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Extension Moment (extension + moment)
Selected AbstractsTherapeutic effects of functional electrical stimulation of the upper limb of eight children with cerebral palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 11 2000P A Wright BSc PhD Functional electrical stimulation (FES) of the upper limb has been used for patients with a variety of neurological conditions, although few studies have been conducted on its use on the upper limb of children with cerebral palsy (CP). The aim of this study was to investigate the effect of cyclic FES on the wrist extensor muscles of a group of eight children (five boys, three girls) with hemiplegic CP (mean age 10 years). The study design involved a baseline (3 weeks), treatment (6 weeks), and follow-up (6 weeks). FES was applied for 30 minutes daily during the treatment period of the study. Improvements in hand function (p,0.039) and active wrist extension (p=0.031) were observed at the end of the treatment period. These improvements were largely maintained until the end of the follow-up period. No significant change was observed in the measurements of wrist extension moment during the treatment period (p=0.274). Hand function in this group of children improved after they were exposed to FES of wrist extensor muscles. This suggests that FES could become a useful adjunct therapy to complement existing management strategies available for this patient population. [source] Stress analysis of the anterior tibial post in posterior stabilized knee prosthesesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2007Chang-Hung Huang Abstract Recent retrieval studies have indicated a high incidence of polyethylene wear on the anterior tibial post caused by impingement. This study investigated the influences of post-cam design features and component alignment on the stress distribution in the anterior tibial post when subjected to the impingement loading. Two three-dimensional finite element models of posterior stabilized knee prostheses were constructed, one with flat on flat (FF) and another with curve on curve (CC) contact surfaces between anterior tibial post and femoral cam. The polyethylene insert was modeled with elastoplastic properties. Nine cases, three hyperextension angles (0°, 5°, and 10°) combined with three axial tibial rotations (0°, 2.5°, and 5°) simulating different component alignments were analyzed. A vertical compressive load of 2,000 N and an extension moment of 45 Nm were applied simultaneously. The FF model had larger stress increases than the CC model in both hyperextension and tibial rotation compared with the neutral position. The maximum increase for the FF model was 68% in peak contact stress, 125% in von Mises stress, and 58% in tensile stress in the extreme case of 10° of hyperextension combined with 5° of axial rotation. Stress concentration was found at the anterior corner of the post in the FF model; this was not found in the CC model. The curve on curve design can reduce edge loading on the tibial post, especially during axial tibiofemoral rotation. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:442,449, 2007 [source] Altered loading during walking and sit-to-stand is affected by quadriceps weakness after total knee arthroplastyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2005Ryan L. Mizner Abstract Purpose: Total knee arthroplasty (TKA) successfully reduces pain, but has not achieved comparable improvements in function. We hypothesized that quadriceps strength affects performance by altering loading and movement patterns during functional tasks. Methods: Fourteen subjects with isolated, unilateral TKA were tested three months after surgery. Quadriceps strength was assessed isometrically and kinematics, kinetics, and EMG were collected during level walking and sit-to-stand (STS). Function was assessed using the timed up and go test (TUG), stair climbing test (SCT), and the 6 min walk test (6MW). Results: Functional performance was significantly related to the quadriceps strength of both legs, but was more strongly related to the uninvolved strength (involved rho = ,0.43 with TUG; ,0.65 with SCT; 0.64 with 6MW) (uninvolved rho = ,0.63 with TUG; ,0.68 with SCT; 0.77 with 6MW). During STS, subjects shifted weight away from the operated limb (p <0.01). Quadriceps muscle activity and the extension moments at the knee and hip were smaller in the involved compared to the uninvolved (p <0.05). The amount of asymmetry in knee excursion during weight acceptance in gait, the asymmetry in weight bearing from sit-to-stand, and the uninvolved hip extension moment during STS were related to the amount of asymmetry in quadriceps strength (rho > 0.56, p < 0.05). Conclusions: Quadriceps weakness in patients with TKA has a substantial impact on the movement patterns and performance of the knee during functionally important tasks. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] In vivo load sharing among the quadriceps componentsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2003Li-Qun Zhang Abstract Knee extension is always performed with coordinated contractions of multiple quadriceps muscle components: however, how the load is shared among them under normal and pathological conditions is unclear. We hypothesized that: the absolute moment generated by each quadriceps component increases with the total knee extension moment; the relative contribution and its dependence on the total knee extension moment are different for different quadriceps components; and the centrally located large vastus intermedius (VI) is favored by the central nervous system at low levels of activation. Electrical stimulation was used to activate each quadriceps component selectively in six human subjects. The relationship between the knee extension moment generated by an individual quadriceps component and the corresponding compound muscular action potential (M -wave) over various contraction levels was established for each quadriceps component. This relationship was used to calibrate the corresponding EMG signal and determine load sharing among quadriceps components during submaximal isometric voluntary knee extension. The VI contributed the most (51.8,39.6%) and vastus medialis the least (9.5,12.2%) to knee extension moment (P < 0.05). As the knee extension moment increased, the relative contribution of the VI decreased (P = 0.017) while the relation contribution of the vastus lateralis and medialis increased (P , 0.012). The absolute moment generated by each quadriceps component always increased with the total knee extension moment (P < 0.002). Our in vivo approach determined subject- and condition-specific load sharing among individual muscles and showed that the central nervous system utilized the centrally located, uniarticular VI in submaximal isometric knee extension. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Human jaw muscle strength and size in relation to limb muscle strength and sizeEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2004M. C. Raadsheer The aim of the present study was to investigate to what extent general factors (e.g. genotype, hormones) and factors at the craniofacial level (e.g. craniofacial size, jaw muscle architecture) contribute to the size and strength of the jaw muscles. A strong relationship of jaw muscle size and strength with that of other muscles would argue for general influences, whereas a weak relationship would argue for craniofacial influences. In 121 adult individuals, moments of maximal bite force, arm flexion force and leg extension force were measured. In addition, thicknesses of jaw muscles, arm flexor muscles and leg extensor muscles were measured using ultrasound. Relationships were assessed by using a principal component analysis. In females, one component was found in which all force moments were represented. Bite force moment, however, loaded very low. In males, two components were found. One component loaded for arm flexion and leg extension moments, the other loaded for bite force moments. In both females and males, only one component was found for the muscle thicknesses in which all muscle groups loaded similarly. It was concluded that the size of the jaw muscles was significantly related to the size of the limb muscles, suggesting that they were both subject to the same general influences. Maximal voluntary bite force moments were not significantly related to the moments of the arm flexion and leg extension forces, suggesting that besides the general influence on the muscle size, variation in bite force moment was also influenced by local variables, such as craniofacial morphology. [source] Altered loading during walking and sit-to-stand is affected by quadriceps weakness after total knee arthroplastyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2005Ryan L. Mizner Abstract Purpose: Total knee arthroplasty (TKA) successfully reduces pain, but has not achieved comparable improvements in function. We hypothesized that quadriceps strength affects performance by altering loading and movement patterns during functional tasks. Methods: Fourteen subjects with isolated, unilateral TKA were tested three months after surgery. Quadriceps strength was assessed isometrically and kinematics, kinetics, and EMG were collected during level walking and sit-to-stand (STS). Function was assessed using the timed up and go test (TUG), stair climbing test (SCT), and the 6 min walk test (6MW). Results: Functional performance was significantly related to the quadriceps strength of both legs, but was more strongly related to the uninvolved strength (involved rho = ,0.43 with TUG; ,0.65 with SCT; 0.64 with 6MW) (uninvolved rho = ,0.63 with TUG; ,0.68 with SCT; 0.77 with 6MW). During STS, subjects shifted weight away from the operated limb (p <0.01). Quadriceps muscle activity and the extension moments at the knee and hip were smaller in the involved compared to the uninvolved (p <0.05). The amount of asymmetry in knee excursion during weight acceptance in gait, the asymmetry in weight bearing from sit-to-stand, and the uninvolved hip extension moment during STS were related to the amount of asymmetry in quadriceps strength (rho > 0.56, p < 0.05). Conclusions: Quadriceps weakness in patients with TKA has a substantial impact on the movement patterns and performance of the knee during functionally important tasks. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] | ||||||||||