Anatomical principles of ankle denervation - An update

BACKGROUND

Denervation is a surgical option in ankle arthrosis when conservative therapy has failed. Sectioning all joint branches is essential for its success. The locations of the articular branches of the saphenous (Sa), tibial (Ti), sural (Su), superficial (Ps) and deep peroneal (Pp) nerves are specified.

METHODS

In 16 cryopreserved specimens, the courses of the nerves were prepared. Their articular branches were identified, and their respective locations documented by using a new reference system.

RESULTS

The articular branches to the ankle ranged from 5 to 30 cm measured from the foot sole. The Sa should be transected at 22.5 cm, the Su at 20 cm, and the Pp at 15 cm. The Ti should be skeletonized up to 25 cm. Epifascial dissection of the Ps is to be performed below 15 cm.

CONCLUSION

The study specifies the joint branches of the ankle in an intraoperatively reproducible reference system and thus minimizes the required skin incisions.

Proximity of percutaneous tibial nerve stimulation needle insertion to surrounding anatomic structures: a cadaveric study

BACKGROUND

Percutaneous tibial nerve stimulation is a third-line treatment for overactive bladder and urgency urinary incontinence. During the procedure, a needle is inserted cephalad to the medial malleolus and posterior to the tibia. In recent years, permanent implants and leads have been developed for insertion into the medial ankle via a small incision. There are many important structures present in the medial compartment of the ankle, including the great saphenous vein, saphenous nerve, tibial nerve, posterior tibial vessels, and tendons of the posterior compartment leg muscles.

OBJECTIVE

The primary objective of this study was to identify the proximity of the percutaneous tibial nerve stimulation needle placed per Food and Drug Administration-approved device instructions to nearby important anatomic structures. The secondary objectives were to identify the proximity of the tibial nerve to the needle site, identify clinically relevant ankle anatomic structures, and confirm the tibial nerve and posterior tibial vasculature by histologic analysis.

STUDY DESIGN

Detailed medial ankle dissections were performed bilaterally on 10 female lightly embalmed anatomic donors (cadavers) obtained from the Willed Body Program at the University of Louisville. A pin was inserted at the percutaneous tibial nerve stimulation needle site, and the medial ankle was minimally dissected so the surrounding anatomic structures were visible but not disrupted. The shortest distance from the pin to the selected structures of the medial ankle region was measured. On completion of each dissection and set of measurements, tissue was harvested for histologic examination. The distances between the pin and each structure were assessed using means and standard deviations. A paired t test was used to assess the difference in the locations between the left and right ankles. Statistical analysis was performed on left-sided, right-sided, and combined measurements. An 80% prediction interval was found to represent the expected range of values for the measurement of a new cadaver or patient, and the 95% confidence interval of the mean was computed to characterize the average distance across all cadavers or patients.

RESULTS

The medial ankle of 10 adult female lightly embalmed cadavers were examined bilaterally. Dissections were completed from October 2021 to July 2022. Of note, 80% prediction intervals for the tibial nerve, the posterior tibial artery or vein, and the flexor digitorum longus tendon had a lower range of 0.0 mm from the pin and extending to 12.1, 9.5, and 13.9 mm, respectively. Moreover, 2 of the structures were found to be asymmetrical between the right and left ankles. The great saphenous vein was further from the pin on the left (20.5 mm [standard deviation of 6.4 mm] on the left vs 18.1 mm [standard deviation of 5.3 mm] on the right; P=.04). The calcaneal (Achilles) tendon was further from the pin on the right side (13.2 mm [standard deviation of 6.8 mm] vs 7.9 mm [standard deviation of 6.7 mm]; P=.04). Tibial neurovascular structures were confirmed with microscopic analysis.

CONCLUSION

The anatomic structures within the medial ankle lie unexpectedly close to the percutaneous tibial nerve stimulation needle site as noted per Food and Drug Administration-approved device instructions. There is a possibility that some medial ankle structures are not symmetrical. It is crucial that practitioners understand medial ankle anatomy when performing percutaneous tibial nerve stimulation or permanent device insertion.

Sural nerve: imaging anatomy and pathology

High resolution ultrasound (US) and magnetic resonance (MR) neurography are both imaging modalities that are commonly used for assessing peripheral nerves including the sural nerve (SN). The SN is a cutaneous sensory nerve which innervates the lateral ankle and foot to the base of the fifth metatarsal. It is formed by contributing nerves from the tibial and common peroneal nerves with six patterns and multiple subtypes described in literature. In addition to the SN being a cutaneous sensory nerve, the superficial location enables the nerve to be easily biopsied and harvested for a nerve graft, as well as increasing the susceptibility to traumatic injury. As with any peripheral nerves, pathologies such as peripheral nerve sheath tumors and neuropathies can also affect the SN. By utilizing a high frequency probe in US and high-resolution MR neurography, the SN can be easily identified even with the multiple variations given the standard distal course. US and MRI are also useful in determining pathology of the SN given the specific image findings that are seen with peripheral nerves. In this review, we evaluate the normal imaging anatomy of the SN and discuss common pathologies identified on imaging.

Lateral popliteal block in foot and ankle surgery: Comparing ultrasound guidance to nerve stimulation. A prospective randomized trial

BACKGROUND

The popliteal block has several benefits in foot and ankle surgery. It reduces postoperative pain, limits the use of narcotics and facilitates early discharge. The aim of this prospective randomized trial was to evaluate whether ultrasound guidance improves block characteristics compared to the nerve stimulation technique in lateral popliteal blocks.

METHODS

Patients were randomized to receive either a lateral popliteal block using neurostimulation or ultrasound guidance. Block performance time, number of needle pricks, number of redirections were recorded. Pain upon admission to and discharge from post anesthesia care unit (PACU) was recorded. Block duration, patient satisfaction, pain at block site and amount of opioids used in PACU and between subsequent followup visits was recorded. Patients were followed for 12 weeks postoperatively.

RESULTS

There was no statistically significant difference between the two groups in terms of number of pricks, time for the block to wean, pain upon admission to PACU, amount of opioids received in PACU, pain upon discharge from PACU, pain at the operative site, pain at the block site, toe motor function and toe sensation. There was a statistically significant difference in the block procedure performance time between the two groups, with the control group being faster (P<0.0001). A significantly larger number of patients in the control group required more than three needle redirections (P=0.0060).

CONCLUSIONS

The lateral sciatic popliteal block using nerve stimulation had similar block characteristics and patient satisfaction with a significantly faster performance time compared to the ultrasound guided technique.

LEVEL OF EVIDENCE

Level I, prospective randomized study.

Ankle and Foot Spasticity Patterns in Chronic Stroke Survivors with Abnormal Gait

Chronic stroke survivors with spastic hemiplegia have various clinical presentations of ankle and foot muscle spasticity patterns. They are mechanical consequences of interactions between spasticity and weakness of surrounding muscles during walking. Four common ankle and foot spasticity patterns are described and discussed through sample cases. The patterns discussed are equinus, varus, equinovarus, and striatal toe deformities. Spasticity of the primary muscle(s) for each deformity is identified. However, it is emphasized that clinical presentation depends on the severity of spasticity and weakness of these muscles and their interactions. Careful and thorough clinical assessment of the ankle and foot deformities is needed to determine the primary cause of each deformity. An understanding of common ankle and foot spasticity patterns can help guide clinical assessment and selection of target spastic muscles for botulinum toxin injection or nerve block.

Musculoskeletal ultrasonography combined with electromyography in the diagnosis of massage-inducted lateral plantar nerve injury: A case report

INTRODUCTION

It is well known that foot massage is a very prevalent stress relief method in China. Literatures have reported various massage-inducted peripheral nerve injuries. However, massage-inducted lateral plantar nerve (LPN) injury is very rare. Here, we represent an unusual case of massage-inducted LPN damage, and we also report the diagnostic method of this patient using musculoskeletal ultrasonography combined with electromyography (EMG).

PATIENT CONCERNS

A 21-year-old woman presented symptoms of redness, swelling, pain and numbness in the medial right ankle joint for 2 days.

DIAGNOSIS

The results of musculoskeletal ultrasonography and EMG provide great help for doctors to make accurate diagnosis. The patient was eventually diagnosed with LPN injury.

INTERVENTIONS

No further foot massage was allowed. Vitamin B12 was taken orally for 2 months. Conservative therapy, including electrical stimulation therapy and infrared therapy, was conducted. Besides, active rehabilitation training was also performed.

OUTCOMES

The discomfort symptoms were relieved significantly after 2 months conservative treatment. Clinical symptoms and EMG examination illustrated satisfactory result during follow up time.

CONCLUSION

The report showed that the masseur should be very careful when doing foot massage to prevent nerve damage. Besides, musculoskeletal ultrasonography combined with EMG can provide important evidence for accurate and effective diagnosis of LPN injury.

Somatotopic Mapping of the Developing Sensorimotor Cortex in the Preterm Human Brain

In the mature mammalian brain, the primary somatosensory and motor cortices are known to be spatially organized such that neural activity relating to specific body parts can be somatopically mapped onto an anatomical "homunculus". This organization creates an internal body representation which is fundamental for precise motor control, spatial awareness and social interaction. Although it is unknown when this organization develops in humans, animal studies suggest that it may emerge even before the time of normal birth. We therefore characterized the somatotopic organization of the primary sensorimotor cortices using functional MRI and a set of custom-made robotic tools in 35 healthy preterm infants aged from 31 + 6 to 36 + 3 weeks postmenstrual age. Functional responses induced by somatosensory stimulation of the wrists, ankles, and mouth had a distinct spatial organization as seen in the characteristic mature homunculus map. In comparison to the ankle, activation related to wrist stimulation was significantly larger and more commonly involved additional areas including the supplementary motor area and ipsilateral sensorimotor cortex. These results are in keeping with early intrinsic determination of a somatotopic map within the primary sensorimotor cortices. This may explain why acquired brain injury in this region during the preterm period cannot be compensated for by cortical reorganization and therefore can lead to long-lasting motor and sensory impairment.

Effects of posture and coactivation on corticomotor excitability of ankle muscles

BACKGROUND

The use of transcranial magnetic stimulation (TMS) to evaluate corticomotor excitability of lower limb (LL) muscles can provide insights about neuroplasticity mechanisms underlying LL rehabilitation. However, to date, a majority of TMS studies have focused on upper limb muscles. Posture-related activation is an important under-investigated factor influencing corticomotor excitability of LL muscles.

OBJECTIVE

The purpose of this study was to evaluate effects of posture and background activation on corticomotor excitability of ankle muscles.

METHODS

Fourteen young neurologically-unimpaired participants (26.1±4.1 years) completed the study. TMS-evoked motor evoked potentials (MEPs) were recorded from the tibialis anterior (TA) and soleus during 4 conditions - standing, standing coactivation, sitting, and sitting coactivation. TA and soleus MEP amplitudes were compared during: (1) standing versus sitting;(2) standing coactivation (standing while activating both TA and soleus) versus sitting coactivation; and (3) standing coactivation versus standing. For each comparison, background EMG for TA and soleus were matched. Trial-to-trial coefficient of variation of MEP amplitude and coil-positioning errors were additional dependent variables.

RESULTS

No differences were observed in TA or soleus MEP amplitudes during standing versus sitting. Compared to sitting coactivation, larger MEPs were observed during standing coactivation for soleus but not TA. Compared to standing, the standing coactivation task demonstrated larger MEPs and reduced trial-to-trial MEP variability.

CONCLUSION

Our findings suggest that incorporation of measurements in standing in future TMS studies may provide novel insights into neural circuits controlling LL muscles. Standing and standing coactivation tasks may be beneficial for obtaining functionally-relevant neuroplasticity assessments of LL musculature.

Study protocol for a pilot, randomised, double-blinded, placebo controlled trial of perineural local anaesthetics and steroids for chronic post-traumatic neuropathic pain in the ankle and foot: the PREPLANS study

INTRODUCTION

Peripheral neuropathic pain (PNP) associated with trauma is often refractory to treatment. Administration of local anaesthetics (LA) and steroids around injured nerves has been proposed as an option for patients unresponsive to conventional treatments for refractory PNP following trauma. There is insufficient evidence to support a large, potentially expensive, full-scale randomised controlled trial (RCT) that involves comparison of effects of perineural steroids and LA against LA or saline injections on analgesia, physical and psychological functioning, and quality of life. There is also a lack of data that would allow estimation of analgesic efficacy or sample size for the full-scale RCT. The objective of this pilot RCT is to yield information to support planning of a full-scale RCT in this population.

METHODS AND ANALYSIS

30 participants with post-traumatic PNP in the ankle and foot of moderate-to-severe intensity and duration of more than 3 months will be enrolled in this pilot RCT. Participants will be randomised to receive three ultrasound-guided perineural injections of 0.9% saline, 0.25% bupivacaine (a long-acting LA) or a combination of 0.25% bupivacaine and a steroid (methylprednisolone 16 mg per nerve) at weekly intervals. The primary objectives are to determine the feasibility and sample size of a full-scale RCT in this population. The secondary objectives are to evaluate the effect of study interventions on analgesia, persistence of neuropathic pain, psychological and physical function, quality of life and participants' global impression of change at 1 and 3 months after the interventions. In addition, adverse effects associated with perineural injections and with systemic absorption of steroids will also be recorded.

ETHICS AND DISSEMINATION

The protocol was approved by the University Health Network Research Ethics Board (UHN REB number 15-9584-A). The results will be disseminated in peer-reviewed journals and at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT02680548; Pre-results.

Increased intensity and reduced frequency of EMG signals from feline self-reinnervated ankle extensors during walking do not normalize excessive lengthening

Kinematics of cat level walking recover after elimination of length-dependent sensory feedback from the major ankle extensor muscles induced by self-reinnervation. Little is known, however, about changes in locomotor myoelectric activity of self-reinnervated muscles. We examined the myoelectric activity of self-reinnervated muscles and intact synergists to determine the extent to which patterns of muscle activity change as almost normal walking is restored following muscle self-reinnervation. Nerves to soleus (SO) and lateral gastrocnemius (LG) of six adult cats were surgically transected and repaired. Intramuscular myoelectric signals of SO, LG, medial gastrocnemius (MG), and plantaris (PL), muscle fascicle length of SO and MG, and hindlimb mechanics were recorded during level and slope (±27°) walking before and after (10-12 wk postsurgery) self-reinnervation of LG and SO. Mean myoelectric signal intensity and frequency were determined using wavelet analysis. Following SO and LG self-reinnervation, mean myoelectric signal intensity increased and frequency decreased in most conditions for SO and LG as well as for intact synergist MG (P < 0.05). Greater elongation of SO muscle-tendon unit during downslope and unchanged magnitudes of ankle extensor moment during the stance phase in all walking conditions suggested a functional deficiency of ankle extensors after self-reinnervation. Possible effects of morphological reorganization of motor units of ankle extensors and altered sensory and central inputs on the changes in myoelectric activity of self-reinnervated SO and LG are discussed.

Ultrasound-Guided Ankle Blocks: A Review of Current Practices

Ankle blocks are routinely indicated for surgical anesthesia and postoperative analgesia of procedures involving the foot. Traditionally, ankle blocks have been performed by relying on landmark identification of nerves. The literature regarding the performance and efficacy of ankle blocks is inconsistent. This can be attributed to several variables, such as provider technique, differences in patient populations, and the type and volume of local anesthetics administered. As with other peripheral nerve blocks originally performed using landmark technique, ultrasound imaging is now being incorporated into these procedures. Ultrasound guidance provides the anesthetist with several advantages over landmark techniques. The ability to identify peripheral nerves, view needle movements in real-time, and observe the spread of local anesthetic has been shown to result in greater block efficacy, even with reduced volumes of local anesthetic. Additionally, ultrasound imaging gives the provider the option to perform regional anesthesia in specific patient populations not considered possible when using landmark technique. Despite the limited literature on ultrasound-guided ankle blocks, outcome metrics seem to be consistent with those of other peripheral nerve blocks performed using this technology.

Recruitment of muscle synergies is associated with endpoint force fluctuations during multi-directional isometric contractions

It has long been assumed that the human central nervous system uses flexible combinations of several muscle synergies to effortlessly and efficiently control redundant movements. However, whether muscle synergies exist in the neural circuit remains controversial, and it is critical to examine the association between the recruitment pattern of synergies and motor output. In this study, we examined the relationship between the activation of muscle synergies and endpoint force fluctuations in the presence of signal-dependent noise. Subjects performed multi-directional isometric force generations around the right ankle on the sagittal plane. We then extracted muscle synergies from measured electromyogram (EMG) data using nonnegative matrix factorization. As a result, the sum of the activation of muscle synergies was correlated with the endpoint force variability from the desired directions. Furthermore, we determined that the activation trace of each synergy reflected the endpoint force fluctuations using cross-correlation analysis. Therefore, these results suggest that muscle synergies statistically calculated from EMG data should be related to the motor output.

Noninvasive neurostimulation in chronic stroke: a double-blind randomized sham-controlled testing of clinical and corticomotor effects

BACKGROUND

Repetitive peripheral magnetic stimulation (RPMS) is a painless and noninvasive method to produce afferents via the depolarization of the peripheral nervous system. A few studies tested RPMS after-effects on cerebral plasticity and motor recovery in stroke individuals, but evidences remain limited.

OBJECTIVES

This study aimed to explore whether RPMS could mediate improvements in corticomotor and clinical outcomes associated with ankle impairments in chronic stroke.

METHODS

Eighteen subjects with chronic stroke were randomly allocated to RPMS or sham group and compared to 14 healthy subjects. Stimulation was applied over the paretic tibialis anterior (TA). Ankle impairments on the paretic side and ipsilesional TA cortical motor representation were tested clinically and by transcranial magnetic stimulation (TMS), respectively.

RESULTS

In the RPMS group, ankle dorsiflexion mobility and maximal isometric strength increased and resistance to plantar flexor stretch decreased. The magnitude of change seemed to be related to cortical and corticospinal integrity. Sham stimulation yielded no effect. Changes in TMS outcome and their relationships with clinical improvements were limited.

CONCLUSIONS

RPMS improved ankle impairments in chronic stroke likely by a dynamic influence of sensory inputs on synaptic plasticity. The neurophysiological mechanisms potentially underlying the clinical effects are unclear. More studies are warranted to test the spinal and hemispheric changes responsible for the clinical improvements with emphasis on circuits spared by the lesion.

Posterior ankle and hind foot arthroscopy - how do you responsibly learn this new technique?

Posterior ankle and hind foot arthroscopy has become an important diagnostic and therapeutic tool when dealing with ankle pathology. Although not yet widely adopted it is gaining popularity and there have been various descriptions of the technique [1] and its outcomes [2,3]. With posterior arthroscopy there are well-documented risks of injury to the sural nerve and medial neurovascular bundle in particular [7-9]. These risks need to be carefully considered, particularly by surgeons early in the learning curve of what is undoubtedly a challenging technique. In an ideal world there should be scope for regular simulation to be integrated into a consultant's working week and this would allow them to be prepared for untoward incidences and also learn new techniques such as hind-foot arthroscopy in a safe environment prior to introduction into clinical practice.

Diabetic foot and exercise therapy: step by step the role of rigid posture and biomechanics treatment

Lower extremity ulcers represent a serious and costly complication of diabetes mellitus. Many factors contribute to the development of diabetic foot. Peripheral neuropathy and peripheral vascular disease are the main causes of foot ulceration and contribute in turn to the growth of additional risk factors such as limited joint mobility, muscular alterations and foot deformities. Moreover, a deficit of balance, posture and biomechanics can be present, in particular in patients at high risk for ulceration. The result of this process may be the development of a vicious cycle which leads to abnormal distribution of the foot's plantar pressures in static and dynamic postural conditions. This review shows that some of these risk factors significantly improve after a few weeks of exercise therapy (ET) intervention. Accordingly it has been suggested that ET can be an important weapon in the prevention of foot ulcer. The aim of ET can relate to one or more alterations typically found in diabetic patients, although greater attention should be paid to the evaluation and possible correction of body balance, rigid posture and biomechanics. Some of the most important limitations of ET are difficult access to therapy, patient compliance and the transitoriness of the results if the training stops. Many proposals have been made to overcome such limitations. In particular, it is important that specialized centers offer the opportunity to participate in ET and during the treatment the team should work to change the patient's lifestyle by improving the execution of appropriate daily physical activity.

Neuroma of medial dorsal cutaneous nerve of superficial peroneal nerve after ankle arthroscopy

Superficial peroneal neuropathy is a known complication of foot and ankle arthroscopy. A 27-year-old man developed pain and paresthesia on the medial side of the dorsum of his left foot after ankle arthroscopy. An electrodiagnostic study revealed conduction abnormality in the medial branch of superficial peroneal nerve, in which neuroma-in-continuity was subsequently detected by ultrasonography. After neuroma excision and nerve graft, the subject's neuropathic pain was substantially improved.

Success of ultrasound guided popliteal sciatic nerve catheters is not influenced by nerve stimulation

BACKGROUND

There is debate as to whether nerve stimulation (NS) is required to place peripheral nerve catheters when using ultrasound (US) guidance. There is conflicting evidence for whether stimulating catheters improve postoperative analgesia compared to non-stimulating catheters. The use of US in combination with NS has been shown to be superior to NS alone in terms of popliteal nerve blockade. Given the previously published reports, we hypothesized that there is improvement in sensory and motor blockade for stimulating popliteal perineural catheters placed under US guidance when NS is used.

METHODS

Following IRB approval, 21 patients undergoing elective foot and ankle surgery were randomly assigned to either a US or US+NS-guided continuous popliteal sciatic nerve block using a lateral approach. The primary end-point of the study was successful nerve blockade at 20 minutes. Secondary end-points included: block performance time, minimum stimulating current, pain scores on postoperative day 1 and day 2, and patient satisfaction.

RESULTS

There was no significant difference in successful nerve blockade at 20 minutes in the US versus US+NS groups (73% vs. 80%, p = 1). Procedure time was significantly shorter in the US only group (median 62 seconds vs. 130.5 seconds, p < 0.01). Postoperative pain scores and overall patient satisfaction were not significantly different between the two groups.

CONCLUSION

We have found that the addition of NS provides no benefit over US alone. US alone was associated with a significantly shorter block performance time. US+NS showed no significant difference in pain control, patient satisfaction, or block success.

Polarity independent effects of cerebellar tDCS on short term ankle visuomotor learning

BACKGROUND

Transcranial direct current stimulation (tDCS), an emerging technique of noninvasive brain stimulation, has shown to produce beneficial neural effects in consequence with improvements in motor behavior. There are not many studies examining the use of tDCS for lower limb motor control and learning. Most studies using tDCS for facilitating lower limb motor coordination have applied tDCS to the lower limb motor cortex (M1). As the cerebellum is also critically involved in movement control, it is important to dissociate the effect of tDCS on the cerebellum and M1 with respect to lower limb motor control before we begin the application of tDCS as a neuromodulatory tool.

OBJECTIVE/HYPOTHESIS

The purpose of this study was to determine the effects of cerebellar vs. motor cortical tDCS on short term ankle visuomotor learning in healthy individuals.

METHODS

Eight healthy individuals practiced a skilled ankle motor tracking task while receiving either facilitatory anodal tDCS to cerebellum, inhibitory cathodal tDCS to cerebellum, facilitatory anodal tDCS to M1, inhibitory cathodal tDCS to M1 or sham stimulation. Pre- and post-measures of changes in cortical excitability of the tibialis anterior muscle and measures of tracking accuracy were assessed.

RESULTS

Anodal cerebellar, cathodal cerebellar, and anodal M1 stimulation improved target-tracking accuracy of the ankle. This was not dependent on the observed changes in motor cortical excitability of the tibialis anterior muscle.

CONCLUSION(S)

Polarity independent effects of tDCS on cerebellum were observed. The present study shows that modulation effects of tDCS can occur because of changes in the cerebellum, a structure implicated in several forms of motor learning, providing an additional way in which tDCS can be used to improve motor coordination.

Tibialis anterior architecture, strength, and gait in individuals with cerebral palsy

INTRODUCTION

The relationship of tibialis anterior (TA) muscle architecture, including muscle thickness (MT), cross-sectional area (CSA), pennation angle (PA), and fascicle length (FL), to strength and ankle function was examined in ambulatory individuals with CP and unilateral foot drop.

METHODS

Twenty individuals with CP participated in muscle ultrasound imaging, unilateral strength testing, and three-dimensional gait analysis.

RESULTS

Muscle size (MT and CSA) was positively related to strength, fast gait velocity, and ankle kinematics during walking. Higher PA was related to a more dorsiflexed ankle position at initial contact and inversely with fast gait velocity. FL was related to strength, fast velocity, and step length at a self-selected speed.

CONCLUSIONS

Muscle architecture partially explains the degree of impairment in strength and ankle function in CP. Treatments to increase TA size and strength may produce some gait improvement, but other factors that may contribute to ankle performance deficits must be considered.

Electrodiagnostic evaluation of lower extremity neurogenic problems

Electrodiagnosis is a powerful tool for evaluating lower extremity disorders that stem from the peripheral nervous system. Electrodiagnostic testing can help differentiate neurogenic versus non-neurogenic causes of complaints such as pain, weakness, and paresthesias. It can help practitioners pinpoint the anatomic location and reveal the underlying pathology in peripheral nerve lesions. This article focuses on the electrodiagnostic evaluation of neurogenic processes that present as foot and ankle symptoms.

Non-invasive brain stimulation enhances fine motor control of the hemiparetic ankle: implications for rehabilitation

We set out to answer two questions with this study: 1. Can stroke patients improve voluntary control of their paretic ankle by practising a visuo-motor ankle-tracking task? 2. Are practice effects enhanced with non-invasive brain stimulation? A carefully selected sample of chronic stroke patients able to perform the experimental task attended three data collection sessions. Facilitatory transcranial direct current stimulation (tDCS) was applied in a random order over the lower limb primary motor cortex of the lesioned hemisphere or the non-lesioned hemisphere or sham stimulation was delivered over the lesioned hemisphere. In each session, tDCS was applied as patients practiced tracking a sinusoidal waveform for 15 min using dorsiflexion-plantarflexion movements of their paretic ankle. The difference in tracking error prior to, and after, the 15 min of practice was calculated. A practice effect was revealed following sham stimulation, and this effect was enhanced with tDCS applied over the lesioned hemisphere. The practice effect observed following sham stimulation was eliminated by tDCS applied over the non-lesioned hemisphere. The study provides the first evidence that non-invasive brain stimulation applied to the lesioned motor cortex of moderate- to well-recovered stroke patients enhances voluntary control of the paretic ankle. The results provide a basis for examining whether this enhanced ankle control can be induced in patients with greater impairments and whether enhanced control of a single or multiple lower limb joints improves hemiparetic gait patterns.

Locomotor changes in length and EMG activity of feline medial gastrocnemius muscle following paralysis of two synergists

The mechanism of the compensatory increase in electromyographic activity (EMG) of a cat ankle extensor during walking shortly after paralysis of its synergists is not fully understood. It is possible that due to greater ankle flexion in stance in this situation, muscle spindles are stretched to a greater extent and, thus, contribute to the EMG enhancement. However, also changes in force feedback and central drive may play a role. The aim of the present study was to investigate the short-term (1- to 2-week post-op) effects of lateral gastrocnemius (LG) and soleus (SO) denervation on muscle fascicle and muscle–tendon unit (MTU) length changes, as well as EMG activity of the intact medial gastrocnemius (MG) muscle in stance during overground walking on level (0%), downslope (−50%, presumably enhancing stretch of ankle extensors in stance) and upslope (+50%, enhancing load on ankle extensors) surfaces. Fascicle length was measured directly using sonomicrometry, and MTU length was calculated from joint kinematics. For each slope condition, LG-SO denervation resulted in an increase in MTU stretch and peak stretch velocity of the intact MG in early stance. MG muscle fascicle stretch and peak stretch velocity were also higher than before denervation in downslope walking. Denervation significantly decreased the magnitude of MG fascicle shortening and peak shortening velocity during early stance in level and upslope walking. MG EMG magnitude in the swing and stance phases was substantially greater after denervation, with a relatively greater increase during stance of level and upslope walking. These results suggest that the fascicle length patterns of MG muscle are significantly altered when two of its synergists are in a state of paralysis. Further, the compensatory increase in MG EMG is likely mediated by enhanced MG length feedback during downslope walking, enhanced feedback from load-sensitive receptors during upslope walking and enhanced central drive in all walking conditions.

[Regional anaesthesia of the foot achieved from two cutaneous points of injection: an anatomical study]

PURPOSE OF THE STUDY Regional anaesthesia for the lower extremity distal to the ankle joint, knows as anaesthetic ankle block or foot block, involves a series of injections of local anaesthetic to block the peripheral nerves that supply innervation to the foot. Since the tibial nerve block is not always effective, the aim of this study was to design a modified technique of anaesthetic application. MATERIAL The study was carried out on 30 human cadavers provided by the Institute of Anatomy, 1st Faculty of Medicine, Charles University in Prague, and included data on a total of 60 lower extremities. METHODS Information about position of the tibial nerve (or its branches, i.e., the medial plantar and lateral plantar nerves) and the sural nerve was obtained using a set of special measurement devices designed for this purpose. The following distances were measured; the length of a basic line, i.e., distance between the posterior margin of the medial maleollus and the medial edge of the Achilles tendon (at the level of the upper part of the heel bone); the distance between the medial edge of the Achilles tendon and the tibial nerve; and the distance between the tibial nerve (its deep location) in the neurovascular plexus and the basic line. The location of the sural nerve behind the lateral maleollus was found by measuring the nerve distance from the posterior margin of the lateral maleollus and measuring the distance between this margin and the lateral edge of th Achilles tendon. RESULTS The distance between the posterior margin of the medial maleollus (medial edge of the sulcus for the posterior tibial muscle tenton) and the medial edge of the Achilles tendon (at the level of the upper part of the heel bone) was 46.3 mm +/- 5.2 mm. The depth of tibial nerve location, i.e. distance from the basic line to the neurovascular plexus, was 11.6 mm +/- 1.3 mm. The distance between the posterior margin of the lateral maleollus and the lateral edge of the Achilles tendon (at the level of the upper part of the heel bone) was 37.1 mm +/- 4.3 mm. The sural nerve was located at a distance of approximately 18.3 mm +/- 1.9 mm from the posterior edge of the lateral maleollus. DISCUSSION The study was concluded by proposing a modified technique of local anaesthetic ankle block using two points of anaesthetic injection. The first point is located immediately in front of the medial edge of the Achilles tendon and above the upper edge of the calcaneus. The anaesthetic applied will block the tibial and sural nerves, with the sural nerve being blocked by the anaesthetic delivered with a needle advanced through the soft tissues ventral to the Achilles tendon. The second area of application is located at 2 cm above the ventral fold of the ankle joint on the lateral edge of the anterior tibial muscle tendon and provides subcutaneous infiltration anaesthesia for the superficial and deep peroneal nerves and the saphenous nerve. CONCLUSIONS The results of this anatomical study provided a basis for a modified technique of regional anaesthesia of the foot. Its major clinical attributes involve reduced necessity to manipulate with the patient, and sensory and motor blockage of all nerves supplying innervation to the foot from only two points of injection. Key words: ankle block, foot block, regional anaesthesia.