Symptomatic Cam Femoroacetabular Impingement Research Articles

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.

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

Pre- and postoperative in silico biomechanics in individuals with cam morphology during stair tasks

BackgroundOsteochondroplasty for cam femoroacetabular impingement is a common treatment to improve hip function and prevent joint degeneration. The purpose was to compare in-silico hip biomechanics during stair tasks in pre- and postoperative patients matched with healthy controls. MethodsTen symptomatic cam femoroacetabular impingement patients performed stair ascent and descent pre- and 2 years postoperatively. Patients were age, and body-mass-index matched to controls. Full-body kinematics and kinetics were computed and, muscle and hip contact forces were estimated using musculoskeletal modeling and static optimization. Stance-phases were time-normalized and compared using statistical non-parametric mapping. FindingsPreoperatives showed lower hip abduction than controls during stairs ascent (76–100%, P = .007). Pre- and postoperative showed lower hip external rotation compared to controls on stair ascent (Pre-op vs controls: 71–100%, P = .005; Post-op vs controls: 72–100%, P = .01) and stair descent (Pre-op vs controls: 0–62%, P = .001; Post-op vs controls: 0–60%, P = .001). Postoperatives showed lower iliacus force compared to preoperative (1–3%, P = .012) and control (3–6%, P = .008), and higher gluteus maximus and piriformis forces compared to controls during stair descent. Lower postoperative anterior hip contact force (0–7%, P = .004) during descent, and superior (33–35%, P = .018) during ascent compared to controls were observed. Postoperative contact forces were medialized compared to preoperative (0–2%, P = .011) and controls (1–2%, P = .016). InterpretationForcing participants to adhere to standardized step length/rise minimized sagittal kinematic differences between conditions and groups. Persistent reduced hip external rotation postoperatively and minor muscle force adaptations led to reduced superior hip contact force during stair ascent and reduced anterior and more medialized contact forces during stair descent.

Distinct Pattern of Inflammation of Articular Cartilage and the Synovium in Early and Late Hip Femoroacetabular Impingement

Background: The molecular mechanism of how femoroacetabular impingement (FAI) morphology leads to hip osteoarthritis (OA) is yet to be determined. The expression and location of inflammation-related molecules during early- and late-stage FAI have not been previously described. Moreover, the characterization of intra-articular inflammation away from the cam deformity as well as the nature of adjacent synovial tissue have also not been extensively reported. Hypothesis: Early-stage FAI has a similar expression of inflammation-related markers in the head-neck and acetabular cartilage but less synovitis than late-stage FAI. Study Design: Controlled laboratory study. Methods: Head-neck cartilage, acetabular cartilage, and synovial samples were obtained from patients undergoing hip preservation surgery for the treatment of symptomatic cam FAI (early FAI group; n = 15) and advanced OA secondary to cam FAI (late FAI group; n = 15). Samples procured from healthy young adult donors served as the control group (n = 7). Cartilage degeneration was assessed by histology, and the expression of inflammation-related proteins (interleukin–1 beta [IL-1β], matrix metalloproteinase–13 [MMP-13], a disintegrin and metalloproteinase with thrombospondin motifs–4 [ADAMTS-4], type II collagen [COL2], and aggrecan neoepitope [NITEGE]) was measured by immunostaining. Synovial samples in the early and late FAI groups were examined for synovitis and the expression of IL-1β. Results: Head-neck cartilage in the early FAI group showed significantly more degeneration than the control group and an increased expression of inflammation-related proteins (IL-1β: 69.7% ± 18.1% vs 20.2% ± 4.9%, respectively; MMP-13: 79.6% ± 12.6% vs 25.3% ± 9.5%; ADAMTS-4: 83.9% ± 12.2% vs 24.3% ± 11.1%; NITEGE: 89.7% ± 7.7% vs 39.8% ± 20.5%) (P < .001). Head-neck and acetabular cartilage in the early and late FAI groups showed a similar degree of degeneration. Moreover, a similar expression of inflammation-related proteins was observed between the early and late FAI groups for head-neck cartilage (IL-1β: 69.7% ± 18.1% vs 72.5% ± 13.2%; MMP-13: 79.6% ± 12.6% vs 71.4% ± 18.8%; ADAMTS-4: 83.9% ± 12.2% vs 82.6% ± 12.5%; COL2: 93.6% ± 3.9% vs 92.5% ± 5.8%; NITEGE: 89.7% ± 7.7% vs 95.7% ± 4.7%) and acetabular cartilage (IL-1β: 83.3% ± 24.8% vs 80.7% ± 15.6%; MMP-13: 94.3% ± 9.7% vs 85.2% ± 12.3%; ADAMTS-4: 98.5% ± 2.3% vs 98.4% ± 3.4%; COL2: 99.8% ± 0.7% vs 99.7% ± 1.1%; NITEGE: 96.7% ± 6.7% vs 99.2% ± 2.2%). In contrast, synovitis was minimal with a low expression of IL-1β in the early FAI group compared with the late FAI group. Conclusion: Hip cartilage exhibited an OA phenotype in patients with early-stage FAI, similar to what was observed in hip OA secondary to FAI. Severe synovitis was only evident with late-stage FAI. Clinical Relevance: This study supports the concept that early hip impingement is associated with cartilage degeneration and catabolism.

Intraarticular Inflammation and Catabolic Markers in Femoroacetabular Impingement during Progression of Disease -comparison between early and late stage disease-

Objectives:Femoroacetabular impingement (FAI) has been proposed as an etiologic factor in up to 50% of osteoarthritis hips (OA). Inflammation is thought to be one of the main initiators of hip OA, yet little is known about the location and progression of intraarticular inflammation in FAI hips. The aim of this study is to characterize inflammation and catabolic markers in the early and late stage of FAI hips in patients with symptomatic Cam FAI.Methods:Head-neck cartilage, acetabular cartilage, and synovial samples were obtained from 30 patients undergoing hip surgery. Fifteen patients had a diagnosis of symptomatic Cam FAI (early FAI-symptomatic FAI) and 15 presented with advanced OA secondary to Cam FAI (late FAI/secondary OA). Control cartilage samples were procured from the head-neck junction of 7 osteochondral fresh allografts from healthy young-adult donors (control). Radiographically, the α-angle was utilized to confirm hip impingement and Tönnis grade was used to define pre-OA (Tönnis grade 0-1) and advanced OA (Tönnis grade >2). Safranin O stained sections were used to assess cartilage degeneration using the Mankin score. Immunostaining of IL-1β, MMP-13, ADAMTS-4, type II collagen (COL2), and the NITEGE aggrecan neoepitote was performed to evaluate inflammation and catabolic markers. Quantification of immunopositive cells was performed and one-way analysis of variance with Tukey’s post hoc test was applied to analyze differences between groups.Results:Characteristics of the study participants are presented in Table 1. Cartilage from the impingement zone (head-neck and acetabulum) of hips with early and late FAI showed microscopic osteoarthritic degenerative changes. Compared to control, head-neck cartilage from early and late stage FAI hips highly expressed inflammatory and catabolic markers IL-1β (69.7±18.1, 72.5±13.2 vs 20.2±4.9), MMP-13 (79.6±12.6, 71.4±18.8 vs 25.3±9.5), ADAMTS-4 (83.9±12.2, 82.6±12.5 vs 24.3±11.1), NITEGE (89.7±7.7, 95.7±4.7 vs 39.8±20.5) (p<0.05). Expression for COL2 was similar among groups (93.6±3.9, 92.5±5.8 vs 95.4±6.4, p=0.4892). Finally, percent of immunopositive cells for IL-1β, MMP-13, ADAMTS-4, and ACAN were positively correlated with Mankin score (r=0.52-0.75; p<0.001). The percentage of immunopositive cells present in acetabular cartilage was similar in both early and late FAI (IL-1β: 83.3 ± 24.8, 80.7 ± 15.6, 80.9 ± 26.3, p = 0.9571; MMP-13: 94.3 ± 9.7, 85.2 ± 12.3, 93.3 ± 10.3, p = 0.0653; ADAMTS-4: 98.5 ± 2.3, 98.4 ± 3.4, 99.2 ± 3.0, p = 0.6997, COL2: 99.8 ± 0.7, 99.7 ± 1.1, 98.6 ± 3.6, p = 0.3830). Additionally, inflammatory and catabolic markers were secreted to the ECM (extracellular matrix) in late FAI but not in early FAI. (Figure 1) Synovitis was minimal in early FAI but severe in late FAI. The average synovitis score was lower in early FAI than late FAI (2.5 ± 1.7, 4.4 ± 1.6; p=0.0086). Lower IL-1β expression levels were noted in synovium from early FAI compared to late FAI (p=0.001).Conclusion:Osteoarthritic degenerative changes, inflammation and catabolic markers are evident in the cartilage from the head-neck and acetabulum (impingement zone) in patients with hip FAI morphology during early and late stage disease. In late disease, increase expression of these markers are also observed in the ECM. Severe synovitis, however, was only evident in late stage disease. This study defines joint specific location and timing of inflammation relative to the disease process, suggesting the impingement area is a potential mediator of inflammation and joint degeneration during disease progression.

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

Background: Cam-type femoroacetabular impingement (FAI) is a causative factor for hip pain and early hip osteoarthritis. Although cam FAI can alter hip joint biomechanics, it is unclear what role muscle forces play and how they affect the hip joint loading. Purpose/Hypothesis: The purpose was to examine the muscle contributions and hip contact forces in individuals with symptomatic cam FAI during level walking. Patients with symptomatic cam FAI would demonstrate different muscle and hip contact forces during gait. Study Design: Controlled laboratory study. Methods: Eighteen patients with symptomatic cam FAI were matched for age and body mass index with 18 control participants. Each participant’s walking kinematics and kinetics were recorded throughout a gait cycle (ipsilateral foot-strike to ipsilateral foot-off) by use of a motion capture system and force plates. Muscle and hip contact forces were subsequently computed by use of a musculoskeletal modeling program and static optimization methods. Results: The FAI group walked slower and with shorter steps, demonstrating reduced joint motions and moments during contralateral foot-strike, compared with the control group. The FAI group showed reduced psoas major (median, 1.1 newtons per bodyweight [N/BW]; interquartile range [IQR], 1.0-1.5 N/BW) and iliacus forces (median, 1.2 N/BW; IQR, 1.0-1.6 N/BW), during contralateral foot-strike, compared with the control group (median, 1.6 N/BW; IQR, 1.3-1.6 N/BW, P = .004; and median, 1.5 N/BW; IQR, 1.3-1.6 N/BW, P = .03, respectively), which resulted in lower hip contact forces in the anterior (P = .026), superior (P = .02), and medial directions (P = .038). The 3 vectors produced a resultant peak force at the anterosuperior aspect of the acetabulum for both groups, with the FAI group demonstrating a substantially lower magnitude. Conclusion: FAI participants altered their walking kinematics and kinetics, especially during contralateral foot-strike, as a protective mechanism, which resulted in reduced psoas major and iliacus muscle force and anterosuperior hip contact force estimations. Clinical Relevance: Limited hip mobility not only is attributed to bone-on-bone impingement, caused by cam morphology, but could be attributed to musculature as well. Not only would the psoas major and iliacus be able to protect the hip joint during flexion-extension, athletic conditioning could further strengthen core muscles for improved hip mobility and pelvic balance.

Comparison of MRI, CT, Dunn 45° and Dunn 90° alpha angle measurements in femoroacetabular impingement.

To determine if a significant difference existed among alpha angle measurements between 4 imaging techniques, axial oblique CT and MRI, Dunn 45° and Dunn 90° plain radiographs, in patients with symptomatic cam femoroacetabular impingement (FAI) and labral tear. A single-surgeon prospective radiographic analysis of consecutive non-arthritic and non-dysplastic -patients with symptomatic FAI and labral tears who underwent surgery was performed. Alpha angle was measured using standard techniques as described by Nötzli. Cam morphology was defined via alpha angle measurement of >50.5 degrees. Group comparisons were made using ANOVA and chi-squared test. Sample size calculation was performed prior to study enrollment. 31 subjects (16 female; 33.5 ± 10.5 years mean age) were included. There was a significant difference in alpha angle measurements between all 4 imaging techniques (F [3,120] = 8.144; p<0.001), with the Dunn 45° view (66.3 ± 11.4°) significantly greater than all 3 other techniques (Dunn 90° [57.5 ± 10.7°; p = 0.015], MRI [53.3 ± 11.5°; p<0.001], and CT (54.9 ± 11.6°; p = 0.001). There was no significant difference in alpha angle between Dunn 90°, MRI, and CT. There was a significant difference in the observed number of hips with cam morphology between imaging techniques (χ2 9.4; p = 0.025). The Dunn 45° radiograph yielded a significantly higher alpha angle than Dunn 90°, axial oblique MRI, and CT imaging modalities. Use of the Dunn 90° or axial oblique MRI or CT as the threshold for cam osteoplasty may result in untreated symptomatic cam FAI. The authors recommend the Dunn 45° radiograph as the most sensitive evaluation of cam morphology.

Properties of the cartilage layer from the cam-type hip impingement deformity

Femoro-acetabular impingement (FAI) is associated with significant acetabular cartilage damage and degenerative arthritis. To understand the contact stress and thus biomechanical mechanisms that may contribute to degeneration, the material behaviour of the cartilage layer is required. The objective of this study is to determine the fibril-reinforced poroelastic properties and composition of cartilage from cam deformities and to compare to those of normal cartilage. Patients undergoing surgical treatment of a symptomatic cam FAI deformity were recruited from the clinical practice of one of the authors. Osteochondral specimens were retrieved from the deformity during surgery using a trephine. Control specimens were retrieved from the anterior femoral head bearing surface during autopsy procedures. Indentation stress-relaxation tests were performed to determine the modulus (ES), Poisson’s ratio (ν) and permeability (k0) of the poroelastic component, and the strain-independent (E0) and -dependent (Eε) moduli of the fibril-reinforcement using finite element analysis and optimization. Safranin-O staining was used to quantify proteoglycan content. ES and ν were 71% and 37% lower, respectively, in Cam specimens compared to controls, and k0 was approximately triple that of Control specimens (p<0.05). No significant differences were seen in the fibrillar components, E0 and Eε. Proteoglycan content was substantially depleted in Cam specimens, and was correlated with ES, ν and k0. This study showed that cartilage from the cam deformity exhibits severe degeneration in terms of the mechanical behaviour and composition changes, and is consistent with osteoarthritis. This further supports the hypothesis that FAI is a cause of hip osteoarthritis.

Is the contralateral hip at risk in patients with unilateral symptomatic cam femoroacetabular impingement? A quantitative T1ρ MRI study

To assess the profile of weight-bearing cartilage of hips with a cam deformity using T1ρ magnetic resonance imaging (MRI) and evaluate for a side-to-side difference in the T1ρ profile of patients with bilateral cam morphology but only unilateral hip pain. 19 patients with bilateral cam morphology undergoing osteochondroplasty for unilateral hip pain were prospectively recruited. Anterior and anterosuperior alpha angles were measured using computer tomography. All patients underwent bilateral 1.5T T1ρ MRI. The cartilage bilayer of the hip joint was evaluated and the mean T1ρ relaxation time calculated for each quadrant of the weight-bearing surface. Mean T1ρ relaxation times were not significantly different when each quadrant was compared to the rest of the weight-bearing surface of the symptomatic (P = 0.068) and asymptomatic hips (P = 0.102). There was also no significant side-to-side difference between the same quadrants of symptomatic and asymptomatic hips. No correlation was detected between alpha angle and the mean T1ρ relaxation time in each quadrant. There was no significant difference in mean alpha angles between the symptomatic and asymptomatic sides at the anterior (54.2 vs 56.0°; P = 0.382) and anterosuperior positions (65.1 vs 65.2°; P = 0.971). We conclude that previously observed regional variation in T1ρ values of normal hips is altered in hips with cam morphology. No difference in T1ρ values between symptomatic and asymptomatic cam hips was demonstrated. Therefore, regardless of the presence of hip pain, a cam deformity may predispose to hip joint cartilage degradation and increase the risk of hip osteoarthritis.

Symptomatic Femoroacetabular Impingement: Does the Offset Decrease Correlate With Cartilage Damage? A Pilot Study

Current measures of the reduced head-neck offset such as residual deformity of slipped capital femoral epiphysis (SCFE) including the alpha angle, which measures the femoral head-neck sphericity but does not account for acetabular abnormalities, do not represent the true magnitude of the deformity and the mechanical consequences. The beta angle (angle between the femoral head-neck junction and acetabular rim) accounts for the morphology of both the acetabulum and femur and, thus, may be the more appropriate parameter for assessing SCFE deformity. We determined (1) whether the beta angle could be reliably measured on MRI; and (2) whether the beta angle correlates with the cartilage status. We recruited 10 adult patients (mean age, 28 years) with symptomatic cam femoroacetabular impingement and 15 asymptomatic volunteers (mean age, 24 years) to have three-dimensional MRI including delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) for cartilage status assessment. Corresponding alpha angles, beta angles, and acetabular dGEMRIC indices were obtained in seven radial reformats to assess the hip in seven regions (anterior to superior and posterior). We noted high reproducibility for both alpha and beta angle measurements. The dGEMRIC indices correlated with beta angles in the superoinferior and superior regions but not the alpha angles. Beta angle measurement in radial MR images is reproducible and appears to correspond to cartilage damage in the superior regions of the hip. The beta angle may be a useful parameter to assess hip deformity in the followup of SCFE although further confirmation is warranted.

Increased acetabular subchondral bone density is associated with cam-type femoroacetabular impingement

Femoroacetabular impingement (FAI) has been associated with significant acetabular cartilage damage and subsequent degenerative arthritis. Subchondral bone, often neglected in osteoarthritis studies, may play an important role in the degenerative cascade. Hence the goal of this study was to assess acetabular subchondral bone mineral density (BMD) in subjects with asymptomatic or symptomatic cam deformities compared to normal control subjects. The relationship between BMD and the alpha angle, a quantitative measure of the deformity, was also analyzed. Patients diagnosed with symptomatic cam FAI were recruited ('Surgical') as well as subjects from the general asymptomatic population, classified from CT imaging as normal ('Control') or having a cam deformity ('Bump') based on their alpha angle measurement. There were 12 subjects in each group. All subjects underwent a CT scan with a calibration phantom. BMD was calculated in regions of interest around the acetabulum from CT image intensity and the phantom calibration. BMD was compared between groups using spine BMD as a covariate. The relationship between BMD and alpha angle was assessed by linear regression. In the antero-superior regions bone density was 15-34% higher in the Bump group (P<0.05) and 14-38% higher in the Surgical group (P<0.05) compared to Controls. BMD correlated positively with the alpha angle measurements (R(2)=0.44, P<0.001). BMD was elevated in subjects with cam-type deformities, with the severity of the deformity more correlative than symptom status. Similarities to the symptomatic group suggest that hips with an asymptomatic deformity may already be in early stages of joint degeneration.

The effects of cam femoroacetabular impingement corrective surgery on lower-extremity gait biomechanics

Surgery to correct cam femoroacetabular impingement (FAI) is increasingly popular. Nevertheless, no known study has analyzed both the three-dimensional lower-extremity joint kinematics and kinetics to quantify FAI surgical outcomes. The purpose of this study was to determine the effects of FAI surgery on the affected lower-extremity joint mechanics during gait by comparing the three-dimensional hip, knee, ankle and pelvic angular displacements, as well as the hip, knee and ankle moments and powers of preoperative and postoperative FAI groups, and a healthy control group. Ten patients with unilateral symptomatic cam FAI, who underwent corrective surgery using an open or combined technique, participated in the biomechanical analysis of level walking preoperatively and postoperatively. Thirteen healthy control subjects provided normative data. Results showed that gait biomechanics of FAI patients did not return to normal after surgery. Postoperatively, patients had reduced hip frontal and sagittal plane ROM, smaller peak hip abduction and internal rotation moments, and decreased peak hip power generation compared to the control group. Despite reductions in hip pain, hip impairments and trends detected preoperatively, perhaps due to modified gait patterns, persisted postoperatively. Additional discrepancies in lower-extremity joint mechanics were observed postoperatively, which are believed to have resulted from partial muscle impairment caused by the surgical approaches. Further research is required to confirm the reasons for which lower-extremity gait mechanics of FAI patients do not return to normal following surgery. Clarifying these causes could help improve surgical techniques and rehabilitation programs for the treatment of FAI, and thus improve surgical outcomes.

Preoperative and Postoperative Lower-Extremity Joint and Pelvic Kinematics During Maximal Squatting of Patients with Cam Femoro-Acetabular Impingement

Understanding how the function of the lower extremity joints during everyday movements following surgery to treat cam femoro-acetabular impingement is essential to assess whether surgical intervention effectively restores the normal biomechanics of the hip. The purpose of this study was to compare preoperative and postoperative lower-extremity joint and pelvic angular displacements during maximal depth squatting of patients with unilateral symptomatic cam femoro-acetabular impingement. Ten participants were compared with respect to their preoperative and postoperative test results. The participants were between eighteen and fifty years of age and had a positive impingement test and visible cam deformity on anteroposterior and Dunn view radiographs. Postoperative testing for each participant occurred between eight and thirty-two months following surgical intervention. Three-dimensional lower-limb joint and pelvic kinematics of participants were collected during maximal depth squats. Postoperatively, participants squatted to a greater mean maximal depth than they did preoperatively. Postoperative knee flexion and ankle dorsiflexion angles of the affected extremity at maximal depth were significantly greater than preoperative values. The postoperative sum of all joint angles of the affected limb at maximal squat depth was significantly larger than the preoperative sum. No significant differences were detected between the preoperative and postoperative measurements of the patients with cam impingement with respect to the kinematics of the affected hip at maximal squat depth, the pelvic angular displacements at maximal squat depth, or the overall pelvic range of motion during maximal deep squatting (p > 0.05). The squat performance improved postoperatively, likely because of the combined effects of increased knee and ankle angles as well as a greater acetabular opening and thus reduced anterior femoral head coverage, allowing increased posterior pelvic pitch during the descent phase of the squat. Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Surgical hip dislocation in symptomatic cam femoroacetabular impingement: what matters in early good results?

In order to assess outcome and possible predictors of early good results, a prospective study on 22 patients who were treated with save surgical hip dislocation for symptomatic isolated cam-type femoroacetabular impingement (FAI) was performed. After a follow-up of 6 and 12 months, standard clinical and radiographic parameters were recorded. A statistically significant improvement of the clinical status according to the Harris hip score could be assessed at six months (p-value = 0.003) and 12 months (p-value = 0.001) post-surgery. By comparing standard clinical and radiographic preoperative parameters with various follow-up outcomes, we revealed no specific parameter with predictive value. These findings are important for centers that have just started to use this surgical technique and are still identifying their learning curve.

JOSEPH C. MCCARTHY, MD, on “Combined Hip Arthroscopy and Limited Open Osteochondroplasty for Anterior Femoroacetabular Impingement” by John C. Clohisy, MD, et al.

The authors analyze thirty-five patients following arthroscopic and limited open femoral osteoplasty for symptomatic cam femoroacetabular impingement. Although the follow-up was short (less than three years), all patients were followed for at least two years after surgery. The fact that five additional patients were lost to follow-up prior to two years demonstrates the difficulty in locating young, mobile patients following nonprosthetic procedures. Given the importance of a complete data set, this study illustrates the potential benefits of a national registry that makes use of a unique HIPAA-protected patient identifier. The authors enumerated their clinical and radiographic …

Combined Arthroscopic and Modified Open Approach for Cam Femoroacetabular Impingement: A Preliminary Experience

We report our case series of patients undergoing surgical treatment (femoral osteoplasty) for symptomatic cam femoroacetabular impingement (FAI). Clinical results using a modified Heuter anterior approach combined with adjunctive hip arthroscopy are presented. A chart review of 16 hips (14 consecutive patients) was conducted. Radiographic parameters (alpha angle, head-neck offset, and Tönnis grade) were compared preoperatively and postoperatively. Clinical features (range of motion, provocative testing, and Harris hip score) were assessed. At 2.0 years, mean hip flexion improved from 94.1 degrees to 110.0 degrees (P < .01) and internal rotation from 7.1 degrees to 12.3 degrees (P = .02). The mean alpha angle improved from 64.5 degrees to 43.3 degrees (P < .01), whereas the mean femoral head-neck offset improved from 1.9 to 9.6 mm (P < .01). The mean Harris hip score improved from 63.8 to 76.1 (P = .01). No deterioration in overall radiographic Tönnis grades was present at last follow-up. The combination of hip arthroscopy with a limited anterior approach (Heuter) is a useful technique for patients with cam or cam-dominant FAI lesions. We believe the limited anterior approach with open osteoplasty presents a reasonable alternative to arthroscopic methods of osteoplasty with minimal drawbacks in the event that total hip arthroplasty is indicated in the future. Level IV, therapeutic case series.