@article{howe_dixit_saul_fisher_2022, title={A Direct Comparison of Node and Element-Based Finite Element Modeling Approaches to Study Tissue Growth}, volume={144}, ISSN={["1528-8951"]}, DOI={10.1115/1.4051661}, abstractNote={Abstract
               Finite element analysis is a useful tool to model growth of biological tissues and predict how growth can be impacted by stimuli. Previous work has simulated growth using node-based or element-based approaches, and this implementation choice may influence predicted growth, irrespective of the applied growth model. This study directly compared node-based and element-based approaches to understand the isolated impact of implementation method on growth predictions by simulating growth of a bone rudiment geometry, and determined what conditions produce similar results between the approaches. We used a previously reported node-based approach implemented via thermal expansion and an element-based approach implemented via osmotic swelling, and we derived a mathematical relationship to relate the growth resulting from these approaches. We found that material properties (modulus) affected growth in the element-based approach, with growth completely restricted for high modulus values relative to the growth stimulus, and no restriction for low modulus values. The node-based approach was unaffected by modulus. Node- and element-based approaches matched marginally better when the conversion coefficient to relate the approaches was optimized based on the results of initial simulations, rather than using the theoretically predicted conversion coefficient (median difference in node position 0.042 cm versus 0.052 cm, respectively). In summary, we illustrate here the importance of the choice of implementation approach for modeling growth, provide a framework for converting models between implementation approaches, and highlight important considerations for comparing results in prior work and developing new models of tissue growth.}, number={1}, journal={JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME}, author={Howe, Danielle and Dixit, Nikhil N. and Saul, Katherine R. and Fisher, Matthew B.}, year={2022}, month={Jan} }
 @article{howe_cone_piedrahita_spang_fisher_2022, title={Age- and Sex-Specific Joint Biomechanics in Response to Partial and Complete Anterior Cruciate Ligament Injury in the Porcine Model}, volume={57}, ISSN={["1938-162X"]}, DOI={10.4085/1062-6050-565-21}, abstractNote={
                  Context
                  Pediatric anterior cruciate ligament (ACL) injury rates are increasing and are highest in female adolescents. Complete ACL tears are typically surgically reconstructed, but few guidelines and very limited data exist regarding the need for surgical reconstruction or rehabilitation for partial ACL tears in skeletally immature patients.
               
               
                  Objective
                  To evaluate the effects of partial (anteromedial bundle) and complete ACL transection on joint laxity and tissue forces under anterior and rotational loads in male and female stifle joints throughout skeletal growth in the porcine model.
               
               
                  Design
                  Descriptive laboratory study.
               
               
                  Setting
                  Laboratory.
               
               
                  Patients or Other Participants
                  We studied 60 male and female Yorkshire crossbreed pigs aged 1.5, 3, 4.5, 6, and 18 months (n = 6 pigs per age per sex).
               
               
                  Main Outcome Measure(s)
                  Joint laxity was measured in intact, anteromedial bundle-transected, and ACL-transected joints under applied anterior-posterior drawer and varus-valgus torque using a robotic testing system. Loading of the soft tissues in the stifle joint was measured under each condition.
               
               
                  Results
                  Anterior-posterior joint laxity increased by 13% to 50% (P < .05) after anteromedial bundle transection and 75% to 178% (P < .05) after ACL transection. Destabilization after anteromedial bundle transection increased with age (P < .05) and was greater in late female than late male adolescents (P < .05). In anteromedial bundle-transected joints, the posterolateral bundle resisted the anterior load. In ACL-transected joints, the medial collateral ligament (MCL) contribution was largest, followed by the medial meniscus. The MCL contribution was larger and the medial meniscus contribution was smaller in male versus female specimens.
               
               
                  Conclusions
                  Partial ACL transection resulted in moderate increases in joint laxity, with the remaining bundle performing the primary ACL function. Destabilization due to partial ACL transection (anteromedial bundle) was largest in late adolescent joints, indicating that operative treatment should be considered in active, late-adolescent patients with this injury. Increased forces on the MCL and medial meniscus after ACL transection suggested that rehabilitation protocols may need to focus on protecting these tissues.
               }, number={9-10}, journal={JOURNAL OF ATHLETIC TRAINING}, author={Howe, Danielle and Cone, Stephanie G. and Piedrahita, Jorge A. and Spang, Jeffrey T. and Fisher, Matthew B.}, year={2022}, month={Sep}, pages={978–989} }
 @article{cone_barnes_howe_fordham_fisher_spang_2021, title={Age- and sex-specific differences in ACL and ACL bundle size during adolescent growth}, ISSN={["1554-527X"]}, DOI={10.1002/jor.25198}, abstractNote={AbstractAnterior cruciate ligament (ACL) injuries are increasingly common in adolescents, and injuries in this age‐group are associated with many unique challenges. Recent large animal studies suggest that the size and function of the major bundles of the ACL change differently throughout skeletal growth. To better aid clinical treatment of pediatric partial ACL tears and better predict outcomes from age‐specific treatments, there is a need to measure changes in ACL bundle size in humans during growth. As such, the objective of this study was to compare changes in the length and cross‐sectional area (CSA) of the ACL and its primary bundles in adolescent human subjects. Magnetic resonance imaging (MRI) scans were analyzed to determine the visibility and integrity of the ACL and its anteromedial and posterolateral bundles. MRI scans were considered from a retrospective database of subjects ranging from 10 to 18 years of age. The ACL and its anteromedial and posterolateral bundles were segmented and reconstructed into 3D models, and length and CSA were calculated. Total ACL length and CSA were greater in males compared with females, with a statistically significant interaction between age and sex for CSA. Sex had a significant effect on the CSA of both bundles. These sex‐dependent differences emerge with moderate to large effect sizes (range: d = 0.50 to d = 1.23) beginning around 13 years of age. Along with ACL bundle structure–function relationships previously established in preclinical animal models, these findings may point toward biomechanical changes in the adolescent human ACL.}, journal={JOURNAL OF ORTHOPAEDIC RESEARCH}, author={Cone, Stephanie G. and Barnes, Ryan H. and Howe, Danielle and Fordham, Lynn A. and Fisher, Matthew B. and Spang, Jeffrey T.}, year={2021}, month={Nov} }
 @article{howe_cone_piedrahita_collins_fordham_griffith_spang_fisher_2021, title={Sex-specific biomechanics and morphology of the anterior cruciate ligament during skeletal growth in a porcine model}, volume={11}, ISSN={["1554-527X"]}, DOI={10.1002/jor.25207}, abstractNote={AbstractPediatric anterior cruciate ligament (ACL) injuries are on the rise, and females experience higher ACL injury risk than males during adolescence. Studies in skeletally immature patients indicate differences in ACL size and joint laxity between males and females after the onset of adolescence. However, functional data regarding the ACL and its anteromedial and posterolateral bundles in the pediatric population remain rare. Therefore, this study uses a porcine model to investigate the sex‐specific morphology and biomechanics of the ACL and its bundles throughout skeletal growth. Hind limbs from male and female Yorkshire pigs aged early youth to late adolescence were imaged using magnetic resonance imaging to measure the size and orientation of the ACL and its bundles, then biomechanically tested under anterior‐posterior drawer using a robotic testing system. Joint laxity decreased (p < 0.001) while joint stiffness increased (p < 0.001) throughout skeletal growth in both sexes. The ACL was the primary stabilizer against anterior tibial loading, while the functional role of the anteromedial bundle increased with age (p < 0.001), with an earlier increase in males. ACL and posterolateral bundle cross‐sectional area and ACL and anteromedial bundle length were larger in males than females during adolescence (p < 0.01 for all), while ACL and bundle sagittal angle remained similar between sexes. Additionally, in situ ACL stiffness versus cross‐sectional area regressions were significant across skeletal growth (r2 = 0.75, p < 0.001 in males and r2 = 0.64, p < 0.001 in females), but not within age groups. This study has implications for age and sex‐specific surgical intervention strategies and suggests the need for human studies.}, journal={JOURNAL OF ORTHOPAEDIC RESEARCH}, author={Howe, Danielle and Cone, Stephanie G. and Piedrahita, Jorge A. and Collins, Bruce and Fordham, Lynn A. and Griffith, Emily H. and Spang, Jeffrey T. and Fisher, Matthew B.}, year={2021}, month={Nov} }
 @misc{cone_howe_fisher_2019, title={SIZE AND SHAPE OF THE HUMAN ANTERIOR CRUCIATE LIGAMENT AND THE IMPACT OF SEX AND SKELETAL GROWTH}, volume={7}, ISSN={["2329-9185"]}, DOI={10.2106/JBJS.RVW.18.00145}, abstractNote={
            Background:
            High rates of anterior cruciate ligament (ACL) injury and surgical reconstruction in both skeletally immature and mature populations have led to many studies investigating the size and shape of the healthy ligament. The purposes of the present study were to compile existing quantitative measurements of the geometry of the ACL, its bundles, and its insertion sites and to describe effects of common covariates such as sex and age.
          
          
            Methods:
            A search of the Web of Science was conducted for studies published from January 1, 1900, to April 11, 2018, describing length, cross-sectional area, volume, orientation, and insertion sites of the ACL. Two reviewers independently screened and reviewed the articles to collect quantitative data for each parameter.
          
          
            Results:
            Quantitative data were collected from 92 articles in this systematic review. In studies of adults, reports of average ACL length, cross-sectional area, and volume ranged from 26 to 38 mm, 30 to 53 mm2, and 854 to 1,858 mm3, respectively. Reported values were commonly found to vary according to sex and skeletal maturity as well as measurement technique.
          
          
            Conclusions:
            Although the geometry of the ACL has been described widely in the literature, quantitative measurements can depend on sex, age, and measurement modality, contributing to variability between studies. As such, care must be taken to account for these factors. The present study condenses measurements describing the geometry of the ACL, its individual bundles, and its insertion sites, accounting for common covariates when possible, to provide a resource to the clinical and scientific communities.
          
          
            Clinical Relevance:
            Quantitative measures of ACL geometry are informative for developing clinical treatments such as ACL reconstruction. Age and sex can impact these parameters.
          }, number={6}, journal={JBJS REVIEWS}, author={Cone, Stephanie G. and Howe, Danielle and Fisher, Matthew B.}, year={2019}, month={Jun} }