Biology subjects

Schmidt, E. C.

Publications and source records attributed to Schmidt, E. C..

3 recordsLinked to original sources

bioRxiv2019

Ultrasound Echogenicity is Associated with Achilles Tendon Fatigue Damage in a Cadaveric Loading Model

Achilles tendon disorders are among the most difficult sports-related injuries to predict with current diagnostic tools. The purpose of this study was to identify a clinically useful marker for early tendon damage. We hypothesized that alterations in mean echogenicity are linked with changes in vitro tendon mechanics. To test our hypothesis, we harvested Achilles tendons from 10 fresh-frozen cadaveric feet and cyclically fatigued them using a universal test frame while we continuously acquired ultrasound images. Throughout this fatigue protocol, we applied 2 stress tests every 500 loading cycles to quantify changes in ultrasound imaging echogenicity. We continued this fatigue protocol until each tendon either failed completely or survived 150,000 cycles. Tendons that failed during the fatigue loading (6/10) underwent greater changes in mean echogenicity compared to tendons that did not fail (P = 0.031). These tendons that failed during fatigue loading demonstrated greater changes in mean echogenicity that surpassed 1.0%; whereas survivor tendons exhibited less than 0.5% changes in mean echogenicity. We found that changes in mean echogenicity measured with ultrasound increased proportionally with increased tendon damage. The magnitude of these changes was relatively small (<1.5% change in mean echogenicity) but may be an effective predictor of tendon failure. Mean echogenicity is a promising marker for quantifying fatigue damage in cadaveric Achilles tendons during a stress test. Although these changes cannot be detected with the naked eye, computer-based predictive models may effectively assess risk of tendon damage in physically active adults. Level of evidenceControlled laboratory experiment

bioengineering↗

bioRxiv2018

Parameterization of Proximal Humerus Locking Plate Impingement with In Vitro, In Silico, and In Vivo Techniques

BackgroundLocked plating of displaced proximal humerus fractures is common, but rates of subacromial impingement remain high. Computational predictions of implant impingement have yet to be sufficiently explored in proximal humerus fixation. The goal of this study was to utilize a multidisciplinary approach to elucidate the relationships between common surgical parameters, anatomical variability, and the likelihood of plate impingement.\n\nMethodsThe experiment was completed in three phases. First, a controlled in vitro experiment was conducted to simulate impingement. Second, a dynamic in silico musculoskeletal model was developed to simulate changes to implant geometry, surgical techniques, and acromial anatomy, where a collision detection algorithm was used to simulate contact between the plate and acromion. Finally, in vivo shoulder kinematics were recorded for nine activities of daily living and motions that created a high likelihood of impingement were identified.\n\nResultsImpingement was measured at 73.3{+/-}14.5{degrees} abduction in the cadaveric model and 92.0{degrees}{+/-}34.0{degrees} with computational simulations. Impingement events were limited to ranges of motion between 10-40{degrees} of cross-body adduction. Activities of daily living, such as combing ones hair, lifting and object overhead, and reaching behind ones head are likely to cause impingement.\n\nDiscussion and ConclusionThis multidisciplinary experiment quantified key preoperative factors to assist with implantation decisions. Results demonstrated that proximal implant placement, superior translation of the humeral center of rotation, increases in plate thickness, and increases in acromial tilt all increase the likelihood of impingement. Careful preoperative planning that includes these factors could help guide operative decision making and improve clinical outcomes.\n\nLevel of Evidence: V

bioengineering↗

bioRxiv2018

Mechanical and Microstructural Properties of Pediatric Anterior Cruciate Ligaments and Autograft Tendons used for Reconstruction

BackgroundOver the last several decades there has been a steady increase in pediatric ACL tears, particularly in young female basketball and soccer players. Because allograft tissue for pediatric ACL reconstruction (ACLR) has shown high rates of failure, autograft tissue may be the best option for ACLR in this population. However, the differences in structure and mechanical behavior of these tissues are not clear.\n\nPurposeThis study sought to characterize mechanical and microstructural properties in pediatric ACLs and autograft tissues using a rare cadaveric cohort (mean age 9.2 years).\n\nStudy DesignDescriptive laboratory study.\n\nMethodsACLs, patellar tendons, quadriceps tendons, semitendinosus tendons, and iliotibial bands (ITBs) were harvested from five fresh-frozen pediatric knee specimens (3M, 2F) and subjected to a tensile loading protocol. A subset of contralateral tissues were analyzed using brightfield, polarized light, and transmission electron microscopy.\n\nResultsPatellar tendons exhibited values for ultimate stress (5.2{+/-}3.1 MPa), ultimate strain (35.3{+/-}12.5%), and Youngs Modulus (27.0{+/-}8.0 MPa) that were most similar to the ACL (5.2{+/-}2.2 MPa; 31.4{+/-}9.9%; 23.6{+/-}15.5 MPa). Semitendinosus tendons and ITBs were stronger but less compliant than the quadriceps or patellar tendons. ITBs exhibited crimp wavelengths (24.3{+/-}3.1 um) and collagen fibril diameters (67.5{+/-}19.5 nm) that were most similar to the ACL (24.4{+/-}3.2 um; 69.7{+/-}20.3 nm).\n\nConclusionThe mechanical properties of the patellar tendon were almost identical to that of the ACL. The ITB exhibited increased strength and similar microstructure to the native ACL. These findings are not entirely congruent to studies examining adult tissues.\n\nClinical RelevanceResults suggest that ITB tissue may be the preferable choice as an autograft tissue in pediatric ACL reconstructions.\n\nKey TermsPediatric, ACL reconstruction, mechanical properties, microstructural properties, patella tendon grafts, quadriceps tendon grafts, hamstring grafts\n\nWhat is Known about the SubjectDue to the extreme rarity of pediatric cadaveric specimens, very little is known about these tissues.\n\nWhat this Study Adds to Existing KnowledgeThis suite of data can be used to further optimize the design and selection of grafts for reconstruction and may provide insight into the development of constitutive musculoskeletal models.

bioengineering↗