Effect of estrogen on cellular metabolism of the human anterior cruciate ligament

Relaxin as a treatment for musculoskeletal fibrosis: What we know and future directions

Fibrotic changes in musculoskeletal diseases arise from the abnormal buildup of fibrotic tissue around the joints, leading to limited mobility, compromised joint function, and diminished quality of life. Relaxin (RLX) attenuates fibrosis by accelerating collagen degradation and inhibiting excessive extracellular matrix (ECM) production. Further, RLX disrupts myofibroblast activation by modulating the TGF-β/Smads signaling pathways, which reduces connective tissue fibrosis. However, the mechanisms and effects of RLX in musculoskeletal pathologies are emerging as increasing research focuses on relaxin's impact on skin, ligaments, tendons, cartilage, joint capsules, connective tissues, and muscles. This review delineates the actions of relaxin within the musculoskeletal system and the challenges to its clinical application. Relaxin shows significant potential in both in vivo and in vitro studies for broadly managing musculoskeletal fibrosis; however, challenges such as short biological half-life and sex-specific responses may pose hurdles for clinical use.

Sex diferences in serum and synovial fluid C-reactive protein concentration in healthy dogs

Differences between serum C-reactive protein (SCRP) and synovial fluid C-reactive protein (SFCRP) concentrations in healthy animals may be influenced by the sex of the individual and associated with various factors. The objective of this study was to evaluate the disparities in SCRP and SFCRP concentrations between females and males, as well as within each sex. Sixty healthy dogs (N = 60), comprising both sexes, were enrolled in the study. Peripheral blood and knee synovial fluid samples were collected for SCRP and SFCRP analysis, respectively. Serum C-reactive protein (SCRP) and SFCRP concentrations were measured, with mean of 9.61 ± 4.96 mg/L for SCRP and 1.28 ± 3.05 mg/L for SFCRP. Notably, SFCRP concentrations were consistently lower than SCRP concentrations in both sexes. Statistically significant differences were observed between sexes for both SCRP (P = 0.021) and SFCRP (P = 0.007). Further analysis within females revealed statistically significant differences between SCRP and SFCRP concentrations (P = 0.002), whereas in males, such differences were not significant (P = 0.175). Additionally, weak correlations were found between SCRP and SFCRP concentrations for both sexes (females r = 0.07; males r = 0.29). Joint capsule thickness was assessed using ultrasonography, revealing thicker joint capsules in males. A robust positive association was noted between joint capsule thickness and the SFCRP concentration in both sexes. These findings offer valuable insights into the dynamics of CRP in the context of joint health in male and female patients, elucidating the underlying pathological mechanisms of joint disease and inflammation. Overall, this underscores the importance of considering sex-specific factors in the assessment and management of joint health, as well as in the design and interpretation of studies involving SFCRP concentrations.

Balance test results in different hormonal statuses of the menstruation cycle. Are females more susceptible to lower extremities injuries on different days of their menstruation cycles?

BACKGROUND

The Star Excursion Balance Test (SEBT) and its modification(mSEBT) as dynamic tests have been shown to have high reliability and validity for the prediction of lower extremities injuries including ACL ones. No previous study has compared mSEBT performance measures in different hormonal statuses of the menstrual cycle in naturally menstruating women. So aim of the study was comparison of mSEBT performance measures in days of the menstruation cycle with the peak of estrogen and progesterone hormones in naturally menstruating women.

METHODS

After a pilot study for estimation of sample size, mSEBT performance measures in a sample of 18 healthy women with regular menstrual cycles were compared two times in their cycles, first in the peak of estrogen (mid-cycle) and second in time of peak of progesterone (one week later). The test was performed 2 times using either the right or left leg as the stance and reach limb.

FINDINGS

No significant difference between days with estrogen and progesterone peaks with right or left reach limb was seen for the percentage of reach in any direction or the composite reach on the mSEBT performance.

CONCLUSION

It seems that there is the same risk for lower extremities injuries in estradiol and progesterone peak days of normal menstruating women.

The impact of the menstrual cycle on orthopaedic sports injuries in female athletes

There is a disparity in sport-related injuries between sexes, with females sustaining non-contact musculoskeletal injuries at a higher rate. Anterior cruciate ligament ruptures are between two and eight times more common than in males, and females also have a higher incidence of ankle sprains, patellofemoral pain, and bone stress injuries. The sequelae of such injuries can be devastating to an athlete, resulting in time out of sport, surgery, and the early onset of osteoarthritis. It is important to identify the causes of this disparity and introduce prevention programmes to reduce the incidence of these injuries. A natural difference reflects the effect of reproductive hormones in females, which have receptors in certain musculoskeletal tissues. Relaxin increases ligamentous laxity. Oestrogen decreases the synthesis of collagen and progesterone does the opposite. Insufficient diet and intensive training can lead to menstrual irregularities, which are common in female athletes and result in injury, whereas oral contraception may have a protective effect against certain injuries. It is important for coaches, physiotherapists, nutritionists, doctors, and athletes to be aware of these issues and to implement preventive measures. This annotation explores the relationship between the menstrual cycle and orthopaedic sports injuries in pre-menopausal females, and proposes recommendations to mitigate the risk of sustaining these injuries.

Menstrual Cycle and Sport Injuries: A Systematic Review

The presence of female athletes has only increased in recent years, as has the incidence of injuries in female sports activities. These injuries are conditioned by multiple factors, including hormonal agents. It is estimated that the menstrual cycle may be related to the predisposition to suffer an injury. However, a causal relationship has not yet been established. The aim of this study was to analyse the relationship between the menstrual cycle and injuries in female sports practice. A systematic search of the scientific literature available in PubMed, Medline, Scopus, Web of Science, and Sport Discus was carried out in January 2022. With 138 articles, only eight studies were found that met the selection criteria for this study. Peak estradiol is associated with increased laxity, strength, and poor use of neuromuscular control. Thus, the ovulatory phase is associated with an increased risk of injury. In conclusion, it seems that hormonal fluctuations throughout the menstrual cycle alter values such as laxity, strength, body temperature, and neuromuscular control, among others. This fact causes women to constantly adapt to hormonal variations, which exposes them to a higher risk of injury.

Knee Laxity in the Menstrual Cycle after Anterior Cruciate Ligament Reconstruction: A Case Series

The aim of this study was to compare anterior knee laxity (AKL), genu recurvatum (GR), and muscle stiffness between reconstructed and contralateral sides in females who underwent anterior cruciate ligament (ACL) reconstruction during early follicular and ovulatory phases. AKL was measured as an anterior displacement of the tibia using a KS measure. GR was measured as the range of motion of knee hyperextension using a hyperextension apparatus. Muscle stiffness was measured for semitendinosus (ST) and biceps femoris long head (BF) using a MyotonPRO. The study investigated eighteen knees in nine females (Age, 20.4 ± 1.5 years; BMI, 21.5 ± 1.5) with normal menstrual cycles at least 1 year after reconstruction using hamstring autograft. E2 (Estradiol) concentration did not differ between the two phases, but AKL on the reconstructed side was lower during the ovulatory phase (8.3 [5.9-9.3] mm) than during the early follicular phase (9.4 [7.3-9.7] mm) (p = 0.044, r = 0.756), whereas there was no significant difference between the two phases on the contralateral side. AKL side-to-side difference, GR, and muscle stiffness (ST and BF) on both sides did not differ in either phase. These results indicate that AKL may behave differently on the reconstructed and contralateral sides during the menstrual cycle.

Relationship between Changes in Foot Arch and Sex Differences during the Menstrual Cycle

This study investigated the relationship between changes in foot characteristics and sex differences during the menstrual cycle in healthy male and female university students. We examined 10 female subjects and 14 male subjects. The menstrual cycle was divided into the three phases: the early follicular phase, ovulatory phase, and luteal phase via basal body temperature, an ovulation kit, and salivary estradiol and progesterone concentration measurements. Foot characteristics required for the calculation of the arch height index (AHI) were measured using a three-dimensional foot scanner under conditions of 10% and 50% weight-bearing loads. Arch height at 50% of foot length and truncated foot length were measured, and AHI was calculated by dividing arch height by truncated foot length. Arch height flexibility (AHF) was defined as the change in arch height from 10% weight-bearing load to 50% weight-bearing load. AHI was significantly lower in females than in males in the early follicular and ovulatory phases but did not differ significantly between males and females in each phase. AHF did not differ significantly between males and females in each phase. AHI and AHF showed no periodic fluctuation, suggesting that sex differences in AHF may be absent.

Sexual Dimorphisms in Anterior Cruciate Ligament Injury: A Current Concepts Review

Background:

Although most anterior cruciate ligament (ACL) injuries occur in male athletes, female athletes are consistently observed to be at a higher risk for sports-specific ACL injury.

Purpose:

To provide a thorough review of what is known about the sexual dimorphisms in ACL injury to guide treatment and prevention strategies and future research.

Study Design:

Narrative review.

Methods:

We conducted a comprehensive literature search for ACL-related studies published between January 1982 and September 2017 to identify pertinent studies regarding ACL injury epidemiology, prevention strategies, treatment outcomes, and dimorphisms. By performing a broad ACL injury search, we initially identified 11,453 articles. After applying additional qualifiers, we retained articles if they were published in English after 1980 and focused on sex-specific differences in any of 8 different topics: sex-specific reporting, difference in sports, selective training, hormonal effects, genetics, neuromuscular and kinematic control, anatomic differences, and outcomes.

Results:

A total of 122 articles met the inclusion criteria. In sum, the literature review indicated that female athletes are at significantly higher risk for ACL injuries than are their male counterparts, but the exact reasons for this were not clear. Initial studies focused on intrinsic differences between the sexes, whereas recent studies have shifted to focus on extrinsic factors to explain the increased risk. It is likely both intrinsic and extrinsic factors contribute to this increased risk, but further study is needed. In addition to female patients having an increased risk for ACL injuries, they are less likely than are male patients to undergo reconstructive surgery, and they experience worse postsurgical outcomes. Despite this, reconstructive surgery remains the gold standard when knee stability, return to sports, and high functional outcome scores are the goal, but further research is needed to determine why there is disparity in surgical rates and what surgical techniques optimize postsurgical outcomes for female patients.

Conclusion:

Male athletes often predominated the research concerning ACL injury and treatment, and although sex-specific reporting is progressing, it has historically been deficient. ACL injuries, prevention techniques, and ACL reconstruction require further research to maximize the health potential of at-risk female athletes.

Anabolic Androgenic Steroids in Orthopaedic Surgery: Current Concepts and Clinical Applications

Despite the well-documented effects of testosterone and its synthetic derivatives—collectively termed anabolic androgenic steroids (AASs)—on the musculoskeletal system, the therapeutic use of these agents has received limited investigation within the field of orthopaedic surgery. In the last 2 decades, preclinical and clinical research has started to identify promising applications of the short-term use of AASs in the perioperative period. There is evidence to suggest that AASs may improve postoperative recovery after anterior cruciate ligament reconstruction and total joint arthroplasty. In addition, AASs may augment the biological healing environment in specific clinical scenarios including muscle injury, fracture repair, and rotator cuff repair. Current literature fails to present strong evidence for or against the use of AASs in orthopaedics, but there is continuous research on this topic. The purpose of this study was to provide a comprehensive overview of the current status of AAS applications in orthopaedic surgery, with an emphasis on preclinical data, clinical studies, and future directions.

The effect of the menstrual cycle on collagen metabolism, growth hormones and strength in young physically active women

This study aimed to investigate the effect of the menstrual cycle on strength, functioning of the GH/IGF-1 axis and collagen metabolism in physically active women. Twenty-four physically active and eumenorrheic women volunteered to participate in the study (body mass 60.3 ± 9.18 kg, age 21.8 ± 0.92 years). Blood samples were obtained between the 5th and 8th days (the follicular phase) and between the 19th and 22th days (the luteal phase) of the menstrual cycle to determine sex steroid concentrations (follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), oestradiol (E2) and progesterone (P)). Also insulin-like growth factor 1 (IGF-1) and collagen metabolism markers (synthesis (PICP) and breakdown (ICTP)) and maximum voluntary contraction (MVC) were measured. MVC was higher in the luteal phase 164.1 ± 34.77 [N m] (F(1.23) = 4.59; p = 0.043). The recorded collagen synthesis marker (PICP = 296.4 ± 35.61 [ng/ml]) was at the upper level of the reference range (30-300), with an insignificant decrease in the luteal phase (Z = 1.612; p = 0.107) and a significant increase in oestradiol concentration (Z = 4.286; p = 0.0001). The marker of collagen breakdown (ICTP = 4.16 ± 0.68 [μg/l]) was reduced by 6.8% in the same phase (Z = 1.764; p = 0.137). The variability of physical abilities (MVC) during the menstrual cycle showed that menstrual status should be taken into account in determination of the training loads. Increasing the load in the luteal phase seems to be favoured by a beneficial change in collagen metabolism (lower synthesis decrease, lower breakdown increase) observed in physically active women.

Comparison of anterior knee laxity, stiffness, genu recurvatum, and general joint laxity in the late follicular phase and the ovulatory phase of the menstrual cycle

BACKGROUND

One risk factor for anterior cruciate ligament (ACL) injury may be fluctuations in female hormones. This study examined variability in joint laxity, as a risk factor for ACL injury, during the menstrual cycle.

METHODS

Subjects were 15 female university students with regular menstrual cycles. We measured estradiol (E2) concentration, anterior knee laxity (AKL), stiffness, genu recurvatum (GR), and general joint laxity (GJL) during the late follicular and ovulatory phases. AKL was measured as anterior tibial displacement of the femur after application of 44-, 89-, and 133-N loads on the tibia. Stiffness was calculated as Δforce/Δdisplacement at loads of 44-89 N and between 89 and 133 N. GR was measured prone, with the base of the patella distal to the edge of the bed. The University of Tokyo joint laxity test was used to evaluate GJL.

RESULTS

E2 concentration was significantly higher in the ovulatory phase than in the late follicular phase (p = 0.018), AKL and stiffness did not differ significantly between phases, and GR and GJL were significantly higher in the ovulatory phase than in the late follicular phase (p = 0.011, 0.031).

CONCLUSION

These findings suggest that E2 concentrations may affect GR and GJL during the menstrual cycle.

Relationship Between Anterior Knee Laxity and General Joint Laxity During the Menstrual Cycle

Background

Anterior cruciate ligament (ACL) injury has been reported to have a higher incidence in women than in men.

Purpose/Hypothesis

The purpose was to examine the relationship of anterior knee laxity (AKL), stiffness, and generalized joint laxity (GJL) with respect to the menstrual cycle. It was hypothesized that AKL and GJL would increase during the ovulation phase, when estrogen levels are high.

Study Design

Descriptive laboratory study.

Methods

A total of 15 female university students aged >20 years and with normal menstrual cycles were evaluated. AKL was measured as anterior tibial displacement of the femur after application of 44-, 89-, and 133-N loads to the tibia. Stiffness was calculated as Δ force/Δ displacement at loads between 44 and 89 N and between 89 and 133 N. The University of Tokyo joint laxity test was used for evaluation of GJL. The participants' menstrual cycle was divided into the early follicular, late follicular, ovulation, and luteal phases using the basal body temperature method and an ovulation kit; AKL and GJL were measured once during each phase. Participants were also stratified according to the presence or absence of genu recurvatum (GR).

Results

There was no significant difference in AKL, stiffness, or GJL among the menstrual phases. In the GR group, AKL values at 89 N and 133 N were significantly higher in the ovulation phase than in the early follicular phase (P = .025 and P =.018, respectively); there were no significant differences in AKL among the phases in the non-GR group. In addition, the GR group in the ovulation phase had significantly higher AKL values at 44 N, 89 N, and 133 N compared with the non-GR group (P = .013, P = .005, and P = .010, respectively). There were no significant differences in GJL among the phases in the GR or non-GR groups.

Conclusion

Women with GR may have increased AKL in the ovulation phase when compared with the early follicular phase, which may be a risk factor for ACL injury.

Clinical Relevance

The results of this study suggest that the ovulation phase may be related to the greater incidence of ACL injuries in women.

The Measurement of Stiffness for Major Muscles with Shear Wave Elastography and Myoton: A Quantitative Analysis Study

The present study was performed to assess the relationship between hand-held myotonometer MyotonPRO and shear wave elastography (SWE) measurements of lower limb muscle stiffness during resting and active voluntary contraction. Forty healthy young adults, (20 males and 20 females) participated in the study. The stiffness of each subject’s rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) was measured repeatedly by MyotonPRO and SWE. Moderate to strong correlations between the two methods’ measurements were found for both resting and active voluntary contraction. (r = 0.416–0.669, p < 0.05; r = 0.398–0.594, p < 0.05, respectively). Muscle stiffness at rest was significantly lower compared contraction in all four muscles measured by both methods (p < 0.05). Intra-rater reliabilities were generally lower when measurements were taken during contraction. Additionally, when compared by gender, muscle stiffness measured by MyotonPRO was significantly higher at rest in men compared to women, except for the TA. However, a significant difference was found in TA muscle stiffness by gender when measured with SWE. When muscles were contracted, all muscles showed significantly higher stiffness in men compared to women. There were moderate to good correlations in muscle stiffness between measurements of SWE and MyotonPRO at rest and during active voluntary contraction. Additionally, both instruments showed good intra-rater reliability.

Greater Muscle Stiffness during Contraction at Menstruation as Measured by Shear-Wave Elastography

It is important to measure mechanical properties of muscle, since muscle stiffness is an important component of stabilizing or controlling joint stability. The levels of sex hormones especially estrogen vary over the phase of the menstrual cycle and impact the mechanical properties of soft tissue such as muscle, tendon, and ligaments due to the presence of 17-β estradiol receptor in human connective tissues. Recently, shear-wave elastography (SWE), based on ultrasound imaging, has been used as an accurate technique for visualizing and assessing tissue stiffness. The purpose of this study was to compare the muscle stiffness at rest and during contraction condition between the early follicular phase (menstruation) and ovulation in young women, measured using SWE. Thirty-seven young women with regular menstrual cycles completed this study throughout one full menstrual cycle. Stiffness of lower limb muscles such as the rectus femoris, biceps femoris, tibialis anterior, and medial gastrocnemius was measured at resting and during contraction conditions using SWE during menstruation and ovulation. All muscles showed significantly greater stiffness during the menstruation than ovulation when muscles were actively contracted (P < 0.05), whereas no significant differences in muscle stiffness at rest were noted across phase of the menstrual cycle. These significant findings suggest that muscular factors are changed with estradiol fluctuations; muscles are less stiff during ovulation where the levels of estradiol peak when muscles in a contraction condition. As muscle stiffness is an important part of joint stability, these differences should be recognized to prevent the risk of musculoskeletal injuries.

Orthopaedic Care of the Transgender Patient

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A transgender person is defined as one whose gender identity is incongruent with their biological sex assigned at birth. This highly marginalized population numbers over 1.4 million individuals in the U.S.; this prevalence skews more heavily toward younger generations and is expected to increase considerably in the future.

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Gender-affirming hormone therapy (GAHT) has physiologic effects on numerous aspects of the patient's health that are pertinent to the orthopaedic surgeon, including bone health, fracture risk, and perioperative risks such as venous thromboembolism and infection.

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Language and accurate pronoun usage toward transgender patients can have a profound effect on a patient's experience and on both objective and subjective outcomes.

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Gaps in research concerning orthopaedic care of the transgender patient are substantial. Specific areas for further study include the effects of GAHT on fracture risk and healing, outcome disparities and care access across multiple subspecialties, and establishment of perioperative management guidelines.

The Menstrual Cycle May Affect Anterior Knee Laxity and the Rate of Anterior Cruciate Ligament Rupture: A Systematic Review and Meta-Analysis

BACKGROUND

Women have a higher risk of anterior cruciate ligament (ACL) tears than men, the causes of which are multifactorial. The menstrual cycle and its hormonal effect on the knee may contribute to knee laxity and ACL injury. This work reviewed published studies examining the effects of the phases of the menstrual cycle on anterior knee laxity and the rate of ACL tears.

METHODS

A systematic review with meta-analysis and meta-regression was performed. Studies with data comparing the menstrual cycle phase with ACL injury or anterior knee laxity were included for analysis. Data with regard to patient demographic characteristics, anterior knee laxity, ACL injury, and menstrual cycle phases were extracted from the included studies.

RESULTS

In this study, 1,308 search results yielded 396 articles for review, of which 28 met inclusion criteria. Nineteen studies of knee laxity with 573 combined subjects demonstrated a mean increase in laxity (and standard deviation) of 0.40 ± 0.29 mm in the ovulatory phase compared with the follicular phase and a mean increase in laxity of 0.21 ± 0.21 mm in the luteal phase compared with the follicular phase. Nine studies examining ACL tears with 2,519 combined subjects demonstrated a decreased relative risk (RR) of an ACL tear in the luteal phase compared with the follicular and ovulatory phases combined (RR, 0.72 [95% confidence interval, 0.56 to 0.89]). There were no differences in ACL tear risk between any of the other phases.

CONCLUSIONS

An increased risk of an ACL tear does not appear to be associated with periods of increased laxity in this meta-analysis. Although this suggests that hormonal effects on an ACL tear may not be directly related to increases in knee laxity, the methodologic heterogeneity between published studies limits the conclusions that can be drawn and warrants further investigation.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Sensitivity of the fasciae to sex hormone levels: Modulation of collagen-I, collagen-III and fibrillin production

Although it is now recognized that women suffer from myofascial pain to a greater extent than men, and that the muscular fasciae can respond to hormonal stimuli, thanks to the expression of sex hormone receptors, how the fasciae can modify their structure under hormonal stimulation is not clear. In this work, an immunocytochemical analysis of collagen-I, collagen-III and fibrillin were carried out on fibroblasts isolated from human fascia lata after in vitro treatment with various levels of sex hormones β-estradiol and/or relaxin-1, according to the phases of a woman's period (follicular, periovulatory, luteal, post-menopausal phases and pregnancy). This study demonstrates for the first time that fascial cells can modulate the production of some components of the extracellular matrix according to hormone levels, when treated with β-estradiol: collagen-I falls from 6% of positivity in the follicular phase to 1.9 in the periovulatory phase. However, after the addition of relaxin-1 to the cell culture, the production of extracellular matrix decreased and remained at the same level (1.7% of collagen-I, at both follicular and periovulatory levels of hormones). These results confirm the antifibrotic function of relaxin-1, thanks to its ability to reduce matrix synthesis. They are also a first step in our understanding of how some hormonal dysfunctions in women can cause a dysregulation of extracellular matrix production in fasciae.

Effect of Estrogen on Musculoskeletal Performance and Injury Risk

Estrogen has a dramatic effect on musculoskeletal function. Beyond the known relationship between estrogen and bone, it directly affects the structure and function of other musculoskeletal tissues such as muscle, tendon, and ligament. In these other musculoskeletal tissues, estrogen improves muscle mass and strength, and increases the collagen content of connective tissues. However, unlike bone and muscle where estrogen improves function, in tendons and ligaments estrogen decreases stiffness, and this directly affects performance and injury rates. High estrogen levels can decrease power and performance and make women more prone for catastrophic ligament injury. The goal of the current work is to review the research that forms the basis of our understanding how estrogen affects muscle, tendon, and ligament and how hormonal manipulation can be used to optimize performance and promote female participation in an active lifestyle at any age.

Menstrual cycle variation and gender difference in muscle stiffness of triceps surae

BACKGROUND

We aimed to investigate the menstrual cycle variation and the gender difference of the triceps surae muscle stiffness and passive stiffness of the ankle joint.

METHODS

The subjects of the study included 12 healthy young women and 12 healthy young men. Shear elastic moduli of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles were measured as an index of muscle stiffness using shear wave elastography. The passive stiffness of the ankle joint was calculated from passive torque when the ankle joint was passively dorsiflexed. Measurements were conducted in the follicular, ovulatory, and luteal phases to examine the menstrual cycle variation.

FINDINGS

There was no difference noted in the passive stiffness or triceps surae muscle stiffness for young women in the menstrual cycle. As for gender differences, passive stiffness in all menstrual phases in women was lower while the soleus muscle stiffness in women was higher, compared to that in men.

INTERPRETATION

Our findings suggest that passive stiffness and muscle stiffness did not differ in the menstrual cycle. In addition, the measured part of the soleus was more tensioned in women than in men.

The influence of ovulation on postural stability (Biodex Balance System) in young female

The purpose of this study was to examine the influence of ovulation (OV) on dynamic balance in young female. Thirty-two eumenorrheic healthy women participated in Biodex Balance System (BBS) test for postural stability and a limit of stability menstrual cycle. BBS was tested in the menses (MS), OV, and luteal phase (LP). The limits of stabilities (total, forward-left, forward-right, backward-left, and backward-right) were significantly higher in the OV (total, 61.44±14.77; forward-left, 67.50± 15.17; forward-right, 69.50±14.43; backward-left, 64.00±20.32; and back-ward-right, 69.06±13.59) than in the MS (total, 55.44±14.63; forward-left, 60.00±15.98; forward-right, 62.17±9.78; backward-left, 57.83±19.09; and backward-right, 57.28±13.73). Furthermore, the LP (65.11±13.79) was a significantly higher limit of stability than MS (57.28±13.73) during back-ward-right. The present study showed that estrogen negatively influences postural stability. The postural sway in limits of stabilities (total, forward-left, forward-right, backward-left, and backward-right) were significantly the greatest in the OV. Since there is a different postural stability between MS, OV, and LP, this should be taken into account when devising training programs to avoid risk factor of fall and joint injury.

Possible association of oestrogen and Cryba4 with masticatory muscle tendon-aponeurosis hyperplasia

OBJECTIVE

Masticatory muscle tendon-aponeurosis hyperplasia, which is associated with limited mouth opening, progresses very slowly from adolescence. The prevalence rates of this disease are higher among women than among men, suggesting oestrogen involvement. As parafunctional habits are frequently observed, mechanical stress is likely involved in the pathogenesis and advancement of this disease. To elucidate the pathological condition, we examined the effect of oestrogen on tenocyte function and the relationship between mechanical stress and crystallin beta A4 (Cryba4), using murine TT-D6 tenocytes.

MATERIALS AND METHODS

Cell proliferation assays, RT-PCR, real-time RT-PCR, Western blot analysis and mechanical loading experiments were performed.

RESULTS

The physiological dose of oestrogen increased the levels of scleraxis and tenomodulin in TT-D6 tenocytes. In contrast, forced expression of Cryba4 inhibited scleraxis expression in these cells. Surprisingly, oestrogen significantly promoted cell differentiation in the Cryba4-overexpressing TT-D6 tenocytes. Moreover, tensile force induced Cryba4 expression in these tendon cells.

CONCLUSION

Oestrogen and Cryba4 may be associated with the progression of masticatory muscle tendon-aponeurosis hyperplasia.

Changes in the Width of the Tibiofibular Syndesmosis Related to Lower Extremity Joint Dynamics and Neuromuscular Coordination on Drop Landing During the Menstrual Cycle

Background:

Many injuries of the lower extremities, especially the knee and ankle, occur during sports activity, and the incidence rate is higher in women than in men.

Hypothesis:

The hypothesis was that phases of the menstrual cycle affect the width of the tibiofibular syndesmosis during drop landing in healthy young women and that such changes at the tibiofibular joint also affect the dynamics and neuromuscular coordination of the lower extremities.

Study Design:

Descriptive laboratory study.

Methods:

Participants included 28 healthy young women (mean age, 21.0 ± 0.8 years). Blood samples were collected to determine plasma levels of estradiol and progesterone immediately before the performance of the task: drop landing on a single leg from a 30-cm platform. Using ultrasonography, the distance between the tibia and the distal end of the fibula, regarded as the width of the tibiofibular syndesmosis, was measured in an upright position without flexion of the ankle. The peak ground-reaction force (GRF) on landing was measured using a force platform. The time to peak GRF (Tp-GRF) was measured as the time from initial ground contact to the peak GRF. Hip, knee, and ankle joint angles during the single-leg landing were calculated using a 3-dimensional motion analysis system. Muscle activities of the lower extremities were measured using surface electromyography.

Results:

The width of the tibiofibular syndesmosis was significantly greater in the luteal phase when compared with the menstrual, follicular, and ovulation phases (by 5%-8% of control). Also, during the luteal phase, the Tp-GRF was significantly shorter than in the follicular phase (by 6%); hip internal rotation and knee valgus were significantly greater than in the menstrual phase (by 43% and 34%, respectively); knee flexion was significantly less than in the menstrual and follicular phases (by 7%-9%); ankle dorsiflection was significantly less than in the follicular phase (by 11%); ankle adduction and eversion were significantly greater than in the menstrual and follicular phases (by 26%-46%, and 27%-33%, respectively); and activation of the gluteus maximus before landing was significantly lower than in the menstrual and follicular phases (by 20%-22%).

Conclusion:

The luteal phase appears to be associated with decreased strength and laxity of the ankle as well as lower extremity muscle activity in women. The changes presumably represent a greater risk for sports injuries.

Clinical Relevance:

The results of this study suggest that the luteal phase may be related to the greater incidence of lower extremity injuries in women.

The effect of estrogen on tendon and ligament metabolism and function

Tendons and ligaments are crucial structures inside the musculoskeletal system. Still many issues in the treatment of tendon diseases and injuries have yet not been resolved sufficiently. In particular, the role of estrogen-like compound (ELC) in tendon biology has received until now little attention in modern research, despite ELC being a well-studied and important factor in the physiology of other parts of the musculoskeletal system. In this review we attempt to summarize the available information on this topic and to determine many open questions in this field.

Female hormones: do they influence muscle and tendon protein metabolism?

Due to increased longevity, women can expect to live more than one-third of their lives in a post-menopausal state, which is characterised by low circulating levels of oestrogen and progesterone. The aim of this review is to provide insights into current knowledge of the effect of female hormones (or lack of female hormones) on skeletal muscle protein turnover at rest and in response to exercise. This review is primarily based on data from human trials. Many elderly post-menopausal women experience physical disabilities and loss of independence related to sarcopenia, which reduces life quality and is associated with substantial financial costs. Resistance training and dietary optimisation can counteract or at least decelerate the degenerative ageing process, but lack of oestrogen in post-menopausal women may reduce their sensitivity to these anabolic stimuli and accelerate muscle loss. Tendons and ligaments are also affected by sex hormones, but the effect seems to differ between endogenous and exogenous female hormones. Furthermore, the effect seems to depend on the age, and as a result influence the biomechanical properties of the ligaments and tendons differentially. Based on the present knowledge oestrogen seems to play a significant role with regard to skeletal muscle protein turnover. Therefore, oestrogen/hormonal replacement therapy may counteract the degenerative changes in skeletal muscle. Nevertheless, there is a need for greater insight into the direct and indirect mechanistic effects of female hormones before any evidence-based recommendations regarding type, dose, duration and timing of hormone replacement therapy can be provided.

The Effect of Menstrual Cycle and Contraceptives on ACL Injuries and Laxity: A Systematic Review and Meta-analysis

BACKGROUND

Women are at substantially greater risk for anterior cruciate ligament (ACL) injuries than are men.

PURPOSE

To conduct a systematic review and meta-analysis of the literature to clarify the effect of the menstrual cycle and contraceptives on the laxity of and noncontact injuries to the ACL.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

Searches were conducted using MEDLINE (1946-August 2016), the Cochrane Library Database, clinical trial registries, and related reference lists. Search terms included athletic injuries, knee injuries, ligaments, joint instability, menstrual cycle, ovulation, hormones, and contraceptives. Investigators independently dually abstracted and reviewed study details and quality using predefined criteria and evaluated overall strength of evidence using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) criteria.

RESULTS

Twenty-one studies totaling 68,758 participants were included: 5 on the menstrual cycle and ACL injury, 7 on hormonal contraceptives and ACL injury, as well as 13 on menstrual cycle and ligament laxity. Four of 5 studies of women not using hormonal contraception indicated that the luteal phase was the least associated with ACL injuries. The 2 largest and highest quality studies on hormonal contraceptives suggested that hormonal contraceptives may be protective against ACL injury. Six of 12 studies on ACL laxity provided quantitative data for meta-analysis, finding significantly increased laxity during the ovulatory phase compared with the follicular phase.

CONCLUSION

The literature suggests an association between hormonal fluctuations and ACL injury. Recent studies have suggested that oral contraceptives may offer up to a 20% reduction in risk of injury. The literature on ACL injuries and the menstrual cycle has more than doubled over the past decade, permitting quantitative analysis for the first time. However, the overall strength of this evidence is low. Promising potential directions for future research include long-term observational studies with ongoing hormonal assays and large interventional trials of follicular suppression, including newer hormonal methods.

Effects of the menstrual cycle on lower-limb biomechanics, neuromuscular control, and anterior cruciate ligament injury risk: a systematic review

OBJECTIVE

Anterior cruciate ligament (ACL) injury has a devastating impact on physical and psychological disability. Rates of ACL rupture are significantly greater in females than males during the same sports. Hormonal mechanisms have been proposed but are complex and poorly understood. This systematic review evaluates the effects of menstrual cycle on: 1) lower-limb biomechanics, 2) neuromuscular control, and 3) ACL injury risk.

METHODS

The MEDLINE, CINAHL, SPORTSDiscus, Web of Science, and Google Scholar databases were searched from inception to August 2016 for studies investigating the effects of the menstrual cycle on lower-limb biomechanics, neuromuscular control, and ACL injury risk in females. Three independent reviewers assessed each paper for inclusion and two assessed for quality.

RESULTS

Seventeen studies were identified. There is strong evidence that: 1) greatest risk of ACL injury is within the pre-ovulatory phase of the menstrual cycle, and 2) females with greater ACL laxity in the pre-ovulatory phase experience greater knee valgus and greater tibial external rotation during functional activity.

CONCLUSION

Females are at greatest risk of ACL injury during the pre-ovulatory phase of the menstrual cycle through a combination of greater ACL laxity, greater knee valgus, and greater tibial external rotation during functional activity.

LEVEL OF EVIDENCE

Ib.

Expression of sex steroid hormone receptors in human skeletal muscle during the menstrual cycle

AIM

Variations in sex hormone levels during the menstrual cycle may affect neuromuscular performance and the risk of sustaining musculoskeletal injury in women. The aim of this study was to investigate mRNA and protein levels for sex steroid hormone receptors in skeletal muscle in three distinct phases of the menstrual cycle.

METHODS

Fifteen, healthy women with regular menstrual cycles participated in the study. Muscle biopsies from the vastus lateralis were obtained in three hormonally verified phases of the menstrual cycle for each individual, that is the follicular phase, the ovulatory phase and the luteal phase. mRNA and protein levels of oestrogen (ERα and ERβ), progesterone (PR) and androgen (AR) receptors were analysed.

RESULTS

There was an overall significant variation in mRNA and protein levels of ERα and PR across the menstrual cycle. mRNA and protein levels of ERα were highest in the follicular phase when oestradiol levels were low, whereas protein levels of PR were highest in the luteal phase when progesterone levels were high. mRNA levels of PR were highest in the ovulatory phase. No significant variation in AR levels was detected across the menstrual cycle. ERβ levels were very low in all three phases of the menstrual cycle.

CONCLUSION

Significant variations in mRNA and protein levels of ERα and PR were detected in skeletal muscle during three confirmed phases of the menstrual cycle. These results may have an impact on effects of muscular training and sports injuries in women.

Key components and potential benefits of a comprehensive approach to women's musculoskeletal health

Over the last 40 years there has been a significant increase in the number of female athletes, as well as a rise in musculoskeletal injuries observed in women. There is sufficient evidence from past medical research identifying various musculoskeletal injuries and conditions that more commonly affect women, such as osteoarthritis, osteoporosis, stress fractures, and anterior cruciate ligament tears. Several women's sports medicine and musculoskeletal health programs have been developed throughout the United States in an attempt to provide more tailored care to the female athlete. The goal of a comprehensive approach to women's musculoskeletal health is to create an interdisciplinary team to facilitate treatment for a variety of injuries and related conditions. This manuscript outlines the musculoskeletal conditions that commonly affect women and highlights the various etiologies of these sex disparities. We discuss the role of interdisciplinary women's musculoskeletal health and sports medicine programs, and define the potential benefits of such an approach. Future studies should focus on assessing the outcomes of multidisciplinary women's sports medicine programs as current literature in this area is lacking.

Greater Reduction of Balance as a Result of Increased Plantar Fascia Elasticity at Ovulation during the Menstrual Cycle

One of the sexual hormones, estrogen, increases elasticity of human connective tissue such as the anterior cruciate ligament during the menstrual cycle in women. In the present investigation, the plantar fascia was investigated to see if there is a difference in elasticity with the menstrual cycle. Fifteen young healthy females in the age range of 18-35 years old with a regular menstrual cycle were tested twice throughout one full menstrual cycle; once during the early follicular phases and once at ovulation. Foot length, while standing on both feet and one foot were used to assess plantar fascia elasticity, ultrasound measured plantar fascia thickness while lying and standing, and posture sway and tremor using a balance platform during 8 different balance tests were assessed to see the impact of elasticity changes. Foot length increased significantly at ovulation compared to menstruation when standing on two feet (p = 0.03) and standing on one foot (p < 0.001). There was also a significant increase in plantar fascia in thinning per kilogram weight applied to the foot at ovulation compared to menstruation (p = 0.014). Associated with this increase in elasticity at ovulation, there was a reduction in balance in the most difficult balance tasks and an increase in tremor during ovulation (p < 0.05). Plantar fascia elasticity change during the menstrual cycle might have effects on posture sway and tremor, which could have a potential risk of falling. Therefore, healthy professionals working with young female adults should recognize these physiological effects.

Does menopausal hormone therapy (MHT), exercise or a combination of both, improve pain and function in post-menopausal women with greater trochanteric pain syndrome (GTPS)? A randomised controlled trial

BACKGROUND

Greater trochanteric pain syndrome (GTPS) is pathology in the gluteus medius and minimus tendons and trochanteric bursa that causes debilitating tendon pain and dysfunction, particularly in post-menopausal women. Limited evidence in clinical studies suggests hormone changes after menopause may have a negative effect on tendon. This protocol describes a randomised controlled trial comparing the effectiveness of menopausal hormone therapy (MHT) and exercise therapy in reducing pain and dysfunction associated with GTPS in post-menopausal women.

METHOD

One hundred and sixteen post-menopausal women will be recruited and randomised to receive one of two exercise programs (sham or targeted intervention exercise) and transdermal creams (MHT cream containing oestradiol 50mcg and norethisterone acetate 140mcg or placebo cream). Interventions will be 12-weeks in duration and outcomes will be examined at baseline, 12-weeks and 52-weeks. The primary outcome measure will be the VISA-G questionnaire and secondary outcomes measures will include three hip pain and function questionnaires (Hip dysfunction and Osteoarthritis Outcome Score, Oxford Hip Score, Lateral Hip Pain questionnaire), a global change in symptom questionnaire (using a 15-point Likert scale) and a quality of life measure (AQoL-8D questionnaire). Data will be analysed using the intention to treat principle.

DISCUSSION

This study is the first randomised controlled trial to compare the effectiveness of menopausal hormone therapy therapy alone, and with the combination of exercise therapy, to treat pain and dysfunction associated with GTPS. This study has been pragmatically designed to ensure that the interventions in this study can be integrated into policy and clinical practice if found to be effective in the treatment of GTPS in post-menopausal women. If successful, there is potential for this treatment regimen to be explored in future studies of other persistent tendon conditions in the post-menopausal population.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12614001157662 Registered 31 October 2014.

Do Oral Contraceptives Alter Knee Ligament Damage with Heavy Exercise?

Hormones such as estradiol have an effect on human connective tissue, making women more susceptible to knee injuries. Indeed, women have a greater risk for non-contact injuries of anterior cruciate ligament (ACL) compared to men when participating in the same sports. The purpose of the present study was to examine the difference in ACL laxity after an eccentric exercise in the lower limbs in young healthy women between oral contraceptive pill (OCP) users and non-OCP users to see the effect of OCP on ACL laxity. Forty young healthy women participated in the experiments (25 with normal menstrual cycle and 15 with taking OCP). ACL laxity and a visual analog pain scale were measured before and after a bout of squat. OCP users had more pain than non-OCP users after heavy exercise (p < 0.001). Both groups showed a significant reduction in ACL laxity on the 2nd day after exercise (p < 0.05). While ACL laxity was always less in the OCP group, when expressed as a percent change from baseline, the ACL laxity change was similar in both groups (p > 0.05). We found that there was no statistically significant difference in ACL laxity recovery over time in response to the delayed onset muscle soreness after a bout of squat between two groups. However, health professionals working with young female adults should recognize that OCP users with less ACL laxity are at higher risk for having knee injuries because of ACL stiffness when doing exercise.

Knee Laxity Variations in the Menstrual Cycle in Female Athletes Referred to the Orthopedic Clinic

Background

Anterior cruciate ligament (ACL) rupture is the biggest concern for orthopedic surgeons who are involved in sports injuries, so most of ACL reconstruction surgeries are sports related. ACL injuries in female athletes are 2 - 8 times more common than male athletes in similar sport injuries.

Objectives

The aim of this study was to compare knee laxity changes in the menstrual cycle in female athletes referred to the orthopedic clinic of Imam Khomeini hospital in the north of Iran, Sari, 2013.

Patients and Methods

The present descriptive study was conducted on 40 female athletes that were referred to the orthopedic clinic. Hormone levels, such as estrogen and progesterone were assessed by one laboratory in 3 phases of the menstrual cycle. We used Lachman test and anterior drawer test for knee laxity rate. The descriptive statistics were calculated as indices of central distribution of bonds (x ± SD) and relative frequency distribution was used for qualitative variables.

Results

The results of the current study showed that there is no significant difference in ACL laxity in female athletes in three phases of menstrual cycle; namely menstruation time, ovulation time and mid-luteal phase.

Conclusions

Despite numerous studies and research in the field of knee laxity and effects of female hormones, many researchers do not agree about the effect of female hormones on knee laxity. The current study also reported no relationship between female hormones and knee laxity, while statistics show fundamental difference between male and female athletes.

The influence of sex hormones on anterior cruciate ligament ruptures in males

PURPOSE

The purpose of this study is to determine the difference in the concentrations of testosterone, 17-β estradiol and progesterone between male patients with and without ACL rupture, as well as the possible effect of these hormones on generalized joint laxity.

METHODS

Male subjects with non-contact knee joint injury were included in this study. Two groups were formed: the examined group, consisting of subjects with ACL rupture and the control group consisting of patients without ACL rupture. After this, the patients from these two groups were paired off on the basis of three factors, level of professional involvement in sports (including the type of sports activity), left or right side of the body and the age of the subjects. In the end, there were 29 pairs (58 subjects). The concentration of sex hormones was determined from saliva specimens with the aid of the Salimetrics enzyme immunoassay. The testing of generalized joint laxity was performed with the aid of the "laxity score" according to Beighton et al.

RESULTS

Subjects with ACL rupture have highly statistically significantly greater concentrations of testosterone (p < 0.01), statistically significantly greater concentrations of 17-β estradiol (p < 0.05), and a highly statistically significantly greater generalized joint laxity score than subjects with an intact ACL (p < 0.01).

CONCLUSION

Increased concentrations of testosterone or 17-β estradiol may be a risk factor leading to ACL rupture. Also, generalized joint laxity may be a factor leading to ACL rupture, but none of the monitored hormones can be set down as the cause of its existence. Young male athletes with higher concentrations of testosterone and greater hyperelasticity should plan preventive programs of physiotherapy for ACL preservation since they present a vulnerable group susceptible to ACL rupture.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

The influence of sex hormones on anterior cruciate ligament rupture: female study

PURPOSE

The purpose of this study was to determine the difference in the concentrations of testosterone, 17-β estradiol and progesterone between female patients with and without ACL rupture and the possible effect of these hormones on generalised joint laxity.

METHODS

Female subjects with non-contact knee joint injury were included in this study. They were divided into two groups: the examined group, consisting of female subjects with ACL rupture, and the control group, consisting of female patients without ACL rupture. In the next step, the patients from these two groups were paired off on the basis of three factors: the level of professional sports involvement (including the type of sports activity), the side of the body where the injury had occurred (left or right) and the age of the subjects. In the end, there were 12 pairs (24 subjects). The concentrations of sex hormones were established from saliva specimens with the aid of the Salimetrics enzyme immunoassay. Generalised joint laxity was tested with the aid of the "laxity score" according to Beighton, Solomon and Soskolne.

RESULTS

Female subjects with ACL rupture had significantly lower concentrations of testosterone (p < 0.01), significantly lower concentrations of 17-β estradiol (p < 0.05) and significantly lower concentrations of progesterone (p < 0.01) than female subjects with intact ACL.

CONCLUSIONS

Decreased concentrations of testosterone, 17-β estradiol or progesterone may be a risk factor leading to ACL rupture. The concentrations of these hormones do not affect generalised joint laxity. Additional research on a larger group of patients is necessary to further determine the effects of these hormones on generalised joint laxity and ACL ruptures. Young female athletes with lower concentrations of sex hormones are more prone to anterior cruciate ligament rupture which is why they need to reduce their sports activities during the pre-ovulatory phase of the menstrual cycle, when these concentrations are additionally reduced.

Estrogen inhibits lysyl oxidase and decreases mechanical function in engineered ligaments

Women are more likely to suffer an anterior cruciate ligament (ACL) rupture than men, and the incidence of ACL rupture in women rises with increasing estrogen levels. We used an engineered ligament model to determine how an acute rise in estrogen decreases the mechanical properties of ligaments. Using fibroblasts isolated from human ACLs from male or female donors, we engineered ligaments and determined that ligaments made from female ACL cells had more collagen and were equal in strength to those made from male ACL cells. We then treated engineered ligaments for 14 days with low (5 pg/ml), medium (50 pg/ml), or high (500 pg/ml) estrogen, corresponding to the range of in vivo serum estrogen concentrations and found that collagen within the grafts increased without a commensurate increase in mechanical strength. Mimicking the menstrual cycle, with 12 days of low estrogen followed by 2 days of physiologically high estrogen, resulted in a decrease in engineered ligament mechanical function with no change in the amount of collagen in the graft. The decrease in mechanical stiffness corresponded with a 61.7 and 76.9% decrease in the activity of collagen cross-linker lysyl oxidase with 24 and 48 h of high estrogen, respectively. Similarly, grafts treated with the lysyl oxidase inhibitor β-aminoproprionitrile (BAPN) for 24 h showed a significant decrease in ligament mechanical strength [control (CON) = 1.58 ± 0.06 N; BAPN = 1.06 ± 0.13 N] and stiffness (CON = 7.7 ± 0.46 MPa; BAPN = 6.1 ± 0.71 MPa) without changing overall collagen levels (CON = 396 ± 11.5 μg; BAPN = 382 ± 11.6 μg). Together, these data suggest that the rise in estrogen during the follicular phase decreases lysyl oxidase activity in our engineered ligament model and if this occurs in vivo may decrease the stiffness of ligaments and contribute to the elevated rate of ACL rupture in women.

Is the use of oral contraceptives associated with operatively treated anterior cruciate ligament injury? A case-control study from the Danish Knee Ligament Reconstruction Registry

BACKGROUND

The incidence of anterior cruciate ligament (ACL) injuries is 2 to 9 times higher in women than in men. In addition, in vitro studies have demonstrated that ACL is an estrogen target tissue, and some studies have therefore suggested a protective association between oral contraceptives (OC) and the likelihood of sustaining ACL injury.

HYPOTHESIS

There is a protective association between OC use and the likelihood of operatively treated ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

The study population included 4497 women with an operatively treated ACL injury registered in the Danish Knee Ligament Reconstruction Registry for the 2005 to 2011 period and 8858 age-matched controls with no ACL injury. The study evaluated exposure to OC use at the time of ACL injury (index date) and in the 5 previous years ("ever user") or no OC use ("never user"). Ever users were further classified as either new users (patients who redeemed their first prescription within the first year before the index date), long-term users (redeemed additional prescriptions 1 to 5 years before the index date), or recent users (redeemed their most recent prescription >1 year before the index date). Finally, a dose-response analysis of OC use was performed. Conditional logistic regression was used to calculate the relative risk (RR) with a 95% CI of sustaining an operatively treated ACL injury according to OC use.

RESULTS

The adjusted RR associating OC with ACL injury was 0.82 (95% CI, 0.75-0.90) between ever users and never users. Furthermore, there was a decreased RR of sustaining ACL injury of 0.80 (95% CI, 0.74-0.91) in long-term users and 0.81 (95% CI, 0.72-0.89) in recent users. Using OC for more than 4 years did not seem to alter the likelihood of sustaining an operatively treated ACL injury.

CONCLUSION

This population-based pharmacoepidemiological study including 13,355 women indicates that a protective association exists between OC use and the likelihood of sustaining an operatively treated ACL injury. Although this study does indicate a protective association of OC use, OC should not be used as a prophylactic measure before additional clinical studies have further clarified the biological and causal association between OC use and the likelihood of sustaining operatively treated ACL injury.

The effect of ascorbic acid and fluid flow stimulation on the mechanical properties of a tissue engineered pelvic floor repair material

Synthetic non-degradable meshes used in pelvic floor surgery can cause serious complications such as tissue erosion. A repair material composed of an autologous oral fibroblast seeded degradable polylactic acid scaffold may be a viable alternative. The aims of this study were to investigate the effects of media supplementation with additives (ascorbic acid-2-phosphate, glycolic acid and 17-β-oestradiol) on the mechanical properties of these scaffolds. Oral fibroblasts were isolated from buccal mucosa. The effects of the three additives were initially compared in two-dimensional culture to select the most promising collagen stimulating additive. Sterile electrospun scaffolds were seeded with 500,000 oral fibroblasts and fixed in 6-well plates and subjected to ascorbic acid-2-phosphate (the best performing additive) and/or mechanical stimulation. Mechanical stimulation by fluid shear stress was induced by rocking scaffolds on a platform shaker for 1 h/day for 10 of 14 days of culture. In two-dimensional culture, ascorbic acid-2-phosphate (concentrations from 0.02 mM to 0.04 M) and glycolic acid (10 µM) led to significantly greater total collagen production, but ascorbic acid-2-phosphate at 0.03 mM produced the greatest stimulation (of the order of >100%). In three-dimensional culture, mechanical stimulation alone gave non-significant increases in stiffness and strength. Ascorbic acid-2-phosphate (0.03 mM) significantly increased collagen production in the order 280% in both static and mechanically stimulated scaffolds (p < 0.0001). There was no additional effect of mechanical stimulation. Dense collagen I fibres were observed with ascorbic acid-2-phosphate supplementation. Uniaxial tensiometry showed that strength (p < 0.01) and stiffness (p <0.05) both improved significantly. A combination of ascorbic acid-2-phosphate and mechanical stimulation led to further non-signficant increases in strength and stiffness. In conclusion, a pelvic floor repair material with improved mechanical properties can be developed by supplementing culture media with ascorbic acid-2-phosphate to increase collagen I production. Future studies will assess the change in mechanical properties after implantation in an animal model.

Anterior cruciate ligament elasticity and force for flexion during the menstrual cycle

Background

A high occurrence of knee injuries have been observed in women during the menstrual cycle (MC). As a result, numerous studies have been conducted regarding knee ligament elasticity during the MC. Some researchers believe that since estrogen receptor b exists in ligaments and tendons in the knee, estrogen may modulate towards a state of laxity. However, increased tissue temperature also observed during the MC can predispose ligament and tendon laxness. Therefore, the purpose of this study was to assess in women the relationship between Estradiol (E2) serum concentrations and tissue temperature during the MC and their combined effect on knee laxity.

Material/Methods

Ten non-athletic young healthy females, 18 to 30 years of age participated in the study. E2 serum concentrations, anterior cruciate ligament (ACL) elasticity, and force to flex the knee (FFK), knee flexion-extension hysteresis (KFEH) were assessed both at ambient temperature (22°C) and after 38°C warming. Testing was performed multiple times during the participant’s MC, for one full MC.

Results

ACL elasticity was significantly higher (P<0.01) and FFK and KFEH were significantly lower (p<0.05) during ovulation when E2 levels were highest. ACL elasticity was still higher during ovulation after warming to 38°C. But, the effects of MC on FFK and KFEH were reduced by tissue warming.

Conclusions

ACL elasticity, FFK, and KFEH was affected not only by E2 but also tissue temperature. However, E2 had more impact on ACL elasticity while tissue temperature had more impact on FFK and KFEH at 38°C warming.

Differences in anterior cruciate ligament elasticity and force for knee flexion in women: oral contraceptive users versus non-oral contraceptive users

Eighty-two percent of sexually active women aged 15-44 have used oral contraceptive pills (OCP) in the United States. The OCP, an exogenous source of synthetic forms of steroid hormones, prevents ovulation. Hormone changes during the menstrual cycle (MC) are believed to have an impact on anterior cruciate ligament (ACL) laxity due to estrogen. Because the estrogen receptor β resides on human connective tissue, OCP may have potential impact on tendon and ligament synthesis, structure, and biomechanical properties. Temperature has also been known to have an effect on tissue elasticity. Therefore, the purpose of this study was to investigate the differences in ACL elasticity, force to flex the knee (FFK), and knee flexion-extension hysteresis (KFEH) between OCP users and non-OCP users. To investigate these changes, two different knee temperatures were measured. Nineteen young females were divided into two groups: OCP users and non-OCP users. Blood for estradiol serum concentration (E2) was taken before beginning the tests. ACL elasticity, FFK, and KFEH were assessed both at ambient temperature (22 °C) and after 38 °C warming of the leg to stabilize tissue temperature. Assessments were performed four times during the MC. Throughout the MC, ACL elasticity, FFK, and KFEH fluctuated in non-OCP users, but not in OCP users. At ambient temperature, ACL elasticity was significantly lower and FFK and KFEH were significantly higher in OCP users than non-OCP users (p < 0.05). But, no significant differences in FFK and KFEH between the two groups were found after warming to 38 °C.

Effects of androgens on cultured cells derived from canine anterior cruciate ligament

Anterior cruciate ligament (ACL) fibroblasts obtained from beagle dogs were cultured in basal medium containing different concentrations of 1 to 10(-3) µM 5α-dihydrotestosterone (DHT) and in basal medium itself as a control. It was demonstrated that DHT promoted cell proliferation activity, expression of androgen receptor, and collagen synthesis in ACL fibroblasts as compared with control. These results suggest that sex hormones are involved in the sex difference seen in ACL rupture of dogs.

Morphometric analyses of the body and the branches of the normal third interosseous muscle (suspensory ligament) in Standardbreds

The third interosseous muscle (suspensory ligament, TIOM) is composed of connective tissue (CT) with a variable proportion of muscle (MT) and adipose tissue (AT). The aim of our study is to quantify the CT, MT and AT within the body and the branches of right thoracic and pelvic limbs TIOM in sound horses to determine whether there are differences in CT, MT and AT between age, sex, limbs and levels. Right limbs from 11 sound horses were collected. Samples from 6 levels of the TIOM were embedded in paraffin or in Tissue-Tek(®) . Most of the paraffin sections were shredded. Using the cryosection, some artefacts appeared. Cryoprotection was carried out, which produced the best results. Hematoxylin-phloxine-saffron and Hematoxylin-eosin gave a good contrast of colours between the tissues observed allowing the use of an image analysis programme to calculate percentage of each tissue within the TIOM. The percentage of MT and AT decreased significantly (P < 0.0001), whereas the percentage of CT increased significantly (P < 0.0001) with age and when descending from the proximal to the distal level of the TIOM. The percentage of MT was significantly higher (P < 0.0001) in females than males, while the percentage of CT was significantly higher (P < 0.0001) in males than females. The percentage of AT was significantly higher (P = 0.0278) in pelvic limbs than in thoracic limbs. These results confirm the variation in tissue composition within the TIOM of sound horses.

Impact of oral contraceptive use and menstrual phases on patellar tendon morphology, biochemical composition, and biomechanical properties in female athletes

Sex differences exist with regards to ligament and tendon injuries. Lower collagen synthesis has been observed in exercising women vs. men, and in users of oral contraceptives (OC) vs. nonusers, but it is unknown if OC will influence tendon biomechanics of women undergoing regular training. Thirty female athletes (handball players, 18-30 yr) were recruited: 15 long-term users of OC (7.0 ± 0.6 yr) and 15 nonusers (>5 yr). Synchronized values of patellar tendon elongation (obtained by ultrasonography) and tendon force were sampled during ramped isometric knee extensor maximum voluntary contraction to estimate mechanical tendon properties. Furthermore, tendon cross-sectional area and length were measured from MRI images, and tendon biopsies were obtained for analysis of tendon fibril characteristics and collagen cross-linking. Overall, no difference in tendon biomechanical properties, tendon fibril characteristics, or collagen cross-linking was observed between the OC users and nonusers, or between the different phases of the menstrual cycle. In athletes, tendon cross-sectional area in the preferred jumping leg tended to be larger than that in the contralateral leg (P = 0.09), and a greater absolute (P = 0.01) and normalized tendon stiffness (P = 0.02), as well as a lower strain (P = 0.04), were observed in the jumping leg compared with the contralateral leg. The results indicate that long-term OC use or menstrual phases does not influence structure or mechanical properties of the patellar tendon in female team handball athletes.

Changes in serum collagen markers, IGF-I, and knee joint laxity across the menstrual cycle

Variations in serum markers of collagen production (CICP) and degradation (ICTP), insulin-like growth factor I (IGF-I) and anterior knee laxity (AKL) were measured in 20 women [10 with spontaneous cycles (eumenorrheic), 10 using oral contraceptives] over 5 consecutive days at menses (M1-M5, 1st pill week), the initial estrogen rise near ovulation (O1-O5, 2nd pill week), the initial progesterone rise of the early luteal phase (EL1-EL5, 3rd pill week) and post-progesterone peak of the late luteal phase (LL1-LL5, 4th pill week). ICTP was higher in oral contraceptive women (5.3 ± 1.7 vs. 3.7 ± 1.3 µg/L; p = 0.030), primarily during days near ovulation and the early luteal phase when concentrations decreased in eumenorrheic women (p = 0.04). IGF-I concentrations increased during menses then decreased and remained lower during the early and late luteal phase in oral contraceptive women, resulting in lower concentrations compared to eumenorrheic women at EL2 and LL1 (p = 0.03). CICP decreased in early and late luteal days (p <0.01), and there was a trend toward lower concentrations in eumenorrheic versus oral contraceptive women (85.7 ± 35.7 ng/ml vs. 123.2 ± 49.8 ng/ml; p = 0.07). Lower CICP and greater IGF-I concentrations predicted greater AKL across the 20 cycle days in both groups (R(2)  = 0.310 and 0.400). Sex hormone concentration changes across the menstrual cycle are of sufficient magnitude to influence collagen metabolism, and may indirectly influence knee structure and function.

Sex hormone regulation of collagen concentrations in cranial cruciate ligaments of sexually immature male rabbits

OBJECTIVE

To investigate the effects of gonadectomy on collagen homeostasis in cranial cruciate ligaments of male rabbits.

ANIMALS

30 sexually immature (16-week-old) male New Zealand White rabbits.

PROCEDURES

Rabbits were randomly assigned to 5 groups of 6 rabbits each: sexually intact, placebo (control group); castrated, placebo; castrated, testosterone; castrated, dihydrotestosterone; and castrated, 17β-estradiol (E(2)). Control rabbits underwent a sham operation, and all other rabbits underwent gonadectomy. At the time of gonadectomy, the placebo and sex hormones were administered via slow-release pellets implanted subcutaneously as assigned. After 21 days of hormone supplementation, measurements were obtained of serum testosterone and E(2) concentrations, ligament collagen characteristics, and androgen receptor, estrogen receoptor α, and matrix metalloproteinase expression.

RESULTS

Following gonadectomy and hormone supplementation, the treatment groups differed in serum testosterone and E(2) concentrations to various degrees. Collagen concentrations were lower and fiber diameters higher in the absence of sex hormones, in association with the degrees of estrogen receptor a and androgen receptor expression. Although differences were detected among the groups in matrix metalloproteinase expression, these differences were not significant.

CONCLUSIONS AND CLINICAL RELEVANCE

Sex hormones appeared to play a role in cranial cruciate ligament homeostasis in male rabbits. Physiologic changes triggered by the lack of sex hormones following gonadectomy in sexually immature rabbits may potentially predispose those rabbits to orthopedic injuries.

Menstrual cycle and knee joint position sense in healthy female athletes

PURPOSE

The aim of this study was to investigate the effect of menstrual cycle on knee joint position sense (JPS) in healthy female athletes.

METHODS

Sixteen healthy female athletes participated in this study. Serum estrogen and progesterone levels were collected during the three phases of menstrual cycle. The knee JPS was also measured during the same phases using a system comprise of skin markers, digital photography, and AutoCAD software. Absolute angular errors were calculated as well as changes in hormone levels between the three phases.

RESULTS

Serum estrogen concentration was significantly higher during the mid-luteal (179.5 Pg/ml) and mid-follicular (125.6 Pg/ml) phases as compared with the early-follicular (menses) (22.8 Pg/ml) phase (P = 0.0001). Also serum progesterone concentration was significantly higher during the mid-luteal phase (7.35 Ng/ml) as compared with the menses (0.58 Ng/ml) and mid-follicular (0.5 Ng/ml) phases (P = 0.0001). The greatest amount of mean (SD) value of absolute error was at menses (4.2°), and the least amount of it was at mid-luteal (2.5°) phase. Also, a significant difference was observed within three phases of menstrual cycle (P = 0.025).

CONCLUSION

The result of this study suggests that healthy female athletes have different levels of knee JPS across a menstrual cycle. JPS accuracy decreases in menses, when circulating sex-hormones levels are low. Therefore, female athletes are at higher risk of injury at menses and improving their awareness regarding the knee injury risk factors can be a fundamental step toward preventing injuries.

LEVEL OF EVIDENCE

Case series, Level IV.

Revascularization process of the bone--patellar tendon--bone autograft evaluated by contrast-enhanced magnetic resonance imaging 6 and 12 months after anterior cruciate ligament reconstruction

BACKGROUND

Contrast-enhanced magnetic resonance imaging (MRI) studies conducted on animal models have shown that the observed signal intensity changes are related to the degree of graft vascularity and its biomechanical properties.

PURPOSE

To evaluate by contrast-enhanced MRI the revascularization process at 3 distinct sites discerned in relation to the surrounding microenvironment along the course of bone-patellar tendon-bone (BPTB) autograft in uncomplicated human anterior cruciate ligament (ACL)-reconstructed knees.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Thirty-two male patients were assessed with a 3-dimensional fast field echo/short tau inversion recovery (FFE/STIR) MRI sequence at the third postoperative day and at time intervals of 6 and 12 months after surgery. Signal-to-noise quotient (SNQ) was calculated for 3 specific graft sites (intra-articular site, intraosseous tibial tunnel site, and intraosseous juxta screw site) before and after gadolinium administration. Comparisons of the enhancement index (EI: SNQ(after)/SNQ(before) gadolinium) were performed independently for each graft site and time interval.

RESULTS

Three days postoperatively, insufficient vascularization was noticed at the 3 sites. Six and 12 months after surgery, the enhancement index was significantly increased in all 3 sites (P < .001). The intra-articular site, 6 months postoperatively, achieved satisfactory contrast medium uptake (enhancement index >1), with significantly higher enhancement index values compared with the other 2 sites (P < .001). Twelve months after surgery, only the intraosseously enclosed sites displayed an increase of the enhancement index, although nonsignificant (P = .09 and P = .07, respectively).

CONCLUSION

Revascularization of the graft occurs gradually along its length, with the intra-articular site being the first and the faster part to complete this phase, while both the intraosseous sites are still in progress throughout the first postoperative year. Revascularization is an important link at the intrinsic healing chain of the ACL graft. The surrounding microenvironment does seem to play a significant role in this process, and the differences in its composition along the graft course are reflected at the revascularization progress of the corresponding sites.