Histological and molecular characterization of the femoral attachment of the human ligamentum capitis femoris

Multicenter Outcomes After Hip Arthroscopy: Comparative Analysis of Patients Undergoing Concomitant Labral Repair and Ligamentum Teres Debridement Versus Isolated Labral Repair

Background:

Increased attention has been directed toward the ligamentum teres (LT) and its association with acetabular coverage, labral pathology, and hip microinstability; however, few studies have evaluated whether LT pathology influences the rate of clinically significant outcome improvement after hip arthroscopy.

Purpose:

To determine if patients with femoroacetabular impingement syndrome (FAIS) undergoing labral repair and concomitant LT debridement achieve outcomes similar to patients without LT pathology undergoing labral repair.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

We conducted a retrospective review of a prospectively maintained multicenter database for hip arthroscopy. Included were patients with FAIS who underwent primary labral repair and who had preoperative and minimum 2-year postoperative outcome scores. Patients diagnosed with concomitant partial LT tear were identified and matched 1:3 according to age, sex, and body mass index (BMI) to patients without LT pathology. The following clinical outcomes were compared between groups: modified Harris Hip Score, Hip Outcome Score–Activities of Daily Living, Hip Outcome Score–Sport Subscale, International Hip Outcome Tool, and visual analog scale for pain and satisfaction. Achievement of the minimal clinically important difference and patient acceptable symptomatic state was also compared between groups.

Results:

This study included 124 patients with FAIS with labral tear and concomitant partial LT tear and 372 patients with labral tear and no LT pathology. The age, BMI, and sex of the matched cohort were 38.0 ± 12.0 years (mean ± SD), 24.3 ± 3.6 kg/m2, and 62.0% female, respectively. No significant difference in age, BMI, sex, workers’ compensation status, or duration of pain was observed at baseline. Analysis of radiographic parameters indicated that patients who underwent isolated labral repair had a lower preoperative Tönnis angle (4.8° ± 4.4° vs 6.3° ± 5.4°; P = .006). There were no significant differences between groups on any pre- or postoperative outcome measure, and there were no significant differences in the proportion of patients who achieved the minimal clinically important difference or patient acceptable symptomatic state on any outcome measure.

Conclusion:

Patients with labral tear and concomitant partial LT tear experienced similar preoperative scores and achieved similar outcomes as patients with isolated labral tears after hip arthroscopy.

All About the Ligamentum Teres: From Biomechanical Role to Surgical Reconstruction

Intriguing anatomists and surgeons for centuries, the exact function and biomechanical significance of the ligamentum teres (LT) remains incompletely understood. The LT, also described as the ligamentum femoris capitis, is an intra-articular extrasynovial ligament extending from the cotyloid fossa of the acetabulum to the fovea on the femoral head. Some studies have described it as a vestigial structure in the adult hip. More recent biomechanical studies, however, along with histological and anatomical studies, have suggested the LT to have an important function in proprioception, nociception, and as a secondary stabilizer of the hip joint. The advent and increased utilization of hip arthroscopy to treat hip pathology over the past two decades has ignited a renewed interest in the role of the LT, as well as techniques and indications for management of pathology. In the constellation of intra-articular pain generators of the hip, LT injuries have historically been difficult to diagnose through physical examination or advanced imaging. Numerous classification systems have been proposed based on arthroscopic appearance, and for most cases, conservative management is adequate. In patients undergoing hip arthroscopy, LT débridement usually suffices, although in cases of persistent pain and severe instability, reconstruction of the ligament may be indicated. Multiple methods for reconstruction have been described, with the greatest variation in the method of acetabular fixation of the graft. Future research should focus on clarifying the role of the LT, appropriate surgical indications for reconstruction, and optimization of graft fixation within the acetabulum.

CLINICAL RELEVANCE of the LIGAMENTUM TERES: A LITERATURE REVIEW

Background

The ligamentum teres (LT) continues to be a structure of debate and interest. Previously thought of as a vestigial structure, an awareness of LT pathology and its potential importance has increased with the expansion of hip arthroscopy.

Purpose

To provide a comprehensive literature synthesis on the LT and provide clinicians with the most current research regarding the LT and its anatomical features, functional relevance, prevalence of injury, risk factors for injury, clinical presentation, and treatment for pathology.

Methods

A systematic literature search was conducted using Medline/PubMed, CINAHL/EBSCO, and Cochrane/Wiley databases/platforms using the following search terms: ligament, ligament teres, hip, femur, femoral head, round ligament.

Results

This search yielded 1284 articles of which 44 met the inclusion/exclusion criteria and contributed to this manuscript. Information on the LT was summarized into the following areas: anatomy, function, injury prevalence, risk factors, mechanism of injury, duration of symptoms, clinical presentation (symptoms, range of motion, functional limitations, special testing), imaging, and treatment.

Conclusions

The results of this review supported the following: 1) the LT has a function in restraining hip rotation range of motion; 2) the prevalence of LT pathology in any given population may be largely dependent on the severity of bony deformity (either femoroacetabular impingement(FAI) or dyplasia) and activity level; 3) older age and acetabular bony deformity (either FAI or dyplasia) are risk factors for generalized LT pathology; 4) unique signs and symptoms are difficult to identify because LT pathology rarely occurs in isolation and is likely the end-stage consequence of other hip pathology; 5) the presence of LT pathology may negatively affect an individual's ability to function; and 6) surgical debridement is recommend for pain relief of partial LT tears with reconstruction possible for complete LT tears when complaints of instability are noted.

Level of Evidence

3.

Neurovascular structures of the ligament of the head of femur

The ligament of the head of femur (LHF), or ligamentum teres, is believed to provide blood supply to the head of femur and mechanical stability to the hip joint. But these functions in the adult are often debated. The existence and distribution of neurovascular structures within the ligament are not widely documented. This study examined the blood vessels and nervous tissue within the LHF to determine whether the ligament may have a vascular and proprioceptive function at the hip joint. Histological sections from the LHF from 10 embalmed hips (six female, four male; mean age 80.4 ± 8.7 years) were cut at three levels: the foveal attachment, mid-length and its base where it attaches to the transverse acetabular ligament. Sections were stained with haematoxylin and eosin to study general tissue architecture or with von Willebrand factor and neurofilament to identify blood vessels and nervous tissue, respectively. The proportion of the ligament's cross-sectional area occupied by blood vessels was expressed as a vascularity index (VI). Nerve endings within the ligament were identified and morphologically classified. Comparisons between the VI at the three levels, or between the tissue layers of the ligament, were made using 95% confidence intervals; statistical significance was set P < 0.05. The ligament tissue comprised three distinct layers: a synovial lining with cuboidal cells, a sub-synovial zone formed of loose connective tissue and the ligament proper composed of dense collagen bundles. Patent blood vessels and nerve fibres were present both in the sub-synovial zone and the ligament proper; Pacinian corpuscles and free nerve endings were found scattered only in the sub-synovial zone. The VI of the ligament proper at the fovea was significantly higher than its middle (P = 0.01) and basal levels (P = 0.04); it was also higher than that of the sub-synovial layer (P = 0.04). The LHF has three histologically distinct zones, and blood vessels and nerves are distributed both in the sub-synovial layer and ligament proper. Higher vascularity within the ligament proper at its foveal insertion suggests a possible nutritive role of the LHF to the adult head of femur. The presence of nerves and nerve receptors indicates the ligament is involved in the perception of pain and proprioception, thereby contributing to mechanical stability of the joint.

The role of the ligamentum teres in the adult hip: redundant or relevant? A review

The ligamentum teres (LT) has traditionally been described as a redundant structure with no contribution to hip biomechanics or function. There has been renewed interest in the LT as a source of hip pathology due to the high prevalence of LT pathology observed at the time of hip arthroscopy. The LT acts a secondary stabilizer to supplement the work of the capsular ligaments and works in a sling-like manner to prevent subluxation of the hip at the extremes of motion. The presence of free nerve endings within the LT indicates a definite role in pain generation, with the LT undergoing various mechanical and histological adaptations to hip pathology.

Optical anisotropy reveals molecular order in a mouse enthesis

Entheses are specialized biological structures that functionally anchor tendons to bones. The complexity, mechanical characteristics and properties of the entheses, particularly those related to exercise, mechanical load and pathologies, have been extensively analyzed; however, the macromolecular organization of the enthesis fibers, as assessed by polarization microscopy, has not yet been investigated. Morphological and optical anisotropy characteristics, such as birefringence, linear dichroism (LD) and differential interference contrast (DIC-PLM) properties, are thus analyzed in this study of a healthy adult mouse calcaneal tendon-bone enthesis. The molecular and supramolecular order of collagen and GAGs was determined for the collagen bundles of this enthesis. Based on a birefringence plot pattern as well as on metachromasy and linear dichroism after toluidine blue staining at pH 4.0, a similarity between the calcaneal tendon-bone enthesis and cartilage during ossification may be assumed. This similarity is assumed to favor the adequacy of this enthesis to support a compressive load. Considering that the collagen-proteoglycan complexes and the enthesis fibers themselves have a chiral nature, these structures could be acting via reciprocal signaling with the cellular environment of the enthesis.

Age-related decrease of the phosphorus content in the ligamentum capitis femoris of monkeys

To elucidate compositional changes of the ligament with aging, the authors investigated age-related changes of elements in the ligamentum capitis femoris (LCF) of monkeys with a wide range of ages by direct chemical analysis. Used rhesus and Japanese monkeys consisted of 9 males and 22 females, ranging in age from newborn to 31 years (average age = 10.4 ± 10.9 years). After incineration with nitric acid and perchloric acid, element contents were determined by inductively coupled plasma-atomic emission spectrometry. It was found that the P content decreased significantly in the LCFs of monkeys with aging, but other six element contents, Ca, S, Mg, Zn, Fe, and Na, did not change significantly with aging. Assuming that the P content indicated the active cell density and the S content indicated the protein amount, an age-related change of the mass ratio of P/S was examined in the LCFs. The mass ratio of P/S decreased significantly in the LCFs in childhood. Regarding the relationships among elements, significant direct correlations were found among the Ca, P, S, and Mg contents in the LCFs. It was suggested that the active cell density of the connective tissue cells might decrease significantly in the LCF in childhood.