The Everted Acetabular Labrum: Patho-anatomy, Magnetic Resonance Imaging and Arthroscopic Findings of a Native Variant

The Windshield Wiper Sign Is an Instability-Related Osteochondral Defect of the Anterolateral Femoral Head

PURPOSE

To investigate a radiographic sign believed to be indicative of hip instability and acetabular suction seal disruption in the native hip, coined the "windshield wiper" (WSW) sign.

METHODS

A retrospective review was performed for patients who underwent periacetabular osteotomy (PAO) with the senior author between March 2021 and September 2023. A WSW sign was identified on plain films as a concave or flat osteochondral defect on the anterolateral femoral head extending medial to the head-neck junction with resultant loss of femoral head sphericity in the native hip. Every patient underwent a standardized series of radiographs, as well as computed tomography and magnetic resonance imaging. All patients underwent arthroscopy before PAO to address intra-articular pathology and other indicated procedures. The osteochondral defect and resultant suction seal disruption were verified during arthroscopy. These patients were then compared with a control group of arthroscopically treated hips without hip instability.

RESULTS

Of 250 patients reviewed, a total of 19 hips in 17 patients (prevalence of 7.6%) demonstrated radiographic evidence of the WSW sign. All patients with a WSW sign presented with symptomatic clinical hip instability requiring a PAO. The mean patient age was 31.2 years, with a mean lateral center-edge angle (LCEA) of 14.3°. There were 13 hips (68.4%) with dysplasia, 4 (21.1%) with borderline dysplasia, and 2 (10.5%) with a normal LCEA. All patients with a WSW sign and LCEA ≥ 20° displayed significant femoral antetorsion abnormalities. All arthroscopic videos and images demonstrated a compromised suction seal. Of the 50 control group hips reviewed, the WSW sign was not identified.

CONCLUSIONS

The WSW sign is an uncommon radiographic finding in patients with hip instability. When identified, it can be predictive of substantial instability, especially in cases which are otherwise considered borderline dysplasia or normal based on LCEA.

LEVEL OF EVIDENCE

Level III, retrospective comparative case control study.

MR Imaging Evaluation of Hip Dysplasia in the Young Adult

Hip dysplasia in the young adult population is a significant contributing factor in the development of early osteoarthritis. Diagnosis and treatment planning relies on a comprehensive imaging assessment of the hip joint morphology to better detect and characterize disease. This article discusses the various diagnostic markers of hip dysplasia in the adult population on radiography, computed tomography, and MR imaging.

The Principles of Hip Joint Preservation

The three primary factors involved in preservation of the hip joint include femoroacetabular impingement (FAI), hip dysplasia/instability, and femoral torsion abnormalities. Each of these factors affects the health of the acetabular labrum and femoroacetabular cartilage. The appropriate surgical treatments for each of these factors include arthroscopic or open femoroplasty/acetabuloplasty for FAI, periacetabular osteotomy for hip dysplasia/instability, and derotational femoral osteotomy for femoral torsion abnormalities. When evaluating patients with prearthritic hip conditions, orthopaedic surgeons should be aware of the various factors involved in hip joint preservation and, if surgery is indicated, the surgeon should be sure to address all factors that need surgical treatment rather than focusing on the commonly diagnosed issue or visible injury, for example, a labral tear. If any of these factors is ignored, the hip joint may not thrive. The purpose of this review was to explain the importance of the most common factors involved in hip joint preservation and the appropriate surgical treatments for pathology in these factors.

Bibliometric analysis of the acetabular labrum

The acetabular labrum (AL) plays a crucial role in the normal physiological functioning of the hip joint. This study aims to present an overview of the current status and research hotspots concerning the AL and to explore the field from a bibliometric perspective. A total of 1918 AL-related records published between January 1, 2000 and November 8, 2023 were gathered from the Web of Science Core Collection database. By utilizing tools such as HisCite, CiteSpace, VOSviewer, and the R package "bibliometrix," the regions, institutions, journals, authors, and keywords were analyzed to predict the latest trends in AL research. Global research interest and publication output related to this topic continues to escalate. The United States leads in international collaborations, number of publications, and citation frequency, underscoring its preeminent position in this field. The American Hip Institute emerged as the most prolific institution, making the greatest contribution to publications. Notably, Arthroscopy and the American Journal of Sports Medicine are the 2 most popular journals in this domain, accounting for 13.29% and 10.1% of publications, respectively, and were also found to be the most co-cited journals. Amongst authors, Benjamin G. Domb leads with 160 articles (8.35%), while Marc J. Philippon is the most frequently cited author. The keyword co-occurrence network showed 3 hot clusters, including "AL," "femoral acetabular impingement (FAI)," and "osteoarthritis." In addition, "survivorship," "FAI," and "patient-reported outcomes" were identified as trending topics for future exploration. This study represents the first comprehensive bibliometric analysis, summarizing the present state and future trends in AL research. The findings serve as a valuable resource for scholars, offering practical insights into key information within the field and identifying potential research frontiers and emerging directions in the near future.

The Everted Acetabular Labrum: Outcomes of Surgical Management

BACKGROUND

An everted acetabular labrum (EL) is a pathologic variant in which the labrum is flipped to the capsular side of the acetabular rim. An iatrogenic EL is a known complication of a poorly executed labral repair, and a recent study described the native acetabular EL.

PURPOSE

To analyze surgical outcomes after advancement or reconstruction of an EL in a native hip.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This was a multicenter retrospective review of prospectively collected data on primary hip arthroscopic surgeries performed between 2013 and 2023. An EL was identified arthroscopically as a labrum-femoral head gap while off traction in the native hip. All patients with EL who were analyzed in this study underwent arthroscopic labral repair and advancement or labral augmentation or reconstruction. Patients with hip dysplasia also underwent periacetabular osteotomy with or without a derotational femoral osteotomy. Patient-reported outcomes (PROs) were assessed using the 12-item International Hip Outcome Tool (iHOT-12) and the Nonarthritic Hip Score. PROs were obtained preoperatively and up to 24 months after surgery. PROs were compared with those of a case-matched control cohort in a 1:2 ratio. Only patients with PROs available at ≥1 year postoperatively were included in the outcome analysis.

RESULTS

A total of 111 patients (129 hips) with EL during the study period were identified, with PROs available in 96 hips. The mean age of patients with EL was 30.5 years, and women made up 87% of the cohort. Of the 129 hips with an EL, an isolated diagnosis of an EL was present in 11.6% of hips. Deficient acetabular coverage (lateral center-edge angle <25°) was seen in 40.6% of EL hips. No difference was seen in iHOT-12 scores between EL and control groups at 12- or 24-month follow-up (P = .18 and .94, respectively). Patients with EL reported a significant improvement of PROs at latest follow-up (P < .001 for iHOT-12 and Nonarthritic Hip Score).

CONCLUSION

Surgical management of a native EL with restoration of the labral seal on the femoral head and correction of concomitant pathologies resulted in significant clinical improvement, with postoperative outcome scores comparable to those of patients without an EL. These findings provide evidence supporting surgical intervention for a native EL.

Magnetic Resonance Imaging Approximates Labral Width at the 9-, 12-, and 3-O'Clock Positions in the Setting of Revision Hip Arthroscopy

PURPOSE

To compare preoperative magnetic resonance imaging (MRI) and intraoperative measurements of labral width and determine whether MRI can reliably predict labral width in the setting of revision surgery.

METHODS

Patients who underwent revision hip arthroscopy with labral repair performed by a single surgeon from January 2008 to December 2015 were identified retrospectively from a prospectively collected database. The width of the labrum was measured intraoperatively at the time of surgery. Two orthopaedic surgeons performed labral width measurements on MRI scans at 3 standardized locations using the clock-face method. Interobserver and intraobserver reliabilities were calculated, and comparisons between intraoperatively measured labral widths and MRI measurements were performed.

RESULTS

Fifty-eight patients who underwent revision hip arthroscopy were enrolled in the study. The average labral width measurements at the 3-, 12-, and 9-o'clock positions were 7.4 mm (standard deviation [SD], 1.2 mm), 7.5 mm (SD, 1.4 mm), and 6.6 mm (SD, 1.2 mm), respectively, on MRI compared with 6.7 mm (SD, 2.1 mm), 6.5 mm (SD, 2.5 mm), and 7.0 mm (SD, 1.9 mm), respectively, when measured intraoperatively. The average intraoperative measurements were smaller than the MRI measurements at the 3-o'clock (P = .03) and 12-o'clock (P = .01) positions. The inter-rater intraclass correlation coefficients between the 2 surgeons exhibited good agreement (0.612) at the 3-o'clock position, fair agreement (0.498) at the 12-o'clock position, and poor agreement (0.171) at the 9-o'clock position. The positive predictive values of the MRI measurements were 72% at the 3-o'clock position, 68% at the 12-o'clock position, and 88% at the 9-o'clock position for identifying a labral width of 6 mm or greater.

CONCLUSIONS

The results of this study show that MRI-measured labral width and actual labral width measured at the time of revision arthroscopy are usually within 1 mm of each other.

LEVEL OF EVIDENCE

Level II, diagnostic study investigating diagnostic test.

Imaging of Anatomical Variants Around the Hip

Considering the current widespread use of imaging as an integral part of managing hip pain, variable hip geometries and anatomical variants are increasingly being detected. These variants are commonly found in the acetabulum and proximal femur, as well as the surrounding capsule-labral tissues. The morphology of specific anatomical spaces confined by the proximal femur and the bony pelvis may also vary significantly among individuals. Familiarity with the spectrum of imaging appearances of the hip is necessary to identify variant hip morphologies with or without potential clinical relevance and reduce an unnecessary work-up and overdiagnosis. We describe anatomical variations and variable morphologies of the bony structures comprising the hip joint and the soft tissues, around the hip. The potential clinical significance of these findings is further analyzed in conjunction with the patient's profile.

Radiographic Parameters of Adult Hip Dysplasia

As knowledge about the origin and morphologic characteristics of hip pain in the young adult has evolved, so too has the clinician's ability to assess for various pathologies of the hip on radiographs, magnetic resonance imaging (MRI)/magnetic resonance arthrography (MRA), and computed tomography (CT). Because there is no algorithm at this time directly indicating what to do in more subtle hip morphologies, such as microinstability and borderline hip dysplasia (BHD), a skilled hip preservation specialist must use multiple imaging sources and know how to interpret them correctly. Imaging parameters used in the workup for hip dysplasia and BHD include the lateral center-edge angle, Tönnis angle, iliofemoral line, and presence of an upsloping lateral sourcil or everted labrum, among many others. The purpose of this narrative review was to detail various established criteria and parameters on anteroposterior pelvis plain radiographs, MRI/MRA, and CT that assist in defining the nature and severity of instability present in a dysplastic hip, thereby aiding in the development of patient-specific surgical treatment plans.

Editorial Commentary: Revision Hip Arthroscopy in Patients Older Than 40 Has a Higher Rate of Conversion to Total Hip Arthroplasty-Get It Right the First Time, and the Second

Getting hip arthroscopy right the first time is critical to the overall patient outcome. This involves proper patient selection, with avoidance of arthritis, understanding the pathology of each hip, and properly executing the surgery. Care must be taken to restore labral function and preserve capsule function while accurately resecting pincer or cam impingement. While good results can be achieved in patients older than 40 years of age, an opportunity exists for improved optimization of clinical outcomes. Moreover, revision hip arthroscopy in patients older than 40 years of age has a higher rate of conversion to total hip arthroplasty. Again, get it right the first time, and carefully consider indications for revision hip arthroscopy in patients older than 40 years of age if there is a second time.

Arthroscopy Honors Award-Winning Articles and Authors: Our Annual Research Awards

With genuine gratitude to the AANA Education Foundation for their unstinting support, it is our honor to announce Arthroscopy's Annual Awards for the best Clinical Research, Basic Science Research, Resident/Fellow Research, and Systematic Reviews published in 2022, as well as the Most Downloaded and Most Cited papers published 5 years ago. And as is customary in January, our editors update their disclosures of potential conflicts of interest, as we require of authors, and we update our masthead to introduce new members of our Editorial Board and Social Media Board.

Editorial Commentary: Hip Primary Labral Repair Versus Reconstruction: Equally Successful Outcomes Can Be Achieved Based on Proper Indications

One of the core principles of hip arthroscopy is preservation of the acetabular labrum. Compromise of the biomechanical function of the labrum underlies a significant symptom source in patients undergoing hip preservation surgery. As surgical techniques continue to improve and evolve beyond labral repair, increased use of advanced arthroscopic procedures like segmental and circumferential reconstruction shed further light on the optimal labral intervention. In the revision setting, labral deficiency warrants labral reconstruction or augmentation. Both segmental and circumferential techniques may significantly improve patient-reported outcomes. However, in the primary setting, controversy exists not necessarily in the surgical technique, but more in the indications to perform which specific labral intervention. Reasonable indications for primary labral reconstruction include a calcified or ossified labrum, irreparable labral tissue, and hypotrophy of the labrum (less than 2-3 mm) with a proven deficient suction seal without resistance to axial distraction. Short-term multicenter studies demonstrate similar success rates between primary labral reconstruction and repair using validated patient-report outcome scores. Mid- and long-term clinical and economic investigations comparing labral reconstruction and repair are needed to determine the role of primary reconstruction in modern arthroscopic hip preservation surgery.

Editorial Commentary: The Everted Acetabular Labrum. It Is Not Just a Small Labrum

Everted, hypoplastic acetabular labra represent a variant of acetabular rim development. It is important to be able to recognize this pathology on magnetic resonance imaging and at the time of hip arthroscopy. Proper intraoperative identification of this variant that does not make contact with the femoral head is critical to being able to successfully restore this contact, often through labral advancement, acetabuloplasty of the abnormal rim development, and occasionally labral augmentation. A broad awareness among hip arthroscopy surgeons of this topic will lead to improved clinical outcomes after hip arthroscopy for a challenging cohort.