclusive as clinical findings may be unclear or misleading, often simulating other disorders. With current improvements in imaging techniques and better understanding of hip impingement related pathomechanisms, these entities can be accurately diagnosed. In addition, preoperative imaging has allowed for targeted treatment planning. This article provides an overview of the various types of hip impingement, including femoroacetabular impingement, ischiofemoral impingement, snapping hip syndrome, greater trochanteric-pelvic and subspine impingement. Current literature data regarding their pathogenesis, clinical manifestation and imaging work-up are discussed.

Gender-Dependent Differences in Hip Range of Motion and Impingement Testing in Asymptomatic College Freshman Athletes

BACKGROUND

Athletic activity is a proposed factor in the development and progression of intra-articular hip pathology. Early diagnosis and preventive treatments in "at-risk" athletes are needed.

OBJECTIVES

Our primary objective was to report hip range of motion (ROM) and prevalence of positive impingement testing in asymptomatic college freshman athletes. Our secondary objective was to determine whether an association exists between hip ROM and a positive flexion-adduction-internal rotation (FADIR) test.

DESIGN

Cross-sectional study.

SETTING

Collegiate athletic campus.

PARTICIPANTS

Four hundred thirty (299 male, 131 female) freshman athletes reporting no current or previous hip pain.

METHODS

During the athletes' preseason medical screening, trained examiners performed a hip-specific exam to obtain data for hip ROM and impingement testing.

MAIN OUTCOME MEASUREMENTS

Bilateral passive ROM measures included hip flexion, and hip internal and external rotation with the hip flexed 0° and 90°.

RESULTS

Mean age of male participants was 18.5 ± 0.8 and female participants was 18.3 ± 0.6 years (P = .003). Male participants demonstrated less hip ROM than female participants in flexion (115.8 ± 11.2° versus 122.0 ± 10.5°, P < .001), internal rotation in 90° flexion (26.9 ± 9.8° versus 34.7 ± 10.7°, P < .001) and 0° flexion (29.0 ± 9.8° versus 38.9 ± 10.1°, P < .001), and external rotation in 90° flexion (44.7 ± 10.9° versus 49.7 ± 10.4°, P < .001) but not for external rotation in 0° flexion (39.8 ± 11.1° versus 37.6 ± 11.5°, P = .06). Pain with FADIR test on the right and left hip were reported in 11.9% and 14.5% of athletes, respectively. Gender and a positive FADIR were not related (male 12.2%, female 15.3%, P = .36).

CONCLUSIONS

In asymptomatic college freshman athletes, male athletes generally demonstrated less hip ROM than female athletes. In addition, a positive FADIR was more prevalent than previously reported in healthy young adults. Preseason screenings that use these baseline data in conjunction with other examination findings may allow identification of athletes at future risk for hip pain and/or injury.

LEVEL OF EVIDENCE

IV.

A Comparison of Clinical Outcome Between Athletes and Nonathletes Undergoing Hip Arthroscopy for Femoroacetabular Impingement

OBJECTIVE

To compare the clinical outcome of arthroscopic surgery for femoroacetabular impingement (FAI) between athlete and nonathlete patients.

DESIGN

Retrospective case-control study. Level of Evidence III.

PATIENTS AND METHODS

Seventy-four patients who underwent arthroscopic FAI correction from March 2009 to April 2012 were enrolled in this study. The patients were divided into 2 groups, according to their sports participation (47 in the athlete group and 27 in the nonathlete group).

MAIN OUTCOME MEASURES

We reviewed clinical and radiographic data for all patients, up to a minimum of 2 years after surgery. We used analysis of covariance to compare the mean patient reported outcome scores including modified Harris hip score (MHHS) and the nonarthritis hip score (NAHS) preoperatively, at 6, 12, and 24 months after surgery.

RESULTS

The mean age at the time of surgery in the athlete group was significantly lower than that in the nonathlete group. Although there was no significant difference in preoperative MHHS and NAHS, the mean NAHS at 6, 12, and 24 months postoperatively and the mean MHHS at 24 months postoperatively in athletes were significantly higher than that in nonathletes (P < 0.05).

CONCLUSIONS

Although arthroscopic FAI correction and labral preservation surgery is generally beneficial, it appears to provide a better clinical outcome in athletes than in nonathletes.