Implant density is not related to patient-reported outcome in the surgical treatment of patients with idiopathic scoliosis.

Aims: There is little information about the optimum number of implants to be used in the surgical treatment of idiopathic scoliosis. Retrospective analysis of prospectively collected data from the Swedish spine register was undertaken to discover whether more implants per operated vertebra (implant density) leads to a better outcome in the treatment of idiopathic scoliosis. The hypothesis was that implant density is not associated with patient-reported outcomes, the correction of the curve or the rate of reoperation. Patients and Methods: A total of 328 patients with idiopathic scoliosis, aged between ten and 20 years at the time of surgery, were identified in the Swedish spine register (Swespine) and had patient reported outcomes including the Scoliosis Research Society 22r instrument (SRS-22r) score, EuroQol 5 dimensions quality of life, 3 level (EQ-5D-3L) score and a Viual Analogue Score (VAS) for back pain, at a mean follow-up of 3.1 years and reoperation data at a mean follow-up of 5.5 years. Implant data and the correction of the curve were assessed from radiographs, preoperatively and a mean of 1.9 years postoperatively. The patients were divided into tertiles based on implant density. Data were analyzed with analysis of variance, logistic regression or log-rank test. Some analyses were adjusted for gender, age at the time of surgery, the flexibility of the major curve and follow-up. Results: The mean number of implants per operated vertebra in the low, medium and high-density groups were 1.36 (1.00 to 1.54), 1.65 (1.55 to 1.75) and 1.91 (1.77 to 2.00), respectively. There were no statistically significant differences in the correction of the curve, the SRS-22r total score, EQ-5D-3L index or number of reoperations between the groups (all p > 0.34). In the SRS-22r domains, self-image was marginally higher in the medium implant density group (p = 0.029) and satisfaction marginally higher in the high implant density group (p = 0.034). Conclusion: These findings suggest that there is no clear advantage in using a high number of implants per operated vertebra in the surgical treatment of patients with idiopathic scoliosis. Cite this article: Bone Joint J 2018;100-B:1080-6.

Mechanical output and electromyographic parameters in males and females during fatiguing knee-extensions.

The purpose of this study was to elucidate if the m. quadriceps femoris was fully activated during the first contractions of a series of repetitive maximal contractions and if there was any difference in the development of fatigue between sexes. To do this sixteen untrained subjects performed two series of contractions in an isokinetic dynamometer: one series of single maximum contractions and one series of repetitive maximum contractions. The EMG activity of m. vastus lateralis, m. vastus medialis and m. rectus femoris was recorded. The subjects were unable to perform maximum effort during the first repetitions of each trial, which might influence the results of fatigue studies, if these contractions are chosen as reference. We also found in contrast to other studies a decrease in RMS between the reference contraction and the fatigue level. We have not been able to display any difference between males and females during fatigue either in relative mechanical output nor in electromyographic parameters or experience in fatigue during isokinetic knee-extensions.

Inter-relationship between muscle morphology, mechanical output and electromyographic activity during fatiguing dynamic knee-extensions in untrained females.

Changes in mechanical performance and electromyographic activity during fatiguing dynamic knee-extensions were evaluated with respect to muscle fibre type composition of the vastus lateralis muscle in nine sedentary female [23 (3) years] volunteers. The subjects performed 150 repetitive maximum knee-extensions using a Cybex dynamometer at 1.57 rad x s(-1). EMG activity was recorded from the vastus lateralis, the vastus medialis and the rectus femoris muscles. For each contraction, mean power frequency (MPF) and the root mean square (RMS) of the EMG were calculated, simultaneously with the peak torque (PT), contractional work (CW) and the mean power (MP). The MPF showed an initial decrease followed by a stable phase. The RMS increased during the initial seven contractions, after which a period of variability was displayed until about the 60th contraction. At the plateau level (last 50 contractions) the relative RMS values were not significantly different from the initial values. The PT, CW and MP increased during the initial five to ten contractions, after which a two-phase pattern was displayed, with a gradual decline followed by a stable phase. The absolute plateau level of MPF for the vastus lateralis muscle showed a significant negative correlation with the area percentage of type-1 fibres (r = -0.71). Significant correlations were also demonstrated to occur between the absolute plateau levels of PT, CW and MP and the relative proportion of type-1 fibres (r = 0.80, r = 0.82 and r = 0.82 respectively). Thus, in female subjects the mechanical performance and the MPF during fatigue are at least partly determined by muscle morphology.

Do muscle fibre size and fibre angulation correlate in pennated human muscles?

Several studies have reported estimations of the total number of fibres in a muscle, e.g. before and after training or before and after inactivity. In those investigations a combination of computed tomographic estimations of muscle size and morphological studies of fibre size has most often been used. There have been doubts about the reliability of those studies on pennate muscles, since changes in muscle fibre size have been said to alter fibre angulation and thus the number of fibres that will cross a section. If such an alteration in fibre angulation takes place with an increase in fibre size, there ought to be some correlation between fibre size and fibre angulation. The present study was designed to test whether repetitive estimations of muscle fibre angulation could be performed in vivo and if any such correlation could be found between fibre size and fibre angulation. A group of 15 women volunteered to take part in the study. Repeated ultrasonographic recordings were made on five subjects on 3 consecutive days to test the repeatability of ultrasonographic measurement of fibre angulation. Both muscle morphological analyses and ultrasonographic measurements of fibre angulation were performed on the other 10 subjects. Ultrasonographic measurement of fibre angulation was found to be reproducible since no variation between measurements made on different days was found. When trying to correlate muscle fibre size to the muscle fibre angulation, measured ultrasonographically, no significant correlation was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Dependence of the mean power frequency of the electromyogram on muscle force and fibre type.

The aim of this study was to investigate whether the mean power frequency of the electromyogram of the knee extensors was force and/or muscle fibre-type dependent. Ten female subjects performed a gradually increasing static knee extension (5 seconds duration) using an isokinetic dynamometer. Electromyogram-signals were obtained from the vastus lateralis, vastus medialis and the rectus femoris muscles. The torque signal and the three electromyogram signals were recorded on a tape recorder. From the electromyogram recordings the mean power frequency and the signal amplitude were determined. Muscle biopsies were later obtained from the right vastus lateralis and stained for alkaline and acid mATPase for the determination of fibre-type proportion and areas. Both the mean power frequencies and the signal amplitudes of the three knee extensors were positively torque dependent. Furthermore it was found that the fibre type proportion and the regression coefficient of the torque (%)-mean power frequency relationship were positively correlated. Also a negative correlation existed between the type-1 (%) proportion and the intercept of the individual torque (%)-mean power frequency relationships. In contrast to proposed models of the electromyogram signal no correlation was found between the mean power frequency and the fibre area.

Do the fibre-type proportion and the angular velocity influence the mean power frequency of the electromyogram?

The dependence of the mean-power frequency and the signal amplitude of the electromyogram (EMG) on the angular velocity and the fiber-type proportion were investigated in nine female volunteers. The subjects were required to perform maximum knee extensions using an isokinetic dynamometer at different angular velocities; 0.57, 1.05, 1.57, 2.09 and 3.14 rad s-1. Electromyographic signals were obtained from the vastus lateralis, vastus medialis and the rectus femoris muscles. The angle and the torque signals were recorded simultaneously with the three EMG signals on a tape-recorder. From the EMG recordings the mean power frequency (MPF) and the signal amplitude were determined. Muscle biopsies were later obtained from the right vastus lateralis and stained for alkaline and acid mATPase for the determination of fibre-type proportions and areas. Neither the signal amplitude nor the MPF of the EMG of the three muscles were dependent on the angular velocity. The MPF of the vastus lateralis correlated significantly (r = -0.93) with the type 1 fibre proportion at 1.57 rad s-1. However, there was no significant correlation between the areas of the fibre types, alone or together, and the MPF. In conclusion the fibre-type proportion was the major factor behind the MPF irrespective of angular velocity.

Ultrastructural changes and enzyme activities for energy production in hearts concomitant with tumor-associated malnutrition.

Morphometric data on left ventricular papillary muscle structures have been determined in tumor-induced malnutrition and related to the maximum activities of key enzymes for energy production in the whole myocardium. Adult, nongrowing mice with a syngeneic sarcoma were used to represent a condition of cancer associated host tissue wasting. Hearts from mice 11 days after tumor implantation showed atrophy and a significantly reduced amount of myofibrillar, soluble, and collagen proteins than hearts from control animals. The cross-sectional area of myocardial cells was 33% smaller in tumor-bearing mice (p less than 0.025), but the total number of capillaries and the residual interstitial volume were similar in the two groups. The total number of subcellular structures per cell, such as mitochondria, myofibrils, and myosin filaments per myofiber, were significantly lower in the tumor-bearing animals (p less than 0.025). Conversely, the proportion of myofibrils was higher (p less than 0.05) in tumor-bearing animals while the proportion of mitochondria was lower. Maximum activities (Vmax) of selected regulatory key enzymes for energy production (glycogenolytic, glycolytic, and mitochondrial) were not significantly altered in hearts from tumor-bearing mice. The results support the conclusion that myocardial functional capacity is better preserved than overall structural components would imply in tumor-host associated malnutrition, which is probably secondary to deprived food intake. Teleologically, this may be a means by which functional deterioration of the heart is minimized during the induction of malnutrition.

Distribution of fibre sizes in human skeletal muscle. An enzyme histochemical study in m tibialis anterior.

The aim of the study was to determine the fibre size distribution within the human m tibialis anterior. Ten-micron thick cross-sections of the whole muscle were enzyme histochemically stained for myofibrillar ATPase at pH 9.4. The cross-sectional area of 100 fibres with low (type 1) ATPase and high (type 2) ATPase activity was measured in three different regions (superficial, central and deep). Both the type 1 and type 2 fibres were found to be larger in the deep region than in the central or superficial regions. The variation in fibre size could not be explained by the cryofixation or cryo-embedding techniques used. The data suggest that muscle adaptation to physical demands may not only occur by means of variation in types and number of muscle fibres, but also by variation in fibre size over the muscle cross-section.