Anterolateral Head-neck Junction Research Articles

Characterizing the Residual SCFE Deformity: Utility of the 45-degree Dunn View.

After treatment with in situ stabilization, slipped capital femoral epiphysis (SCFE) patients have variable degrees of deformity that can contribute to femoroacetabular impingement (FAI). To evaluate the severity of residual deformity most physicians currently use biplanar radiographs of an anteroposterior pelvis which profiles the lateral head-neck deformity and a frog lateral view which profiles the anterior head-neck deformity. However, the assessment of FAI morphology commonly relies on the 45-degree Dunn view to profile the anterolateral head-neck junction where FAI deformity is maximal. Therefore, the purpose of this study was to compare the magnitude of residual SCFE deformity detected on the frog lateral radiograph to the 45-degree Dunn radiograph. A retrospective review of radiographic images of 50 hips (47 patients) diagnosed with SCFE at a single academic institution from 2014 to 2018 was performed. The group included 25 hips evaluated postoperatively after fixation (Group 1) and 25 hips presenting with residual symptomatic SCFE deformity after previous pinning (Group 2). The alpha angle was assessed on both the 45-degree Dunn and frog lateral views for comparison. The modified Southwick slip angle was assessed on the frog lateral view only as a measure of SCFE severity. The Dunn view showed the maximal residual SCFE deformity as measured by the alpha angle in 88% (44/50) of cases. Overall, the mean alpha angle (70.7 degree vs. 60.1 degree, P <0.001) was significantly larger on the Dunn view as compared with frog lateral. Subgroup analysis showed a larger alpha angle on Dunn view compared with frog lateral in both immediate postoperative and residual SCFE deformities as well: Group 1 (69.5 degree vs. 60.9 degree, P <0.001) and Group 2 (71.9 degree vs. 59.3 degree, P <0.001). In patients with SCFE, the maximal residual deformity of the proximal femur can typically be seen on the 45-degree Dunn view, rather than on the frog lateral view. Our findings suggest the 45-degree Dunn view may be beneficial part of the postoperative assessment of SCFEs to quantify the true maximal deformity present. Level IV.

Otto Aufranc Award: Identification of Key Molecular Players in the Progression of Hip Osteoarthritis Through Transcriptomes and Epigenetics.

This study aimed: (1) to compare the transcriptome profile of articular cartilage in cam-FAI (early stage) to advanced OA secondary to cam-FAI (late stage) and (2) to investigate epigenetic changes through the expression of DNA methylation enzymes DNMT3B, DNMT1, and DNMT3A and peroxisome proliferator-activated receptor gamma (PPARγ) in human cartilage samples during the progression of hip OA. Full-thickness cartilage samples were collected from the anterolateral head-neck junction (impingement zone) of 22 patients (9 early-FAI and 13 late-FAI). RNA sequencing and invitro cartilage cultures with histological analysis and immunohistochemistry staining for PPARγ and DNMT3B were performed. Target gene validation was confirmed with RT-PCR. Fifty genes and 42 pathways were identified differentially between early and late-FAI (fold change <-1.5 or >1.5, P < .01). PPARγ and DNMT3B were gradually suppressed with disease progression. Contrarily, disease progression induced expression of DNMT1/3A. By comparing comprehensive gene expression in early and late stage hip degeneration at the whole-genome level, distinct transcriptome profiles for early and late stage disease were identified along with key molecular contributors to the progression of hip OA. Preservation of endogenous PPARγ may have therapeutic potential to delay or prevent hip OA.

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

The shape of the hip joint as a risk factor for osteoarthritis

Purpose: Cam-type femoroacetabular impingement characterized by extra bone formation at the anterolateral head-neck junction of the hip creates a non-spherical femoral head, known as a cam deformity. The cam deformity is forced into the acetabulum during flexion and internal rotation of the hip, leading to structural damage as acetabular labrum tears and cartilage delamination. This damage might gradually lead to osteoarthritis. Cam deformity and subtle acetabular dysplasia are recently recognized as relevant risk factors for hip osteoarthritis (HOA). In subtle acetabular dysplasia, the femoral head has contact with a small area of the shallowacetabulum. Therefore, more focal stress is put on this small area, which provides insufficient coverage for the femur. Cumulative articular surface contact stress above a critical threshold in dysplastic joints causes joint degeneration. However, the influence of these deformities on HOA incidence compared with other risk factors including age, gender, and body mass index (BMI) and the effect modification of other known determinants on these associations are not yet known. Methods: Participants of Rotterdam Study (RS-I: n = 2960, RS-II: n = 1470) including men and women aged >55 years with a Kellgren and Lawrence (K/L) grade ≥1 at baseline and mean follow-up of 9.2 years were included in the study. Incident radiographic HOA was defined as a K/L grade of ≥2 or a total joint replacement at follow-up. The shape of the proximal femur and the acetabulumwere outlined by a set of points (23 points, Figure 1) that were positioned on pre-defined anatomical landmarks on the anteroposterior pelvic radiographs using statistical shape modeling software. Using this point set, alpha and center-edge (CE) angles, parameters that quantify these deformities were calculated. Acetabular dysplasia and cam deformity were defined as the presence of a CE angle 60°, respectively (Figure 1). Using generalized estimating equation models, odds ratios were calculated to assess the associations between both hip deformities and the development of HOA. Results: At the follow-up times, 234 and 179 cases of HOAwere identified for RS-I and RS-II, respectively. Incident OA was defined in 281 hips within RS-I among that 12.2% (n = 34) had cam deformity and 8.3% (n = 23) had acetabular dysplasia, while out of 218 hips with incident OA in RS-II,16.1% (n = 35) had cam deformity and 7.3% (n = 16) had dysplasia. In pooled data analyses (Table 1), individuals with cam deformity had a two-fold increased risk for developing osteoarthritis (OR = 2.0, 95% CI= 1.48-2.71, p = 0.00001) compared with individuals without cam deformity. Moreover, subtle acetabular dysplasia was significantly associated with increased risk of HOA (OR = 1.96, 95% CI = 1.35-2.84, p = 0.0004). Both associations were independent of known risk factors of HOA such as age, sex, and BMI and were only significantly associated with development of OA in younger individuals. These bony deformities were independently related to the outcomewhen included in the samemodel (camdeformity: OR (95% CI) = 2.03 (1.50-2.76), hip dysplasia: OR (95% CI) = 2.03 (1.41-2.92)). The results were almost consistent in both cohorts. Conclusions: Individuals with cam deformity and acetabular dysplasia are strongly predisposed to progression to HOA independently from other well known risk factors of age, sex, and BMI. Interestingly, both deformities were only predisposing to OA in relatively young individuals. Therefore, early identification of these conditions is important and might provide an opportunity to prevent hip osteoarthritis. (Figure Presented).

Femoroacetabular impingement osteoplasty: is any resected amount safe? A laboratory based experiment with sawbones.

There is an increased risk of fracture following osteoplasty of the femoral neck for cam-type femoroacetabular impingement (FAI). Resection of up to 30% of the anterolateral head-neck junction has previously been considered to be safe, however, iatrogenic fractures have been reported with resections within these limits. We re-evaluated the amount of safe resection at the anterolateral femoral head-neck junction using a biomechanically consistent model. In total, 28 composite bones were studied in four groups: control, 10% resection, 20% resection and 30% resection. An axial load was applied to the adducted and flexed femur. Peak load, deflection at time of fracture and energy to fracture were assessed using comparison groups. There was a marked difference in the mean peak load to fracture between the control group and the 10% resection group (p < 0.001). The control group also tolerated significantly more deflection before failure (p < 0.04). The mean peak load (p = 0.172), deflection (p = 0.547), and energy to fracture (p = 0.306) did not differ significantly between the 10%, 20%, and 30% resection groups. Any resection of the anterolateral quadrant of the femoral head-neck junction for FAI significantly reduces the load-bearing capacity of the proximal femur. After initial resection of cortical bone, there is no further relevant loss of stability regardless of the amount of trabecular bone resected. Based on our findings we recommend any patients who undergo anterolateral femoral head-neck junction osteoplasty should be advised to modify their post-operative routine until cortical remodelling occurs to minimise the subsequent fracture risk.

Cam-type deformities strongly predict total hip replacement within 5 years in those with early symptomatic OA: a prospective cohort study (check)

Purpose: Femoroacetabular Impingement (FAI) is a cause of hip pain and might induce osteoarthritis (OA) of the hip due to abnormal contact between the femoral neck and acetabulum. Two types of FAI can be distinguished: pincer and cam impingement. Pincer impingement is caused by overcoverage of the acetabulum relative to the femoral head, and cam impingement is caused by extra bone formation -a cam-type deformity- in the anterolateral head-neck junction. For cam impingement, the only treatment available is a surgical resection of the cam-type deformity, which nowadays is performed with increasing frequency in young adults. However, the relation between those two types of impingement and the development of OA is unclear. The aim of this study was to determine the relation between cam impingement and pincer impingement on the development of both early OA and end-stage OA after 5 years. Methods: Individuals were extracted from the CHECK (cohort hip and cohort knee) study. CHECK is a prospective cohort study of individuals with assumed early symptomatic OA of knee or hip. Of the 1002 individuals, a random subset of 865 had standardized anteroposterior radiographs (AP) taken at both baseline and 5 years follow-up. AP-pelvic radiographs of sufficient quality were obtained in 723 subjects at baseline and in 770 subjects at the 5 years follow-up. The shape of the proximal femur and acetabulum on the AP radiographs was assessed using statistical shape modelling (SSM). Parameters used to quantify FAI morphology were automatically calculated from the point set of the SSM, using Matlab. For cam impingement, the alpha angle and Triangular Index Ratio (TIR) were measured. Threshold values used to quantify a cam-type deformity were 60 degrees and 83 degrees for the alpha angle, and 0.05 for the TIR. To quantify a pincer deformity, the Lateral Center Edge angle (LCE) was used at a threshold value of 40 degrees. Further, all radiographs were scored for OA according to the K&L classification. The outcome measure for early OA were hips progressing from K&L=0 at baseline to K&L=1 after 5 years. Hips that had received Total Hip Replacement (THR) at follow-up were classified as end-stage OA. The strength of the relation between the impingement parameters and both outcome measures was expressed by means of Odds Ratios (ORs) using Generalized Estimating Equations. Results: For this study, 682 females (mean age 55.8) and 183 males (mean age 56.4) were included. At baseline, 75% of the hips had no signs of OA (K&L=0) whereas 25% had doubtful OA (K&L=1). Crude and adjusted ORs for impingement parameters in relation with the development of both early OA and end-stage OA are displayed in table 1. No relation was found between any impingement parameter and the development of early OA. The measures for a cam-type deformity were strongly associated with end-stage OA. Especially the OR for a severe cam-type deformity (alpha angle > 83 degrees) was high (10.88, 95% CI 5.21 - 22.69, p < 0.001). No association was found between a pincer deformity and the development of end-stage OA. Further, the risk for receiving THR when having a cam-type deformity as determined by an alpha angle > 83 degrees, > 60 degrees, and by an TIR > 0.05 was 23.3%, 9.6%, and 8.8% respectively. Conclusions: A cam-type deformity is strongly related to the development of end-stage OA after 5 years, whereas a pincer deformity is not. Our results indicate that individuals having a cam-type deformity that present with the first onset of hip complaints are at high risk (OR 11.3) for fast progression to end-stage OA. Cam impingement might thus be the first risk factor that is highly predictive of fast progression for hip OA. Interestingly, it may be diagnosed and treated before hip damage is present which might prevent hip OA.

Quality of Life Following Femoral Head-Neck Osteochondroplasty for Femoroacetabular Impingement

Femoroacetabular impingement has been recently described as a common cause of hip pain and labral tears in young adults. We evaluated the early clinical results and quality of life after osteochondroplasty of the femoral head-neck junction for the treatment of femoroacetabular impingement. Thirty-seven hips in thirty-four patients with persistent hip pain and a mean age of 40.5 years underwent surgical dislocation of the hip and osteochondroplasty of the femoral head-neck junction for the treatment of camtype femoroacetabular impingement. All of the patients had had preoperative evidence of pathological changes in the labrum on imaging. The clinical course and the quality of life were assessed postoperatively. The mean score on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) increased from 61.2 points preoperatively to 81.4 points at a mean of 3.1 years postoperatively (p < 0.001), the mean University of California at Los Angeles (UCLA) activity score increased from 4.8 to 7.5 points (p < 0.001), the mean Short Form-12 (SF-12) physical component score increased from 37.3 to 45.6 points (p < 0.001), and the mean SF-12 mental component score increased from 46.4 to 51.2 points (p = 0.031). None of the hips underwent additional reconstructive surgery. There were no cases of osteonecrosis. Nine patients underwent screw removal from the greater trochanter because of persistent bursitis. Six of the thirty-four patients were dissatisfied with the outcome. Cam-type femoroacetabular impingement is associated with insufficient concavity at the anterolateral head-neck junction and with pathological changes in the labrum. Osteochondroplasty of the femoral head-neck junction following surgical dislocation of the hip joint is safe and effective and can provide a significant improvement in the overall quality of life of most patients. Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Quality of Life Following Femoral Head-Neck Osteochondroplasty for Femoroacetabular Impingement

Background: Femoroacetabular impingement has been recently described as a common cause of hip pain and labral tears in young adults. We evaluated the early clinical results and quality of life after osteochondroplasty of the femoral head-neck junction for the treatment of femoroacetabular impingement. Methods: Thirty-seven hips in thirty-four patients with persistent hip pain and a mean age of 40.5 years underwent surgical dislocation of the hip and osteochondroplasty of the femoral head-neck junction for the treatment of camtype femoroacetabular impingement. All of the patients had had preoperative evidence of pathological changes in the labrum on imaging. The clinical course and the quality of life were assessed postoperatively. Results: The mean score on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) increased from 61.2 points preoperatively to 81.4 points at a mean of 3.1 years postoperatively (p < 0.001), the mean University of California at Los Angeles (UCLA) activity score increased from 4.8 to 7.5 points (p < 0.001), the mean Short Form-12 (SF-12) physical component score increased from 37.3 to 45.6 points (p < 0.001), and the mean SF-12 mental component score increased from 46.4 to 51.2 points (p = 0.031). None of the hips underwent additional reconstructive surgery. There were no cases of osteonecrosis. Nine patients underwent screw removal from the greater trochanter because of persistent bursitis. Six of the thirty-four patients were dissatisfied with the outcome. Conclusions: Cam-type femoroacetabular impingement is associated with insufficient concavity at the anterolateral head-neck junction and with pathological changes in the labrum. Osteochondroplasty of the femoral head-neck junction following surgical dislocation of the hip joint is safe and effective and can provide a significant improvement in the overall quality of life of most patients. Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Morphological variations of residual hip dysplasia in the adult

Common understanding of residual hip dysplasia of the adult characterizes it as a uniform, anterolateral insufficiency of femoral head coverage; the proximal femur may or may not have increased valgus and antetorsion. This view is reflected by the parameters used for quantification but also by the classic surgical approaches to compensate or correct the deformity. More than two decades of dedication to hip dysplasia and its surgical treatment, but also the application of modern diagnostic tools such as magnetic resonance arthrography have allowed us to portray hip dysplasia more polymorphically showing a number of additional aspects with pathophysiologic, therapeutic and prognostic valence. The rim in acetabular dysplasia shows a variety of pathomorphologies ranging from hypertrophy and tearing of the labrum including fatigue fracture of the rim to degeneration with ganglion formation within the labrum, the capsule or the acetabular bone. Such rim pathology may explain sudden onset of pain but also influences the prognosis of joint preserving surgery. It is a rather new understanding that the acetabular morphology in hip dysplasia is not uniform. Pure lateral and pure anterior deficiency of coverage are small but interesting subgroups. Together with the frequent retroversion of the acetabulum these morphological and spatial aspects require special attention for a precise individual correction of the deformity. Finally, minor morphological abnormalities of the antero-lateral head-neck junction have been found to favor impingement after correction of the acetabulum. Knowledge of this problem has prompted a routine check of internal rotation in flexion during surgery and eventual arthrotomy and osteochondroplasty of the impinging site of the head and neck junction.

Morphological Variations of Residual Hip Dysplasia in the Adult

Common understanding of residual hip dysplasia of the adult characterizes it as a uniform, anterolateral insufficiency of femoral head coverage; the proximal femur may or may not have increased valgus and antetorsion. This view is reflected by the parameters used for quantification but also by the classic surgical approaches to compensate or correct the deformity. More than two decades of dedication to hip dysplasia and its surgical treatment, but also the application of modern diagnostic tools such as magnetic resonance arthrography have allowed us to portray hip dysplasia more polymorphically showing a number of additional aspects with pathophysiologic, therapeutic and prognostic valence. The rim in acetabular dysplasia shows a variety of pathomorphologies ranging from hypertrophy and tearing of the labrum including fatigue fracture of the rim to degeneration with ganglion formation within the labrum, the capsule or the acetabular bone. Such rim pathology may explain sudden onset of pain but also influences the prognosis of joint preserving surgery. It is a rather new understanding that the acetabular morphology in hip dysplasia is not uniform. Pure lateral and pure anterior deficiency of coverage are small but interesting subgroups. Together with the frequent retroversion of the acetabulum these morphological and spatial aspects require special attention for a precise individual correction of the deformity. Finally, minor morphological abnormalities of the antero-lateral head-neck junction have been found to favor impingement after correction of the acetabulum. Knowledge of this problem has prompted a routine check of internal rotation in flexion during surgery and eventual arthrotomy and osteochondroplasty of the impinging site of the head and neck junction.

Femoroacetabular impingement caused by a femoral osseous head–neck bump deformity: clinical, radiological, and experimental results

Femoroacetabular impingement is often associated with reduced femoral anteversion or an osseous bump deformity on the femoral head–neck junction. We report prospectively on 17 patients showing an osseous bump at the anterolateral head–neck junction on radiography (22 hips) and typical signs of femoroacetabular impingement on clinical examination. Following three plans of treatment, nine patients (10 hips) underwent nonoperative treatment, and eight patients (12 hips) had surgery. In eight hips with labral defects but minor cartilage damage, the bump was surgically removed via trochanter flip osteotomy. Two hips were treated surgically through an anterior surgical approach without hip dislocation. Four hips with severe signs of osteoarthritis and significantly reduced range of motion underwent total replacement. To elucidate a local osteogenic differential potential, tissue specimens of the perilesional capsule were investigated immunohistochemically. Various antigens and protein synthesis products served to identify osteoblastic and progenitor cells. There was a significant improvement in internal rotation and pain relief in patients who underwent surgical resection of the osseous bump. No avascular osteonecrosis or other significant severe side effects were observed during follow-up. In contrast, no nonoperatively treated patients improved. Furthermore, immunohistochemical studies showed perilesional recruitment of osteoprogenitor cells.