Background Femoroacetabular impingement (FAI) represents a constellation of anatomical and clinical features, but definitive diagnosis is often difficult. The high prevalence of cam deformity of the femoral head in the asymptomatic population as well as clinical factors leading to the onset of symptoms raises questions as to what other factors increase the risk of cartilage damage and hip pain.Questions/purposes The purpose was to identify any differences in anatomical parameters and squat kinematics among symptomatic, asymptomatic, and control individuals and if these parameters can determine individuals at risk of developing symptoms of cam FAI. Methods Forty-three participants (n = 43) were recruited and divided into three groups: symptomatic (12), asymptomatic (17), and control (14). Symptomatic participants presented a cam deformity (identified by an elevated alpha angle on CT images), pain symptoms, clinical signs, and were scheduled for surgery. The other recruited volunteers were blinded and unaware whether they had a cam deformity. After the CT data were assessed for an elevated alpha angle, participants with a cam deformity but who did not demonstrate any clinical signs or symptoms were considered asymptomatic, whereas participants without a cam deformity and without clinical signs or symptoms were considered healthy control subjects. For each participant, anatomical CT parameters (axial alpha angle, radial alpha angle, femoral head-neck offset, femoral neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version) were evaluated. Functional squat parameters (maximal squat depth, pelvic range of motion) were determined using a motion capture system. A stepwise discriminant function analysis was used to determine

Background Advance care planning (ACP) facilitates identification and documentation of patients’ treatment preferences. Its goal aligns with that of palliative care – optimizing quality of life of seriously ill patients. However, concepts of ACP and palliative care remain poorly recognized in Chinese population. This study aims at exploring barriers to ACP from perspective of seriously ill patients and their family caregivers. Methods This is a qualitative study conducted in a Palliative Day Care Centre of Hong Kong between October 2016 and July 2017. We carried out focus groups and individual interviews for the seriously ill patients and their family caregivers. A semi-structured interview guide was used to explore participants’ experiences and attitudes about ACP. Qualitative content analysis was adopted to analyze both manifest content and latent content. Results A total of 17 patients and 13 family caregivers participated in our study. The qualitative analysis identified four barriers to ACP: 1) limited patients’ participation in autonomous decision making, 2) cognitive and emotional barriers to discussion, 3) lack of readiness and awareness of early discussion, and 4) unprepared healthcare professionals and healthcare system. Conclusions Participations of seriously ill patients, family caregivers and healthcare workers in ACP initiation are lacking respectively. A series of interventions are necessary to resolve the barriers.

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.

Background: Cam femoroacetabular impingement (FAI) can impose elevated mechanical loading in the hip, potentially leading to an eventual mechanical failure of the joint. Since in vivo data on the pathomechanisms of FAI are limited, it is still unclear how this deformity leads to osteoarthritis. Purpose: The purpose of this study was to examine the effects of cam FAI on hip joint mechanical loading using finite element analysis, by incorporating subject-specific geometries, kinematics, and kinetics. Questions: The research objectives were to address and determine: (1) if hips with cam FAI demonstrate higher maximum shear stresses, in comparison with control hips; (2) the magnitude of the peak maximum shear stresses; and (3) the locations of the peak maximum shear stresses. Methods: Using finite element analysis, two patient models were control-matched and simulated during quasistatic positions from standing to squatting. Intersegmental hip forces, from a previous study, were applied to the subjectspecific hip geometries, segmented from CT data, to evaluate the maximum shear stresses on the acetabular cartilage and underlying bone. Results: Peak maximum shear stresses were found at the anterosuperior region of the underlying bone during squatting. The peaks at the anterosuperior acetabulum were substantially higher for the patients (15.2±1.8 MPa) in comparison with the controls (4.5±0.1 MPa). Conclusions: Peaks were not situated on the cartilage, but instead located on the underlying bone. The results correspond with the locations of initial cartilage degradation observed during surgical treatment and from MRI. Clinical Relevance: These findings support the pathomechanism of cam FAI. Changes may originate from the underlying subchondral bone properties rather than direct shear stresses to the articular cartilage.

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. Symptomatic cam FAI demonstrate different muscle and hip contact forces during gait. Study Design: Controlled laboratory study. Methods: Eighteen patients with symptomatic cam FAI (nFAI = 18) were age-and BMI-matched with eighteen control participants (nCON = 18). Each participant's walking kinematics and kinetics were recorded throughout a gait cycle (ipsilateral foot-strike to ipsilateral foot-off), using a motion capture system and force plates. Muscle and hip contact forces were subsequently computed using a musculoskeletal modelling 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 to the CON group. The FAI group showed reduced psoas major (median = 1.1, interquartile range (IQR) = 1.0-1.5 Newton/bodyweight (N/BW)) and iliacus forces (median = 1.2, IQR = 1.0-1.6 N/BW), during contralateral foot-strike, compared to the CON group (median = 1.6, IQR = 1.3-1.6 N/BW, p = 0.004; and median = 1.5, IQR = 1.3-1.6 N/BW, p = 0.03, respectively); which resulted in lower hip contact forces in the anterior (p = 0.026), superior (p = 0.02), and medial directions (p = 0.038). The three 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. 4 Conclusions: FAI participants altered their walking kinematics and kinetics, especially during contralateral foot-strike as a protective mechanism, and resulted in reduced psoas major and iliacus muscle force and anterosuperior hip contact force estimations. Clinical Relevance: Limited hip mobility is not only attributed to bone-on-bone impingement, caused by the 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.

Background It is still unclear why many individuals with a cam morphology of the hip do not experience pain. It was recently reported that a decreased femoral neck-shaft angle may also be associated with hip symptoms. However, the effects that different femoral neck-shaft angles have on hip stresses in symptomatic and asymptomatic individuals with cam morphology remain unclear.Questions/purposes We examined the effects of the cam morphology and femoral neck-shaft angle on hip stresses during walking by asking: (1) Are there differences in hip stress characteristics among symptomatic patients with cam morphology, asymptomatic individuals with cam morphology, and individuals without cam morphology? (2) What are the effects of high and low femoral neck-shaft angles on hip stresses? Methods Six participants were selected, from a larger cohort, and their cam morphology and femoral neck-shaft angle parameters were measured from CT data. Two participants were included in one of three groups: (1) symptomatic with cam morphology; (2) asymptomatic with a cam morphology; and (3) asymptomatic control with no cam morphology with one participant having the highest femoral neck-shaft angle and the other participant having the lowest in each subgroup. Subject-specific finite element models were reconstructed and simulated during the stance phase, near pushoff, to examine maximum shear stresses on the acetabular cartilage and labrum. Results The symptomatic group with cam morphology indicated high peak stresses (6.3-9.5 MPa) compared with the asymptomatic (5.9-7.0 MPa) and control groups (3.8-4.0 MPa). Differences in femoral neck-shaft angle influenced both symptomatic and asymptomatic groups; participants with the lowest femoral neck-shaft angles had higher peak stresses in their respective subgroups. There were no differences among control models. Conclusions Our study suggests that the hips of individuals with a cam morphology and varus femoral neck angle may be subjected to higher mechanical stresses than those with a normal femoral neck angle. Clinical Relevance Individuals with a cam morphology and decreased femoral neck-shaft angle are likely to experience severe hip stresses. Although asymptomatic

ä Hip joint capsular ligaments (iliofemoral, ischiofemoral, and pubofemoral) play a predominant role in functional mobility and joint stability. ä The zona orbicularis resists joint distraction (during neutral positions), and its aperture mechanism stabilizes the hip from adverse edge-loading (during extreme hip flexion-extension). ä To preserve joint function and stability, it is important to minimize capsulotomy size and avoid disrupting the zona orbicularis, preserve the femoral head size and neck length, and only repair when or as necessary without altering capsular tensions. ä It is not fully understood what the role of capsular tightness is in patients who have cam femoroacetabular impingement and if partial capsular release could be beneficial and/or therapeutic. ä During arthroplasty surgery, a femoral head implant that is nearly equivalent to the native head size with an optimal neck-length offset can optimize capsular tension and decrease dislocation risk where an intact posterior hip capsule plays a critical role in maintaining hip stability. Characteristics Anatomy Human ligaments consist of predominantly type-I collagen (85%) and combinations of type III, V, VI, XI, and XIV (15%) 21,22. Within the hip joint, higher ratios of type-III collagen in the ligamentous capsule are associated with hip instability 23,24 , whereas elevated levels in the cartilage are associated with Disclosure: The authors indicated grant support from the Engineering and Physical Sciences Research Council (EPSRC) (EP/K027549/1 and EP/ N006267/1) and the Wellcome Trust (088844/Z/09/Z), during the conduct of the study. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked "yes" to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work (http://links.lww.com/JBJS/F511).

No abstract