Attachment of dissimilar materials is a major challenge because high levels of localized stress may develop at their interfaces. An effective biologic solution to this problem exists at one of nature's most extreme interfaces: the attachment of tendon (a compliant, structural "soft tissue") to bone (a stiff, structural "hard tissue"). The goal of our study was to develop biomechanical models to describe how the tendon-to-bone insertion derives its mechanical properties. We examined the tendon-to-bone insertion and found two factors that give the tendon-to-bone transition a unique grading in mechanical properties: 1), a gradation in mineral concentration, measured by Raman spectroscopy; and 2), a gradation in collagen fiber orientation, measured by polarized light microscopy. Our measurements motivate a new physiological picture of the tissue that achieves this transition, the tendon-to-bone insertion, as a continuous, functionally graded material. Our biomechanical model suggests that the experimentally observed increase in mineral accumulation within collagen fibers can provide significant stiffening of the partially mineralized fibers, but only for concentrations of mineral above a "percolation threshold" corresponding to formation of a mechanically continuous mineral network within each collagen fiber (e.g., the case of mineral connectivity extending from one end of the fiber to the other). Increasing dispersion in the orientation distribution of collagen fibers from tendon to bone is a second major determinant of tissue stiffness. The combination of these two factors may explain the nonmonotonic variation of stiffness over the length of the tendon-to-bone insertion reported previously. Our models explain how tendon-to-bone attachment is achieved through a functionally graded material composition, and provide targets for tissue engineered surgical interventions and biomimetic material interfaces.
We applied Raman spectroscopy to monitor the distribution of minerals and the degree of mineralization across the tendon-bone insertion site in the shoulders of five rats. We acquired Raman spectra from 100 to 4000 Δcm -1 on individual 1 μm points across the 120 μm wide transition zone of each tissue sample and identified all the peaks detected in pure tendon and in pure bone, as well as in the transition zone. The intensity of the 960 Δcm -1 P-O stretch for apatite (normalized to either the 2940 Δcm -1 C-H stretch or the 1003 Δcm -1 C-C stretch for collagen) was used as an indicator of the abundance of mineral. We relate the observed histological morphology in the tissue thin section with the observed Raman peaks for both the organic component (mostly collagen) and the inorganic component (a carbonated form of the mineral apatite) and discuss spectroscopic issues related to peak deconvolution and quantification of overlapping Raman peaks. We show that the mineral-tocollagen ratio at the insertion site increases linearly (R 2 = 0.8 for five samples) over the distance of 120 μm from tendon to bone, rather than abruptly, as previously inferred from histological observations. In addition, narrowing of the 960 Δcm -1 band across the traverse indicates that the crystalline ordering within the apatite increases concomitantly with the degree of mineralization. This finding of mineral gradation has important clinical implications and may explain why the uninjured tendon-to-bone connection of the rotator cuff can sustain very high stress concentrations without failure. Our finding is also consistent with recent mechanical models and calculations developed to better understand the materials properties of this unusually strong interface.
ImportanceWhole-blood (WB) resuscitation has gained renewed interest among civilian trauma centers. However, there remains insufficient evidence that WB as an adjunct to component therapy–based massive transfusion protocol (WB-MTP) is associated with a survival advantage over MTP alone in adult civilian trauma patients presenting with severe hemorrhage.ObjectiveTo assess whether WB-MTP compared with MTP alone is associated with improved survival at 24 hours and 30 days among adult trauma patients presenting with severe hemorrhage.Design, Setting, and ParticipantsThis retrospective cohort study using the American College of Surgeons Trauma Quality Improvement Program databank from January 1, 2017, and December 31, 2018, included adult trauma patients with a systolic blood pressure less than 90 mm Hg and a shock index greater than 1 who received at least 4 units of red blood cells within the first hour of emergency department (ED) arrival at level I and level II US and Canadian adult civilian trauma centers. Patients with burns, death within 1 hour of ED arrival, and interfacility transfers were excluded. Data were analyzed from February 2022 to September 2022.ExposuresResuscitation with WB-MTP compared with MTP alone within 24 hours of ED presentation.Main Outcomes and MeasuresPrimary outcomes were survival at 24 hours and 30 days. Secondary outcomes selected a priori included major complications, hospital length of stay, and intensive care unit length of stay.ResultsA total of 2785 patients met inclusion criteria: 432 (15.5%) in the WB-MTP group (335 male [78%]; median age, 38 years [IQR, 27-57 years]) and 2353 (84.5%) in the MTP-only group (1822 male [77%]; median age, 38 years [IQR, 27-56 years]). Both groups included severely injured patients (median injury severity score, 28 [IQR, 17-34]; median difference, 1.29 [95% CI, −0.05 to 2.64]). A survival curve demonstrated separation within 5 hours of ED presentation. WB-MTP was associated with improved survival at 24 hours, demonstrating a 37% lower risk of mortality (hazard ratio, 0.63; 95% CI, 0.41-0.96; P = .03). Similarly, the survival benefit associated with WB-MTP remained consistent at 30 days (HR, 0.53; 95% CI, 0.31-0.93; P = .02).Conclusions and RelevanceIn this cohort study, receipt of WB-MTP was associated with improved survival in trauma patients presenting with severe hemorrhage, with a survival benefit found early after transfusion. The findings from this study are clinically important as this is an essential first step in prioritizing the selection of WB-MTP for trauma patients presenting with severe hemorrhage.
Prognostic and epidemiological, level IV.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.