- Email: [email protected]
Residual limb length and gait kinematics in transfemoral and knee disarticulation amputees: Preliminary results
Published posters / Gait & Posture 24S (2006) S98–S289
S265
Table 1 Mean and S.D. for five important parameters (9 clusters and N = 342) Parameters
Walking velocity
Range of ankle motion during push off
Mean
S.D.
Mean
S.D.
Mean
S.D.
Mean
S.D.
Mean
S.D.
Cluster 1 Cluster 2 Cluster 3 Cluster 4 Cluster 5 Cluster 6 Cluster 7 Cluster 8 Cluster 9
1.1 0.6 1.0 1.1 1.0 1.2 1.0 0.8 0.9
0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.2
20.1 14.7 20.3 23.7 23.1 31.5 18.4 14.1 13.6
4.8 6.0 7.1 7.9 7.0 7.8 4.8 3.5 5.2
2.13 0.73 1.20 2.15 1.73 1.48 1.44 0.80 0.61
0.70 0.60 0.40 0.60 0.70 0.20 0.50 0.30 0.40
13.7 34.3 24.4 27.5 15.8 39.5 26.0 15.3 33.3
6.6 12.5 8.5 7.3 7.3 8.6 7.4 8.2 6.4
44.1 30.8 47.0 51.1 46.1 41.0 32.7 37.9 39.0
5.7 8.2 6.9 8.1 6.7 10.0 10.1 6.0 8.8
involvement by showing a discrete foot drop during swing phase. The ankle of patients in cluster 3 was in plantar flexion during the main part of the gait cycle. Because of the characteristics this cluster was called reversed second ankle rocker with premature knee extension. Cluster 4, double bump with jump knee, was characterised by a double bump pattern at the ankle and an increased flexion at the hip (p4/1, 4/5, 4/7, 4/8 and 4/9 < 0.001) and the knee. Patients of cluster 5 were presented with a recurvatum knee. These children walked slower (significantly different between all clusters p < 0.001 except for cluster 9) compared to normal subjects, with a clearly decreased ankle power generation at push off (p5/1, 5/2, 5/3, 5/4, 5/6 and 5/7 < 0.001). Cluster 6 was characterised by a neutral to dorsiflexed ankle, with a double bump pattern in the sagittal plane. Therefore this cluster was called apparent equinus. Due to the reversed second ankle rocker, these patients had a large power absorption at the ankle at midstance (p6/2, 6/4, 6/7 and 6/8 < 0.001). Several features of cluster 6 indicated a stiff knee pattern and a flexed hip. Cluster 7, mild crouch, demonstrated an increased dorsiflexion at loading response (p7/1, 7/2, 7/3, 7/5 and 7/9 < 0.001). Also typical for this group was the increased knee flexion throughout the stance phase. The most outstanding feature of cluster 8 was the severe crouch pattern. Furthermore the ankle showed a lack of plantar flexion during the gait cycle (p8/2, 8/3, 8/5 and 8/9 < 0.0001). Patients in cluster 9 demonstrated continuous plantar flexion at the ankle and flexion at the hip and knee, and could therefore be described as a typical triple flexion pattern. The S.D. and mean of five important parameters were illustrated in Table 1.
Max ankle power generation at Psw
Knee angle at IC
Range of sag. hip motion in stance
ters [3]. Gage’s [1] type A1 and type H2 are analogous with respectively cluster 2 and cluster 9 of this recent study. Cluster 1 is similar to the mild group described by Lin [4]. The “apparent equinus and “the double bump with jump knee” show resemblances with the jump group by Lin [4]. The “severe crouch group” of this recent study matches with the “crouch group”. Three out of four patterns, described by Rodda and Graham [5] shows similarities with the patterns described in this recent study. Clusters 4 and 6 correspond best with the “apparent equinus group”. Clusters 7 and 8 match best with the “crouch gait” and cluster 3 resembles the “true equinus group” described by Rodda and Graham [5].
References [1] [2] [3] [4] [5]
Gage JR. London: Mac Keith Press; 2004. Dobson F, Morris M, Baker R, Graham HK. Gait Posture 2006. Winters F, Gage JR, Hicks R. J Bone Joint Surg 1987;69-A(3):437–41. Lin CJ. Gait Posture 2000;11:171–5. Rodda J, Graham HK. Eur J Neurol 2001;8:98–108.
doi:10.1016/j.gaitpost.2006.11.181 PP-115 Residual limb length and gait kinematics in transfemoral and knee disarticulation amputees: Preliminary results Brian S. Baum ∗ , Jill S. Lipton, Barri L. Schnall, John E. Tis Walter Reed Army Medical Center, Washington, DC, USA
1. Summary/conclusions 6. Discussion While the patterns identified by cluster analysis appear to have statistical validity, none has become widely accepted or is regularly used by clinicians. Because of the inclusion criterion that children needed to walk independently, no severely involved pathology was detected. This might explain the fact that most of the patterns in this study showed dorsiflexion in stance, resulting in little agreement with the research of Win-
Preliminary results indicated no correlation between limb ratio (residual versus intact femoral length) and kinematics in unilateral transfemoral and knee disarticulation patients with limb ratios greater than 50%. This may indicate that midto long residual limb lengths do not dramatically alter gait, thus affording the surgeon more flexibility in choosing the amputation level in order to preserve soft tissue quality and improve prosthetic fitting.
S266
Published posters / Gait & Posture 24S (2006) S98–S289
2. Introduction Knowledge of the kinematic profile of modern transfemoral (TF) and knee disarticulation (KD) amputee gait will lead to better understanding of the mechanisms behind the increased metabolic cost of amputees [1]. Further delineating the effects of residual limb length on gait will give valuable information to guide surgical decision making. Few studies have examined unilateral TF gait kinematics and, to our knowledge, only one study has correlated femoral residual limb lengths and gait variables [2]. No literature was found on KD gait kinematics, and no studies have reported kinematic results for either population including only young, otherwise healthy subjects who use modern microprocessorcontrolled prostheses. A wide range of values are reported between subjects in gait variables [2–5] suggesting that TF amputees are not a uniform group, and most studies investigating this population are plagued by small populations. Therefore, the purpose of this study was to describe kinematic trends correlated with the length of the residual femur in TF and KD amputees. It was hypothesized that shorter limb lengths would correlate with greater kinematic gait deviations, specifically related to hip flexion, pelvic tilt, trunk lateral flexion, and trunk forward lean.
Fig. 1. Pelvic tilt of two amputee subjects with limb ratios of 57% (blue) and 100% (red) compared with ±1 S.D. of the control group average (gray). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
3. Statement of clinical significance Identifying how residual limb lengths affect gait will help guide surgeons choose the level at which to perform amputations to preserve soft tissue quality and improve prosthetic fitting. 4. Methods
Fig. 2. Correlation of limb ratio to pelvic tilt excursion including all data points (red) and with an outlier removed (blue). The outlying data point has been highlighted red. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
Ten traumatic unilateral amputees (9 TF, 1 KD) performed gait analyses wearing C-Leg (Otto Bock, Germany) knee units, which was their every-day prosthetic limb. Ten age, height, and weight matched controls were tested for comparison. The residual and intact limbs of the amputee group were measured to determine the limb ratio (residual femoral length relative to intact femoral length). Gait analysis was performed using eight Eagle® cameras (Motion Analysis Corp., USA) while subjects walked across an 8-m walkway at their self-selected velocity. At least six trials were collected for averaging purposes. Limb ratio was correlated with kinematic parameters using Pearson’s correlation coefficient. Differences between amputee and control groups were determined using Student’s paired t-test. For all statistical tests, significance was set at p < 0.05.
control group had an age, height, and weight of 29.3 (5.6) years, 176.4 (7.7) cm, and 80.8 (8.8) kg, respectively. Femoral residual limb ratios ranged from 57 to 100%. Amputees had significantly slower cadence, greater step width, and asymmetric support time (longer on the affected limb) compared to controls (p < 0.05 for all), but no difference in velocity was observed. Amputees had significantly greater trunk forward lean, lateral flexion, and rotation excursions; greater anterior pelvic tilt average and excursion (Fig. 1); and greater unaffected hip flexion range and peak flexion than the control group (p ≤ 0.03 for all). Limb ratio did not correlate with any kinematic parameter; however, after removing an outlier, the pelvic tilt excursion correlation increased to R2 = 0.61 (Fig. 2), which was significant.
5. Results
6. Discussion
The amputee group had an average (S.D.) age of 28.4 (6.9) years, height of 179.7 (7.6) cm, weight of 81.0 (10.9) kg, and time from injury of 254 (range: 124–615) days. The
The temporal-spatial results generally matched well with other studies [2,5]. Interestingly, there was no difference in velocity between the amputee and control groups, and the
Published posters / Gait & Posture 24S (2006) S98–S289
velocity of the amputee group (1.12 m/s) was greater than the self-selected velocities reported in other studies [1–3]. This difference may be attributed to a unique military population generally consisting of very fit soldiers who are motivated to either return to duty or return to active lifestyles. A significant correlation existed between smaller limb ratios and increased pelvic tilt excursion only after removing an “outlier” from the group, increasing the value from R2 = 0.33 to R2 = 0.61. This highlights the need for a larger study population, but it is anticipated that a significant correlation will arise for this variable. Consequently, as residual limbs of unilateral TF amputees get shorter, the pelvis may be used more as a mode to swing the prosthetic leg forward. This compensation may result in increases in energy cost during gait. Metabolic cost was not tested, so a direct comparison cannot be made, but this calls for the need to concurrently examine gait and metabolic cost in this group of patients. No correlation existed between limb ratio and any other kinematic parameter. Therefore, residual femoral limb lengths greater than 50% of the intact limb may not have profound effects on gait parameters, thus allowing surgeons to resect more of the residual limb to allow for complex modern prostheses and to preserve soft tissue quality. It remains to be seen whether the current observations will persist with a larger sample size and whether patients with shorter femoral residual limbs have more deviant gait patterns. More research is needed to answer these questions and to further delineate the effects of limb length on gait patterns and efficiency.
References [1] [2] [3] [4] [5]
Waters RL, et al. JBJS 1976;58-A:42–6. Jaegers SMHJ, et al. Arch Phys Med Rehabil 1995;76:736–42. Boonstra AM, et al. Arch Phys Med Rehabil 1996;77:515–20. Michaud SB, et al. J Rehabil Res Dev 2000;37:1–10. Rabuffetti M, et al. Prosth Orthot Int 2005;29:183–92.
doi:10.1016/j.gaitpost.2006.11.182 PP-116 A comparison of gait initiation in typically developing children and children with cerebral palsy Carrie Stackhouse a,∗ , Carole Tucker a , Patricia A. b b Shewokis , Margo Orlin , Kyle Josephic a , Sam Pierce a , Brian Smith a , James McCarthy a a b
Shriners Hospital for Children, Philadelphia, PA, USA Drexel University, Philadelphia, PA, USA
1. Summary/conclusions The motor program for gait initiation (GI) is present in children with cerebral palsy (CP), however, anticipatory movements are less efficient resulting in reduced forward
S267
momentum development compared to children with typical development (TD).
2. Introduction When initiating gait, the goal is to maintain dynamic balance while the body’s center of mass (CoM) moves outside the base of support. This presents a challenge for children with CP who may have difficulty maintaining balance even in static situations. In healthy adults, anticipatory adjustments during GI create a characteristic shift of the center of pressure (CoP) posteriorly and laterally towards the stance foot to assist with the subsequent increase in the forward momentum necessary for effective stepping. In older-adults, an age-related decline in GI biomechanics occurs and the momentum developing capacity of the older adults is reduced producing alternative GI strategies [1]. Development of GI in TD children follows a progression of increases in the magnitude of muscle activation and CoP displacement resulting in a greater forward velocity. In younger children the posterior shift in CoP does not correlate to development of forward momentum [2]. There is limited information on central mechanisms of GI in children with CP.
3. Statement of clinical significance Evaluation of the GI motor program in children with CP is a way to characterize impairment of the motor control system and to determine the efficacy of interventions aimed at improving movement coordination and balance.
4. Methods Ground reaction forces, surface electromyography (EMG), and 3-D motion data were acquired during GI at three different self-selected speeds (slow, medium, and fast) from 10 children with CP (6 spastic diplegia, 4 hemiplegia) and 18 children of TD ages 7–12 years. EMG data were collected bilaterally from the following muscles: rectus femoris, vastus lateralis, medial hamstring, tibialis anterior, medial gastrocnemius, and soleus. The subject was instructed to stand quietly with their arms comfortably at their sides, to look straight ahead and to start walking upon hearing an auditory cue. A representative trial at each speed was selected for analysis. A marker placed on the sacrum was tracked in order to estimate the location of the body’s CoM. CoP during GI was evaluated from the time of the first indication of intent to initiate gait (defined by the point at which the CoP trajectory velocity reached a critical threshold) until the time both feet had moved off the force plate. CoP trajectories were normalized in the anterior–posterior (AP) direction to foot length and in the mediolateral (ML) direction to stance width.
S265
Table 1 Mean and S.D. for five important parameters (9 clusters and N = 342) Parameters
Walking velocity
Range of ankle motion during push off
Mean
S.D.
Mean
S.D.
Mean
S.D.
Mean
S.D.
Mean
S.D.
Cluster 1 Cluster 2 Cluster 3 Cluster 4 Cluster 5 Cluster 6 Cluster 7 Cluster 8 Cluster 9
1.1 0.6 1.0 1.1 1.0 1.2 1.0 0.8 0.9
0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.2
20.1 14.7 20.3 23.7 23.1 31.5 18.4 14.1 13.6
4.8 6.0 7.1 7.9 7.0 7.8 4.8 3.5 5.2
2.13 0.73 1.20 2.15 1.73 1.48 1.44 0.80 0.61
0.70 0.60 0.40 0.60 0.70 0.20 0.50 0.30 0.40
13.7 34.3 24.4 27.5 15.8 39.5 26.0 15.3 33.3
6.6 12.5 8.5 7.3 7.3 8.6 7.4 8.2 6.4
44.1 30.8 47.0 51.1 46.1 41.0 32.7 37.9 39.0
5.7 8.2 6.9 8.1 6.7 10.0 10.1 6.0 8.8
involvement by showing a discrete foot drop during swing phase. The ankle of patients in cluster 3 was in plantar flexion during the main part of the gait cycle. Because of the characteristics this cluster was called reversed second ankle rocker with premature knee extension. Cluster 4, double bump with jump knee, was characterised by a double bump pattern at the ankle and an increased flexion at the hip (p4/1, 4/5, 4/7, 4/8 and 4/9 < 0.001) and the knee. Patients of cluster 5 were presented with a recurvatum knee. These children walked slower (significantly different between all clusters p < 0.001 except for cluster 9) compared to normal subjects, with a clearly decreased ankle power generation at push off (p5/1, 5/2, 5/3, 5/4, 5/6 and 5/7 < 0.001). Cluster 6 was characterised by a neutral to dorsiflexed ankle, with a double bump pattern in the sagittal plane. Therefore this cluster was called apparent equinus. Due to the reversed second ankle rocker, these patients had a large power absorption at the ankle at midstance (p6/2, 6/4, 6/7 and 6/8 < 0.001). Several features of cluster 6 indicated a stiff knee pattern and a flexed hip. Cluster 7, mild crouch, demonstrated an increased dorsiflexion at loading response (p7/1, 7/2, 7/3, 7/5 and 7/9 < 0.001). Also typical for this group was the increased knee flexion throughout the stance phase. The most outstanding feature of cluster 8 was the severe crouch pattern. Furthermore the ankle showed a lack of plantar flexion during the gait cycle (p8/2, 8/3, 8/5 and 8/9 < 0.0001). Patients in cluster 9 demonstrated continuous plantar flexion at the ankle and flexion at the hip and knee, and could therefore be described as a typical triple flexion pattern. The S.D. and mean of five important parameters were illustrated in Table 1.
Max ankle power generation at Psw
Knee angle at IC
Range of sag. hip motion in stance
ters [3]. Gage’s [1] type A1 and type H2 are analogous with respectively cluster 2 and cluster 9 of this recent study. Cluster 1 is similar to the mild group described by Lin [4]. The “apparent equinus and “the double bump with jump knee” show resemblances with the jump group by Lin [4]. The “severe crouch group” of this recent study matches with the “crouch group”. Three out of four patterns, described by Rodda and Graham [5] shows similarities with the patterns described in this recent study. Clusters 4 and 6 correspond best with the “apparent equinus group”. Clusters 7 and 8 match best with the “crouch gait” and cluster 3 resembles the “true equinus group” described by Rodda and Graham [5].
References [1] [2] [3] [4] [5]
Gage JR. London: Mac Keith Press; 2004. Dobson F, Morris M, Baker R, Graham HK. Gait Posture 2006. Winters F, Gage JR, Hicks R. J Bone Joint Surg 1987;69-A(3):437–41. Lin CJ. Gait Posture 2000;11:171–5. Rodda J, Graham HK. Eur J Neurol 2001;8:98–108.
doi:10.1016/j.gaitpost.2006.11.181 PP-115 Residual limb length and gait kinematics in transfemoral and knee disarticulation amputees: Preliminary results Brian S. Baum ∗ , Jill S. Lipton, Barri L. Schnall, John E. Tis Walter Reed Army Medical Center, Washington, DC, USA
1. Summary/conclusions 6. Discussion While the patterns identified by cluster analysis appear to have statistical validity, none has become widely accepted or is regularly used by clinicians. Because of the inclusion criterion that children needed to walk independently, no severely involved pathology was detected. This might explain the fact that most of the patterns in this study showed dorsiflexion in stance, resulting in little agreement with the research of Win-
Preliminary results indicated no correlation between limb ratio (residual versus intact femoral length) and kinematics in unilateral transfemoral and knee disarticulation patients with limb ratios greater than 50%. This may indicate that midto long residual limb lengths do not dramatically alter gait, thus affording the surgeon more flexibility in choosing the amputation level in order to preserve soft tissue quality and improve prosthetic fitting.
S266
Published posters / Gait & Posture 24S (2006) S98–S289
2. Introduction Knowledge of the kinematic profile of modern transfemoral (TF) and knee disarticulation (KD) amputee gait will lead to better understanding of the mechanisms behind the increased metabolic cost of amputees [1]. Further delineating the effects of residual limb length on gait will give valuable information to guide surgical decision making. Few studies have examined unilateral TF gait kinematics and, to our knowledge, only one study has correlated femoral residual limb lengths and gait variables [2]. No literature was found on KD gait kinematics, and no studies have reported kinematic results for either population including only young, otherwise healthy subjects who use modern microprocessorcontrolled prostheses. A wide range of values are reported between subjects in gait variables [2–5] suggesting that TF amputees are not a uniform group, and most studies investigating this population are plagued by small populations. Therefore, the purpose of this study was to describe kinematic trends correlated with the length of the residual femur in TF and KD amputees. It was hypothesized that shorter limb lengths would correlate with greater kinematic gait deviations, specifically related to hip flexion, pelvic tilt, trunk lateral flexion, and trunk forward lean.
Fig. 1. Pelvic tilt of two amputee subjects with limb ratios of 57% (blue) and 100% (red) compared with ±1 S.D. of the control group average (gray). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
3. Statement of clinical significance Identifying how residual limb lengths affect gait will help guide surgeons choose the level at which to perform amputations to preserve soft tissue quality and improve prosthetic fitting. 4. Methods
Fig. 2. Correlation of limb ratio to pelvic tilt excursion including all data points (red) and with an outlier removed (blue). The outlying data point has been highlighted red. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
Ten traumatic unilateral amputees (9 TF, 1 KD) performed gait analyses wearing C-Leg (Otto Bock, Germany) knee units, which was their every-day prosthetic limb. Ten age, height, and weight matched controls were tested for comparison. The residual and intact limbs of the amputee group were measured to determine the limb ratio (residual femoral length relative to intact femoral length). Gait analysis was performed using eight Eagle® cameras (Motion Analysis Corp., USA) while subjects walked across an 8-m walkway at their self-selected velocity. At least six trials were collected for averaging purposes. Limb ratio was correlated with kinematic parameters using Pearson’s correlation coefficient. Differences between amputee and control groups were determined using Student’s paired t-test. For all statistical tests, significance was set at p < 0.05.
control group had an age, height, and weight of 29.3 (5.6) years, 176.4 (7.7) cm, and 80.8 (8.8) kg, respectively. Femoral residual limb ratios ranged from 57 to 100%. Amputees had significantly slower cadence, greater step width, and asymmetric support time (longer on the affected limb) compared to controls (p < 0.05 for all), but no difference in velocity was observed. Amputees had significantly greater trunk forward lean, lateral flexion, and rotation excursions; greater anterior pelvic tilt average and excursion (Fig. 1); and greater unaffected hip flexion range and peak flexion than the control group (p ≤ 0.03 for all). Limb ratio did not correlate with any kinematic parameter; however, after removing an outlier, the pelvic tilt excursion correlation increased to R2 = 0.61 (Fig. 2), which was significant.
5. Results
6. Discussion
The amputee group had an average (S.D.) age of 28.4 (6.9) years, height of 179.7 (7.6) cm, weight of 81.0 (10.9) kg, and time from injury of 254 (range: 124–615) days. The
The temporal-spatial results generally matched well with other studies [2,5]. Interestingly, there was no difference in velocity between the amputee and control groups, and the
Published posters / Gait & Posture 24S (2006) S98–S289
velocity of the amputee group (1.12 m/s) was greater than the self-selected velocities reported in other studies [1–3]. This difference may be attributed to a unique military population generally consisting of very fit soldiers who are motivated to either return to duty or return to active lifestyles. A significant correlation existed between smaller limb ratios and increased pelvic tilt excursion only after removing an “outlier” from the group, increasing the value from R2 = 0.33 to R2 = 0.61. This highlights the need for a larger study population, but it is anticipated that a significant correlation will arise for this variable. Consequently, as residual limbs of unilateral TF amputees get shorter, the pelvis may be used more as a mode to swing the prosthetic leg forward. This compensation may result in increases in energy cost during gait. Metabolic cost was not tested, so a direct comparison cannot be made, but this calls for the need to concurrently examine gait and metabolic cost in this group of patients. No correlation existed between limb ratio and any other kinematic parameter. Therefore, residual femoral limb lengths greater than 50% of the intact limb may not have profound effects on gait parameters, thus allowing surgeons to resect more of the residual limb to allow for complex modern prostheses and to preserve soft tissue quality. It remains to be seen whether the current observations will persist with a larger sample size and whether patients with shorter femoral residual limbs have more deviant gait patterns. More research is needed to answer these questions and to further delineate the effects of limb length on gait patterns and efficiency.
References [1] [2] [3] [4] [5]
Waters RL, et al. JBJS 1976;58-A:42–6. Jaegers SMHJ, et al. Arch Phys Med Rehabil 1995;76:736–42. Boonstra AM, et al. Arch Phys Med Rehabil 1996;77:515–20. Michaud SB, et al. J Rehabil Res Dev 2000;37:1–10. Rabuffetti M, et al. Prosth Orthot Int 2005;29:183–92.
doi:10.1016/j.gaitpost.2006.11.182 PP-116 A comparison of gait initiation in typically developing children and children with cerebral palsy Carrie Stackhouse a,∗ , Carole Tucker a , Patricia A. b b Shewokis , Margo Orlin , Kyle Josephic a , Sam Pierce a , Brian Smith a , James McCarthy a a b
Shriners Hospital for Children, Philadelphia, PA, USA Drexel University, Philadelphia, PA, USA
1. Summary/conclusions The motor program for gait initiation (GI) is present in children with cerebral palsy (CP), however, anticipatory movements are less efficient resulting in reduced forward
S267
momentum development compared to children with typical development (TD).
2. Introduction When initiating gait, the goal is to maintain dynamic balance while the body’s center of mass (CoM) moves outside the base of support. This presents a challenge for children with CP who may have difficulty maintaining balance even in static situations. In healthy adults, anticipatory adjustments during GI create a characteristic shift of the center of pressure (CoP) posteriorly and laterally towards the stance foot to assist with the subsequent increase in the forward momentum necessary for effective stepping. In older-adults, an age-related decline in GI biomechanics occurs and the momentum developing capacity of the older adults is reduced producing alternative GI strategies [1]. Development of GI in TD children follows a progression of increases in the magnitude of muscle activation and CoP displacement resulting in a greater forward velocity. In younger children the posterior shift in CoP does not correlate to development of forward momentum [2]. There is limited information on central mechanisms of GI in children with CP.
3. Statement of clinical significance Evaluation of the GI motor program in children with CP is a way to characterize impairment of the motor control system and to determine the efficacy of interventions aimed at improving movement coordination and balance.
4. Methods Ground reaction forces, surface electromyography (EMG), and 3-D motion data were acquired during GI at three different self-selected speeds (slow, medium, and fast) from 10 children with CP (6 spastic diplegia, 4 hemiplegia) and 18 children of TD ages 7–12 years. EMG data were collected bilaterally from the following muscles: rectus femoris, vastus lateralis, medial hamstring, tibialis anterior, medial gastrocnemius, and soleus. The subject was instructed to stand quietly with their arms comfortably at their sides, to look straight ahead and to start walking upon hearing an auditory cue. A representative trial at each speed was selected for analysis. A marker placed on the sacrum was tracked in order to estimate the location of the body’s CoM. CoP during GI was evaluated from the time of the first indication of intent to initiate gait (defined by the point at which the CoP trajectory velocity reached a critical threshold) until the time both feet had moved off the force plate. CoP trajectories were normalized in the anterior–posterior (AP) direction to foot length and in the mediolateral (ML) direction to stance width.