Does Removal of Subchondral Cortical Bone Provide Sufficient Resection Depth for Treatment of Cam Femoroacetabular Impingement?

Statistical multi-level shape models for scalable modeling of multi-organ anatomies

Statistical shape modeling is an indispensable tool in the quantitative analysis of anatomies. Particle-based shape modeling (PSM) is a state-of-the-art approach that enables the learning of population-level shape representation from medical imaging data (e.g., CT, MRI) and the associated 3D models of anatomy generated from them. PSM optimizes the placement of a dense set of landmarks (i.e., correspondence points) on a given shape cohort. PSM supports multi-organ modeling as a particular case of the conventional single-organ framework via a global statistical model, where multi-structure anatomy is considered as a single structure. However, global multi-organ models are not scalable for many organs, induce anatomical inconsistencies, and result in entangled shape statistics where modes of shape variation reflect both within- and between-organ variations. Hence, there is a need for an efficient modeling approach that can capture the inter-organ relations (i.e., pose variations) of the complex anatomy while simultaneously optimizing the morphological changes of each organ and capturing the population-level statistics. This paper leverages the PSM approach and proposes a new approach for correspondence-point optimization of multiple organs that overcomes these limitations. The central idea of multilevel component analysis, is that the shape statistics consists of two mutually orthogonal subspaces: the within-organ subspace and the between-organ subspace. We formulate the correspondence optimization objective using this generative model. We evaluate the proposed method using synthetic shape data and clinical data for articulated joint structures of the spine, foot and ankle, and hip joint.

The Modified Longitudinal Capsulotomy by Outside-In Approach in Hip Arthroscopy for Femoroplasty and Acetabular Labrum Repair-A Cohort Study

Hip arthroscopy is difficult to perform due to the limited arthroscopic view. To solve this problem, the capsulotomy is an important technique. However, the existing capsulotomy approaches were not perfect in the surgical practice. Thus, this study aimed to propose a modified longitudinal capsulotomy by outside-in approach and demonstrate its feasibility and efficacy in arthroscopic femoroplasty and acetabular labrum repair. A retrospective cohort study was performed and twenty-two postoperative patients who underwent hip arthroscopy in our hospital from January 2019 to December 2021 were involved in this study. The patients (14 females and 8 males) had a mean age of 38.26 ± 12.82 years old. All patients were diagnosed cam deformity and labrum tear in the operation and underwent arthroscopic femoroplasty and labrum repair by the modified longitudinal capsulotomy. The mean follow-up time was 10.4 months with a range of 6−12 months. There were no major complications, including infection, neurapraxias, hip instability or revision in any patients. The average mHHS were 74.4 ± 15.2, 78.2 ± 13.7 and 85.7 ± 14.5 in 3 months, 6 months and 12 months after surgery, respectively, which were all better than that before surgery (44.9 ± 8.6) (p < 0.05). The average VAS were 2.8 ± 1.2, 1.5 ± 0.6 and 1.2 ± 0.7 in 3 months, 6 months and 12 months after surgery, respectively, which were all lower than that before surgery (5.5 ± 2.0) (p < 0.05). The modified longitudinal capsulotomy by outside-in approach is proved to be a safe and feasible method for hip arthroscopy considering to the feasibility, efficacy and security. The arthroscopic femoroplasty and labrum repair can be performed conveniently by this approach and the patient reported outcomes after surgery were better that before surgery in short-term follow-up. This new method is promising and suggested to be widely used clinically.

Editorial Commentary: Not Yet Convinced That the Femoroacetabular Impingement Resection (Fair) Arc Measurement Provides a "Fair" Assessment of Cam Resection Principles

Hip arthroscopy has proven to be an effective surgical approach for the treatment of femoroacetabular impingement (FAI) syndrome. Studies have shown that patients typically have improved functional outcomes and high rates of return to activity following cam lesion resection and reshaping of the femoral head-neck junction. However, despite these favorable outcomes, there is still a steep and well-recognized learning curve in FAI hip arthroscopy. Although it is common dogma to consider an ideal reshaping of the femoral head-neck junction as being perfectly spherical, the ability to achieve this intraoperatively can be quite challenging. A new tool is the "femoroacetabular impingement resection (FAIR) arc," measured on a 45° Dunn lateral radiograph where a best-fit circle incorporates the region immediately inferior to the anteroinferior iliac spine, the subspine region, and lateral femoral neck base. The maximal radial distance height is then measured from the circumference of this circle to the apex of the cam lesion. This radiographic aid may assist with intraoperative estimate of appropriate cam lesion resection depth. While I tend to utilize preoperative radiographs and intra-operative neck sclerosis to determine cam resection depth, I continue to seek out other ways to effectively perform a femoral osteoplasty. While my initial attempt to utilize the FAIR index in my practice did not seem effective, I will continue to test this measurement in my patients.

Sclerotic lesions of the femoral head-neck junction for diagnosis of femoroacetabular impingement

The morphological characteristics associated with a diagnosis of femoroacetabular impingement (FAI) observed on plain radiographs can also be seen in subjects without hip joint symptoms. Therefore, the purpose of this study was to investigate whether sclerotic lesions on femoral head-neck junction (FHNJ) could be used as a supplemental diagnostic feature. A total of 128 hips from 119 patients (43 male and 76 female) diagnosed with FAI and 24 hips from 21 patients (2 male and 19 female) with other hip pathologies as control were compared in this study. Using standing frog-leg plain radiographs, the prevalence of sclerotic lesions on the FHNJ was established. Additionally, the pixel intensity (PI) of the sclerotic lesions between the FAI and the control groups were quantitatively compared. Sclerotic lesions were present in 96.1% of FAI hips (123 of 128) and only 37.5% of control hips (9 of 24) (p < 0.05). The ratio of PI in the FAI group was significantly higher (approximately 10%) than in the control group (p < 0.05). The evaluation of sclerotic lesions may be used as a supplement to aid in the diagnosis of FAI.

Arthroscopic Femoral Osteochondroplasty for Cam-type Femoroacetabular Impingement: Cortical-Cancellous Sclerotic Boundary Guides Resection Depth

Hip arthroscopy and femoral osteochondroplasty are commonly used in the treatment of femoroacetabular impingement (FAI). Determining the correct resection depth of the femoral head-neck cam lesion intraoperatively can be challenging. Both inadequate resection and over-resection may result in complications, underlying the importance of using a consistent and accurate technique when resecting and reshaping the proximal femur. Osseous resection to a depth of the subchondral cortical-cancellous bone margin in individuals with FAI has been shown to restore proximal femoral anatomy to within submillimeter differences when compared with control subjects without FAI. This bony boundary may be used as an intraoperative guide to consistently achieve appropriate resection depth. The sclerotic margin indicating the extent of the cam-type deformity can be evaluated with preoperative radiographs and recreated fluoroscopically, giving the surgeon a reliable intraoperative template. In addition, changes in clinical appearance during arthroscopy, particularly identification of the underlying trabecular structure at the cortical-cancellous border during resection, provides a visible, reliable intraoperative guide to resection depth.

Advances in FAI Imaging: a Focused Review

PURPOSE OF REVIEW

Femoroacetabular impingement (FAI) is one of the main causes of hip pain in young adults and poses clinical challenges which have placed it at the forefront of imaging and orthopedics. Diagnostic hip imaging has dramatically changed in the past years, with the arrival of new imaging techniques and the development of magnetic resonance imaging (MRI). This article reviews the current state-of-the-art clinical routine of individuals with suspected FAI, limitations, and future directions that show promise in the field of musculoskeletal research and are likely to reshape hip imaging in the coming years.

RECENT FINDINGS

The largely unknown natural disease course, especially in hips with FAI syndrome and those with asymptomatic abnormal morphologies, continues to be a problem as far as diagnosis, treatment, and prognosis are concerned. There has been a paradigm shift in recent years from bone and soft tissue morphological analysis towards the tentative development of quantitative approaches, biochemical cartilage evaluation, dynamic assessment techniques and, finally, integration of artificial intelligence (AI)/deep learning systems. Imaging, AI, and hip preserving care will continue to evolve with new problems and greater challenges. The increasing number of analytic parameters describing the hip joint, as well as new sophisticated MRI and imaging analysis, have carried practitioners beyond simplistic classifications. Reliable evidence-based guidelines, beyond differentiation into pure instability or impingement, are paramount to refine the diagnostic algorithm and define treatment indications and prognosis. Nevertheless, the boundaries of morphological, functional, and AI-aided hip assessment are gradually being pushed to new frontiers as the role of musculoskeletal imaging is rapidly evolving.

Which Two-dimensional Radiographic Measurements of Cam Femoroacetabular Impingement Best Describe the Three-dimensional Shape of the Proximal Femur?

BACKGROUND

Many two-dimensional (2-D) radiographic views are used to help diagnose cam femoroacetabular impingement (FAI), but there is little consensus as to which view or combination of views is most effective at visualizing the magnitude and extent of the cam lesion (ie, severity). Previous studies have used a single image from a sequence of CT or MR images to serve as a reference standard with which to evaluate the ability of 2-D radiographic views and associated measurements to describe the severity of the cam lesion. However, single images from CT or MRI data may fail to capture the apex of the cam lesion. Thus, it may be more appropriate to use measurements of three-dimensional (3-D) surface reconstructions from CT or MRI data to serve as an anatomic reference standard when evaluating radiographic views and associated measurements used in the diagnosis of cam FAI.

QUESTIONS/PURPOSES

The purpose of this study was to use digitally reconstructed radiographs and 3-D statistical shape modeling to (1) determine the correlation between 2-D radiographic measurements of cam FAI and 3-D metrics of proximal femoral shape; and 2) identify the combination of radiographic measurements from plain film projections that were most effective at predicting the 3-D shape of the proximal femur.

METHODS

This study leveraged previously acquired CT images of the femur from a convenience sample of 37 patients (34 males; mean age, 27 years, range, 16-47 years; mean body mass index [BMI], 24.6 kg/m, range, 19.0-30.2 kg/m) diagnosed with cam FAI imaged between February 2005 and January 2016. Patients were diagnosed with cam FAI based on a culmination of clinical examinations, history of hip pain, and imaging findings. The control group consisted of 59 morphologically normal control participants (36 males; mean age, 29 years, range, 15-55 years; mean BMI, 24.4 kg/m, range, 16.3-38.6 kg/m) imaged between April 2008 and September 2014. Of these controls, 30 were cadaveric femurs and 29 were living participants. All controls were screened for evidence of femoral deformities using radiographs. In addition, living control participants had no history of hip pain or previous surgery to the hip or lower limbs. CT images were acquired for each participant and the surface of the proximal femur was segmented and reconstructed. Surfaces were input to our statistical shape modeling pipeline, which objectively calculated 3-D shape scores that described the overall shape of the entire proximal femur and of the region of the femur where the cam lesion is typically located. Digital reconstructions for eight plain film views (AP, Meyer lateral, 45° Dunn, modified 45° Dunn, frog-leg lateral, Espié frog-leg, 90° Dunn, and cross-table lateral) were generated from CT data. For each view, measurements of the α angle and head-neck offset were obtained by two researchers (intraobserver correlation coefficients of 0.80-0.94 for the α angle and 0.42-0.80 for the head-neck offset measurements). The relationships between radiographic measurements from each view and the 3-D shape scores (for the entire proximal femur and for the region specific to the cam lesion) were assessed with linear correlation. Additionally, partial least squares regression was used to determine which combination of views and measurements was the most effective at predicting 3-D shape scores.

RESULTS

Three-dimensional shape scores were most strongly correlated with α angle on the cross-table view when considering the entire proximal femur (r = -0.568; p < 0.001) and on the Meyer lateral view when considering the region of the cam lesion (r = -0.669; p < 0.001). Partial least squares regression demonstrated that measurements from the Meyer lateral and 90° Dunn radiographs produced the optimized regression model for predicting shape scores for the proximal femur (R = 0.405, root mean squared error of prediction [RMSEP] = 1.549) and the region of the cam lesion (R = 0.525, RMSEP = 1.150). Interestingly, views with larger differences in the α angle and head-neck offset between control and cam FAI groups did not have the strongest correlations with 3-D shape.

CONCLUSIONS

Considered together, radiographic measurements from the Meyer lateral and 90° Dunn views provided the most effective predictions of 3-D shape of the proximal femur and the region of the cam lesion as determined using shape modeling metrics.

CLINICAL RELEVANCE

Our results suggest that clinicians should consider using the Meyer lateral and 90° Dunn views to evaluate patients in whom cam FAI is suspected. However, the α angle and head-neck offset measurements from these and other plain film views could describe no more than half of the overall variation in the shape of the proximal femur and cam lesion. Thus, caution should be exercised when evaluating femoral head anatomy using the α angle and head-neck offset measurements from plain film radiographs. Given these findings, we believe there is merit in pursuing research that aims to develop the framework necessary to integrate statistical shape modeling into clinical evaluation, because this could aid in the diagnosis of cam FAI.

There Is a Significant Discrepancy Between "Big Data" Database and Original Research Publications on Hip Arthroscopy Outcomes: A Systematic Review

PURPOSE

The purpose of this study was to compare (1) major complication, (2) revision, and (3) conversion to arthroplasty rates following hip arthroscopy between database studies and original research peer-reviewed publications.

METHODS

A systematic review was performed using PRISMA guidelines. PubMed, SCOPUS, SportDiscus, and Cochrane Central Register of Controlled Trials were searched for studies that investigated major complication (dislocation, femoral neck fracture, avascular necrosis, fluid extravasation, septic arthritis, death), revision, and hip arthroplasty conversion rates following hip arthroscopy. Major complication, revision, and conversion to hip arthroplasty rates were compared between original research (single- or multicenter therapeutic studies) and database (insurance database using ICD-9/10 and/or current procedural terminology coding terminology) publishing studies.

RESULTS

Two hundred seven studies (201 original research publications [15,780 subjects; 54% female] and 6 database studies [20,825 subjects; 60% female]) were analyzed (mean age, 38.2 ± 11.6 years old; mean follow-up, 2.7 ± 2.9 years). The database studies had a significantly higher age (40.6 + 2.8 vs 35.4 ± 11.6), body mass index (27.4 ± 5.6 vs 24.9 ± 3.1), percentage of females (60.1% vs 53.8%), and longer follow-up (3.1 ± 1.6 vs 2.7 ± 3.0) compared with original research (P < .0001 for all). Ninety-seven (0.6%) major complications occurred in the individual studies, and 95 (0.8%) major complications occurred in the database studies (P = .029; relative risk [RR], 1.3). There was a significantly higher rate of femoral neck fracture (0.24% vs 0.03%; P < .0001; RR, 8.0), and hip dislocation (0.17% vs 0.06%; P = .023; RR, 2.2) in the database studies. Reoperations occurred at a significantly higher rate in the database studies (11.1% vs 7.3%; P < .001; RR, 1.5). There was a significantly higher rate of conversion to arthroplasty in the database studies (8.0% vs 3.7%; P < .001; RR, 2.2).

CONCLUSIONS

Database studies report significantly increased major complication, revision, and conversion to hip arthroplasty rates compared with original research investigations of hip arthroscopy outcomes.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I-IV studies.