The effect of relaxin on the female anterior cruciate ligament: Analysis of mechanical properties in an animal model

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.

Knee Laxities Changes with Sex-steroids throughout the Menstrual Cycle Phases in Athlete and Non-athlete Females

Objective:  Our study investigated changes of knee laxities in athletes and non-athletes females and relationship between knee laxity and sex-steroid at menstrual cycle phases. Methods:  Forty six healthy females, twenty four athletes and twenty two non-athletes not on hormone contraceptive pills, had no previous knee injuries and with regular menstrual cycles for 3 consecutive months, participated in the study. Medial and lateral knee laxities were determined by varus-valgus tests at follicular, ovulatory and luteal phases. Serum level of relaxin, estrogen, progesterone and testosterone were determined by ELISA and radioimmunoassay. Results:  Knee laxities in athletes and non-athletes at 0° and 20° flexion were the highest in luteal phase with non-athletes possess greater laxity than athletes. Positive correlation between progesterone and relaxin levels with knee laxities were observed. Meanwhile, the levels of both hormones were highest in the luteal phase. Conclusion:  Increased medial and lateral knee laxities in athletes and non-athletes associated with high serum progesterone and relaxin levels in luteal phase may contribute toward increased risk of non-contact knee injury. However, lower knee laxity in athletes than non-athletes suggest that exercise could be a protective factor.

Effects of pregnancy and lactation on muscle-tendon morphology

Pregnancy and lactation hormones have been shown to mediate anatomical changes to the musculoskeletal system that generates animal movement. In this study, we characterize changes in the medial gastrocnemius muscle, its tendon and aponeuroses that are likely to have an effect on whole animal movement and energy expenditure, using the rat model system, Rattus norvegicus. We quantified muscle architecture (mass, cross-sectional area, and pennation angle), muscle fiber type and diameter, and Young's modulus of stiffness for the medial gastrocnemius aponeuroses as well as its contribution to Achilles tendon in three groups of three-month-old female rats: virgin, primiparous pregnant, and primiparous lactating animals. We found that muscle mass drops by 23% during lactation but does not change during pregnancy. We also found that during pregnancy muscle fibers switch from Type I to IIa and during lactation from Type IIb to Type I. The stiffness of connective tissues that has a demonstrated role in locomotion, the aponeurosis and tendon, also changed. Pregnant animals had a significantly less stiff aponeurosis. However, tendon stiffness was most affected during lactation, with a significant drop in stiffness and interindividual variation. We propose that the energetic demands of locomotion may have driven the evolution of these anatomical changes in muscle-tendon units during pregnancy and lactation to ensure more energy can be allocated to fetal development and lactation.

Pediatric anterior cruciate ligament tears and associated lesions: Epidemiology, diagnostic process, and imaging

The incidence of anterior cruciate ligament injuries in skeletally immature patients has increased in recent years. The gold standard treatment of this type of trauma in children is not yet established. Conservative management may underestimate the risk of new meniscal and chondral tears; on the other hand, a more interventional approach may expose the patient to iatrogenic damage to the growth plate. A correct approach to the skeletally immature patient with knee trauma is therefore essential to guide the decision-making process. This review article aims to present an update on the epidemiology and diagnostic process of pediatric patients with anterior cruciate ligament tears and possible associated injuries. Level of Evidence: V.

Etiopathogenesis of Canine Cruciate Ligament Disease: A Scoping Review

The spontaneous rupture of the cranial cruciate ligament in dogs remains a pathoetiologic puzzle. Despite much progress in research over the past years, the systemic and local mechanisms leading to ligament degeneration and structural failure remain largely obscure. This scoping review focuses on pathogenesis and aims at summarizing and interpreting today's knowledge on causes of canine cruciate ligament rupture, i.e., the multifactorial mechanisms leading to degenerative stifle joint disease with collagen matrix degeneration and structural failures. Thus, the initial view of traumatic ligament rupture, fostered by "wear and tear", has clearly been replaced by a new concept of systemic processes linked to progressive degenerative joint disease and ligament failure; thus, the term "cranial cruciate ligament disease" has been coined and is generally accepted. In addition, cruciate ligament rupture in people shares some similarities with the lesion in dogs; therefore, the review also includes comparative studies. The methods used were based on the PRISMA-ScR model (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews).

Immunoexpression of Relaxin and Its Receptors in Stifle Joints of Dogs with Cranial Cruciate Ligament Disease

Simple Summary

Spontaneous cranial cruciate ligament rupture is one of the most frequently encountered joint diseases in dogs, often leading to disabling chronic progressive osteoarthritis. The cause of the progressive intra-articular collagen matrix degradation, leading to tear and mechanical failure, is unknown. A variety of contributing factors has been found, however, an initiating mediator triggering the collagen degrading cascade remains to be identified. Our finding of strong relaxin- and relaxin receptor expression on intra-articular target tissues, such as on ligament fibrocytes and synovial membranes, renders relaxin a candidate for pathogenetic involvement, for collagen lysis, and progressive ligament fiber disruption. If confirmed, this opens the way for medical treatment of the disease in its early stages. In addition, further proof of relaxin involvement in canine osteoarthritis and ligament rupture would constitute a useful spontaneous animal model for human disease.

Abstract

The etiology of spontaneous cranial cruciate ligament rupture in dogs is unknown despite being one of the most impacting orthopedic diseases in dogs. Numerous studies have contributed to the understanding of a multifactorial pathogenesis, this, however, without identifying a pivotal link to explain progressive collagen degeneration and osteoarthritic changes. In human medicine, recent reports have identified relaxin as a triggering factor in ligament ruptures in knee and metacarpal joints. We thus hypothesized that relaxin might also play a role in canine cruciate ligament rupture. Relaxin’s primarily known property is connective tissue remodeling through collagenolysis. We therefore investigated relaxin and its cognate receptors LGR7/LGR8 in 18 dogs with cranial cruciate ligament disease (CCLD) and compared them to a group of dogs with normal stifle joints. Applying immunohistochemistry (IHC), double immunofluorescence (dIF), and western blot analysis (WB), we found strong and significantly increased expression of both relaxin and its receptors in ruptured cruciate ligaments, and in synovial membranes. Pattern of immuno-staining on dIF strongly suggests relaxin binding to primed receptors and activation of signaling properties, which in turn may have affected collagen matrix metabolism. Thus, in canine cranial cruciate ligament disease, relaxin/receptor signaling may be a primary trigger for collagen fiber degradation and collagen lysis, eventually followed by ligament rupture.

Mechanisms Underlying Lumbopelvic Pain During Pregnancy: A Proposed Model

Up to 86% of pregnant women will have lumbopelvic pain during the 3rd trimester of pregnancy and women with lumbopelvic pain experience lower health-related quality of life during pregnancy than women without lumbopelvic pain. Several risk factors for pregnancy-related lumbopelvic pain have been identified and include history of low back pain, previous trauma to the back or pelvis and previous pregnancy-related pelvic girdle pain. During pregnancy, women go through several hormonal and biomechanical changes as well as neuromuscular adaptations which could explain the development of lumbopelvic pain, but this remains unclear. The aim of this article is to review the potential pregnancy-related changes and adaptations (hormonal, biomechanical and neuromuscular) that may play a role in the development of lumbopelvic pain during pregnancy. This narrative review presents different mechanisms that may explain the development of lumbopelvic pain in pregnant women. A hypotheses-driven model on how these various physiological changes potentially interact in the development of lumbopelvic pain in pregnant women is also presented. Pregnancy-related hormonal changes, characterized by an increase in relaxin, estrogen and progesterone levels, are potentially linked to ligament hyperlaxity and joint instability, thus contributing to lumbopelvic pain. In addition, biomechanical changes induced by the growing fetus, can modify posture, load sharing and mechanical stress in the lumbar and pelvic structures. Finally, neuromuscular adaptations during pregnancy include an increase in the activation of lumbopelvic muscles and a decrease in endurance of the pelvic floor muscles. Whether or not a causal link between these changes and lumbopelvic pain exists remains to be determined. This model provides a better understanding of the mechanisms behind the development of lumbopelvic pain during pregnancy to guide future research. It should allow clinicians and researchers to consider the multifactorial nature of lumbopelvic pain while taking into account the various changes and adaptations during pregnancy.

Characterization of knee dysfunction and related risk factors during pregnancy

BACKGROUND

Knee pain can be a common complaint during pregnancy; however, the severity of symptoms and their associated risk factors have not been described.

QUESTIONS/PURPOSES

The aim of this study was to characterize knee-related dysfunction and describe risk factors in a general obstetric population.

PATIENTS AND METHODS

Patients in obstetric clinics completed the International Knee Documentation Committee (IKDC) questionnaire to assess their knee function, as well as the Pregnancy Physical Activity Questionnaire (PPAQ), a validated tool to assess physical activity. Age, weeks gestation, height, weight, and history of knee problems prior to pregnancy were analyzed to identify independent associations with IKDC score and determine predictors of knee dysfunction.

RESULTS

310 patients were included in this study, of which 68, 111 and 131 were in their first, second and trimesters, respectively. Mean age of the total study group was 30.3 ± 5.5 years. Knee function decreased with each trimester, from a mean IKDC score of 88.9 ± 13.0 in the first trimester, 84.5 ± 16.8 in the second, and 82.0 ± 20.0 in the third, with corresponding decreases in activity levels of 258.5 ± 141.7, 254.0 ± 141.5, and 246.1 ± 156.6 MET-h/wk. Of the total study group, 26.1% had IKDC scores <75, including 13.2%, 25.2%, and 33.6% in the first, second and third trimesters. Risk factors for knee dysfunction included high activity levels of PPAQ ≥ 500 MET-h/wk (OR 2.8), history of knee problems (OR 2.7), age <25 years (OR 2.6), and BMI ≥ 30 kg/m² (OR 1.9).

CONCLUSION

In our cohort, 26.1% of pregnant women reported severe knee dysfunction, and this was associated with high levels of activity, younger age, greater BMI, and history of knee problems. These findings may have implications for women who wish to maintain training and fitness during pregnancy. Future studies are recommended to assess the need for intervention, as well as to identify optimal methods to prevent and address symptoms in this population.

LEVEL OF EVIDENCE

IV, Case Series.

Greater presence of receptors for relaxin in the ligamentum teres of female infants who undergo open reduction for developmental dysplasia of the hip

BACKGROUND

While many factors involved in the etiology of developmental dysplasia of the hip (DDH), one of which is the hormone relaxin. Relaxin concentrations in patients with DDH may lead to pathodynamic changes during hip development by altering the physiological nature of the ligament, as well as by long-term exposure to relaxin during pregnancy. Our objective in this study was to determine the number of relaxin receptors in the ligamentum teres and their role in causing DDH.

METHODS

We identified 26 infants between birth and 3 years of age who had undergone open reduction for DDH between 2010 and 2012. 12 hips of 12 miss abortus fetus between 20 to 35 weeks of gestation were used as control group. Specimens obtained from two groups were stained with Relaxin-2 antibody, and the amount of staining for relaxin receptors was determined using an ordinal H score.

RESULTS

The mean (SD) H scores of infants with DDH were significantly higher than those of controls: 215 (59) versus 52 (48); P = 0.00; 95% CI. Statistically significant difference between the two groups in terms of gender was not found.

CONCLUSION

As a result, increased number of relaxin receptors in the ligamentum teres could be a risk factor for DDH.

LEVEL OF EVIDENCE

Level 2, Prospective comparative study.

The Effects of Mechanical Scale on Neural Control and the Regulation of Joint Stability

Recent work has demonstrated how the size of an animal can affect neural control strategies, showing that passive viscoelastic limb properties have a significant role in determining limb movements in small animals but are less important in large animals. We extend that work to consider effects of mechanical scaling on the maintenance of joint integrity; i.e., the prevention of aberrant contact forces within joints that might lead to joint dislocation or cartilage degradation. We first performed a literature review to evaluate how properties of ligaments responsible for joint integrity scale with animal size. Although we found that the cross-sectional area of the anterior cruciate ligament generally scaled with animal size, as expected, the effects of scale on the ligament’s mechanical properties were less clear, suggesting potential adaptations in passive contributions to the maintenance of joint integrity across species. We then analyzed how the neural control of joint stability is altered by body scale. We show how neural control strategies change across mechanical scales, how this scaling is affected by passive muscle properties and the cost function used to specify muscle activations, and the consequences of scaling on internal joint contact forces. This work provides insights into how scale affects the regulation of joint integrity by both passive and active processes and provides directions for studies examining how this regulation might be accomplished by neural systems.

Effect of Lateral Extra-articular Tenodesis on Anterior Cruciate Ligament Graft Incorporation

Background:

It has been shown that adding lateral extra-articular tenodesis (LET) to standard anterior cruciate ligament (ACL) reconstruction significantly decreases the loads on the ACL composite graft. To date, the possible effect of LET on ACL graft incorporation is not known.

Purpose:

To compare the incorporation in tibial bone tunnels of a standard quadrupled semitendinosus (ST4) graft to an ST4 graft plus LET at 1 year postoperatively using magnetic resonance imaging (MRI).

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A total of 62 patients who underwent ACL reconstruction were enrolled prospectively: 31 received an ST4 graft, and 31 received an ST4 graft plus LET. Graft incorporation was evaluated with MRI at the 1-year follow-up visit. The following parameters were evaluated: signal-to-noise quotient (SNQ), tibial tunnel widening, graft healing, and graft maturity according to the Howell scale. The primary endpoint was the SNQ of the ST4 graft at 1 year postoperatively; this parameter was adjusted because of unequal baseline characteristics between groups. Clinical and functional outcomes as well as incorporation of the graft were analyzed as secondary endpoints.

Results:

The mean adjusted SNQ was 0.5 ± 2.1 (95% CI, 0.4-4.6) in the ST4 + LET group and 5.9 ± 3.7 (95% CI, 4.7-7.0) in the ST4 group (P = .0297). The mean tibial tunnel widening was 73.7% ± 42.2% in the ST4 + LET group versus 77.5% ± 46.7% in the ST4 group (P = .5685). Howell grade I, indicative of better graft maturity, was statistically more frequent in the ST4 + LET group (P = .0379). No statistically significant difference was seen between groups in terms of graft healing (P = .1663). The Lysholm score was statistically higher in the ST4 + LET group (P = .0058). No significant differences were found between groups in terms of the International Knee Documentation Committee subjective score (P = .2683) or Tegner score (P = .7428). The mean SNQ of the LET graft at the 1-year follow-up visit was 2.6 ± 4.9.

Conclusion:

At 1 year postoperatively, the MRI appearance of ACL grafts showed generally better incorporation and maturation when combined with LET.

The Role of Obstetric Factors, miRNA-30d and miRNA-181a in Postpartum Women with Pelvic Organ Prolapse

Background

The diagnosis of postpartum pelvic organ prolapse (POP) relies on symptoms combined with pelvic organ prolapse-quantification (POP-Q) and lacks serological indicators. The objective of this study was to assess serum elastin, type I collagen, miRNA-30d, and miRNA-181a in the early postpartum period to identify hematologic predictors of POP.

Material and Methods

The study included 1013 42- to 60-day-postpartum women who had delivered at Quanzhou Women's and Children's Hospital from October 1, 2016, to October 31, 2017. This study was performed in accordance with the Declaration of Helsinki. The pregnancy and childbirth characteristics and pelvic floor function were evaluated. Forty cases with and without POP were matched, and serum elastin and type I collagen were determined by enzyme-linked immunosorbent assay (ELISA). Reverse-transcription polymerase chain reaction (RT-PCR) was used to detect miRNA-30d and miRNA-181a in 15 pairs.

Results

Of the 1013 women recruited, 699 (69.00%) were diagnosed with POP. The mean age was 29.00 years old, and the mean body mass index (BMI) was 22.6 kg/m². In the univariate analysis, age ≥35 years (OR, 1.449; 95% CI, 0.965, 2.298), postpartum BMI ≥ 24 (OR, 4.402; 95% CI, 2.657, 6.148), neonatal weight ≥4 kg (OR, 4.832; 95% CI, 1.373, 17.290) and vaginal delivery (OR, 2.751; 95% CI, 1.855, 4.081) were risk factors for postpartum POP. There were no significant differences in the concentrations of serum elastin and type I collagen between the groups (P=0.52; P=0.26). There were significant differences in the concentrations of miRNA-30d and miRNA-181a between the groups (P=0.004; P=0.003).

Conclusion

miRNA-30d and miRNA-181a tended to be increased in women with POP and could be potential clinical predictors.

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.

Cardiopulmonary exercise testing during pregnancy

The goal of this review is to examine practical considerations when conducting cardiopulmonary exercise testing during pregnancy. In a clinical and research setting, cardiopulmonary exercise testing during pregnancy is valuable in identifying underlying cardiopulmonary conditions, stratifying the risk of adverse pregnancy outcomes, as well as establishing exercise tolerance/limitations. This review encompasses information regarding the unique physiological adaptations that occur throughout gestation (e.g., changes in resting heart rate, blood pressure, glucose, etc.) and how these adaptations impact the interpretation of physiological measurements. There are also key concerns that are unique to pregnant populations that should be considered when participating in exercise (i.e., fetus, ventilation, thermoregulation, urinary incontinence, low back pain, and pelvic girdle pain). This step-by-step review of cardiopulmonary exercise testing outlines pregnancy related adjustments to standardized methods (i.e., screening/documentation, pre- and post-test measurements, protocol specifics, modality selection, and fetal monitoring) which should be considered for the safety of both the participant and fetus. Currently, pregnancy specific exercise testing guidelines are lacking. Therefore, we will be discussing the limitations of current recommendations such as a safe cut off for resting heart rate and pregnancy specific test termination criteria.

Assessment of luteinizing hormone receptor expression in structural support tissues of canine hip and femorotibial joints

OBJECTIVE

To determine whether luteinizing hormone receptors (LHRs) are expressed in canine femoral head subchondral bone (FHSB), hip joint round ligament (RL), cranial cruciate ligament (CCL), and femorotibial joint synovium (FJS) specimens.

SAMPLE

1 specimen each of the FHSB, RL, CCL, and FJS obtained from the left hind limbs of 19 fresh canine cadavers.

PROCEDURES

1 section of each FHSB, RL, CCL, and FJS specimen was processed with rabbit polyclonal IgG anti-human LHR antibody, and 1 section was treated with negative control reagents. Percentage immunoexpression of LHRs in FHSB and FJS sections was analyzed by assessment of 100 bone marrow cells or synoviocytes in 3 adjacent hpf (400×). In each RL and CCL section, immunoexpression of LHRs in fibrocytes was semiquantitatively analyzed on the basis of the mean of the product of percentage staining score (from 0 [no staining] to 3 [> 50% of cells stained]) and staining intensity score (from 0 [no staining] to 2 [moderate to strong staining]) for 3 adjacent hpf.

RESULTS

All tissues examined had variable LHR expression. Expression of LHRs in FHSB, CCL, or FJS specimens did not differ between sexes or between sexually intact and gonadectomized dogs. However, RL specimens from female dogs had significantly greater LHR expression scores, compared with findings for male dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that LHRs are expressed in structural support tissues of canine hip and femorotibial joints. Further research is required to determine the LHRs' function, mechanism of action, and potential contribution to the pathogenesis of hip dysplasia or CCL rupture in dogs.

Young age, female gender, Caucasian race, and workers' compensation claim are risk factors for reoperation following arthroscopic ACL reconstruction

PURPOSE

Given the increasing incidence of arthroscopic anterior cruciate ligament reconstruction (ACLR), mid- to long-term rates of reoperations were investigated on the ipsilateral knee following ACLR.

METHODS

New York Statewide Planning and Research Cooperative Systems (SPARCS) database was queried from 2003 to 2012 to identify patients with a primary ICD-9 diagnosis for ACL tear and concomitant CPT code for ACLR. Patients were longitudinally followed for at least 2 years to determine incidence and nature of subsequent ipsilateral knee procedures.

RESULTS

The inclusion criteria were met by 45,231 patients who had undergone ACLR between 2003 and 2012. Mean age was found to be 29.7 years (SD 11.6). Subsequent ipsilateral outpatient knee surgery after a mean of 25.7 ± 24.5 months was performed in 10.7% of patients. Revision ACLR was performed for nearly one-third of reoperations. Meniscal pathology was addressed in 58% of subsequent procedures. Age 19 or younger, female gender, worker's compensation (WC) insurance, and Caucasian race were identified as independent risk factors for any ipsilateral reoperation. An initial isolated ACLR and initial ACLR performed by a high-volume surgeon were found to be independently associated with lower reoperation rates. Tobacco use was not significant. Survival rates of 93.4%, 89.8% and 86.7% at 2-, 5- and 10 years, respectively, were found for any ipsilateral reoperation.

CONCLUSION

A 10.7% ipsilateral reoperation rate at an average of 25.9 (SD 24.5) months after ACLR and an overall ACLR revision rate of 3.1% were demonstrated by the analysis. Meniscal pathology was addressed in the majority of subsequent interventions. Age 19 or younger, female gender, Caucasian race, and WC claim were associated with reoperation. Initial isolated ACLR and procedure performed by high-volume surgeon were associated with reduced reoperation.

LEVEL OF EVIDENCE

Level III.

Awareness of Anterior Cruciate Ligament Injury-Preventive Training Programs Among Female Collegiate Athletes

CONTEXT

Neuromuscular training programs can reduce the rate of noncontact anterior cruciate ligament (ACL) injuries, particularly in female athletes.

OBJECTIVE

To assess the awareness of, experience with, and factors associated with participation in preventive training programs (PTPs) among female collegiate athletes and their knowledge of ACL injuries.

DESIGN

Cross-sectional study.

SETTING

National Collegiate Athletic Association (NCAA) sports programs.

PATIENTS OR OTHER PARTICIPANTS

A total of 440 female NCAA athletes (age = 20 ± 1 years) representing 20 sports during the 2017-2018 academic year.

MAIN OUTCOME MEASURE(S)

We used a 12-item survey to collect data on each participant's age, sport, position, college, NCAA division, and awareness of and experience with PTPs. We performed descriptive statistics and used odds ratios (ORs) to assess relationships between demographic data and awareness of or interest in PTPs.

RESULTS

Of the 440 respondents, 85% (n = 373) knew that female athletes were at higher risk for sustaining ACL injuries than male athletes, and 89% (n = 391) knew that ACL injuries were preventable. Thirty-three percent (n = 143) were familiar with the concept of ACL PTPs. Only 15% (n = 64) had ever performed PTPs, but 89% (n = 391) reported they would perform a daily PTP if it could prevent ACL injuries. Fifty-two of the 64 respondents (81%) who had performed PTPs said athletic trainers or coaches oversaw the PTPs. Participants were more likely to be familiar with ACL PTPs if they (OR = 3.5; 95% confidence interval [CI] = 2.0, 5.8) or a teammate (OR = 4.6; 95% CI = 2.1, 9.8) had sustained an ACL injury. Respondents were more willing to perform PTPs if they (OR = 2.3; 95% CI = 0.80, 6.6) or a teammate (OR = 3.4; 95% CI = 1.8, 6.6) had sustained an ACL injury.

CONCLUSIONS

Although 89% of respondents expressed interest in performing daily ACL PTPs, only 15% had performed such programs, and only 33% were familiar with the concept of ACL PTPs.

Preliminary Evaluation of Dynamic Knee Valgus and Serum Relaxin Concentrations After ACL Reconstruction

Background:

Athletes who have sustained a tear of the anterior cruciate ligament (ACL) are at a greater risk of re-tear and of developing other adverse outcomes, such as knee osteoarthritis, compared with uninjured athletes. Relaxin, a peptide hormone similar in structure to insulin, has been shown to interfere with the structural integrity of the ACL in female individuals. The purpose of the present study was to evaluate dynamic knee valgus and the serum relaxin concentration (SRC) in athletes who had previously sustained a torn ACL and in those who had not.

Methods:

The study included 22 female athletes, divided into 2 groups: those who had previously sustained a torn ACL (4 participants; torn ACL in the dominant leg in all cases) and those who had not (18 participants). Kinematic data were collected at 100 Hz. To assess dynamic knee valgus, participants performed a single-leg squat, a single-leg crossover dropdown, and a drop vertical jump at 2 time points in the menstrual cycle of the patient, pre-ovulatory and mid-luteal. SRC was determined with use of the Human Relaxin-2 Immunoassay using a blood sample obtained during the mid-luteal phase of the menstrual cycle.

Results:

Independent samples t tests were utilized to compare the differences in dynamic knee valgus and SRC between groups. For the single-leg squat, participants with a prior torn ACL were found to have significantly higher dynamic knee valgus at the mid-luteal phase but not at the pre-ovulatory phase. For the drop vertical jump and single-leg crossover dropdown, participants with a prior torn ACL were found to have significantly higher dynamic knee valgus at both the pre-ovulatory and mid-luteal phases. SRC was also significantly higher among participants with a prior torn ACL.

Conclusions:

Participants who had previously sustained a torn ACL had higher SRC and more dynamic knee valgus compared with those who had not. Further investigation of the effects of hormones as a risk factor for reinjury in participants with a prior ACL tear may be worthwhile. In addition, it may be worth monitoring hormonal and biomechanical properties in athletes during the long-term recovery from ACL reconstruction.

Level of Evidence:

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

The Effect of Oral Contraceptive Hormones on Anterior Cruciate Ligament Strength

BACKGROUND

Women are 2 to 9 times more likely to experience an anterior cruciate ligament (ACL) injury than men. Various hormones including relaxin, progesterone, and estrogen influence ACL strength. Oral contraceptives (OCs) alter these hormone levels; however, studies have yet to comprehensively compare different OCs' effects on the ACL.

HYPOTHESIS

OCs with increased progestin-to-estrogen ratios will (1) increase ACL collagen expression, (2) decrease ACL matrix metalloproteinase expression, and (3) increase ACL strength.

STUDY DESIGN

Controlled laboratory study.

METHODS

Untreated female rats were compared with rats treated with 1 of 5 clinically used OCs: norethindrone (NE) only, NE plus ethinylestradiol (EE), etynodiol diacetate (ED) plus EE, norgestimate (NG) plus EE, and drospirenone (DS) plus EE. Doses were scaled from human doses to account for differences in bioavailability and body weight, and OCs were administered daily via oral gavage for 4 rat estrous cycles (20 days). A total of 36 rats were then sacrificed (6 rats/group). ACLs underwent biomechanical testing to assess ACL strength, stiffness, and maximum load before failure. ACL specimens were also isolated for quantitative real-time polymerase chain reaction analysis to assess collagen, matrix metalloproteinase, and relaxin receptor-1 expression.

RESULTS

While the primary structural property of interest (ACL maximum load before failure) was not significantly improved by OC treatment, the main material property of interest (ACL strength) in rats treated with NE only, DS + EE, ED + EE, and NE + EE was significantly increased compared with untreated controls (P = .001, P = .004, P = .004, and P = .04, respectively). The order from strongest to weakest ACLs, which was also the same order as the highest to lowest progestin-to-estrogen ratios, was groups treated with NE only, DS + EE, ED + EE, NE + EE, and lastly NG + EE. Higher ratio formulations also increased the expression of type I collagen (P = .02) and decreased the expression of matrix metalloproteinase-1 (P = .04).

CONCLUSION

OC formulations with higher progestin-to-estrogen ratios may be more protective for the ACL than formulations with lower ratios.

CLINICAL RELEVANCE

OC formulations with high progestin-to-estrogen ratios may benefit female athletes by reducing their ACL injury risk by decreasing the effects of relaxin on the ACL.

Oral contraceptives provide protection against anterior cruciate ligament tears: a national database study of 165,748 female patients

Objective: Anterior cruciate ligament (ACL) tears are more prevalent in females than males. One of the factors responsible for this may be the variation in levels of estrogen and progesterone. The purpose of this study was to determine the potentially protective effects of oral contraceptive pills (OCPs) on ACL tears.Methods: The PearlDiver database (www.pearldiverinc.com, Fort Wayne, IN) was queried for all OCP users amongst females aged 15-49. Female experiencing an ACL tear and undergoing surgery (CPT 29,888) were compared to a control group of females undergoing surgery for an ACL tear, but not on OCPs. Chi-squared testing was used to assess for significant differences in the rate of ACL reconstruction for the OCP and non-OCP users, according to age groups broken down into age intervals of 5 years.Results: There were a total 82,874 patients in both the OCP and non-OCP groups. There was a total of 569 (0.69%) ACL reconstructions in the non-OCP group and 465 (0.56%) in the OCP group (p< 0.001). In the non-OCP group, patients aged 15-19 accounted for 29.35% of all ACL reconstructions, whereas, in the OCP group, this same age group only accounted for 13.33%. Among all age groups, the odds ratios for experiencing an ACL reconstruction while on OCP was 0.82 (χ² = 0.001, 95% CI 0.72-0.92) compared to not using OCP. This protective effect was driven primarily by the 15-19 age group (odds ratio 0.37 (χ² < 0.001, 95% CI 0.27-0.50)). The number need to treat for OCP usage in the 15-19 age group was six patients.Conclusions: OCPs have a protective effect on ACL tear, especially in the 15-19 age group, which exhibited a 63% reduction in the rate of tear. Consideration should be given to prescribing OCPs to younger athletes, after careful assessment of the risks of these commonly prescribed medications.Level of evidence: III.

Effect of Oral Contraceptives on Soft Tissue Injury Risk, Soft Tissue Laxity, and Muscle Strength: A Systematic Review of the Literature

Background

Female patients are more likely than male patients to experience various musculoskeletal (MSK) injuries. Because MSK tissues are sensitive to the female hormones relaxin, estrogen, and progesterone, studies have examined whether hormonal contraceptives, which change female hormone levels, can alter the female MSK injury risk. These studies have reached contradictory conclusions, leaving unclear the influence of hormonal contraception on female MSK injury risk.

Hypothesis

Hormonal contraceptives act to decrease female soft tissue injury risk and soft tissue laxity.

Study Design

Systematic review; Level of evidence, 3.

Methods

Reviewers searched for clinically relevant studies evaluating the relationship between hormonal contraceptive use and soft tissue injuries, soft tissue laxity, muscle injuries, and muscle strength in the PubMed, Cochrane, Scopus, CINAHL, and Embase databases. Studies meeting inclusion criteria were scored by 2 independent researchers for risk of bias, imprecision, inconsistency, and indirectness with a template designed using the British Medical Journal Clinical Evidence GRADE (Grades of Recommendation Assessment, Development and Evaluation) scoring system and GRADEPro guidelines. Scores were uploaded into the GRADEPro scoring system software, which calculated each study's final GRADE score (very low, low, moderate, or high quality).

Results

A total of 29 studies met inclusion criteria. Of the 7 studies evaluating oral contraceptive (OC) use and soft tissue injury risk, only 2 received a high quality-of-evidence score; all other studies received a very low score. The high-quality studies concluded that OC use decreases anterior cruciate ligament (ACL) injury risk. Only 1 of the 10 studies evaluating OC use and soft tissue laxity was found to have a high quality of evidence; this study determined that OC use decreases ACL laxity.

Conclusion

Higher quality studies suggest that OCs decrease a female patient's risk of ACL injuries and ACL laxity. The strength of these findings, however, is weak. Female patients are up to 8 times more likely to tear their ACLs than male patients. OCs may serve a therapeutic role in decreasing the sex disparity in ACL injury rates.

Sex Differences in Common Sports Injuries

Common sports injuries include bone stress injuries (BSIs), anterior cruciate ligament (ACL) injuries, and concussions. Less commonly recognized are the specific sex differences in epidemiology, risk factors, and outcomes of these conditions by sex. An understanding of these factors can improve their clinical management, from prescribing appropriate prehabilitation to guiding postinjury rehabilitation and return to play. This narrative review summarizes the sex differences in the diagnosis and management of BSIs, ACL injuries, and concussions. Although BSIs are more common in female athletes, risk factors for both sexes include prior injury and relative energy deficiency in sport (RED-S). Risk factors in female athletes include smaller calf girth, femoral adduction, and higher rates of loading. Female athletes are also at greater risk for developing ACL injuries in high school and college, but their injury rate is similar in professional sports. Increased lateral tibial slope, smaller ACL size, and suboptimal landing mechanics are additional risk factors more often present in female athletes. Male athletes are more likely to have ACL surgery and have a higher rate of return to sport. Concussions occur more commonly in female athletes; however, female athletes are also more likely to report concussions. Male athletes more commonly sustain concussion through contact with another player. Female athletes more commonly sustain injury from contact with playing equipment. Managing post-concussion symptoms is important, and female athletes may have prolonged symptoms. An understanding of the sex-specific differences in these common sports injuries can help optimize their prehabilitation and rehabilitation. LEVEL OF EVIDENCE: IV.

Multiligament Knee Injuries in Older Adolescents: A 2-Year Minimum Follow-up Study

Background:

Multiligament knee injuries cause significant functional impairment. Adults undergoing anatomic reconstruction of multiligament knee injuries have excellent outcomes postoperatively. However, less is known about the outcomes in adolescent patients following multiligament reconstruction.

Purpose/Hypothesis:

We aimed to assess patient outcomes and failure rates following unstaged multiligament reconstruction in an adolescent population at a minimum 2-year follow-up. We hypothesized that outcomes of multiligament reconstruction in these patients would be comparable to previously reported outcomes in the adult population.

Study Design:

Case series; Level of evidence, 4.

Methods:

The study included patients who had undergone multiligament knee reconstruction at 19 years of age or younger and had at least 2 years of follow-up. All procedures were performed by the same surgeon. Exclusion criteria included patient age 14 years or younger at the time of surgery, open physes, prior ipsilateral meniscal or knee ligament surgery, or a tibial plateau fracture at the time of injury. Multiligament reconstruction was defined as a reconstruction of at least 1 cruciate ligament and at least 1 component of the posterolateral corner or the medial knee. Patients were evaluated according to Lysholm score, Tegner score, Short Form–12 physical component summary (SF-12 PCS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and postoperative patient satisfaction.

Results:

Twenty patients (mean age, 17.7 years; mean follow-up, 37.1 months) were included in this study. No patient required additional ligament surgery after the index surgery because of graft failure. The median preoperative Lysholm score was 49.5 (range, 18-90), and the median postoperative Lysholm score was 86 (range, 44-100) (P < .001). The median preoperative Tegner activity score was 2 (range, 0-9), and the median postoperative Tegner activity score was 6 (range, 2-10) (P = .012). The median SF-12 PCS improved from 40.5 preoperatively to a median of 56.1 postoperatively (P < .001). WOMAC total score improved from a median of 26.5 preoperatively to a median of 2 postoperatively (P < .001). Median postoperative patient satisfaction was 10 (range, 5-10).

Conclusion:

Single-stage multiligament knee reconstruction is a reliable procedure that improves knee function at 2-year follow-up in adolescent patients. Patient satisfaction was excellent, but longer follow-up in a larger series of patients is required to determine the long-term benefits of multiligament reconstruction in this patient population.

Early complications of acromioclavicular joint reconstruction requiring reoperation

PURPOSE

Prior studies have reported high complication rates with acromioclavicular joint reconstruction (ACJR). However, many of these reports have suffered from small sample sizes and inclusion of older surgical techniques. The purpose of this study was to determine the rates of early complications requiring reoperation in patients treated with ACJR.

METHODS

From 2007 to 2011, patients who were treated with ACJR were identified using the PearlDiver database, a large insurance database in the USA. The following reoperations were then queried from this patient cohort: irrigation and debridement within 30 days of index surgery, manipulation under anaesthesia (MUA) of the shoulder joint within 3 months of index surgery, and revision ACJR, distal clavicle excision, and removal of hardware within 6 months of index surgery.

RESULTS

In total, 2106 patients treated with ACJR were identified. The reoperation rates for irrigation and debridement, MUA, revision ACJR, distal clavicle excision, and removal of hardware were 2.6, 1.3, 4.2, 2.8, and 6.2 %, respectively. Patients ≥35 years of age and females more likely to undergo a reoperation after ACJR. Specifically, patients ≥35 years of age were more likely to undergo MUA and revision ACJR, while patients ≥50 years of age were more likely to undergo an irrigation and debridement. Females were more likely than males to undergo revision ACJR and distal clavicle excision.

CONCLUSIONS

Older patients and females were more likely to experience postoperative complications requiring reoperations, including revision ACJR, distal clavicle excision, and irrigation and debridement. By analysing a large cohort of patients across multiple centres and providers, this study provides valuable insight into the recent complication profiles of ACJR, allowing surgeons to appropriately counsel patients on the risks of these procedures.

LEVEL OF EVIDENCE

IV.

Oral contraceptive therapy reduces serum relaxin-2 in elite female athletes

AIM

Recent investigations have demonstrated that athletes with high relaxin-2 levels have a high risk of anterior cruciate ligament injuries, while athletes taking oral contraceptives (OC) have low relaxin-2 levels. It has not yet been clarified whether taking OC reduces relaxin-2 levels. The purpose of this study was to investigate changes in relaxin-2 levels in athletes taking OC.

METHODS

Levels of relaxin-2, estradiol, progesterone, luteinizing hormone and follicle-stimulating hormone were measured in serum samples (n = 183) from 106 elite female athletes. Five athletes with serum relaxin-2 concentrations > 6 pg/mL during the luteal phase were recruited to assess the effect of OC therapy.

RESULTS

Serum relaxin-2 concentrations were significantly higher during the luteal phase (n = 57) than in the follicular phase (n = 72), or in athletes on OC therapy (n = 10) (P < 0.001, P < 0.001 and P < 0.05, respectively). In the luteal phase, 36.8% (21/57) of the athletes had relaxin levels > 6 pg/mL. In 23 athletes, serum relaxin-2 concentrations were measured during both the follicular and luteal phases, revealing that relaxin-2 levels were significantly higher in the luteal phase compared with the follicular phase. In 5 out of 23 athletes, serum relaxin-2 concentrations were > 6 pg/mL in the luteal phase and during the second cycle of OC therapy, relaxin-2 concentrations decreased dramatically to below the detection limit (0.26 pg/mL).

CONCLUSIONS

High serum relaxin-2 concentrations were only detected during the luteal phase. In athletes with high relaxin-2 concentrations during the luteal phase, OC therapy decreased serum relaxin-2 levels.

Hormone receptor expression in human fascial tissue

Many epidemiologic, clinical, and experimental findings point to sex differences in myofascial pain in view of the fact that adult women tend to have more myofascial problems with respect to men. It is possible that one of the stimuli to sensitization of fascial nociceptors could come from hormonal factors such as estrogen and relaxin, that are involved in extracellular matrix and collagen remodeling and thus contribute to functions of myofascial tissue. Immunohistochemical and molecular investigations (real-time PCR analysis) of relaxin receptor 1 (RXFP1) and estrogen receptor-alpha (ERα) localization were carried out on samples of human fascia collected from 8 volunteers patients during orthopedic surgery (all females, between 42 and 70 yrs, divided into pre- and post-menopausal groups), and in fibroblasts isolated from deep fascia, to examine both protein and RNA expression levels. We can assume that the two sex hormone receptors analyzed are expressed in all the human fascial districts examined and in fascial fibroblasts culture cells, to a lesser degree in the post-menopausal with respect to the pre-menopausal women. Hormone receptor expression was concentrated in the fibroblasts, and RXFP1 was also evident in blood vessels and nerves. Our results are the first demonstrating that the fibroblasts located within different districts of the muscular fasciae express sex hormone receptors and can help to explain the link between hormonal factors and myofascial pain. It is known, in fact, that estrogen and relaxin play a key role in extracellular matrix remodeling by inhibiting fibrosis and inflammatory activities, both important factors affecting fascial stiffness and sensitization of fascial nociceptors.

The Intracellular Effect of Relaxin on Female Anterior Cruciate Ligament Cells

BACKGROUND

Female collegiate athletes with serum relaxin concentrations above 6.0 pg/mL have been shown to have more than 4 times increased risk for anterior cruciate ligament (ACL) tears. However, the intracellular effect of relaxin on ACL cells has not been elucidated.

HYPOTHESES

The hypotheses were that relaxin binding to receptors on female ACL cells will result in (1) an increase in matrix metalloproteinase (MMP) and decrease in tissue inhibitor of metalloproteinase (TIMP) gene expression, (2) a decrease in collagen and alpha smooth muscle actin (αSMA) expression, (3) inhibition of transforming growth factor β1 (TGFβ1)-induced fibrosis, and (4) an increase in cyclic adenosine 3',5'-monophosphate (cAMP) production and that these changes will not be observed in male ACL cells.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ligament cells from ACL tissue were isolated from 7 male and 7 female human donors and expanded in vitro. The cells were incubated with escalating concentrations of relaxin-2, as well as with TGFβ1 or 17β-estradiol in certain groups. Cells were then lysed and analyzed for MMP1 (collagenase-1), MMP3 (stromelysin-1), MMP13 (collagenase-3), TIMP1, type I collagen, type III collagen, and/or αSMA mRNA expression using quantitative real-time polymerase chain reaction. Intracellular cAMP levels were assessed via an enzyme-linked immunoassay.

RESULTS

ACL cells primed with estrogen and treated with 10 ng/mL and 100 ng/mL relaxin illustrated increased MMP1 expression (P = .012 and .006, respectively) and MMP3 expression (P = .005 and .001, respectively). Treatment with 100 ng/mL relaxin decreased αSMA expression (P = .001). When ACL tissue isolated from female donors with a history of oral contraceptive use was excluded from the analysis, 100 ng/mL of relaxin decreased type I collagen (P = .005) and type III collagen (P = .028) expression in cells primed with estrogen. Relaxin exhibited no significant effect on male-derived ACL cells.

CONCLUSION

Relaxin-2 significantly upregulated intracellular processes in human female ACL cells, but no effect was observed in male cells. Relaxin increased MMP (MMP1 and MMP3) and decreased αSMA and type I and III collagen expression, which may act to alter the structural integrity of the ACL tissue over time.

CLINICAL RELEVANCE

Female athletes with higher circulating relaxin levels may be more susceptible to ACL injury.

Changes in Knee Laxity and Relaxin Receptor Isoforms Expression (RXFP1/RXFP2) in the Knee throughout Estrous Cycle Phases in Rodents

The changes in knee laxity and relaxin receptor expression at different phases of rodent estrous cycle are not known. Here, changes in the parameter were investigated in rats at different phases of the estrous cycle. Estrous cycle phases of intact female rats were determined by cytological examination of the vaginal smear. Following phase identification, blood was collected for serum hormone analyses. Knee passive range of motion (ROM) was determined by using a digital miniature goniometer. The animals were then sacrificed and patellar tendon, collateral ligaments and hamstring muscles were harvested for relaxin/insulin-like family peptide receptor 1 and 2 (RXFP1/RXFP2) analyses. Knee passive ROM was the highest at proestrus followed by diestrus and the lowest at estrus. Estrogen level was the highest at proestrus while progesterone and relaxin levels were the highest at diestrus. A strong correlation was observed between relaxin and progesterone levels. At proestrus, expression of RXFP1 and RXFP2 proteins and mRNAs were the highest at proestrus followed by diestrus and estrus. The finding shows that higher level of progesterone and relaxin in diestrus might be responsible for higher laxity of knee joint in rats.

Relaxin and insulin-like peptide 3 in the musculoskeletal system: from bench to bedside

Skeletal muscles and bones form a joined functional unit sharing a complex mechanical, biochemical and hormonal crosstalk. A number of factors, including sex hormones, physiologically regulate the musculoskeletal system. Striking gender differences in muscle and bone mass, and function are mainly caused by distinct actions exerted by oestrogens and androgens. However, relaxin and relaxin-related peptides, such as insulin-like peptide 3 (INSL3), might contribute to these sex-associated differences in physiological and pathological conditions (such as osteoporosis and sarcopenia). Relaxin is a 'pregnancy' hormone, but it is also produced from the prostate gland, and has recently attracted attention as a potential drug for cardiovascular disorders and fibrosis. In contrast, INSL3 is a male-specific hormone produced by the Leydig cells of the testis with a fundamental role in testicular descent during fetal life. Recent evidence suggests that both hormones have interesting roles in the musculoskeletal system. Relaxin and INSL3, by finely tuning bone formation and resorption, are involved in bone remodelling processes, and relaxin contributes to the healing of injured ligaments and promotes skeletal muscle regeneration. Here, we review the most recent findings on the effects of relaxin and INSL3 on skeletal muscle and the cell components of bone. In the light of the experimental evidence available and animal models, their clinical implications are also discussed.

LINKED ARTICLES

This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.

Estrogen receptor (ER)-α, β and progesterone receptor (PR) mediates changes in relaxin receptor (RXFP1 and RXFP2) expression and passive range of motion of rats' knee

PURPOSE

The high risk of knee injuries in female may be associated with sex-steroid hormone fluctuations during the menstrual cycle by its effect on ligaments and tendons stiffness. This study examined changes in knee range of motion in presence of estrogen and progesterone and investigated the interaction of their antagonists to relaxin receptors.

METHOD

Sixty WKY rats were divided into 10 different groups receiving 17β-estradiol (0.2, 2, 20 and 50 μg/kg), progesterone (4 mg/kg), estrogen receptor (ER) antagonist ICI 182/780, ERβ antagonist PHTPP, ERα antagonist MPP, and mifepristone in presence of estrogen and progesterone. Physiologic dose were injected subcutaneously 30 min before of hormone injection for 3 days consequently. Sham group received peanut oil (vehicle) also for 3 consecutive days. Following the treatment administrations, the knee range of motion and RXFP1/RXFP2 mRNA and protein expression were examined in the patellar tendon, lateral collateral ligament, and hamstring muscle.

RESULTS

Our data showed that the knee range of motion was significantly increased in progesterone and high doses estrogen treatment but not significantly increased in low doses of estrogen treatment. The range of motion was decreased in the presence of estrogen receptor (ER) antagonist ICI 182/780, ERβ antagonist PHTPP, ERα antagonist MPP, and mifepristone, independently.

CONCLUSION

Progesterone and high doses of estrogen treatment resulted in the highest range of knee laxity correlated to expression of both relaxin receptor isoforms in knee tissues. Our findings thus suggested that female subjects are more vulnerable toward non-traumatic knee injury due to estrogen and progesterone fluctuation as compared to male subjects.

Detection of relaxin receptor in the dorsoradial ligament, synovium, and articular cartilage of the trapeziometacarpal joint

Basilar thumb osteoarthritis (OA) is postulated to occur due to ligament attenuation of the trapeziometacarpal (TM) joint. Relaxin is a peptide hormone, which loosens ligaments before childbirth, through remodeling of the extracellular matrix via upregulation of matrix metalloproteases (MMPs). We postulated that relaxin family peptide receptor 1 (RXFP-1), the receptor for circulating relaxin, was present in tissues of the TM joint. Ligaments and synovium were sampled from 15 patients during surgery for TM arthritis. We obtained trapezial cartilage from two autopsy donors and four patients. Tissues were fixed, paraffin embedded, and sectioned at 5 µm, then were immunostained for RXFP-1, as well as MMP-1, and MMP-13, using rabbit anti-human polyclonal antibodies. Eight DRL samples showed positive immunostaining for relaxin receptor, with 14/15 positively stained in synovium. Greater staining was seen in specimens obtained from women with more severe TM arthritis. Trapezial cartilage demonstrated receptor staining within chondrocytes in the middle and deep zones. Immunostaining for MMPs co-localized with relaxin receptor staining. Relaxin receptors are present at the ligament, cartilage, and synovium of the TM joint, indicating that it is a potential target for relaxin. This suggests that circulating relaxin may impact joint stability. The role of relaxin in cartilage and synovium may be related to its role in collagen regulation as a possible tissue response to OA.

Testosterone reduces knee passive range of motion and expression of relaxin receptor isoforms via 5α-dihydrotestosterone and androgen receptor binding

Ovarian steroids such as estrogen and progesterone have been reported to influence knee laxity. The effect of testosterone, however, remains unknown. This study investigated the effect of testosterone on the knee range of motion (ROM) and the molecular mechanisms that might involve changes in the expression of relaxin receptor isoforms, Rxfp1 and Rxfp2 in the patella tendon and lateral collateral ligament of the female rat knee. Ovariectomized adult female Wistar rats received three days treatment with peanut oil (control), testosterone (125 and 250 μg/kg) and testosterone (125 and 250 μg/kg) plus flutamide, an androgen receptor blocker or finasteride, a 5α-reductase inhibitor. Duplicate groups received similar treatment however in the presence of relaxin (25 ng/kg). A day after the last drug injection, knee passive ROM was measured by using a digital miniature goniometer. Both tendon and ligament were harvested and then analysed for protein and mRNA expression for Rxfp1 and Rxfp2 respectively. Knee passive ROM, Rxfp1 and Rxfp2 expression were significantly reduced following treatment with testosterone. Flutamide or finasteride administration antagonized the testosterone effect. Concomitant administration of testosterone and relaxin did not result in a significant change in knee ROM as compared to testosterone only treatment; however this was significantly increased following flutamide or finasteride addition. Testosterone effect on knee passive ROM is likely mediated via dihydro-testosterone (DHT), and involves downregulation of Rxfp1 and Rxfp2 expression, which may provide the mechanism underlying testosterone-induced decrease in female knee laxity.

Sex-steroid regulation of relaxin receptor isoforms (RXFP1 & RXFP2) expression in the patellar tendon and lateral collateral ligament of female WKY rats

The incidence of non-contact knee injury was found higher in female than in male and is related to the phases of the menstrual cycle. This raised the possibility that female sex-steroids are involved in the mechanism underlying this injury via affecting the expression of the receptors for relaxin, a peptide hormone known to modulate ligament laxity. Therefore, this study aims to investigate the effect of sex-steroids on relaxin receptor isoforms (RXFP1 & RXFP2) expression in the ligaments and tendons of the knee.

METHODS

Ovariectomized adult female WKY rats were treated with different doses of estrogen (0.2, 2, 20 μg/kg), progesterone (4mg) and testosterone (125 & 250μg/kg) for three consecutive days. At the end of the treatment, the animals were sacrificed and the patellar tendon and lateral collateral ligament were harvested for mRNA and protein expression analyses by Real Time PCR and Western blotting respectively.

RESULTS

RXFP1, the main isoform expressed in these knee structures and RXFP2 showed a dose-dependent increase in expression with estrogen. Progesterone treatment resulted in an increase while testosterone caused a dose-dependent decrease in the mRNA and protein expression of both relaxin receptor isoforms.

DISCUSSION

Progesterone and high dose estrogen up-regulate while testosterone down-regulates RXFP1 and RXFP2 expression in the patellar tendon and lateral collateral ligament of rat's knee.

CONCLUSION

Relaxin receptor isoforms up-regulation by progesterone and high dose estrogen could provide the basis for the reported increase in knee laxity while down-regulation of these receptor isoforms by testosterone could explain low incidence of non-contact knee injury in male.

Meniscus tear patterns in relation to skeletal immaturity: children versus adolescents

BACKGROUND

Meniscus tear patterns in the pediatric population have not been well described.

PURPOSE

To delineate the pattern of meniscus tears and the likelihood of repair at the time of surgery in both children and adolescents.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A retrospective review was performed on all patients between the ages of 10 and 19 years who underwent arthroscopic surgery for a meniscus injury at a single institution. Patients with open growth plates were classified as children, while those with closed growth plates were classified as adolescents. Demographic data were documented, including age, sex, body mass index (BMI), mechanism of injury, and time from injury to surgery. Operative reports and intraoperative photographs were used to assess the tear pattern (type, location, zone) as well as all concomitant procedures and injuries. Tears were classified as discoid, vertical, bucket-handle, radial, oblique, horizontal, fray, root detachment, or complex.

RESULTS

Of the 293 patients reviewed, 197 (67%) had lateral meniscus tears, 65 (22%) had medial meniscus tears, and 31 (11%) had tears to both menisci. The cohort was separated into 119 (41%) children (mean age, 13.5 years) and 174 (59%) adolescents (mean age, 16.4 years). Children were more likely to have discoid meniscus tears, lower BMI, and meniscus injuries not associated with ligamentous injuries (P < .05). The rate of associated ligament injuries in children was 28% compared with 51% in adolescents. Overall, the most frequent tear pattern was complex (28%), followed by vertical (16%), discoid (14%), bucket-handle (14%), radial (10%), horizontal (8%), oblique (5%), fray (3%), and root detachment (2%). Complex tears were associated with boys (32% vs 20% in girls; P < .03) and greater mean BMI (27.4 vs 25.1 kg/m(2) in those with noncomplex tears; P < .002), even when taking sex into account. Surgical repair was performed in 47% of all cases (56% in those treated within 3 months of injury vs 42% in those treated after 6 months; P < .03), and there was no difference in the repair rate between the two age groups (49% in children vs 46% in adolescents; P > .05).

CONCLUSION

Adolescents and children sustain more complex meniscus injuries that are often less repairable than previously reported in the literature. Factors that are associated with greater tear complexity include male sex and obesity. Our findings also suggest that the earlier treatment of meniscus tears may increase the likelihood of repair in younger patients.

The effect of relaxin on the musculoskeletal system

Relaxin is a hormone structurally related to insulin and insulin-like growth factor, which exerts its regulatory effect on the musculoskeletal and other systems through binding to its receptor in various tissues, mediated by different signaling pathways. Relaxin alters the properties of cartilage and tendon by activating collagenase. This hormone is also involved in bone remodeling and healing of injured ligaments and skeletal muscle. In this review, we have summarized the literature on the effect of relaxin in musculoskeletal system to provide a broad perspective for future studies in this field.

Relationship of serum relaxin to generalized and trapezial-metacarpal joint laxity

PURPOSE

The reproductive hormone relaxin acts to loosen pelvic ligaments in preparation for childbirth and is thought to be a mediator of joint laxity. The purpose of this study was to evaluate the correlation of serum relaxin with radiographic laxity at the trapezial-metacarpal joint and with generalized joint laxity.

METHODS

We enrolled 289 healthy subjects prospectively. Participants completed a demographic questionnaire and were examined for generalized joint hypermobility using the Beighton-Horan scale. Stress radiographs of the trapezial-metacarpal joint were obtained in 163 subjects (56%). Blood samples were collected, and serum relaxin was measured for 287 subjects using enzyme-linked immunosorbent assay for human relaxin-2.

RESULTS

The mean serum relaxin level among all subjects was 1.84 pg/mL (range, 0-45.25 pg/mL). Relaxin was not detectable in 166 of 287 samples, whereas the mean serum relaxin level among the 121 subjects with a detectable relaxin level (of 287 total relaxin samples) was 4.37 pg/mL (range, 0.46-45.25 pg/mL). Mean trapezial-metacarpal subluxation ratio scores were higher among those with a detectable relaxin level compared to those without a detectable relaxin level (0.34 vs 0.30 pg/mL). The average Beighton-Horan laxity score was 1.8 (range, 0-9). There was no correlation between generalized joint laxity measures and serum relaxin levels.

CONCLUSIONS

In a large volunteer population, we demonstrated a relationship between circulating relaxin and trapezial-metacarpal joint laxity. However, we were unable to show a direct link between serum relaxin and generalized joint laxity.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

Reconstruction of the anterior cruciate ligament in the skeletally immature athlete: a review of current concepts: AAOS exhibit selection

Intrasubstance tears of the anterior cruciate ligament (ACL) were once considered a rare injury in skeletally immature athletes but are now observed with increasing frequency. Treatment strategies have evolved as recent studies have identified unique considerations specific to the skeletally immature patient. The current literature now supports the trend toward early operative treatment to restore knee stability and prevent progressive meniscal and/or articular cartilage damage, but the optimal approach to ACL reconstruction in this age group remains controversial. Despite the reported clinical success of transphyseal reconstruction, iatrogenic growth disturbance secondary to physeal damage remains a genuine concern. The reluctance to place drill-holes across open physes has led to the development of numerous "physeal-sparing" reconstruction techniques using anatomic femoral and tibial footprints that have adequately restored anteroposterior and rotational knee stability in biomechanical studies but have demonstrated mixed results in the clinical setting. The intent of this review is to (1) highlight the unique anatomic considerations pertaining to ACL reconstruction in the skeletally immature athlete, (2) discuss preoperative clinical and radiographic assessment of the pediatric patient with a suspected ACL injury, (3) review transphyseal and physeal-sparing reconstruction techniques and highlight surgical technical considerations, (4) present clinical outcomes according to patient and technique-specific factors, and (5) review age-specific injury prevention treatment strategies and a novel treatment algorithm based on skeletal maturity. ACL reconstruction in the skeletally immature athlete typically results in a successful clinical outcome, yet the optimal surgical technique is still controversial. This review will help guide the management of ACL injuries in the pediatric athlete.

Arthrofibrosis after anterior cruciate ligament reconstruction in children and adolescents

INTRODUCTION

Arthrofibrosis is a known complication after anterior cruciate ligament (ACL) reconstruction. ACL reconstruction is being performed with increased frequency in the pediatric population. The purpose of this study was to determine the prevalence of arthrofibrosis in children and adolescents and to identify risk factors for arthrofibrosis.

METHODS

The study design was a retrospective case series. Medical records for 1016 consecutive ACL reconstructions in patients aged 7 to 18 years old between 1995 to 2008 at a major tertiary care children's hospital were reviewed to identify cases of postoperative arthrofibrosis. Arthrofibrosis was defined as a loss of 5 degrees or more extension compared with the contralateral knee that required a follow-up procedure or a loss of 15 degrees or more flexion compared with the contralateral knee that required a follow-up procedure. Patient data were recorded and analyzed using bivariate models to identify predictors for arthrofibrosis. Further, we reviewed the clinical course of patients with treated arthrofibrosis to assess functional outcomes of this complication.

RESULTS

Nine hundred two patients with 933 knees met the inclusion criteria for this study, of which 60% were female. The mean age at the time of surgery was 15 years (range, 7 to 18 y), and the average follow-up from original ACL reconstruction was 6.3 years (range, 1.6 to 14.2 y). The overall prevalence of arthrofibrosis in our cohort was 8.3%, with 77 of the 933 knees had at least 1 procedure to treat arthrofibrosis after ACL reconstruction. Risk factors for arthrofibrosis were female sex (11.1% females, P = 0.0001), patients aged 16 to 18 years [11.6%; odds ratio (OR) 3.51; P = 0 .007], patellar tendon autograft (OR, 1.7; P = 0.026), and concomitant meniscal repair (OR, 2.08; P = 0.007). Prior knee surgery and ACL reconstruction within 1 month of injury were not significantly associated with arthrofibrosis after ACL reconstruction. Fifty-three patients had a minimum of 6 months clinical follow-up after the procedure for arthrofibrosis. Of these, 46 patients (86.8%) had full range of motion at follow-up. Thirty-two patients (60.4%) were asymptomatic at final follow-up. Eleven patients (20.8%) complained of some persistent pain.

CONCLUSIONS

The rate of arthrofibrosis after ACL reconstruction in children and adolescents is 8.3%. Risk factors for arthrofibrosis are female sex, older adolescents, concurrent meniscal repair, and reconstruction with patellar tendon autograft. Surgical treatment for arthrofibrosis after ACL reconstruction in pediatric patients can satisfactorily regain motion in the reconstructed knee; however functional outcome may be compromised.

LEVEL OF EVIDENCE

Level 4.

A Roadmap for the Design of Bioreactors in Mechanobiological Research and Engineering of Load-Bearing Tissues

In the field of tissue engineering, a bioreactor is a valuable instrument that mimics a physiological environment to maintain live tissues in vitro. Although bioreactors are conceptually relatively simple, the vast majority of current bioreactors (commercial and custom-built) are not fully adapted to current research needs. Designing the optimal bioreactor requires a very thorough approach to a series of steps in the product development process. These four basic steps are: (1) identifying the needs and technical requirements, (2) defining and evaluating the related concepts, (3) designing the apparatus and drawing up the blueprints, and (4) building and validating the apparatus. Furthermore, the design has to be adapted to the specific purpose of the research and how the tissues will be used. In the emerging field of bioreactor research, roadmaps are needed to assist tissue engineering researchers as they embark on this process. The necessary multidisciplinary expertise covering micromechanical design, mechatronics, viscoelasticity, tissue culture, and human ergonomics is not necessarily available to all research teams. Therefore, the challenge of adapting and conducting each step in the product development process is significant. This paper details our proposal for a roadmap to accompany researchers in identifying their needs and technical requirements: step one in the product development process. Our roadmap proposal is set up in two phases. Phase 1 is based on the analysis of the bioreactor use cycle and phase 2 is based on the analysis of one specific and critical step in the use cycle: conducting stimulation and characterization protocols with the bioreactor. A meticulous approach to these two phases minimizes the risk of forgetting important requirements and strengthens the probability of acquiring or designing a high performance bioreactor.

Prospective correlation between serum relaxin concentration and anterior cruciate ligament tears among elite collegiate female athletes

BACKGROUND

The female anterior cruciate ligament may be more susceptible to injury than the male anterior cruciate ligament because of the gender-specific expression of receptors for relaxin, a collagenolytic hormone that promotes remodeling of the anterior cruciate ligament.

PURPOSE

This study was undertaken to investigate whether collegiate female athletes with elevated serum relaxin concentrations (SRC) sustain anterior cruciate ligament tears at an increased rate compared with those with lower SRC.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

From 2005 to 2010, 143 Division I female athletes from 2 universities participating in sports at high risk for anterior cruciate ligament tears (basketball, lacrosse, field hockey, soccer, gymnastics, and volleyball) were recruited to participate. Questionnaires and urine luteinizing hormone (LH) tests were used to determine participants' anterior cruciate ligament injury and menstrual history and to identify their mid-luteal phase or projected cycle days 21 to 24. Serum samples were obtained for progesterone and relaxin ELISA (enzyme-linked immunosorbent assay) analysis. Participants were monitored for anterior cruciate ligament injury over their 4-year National Collegiate Athletic Association athletic career.

RESULTS

A total of 128 participants completed the study and were eligible for data analysis. The cumulative incidence of complete anterior cruciate ligament tear over the 4-year study period was 21.9%, and varied significantly by sport (P < .001). The mean SRC for athletes with anterior cruciate ligament tears (6.0 ± 8.1 pg/mL) was significantly higher than that for those without anterior cruciate ligament tears (1.8 ± 3.4 pg/mL; P = .013). In subgroup analysis of the 46 athletes who had detectable SRC, the cumulative incidence of anterior cruciate ligament tear was 14 of 46 (30.4%); the mean SRC among athletes with anterior cruciate ligament tears (14 of 46) was 12.1 ± 7.7 pg/mL and without anterior cruciate ligament tears (32 of 46), 5.7 ± 3.6 pg/mL (P = .002). When 6.0 pg/mL was set as the SRC cutoff for screening athletes for risk of anterior cruciate ligament tear in the subgroup with detectable relaxin levels, the test had 71% sensitivity, 69% specificity, 52% positive predictive value, 88% negative predictive value, and a relative risk of 4.4. These values were significant by χ(2) test (P = .003) and receiver operating characteristic analysis (P = .002).

CONCLUSION

Elite female athletes with anterior cruciate ligament tears have higher SRC than those without tears. Those with an SRC greater than 6.0 pg/mL had over 4 times increased risk for a tear.

CLINICAL RELEVANCE

Females with higher serum relaxin levels may be at increased risk for anterior cruciate ligament tears. Further investigation of the clinical utility of SRC testing is warranted.

Variations in dynamic knee valgus and gluteus medius onset timing in non-athletic females related to hormonal changes during the menstrual cycle

It has been suggested that activities of daily living could contribute to the occurrence of ACL injury in females. Currently, no studies have focused on the lower extremity behavior of a non-athletic population to compare or understand the lower extremity adeptness towards daily movements that mimic athletic tasks. Our hypothesis was that increased knee valgus angles would occur during the late follicular phase of the menstrual cycle accompanied by different onset timing of the gluteus medius muscle. In a controlled laboratory study, 23 non-athletic collegiate females participated and 15 subjects comprised the final sample for statistical analysis. Subjects performed a single leg drop landing maneuver while 3-D knee kinematics and gluteus medius muscle onset timing were assessed throughout three distinct phases of the menstrual cycle, confirmed by blood hormone analysis. In general, knee valgus angles were significantly less in the luteal phase compared to both follicular phases (p<0.005), while differences were not observed for gluteus medius onset timing (p=0.936). As a decreased knee joint valgus angle was observed during the luteal phase, it was hypothesized that the hormone progesterone could significantly influence knee kinematics during a dynamic task. However, such influence was not observed for gluteus medius EMG onset timing as a significant correlation between gluteus medius onset timing and knee valgus angle could not be determined.

Serum relaxin levels affect the in vivo properties of some but not all tendons in normally menstruating young women

Relaxin (hRLX) is a hormone reported to affect collagen synthesis. Its effects are also thought to be modulated by other sex hormones, including oestrogen, which has previously been found to be associated with alterations of in vivo tendon properties. There is thus a potential for hRLX to impact on collagen, which could result in tendon structural and mechanical properties being modified. The present study therefore aimed to determine any interaction between hRLX and tendon stiffness, in normally menstruating women (n = 12). Tendon properties were determined using a combination of dynamometry and B-mode ultrasound, whilst serum hRLX levels were established by ELISA. Serum hRLX level was seen to be negatively associated with patellar tendon stiffness (r = -0.56; P < 0.001), explaining 31% of the variance in this parameter. There was no association between hRLX and gastrocnemius tendon stiffness (P > 0.05), or with the cross-sectional area of either of the two tendons (P > 0.05). In young, normally menstruating women, hRLX appears to have a significant effect on the patellar but not the gastrocnemius tendon stiffness. Where it has an effect, this appears to be on the intrinsic properties rather than on the dimensions of said tendon. Future work to elucidate the physiological cause of this selectivity in the impact of relaxin will be key to mapping the impact of the endocrine system on the phenotype of tendinous tissue.

Trends in serum relaxin concentration among elite collegiate female athletes

PURPOSE

This study was designed to investigate the relationship between serum relaxin concentration (SRC) and menstrual history and hormonal contraceptive use among elite collegiate female athletes. Evaluation of SRC in athletes is necessary, because relaxin has been associated with increased knee joint laxity and decreased anterior cruciate ligament (ACL) strength in animal models.

METHODS

National Collegiate Athletic Association Division I female athletes participating in sports at high risk for ACL tears - basketball, field hockey, gymnastics, lacrosse, soccer, and volleyball - were invited to participate. All participants completed a questionnaire about their menstrual history and hormonal contraceptive use. Venipuncture was performed to obtain samples of serum progesterone and relaxin. Samples were obtained during the mid-luteal phase from ovulating participants, and between the actual or projected cycle days 21 to 24, from anovulatory participants. Serum concentration of relaxin and progesterone was determined by ELISA and the data were analyzed using SPSS statistical software with significance set at P = 0.05.

RESULTS

169 female athletes participated. The mean SRC among all participants was 3.08 ± 6.66 pg/mL). The mean SRC differed significantly between those participants using hormonal contraceptives (1.41 pg/mL) and those not using hormonal contraceptives (3.08 pg/mL, P = 0.002). Mean SRC was lowest among amenorrheic participants (1.02 pg/mL) and highest among oligomenorrheic participants (3.71 pg/mL) and eumenorrheic participants (3.06 pg/mL); these differences were not significant (P = 0.53). Mean serum progesterone concentration (SPC) differed significantly between those participants using hormonal contraceptives (2.80 ng/mL), and those not using hormonal contraceptives (6.99 ng/mL, P < 0.0001).

CONCLUSIONS

There is a positive correlation between serum progesterone and SRC and an attenuation of SRC with hormonal contraceptive use. Our results underscore the significant role that hormonal contraceptives can play in decreasing relaxin levels, if future investigations establish a link between relaxin levels and ligamentous injury among female athletes.