Tensile properties of the hip joint ligaments are largely variable and age-dependent - An in-vitro analysis in an age range of 14-93 years.

INTRODUCTION: Hip joint stability is maintained by the surrounding ligaments, muscles, and the atmospheric pressure exerted via these structures. It is unclear whether the ligaments are capable of preventing dislocation solely due to their tensile properties, and to what extent they undergo age-related changes. This study aimed to obtain stress-strain data of the hip ligaments over a large age range. METHODS: Stress-strain data of the iliofemoral (IL), ischiofemoral (IS) and pubofemoral ligament (PF) were obtained from cadavers ranging between 14 and 93 years using a highly standardized setting. Maximum strains were compared to the distances required for dislocation. RESULTS: Elastic modulus was 24.4 (IL), 22.4 (IS) and 24.9N/mm2 (PF) respectively. Maximum strain was 84.5%, 86.1%, 72.4% and ultimate stress 10.0, 7.7 and 6.5N/mm2 for the IL, IS and PF respectively. None of these values varied significantly between ligaments or sides. The IS' elastic modulus was higher and maximum strain lower in males. Lower elastic moduli of the PF and higher maximum strains for the IS and PF were revealed in the ≥55 compared to the <55 population. Maximum strain exceeded the dislocation distance of the IS without external hip joint rotation in females, and of the IS and cranial IL under external rotation in both genders. DISCUSSION: Tensile and failure load properties of the hip joint ligaments are largely variable. The IS and PF change age-dependently. Though the hip ligaments contribute to hip stability, the IS and cranial IL may not prevent dislocation due to their elasticity.

A preliminary technical study on sodium dodecyl sulfate-induced changes of the nano-structural and macro-mechanical properties in human iliotibial tract specimens.

INTRODUCTION: Acellular scaffolds are frequently used for the surgical repair of ligaments and tendons. Even though data on the macro-mechanical properties related to the acellularization process exist, corresponding data on the nano-structural properties are still lacking. Such data would help identify target proteins of the formed extracellular matrix that are chemically altered by the acellularization. In this study we examined the altered structure by comparing molecular properties of collagens from native and acellular iliotibial tract samples to the macroscopic stress-strain behavior of tract samples. MATERIAL AND METHODS: Matched pairs of five human iliotibial tract samples were obtained from five donors (mean age 28.2±4.7 years). One of each pair was acellularized using 1vol% sodium dodecyl sulfate (SDS) for 7 days. (13)C magic angle spinning nuclear magnetic resonance spectroscopy ((13)C CP MAS NMR) was utilized to compare the collagen overall secondary structure and internal dynamics of collagen-typical amino acid proteins. The resulting data was compared to age-matched stress-strain data of tract samples obtained in an uniaxial tensile setup and histologically. RESULTS: Typical and nearly identical collagen (13)C CP MAS NMR spectra were found in the tract samples before and after acellularization with SDS. The characteristic collagen backbone remained intact in the native and acellular samples. Collagen molecular composition was largely unaltered in both conditions. Furthermore, a similar dynamic behavior was found for the amino acids Hyp γ, Pro α/Hyp α, Ala α, Gly α and Ala ß. These minute alterations in the collagens' molecular properties related to acellularization with SDS were in line with the similarly minute changes in the macro-mechanical tensile behavior, such as the elastic modulus and ultimate stress. Histology showed intact type I collagens, minute amounts of elastins before and after acellularization and evidence for acellularization-induced reductions of proteoglycans. DISCUSSION: Nano-structural properties of collagens are minutely affected by SDS treatment for acellularization, indicated by the molecular composition and dynamics. The lacking acellularization-related changes in the molecular structure properties of collagens in iliotibial tract samples are in line with the small alterations in their macro-mechanical tensile behavior. Though the given setup approaches soft tissue mechanics from both scaling extremes of mechanical testing, further structural analyzes are needed in a larger sample size to substantiate these findings.

[On the forensic relevance of orphan diseases]. / Zur forensischen Relevanz seltener Erkrankungen.

A 40-year-old woman died shortly after complaining of non-specific symptoms after a pharmacist had accidentally given her the wrong medication. The woman's partner was not familiar with her medical history and the medical file had to be obtained from the family doctor. Autopsy findings and histological examination confirmed the clinically diagnosed autoimmune polyglandular syndrome without a tangible cause of death. Poisoning could not be demonstrated and no relation between the dosage error and death could be established. Laboratory tests revealed diabetic coma with ketoacidosis as the cause of death, which was probably caused by a prolonged lack of insulin administration. In addition to the clarification of legal issues, the complete post-mortem examination of orphan diseases is also relevant for achieving a better understanding of differential diagnostic aspects and complex pathophysiological contexts. Moreover, the genetic background often underlying such diseases should be a reason to inform the family of the deceased about the autopsy results. Only then can secondary preventive measures be taken in time.

Severe cardiac trauma or myocardial ischemia? Pitfalls of polytrauma treatment in patients with ST-elevation after blunt chest trauma.

INTRODUCTION: Thoracic injuries are the third most common injuries in polytrauma patients. The mechanism of injury and the clinical presentation are crucially important for adequate emergency treatment. PRESENTATION OF CASE: Here we present a case of a 37-year-old male who was admitted to our level-1 trauma center after motor vehicle accident. The emergency physician on scene presented the patient with a myocardial infarction. During initial clinical trauma assessment the patient developed circulatory insufficiency so that cardiopulmonary resuscitation was necessary. Considering the preclinical and clinical course it was decided to proceed with thrombolysis. Despite consistently sufficient resuscitation measures circulatory function was not restored and the patient remained in asystole and passed away. DISCUSSION: The initial assessment showed cardiopulmonary instability. After applying thrombolysis a therapeutic point of no return was reached because surgical intervention was impossible but autopsy findings showed severe myocardial and pulmonary contusions likely due to shear forces. CONCLUSION: This case outlines the importance of understanding the key mechanism of injury and the importance of communication at each stage of healthcare transfer. A transesophageal echocardiography can help to identify injuries after myocardial contusion.

Quantification of material slippage in the iliotibial tract when applying the partial plastination clamping technique.

The objective of this study was to evaluate the potential of the partial plastination technique in minimizing material slippage and to discuss the effects on the tensile properties of thin dense connective tissue. The ends of twelve iliotibial tract samples were primed with polyurethane resin and covered by plastic plates to provide sufficient grip between the clamps. The central part of the samples remained in an anatomically unfixed condition. Strain data of twelve partially plastinated samples and ten samples in a completely anatomically unfixed state were obtained using uniaxial crosshead displacement and an optical image tracking technique. Testing of agreement between the strain data revealed ongoing but markedly reduced material slippage in partially plastinated samples compared to the unfixed samples. The mean measurement error introduced by material slippage was up to 18.0% in partially plastinated samples. These findings might complement existing data on measurement errors during material testing and highlight the importance of individual quantitative evaluation of errors that come along with self-made clamping techniques.

Comparison of modified Thiel embalming and ethanol-glycerin fixation in an anatomy environment: Potentials and limitations of two complementary techniques.

Thiel-fixed specimens have outstandingly lifelike visual and haptic properties. However, the original Thiel method is expensive and requires an elaborate setup. It is therefore of principal interest to modify the Thiel method in order to make it available to a broader user group. A modified Thiel embalming method will be described in detail and compared to ethanol-glycerin fixation with the help of illustrative examples. The visual properties, haptic properties, the usability for performing histological investigations, costs and potential health aspects will be considered. Tissues fixed with the modified Thiel technique gave results similar to the original method, providing more realistic visual and haptic properties than ethanol-glycerin embalming. However, Thiel fixation is significantly more expensive and requires more precautions to minimize potential health hazards than ethanol-glycerin-fixed tissues. In contrast to ethanol-glycerin-fixed specimens, the Thiel-fixed specimens are not suitable for histological investigations. Both modes of fixation are inappropriate for biomechanical testing. Modified Thiel embalming simplifies the availability of body donors with lifelike properties and has cost-saving advantages to the original technique. Thiel-embalmed body donors are ideally suited for clinical workshops but have restrictions for student dissection courses in facilities with limited storage space, air circulation or technical staff. Vice versa, ethanol-glycerin-fixed body donors are well suited for student dissection courses in such an environment but are limited in their use for clinical workshops. Modified Thiel embalming therefore ideally complements ethanol-glycerin fixation in order to provide customized solutions for clinical workshops and student dissection courses in a wide range of applications.

Acute aortic dissection caused by Clostridium septicum aortitis.

Clostridium septicum aortitis is a rare cause of aortic dissection. So far, only 28 cases have been described in literature before. Most of these cases occurred in elderly patients and an association to colonic neoplasms and/or atherosclerosis has been witnessed frequently. Here we report the case of a 32-year-old man with fatal aortic dissection due to aortic infection with C. septicum. Beside a case of a 22-year-old man who died of aortic dissection due to C. septicum aortitis this is the second case of C. septicum aortitis in a young individual with no signs of colonic neoplasms or atherosclerosis.

Do cells contribute to tendon and ligament biomechanics?

INTRODUCTION: Acellular scaffolds are increasingly used for the surgical repair of tendon injury and ligament tears. Despite this increased use, very little data exist directly comparing acellular scaffolds and their native counterparts. Such a comparison would help establish the effectiveness of the acellularization procedure of human tissues. Furthermore, such a comparison would help estimate the influence of cells in ligament and tendon stability and give insight into the effects of acellularization on collagen. MATERIAL AND METHODS: Eighteen human iliotibial tract samples were obtained from nine body donors. Nine samples were acellularized with sodium dodecyl sulphate (SDS), while nine counterparts from the same donors remained in the native condition. The ends of all samples were plastinated to minimize material slippage. Their water content was adjusted to 69%, using the osmotic stress technique to exclude water content-related alterations of the mechanical properties. Uniaxial tensile testing was performed to obtain the elastic modulus, ultimate stress and maximum strain. The effectiveness of the acellularization procedure was histologically verified by means of a DNA assay. RESULTS: The histology samples showed a complete removal of the cells, an extensive, yet incomplete removal of the DNA content and alterations to the extracellular collagen. Tensile properties of the tract samples such as elastic modulus and ultimate stress were unaffected by acellularization with the exception of maximum strain. DISCUSSION: The data indicate that cells influence the mechanical properties of ligaments and tendons in vitro to a negligible extent. Moreover, acellularization with SDS alters material properties to a minor extent, indicating that this method provides a biomechanical match in ligament and tendon reconstruction. However, the given protocol insufficiently removes DNA. This may increase the potential for transplant rejection when acellular tract scaffolds are used in soft tissue repair. Further research will help optimize the SDS-protocol for clinical application.

Ultimate stress and age-dependent deformation characteristics of the iliotibial tract.

BACKGROUND AND AIMS: To understand biomechanics of ligaments and tendons data on their material properties are necessary. The iliotibial tract is a suitable model for virtual pelvic or lower extremity ligaments due to its parallel fibers, which facilitates biomechanical testing. Here, we determined Young's modulus (YM) as secant stiffness between defined limits of the iliotibial tract and correlated the data to ultimate stress (US) of the specimens and to age, gender and body weight of the body donors. MATERIALS AND METHODS: Thirty eight specimens from 12 iliotibial tracts of 10 young donors (mean age 31.2±9.1 years) were investigated biomechanically. After preconditioning, YM were determined in the ranges of 0-4 and 4-11 N/mm² of applied stress and from 4N/mm² of applied stress to US. RESULTS: YM of the specimens were 84.7±30.2 (0-4 N/mm²), 335.4±101.9 (4-11 N/mm²), and 369.1±191.5 (4 N/mm² to US) N/mm², respectively. The mean US was 35.8±16.4 N/mm². YM and US correlated closely in the ranges of 4-11 N/mm² (r=0.95) and 4 N/mm² to US (r=0.91). YM did not correlate to age, body weight or gender within these young donors. Concerning tissue behavior a decrease of YM, i.e. weakening, is more common than an increase of YM, i.e. stiffening, before specimen failure. Overall, YM of specimens from young donors were significantly lower compared to those of old donors. DISCUSSION AND CONCLUSIONS: This is the first study providing age-dependent nonlinear stiffness properties of the iliotibial tract. YM is significantly lower in young than in old donors and is thus a subject of alteration during life time.

Deformation behavior of the iliotibial tract under different states of fixation.

BACKGROUND AND OBJECTIVE: The iliotibial tract (tract) is an important structure for the biomechanics of both the hip and knee joint. While a detailed characterization of its mechanical properties might help to better understand its specific role in the load transfer from the pelvis to femur and tibia, determination of those properties is complicated by its particular structure of thin fibers in the fresh state. Moreover, although the tracts mechanical properties are often derived from cadaveric material chemically fixed with either ethanol or formaldehyde, the influence of such fixation methods remains to be elucidated. Aim of this study was to determine Young's modulus (tensile modulus, YM) of the tract. We hypothesized that either ethanol or formaldehyde fixation would significantly increase the YM compared to the tracts condition in a fresh state. MATERIAL AND METHODS: 13 specimens of tract were gained from donators. The ends of the probes were plastinated with resin creating a sharp interface between the clamp and the probe to prevent material slippage. The specimens were measured in their fresh state, under ethanol- and formaldehyde-fixed conditions and re-measured after rinsing with tap water. RESULTS: The YM of the fresh probes averaged 397.3N/mm(2) with a standard deviation (SD) of 151.5N/mm(2). The YM of the ethanol-fixed specimens was significantly higher (673.2N/mm(2), SD 328.5N/mm(2), p<0.05). After rinsing with tap water, the YM decreased to 95% of the fresh condition value (377.4N/mm(2), SD 144.5N/mm(2), non-significant change from fresh). After formaldehyde fixation, the YM reached 490.3N/mm(2) (SD 143.0N/mm(2), p<0.05). When the formaldehyde-fixed specimens were rinsed, the YM was 114% of the value of the fresh condition (452.6N/mm(2), SD 115.1N/mm(2), non-significant change from fresh). CONCLUSIONS: This study found a significant influence of the chemical fixation method on the YM of the IT tract. If such fixation is required, our results suggest using a treatment with ethanol and subsequent rinsing that results in minimal changes to the tracts YM. Furthermore, plastination of the ends of the specimens could be crucial to allow in vitro determination of valid YM of ligaments data that can then be integrated with confidence in further finite element analyses.