Ultrashort echo time T21 values decrease in tendons with application of static tensile loads

In early stages of tendon disease, mechanical properties may become altered prior to changes in morphological anatomy. Ultrashort echo time (UTE) magnetic resonance imaging (MRI) can be used to directly detect signal from tissues with very short T2 values, including unique viscoelastic tissues such as tendons. The purpose of this study was to use UTE sequences to measure T2¹, T1 and magnetization transfer ratio (MTR) variations of tendon samples under static tensile loads. Six human peroneal tendons were imaged before and under static loading using UTE sequences on a clinical 3 T MRI scanner. Tendons were divided into two static tensile loading groups: group A that underwent one-step loading (15 N) and group B that underwent two-step loading (15 and 30 N). The T2¹, T1 and MTR variations were investigated in two selected section regions of interest (ROIs), including whole and core sections. Mean T2¹ values for the first step of loading (groups A and B) in both whole section and core section ROIs were significantly decreased by 13 ± 7% (P = 0.028) and 16 ± 5% (P = 0.017), respectively. For the second loading step (group B), there was a consistent, but non-significant reduction in T2¹ value by 9 ± 2% (P = 0.059) and 7 ± 5% (P = 0.121) for whole and core sections, respectively. Mean T1 did not show any consistent changes for either loading steps (P > 0.05). Mean MTR increased slightly, but not significantly for both loading steps (P > 0.05). Significant differences were found only in T2¹ values of tendons by static tensile load application. Therefore, T2¹ monitoring during loading is suggested for quantitative investigation of the tendons biomechanics.     

Effects of carrier,sterilisation method,and incubation on survival of Bradyrhizobium japonicum in soybean (Glycine max L.) inoculants

The production and quality of rhizobial inoculants in many developing countries is limited by the availability of suitable carriers or technological limitations. Experiments were conducted to evaluate the potential of various inexpensive and widely available carrier materials. The carriers, evaluated, were: perlite with pH adjusted with calcium carbonate or charcoal, 1:4 mixtures of perlite and malt residue, sugarcane bagasse, coal, and rice husk. We also contrasted sterilisation procedures (autoclaving or gamma irradiation) and incubation after injection (with or without initial two weeks incubation at 28 °C) for these various carriers. Survival of Bradyrhizobium japonicum strain CB1809 was monitored over a period of 6 months upon storage at 4 °C. Most carriers evaluated, were able to maintain rhizobial populations of more than 1 × 10⁹ rhizobia per gram of inoculant over that time period, with mixtures of perlite with either sugarcane bagasse or malt residue supporting the largest rhizobial populations and a mixture of perlite and rice husk the lowest. All carriers supported rhizobial growth over the 6 months period. Initially, rhizobial populations were greater with gamma irradiation than autoclaving, however after 6 months, this response was significant only with the perlite and sugarcane bagasse mixture. The incubation of the inoculant after injection also ultimately did not benefit rhizobial levels for any of the carriers, tested. Using simple sterilisation procedures and without incubating after injection, perlite based carriers can produce high quality inexpensive inoculants, maintaining bacterial populations of more than 1 × 10⁹/g rhizobia for at least 6 months.     

Alterations in damage processes in dense cancellous bone following gamma-radiation sterilization

Structurally intact cancellous bone allograft is an attractive tissue form because its high porosity can provide space for delivery of osteogenic factors and also allows for more rapid and complete in-growth of host tissues. Gamma radiation sterilization is commonly used in cancellous bone allograft to prevent disease transmission. Commonly used doses of gamma radiation sterilization (25–35 kGy) have been shown to modify cortical bone post-yield properties and crack propagation but have not been associated with changes in cancellous bone material properties. The purpose of this study was to determine the effects of irradiation on the elastic and yield properties and microscopic tissue damage processes in dense cancellous bone. Cancellous bone specimens (13 control, 14 irradiated to 30 kGy) from bovine proximal tibiae were tested in compression to 1.3% apparent strain and examined for microscopic tissue damage. The yield strain in irradiated specimens (0.93±0.11%, mean±SD) did not differ from that in control specimens (0.90±0.11%, p=0.44). No differences in elastic modulus were observed between groups after accounting for differences in bone volume fraction. However, irradiated specimens showed greater residual strain (p=0.01), increased number of microfractures (p=0.02), and reduced amounts of cross-hatching type damage (p<0.01). Although gamma radiation sterilization at commonly used dosing (30 kGy) does not modify elastic or yield properties of dense cancellous bone, it does cause modifications in damage processes, resulting in increased permanent deformation following isolated overloading.     

Biodosimetry using micronucleus assay in acute partial body therapeutic irradiation

Biological dosimetry provides information on the absorbed dose and its distribution in the body for an early assessment of irradiation consequences in exposed individuals. In this study, an effort has been made to see the applicability of biological dosimetry using micronuclei assay for dose estimation in therapeutic irradiation of cancer patients in acute high dose partial body irradiation. Dose estimation in partial body irradiations was done on the basis of Dolphin's contaminated Poisson method, using the in vitro dose response calibration curve. The equivalent whole body dose and the dose to the irradiated part of the body were estimated to be 1.8 ± 0.1 Gy and 6.4 ± 0.3 Gy, respectively. The estimated percentage of irradiated blood and the fraction of cells exposed were 41.5 ± 1.6% and 10.4 ± 0.8%, respectively. The estimated fraction of irradiated cells was comparable with the actual volume of irradiation.     

Effect of low dose and moderate dose gamma irradiation on the mechanical properties of bone and soft tissue allografts

The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner. At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at a low absorbed dose (18.3–21.8 kGy) and a moderate absorbed dose (24.0–28.5 kGy), using conventional compressive and tensile testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups. Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support the use of low dose irradiation.     

The influence of cryopreservation and quick-freezing on the mechanical properties of tendons

In order to maintain their native properties, cryopreserved tendons are usually used in biomechanical research and in transplantation of allogenic tendon grafts. The use of different study protocols leads to controversy in literature and thus complicates the evaluation of the current literature. The aim of this study consisted in examining the influence of different freezing and thawing temperatures on the mechanical properties of tendons. 60 porcine tendons were frozen at either −80 °C or −20 °C for 7 days and thawed at room or body temperature for 240 or 30 min, respectively. A subgroup of ten tendons was quick-frozen with liquid nitrogen (−196 °C) for 2 s before cryopreservation. Biomechanical testing was performed with a material testing machine and included creep, cyclic and load-to-failure tests. The results showed that freezing leads to a reduced creep strain after constant loading and to an increased secant modulus. Freezing temperature of −80 °C increased the secant modulus and decreased the strain at maximum stress, whereas thawing at room temperature reduced the maximum stress, the strain at initial tendon failure and the Young’s Modulus. Quick-freezing led to increased creep strain after constant loading, increased strain at initial failure in the load-to-failure test, and decreased strain at maximum stress. When cryopreserving, tendons for scientific or medical reasons, freezing temperature of −20 °C and thawing temperature of 37.5 °C are recommended to maintain the native properties of tendons. A treatment with liquid nitrogen in the sterilization process of tendon allografts is inadvisable because it alters the tendon properties negatively.     

Reproducibility of a non-invasive ultrasonic technique of tendon force measurement,determined in vitro in equine superficial digital flexor tendons

A non-invasive ultrasonic (US) technique of tendon force measurement has been recently developed. It is based on the relationship demonstrated between the speed of sound (SOS) in a tendon and the traction force applied to it. The objectives of the present study were to evaluate the variability of this non-linear relationship among 7 equine superficial digital flexor (SDF) tendons, and the reproducibility of SOS measurements in these tendons over successive loading cycles and tests. Seven SDF tendons were equipped with an US probe (1 MHz), secured in contact with the skin overlying the tendon metacarpal part. The tendons were submitted to a traction test consisting in 5 cycles of loading/unloading between 50 and 4050 N. Four tendons out of the 7 were submitted to 5 additional cycles up to 5550 N. The SOS-tendon force relationships appeared similar in shape, although large differences in SOS levels were observed among the tendons. Reproducibility between cycles was evaluated from the root mean square of the standard deviations (RMS-SD) of SOS values observed every 100 N, and of force values every 2 m/s. Reproducibility of SOS measurements revealed high between successive cycles: above 500 N the RMS-SD was less than 2% of the corresponding traction force. Reproducibility between tests was lower, partly due to the experimental set-up; above 500 N the difference between the two tests stayed nevertheless below 15% of the corresponding mean traction force. The reproducibility of the US technique here demonstrated in vitro has now to be confirmed in vivo.     

Comparison of Ephestia kuehniella eggs sterilization methods for Trichogramma rearing

Mass production is necessary to ensure the availability of biological control agents for the suppression of target pests. Many rearing hosts need to be sterilized to prevent development. Host egg sterilization also allows their storage for a longer period. Ephestia kuehniella eggs are frequently used as hosts for Trichogramma parasitoïds but they must be sterilized to prevent larvae from emerging and eating the unhatched parasitized eggs. Three sterilization methods were examined: UV irradiation, freezing at −15 °C and vitrification (liquid nitrogen submersion). The dosage and exposure duration to provide egg sterilization were determined and then the suitability of hosts sterilized by the different methods were compared. E. kuehniella eggs abortion was achieved after 15 min by UV irradiation, 4 h by freezing at −15 °C and 30 s by vitrification. Vitrification resulted in significantly lower parasitoids production with a global emergence rate of 28.7%, compared to UV irradiation (75.1%), freezing at −15 °C (77.4%) and control (80.9%). Host eggs sterilization method did not affect sex-ratio, occurrence of malformation in adults, and female walking speed. Fecundity was significantly reduced in the females emerging from UV irradiated (37.2 offsprings) and vitrified (36.9 offsprings) eggs, compared to control (43.1 offsprings).     

Temperature-dependent viscoelastic properties of the human supraspinatus tendon

Temperature effects on the viscoelastic properties of the human supraspinatus tendon were investigated using static stress-relaxation experiments and the quasi-linear viscoelastic (QLV) theory. Twelve supraspinatus tendons were randomly assigned to one of two test groups for tensile testing using the following sequence of temperatures: (1) 37, 27, and 17 °C (Group I, n=6), or (2) 42, 32, and 22 °C (Group II, n=6). QLV parameter C was found to increase at elevated temperatures, suggesting greater viscous mechanical behavior at higher temperatures. Elastic parameters A and B showed no significant difference among the six temperatures studied, implying that the viscoelastic stress response of the supraspinatus tendon is not sensitive to temperature over shorter testing durations. Using regression analysis, an exponential relationship between parameter C and test temperature was implemented into QLV theory to model temperature-dependent viscoelastic behavior. This modified approach facilitates the theoretical determination of the viscoelastic behavior of tendons at arbitrary temperatures.     

Fast protocol for radiochromic film dosimetry using a cloud computing web application

PurposeTo investigate the feasibility of a fast protocol for radiochromic film dosimetry to verify intensity-modulated radiotherapy (IMRT) plans.Method and materialsEBT3 film dosimetry was conducted in this study using the triple-channel method implemented in the cloud computing application (Radiochromic.com). We described a fast protocol for radiochromic film dosimetry to obtain measurement results within 1 h.Ten IMRT plans were delivered to evaluate the feasibility of the fast protocol. The dose distribution of the verification film was derived at 15, 30, 45 min using the fast protocol and also at 24 h after completing the irradiation. The four dose maps obtained per plan were compared using global and local gamma index (5%/3 mm) with the calculated one by the treatment planning system. Gamma passing rates obtained for 15, 30 and 45 min post-exposure were compared with those obtained after 24 h.ResultsSmall differences respect to the 24 h protocol were found in the gamma passing rates obtained for films digitized at 15 min (global: 99.6% ± 0.9% vs. 99.7% ± 0.5%; local: 96.3% ± 3.4% vs. 96.3% ± 3.8%), at 30 min (global: 99.5% ± 0.9% vs. 99.7% ± 0.5%; local: 96.5% ± 3.2% vs. 96.3 ± 3.8%) and at 45 min (global: 99.2% ± 1.5% vs. 99.7% ± 0.5%; local: 96.1% ± 3.8% vs. 96.3 ± 3.8%).ConclusionsThe fast protocol permits dosimetric results within 1 h when IMRT plans are verified, with similar results as those reported by the standard 24 h protocol.     

Dose distribution homogeneity in two TBI techniques—Analysis of 208 irradiated patients conducted in Stanislaw Leszczynski Memorial Hospital,Katowice

BackgroundTo analyze and compare dose distribution homogeneity in selected points (especially in the chest wall region) for patients irradiated with two different TBI techniques to achieve a uniform total dose (excluding lungs area) specified in the range of 11.4–14.0 Gy.Material and methodsFrom August 2000 to December 2009, a group of 158 patients was treated by the use of 15 MV photon irradiation consisting of six fractions: four opposed lateral and two anterior–posterior/posterior–anterior (AP/PA). Patients were irradiated with the fraction dose of 2 Gy twice a day for 3 consecutive days. The prescribed dose to PC point (specified at intersection of the beam axis with the mid-plane of the patient irradiated laterally) was 12 Gy. Since January 2010 until closing the study, another group of 50 patients was treated according to a modified protocol. The treatment was carried out in six lateral fractions only, twice a day, for three following days and a lateral lung shield was used for a part of total irradiation time. The measurements of doses in 20 selected points of patient's body were carried out by means of MOSFET detectors.ResultsThe modified TBI technique allows to achieve an expected homogenous dose in the points of interest similar to that obtained by using the initial protocol. The calculated and measured in vivo doses met the specified range of 11.4–14 Gy for both applied TBI protocols.ConclusionsOur results indicate that for all patients the homogenous dose distribution in the specified range was achieved.     

Effect of storage conditions of blood on radiation-induced chromosomal aberrations and apoptosis in human lymphocytes

To evaluate the effect of storage conditions of blood on the direct relationship between radiation-induced chromosome aberrations and apoptosis in human peripheral blood lymphocytes, whole blood was irradiated with 3 Gy X-rays. Directly after irradiation, a sample of blood was analyzed for chromosome damage and proliferation index, after phytohaemagglutinin stimulation and incubation at 37 °C for 56 h. Blood samples were stored for 48 h at 4 and 20 °C with or without phytohaemagglutinin and analyzed for cell viability and apoptosis at 0, 24 and 48 h storage time. After 48 h of storage, unstimulated cultures were stimulated to proliferate. These samples and cultures stimulated immediately before storage were incubated at 37 °C for 56 h and analyzed for chromosome damage and proliferation index. Metaphases were examined for the presence of dicentrics, excess acentrics, and rings. Storage at 20 °C without phytohaemagglutinin for 48 h increases significantly the yield of apoptosis and decreases significantly the yield of dicentrics. During 48 h of storage time the presence of phytohaemagglutinin and the temperature of 4 °C protected the irradiated lymphocytes from apoptosis allowing accurate estimation of the real yield of radiation-induced chromosome damage. Therefore these blood-storage conditions enable analysis in metaphase and may offer some advantages for biodosimetry of absorbed radiation dose.     

Achilles tendon stress is more sensitive to subject-specific geometry than subject-specific material properties: A finite element analysis

This study used subject-specific measures of three-dimensional (3D) free Achilles tendon geometry in conjunction with a finite element method to investigate the effect of variation in subject-specific geometry and subject-specific material properties on tendon stress during submaximal isometric loading. Achilles tendons of eight participants (Aged 25–35 years) were scanned with freehand 3D ultrasound at rest and during a 70% maximum voluntary isometric contraction. Ultrasound images were segmented, volume rendered and transformed into subject-specific 3D finite element meshes. The mean (±SD) lengths, volumes and cross-sectional areas of the tendons at rest were 62 ± 13 mm, 3617 ± 984 mm³ and 58 ± 11 mm² respectively. The measured tendon strain at 70% MVIC was 5.9 ± 1.3%. Subject-specific material properties were obtained using an optimisation approach that minimised the difference between measured and modelled longitudinal free tendon strain. Generic geometry was represented by the average mesh and generic material properties were taken from the literature. Local stresses were subsequently computed for combinations of subject-specific and generic geometry and material properties. For a given geometry, changing from generic to subject-specific material properties had little effect on the stress distribution in the tendon. In contrast, changing from generic to subject-specific geometry had a 26-fold greater effect on tendon stress distribution. Overall, these findings indicate that the stress distribution experienced by the living free Achilles tendon of a young and healthy population during voluntary loading are more sensitive to variation in tendon geometry than variation in tendon material properties.     

Characterization of stochastic noise and post-irradiation density growth for reflective-type radiochromic film in therapeutic photon beam dosimetry

The aim of this study is to investigate the dosimetric uncertainty of stochastic noise and the post-irradiation density growth for reflective-type radiochromic film to obtain the appropriate dose from the exactly controlled film density. Film pieces were irradiated with 6-MV photon beams ranging from 0 to 400 cGy. The pixel values (PVs) of these films were obtained using a flatbed scanner at elapsed times of 1 min to 120 h between the end of irradiation and the film scan. The means and standard deviations (SDs) of the PVs were calculated. The SDs of the converted dose scale, u_sd, and the dose increases resulting from the PV increases per ±29 min at each elapsed time, u_time, were computed. The combined dose uncertainties from these two factors, u_c, were then calculated. A sharp increase in the PV occurred within the first 3 h after irradiation, and a slight increase continued from 3 h to 120 h. u_sd was independent of post-irradiation elapsed time. Sharp decreases in u_time were obtained within 1 h after irradiation, and slight decreases in u_time were observed from 1 to 24 h after irradiation. u_c first decreased 1 h after irradiation and remained constant afterward. Assuming that the post-irradiation elapsed times of all of the related measurements are synchronized within ±29 min, the elapsed time should be at least 1 h in our system. It is important to optimize the scanning protocol for each institution with consideration of the required measurement uncertainty and acceptable latency time.     

Validation of a method for “dose of the day” calculation in head-neck tomotherapy by using planning ct-to-MVCT deformable image registration

PurposeThe aim of this study was to test the feasibility and dosimetric accuracy of a method that employs planning CT-to-MVCT deformable image registration (DIR) for calculation of the daily dose for head and neck (HN) patients treated with Helical Tomotherapy (HT).MethodsFor each patient, the planning kVCT (CTplan) was deformably registered to the MVCT acquired at the 15th therapy session (MV15) with a B-Spline Free Form algorithm using Mattes mutual information (open-source software 3D Slicer), resulting in a deformed CT (CTdef). On the same day as MVCT15, a kVCT was acquired with the patient in the same treatment position (CT15). The original HT plans were recalculated both on CTdef and CT15, and the corresponding dose distributions were compared; local dose differences <2% of the prescribed dose (DD2%) and 2D/3D gamma-index values (2%-2 mm) were assessed respectively with Mapcheck SNC Patient software (Sun Nuclear) and with 3D-Slicer.ResultsOn average, 87.9% ± 1.2% of voxels were found for DD2% (on average 27 slices available for each patient) and 94.6% ± 0.8% of points passed the 2D gamma analysis test while the 3D gamma test was satisfied in 94.8% ± 0.8% of body’s voxels.ConclusionsThis study represents the first demonstration of the dosimetric accuracy of kVCT-to-MVCT DIR for dose of the day computations. The suggested method is sufficiently fast and reliable to be used for daily delivered dose evaluations in clinical strategies for adaptive Tomotherapy of HN cancer.     

Whole body protection against lethal ionizing radiation in mice by REC-2001: A semi-purified fraction of Podophyllum hexandrum

The current study has concentrated on assessment of the radioprotective potential of REC-2001, a semi-purified fraction of rhizomes of Podophyllum hexandrum, in Swiss albino Strain ‘A’ mice exposed to 10 Gy whole-body gamma radiation. Animals were treated with 10 and 15 mg/kg b wt (i.p.) of REC-2001 1 h prior to exposure to a lethal dose of γ-radiation (10 Gy) and observed upto 30 days. For analysis of maximum tolerable dose (MTD), LD₅₀ and acute toxic dose, different concentrations of the extract were administered to animals and their mortality and morbidity status was observed upto 72 h and one week, respectively. Dose reduction factor (DRF) was determined by exposing REC-2001 pre-treated mice to supra-lethal doses of γ-radiation. Endogenous spleen colony forming units (CFU), DNA strand breaks in thymocytes (alkaline halo assay) and lipid degradation was studied to understand the mechanism of radioprotection . A single dose of REC-2001 (10 and 15 mg/kg b wt i.p.) exhibited >90% survival in the pre-treated irradiated group versus no survival in radiation control group. Single doses of upto 75 mg/kg b wt (i.p.) did not cause any mortality (MTD) in mice. REC-2001, a dose of 90 mg/kg b wt, resulted in 50% mortality (LD₅₀), while the LD₁₀₀ was 115 mg/kg b wt REC-2001 exhibited a DRF of 1.62. CFU counts in the REC-2001 treated group were found significantly high (5.33/spleen) as compared to controls. Exposure of thymocytes to 10 Gy radiation resulted in increased halo diameter (45±3 μm) in comparison to untreated controls (8±1 μm). REC-2001 administration (500 μg/ml) decreased the halo diameter to 15±2 μm. Radiation-induced lipid degradation was also inhibited by REC-2001. The present study has revealed that REC-2001 is a promising radioprotective fraction that can be effectively used against lethal doses of γ-radiation after further investigations in higher animal models.     

Preparation and properties of carboxylated styrene-butadiene rubber/cellulose nanocrystals composites

A series of carboxylated styrene-butadiene rubber (XSBR)/cellulose nanocrystals (CNs) latex composites were successfully prepared. The vulcanization process, morphology, dynamic viscoelastic behavior, dynamic mechanical property, thermal and mechanical performance of the XSBR/CNs composites were investigated in detail. The results revealed that CNs were dispersed uniformly in the XSBR matrix and formed a strong filler–filler network. The dynamic mechanical analysis (DMA) showed that the glass transition temperature (T_g) of XSBR matrix was shifted from 48.45 to 50.64 °C with 3 phr CNs, but decreased from 50.64 to 46.28 °C when further increasing CNs content up to 15 phr. The composites exhibited a significant enhancement in tensile strength (from 16.9 to 24.1 MPa) and tear strength (from 43.5 to 65.2 MPa) with loading CNs from 0 to 15 phr. In addition, the thermo-gravimetric analysis (TGA) showed that the temperature at 5% weight loss of the XSBR/CNs composites decreased slightly with an increase of the CNs content.     

Photochemical and enzymatic synthesis of methanol from formaldehyde with alcohol dehydrogenase from Saccharomyces cerevisiae and water-soluble zinc porphyrin

We evaluated the photochemical and enzymatic synthesis of methanol from formaldehyde with alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae and NAD⁺ photoreduction by the visible-light sensitization of zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS) in the presence of methylviologen (MV²⁺), diaphorase, and triethanolamine (TEOA). When the sample solution containing ZnTPPS, MV²⁺, NAD⁺, diaphorase, and TEOA in potassium phosphate buffer solution was irradiated, the NADH produced increased with the irradiation time. After irradiation for 180 min, the conversion yield of NAD⁺ to NADH was about 60% under 0.1 mM NAD⁺ condition. The methanol production also depended on the conversion yield of NAD⁺ to NADH. After irradiation for 180 min, 0.38 μM of methanol was produced from formaldehyde (16 μM). The conversion ratio of formaldehyde to methanol was about 2.3%. This result indicates that a system for the photochemical synthesis of methanol from formaldehyde was developed with ADH and the NADH produced by the photosensitization of ZnTPPS in water media.     

Mechanical,histological, and functional properties remain inferior in conservatively treated Achilles tendons in rodents: Long term evaluation

Conservative treatment (non-operative) of Achilles tendon ruptures is suggested to produce equivalent capacity for return to function; however, long term results and the role of return to activity (RTA) for this treatment paradigm remain unclear. Therefore, the objective of this study was to evaluate the long term response of conservatively treated Achilles tendons in rodents with varied RTA. Sprague Dawley rats (n = 32) received unilateral blunt transection of the Achilles tendon followed by randomization into groups that returned to activity after 1-week (RTA1) or 3-weeks (RTA3) of limb casting in plantarflexion, before being euthanized at 16-weeks post-injury. Uninjured age-matched control animals were used as a control group (n = 10). Limb function, passive joint mechanics, tendon properties (mechanical, histological), and muscle properties (histological, immunohistochemical) were evaluated. Results showed that although hindlimb ground reaction forces and range of motion returned to baseline levels by 16-weeks post-injury regardless of RTA, ankle joint stiffness remained altered. RTA1 and RTA3 groups both exhibited no differences in fatigue properties; however, the secant modulus, hysteresis, and laxity were inferior compared to uninjured age-matched control tendons. Despite these changes, tendons 16-weeks post-injury achieved secant stiffness levels of uninjured tendons. RTA1 and RTA3 groups had no differences in histological properties, but had higher cell numbers compared to control tendons. No changes in gastrocnemius fiber size or type in the superficial or deep regions were detected, except for type 2x fiber fraction. Together, this work highlights RTA-dependent deficits in limb function and tissue-level properties in long-term Achilles tendon and muscle healing.