Dorsiflexion Position Research Articles

A cadaver study revisiting the original methodology of Lauge-Hansen and a commentary on modern usage.

The study by Lauge-Hansen published in the Archives of Surgery in 1950 still stands as the seminal work for our understanding of the pathomechanics of ankle fractures. The purpose of the present study was to recreate Lauge-Hansen's experiments for the supination-external rotation (SER) fracture mechanism and to determine whether the predicted sequence of osseous and soft-tissue injury is reproducible on the basis of his originally described methodology. Ten fresh-frozen cadaver specimens amputated above the knee were utilized. The foot was axially loaded in a position of neutral dorsiflexion and supination. External rotation was applied manually in accordance with Lauge-Hansen's description until osseous and/or soft-tissue injury occurred. Fluoroscopic images were made and anatomic dissection was performed. Although several specimens exhibited findings consistent with certain stages of the SER injury pattern, no specimen demonstrated the complete sequence of predicted osseous and soft-tissue injury. Loading cadaver specimens with an SER mechanism utilizing a methodology similar to that in the original experiments by Lauge-Hansen does not reliably produce the sequence of osseous and soft-tissue injury predicted by Lauge-Hansen.

Provocative mechanical tests of the peripheral nervous system affect the joint torque-angle during passive knee motion.

This study aimed to determine the influence of the head, upper trunk, and foot position on the passive knee extension (PKE) torque-angle response. PKE tests were performed in 10 healthy subjects using an isokinetic dynamometer at 2°/s. Subjects lay in the supine position with their hips flexed to 90°. The knee angle, passive torque, surface electromyography (EMG) of the semitendinosus and quadriceps vastus medialis, and stretch discomfort were recorded in six body positions during PKE. The different maximal active positions of the cervical spine (neutral; flexion; extension), thoracic spine (neutral; flexion), and ankle (neutral; dorsiflexion) were passively combined for the tests. Visual analog scale scores and EMG were unaffected by body segment positioning. An effect of the ankle joint was verified on the peak torque and knee maximum angle when the ankle was in the dorsiflexion position (P < 0.05). Upper trunk positioning had an effect on the knee submaximal torque (P < 0.05), observed as an increase in the knee passive submaximal torque when the cervical and thoracic spines were flexed (P < 0.05). In conclusion, other apparently mechanical unrelated body segments influence torque-angle response since different positions of head, upper trunk, and foot induce dissimilar knee mechanical responses during passive extension.

Isokinetic Training Effect of Ankle Positions on Knee Extensor Strength

[Purpose] The purpose of this study was to determine which ankle position most influences knee extensor strength in training programs for strengthening the knee extensors using three different active ankle positions. [Subjects] Twenty-one healthy adults (6 males and 15 females) participated in this study. [Methods] Subjects were trained isokinetically in knee extension and flexion at 70 or 80% of 1RM under three actively and naturally fixed, contracted ankle conditions: dorsiflexion, plantarflexion, and resting position. After each group successfully executed the training four times a week for three weeks, mean peak torque (PT) and total work (TW) variables were measured and compared at 60°/sec and 180°/sec among the three groups. [Results] Significant differences were revealed in knee extensor TW at 60°/sec, PT and TW at 180°/sec, with the greatest PT and TW observed with the ankle in active dorsiflexion position. [Conclusion] These results suggest that active ankle dorsiflexion in a knee strength training program may be more effective at increasing knee extensor strength than a resting or plantarflexion position.

The injury mechanism and surgical treatment of distal radius fracture combined with ipsilateral elbow dislocation

Objective To investigate the injury mechanism and surgical treatment oi distal radius fracture combined with ipsilateral elbow dislocation.Methods From December 2007 to April 2011,7 cases of distal radius fracture combined with ipsilateral elbow dislocation were admitted into our department.The distal radius fractures were classified according to AO/ASIF classification:3 cases of type A3,2 cases of type C1 and 2 cases of type C3 fractures.All had posterior dislocation of the elbow.Concomitant type I Regan-Morrey coronoid tip fracture was seen in 2 patients.2 patients had early signs of forearm compartment syndrome.Among the 7 elbow dislocations,6 cases were treated with collateral ligament repair.The distal radius fractures all underwent open reduction and internal fixation.Forearm deep fascia decompression was done in the 2 cases with compartment syndrome.Results Postoperatively the patients were follow-up for an average of 16.4 months (range,9 to 26 months).There was no re-fracture or dislocation,and no wound infections.The distal forearm wound was closed secondarily in the 2 cases of forearm decornpression.All the distal radius fractures healed after 6 months.The elbows were all stable.A small amount of heterotopic ossification was seen in 2 cases,but did not affect elbow movement.Cooney wrist score was 89.5 (range,75 to 100),rating the wrist function as excellent in 2 cases,good in 3 cases,fair in 1 case and poor in 1 case.Mayo elbow score was 90.5 (range,75 to 100),rating the elbow function as excellent in 4 cases,good in 2 cases and fair in 1 case.DASH score averaged 5 (range,2 to 11).Conclusion Distal radial fractures combined with ipsilateral elbow dislocations were mostly high-energy injury.The injury mechanism is the eversion,supination and axial stress to the upper limb with wrist in dorsiflexion position and elbow in extension position.This injury is prone to forearm compartment syndrome.Surgical repair of elbow ligaments and fixation of the distal radius fracture can achieve good results. Key words: Radius fractures; Surgical procedures, operative; Elbow dislocation; Injury mechanism

A popliteal artery entrapment syndrome after by-pass surgery.

A 36-year-old male was admitted to our radiology department with a presentation of claudication on the left side for two weeks after femoral artery to tibial artery by-pass surgery. Upon physical examination, the left leg appeared pale and cold. Left magnetic resonance angiography (MRA) with gadolinium was performed from the superficial femoral arteries through the proximal portion of the popliteal fossa. The images included the bilateral popliteal arteries during dorsiflexion, plantar extension and neutral positions. There appeared to be a left venous graft that was patent. It arose from the proximal popliteal artery and traveled to the anterior tibial artery. The graft was patent at the visualized aspect. There appeared to be a mild to moderate degree of stenosis of the popliteal artery in the neutral position. There was severe stenosis of the same segment of the popliteal artery during knee extension. The popliteal artery was compressed by the slip of the medial head of the gastrocnemius, which arose more laterally than normal (Figure 1 A–C). Figure 1. 3D gadolinium-enhanced MRA images reveal the mild degree of stenosis of the popliteal artery in the neutral and dorsiflexion positions (A, B); there is severe stenosis of the same segment of the popliteal artery in the extension position (C). These images ... Popliteal artery entrapment syndrome (PAES) is a rare congenital vascular pathology caused by a compression of the popliteal artery by adjacent muscle and tendon structures. This condition is most commonly observed in young men with ischemic symptoms of the lower extremities. Extrinsic arterial compression causes chronic vascular micro trauma, early arteriosclerosis and thrombus formation, leading to distal ischemia [1, 2]. The classic presentation, which includes calf or foot claudication or pain on exertion, can have many other etiologies, including atherosclerosis, exertional compartment syndrome, and other musculoskeletal or neurogenic disorders. The most commonly used classification of PAES was described by Love and Whalen [3]. Our case had type III PAES. The incidence of popliteal entrapment has been described to be between 0.165% and 3.5% [2, 4]. Noninvasive tests, such as duplex ultrasound and axial imaging, including multi detector computed tomography angiography (MDCTA) or MRA, can help identify the anatomical abnormalities [1, 4]. In conclusion, MRA MDCTA is a safe, rapid, and noninvasive diagnostic imaging technique that enables clinicians to determine the underlying pathology and the complications of PAES.

Effects of Prolonged Stretching and Thermotherapy on Muscle Contracture of Immobilized Rat Soleus Muscle

Purpose) We examined the effects of prolonged stretching and thermotherapy on muscle contracture of immobilized rat soleus muscles by determining ankle joint range of motion (ROM), collagen fibril arrangement in the endomysium and insoluble collagen content. (Methods) In the experimental group, bilateral ankle joints of each rat were fixed in full plantar flexion with plaster casts for four weeks. Then, the experimental group animals were randomly partitioned into five groups: 1) immobilization alone; and 2) spontaneous recovery, 3) prolonged stretching, 4) thermotherapy, and 5) prolonged stretching immediately following thermotherapy for 2 weeks after cast removal. Prolonged stretching of the soleus muscle (30 min/day) was conducted by maintaining the dorsiflexion position of the ankle joint. Thermotherapy consisted of immersion of bilateral hindlimbs (20 min/day) in hot water (42 °C). Under anesthesia, both treatments were performed six days per week during the two-week remobilization. (Results) Immobilization led to decreased ROM, collagen fibril movement in the endomysium and increased in - soluble collagen. Prolonged stretching and the combination of stretching and thermotherapy accelerated ameliora- tion of the ROM limitation and diminished collagen fibril movement. (Conclusion) Our findings suggest that while thermotherapy does not exert a specific effect on muscle contracture, prolonged stretching can promote recovery.

Features of hindfoot 3D kinetics in flat foot in ankle-joint maximal dorsiflexion and plantarflexion

BackgroundIt is difficult to evaluate the kinematics of flat foot from 2D images, and no definitive methods have so far been established to diagnose flat foot. This study evaluated hindfoot kinetics through the progression of posterior tibial tendon dysfunction (PTTD) in patients with stages II and III PTTD flat foot compared with those in normal patients under dorsiflexion and plantarflexion conditions using 3D computed tomography (CT) reconstruction images. MaterialsCT images were taken of 26 normal and 32 flat feet in neutral, plantarflexion, and dorsiflexion positions of the ankle joint, from which 3D virtual models were made of each hindfoot bone. The 3D bone motion of these models was calculated using volume merge methods in three major planes. ResultsTibiotalar-joint motion in ankle-joint plantar-flexion became less plantarflexed (normal –41.2°, stage II –33.5°, stage III –25.3°) and less adducted (normal –13.9°, stage II –10.7°, stage III –5.6°) as the stage progressed. Talocalcaneal-joint motion in stage III became more plantarflexed (normal –0.8°, stage II –3.0°, stage III –8.7°) and more adducted (normal –0.3°, stage II –4.7°, stage III –10.3°) as the stage progressed. Talonavicular-joint motion in stage III became more plantarflexed (normal –7.2°, stage II –7.6°, stage III –14.9°) and more adducted (normal 1.0°, stage II –7.3°, stage III –17.9°) as the stage progressed. ConclusionsTibiotalar-joint plantarflexion decreased and talocalcaneal and talonavicular-joint adduction increased in the maximal ankle-joint plantarflexion in stage II in comparison with normal cases. Tibiotalar-joint plantarflexion and adduction were decreased and of the talocalcaneal and talonavicular joints increased in stage III in comparison with stage II cases.

Ankle Taping Can Improve Proprioception in Healthy Volunteers

Taping is a common technique to treat inversion ankle sprains, but the effects of tape on proprioception are still not clear. The purpose of this study was to establish whether proprioception would be modified by the use of ankle tape. To do so we studied joint position sense (JPS) in healthy volunteers using three-dimensional (3D) movement analysis systems. Forty healthy volunteers (mean age and SD = 23.2 ± 4.2) were asked to actively reproduce four different ankle positions: 10 degrees of dorsiflexion, neutral, 10 degrees and 20 degrees of plantarflexion. The absolute difference between the estimated angle and the target angle was used to assess JPS. This difference was named Error. Subjects were randomly assigned to the control (n = 21) or the intervention (n = 19) groups. Members of the intervention group received ankle tape for a lateral ligament sprain in the non-dominant leg. A t-test was used to evaluate the results. Tape significantly improved JPS for the dorsiflexion position (p = 0.038). Neutral was the most accurately reproduced position, and the remaining positions were overestimated for both groups. Taping improved proprioception in healthy volunteers, and 3D movement analysis was a useful method to accurately quantify joint position sense. Because ankle proprioception is critical to the functional success of surgical and rehabilitation treatments, these results regarding proprioception are of particular importance because ankle taping is often used in preventing ankle sprains and it is a common treatment after ankle injuries.

Effect of Tanner Stage on Proprioception Accuracy

The aim of this study was to compare the proprioceptive accuracy in the dominant and nondominant lower extremities between early and late stages of adolescence in boys. Participants displaying sexual development consistent with Tanner stages I or II were included in the early adolescent group, and those displaying development consistent with Tanner Stages IV or V were included in the late adolescent group. Proprioception was evaluated using the following 4 tests: one-leg-standing test, a single-limb-hopping test, an active angle-reproduction test, and a passive angle-reproduction test. There were statistically significant differences between the early and late stages of adolescence in nondominant ankles with regard to this single-limb-standing test. There were no statistically significant differences between the early and late adolescent stages, and between dominant and nondominant extremities with regard to the single-limb-hopping test. There were no statistically significant differences between early and late adolescent stages with regard to passive and active ankle plantar- and dorsiflexion position reproduction. Based on these findings, we concluded that sexual maturation categorized by Tanner stage does not affect proprioceptive ability in adolescent individuals. Clinical relevance: This method, as a clinical assessment of detecting deficits in neuromuscular control examined by foot and ankle surgeons and a rehabilitation technique to treat functional instability of the ankle used by physical therapists, might be applied to adolescents. Therefore, clinicians may obtain reliable information from the functional test battery during the assessment of ankle joint performance in adolescents.

Influence of Initial Foot Dorsal Flexion on Vertical Jump and Running Performance

Several studies (on an inclined platform or with special shoes) have reported improved jump performance when the ankle was in a dorsiflexion (DF) position. The present study aims to test whether shoes inducing moderate DF modify vertical jump performance and energy cost. Twenty-one young, healthy female subjects (30 +/- 6 yr, 58 +/- 6 kg, O2max 45 +/- 3 mLxkg-1xmin-1, mean +/- SD) participated in the study. Jump performance was tested with subjects either wearing 4 degrees DF or standard (S) shoes. The jump tests (performed on a force platform) consisted of squat jump (SJ), countermovement jump (CMJ), and continuous jumps (CJ) during 15 seconds. Measured parameters were jump height, speed at take off, and maximal and average power. Oxygen uptake was measured on a treadmill while subjects ran at 95% of the anaerobic threshold during a 7-minute steady-state period. As compared with S shoes, DF shoes significantly improved the height of SJ (31 +/- 4 cm vs. 34 +/- 4 cm, p = 0.0001), CMJ (32 +/- 4 cm vs. 34 +/- 4 cm, p = 0.0004), and CJ (17.5 +/- 4.2 cm vs. 22.0 +/- 6.0 cm, p = 0.0001). Speed at take off was also significantly higher. Mean power significantly increased in SJ and CJ but not in CMJ. Oxygen uptake was not different between conditions (p = 0.40). Dorsiflexion shoes induce a significant increase in jump performance. These results are in accordance with the concept that a DF of the ankle may induce an increase of the length and strength of the triceps surae (higher torque). However, wearing DF shoes did not require more energy during running. Dorsiflexion shoes could be used to increase jump performance in several sports such as volleyball in which jump height is essential.

Test–retest reliability of the soleus H-reflex is affected by joint positions and muscle force levels

The purpose of this study was to determine the test–retest reliability of the soleus (SOL) H-reflex during rest and isometric contractions at 10%, 30%, and 50% of the maximal voluntary force (MVC) at the ankle joint angles of neutral (0°), plantarflexion (20°), and dorsiflexion (−20°) respectively, in a sitting position. Ten healthy participants, with mean age of 24.9 ± 5.0 (SD) years, height 168.3 ± 8.8 cm, weight 62.7 ± 12.3 kg, were tested for the SOL H-reflex (H max) on two separate occasions within 7 days. The intraclass correlation coefficient (ICC) for the test–retest of the SOL H-reflex during rest was found to be high at ankle joint angle of neutral (ICC = 0.92) and plantarflexion (0.96), and moderate at dorsiflexion (0.75). Inconsistent ICC values (range from 0.62 to 0.97) were found during the submaximal voluntary contractions at the three ankle joint positions. High ICCs were also found in H max/M max ratio at neutral (0.86), plantarflexion (0.96), and dorsiflexion (0.84) positions. It was concluded that the test–retest reliability of the SOL H-reflex was affected by the intensity of voluntary contraction and ankle joint position. The H-reflex demonstrated a higher reliability at the neutral and plantarflexion positions than that at the dorsiflexion position during rest, and a higher reliability at 10% MVC than that at 30% and 50% MVC.

In Vivo Three-Dimensional Analysis of Hindfoot Kinematics

Knowledge of normal bone motion of the foot is important for understanding the gait as well as for various pathologies; however, the pattern of 3D motion is not completely understood. The aim of this study was to quantify the in vivo motion of the tibiotalar joint, talocalcaneal joint, and talonavicular joint in normal adult feet using a noninvasive (e.g., nonsurgical) measurement technique. CT images were taken of both feet of ten normal young adults (six males, four females) in neutral, plantarflexion, and dorsiflexion positions of the ankle joint, from which 3D virtual models were made of each mid-hind foot bones. The 3D bone motion of these models was calculated using volume merge methods in three major planes. These data were used to analyze the relationship between the motion of the ankle joint and each other joint. Tibiotalar rotation was observed in dorsiflexion, abduction, and eversion during maximal dorsiflexion of the ankle joint. Talocalcaneal and talonavicular rotation was very small because the ankle joint motion was limited to the sagittal plane. Tibiotalar rotation was also observed in plantarflexion and adduction during maximal plantarflexion of the ankle joint, and talocalcaneal rotation was very small. Talonavicular rotation was observed in plantarflexion and inversion. The motion of the x-axis and the z-axis of tibiotalar joint, and the x-axis and the y-axis of the talonavicular and talocalcaneal joint were associated with the ankle motion. Bone motion could be easily and accurately calculated using volume merge methods more effectively than it could with other methods. The data elucidates the baseline segmental motion for comparison with symptomatic subjects which could help us to better understand pathokinematics of various foot and ankle pathologies.

Joint angle dependence of intermuscle difference in postactivation potentiation

The purpose of this study was to examine the effect of ankle joint angle on the intermuscle difference in postactivation potentiation (PAP) between the medial gastrocnemius (MG) and soleus (SOL) muscles. At the neutral position of joint angle, dorsiflexion of 20 degrees , and plantarflexion of 20 degrees , twitch responses were evoked by stimulating the posterior tibial nerve with supramaximal intensity before and after a 10-s maximal voluntary plantarflexion at each joint angle. Mechanical properties of the MG and SOL muscles were assessed simultaneously and separately by using mechanomyography (MMG), and the extent of potentiation of each muscle was evaluated by peak-to-peak amplitude of the MMG signal. The MG showed greater potentiation than the soleus after the conditioning MVC in the neutral and dorsiflexion position, while in the plantarflexion position no significant difference was found in PAP between MG and SOL. These results suggest that the difference in the magnitude of PAP between synergistic muscles is determined by a combination of the joint angle- and fiber composition-dependence of PAP.

Viscoelastic Creep In Human Skeletal Muscle

INTRODUCTION: Viscoelastic creep can be defined as the increase in tissue length under a constant force or torque. PURPOSE: To examine viscoelastic creep in the plantar flexor muscles. METHODS: Thirteen healthy participants (mean age ± SD = 22 ± 3 yrs; stature = 168 ± 12 cm; mass = 69 ± 17 kg) performed four 30-s constant-torque passive stretches of the plantar flexor muscles on a calibrated Biodex System 3 dynamometer. Each 30-s passive stretch was completed by the dynamometer lever arm by passively dorsiflexing the foot at 5°/s to the point of discomfort, but not pain as acknowledged by the participant. This was quantified as the maximum tolerable passive torque threshold (i.e. 33 N·m), which was held constant for all 4 stretches while the change in dorsiflexion position was monitored under the constant passive torque. Each 30-s passive stretch was separated by 20 s of rest. Position (°) values were sampled from the dynamometer at 1 KHz during the stretches and were quantified at every 5-s period (0, 5, 10, 15, 20, 25, and 30 s). In addition, the percent change in position was quantified for each 5-s epoch (0-5, 5-10, 10-15, 15-20, 20-25, and 25-30 s) relative to the total increase in range of motion (ROM) for each 30-s stretch. A two-way repeated measures ANOVA [stretch × time; 4 × 7] was used to analyze the absolute changes in position, whereas a two-way repeated measures ANOVA [stretch × time; 4 × 6] was used to analyze the percent changes in ROM. RESULTS: For each 30-s stretch, the absolute position increased such that 0 < 5 < 10 < 15 < 20 < 25 < 30 s (P<0.05). At all time points, the position for stretch 1 was less than stretches 2 - 4 (P<0.05), and stretch 2 was less than stretches 3 - 4 (P<0.05). There were no differences at any time points between stretches 3 and 4 (P>0.05). The percent changes in ROM were the same for stretches 1, 2, 3, and 4 during each epoch (P<0.05), however, as the stretch progressed for 30 s, the relative increases in ROM diminished. CONCLUSIONS: During these constant-torque stretches, most of the increases in range of motion occurred as a result of the first two 30-s stretches, since there were no differences in dorsiflexion position between stretches 3 and 4. In addition, the relative changes in ROM that occurred during each of the four 30-s stretches were the same, but the greatest increases (42%) occurred during the first 5-s.

The Influence of Foot Position on Stretching of the Plantar Fascia

A recent study found nonweightbearing stretching exercises specific to the plantar fascia to be superior to the standard program of weightbearing Achilles tendon-stretching exercises in patients with chronic plantar fasciitis. The present study used a cadaver model to demonstrate the influence of foot and ankle position on stretching of the plantar fascia. Twelve fresh-frozen lower-leg specimens were tested in 15 different configurations representing various combinations of ankle and metatarsophalangeal (MTP) joint dorsiflexion, midtarsal transverse plane abduction and adduction, and forefoot varus and valgus. Measurements were recorded by a differential variable reluctance transducer (DVRT) implanted into the medial band of the plantar fascia, and primary measurement was a percent deformation of the plantar fascia (stretch) with respect to a reference position (90 degrees ankle dorsiflexion, 0 degrees midtarsal and forefoot orientation, and 0 degrees MTP dorsiflexion). Ankle and MTP joint dorsiflexion produced a significant increase (14.91%) in stretch compared to the position of either ankle dorsiflexion alone (9.31% increase, p < 0.001) or MTP dorsiflexion alone (7.33% increase, p < 0.01). There was no significant increase in stretch with positions of abduction or varus (2.49%, p = 0.27 and 0.55%, p = 0.79). This study provides a mechanical explanation for enhanced outcomes in recent clinical trials using plantar fascia tissue-specific stretching exercises and lends support to the use of ankle and MTP joint dorsiflexion when employing stretching protocols for nonoperative treatment in patients with chronic proximal plantar fasciitis.

Responses of Purkinje-cells of the cerebellar anterior vermis to stimulation of vestibular and somatosensory receptors

In decerebrate cats, sinusoidal rotation of the forepaw around the wrist modifies the activity of the ipsilateral forelimb extensor triceps brachii (TB) and leads to plastic changes of adaptive nature in the gain of vestibulospinal (VS) reflexes (VSRs). Both effects are depressed by functional inactivation of the cerebellar anterior vermis, which also decreases the gain of VSRs. In order to better understand the mechanisms of these phenomena, the simple spike activity of Purkinje (P-) cells was recorded from the vermal cortex of the cerebellar anterior lobe during individual and/or combined stimulation of somatosensory wrist, neck and vestibular receptors. About one third of the recorded units were affected by sinusoidal rotation of the ipsilateral forepaw around the wrist axis (0.16 Hz, ±10°). Most of these neurons (∼60%) increased their activity during ventral flexion of the wrist and decreased it during the oppositely directed movement, with an average phase lag of −141° with respect to the position of maximal dorsiflexion. The remaining cells (∼40%) were excited during dorsiflexion of the wrist, with an average phase lead of 59° with respect to the extreme dorsal flexion. Both populations showed comparable response gains, with an average value of 0.42±0.52, S.D., imp/s/deg. About half of the recorded units were also tested during sinusoidal roll tilt of the animal around the longitudinal axis (0.16 Hz, ±10°), leading to stimulation of labyrinthine receptors. When both stimuli were applied simultaneously, the responses to combined stimulation usually corresponded to the sum of individual responses. While the phase distribution of somatosensory responses was clearly bimodal, vestibular responses showed phase angle values uniformly scattered between ±180° and 0°, so that, during combined stimulation, each neuron could be maximally activated by coupling the two stimuli with a particular phase relation. Finally, a proportion of the recorded neurons was also tested during sinusoidal rotation of the body around its longitudinal axis, with the head fixed in space, leading to stimulation of neck receptors. The proportion of neurons affected by individual stimulation of vestibular or neck receptors (81% and 72%, respectively) was larger than that of wrist-driven neurons. Convergence of signals from vestibular, somatosensory wrist and neck receptors was found in 18% of the neurons analyzed. In conclusion, the results of this study show that somatosensory signals from the forelimb: i) modulate the activity of a sizeable proportion of neurons located within the cerebellar anterior vermis and ii) interact widely with labyrinthine and neck signals at this level. Moreover, iii) this corticocerebellar region is largely dominated by vestibular and neck signals that may be utilized to build up a neuronal representation of the position of body in space. These findings suggest that: 1) the modulation of TB activity induced by rotation of the ipsilateral wrist may at least partially depend upon the simultaneous changes in P-cell activity and 2) the interaction of vestibular and somatosensory wrist signals at P-cell level may represent the substrate of the plastic changes that affect the VSR when animal tilt and wrist rotation are driven together. A preliminary report of these data has been presented [ Bruschini L, Manzoni D, Pompeiano O (2000) Responses of cerebellar Purkinje cells to forepaw rotation in decerebrate cat. Pflügers Arch 440:R31].

Analysis of Ankle-Hindfoot Stability in Multiple Planes: An in vitro Study

It is necessary to have an understanding of ankle and hindfoot motion and stability to accurately diagnosis and treat ankle-hindfoot disorders. We devised an ankle ligament testing apparatus to more critically determine ankle stability in all planes with a constant rotational force applied (inversion, eversion, internal rotation, external rotation) throughout the range of sagittal plane motion in 13 cadaver specimens. Three-dimensional kinematics were determined with a magnetic tracking device. With inversion force applied, calcaneal-tibial inversion was greatest in maximal plantarflexion (mean 22.1 +/- 6.0 degrees) and gradually decreased with dorsiflexion, which indicated that the ankle had the most inversion instability in plantarflexion. With eversion force applied, calcaneal-tibial eversion gradually increased with increasing dorsiflexion to 12.7 +/- 7.4 degrees indicating that the most eversion instability was in dorsiflexion. With internal rotation force applied, calcaneal-tibial internal rotation from plantarflexion to neutral ankle position increased. With external rotation force application, external rotation from neutral to maximal dorsiflexion increased. Ankle laxity was not constant but varied depending on the plantarflexion-dorsiflexion position and the direction of the applied force. The degree of ankle laxity was greater with inversion and internal rotation torque. Variation in laxity between specimens was observed, consistent with previous reports. These data indicate that the ankle is less stable in plantarflexion when inversion and internal rotation forces are applied. This may explain why the lateral ankle ligaments are most prone to injury in this position. The ankle was less stable in dorsiflexion when eversion and external rotation forces were applied. This is consistent with the observation that deltoid ligament injuries occur in the neutral to dorsiflexion position. The study demonstrates the importance of examining patients with suspected ankle ligament injuries in several ankle positions. The ankle testing device has potential application for in vivo testing of patients with suspected ankle ligament instability.

Effect of head position and visual condition on balance control in inverted stance

This study analyzed the effect of head position and visual condition on the control of balance in handstand, a gymnastics posture that necessitates adaptation of sensory information processing. Five expert gymnasts participated. Centre of pressure trajectories and kinematics of different body segments were recorded. The gymnasts were instructed to maintain three handstands as long as possible in four head positions, with and without vision. Performances and postural stability was much better in the standard and dorsiflexion positions than in the aligned and ventroflexion positions under the two conditions of vision. Performances were lower without vision in the standard and dorsiflexion position. If vision clearly plays an important role, yet the tonic neck reflexes also seem to contribute greatly to control body sways during inverted posture.

Quantitative analysis of ankle hypertonia after prolonged stretch in subjects with stroke

The aims of this study are to validate the hypertonia treatment/assessment system and to quantify the immediate effect of prolonged muscle stretch (PMS) on the inhibition of ankle hypertonia in stroke patients. For PMS treatment, ankle plantarflexors were stretched with a constant torque in 25 subjects with hemiplegia and ankle plantarflexors hypertonia. Using the developed hypertonia treatment/assessment system, the effects of the PMS treatment were quantified by comparing the reactive torque measurements of the ankle joint before and after the treatment sessions in terms of elastic (elastic-inertia) ( K ei) and viscous ( K v) components. It was shown that an application of PMS for 30 min using a constant stretching force, approximately 80% of the torque measured at the maximal passive ROM dorsiflexion position, significantly reduces both components of the ankle joint torque ( P<0.05). The present results suggested that the application of PMS with a constant torque could reduce not only the elasticity of the hypertonic muscles, but also their viscosity in the stroke patients.

Mechanomyographic and electromyographic responses of the triceps surae during maximal voluntary contractions

The objective of this study was to examine the effect of joint angle on the electromyogram (EMG) and mechanomyogram (MMG) during maximal voluntary contraction (MVC). Eight subjects performed maximal isometric plantar flexor torque productions at varying knee and/or ankle angles. Maximal voluntary torque, EMG, and MMG from the soleus (Sol), medial (MG) and lateral gastrocnemius (LG) muscles were measured at different joint angles. At varying knee angles, the root mean squared (rms) MMG amplitude of the MG and LG increased with knee joint extension from 60° to 180° (full extension) in steps of 30°, whereas that of the Sol was constant. At varying ankle angles, the rms-MMG of all muscles (Sol, MG, and LG) decreased with torque as ankle joint extending from 80° (10° dorsiflexion position) to 120° (30° plantar flexion position) in steps of 10°. In each case, changes in the rms-MMG of the three muscles were almost parallel to those in torque. In contrast, there were no significant differences in the rms-EMG of all muscles among all joint angles. Our data suggest that the MMG amplitudes recorded from individual muscles during MVCs can represent relative torque–angle relationships that cannot be represented by the EMG signals.