Three-dimensional gait analysis can shed new light on walking in patients with haemophilia.

In patients with haemophilia (PWH) (from Greek "blood love"), the long-term consequences of repeated haemarthrosis include cartilage damage and irreversible arthropathy, resulting in severe impairments in locomotion. Quantifying the extent of joint damage is therefore important in order to prevent disease progression and compare the efficacy of treatment strategies. Musculoskeletal impairments in PWH may stem from structural and functional abnormalities, which have traditionally been evaluated radiologically or clinically. However, these examinations are performed in a supine position (i.e., non-weight-bearing condition). We therefore suggest three-dimensional gait analysis (3DGA) as an innovative approach designed to focus on the functional component of the joint during the act of walking. This is of the utmost importance, as pain induced by weight-bearing activities influences the functional performance of the arthropathic joints significantly. This review endeavors to improve our knowledge of the biomechanical consequences of multiple arthropathies on gait pattern in adult patients with haemophilia using 3DGA. In PWH with arthropathy, the more the joint function was altered, the more the metabolic energy was consumed. 3DGA analysis could highlight the effect of an orthopedic disorder in PWH during walking. Indeed, mechanical and metabolic impairments were correlated to the progressive loss of active mobility into the joints.

Selective bilateral activation of leg muscles after cutaneous nerve stimulation during backward walking.

During human locomotion, cutaneous reflexes have been suggested to function to preserve balance. Specifically, cutaneous reflexes in the contralateral leg's muscles (with respect to the stimulus) were suggested to play an important role in maintaining stability during locomotor tasks where stability is threatened. We used backward walking (BW) as a paradigm to induce unstable gait and analyzed the cutaneous reflex activity in both ipsilateral and contralateral lower limb muscles after stimulation of the sural nerve at different phases of the gait cycle. In BW, the tibialis anterior (TA) reflex activity in the contralateral leg was markedly higher than TA background EMG activity during its stance phase. In addition, in BW a substantial reflex suppression was observed in the ipsilateral biceps femoris during the stance-swing transition in some participants, while for medial gastrocnemius the reflex activity was equal to background activity in both legs. To test whether the pronounced crossed responses in TA could be related to instability, the responses were correlated with measures of stability (short-term maximum Lyapunov exponents and step width). These measures were higher for BW compared with forward walking, indicating that BW is less stable. However, there was no significant correlation between these measures and the amplitude of the crossed TA responses in BW. It is therefore proposed that these crossed responses are related to an attempt to briefly slow down (TA decelerates the center of mass in the single-stance period) in the light of unexpected perturbations, such as provided by the sural nerve stimulation.

Similar muscles contribute to horizontal and vertical acceleration of center of mass in forward and backward walking: implications for neural control.

Leg kinematics during backward walking (BW) are very similar to the time-reversed kinematics during forward walking (FW). This suggests that the underlying muscle activation pattern could originate from a simple time reversal, as well. Experimental electromyography studies have confirmed that this is the case for some muscles. Furthermore, it has been hypothesized that muscles showing a time reversal should also exhibit a reversal in function [from accelerating the body center of mass (COM) to decelerating]. However, this has not yet been verified in simulation studies. In the present study, forward simulations were used to study the effects of muscles on the acceleration of COM in FW and BW. We found that a reversal in function was indeed present in the muscle control of the horizontal movement of COM (e.g., tibialis anterior and gastrocnemius). In contrast, muscles' antigravity contributions maintained their function for both directions of movement. An important outcome of the present study is therefore that similar muscles can be used to achieve opposite functional demands at the level of control of the COM when walking direction is reversed. However, some muscles showed direction-specific contributions (i.e., dorsiflexors). We concluded that the changes in muscle contributions imply that a simple time reversal would be insufficient to produce BW from FW. We therefore propose that BW utilizes extra elements, presumably supraspinal, in addition to a common spinal drive. These additions are needed for propulsion and require a partial reconfiguration of lower level common networks.

Impact of ankle osteoarthritis on the energetics and mechanics of gait: the case of hemophilic arthropathy.

BACKGROUND: Osteoarthritis may affect joints in any part of the body, including the ankle. The purpose of this study was to assess the impact of ankle osteoarthritis on the energetics and mechanics of gait, while taking into account the effect of slower speed generally adopted by patients with osteoarthritis. METHODS: Using a motion analysis system, synchronous kinematic, kinetics, spatiotemporal, mechanics and metabolic gait parameters were measured in 10 patients diagnosed with ankle osteoarthritis consecutive to hemophilia. The subjects walked at a self-selected speed and their performance was compared to speed-matched normal values obtained in healthy control subjects. FINDINGS: Speed-normalization using a Z-score transformation showed a significant increase in metabolic cost (Z=1.78; P=0.006) and decrease in mechanical work (Z=-0.97; P=0.009). As a consequence, muscular efficiency also decreased (Z=-0.97; P=0.001). These changes were associated with a surprising efficacy of the pendular mechanism, i.e., an improved recovery index (Z=0.97; P=0.004). INTERPRETATION: Our findings suggest that patients with ankle osteoarthritis adopt a walking strategy which improves recovery through the pendular mechanism. This may be a compensatory mechanism in order to economize energy which would counterbalance the energy waste due to low muscle efficiency. These modifications are proportional to the impaired ankle function. Our data provides a quantitative baseline to better understand the dynamics of ankle osteoarthritis and determine the individual role that lower limb joints play in the multiple chronic joint affections.

Altered arm posture in children with cerebral palsy is related to instability during walking.

BACKGROUND: Toddlers learning to walk adopt specific 'guard' arm postures to maintain their balance during forward progression. In Cerebral Palsy (CP), the cause of the altered arm postures during walking has not been studied. AIM: To investigate whether the altered arm posture in children with CP is a compensation for instability during walking. METHODS: Vertical and horizontal hand position, and upper arm elevation angle in the sagittal plane were determined in eleven children with unilateral CP, fifteen children with bilateral CP using 3D gait analysis and compared to twenty-four TD children. A correlation analysis of these measures of arm posture to step width was made to examine the relationship between arm posture and instability. RESULTS: The hand position of children with CP was more elevated and anterior, and their upper arm was rotated more posterior than TD children. Children with unilateral CP held their most affected hand higher than their least affected. Increasing the speed accentuated the differences between groups for hand elevation. Step width correlated positively with horizontal hand position of the least affected arm in children with CP. CONCLUSION: Children with CP appear to rely on 'guard' arm postures as a compensation strategy to maintain balance while walking comparable to newly walking toddlers. Importantly, this pattern is seen on the least affected side. The substantially altered arm posture on the most affected side in children with unilateral CP, however, suggests that spasticity and associated movements are also important contributing factors.

Arm swing during walking at different speeds in children with Cerebral Palsy and typically developing children.

Children with Cerebral Palsy (CP) have difficulties walking at a normal or high speed. It is known that arm movements play an important role to achieve higher walking speeds in healthy subjects. However, the role played by arm movements while walking at different speeds has received no attention in children with CP. Therefore we investigated the use of arm movements at two walking speeds for children with diplegia (DI) and hemiplegia (HE) as compared to typically developing (TD) children. Arm and leg swing lengths were determined in 11 HE children and 15 DI children and compared to 24 TD children using 3D gait analysis at their preferred and "as fast as possible" walking speeds. We found that TD children increased walking speed more than both CP groups. HE children showed larger arm swings on the non-hemiplegic compared to the hemiplegic side for both walking speeds. In contrast to TD or DI children, the HE group did not show an increase in arm swing length with increasing walking speed. Their leg swing length was larger on the non-hemiplegic than on the hemiplegic side but only at the preferred walking speed. The DI children exhibited smaller leg swings at both walking speeds. Since arm swing is used both by DI (to increase speed) and by HE children (to compensate for the reduced movement on the affected side) it is argued that these movements are important and should be allowed (or even encouraged) in gait training procedures (such as treadmill training).

Reducing the energy cost of hemiparetic gait using center of mass feedback: a pilot study.

BACKGROUND: Hemiparetic gait following stroke requires substantial energy consumption, which would promote deconditioning and disability. Optimal modalities for decreasing this energy cost remain challenging. Excessive energy consumption, however, seems to be mainly due to extra positive muscle work to substantially lift the body's center of mass (CM) against gravity during the paretic limb swing. OBJECTIVE: The authors tested a new rehabilitation strategy in a pilot study to specifically reduce the energy cost in hemiparetic gait. METHODS: Six chronic hemiparetic patients underwent a 6-week gait training program on a treadmill with real-time feedback of their CM and were asked to reduce its increased vertical displacement. The authors assessed the walking energy cost, vertical CM displacement, kinematics, and electromyogram activity without feedback before and after treatment. RESULTS: After treatment, the vertical CM displacement decreased by 10% (P = .005), particularly when the CM vaulted over the nonparetic limb in stance, and the energy cost decreased markedly by 30% (P = .009). The paretic knee flexion in swing increased concomitantly by 45% and muscle co-contraction decreased significantly in both thigh muscles by 15%. CONCLUSIONS: The rehabilitation approach followed in this study seems remarkably effective in decreasing the walking energy cost. By treating the compensatory strategy (ie, the increased CM displacement), we also appear to treat primary deviations such as poststroke knee impairments, which is novel and complementary to current concepts in rehabilitation. This new approach is promising and merits further investigation.

The up and down bobbing of human walking: a compromise between muscle work and efficiency.

Human walking has a peculiar straight-legged style. Consequently, the body's centre of mass (CM) moves up and down with each step, which is noticeable in their up and down head bobbing while walking. This vertical CM movement enables humans to save energy via a pendulum-like mechanism but is probably a relatively recent locomotor innovation insofar as earliest bipeds may have walked flexed and flat. We investigated the mechanics, energetics, muscle efficiency and optimization of human walking by decreasing and increasing the vertical CM displacement (flat and bouncy walking) in comparison to normal walking at six speeds (1-6 km h(-1)). In both flat and bouncy walking, the pendular mechanism was reduced and the energy cost was increased. However, this increase was unexpectedly much sharper in flat walking where muscles provided normal mechanical work but with a decrease in muscle efficiency. In bouncy walking, muscles provided extra mechanical work in an efficient way. Our results showed that not only do humans bob up and down in normal walking to save energy via a pendulum-like mechanism but also to make their muscles work efficiently. Actually, walking flat makes the muscles work in unfavourable conditions that waste energy. Furthermore, we are still close to a flat CM displacement relative to our current ability to change this displacement, which suggests that reducing vertical CM displacement is indeed important but only to certain limits. Evolution may ultimately have chosen the best compromise between flat locomotion that requires little work to move and bouncy locomotion that improves muscle efficiency to minimize energy consumption.

Influence of equinus treatments on the vertical displacement of the body's centre of mass in children with cerebral palsy.

We assessed the influence of equinus gait treatments on the vertical displacement of the body's centre of mass (COM) in 21 patients with cerebral palsy (14 males, 7 females; mean age 8 y 9 mo [SD 2 y]; range 3 y 7 mo-17 y) presenting different topographical types (quadriplegia, n = 1; diplegia, n = 6; right hemiplegia, n = 6; and left hemiplegia, n = 8). Vertical COM displacement was computed from ground reaction forces, and lower limb kinematics was recorded simultaneously. Equinus gait was treated with non-operative treatments (i.e. botulinum toxin injections and stretching casts) in 14 patients, and with operative treatments in seven patients. After non-operative treatments, the entire ankle displacement shifted towards dorsiflexion throughout the gait cycle, but the amplitude of the third foot rocker (TR) and vertical COM displacement remained unchanged. However, after operative treatments, the amplitude of TR increased and vertical COM displacement decreased. A negative linear correlation was found between the former variables in all the patients where 53% of the changes in their vertical COM displacement, after equinus gait treatments, were explained by the changes in TR amplitude. In fact, TR remains a main gait determinant, reducing the vertical COM displacement after equinus gait treatment and influencing the general gait pattern.

Influence of gait pattern on the body's centre of mass displacement in children with cerebral palsy.

We assessed the influence of digitigrade gait pattern, topographical types, severity of motor involvement, and locomotor experience on the body's centre of mass (COM) displacement during gait in children with spastic cerebral palsy (CP). Three-dimensional COM displacements were computed from ground reaction forces in 51 independent digitigrade walkers (29 males, 22 females; mean age 10 years 6 months, SD 2 years 7 months, range 7 to 15 years). Results obtained from 10 participants without disabilities (five males, five females), in the same age range as the patients with CP, were used as a reference plantigrade group. Vertical and forward COM displacements were significantly different between the digitigrade and the plantigrade walkers. Neither the topographical type (quadriplegia, n=5; diplegia, n=20; right hemiplegia, n=13; left hemiplegia, n=13), nor the severity of motor involvement, nor the locomotor experience influenced COM displacements. We conclude that the COM displacement during gait in patients with CP was mainly influenced by the digitigrade gait pattern encountered in this neurological disorder rather than the different topographical types and motor involvements.