Bilateral congenital absence of the long head of the biceps tendon

Absence of the long head of the biceps tendon is a rare anomaly particularly when it occurs bilaterally. We present the magnetic resonance and arthroscopy findings in a patient with bilateral congenital absence of the long head of the biceps who presented with bilateral shoulder pain. Identification of a shallow or absent intertubercular groove may aid in differentiating congenital absence of the long head of the biceps from a traumatic tendon rupture.     

Rupture of the proximal or distal tendon of the biceps humeri – surgical treatment?

Summary We reviewed 77 conservatively and 164 operatively treated cases of rupture of the long head of the biceps documented in the literature. Refixation offers a small but relatively constant improvement of flexion and supination power and thus reduces the number of cases with remaining light or marked weakness by one third. Deformity by the slipped muscle can be corrected effectively. As complications are uncommon surgery should be recommended to young and active patients and should at least be offered to less active patients. Thirteen patients were re-examined after operative repair for distal biceps tendon avulsion and 277 reported cases were reviewed. After conservative management (n = 20) the power of flexion remains reduced by 30 %–40 %, that of supination by more than 50 %. The loss of flexion power, as well as the deformity can be nicely diminished by attachment of the distal biceps to the brachialis muscle (n = 22). There are no complications documented regarding this procedure. The anatomic reinsertion (n = 248) additionally reduces the loss of supination power to 0 %–25 %, but bears a higher risk of complications. The double-incision technique (n = 105 of 248) does not necessarily decrease this risk. There are as many nerve injuries reported as with the single-anterior approach. Additionally we are faced with the problem of radioulnar synostosis. The use of suture anchors provides a nice way of fixation of the tendon but does not facilitate the approach to the tuberosity. The distal biceps tendon rupture should be treated operatively. The adequate method of repair is to be determined individually.      

Cortical facilitation of cutaneous reflexes in leg muscles during human gait

During human gait, cortical convergence on sural nerve reflex pathways was investigated by means of transcranial magnetic stimulation (TMS) of the cortex in five phases of the step cycle during human walking on a treadmill. Muscular responses to paired electrical and magnetic stimulation were compared with the linear summation of the individual stimuli. For both the tibialis anterior (TA) and biceps femoris (BF) muscles, the averaged data of four subjects showed a significant facilitation mainly in the swing phase of the step cycle. It is suggested that facilitation of corticospinal input onto cutaneous reflex pathways is enhanced specifically in these periods of the step cycle.     

Interaction between the long-latency stretch reflex and voluntary electromyographic activity prior to a rapid voluntary motor reaction

In vivo electrochemical detection of endogenous neurotransmitters was done in the dorsal raphe nucleus of urethane-anesthetized male Sprague-Dawley rats. Stereotaxically implanted carbon paste electrodes were scanned using a cyclic voltammetry amplifier with semiderivative signal processing over the potential range--0.2 to +0.5 V at the rate of 10 mV/s. Two distinct peaks were observed at +0.15 V (peak 1) and +0.25 V (peak 2), respectively. Peak identification was assessed by comparing the oxidation potential observed in vivo with those observed in in vitro experiments using pure catecholamines, indoleamines and their metabolites as well as ascorbic acid. Further characterization of in vivo peaks was done by observing changes in electrochemical peaks as well as tissue neurotransmitter concentrations after pharmacological manipulations. p-Chlorophenylalanine, m-hydroxybenzylhydrazine (NSD-1015), pargyline, alpha-methyl-p-tyrosine and fusaric acid were administered in an effort to block catecholamine or serotonin synthesis or degradation. Results of these experiments revealed that peak 1 primarily represents extracellular norepinephrine, while peak 2 is primarily produced by extracellular 5-hydroxyindoleacetic acid (5-HIAA).     

Human servo responses to load disturbances in fatigued muscle

Short and long latency EMG responses to muscle stretch and shortening were investigated in the triceps brachii muscle of 16 human subjects during a fatiguing isometric contraction. Increased amplitude reflex responses to stretch, and accentuated reductions in EMG in response to shortening, were evident as fatigue progressed in the majority of subjects. These changes indicate internal compensatory adjustments in the nervous system offsetting the deleterious mechanical effects of muscular fatigue.