Synovial plicae of the hip: evaluation using MR arthrography in patients with hip pain

History of the hip joint pectineofoveal fold

Although Josias Weitbrecht described the retinacula of the hip joint in his 1742 Syndesmologia, the anatomist Cesare Amantini of Perugia specifically studied the medial retinacula he referred to as the pectineofoveal fold in a late 19th-century monograph. This particular synovial fold stretches from the lesser trochanter to the osteocartilaginous junction of the femoral head along a virtual line connecting the lesser trochanter and the fovea for the ligament of the head. Although mentioned by some anatomists and radiologists, and despite its possible involvement in specific hip joint pathologies (fractures, impingements), it is surprising that Amantini's pectineofoveal fold remains ignored by most anatomy and clinical anatomy books. This study aims to verify if Cesare Amantini effectively drew attention to this synovial fold for the first time and coined the term "pectineofoveal fold," as well as determine whether most classical textbooks (i.e., published from 1890 to 2017) acknowledge the discovery and include it in the description of the hip joint. A possible evolutionary link between this synovial fold and the ambiens and pectineus muscles exists and should be discussed.

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.

[Direct MR Arthrography of the Hip: Diagnosis and Pitfalls of Acetabular Labral Lesions]

Tearing of the acetabular labrum is a common cause of chronic hip pain. MR arthrography (MRA) of the hip is the imaging procedure of choice for the evaluation of acetabular labrum. Familiarity with the various imaging findings of MRA of the hip allows recognition of normal variants and differentiation from true pathologic conditions. This article comprehensively reviews the technical aspects and interpretation of MRA of the hip. The appearances of normal and abnormal labra in MRA are discussed. Potential pitfalls in labral tear interpretation, such as sulci around the hip, normal variants of the labrum and plicae, and osseocartilaginous and soft tissue lesions identified on MRA of the hip are also described.

Hip preservation surgery and the acetabular fossa

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells.

Cite this article: Bone Joint Res 2020;9(12):857–869.

Clinical Anatomy of the Ligament of the Head of Femur

The ligament of the head of femur (LHF) has gained clinical attention recently and is reported to contribute to hip stability. This study explores its morphology and morphometry, information that may help inform surgical decision making. Gross anatomical dissections were undertaken on 229 embalmed hips from European (n = 105) and Thai (n = 124) adult cadavers to examine LHF anatomy. Ligament morphometry was statistically compared at different sites, between sexes and sides. The origin of ligamental arteries and absence of the ligament were documented. The LHF was pyramidal or quadrangular in shape. Sub-synovial fibrous bands originated from the transverse acetabular ligament, edges of the acetabular notch, and acetabular floor; less frequently from the hip joint capsule. Distally, the ligament flattened and converged onto the fovea capitis. The ligament was 22.3 ± 4.4 mm long and was significantly wider (P = 0.001) and thicker (P = 0.0003) at the fovea, compared to its mid-zone. Branches of the obturator artery entered the acetabular foramen inferomedially and penetrated the middle third of the LHF. Blood vessels ran within the LHF and appeared to enter the fovea. The ligament was absent in 2.8% of Thai hips and there were no significant sex or side differences in ligament dimensions. The morphology of the LHF is complex. While individual variation was apparent, blood vessels were seen in the distal ligament. Precise information on LHF morphometry and attachment sites will help inform appropriate graft dimensions and choice of fixation sites necessary for ligament reconstruction. Clin. Anat., 2018. © 2018 Wiley Periodicals, Inc. Clin. Anat., 2018. © 2018 Wiley Periodicals, Inc.

Usefulness of MR arthrography of the hip with leg traction in the evaluation of ligamentum teres injuries

PURPOSE

To retrospectively evaluate the diagnostic accuracy of magnetic resonance (MR) arthrography of the hip with leg traction in the evaluation of ligamentum teres lesions and to evaluate whether there is increased articular distraction, possibly indicating secondary instability, in hips with ligamentum teres injuries.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained for this retrospective study. MR arthrograms of the hip with leg traction of 184 consecutive patients, including 108 men (mean age, 32.6 years; range, 19-53 years) and 76 women (mean age, 38.5 years; range, 18-56 years), who underwent hip arthroscopy were assessed for the presence of ligamentum teres lesions. The MR arthrographic findings were independently assessed by two radiologists who were blinded to the arthroscopic results. The inclusion criteria stipulated no previous surgery, arthroscopy within 1 month after MR arthrography, and availability of a detailed surgical report with ligamentum teres findings. The arthroscopy findings served as the reference standard. Sensitivity, specificity, accuracy, and K statistics for interobserver and intraobserver agreement were calculated.

RESULTS

At arthroscopy, 32 ligamentum teres injuries were found. The ligamentum teres was normal in 152 (82.6%) patients and had suffered low-grade partial tears in 15 (8.1%) patients, high-grade partial tears in 10 (5.4%) patients, and complete ruptures in 7 (3.8%) patients. MR arthrography with axial traction demonstrated moderate sensitivity and high specificity for both low-grade (62/93%) and high-grade (66/96%) partial tears. Grouping low- and high-grade partial tears increased the diagnostic performance of MR arthrography, yielding a sensitivity of 87% and a specificity of 95%. For complete ligamentum teres tears, MR arthrography with leg traction demonstrated high sensitivity (92%) and specificity (98%). Articular distraction was significantly increased in patients with complete ruptures of the ligamentum teres (p = 0.001).

CONCLUSION

MR arthrography with leg traction offers accurate diagnosis of ligamentum teres injuries. Patients with complete tears of the ligamentum teres exhibit increased articular distraction that may indicate secondary hip instability.

Magnetic Resonance Imaging of the Hip

Hip pain is common in all age groups, and osteoarthritis of this joint is an increasingly recognized problem particularly in aging populations. One of the primary goals in the diagnostic evaluation in patients with hip pain is to identify and correct pathologies that could progress to osteoarthritis. Magnetic resonance imaging (MRI) has become an important noninvasive method for characterizing hip anatomy and pathology in these patients. Improvements in MRI hardware and techniques have allowed high spatial and contrast resolution imaging to detect subtle abnormalities, such as acetabular labral and articular cartilage injuries, which often contribute to patient symptoms. Newer MRI techniques, such as delayed gadolinium-enhanced MRI of cartilage and T2 mapping, can give insight into the biochemical structure of tissues such as the articular cartilage. In turn, these can allow quantitative assessment and enable imagers to more directly compare the findings of patients at earlier stages of disease. It is important to understand the fundamental principles of various MRI techniques and their limitations to know when these techniques can best be applied. In addition, understanding of normal hip anatomy and common anatomic variants is useful for being able to accurately detect and localize areas of pathology and to prevent misinterpreting normal structures as diseased. The aims of this work were to briefly review normal hip anatomy and common anatomic variants seen on routine MRI examination, to discuss principles often used in high-resolution hip MRI and newer techniques for biochemical evaluation, and to examine several intra-articular pathologic conditions of the hip joint that are of current clinical interest.

Use of MR arthrography in detecting tears of the ligamentum teres with arthroscopic correlation

OBJECTIVE

To demonstrate the normal appearance of the ligamentum teres on MR arthrography (MRA) and evaluate the accuracy of MRA in detecting ligamentum teres tears with arthroscopic correlation.

MATERIALS AND METHODS

Institutional Review Board approval was obtained with a waiver for informed consent because of the retrospective study design. A total of 165 cases in 159 patients (111 females, 48 males; mean age 41 ± 12 years) who underwent both MRA and hip arthroscopy were evaluated for appearance of the ligamentum teres, including the size, number of bundles, and ligamentum teres tears. Marrow edema of the fovea capitis adjacent to the ligamentum teres insertion and the presence of hip plicae were also recorded.

RESULTS

The mean thickness and length of the ligamentum teres were 3.5 ± 1.5 mm and 25.2 ± 3.8 mm, respectively. Sensitivity, specificity, positive and negative predictive value, and accuracy of MRA for the detection of ligamentum teres tears were 78, 97, 74, 97, and 95%, respectively.

CONCLUSION

MRA is an accurate method to evaluate the normal morphology and to detect tears of the ligamentum teres.

MRI of the hip for the evaluation of femoroacetabular impingement; past, present, and future

The concept of femoroacetabular impingement (FAI) has, in a relatively short time, come to the forefront of orthopedic imaging. In just a few short years MRI findings that were in the past ascribed to degenerative change, normal variation, or other pathologies must now be described and included in radiology reports, as they have been shown, or are suspected to be related to, FAI. Crucial questions have come up in this time, including: what is the relationship of bony morphology to subsequent cartilage and labral damage, and most importantly, how is this morphology related to the development of osteoarthritis? In this review, we attempt to place a historical perspective on the controversy, provide guidelines for interpretation of MRI examinations of patients with suspected FAI, and offer a glimpse into the future of MRI of this complex condition.

Hip anatomic variants that may mimic pathologic entities on MRI: nonlabral variants

OBJECTIVE

The hip has several anatomic variants that may be mistaken for pathologic abnormalities. The radiologist needs to be able to distinguish these variants from true abnormalities. In this review, we present nonlabral variants of the hip that can be seen on MRI.

CONCLUSION

The hip has multiple anatomic variants that may mimic disease on hip MRI. Like labral variants, nonlabral variants can be confused for true abnormalities.

Femoroacetabular impingement: role of imaging

The femoroacetabular impingement (FAI) is an impingement characterized by repetitive abutment between the femur and the acetabular rim during hip motion due to loss of joint clearance (Imam and Khanduja in Int Orthop 35(10):1427-1435, 2011; James et al. in AJR Am J Roentgenol 187(6):1412-1419, 2006). Femoroacetabular impingement (FAI) can be classified as either cam or pincer type, and it can be differentiated on the basis of a predominance of either a femoral or an acetabular abnormality (Pfirrmann et al. in Radiology 244(2):626, 2007; Ganz et al. in Clin Orthop Relat Res 466(2):264-272, 2008). In cases of cam FAI, the nonspherical shape of the femoral head at the femoral head-neck junction and reduced depth of the femoral waist lead to abutment of the femoral head-neck junction against the acetabular rim. In cases of pincer FAI, acetabular overcoverage limits the range of motion and leads to a conflict between the acetabulum and the femur. The most important role of preoperative MR evaluation in patients affected by FAI is the accurate assessment of the damage's extension.

MR imaging of normal hip anatomy

Understanding normal anatomy of the hip is important for diagnosing its pathology. MR arthrography is more sensitive for the detection of intra-articular pathology than noncontrast MR imaging. Important elements of the osseous structures on MR imaging include the alignment and the marrow. Acetabular ossicles may be present. Normal variations involving the cartilage include the supra-acetabular fossa and the stellate lesion. Important muscles of the hip are the sartorius, rectus femoris, iliopsoas, gluteus minimus and medius, adductors, and hamstrings. The iliofemoral, ischiofemoral, and pubofemoral ligaments represent thickenings of the joint capsule that reinforce and stabilize the hip joint. Normal variations in the labrum include labral sulcus and absent labrum. The largest nerves in the hip and thigh are the sciatic nerve, the femoral nerve, and the obturator nerve.

The retinacula of Weitbrecht in the adult hip

PURPOSE

The aim of the study was to describe the retinacula of Weitbrecht in the adult hip.

MATERIALS AND METHODS

Specimens were obtained from 30 adult hips, average age was 77 years (age range 43-91 years), 8 specimens were fixed by formalin solution and 22 were not fixed.

RESULTS

Anterior retinaculum was found in 40% of examined specimens. The anterior retinaculum was in 83% of cases formed by a flat plate and in 17% by two to three parallel bands. Medial retinaculum was present constantly, extending from the attachment of the articular capsule at the base of the lesser trochanter towards the fovea capitis femoris as far as the edge of the articular cartilage. Typically, the retinaculum had the form of an inverted "T". Of the three retinacula, the medial one was the strongest. Lateral retinaculum was also present constantly. In 89% of cases, it had the form of a quadrilateral plate adjacent to the upper surface of the femoral neck. This plate arises from the insertion of the articular capsule on the upper part of the femoral neck at the base of the greater trochanter close to the trochanteric fossa. The plate extended along the upper edge of the femoral neck as far as the edge of the articular cartilage. Microscopic examination revealed fine blood vessels running through the retinacula.

CONCLUSION

Lateral retinaculum and medial retinaculum are constant synovial plicae in terms of both occurrence and localization. Nutritive arteries run through both the plicae to supply the femoral head.