The effect of level of spinal cord injury on shoulder joint kinetics during manual wheelchair propulsion.

OBJECTIVE: The effects of spinal cord injury level on shoulder kinetics during manual wheelchair propulsion were studied. DESIGN: Single session data collection in a laboratory environment. METHODS: Male subjects were divided into four groups: low level paraplegia (n=17), high level paraplegia (n=19), C7 tetraplegia (C7, n=16) and C6 tetraplegia (C6, n=17). Measurements were recorded using a six-camera VICON motion analysis system, a strain gauge instrumented wheel, and wheelchair ergometer. Shoulder joint forces and moments were calculated using the inverse dynamics approach. RESULTS: Mean self-selected propulsion velocity was higher in the paraplegic (low paraplegia=90.7 m/min; high paraplegia=83.4 m/min) than tetraplegic (C7=66.5 m/min; C6=47.0 m/min) groups. After covarying for velocity, no significant differences in shoulder joint moments were identified. However, superior push force in subjects with tetraplegia (C7=21.4 N; C6=9.3 N) was significantly higher than in those with high paraplegia (7.3 N), after covarying velocity. CONCLUSIONS: The superior push force in the tetraplegic groups coupled with weakness of thoraco-humeral depressors increases susceptibility of the subacromial structures to compression. RELEVANCE: Increased vertical force at the shoulder joint, coupled with reduced shoulder depressor strength, may contribute to shoulder problems in subjects with tetraplegia. Wheelchair design modifications, combined with strength and endurance retention, should be considered to prevent shoulder pain development.

Electromyographic and kinematic analysis of the shoulder during four activities of daily living in men with C6 tetraplegia.

The pattern of motor paralysis that commonly follows C6 tetraplegia creates an increased demand on upper limb function. The present investigation documented shoulder motion and muscular activity during planar motions and four activities of daily living (ADLs) in 15 men with spinal cord injuries (SCI) resulting in C6 tetraplegia. Three-dimensional (3-D) shoulder motion was recorded using a VICON motion system, and intramuscular electrodes recorded electromyographic (EMG) activity of 12 shoulder muscles. Active flexion and abduction required greater EMG than control subjects lifting a 2-kg weight. Relative EMG was similar for most muscles during hair combing, drinking, and reaching forward, although increased humeral elevation commonly resulted in a greater relative muscular effort. Hair combing had the most humeral elevation (90 degrees) with moderate to high levels of activation (32% to 63% maximum) recorded in the anterior deltoid, supraspinatus, infraspinatus, and scapular muscles. During reaching for the perineum, posterior deltoid and subscapularis activity dominated.

Three dimensional upper extremity motion during manual wheelchair propulsion in men with different levels of spinal cord injury.

This investigation compared three dimensional upper extremity motion during wheelchair propulsion in persons with 4 levels of spinal cord injury: low paraplegia (n=17), high paraplegia (n=19), C7 tetraplegia (n=16), and C6 tetraplegia (n=17). Upper extremity motion was recorded as subjects manually propelled a wheelchair mounted on a stationary ergometer. For all motions measured, subjects with paraplegia had similar patterns suggesting that the wheelchair backrest adequately stabilizes the trunk in the absence of abdominal musculature. Compared with paraplegic subjects, those with tetraplegia differed primarily in the strategy used to contact the wheel. This was most evident among subjects with C6 tetraplegia who had greater wrist extension and less forearm pronation.

Isolation of the vastus medialis oblique muscle during exercise.

The purpose of this study was to selectively challenge the vastus medialis oblique muscle in comparison with the vastus lateralis, the vastus intermedius, and the vastus medialis longus muscles by performing nine sets of strengthening exercises. These knee rehabilitation exercise included isometric knee extension with the hip at neutral, 30 degrees external, and 30 degrees internal rotation; isokinetic knee extension through full range; isokinetic knee extension in the terminal 30 degrees arc; sidelying ipsilateral and contralateral full knee extension; and stand and jump from full squat. Electrical activity of the vastus medialis oblique, the vastus lateralis, the vastus intermedius, and the vastus medialis longus muscles was measured in eight uninjured subjects. Our study showed that isometric exercises in neutral and external rotation of the hip will challenge both the vastus medialis oblique and the vastus lateralis muscles. The results suggest that the electromyographic activity of the vastus medialis oblique muscle was not significantly greater than that of the vastus lateralis, the vastus intermedius, and the vastus medialis longus muscles during the nine sets of exercises. Results suggest that the vastus medialis oblique muscle cannot be significantly isolated during these exercises.

Assessment of rearfoot motion: passive positioning, one-legged standing, gait.

Earlier studies that address assessment of the subtalar joint (STJ) by measuring rearfoot motion used a goniometer to evaluate intertester reliability. Few investigations have determined how positions of the rearfoot, assessed manually (passive range of motion) or statically in one-legged standing, compare with those occurring during walking. The purpose of this study was to determine the following: (1) the intertester reliability of positioning the STJ in neutral, maximum inversion, and maximum eversion; (2) the reliability of the rearfoot position during relaxed one-legged standing; and (3) how these positions compare to rearfoot motion during walking. An electrogoniometer attached to the lateral aspect of the lower leg and heel was used to record the position of the rearfoot during testing procedures. Ten healthy volunteers participated. Rearfoot position was recorded during relaxed one-legged standing and during free and fast walking. Additionally, rearfoot position was recorded while each of three physical therapists positioned the STJ in neutral, maximum inversion, and maximum eversion. Intertester reliability for positioning the STJ in neutral, maximum inversion, and maximum eversion yielded intraclass correlation coefficients of 0.76, 0.37, and 0.39, respectively. Reliability of relaxed one-legged standing had an intraclass correlation coefficient of 0.92. The rearfoot position in relaxed one-legged standing and the maximum eversion position occurring during gait were not significantly different. These findings suggest that there is good intertester reliability in positioning the STJ in neutral. Additionally, the rearfoot position in relaxed one-legged standing may be used to approximate the maximum eversion position that occurs during gait.

Shoulder joint kinetics during the push phase of wheelchair propulsion.

The purpose of this investigation was to quantify the forces and moments at the shoulder joint during free, level wheelchair propulsion and to document changes imposed by increased speed, inclined terrain, and 15 minutes of continuous propulsion. Data were collected using a six-camera VICON motion analysis system, a strain gauge instrumented wheel, and a wheelchair ergometer. Seventeen men with low level paraplegia participated in this study. Shoulder joint forces and moments were calculated using a three-dimensional model applying the inverse dynamics approach. During free propulsion, peak shoulder joint forces were in the posterior (46 N) and superior directions (14 N), producing a peak resultant force of 51 N at an angle of 185 degrees (180 degrees = posterior). Peak shoulder joint moments were greatest in extension (14 Newton-meters [Nm]), followed by abduction (10 Nm), and internal rotation (6 Nm). With fast and inclined propulsion, peak vertical force increased by greater than 360%, and the increase in posterior force and shoulder moments ranged from 107% to 167%. At the end of 15 minutes of continuous free propulsion, there were no significant changes compared with short duration free propulsion. The increased joint loads documented during fast and inclined propulsion could lead to compression of subacromial structures against the overlying acromion.

Segment velocities in normal and transtibial amputees: prosthetic design implications.

Dynamic elastic response foot and ankle prostheses (Seattle-Lite, Flex Foot, etc.) used by transtibial amputees feature substantial design improvements over conventional designs (SACH, Single Axis, etc.). Despite this progress, transtibial amputees continue to expend greater energy than normals. Increased residual limb EMG data and altered gait patterns suggest that impaired mobility may be the cause of overactive muscles in early stance. Prosthetic mobility was therefore quantified by measuring foot, shank and thigh velocities in nine transtibial amputees, wearing three different foot designs: Single Axis (SA), Seattle Lite (SL) and Flex Foot (FF). The magnitude, timing and rate of segment velocities for each prosthetic design, characterizing early stance mobility, were compared with corresponding measures in normal, nonamputee (NA) controls using Dunnett's test. Regardless of foot type, transtibial (TT) amputees walked slower than non amputee controls (63.3-65.8 m/min versus 78.5 m/min, p < 0.05) and their stride length was shorter (1.21-1.26 m versus 1.41 m, p < 0.01). In early stance, peak foot and shank velocities were lower (p < 0.01) for both the SL and FF while only shank velocity was lower (p < 0.01) with the SA compared to NA controls. Significant delays in the timing of early stance events such as peak shank velocity, peak ankle plantarflexion and peak knee flexion compromised shank and knee stability in TT amputees. Foot and shank mobility was uncontrolled with the SA design while ankle mobility was restricted by the FF and SL feet. In NA controls on the other hand, appropriate timing and rate of segment velocity changes preserved dynamic stability and forward progression in early stance. This was evidenced by rapid decreases in foot and shank velocity as the thigh velocity increased during weight acceptance. Future prosthetic designs should provide TT amputees with improved ankle mobility that attempt to capture the dynamic characteristics of a normal articulation between the foot and shank segments during the early stance weight acceptance period.

Tibialis anterior transfer for calcaneal deformity: a postoperative gait analysis.

We retrospectively evaluated seven children who had low-lumbar-level spina bifida and who had undergone bilateral transfer of tibialis anterior to the calcaneus. The mean age at the time of operation was 8 years (range, 3-12), and the patients were monitored for an average of 40 months (range, 24-60). All children underwent a postoperative gait analysis to assess the function of the transfer and the need for continued postoperative bracing. Transfer of the tibialis anterior muscle to the calcaneus arrested progression of the calcaneal deformity; however, the transfer could not prevent excessive dorsi-flexion of the ankle during stance. The use of a pretibial ankle-foot orthosis improved velocity, increased stride length, decreased quadriceps activity at terminal stance, and led to decreased energy expenditure. We conclude that continued bracing is necessary to provide a more normal appearing and energy-efficient gait.

Three-dimensional kinematics of wheelchair propulsion.

A three-dimensional (3-D) biomechanical model was used to determine upper extremity kinematics of 16 male subjects with low-level paraplegia while performing wheelchair propulsion (WCP). A six-camera VICON motion analysis system was used to acquire the coordinate data of ten anatomic markers. Joint axes for the wrist and elbow were defined along with the planes of motion for the upper arm (humerus) and trunk. The group's mean and standard deviation profiles were graphed for eight of the nine rotations measured during WCP. Variability in the intercycle and intersubject movement patterns were calculated using the root mean square standard deviation (RMS sigma) and the coefficient of variation (CV). Motion pattern similarities were quantified using the coefficient of multiple correlation (CMC). The intercycle (Nc > or = 6) motion patterns of individual subjects were highly consistent, similar, and repeatable during WCP. This was confirmed by low CVc values (3-31%), high CMCc values (0.724-0.996) and RMS sigma c values below 3.2 degrees. For the group, mean values of the propulsion velocity, cadence, and propulsion cycle duration were 89.7 m/min, 66.1 pushes/min, and 0.96 s, respectively. Humeral plane and rotation showed large excursions (76.1-81.6 degrees), while trunk lean and forearm carrying angle displayed relatively small ranges of motion (5.5-10.9 degrees). The intersubject (N3 = 16) motion patterns were less similar compared to individual intercycle patterns. This was evidenced by higher CVc values (12-128%) and lower CMC3 values (0.418-0.935). Intersubject humeral patterns were the most consistent while trunk lean was the least consistent. Intersubject root mean square standard deviations (RMS sigma c) were more than three times the corresponding intercycle values for all nine rotations.

Temporal-spatial characteristics of wheelchair propulsion. Effects of level of spinal cord injury, terrain, and propulsion rate.

The purpose of this investigation was to compare the temporal-spatial characteristics of wheelchair propulsion (velocity, cycle distance, and cadence) of customary wheelchair users in conditions designed to simulate community settings. Seventy adult males with spinal cord injuries (SCI) were grouped by their level of SCI: low paraplegia (n = 17); high paraplegia (n = 19); C-7 tetraplegia (n = 17); C-6 tetraplegia (n = 17). Testing was performed in a wheelchair that had the right pushrim instrumented with force transducers. Participants propelled the test wheelchair at a self-selected, free, and fast pace over tile and carpeted floors. A wheelchair ergometer was designed to simulate loads encountered during propulsion over graded surfaces. Participants propelled the test wheelchair during ergometer simulation of 4% and 8% grades. Mean velocity, cycle distance, and cadence were calculated for each group in all test conditions. A two-way repeated measures analysis of variance and simple main effects testing for comparison across conditions and between groups were performed. For all test conditions, participants with low paraplegia were the fastest and had the longest cycle distance. With successively higher levels of SCI, velocities were slower and cycle distances shorter. During free propulsion on tile, velocities ranged from 95 m/min in low paraplegics to 55 m/min in C-6 tetraplegics. Fast propulsion velocity increased to 141 and 55 m/min, respectively. There was a significant main effect of surface for velocity such that the carpet condition was slower than the tile for all groups. Differences in velocity were most often the result of changes in cycle distance. High and low paraplegic groups were statistically similar for all test conditions. Participants with C-6 tetraplegia were significantly slower than all other groups for most test conditions. Because their fast propulsion velocities were slower than typical community demands, their ability to function independently outside the hospital setting has been further questioned.

Electromyographic analysis of the shoulder muscles during depression transfers in subjects with low-level paraplegia.

OBJECTIVE: To document and compare the intensity of selected shoulder muscle activity during depression transfers. DESIGN: Intramuscular electrodes were used to record the activity of 12 shoulder muscles while transferring to and from a wheelchair. PARTICIPANTS: Twelve adult men with spinal cord injuries resulting in low paraplegia. OUTCOME MEASURES: Three phases of the transfer were analyzed: preparation, lift, and descent. Median intensities were compared between muscles, transfer phase, and direction of transfer using Freidman's test. RESULTS: Trunk elevation was accomplished mainly by sternal pectoralis major and latissimus dorsi activity. Lateral body displacement required other muscles to control the elevated body. Rotator cuff muscles contributed to shift mechanics and, together with anterior deltoid, provided anterior glenohumeral wall protection. Lower serratus anterior stabilized the scapulothoracic articulation and contributed to the lateral movement. CONCLUSIONS: Assessment of depression transfer skill should not be based on the ability to lift body weight. Movement of the trunk required vigorous activity of key shoulder musculature. Differences in leading and trailing arm EMG intensities will assist in modifying transfer style in individuals with weakness, strength imbalances, and shoulder pathologies.

Electromyographic activity of shoulder muscles during wheelchair propulsion by paraplegic persons.

OBJECTIVE: Phasing and intensity of shoulder muscle activity during wheelchair propulsion were documented to identify muscles at risk for fatigue and overuse. DESIGN AND PARTICIPANTS: Electromyographic (EMG) activity of 12 muscles was recorded with wire electrodes in 17 paraplegic men during propulsion on a stationary ergometer. MAIN OUTCOME MEASURES: Push and recovery phases of the propulsion cycle were determined with an instrumented pushrim. Onset and cessation of EMG were compared between muscles with a repeated measures ANOVA. Average and peak EMG intensity also were identified. RESULTS: All muscles functioned either in push or recovery phases, except supraspinatus, which displayed both patterns, and latissimus dorsi, which was inconsistent. The 6 push phase muscles--anterior deltoid, sternal pectoralis major, supraspinatus, infraspinatus, serratus anterior, and long head of biceps brachii--had onsets in late recovery (78% to 93% cycle) with peak EMG in the first 10% of the cycle. Pectoralis major and supraspinatus had the highest peak (58% and 67%MAX) and average (35% and 27%MAX) EMG intensities in this group. Cessation occurred in late push (17% to 23% cycle) except in biceps brachii (8% cycle) (p < .01). The 5 recovery muscles--middle and posterior deltoid, subscapularis, supraspinatus, and middle trapezius--had EMG onsets in late push (17% to 26% cycle) with moderate average intensities (21% to 32%MAX). These muscles had two EMG peaks (end of push and mid-recovery). Cessation was in late recovery (82% to 91% cycle). CONCLUSIONS: Muscles most vulnerable for fatigue were pectoralis major, supraspinatus, and recovery muscles. Endurance training was recommended.

Classification of walking handicap in the stroke population.

BACKGROUND AND PURPOSE: The limited walking ability that follows a stroke restricts the patient's independent mobility about the home and community, a significant social handicap. To improve the in-hospital prediction of functional outcome, the relationships between impairment, disability, and handicap were assessed with clinical measures in 147 stroke patients. METHODS: The patients' level of functional walking ability at home and in the community was assigned by expert clinicians to one of the six categories of a modified Hoffer Functional Ambulation scale at least 3 months after discharge. A 19-item questionnaire was further used to assess current customary mobility of the subjects. Functional muscle strength and proprioception were tested, and walking velocity was measured. RESULTS: The significant indicators of impairment, upright motor control knee flexion and extension strength, differentiated household from community ambulators. The addition of velocity improved the functional prediction. Proprioception was clinically normal in all walkers. The validity of the criteria for the six levels of walking handicap was confirmed statistically. Stepwise discriminant analysis reduced the ambulation activities on the questionnaire from 19 to 7. Redefinition of the criteria for patient classification using the coefficients and constants of the seven critical functions improved the prediction of patient walking ability to 84%. CONCLUSIONS: The results of this study offer a quantitative method of relating the social disadvantage of stroke patients to the impairment and disability sustained. The measurement of therapeutic outcome in relation to the social advantage for the patient would allow more efficient standardization of treatment and services.

Electromyographic analysis of shoulder muscles of men with low-level paraplegia during a weight relief raise.

The purpose of this study was to define the demand on the shoulder musculature during performance of a weight relief raise. Intramuscular electromyographic activity of 12 shoulder muscles was recorded in 13 pain-free subjects with paraplegia while elevating the trunk from a sitting position. Upper extremity motion was determined by elbow electrogoniometry and video recordings. Three phases of the raise were analyzed: initial loading, lift, and hold. During the lift phase, high level triceps long head activity (54% manual muscle test [MMT]) produced elbow extension, whereas moderate- to high-level activity of the sternal pectoralis major (32% MMT) and latissimus dorsi (58% MMT) elevated the trunk on the fixed humerus. Deltoid, supraspinatus, infraspinatus, subscapularis, middle trapezius, serratus anterior, and biceps long head played minimal roles (< 25% MMT). Thoracohumeral muscle activity, by transferring the load on the humerus directly to the trunk, functionally circumvented the glenohumeral joint. This would reduce the potential for impingement of the rotator cuff.

Isometric shoulder torque in subjects with spinal cord injury.

The etiology of shoulder pain in spinal cord injured (SCI) patients has been attributed to overuse, with dysfunction being more prevalent as the time since injury increases. Impingement syndrome, the most common diagnosis in this population, may be related to weakness of the rotator cuff and shoulder girdle musculature. Shoulder dysfunction is greater in subjects with SCI than in able-bodied patients; consequently, this study compares isometric strength of quadriplegic and paraplegic subjects to able-bodied controls. Peak isometric torque for internal rotation, external rotation, and scapular elevation was assessed using a Lido isokinetic dynamometer. The strength (torque) values of the quadriplegic group were significantly lower than the control group and paraplegic group for all motions tested (p < .0005). The only significant difference between the paraplegic and able-bodied groups was found with internal rotation (p < .0001). These results indicate that quadriplegic patients may be at greater risk for shoulder pathology because of both muscular limitation and increased functional demand.

The Rancho EMG analyzer: a computerized system for gait analysis.

This paper describes a computer system which accurately defines the EMG patterns of the lower extremities during gait. Footswitches are used to identify the temporal relationships and determine the phases of the gait cycle. Fine wire electrodes, inserted in the desired muscles of the patient being tested, provide EMG signals for comparison with a normal database. The system is also usable with surface electrodes when an appropriate normal database for surface electrodes is incorporated. Descriptive qualifiers (such as 'premature onset', 'delayed cessation', 'no clinically significant EMG', 'continuous activity' etc.) are used to produce a clinically relevant printed (textual) report. The intensity filtered average (IFA) of the EMG is shown graphically with the representative profile of each stride. The IFAs for all muscles tested can be plotted together (up to six on a page) and the graphic representation of the 'raw' EMG can be produced. The methods of generating the normal database by creating time-adjusted mean profiles (TAMP) are enumerated. The clinical use of the system is discussed. A detailed analysis of 31 of the most recent patient tests for which the system was used provides an indication of its accuracy. For 86% of the 428 muscle tests examined, the EMG analyser was considered to have given the correct result as compared with a visual analysis of the raw EMG record by a trained expert. Recommendations for the use and future improvements of the EMG analyser are made.

Quadriceps force and myoelectric activity during flexed knee stance.

The purpose of this study was to determine the quadriceps demand during single limb stance with the knee in five positions of flexion (0 degree -60 degrees). Two variables were used to estimate the quadriceps demands: the integrated electromyogram (EMG) of three vasti and the torque about the knee joint. Ten normal subjects 23-29 years of age were tested. Myoelectric activity was recorded with intramuscular electrodes and knee joint angle with an electrogoniometer. The EMG data were integrated and normalized. A visible vector system was used to determine knee flexion torque. A significant linear correlation was found between values of patellar ligament force and knee angle (R2 = 0.86). The patellar ligament force increased 4.16% of body weight per degree of knee flexion between 0 degree and 60 degrees. Both vector-estimated quadriceps force and normalized EMG showed significant correlations with knee angle (R2 = 0.91 and R2 = 0.88, respectively). Both exhibited a slower rate of rise below 30 degrees flexion and a higher rate of rise above 30 degrees. The authors' findings suggest that the stabilizing effects of plantar flexors (except gastrocnemius) on the knee joint, changing muscle moment arm length, and force ratio between the patellar ligament and quadriceps muscle with respect to knee angle are primary reasons for the quadratic normalized integrated EMG (NIEMG)-force nonlineality during flexed stance. This might indicate the existence of a critical angle of knee flexion contracture beyond which patients cope poorly with standing and functional ambulation.

Valgus deformities of the feet and characteristics of gait in patients who have rheumatoid arthritis.

To investigate the cause of valgus deformity of the hindfoot in patients who have rheumatoid arthritis and to characterize the effects of the deformity on gait, two groups of patients were evaluated clinically, radiographically, and with gait analysis in the laboratory. Group 1 consisted of seven patients who had seropositive rheumatoid arthritis and normal alignment of the feet and Group 2, of ten patients who had rheumatoid arthritis and valgus deformity of the hindfoot. In Group 2, the disease was of longer duration and the feet were more painful than in Group 1. There was no evidence of muscular imbalance, equinus contracture, valgus deformity of the tibiotalar joint, or isolated deficiency of the tibialis posterior (such as weakness, tenosynovitis, or rupture of the tendon) that could have contributed to the development of the valgus deformity. In the patients who had valgus deformity, quantitated electromyography demonstrated that the intensity and duration of activity of the tibialis posterior was significantly increased, apparently in an effort to support the collapsing longitudinal arch of the foot. Gait studies revealed decreases in velocity, stride length, and single-limb-support time, as well as delayed heel-rise in both groups, but the decreases were more marked in the patients who had valgus deformity. The results of this study suggest that valgus deformity of the hindfoot in rheumatoid patients results from exaggerated pronation forces on the weakened and inflamed subtalar joint. These forces are caused by alterations in gait secondary to symmetrical muscular weakness and the effort of the patient to minimize pain in the feet. Radiographs also suggested an association between the valgus deformity of the feet and valgus deformity of the knees in patients who have rheumatoid arthritis.

Pelvic exercise and gait in hemiplegia.

The purpose of this study was to describe and compare the gait of 20 patients with hemiplegia secondary to cerebrovascular accident (CVA) before and after a treatment regimen of resisted pelvic motions. Ten women and 10 men were studied, with a mean age of 48 years and a mean duration post-CVA of two months. Nine subjects (45%) were right hemiplegic, and 11 subjects (55%) were left hemiplegic. Treatment consisted of four sets of five repetitions each of manually resisted pelvic anterior-elevation and posterior-depression movements on the involved side. An insole footswitch system, knee electrogoniometer, and force walking aid were used in gait analysis performed before treatment, immediately after treatment (posttest 1), and 30 minutes after treatment (posttest 2). Results showed significant overall improvement in gait in posttest 1 (p less than .005) compared with the pretest. This improvement, however, was not maintained in posttest 2. Ten patients improved overall in posttest 1; only 4 patients also showed improvement in posttest 2. The major improvements seen immediately after treatment were observed in stance stability and limb advancement in the involved limb. More research is needed to identify an optimum treatment with carry-over using this technique.