The Natural History of Femoroacetabular Impingement

A novel radiographic finding for estimation of the cortical-cancellous boundary: A magnetic resonance imaging case series of patients with femoroacetabular impingement

Purpose

To determine if comparing alpha angle measurements of the outer cortical margin (preoperative alpha angle) and the inner cortical margin (theoretical postoperative alpha angle) on magnetic resonance imaging (MRI) can estimate the amount of sclerotic bone that needs to be resected to restore the alpha angle to normative values (<55⁰) in patients with symptomatic femoroacetabular impingement (FAI).

Methods

A retrospective review was conducted on patients with FAI undergoing primary hip arthroscopy and CAM osteoplasty from June 2013 to February 2017. Inclusion criteria were radiologist-measured alpha angles >70° on 3T oblique axial MRI, unilateral primary hip arthroscopy, and age ≥18. Exclusions included previous hip surgery, hip trauma, avascular necrosis, advanced osteoarthritis, dysplasia, poor quality images, or missing MRI images. Alpha angles were measured preoperatively using the outer cortical margin and postoperatively using the inner cortical margin of femur. Surgeries were performed by the senior surgeon. Paired t-tests compared preoperative and postoperative alpha angles, and intraclass correlation coefficients (ICC) were used to assess inter-rater and intra-rater reliability.

Results

One hundred patients (100 hips) were included with an average age of 40.8 years (range, 18.7-64.9), with 75 % being male (n = 75). The average BMI was 24.7 ± 3.9 (range, 17.1-38.8). The average maximum alpha angle at the outer cortical margin was 77.0 ± 4.2° (range, 70.0-90.8), with an ICC for inter-rater reliability of 0.861, indicating excellent agreement. The average inner cortical alpha angle was 46.4 ± 3.4° (range, 36.5-55.4), significantly less than 55° (p<0.001). The mean difference between the outer and inner cortical alpha angles was -30.6 ± 5.1° (p< 0.001).

Conclusions

The difference between outer and inner cortical alpha angles on MRI can accurately estimate the amount of sclerotic bone resection needed to restore the alpha angle to normative values in patients with FAI. This information may be directly applied clinically marker to assess adequacy of CAM resection.

Revealing a Natural Model of Pre-Osteoarthritis of the Hip Through Study of Femoroacetabular Impingement

Femoroacetabular impingement (FAI) is considered the mechanical cause of hip osteoarthritis (OA). Surgical intervention involves labrum repair and osteochondroplasty to remove the impingement, alleviating symptoms. Nevertheless, some patients progress to hip OA after surgery, indicating that factors other than mechanical abnormality are contributing to hip OA progression. This review article discusses our laboratory's studies on hip FAI and OA, undertaken to identify key molecular players in the progression of hip OA. Transcriptome analysis identified peroxisome proliferator activated receptor gamma (PPARγ) as a crucial molecule in early hip OA. PPARγ, widely expressed in chondrocytes, has a protective role in preventing OA, but its true mechanism remains unknown. We observed a dysregulation of DNA methyltransferase (DNMT) in the progression of hip OA, with high expression of DNMT1 and 3A and downregulation of DNMT3B. Moreover, we established that DNMT3A is the main molecule that is binding to PPARγ promoter CpG area, and hypermethylation of this area occurs during disease progression. This suggests that epigenetic changes are a main mechanism that regulates PPARγ expression. Finally, we developed a novel rabbit model of hip FAI and OA and are currently performing studies to validate our small-animal model to human FAI.

Femoral and acetabular features explain acetabular contact pressure sensitivity to hip internal rotation in persons with cam morphology: A finite element analysis

BACKGROUND

Femoroacetabular impingement is characterized by premature contact between the proximal femur and acetabulum. The loss of femoral head-neck concavity associated with cam morphology leads to mechanical impingement during hip flexion and internal rotation. Other femoral and acetabular features have been linked with mechanical impingement but have not been comprehensively investigated. This study sought to determine which bony features are most influential in contributing to mechanical impingement in persons with a cam morphology.

METHODS

Twenty individuals (10 female, 10 male) with a cam morphology participated. Finite element analyses incorporating subject-specific bony geometry derived from computed tomography scans were used to determine which femoral (alpha angle and femoral neck-shaft angle) and acetabular (anteversion angle, inclination angle, depth, and lateral center-edge angle) features accentuate acetabular contact pressure with increasing degrees of hip internal rotation with the hip flexed to 90°. To determine the best predictors of acetabular contact pressure sensitivity to internal rotation, all morphological variables were included in a stepwise regression with the final model subjected to a bootstrapping procedure.

FINDINGS

The stepwise regression revealed that femoral neck-shaft angle, acetabular anteversion angle, acetabular inclination angle, and acetabular depth were the best combination of variables to predict contact pressure sensitivity to internal rotation, explaining 55% of the variance. Results of the bootstrap analysis revealed that a median value of 65% [37%, 89%] variance in sensitivity could be explained by these morphological variables.

INTERPRETATION

Mechanical impingement and the concomitant acetabular contact pressure are modulated by multiple femoral and acetabular features in persons with a cam morphology.

It's not arthritis! Resolution of the illusion of joint space narrowing with acetabuloplasty and labral reconstruction for the calcified labrum

Labral calcification may be part of the natural history of untreated femoroacetabular impingement syndrome (FAIS) in certain patients, making it a potential target for intervention with the goal of preserving the hip joint. The purpose of this study was to investigate if calcified labra create the appearance of lateral joint space narrowing and report minimum 2-year patient-reported outcome measures (PROMs) after treating patients with arthroscopic acetabuloplasty and labral reconstruction. Prospectively collected data on patients who underwent primary hip arthroscopy for FAIS and labral tearing from February 2015 to April 2021 were reviewed. Patients treated with primary labral reconstruction for an intraoperatively confirmed diagnosis of labral calcification were included. A sub-analysis was performed for patients with a minimum of 2-year follow-up. Preoperative and postoperative PROMs for the modified Harris hip score, nonarthritic hip score, the International Hip Outcome Tool-12 and visual analog scale for pain were recorded. Forty-six hips (46 patients) were included, with 19 hips in the sub-analysis. There was a significant increase in apparent lateral joint space width (JSW) measured on supine anteroposterior (AP) pelvis radiographs with no significant changes in medial and central JSW and significant decreases in the lateral and anterior center-edge angles and alpha angle. Patients experienced significant increases in PROMs and high rates of achieving psychometric thresholds. Patients presenting with FAIS and calcified labra may have apparent lateral joint space narrowing on pre-operative supine AP pelvis radiographs. These patients have low rates of full-thickness femoral head and acetabular cartilage pathology, this apparent narrowing can be corrected and excellent outcomes and survivorship can be achieved, with primary labral reconstruction.

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.

Outcomes in Pediatric Hip FAI Surgery: a Scoping Review

PURPOSE OF REVIEW

Femoracetabular impingement (FAI) is a common source of hip pain in children and adolescents. While nonoperative therapies and open surgical procedures can be effective, hip arthroscopy is a minimally invasive treatment option with substantial benefit. The purpose of this paper is to evaluate the current role of hip arthroscopy in treating FAI within the pediatric population. This article examines its efficacy through a review of hip arthroscopy outcomes in the contemporary orthopaedic literature.

RECENT FINDINGS

Morphologic changes in the acetabulum and proximal femur seen in FAI can be attributed to a multitude of etiologies-including idiopathic FAI, Legg-Calve-Perthes, and slipped capital femoral epiphysis. In general, arthroscopic treatment of FAI secondary to these conditions leads to statistically significant improvements in pain and patient-reported outcomes in the short and long term. In the pediatric athlete, repetitive stress on the hip perpetuates FAI and can drastically hinder performance. Hip arthroscopy allows for a high rate of return to sport with minimal morbidity in this population. Overall, pediatric hip arthroscopy is effective in treating FAI secondary to a wide variety of conditions. Despite its clinical benefits, patients and their families should be counseled regarding alternative treatments, potential complications, and return to play.

The Circumferential Femoroplasty: An All-Arthroscopic Technique for Addressing a Challenging Hip Deformity

Femoroacetabular impingement is recognized as a common cause of hip pain. Cam-type femoroacetabular impingement results from abnormal contact between an aspherical femoral head and the acetabular rim during hip range of motion, leading to labral tearing, cartilage damage, and, eventually, osteoarthritis. Arthroscopic correction of this bony deformity has been well described, particularly in the anterolateral quadrant of the femoral neck. Some deformities extend well beyond this quadrant, involving most or all of the circumference of the femoral neck, making arthroscopic decompression a challenge. We present a post-less, all-arthroscopic technique for performing a circumferential cam decompression using 3-dimensional preoperative planning software and interactive fluoroscopy-integrated computer vision interface.

A prospective cohort study on cam morphology and its role in progression of osteoarthritis

Background

Cam morphology contributes to the development of hip osteoarthritis (OA) but is less studied in the general population. This study describes its associations with clinical and imaging features of hip OA.

Methods

Anteroposterior hip radiographs of 1019 participants from the Tasmanian Older Adult Cohort (TASOAC) were scored at baseline for α angle (cam morphology) in both hips. Using the Altman's atlas, radiographic hip OA (ROA) was assessed at baseline. Hip pain and right hip structural changes were assessed on a subset of 245 magnetic resonance images (MRI) at 5 years. Joint registry data for total hip replacement (THR) was acquired 14 years from baseline.

Results

Of 1906 images, cam morphology was assessed in 1016 right and 890 left hips. Cross‐sectionally, cam morphology modestly associated with age (prevalence ratio [PR]: 1.02 P = .03) and body mass index (BMI) (PR: 1.03‐1.07, P = .03) and strongly related to male gender (PR: 2.96, P < .001). Radiographically, cam morphology was prevalent in those with decreased joint space (PR: 1.30 P = .03) and osteophytes (PR: 1.47, P = .03). Longitudinally, participants with right cam and high BMI had more hip pain (PR: 17.9, P = .02). At the end of 5 years of follow‐up these participants were also more likely to have structural changes such as bone marrow lesions (BMLs) (PR: 1.90 P = .04), cartilage defects (PR: 1.26, P = .04) and effusion‐synovitis at multiple sites (PR: 1.25 P = .02). Cam morphology at baseline in either hip predicted up to threefold risk of THR (PR: 3.19, P = .003) at the end of 14 years.

Conclusion

At baseline, cam morphology was linked with age, higher weight, male gender, early signs of radiographic OA such as joint space narrowing (JSN) and osteophytes (OST). At follow‐up, cam predicted development of hip BMLs, hip effusion‐synovitis, cartilage damage and THR. These findings suggest that cam morphology plays a significant role in early OA and can be a precursor or contribute to hip OA in later life.

Bilateral hip arthroscopy for treating femoroacetabular impingement: a systematic review

PURPOSE

Femoroacetabular impingement (FAI) is a hip disorder which can often present bilaterally. The purpose of this systematic review was to explore the current practices for bilateral hip arthroscopy in treating FAI as they relate to outcomes and complications.

METHODS

This review has been conducted according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). The electronic databases PubMed, MEDLINE, EMBASE, and CENTRAL (Cochrane Central Register of Controlled Trials) were searched from data inception to October 18th, 2020. The Methodological Index for Non-randomized Studies (MINORS) was used to assess study quality. Data are presented descriptively.

RESULTS

Overall, 19 studies were identified, comprising 957 patients (48.6% male) with a mean age of 27.9 ± 7.1 years and a mean follow-up of 31.7 ± 20.8 months. The majority of patients were treated with a staged bilateral hip arthroscopy (78.5%) with a mean duration between surgeries of 7.1 ± 4.0 months. Significant preoperative-to-postoperative improvements for clinical outcomes such as pain, hip function, and health-related daily living as well as radiographic outcomes were reported in six studies for staged procedures (p < 0.05) and three studies for simultaneous procedures (p < 0.02). Significant improvements in patient-reported outcomes (e.g., HOS-ADL, Pain, HOS-SS, mHHS, and NAHS) were found in favor of those undergoing a shorter delay between surgeries in three studies (i.e., < 3, 10 or 17 months) (p < 0.05) compared to those who had delayed surgeries (i.e., > 3, 10, or 17 months). The overall complication rate was 10.1% (97/957).

CONCLUSIONS

Bilateral surgery for FAI yields improved outcomes postoperatively and complication rates similar to unilateral surgery. The overall complication rate was 10.1% with the most common complication being revision surgery. Staged bilateral surgery is more commonly performed than simultaneous surgery. Clinicians should consider preoperative imaging, clinical history, and patient values when deciding between staged and simultaneous procedures for bilateral FAI surgery. Future studies are required to determine the optimal indications for simultaneous versus staged procedures, as well as the ideal timing between surgeries for the latter.

LEVEL OF EVIDENCE

Level IV.

Changes in Hip Capsule Morphology after Arthroscopic Treatment for Femoroacetabular Impingement Syndrome with Periportal Capsulotomy are Correlated With Improvements in Patient-Reported Outcomes

PURPOSE

To assess the correlation between changes in hip capsule morphology with improvements in patient-reported outcome (PRO) scores after arthroscopic surgery for femoroacetabular impingement syndrome (FAIS) using the periportal capsulotomy technique.

METHODS

Twenty-eight patients with cam morphology FAIS (without arthritis, dysplasia, or hypermobility) were prospectively enrolled before arthroscopic labral repair and femoroplasty through periportal capsulotomy (anterolateral/midanterior portals) without closure. Patients completed the Hip Disability and Osteoarthritis Outcomes Score (HOOS) and had nonarthrographic 3T magnetic resonance imaging (MRI) scans of the affected hip before and 1 year after surgery. Anterior capsule thickness, posterior capsule thickness, anterior-posterior capsule thickness ratio, and proximal-distal anterior capsule thickness ratio were measured on axial-oblique MRI sequences. Pearson correlation coefficients were calculated to determine the association between hip capsule morphology and PRO scores.

RESULTS

Postoperative imaging showed that for all 28 patients (12 female), labral repairs and capsulotomies had healed within 1 year of surgery. Analysis revealed postoperative decreases in anterior hip capsule thickness (1395.4 ± 508.4 mm³ vs 1758.4 ± 487.9 mm³; P = .003) and anterior-posterior capsule thickness ratio (0.92 ± 0.33 vs 1.12 ± 0.38; P = .02). Higher preoperative anterior-posterior capsule thickness ratio correlated with lower preoperative scores for HOOS pain (R = -0.43; P = .02), activities of daily living (ADL) (R = -0.43; P = .02), and sport (R = -0.38; P = .04). Greater decrease from preoperative to postoperative anterior-posterior capsule thickness ratio correlated with greater improvement for HOOS pain (R = -0.40; P = .04), ADL (R = -0.45; P = .02), and sport (R = -0.46; P = .02).

CONCLUSIONS

Periportal capsulotomy without closure demonstrates capsule healing by 1 year after arthroscopic FAIS treatment. Changes in hip capsule morphology including decreased anterior-posterior capsule thickness ratio after surgery may be correlated with improvements in patient pain, function, and ability to return to sports.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Association between hip joint impingement and lumbar disc disease in elite rowers

Objectives

Lumbar disc disease is a known cause of back pain. Increasingly it is thought that cam morphology of the hip may have a causal role in development of lumbar disc disease. The aim of this study was to describe the morphology of the hip and investigate the association of cam morphology with lumbar disc disease observed on MRI in elite rowers.

Methods

Cross-sectional observational study of 20 elite rowers (12 male, 8 female, mean age 24.45, SD 2.1). Assessment included clinical examination, questionnaires, 3T MRI scans of the hips and lumbar spine. Alpha angle of the hips and Pfirrmann score of lumbar discs were measured.

Results

85% of rowers had a cam morphology in at least one hip. Alpha angle was greatest at the 1 o’clock position ((bone 70.9 (SD 16.9), cartilage 71.4 (16.3)). 95% of the group were noted to have labral tears, but only 50% of the group had history of groin pain. 85% of rowers had at least one disc with a Pfirrmann score of 3 or more and 95% had a history of back pain. A positive correlation was observed between the alpha angle and radiological degenerative disc disease (correlation coefficient=3.13, p=0.012). A negative correlation was observed between hip joint internal rotation and radiological degenerative disc disease (correlation coefficient=−2.60, p=0.018).

Conclusions

Rowers have a high prevalence of labral tears, cam morphology and lumbar disc disease. There is a possible association between cam morphology and radiological lumbar degenerative disc disease, however, further investigation is required.

Relationship between cam morphology, hip symptoms, and hip osteoarthritis: the Musculoskeletal pain in Ullersaker STudy (MUST) cohort

BACKGROUND

The primary aim of this study was to determine the prevalence of cam morphology in a cohort of people aged 40-55 years. Secondary aims were to: (1) determine differences in participant characteristics, physical impairments, radiographic and ultrasound appearances of people with and without cam morphology; and (2) explore associations between cam morphology and radiographic measures of hip osteoarthritis (OA).

METHODS

107 people (68% women; 49 ± 4 years) from the Musculoskeletal pain in Ullensaker (MUST) Study underwent the clinical and imaging examinations. Examinations included questionnaires, hip range, functional task performance, pelvic radiographs and ultrasound. Alpha angle and radiographic hip OA (Kellgren Lawrence (KL) and minimal joint space (MJS)) were determined.

RESULTS

The prevalence of cam morphology was 42% and was bilateral in 47%. People with cam morphology were 6 times more likely to have a KL score ⩾2 (adjusted odds ratio [95% confidence intervals, p-value]) 6.386 [1.582-37.646, p = 0.012]) and 4 times more likely to have MJS <2.0 mm (adjusted odds ratio 4.032 [1.031-12.639, p = 0.045]). The prevalence of radiographic OA features ranged from 4-13% in people with cam morphology, and 0-3% in those without. Those with cam morphology also demonstrated reduced hip flexion and rotation range (p = 0.018-0.036) compared with those without. There was no association between ultrasonic features and patient reported outcomes, and cam morphology.

CONCLUSIONS

In a cohort aged 40-55 years, the prevalence of cam morphology was high (42%), with a significant relationship between cam morphology and radiographic measures of hip OA. Further longitudinal studies should explore the relationship between cam morphology and hip OA in younger people.

Outcomes following surgical management of femoroacetabular impingement: a systematic review and meta-analysis of different surgical techniques

Outcomes following different types of surgical intervention for femoroacetabular impingement (FAI) are well reported individually but comparative data are deficient. The purpose of this study was to conduct a systematic review (SR) and meta-analysis to analyze the outcomes following surgical management of FAI by hip arthroscopy (HA), anterior mini open approach (AMO), and surgical hip dislocation (SHD). This SR was registered with PROSPERO. An electronic database search of PubMed, Medline, and EMBASE for English and German language articles over the last 20 years was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We specifically analyzed and compared changes in patient-reported outcome measures (PROMs), α-angle, rate of complications, rate of revision, and conversion to total hip arthroplasty (THA). A total of 48 articles were included for final analysis with a total of 4,384 hips in 4,094 patients. All subgroups showed a significant correction in mean α angle postoperatively with a mean change of 28.8° (95% confidence interval (CI) 21 to 36.5; p < 0.01) after AMO, 21.1° (95% CI 15.1 to 27; p < 0.01) after SHD, and 20.5° (95% CI 16.1 to 24.8; p < 0.01) after HA. The AMO group showed a significantly higher increase in PROMs (3.7; 95% CI 3.2 to 4.2; p < 0.01) versus arthroscopy (2.5; 95% CI 2.3 to 2.8; p < 0.01) and SHD (2.4; 95% CI 1.5 to 3.3; p < 0.01). However, the rate of complications following AMO was significantly higher than HA and SHD. All three surgical approaches offered significant improvements in PROMs and radiological correction of cam deformities. All three groups showed similar rates of revision procedures but SHD had the highest rate of conversion to a THA. Revision rates were similar for all three revision procedures.

Femoroacetabular Impingement and Labral Tear: From the Most Highly Cited Articles to Research Interests

Objective

To highlight the characteristics of the most highly cited articles and propose the research interests over the past decades in the field of femoroacetabular impingement (FAI) and labral tear.

Methods

The ISI Web of Science database (Clarivate Analytics, New York, the United States) was utilized for the identification of articles on 15 December 2020. FAI and labral tear‐related articles (1138 articles) were retrieved, of which the 100 most‐cited articles (top 100) were identified. Subsequent analysis included citation density (citations/article age), authorship, institution, journal, geographic distribution, level of evidence, and theme.

Results

The number of citations per article ranged from 66 to 1189 with a mean of 163.31. The majority of articles were published in the United States (all articles/top 100 = 655/57) and Switzerland (85/22). University of Bern (n = 10) was the most prolific institution. The journal with the most of articles was Arthroscopy: The Journal of Arthroscopic and Related Surgery. The most prolific coauthor (all articles) or first authors (top 100) was Domb (n = 109) and Philippon (n = 6), respectively. The evidence with the most articles is level IV (n = 41). The top three most popular topics of research article were outcomes of surgery (n = 23), imaging diagnosis (n = 18), and comparison of surgery (n = 8). The top four most prevalent themes of review were labral tears (n = 3), FAI (n = 3), comparison of surgery imaging diagnosis, and outcomes of surgery (both n = 2). Six keywords with the newest average publication year, including FAI syndrome (average publication year = 2019.50), patient‐reported outcomes (2019.43), femoroplasty (2018.60), clinical outcomes (2018.17), borderline dysplasia (2018.00), and capsule (2018.00). Five keywords with the highest average citations, including outcome (average citations = 88.50), alpha angle (58.00), complications (55.86), revision hip arthroscopy (49.00), and systematic review (46.14).

Conclusions

Outcomes research is the most popular research interest and patient‐reported outcome instruments might be further and widely used in the emerging articles in the near future. The field of FAI and labral tear has shown an obvious trend of development and is steadily evolving. It could be predicted that there will be an increasing number of publications in the following years, with the United States and Switzerland maintaining leadership in this field.

The lateral joint space width is essential for the outcome after arthroscopically assisted mini-open arthrotomy for treatment of a femoroacetabular impingement: an analysis of prognostic factors for the success of this hip-preserving technique

PURPOSE

The purpose of this study was to analyze predicting factors for a conversion to a total hip replacement (THR) after mini-open arthrotomy for treatment of femoroacetabular impingement (FAI).

METHODS

Between 2011 and 2016, we identified 32 patients, who were treated for FAI with a mini-open arthrotomy and received after mean time of 2.1 ± 1.4 years a THR. These patients were compared to 47 cases who did not receive a THR (mean follow-up: 4.3 ± 0.7 years) to explore pre- and intra-operative factors associated with a conversion to THR. The results were presented in separated Kaplan-Meier curves with log rank test for significance and hazard ratios.

RESULTS

A lateral joint space width of > 4 mm showed a higher THR-free survival rate compared to < 4 mm (p = 0.001); analogously one-sided (acetabular/femoral) 3-4° cartilage damage had a comparable THR-free survival rate than 1-2° kissing lesions (p = 0.001). Furthermore, an intact labrum without treatment and good cartilage status, a refixed labrum after rim resection in case of a pincer type FAI, or a refixed teared labrum were associated with a longer THR-free time than an untreated labrum accompanied by a poor cartilage status or an ossified labrum (p = 0.002). The strongest independent factor for a conversion to THR was femoral cartilage damage grade 1 and higher (p = 0.046). However, the rate of available patients was 53.0%.

CONCLUSION

The success of a joint-preserving mini-open arthrotomy seems to be dependent on the status of the radiological joint space width and the intra-operative cartilage status of the lateral edge.

Increased prevalence of femoroacetabular impingement on the elderly with fractures of the proximal femur

Objectives: Femoroacetabular impingement (FAI) has been recently related to several pathologies, besides chondral injury and hip arthritis. We aim to investigate the prevalence of FAI morphology in an elderly cohort hospitalized due to a proximal femur fracture and compare these findings to a control group. We hypothesize that limited medial rotation due to FAI’s morphology could increase stresses to the proximal femur, acting as a facilitating mechanism for fractures in this region. Therefore, a higher prevalence of FAI morphology would be present in the study group. Methods: A retrospective cross-sectional study was performed based on the analysis of radiographic images in AP and lateral views of the fractured hip. Firstly, we have set to measure FAI prevalence in an elderly cohort victimized by fractures of the proximal by measures of the alpha, Tönnis, and lateral center edge angles of a hundred consecutive patients hospitalized for proximal femur fractures. Secondly, we have analyzed the possible relationship between the FAI subtypes and the type of fracture. Finally, we have compared this sample’s data with that of a similar control cohort not affected by fracture. Results: The cohort in this study displayed a higher prevalence of pathological changes in the Tönnis, center-edge, and alpha angles with odds ratios of 3.41, 2.56, and 4.80, respectively (with statistical significance). There was also a significant relationship between cam-type FAI and intertrochanteric fractures, corroborating our initial hypotheses. Conclusions: This study demonstrated that a cohort of older patients affected by fractures of the proximal femur had an increased prevalence of radiographic signs of femoroacetabular impingement. Furthermore, this is the first study demonstrating a statistically significant relationship of cam-type FAI with intertrochanteric fractures, suggesting a possible cause and effect relationship.

FUNCTIONAL OUTCOMES OF ARTHROSCOPIC TREATMENT IN 230 FEMOROACETABULAR IMPINGEMENT CASES

Objective:

To analyze the functional outcomes after arthroscopic treatment of femoroacetabular impingement (FAI).

Methods:

194 patients (131 males and 63 females), with a mean age of 39 (15-68) years old for men and 43 (16-58) years old for women. The average follow-up was 17 months (2 to 71). 103 patients presented Cam-type FAI, 102 mixed and 25 Pincer. “Unilateral” arthroscopy was performed in 161 cases, “Bilateral” (only once each side) in 46 cases and, “Multiple” (more than one procedure on the same hip) in 23. The female sex was prevalent in the Pincer type FAI (76%), while males were prevalent in Mixed and Cam type, 74.5% and 72.8%, respectively.

Results:

The mean HHSpre score was 63.7 and 87.1 for HHSpost, i.e. 73.11%. Differences appeared between “mixed” and “unilateral” groups. The complications percentage in this series was 18.7% and 7% progressed to total hip arthroplasty.

Conclusion:

The arthroscopic FAI treatment improved the postoperative clinical scores of these patients, especially in cases of mixed-type FAI, which presented a higher improvement rate. Insufficient femoral osteoplasty was the main cause for surgical re-intervention, particularly in the initial cases of this series. Level of Evidence II, Retrospective study.

A Comparative Cohort Study With a 20-Year Age Gap: Hip Resurfacing in Patients Aged ≤35 Years and Patients Aged ≥55 Years

Background

This single-center retrospective cohort study aimed to evaluate and compare implant survival and patient-reported outcome measures in 2 distinct age groups separated by 20 years who underwent hip resurfacing arthroplasty (HRA).

Methods

Between 2005 and 2014, 2042 HRAs were performed by a single-surgeon, and 75 and 377 hips from patients aged ≤35 years and ≥55 years, respectively, were included in this study. Implant survival was determined for all available hips. Clinical features and patient-reported outcome measures were collected.

Results

Seven hips were revised, 4 for aseptic loosening of one or both components, one for infection, one for accelerated wear and metallosis, and one for femoral neck fracture. There was no difference in all-cause 10-year revision, with 97.1% (95% confidence interval 80.9 to 99.6) and 99.6% (95% confidence interval: 97 to 99.9) survivorship in younger and older patients, respectively (P = .246). Preoperatively, younger patients were less active than older patients on the Lower Extremity Activity Scale (LEAS) or University of California, Los Angeles, activity scale, but at follow-up, younger patients outpaced older ones.

Conclusion

Original to our study was the isolation and comparison of 2 distinct age groups. With excellent results in disparate age groups, HRA can be applied to a broad patient demographic and is suitable for those patients who want to achieve a high activity level as defined by Lower Extremity Activity Scale or University of California, Los Angeles, scores.

Historical analysis of the diagnosis and management of femoroacetabular impingement prior to the year 2000: a systematic review

 

This systematic review aims to assess the diagnosis, indications and treatment of femoroacetabular impingement (FAI) prior to the year 2000 and to determine if historical concepts remain applicable today. PUBMED, MEDLINE and EMBASE were searched for literature evaluating the diagnosis/treatment of FAI prior to 2000. Cadaver/non-human, non-English and review studies were excluded. Quality assessment was performed using the Methodological Index for Non-Randomized Studies. Nine studies comprising 307 patients [315 hips; mean age of 32.6 ± 2.4 years (range, 12-58)] were included. Patients reported groin pain. Magnetic resonance arthrography (MRA; n = 76) and the anterior impingement test (AIT) (n = 88) were used to diagnose impingement. Surgical dislocation with a trochanteric flip osteotomy (n = 237) and Bernese periacetabular osteotomy (n = 40) were common treatments. Pain and range of motion improved for patients. Overall complication rate was 35% (n = 99), with heterotopic ossification (n = 79) most commonly reported. Prior to 2000, there was low quantity and quality of research on the diagnosis/management of FAI. Diagnostic evaluation was primarily through clinical examination (i.e. groin pain and AIT). MRA was occasionally used to detect labral degeneration; however, utilization of computed tomography (CT) and diagnostic injections were not reported. Surgical dislocation and osteotomies of the acetabulum yielded desirable short-term clinical outcomes with a moderate complication rate. No study reported using arthroscopy for FAI management prior to 2000. Clinicians today can learn from historical principles (i.e. clinical diagnosis of FAI, management with surgical correction of femoral head-neck offset) while applying novel techniques (i.e. CT, injections, arthroscopic surgical techniques and rehabilitation) to improve patient outcomes.

Level of Evidence

IV (systematic review of III and IV evidence).

Optimal Treatment of Cam Morphology May Change the Natural History of Femoroacetabular Impingement

BACKGROUND

There is debate in the literature whether cam morphology is associated with increased risk for hip osteoarthritis. The capability of femoroplasty to alter the natural history of cam morphology is still in question.

PURPOSE

To (1) investigate the correlation between cam morphology and damage to the articular cartilage and (2) assess whether correction of the cam morphology affects survivorship of the joint, progression to arthroplasty, and functional patient-reported outcome scores.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Data were prospectively collected for patients presenting for hip arthroscopy between February 2008 and April 2017. Cases were divided into 3 groups: control group with an alpha angle <50° pre- and postoperatively, treated group with an alpha angle >55° preoperatively and <50° postoperatively, and a group with an alpha angle >55° pre- and postoperatively. All patients had minimum 2-year postoperative follow-up for the modified Harris Hip Score, the Non-arthritic Hip Score, and visual analog scale for pain. Conversion to total hip arthroplasty was recorded.

RESULTS

A 1:1:1 match successfully yielded 98 hips for each group. Follow-up time was 50.77 ± 24.60 months (mean ± SD). The pre- and postoperative mean alpha angles were 45.2°± 3.4° and 40.6°± 4.3° in the control group, respectively; 66.2°± 8.4° and 42.3°± 5.9° in the treated group; and 68.5°± 9.4° and 61.4°± 7.6° in the alpha >55° group. Intraoperatively, the alpha >55° and treated groups had greater acetabular cartilage damage than the control group (P = .0245 and P = .0036, acetabular labrum articular disruption, respectively; P = .0347 and P = .0211, acetabular Outerbridge). The alpha >55° group achieved the patient acceptable symptomatic state for the modified Harris Hip Score (58.2%) significantly less than the treated (75.5%; P = .0100) and control (73.5%; P = .0239) groups. Progression to arthroplasty was significantly higher in the alpha >55° group (n = 17) when compared with the control (n = 8) and treated (n = 10) groups (P = .0034 and P = .0338, respectively).

CONCLUSION

Cam deformity was associated with higher-grade damage of the acetabular articular cartilage. An alpha angle >55° after surgery was associated with lower native hip joint survivability and less successful functional outcomes when compared with that of treated cam deformity as well as no deformity. These data suggest that correcting the cam deformity may positively affect the natural history of these patients.

Running with Femoral Acetabular Impingement: Operative Vs Nonoperative Treatment

A 31-year-old female lawyer presents with right hip pain starting approximately 3 years ago and worsening over the past 2 to 3 months. She is an avid runner, running 20 to 30 miles weekly, and noticed that her pain started after a running program training for the marathon. Her pain is primarily over the lateral aspect of her hip with some radiation into the groin. The pain is made worse with impact exercises such as running and made better with walking and cycling. She has done physical therapy for the past 3 months without any significant improvement. She has not had any injections or taken anti-inflammatories because of a history of gastric ulcer disease. On physical examination she has mild tenderness over her right greater trochanter and her range of motion tests are full in terms of flexion, internal rotation, and external rotation. She has a positive FADIR (flexion-adduction-internal rotation) impingement that causes both groin and lateral hip pain. Radiograph of the right hip revealed preservation of the joint space and an anterior cam lesion with reduced offset at the femoral head neck junction. Magnetic resonance imaging (MRI) of the right hip revealed a tear at the anterior superior labrum at the 1 to 2 o'clock position along with subjacent bone marrow edema in the femoral head that is likely reactive. Computed tomography (CT) scan of the right hip confirmed a combined cam and pincer type femoral acetabular impingement of the right hip with overcoverage of the femoral head. There was 15° of femoral anteversion and the coronal lateral center of edge angle (LCEA) is 34°. Dr. Peter Moley argues that a focused rehabilitation program to restore strength and motor control of the deep hip stabilizers will provide optimal functional recovery. Dr. Jakub Tatka argues that right hip arthroscopy with labral repair and possible osteochondralplasty are indicated in order to prevent early hip arthritis and prevent long-term sequela of femoral acetabular impingement.

Return to Sport After Femoroacetabular Impingement Surgery and Sport-Specific Considerations: a Comprehensive Review

PURPOSE OF REVIEW

Recent advancements in surgical technology and techniques have improved functional results for operative treatment of femoroacetabular impingement syndrome (FAIS). Few studies have comprehensively evaluated the literature regarding return to sport criteria, timing, level, and rates. The purpose of this study was to review recent studies regarding return to play after surgical correction of FAIS. We will specifically evaluate the level of return to play and look to compare pre- and postoperative competition levels when available. We will also analyze timing of return to play from injury to surgery. Additionally, we will elucidate any sport-specific criteria that may determine readiness for return.

RECENT FINDINGS

Athletes with FAIS treated non-operatively have a low rate of return to sport and are often functionally limited in their level of performance. Surgical management of FAIS includes hip arthroscopy as well as open techniques. Current literature suggests a high rate of return to sport after contemporary surgery for FAIS at 87-93% overall. Rate of return to the same level of competition following surgery for FAIS is 55-83% in pooled studies. Limited evidence is available comparing postoperative rehabilitation protocols and timing of return among different sports. Operative treatment of FAIS results in high rates of return to sport and functional performance. The results of this study may help educate patients preoperatively in regard to the likelihood of functional return to sport and sport-specific considerations. Further research evaluating rehabilitation protocols and return criteria may better elucidate timing intervals for patients to maximize function while limiting complications.

Pathomechanics Underlying Femoroacetabular Impingement Syndrome: Theoretical Framework to Inform Clinical Practice

Over the last decade, there has been a marked increase in attention to, and interest in, femoroacetabular impingement syndrome (FAIS). Despite continued efforts by researchers and clinicians, the development, progression, and appropriate treatment of FAIS remains unclear. While research across various disciplines has provided informative work in various areas related to FAIS, the underlying pathomechanics, time history, and interaction between known risk factors and symptoms remain poorly understood. The purpose of this perspective is to propose a theoretical framework that describes a potential pathway for the development and progression of FAIS. This paper aims to integrate relevant knowledge and understanding from the growing literature related to FAIS to provide a perspective that can inform future research and intervention efforts.

Achieving a Perfectly Spherical Femoroplasty: Pearls, Pitfalls, and Optimal Surgical Technique

Femoroacetabular impingement describes a pathologic interaction between the bony femoral head/neck junction and acetabulum. Cam-type femoroacetabular impingement results from an aspherical femoral head architecture, which increases early contact along the acetabular surface during hip range of motion. Errant arthroscopic femoroplasty recently has been discussed within the literature to describe a preventable etiology of failed hip arthroscopy, most notably cam over- and under-resection. We present an arthroscopic surgical technique for achieving the perfectly spherical femoroplasty, meant to minimize complications and improve postoperative outcomes.

The clinical presentation, diagnosis and pathogenesis of symptomatic sports-related femoroacetabular impingement (SRFAI) in a consecutive series of 1021 athletic hips

AIM

To examine the pathogenesis and clinical presentation of sports-related femoroacetabular impingement (SRFAI) in a large consecutive series of symptomatic athletes.

METHODS

Between January 2009 and February 2017 prospectively collected data from competitive athletes within the Gaelic Athletic Association (GAA), and who subsequently underwent arthroscopic treatment for symptomatic FAI, were analysed. Data was collected using internationally validated health questionnaires (Harris Hip Score, UCLA, SF-36, WOMAC) and recognised clinical (ROM, symptom presentation, provocation tests) and radiological (AP pelvis, Dunn, False profile) indicators/measures of FAI.

RESULTS

A total of 1021 consecutive cases (mean 26.6 ± 6.2 years) were included. In every case, conservative treatment failed to resolve symptoms with athletes attending an average of 2.4 ± 1.1 health care professionals prior to referral. Symptoms developed gradually (78%) and consisted primarily of groin pain (76.1%) and hip stiffness (76.5%) following activity. An acetabular rim deformity (pincer) was present in all cases; a cam deformity in 72.1%. The prevalence and degree of cam deformity increased with progressing age groups (p < 0.001); mean lateral centre-edge angle remained static (p = 0.456). Increasing CEA, alpha angle and presence of rim fracture was associated with a reduction in all ranges of hip movement (p < 0.001).

CONCLUSION

Symptomatic SRFAI presented in this large series of GAA athletes failed to resolve with non-operative treatment. Increasing hip deformity resulted in poorer ROM. Abnormal acetabular morphology remains static with increasing athletic age while cam deformity is progressive and most likely a secondary pathology.

Correlation between hip osteoarthritis and proximal femoral fracture site: could it be protective for intracapsular neck fractures? A retrospective study on 320 cases

Proximal femoral fractures affect elderly people, showing high morbidity and mortality incidence resulting in a major economic burden on national healthcare systems. Understanding the causes of these injuries is of paramount importance to prevent the serious consequences of these fractures.

INTRODUCTION

Hip osteoarthritis and proximal femoral fractures mainly affect elderly patients. Several authors, in their studies, tried to document a correlation between these conditions, but the results are conflicting. The aim of this study was to evaluate the relationship between hip osteoarthritis and the fracture site. Secondly, to evaluate if the grade of osteoarthritis could influence the fracture pattern.

METHODS

A retrospective study on 320 patients admitted for hip fracture between June 2015 and December 2016 was carried on. Radiographic images were evaluated, assessing the type of fracture, presence and grade of osteoarthritis according to Kellgren-Lawrence and Tönnis classifications, and their correlations.

RESULTS

Osteoarthritis was found to affect the fracture site showing a higher prevalence among subjects with extracapsular than those with intracapsular fractures (p < 0.00001). Patients with radiographic signs of arthritis had mainly trochanteric fracture. Conversely, patients without arthritis more frequently presented a femoral neck fracture. This correlation was even more significant as the severity of the OA increased.

CONCLUSIONS

Results support the hypothesis that hip osteoarthritis could represent a protective factor for intracapsular fractures and a risk factor for trochanteric ones. The severity of arthritis is also associated with the fracture pattern.

SHORT-TERM OUTCOMES OF CONSERVATIVE TREATMENT FOR FEMOROACETABULAR IMPINGEMENT: A SYSTEMATIC REVIEW AND META-ANALYSIS

BACKGROUND

Femoroacetabular Impingement (FAI) is becoming increasingly more common with noted impairments in physical function, increased pain, and decreased quality of life. Typically, a conservative approach is used through physical therapy or intra-articular injections before an invasive surgical approach is utilized. Identifying the proper course of conservative care by the clinician will aid in improving outcomes.

PURPOSE

The purpose of this systematic review and meta-analysis was to investigate short-term effects of conservative physical therapy and intra-articular injections on pain and physical function measures in patients with FAI.

STUDY DESIGN

Systematic Review & Meta-Analysis.

METHODS

A systematic review and meta-analysis were completed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and registered with the International Prospective Registry of Systematic Reviews. A literature review was performed in May 2018 using Pubmed, CINAHL, Proquest, and Scopus. Inclusion criteria included humans classified as having femoroacetabular impingement, conservative rehabilitation, and utilization of outcome measures in the domains of pain or function. Exclusion criteria included absence of skilled interaction and study protocols that were not completed.

RESULTS

Seven studies were included that summarized physical therapy or intra-articular injection outcomes for femoroacetabular impingement management. Results showed that conservative interventions for short-term periods are effective in reducing pain and improving function for femoroacetabular impingement. Overall, physical therapy revealed moderate to large effect sizes and statistically significant differences in both pain (SMD, 0.91, CI: 0.07, 1.76, p=0.030) and function (SMD, 0.80, CI: 0.34, 1.28, p=0.001) for femoroacetabular impingement. Intra-articular injection demonstrated small effect sizes for pain outcomes (SMD, 0.29, CI: -1.25, 1.83, p = 0.710) and small to moderate effect size for improvement in function (SMD, 0.49, CI: 0.03, 0.96, p = 0.040).

CONCLUSIONS

Physical therapy demonstrated positive results to self-reported pain and function and may hold more promise than intra-articular injection alone. Common treatments that were associated with improved outcomes were patient education, activity modification, manual therapy, and strengthening. There are a limited number of high-quality articles on this topic, which should be addressed in future research.

LEVEL OF EVIDENCE

1a.

Hip Joint Torsional Loading Before and After Cam Femoroacetabular Impingement Surgery

BACKGROUND

Surgical management of cam femoroacetabular impingement (FAI) aims to preserve the native hip and restore joint function, although it is unclear how the capsulotomy, cam deformity, and capsular repair influence joint mechanics to balance functional mobility.

PURPOSE

To examine the contributions of the capsule and cam deformity to hip joint mechanics. Using in vitro, cadaveric methods, we examined the individual effects of the surgical capsulotomy, cam resection, and capsular repair on passive range of motion and resistance of applied torque.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twelve cadaveric hips with cam deformities were skeletonized to the capsule and mounted onto a robotic testing platform. The robot positioned each intact hip in multiple testing positions: (1) extension, (2) neutral 0°, (3) flexion 30°, (4) flexion 90°, (5) flexion-adduction and internal rotation (FADIR), and (6) flexion-abduction and external rotation. Then the robot performed applicable internal and external rotations, recording the neutral path of motion until a 5-N·m of torque was reached in each rotational direction. Each hip then underwent a series of surgical stages (T-capsulotomy, cam resection, capsular repair) and was retested to reach 5 N·m of internal and external torque again after each stage. During the capsulotomy and cam resection stages, the initial intact hip's recorded path of motion was replayed to measure changes in resisted torque.

RESULTS

Regarding changes in motion, external rotation increased substantially after capsulotomies, but internal rotation only further increased at flexion 90° (change +32%, P = .001, d = 0.58) and FADIR (change +33%, P < .001, d = 0.51) after cam resections. Capsular repair provided marginal restraint for internal rotation but restrained the external rotation compared with the capsulotomy stage. Regarding changes in torque, both internal and external torque resistance decreased after capsulotomy. Compared with the capsulotomy stage, cam resection further reduced internal torque resistance during flexion 90° (change -45%, P < .001, d = 0.98) and FADIR (change -37%, P = .003, d = 1.0), where the cam deformity accounted for 21% of the intact hip's torsional resistance in flexion 90° and 27% in FADIR.

CONCLUSION

Although the capsule played a predominant role in joint constraint, the cam deformity provided 21% to 27% of the intact hip's resistance to torsional load in flexion and internal rotation. Resecting the cam deformity would remove this loading on the chondrolabral junction.

CLINICAL RELEVANCE

These findings are the first to quantify the contribution of the cam deformity to resisting hip joint torsional loads and thus quantify the reduced loading on the chondrolabral complex that can be achieved after cam resection.

[Cartilage regeneration surgery on the hip : What is feasible?]

Localized cartilage defects at the hip are mainly caused by pre-arthritic deformities, particularly by cam-type femoroacetabular impingement (FAI). Timely elimination of symptomatic deformities can prevent further progression such as cartilage defects. As the defects mostly occur in the anterolateral part of the acetabulum, they can be easily treated either by open surgery or by arthroscopy. To date the most effective methods of treatment are bone marrow stimulation, with or without a covering of biomaterials, and autologous chondrocyte transplantation. In selected cases, readaptation of the damaged cartilage can be attempted by biological procedures. In the present article, the findings reported in current studies on these procedures are summarized and discussed in detail. An outlook is given regarding possible future treatment concepts.

Patient-specific parameterised cam geometry in finite element models of femoroacetabular impingement of the hip

BACKGROUND

Impingement resulting in soft tissue damage has been observed in hips with abnormal morphologies. Geometric parameterisation can be used to automatically generate a range of bone geometries for use in computational models, including femurs with cam deformity on the femoral neck.

METHODS

This study verified patient-specific parametric finite element models of 20 patients with cam deformity (10 female, 10 male) through comparison to their patient-specific segmentation-based equivalents. The parameterisation system was then used to generate further models with parametrically defined geometry to investigate morphological changes in both the femur and acetabulum and their effects on impingement.

FINDINGS

Similar findings were observed between segmentation-based and parametric models when assessing soft tissue strains under impingement conditions, resulting from high flexion and internal rotations. Parametric models with cam morphology demonstrated that clinically used alpha angles should not be relied on for estimating impingement severity since planar views do not capture the full three-dimensional geometry of the joint. Furthermore, the parametric approach allowed study of labral shape changes, indicating higher strains can result from bony overcoverage.

INTERPRETATION

The position of cams, as well as their size, can affect the level of soft tissue strain occurring in the hip. This highlights the importance of reporting the full details of three-dimensional geometry used when developing computational models of the hip joint and suggests that it could be beneficial to stratify the patient population when considering treatment options, since certain morphologies may be at greater risk of elevated soft tissue strain.

Characterization of proximal femoral anatomy in the skeletally-immature patient

PURPOSE

The morphology of the proximal femur has been extensively studied in the adult population. However, no literature providing a comprehensive evaluation of the anatomy in paediatric patients exists. The current study aims to characterize such anatomy in skeletally-immature patients, examine potential differences between genders, and analyze how these anatomical parameters change with age.

METHODS

Cadaveric femurs from the Hamann-Todd Osteological Collection were examined. Specimens with open physes and no skeletal disease or deformity were included for analysis. Age and gender were recorded for each specimen. Each femur was photographed in standardized modified axial and anteroposterior views. In all, 14 proximal femoral anatomical parameters were measured from these photographs. Comparisons between genders and age were calculated.

RESULTS

A total of 43 femurs from ages four to 17 years met inclusion criteria. The majority were female (56%); no difference existed in age between genders (p = 0.62). The specimens had a neutral mean neck-shaft angle (130.7º) and anteversion (12.8º), and the sphericity of the ossified femoral heads was symmetrical. Male specimens had significantly higher alpha angles (p = 0.01), posterior offset (p = 0.02), neck width (p = 0.04) and head-neck length ratio (p = 0.02) values than female specimens. Strong positive correlations exist between length/size parameters and age, while negligible correlations were noted for angular measurements.

CONCLUSIONS

This study establishes reference values for a comprehensive list of anatomical parameters for the skeletally-immature ossified proximal femur. It highlights gender differences in morphology and demonstrates that angular characteristics remain relatively stable while length parameters generally increase with age.

LEVEL OF EVIDENCE

Level III Diagnostic.

Population-based prevalence of multiple radiographically-defined hip morphologies: the Johnston County Osteoarthritis Project

OBJECTIVE

To provide the first prevalence estimates of different radiographic hip morphologies relevant to dysplasia and femoroacetabular impingement in a well-characterized USA population-based cohort.

METHODS

Cross-sectional data were from the baseline examination (1991-1997) of a large population-based prospective longitudinal cohort study (The Johnston County Osteoarthritis Project). HipMorf software (Oxford, UK) was used to assess hip morphology on anteroposterior (AP) pelvis radiographs. Weighted, sex-stratified prevalence estimates and 95% confidence intervals for four key hip morphologies (AP alpha angle, triangular index sign, lateral center edge angle (LCEA), and protrusio acetabula) were derived and further stratified by age, race and body mass index (BMI).

RESULTS

A total of 5192 hips from 2596 individuals were included (31% African American, 43% male, mean age 63 years, mean BMI 29 kg/m²). Cam morphology was seen in more than 25% of men and 10% of women. Mild dysplasia was present in about 1/3 of men and women, while pincer morphology was identified in 7% of men and 10% of women. Femoral side (cam) morphologies were more common and more frequently bilateral among men, while pincer morphologies were more common in women; mixed morphologies were infrequent. African-Americans were more likely to have protrusio acetabula than whites.

CONCLUSION

We report the first population-based prevalence estimates of radiographic hip morphologies relevant to femoroacetabular impingement (FAI) and dysplasia in the USA. These morphologies are very common, with ¼ men and 1/10 women having cam morphology, 1/3 of all adults having mild dysplasia, and 1/15 men and 1/10 women having pincer morphology in at least one hip.

Femoroacetabular impingement causes osteoarthritis of the hip by migration and micro-instability of the femoral head

Femoroacetabular impingement is the condition whereby parts of the proximal femur mechanically collide with the acetabular rim leading to adjacent and contrecoup acetabular damage. Evidence is growing that at least for cam impingement, and perhaps less so for pincer impingement, there is a relation to the development of osteoarthritis. It has been demonstrated that surgery for impingement can improve function and decrease pain. Intuitively, it would then make sense that surgical intervention would prevent further degeneration. However, available literature to date cannot assure that it does. Therefore, the impingement itself seems not a sufficient cause to consistently cause osteoarthritis. For many years we have observed a phenomenon whereby the femoral head 'migrates' anteriorly and superiorly in the acetabulum in patients with cam impingement. The same, but less constant, can be observed in pincer impingement, where the head may migrate posteriorly and medially. Migration of the femoral head is known in the literature and seen as caused by, or as part of, osteoarthritis of the hip. We suggest that the migration is caused by the impingement, and that the femoral head wanders into the impingement-related area with cartilage damage. In cam impingement this may be anterolateral, in pincer impingement posteromedial. The effect must be a huge increase in compression forces, especially in cam impingement. The migration may even lead to, or be a sign of, micro-instability of the femoral head in the acetabulum, which may produce an increase in shear forces. We therefore hypothesise that impingement may lead to osteoarthritis by means of migration and the possible existence of micro-instability of the femoral head. Detecting and quantifying these phenomena seem of uttermost importance and may add a new dimension to conservative hip surgery.

Hip Osteoarthritis: Etiopathogenesis and Implications for Management

Highly prevalent among the elderly, hip osteoarthritis (OA) carries a heavy burden of disease. Guidelines for the management of hip OA are often extrapolated from knee OA research, despite clear differences in the etiopathogenesis and response to treatments of OA at these sites. We propose that hip OA requires specific attention separate from other OA phenotypes. Our understanding of the etiopathogenesis of hip OA has seen significant advance over the last 15 years, since Ganz and colleagues proposed femoroacetabular impingement (FAI) as an important etiological factor. This narrative review summarizes the current understanding of the etiopathogenesis of hip OA and identifies areas requiring further research. Therapeutic approaches for hip OA are considered in light of the condition’s etiopathogenesis. The evidence for currently adopted management strategies is considered, especially those approaches that may have disease-modifying potential. We propose that shifting the focus of hip OA research and public health intervention to primary prevention and early detection may greatly improve the current management paradigm.