Cam Femoroacetabular Impingement Research Articles

Beyond the Patella: Treatment of Cam Femoroacetabular Impingement Syndrome Improves Anterior Knee Pain

ObjectivesThis study aimed to investigate if there is a relationship between cam femoroacetabular impingement syndrome (cam-FAIS) and chronic anterior knee pain (AKP). MethodsThis is a pilot retrospective review of 12 AKP patients with no structural anomalies in the patellofemoral joint and no skeletal malalignment in the lower limbs. All the patients were resistant to proper conservative treatment for AKP (AKP-R). Subsequently, these patients developed pain in the ipsilateral hip several months later, and upon evaluation, were diagnosed with cam-FAIS. Arthroscopic femoral osteoplasty and labral repair were performed and clinical follow-up of hip and knee pain and function (Kujala Score and Non-arthritic Hip Score -NAHS-) was carried out. ResultsAll the patients showed improvement in the knee and hip pain scores with a statistically significant clinical difference in all of them at 69 months follow up (range: 18 to 115) except one patient without improvement in the groin VAS score post-operatively. Visual analogical scale (VAS) of knee pain improved from 6.3 (range: 5 to 8) to a postoperative 0.5 (range: 0 to 3.5), (p<0.001). The VAS of groin pain improved from 4.4 (range: 2 to 8) to a postoperative 0.9 (range: 0 to 3), (p<0.001). NAHS improved from a preoperative 67.9 (range: 28.7 to 100) to a postoperative 88 (range: 70 to 100), (p<0.015) and Knee Kujala's score improved from a preoperative 48.7 (range: 22 to 71) to a postoperative 96 (range: 91 to 100), (p<0.001). ConclusionThis study's principal finding suggests an association between cam-FAIS and AKP-R in young patients who exhibit normal knee imaging and lower limbs skeletal alignment. Addressing cam-FAIS in these cases leads to resolution of both groin and knee pain, resulting in improved functional outcomes for both joints. Study DesignRetrospective cohort series with a single contemporaneous long-term follow-up. Level of EvidenceIV

Anterior knee pain patients without structural knee abnormalities and normal lower limb skeletal alignment have a higher prevalence of cam-femoroacetabular impingement syndrome than the general population

ObjectivesThis study aimed to ascertain the prevalence of cam femoroacetabular impingement syndrome (cam-FAIS) in anterior knee pain (AKP) patients devoid of both structural patellofemoral joint abnormalities and lower limb skeletal malalignment. A secondary objective was to examine pain and disability differences between AKP patients with and without cam-FAIS. MethodsA total of 209 AKP patients were screened for eligibility. Inclusion criteria were normal imaging studies and normal lower limb alignment, and exclusion criteria were previous knee surgery and knee and/or hip osteoarthritis. Of those, 49 (23.4%) were eligible and this number matched a previous power analysis to detect statistically significant differences in prevalence of cam-FAIS in a population of AKP patients. The first step in the study sequence was to ask the patient whether they had groin pain. If so, the impingement test was done. Then, the femoral cam morphology defined by an alpha angle greater than or equal to 55° in a 45° Dunn axial view of the hip was ruled out. Additionally, patients completed Kujala and International Knee Documentation Committee (IKDC) functional knee scores for disability assessment. General population control group was obtained from literature. ResultsThe study included 9 males and 40 females, with an average age of 36 (20–50, ±SD 8.03) years. Groin pain and positive impingement test were found in 26/49 patients (53%). An alpha angle ≥55° was observed in 35/49 patients (71%). A combination of groin pain, positive impingement test and an alpha angle ≥55° was seen in 18/49 patients (37%). The AKP patients with groin pain, a positive impingement test and an alpha angle ≥55° exhibited statistically similar pain and disability levels as AKP patients without cam-FAIS. ConclusionThe results of this study suggest that AKP patients without structural abnormalities in the patellofemoral joint and without lower limbs malalignment have a statistically significantly higher prevalence of cam-FAIS than the general population. Moreover, AKP patients with cam-FAIS have a statistically similar degree of pain and disability than AKP patients without it. Study designCross-sectional study. Level of EvidenceIV.

Femurs in patients with hip dysplasia have fundamental shape differences compared with cam femoroacetabular impingement

ABSTRACT Femoral deformities are common in developmental dysplasia of the hip (DDH), but decisions about how to treat them are not standardized. Of interest are deformities that may be akin to cam femoroacetabular impingement (FAI). We used three-dimensional and two-dimensional measures to clarify the similarities and differences in proximal femur shape variation among female patients with DDH (n = 68) or cam FAI (n = 60). Three-dimensional measures included femoral head asphericity, as well as shape variation using statistical shape modeling and principal component analysis (PCA). Two-dimensional measures included the α-angle, head–neck offset (HNO) and the neck–shaft angle (NSA). Significant shape variations were captured in the first five PCA modes, with the greatest shared variation between groups being the length from the lesser trochanter to the femoral head and greater trochanter height. Variations unique to DDH were irregularities at different areas of the femoral head, but not at the lateral femoral head–neck junction where variation was strong in FAI. The FAI group also had unique variations in greater trochanter shape. DDH femoral heads were less spherical, as indicated by larger sphere-fitting errors (P &amp;lt; 0.001). Radiographically, the DDH group had significantly smaller α-angles (P &amp;lt; 0.001), larger head–neck offsets (P = 0.02) and larger NSAs (P &amp;lt; 0.001). Both the articular and extra-articular regions of the proximal femur have distinct shape features in DDH and cam FAI that can uniquely affect the biomechanics of each disorder. Accordingly, approaches to addressing each disorder should be unique.

Soft Tissue Cam Impingement in Adolescents: MRI Reveals Impingement Lesions Underappreciated on Radiographs

Background: Femoroacetabular impingement (FAI) has been described as repetitive and abnormal contact between a structurally abnormal proximal femur (cam) and/or acetabulum (pincer), occurring during the terminal range of motion of the hip. While cam and pincer lesions have traditionally been defined as osseous abnormalities, there may be a subset of adolescent patients whose impingement is primarily soft tissue (nonosseous). The existence of a nonosseous cam lesion in adolescents with FAI has not been well described. Purpose: To identify and characterize a series of adolescent patients with nonosseous (soft cam) FAI identified on magnetic resonance imaging (MRI) and compare these patients’ clinical presentation and outcome with those of a cohort with primary osseous cam FAI in the same age group. Study Design: Case series; Level of evidence, 4. Methods: A prospective institutional registry of patients with symptomatic FAI was reviewed. Patients were included if they had an MRI scan and a lateral radiograph of the hip (45° Dunn or frog) at a baseline visit. On MRI, the anterolateral femoral head was evaluated using radial, coronal, sagittal, or axial oblique sequences. A soft cam lesion was identified by the presence of soft tissue thickening of ≥2 mm at the anterolateral femoral head-neck junction. An alpha angle was measured on MRI scans and radiographs when a lesion was identified. The cohort with soft cam lesions was reviewed and findings and outcomes were compared with those of a cohort with osseous cam lesions. Continuous variables were first examined for normality, and then nonparametric tests—such as the Kruskal-Wallis test—were considered. The change between pre- and postoperative patient-reported outcomes (PROs) was described by mean and standard deviation and evaluated with an independent-samples t test. Results: A total of 31 (9.3%) of 332 hips (mean age, 16.4 years [range 13.1-19.6 years]; women, 83.9%) were identified with a soft tissue impingment lesion on MRI at the femoral head-neck junction between the 12 and 3 o'clock positions. These lesions demonstrated a thickened perichondral ring (71%), periosteal thickening (26%), or a cartilaginous epiphyseal extension (3%). The mean alpha angle on MRI was greater than on radiographs (63.5°± 7.9° vs 51.3°± 7.9°; P < .0001). A total of 22 patients (71%) with soft impingement underwent hip preservation surgery. When compared with patients in the osseous cohort who also underwent surgical management, both groups showed similar significant improvements from pre- to postoperatively (soft: modified Harris Hip Score [mHHS], 26.9 ± 18.2; Hip disability and Osteoarthritis Outcome Score [HOOS], 31.4 ± 22.9; osseous: mHHS, 22.8 ± 20.8; HOOS, 27.4 ± 20.1; P < .0001), with a mean follow-up of 3.4 years (range, 1-7 years) in the soft cam cohort and 3 years (1-10.1 years) in the osseous cam cohort. Conclusion: Clinicians should be aware of nonosseous or soft cam lesions that cause impingement in adolescent patients without an obvious osseous cam on radiographs. MRI is required to detect these soft cam lesions. When nonoperative treatment fails, the PROs in these patients after operative management are comparable with those in patients with osseous cam lesions. Further research is needed to determine whether the soft cam precedes an osseous cam or whether it is a separate entity.

Analysis of cam location characteristics in FAI syndrome patients from 3D MR images demonstrates sex-specific differences.

Cam femoroacetabular impingement (FAI) syndrome is associated with hip osteoarthritis (OA) development. Hip shape features, derived from statistical shape modeling (SSM), are predictive for OA incidence, progression, and arthroplasty. Currently, no three-dimensional (3D) SSM studies have investigated whether there are cam shape differences between male and female patients, which may be of potential clinical relevance for FAI syndrome assessments. This study analyzed sex-specific cam location and shape in FAI syndrome patients from clinical magnetic resonance examinations (M:F 56:41, age: 16-63 years) using 3D focused shape modeling-based segmentation (CamMorph) and partial least squares regression to obtain shape features (latent variables [LVs]) of cam morphology. Two-way analysis of variance tests were used to assess cam LV data for sex and cam volume severity differences. There was no significant interaction between sex and cam volume severity for the LV data. A sex main effect was significant for LV 1 (cam size) and LV 2 (cam location) with medium to large effect sizes (p < 0.001, d > 0.75). Mean results revealed males presented with a superior-focused cam, whereas females presented with an anterior-focused cam. When stratified by cam volume, cam morphologies were located superiorly in male and anteriorly in female FAI syndrome patients with negligible, mild, or moderate cam volumes. Both male and female FAI syndrome patients with major cam volumes had a global cam distribution. In conclusion, sex-specific cam location differences are present in FAI syndrome patients with negligible, mild, and moderate cam volumes, whereas major cam volumes were globally distributed in both male and female patients.

Which Acetabular Measurements Most Accurately Differentiate Between Patients and Controls? A Comparative Study.

Which Acetabular Measurements Most Accurately Differentiate Between Patients and Controls? A Comparative Study.

Poster 112: Epigenetic Dysregulation during the OA Progression in Hip FAI

Objectives: Femoroacetabular impingement (FAI) is considered a leading cause of early hip OA, but initial molecular mechanisms that lead FAI patients to OA progression remains to be elucidated. Recent articles revealed that epigenetic changes are associated with OA progression, specifically, DNA methyltransferase 3B (DNMT3B) plays a critical role on cartilage homeostasis by attenuating catabolic gene expression. This study aimed to examine the catabolic state of articular chondrocyte (ACs) during OA progression in hip FAI disease, particularly the expressions of DNMT3B and 4-aminobutyrate aminotransferase (ABAT, downstream of DNMT3B), to assess how epigenetic dysregulation contributes to OA progression. Methods: Full-thickness cartilage samples were collected from the impingement zone. In total, twelve patients underwent hip preservation surgery for cam FAI (early-FAI) and twelve patients underwent total hip replacement for advanced OA secondary to cam FAI (late FAI-OA) were included in this study. As a non-disease (ND) group, five healthy samples were procured from hip joint cadavers. The explants were cultured in unstimulated conditions or catabolic stimulus (IL1β). Histological analyses was performed with safranin-O/fast-green. Gene expression was analyzed via qPCR for GAPDH, DNMT3B, ABAT, MMP-13, and COL10A1. Protein expression was analyzed by western blotting analysis for DNMT3B and ABAT. Methylation specific PCR was performed to assess the methylation status at ABAT promoter (epigenetic change). Results: The early FAI group included younger subjects with lower Tönnis grade than the late FAI OA group; however, there were no significant differences in gender, BMI, and α-angle between groups. Cartilage samples in early-FAI and late FAI-OA showed a histological OA phenotype (Figure 1A). RT-PCR confirmed increased expression of MMP-13 and COL10A1 in early and late FAI-OA (Figure 1B), confirming cartilage degeneration, catabolism, and chondrocyte hypertrophy when compared to ND group. Interestingly, RT-PCR revealed that expression of DNMT3B gradually declined as the disease progressed (ND vs early p&lt;0.001, early vs late p=0.016), while ABAT increased as the disease progressed (ND vs early p&lt;0.001, early vs late p=0.035, Figure 1B). IF staining confirmed that DNMT3B was abundantly expressed in chondrocytes of normal cartilage but the expression gradually decreased with disease progression, contrary ABAT expression gradually increased as the disease progressed (Figure 1C). These results were supported by protein expression in western blotting analysis (Figure 1D). In MSP analysis, the human ABAT promoter is characterized by a typical CpG island (Figure 2A, blue area). Additionally, there was hypomethylation at the ABAT promoter during end stage of disease (ND vs early p=0.022, early vs late p=0.042) (Figure 2B). Catabolic stimulus with IL1β for early FAI and late FAI-OA, accentuated the ABAT promoter hypomethylation (early FAI: nontreatment vs IL1β p=0.056, late FAI-OA: nontreatment vs IL1β p=0.015, Figure 2C) and resulted in further overexpression of ABAT and catabolic markers and decreased expression of DNMT3B (Figure 3A-C). These findings are supported by protein expression in western-blotting analysis (Figure 3D). Conclusions: In the present study, histological findings were similar in early and late FAI, but DNMT3B expression levels gradually decreased with OA progression, while ABAT and catabolic marker expression levels increased, suggesting a less catabolic phenotype in the early stage of disease. MSP analysis confirmed ABAT promoter hypo-methylation (epigenetically dysregulation) as hip OA progresses. Notably, in the current study, the inflammatory stimulus with IL1β further reduced DNA methylation at the ABAT promoter and resulted in a concomitant excessive increase of ABAT and catabolic markers in human hip OA ACs. This study suggests, for the first time, that cartilage degeneration in the impingement zone in hip FAI is progressive at the molecular level and may be controlled in part by an epigenetic dysregulation. Understanding the mechanism of OA disease in hip FAI will potentially provide concomitant interventional treatment to hip pre-OA disease.

Poster 113: Epigenetic Regulation of PPARγ Rescues Articular Chondrocytes from Catabolic State Suggesting PPARγ as a Potential Target to Slow Down Progression of OA in Hip FAI

Objectives: Hip Femoroacetabular impingement (FAI) has a high prevalence of chondral lesions, and the severity of chondral damage is associated with an increased risk of postoperative OA progression, but the mechanisms of cartilage degeneration in OA progression remains unclear. Peroxisome proliferator- activated receptor-gamma (PPARγ) is widely expressed in healthy articular chondrocytes (ACs) and plays an essential role in cartilage homeostasis. Recent investigations into OA pathogenesis have revealed that hyper or hypomethylation (by DNMTs) of OA susceptibility genes are involved in OA progression, especially downregulation of PPARγ has been linked to OA progression. This study aimed to investigate the expression of PPARγ and DNA methyltransferases enzymes (DNMT1 and DNMT3A) during progression of hip disease and 2) methylation changes in the PPARγ promoter area during progression of hip disease. Methods: Full-thickness cartilage samples were collected from the impingement zone. Twelve patients underwent hip preservation surgery for cam FAI (early FAI) and twelve patients underwent total hip replacement for advanced OA secondary to cam FAI (late FAI-OA) were included. As a non-disease (ND) group, six healthy samples were procured from hip joint cadavers. Cartilage explants were cultured in unstimulated conditions or catabolic stimulus (IL1β) with or without DNA demethylating agent 5-Aza-2’- deoxycytidine (5Aza). Histological analysis was performed with safranin O/fast green. Gene expression was analyzed via qPCR for GAPDH, DNMT1, DNMT3A, PPARγ, MMP13, and COL10A1. Methylation specific PCR (MSP) was performed to assess the methylation status at PPARγ promoter site. Chromatin immunoprecipitation (ChIP) assay was performed to confirm an interaction between DNMT3A and the PPAR promoter region. Results: The early FAI group included younger subjects than the late FAI OA group. Cartilage samples in early and late FAI-OA displayed a histological OA phenotype (Figure 1A). ACs in early and late FAI-OA displayed increased expression of catabolism and chondrocyte hypertrophy markers ( MMP13: ND vs early p&lt;0.001, ND vs late p&lt;0.001, COL10A1: ND vs early p&lt;0.001, ND vs late p&lt;0.001, Figure. 1B). Contrary, expression of PPARγ gradually declined as the disease progressed (ND vs early p=0.001, early vs late p=0.003, Figure. 1B). IF analysis also displayed a gradual decrease of the PPARγ expression during disease progression (ND vs early p=0.001, early vs late p=0.041, Figure 1C). In the assessment of the epigenetic mechanisms of aberrant DNA methylation in OA progression, overexpression of DNMT1 and DNMT3A levels was observed with disease progression in RT-PCR ( DNMT1: ND vs early p&lt;0.001, early vs late p=0.041, DNMT3A: ND vs early p=0.015, early vs late p=0.053,Figure 2A) and IF analysis ( DNMT1: ND vs early p&lt;0.001, early vs late p&lt;0.001, DNMT3A: ND vs early &lt;0.001, early vs late p=0.008, Figure 2B). Next, in MSP analysis, human PPARγ promoter was featured by typical CpG islands (Figure 3A). As the OA progresses, hypermethylation at PPARγ promoter (ND: 9%, Early-FAI: 34%, Late FAI-OA: 48%) was observed (Figure 3B), and ChIP assay confirmed DNMT3A interaction with the CpG PPARγ promoter area (Figure 3C). IL1β stimulus increased PPARγ promoter methylation for early (34% to 57%, p=0.016, Figure 3D) and late stages (48% to 79%, p=0.001, Figure 3D) resulting in suppression of PPARγ expression (P=0.073, Figure 3F). Contrary, treatment with 5Aza (a DNA demethylator) brought the level of methylation back to 37% for early FAI ( p=0.033, Figure 3D) and 46% for late FAI-OA (p&lt;0.001, Figure 3D), reversed the PPARγ suppression induced by IL1β (early- FAI p=0.009, and late FAI-OA ACs p&lt;0.001 Figure 3F) and decreased expression of MMP-13 and COL10A1 induced by IL1β (early-FAI p=0.009, Figure 4C and late FAI-OA ACs p&lt;0.001 Figure 3F). PPARγ inhibitor rescued cells from the catabolic phenotype. (Fig.3E, F), suggesting that restoration of PPARγ by 5Aza contributes significantly to the cartilage protective effect. Conclusions: This current study demonstrates that PPARγ expression was gradually suppressed via promoter hypermethylation during OA progression in hip FAI. Moreover, the inflammatory stimulus with IL1β further increased catabolic markers and enhanced PPARγ suppression via promoter excessive hypermethylation in human hip ACs. Notably, DNA demethylating agent (5 aza) prevents the IL1β induced PPARγ promoter hypermethylation rescuing PPARγ and alleviating cartilage degenerative damage. Certainly, for patients with symptomatic hip FAI, surgical correction should be prioritized to suppress inflammation, but our observations suggests that critical epigenetic dysregulation occurs during the progression of hip OA. Future investigations will be needed to confirm if regulation of these epigenetic changes could potentially complement surgical treatment to minimize OA progression in hip FAI.

DOES BONE TURNOVER EXPLAIN HIGH BONE DENSITY IN FEMOROACETABULAR IMPINGEMENT? AN ANALYSIS OF PET AND CT IMAGING

Femoroacetabular impingement (FAI) results from a morphological deformity of the hip and is associated with osteoarthritis (OA). Increased bone mineral density (BMD) is observed in the antero-superior acetabulum rim where impingement occurs. It is hypothesized that the repeated abnormal contact leads to damage of the cartilage layer, but could also cause a bone remodelling response according to Wolff's Law. Thus the goal of this study was to assess the relationship between bone metabolic activity measured by PET and BMD measured in CT scans.Five participants with asymptomatic cam deformity, three patients with uni-lateral symptomatic cam FAI and three healthy controls were scanned in a 3T PET-MRI scanner following injection with [18F]NaF. Bone remodelling activity was quantified with Standard Uptake Values (SUVs). SUVmax was analyzed in the antero-superior acetabular rim, femoral head and head-neck junction. In these same regions, BMD was calculated from CT scans using the calibration phantom included in the scan. The relationship between SUVmax and BMD from corresponding regions was assessed using the coefficient of determination (R2) from linear regression.High bone activity was seen in the cam deformity and acetabular rim. SUVmax was negatively correlated with BMD in the antero-superior region of the acetabulum (R2=0.30, p=0.08). SUVmax was positively correlated with BMD in the antero-superior head-neck junction of the femur (R2=0.359, p=0.067). Correlations were weak in other regions.Elevated bone turnover was seen in patients with a cam deformity but the relationship to BMD was moderate. This study demonstrates a pathomechanism of hip degeneration associated with FAI deformities, consistent with Wolff's law and the proposed mechanical cause of hip degeneration in FAI. [18F]-NaF PET SUV may be a biomarker of degeneration, especially in early stages of degeneration, when joint preservation surgery is likely to be the most successful.

Epigenetic dysregulation of articular cartilage during progression of hip femoroacetabular impingement disease.

Femoroacetabular impingement (FAI) is an important trigger of hip osteoarthritis (OA). Epigenetic changes in DNA methyltransferase 3B (DNMT3B) attenuate catabolic gene expression in cartilage hemostasis. This study aimed to examine the articular chondrocyte catabolic state and DNMT3B and 4-aminobutyrate aminotransferase promoter (ABAT) expression during OA progression in FAI. Cartilage samples were collected from the impingement zone of 12 patients with cam FAI (early-FAI) and 12 patients with advanced OA secondary to cam FAI (late-FAI-OA). Five healthy samples were procured from cadavers (ND: nondiseased). Explants were cultured under unstimulated conditions, catabolic stimulus (IL1β), or anabolic stimulus (TGFβ). Histology was performed with safranin-O/fast-green staining. Gene expression was analyzed via qPCR for GAPDH, DNMT3B, ABAT, MMP-13, COL10A1. Methylation specific PCR assessed methylation status at the ABAT promoter. Cartilage samples in early-FAI and late-FAI-OA showed a histological OA phenotype and increased catabolic marker expression (MMP13/COL10A1, ND vs.early-FAI, p = 0.004/p < 0.001, ND vs.late-FAI-OA, p < 0.001/p < 0.001). RT-PCR confirmed DNMT3B underexpression (ND vs.early-FAI, p < 0.001, early-FAI vs.late-FAI-OA, p = 0.016) and ABAT overexpression (ND vs.early-FAI, p < 0.001, early vs.late-FAI-OA, p = 0.035) with advanced disease. End-stage disease showed ABAT promoter hypomethylation. IL1β stimulus accentuated ABAT promoter hypomethylation and led to further ABAT and catabolic marker overexpression in early-FAI and late-FAI-OA while TGFβ normalized these alterations in gene expression. Catabolic and epigenetic molecule expression suggested less catabolism in early-stage disease. Sustained inflammation induced ABAT promoter hypo-methylation causing a catabolic phenotype. Suppression of ABAT by methylation control could be a new target for therapeutic intervention to prevent OA progression in hip FAI.

Acetabular labrum and cartilage contact mechanics during pivoting and walking tasks in individuals with cam femoroacetabular impingement syndrome

Femoroacetabular impingement syndrome (FAIS) is a motion-related pathology of the hip characterized by pain, morphological abnormalities of the proximal femur, and an elevated risk of joint deterioration and hip osteoarthritis. Activities that require deep flexion are understood to induce impingement in cam FAIS patients, however, less demanding activities such as walking and pivoting may induce pain as well as alterations in kinematics and joint stability. Still, the paucity of quantitative descriptions of cam FAIS has hindered understanding underlying hip joint mechanics during such activities. Previous in silico studies have employed generalized model geometry or kinematics to simulate impingement between the femur and acetabulum, which may not accurately capture the interplay between morphology and motion. In this study, we utilized models with participant-specific bone and articular soft tissue anatomy and kinematics measured by dual-fluoroscopy to compare hip contact mechanics of cam FAIS patients to controls during four activities of daily living (internal/external pivoting and level/incline walking). Averaged across the gait cycle during incline walking, patients displayed increased strain in the anterior joint (labrum strain: p-value = 0.038, patients: 11.7 ± 6.7 %, controls: 5.0 ± 3.6 %; cartilage strain: p-value = 0.029, patients: 9.1 ± 3.3 %, controls: 4.2 ± 2.3). Patients also exhibited increased average anterior cartilage strains during external pivoting (p-value = 0.039; patients: 13.0 ± 9.2 %, controls: 3.9 ± 3.2 %]). No significant differences between patient and control contact area and strain were found for level walking and internal pivoting. Our study provides new insights into the biomechanics of cam FAIS, including spatiotemporal hip joint contact mechanics during activities of daily living.

Gluteal activation during squatting reduces acetabular contact pressure in persons with femoroacetabular impingement syndrome: A patient-specific finite element analysis

BackgroundFemoroacetabular impingement syndrome is a motion-related clinical disorder resulting from abnormal hip joint morphology. Mechanical impingement, in which the aspherical femoral head (cam morphology) abuts with the acetabular rim, is created with simultaneous hip flexion, internal rotation, and adduction. Impaired function of the gluteal muscles may be contributory to femoroacetabular impingement syndrome progression. The purpose of this study was to assess the influence of gluteal muscle recruitment on acetabular contact pressure during squatting in persons with cam femoroacetabular impingement syndrome. MethodsEight individuals (4 males, 4 females) with a diagnosis of cam femoroacetabular impingement syndrome underwent CT imaging of the pelvis and proximal femora, and a biomechanical assessment of squatting (kinematics, kinetics, and electromyography). Two maximal depth bodyweight squat conditions were evaluated: 1) non-cued squatting; and 2) cued gluteal activation squatting. Utilizing subject-specific electromyography-driven hip and finite element modeling approaches, hip muscle activation, kinematics, bone-on-bone contact forces, and peak acetabular contact pressure were compared between squat conditions. FindingsModest increases in gluteus maximus (7% MVIC, P < 0.0001) and medius (6% MVIC, P = 0.009) activation were able to reduce hip internal rotation on average 5° (P = 0.024), and in doing so reduced acetabular contact pressure by 32% (P = 0.023). Reductions in acetabular contact pressure occurred despite no change in hip abduction and increased bone-on-bone contact forces occurring in the cued gluteal activation condition. InterpretationOur findings highlight the importance of gluteal activation in minimizing mechanical impingement and provide a foundation for interventions aimed at preventing the development and progression of femoroacetabular impingement syndrome.

Does Femoral Osteoplasty Improve Long-term Clinical Outcomes and Survivorship of Hip Arthroscopy? A 15-Year Minimum Follow-up Study

Background: Although femoral osteoplasty is common practice in treating cam-type femoroacetabular impingement (FAI), long-term data are lacking that support the ability of this procedure to optimize outcomes and alter natural history. Purpose: To compare long-term clinical outcomes and survivorship of treatment for symptomatic FAI via arthroscopic correction of labral or chondral pathology with and without femoral osteoplasty. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective cohort study was performed across 2 consecutive cohorts of patients with isolated cam-type FAI who underwent hip arthroscopic treatment of labral or chondral pathology without femoral osteoplasty (HS group) or with femoral osteoplasty (HS-OST group). These unique cohorts were established at a distinct transition time in our practice before and after adoption of femoral osteoplasty for treatment of FAI. Clinical outcomes were measured using the modified Harris Hip Score (mHHS). Kaplan-Meier analysis was used to assess for total hip arthroplasty (THA)–free and reoperation-free survivorship. Results: The final HS group included 17 hips followed for 19.7 ± 1.2 years, and the final HS-OST group included 23 hips followed for 16.0 ± 0.6 years. No significant patient or morphological differences were found between groups. Compared with the HS group, the HS-OST group had significantly higher final mHHS (82.7 vs 64.7 for HS-OST vs HS, respectively; P = .002) and mHHS improvement (18.4 vs 6.1; P = .02). The HS-OST group also had significantly greater 15-year THA-free survivorship versus the HS group (78% vs 41%, respectively; P = .02) and reoperation-free survivorship (78% vs 29%; P = .003). Conclusion: This study demonstrated superior long-term clinical outcomes and survivorship with combined arthroscopy and femoral osteoplasty compared with hip arthroscopy alone. These long-term data strongly support the practice of femoral osteoplasty in patients with cam FAI morphologies and suggest that this treatment alters the natural history of FAI at long-term follow-up.

Paper 44: Does femoral osteoplasty enhance clinical outcomes and survivorship of FAI surgery at long-term follow-up beyond fifteen years?

Objectives:Cam-type femoroacetabular impingement (FAI) is now well-established as a risk factor for intra-articular damage (labrum and articular cartilage) and secondary osteoarthritis. Long-term studies of FAI surgery are critical in understanding clinical outcomes, refining surgical treatments and predicting osteoarthritis progression. Nevertheless, studies beyond 15 years are uncommon. Although femoral osteoplasty is now common practice in treating cam FAI, long-term data supportive of this procedure and its ability to alter the natural history of FAI are not available. The purpose of this study was to analyze the long-term clinical outcomes and survivorship of symptomatic FAI treatment by arthroscopic correction of labral pathology alone or in combination with femoral osteoplasty (structural FAI correction).Methods:A retrospective comparative study was performed on two consecutive, longitudinal cohorts of patients with isolated cam-type FAI that underwent surgical treatment of labral pathology either with femoral osteoplasty (HSLO group, 23 hips) or without femoral osteoplasty (HS group, 17 hips). These cohorts were captured immediately prior to and after implementation of femoral osteoplasty into our practice and have been previously reported on at mean 2-year followup. The current study investigated clinical outcomes and survivorship at minimum 15-year followup. Patients with pincer or combined cam-pincer morphologies were excluded. Clinical outcomes were measured with the modified Harris hip score (mHHS). Kaplan-Meier survival was assessed for THA-free and reoperation-free survivorship.Results:The HSLO group included 23 hips followed for a mean of 16.0 ±0.6 years, and the HS group 17 hips followed for 19.7 ±1.2. The HSLO group had a significantly higher final mHHS (82.7 vs. 64.7, p=0.002) and mHHS improvement (18.4 vs. 6.1, p=0.02) compared to the HS group. The rate of THA conversion (22% vs. 59%, P=0.02) and overall reoperation (22% vs. 70%, P=0.003) were significantly lower in the HSLO group. THA conversion occurred at a mean of 5.8 ±2.5 years postoperatively in the HSLO group, and 7.1 ±4.0 years in the HS group. The HSLO group had significantly greater 15-year THA-free survivorship (78% vs 41%, p=0.02) and reoperation-free survivorship (78% vs. 29%, p=0.003) by Kaplan-Meier analysis.Conclusions:This study demonstrates better long-term clinical outcomes and survivorship with combined arthroscopy and femoral osteoplasty compared to arthroscopy alone. These long-term data strongly support the current practice of femoral osteoplasty in patients with cam FAI morphologies and suggest that this treatment alters the natural history of FAI.Figure 1.Comparative Survival

Poster 196: Articular Chondrocytes in Hip Femoroacetabular Impingement Present a Less Catabolic Phenotype than Late Stage of Disease

Objectives:Pathophysiologic mechanisms during osteoarthritis (OA) have been primarily identified using tissues harvested from end stage of disease. However, it is likely that the disease-initiating molecular changes have already occurred in early-stage diseased joints. Femoroacetabular impingement (FAI) has an etiologic role in up to 50% of hip osteoarthritis (OA) and offers a unique opportunity to study molecular changes during early stage OA. Cartilage samples from the impingement zone of FAI patients express catabolic inflammatory molecules. Previously, we have confirmed that DNA methyltransferase 3B (DNMT3B) regulates post-natal articular cartilage homeostasis and 4 aminobutyrate aminotransferase (ABAT) is a downstream target for DNMT3B and attenuates catabolic gene expression. The purpose of the present study is to examine the catabolic state of ACs during progression of disease in hip FAI, specifically, to investigate the catabolic phenotype and to assess the expression levels of DNMT3B and ABAT during early (FAI) and late stage disease (OA-FAI).Methods:Full-thickness cartilage samples were collected from the anterolateral head-neck junction (impingement zone) of 11 patients. 5 patients underwent hip preservation surgery for symptomatic cam FAI (early stage OA- FAI) and 6 patients underwent total hip replacement for advanced OA secondary to cam FAI (late stage FAI-OA). As a non-disease (ND) group, 4 healthy samples were procured from hip joint cadavers. A liberator was used to harvest full thickness tissue samples for cartilage explant cultures. The cartilage tissues were washed several times using antibiotics and incubated at 37 °C and 5% CO2 for 24h. Subsequently, the explants were cultured in unstimulated conditions (no-treatment), under anabolic (TGFβ) and catabolic stimulus (IL-1β) for 48h. After culture, sections were stained with safranin O and fast green for histological analysis and cartilage degeneration was graded based on the Mankin score. RNA was isolated from explants, gene expression was analyzed via qPCR for the following specific markers: GADPH (housekeeping gene), DNMT3B, ABAT, MMP-13, and Type X collagen (COL10A1) (Figure-1). Comparisons among three groups were performed using one-way analysis of variance followed by the post hoc Bonferroni correction test.Results:Histological Mankin-scores are shown in Figure-2. Cartilage samples without treatment in ND group showed normal hyaline cartilage. However, reduction in safranin-O staining with significant increase of Mankin-score was observed under catabolic stimulus of IL-1β (Figure-2A). Contrary, in early FAI and late FAI-OA group, degenerative changes including superficial irregularities with some clefts, cell cloning, and reduced staining was observed in unstimulated conditions and became more pronounced when treated with IL-1β (Figure-2A and B). Degenerative changes were alleviated by anabolic stimulus with TGFβ1 (Figure-2B). qPCR revealed that compared to ND group, the expression levels of ABAT, MMP-13 and COL10A1 were increase in the early-FAI and late FAI-OA confirming a catabolic phenotype. Contrary, expression of DNMT3B gradually declined as the disease progressed showing significant differences between early-FAI and late FAI-OA (Figure-3B). Remarkably, although histological findings were similar between early and late stage FAI, catabolic molecule expression varied between early and late stage of disease suggesting a more catabolic phenotype state for late stage of disease.Conclusions:This current study provides initial data regarding the catabolic state of human ACs in early and late stage of hip FAI disease and characterized a catabolic phenotype of ACs from impingement zone in FAI. Importantly, although histological findings were similar between early and late stage FAI, catabolic molecule expression varied suggesting a less catabolic phenotype for early stage of disease. Most interestingly, the expression of DNMT3B gradually decrease as the disease progresses, and ABAT expression increase. Identification of these changes of methylation profiles during disease progression can distinguish pre- and early disease states from end diseased state and could provide a potential intervention to stop the OA progression in the near future. Future interventional therapies will confirm if ACs from early stage of disease can be rescued to a normal phenotype.

Poster 197: Understanding the Biological Pathway of Progression of Hip OA Disease through Transcriptome Analysis

Poster 197: Understanding the Biological Pathway of Progression of Hip OA Disease through Transcriptome Analysis

Patients with cam-type femoroacetabular impingement demonstrate increased change in bone-to-bone distance during walking: A dual fluoroscopy study.

Cam-type femoroacetabular impingement (FAI) syndrome is a painful, structural hip disorder. Herein, we investigated hip joint mechanics through in vivo, dynamic measurement of the bone-to-bone distance between the femoral head and acetabulum in patients with cam FAI syndrome and morphologically screened controls. We hypothesized that individuals with cam FAI syndrome would have larger changes in bone-to-bone distance compared to the control group, which we would interpret as altered joint mechanics as signified by greater movement of the femoral head as it articulates within the acetabulum. Seven patients with cam FAI syndrome and 11 asymptomatic individuals with typical morphology underwent dual fluoroscopy imaging during level and inclined walking (upward slope). The change in bone-to-bone distance between femoral and acetabular bone surfaces was evaluated for five anatomical regions of the acetabulum at each timepoint of gait. Linear regression analysis of the bone-to-bone distance considered two within-subject factors (activityand region) and one between-subjects factor (group). Across activities, the change in minimum bone-to-bone distance was 1.38-2.54 mm for the cam FAI group and 1.16-1.84 mm for controls. In all regions except the anterior-superior region, the change in bone-to-bone distance was larger in the cam group than the control group (p ≤ 0.024). An effect of activity was detected only in the posterior-superior region where larger changes were noted during level walking than incline walking. Statement of clinical significance: Patients with cam FAI syndrome exhibit altered hip joint mechanics during the low-demand activity of walking; these alterations could affect load transmission, and contribute to pain, tissue damage, and osteoarthritis.

Rate of continued conservative management versus progression to surgery at minimum 1-year follow-up in patients with pre-arthritic hip pain.

Extensive literature has described surgical outcomes for pre-arthritic hip pain, but the proportion of patients who progress to surgery remains unknown. To determine the proportion of patients who present to a tertiary referral center for pre-arthritic hip pain and progress to surgery at minimum 1-year follow-up. Retrospective cohort study. Single tertiary care academic medical center. Patients ages 13 to 40 years who presented for initial evaluation to a conservative or surgical orthopedic specialist and were diagnosed with pre-arthritic hip pain (n=713 patients, 830 hips). Not applicable. The primary outcome was the rate of progression to surgery at minimum 1-year follow-up for the entire cohort. Predictors of progression to surgery were determined for the entire cohort and for radiographically defined subgroups using multiple logistic regression. Candidate predictors included baseline demographic, radiographic, clinical diagnosis, and patient-reported outcome measures. In a cohort with a mean age of 25.4 (SD 8.1) years, 72.7% female, and mean follow-up of 2.6 (range 1.0-4.8) years, 429 of 830 hips (51.7%, 95% confidence interval [CI] 48.2% to 55.1%) progressed to surgery. Predictors of surgical progression in the entire cohort included younger age (OR 0.95/year, 95% CI 0.93 to 0.98), pain duration longer than 6 months (ORs 1.87-2.03, p ≤ .027), worse physical function (OR 0.96/Patient-Reported Outcomes Measurement Information System [PROMIS] point, 0.92 to 0.99), and a clinical diagnosis of femoroacetabular impingement (FAI) (OR 3.47, 2.05 to 5.89), acetabular dysplasia (OR 2.75, 1.73 to 4.35), and/or labral tear (OR 10.71, 6.98 to 16.47). Radiographic dysplasia (lateral center edge angle <20 degrees) increased the likelihood of surgery in all subgroups (ORs 2.05-8.47, p ≤ .008). Increasing maximum α angle increased the likelihood of surgery in patients with severe cam FAI (α > 63 degrees) (OR 1.03/degree, 1.00 to 1.06). Almost half of patients with pre-arthritic hip pain did not progress to surgery at a minimum 1-year follow-up. A trial of conservative management is likely worthwhile in most patients.

Lower pelvic tilt, lower pelvic incidence, and increased external rotation of the iliac wing in patients with femoroacetabular impingement due to acetabular retroversion compared to hip dysplasia.

AimsThe effect of pelvic tilt (PT) and sagittal balance in hips with pincer-type femoroacetabular impingement (FAI) with acetabular retroversion (AR) is controversial. It is unclear if patients with AR have a rotational abnormality of the iliac wing. Therefore, we asked: are parameters for sagittal balance, and is rotation of the iliac wing, different in patients with AR compared to a control group?; and is there a correlation between iliac rotation and acetabular version?MethodsA retrospective, review board-approved, controlled study was performed including 120 hips in 86 consecutive patients with symptomatic FAI or hip dysplasia. Pelvic CT scans were reviewed to calculate parameters for sagittal balance (pelvic incidence (PI), PT, and sacral slope), anterior pelvic plane angle, pelvic inclination, and external rotation of the iliac wing and were compared to a control group (48 hips). The 120 hips were allocated to the following groups: AR (41 hips), hip dysplasia (47 hips) and cam FAI with normal acetabular morphology (32 hips). Subgroups of total AR (15 hips) and high acetabular anteversion (20 hips) were analyzed. Statistical analysis was performed using analysis of variance with Bonferroni correction.ResultsPI and PT were significantly decreased comparing AR (PI 42° (SD 10°), PT 4° (SD 5°)) with dysplastic hips (PI 55° (SD 12°), PT 10° (SD 6°)) and with the control group (PI 51° (SD 9°) and PT 13° (SD 7°)) (p < 0.001). External rotation of the iliac wing was significantly increased comparing AR (29° (SD 4°)) with dysplastic hips (20°(SD 5°)) and with the control group (25° (SD 5°)) (p < 0.001). Correlation between external rotation of the iliac wing and acetabular version was significant and strong (r = 0.81; p < 0.001). Correlation between PT and acetabular version was significant and moderate (r = 0.58; p < 0.001).ConclusionThese findings could contribute to a better understanding of hip pain in a sitting position and extra-articular subspine FAI of patients with AR. These patients have increased iliac external rotation, a rotational abnormality of the iliac wing. This has implications for surgical therapy with hip arthroscopy and acetabular rim trimming or anteverting periacetabular osteotomy (PAO).Cite this article: Bone Jt Open 2021;2(10):813–824.

Muscle and Hip Contact Forces in Asymptomatic Men With Cam Morphology During Deep Squat.

Cam morphology is defined as an aspherical femoral head-neck junction that causes abnormal contact of the acetabular rim with the anterior hip. Imaging confirmation of the cam morphology, associated with clinical signs and pain in the hip or groin, is characterized as femoroacetabular impingement (FAI) syndrome. Although some individuals with cam morphology do not experience any symptoms, sparse studies have been done on these individuals. Understanding the way asymptomatic individuals generate muscle forces may help us to better explain the progression of the degenerative FAI process and discover better ways in preventing the onset or worsening of symptoms. The purpose of this study was to compare the muscle and hip contact forces of asymptomatic cam morphology (ACM) and FAI syndrome men compared to cam-free healthy controls during a deep squat task. This prospective study compared 39 participants, with 13 in each group (ACM, FAI, and control). Five deep squatting trials were performed at a self-selected pace while joint trajectories and ground reaction forces were recorded. A generic model was scaled for each participant, and inverse kinematics and inverse dynamics calculated joint angles and moments, respectively. Muscle and hip contact forces were estimated using static optimization. All variables were time normalized in percentage by the total squat cycle and both muscle forces and hip contact forces were normalized by body weight. Statistical non-parametric mapping analyses were used to compare the groups. The ACM group showed increased pelvic tilt and hip flexion angles compared to the FAI group during the descent and ascent phases of the squat cycle. Muscle forces were greater in the ACM and control groups, compared to the FAI group for the psoas and semimembranosus muscles. Biceps femoris muscle force was lower in the ACM group compared to the FAI group. The FAI group had lower posterior hip contact force compared to both the control and ACM groups. Muscle contraction strategy was different in the FAI group compared to the ACM and control groups, which caused different muscle force applications during hip extension. These results rebut the concept that mobility restrictions are solely caused by the presence of the cam morphology and propose evidence that symptoms and muscle contraction strategy can be the origin of the mobility restriction in male patients with FAI.