A computational method for estimating trunk muscle activations during gait using lower extremity muscle synergies

One of the surgical treatments for pelvic sarcoma is the restoration of hip function with a custom pelvic prosthesis after cancerous tumor removal. The orthopedic oncologist and orthopedic implant company must make numerous often subjective decisions regarding the design of the pelvic surgery and custom pelvic prosthesis. Using personalized musculoskeletal computer models to predict post-surgery walking function and custom pelvic prosthesis loading is an emerging method for making surgical and custom prosthesis design decisions in a more objective manner. Such predictions would necessitate the estimation of forces generated by muscles spanning the lower trunk and all joints of the lower extremities. However, estimating trunk and leg muscle forces simultaneously during walking based on electromyography (EMG) data remains challenging due to the limited number of EMG channels typically used for measurement of leg muscle activity. This study developed a computational method for estimating unmeasured trunk muscle activations during walking using lower extremity muscle synergies. To facilitate the calibration of an EMG-driven model and the estimation of leg muscle activations, EMG data were collected from each leg. Using non-negative matrix factorization, muscle synergies were extracted from activations of leg muscles. On the basis of previous studies, it was hypothesized that the time-varying synergy activations were shared between the trunk and leg muscles. The synergy weights required to reconstruct the trunk muscle activations were determined through optimization. The accuracy of the synergy-based method was dependent on the number of synergies and optimization formulation. With seven synergies and an increased level of activation minimization, the estimated activations of the erector spinae were strongly correlated with their measured activity. This study created a custom full-body model by combining two existing musculoskeletal models. The model was further modified and heavily personalized to represent various aspects of the pelvic sarcoma patient, all of which contributed to the estimation of trunk muscle activations. This proposed method can facilitate the prediction of post-surgery walking function and pelvic prosthesis loading, as well as provide objective evaluations for surgical and prosthesis design decisions

Immunological evaluation of children with recurrent ear, nose, and throat (ENT) infections

Background: Recurrent and chronic infections of ear, nose, and throat (ENT) such as sinusitis (rhinosinusitis) and otitis media are one of the most common health care problems worldwide and significantly impact quality of life in both children and adults. Antibody deficiencies are the most common type of primary immunodeficiency and also the most likely to present with recurrent ENT infections. Methods: A study was carried out to search for underlying immunodeficiencies in 103 patients with recurrent or chronic ear, nose and throat infections. Serum total IgG, IgA, and IgM levels were measured by kinetic nephelometry, and IgG subclasses by enzyme-linked immunosorbent assay (ELISA). All patients were immunized intramuscularly with polyvalent pneumococcal vaccine (PENEUMO 23). Blood samples were drawn immediately before and 21 days after vaccination and antibodies to pneumococcal antigens were measured using a modified ELISA technique. Finding: Of 103 patients twenty one (20%) were found to have an immunodeficiency. One had a common variable immunodeficiency (CVID), 5 had selective IgA deficiency (one of them was associated with IgG2 deficiency and one with specific antibody deficiency). Eight patients had IgG-subclass deficiency including seven with an IgG2 deficiency and one patient with IgG3 deficiency. In 75 patients antibody titers of whole pneumococcal antigens were determined before and 21 days after immunization. Ten patients were found to have abnormally low antibody titers. Conclusion: The results of this study suggest that in a subpopulation of patients with a long standing history of ENT infections, a low serum immunoglobulin concentration or hypo responsiveness to pneumococcal antigen would be associated with susceptibility to recurrent infections