James A. Ashton‐Miller

Although vaginal birth has the highest risk of musculoskeletal injury per hour of exposure of any natural human activity, the resulting injuries often go unrecognized - sometimes for decades. The types of tissues injured during a difficult vaginal birth are similar to those involved in other musculoskeletal injuries. It is not widely appreciated that multiple structures can be injured, including pubic bone stress fractures, injury to the nerve innervating the right or left levator ani (LA) muscle, stretch injuries of the LA muscles themselves, and/or passive tissue stretch injuries to the perineal body (PB), perineal membrane (PM), and endopelvic fascia. Complicating the issue further is the possibility that each structure can be injured to differing extents, and the injuries can occur in a variety of combinations. As a contribution to the existing literature, the relevant information is tabulated for the first time in a pelvic floor musculoskeletal injury classification system, supported by illustrations for easy reference. Because early identification and interventions can help reduce, and even prevent, long-term symptoms, it is important to screen postpartum athletes and refer them to pelvic health specialists when appropriate. This will help benefit these athletes by fostering appropriate interdisciplinary collaboration with their sports medicine care team.

INTRODUCTION AND HYPOTHESIS: The perineal membrane (PM), perineal body, and levator ani muscles form the perineal complex, which is responsible for hiatal closure. Yet failures in its connective tissues that may lead to hiatal closure impairment are poorly understood. We tested the hypothesis that pelvic organ prolapse involves PM abnormalities by comparing PM morphology between young women with prolapse and parous controls using a validated MRI-based reconstruction and analysis technique. METHODS: . Six PM parameters were measured: swinging door angle, visible bony origin length, hiatal anteroposterior diameter and area, PM surface area, and midline separation. Group comparisons used t tests, with Cohen's d, correlations, and stepwise regression analysis. RESULTS: Resting MRIs from 17 young parous women (aged < 40 years) with prolapse and 20 parous controls were compared. Women with prolapse showed 23% greater midline separation of the PM, 30% larger hiatal area, 26% larger hiatal anteroposterior diameter, 17% longer bony origin, and 26% larger PM surface area (all p ≤ 0.002, d = 1.1-1.6); swinging door angle was similar between groups (p = 0.60). Levator ani status, midline separation, and PM surface area independently predicted prolapse, explaining 76% of variance. CONCLUSIONS: The PM structure was altered in those with prolapse through loss of central PM connection, hiatal elongation, and hiatal widening. Larger studies are needed to confirm and guide targeted repair techniques that could potentially prevent prolapse development and/or progression.

Failure of the urogenital hiatus to remain closed in women is a major contributor to prolapse operation failure and development of prolapse after childbirth. This article presents a conceptual framework, the Urogenital Hiatus Closure System (UHCS), that explains how anatomic and neuromuscular elements interact to maintain, or fail to maintain, hiatal closure. Clinical observations demonstrate that no single structure reliably predicts hiatus size; instead, hiatal behavior results from the integrated functional components. The UHCS has three primary elements: the levator ani muscle, neuromotor control, and Level III connective tissues of the perineal complex-each of which can be injured, partially compensated, or overloaded. These structures form a neuromechanically integrated unit in which the medial levator ani, the perineal membrane and its central connection, and the afferent-efferent control loops work to provide resting tone, active contraction, resistance to dilation, and spatial alignment. A principle of the model is redundancy: failure in one component may not enlarge the hiatus, but combinations of failures exceed compensatory capacity and result in failure. It links Level III mechanics to Level I-II support by demonstrating how an open hiatus increases forces on apical and paravaginal tissues, driving a feed-forward cycle of prolapse dilation and muscle elongation. Conceptually, the UHCS is an interacting triad influenced by functional modifiers-loading conditions, prolapse effects, muscle length, motor activation, and connective-tissue properties-that determine hiatus size. This systems-based approach can guide classification of failure patterns to inform biomechanical, anatomical, and therapeutic research.

OBJECTIVES: Stress urinary incontinence (SUI) has been linked to excessive urethral mobility, yet clinical evaluation has been largely limited to assessing maximal excursion rather than capturing the full dynamics of visible urethral movement. In this study, we hypothesize that an automated, ultrasound-based method can objectively differentiate urethral mobility patterns between women with SUI and continent controls. METHODS: We used a previously validated optical flow-based algorithm to automatically track urethral motion from transperineal ultrasound images during cough, Valsalva maneuver, and pelvic muscle contraction (PMC) in 11 women with SUI and 10 continent controls. Urethral motion was assessed by defining three regions of interest along the urethra (proximal, mid, and distal). Segmental urethral kinematics were computed and statistically compared between groups. RESULTS: Substantial variability and overlap between groups were observed, with coefficient of variation ranging 25%-90%. On average, women with SUI demonstrated significantly larger urethral displacement compared to controls, particularly at the proximal segment during Valsalva (10.6 ± 1.2 mm vs. 6.0 ± 0.6 mm, p < 0.01), with pronounced inferior-posterior motion. Additionally, displacement between the upper and lower urethra was significantly larger in the SUI group (0.47 ± 0.10 mm/mm vs. 0.13 ± 0.03 mm/mm, p < 0.05), indicating localized hypermobility particularly near the proximal urethra. Maneuver-specific differences were also noted within the SUI group, with Valsalva producing significantly larger and less uniform urethral movements compared to cough (10.6 ± 1.2 mm vs. 6.6 ± 0.5 mm, p < 0.05). CONCLUSION: Our results demonstrate that the automated method is capable of capturing urethral mobility characteristics associated with SUI. Significant inter-individual variability in both continent and SUI groups indicates that urethral kinematics are heterogeneous. The detailed kinematic data have the potential to identify distinct sub-types of urethral mobility, facilitating systematic comparisons with underlying structural and neuromuscular defects. This approach can move clinical evaluation from simple group comparisons toward personalized SUI diagnosis and targeted treatment selection. Future studies with larger sample sizes and inclusion of additional pelvic floor conditions will be needed to validate these findings and advance their translation into clinical practice.

BACKGROUND: Current evidence indicates that pelvic organ prolapse development after childbirth is strongly associated with an enlarged hiatus. However, few childbirth-related injuries beyond anal sphincter lacerations and levator ani avulsion—which explain less than a quarter of hiatal enlargement—have been investigated. Other types of injuries that lead to an enlarged hiatus and contribute to prolapse development remain incompletely explored. The perineal complex components (perineal membrane, perineal body, and levator ani) are responsible for hiatal closure and form a distinct anatomical and functional unit. Yet how and whether this complex is injured during childbirth and how such injuries can be identified through imaging has not been well characterized in the literature. OBJECTIVE: We sought to evaluate the perineal complex components using 3-dimensional endovaginal ultrasound at 6 months postpartum and how potential defect patterns are influenced by mode of delivery. Additionally, we explored how potential defect patterns are associated with clinical and obstetric data. STUDY DESIGN: This was a secondary analysis of data from a prospective longitudinal study of postpartum women at high risk for pelvic floor injury. We used 6-month 3-dimensional endovaginal ultrasound images and data to evaluate the 3 perineal complex components and developed and applied a scoring system to assess for potential imaging abnormalities. RESULTS: A total of 126 women were included in the present study. In women with no visible anatomic abnormality, there was a convergence of tissue to the midline at the perineal body level that was not present in other scans. This configuration was divided into 2 features: an hourglass appearance and a visible transverse band, which together we termed the Hourglass-Band pattern. In women with a vaginal delivery (n=94), the 2 features were 2.4 and 4.1 times more likely to be absent, respectively. The Hourglass-Band pattern was altered in 45% of vaginal deliveries, indicating level III imaging abnormalities in nearly half the cohort and highlighting the prevalence of childbirth-related changes among high-risk women. In the cesarean delivery control group (n=32), an altered Hourglass-Band pattern was seen in 16% of subjects, suggesting the possibility of anatomical variation or differences in sonographic tissue characteristics. CONCLUSION: The altered Hourglass-Band pattern is an imaging abnormality that is strongly associated with difficult vaginal birth, distinct from levator ani avulsion and anal sphincter laceration, and potentially repairable. If confirmed as a childbirth-related injury, studying Hourglass-Band alterations could enhance our understanding of alternative injury mechanisms and inform pelvic floor injury prevention and recovery strategies postpartum.

Background Accurately outlining (“segmenting”) pelvic organs from magnetic resonance imaging (MRI) scans is crucial for studying pelvic organ prolapse. The labor-intensive process of segmentation that identifies which pixels correspond to a particular organ in MRI datasets imposes a significant bottleneck on training Artificial Intelligence (AI) to do automated segmentation techniques, underscoring a need for methods that can operate effectively with minimal pre-labeled data. Objectives The aim of this study is to introduce a novel semi-supervised learning process that uses limited data annotation in pelvic MRI to improve automated segmentation. By effectively using both labeled and unlabeled MRI data, our approach seeks to improve the accuracy and efficiency of pelvic organ segmentation, thereby reducing the reliance on extensive labeled datasets for AI model training. Study Design The study used a semi-supervised deep learning framework for uterus and bladder segmentation, in which a model is trained using both a small number of expert-outlined structures and a large number of unlabeled scans, leveraging the information from the labeled data to guide the model and improve its predictions on the unlabeled data. It involved 4,103 MR images from 48 female subjects. This approach included self-supervised learning of image restoration tasks for feature extraction and pseudo-label generation, followed by combined supervised learning on labeled images and unsupervised training on unlabeled images. The method’s performance was evaluated quantitatively using the Dice Similarity Coefficient (DSC), Average Surface Distance (ASD), and 95% Hausdorff Distance (HD95). For statistical analysis, two-tailed paired t-tests were conducted for comparison. Results This framework demonstrated the capacity to achieve segmentation accuracy comparable to traditional methods while requiring only about 60% of the typically necessary labeled data. Specifically, the semi-supervised approach achieved DSCs of 0.84±0.04, ASDs of 13.98±0.93, HD95s of 2.15±0.40 for the uterus, and 0.92±0.05, 2.51±0.83, 2.88±0.17 for the bladder respectively (P-value<0.001 for all), outperforming both the baseline supervised learning and transfer learning models. Additionally, 3D reconstructions using the semi-supervised method exhibited superior details in the visualized organs. Conclusion This study’s semi-supervised learning framework wherein the full use of unlabeled data markedly reduces the necessity for extensive manual annotations, achieving high segmentation accuracy with substantially fewer labeled images that can enhance clinical evaluation and advance medical image analysis by reducing the dependency on large-scale labeled pelvic MRI datasets for training.

Abstract Background Recent prospective research indicates that unipedal stance time (UST) of &lt; 15 s in middle/older adults increases their risk of repetitive falls within 5 to 10 years. Aim To determine the extent that clinical measures of three physiologic capacities, peripheral afferent acuity, processing speed, and proximal frontal plane strength, are responsible for UST. Methods UST, distal lower limb clinical vibratory sense, short latency go/no-go accuracy using ReacStick, and lateral plank time, were evaluated in a cohort ( n = 172, 51% female, age 64.8 +/- 9.6 years) with diabetic neuropathy ( n = 31), cirrhosis ( n = 94), and no known neurologic disease ( n = 47) using age, body mass index (BMI), sex, and medication number as covariates. Results Multivariate analyses demonstrated that the three variables separately, and as a composite variable (vibration time + reaction accuracy/2 + lateral plank time), were associated with UST (adjusted R 2 = 0.66 and 0.65, respectively) for the entire group, and for diabetic neuropathy, cirrhosis, and no known disease groups separately (adjusted R 2 = 0.59, 0.60, and 0.68, respectively). The composite variable also classified participants into those with UST &gt; and &lt; 15 s (receiver operator characteristics area under the curve (AUC) = 0.92 (95% CI = 0.88, 0.96)). Discussion These findings allow clinicians to identify specific physiologic deficits and develop targeted intervention strategies to improve UST. Conclusion Clinical estimates of three physiologic capacities predict almost 2/3 of UST variability in middle/older people, rendering age, BMI, sex, and medication number less relevant.

Objective: Levator ani (LA) muscle injury during childbirth is an important contributor to the development of pelvic floor disorders (PFDs). Understanding the mechanisms of LA muscle damage and healing is crucial for developing individualized recovery plans and preventive measures. Although muscle avulsion has been extensively studied, the internal rearrangement of muscle structure has not. Current evaluation by palpation or force measurement can be limited due to pain and motivation. An objective evaluation of internal muscle structure has the advantage of being independent of these subjective factors. The objective of this study was to evaluate the feasibility of using 3-D transvaginal ultrasound (US) imaging combined with quantitative texture analysis for assessing deep LA muscle injuries and monitoring tissue microstructural changes involved in healing over time in postpartum women. By providing insights into recovery mechanisms, this approach has the potential to track muscle repair and quantify the progression of tissue healing. Methods: This is a secondary analysis of 3-D transvaginal US images performed on women who were at high risk for LA muscle injuries following vaginal delivery but did not have muscle avulsion (n = 15), and on women who underwent cesarean section (C-section) before the second stage of labor (n = 10) as controls. Imaging data were collected at 2 wk, 6 wk and 6 mo postpartum for the vaginal delivery group, and at 6 wk and 6 mo for the C-section group. Texture “features” (93 in total) that result from image characteristics (i.e., local pixel-intensity differences and adjacency relationships) were extracted from the US images using six classical texture analysis techniques. Feature reduction was implemented by calculating the Pearson correlation coefficient (PCC) and removing features with high similarity (|PCC| >0.8). Three feature-selection methods were employed: linear mixed effects analysis of variance, receiver operator characteristic analysis and least absolute shrinkage and selection operator regression. Features selected by at least two methods were used to train a random Forest classification model, with the dataset split into 70% training and 30% testing sets. Results: Four texture features were identified as potential imaging biomarkers associated with structural changes in the LA muscle during recovery. Average percentage changes of these four features (12.2% ± 2.3%) were observed between 2 and 6 wk postpartum in the vaginal delivery group. In contrast, smaller changes between 6 wk and 6 mo were noted in the vaginal delivery group and C-section group over the same period (6.0% ± 1.2% and 6.6% ± 2.3%, respectively). The random Forest model achieved a classification accuracy of 78% at distinguishing different time points based on the selected features. Conclusion: US image texture analysis detected systematic changes in muscle echotexture between 2 and 6 wk postpartum, recognized as a crucial period for healing. This suggests that the proposed approach could meaningfully complement current evaluation techniques. By providing objective imaging metrics, this method may be useful in studying rates of recovery independent of current subjective methods that are based on voluntary contraction. It can also be used to compare different recovery protocols and ultimately improve patient outcomes.

This paper describes a novel wearable personal uroflowmeter and its use to log urine leakage episodes in women. Consisting of a miniature flow rate sensor attached under the urethral meatus, it recorded both urine flow rate and volume during activities of daily living. The sensor communicated with a determining unit incorporating a microcontroller and an inertial measurement unit worn at the waist, facilitating the post-hoc determination of which activities and changes in pose caused leakage. Six women participated in a feasibility study performed in a clinical setting. The results indicate that the uroflowmeter was 97.5% accurate in assessing micturition flow compared to gold standard uroflowmetry and leakage measurements. The system also provides subject-specific information on the relationship between physical activity and urine leakage, thereby eliminating errors due to missing data and recall bias in bladder leakage diaries and circumventing the limitations of office-based uroflowmeters.

Urinary incontinence affects many women, yet there are no monitoring devices capable of accurately capturing flow dynamics during everyday activities. Building on our initial development of a wearable personal uroflowmeter, this study enhances the device’s performance under realistic, dynamic conditions similar to those encountered in daily living. We integrated an optimized eight-vane Etoile flow conditioner with a 0.2D opening into the device. Both computational fluid dynamics simulations and experimental tests demonstrated that this flow conditioner significantly reduced turbulence intensity by 82% and stabilized the axial velocity profile by 67%, increasing the R2 of flow rate measurements from 0.44 to 0.92. Furthermore, our machine learning framework—utilizing a support vector machine (SVM) and an extreme gradient boosting (XGBoost) model with principal component analysis (PCA)—accurately predicted the true flow rate with high correlations, robust performance, and minimal overfitting. For the test dataset, the SVM achieved a correlation of 0.86, an R2 of 0.74, and an MAE of 2.8, whereas the XGBoost-PCA model exhibited slightly stronger performance, with a correlation of 0.88, an R2 of 0.76, and an MAE of 2.6. These advances established a solid foundation for developing a reliable, wearable uroflowmeter capable of effectively monitoring urinary incontinence in real-world settings.

An enlarged urogenital hiatus is as important as apical support or fascial attachment failures in the development of prolapse and is strongly related to operative failure, yet we lack a conceptual model for factors responsible for hiatal failure. For a conceptual model to be valid, it cannot be proven false by empirical observation. We present six clinical observations with which future model development must be consistent. (1) Perineal body damage alone does not explain an enlarged urogenital hiatus. Three women have complete 4th degree lacerations but small hiatuses. (2) Levator damage is not a sole causal factor. One woman has bilateral levator avulsion but a normal hiatus, while another has intact muscles and an enlarged hiatus. (3) Hiatal assessment during straining is incomplete. Two women with similar straining urogenital hiatuses of 6-7 cm have respective 1.5 cm and 7 cm resting hiatuses. (4) Urogenital hiatus measurements during straining are confounded by Valsalva effort strength. Urogenital hiatus size increases by 30%, 51%, and 181% in one woman depending on straining strength. (5) Hiatal closure during pelvic muscle contraction differs widely. One woman can close her hiatus from 3.5 cm to 1.5 cm, while another shows no reduction despite evidence of contraction. (6) Prolapse/hiatus interactions occur with advancing age. One woman experiences progressive hiatal enlargement over 31 years. Our clinical observations reveal the complexity of the multiple factors involved in hiatal failure and support the need for a unified disease model consistent with these factors on which to base future research.

OBJECTIVES: Stress urinary incontinence (SUI) is a prevalent condition that can significantly affect quality of life. Urethral mobility is an important factor in SUI and transperineal ultrasound (TPUS) imaging can provide clear visualization of this movement; however, its quantification has been limited. An automated system to track and quantify urethral movement could provide richer information and reduce inter-observer effects on measurements. METHODS: As proof-of-concept for technique development, we used TPUS cine loops obtained on commercial scanners (GE Healthcare and Philips Healthcare) from consented research volunteers. We developed the tracking software based on fundamental concepts from computer vision, specifically corner detection and optical flow-based tracking algorithms. In doing so we account for inadvertent probe movements by using the symphysis pubis as a reference coordinate system. RESULTS: The system successfully tracks the motion of the urethra during Valsalva maneuvers. It accurately captures and quantifies complex movements, including directional shifts, rotations, displacement vectors of different structures, and the trajectory of motion. These measurements are corrected for any probe movement. We demonstrated the system's efficiency and reliability in near real-time analysis across various ultrasound platforms and video formats. The intraclass correlation coefficients exceeded 0.89 and 0.5 for intra- and inter-rater reliability, respectively. CONCLUSIONS: By providing detailed, objective measurements of urogenital movement, this approach has potential to advance the understanding, diagnosis and treatment of SUI, which in turn, can help tailor more effective treatment strategies. This methodology paper confirms the feasibility of automated quantification of urethral mobility.

Background The lower birth canal is the final constriction through which a fetal head must pass for delivery. Unfortunately, injuries to the lower birth canal tissues occur in up to 19% of first-time vaginal deliveries due to the 300% stretch required. Methods This is a secondary analysis of data from 56 healthy nullipara recorded by a lower birth canal dilator during the first stage of labor. A four parameter Fractional Zener rheological Model was used to characterize the canal viscoelastic properties during the first stage of labor. We tested the (null) hypothesis that the Model constants identified during the initial 20 second ramp-and-5-minute-hold dilation from 40 to 55 mm will not accurately predict the final hoop tension after 60 minutes of slower dilation. Findings The null hypothesis was rejected in that when the four Model parameters were calculated for all nullipara from the 20-second-ramp-and-5-minute-hold data, the relative fit error was 8 ± 4%, and the relative prediction error after 60 minutes of dilation was 10 ± 5%. Furthermore, when the Model constants were instead calculated from the 20 s ramp and only the initial 90 s of the 5-min-hold, the error was still acceptable: 13 ± 4% for relative fit and 13 ± 18% for relative prediction. Interpretation Two minutes is sufficient to characterize canal viscoelastic properties during the first stage of labor and identify those with stiffer tissues at higher risk for a pelvic floor injury during delivery. This could form the basis for a clinical test predicting injury.

Background: A large urogenital hiatus in Level III results in a higher risk of developing pelvic organ prolapse after birth and failure after prolapse surgery. Deepening of the pelvic floor and downward rotation of the levator plate have also been linked to prolapse. Currently we lack data that evaluates how these measures relate to one another and to prolapse occurrence and size. Objective: This study uses measurements from a published conceptual model to compare women with and without prolapse to determine the magnitude of difference between cases and controls and to quantify the interrelationships among different aspects of pelvic floor shape and structure. Study design: Ninety-one women with anterior predominant prolapse and uterus in situ who had 3D MRI and 30 similar women with normal support were studied. Resting scans were used to avoid the influence of the prolapse dilating the hiatus. Measurements assessed three domains: hiatus size (urogenital and levator hiatus); length of the surrounding pelvic floor muscles (pubovisceral, puborectal, iliococcygeal muscles); the shelf-like posterior pelvic floor (levator plate shape, levator bowl volume), and bony pelvic dimensions. Effect sizes were calculated and principal component shape analysis performed to evaluate levator plate shape. Z scores were calculated and a value greater than 1.68 (95th percentile) was considered the “failure” criterion. Frequency and severity of structural support site failure were analyzed by prolapse size. Results: Resting urogenital and levator hiatal areas were 68% and 59% larger in the prolapse group compared to controls. These area enlargements were 2–4 times larger than the anterior-posterior dimension enlargements (urogenital hiatus 36%; levator hiatus 13%). The greatest muscle length differences between groups occurred in the pubovisceral (34%) and puborectal (25%) muscles compared to the iliococcygeal muscle (8%)—roughly half the area differences. Levator bowl volume was 63% deeper with prolapse. Urogenital hiatus and levator hiatus areas were strongly correlated with pubovisceral and puborectal muscle length (.7 to .8), while iliococcygeal muscle length had lower correlations (.4 to .5). Levator bowl volume correlated strongly with hiatal enlargement (.7 to .8) and muscle length (pubovisceral and puborectal muscles), moderately so with levator plate and iliococcygeal muscle, and weakly with bony dimension. Failure frequency increased with prolapse size for urogenital hiatus anterior-posterior (p=.001) and area (p=.019). By contrast, levator hiatus area was similar for all prolapse sizes (p=.288), while levator hiatus anterior-posterior failure was more common in larger prolapses (p=.018) but with smaller percentages of failure than levator hiatus area (p<.01). Both levator bowl volume (p=.015) and levator plate (p=.045) trended toward increasing failure with larger prolapse sizes. Among women with enlarged urogenital hiatus at straining, 43% and 28% had normal urogenital hiatus anterior-posterior and area at rest, respectively. Conclusion: Changes in the shape and dimensions of the pelvic floor are complex and are not captured by a single measure (such as the urogenital hiatus anterior-posterior dimension, which does not capture its lateral expansion). The failure patterns were different between small and large prolapses. Understanding why could lead to improved prevention and treatments for Level III failures.

Abstract Purpose Primary anterior cruciate ligament (ACL) reconstruction graft failure remains a significant health concern in young patients. Despite the high incidence of poor graft integration in these patients and the resulting high failure rate, little consideration has been given to the quality of the bone into which the graft is anchored at reconstruction. Therefore, we investigated post ACL injury mineralized tissue changes in the ACL femoral entheses of young males and compared them to changes previously reported for young females. Methods ACL femoral entheses and adjacent bone specimens were harvested from the injured knees of 51 young males during primary ACL reconstructive surgery and from 10 non‐injured male cadaveric donors. The specimens were imaged via nano‐computed tomography and analyzed for volumetric bone mineral density (vBMD) and architectural changes. Results Male femoral ACL explant specimens had significantly lower cortical vBMD ( p &lt; 0.001), lower relative bone volume (BV/TV, p = 0.027) and greater cortical bone porosity (Ct.Po, p = 0.027) but similar trabecular bone parameters ( p 's &gt; 0.05) to those of control specimens from male cadaveric donors. Cortical and trabecular bone loss increased significantly with time from ACL injury to reconstructive surgery ( p 's &lt; 0.05). While cortical loss occurred in both males and females, significant trabecular loss occurred only in females ( p = 0.009). Conclusion Femoral entheseal bone loss occurs in males following ACL injury. This bone loss increases with time following ACL injury, with cortical bone loss occurring sooner after injury than trabecular bone loss. The effects of ACL injury and time from injury to surgery on trabecular bone microarchitecture differed between male and female patients. Level of Evidence N/A.

OCCUPATIONAL APPLICATIONSAssessing workers’ strength capacities is a common practice prior to return to work following injury or illness, or assessing capabilities for strenuous jobs. Because it requires 50% or more of maximum strength capacity, hip abductor muscle strength is a strong predictor of both middle- and older-aged individuals’ ability to reliably balance on one leg and of their risk of falls. Our results suggest subjects were able to augment their hip abductor moment during unipedal weight stance via gluteus maximus activity. Weight-bearing hip abduction strength measures are important for assessing worker capacity for jobs requiring reliable unipedal balance whether during lateral loading, while walking in gusty winds, on slippery footing or resisting lateral deck movements on board ship or train. Measurements of hip abductor strength should be made in a full unipedal weight bearing posture; non-weight-bearing measurements significantly underpredicted hip abductor strength as well as endurance.

A decrease in urethral closure pressure is one of the primary causes of stress urinary incontinence in women. Atrophy of the urethral muscles is a primary factor in the 15 % age-related decline in urethral closure pressure per decade. Incontinence not only affects the well-being of women but is also a leading cause of nursing home admission. The objective of this research was to develop a noninvasive test to assess urethral tissue microenvironmental changes using multiparametric ultrasound (mpUS) imaging technique. Transperineal B-scan ultrasound (US) data were captured using clinical scanners equipped with curvilinear or linear transducers. Imaging was performed on volunteers from our institution medical center (n = 15, 22 to 76 y.o.) during Valsalva maneuvers. After expert delineation of the region of interest in each frame, the central axis of the urethra was automatically defined to determine the angle between the urethra and the US beam for further analysis. By integrating angle-dependent backscatter with radiomic texture feature analysis, a mpUS technique was developed to identify biomarkers that reflect subtle microstructural changes expected within the urethral tissue. The process was repeated when the urethra and US beam were at a fixed angle. Texture selection was conducted for both angle-dependent and angle-independent results to remove redundancies. Ultimately, a distinct biomarker was derived using a random forest regression model to compute the urethra score based on features selected from both processes. Angle-dependent backscatter analysis shows that the calculated slope of US mean image intensity decreased by 0.89 (±0.31) % annually, consistent with the expected atrophic disorganization of urethral tissue structure and the associated reduction in urethral closure pressure with age. Additionally, textural analysis performed at a specific angle (i.e., 40 degrees) revealed changes in gray level nonuniformity, skewness, and correlation by 0.08 (±0.04) %, −2.16 (±1.14) %, and −0.32 (±0.35) % per year, respectively. The urethra score was ultimately determined by combining data selected from both angle-dependent and angle-independent analysis strategies using a random forest regression model with age, yielding an R 2 value of 0.96 and a p-value less than 0.001. The proposed mpUS tissue characterization technique not only holds promise for guiding future urethral tissue characterization studies without the need for tissue biopsies or invasive functional testing but also aims to minimize observer-induced variability. By leveraging mpUS imaging strategies that account for angle dependence, it provides more accurate assessments. Notably, the urethra score, calculated from US images that reflect tissue microstructural changes, serves as a potential biomarker providing clinicians with deeper insight into urethral tissue function and may aid in diagnosing and managing related conditions while helping to determine the causes of incontinence.

Abstract Introduction and Hypothesis Vaginal dimensions have clinical and surgical implications. We sought to quantify the differences between vaginal and labial dimensions in healthy ethnic Chinese and Western women with normal pelvic organ support. Methods This is a cross-sectional study of a convenience sample of ethnic Chinese nullipara (n = 33) and Western nullipara (n= 33) women recruited for research purposes. For each subject, magnetic resonance imaging was used to quantify the vaginal and labial dimensions. Specifically, we identified the anterior and posterior vaginal wall, the outline of the cervix in the mid-sagittal and coronal planes, and the distance from the labia majora to the hymenal ring at the urethral meatus. Results The vaginal and labial dimensions of ethnic Chinese nullipara were 9-21 % smaller than those of Western nullipara; however, the relative orientation of the cervix to the vaginal opening was not different. Conclusions Significant group differences in vaginal and labial dimensions were found, with Chinese nullipara dimensions being up to 21% smaller than those of Western nullipara. Brief Summary Ethnic Chinese women have smaller vaginal and labial dimensions than Western women. These differences have clinical and surgical implications.

Sir In their paper Dr. Gan and colleagues [1Gan B. Zheng S. Wu X. Li X. The predicting value of the ratio of levator hiatus diameter to fetal head circumference in pregnant women at 37 weeks of gestation in the progression of the second stage of labor and levator ani injury 6 weeks postpartum”.Heliyon. 2024 Feb 1; 10e25636Abstract Full Text Full Text PDF Scopus (0) Google Scholar] used intrapartum ultrasound scanning to test the very reasonable hypothesis that the ratio of levator hiatus diameter to head circumference might be used to predict the duration of the second stage of labor as well as the risk for levator ani injury. Simply put, when a large fetal head must be pushed through a smaller hiatus, one might expect that this might be associated with a longer second stage of labor as well as a higher risk for levator injury. Their results confirm this idea. This is a useful contribution to the literature on this topic because of its potential for use as a screening tool. In the future one might be able to use it to minimize the risk of long second stages as well as the risk for levator and hiatal injuries. But this idea is not new. In their Introduction reviewing the literature, the authors fail to acknowledge the prior ultrasound study of Rostaminia et al. [2Rostaminia G. Peck J.D. Delft, R K.V. et al.New measures for predicting birth-related pelvic floor trauma.Female Pelv Med Reconstr Surg Open Access. 2016; 22: 292-296Crossref PubMed Scopus (0) Google Scholar] who were the first to attempt such predictions. A weakness of the Rostaminia et al. approach in terms of clinical applicability was the fact that they used postpartum measures of head circumference rather than prepartum measures to test the ratio. In a study published the same year, Tracy et al. [3Tracy P.V. DeLancey J.O. Ashton-Miller J.A. A geometric capacity-demand analysis of maternal levator muscle stretch required for vaginal delivery.J Biomech Eng. 2016; 138 (2016)021001Crossref Scopus (22) Google Scholar] developed and tested what they called the “Capacity-Demand” ratio - the very same ratio being tested by Gan et al. In that paper they laid out the theoretical framework for the ratio, with the “capacity” quantifying the size of the mother’s outlet and the “demand” the size of the baby’s head. When the capacity is very much larger than the demand the birth can proceed easily. When it is close to the demand, the outcome is uncertain. When the capacity is much less than the demand, a longer second stage can be expected, and a vacuum/forceps intervention will be necessary. They directly tested that idea using a computer model based on the published variations in the two parameters constituting the Capacity-Demand ratio. They used a similar approach for the risk for risk of levator injury which they refined in a follow-up paper, Tracy et al. [4Tracy P.V. Wadhwani S. Triebwasser J. S A. et al.On the variation in maternal birth canal in vivo viscoelastic properties and their effect on the predicted length of active second stage and levator ani tears.J Biomech. 2018; 74: 64-71Crossref PubMed Google Scholar] by adding actual measures of distal maternal birth canal tissue elasticity and viscosity during the first stage of labor to predict the length of the active second stage of labor and risk for levator injury, both goals of the Gan et al. paper. It is incumbent upon any authors to exercise due diligence and find the earlier papers addressing the central problem addressed in their paper. These are usually summarized briefly in the Introduction of the paper. It would have been normal scientific etiquette for Gan et al. to have acknowledged the papers most relevant to the central idea tested in their paper, namely the “Capacity-Demand” ratio as a prediction tool: those papers are easily found in a Google search using key words like “levator hiatus fetal head prediction”, including the three papers mentioned above. It matters not that the Rostaminia et al. paper employed an ultrasound method to measure one of the capacity-demand variables and a physical method to measure the other, or that the Tracy et al. papers employed morphological, biomechanical and in vivo tissue property data in predictive computer models. All three tested the central idea of the predictive ability of the capacity-demand ratio six or more years prior to Gan et al. Finally, in the Discussion of a scientific paper it is usual practice to consider how the results in that paper corroborate and extend findings already published in the literature on the central focus of the paper, a discussion that again is missing in the Gan et al. paper because the most salient papers were never cited. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Basic Research & Pathophysiology (MP59)1 May 2024MP59-09 ONE STEP CLOSER TO a CATHETER-FREE PRESSURE FLOW STUDY: SUBHARMONIC-AIDED PRESSURE ESTIMATION OF HUMAN BLADDERS USING CONTRAST ULTRASONOGRAPHY Kourosh Kalayeh, J. Brian Fowlkes, John O. DeLancey, James A. Ashton-Miller, William W. Schultz, and Bryan S. Sack Kourosh KalayehKourosh Kalayeh , J. Brian FowlkesJ. Brian Fowlkes , John O. DeLanceyJohn O. DeLancey , James A. Ashton-MillerJames A. Ashton-Miller , William W. SchultzWilliam W. Schultz , and Bryan S. SackBryan S. Sack View All Author Informationhttps://doi.org/10.1097/01.JU.0001009476.18935.3b.09AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Urodynamic tests require a urethral catheter resulting in non-physiologic pressure flow measurements. We have previously shown that an ultrasound-based technology, known as subharmonic-aided pressure estimation (SHAPE), can effectively measure pressure in a bladder phantom. In this study, we measure bladder pressure using this technology in adult female volunteers. We hypothesize that SHAPE may be a viable alternative for measuring bladder pressure non-invasively. METHODS: The urodynamic tests were performed with a standard urodynamic system. The GE Healthcare LOGIQ® E10 ultrasound scanner equipped with the SHAPE mode and the C2-9 probe was used for ultrasound scanning. Lumason® ultrasound contrast agent was diluted in normal saline at a 500:1 dilution and infused via the urodynamic system. The bladders were filled from an initial volume of 60 to 270 mL at a filling rate of 30 mL/min. During the test the bladder was pressurized through Valsalva maneuvers by the subject (pressurization event). Probe location differences were assessed on the abdomen and perineum. The pressure values from the urodynamics catheter and the subharmonic signals were recorded for offline analysis to determine the SHAPE conversion factor in dB/cmH2O. RESULTS: We observed an inverse linear relationship between SHAPE signal and changes in bladder pressure during filling and post filling, for both transabdominal and transperineal imaging. The accompanying figure serves as an illustrative example of these findings. For this example, SHAPE conversion factors are −0.06 and −0.08 dB/cmH2O with R2=0.86 and 0.93 for transabdominal and transperineal orientations, respectively. CONCLUSIONS: Based on these preliminary human subject findings, our study shows the potential of SHAPE as a catheter-free viable alternative for measuring bladder pressure. SHAPE can measure changes in bladder pressure during filling and post-filling in both transabdominal and transperineal imaging modes. These initial findings are promising but require further validation to confirm SHAPE's efficacy and clinical applicability during voiding. Download PPT Source of Funding: Supported by NIH-RC2-DK-122379 © 2024 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 211Issue 5SMay 2024Page: e960 Advertisement Copyright & Permissions© 2024 by American Urological Association Education and Research, Inc.Metrics Author Information Kourosh Kalayeh More articles by this author J. Brian Fowlkes More articles by this author John O. DeLancey More articles by this author James A. Ashton-Miller More articles by this author William W. Schultz More articles by this author Bryan S. Sack More articles by this author Expand All Advertisement PDF downloadLoading ...

Increasing chair recline during seated computer work may reduce the load placed on the upper trapezius (UT), a common location of pain for those with idiopathic chronic neck pain. This study determined the effect of increasing chair recline on UT stiffness and muscle activity during computer work in people with and without idiopathic chronic neck pain. Surface electromyography and ultrasound shear wave elastography were collected from three subdivisions of the UT in 15 individuals with idiopathic chronic neck pain and 15 sex-matched healthy controls. Participants sat in a standardized computer-work setup while chair recline (0°, 25°, 45°) and head and neck position (self-selected, neutral, flexed) were systematically adjusted and maintained for 2.5-min intervals. Repeated-measures ANOVAs were completed for each sex, muscle, and data type, with group (chronic neck pain, control), chair recline (0°,25°,45°), head and neck position (self-selected, flexed, neutral), and side of collected data (dominant, non-dominant) as fixed factors. Men with idiopathic chronic neck pain demonstrated greater UT stiffness in the cranial subdivision when compared to healthy men. Additionally, the 25° and 45° recline levels increased the stiffness of men's dominant UT compared to men's non-dominant UT. Women's UT was more affected by head and neck position, and a neutral head and neck position resulted in lower UT activation, but higher UT stiffness for the cranial subdivision and midway between C-7 and the acromion process. Overall, our findings suggest that the commonly suggested neutral position may not be a beneficial prompt when positioning someone during seated computer work.

Introduction Urogenital hiatus enlargement is a critical factor associated with prolapse and operative failure. This study of the perineal complex was performed to understand how interactions among its three structures: the levator ani, perineal membrane, and perineal body—united by the vaginal fascia—work to maintain urogenital hiatus closure. Methods Magnetic resonance images from 30 healthy nulliparous women with 3D reconstruction of selected subjects were used to establish overall geometry. Connection points and lines of action were based on perineal dissection in 10 female cadavers (aged 22–86 years), cross sections of 4 female cadavers (aged 14–35 years), and histological sections (cadavers aged 16 and 21 years). Results The perineal membrane originates laterally from the ventral two thirds of the ischiopubic rami and attaches medially to the perineal body and vaginal wall. The levator ani attaches to the perineal membrane’s cranial surface, vaginal fascia, and the perineal body. The levator line of action in 3D reconstruction is oriented so that the levator pulls the medial perineal membrane cranio-ventrally. In cadavers, simulated levator contraction and relaxation along this vector changes the length of the membrane and the antero–posterior diameter of the urogenital hiatus. Loss of the connection of the left and right perineal membranes through the perineal body results in diastasis of the levator and a widened hiatus, as well as a downward rotation of the perineal membrane. Conclusion Interconnections involving the levator ani muscles, perineal membrane, perineal body, and vaginal fascia form the perineal complex surrounding the urogenital hiatus in an arrangement that maintains hiatal closure.

Pelvic floor disorders after childbirth have distressing lifelong consequences for women, requiring more than 300,000 women to have surgery annually. This represents approximately 10% of the 3 million women who give birth vaginally each year. Vaginal birth is the largest modifiable risk factor for prolapse, the pelvic floor disorder most strongly associated with birth, and is an important contributor to stress incontinence. These disorders require 10 times as many operations as anal sphincter injuries. Imaging shows that injuries of the levator ani muscle, perineal body, and membrane occur in up to 19% of primiparous women. During birth, the levator muscle and birth canal tissues must stretch to more than 3 times their original length; it is this overstretching that is responsible for the muscle tear visible on imaging rather than compression or neuropathy. The injury is present in 55% of women with prolapse later in life, with an odds ratio of 7.3, compared with women with normal support. In addition, levator damage can affect other aspects of hiatal closure, such as the perineal body and membrane. These injuries are associated with an enlarged urogenital hiatus, now known as antedate prolapse, and with prolapse surgery failure. Risk factors for levator injury are multifactorial and include forceps delivery, occiput posterior birth, older maternal age, long second stage of labor, and birthweight of >4000 g. Delivery with a vacuum device is associated with reduced levator damage. Other steps that might logically reduce injuries include manual rotation from occiput posterior to occiput anterior, slow gradual delivery, perineal massage or compresses, and early induction of labor, but these require study to document protection. In addition, teaching women to avoid pushing against a contracted levator muscle would likely decrease injury risk by decreasing tension on the vulnerable muscle origin. Providing care for women who have experienced difficult deliveries can be enhanced with early recognition, physical therapy, and attention to recovery. It is only right that women be made aware of these risks during pregnancy. Educating women on the long-term pelvic floor sequelae of childbirth should be performed antenatally so that they can be empowered to make informed decisions about management decisions during labor.

We compared the ability of seven machine learning algorithms to use wearable inertial measurement unit (IMU) data to identify the severe knee loading cycles known to induce microdamage associated with anterior cruciate ligament rupture. Sixteen cadaveric knee specimens, dissected free of skin and muscle, were mounted in a rig simulating standardized jump landings. One IMU was located above and the other below the knee, the applied three-dimensional action and reaction loads were measured via six-axis load cells, and the three-dimensional knee kinematics were also recorded by a laboratory motion capture system. Machine learning algorithms were used to predict the knee moments and the tibial and femur vertical forces; 13 knees were utilized for training each model, while three were used for testing its accuracy (i.e., normalized root-mean-square error) and reliability (Bland-Altman limits of agreement). The results showed the models predicted force and knee moment values with acceptable levels of error and, although several models exhibited some form of bias, acceptable reliability. Further research will be needed to determine whether these types of models can be modified to attenuate the inevitable in vivo soft tissue motion artifact associated with highly dynamic activities like jump landings.

Several 2-dimensional and 3-dimensional measurements have been used to assess changes in pelvic floor structures and shape. These include assessment of urogenital and levator hiatus dimensions, levator injury grade, levator bowl volume, and levator plate shape. We argue that each assessment reflects underlying changes in an individual aspect of the overall changes in muscle and fascial structures. Vaginal delivery, aging, and interindividual variations in anatomy combine to affect pelvic floor structures and their connections in different ways. To date, there is no unifying conceptual model that permits the evaluation of how these many measures relate to one another or that reflects overall pelvic floor structure and function. Therefore, this study aimed to describe a unified pelvic floor conceptual model to better understand how the aforementioned changes to the pelvic floor structures and their biomechanical interactions affect pelvic organ support with vaginal birth, prolapse, and age. In this model, the pelvic floor is composed of 5 key anatomic structures: the (1) pubovisceral, (2) puborectal, and (3) iliococcygeal muscles with their superficial and inferior fascia; (4) the perineal membrane or body; and (5) the anal sphincter complex. Schematically, these structures are considered to originate from pelvic sidewall structures and meet medially at important connection points that include the anal sphincter complex, perineal body, and anococcygeal raphe. The pubovisceral muscle contributes primarily to urogenital hiatus closure, whereas the puborectal muscle is mainly related to levator hiatus closure, although each muscle contributes to the other. Dorsally and laterally, the iliococcygeal muscle forms a shelflike structure in women with normal support that spans the remaining area between these medial muscles and attachments to the pelvic sidewall. Other features include the levator plate, bowl volume, and anorectal angle. The pelvic floor conceptual model integrates existing observations and points out evident knowledge gaps in how parturition, injury, disease, and aging can contribute to changes associated with pelvic floor function caused by the detachment of one or more important connection points or pubovisceral muscle failure.

The semantic segmentation of pelvic organs via MRI has important clinical significance. Recently, deep learning-enabled semantic segmentation has facilitated the three-dimensional geometric reconstruction of pelvic floor organs, providing clinicians with accurate and intuitive diagnostic results. However, the task of labeling pelvic floor MRI segmentation, typically performed by clinicians, is labor-intensive and costly, leading to a scarcity of labels. Insufficient segmentation labels limit the precise segmentation and reconstruction of pelvic floor organs. To address these issues, we propose a semi-supervised framework for pelvic organ segmentation. The implementation of this framework comprises two stages. In the first stage, it performs self-supervised pre-training using image restoration tasks. Subsequently, fine-tuning of the self-supervised model is performed, using labeled data to train the segmentation model. In the second stage, the self-supervised segmentation model is used to generate pseudo labels for unlabeled data. Ultimately, both labeled and unlabeled data are utilized in semi-supervised training. Upon evaluation, our method significantly enhances the performance in the semantic segmentation and geometric reconstruction of pelvic organs, Dice coefficient can increase by 2.65% averagely. Especially for organs that are difficult to segment, such as the uterus, the accuracy of semantic segmentation can be improved by up to 3.70%.

Background: It is not known mechanistically whether a steeper lateral posterior tibial slope (LTS) leads to an increase in anterior tibial translation (ATT) as well as internal tibial rotation (ITR) during a given jump landing. Hypothesis: A steeper LTS will result in increased ATT and ITR during simulated jump landings when applying knee compression, flexion, and internal tibial torque of increasing severity. Study Design: Descriptive laboratory study. Methods: Seven pairs of cadaveric knees were harvested from young male adult donors (mean ± SD; age, 25.71 ± 5.53 years; weight, 71.51 ± 4.81 kg). The LTS of each knee was measured by a blinded observer from 3-T magnetic resonance images. Two sets of 25 impact trials of ∼700 N (1× body weight [BW] ±10%) followed by 2 sets of 25 trials of 1400 N (2× BW ±10%) were applied to a randomly selected knee of each pair. Similarly, on the contralateral knee, 2 sets of 25 impact trials of ∼1800 N (2.5× BW ±10%) followed by 2 sets of 25 trials of ∼2100 N (3× BW ±10%) were applied. Three-dimensional knee kinematics, including ATT and ITR, were measured at 400 Hz using optoelectronic motion capture. Two-factor linear mixed effect models were used to determine the relationship of LTS to ATT and ITR as impact loading increased. Results: As LTS increased, so did ATT and ITR during increasingly severe landings. LTS had an increasing effect on ATT (coefficient, 0.50; 95% CI, 0.29-0.71) relative to impact force (coefficient, 0.52; 95% CI, 0.50-0.53). ITR was proportional to LTS (coefficient, 1.36; 95% CI, 0.80-1.93) under increasing impact force (coefficient, 0.49; 95% CI, 0.47-0.52). For steeper LTS, the increase in ITR was proportionally greater than the increase in ATT. Conclusion: In male knee specimens, a steeper LTS significantly increased ATT and ITR during jump landings. Clinical Relevance: Increases in ITR and ATT during jump landings lead to increased strain on the anterior cruciate ligament and are therefore associated with greater risk of ligament failure.

Approximately 300,000 anterior cruciate ligament (ACL) tears occur annually in the United States, half of which lead to the onset of knee osteoarthritis within 10 years of injury. Repetitive loading is known to result in fatigue damage of both ligament and tendon in the form of collagen unravelling, which can lead to structural failure. However, the relationship between tissue's structural, compositional, and mechanical changes are poorly understood. Herein we show that repetitive submaximal loading of cadaver knees causes an increase in co-localised induction of collagen unravelling and tissue compliance, especially in regions of greater mineralisation at the ACL femoral enthesis. Upon 100 cycles of 4× bodyweight knee loading, the ACL exhibited greater unravelled collagen in highly mineralized regions across varying levels of stiffness domains as compared to unloaded controls. A decrease in the total area of the most rigid domain, and an increase in the total area of the most compliant domain was also found. The results highlight fatigue-driven changes in both protein structure and mechanics in the more mineralized regions of the ACL enthesis, a known site of clinical ACL failure. The results provide a starting point for designing studies to limit ligament overuse injury.

Introduction: Recent evidence has emerged suggesting that a non-contact anterior cruciate ligament (ACL) tear can result from repetitive submaximal loading of the ligament. In other words, when the intensity of ACL-straining athletic activities is increased too rapidly, microdamage can accumulate in the ligament beyond the rate at which it can be repaired, thereby leading to material fatigue in the ligament and its eventual failure. The objective of this survey-based exploratory study was to retrospectively determine whether the levels of various athletic activities performed by ACL-injured patients significantly changed during the 6 months before injury. Methods: Forty-eight ACL-injured patients completed a survey to characterize their participation in various activities (weightlifting, sport-specific drills, running, jumping, cutting, pivoting/twisting, and decelerating) at three timepoints (1 week, 3 months, 6 months) prior to ACL injury. Activity scores, which summarized the frequency and intensity of each activity, were calculated for each patient at each time interval. A series of linear mixed-effects regression models was used to test whether there was a significant change in levels of the various activities in the 6-month period leading up to ACL injury. Results: Patients who sustained a non-contact ACL injury markedly increased their sport-specific drills activity levels in the time leading up to injury ( p = 0.098), while those patients who sustained a contact ACL injury exhibited no change in this activity during the same time period ( p = 0.829). Levels of running, jumping, cutting, pivoting/twisting, and decelerating increased for non-contact ACL-injured patients but decreased for contact ACL-injured patients, though not significantly ( p values &amp;gt; 0.10). Weightlifting activity significantly decreased leading up to injury among contact ACL-injured patients ( p = 0.002). Discussion: We conclude that levels of ACL-straining athletic activities or maneuvers in non-contact ACL-injured patients markedly increased in the 6 months leading up to their injury, providing evidence that changing levels of certain activities or maneuvers may play a role in ACL injury risk. This warrants further investigation of the hypothesis that too rapid an increase in activities or maneuvers known to place large loads on the ACL can cause microdamage to accumulate in the ligament, thereby leading to failure.

BACKGROUND: Overuse ligament and tendon injuries are prevalent among recreational and competitive adolescent athletes. In vitro studies of the ligament and tendon suggest that mechanical overuse musculoskeletal injuries begin with collagen triple-helix unraveling, leading to collagen laxity and matrix damage. However, there are little in vivo data concerning this mechanism or the physiomechanical response to collagen disruption, particularly regarding the anterior cruciate ligament (ACL). PURPOSE: To develop and validate a novel in vivo animal model for investigating the physiomechanical response to ACL collagen matrix damage accumulation and propagation in the ACL midsubstance, fibrocartilaginous entheses, and subchondral bone. STUDY DESIGN: Controlled laboratory study. METHODS: C57BL/6J adolescent inbred mice underwent 3 moderate to strenuous ACL fatigue loading sessions with a 72-hour recovery between sessions. Before each session, randomly selected subsets of mice (n = 12) were euthanized for quantifying collagen matrix damage (percent collagen unraveling) and ACL mechanics (strength and stiffness). This enabled the quasi-longitudinal assessment of collagen matrix damage accrual and whole tissue mechanical property changes across fatigue sessions. Additionally, all cyclic loading data were quantified to evaluate changes in knee mechanics (stiffness and hysteresis) across fatigue sessions. RESULTS: = .02) higher compared with the nonloaded controls. CONCLUSION: This study confirmed the hypothesis that in vivo ACL collagen matrix damage increases with tissue fatigue sessions, adversely impacting ACL mechanical properties. Moreover, the in vivo ACL findings were consistent with in vitro overloading research in humans. CLINICAL RELEVANCE: The outcomes from this study support the use of this model for investigating ACL overuse injuries.

Urinary chloride concentration is a valuable health metric that can aid in the early detection of serious conditions, such as acid base disorders, acute heart failure, and incidences of acute renal failure in the intensive care unit. Physiologically, urinary chloride levels frequently change and are difficult to measure, involving time-consuming and inconvenient lab testing. Thus, near real-time simple sensors are needed to quickly provide actionable data to inform diagnostic and treatment decisions that affect health outcomes. Here, we introduce a chronopotentiometric sensor that utilizes commercially available screen-printed electrodes to accurately quantify clinically relevant chloride concentrations (5-250 mM) in seconds, with no added reagents or electrode surface modification. Initially, the sensor's performance was optimized through the proper selection of current density at a specific chloride concentration, using electrical response data in conjunction with scanning electron microscopy. We developed a unique swept current density algorithm to resolve the entire clinically relevant chloride concentration range, and the chloride sensors can be reliably reused for chloride concentrations less than 50 mM. Lastly, we explored the impact of pH, temperature, conductivity, and additional ions (i.e., artificial urine) on the sensor signal, in order to determine sensor feasibility in complex biological samples. This study provides a path for further development of a portable, near real-time sensor for the quantification of urinary chloride.