Anatomical study of the synovial plicae of the hip joint

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.

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.

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.

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.

Magnetic resonance imaging of hip joint cartilage and labrum

Hip joint instability and impingement are the most common biomechanical risk factors that put the hip joint at risk to develop premature osteoarthritis. Several surgical procedures like periacetabular osteotomy for hip dysplasia or hip arthroscopy or safe surgical hip dislocation for femoroacetabular impingement aim at restoring the hip anatomy. However, the success of joint preserving surgical procedures is limited by the amount of pre-existing cartilage damage. Biochemically sensitive MRI techniques like delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) might help to monitor the effect of surgical or non-surgical procedures in the effort to halt or even reverse joint damage.

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.

MR imaging of the hip: normal anatomic variants and imaging pitfalls

MR imaging of the hip is one of the most common musculoskeletal MR imaging studies performed today to assess for occult fractures, acetabular labral tears, hyaline cartilage loss, and musculotendinous injuries. Several developmental variations are seen in the hip, which can be mistaken for disease or potentially even contribute to the development of a pathologic condition. As in any imaging study, it is important to be cognizant of these variations as well as associated findings that help distinguish between true abnormality and developmental variation when interpreting an MR image of the hip. This article describes the numerous variants of the hip that are frequently seen on arthrographic and nonarthrographic MR imaging examinations.

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

OBJECTIVE

The appearance and distribution of the intra-articular plicae of the hip have been addressed in few reports in the anatomic and radiological literature. This study aims to determine the prevalence of visible synovial hip plicae using MR arthrography and to measure the association of visible synovial hip plicae with MR arthrographic diagnosis of labral tears, femoroacetabular impingement, and osteoarthritis.

MATERIALS AND METHODS

Following institutional review board approval, 63 direct MR arthrographic examinations of the hip in 61 patients with a clinical history of hip pain were retrospectively reviewed by two experienced musculoskeletal radiologists in consensus. The following variables were measured using a binary system (0 = absent; 1 = present): labral plica, neck plica, ligamental plica, labral tear, femoroacetabular impingement, and osteoarthritis. The surgical reports and arthroscopic images of 10 patients were reviewed. Statistical analysis was performed using the Fisher's exact test.

RESULTS

In all 63 cases at least one plica was visualized on MR-arthrographic images. Labral, neck, and ligamental plicae were found with a prevalence of 76, 97, and 78%, respectively. There was no statistically significant association between the presence of labral tears, femoroacetabular impingement, and osteoarthritis among patients with visible labral, neck, and ligamental plicae. The prevalence of labral tears, femoroacetabular impingement, and osteoarthritis in our patient population was 79, 28, and 28%, respectively. The presence of intra-articular plicae was the only MR-arthrographic finding in 5 of our 63 symptomatic cases.

CONCLUSION

Visible labral, neck, and/or ligamental plicae are highly prevalent on MR-arthrographic images of the hip performed in the setting of hip pain. There was no statistically significant association between the presence of labral tears, femoroacetabular impingement, and osteoarthritis and visible labral, neck, and ligamental plicae.

Symptomatic hip plica: MR arthrographic and arthroscopic correlation

Two cases of unilateral hip pain are reported in which MR arthrography demonstrated a prominent band medial to the ligamentum teres, running in the AP direction, consistent with a hip plica. Both patients underwent hip arthroscopy with resection of the band. No labral tear or additional intra-articular pathological features was identified in either case. Both patients became asymptomatic following surgery and have remained such. The pathology report demonstrated the specimens to be a synovial band with fibroconnective tissue. This is the first MR arthrographic report of the identification and resection of a symptomatic hip plica. The symptomatic plica may represent an alternative diagnosis for mechanical hip pain.

Magnetic resonance arthrography

Magnetic resonance arthrography is widely used throughout the world for joint imaging. It extends the capabilities of conventional MR imaging because contrast solution distends the joint capsule, outlines intraarticular structures, and extends into soft tissue tears and defects. MR arthrography exploits the natural advantages gained from a joint effusion and can be performed on any joint.

MRI appearance of the pectinofoveal fold

OBJECTIVE

The pectinofoveal fold is an intraarticular structure of the hip that has had only limited study in the clinical and anatomic literature. This fold may resemble a hip plica; however, symptomatic hip plicae are now being recognized and treated at hip arthroscopy. We wished to determine the frequency and appearance of the pectinofoveal fold on hip MR arthrography. By defining the variations in its appearance, the normal pectinofoveal fold can be distinguished from pathologic hip plicae.

MATERIALS AND METHODS

One hundred fifty-two hip MR arthrography examinations of patients who subsequently underwent hip arthroscopy were retrospectively reviewed. Each MR examination was reviewed for the presence of a pectinofoveal fold. If present, the fold was measured in the anteroposterior, mediolateral, and superior-inferior dimensions; evaluated for smooth or irregular contour; and evaluated for a femoral or capsular site of insertion.

RESULTS

The pectinofoveal fold was visualized on hip MR arthrograms in 144 of the 152 (95%) patients and visualized at hip arthroscopy in 150 of the 152 (99%) patients. The average thickness of the fold was 2.6 mm (range, 1-13 mm) in the mediolateral dimension and 17 mm (range, 1-32 mm) in the anteroposterior dimension. The average length of the fold in the superior-inferior dimension was 23.3 mm (range, 7-44 mm). The pectinofoveal fold had a smooth contour in 75 of the 144 (52%) patients with examinations that showed the fold and an irregular contour in 69 of 144 (48%) patients. The fold was found to insert onto the capsule in 108 of 144 (75%) patients and onto the femur in the remaining 36.

CONCLUSION

The pectinofoveal fold should almost always be visualized at MR arthrography. The fold can have various appearances and attachment sites, and these normal variations should not be mistaken for fold abnormalities. These findings should be useful in distinguishing this normal structure from normal and pathologic plicae.

Arthroscopic treatment of a symptomatic hip plica

Synovial plicae are detected most readily by diagnostic arthroscopy. As arthroscopic techniques are applied more frequently to various joints, it should be expected that the diagnosis of plica syndrome will become more common. The authors present a case of symptomatic plica in the hip of a competitive runner, who was treated with arthroscopic resection.