Structural characteristics of the subscapularis muscle in children with medial rotation contracture of the shoulder after obstetric brachial plexus injury.

The aim of this study was to obtain a better understanding of the cause of the medial rotation contracture of the shoulder after obstetric brachial plexus lesions by studying the morphology of the shortened subscapularis muscle. Muscle biopsy specimens were harvested from 13 children with obstetric brachial plexus palsy who underwent corrective surgery for the rotation contracture. The majority of the subscapularis muscle biopsy samples had an essentially normal morphology and showed a predominance of type I myosin heavy chain isoform, while one biopsy showed signs of marked fibrosis and a predominance of type II myosin heavy chain isoform. The findings support the assumption that shortening of the subscapularis is caused primarily by the nerve injury, which weakens the antagonistic lateral rotators, but that direct injury to the muscle might be a contributory factor.

Immunohistochemical evidence of local production of catecholamines in cells of the muscle origins at the lateral and medial humeral epicondyles: of importance for the development of tennis and golfer's elbow?

BACKGROUND: Tennis elbow (TE) is a painful condition affecting the common extensor origin at the lateral humeral epicondyle. Colour Doppler examination has shown increased blood flow at this site and the sensory, and sympathetic innervation patterns have been delineated. However, it is not known whether there is local production of catecholamines and/or acetylcholine in this tissue, which is the case in patellar and Achilles tendinopathies. OBJECTIVE: To investigate the possible presence of local production of catecholamines and acetylcholine in non-neuronal cells (fibroblasts) in connective tissue at the muscle origin at the lateral humeral epicondyle in patients with TE. DESIGN: Immunohistochemical studies were performed on biopsies taken from the extensor origin in patients with TE and in pain-free controls. For reference purpose, biopsies from the flexor origin in patients with golfer's elbow (GE) were also studied. PATIENTS: Seven patients with TE and four patients with GE. Six healthy asymptomatic individuals served as controls. METHOD: Immunohistochemistry, using antibodies detecting synthesising enzymes for catecholamines (tyrosine hydroxylase; TH) and acetylcholine (choline acetyltransferase; ChAT). RESULTS: TH-like immunohistochemical reactions were seen in fibroblasts in four of the seven patients with TE and two of the four patients with GE. No such reactions were detected in controls (0/6). No ChAT reactions were seen in any of the investigated specimens. CONCLUSIONS: There is evidence of local, non-neuronal production of catecholamines, but not acetylcholine, in fibroblasts in the tissue at the muscle origin at the lateral and medial epicondyles in patients with TE and GE, respectively, which might have an influence on blood vessel regulation and pain mechanisms in these conditions.

Subscapularis muscle mechanics in children with obstetric brachial plexus palsy.

This study investigates the passive mechanical properties of the subscapularis muscle in children with a contracture as a result of obstetrical brachial plexus palsy. Muscle biopsies were harvested from nine children undergoing open surgery for shoulder contracture. Passive mechanical testing of single cells and muscle bundles was performed. Corresponding comparisons were made using muscle biopsies from seven healthy controls. Single muscle fibres from patients with obstetric brachial plexus palsy displayed a shorter slack sarcomere length, linear deformation of the fibre within a wider zone of sarcomere length and a greater relative increase in stiffness compared with muscle bundles. We conclude that secondary changes in muscle fibre properties will occur as a result of a longstanding lack of sufficient passive stretch, leading to compensatory changes in the extracellular matrix. These results suggest the presence of a dynamic feedback system constituting a muscle-to-extracellular matrix communication interface.

In vivo investigation of ECRB tendons with microdialysis technique--no signs of inflammation but high amounts of glutamate in tennis elbow.

We used the microdialysis technique to study concentrations of substances in the extensor carpi radialis brevis (ECRB) tendon in patients with tennis elbow. In 4 patients (mean age 41 years, 3 men) with a long duration of localized pain at the ECRB muscle origin, and in 4 controls (mean age 36 years, 2 men) with no history of elbow pain, a standard microdialysis catheter was inserted into the ECRB tendon under local anesthesia. The local concentrations of the neurotransmitter glutamate and prostaglandin E2 (PGE2) were recorded under resting conditions. Samplings were done every 15 minutes during a 2-hour period. We found higher mean concentrations of glutamate in ECRB tendons from patients with tennis elbow than in tendons from controls (215 vs. 69 micromoL/L, p < 0.001). There were no significant differences in the mean concentrations of PGE2 (74 vs. 86 pg/mL). In conclusion, in situ microdialysis can be used to study certain metabolic events in the ECRB tendon of the elbow. Our findings indicate involvement of the excitatory neurotransmitter glutamate, but no biochemical signs of inflammation (normal PGE2 levels) in ECRB tendons from patients with tennis elbow.

Sympathetic and sensory innervations are heterogeneously distributed in relation to the blood vessels at the extensor carpi radialis brevis muscle origin of man.

By using immunohistochemistry and antibodies to a general nerve marker, protein gene product (PGP) 9.5, the overall innervation at the extensor carpi radialis brevis (ECRB) muscle origin was investigated in patients with tennis elbow and in healthy controls. The autonomic innervation was studied by using antibodies to neuropeptide Y (NPY), tyrosine hydroxylase (TH), and vasoactive intestinal peptide (VIP). The sensory innervation was visualized by using antibodies to substance P and calcitonin gene-related peptide. PGP 9.5 immunoreactions were detected in association with small blood vessels and arteries and within nerve bundles. There was, however, heterogeneity in the perivascular nerve fiber distribution since some blood vessels exhibited a high degree of PGP 9.5 innervation and some negligible or no such innervation at all. There was marked TH/NPY innervation in the walls of a subpopulation of the arteries, basically no VIP-containing nerves, and sensory innervation restricted to the small blood vessels. These observations show that the ECRB muscle origin is supplied with heterogeneously distributed sympathetic and sensory innervations and, furthermore, that there appears to be an imbalance between the vasoconstrictor and vasodilator innervations along the vascular tree in this region.

Substance P and calcitonin gene-related peptide expression at the extensor carpi radialis brevis muscle origin: implications for the etiology of tennis elbow.

With use of immunohistochemistry and antibodies to substance P and calcitonin gene-related peptide, nerve fibers showing substance P-like and calcitonin gene-related peptide-like immunoreactivity were demonstrated at the origin of the extensor carpi radialis brevis muscle in patients with tennis elbow (n = 6) and in healthy controls (n = 6). The nerve fibers were distributed in association with a subpopulation of small blood vessels and in nerve bundles but were not distributed in the tunica media-adventitia junction of the arterioles. There were no inflammatory-cell infiltrates and few solitary mast cells. The present study gives further evidence to previous suggestions that tennis elbow is not an inflammatory process in the sense of involving inflammatory cells. Frequent mechanical involvement affects sensory innervation, and substance P and calcitonin gene-related peptide may have various important efferent effects, including microvascular leakage and local edema formation; therefore, the observations from this study constitute a morphological substrate for possible effects of substance P and calcitonin gene-related peptide at the origin of the extensor carpi radialis brevis muscle.

Wrist extensor muscle pathology in lateral epicondylitis.

The morphology of the extensor carpi radialis brevis (ECRB) muscle was investigated in 20 patients with longstanding lateral epicondylitis. Muscle biopsies were obtained from the proximal or distal portion of the ECRB and analysed by enzyme- and immunohistochemical methods. Morphological abnormalities were significantly more frequent in patients than controls and included moth-eaten fibres, fibre necrosis and signs of muscle fibre regeneration as well as higher percentages of the fast-twitch oxidative (type 2A) fibre type. Changes were equally distributed proximally and distally. It is concluded that these changes, directly or indirectly, may reflect the cumulative effect of mechanical and/or metabolic overload and that decreased muscular performance in patients with lateral epicondylitis may be due to both elbow pain and physical damage to the ECRB muscle.

Sarcomere length varies with wrist ulnar deviation but not forearm pronation in the extensor carpi radialis brevis muscle.

Extensor carpi radialis brevis (ECRB) sarcomere length was measured in seven patients using intraoperative laser diffraction. Sarcomere length was measured with the forearm in one of four positions: wrist in neutral with regard to radial-ulnar deviation and forearm in neutral rotation, wrist in ulnar deviation and forearm in neutral rotation, wrist in neutral and forearm in pronation, and wrist in ulnar deviation and forearm in pronation. Two-way ANOVA comparing sarcomere length between the four positions revealed a significant effect of ulnar deviation (p < 0.05), no significant effect of pronation (p > 0.7) and no significant interaction (p > 0.9). These results demonstrate that the axes of forearm rotation and wrist radial-ulnar deviation act independently, at least with regard to the ECRB and have implications regarding the etiology of tennis elbow.

Sarcomere length in wrist extensor muscles. Changes may provide insights into the etiology of chronic lateral epicondylitis.

Since the etiology of tennis elbow (lateral epicondylitis) is poorly understood, we studied the anatomical changes in the extensor carpl radialis brevis (ECRB) muscle during elbow joint rotation. Specifically, we measured ECRB sarcomere length, using an intraoperative laser diffraction procedure that measures muscle sarcomere length with an accuracy of +/- 0.05 micron. We found an unexpected biphasic response in ECRB sarcomere length as the elbow was rotated from full extension to full flexion. The initial sarcomere length of 3.49 microns, with the elbow extended, was gradually changed to 3.68 microns, 3.34 microns, 3.81 microns, and 3.45 microns with progressive elbow flexion. Based on the very nonlinear mechanical properties of skeletal muscle, this "double lengthening" of the ECRB during progressive flexion would impose intense eccentric contractions on the muscle itself. Given that eccentric contractions cause muscle injury and subsequent inflammation, these findings may provide insights into the etiology of lateral epicondylitis.

Intraoperative sarcomere length measurements reveal differential design of human wrist extensor muscles.

The design of the wrist extensor muscles was studied using a combination of intraoperative laser diffraction and biomechanical modelling of data obtained from human patients and previously published data. Intraoperatively, the change in sarcomere length per degree joint angle rotation (i.e. dSL/d omega) was measured as the wrist was moved from neutral to full flexion in both the extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) muscles. Sarcomere length change per degree rotation was approximately twice as great for the ECRB compared with the ECRL muscle (9.06 +/- 1.06 versus 4.69 +/- 1.20 nm degree-1, mean +/- S.E.M., N = 7). Muscle fibre length and wrist extensor moment arms were obtained from published data and dSL/d omega calculated. The experimental values for dSL/d omega were extremely close to the calculated values. These data demonstrate that architectural differences between the ECRB and ECRL are accentuated by differences between their wrist extensor moment arms. This differential design may permit the extensor muscles, as a group, to generate high force over a wider range of velocities than would be possible with a single muscle or it may permit conservation of mass such that the two muscles together can generate approximately the same force and excursion as a single muscle but with approximately 30% less mass.

A longitudinal study on the significance of environmental and individual factors associated with the development of essential hypertension.

Altogether 379 men of the same age have been followed for more than 40 years, mainly as regards socioeconomic conditions during the first 10 years as well as cognitive ability measured at the ages of 10 and 20, education, income development, and psychosocial conditions in adulthood. At the age of 48 a health investigation was performed. In order to identify possible risk factors associated with the development of raised blood pressure 38 subjects with essential hypertension were compared with 155 men without any obvious mental or somatic diseases. No differences regarding socioeconomic conditions during childhood could be observed between the two groups. However, there was a very strong difference between father's education and the son's cognitive ability in the group with hypertension. The low income development for the group with hypertension can probably be explained partly by the lower cognitive ability. In the total group there was a positive correlation between IQ at the age of 10 and income at the age of 43 (r = 0.42; p less than 0.001). The hypertensive men were psychosocially disadvantaged with respect to divorce rate and job dissatisfaction, and furthermore they reported low physical activity during leisure time. Hypertensive men were more obese and had inferior respiratory function. The observation that a lower cognitive ability seems to be related to the development of hypertension is compatible with the observation that early mortality in this investigated group has a correlation of a low IQ with poor socioeconomic conditions in childhood.

A comparison of growth in twins and singleton controls of matched age followed longitudinally from 10 to 18 years.

A sample of 323 pairs of twins (94 MZ pairs, 133 DZ like-sexed pairs and 97 DZ unlike-sexed pairs born in 1954/55) were studied longitudinally from 10 to 18 years for boys and 10 to 16 years for girls. Height, weight, age at menarche and peak height and weight velocities (PHV and PWV) were studied. No significant differences occurred between twin categories in any two of these varieties, so in each sex the total twin group was compared with a group of matched singleton controls (380 boys and 360 girls). There were very small differences between the twin boys and their controls in height, weight and PWV-age. PHV occurred somewhat earlier in twin boys than in the controls. The height and weight peaks were significantly lower for the twin boys. For twin girls, however, a height and weight deficit was found during puberty and they also matured a little later than their controls according to both PHV, PWV and menarche. The height and weight peaks were also somewhat lower for the twin girls. One reason for the observed sex differences could be a proportionally higher mortality for twin boys, thus an effect of selective survival.