Purpose: To create an updated and comprehensive overview of the modeling studies that have been done to understand the mechanics underlying deformities of adolescent idiopathic scoliosis (AIS), to predict the risk of curve progression and thereby substantiate etiopathogenetic theories. Methods: In this systematic review, an online search in Scopus and PubMed together with an analysis in secondary references was done, which yielded 86 studies. The modeling types were extracted and the studies were categorized accordingly. Results: Animal modeling, together with machine learning modeling, forms the category of black box models. This category is perceived as the most clinically relevant. While animal models provide a tangible idea of the biomechanical effects in scoliotic deformities, machine learning modeling was found to be the best curve-progression predictor. The second category, that of artificial models, has, just as animal modeling, a tangible model as a result, but focusses more on the biomechanical process of the scoliotic deformity. The third category is formed by computational models, which are very popular in etiopathogenetic parameter-based studies. They are also the best in calculating stresses and strains on vertebrae, intervertebral discs, and other surrounding tissues. Conclusion: This study presents a comprehensive overview of the current modeling techniques to understand the mechanics of the scoliotic deformities, predict the risk of curve progression in AIS and thereby substantiate etiopathogenetic theories. Although AIS remains to be seen as a complex and multifactorial problem, the progression of its deformity can be predicted with good accuracy. Modeling of AIS develops rapidly and may lead to the identification of risk factors and mitigation strategies in the near future. The overview presented provides a basis to follow this development.

Background: Gait adaptability is of utmost importance for keeping balance during gait in patients with knee osteoarthritis, also after total knee arthroplasty (TKA). The aims of this explorative study are: (1) assess the effect of age, knee osteoarthritis and TKA on gait adaptability; (2) assess changes in gait adaptability pre-to post-TKA and (3) their relation to functional outcomes. Methods: Gait adaptability was measured using a Target Stepping Test (TST) in knee osteoarthritis patients before (preTKA) and 12 months after TKA (postTKA) and compared to asymptomatic old (AsOld) and young adults (AsYng). TST imposed an asymmetrical gait pattern with projected stepping targets at high walking speed. Gait adaptability was determined through stepping accuracy on the targets. The Oxford Knee Score (OKS) and Timed-Up-and-Go test (TUG) measured patients’ physical function. Results: 12 preTKA, 8 postTKA, 18 AsYng, 21 AsOld were tested. Age showed no effect on TST-stepping accuracy. PreTKA showed worse TST-stepping accuracy compared to AsYng and AsOld (7.7; 6.2 cm difference). PostTKA showed an improvement of 52% in TST-stepping accuracy compared to preTKA (3.2 cm). Higher stepping accuracy preTKA predicted higher stepping accuracy post-TKA. In addition, low preTKA stepping accuracy predicted more improvement postTKA. Pre-to post-TKA improvement of stepping accuracy was related to improvement on the TUG (Beta = 0.17, p = 0.024), but not to OKS. Conclusions: Gait adaptability is improved following TKA in knee osteoarthritis patients and no longer significantly worse than asymptomatic adults. The relation of gait adaptability to function is shown by its relation to the TUG and shows to have predictive value pre-to post-TKA.

AIMS: For violinists, the shoulder rest is an ergonomic adaptation to reduce musculoskeletal load. In this study, we aimed to evaluate how the height of the shoulder rest affects the violin fixation force and electromyographic (EMG) activity of the superficial neck and shoulder muscles. METHODS: In professional violinists, four different shoulder rest heights during five playing conditions were evaluated. Outcome variables included the jaw-shoulder violin fixation force and bilateral surface EMG of the upper trapezius (mTP), sternocleidomastoid (mSCM), and left anterior part of the left deltoid muscle (mDTA). Playing comfort was subjectively rated on a visual analogic scale (VAS). Linear regression models were estimated to investigate the influence of the shoulder rest height on muscle activity and violin fixation force as well as the muscle activity of the five evaluated muscles on violin fixation force. RESULTS: 20 professional violinists (4 males, 16 females, mean age 29.4 yrs) participated in this study. The shoulder rest condition had a significant effect on playing comfort (p<0.001), with higher shoulder rest conditions associated with decreased subjective playing comfort. The mean violin fixation force for each shoulder rest condition ranged between 2.92 and 3.39 N; higher shoulder rests were related to a higher violin fixation force (p<0.001). CONCLUSION: In this study, violin fixation force and muscle activity of the left mDTA increased while playing with an increasing height of the shoulder rest. As the shoulder rest influences muscle activity patterns and violin fixation force, adjustment of the shoulder rest and positioning of the violin need to be carefully optimized. Med Probl Perform Art 2019;34(1):39-46.

Purpose: The aim of this study is to determine the relationship between complaints of the neck and shoulder region, the jaw-shoulder violin fixation force, and the activity of the neck and shoulder muscles in violinists. Methods: In this case-control study twenty professional violinists were included, of which ten with current complaints of the neck shoulder region and ten without these complaints. A questionnaire including the DASH and NDI was used; violin fixation force and activity of the superficial neck muscles were evaluated in five playing conditions. Results: Each group consisted of eight female and two male violists with a mean age of 29 years. Violinists with complaints had more muscle activity of all evaluated muscles compared to violinists without complaints; complaints were significantly associated with the muscle activity of all evaluated muscles. Complaints were not significantly associated with the violin fixation force. The playing condition significantly predicted the violin fixation force and the activity of all muscles except the left mTP. Conclusions: Violinists with complaints have more muscle activity of some superficial neck and shoulder muscles. Co-contraction is thought to play a relevant role in violinists with these complaints.