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Analysis of cumulative strain in tendons and tendon sheaths
176
bin.
Biomech.
1987; 2: No 3
A mechanical evaluation of an elastic femoral prosthetic stem Studies are being conducted in our laboratory to test the concept of introducing an elastomer to attenuate and damp forces applied to the bone interface in a major weightbearing joint replacement prosthesis. An analogue of a fully constrained intramedullary stem type prosthesis has been developed in a segmental femoral replacement prosthesis of the dog. The layer of silastic was introduced to damp forces at the bone-prosthesis interface. This paper describes the response of this elastomer prosthesis to torsional and bending loads. and defines the upper limits of elastomer strain. The low modulus silastic displayed surprisingly low strain for applied loads, particularly in bending tests, in this prosthetic configuration. The results of these mechanical studies serve as a bench mark for the.eventual design and material selection of an elastomer for human prosthetic use. Newcombe WR. Repo RU. Biomech 19X7; 20: 179-87
Eaton NB. Occhionorelli
J. J
The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes In this study. we explore the relationship between moments in the frontal and sagittal planes. generated by a lifting task, vs the electromyographic (EMG) activity of right and left trunk muscle groups. In particular, we postulate that the functional dependence between erector spinae muscle activity and the applied lifting moments about the spine is as follows: ( I) the sum of left and right erector spinae processed EMG depends on the sagittal plane moment, and (2) the difference of left and right erector spinae processed EMG depends on the frontal plane moment. A simple out-of-sagittal plane physical model. treating the lumbar spine as ;I two degree-of-freedom pivot point is discussed to justify thehe hypotheses. To validate thih model, we collected surface EMG and lifting moment data for ten males performing a grid of frontal and sagittal plant lifting tasks. A digital RMS-to-DC algorithm WI\ dcvclop~d for processing raw EMG. For these tests. we measured EMG for the left and right erector spinae and for the left and right external oblique muscles. The processed EMG signals of the left and right erector spinae muscles are summed and differenced for comparison to the measured sagittal and frontal plane moments. A linear correlation (6) of O.Yh was obtained for the sum of erector spinae EMG vs the sagittal plane moment; a corresponding value of r’ = 0.95 was obtained for the difference vs the frontal plane moment. No correlations (;<0.004) was found for ( 1) the sagittal plane moment and the difference of the left and right erector spinae EMG. and (2) the frontal plane moment and the sum of the left and right erector spinae EMG. Seroussi RE,
Pope MH.
J Biomech
lYK7; 20: 135-46
Eccentric wrist extensor contractions and the force velocity relationship in muscle The torque produced by the wrist extensors during maximal isometric and isokinetic eccentric contractions has been investigated. The torque produced by eccentric contractions was measured at three different velocities: 0.36.0.93. and 164 cm/set. The speeds of contraction were generated by a specially designed apparatus, consisting of a gear drive and an electric motor that would maintain its speed irrespective of the load applied. Tension produced by the wrist extensors
was measured using a load cell. The results indicated that eccentric contractions of the wrist extensors exceed those produced by isometric contractions. The force-velocity relationship during eccentric contractions was determmed to be different from that during concentric contractions. Force values were found to increase as the velocity of eccentric contraction increased. No significant effect of wrist joint angle on torque values was found. nor was there an interaction effect of velocity and joint angle. The implications for rehabilitation of these findings are outlined. Walmsley RP. Pearson N. Stymiest P. J Orthop Ther 1986: 8: 2X8-Y3
Sports Phys
Tendon stiffness: methods of measurement and significance for the control of movement. A review An iappraisal of the role of tendons in transmitting muscle tension to skeletal parts during posture and movement requires accurate knowledge of the mechanical characteristics of the tendon. Here the most important property is tendon stiffness. While it is relatively easy to measure the stiffness of an isolated segment of tendon. more sophisticated methods must be sought to take into account the whole length of tendon. including its intramuscular portion. Two methods are currently available for measurement of whole tendon stiffness: each has a limited range of muscle tensions over which it appears to provide reliable values. one method being better at low tensions. the other at high tensions. Some controversy remains about the precise values obtained in the mid-tension range covered by both methods. Nevertheless it is now possible to achieve reasonable estimates of tendon stiffness over the whole working range of the muscle. An important consideration which has emerged from the discussion is that at low tensions the tendon is much less stiff than at higher tensions. Proske U. Morgan
DL. J Biomech
lY87: 20: 75-82
Analysis of cumulative strain in tendons and tendon sheaths Twenty-five fresh frozen flexor digitorum profundus tendons stratified by sex w’crc’subjected to uniaxial step stress and cyclic loads in twclvc intact human cadaver hands. By attaching specially designed clip strain gage transducers on tendons just proximal and distal to an undisrupted carpal tunnel, the interactions of the tendons, tendon sheath and retinacula were measured. The elastic and viscous response of the tendon composites to step stresses were found to tit fractional power functions of stress and time respectively. A significant and quantifable decrease in strain from the proximal to the distal tendon segment was found to he ;I function of wrist deviation. The results indicate that an accumulation of strain does occur in tendinous tissues during physiologic loading. Goldstein SA. Armstrong Biomech lY87: 20: 1-6
TJ. Chaffin
DB.
Matthews
LS. J
BIOMEDICAL SCIENCES Myoelectric analysis of the paraspinal musculature in relation to automobile driving In this study. the myoelectric
activity of 12 paraspinal
muscles
bin.
Biomech.
1987; 2: No 3
A mechanical evaluation of an elastic femoral prosthetic stem Studies are being conducted in our laboratory to test the concept of introducing an elastomer to attenuate and damp forces applied to the bone interface in a major weightbearing joint replacement prosthesis. An analogue of a fully constrained intramedullary stem type prosthesis has been developed in a segmental femoral replacement prosthesis of the dog. The layer of silastic was introduced to damp forces at the bone-prosthesis interface. This paper describes the response of this elastomer prosthesis to torsional and bending loads. and defines the upper limits of elastomer strain. The low modulus silastic displayed surprisingly low strain for applied loads, particularly in bending tests, in this prosthetic configuration. The results of these mechanical studies serve as a bench mark for the.eventual design and material selection of an elastomer for human prosthetic use. Newcombe WR. Repo RU. Biomech 19X7; 20: 179-87
Eaton NB. Occhionorelli
J. J
The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes In this study. we explore the relationship between moments in the frontal and sagittal planes. generated by a lifting task, vs the electromyographic (EMG) activity of right and left trunk muscle groups. In particular, we postulate that the functional dependence between erector spinae muscle activity and the applied lifting moments about the spine is as follows: ( I) the sum of left and right erector spinae processed EMG depends on the sagittal plane moment, and (2) the difference of left and right erector spinae processed EMG depends on the frontal plane moment. A simple out-of-sagittal plane physical model. treating the lumbar spine as ;I two degree-of-freedom pivot point is discussed to justify thehe hypotheses. To validate thih model, we collected surface EMG and lifting moment data for ten males performing a grid of frontal and sagittal plant lifting tasks. A digital RMS-to-DC algorithm WI\ dcvclop~d for processing raw EMG. For these tests. we measured EMG for the left and right erector spinae and for the left and right external oblique muscles. The processed EMG signals of the left and right erector spinae muscles are summed and differenced for comparison to the measured sagittal and frontal plane moments. A linear correlation (6) of O.Yh was obtained for the sum of erector spinae EMG vs the sagittal plane moment; a corresponding value of r’ = 0.95 was obtained for the difference vs the frontal plane moment. No correlations (;<0.004) was found for ( 1) the sagittal plane moment and the difference of the left and right erector spinae EMG. and (2) the frontal plane moment and the sum of the left and right erector spinae EMG. Seroussi RE,
Pope MH.
J Biomech
lYK7; 20: 135-46
Eccentric wrist extensor contractions and the force velocity relationship in muscle The torque produced by the wrist extensors during maximal isometric and isokinetic eccentric contractions has been investigated. The torque produced by eccentric contractions was measured at three different velocities: 0.36.0.93. and 164 cm/set. The speeds of contraction were generated by a specially designed apparatus, consisting of a gear drive and an electric motor that would maintain its speed irrespective of the load applied. Tension produced by the wrist extensors
was measured using a load cell. The results indicated that eccentric contractions of the wrist extensors exceed those produced by isometric contractions. The force-velocity relationship during eccentric contractions was determmed to be different from that during concentric contractions. Force values were found to increase as the velocity of eccentric contraction increased. No significant effect of wrist joint angle on torque values was found. nor was there an interaction effect of velocity and joint angle. The implications for rehabilitation of these findings are outlined. Walmsley RP. Pearson N. Stymiest P. J Orthop Ther 1986: 8: 2X8-Y3
Sports Phys
Tendon stiffness: methods of measurement and significance for the control of movement. A review An iappraisal of the role of tendons in transmitting muscle tension to skeletal parts during posture and movement requires accurate knowledge of the mechanical characteristics of the tendon. Here the most important property is tendon stiffness. While it is relatively easy to measure the stiffness of an isolated segment of tendon. more sophisticated methods must be sought to take into account the whole length of tendon. including its intramuscular portion. Two methods are currently available for measurement of whole tendon stiffness: each has a limited range of muscle tensions over which it appears to provide reliable values. one method being better at low tensions. the other at high tensions. Some controversy remains about the precise values obtained in the mid-tension range covered by both methods. Nevertheless it is now possible to achieve reasonable estimates of tendon stiffness over the whole working range of the muscle. An important consideration which has emerged from the discussion is that at low tensions the tendon is much less stiff than at higher tensions. Proske U. Morgan
DL. J Biomech
lY87: 20: 75-82
Analysis of cumulative strain in tendons and tendon sheaths Twenty-five fresh frozen flexor digitorum profundus tendons stratified by sex w’crc’subjected to uniaxial step stress and cyclic loads in twclvc intact human cadaver hands. By attaching specially designed clip strain gage transducers on tendons just proximal and distal to an undisrupted carpal tunnel, the interactions of the tendons, tendon sheath and retinacula were measured. The elastic and viscous response of the tendon composites to step stresses were found to tit fractional power functions of stress and time respectively. A significant and quantifable decrease in strain from the proximal to the distal tendon segment was found to he ;I function of wrist deviation. The results indicate that an accumulation of strain does occur in tendinous tissues during physiologic loading. Goldstein SA. Armstrong Biomech lY87: 20: 1-6
TJ. Chaffin
DB.
Matthews
LS. J
BIOMEDICAL SCIENCES Myoelectric analysis of the paraspinal musculature in relation to automobile driving In this study. the myoelectric
activity of 12 paraspinal
muscles