Opposite Limb Research Articles

Bone Stiffness in Children

The decision when to remove the frame after limb lengthening through standard distraction osteogenesis remains a challenge. Multiple studies have attempted to find objective criteria to assess bone healing after fracture or bone lengthening. However, there is a paucity of such data for the pediatric population. The purpose of this study was to correlate data obtained after dual-energy x-ray absorptiometry (DXA) measurement and bending stiffness in children to find an end-point value for the safe removal of an external fixation device. We investigated 16 consecutive children aged between 5.5 and 16.7 years who had 22 lengthenings by callotasis. Twelve femurs and 10 tibiae were lengthened with a monoplane Orthofix external fixator. Fifty simultaneous measurements of bending bone stiffness measured with an Orthometer and DXA scans (bone mineral content [BMC], bone mineral density, volumetric bone mineral density, BMC/1 cm, Area/1 cm, BMC/1 cm, Area) were obtained during healing process. Four femoral fractures were reported after the removal of the external fixation device. Linear regression analysis was used to calculate the squared correlation coefficients for the relation between the DXA scans and the mechanical tests measuring bone stiffness. The bone stiffness measurement of the intact bone was compared with consecutive measurements of the bone stiffness of the regenerate, and it was expressed as a percentage (coefficient). We compared the BMC of the regenerate with the same bone area of the opposite limb. The best correlation was observed for anteroposterior (AP) bone stiffness coefficient and BMC coefficient (R = 0.82). The linear equation was BMC coefficient = 0.5 x AP stiffness coefficient + 30. The end point of 75% of BMC of the regenerate corresponds to 75% of the AP stiffness on DXA scanning; this is the time when we should consider safe removal of the fixator. Our method of comparing bone stiffness and DXA measurements gives an objective healing end point for every patient irrespective of his or her size. This method could allow noninvasive measurement of the end point and identified at-risk population of children, reducing regenerate fracture after bone lengthening.

Muscle-specific variations in use-dependent crossed-facilitation of corticospinal pathways mediated by transcranial direct current (DC) stimulation

The tendency for contractions of muscles in the upper limb to give rise to increases in the excitability of corticospinal projections to the homologous muscles of the opposite limb is well known. Although the suppression of this tendency is integral to tasks of daily living, its exploitation may prove to be critical in the rehabilitation of acquired hemiplegias. Transcranial direct current (DC) stimulation induces changes in cortical excitability that outlast the period of application. We present evidence that changes in the reactivity of the corticospinal pathway induced by DC stimulation of the motor cortex interact systematically with those brought about by contraction of the muscles of the ipsilateral limb. During the application of flexion torques (up to 50% of maximum) applied at the left wrist, motor evoked potentials (MEPs) were evoked in the quiescent muscles of the right arm by magnetic stimulation of the left motor cortex (M1). The MEPs were obtained prior to and following 10 min of anodal, cathodal or sham DC stimulation of left M1. Cathodal stimulation counteracted increases in the crossed-facilitation of projections to the (right) wrist flexors that otherwise occurred as a result of repeated flexion contractions at the left wrist. In addition, cathodal stimulation markedly decreased the excitability of corticospinal projections to the wrist extensors of the right limb. Thus changes in corticospinal excitability induced by DC stimulation can be shaped (i.e. differentiated by muscle group) by focal contractions of muscles in the limb ipsilateral to the site of stimulation.

NTX, highly purified botulinum neurotoxin product, is less likely to spread

Background: Researchers at the consumer group Public Citizen said that Botox(BTX) should carry a black box warning. They reviewed adverse event reports submitted to the FDA and found 16 deaths have been reported. Researchers at the consumer group Public Citizen said the botulinum toxin spreads inside the body causing serious problems. Object: To examine the spreads of botulinum toxins from the injected muscle, comparing the newly developed low molecular weight product NTX with BTX. Method: Either of NTX or BTX is injected into the left anterior limb muscle of ICR mouse, at a dose of 0.5–50 U/kg. In order to assess the effect of botulinum toxin, we measure the ‘traction power’ pursuing after injection. All the procedure is based on the approval of the Ethical Review Board for animal experiment. Results: The ‘traction power’ of the injected limbs shows decrement, dependent both on time course and on injected volume of toxins. The ‘traction power’ of the opposite limb decreased 2 days after injection of NTX 5 U/kg and BTX 2.5 U/kg. By the dosage of 50 U/kg, one death in BTX on the second day, the function of both anterior limbs became extinct. On the third day one mouse was dead by the NTX, but the right anterior limb was going to move in traction measurement. Discussion: Our data show that NTX is less likely to spread inside the body. Although the exact mechanism still remains unclear, this feature is a considerable advantage for the botulinum toxin therapy.

The Effect of Circular External Fixation on Limb Alignment

A full-length standing radiograph of the entire lower extremity is the standard imaging modality for assessing lower limb alignment. However, the effect of an overlying circular external fixator on the radiographic alignment of the lower extremity is not well documented. After correction of angular deformity using a circular external fixator, 29 patients (31 limbs) underwent 2 sets of full-length standing radiographs, one done before, and the other, after removal of the fixator. The difference in the measurement of frontal plane alignment, limb lengths, and rotation between the 2 radiographs was analyzed. The mean absolute difference in the measurement of mechanical axis deviation (MAD) between the 2 radiographs was 11.5 mm (P < 0.0001) for the ipsilateral limb (with the external fixator) and 8.9 mm (P < 0.0001) for the contralateral limb. The mean difference in the radiographic measurement of limb lengths was 20 mm (P < 0.0001) for the ipsilateral and 20.2 mm (P < 0.0001) for the contralateral limb. As the magnitude of MAD and external rotation of the ipsilateral limb increased, a progressive increase in the magnitude of discrepancy in the measurement of MAD between the 2 sets of radiographs was noted. There was no significant effect (P > 0.05) of the patient's age, sex, body mass index, primary diagnosis, duration between the 2 radiographs, and the direction of malalignment found on the discrepancy in the measurement of MAD for both limbs. The standing full-length radiograph with an overlying circular external fixator may not be a reliable indicator of limb alignment and length of the operated extremity. Moreover, the presence of the circular external fixator on the lower extremity can affect the alignment and length of the opposite limb. Clinicians using circular external fixators for lower extremity trauma and reconstruction should be aware of the pitfalls of using a full-length standing radiograph for assessing limb alignment and length during osseous healing. Diagnostic level II.

Design and characterization of a novel permanent magnet synchronous motor used in a growing prosthesis for young patients with bone cancer

Approximately 50 child sarcomas are treated with limb salvage surgery each year in the United Kingdom. These children need an extendable implant that can be lengthened periodically to keep pace with the growth in the opposite limb. Surgically, invasive devices have been used for the past 30 years with intrinsic problems of infection and long-term recurrent trauma to the patient. To eliminate problems associated with the invasive device, a noninvasive extendable prosthesis was developed. The magnetically coupled drive technology used for this prosthesis was a synchronous motor with a gear-driven telescoping shaft. In this design the motor configuration was in two parts: a rotating magnet (rotor) that fitted inside the prosthesis where space was limited and the stator, which was an external device used to extend the prosthesis remotely as the patient grew. This compact external drive produced a focused magnetic flux that required no cooling and operated on a single-phase power supply. The extending mechanism in the implant was able to overcome up to 1300 N force, which is the tension force exerted by the soft tissues during the lengthening procedure. The device has been successfully implanted in 50 patients.

Nerve repair by denatured muscle autografts promotes sustained sensory recovery in leprosy

A total of 38 patients with leprosy and localised nerve damage (11 median at the wrist and 37 posterior tibial at the ankle) were treated by 48 freeze-thawed skeletal muscle autografts ranging between 2.5 cm and 14 cm in length. Sensory recovery was noted in 34 patients (89%) and was maintained during a mean period of follow-up of 12.6 years (4 to 14). After grafting the median nerve all patients remained free of ulcers and blisters, ten demonstrated perception of texture and eight recognised weighted pins. In the posterior tibial nerve group, 24 of 30 repairs (80%) resulted in improved healing of the ulcers and 26 (87%) demonstrated discrimination of texture. Quality of life and hand and foot questionnaires showed improvement; the activities of daily living scores improved in six of seven after operations on the hand, and in 14 of 22 after procedures on the foot. Another benefit was subjective improvement in the opposite limb, probably because of the protective effect of better function in the operated side. This study demonstrates that nerve/muscle interposition grafting in leprosy results in consistent sensory recovery and high levels of patient satisfaction. Ten of 11 patients with hand operations and 22 of 25 with procedures to the foot showed sensory recovery in at least one modality.

Improved long‐term recording of nerve signal by modified intrafascicular electrodes in rabbits

Methods for long-term recording of peripheral nerve activity via intrafascicular electrodes have not been optimized. We compared the long-term functionality of custom-made 95%Pt/5%Ir intrafascicular electrodes containing a proximal spring-like structure to that of conventional straight electrodes. The modified electrode was implanted into the sciatic nerve fascicle of a random hind limb in 14 rabbits for 9 months. A conventional electrode was implanted in the opposite hind limb as a control. Orthodromic and antidromic nerve potentials were sampled and analyzed monthly. Latency, amplitude, and nerve conduction velocity of electrical signals were generally similar within the modified group and straight control group at different time intervals (P > 0.05). However, at the conclusion of the study period, the modified electrode group had a greater number of functioning electrodes (P < 0.05) and a greater total functioning electrode time (P = 0.006). Intrafascicular electrodes with a spring-like structure demonstrated superior potential for long-term electrophysiological monitoring over straight electrodes.

Determination and use of mechanical nociceptive thresholds of the thoracic limb to assess pain associated with induced osteoarthritis of the middle carpal joint in horses

To establish reference mechanical nociceptive threshold (MNT) values of the equine thoracic limb and to assess the use of MNT values to detect pain associated with induced osteoarthritis in the middle carpal joint. 24 adult horses. MNT values were evoked by a pressure algometer at 17 sites within each thoracic limb during 2 baseline sessions conducted an average of 5 days apart. Effects of age, sex, weight, and wither height on MNT values were assessed separately for each site. Tolerance of horses to the procedure was graded subjectively and correlated with MNT values. Synovitis and osteoarthritis were induced arthroscopically in the middle carpal joint of 1 randomly selected thoracic limb. The opposite limb served as a sham-operated control limb. Mechanical nociceptive threshold values were recorded weekly and correlated with clinical, radiographic, and necropsy scores measured over 10 weeks. Lower MNT values corresponded with increased pain, whereas higher MNT values indicated reduced pain. A gradual increase in MNT values was detected from proximal-to-distal sites of the thoracic limbs. High MNT values were recorded for geldings and tall horses. In general, tolerance to procedure scores was positively correlated with overall pooled MNT values within each thoracic limb. From 2 to 6 weeks after surgery, the osteoarthritic limb had significantly reduced MNT values within the carpal region. The osteoarthritic limb also had significant changes in clinical examination, radiographic, and necropsy scores, which were poorly correlated with MNT values. Pressure algometry provided objective assessment of nociception of the thoracic limb; however, MNT values were poorly correlated with clinical variables used to assess osteoarthritis.

Neuro-Physiological Adaptations Associated with Cross-Education of Strength

Cross-education of strength is the increase in strength of the untrained contralateral limb after unilateral training of the opposite homologous limb. We investigated central and peripheral neural adaptations associated with cross-education of strength. Twenty-three right-handed females were randomized into a unilateral training group or an imagery group. A sub-sample of eight subjects (four training, four imagery) was assessed with functional magnetic resonance imaging (fMRI) for patterns of cortical activation during exercise. Strength training was 6 weeks of maximal isometric ulnar deviation of the right arm, four times per week. Peak torque, muscle thickness (ultrasound), agonist-antagonist electromyography (EMG), and fMRI were assessed before and after training. Strength training was highly effective for increasing strength in trained (45.3%; P < 0.01) and untrained (47.1%; P < 0.01) limbs. The imagery group showed no increase in strength for either arm. Muscle thickness increased only in the trained arm of the training group (8.4%; P < 0.001). After training, there was an enlarged region of activation in contralateral sensorimotor cortex and left temporal lobe during muscle contractions with the untrained left arm (P < 0.001). Training was associated with a significantly greater change in agonist muscle EMG pooled over both limbs, compared to the imagery group (P < 0.05). These results suggest that cross-education of strength may be partly controlled by adaptations within sensorimotor cortex, consistent with previous studies of motor learning. However, this research demonstrates the involvement of temporal lobe regions that subserve semantic memory for movement, which has not been previously studied in this context. We argue that temporal lobe regions might play a significant role in the cross-education of strength.

Nitrite Infusion in Humans and Nonhuman Primates

The recent discovery that nitrite is an intrinsic vasodilator and signaling molecule at near-physiological concentrations has raised the possibility that nitrite contributes to hypoxic vasodilation and to the bioactivity of nitroglycerin and mediates the cardiovascular protective effects of nitrate in the Mediterranean diet. However, important questions of potency, kinetics, mechanism of action, and possible induction of tolerance remain unanswered. In the present study, we performed biochemical, physiological, and pharmacological studies using nitrite infusion protocols in 20 normal human volunteers and in nonhuman primates to answer these questions, and we specifically tested 3 proposed mechanisms of bioactivation: reduction to nitric oxide by xanthine oxidoreductase, nonenzymatic disproportionation, and reduction by deoxyhemoglobin. We found that (1) nitrite is a relatively potent and fast vasodilator at near-physiological concentrations; (2) nitrite functions as an endocrine reservoir of nitric oxide, producing remote vasodilation during first-pass perfusion of the opposite limb; (3) nitrite is reduced to nitric oxide by intravascular reactions with hemoglobin and with intravascular reductants (ie, ascorbate); (4) inhibition of xanthine oxidoreductase with oxypurinol does not inhibit nitrite-dependent vasodilation but potentiates it; and (5) nitrite does not induce tolerance as observed with the organic nitrates. We propose that nitrite functions as a physiological regulator of vascular function and endocrine nitric oxide homeostasis and suggest that it is an active metabolite of the organic nitrates that can be used therapeutically to bypass enzymatic tolerance.

EFFECTS OF A PROTEASE SUPPLEMENT ON ECCENTRIC EXERCISE-INDUCED MARKERS OF DELAYED-ONSET MUSCLE SORENESS AND MUSCLE DAMAGE

This investigation examined the effects of a protease supplement on selected markers of muscle damage and delayed-onset muscle soreness (DOMS). The study used a double-blinded, placebo-controlled, crossover design. Twenty men (mean ± SD age = 21.0 ± 3.1 years) were randomly assigned to either a supplement group (SUPP) or a placebo group (PLAC). All subjects were tested for unilateral isometric forearm flexion strength, hanging joint angle, relaxed arm circumference, subjective pain rating, and plasma creatine kinase activity and myoglobin concentration. The testing occurred before (TIME1), immediately after (TIME2), and 24 (TIME3), 48 (TIME4), and 72 (TIME5) hours after a bout of eccentric exercise. During these tests, the subjects in the SUPP group ingested a protease supplement. The subjects in the PLAC group took microcrystalline cellulose. After testing at TIME5 and 2 weeks of rest, the subjects were crossed over into the opposite group and performed the same tests as during visits 1–5, but with the opposite limb. Overall, isometric forearm flexion strength was greater (7.6%) for the SUPP group than for the PLAC group, despite nearly identical (difference = 0.14 N·m, p = 0.940) mean strength values before (TIME1) the eccentric exercise protocol. There were no between-group differences for hanging joint angle, relaxed arm circumference, subjective pain ratings, and plasma creatine kinase activity and myoglobin concentration from TIME1 to TIME5. These findings provided initial evidence that the protease supplement may be useful for reducing strength loss immediately after eccentric exercise and for aiding in short-term strength recovery. The protease supplement had no effect, however, on the perception of pain associated with DOMS or the blood markers of muscle damage.

Monomelic neurogenic syndromes: A prospective study

Monomelic neurogenic syndromes are rare. Their classification and prognostic features have not been addressed in the European population. A prospective study of 17 patients with monomelic neurogenic amyotrophy, of upper or lower limb onset, with progression limited to one limb for three or more years. Clinical and neurophysiological studies were performed in the subsequent 3 or more years. Fifteen patients were of European origin and two were Asian. Those presenting with proximal monomelic weakness or with involvement of the posterior compartment of the lower leg showed no further progression after the initial period of development of the syndrome. Brisk reflexes in wasted muscles did not predict progression. Electromyographic signs of denervation in the opposite limb at presentation did not predict later progression. Transcranial magnetic stimulation (TMS) features of corticospinal dysfunction were a useful predictor of subsequent progression (p=0.01). One patient with lower limb onset developed conduction block with weakness in an upper limb nine years after presentation, and this upper limb weakness responded to IVIg therapy. This adult-onset European group of patients is different as compared with juvenile-onset Asian cases. The clinical syndromes appear heterogeneous, but neurophysiological investigations, in particular TMS, can be helpful in determining prognosis. Multifocal motor neuropathy should be considered when there is progression, even years after onset.

Deep brain stimulation and medication for parkinsonian tremor during secondary tasks

This study examined the efficacy of subthalamic nucleus (STN), deep brain stimulation (DBS), and medication for resting tremor during performance of secondary tasks. Hand tremor was recorded using accelerometry and electromyography (EMG) from 10 patients with Parkinson's disease (PD) and ten matched control subjects. The PD subjects were examined off treatment, on STN DBS, on medication, and on STN DBS plus medication. In the first experiment, tremor was recorded in a quiet condition and during a cognitive task designed to enhance tremor. In the second experiment, tremor was recorded in a quiet condition and during isometric finger flexion (motor task) with the contralateral limb at 5% of the maximal voluntary contraction (MVC) that was designed to suppress tremor. Results showed that: (1) STN DBS and medication reduced tremor during a cognitive task that exacerbated tremor, (2) STN DBS normalized tremor frequency in both the quiet and cognitive task conditions, whereas tremor amplitude was only normalized in the quiet condition, (3) a secondary motor task reduced tremor in a similar manner to STN DBS. These findings demonstrate that STN DBS still suppresses tremor in the presence of a cognitive task. Furthermore, a secondary motor task of the opposite limb suppresses tremor to levels comparable to STN DBS.

Septic Arthritis of the Distal Interphalangeal Joint in Cattle: Comparison of Digital Amputation and Joint Resection by Solar Approach

To determine in cattle with septic arthritis of the distal interphalangeal joint (SADIJ) the efficacy of resection of the distal interphalangeal joint (JRES) as a digit salvage technique compared with digital amputation (DAMP). Prospective, randomized clinical study. German Holstein-Friesian dairy cattle with SADIJ of 1 hind limb (n=52). SADIJ diagnosis was based on clinical examination and radiography. Cows were randomly assigned with owner consent to DAMP (n=26) or JRES (n=26). After JRES, a wooden block was fixed to the partner claw in combination with a tipping claw prophylaxis. After surgery, degree of lameness improved significantly faster after DAMP than after JRES. New claw diseases in the opposite limb occurred more frequently after JRES (n=6) than after DAMP (n=1). New claw defects developed in the partner claw on the operated limb in 6 cows after DAMP compared with 1 after JRES. Tipping claw was observed in 50% of JRES cows at day 180. Mean life span between groups was not significantly different (DAMP=13.5 months, JRES=10.9 months). Higher surgical and postsurgical expenditures for JRES were not counterbalanced by a longer productive life; however, frequent disease of the partner claw of cows after DAMP should be considered a critical point, as this generally leads to culling. The higher expenditure for JRES can be justified only for young, valuable cattle.

Diabetic muscle infarction: a rare complication of advanced diabetes mellitus

Diabetic muscle infarction is a rare complication of diabetes mellitus first described in 1965. It typically arises in patients with long-standing diabetes mellitus who have complications of the disease, including nephropathy, retinopathy, and neuropathy. It typically presents with acute onset of thigh pain with an associated palpable tender mass. Recurrent episodes in the same or opposite limb are common. Laboratory evaluation does not generally show any consistent abnormality except for poor glucose control. Histologic features of diabetic muscle infarction consist of large areas of muscle necrosis and edema. Magnetic resonance imaging (MRI) findings in patients without clinical evidence of infection may be typical enough to make tissue biopsy unnecessary. In the appropriate clinical setting, MRI may obviate invasive testing and is the preferred imaging modality. Treatment is supportive with analgesics, rest, and immobilization.

Primary varicose vein of upper limb: A rare entity

Received 04/10/06; Review Completed 29/10/06; Accepted 08/11/06. A healthy 6-years-old male child reported to us with complaint of soft compressible swellings (four years duration) of right forearm and arm, which were progressively increasing in size. This was not associated with pain and discomfort. Patient did not give history of antecedent trauma or weight lifting. On examination, there were multiple soft, cystic, compressible swellings of approximately 2 x 2 cms. on the medial aspect of right forearm and arm along basilic vein distribution. These swellings disappeared on raising the arm above the head and reappeared on applying the pressure. These varicosities were starting form little finger base and extending upto right axilla (Fig. 1). Surrounding skin was normal. No bruit was audible and both arms were of equal size. Bilateral pulses were normal. Opposite upper limb and bilateral lower limbs were normal. There was no family history of lower limb varicosities. On Duplex examination, there was no evidence of venous reflux or proximal dilation. Ascending phlebography (Varicography) also documented basilic vein varicosities with saccular enlargements. There were no signs suggestive of arterioverious fistula and haemangimatous malformations on both the studies. The patient underwent successful treatment of these varicose veins by sclerotherapy. A varicose vein may be defined as a vein that becomes elongated, dilated, tortuous and thickened due to continuous dilatation under pressure. Primary varicose veins are a common affliction of the lower extremities whereas the upper extremities are rarely affected. The literature has little reference as regards the number of cases, causes and management of upper limb varicose veins1,2. Congenital arteriovenous fistulae or iatrogenic arterioverious fistulae for haemodilaysis causes upper extremity varicose veins. Congenital vascular anomalies, the Klippel Trenaunay Syndrome and the Parkes Weber syndrome are other rare causes of arm varicose veins. Venous outflow obstruction caused by subclavian vein thrombosis can be another uncommon cause2,3. The diagnosis of upper extremity varicose veins can be made by means of a good history and physical examination, besides these, non invasive Doppler Ultrasound or duplex allows visualization and quantification of incompetence or obstruction. Invasive investigations are generally unnecessary but may be required in unusual situations like congenital and anatomical variants, to further define the pathology. Arteriovenous fistulae and congenital vascular anomalies are recognized by these investigations1,2,3. Treatment of upper limb varicosities is similar to that of varicose veins in the legs. The treatment of varicosities due to upper limb arterioverious fistulae is usually surgical and entails either ligation of distal venous limb of a side to side fistula or division of the fistula itself and provides excellent cosmetic and functional outcomes2,3. Sclerotherapy with agents like Sodium tetradecyl sulphate and Polidocanal are useful alternatives to surgery4.

Differential after-effects of bimanual activity on mirror movements

Using a rhythmic isometric force production paradigm, we investigated the after-effects of in-phase and antiphase bimanual performance on the unintended recruitment of the homologous muscles of the opposite limb during subsequent performance of tasks that were unimanual by design. Electromyograms obtained from the muscles of the opposite limb were analyzed in terms of their amplitude and the distribution of their phase relative to that of the intended movements. Preceding bimanual activity had distinct effects on the relative phase (mean and uniformity) of the structured electromyograms. These were particularly pronounced following performance of the in-phase pattern. These findings are discussed in terms of interhemispheric excitation and inhibition.

Arthroplasty of the Distal Radioulnar Joint Using a New Ulnar Head Endoprosthesis: Preliminary Report

To report our experience using a distal ulnar head endoprosthesis to treat painful disorders of the distal radioulnar joint (DRUJ) secondary to (1) instability and (2) arthrosis. Our experience with over 2 years of follow-up study consists of 19 wrists (17 patients). All patients presented complaining of pain and functional disability of the upper limb due to convergence instability or arthrosis of the DRUJ. The patients were studied prospectively. Thirteen patients had a total of 37 previous wrist or DRUJ surgical procedures. Standardized preoperative and postoperative assessments included a patient-reported pain score, a functional satisfaction score, forearm range of motion, grip strength as a percentage of that of the opposite limb, and clinical and radiographic examinations. The Mayo Wrist Score was calculated before surgery and at the last follow-up period. Overall, pain scores decreased 50%, and functional satisfaction scores improved 3-fold. Average grip strength improved by 4 kg, or 16% from preoperative measurements. Forearm rotation was unchanged. All wrists were clinically stable on the latest follow-up examination. Two failures occurred early, at 7 and 14 months. Currently, all prostheses remain clinically and radiographically stable. Implant arthroplasty of the distal ulna combined with an adequate soft-tissue repair is recommended to improve pain, function, and strength of the wrist and forearm. Prosthetic replacement of the distal ulna restored stability to the DRUJ in patients with partial or complete excision of the ulnar head or DRUJ arthrosis and corrected radioulnar impingement. Incidences of complications or revision surgery to date have been low. Larger clinical and radiographic assessments will be needed to determine the long-term success of distal ulna prosthetic replacement. Therapeutic IV.

Lateral bias to the leading limb in an olfactory social signal by male ring‐tailed lemurs

Because ring-tailed lemurs (Lemur catta) show handedness during feeding, I investigated whether they also show lateral preference in the limbs used by males during scent marking. During a bout of marking, a male alternates a variable number of shoulder rubs and arm marks. It is a complex social signal that has both olfactory and visual components and is frequently part of intrasexual agonistic interactions. I used all-occurrences behavior sampling, manually recorded all totally visible bouts, and required a minimum of 50 bouts per animal. The subjects included six wild and four group-living captive male lemurs. I considered limb usage to be lateralized for each individual lemur if the frequency of use of one side was significantly above chance as determined by binomial z-scores at P<.05. I measured consistency of lateral preference by calculating handedness index (HI) scores for each individual. Overall, I recorded 1,583 bouts of scent marking, and 66% of the bouts began with shoulder rubbing. Eight of the 10 males showed a significant, moderately strong lateral preference for the lead limb in the first shoulder rub performed in a bout, and for six of these eight the preferred lead limb for shoulder rubbing was the left one. Six of the 10 males showed a significant but weak lateral preference in the first arm mark, and five of these preferred the opposite limb to that used for the first shoulder rub. Although the preferences were not at the population level, eight of the 10 lemurs showed a lateral bias in the lead limb used for a component of this complex social signal.

Postural Context Alters the Stability of Bimanual Coordination by Modulating the Crossed Excitability of Corticospinal Pathways

The tendency for movements of the upper limbs to be drawn systematically toward one another and to follow similar spatiotemporal trajectories is well known. Although suppression of this tendency is integral to tasks of daily living, its exploitation may prove to be critical in the rehabilitation of acquired hemiplegias. In general, however, the task-related factors that determine the degree of coupling between the upper limbs and the mechanisms that mediate bilateral interactions between neural pathways projecting to the muscles of the arm and hand are not yet well understood. We present evidence that the postural context in which human participants perform upper limb movements determines the relative stability of patterns of bimanual coordination. Manipulation of the axes of rotation of forearm movements reversed the relative stability of simultaneous and alternating patterns of bimanual coordination. Transcranial magnetic stimulation of motor cortex revealed that these manipulations of postural context altered the crossed modulation of excitability in corticospinal pathways that arises from movement of the opposite limb. Furthermore, modulation of responses to electrical stimulation of the cervicomedullary junction indicated that crossed modulation was also expressed at the level of the spinal motoneurons. Our data support the view that crossed modulation of excitability in corticospinal pathways mediates the stability of bimanual coordination. Furthermore, task-related factors that are sufficient to give rise to changes in the stability of bimanual coordination are accompanied by crossed modulation of excitability at multiple levels of the neuraxis, indicative of a failure of inhibitory control.