Pincer Femoroacetabular Impingement Research Articles

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

In daily routine, pincer femoroacetabular impingement (FAI) findings are often seen without a clinical diagnosis of pincer FAI. To assess the presence of pincer FAI MRI findings in asymptomatic volunteers with negative impingement test versus patients with clinically confirmed FAI. Case-control study. Sixty-three asymptomatic volunteers and 63 matched patients with FAI were included. A coronal T1 -weighted turbo spin-echo sequence as well as a 3D oblique transverse water-excitation true fast imaging sequence at 1.5T. The volunteers underwent standard MRI of the hip, and patients underwent MR arthrography of the symptomatic hip using the same MR sequences. Measurements of cranial acetabular version, acetabular depth, and lateral center-edge angle were performed independently by three fellowship-trained musculoskeletal radiologists. Descriptive statistics, Mann-Whitney U-test, Unpaired t-test, receiver operating characteristics (ROC), Intraclass correlation coefficient (ICC). Forty-one percent (26/63, reader 1), 32% and 37% (20 and 23/63, reader 2/3) of asymptomatic volunteers had at least one positive MR finding for pincer-FAI. Patients with pincer or mixed-type FAI had cranial retroversion of the acetabulum of -0.2° ± 7.1 (mean ± standard deviation) for reader 1 and -0.3° ± 5.5/-0.2° ± 4.8 for reader 2 / reader 3, while asymptomatic volunteers had an anteversion of 6.2° ± 6.4 (reader 1) and 3.2° ± 4.9/3.1° ± 6.5 (readers 2/3): This difference was statistically significant (P ≤ 0.002), but there was a large overlap between the groups. Acetabular depth measurements were very similar for patients with either pincer or mixed-type FAI (5.1-5.3 mm ± 3.1) and volunteers (5.2-6.1 mm ± 2.6), without a statistically significant difference (P ≤ 0.50). Lateral center-edge angle was also similar in patients with either pincer or mixed-type FAI (32.1-35.1° ± 9.1) and volunteers (30.7-33.2° ± 6.5), without a statistically significant difference (P ≤ 0.28). There is a large overlap in pincer-type MRI findings between patients with symptomatic FAI and asymptomatic volunteers. More than a third of volunteers exhibited at least one positive pincer-type MRI finding. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1296-1303.

Squatting Biomechanics in Individuals with Symptomatic Femoroacetabular Impingement.

Identification of the biomechanical alterations in individuals with symptomatic femoroacetabular impingement (FAI) is critical to understand the pathology and inform treatments. Yet hip function in this condition is poorly defined. Squatting requires large hip flexion range and involves motion toward the position of hip impingement; thus, it is likely to expose modified biomechanics in these individuals. This study aimed to determine whether hip and pelvis biomechanics differ between individuals with and without symptomatic FAI during an unconstrained deep squat and a constrained squat designed to limit compensation by the pelvis and trunk. Fifteen participants with symptomatic cam-type or combined (cam plus pincer) FAI who were scheduled for arthroscopic surgery and 14 age- and sex-matched controls without FAI underwent three-dimensional motion analysis during the two squatting tasks. Trunk, pelvis, and hip kinematics and hip kinetics were compared between groups. There were no between-group differences in normalized squat depth for either task. Descent speed was slower for the FAI group during the unconstrained squat (P < 0.05). During the constrained squat, individuals with FAI demonstrated greater pelvic rise (P = 0.01) and hip adduction (P = 0.04) on the symptomatic side than controls. The hip external rotation moment was less in FAI patients during descent (P = 0.04), as was transverse plane hip angle variability (P = 0.04). Individuals with symptomatic FAI can squat to a depth comparable with controls, regardless of task design. When the task is constrained, FAI patients demonstrate greater ipsilateral pelvic rise and maintain a more adducted hip position, which may coincide with a compensatory strategy to avoid end range flexion as the hip approaches impingement. These biomechanical alterations may put additional stress on adjacent regions and have relevance for rehabilitation.

CORR Insights®: Complete Circumferential Osseous Extension in the Acetabular Rim Occurs Regardless of Acetabular Coverage.

CORR Insights®: Complete Circumferential Osseous Extension in the Acetabular Rim Occurs Regardless of Acetabular Coverage.

Arthroscopic Hip Surgery in the Elite Athlete: Comparison of Female and Male Competitive Athletes

Background: Few studies have published the results of hip arthroscopic surgery in elite athletes and none studying a significant number of elite female athletes. Purpose: (1) To compare sex-based differences in the ability to return to prior competitive sports activity after arthroscopic hip surgery. (2) To compare sex-based differences in the type of sports activity, diagnosis, and treatment in athletes requiring hip arthroscopic surgery. Study Design: Cohort study; Level of evidence, 3. Methods: Data on all elite athletes who underwent primary hip arthroscopic surgery between 2007 and 2014 were included. Athletes with a Hip Sports Activity Scale (HSAS) score of over 6 were identified. The preoperative evaluation included a medical history, history of sports activity, and hip-specific outcome scores (Modified Harris Hip Score [MHHS] and International Hip Outcome Tool–33 [iHOT-33]). Surgical findings and time to return to competitive sports were documented. Results: Of 547 hips in 484 consecutive patients, 98 elite athletes (49 female) with a mean follow-up of 18.9 ± 12.8 months were identified. Eighty patients desired to return to their original competitive activity: 38 were female (42 hips; mean age, 21.5 ± 3.9 years), and 42 were male (54 hips; mean age, 20.5 ± 1.9 years). Moreover, 84.2% of female athletes and 83.3% of male athletes were able to return to the same level of competition at a mean of 8.3 ± 3.0 and 8.8 ± 2.9 months, respectively. Significant improvements between preoperative and postoperative outcome scores were seen in both groups (all P < .0001). Female athletes had more pincer femoroacetabular impingement (FAI) (P = .0004) and instability (P < .0001). Conversely, male athletes were diagnosed more commonly with combined FAI (P < .0001), demonstrated greater acetabular cartilage damage (P = .0004), and required microfracture more often (P = .0014). Female athletes competed more frequently in flexibility (4/38, 11%; P = .047) and endurance (9/38, 24%) sports, while male athletes participated in cutting (14/42, 33%), contact (6/42, 14%), and asymmetric (13/42, 31%) sports more often. Patients who returned to their baseline level of competition had a shorter duration of symptoms preoperatively (P = .001). Microfracture status did not affect the ability to return to sports. Conclusion: Female and male elite athletes were able to return to competitive sports activity at the same or higher level after hip arthroscopic surgery at a similar rate, although their performance in sports was not measured. Distinct differences in the diagnosis, treatment, and type of sports activity between sexes were seen. The duration of symptoms negatively correlated with outcomes. Microfracture did not affect the return to sports.

Femoroacetabular impingement following an osteotomy for acetabular dysplasia: a commentary on a recently published study

Acetabular dysplasia (AD) is a common cause of hip pain in adolescents. Furthermore, compared to a normally shaped acetabulum, AD results in increased contact stresses due to the smaller weight bearing surface (1). These increased contact stresses are thought to contribute to damage to the labrum and cartilage, thus, increasing the chance of developing osteoarthritis later in life (1-3). In order to prevent this long term sequela, osteotomies have been used to treat AD (4). Two of these osteotomies include the Salter (5) innominate osteotomy and the Pemberton (6) pericapsular osteotomy (7,8). The salter osteotomy consists of stabilizing the reduced hip in the position of function by averting the acetabulum, whereas, the pericapsular osteotomy involves reshaping the dysplastic acetabulum. These two procedures have demonstrated good long-term results (8); however, there is the potential for overcorrection leading to iatrogenic pincer femoroacetabular impingement (FAI). With the development of FAI, some have proposed that this will lead to compression and shear stresses between the labrum and the cartilage, eventually also leading to articular degeneration and ultimately global hip OA (1). This question outlines the importance in publishing mid to long-term results following osteotomies to treat AD.

Cam versus pincer femoroacetabular impingement. Which type is associated with more hip structural damage? An exploratory cross-sectional study

Background: Femoroacetabular impingement (FAI) occurs as a conflict between the proximal femur and the acetabular rim. The purpose of this study was to evaluate MRI findings and look for correlations with pain intensity and duration in each type of FAI separately in an attempt to identify which type is associated with more structural damage. Methods: Forty-four patients (78 hips) diagnosed with either cam or pincer FAI were consecutively recruited in a prospective cohort study. None of our patients had evidence of osteoarthritis (OA) on the initial plain radiography. All patients had contrast-enhanced MRI and CT scans of the hips. All patients filled in a visual analogue scale (VAS) for pain. Results: The frequency of bone marrow edema (BME) was 37% in cam FAI and 20.8% in pincer FAI. In cam FAI, BME positively correlated with pain severity as measured by VAS (P&lt;0.0001), cartilage degradation (P=0.001), pseudocysts (P&lt;0.0001), hip effusion (P=0.013) and reactive synovitis (P&lt;0.0001). However, in pincer FAI, BME only correlated with pain severity (P=0.004) and duration (P=0.011) and did not correlate with other MRI signs of structural hip damage. Conclusions: In cam FAI, BME of the femoral head and neck on MRI positively correlated with chondral damage and synovitis, but not in pincer FAI. This correlation suggests that cam FAI might be associated with a worse long-term prognosis. This finding might have an impact on clinical practice and decision making as it would encourage surgeons to intervene early in cases of cam FAI, thus preventing the possible development of irreversible, established hip OA.

Protrusio acetabuli: a specific pincer hip disease

The pincer effect is an infrequent subtype of femoroacetabular impingement (FAI). In our experience, cam deformities are more common, easier to treat and have more consistent post-operative outcomes than the pincer FAI subtype. In pincer morphologies, over-coverage of the femoral head may occur in a critical area, limiting range of motion and leading to joint damage. Protrusio acetabuli is perhaps the most severe pincer form with global involvement. In these cases, surgical dislocation with acetabular rim trimming is preferred to the arthroscopic technique (1).

Retrospective Analysis of Idiopathic Hip Osteoarthritis Based on Anteroposterior Pelvic Radiograph; Hip Osteoarthritis Caused by Femoroacetabular Impingement

Background: Femoroacetabular Impingement (FAI) means pathological impact between the femoral head-neck junction and the acetabular rim. Objectives: The aim of this retrospective study was to analyze Femoroacetabular Impingement (FAI) signs, which can lead to idiopathic hip osteoarthritis, from preoperative radiographs of patients indicated for total hip replacement as compared to radiographs of patients without this indication. Methods: We examined the preoperative anteroposterior (AP) pelvic radiograph, the pincer and cam FAI signs of patients between 45 and 60 years, who had undergone total hip replacement. We examined in the same group, the operated side and the non-operated hips with osteoarthritis (patients group). In the control group we examined the pelvic radiograph of patients without symptoms between 45 and 60 years old (control, group). Results: In the patient group (215 patients, 313 hips) we noted the signs of FAI in 88% while in the control group (112 patients 224 hips) these signs were found in 8.8% of cases. Conclusions: In 88% of primary osteoarthritis cases we found FAI morphology on the AP pelvic radiograph, similarly to those found in the bibliography, and we considered naming primary osteoarthritis, secondary osteoarthritis caused by FAI. In the majority of cases, early diagnosis with simple, cheap and easily accessible AP pelvic radiograph with low dose of radiationmay also be warranted

CORR Insights®: Is Increased Acetabular Cartilage or Fossa Size Associated With Pincer Femoroacetabular Impingement?

CORR Insights®: Is Increased Acetabular Cartilage or Fossa Size Associated With Pincer Femoroacetabular Impingement?

Is Increased Acetabular Cartilage or Fossa Size Associated With Pincer Femoroacetabular Impingement?

Surgical treatment for pincer femoroacetabular impingement (FAI) of the hip remains controversial, between trimming the prominent acetabular rim and reverse periacetabular osteotomy (PAO) that reorients the acetabulum. However, rim trimming may decrease articular surface size to a critical threshold where increased joint contact forces lead to joint degeneration. Therefore, knowledge of how much acetabular articular cartilage is available for resection is important when evaluating between the two surgical options. In addition, it remains unclear whether the acetabulum rim in pincer FAI is a prominent rim because of increased cartilage size or increased fossa size. We used reformatted MR and CT data to establish linear length dimensions of the lunate cartilage and cotyloid fossa in normal, dysplastic, and deep acetabula. We reviewed the last 200 hips undergoing PAO, reverse PAO, and surgical dislocation for acetabular rim trimming at one institution. We compared MR images of symptomatic hips with acetabular dysplasia (20 hips), pincer FAI (29 hips), and CT scans of asymptomatic hips from patients who underwent CT scans for reasons other than hip pain (20 hips). These hips were chosen sequentially from the underlying pool of 200 potential subjects to identify the first 10 male and the first 10 female hips in each group that met inclusion criteria. As a result of low numbers, we included all hips that had undergone reverse PAO and met inclusion criteria. Cartilage width was measured medially from the cotyloid fossa to the lateral labrochondral junction. Cotyloid fossa linear height was measured from superior to inferior and cotyloid fossa width was measured from anterior to posterior. Superior lunate cartilage width (SLCW) and cotyloid fossa height (CFH) were measured on MR and CT oblique coronal reformats; anterior lunate cartilage width (ALCW), posterior lunate cartilage width (PLCW), and cotyloid fossa width (CFW) were measured on MR and CT oblique axial reformats. Cohorts were compared using multivariate analysis of variance with Bonferroni's adjustment for multiple comparisons. Compared with control acetabula, dysplastic acetabula had smaller SLCW (2.08 ± 0.29 mm versus 2.63 ± 0.42 mm, mean difference = -0.55 mm; 95% confidence interval [CI] = -0.83 to -0.27; p < 0.01), ALCW (1.20 ± 0.34 mm versus 1.64 ± 0.21 mm, mean difference = -0.44 mm; 95% CI = -0.70 to -0.18; p = 0.00), CFH (2.84 ± 0.37 mm versus 3.42 ± 0.57 mm, mean difference = -0.59 mm; 95% CI = -0.96 to -0.21; p < 0.01), and CFW (1.98 ± 0.50 mm versus 2.77 ± 0.33 mm, mean difference = -0.80 mm; 95% CI = -1.16 to -0.42; p < 0.0001). Based on the results, we identified two subtypes of deep acetabula. Compared with controls, deep subtype 1 had normal CFH and CFW but increased ALCW (2.09 ± 0.42 mm versus 1.64 ± 0.21 mm; p < 0.001) and PLCW (2.32 ± 0.36 mm versus 2.00 ± 0.32 mm; p = 0.04). Compared with controls, deep subtype 2 had increased CFH (4.37 ± 0.51 mm versus 3.42 ± 0.57 mm; p < 0.01) and CFW (2.76 ± 0.54 mm versus 2.77 ± 0.33 mm; p = 1.0) but smaller SCLW (2.12 ± 0.40 mm versus 2.63 ± 0.42 mm; p < 0.01). Deep acetabula have two distinct morphologies: subtype 1 with increased anterior and posterior cartilage lengths and subtype 2 with a larger fossa in height and width and smaller superior cartilage length. In patients with deep subtype 1 hips that have increased anterior and posterior cartilage widths, rim trimming to create an articular surface of normal size may be reasonable. However, for patients with deep subtype 2 hips that have large fossas but do not have increased cartilage widths, we propose that a reverse PAO that reorients yet preserves the size of the articular surface may be more promising. However, these theories will need to be validated in well-controlled clinical studies.

Acetabular Version Increases After Closure of the Triradiate Cartilage Complex.

Although the etiology of primary femoroacetabular impingement (FAI) is considered developmental, the underlying pathogenic mechanisms remain poorly understood. In particular, research identifying etiologic factors associated with pincer FAI is limited. Knowledge of the physiologic growth patterns of the acetabulum during skeletal maturation might allow conclusions on deviations from normal development that could contribute to pincer-related pathomorphologies. In a population of healthy children, we asked if there were any differences related to skeletal maturation with regard to (1) acetabular version; (2) acetabular depth/width ratio; and (3) femoral head coverage in the same children as assessed by MRIs obtained 1year apart. We prospectively compared 129 MRIs in 65 asymptomatic volunteers without a known hip disorder from a mixed primary/high school population (mean age, 12.7years; range, 7-16years). All participants underwent two MRI examinations separated by a minimum interval of 1year. Based on the status of the triradiate cartilage complex (open versus closed [TCC]), all hips were allocated to the following groups: "open-open"=open TCC at both MRIs (n=45 hips [22 bilateral]); "open-closed"=open TCC at initial and closed TCC at followup MRI (n=26 hips [13 bilateral]); and "closed-closed" group=closed TCC at both MRIs (n=58 hips [29 bilateral]). We assessed acetabular version in the axial plane at five different locations (5, 10, 15, 20mm below the acetabular dome and at the level of the femoral head) as well as three-dimensional (3-D) acetabular depth/width ratio and 3-D femoral head coverage on six radial MRI sequences oriented circumferentially around the femoral neck axis. Using analysis of variance for multigroup comparisons with Bonferroni adjustment for pairwise comparisons, we compared the results between the initial and followup MRI examinations and among the three groups. Acetabular version was increased in hips of the "open-closed" group at the followup MRI compared with the initial MRI at 5mm (-6±4.6 [95% confidence interval {CI}, -7.6 to -3.6] versus -1±5.0 [95% CI, -3.3 to 0.7]; p<0.001), 10mm (0±4.0 [95% CI, -1.6 to 2.1] versus 7±4.6 [95% CI, 4.4-8.7]; p<0.001), and 15mm (8±5.0 [95% CI, 6.1-10.2] versus 15±4.6 [95% CI, 13.3-17.4]; p<0.001) below the acetabular dome. Acetabular version did not change between the initial and followup MRI in the "open-open" and "closed-closed" groups. Independently of the groups, acetabular version was increased in all hips with a fused TCC compared with hips with an open TCC (mean difference measured at 5mm below the acetabular dome at initial MRI examination: 2°±5.9° [95% CI, 0.2°-3.4°] versus -9° ± 4.4° [95% CI, -9.9° to -7.8°]; p<0.001; at followup MRI examination: 1° ± 5.7° [95% CI, 0.1°-2.7°] versus -9° ± 3.8° [95% CI, -10° to -7.6°]; p<0.001). Both acetabular depth/width ratio and femoral head coverage did not differ among the groups or between the initial and followup MRI examinations within each group. Although acetabular depth/width ratio and femoral head coverage remain relatively constant, acetabular version increases with advancing skeletal maturity. There seems to be a relatively narrow timeframe near physeal closure of the TCC within which acetabular orientation changes to more pronounced anteversion. Further studies with greater numbers and longer followup periods are required to support these findings and determine whether such version changes may contribute to pincer-type pathomorphologies. Level II, prospective study.

Striving for multidisciplinary consensus on the diagnosis and management of patients with femoroacetabular impingement: more evidence is needed

In recent years, abnormal hip joint morphology has emerged as a significant factor responsible for the onset of hip osteoarthritis (OA). This is believed to lead to pathological loading patterns that produce shear stresses on the hip joint over time.1 Ganz et al 2 described two different morphological patterns of femoroacetabular impingement (FAI): cam and pincer FAI. What is the prevalence of FAI morphology in the general population? Estimates vary wildly owing to disparity in the definition of FAI morphology used and in the populations sampled. The proportion of the population with symptoms related to FAI is only a fraction of those with FAI morphology. Furthermore, the presence of severe morphological abnormalities does not always bring about hip OA, suggesting that there are other factors at play in hip OA pathogenesis than just joint morphology. This recently defined clinical problem of FAI with widely disparate definitions available and controversy about management motivated the need for some consensus. This international consensus ( see page 1169 ) provides a broad overview of important questions in this challenging field …

A functional evaluation of pincer femoroacetabular impingement in asymptomatic adults

A functional evaluation of pincer femoroacetabular impingement in asymptomatic adults

Hips With Protrusio Acetabuli Are at Increased Risk for Failure After Femoroacetabular Impingement Surgery: A 10-year Followup.

Protrusio acetabuli is a rare anatomic pattern of the hip in which the femoral head protrudes into the true pelvis. The increased depth of the hip and the excessive size of the lunate surface typically lead to severe pincer-type femoroacetabular impingement (FAI); however, to our knowledge, there are no published mid- or long-term studies on results of circumferential acetabular rim trimming through a surgical hip dislocation for patients with this condition. (1) What is the 10-year survivorship of the hips treated with circumferential rim trimming through a surgical hip dislocation compared with a control group of hips that underwent surgery for pincer FAI but that did not have protrusio acetabuli? (2) What are the factors that were associated with a decreased likelihood of survivorship in those hips with the following endpoints: total hip arthroplasty, Merle d'Aubigné score of less than 15, and/or radiographic progression of osteoarthritis (OA)? (3) Does the radiographic pattern of degeneration differ between the two groups? We performed a case-control study comparing two groups: a protrusio group (32 patients [39 hips]) and a control group (66 patients [86 hips]). The control group consisted of hips treated with a surgical hip dislocation for pincer FAI and did not include hips with a positive protrusio sign or a lateral center-edge angle > 39°. The study group did not differ from the control group regarding the preoperative Tönnis OA score, age, and body mass index. However, the study group had more women, decreased mean height and weight, and lower preoperative Merle d'Aubigné-Postel scores, which were inherent differences at the time of first presentation. During the period in question, the indication for performing these procedures was a painfully restricted range of motion in flexion and internal rotation (positive impingement sign). The mean followup of the protrusio group (9 ± 5 years [range, 2-18 years]) did not differ from the control group (11 ± 1 years [range, 10-13 years], p = 0.109). At the respective minimum followup intervals in the underlying database from which cases and control subjects were drawn, followup was 100% for patients with protrusion who underwent FAI surgery and 97% for patients with FAI who underwent surgery for other anatomic patterns (three of 86 hips). We assessed the Merle d'Aubigné-Postel score, Harris hip score, WOMAC, and UCLA activity score at latest followup. A Kaplan-Meier survivorship analysis of the hip was calculated if any of the following endpoints for both groups occurred: conversion to total hip arthroplasty, a Merle d'Aubigné-Postel score < 15, and/or radiographic progression of OA. Differences in survivorship were analyzed using the log-rank test. At 10-year followup, we found a decreased survivorship of the hip for the protrusio group (51% [95% confidence interval {CI}, 34%-67%]) compared with the control group (83% [95% CI, 75%-91%], p < 0.001) with one or more ofthe endpoints stated. We found four multivariate factors associated with a decreased likelihood of survival of the native hip according to the mentioned endpoints: body mass index > 25 kg/m(2) (adjusted hazard ratio, 6.4; 95% CI, 5.2-8.1; p = 0.009), a preoperative Tönnis OA score ≥ 1 (13.3; 95% CI, 11.8-14.9; p = 0.001), a postoperative lateral center-edge angle > 40° (4.2; 95% CI, 2.8-5.6; p = 0.042), and a postoperative posterior coverage > 56% (6.0; 95% CI, 4.3-7.6; p = 0.037). Preoperatively, joint space narrowing and osteophytes were more frequentposteroinferior(jointspace narrowing 18% versus 2%, p = 0.008; osteophytes 21% versus 4%, p = 0.007),medial (joint space narrowing 33% versus 5%, p < 0.001) and anterior (osteophytes 15% versus 1%, p = 0.004) in the protrusio compared with thecontrol group. After correction in hips with protrusio, progression of joint space narrowing (from 6% to 45%, p = 0.001) and osteophyte formation (from 15% to 52%, p = 0.002) was most pronounced laterally. At 10 years, in 51% of all hips undergoing open acetabular rim trimming for protrusio acetabuli, the hip can be preserved without further radiographic degeneration and a Merle d'Aubigné score > 15. Even with the lack of a control group with nonoperative treatment, isolated rim trimming may not entirely resolve the pathomorphology in protrusio hips given the clearly inferior results compared with surgical hip dislocation for FAI without severe overcoverage. Level III, therapeutic study.

Surgical Outcome of Pincer Femoroacetabular Impingement With and Without Labral Ossification

To describe the clinical findings associated with labral ossification (LO), report the outcomes of arthroscopic treatment, and compare this condition to a control group with femoroacetabular impingement (FAI). A retrospective review of hip arthroscopy patients from 2004 to 2013 was performed to identify patients with a diagnosis of pincer FAI with LO and at least 2 years of follow-up. Diagnosis was made by plain radiograph, computed tomography, magnetic resonance imaging, or intraoperatively. The LO cohort was compared to a chronologically matched control group of FAI patients with pincer FAI but no LO. Patients were prospectively assessed with modified Harris Hip Score (mHHS) preoperatively and then postoperatively at 3, 12, 24, 60, and 120 months. The LO group included 56 hips in 52 patients whereas the control group included 56 hips in 56 patients. Mean follow-up was 36 months for the LO group and 38 for the control group (P= .28). Patients in the LO group were older than those in the control group, with a mean age of 45 versus 30 years (P < .0001), and had more women: 58% female versus 32% male (P < .0001). The LO group patients were more likely to have pain while sitting (65% v 18%) and restricted activities of daily living (40% v 11%) than the control group (P < .0001), and more likely to have pain during a flexion, abduction, external rotation (FABER) test (67% v 36%) (P= .002). Both groups experienced a similar magnitude of improvement in mHHS, but the LO group had a significantly lower preoperative mHHS (49 v 63, P < .001) and final postoperative mHHS (75 v 87, P < .0001) than the control group. Patients with LO represent a unique subset of pincer FAI and are more likely to be older, female, and have more severe symptoms. Hip arthroscopy can be used to treat LO with excision of the ossified fragments or rim, with a reasonable expectation of improvement of symptoms. III, retrospective case-control.

Radiological Assessment of Femoroacetabular Impingement Morphology Using Computed Tomography in an Asymptomatic Young Population

Background:: Femoroacetabular impingement (FAI) is one cause of hip pain, and is an under-recognized cause of early osteoarthritis, especially in young and active people. The prevalence of FAI in adults is approximately 10 – 15% and depending on the clinical and radiographic findings, two types of impingement (which are often present in combination) can be distinguished: the cam type and the pincer type. Most patients (86%) have a combination of both forms of impingement. Objectives:: The aim of our study was to evaluate the prevalence and gender differences in the radiological parameters associated with cam and pincer FAI morphologies in an asymptomatic young population, using computed tomography (CT). Patients and Methods:: A retrospective study was performed on 200 individuals (400 hip joints), ranging from 15 - 40 years of age, who were seen in our hospital between July of 2013 and April of 2014 for nonspecific abdominal pain. Multiplanar reformatted CT images of these patients were assessed for the existence of radiological abnormalities, and six measurements (acetabular version angle, acetabular index, lateral center-edge angle, alpha angle in the oblique axial plane, alpha angle in the radial [one o’clock position] plane, and femoral head neck offset) were made relating to the FAI. Results:: The data showed that 69.2% of the women’s joints and 60.5% of the men’s joints had at least one abnormal parameter associated with the FAI. Of the joints, 34.25% had two or more abnormal parameters, and in 38 (19%) of the patients, these abnormalities were bilateral. Unlike previous studies, we found that only 15% of the joints had mixed FAI morphologies. Conclusion:: The prevalence of radiological parameters associated with FAI is high, even in an asymptomatic young population. This high frequency of features may suggest that the threshold values have been set too low in the current literature, or that these findings may reflect anatomical variation rather than true pathological abnormalities.

Radiographic Comparison of Anterior Acetabular Rim Morphology Between Pincer Femoroacetabular Impingement and Control

To define and compare 3 new parameters (anterior rim angle [ARA], anterior wall angle [AWA], and anterior margin ratio [AMR]), in addition to the lateral center-edge angle of Wiberg and the Tönnis angle, for measuring pincer-type femoroacetabular impingement (FAI) in an asymptomatic versus symptomatic FAI population. We reviewed anteroposterior pelvis radiographs of patients verified to have no hip complaints between December 2009 and December 2011. We also reviewed anteroposterior pelvis radiographs of patients who underwent a rim-trimming procedure for pincer FAI between December 2010 and December 2011. Patients aged older than 65 years or younger than 18 years were excluded. Radiographs with a Tönnis grade of 2 or greater were also excluded. For the group of patients with symptomatic hip impingement, radiographs that did not have a crossover sign were excluded. The 2 cohorts were matched for age, sex, and body mass index. Measurements included the Tönnis angle, lateral center-edge angle of Wiberg, ARA, AWA, and AMR. These measurements were compared between the groups. Seventy-two asymptomatic hips were measured. There were 44 female patients (61%) and 28 male patients (39%), aged 25 to 51 years, in the asymptomatic group. The mean ARA was 88.91° ± 8.06°, the mean AWA was 34.89° ± 8.09°, and the mean AMR was 0.49 ± 0.15. Seventy-two symptomatic hips were measured. There were 40 female patients (56%) and 32 male patients (44%), aged 27 to 58 years, in the symptomatic group. The mean ARA was 82.98° ± 10.82°, the mean AWA was 39.11° ± 9.00°, and the mean AMR was 0.56 ± 0.14. The mean difference in the ARA between asymptomatic patients and symptomatic patients was 5.92° (P= .0001). The mean difference in the AWA was 4.22° (P= .0019). The mean difference in the AMR was 0.07 (P= .0039). Our study provides information on several measurements within an asymptomatic cohort and a symptomatic cohort. Although we found statistically significant differences between the 2 populations, the clinical significance remains unknown. We recommend using this asymptomatic population as a guideline for limits on resection of the anterior acetabular rim. Level III, retrospective comparative study.

Hip joint biomechanics during gait in people with and without symptomatic femoroacetabular impingement

Femoroacetabular impingement (FAI) is a morphological hip condition that can cause hip/groin pain and impaired function in younger active adults, and may lead to stiffness, muscle weakness, structural damage, and hip osteoarthritis. Understanding the impairments associated with FAI is crucial to guide treatment and rehabilitation strategies. Evidence is limited and conflicting about whether hip biomechanics are impaired during walking in people with symptomatic FAI. The objective of this study was to determine whether kinematics and kinetics during gait differ between people with symptomatic FAI and control participants. Fifteen participants diagnosed with symptomatic cam-type or combined (cam plus pincer) FAI who were scheduled for arthroscopic surgery and 14 age-, and sex-matched disease-free controls underwent three-dimensional gait analysis. Tri-planar hip kinematics and kinetics were compared between the two groups. There were limited significant between-group differences with respect to spatiotemporal variables. Participants with FAI walked with less range of motion in the sagittal plane during a gait cycle, but did not exhibit any significant kinematic differences in the frontal or transverse planes. There were no systematic differences in kinetics between the groups in any plane. Findings suggest that individuals with symptomatic FAI have minimal impairments in gait biomechanics. Although these individuals demonstrate reduced hip joint motion in the sagittal plane, the size of the difference is small and its significance for symptoms and function is unclear. More pronounced deficits in hip kinetics and kinematics may be evident during functional tasks that challenge the hip towards the position of impingement.

Treatment of pincer-type femoroacetabular impingement.

Pincer femoroacetabular impingement (FAI) consists of pathological contact between the acetabular labrum and rim and the femoral head-neck junction. Manifold conditions underlie pincer FAI: anatomical abnormalities, malorientation of the acetabulum, torsional abnormalities of the neck and femoral shaft (these defects can be constitutional, post-traumatic or post-surgical), and involvement in sports characterized by repeated and sudden maximum joint excursions. In a high percentage of cases, pincer FAI is associated with cam FAI. The aims of surgical treatment of pincer FAI are to eliminate the cause of the contact and repair the joint damage; the surgery may be open or arthroscopic, performed with an articular or extra-articular approach. Recently, arthroscopic treatment of FAI had a rapid and widespread diffusion due to the advantages it offers compared with the open technique. Arthroscopic treatment can repair the joint damage and in some cases, characterized by minor deformity, compensate for extra-articular defects. The acetabular labrum must always be preserved and sutured; only in extreme cases can it be sacrificed. Post-operative mobilization must respect the healing time of the labral repair.

Femoroacetabular Impingement: Prevalent and Often Asymptomatic in Older Men: The Osteoporotic Fractures in Men Study.

The epidemiology of femoroacetabular impingement (FAI) is important but incompletely understood, because most reports arise from symptomatic populations. Investigating the prevalence of FAI in a community-based cohort could help us better understand its epidemiology and in particular the degree to which it might or might not be associated with hip pain. The purposes of this study were (1) to evaluate the proportion of older (≥65 years of age) men with morphologic abnormalities consistent with FAI; and (2) to assess the association of the morphologic abnormalities with prevalent radiographic hip osteoarthritis (OA) and hip pain. Anteroposterior radiographs were obtained in 4140 subjects (mean age±SD, 77±5 years) from the Osteoporotic Fractures in Men study. We assessed each hip for cam, pincer, and mixed FAI types using validated radiographic definitions. Both intra- and interobserver reproducibility were >0.9. Radiographic hip OA was assessed by an expert reader (intraobserver reproducibility, 0.7-0.8) using validated methods, and summary grades of 2 or greater (on a scale from 0 to 4) were used to define radiographic hip OA. Covariates including hip pain in the last 30 days were collected by questionnaires that were answered by all patients included in this report. Logistic regressions with generalized estimating equations were performed to evaluate the association of radiographic features of FAI and arthrosis. Pincer, cam, or mixed types of radiographic FAI had a prevalence of 57% (1748 of 3053), 29% (886 of 3053), and 14% (419 of 3053), respectively, in this group of older men. Both pincer and mixed types of FAI were associated with arthrosis but not with hip pain (odds ratio [OR], 1.63; 95% confidence interval [CI], 1.25-2.13; p<0.001 for pincer and OR, 2.49; 95% CI, 1.65-3.76; p<0.001 for mixed type). Patients with hips characterized by cam-type FAI had slightly reduced hip pain without the presence of arthrosis compared with hips without FAI (OR, 0.82; 95% CI, 0.68-0.99; p=0.037). A center-edge angle>39° and a caput-collum-diaphyseal angle<125° were associated with arthrosis (OR, 1.53; 95% CI, 1.22-1.94; p<0.001 and OR, 2.09; 95% CI, 1.24-3.51; p=0.006, respectively), but not with hip pain (OR, 0.89; 95% CI, 0.77-1.03; p<0.108 and OR, 0.99; 95% CI, 0.67-1.45; p=0.945, respectively). An impingement angle<70° was associated with less hip pain compared with hips with an impingement angle≥70° (OR, 0.76; 95% CI, 0.61-0.95; p=0.015). FAI is common in older men and represents more of an anatomic variant rather than a symptomatic disease. This finding should raise questions on how age, activities, and this anatomic variant each contribute to result in symptomatic disease. Level III, prognostic study.