Impact of a stance phase microprocessor-controlled knee prosthesis on level walking in lower functioning individuals with a transfemoral amputation.

BACKGROUND: For individuals with transfemoral amputation, walking with a prosthesis presents challenges to stability and increases the demand on the hip of the prosthetic limb. Increasing age or comorbidities magnify these challenges. Computerized prosthetic knee joints improve stability and efficiency of gait, but are seldom prescribed for less physically capable walkers who may benefit from them. OBJECTIVE: To compare level walking function while wearing a microprocessor-controlled knee (C-Leg Compact) prosthesis to a traditionally prescribed non-microprocessor-controlled knee prosthesis for Medicare Functional Classification Level K-2 walkers. STUDY DESIGN: Crossover. METHODS: Stride characteristics, kinematics, kinetics, and electromyographic activity were recorded in 10 participants while walking with non-microprocessor-controlled knee and Compact prostheses. RESULTS: Walking with the Compact produced significant increase in velocity, cadence, stride length, single-limb support, and heel-rise timing compared to walking with the non-microprocessor-controlled knee prosthesis. Hip and thigh extension during late stance improved bilaterally. Ankle dorsiflexion, knee extension, and hip flexion moments of the prosthetic limb were significantly improved. CONCLUSIONS: Improvements in walking function and stability on the prosthetic limb were demonstrated by the K-2 level walkers when using the C-Leg Compact prosthesis. CLINICAL RELEVANCE: Understanding the impact of new prosthetic designs on gait mechanics is essential to improve prescription guidelines for deconditioned or older persons with transfemoral amputation. Prosthetic designs that improve stability for safety and walking function have the potential to improve community participation and quality of life.

Impact of stance phase microprocessor-controlled knee prosthesis on ramp negotiation and community walking function in K2 level transfemoral amputees.

BACKGROUND: Microprocessor controlled prosthetic knees (MPK) offer opportunities for improved walking stability and function, but some devices' swing phase features may exceed needs of users with invariable cadence. One MPK offers computerized control of only stance (C-Leg Compact). OBJECTIVE: To assess Medicare Functional Classification Level K2 walkers' ramp negotiation performance, function and balance while using a non-MPK (NMPK) compared to the C-Leg Compact. STUDY DESIGN: Crossover. METHODS: Gait while ascending and descending a ramp (stride characteristics, kinematics, electromyography) and function were assessed in participant's existing NMPK and again in the C-Leg Compact following accommodation. RESULTS: Ramp ascent and descent were markedly faster in the C-Leg Compact compared to the NMPK (p ≤ 0.006), owing to increases in stride length (p ≤ 0.020) and cadence (p ≤ 0.020). Residual limb peak knee flexion and ankle dorsiflexion were significantly greater (12.9° and 4.9° more, respectively) during single limb support while using the C-Leg Compact to descend ramps. Electromyography (mean, peak) did not differ significantly between prosthesis. Function improved in the C-Leg Compact as evidenced by a significantly faster Timed Up and Go and higher functional questionnaire scores. CONCLUSIONS: Transfemoral K2 walkers exhibited significantly improved function and balance while using the stance-phase only MPK compared to their traditional NMPK.

Comparison of shoulder muscle electromyographic activity during standard manual wheelchair and push-rim activated power assisted wheelchair propulsion in persons with complete tetraplegia.

OBJECTIVES: To compare spatio-temporal propulsion characteristics and shoulder muscle electromyographic activity in persons with cervical spinal cord injury propelling a standard pushrim wheelchair (WC) and a commercially available pushrim-activated power assisted wheelchair (PAPAW) design on a stationary ergometer. DESIGN: Repeated measures. SETTING: Motion analysis laboratory within a rehabilitation hospital. PARTICIPANTS: Men (N=14) with complete (American Spinal Injury Association grade A or B) tetraplegia (C6=5; C7=9). INTERVENTION: Participants propelled a standard pushrim WC and PAPAW during 3 propulsion conditions: self-selected free and fast and simulated 4% or 8% graded resistance propulsion. MAIN OUTCOME MEASURES: Median speed, cycle length, cadence, median and peak electromyographic activity intensity, and duration of electromyographic activity in pectoralis major, anterior deltoid, supraspinatus, and infraspinatus muscles were compared between standard pushrim WC and PAPAW propulsion. RESULTS: A significant (P<.05) decrease in electromyographic activity intensity and duration of pectoralis major, anterior deltoid, and infraspinatus muscles and significantly reduced intensity and push phase duration of supraspinatus electromyographic activity at faster speeds and with increased resistance were seen during PAPAW propulsion. CONCLUSIONS: For participants with complete tetraplegia, push phase shoulder muscle activity was decreased in the PAPAW compared with standard pushrim WC, indicating a reduction in demands when propelling a PAPAW.

Shoulder muscular demand during lever-activated vs pushrim wheelchair propulsion in persons with spinal cord injury.

BACKGROUND/OBJECTIVE: The high demand on the upper limbs during manual wheelchair (WC) use contributes to a high prevalence of shoulder pathology in people with spinal cord injury (SCI). Lever-activated (LEVER) WCs have been presented as a less demanding alternative mode of manual WC propulsion. The objective of this study was to evaluate the shoulder muscle electromyographic activity and propulsion characteristics in manual WC users with SCI propelling a standard pushrim (ST) and LEVER WC design. METHODS: Twenty men with complete injuries (ASIA A or B) and tetraplegia (C6, n = 5; C7, n = 7) or paraplegia (n = 8) secondary to SCI propelled ST and LEVER WCs at 3 propulsion conditions on a stationary ergometer: self-selected free, self-selected fast, and simulated graded resistance. Average velocity, cycle distance, and cadence; median and peak electromyographic intensity; and duration of electromyography of anterior deltoid, pectoralis major, supraspinatus, and infraspinatus muscles were compared between LEVER and ST WC propulsion. RESULTS: Significant decreases in pectoralis major and supraspinatus activity were recorded during LEVER compared with ST WC propulsion. However, anterior deltoid and infraspinatus intensities tended to increase during LEVER WC propulsion. Participants with tetraplegia had similar or greater anterior deltoid, pectoralis major, and infraspinatus activity for both ST and LEVER WC propulsion compared with the men with paraplegia. CONCLUSIONS: Use of the LEVER WC reduced and shifted the shoulder muscular demands in individuals with paraplegia and tetraplegia. Further studies are needed to determine the impact of LEVER WC propulsion on long-term shoulder function.

A comparison of shoulder joint forces during ambulation with crutches versus a walker in persons with incomplete spinal cord injury.

OBJECTIVE: To compare 3-dimensional (3D) shoulder joint reaction forces and stride characteristics during bilateral forearm crutches and front-wheeled walker ambulation in persons with incomplete spinal cord injury (SCI). DESIGN: Cross-sectional cohort study. SETTING: Biomechanics laboratory. PARTICIPANTS: Fourteen adult volunteers with incomplete SCI recruited from outpatient rehabilitation hospital services. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Peak force, rate of loading, and force-time integral were compared for each component of the net 3D shoulder joint reaction force during ambulation with crutches and a walker. Stride characteristics were also compared between assistive device conditions. RESULTS: The largest weight-bearing force was superiorly directed, followed by the posterior force. The superior joint force demonstrated a significantly higher peak and rate of loading during crutch walking (48.9N and 311.6N/s, respectively, vs 45.3N and 199.8N/s, respectively). The largest non-weight-bearing force was inferiorly directed with a significantly greater peak occurring during crutch ambulation (43.2N vs 23.6N during walker gait). Walking velocity and cadence were similar; however, stride length was significantly greater during crutch walking (62% vs 58% of normal). CONCLUSIONS: Shoulder joint forces during assisted ambulation were large. Crutch use increased the superior force but did not increase walking velocity.

Effect of fore-aft seat position on shoulder demands during wheelchair propulsion: part 1. A kinetic analysis.

BACKGROUND/OBJECTIVE: The highly repetitive and weight-bearing nature of wheelchair (WC) propulsion has been associated with shoulder pain among persons with spinal cord injury (SCI). Manipulation of WC seat position is believed to reduce the overall demand of WC propulsion. The objective of this investigation was to document the effect of fore-aft seat position on shoulder joint kinetics. METHODS: Thirteen men with complete motor paraplegia propelled a test WC in 2 fore-aft seat positions during free, fast, and graded conditions. The seat-anterior position aligned the glenohumeral joint with the wheel axle and the seat-posterior position moved the glenohumeral joint 8 cm posteriorly. The right wheel of the test chair was instrumented to measure forces applied to the pushrim. An inverse dynamics algorithm was applied to calculate shoulder joint forces, external moments, and powers. RESULTS: For all test conditions, the superior component of the shoulder joint resultant force was significantly lower in the seat-posterior position. During graded propulsion, the posterior component of the shoulder joint force was significantly higher with the seat posterior. Peak shoulder joint moments and power were similar during free and fast propulsion. During graded propulsion, the seat-posterior position displayed increased internal rotation moment, decreased sagittal plane power absorption, and increased transverse plane power generation. CONCLUSIONS: This investigation provides objective support that a posterior seat position reduces the superior component of the shoulder joint resultant force. Consequently, this intervention potentially diminishes the risk for impingement of subacromial structures.

Effect of fore-aft seat position on shoulder demands during wheelchair propulsion: part 2. An electromyographic analysis.

BACKGROUND/OBJECTIVES: Shoulder pain is common in persons with complete spinal cord injury. Adjustment of the wheelchair-user interface has been thought to reduce shoulder demands. The purpose of this study was to quantify the effect of seat fore-aft position on shoulder muscle activity during wheelchair propulsion. METHODS: Shoulder electromyography (EMG) was recorded while 13 men with paraplegia propelled a wheelchair in the following 2 seat positions: (a) shoulder joint center aligned with the wheel axle (anterior) and (b) shoulder joint center 8 cm posterior to the wheel axle (posterior) in 3 test conditions (free, fast, and graded). Duration of EMG activity and median and peak intensities were compared. RESULTS: During free propulsion, the median EMG intensity of all muscles was similar between anterior and posterior seat positions. The major propulsive muscles (pectoralis major and anterior deltoid) demonstrated significant reductions in their median and peak intensities in the posterior seat position. Pectoralis major median intensity was significantly reduced in the posterior position during fast (52% vs 66% maximal muscle test [MMT]) and graded (41 % vs 49% MMT) conditions, and peak intensity was significantly reduced in the free condition (29% vs 52% MMT) and the fast condition (103% vs 150% MMT). Anterior deltoid intensity was significantly reduced in the posterior position during fast propulsion only (26% vs 31% MMT). For all muscles, EMG duration was similar between positions in all test conditions. CONCLUSIONS: Reduction in the intensity of the primary push phase muscles (pectoralis major and anterior deltoid) during high-demand activities of fast and graded propulsion may reduce the potential for shoulder muscle fatigue and injuries.

Upper extremity kinetics during Lofstrand crutch-assisted gait.

A three-dimensional (3D) biomechanical model was developed to determine upper extremity kinematics and kinetics of persons walking with forearm crutches. Six-component load cells and strain gauges were installed in the crutches to determine crutch forces. A six-camera VICON motion system was used to acquire coordinate data from 24 reflective markers attached to the upper extremities and crutches. Joint axes for the wrist, elbow, and glenohumeral joints were defined and joint forces and moments were determined using inverse dynamics. Accuracy of the crutch instrumentation was established by simultaneously collecting force data from a Kistler forceplate and each crutch during crutch-assisted gait with the respective crutch tip contacting the forceplate. In order to demonstrate the application of this biomechanical model, upper extremity weight bearing forces, joint motion, and stride characteristics were recorded from a subject with T-12 incomplete spinal cord injury (SCI), using a crutch-assisted reciprocal four-point gait pattern. The peak net joint forces and moments were greater for the right arm opposite the weaker left lower extremity. The largest joint forces were directed superiorly (Fz) and the asymmetrical pattern of crutch use was consistent with lower extremity strength differences. During left leg weight acceptance, increased right wrist extension motion and moment were recorded, which may contribute to wrist pathology.

Energy expenditure and gait characteristics of a bilateral amputee walking with C-leg prostheses compared with stubby and conventional articulating prostheses.

OBJECTIVE: To compare energy cost and stride characteristics during walking with 3 different types of prostheses in a person with bilateral knee disarticulations. DESIGN: Single-case study. Setting Pathokinesiology laboratory. PARTICIPANT: A subject with bilateral knee disarticulations and bilateral transradial amputations secondary to meningococcemia with purpura fulminans. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Energy cost, stride characteristics, and motion analysis. RESULTS: When wearing the C-Leg prostheses, the subject walked the farthest and fastest, with an overall lower rate of oxygen consumption and oxygen cost compared with walking with either of the other prostheses. Gait analysis while the patient was wearing the C-Leg prostheses revealed premature hip extension, absence of knee flexion during loading response, and a rate of swing in the referent range. CONCLUSIONS: Walking in a C-leg was the most efficient method of ambulation for our subject.

The supine hip extensor manual muscle test: a reliability and validity study.

OBJECTIVES: To define the relative hip extensor muscle strengths values identified by the 4 grades obtained with a supine manual muscle test (MMT) and to compare these values with those indicated by the traditional prone test. DESIGN: Comparison of 4 manual supine strength grades with isometric hip extension joint torque; kappa statistic-determined interrater reliability, and analyses of variance identified between grade differences in torque. SETTING: Pathokinesiology laboratory. PARTICIPANTS: Adult volunteers recruited from local community and outpatient clinics. Reliability testing: 16 adults with postpolio (31 limbs). Validity testing (2 groups): 18 subjects without pathology (18 limbs), and 26 people with clinical signs of hip extensor weakness (51 limbs). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Supine hip extensor manual muscle grade and isometric hip extension torque. RESULTS: Reliability testing showed excellent agreement (82%). Subjects with pathology had significant differences in mean torque (P<.01) for the assigned grade 5 (176 Nm), grade 4 (103 Nm), grade 3 (67 Nm), and grade 2 (19 Nm). Healthy adults showed significant differences between grade 5 (212 Nm) and grade 4 (120 Nm) in mean torque (P<.05). CONCLUSIONS: The supine MMT is a reliable and valid method with which to assess hip extension strength.

Effects of spinal cord injury level on the activity of shoulder muscles during wheelchair propulsion: an electromyographic study.

OBJECTIVE: To determine the influence of spinal cord injury (SCI) level on shoulder muscle function during wheelchair propulsion. DESIGN: Fine-wire electromyographic activity of 11 muscles was recorded during wheelchair propulsion. SETTING: Biomechanics research laboratory. PARTICIPANTS: Convenience sample of 69 men, in 4 groups by SCI level (low paraplegia, n=17; high paraplegia, n=19; C7-8 tetraplegia, n=16; C6 tetraplegia, n=17). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Timing of muscle activity onset, cessation, and duration, and time of peak intensity for each functional group were compared with 1-way analysis of variance. Median electromyographic intensity was also compared. RESULTS: Two functional synergies were observed: push (anterior deltoid, pectoralis major, supraspinatus, infraspinatus, serratus anterior, biceps) and recovery (middle and posterior deltoid, supraspinatus, subscapularis, middle trapezius, triceps). Push phase activity began in late recovery and ceased in early to late push. Recovery phase muscles functioned from late push to late recovery. Recruitment patterns for the groups with paraplegia were remarkably similar. For subjects with tetraplegia, pectoralis major activity was significantly prolonged compared with subjects with paraplegia (P<.05). Subscapularis activity shifted from a recovery pattern in subjects with paraplegia to a push pattern in persons with tetraplegia. CONCLUSIONS: Level of SCI significantly affected the shoulder muscle recruitment patterns during wheelchair propulsion. Differences in rotator cuff and pectoralis major function require specific considerations in rehabilitation program design.

The influence of walking speed and footwear on plantar pressures in older adults.

OBJECTIVE: To identify the influence of walking velocity and footwear condition on plantar pressure variables in healthy older adults. DESIGN: Single session data collection during varying speed and footwear conditions. BACKGROUND: Elevated plantar pressures are concerning due to the risk of tissue injury, ulceration, and pain. In young adults, increases in plantar pressure have been documented with faster walking speeds and when walking barefoot compared to wearing shoes. These relationships have not been systematically explored in older adults. METHODS: Key plantar pressure factors were recorded as subjects walked barefoot and in comfortable walking shoes across a 10 m walkway at three predetermined velocities (57, 80, 97 m/min). Separate 3x2 analyses of variance with repeated measures identified significant differences in pressure, force, and contact area in eight anatomically defined foot regions across walking speeds and between footwear conditions. RESULTS: Faster walking resulted in higher pressures under all foot regions except for the arch and lateral metatarsal (P

Electromyography of the quadriceps in patellofemoral pain with patellar subluxation.

This study compared muscle activity and timing of gait phases during functional activities in 13 subjects with patellofemoral pain associated with lateral subluxation and in 11 subjects with healthy knees. Fine wire electromyography recorded activity in the vastus lateralis and vastus medialis oblique during walking and ascending and descending stairs. Subjects were filmed to divide the activities into phases and determine timing. The vastus medialis oblique and vastus lateralis had similar patterns during all activities. Subjects with patellofemoral pain had significantly increased activity in the vastus medialis oblique and vastus lateralis compared with the healthy subjects during the most demanding phases of the gait cycle, suggesting a generalized quadriceps weakness in the patients with patellofemoral pain. Timing differences were seen in walking and stair ascending with the subjects with patellofemoral pain spending significantly more time in stance compared with the healthy subjects. This may be an attempt to reduce the load on weak quadriceps. These data reflect a generalized quadriceps muscle weakness, rather than the prevailing theory of quadriceps muscle imbalance as an etiology of patellofemoral pain. Therefore, we support the practice of strengthening the entire quadriceps muscle group, rather than attempting to specifically target the vastus medialis oblique.

Synergy of medial and lateral hamstrings at three positions of tibial rotation during maximum isometric knee flexion.

Rotation of the knee has been used to isolate the strength of the medial and lateral hamstrings during manual testing of the knee flexors. The purpose of this study was to determine if medial and lateral rotation of the knee during manual knee flexor strength testing increased the electromyographic activity of the respective hamstrings. Twenty-three women between 22 and 36 years old with no history of lower extremity injury or disease participated in the study. Indwelling fine wire electrodes were used to record EMG activity of the medial (semitendinosus and semimembranosus) and lateral (long and short heads of the biceps femoris) hamstring muscles during maximally resisted knee flexion with neutral, medial, and lateral rotation of the knee. Repeated measures analysis of variance with post hoc Bonferroni adjustments were used to compare EMG activity across the three tests. EMG activity increased significantly for the target hamstrings during ipsilateral rotation (P<0.05). The semitendinosus had a mean activity of 109% Max. during medial rotation as opposed to 95% Max. during lateral rotation. The semimembranosus averaged 107 and 89% Max. in medial and lateral rotation respectively. Conversely, both the long and short head of the biceps muscle showed significantly higher activity (P<0.05) during lateral compared to medial rotation (110 and 108% compared to 93 and 97%, respectively). Even though the differences are statistically significant they ranged from 2 to 13% only of maximum activity, the clinical importance of this small change in EMG activity is questionable.

Shoulder EMG during depression raise in men with spinal cord injury: the influence of lesion level.

BACKGROUND & OBJECTIVE: The depression-style raise maneuver is commonly performed by persons with spinal cord injury (SCI) to relieve skin pressures and avoid skin ulceration. The demands of this critical activity, however, are not fully documented for individuals with higher spinal cord lesions. The purpose of this investigation was to determine the influence of SCI lesion level on shoulder muscle activity during a depression raise maneuver. EXPERIMENTAL DESIGN: Sample of convenience, group comparison. METHODS: Fine-wire intramuscular electrodes recorded electromyographic (EMG) activity from 12 shoulder muscles in 57 men with SCI while they performed depression raises (C6 tetraplegia, n = 10; C7 tetraplegia, n = 18; high paraplegia, n = 16; low paraplegia, n = 13). EMG intensity was normalized to a manual muscle test (MMT) effort. RESULTS: For persons with paraplegia and C7 tetraplegia, dominant EMG activity was recorded from latissimus dorsi, sternal pectoralis major, and triceps muscles (31%-69% MMT). Tetraplegic groups had significantly greater anterior deltoid activity (C6 = 53%, C7 = 22% MMT) than that recorded in paraplegic groups (high paraplegia = 10%, low paraplegia = 3% MMT). Participants with tetraplegia also had increased infraspinatus activity (C6 = 50%, C7 = 32% MMT) compared with participants with low paraplegia (7% MMT). All other muscles had low or very low EMG activity during the depression raise. CONCLUSIONS: Persons with tetraplegia lack normal strength of the primary muscles used by participants with paraplegia for the depression raise (ie, latissimus dorsi, sternal pectoralis major, and triceps muscles). Although increased anterior deltoid activation assisted with elbow extension, it potentially contributes to glenohumeral joint impingement. Alternate methods of pressure relief should be considered for persons with tetraplegia.

Use of cluster analysis for gait pattern classification of patients in the early and late recovery phases following stroke.

The mixture of gait deviations seen in patients following a stroke is remarkably variable. An objective system for classification of gait patterns for this population could be used to guide treatment planning. Quantitated gait analysis was conducted for 47 individuals at admission to in-patient rehabilitation and again at 6 months post-stroke for 42 subjects. Non-hierarchical cluster analysis was used to classify the gait patterns of patients based on the temporal-spatial and kinematic parameters of walking. Four clusters of patients were identified at both assessment intervals. At the admission test walking velocity, peak knee extension in mid stance and peak dorsiflexion in swing were the three factors that best characterized the groups. At 6 months the explanatory variables were velocity, knee extension in terminal stance, and knee flexion in pre swing. Differences in muscle strength and muscle activation patterns during walking were identified between groups.

Toe walking: muscular demands at the ankle and knee.

OBJECTIVE: To compare the relationship between electromyographic activity and internal moment in heel-toe and toe walking. DESIGN: Simultaneous recording of stride characteristics and kinematic, kinetic, and intramuscular electromyographic data; paired t tests identified significant between-condition differences. SETTING: Gait laboratory. PARTICIPANTS: Ten able-bodied subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Kinematic, moment, power, and electromyographic variables (ankle, knee). RESULTS: Compared with heel-toe walking, toe walking showed greater plantarflexion during stance (P<.001), higher plantarflexor moments (peak, mean) during loading response (P<.001) and midstance (P<.001), lower mean plantarflexor moments during terminal stance (P=.002), premature soleus (P=.001) and gastrocnemius (P<.001) activity, and higher levels of mean soleus and gastrocnemius activity during stance. During toe walking, the peak internal knee extensor moment was lower in midstance (P=.002), and power absorption was reduced in loading response; however, vastus intermedius electromyographic activity was not reduced. CONCLUSIONS: During toe walking, terminal stance soleus and gastrocnemius activity was greater, despite a lower mean internal plantarflexor moment. The dichotomy between internal moments and muscle effort (ie, electromyographic activity) was consistent with the reduction in force-generation capacity of the calf muscles when the ankle was in a plantarflexed position.

Relationship between wire EMG activity, muscle length, and torque of the hamstrings.

OBJECTIVE: To determine the effect of change of muscle length on the torque and wire electromyographic activity of six knee flexor muscles. DESIGN: Maximum isometric knee flexion torque and wire EMG data were collected at nine different positions. BACKGROUND: In vivo EMG-length-tension relationship is difficult to determine because of the interaction between muscle length and moment arm. The study of two-joint muscles allows the change of muscle length at one joint while preserving stable mechanical relationships at the other. This model facilitates understanding of length-tension and EMG-length relationship in vivo. METHODS: Nineteen subjects performed maximum isometric knee flexion contraction at nine positions of varying hip and knee angles. Wire EMG activity was recorded from semitendionsus, semimembranosus, long and short head of the biceps femoris, gracilis and sartorious muscles. RESULTS: As the two-joint hamstrings were lengthened, torque was significantly increased. Maximum isometric torque ranged from 257 to 716 kg cm. The ratio of the torque values to EMG activity of all muscles was increased at longer muscle lengths. A change in the muscle length of the two-joint hamstrings did not produce a consistent change of EMG activity. The short head of the biceps femoris and sartorius muscles increased their activity as the angle of knee flexion increased. CONCLUSIONS: Maximum torque of knee flexion occurs at the most lengthened position of the hamstrings. EMG activity did not consistently change with the change in muscle length. RELEVANCE: Understanding in vivo length-tension relationship and associated EMG activity is important for designing rehabilitation protocols, tendon lengthening and transfer and interpretation of EMG data.