RESUMEN
Background: Total knee arthroplasty (TKA) is one of the most frequently performed orthopedic procedures. The correct positioning and alignment of the components significantly affects prosthesis survival. Considering the current controversy regarding the target of postoperative alignment of TKA, this study evaluated the tension at tibial component interface using two numerical methods. Methods: The stress of the prosthesis/bone interface of the proximal tibial component was evaluated using two numerical methods: the finite element method (FEM) and the new meshless method: natural neighbor radial point interpolation method (NNRPIM). The construction of the model was based on Zimmers NexGen LPS-Flex Mobile® prosthesis and simulated the forces by using a free-body diagram. Results: Tibiofemoral mechanical axis (TFMA) for which a higher number of nodes are under optimal mechanical tension is between 1° valgus 2° varus. For values outside the interval, there are regions under the tibial plate at risk of bone absorption. At the extremities of the tibial plate of the prosthesis, both medial and lateral, independent of the alignment, are under a low stress. In all nodes evaluated for all TFMA, the values of the effective stresses were higher in the NNRPIM when compared with the FEM. Conclusion: Through this study, we can corroborate that the optimal postoperative alignment is within the values that are currently considered of 0 ± 3° varus. It was verified that the meshless methods obtain smoother and more conservative results, which may make them safer when transposed to the clinical practice.
RESUMEN
CONTEXT: Horse riding (HR) has gain popularity in Portugal, thereby increasing the number of related injuries. This study identifies frequently occurring injuries in Portuguese riders, the conditions under which they occur, and preventive measures. DESIGN: A retrospective cohort study. METHODS: We included 216 Portuguese riders practicing HR at the time of the study with ≥1 year of experience. Data were obtained from a questionnaire that characterized first and second rider injuries; we opted for a systematic method to assess the riders' injuries, in a temporal order. Questions regarding demographic data, sports-related background, systematic training workload, number and characteristics of the first 2 injuries, and the need for treatment were included in the questionnaire. RESULTS: Most first and second injuries were musculoskeletal, occurred from falling off the horse during training, and primarily affected the lower limb. Rehabilitation was required in almost 50% of all cases. The occurrence of injury was significantly associated with the number of days of training per week, years of experience, height and weight of the rider, and practice of another sport. Riding different horses was also significantly associated with the number of injuries. CONCLUSIONS: The most frequently occurring injuries during HR are musculoskeletal and in the extremities. Injury prevention is essential in HR, as most riders have at least one injury while practicing. Rehabilitation should involve a physiatrist and core strengthening exercises.
