Search PubMed⌕ Search

Biomedical subjects

M Solomonow

Publications and source records attributed to M Solomonow.

At least 73 records · Page 4Linked to original sources
PubMed1994

Enhanced spino-pelvic fixation for segmental spinal instrumentation: a preliminary biomechanical evaluation.

A new method for spino-pelvic fixation of Luque rods was developed and biomechanically evaluated on cadaveric specimens. The technique is surgically simpler and faster than the Galveston technique because it does not require the complex three-dimensional bending of rods to conform to the medullary cavity of the iliac wings. Spines were tested in axial compression in both bilateral and unilateral ischial weight bearing in the intact condition, instrumented with the new technique, and instrumented with the Galveston technique. Compared to the intact spine, the technique increased bilateral average stiffness by 131% and unilateral average stiffness by 192%. Compared directly to the Galveston technique, the new method exhibited increased average stiffness of 15% in bilateral and 11% in unilateral ischial weight bearing. The new method combines the advantages of a simpler and faster surgical procedure than the Galveston technique with enhanced spino-pelvic fixation with the potential to decrease migration of rods relative to each other and the pelvis.

Aged↗
PubMed1993

Isotonic length/force models of nine different skeletal muscles.

The isotonic length/force relationships of nine skeletal muscles in the cat's hindlimb were determined using electrical stimulation of the sciatic nerve branches. Large variability in the active, passive, total force patterns and elongation ranges was found. The lateral gastrocnemius (LG), medial gastrocnemius (MG), peroneus longus (PL), flexor digitorum longus (FDL), tibialis posterior (TP) and soleus (Sol) showed symmetric active force curves, whereas those of the extensor digitorum longus (EDL), tibialis anterior (TA) and peroneus brevis (PB) were asymmetric. The total force curves of the EDL, LG, MG, FDL, TP and Sol increased quasilinearly through the elongation range, whereas the PL and PB increased in a nonlinear fashion. The TA had an intermediate plateau. The ranges were generally asymmetric, with a longer shortening range than lengthening past the optimum length. A simple model of the active force was fitted to all except the MG, EDL and TA, which are complex, with at least two compartments. These were successfully fitted with a two-compartment model. The variabilities encountered in the various isotonic length/force curves confirm the need to represent muscles according to their architecture to account for the variety of properties exhibited, which reflect their adaptations to their functions.

Animals↗
PubMed1993

Report on a conference on motor prostheses for workplace mobility of paraplegic patients in North America.

On May 18, 1992 a symposium at Case Western Reserve University in Cleveland, Ohio, USA had the goal of defining the tasks needed to reach clinical utility of investigational neural prosthetic ambulation devices. The characteristics and stage of development of four systems were detailed: the Louiiana State University reciprocating gait orthosis (LSU-RGO) with muscle stimulation; the modular hybrid functional neuromuscular stimulation (FNS) orthosis; the Cleveland VA-Case Western Reserve University (VA-CWRU) implant system; and the Parastep system. Multicenter clinical trials are underway for the Parastep system and are planned to start within the next 2 years for the LSU-RGO with muscle stimulation, the VA-CWRU 8-channel system, and the floor reaction orthosis component of the modular hybrid FNS system. Current investigational systems provide little advantage over the standing wheelchair in some occupations but they do expand social, recreational, and exercise capabilities. Disabled people and some leading rehabilitation physicians are willing to test basic ambulation devices but the regulatory approvals must first be obtained for multicenter clinical trials. Corporate partners are central to the development of devices, their clinical testing, and their subsequent marketing. A key requirement for developing and disseminating motor prostheses is the education of clinicians so that they will participate in trials and be prepared to prescribe the prostheses when they reach the market.

Electric Stimulation↗
PubMed1993

Role of tendon properties on the dynamic performance of different isometric muscles.

The effect of the tendon's viscoelastic stiffness on the dynamic performance of muscles with different architecture was determined using the cat's medial gastrocnemius and extensor digitorum longus. Dynamic response models were derived under sinusoidal contraction-relaxation in the range of 0.4-6.0 Hz and between 20 and 80% of the muscles' maximal isometric tension, manipulated by orderly recruitment-derecruitment of motor units together with firing rate increase-decrease. It was shown that, for isometric contractions at the muscle's optimum length, the dynamic response of the muscles was not significantly different before and after dissection of the tendon. Therefore the conclusion that under these conditions the tendon acts like a stiff force transmitter without significantly modifying the muscle's performance was confirmed and extended to muscles with different architecture.

Action Potentials↗
PubMed1992

The isometric length-force models of nine different skeletal muscles.

The length-force relations of nine different skeletal muscles in the hindlimb of the cat were determined experimentally, with electrical stimulation of the sciatic nerve as the activation mode. It was shown that the active-, passive-, and total-force patterns varied widely among the muscles. The tibialis posterior (TP), medial and lateral gastrocnemius (MG, LG) and flexor digitorum longus (FDL) had a symmetric active-force curve, whereas the tibialis anterior (TA), peroneus brevis (PB), peroneus longus (PL), extensor digitorum longus (EDL), and soleus (SOL) had an asymmetric curve which exhibits about 25% of the maximal isometric force at extreme lengths. The SOL, EDL, and LG had a low-level passive force which appeared at short muscle length, whereas all other muscles exhibited initial passive force just before the optimal length. The total force was rising quasi-linearly for the SOL, whereas the other muscles exhibited an intermediate plateau about the optimal length. The LG and FDL had a substantial but temporary intermediate dip in the total force as the muscle was elongated past the optimal length. The elongation range of the various muscles also varied, ranging from +/- 15 to +/- 30% of the optimal length. The elongation range was symmetric for the FDL, LG, MG, TP, SOL, and EDL, and asymmetric for the PL, PB, and TA, being -12 to + 17%, -12 to + 17%, and -35 to + 12%, respectively. Two different models which incorporate muscle architecture were successfully fitted to the experimental data of the muscles except for the MG and TA. The architecture of these two muscles is highly nonhomogeneous and contains compartments with two pennation patterns or two different optimal lengths. New models, which add spatially and temporally the individual characteristics of each compartment of the muscles, were constructed for these two muscles. The new models demonstrated high correlation to the experimental data obtained from the MG and TA. It was concluded that the length-force relation varies widely among various skeletal muscles and is probably dependent on the primary function of the muscle in the context of integrated movement; this is a manifestation of architectural factors such as fiber pennation pattern and angle, cross-sectional area, ratio of muscle to tendon length, distribution of the fiber length within the muscle and compartmental pennation.

Animals↗
PubMed1992

The dynamic performance model of skeletal muscle.

Applications of electrical stimulation to the nerve or muscles associated with a defunct limb joint due to stroke or spinal cord injury are a viable means of restoring a certain level of functional movement to the patient. In this article, the currently acceptable physiology of motor control is outlined and used as a criterion for electrophysiological and biomechanical performance evaluation of contemporary electrical stimulation strategies used by various systems attempting to duplicate such motor control in an effort to restore meaningful limb function. Strategies associated with surface, nerve, intramuscular, and reflex stimulation are critically reviewed with special reference to voluntary sensory motor control of a limb joint rather than an isolated muscle.

Animals↗
PubMed1991

The effect of tendon viscoelastic stiffness on the dynamic performance of isometric muscle.

The effect of tendons viscoelastic stiffness on the dynamic response of the cat's tibialis anterior muscle under isometric conditions was determined. It was shown that the dynamic response model of the muscle derived under sinusoidal contraction-relaxation in the range of 20-80% of its maximal isometric tension was not statistically different before and after the disection of the whole distal tendon. It was suggested that under isometric conditions in the force range of 20-80% of the maximal, the tendon acts as a very stiff force transmission linkage without significantly modifying the muscle's performance.

Animals↗
PubMed1991

Dynamic performance of a load-moving skeletal muscle.

The dynamic response of the tibialis anterior muscle of the cat was determined while it was subjected to sinusoidally varying orderly stimulation of motor units and to different isotonic loads in the range of 14-85% of the maximal isometric force. The dynamic response consisted of three major components: the displacement gain, the displacement attenuation, and a pure time delay. The displacement gain was dependent on the passive load applied to the muscle and the active force generated during contraction, which could be determined from the length-tension relationships and the corresponding shortening velocity. In general, the load displacement decreased as the load mass increased from 25 to 85% of the maximal isometric force. For loads less than 25% of the maximal isometric force, slight decrease in displacement was consistently observed. The displacement attenuation was dependent on the contraction frequency but uniform for all the load masses applied to the muscle. A pure time delay of 5 ms was present and accounted for various physiological processes such as conduction time in nerve and muscle, neuromuscular junction transmission, and excitation-contraction coupling. A quantitative equation was developed to describe the muscle's dynamic response under isotonic conditions and for a wide range of loads for use in various applications.

Animals↗
PubMed1990

The dynamic response model of nine different skeletal muscles.

The frequency response model of nine different skeletal muscles in the hindlimb of the cat was determined with the aide of electrical nerve stimulation which allows orderly stimulation of motor units concurrently with firing rate increase. It was shown that the general model consists of a linear second-order system with double real poles and a pure time delay. The pole values were different for the different muscles, ranging from 1.55 to 2.8 Hz. Similarly, the pure time delay varied from muscle to muscle, ranging from 8 to 17 ms. Statistical analysis demonstrates that under isometric contraction with force oscillations in the range of 10-90% of maximal the model poles are determined, and could be predicted, from the muscles functional and anatomical location in the limb and from its pennation pattern.

Animals↗
PubMed1990

Electromyogram power spectra frequencies associated with motor unit recruitment strategies.

The isolated contributions of motor unit recruitment and firing rate variations to the median frequency of the electromyogram's power density spectrum were determined. Orderly stimulation of the cat gastrocnemius motor units via nerve electrodes gave rise to linearly increasing median frequency regardless of the action potential firing rate of the active motor units. Increase in the discharge rate of all the motor units resulted in nearly constant median frequency. It was concluded that the increasing average conduction velocity during motor unit recruitment is the major contributor to variations in the electromyogram median frequency. The possibility of using the median frequency as the index to identify the recruitment control strategies employed by various muscles during increasing force contraction is suggested.

Action Potentials↗
PubMed1990

The effects of prenatal protein-energy malnutrition on ossification of fetal rat bones: a biochemical study.

In fetal rats whose dams were fed a low-protein diet, 35S sulfate uptake into the growth plate of the long bone and rib was higher than in the control group. The elution pattern of guanidine-HCl extract in gel chromatography revealed that the malnourished group had more high molecular weight proteoglycans in the dissociative condition and a larger aggregated portion in the associative condition than did the control group; however, the same chondroitin-sulfate chain size existed. Calcium content did not differ in both groups. Aggregated proteoglycan or a high molecular weight proteoglycan that existed in the malnourished group probably played an inhibitory role in calcification. Prenatal protein-energy malnutrition may delay the change of proteoglycan character, which could affect mineralization of fetal bones.

Animals↗
PubMed1990

Factors affecting postoperative flexion in total knee arthroplasty.

In the review of 67 cases with total condylar (TC) prostheses, 59 with TC posterior stabilizers, 70 with TC prostheses modified with flat posterior tibial plateau, and 35 with porous-coated arthroplasty (PCA) prostheses, multiple cross-examinations of various factors for postoperative flexion were performed. Follow up was 2 to 9 years. In nearly all cases, no further improvement of flexion was noted after 1 year following surgery. The most influential factor for good postoperative flexion was intense physical therapy, leading to good suprapatellar pouch reconstitution. Residual flexion contracture was more frequent when the posterior cruciate ligament (PCL) was retained in the cases with significant preoperative flexion contracture. However, retention of PCL or preoperative ACL condition did not bear any significance to the ultimate flexion.

Adult↗
PubMed1990

The effect of oxygen tension on collagen synthesis and calcium uptake in newborn rats' calvaria in vitro.

Using newborn rat calvaria, we determined the effects of oxygen tension on bone cell metabolism in vitro. Halved calvaria were incubated in medium either in air or after flushing nitrogen or oxygen and studied for collagen synthesis, calcium uptake, and DNA content. The percentages of DNA content, radioactive proline count in mg of bone tissue, and radioactive proline count combined with counts of medium and bone tissue in the nitrogen-exposed group were less than those of their pair-matched controls. Percent calcium counts per DNA and calcium uptake per mg of tissue were greater in the nitrogen-exposed group than in the pair-matched controls. In contrast, no difference was found in any measurements in the oxygen-exposed group compared with controls. It is concluded that collagen synthesis, in contrast to proline uptake, is not affected by low oxygen, whereas calcium uptake is greatly enhanced. Furthermore, low oxygen tension exerts a greater effect on bone cell metabolism than does the hyperoxic condition.

Animals↗
PubMed1990

Energy consumption in paraplegic ambulation using the reciprocating gait orthosis and electric stimulation of the thigh muscles.

The energy consumption of six thoracic paraplegic persons ambulating in the reciprocating gait orthosis (RGO) with and without functional electric stimulation (FES) of their thigh muscles was determined as a function of walking speed. Plots of Kcal/kg-min and Kcal/kg-m vs walking speed in the RGO and RGO & FES were experimentally determined in this study and compared with the energy cost of walking in the long leg brace (LLB), the hip guidance orthosis (HGO), and an FES walking aid from data available in the literature. The RGO powered with electric stimulation of the thigh muscles required the lowest energy expenditure in Kcal/kg-m across the full range of walking speeds. The RGO, HGO, LLB, and FES walking orthoses ranked second, third, fourth, and fifth respectively. The lowest energy costs in Kcal/kg-min were associated with the RGO & FES, followed by the RGO, HGO, LLB, and FES for walking speeds below .28m/sec. At walking speeds higher than .28m/sec the HGO demonstrates lower energy cost followed by the RGO & FES, RGO, FES, and LLB. At the end of a 30-m walk, patients using the RGO & FES had a mean heart rate (HR) which was 12 beats/min less than the mean HR when using the RGO without FES, 31 beats/min less than the HR when using the LLB, and 42 beats/min less than the HR when using FES only. It was concluded that the FES-powered RGO combines the advantages of a passive mechanical orthosis with those of FES to provide substantial improvements in energy cost which may provide paraplegic persons with a mode of independent ambulation superior to the wheelchair.

Adult↗
PubMed1989

Frequency response model of skeletal muscle: effect of perturbation level, and control strategy.

The frequency response model of the soleus muscle of the cat was determined as a function of various firing rate and recruitment control strategies and at various force oscillation levels. We found that the basic frequency response models of the muscle during individual force oscillations at various control strategies in which the motor unit population of the muscle was fully recruited to obtain 50 per cent and up to 100 per cent of the maximum force, either concurrently with firing rate increase or at constant firing rate, were nearly identical. The model consisted of a second-order, linear low-pass filter with double poles at 1.85 Hz and a pure time delay of 16 ms. The model resulting from only firing rate increase from the frequency of fusion of the smallest motor unit to the maximum tetanic rate of the muscle while all the motor units were continuously active was nonlinear, and depended on the force's oscillation level. This nonlinear response of the rate coding process is also identified as the source of the increased harmonic distortion in the model where the initial 50 per cent of the force was generated by fully recruiting all the motor units, and the final 50 per cent of the force was generated by firing rate increase. We concluded that the basic frequency response model of a muscle under conditions similar to voluntary contraction consists of a linear, second-order system which is robust and independent of control strategy and force perturbation level.

Animals↗
PubMed1989

Method for studying muscle properties under orderly stimulated motor units with tripolar nerve cuff electrode.

An electrical nerve stimulation technique, using single tripolar electrode, was shown to be capable of recruiting motor units according to their size, while allowing simultaneous but independent control of firing rate in the active units. Test paradigms consisting of established fundamental physiological concepts of soleus-gastrocnemius architecture, firing rate behaviour of motor units of different sizes, and their susceptibility to fatigue were employed to validate the technique and demonstrate its utility as a basic and applied research tool.

Animals↗
PubMed1989

Orderly stimulation of skeletal muscle motor units with tripolar nerve cuff electrode.

An electrical nerve stimulation technique, using single tripolar electrode, was shown to be capable of recruiting motor units according to their size, while allowing simultaneous but independent control of firing rate in the active units. Test paradigms consisting of established fundamental physiological concepts of soleus-gastrocnemius architecture, motor units conduction velocity, firing rate behavior of motor units of different sizes, and their susceptibility to fatigue were employed to validate the technique and demonstrate its utility as a basic and applied research tool.

Action Potentials↗