Imaging in Hip Arthroscopy for Femoroacetabular Impingement: A Comprehensive Approach

Feasibility of photon-counting CT for femoroacetabular impingement syndrome evaluation: lower radiation dose and improved diagnostic confidence

OBJECTIVE

The feasibility of low-dose photon-counting detector (PCD) CT to measure alpha and acetabular version angles of femoroacetabular impingement (FAI).

MATERIAL AND METHODS

FAI patients undergoing an energy-integrating detector (EID) CT underwent an IRB-approved prospective ultra-high-resolution (UHR) PCD-CT between 5/2021 and 12/2021. PCD-CT was dose-matched to the EID-CT or acquired at 50% dose. Simulated 50% dose EID-CT images were generated. Two radiologists evaluated randomized EID-CT and PCD-CT images and measured alpha and acetabular version angles on axial image slices. Image quality (noise, artifacts, and visualization of cortex) and confidence in non-FAI pathology were rated on a 4-point scale (3 = adequate). Preference tests of standard dose PCD-CT, 50% dose PCD-CT, and 50% dose EID-CT relative to standard dose EID-CT were performed using Wilcoxon Rank test.

RESULTS

20 patients underwent standard dose EID-CT (~ CTDIvol, 4.5 mGy); 10 patients, standard dose PCD-CT (4.0 mGy); 10 patients, 50% PCD-CT (2.6 mGy). Standard dose EID-CT images were scored as adequate for diagnostic task in all categories (range 2.8-3.0). Standard dose PCD-CT images scored higher than the reference in all categories (range 3.5-4, p < 0.0033). Half-dose PCD-CT images also scored higher for noise and cortex visualization (p < 0.0033) and equivalent for artifacts and visualization of non-FAI pathology. Finally, simulated 50% EID-CT images scored lower in all categories (range 1.8-2.4, p < 0.0033).

CONCLUSIONS

Dose-matched PCD-CT is superior to EID-CT for alpha angle and acetabular version measurement in the work up of FAI. UHR-PCD-CT enables 50% radiation dose reduction compared to EID while remaining adequate for the imaging task.

Assessment of Femoral Torsion on Magnetic Resonance Imaging is More Reliable Using Axial-Oblique Sequences Compared With Standard Axial Slices in Patients With Femoroacetabular Impingement Syndrome

PURPOSE

To determine the agreeability of femoral torsion measurements on axial and oblique axial magnetic resonance imaging (MRI) sequences in patients with femoroacetabular impingement syndrome (FAIS).

METHODS

Patients who underwent primary hip arthroscopy for FAIS between January 2012 to January 2019 were identified. Inclusion criteria were all patients with an MRI scan containing the pelvis and knee imaging. MRI-based measurements of femoral torsion were performed on axial and oblique-axial slices by 2 raters, and inter-rater and intrarater reliability was assessed. Bland Altman plots were constructed to evaluate the agreeability between femoral torsion measurements performed using axial and oblique-axial slices. Bivariate correlation analyses were performed to assess the relationship between measurement methods on each respective scan. A linear regression was performed between measurements performed using axial and oblique-axial sequences.

RESULTS

A total of 164 patients were included. The mean true-axial and oblique axial femoral torsion were 12.2° ± 9.9° and 11.1° ± 9.2°, respectively. The intrarater reliability for axial and oblique-axial measurements were 0.993 and 0.997, respectively. The inter-rater reliability for axial and oblique-axial measurements were 0.925 and 0.965, respectively. The number of differences within the limits of agreement for axial and oblique-axial femoral torsion measurements was 58.54%. On Pearson correlation analysis, strong positive correlations were found between oblique-axial measurements at multiple time points (r = 0.994, P < .001), as well as axial measurements at multiple time points (r = 0.986, P < .001). A strong positive correlation was found between axial and oblique-axial measurements (r = 0.894, P < .001). A significant regression equation indicated that for each additional increase in axial femoral torsion, the oblique-axial femoral torsion increased 0.837 (95% confidence interval 0.772-0.901).

CONCLUSIONS

Femoral torsion values measured on oblique-axial sequences are smaller than on true-axial sequences. Femoral torsion measurements on axial and oblique-axial MRI sequences exhibit poor agreement. Oblique-axial sequences demonstrated greater measurement consistency at multiple timepoints. When evaluating torsional measurements, it is important to delineate which axial sequence was used, especially in patients with suspected severe femoral antetorsion. Standardization of MRI femoral version protocols within one's practice can ensure more consistent decision-making, especially in patients with suspected femoral antetorsion.

LEVEL OF EVIDENCE

Retrospective cohort, level III.

Three-Dimensional Quantification of Cam Resection Using MRI Bone Models: A Comparison of 2 Techniques

Background:

The current clinical standard for the evaluation of cam deformity in femoroacetabular impingement syndrome is based on radiographic measurements, which limit the ability to quantify the complex 3-dimensional (3D) morphology of the proximal femur.

Purpose:

To compare magnetic resonance imaging (MRI)–based metrics for the quantification of cam resection as derived using a best-fit sphere alpha angle (BFS-AA) method and using 3D preoperative-postoperative surface model subtraction (PP-SMS).

Study Design:

Descriptive laboratory study.

Methods:

Seven cadaveric hemipelvises underwent 1.5-T MRI before and after arthroscopic femoral osteochondroplasty, and 3D bone models of the proximal femur were reconstructed from the MRI scans. The alpha angles were measured radially along clockfaces using a BFS-AA method from the literature and plotted as continuous curves for the pre- and postoperative models. The difference between the areas under the curve for the pre- and postoperative models was then introduced in the current study as the BFS-AA–based metric to quantify the cam resection. The cam resection was also quantified using a 3D PP-SMS method, previously described in the literature using the metrics of surface area (FSA), volume (FV), and height (maximum [FH_max] and mean [FH_mean]). Bivariate correlation analyses were performed to compare the metrics quantifying the cam resection as derived from the BFS-AA and PP-SMS methods.

Results:

The mean ± standard deviation maximum pre- and postoperative alpha angle measurements were 59.73° ± 15.38° and 48.02° ± 13.14°, respectively. The mean for each metric quantifying the cam resection with the PP-SMS method was as follows: FSA, 540.9 ± 150.7 mm²; FV, 1019.2 ± 486.2 mm³; FH_max, 3.6 ± 1.0 mm; and FH_mean, 1.8 ± 0.5 mm. Bivariate correlations between the BFS-AA–based and PP-SMS–based metrics were strong: FSA (r = 0.817, P = .012), FV (r = 0.888, P = .004), FH_max (r = 0.786, P = .018), and FH_mean (r = 0.679, P = .047).

Conclusion:

Strong positive correlations were appreciated between the BFS-AA and PP-SMS methods quantifying the cam resection.

Clinical Relevance:

The utility of the BFS-AA technique is primarily during preoperative planning. The utility of the PP-SMS technique is in the postoperative setting when evaluating the adequacy of resection or in patients with persistent hip pain with suspected residual impingement. In combination, the techniques allow surgeons to develop a planned resection while providing a means to evaluate the depth of resection postoperatively.

Radiographic Indices Are Not Predictive of Clinical Outcomes Among 1735 Patients Indicated for Hip Arthroscopic Surgery: A Machine Learning Analysis

BACKGROUND

The relationship between the preoperative radiographic indices for femoroacetabular impingement syndrome (FAIS) and postoperative patient-reported outcome measure (PROM) scores continues to be under investigation, with inconsistent findings reported.

PURPOSE

To apply a machine learning model to determine which preoperative radiographic indices, if any, among patients indicated for the arthroscopic correction of FAIS predict whether a patient will achieve the minimal clinically important difference (MCID) for 1- and 2-year PROM scores.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 1735 consecutive patients undergoing primary hip arthroscopic surgery for FAIS were included from an institutional hip preservation registry. Patients underwent preoperative computed tomography of the hip, from which the following radiographic indices were calculated by a musculoskeletal radiologist: alpha angle, beta angle, sagittal center-edge angle, coronal center-edge angle, neck shaft angle, acetabular version angle, and femoral version angle. PROM scores were collected preoperatively, at 1 year postoperatively, and at 2 years postoperatively for the modified Harris Hip Score (mHHS), the Hip Outcome Score (HOS)-Activities of Daily Living (HOS-ADL) and -Sport Specific (HOS-SS), and the International Hip Outcome Tool (iHOT-33). Random forest models were created for each PROM at 1 and 2 years' follow-up, with each PROM's MCID used to establish clinical meaningfulness. Data inputted into the models included ethnicity, laterality, sex, age, body mass index, and radiographic indices. Comprehensive and separate models were built specifically to assess the association of the alpha angle, femoral version angle, coronal center-edge angle, McKibbin index, and hip impingement index with respect to each PROM.

RESULTS

As evidenced by poor area under the curves and P values >.05 for each model created, no combination of radiographic indices or isolated index (alpha angle, coronal center-edge angle, femoral version angle, McKibbin index, hip impingement index) was a significant predictor of a clinically meaningful improvement in scores on the mHHS, HOS-ADL, HOS-SS, or iHOT-33. The mean difference between 1- and 2-year PROM scores compared with preoperative values exceeded the respective MCIDs for the cohort.

CONCLUSION

In patients appropriately indicated for FAIS corrective surgery, clinical improvements can be achieved, regardless of preoperative radiographic indices, such as the femoral version angle, coronal center-edge angle, and alpha angle. No specific radiographic parameter or combination of indices was found to be predictive of reaching the MCID for any of the 4 studied hip-specific PROMs at either 1 or 2 years' follow-up.

1.5 T magnetic resonance imaging generates accurate 3D proximal femoral models: Surgical planning implications for femoroacetabular impingement

The objective of this study was to validate three-dimensional (3D) proximal femoral surface models generated from a 1.5 T magnetic resonance imaging (MRI) by comparing these 3D models to those derived from the clinical "gold standard" of computed tomography (CT) scan and to ground-truth surface models obtained by laser scans (LSs) of the excised femurs. Four intact bilateral cadaveric pelvis specimens underwent CT and MRI scans and 3D surface models were generated. Six femurs were extracted from these specimens, and the overlying soft tissues were removed. The extracted femurs were then laser scanned to produce a ground-truth surface model. A 3D-3D registration method was used to compare the signed and absolute surface-to-surface distances between the 3D models. Absolute agreement was evaluated using a 95% confidence interval (CI) derived from the precision of the LS ground-truth. Paired samples t tests and Kolmogrov-Smirnov tests were performed to compare the differences between the signed and absolute surface-to-surface distances between the models. The average signed surface-to-surface distances for the MRI vs LS and MRI vs CT models were 0.07 and 0.16 mm, respectively. These differences fell within the 95% CI of ±0.20 mm indicating absolute agreement between the surface models generated from these modalities. The signed surface-to-surface distance was significantly smaller for MRI vs LS ground truth model as compared with the CT vs LS model. Femoral models derived from a 1.5 T MRI scan demonstrated absolute agreement with the clinical gold standard of CT-derived models and were most like LS ground truth models of the excised femurs.

Outcomes of Revision Hip Arthroscopic Surgery: A Systematic Review and Meta-analysis

BACKGROUND

While the indications for primary hip arthroscopic surgery in treating femoroacetabular abnormalities continue to be defined, the indications and outcomes for revision hip arthroscopic surgery remain ambiguous. However, revision hip arthroscopic surgery is performed in 5% to 14% of patients after their index procedure. While patient-reported outcomes (PROs) generally improve after revision procedures, the extent of their improvement is not well defined.

PURPOSE

To determine the outcomes and efficacy of revision hip arthroscopic surgery in patients who remain symptomatic after their index procedure.

STUDY DESIGN

Meta-analysis and systematic review.

METHODS

The terms "hip arthroscopy,""revisions,""outcomes," and "femoroacetabular impingement" were searched in PubMed, Web of Science, Scopus, Cochrane Library, and Google Scholar. After screening, 15 studies were included for review. In addition to hip-specific metrics, functional outcome measures were included. Pooled estimates and 95% CIs were calculated using inverse variance methods.

RESULTS

A total of 4765 hips in 4316 patients were identified. The most common indication for revision surgery was inadequate bony resection during the index procedure. Meta-analysis showed that all PROs improved significantly from baseline to final follow-up after revision hip arthroscopic surgery. Notably, the modified Harris Hip Score (mHHS) increased a mean of 17.20 points after revision hip arthroscopic surgery, the Hip Outcome Score-Activities of Daily Living (HOS-ADL) improved by 13.98, and the visual analog scale (VAS) for pain decreased by 3.16. However, when compared with primary hip arthroscopic surgery, the mean PRO scores after revision hip arthroscopic surgery were lower. After revision hip arthroscopic surgery, the rates of conversion to total hip arthroplasty ranged from 0% to 14.3%, and the rates of further arthroscopic revision ranged from 2% to 14%.

CONCLUSION

Inadequate bony resection represents the most common indication for revision hip arthroscopic surgery. PROs improve significantly after revision hip arthroscopic surgery but remain lower than those of patients undergoing primary hip arthroscopic surgery.

THE ROLE of a BIKE FIT in CYCLISTS with HIP PAIN. A CLINICAL COMMENTARY

Hip pathology is common amongst athletes and the general population. The mechanics of cycling have the potential to exacerbate symptomatic hip pathology and progress articular pathology in patients with morphologic risk factors such as femoroacetabular impingement. A professional fit of the bicycle to the individual which aims to optimize hip joint function can allow patients with hip pathology to exercise in comfort when alternative high impact exercise such as running may not be possible. Conversely improper fit of the bicycle can lead to hip symptoms in otherwise healthy individuals who present with risk factors for hip pain. Accordingly a bike fit can form part of the overall management strategy in a cyclist with hip symptoms. The purpose of this clinical commentary is to discuss hip pathomechanics with respect to cycling, bicycle fitting methodology and the options available to a physical therapist to optimize hip mechanics during the pedaling action.

The Importance of Comprehensive Cam Correction: Radiographic Parameters Are Predictive of Patient-Reported Outcome Measures at 2 Years After Hip Arthroscopy

BACKGROUND

The specific influence of preoperative and postoperative radiographic measurements on patient-reported outcome measures after hip arthroscopy for femoroacetabular impingement (FAI) remains unclear.

PURPOSE

To investigate the relationship between radiographic measurements and 2-year outcomes after hip arthroscopy for the treatment of FAI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A clinical registry of patients undergoing primary hip arthroscopy for FAI between January 1, 2012, and December 31, 2014, was queried. Outcome measures included the Hip Outcome Score (HOS) Activities of Daily Living (ADL), HOS Sport-Specific Subscale (SSS), modified Harris Hip Score (mHHS), and visual analog scale (VAS) for pain and satisfaction. Preoperative and postoperative radiographic measurements were recorded. Univariate analysis was conducted to identify relationships between all radiographic and demographic variables and outcome scores. A multivariate regression analysis, controlling for demographic factors, was used to identify independent associations between radiographic measurements on plain radiographs and patient-reported outcomes.

RESULTS

The authors identified 707 patients who underwent primary hip arthroscopic management for FAI who were included for analysis. Two-year outcome surveys were completed for 78% to 84% of patients. The mean age of the patients was 33.2 ± 12.3 years, and 64.4% of the patients (n = 456) were female. The mean anteroposterior (AP) alpha angle decreased by 34.3° ( P < .0001), false profile alpha angle by 25.2° ( P < .0001), Dunn lateral alpha angle by 28.9° ( P < .0001), lateral center edge angle by 2.6° ( P < .0001), and anterior center edge angle by 3.4° ( P < .0001). The HOS-ADL score increased from 65.7 ± 18.7 preoperatively to 85.9 ± 16.7 postoperatively ( P < .0001), HOS-SSS increased from 43.4 ± 23.1 to 72.6 ± 27.2 ( P < .0001), and mHHS increased from 57.7 ± 14.0 to 79.1 ± 17.2 ( P < .0001). With multivariate analysis, independent predictors of the postoperative HOS-ADL score included the preoperative false profile alpha angle (beta = -0.16, P = .028). Independent predictors of HOS-SSS score were preoperative AP alpha angle (beta = -0.33, P = .032) and preoperative false profile alpha angle (beta = -0.28, P = .041). For the postoperative mHHS score, independent predictors included preoperative AP alpha angle (beta = -0.18, P = .046), preoperative false profile alpha angle (beta = -0.20, P = .014), and postoperative false profile alpha angle (beta = -0.48, P = .035). The preoperative AP alpha angle (beta = 0.28, P = .024) was a significant predictor for the postoperative VAS pain score. The preoperative false profile alpha angle (beta = -0.34, P = .040) was a significant predictor for the postoperative VAS satisfaction score.

CONCLUSION

The authors observed that radiographic measurements, specifically the preoperative false profile alpha angle, AP alpha angle, and postoperative false profile alpha angle, are independent predictors of 2-year clinical outcomes. The femoral-side measurements were the strongest independent predictors of outcomes, especially measurements of the anterior and lateral-based CAM lesion.

Femoroacetabular impingement: a common cause of hip pain

Femoroacetabular impingement (FAI) is a common cause of hip pain that can affect a wide range of patients. It is due to altered bony morphology of the proximal femur and acetabulum, resulting in decreased function and progression to early osteoarthritis. Until the early 2000s, little was known or understood about the significance of FAI as a clinical entity. The field of hip preservation has grown exponentially since that time, and has led to many advances in caring for those with symptomatic impingement. This review details the early diagnosis and proper management of femoroacetabular impingement for the sports medicine practitioner.

Hip arthroscopy for femoroacetabular impingement

The purpose of this article is to give a general overview of femoroacetabular impingement (FAI) and how it could be treated arthroscopically, with some details about indications, the procedure itself and some of the complications associated with the surgery.

FAI is a dynamic condition of the hip that can be a source of pain and disability and could potentially lead to arthritis.

When symptomatic, and if conservative treatment fails, FAI can be addressed surgically.

The goal of surgical treatment for FAI is to recreate the spherical contour of the femoral head, improve femoral offset, normalize coverage of the acetabulum, repair/reconstruct chondral damage and repair/reconstruct the labrum to restore normal mechanics and joint sealing.

Advances in equipment and technique have contributed to an increase in the number of hip arthroscopy procedures performed worldwide and have made it one of the more common treatment options for symptomatic FAI.

Hip arthroscopy is a procedure with an extremely steep and long learning curve.

Cite this article: EFORT Open Rev 2018;3:121-129. DOI: 10.1302/2058-5241.3.170041

Ultrasound imaging and segmentation of bone surfaces: A review

Due to its real-time, non-radiation based three-dimensional (3D) imaging capabilities, ultrasound (US) has been incorporated into various orthopedic procedures. However, imaging artifacts, low signal-to-noise ratio (SNR) and bone boundaries appearing several mm in thickness make the analysis of US data difficult. This paper provides a review about the state-of-the-art bone segmentation and enhancement methods developed for two-dimensional (2D) and 3D US data. First, an overview for the appearance of bone surface response in B-mode data is presented. Then, classification of the proposed techniques in terms of the image information being used is provided. Specifically, the focus is given on segmentation and enhancement of B-mode US data. The review is concluded by discussing future directions of research and additional challenges which need to be overcome in order to make this imaging modality more successful in orthopedics.