Proximal Foot Research Articles

Associations of Region-Specific Foot Pain and Foot Biomechanics: The Framingham Foot Study.

Specific regions of the foot are responsible for the gait tasks of weight acceptance, single-limb support, and forward propulsion. With region foot pain, gait abnormalities may arise and affect the plantar pressure and force pattern utilized. Therefore, this study's purpose was to evaluate plantar pressure and force pattern differences between adults with and without region-specific foot pain. Plantar pressure and force data were collected on Framingham Foot Study members while walking barefoot at a self-selected pace. Foot pain was evaluated by self-report and grouped by foot region (toe, forefoot, midfoot, or rearfoot) or regions (two or three or more regions) of pain. Unadjusted and adjusted linear regression with generalized estimating equations was used to determine associations between feet with and without foot pain. Individuals with distal foot (forefoot or toes) pain had similar maximum vertical forces under the pain region, while those with proximal foot (rearfoot or midfoot) pain had different maximum vertical forces compared to those without regional foot pain (referent). During walking, there were significant differences in plantar loading and propulsion ranging from 2% to 4% between those with and without regional foot pain. Significant differences in normalized maximum vertical force and plantar pressure ranged from 5.3% to 12.4% and 3.4% to 24.1%, respectively, between those with and without regional foot pain. Associations of regional foot pain with plantar pressure and force were different by regions of pain. Region-specific foot pain was not uniformly associated with an increase or decrease in loading and pressure patterns regions of pain.

An Unusual Source of Systemic Thromboembolism

Pulmonary vein thrombosis (PVT) is a rare but potentially life threatening condition. This is a case of pulmonary vein thrombosis presenting with systemic thromboembolism despite treatment with anticoagulation. A 73-year-old woman, with past medical history of hypertension, peripheral arterial disease (PAD), and treated endometrial and breast cancer, presented with complaint of pain in her right foot of one-day-duration. She had a history of PVT diagnosed on chest CT angiogram one month prior to presentation, which was done to exclude pulmonary embolism when she presented with progressively worsening dyspnea. Physical examination was notable for an elderly woman in painful distress, with a cold, pulseless right foot with bluish discoloration of the skin of the forefoot and a clear line of demarcation from the proximal foot. The angiogram revealed occlusion of the right popliteal artery just above the knee with no appreciable blood flow within the distal vessels. Contrast CT of the abdomen and pelvis revealed multiple hypo-enhancing ill-defined hepatic masses, bilateral adrenal masses and mediastinal adenopathy. Echocardiogram revealed a large left ventricular thrombus and hyper-dynamic left ventricular systolic function. She was admitted for acute right foot ischemia and underwent popliteal exploration, open thrombectomy and embolectomy with restoration of pedal flow. However, she had repeat right popliteal exploration two days later due to further ischemic changes in the foot. Post-operatively, she developed multi-organ dysfunction including respiratory failure requiring endotracheal intubation and mechanical ventilation. She was terminally weaned from mechanical ventilation on request by her family and she died on the sixth day of admission. This case describes the occurrence of systemic embolization despite anticoagulation for pulmonary vein thrombosis. The large thrombus found in the left ventricle most likely represents a thrombus in transit from the superior left pulmonary vein en-route systemic embolization with consequent multi-organ dysfunction.

Juxtra Articular Compound Fractures of the Tibia Managed by Percutaneous Anatomical Locked Plating-Feasibility in Indian Rural Population

Introduction: Compound fracture of the tibia is the one of the most common injury encountered by orthopaedic surgeon these days. Diaphyseal compound fractures are well managed by primary interlocking nails with good to excellent results. Metaphyseal juxtraarticular and intraarticular compound fractures of upper and lower end of tibia are not good indication for intramedullary nails due to limitation of short proximal and distal fragment and marked communition at these areas, also mostly intra articular extensions. Till now these fractures were mostly managed by External fixators or rind fixators. Primary conventional open plating in compound fracture is not a preferred method of management till now due to fear of infection and soft tissue complications and risk of plate exposure. We managed these fractures by minimally invasive plating using locked plate and result evaluated. Material and Method: In this study we have taken compound metaphyseal fractures of the tibia for primary plating using locked anatomical plate using minimally invasive technique. Ninety four (94) cases of tibia out of which 50 cases of proximal tibia and 44 cases of distal tibia compound fracture up to grade IIIA were taken for study. In all cases primary skeleton traction were applied followed by wound management using through irrigation using low pressure pulse levage and debridement. Plating was done using MIPPO method within 7 days of injury. Cases were followed up at regular interval and functional outcome assessed by using knee society score for proximal fractures and foot and ankle score for distal tibia fractures. Results: Primary bone was achieved in 88 of 94 cases within usual duration. Low grade infection at fracture site seen in 8 cases and out of these 8 cases union achieved in 5 cases by continuation of same primary fixation. 3 cases required revision surgery with removal of implant and antibiotics cement beads followed by other method of fixation to achieve union. Good to excel

Osteometric sex determination using proximal foot phalanges from a documented human skeletal collection.

Diagnosing sex is vital for developing biological profiles from human skeletal remains. For that purpose, osteometric evaluation of bone size has proven to be usually effective. The present study investigates the degree of sexual dimorphism in proximal foot phalanges from a documented human skeletal collection, known as the Athens collection. Furthermore, it utilizes the data for the development of sex-discriminant formulas in Greek population. The material used consists of 749 proximal foot phalanges (left and right), which belong to 174 adult individuals (91 males and 83 females) that lived during the 20(th) century. The degree of sexual dimorphism reached as high as 16.76 %, with the left side demonstrating higher sexual dimorphism. The 1(st) proximal foot phalanges are proven to be the most sexually dimorphic among the bones of the sample. The minimum sexual dimorphism observed was in the maximum lengths of phalanges, whereas the most sexually dimorphic measurement was the medio-lateral width at midshaft. The discriminant functions developed provide classification accuracies that ranged between 77.1 % and 90.9 % for left and between 72.2 % and 86.6 % for right proximal foot phalanges. The results of this study suggest that proximal foot phalanges are useful for sex determination in Greek population.

Male reproductive system of the red brocade hermit crab Dardanus insignis (Diogenidae) and its relationship to other family members

The reproductive system of hermit crabs shows species-specific morphology, which can be used in phylogenetic analysis. Here, we describe the male reproductive system of the hermit crab Dardanus insignis, including morphological and biometric analyses of the spermatophore, the gonopore, and sperm ultrastructure. The morphological analyses were based on 15 selected specimens and carried out by means of light and electron microscopy. Our results indicate a reproductive system composed of lobular testes attached to a simple straight vas deferens connected to the exterior via ventral gonopores. The gonopores are ovoid, surrounded by dense serrulate setae, and covered by a membranous operculum. The spermatophores exhibit a tripartite structure, with an elongate ovoid ampulla, a long narrow stalk, and a proximal foot. The spermatozoal ultrastructure shows three main regions: an ovoid-oblong acrosomal vesicle, a nucleus, and cytoplasm with three armlike extensions. Some of these characteristics can also be found in other species of Diogenidae within the genus Dardanus and in members of Coenobitidae, a closely related family. The available information on spermatophore and spermatozoal structure may indicate a closer similarity between the genus Dardanus and the Coenobitidae, compared with other members of Diogenidae.

Neanderthal hand and foot remains from Moula‐Guercy, Ardèche, France

The hand and foot remains from Moula-Guercy cave (Ardèche, France) comprise 24 specimens of Eemian age (ca. 120 ka). The specimens include primarily complete elements, which are rare among the Moula-Guercy postcrania. The hand remains have several characteristic Neanderthal traits including a laterally facing (parasagittally oriented) second metacarpal-capitate articulation, a short styloid process, a wide proximal articular surface on the third metacarpal, and absolutely expanded apical tuberosities on the distal hand phalanges relative to modern humans. The foot remains include several incomplete elements along with an antimeric pair of naviculars, a medial cuneiform and cuboid, and a single complete element from each of the distal segments (one each: metatarsal, proximal foot phalanx, intermediate foot phalanx, distal foot phalanx). Consistent among the specimens are relatively wide diaphyses for length in the metatarsals and phalanges and large and prominent muscle attachments, both consistent with previously published Neanderthal morphology. The hand and foot collection from Moula-Guercy is an important dataset for future studies of Neanderthal functional morphology, dexterity, and behavior as it represents a previously undersampled time period for European Neanderthals.

Difference between the effects of one-site and three-site abdominal hot-stone stimulation on the skin-temperature changes of the lower limbs

To determine whether any difference exists in the skin-temperature responses of the lower limbs to hot-stone application relative to one-site and three-site abdominal application. Twenty-five female students participated in experimental sessions after a random allocation: 14 participants received a hot-stone application on the umbilicus, superior-umbilicus, and inferior-umbilicus regions (hereafter referred to as the three-site stimulation group); and 11 participants received the hot-stone application on the umbilicus region only (hereafter referred to as the one-site stimulation group). Heated stones were applied for 9 min to participants in both groups. Four arbitrary frames (the lower leg, ankle, proximal foot, and distal foot regions) were created in order to observe and analyze the skin temperature of a lower limb using a thermograph. Observation periods were as follows: before hot-stone stimulation, immediately after stimulation, and 5, 10, 15, and 20 min after stimulation. There was a significant offset interaction of distal foot skin temperature between the groups. The left-side distal foot skin temperature increased at 15 and 20 min following the three-site abdominal hot-stone stimulation. The right-side distal foot skin temperature increased immediately and at 5, 10, 15, and 20 min following the three-site abdominal hot-stone stimulation. No significant change in distal foot skin temperature was observed following the one-site stimulation. Lower-limb skin temperature was altered following hot-stone stimulation applied to the abdomen, and the one-site stimulation and three-site stimulation yielded different distal foot skin-temperature reactions.

Evaluation of Distally Based Fasciocutaneous Sural Flap for Reconstruction of the Distal Leg, Ankle and Proximal Foot

Objective: The objective of the study is to evaluate the efficacy of reverse sural artery fasciocutaneous flap for coverage of lower third leg, posterior heel, malleoli and hind foot. Patients and methods: Over a period of 4 years, a total of 31 patients with Soft tissue defect of lower third leg, heel, malleoli and hind foot were included. Preoperative data, the age and sex of each patient, cause and site of defect, dimension of flap, transposition of pedicle (through a tunnel or laid open and covered with a skin graft), postoperative results and complications were recorded. All patients were followed up in outpatient department for 12 months. Results: Over a period of 4 years during February 2008 to February 2012, a total of 31 flaps were performed in 31 patients. Sixteenth patients were males and 15 were females. Their ages ranged from 8 to 55 years with a mean age of 31 years. There were three children. Road traffic accidents was the cause of the defects in 19 (61.2%) patients, DM in 5 (15.5%) patients, bullet injuries in three (9.6%) patients, Achilles tendon injuries in two patients (6.4%) patients, Malignant melanoma in one (3.2%) patient and foot amputation stumps in one (3.2%) patient. Postoperatively 24 flaps survived completely while marginal necrosis was seen in 5patients and infection complete flap necrosis occurred in 2 patients. There was no considerable morbidity at donor site and all patients had satisfactory functional outcome. Conclusions: The distally based superficial sural artery flap is a versatile, reliable procedure, useful in reconstruction of lower third leg, heel, and malleoli and hind foot defects. The surgical technique is safe, of short duration and provides alternative to micro surgical reconstruction. Some patients were not completely satisfied with their results mainly due to bulky flap that needed revision or due to parasthesia.

Fossil species of Mallomonas from an Eocene Maar Lake with recessed dome structures: Early attempts at securing bristles to the cell covering?

The genus Mallomonas, the largest within the Class Synurophyceae, consists of motile, unicellular, freshwater heterokonts that are covered with an outer layer of overlapping siliceous scales. The scales are flat, circular to oval structures with taxonomically distinct designs. In addition to scales, the cell coverings of most Mallomonas species contain a second siliceous component known as a bristle. Bristles are composed of a long thin shaft and a flattened proximal foot. The foot of the bristle is fastened under the distal end of a scale in such a way as to allow the shaft to radiate out from the cell and rotate on its axis. For many species, the distal scale margin is distinctly raised, forming a hollow space that secures the bristle foot, and an inverted U-shaped opening from which the shaft emerges. This structure is called the dome. We describe three fossil species of Mallomonas from an Arctic Eocene maar lake that contain domes that are recessed to varying degrees back from the distal scale margin. This design is not known in the modern flora and we hypothesize that it represents an early attempt at securing bristles to the scale coat.

Reproductive apparatus of the male giant hermit crab Petrochirus diogenes (Anomura, Diogenidae): morphology and phylogenetic implications

We describe the male reproductive apparatus of the giant hermit crab Petrochirus diogenes, with morphological and biometric analyses of the spermatophore, the gonopore and the ultrastructure of the spermatozoa. Specimens were collected from the southern coast of Sao Paulo, Brazil. Morphological analyses were done using stereoscopic, light, transmission and scanning electron microscopy. The reproductive system of this hermit crab is composed of elon- gate and lobular testes followed by vasa deferentia that connect to the exterior via gonopores. The gonopores are ovoid and surrounded by setae, and each gonopore is composed of a mem- branous operculum that forms a depression constituting the gonopore opening. The gonopore constitutes a unique structure among the Diogenidae due to its number of setae. The spermato- phores are tripartite, composed of a sperm-containing ampulla, a peduncle and a proximal foot. The spermatozoon has 3 main regions (acrosomal vesicle, nucleus and cytoplasm). The structure of the spermatophore indicates that this species can be considered an exception within Dio- genidae with regard to spermatophore morphology and can therefore be used for phylogenetic inferences.

Shoes that restrict metatarsophalangeal dorsiflexion cause proximal joint compensations

To describe barefoot, shod and in-shoe kinematics during stance phase of walking gait in a normal arched adult population. An equal sample of males and females (n = 24) was recruited. In order to quantify the effect of footwear independent of technical design features, an ASICS shoe (Onitsuka Tiger-Mexico 66, Japan) was used in this study. Markers were applied to three conditions; barefoot, shod, and in-shoe. The calibration markers were used to define static pose. The order of testing was randomised. Participants completed five trials in each condition. Kinematic data were captured using a 12 camera VICON MX40 motion capture system at 100 Hz and processed in Visual3D. A previously developed model was used to describe joint angles 1. A univariate two-way ANOVA was used to identify any differences between the pairs of conditions. Post-hoc Sheff{\'e} tests were used to further interrogate the data for differences. At peak hallux dorsiflexion (Figure 1), during propulsion, the metatarsophalangeal joint (MPTJ) was significantly more dorsiflexed in the barefoot condition compared to the shod condition (p = 0.004). At the same gait event, the tibiocalcaneal joint (TCJ) was significantly more plantarflexed than both the shod and in-shoe conditions (p {\ensuremath{<}} 0.001), and the tarsometatarsal joint (TMTJ) was significantly less dorsiflexed in the barefoot condition compared to the shod and in-shoe conditions (p {\ensuremath{<}} 0.001). The findings of the current study demonstrate that footwear has significant effects on sagittal plane MPTJ joint dorsiflexion at peak hallux dorsiflexion, which results in compensations at proximal foot joints.

The distally based sural flap: A useful tool in the coverage of complex wounds of the distal third of shin and proximal foot

Aim-Background The aim of this paper is to prove that the sural flap in the coverage of complex wounds of the distal third of shin and proximal foot is a safe and effective technique. Coverage of lower extremity defects can be troublesome to the Plastic Surgeon. Usually, these defects are treated with free flaps. However, microvascular reconstruction of leg wounds requires microsurgical expertise and increases operative time. The distally based sural flap offers an appealing alternative to microvascular reconstruction as it can be harvested in a short time without sacrificing a major vessel of the leg, and donor site morbidity is minimal.

Proximal tubules and podocytes are toxicity targets of bucillamine in a mouse model of drug-induced kidney injury

Effective detection of potential nephrotoxicity is crucial for pre-clinical drug development. We evaluated a sensitive animal model for drug-induced kidney injury, which includes hemi-nephrectomy of mice. Although bucillamine and d-penicillamine are used for the treatment of rheumatoid arthritis in Japan, drug-related adverse effects on the kidney can limit their therapeutic utilities. When bucillamine (1000 or 2000 mg/kg/day) or d-penicillamine (2000 mg/kg/day) were orally administered to hemi-nephrectomised BALB/c mice, the urinary protein levels of bucillamine-treated mice, but not of those treated with d-penicillamine, the vehicle, or in bucillamine treated unnephrectomized mice, were significantly increased and remained high during the 4-week drug-loading period. Membranous glomerulonephropathy occasionally seen in bucillamine/d-penicillamine-treated arthritis patients was not reproduced in mice. Instead, our mouse model showed proximal tubular injury and podocyte foot process effacement in the bucillamine-treated kidneys. These two cell types are also the primary targets of the experimental Heymann membranous glomerulonephropathy. Gene expression profiling of the bucillamine-treated mice identified lipocalin 2 as a significantly up-regulated transcript together with cytochrome P450 CYP4a14, a group-specific component, and proprotein convertase subtilisin/kexin type 9. Moreover, large amounts of lipocalin 2 were detected in the urine of the bucillamine-treated mice, but not in the hemi-nephrectomised control mice. These results indicate that hemi-nephrectomy effectively promotes acute kidney injury by bucillamine, which is accompanied by up-regulation of the urinary biomarker lipocalin 2. Our mouse model with initial stage of kidney injury should be useful to analyse the pathogenesis of drug-induced glomerular and tubular injuries.

An unusual cause of joint swelling

A 26-year-old woman came to the rheumatology clinic from Nepal with a 5-year history of joint swelling. She had painful joint movements and chest pain on exertion. Her mother had died suddenly aged 47 years. Examination showed: tendon xanthomas over the bilateral 3 proximal interphalangeal joints (fi gure A), feet, shins and elbows; tuberous xanthomas (fi gure B); palmar xanthomas (fi gure C); eruptive xanthomas (fi gure D); xanthelasmas (fi gure E); and arcus senilis (fi gure E). Total cholesterol was 12·85 mmol/L, LDL 10·54 mmol/L, triglycerides 0·69 mmol/L, HDL 0·62 mmol/L, VLDL 0·47 mmol/L, and apolipoprotein A 0·88 g/L. Angiography showed 70% occlusion of the left anterior descending artery (LAD) and D1 branch (fi gure F), atheroectactic lesions in right common carotid artery and the right subclavian and internal carotid artery. A diagnosis of familial hypercholesterolaemia was made and lipid lowering medication initiated. Coronary artery bypass grafting is planned. Lancet 2010; 375: 1109

Description of the Male Reproductive System of the Hermit Crab Calcinus Tibicen (Decapoda: Anomura: Diogenidae)

We describe the male reproductive system of the intertidal hermit crab Calcinus tibicen, with emphasis on the sexual apparatus, spermatophore, and spermatozoa. The crabs were collected on the rocky shore of Praia Grande Beach, Ubatuba, southeastern Brazil. The morphological analysis, based on 30 specimens, was made with the use of a stereomicroscope, an optical microscope, and scanning and transmission electron microscopes. The male reproductive system is composed of a pair of juxtaposed testes, located dorsally in the pleon. From each testis emerges a vas deferens that links it to the exterior by the gonopores, located on the base of the fifth pair of pereiopods. The vas deferens has three macroscopically distinct regions that contain spermatophores in different stages of maturation. The spermatophore morphology is similar to that of other members of Paguroidea, having a distal, nearly spherical ampulla containing spermatozoa; an approximately cylindrical peduncle; and a proximal foot connecting the spermatophores. We describe, for the first time, the variability in the spermatophore morphology and size in the three regions of the vas deferens using the type species of the genus Calcinus. The spermatozoa have three main regions (the acrosomal vesicle, the nucleus, and the cytoplasm). The morphological similarity of the male reproductive system of C. tibicen with previously studied species of Diogenidae is an indicative of complex phylogenetic relationships among the members of the genus.

Measures to Prevent Complications of Distally Based Neurovascular Sural Flaps

Several publications in recent years have proven unbroken popularity of superficial sural artery flaps for the coverage of defects of the lower leg and proximal foot. However, complications are being discussed rarely. The realistic complication rate is up to 59%, given corresponding comorbidities, risk factors, or performance errors. Twelve distally based neurovascular sural flaps were used for reconstruction of heel, ankle, and lower-leg defects between 2003 and 2005. The following pre- and postoperative procedures were performed as a routine: An additional arteriography was done preoperatively to prove the patency of the peroneal artery. Acoustic Doppler ultrasound was used to identify the lesser saphenous vein and the concomitant vessels (perforators of the peroneal artery) of the sural nerve. An enlarged skin paddle with a tail of skin over the pedicle at the point of rotation was harvested intraoperatively to take pressure off the vessels and facilitate primary closure. Postoperatively, external fixation provides strict immobilization of the affected leg. Following these measures, no flap loss was observed in the presented series, and only few minor complications occurred.

Amputations Through the Hind Foot: A Report of Three Cases Using a Modified Dwyer and Paul Procedure

Salvage of limb length following oblique proximal foot amputations is presented. The technique, results, and follow-up of this procedure are described and compared with other standard procedures. A prospective study was done on 3 adolescents who presented consecutively during years 1999 and 2000. The salvage procedure described was performed on all 3 patients, and they were followed up for an average 3.5 years (range 3-4 years). All patients ambulated soon after surgery using crutches. Union of the graft between the distal tibia and calcaneus was achieved at 6 months, and all patients could walk bare foot as well as using their prosthesis both indoors and outdoors. We conclude that salvage of leg length and preservation of the sole of the foot in its normal plantigrade position by this procedure offers a viable and acceptable option to the surgeon and young patients.

Repetitive Painful Stimulation Produces an Expansion of Withdrawal Reflex Receptive Fields in Humans

The aims of the present study were to investigate whether temporal summation of the nociceptive withdrawal reflex depends on the stimulation site on the sole of the human foot, and to characterize the reflex receptive fields (RRF) of lower limb muscles to repetitive stimulation. The cutaneous RRFs were assessed in 15 subjects in sitting position by recording the EMG from five lower leg muscles and the kinematic responses (ankle, knee, and hip joints) to repetitive painful electrical stimulation. The stimulus consisted of a series of five stimuli (frequency: 3 Hz) delivered randomly at 10 different sites on the sole of the foot. The size of the reflexes increased generally between the first and the second stimulus, however, the increment depended on the stimulation site. In tibialis anterior, the RRF covered the distal sole of the foot and gradually expanded during the stimulus train. No expansion toward the heel area was detected. In soleus, the reflexes were facilitated after the second stimulus at all sites and remained in this state until the last stimulus. In vastus lateralis, biceps femoris, and iliopsoas a gradual expansion of the RRF was seen, resulting in RRFs covering the lateral, distal foot, and part of the proximal foot (iliopsoas). Knee and hip flexion were evoked at all sites. Ankle dorsiflexion was evoked at the distal foot, while ankle plantarflexion was evoked at the heel. The enlargement of the RRF reflects spinal temporal summation leading to gradually stronger reflex responses. The degree of temporal summation was dependent on stimulation site. The facilitation of the withdrawal reflex responses due to repetitive stimulation might have potential applications in the rehabilitation engineering field, where these reflexes could be used to assist gait of patients with central nervous system injuries.

Superficial sural artery flap—a study in 40 cases

The distally based superficial sural artery flap is an important skin flap that can be used for soft tissue defects of the distal lower limb and proximal foot. It is a versatile flap, has a wide arc of rotation and requires minimal expertise. Forty patients with soft tissue defects of the lower leg due to various causes were treated with sural flaps and the results are discussed. The flap was either used as a long pedicled flap or islanded to treat patients with ages ranging from 4 to 75 years. The arc of rotation of the flap was N 90–180° with minimal flap loss in most of the cases. On this basis we would like to reintroduce the safe and reliable use of the sural flap to treat large soft tissue defects of the distal lower limb and the proximal foot.

The development of vesicular acetylcholine transporter immunoreactivity in the hindlimbs of the opossum Monodelphis domestica

Vesicular acetylcholine transporter (VAChT) was revealed immunohistochemically in light microscopy on hindlimb sections of developing opossums, Monodelphis domestica. In the immobile hindlimbs of the newborn, which comprise cartilaginous bones and loose, unstriated myofibers, scant immunolabeled nerve segments and small spherical terminals, presumably growth cones or immature neuromuscular junctions, are found in the muscle tissue of the thigh, leg and proximal foot, decreasing in number and size proximodistally. When the hindlimbs start moving at 1 week, terminals are more numerous and larger, still decreasing proximodistally, and occur in the newly formed interosseous foot muscles. At 4 weeks, when the hindlimbs start supporting weight and quadrupedal locomotion appears, terminals are more numerous, flattened and in comparable size and density in thigh, leg and foot muscles. By 7 weeks, large and completely flat terminals are observed in groups of 3 to 4 at regular intervals along muscle fibers. VAChT expression develops largely postnatally in the opossum hindlimbs, along a proximodistal gradient that parallels somatic and reflex development.