1 2 3 4 5 PM R XXX (2015) 1-8 www.pmrjournal.org 6 7 8 9 10 11 12 13 14 15 16 17 Q2 18 19 20 21 22 23 24 Abstract 25 26 27 Objective: To identify biomechanical and clinical parameters that influence knee flexion (KF) angle at initial contact (IC) and 28 during single limb stance phase of gait in children with spastic cerebral palsy (CP) who walk with flexed-knee gait. 29 Design: Retrospective analysis of gait kinematics and clinical data collected from 2010-2013. 30 31 Setting: Motion & Gait Analysis Laboratory at Lucile Packard Children’s Hospital, Stanford, CA. 32 Participants: Gait analysis data from persons with spastic CP (Gross Motor Function Classification System [GMFCS] I-III) who had no 33 prior surgery were analyzed. Participants exhibiting KF 20 at IC were included; the more-involved limb was analyzed. 34 35 Methods: Outcome measures were analyzed with respect to clinical findings, including passive range of motion, Selective Motor 36 Control Assessment for the Lower Extremity (SCALE), gait kinematics, and musculoskeletal models of muscle-tendon lengths 37 during gait. 38 Main Outcome Measures: KF at IC (KFIC) and minimum KF during single-limb support (KFSLS) were investigated. 39 40 Results: Thirty-four participants met the inclusion criteria, and their data were analyzed (20 males and 14 females, mean age 10.1 41 years, range 5-20 years). Mean KFIC was 34.4 8.4 degrees and correlated with lower SCALE score (r ¼ e0.530, P ¼ .004), later 42 peak KF during swing (r ¼ 0.614, P < .001), and shorter maximal muscle length of the semimembranosus (r ¼ e0.359, P ¼ .037). 43 44 Mean KFSLS was 18.7 14.9 and correlated to KF contracture (r ¼ 0.605, P < .001) and shorter maximal muscle length of the 45 semimembranosus (r ¼ e0.572, P < .001) and medial gastrocnemius (r ¼ e0.386, P ¼ .024). GMFCS correlated more strongly to 46 KF IC (r ¼ 0.502, P ¼ .002) than to KFSLS (r ¼ 0.371, P ¼ .031). Linear regression found that both the SCALE score (P ¼ .001) and 47 delayed timing of peak KF during swing (P ¼ .001) independently predicted KFIC. KF contracture (P ¼ .026) and maximal length of 48 49 the semimembranosus (P ¼ .043) independently predicted KFSLS. 50 Conclusion: Correlates of KFIC differed from those for KFSLS and suggest that impaired selective motor control and later timing of 51 swing-phase KF influence knee position at IC, whereas KF contracture and muscle lengths influence minimal KF in single-limb 52 53 support. These findings have important treatment implications. 54 55 56 57 58 59 motor deficits including muscle weakness, spasticity, Introduction 60 and impaired selective motor control (SMC) [3]. 61 62 Depending on the severity of these deficits and the Children with spastic cerebral palsy (CP) often walk 63 limbs involved, several different gait patterns are with excessive knee flexion (KF). Diminished knee 64 65 observed, typically involving flexed-knee gait [4]. extension during the terminal swing phase results in a 66 Impaired SMC results in abnormal movement patproblematic flexed-knee position at initial contact (IC) 67 terns during gait involving flexion or extension synerand a shortened stride [1]. Short and spastic hamstrings 68 69 gist muscle activation [5-7]. During normal terminal (semimembranosus) are thought to be the primary 70 swing, the combination of hip flexion, knee extension, cause of this abnormality; however, studies based on 71 72 and ankle dorsiflexion requires SMC. At IC, impaired musculoskeletal modeling suggest that multiple factors 73 SMC may result in coupled movement patterns are involved [2]. 74 75 involving co-activation of the quadriceps and gastrocGait abnormalities in children with spastic CP arise 76 nemius [5]. However, the influence of SMC on knee from short muscle-tendon length, as well as interrelated 77 78 79 1934-1482/$ - see front matter ª 2015 by the American Academy of Physical Medicine and Rehabilitation 80 http://dx.doi.org/10.1016/j.pmrj.2015.06.003
Original Research
Biomechanical and Clinical Correlates of Stance-Phase Knee Flexion in Persons With Spastic Cerebral Palsy Dong-wook Rha, MD, Katelyn Cahill-Rowley, MS, Jeffrey Young, MD, Leslie Torburn, DPT, Katherine Stephenson, MS, Jessica Rose, PhD
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Correlates of Stance-Phase Knee Flexion
position during stance phase of gait in CP is not well understood. The aim of this study was to identify clinical parameters and gait biomechanics that may influence KF angle at IC (KFIC) and the minimum KF angle during single-limb support (SLS) (KFSLS) in persons with spastic CP. Parameters that contribute to KFIC and KFSLS may differ, and understanding these primary contributions can better inform treatment decisions.
Methods Gait analysis data from patients with spastic CP who were tested in the Motion & Gait Analysis Lab at Lucile Packard Children’s Hospital at Stanford, CA, from September 2010 to October 2013 were retrospectively reviewed and analyzed. Inclusion criteria for participants were (1) age between 5-20 years, (2) diagnosis of spastic CP, (3) no history of orthopedic surgery, rhizotomy, or use of a baclofen pump, (4) no history of any kind of chemoneurolysis within 6 months of gait analysis, (5) the ability to walk independently without assistive devices for at least 6 m with Gross Motor Function Classification System (GMFCS) levels IeIII, and (6) exhibited excessive knee flexion of at least 20 at IC in at least one limb. The more-involved limb, defined as the limb with greater KFIC, was included in this study. Approval for this analysis was obtained through the Stanford University Institutional Review Board.
Clinical Parameters All clinical measures were routinely recorded as part of the gait analysis by a single experienced senior physiotherapist. The Selective Control Assessment of the Lower Extremity (SCALE), a clinical tool developed to quantify voluntary SMC in patients with CP [7], assesses hip flexion/extension in the side-lying position and knee extension/flexion, ankle dorsiflexion/plantar flexion, subtalar inversion/eversion, and toe flexion/extension in a sitting position. These 5 motions were graded at each joint as “normal” (2 points), “impaired” (1 point), or “unable” (0 points) for a maximum of 10 points per leg. Popliteal angle was measured supine with the contralateral hip in a neutral position [8]. The angle of hip flexion contracture, KF contracture, and ankle dorsiflexion were also measured in the supine position using a goniometer and defined as having a fixed contracture of 5 or greater. When measuring the hip flexion contracture, the contralateral hip was flexed to the chest to stabilize the hip and control for any compensatory pelvic anterior tilt. Ankle plantar flexion contracture was measured with the knee extended.
Gait Kinematics Walking was tested barefoot at a self-selected speed along a 6-m path, and marker trajectories were recorded with an 8-camera optometric system for 3-dimensional (3D) motion analysis (Motion Analysis Corporation, Santa Rosa, CA) at a sampling rate of 100 Hz to measure the kinematic data (angle of each joint) during the gait cycle. A modified Helen Hayes marker set for lower limbs was used: 18 reflective markers were placed on the sacrum, the left and right anterior superior iliac spines, the lateral mid-shaft femur, the lateral knee joint axis, the lateral mid-shaft shank, the lateral malleolus, the calcaneus, the dorsum of foot between the second and third metatarsal heads, the left and right acromion, and the left scapula. For a static calibration trial, 4 additional markers were placed on the right and left medial knee joint axis and medial malleolus. The knee joint center was defined as the midpoint between the lateral and medial knee joint spaces, just inferior to the femoral condyles, and the ankle joint center was defined as the midpoint between the lateral and medial malleolus. Based on the previously described model, OrthoTrak software, version 6.6.4 (Motion Analysis Corporation) was used to calculate joint kinematics, an average of 3 representative trials. Hip, knee, and ankle sagittal plane kinematics were analyzed in relation to KFIC and KFSLS. Muscle-Tendon Length The muscle-tendon length was estimated using the Lower Limb Extremity Model 2010, a 3D computer model of the lower extremity [9]. This model incorporated muscle architecture data collected by Ward et al [10] from 21 adult cadavers and includes geometric representation of the bones, kinematic descriptions of the joints, and Hill-type models for 44 muscle-tendon compartments in the lower limb extremity. We performed inverse kinematics of motion capture data with this model using OpenSim, a freely available biomechanics simulation application [11]. The model was scaled to match the anthropometry of each subject based on the relative distances between pairs of markers measured experimentally and the corresponding markers in the model. The muscle attachments scaled with the segments. Least-squares formulation [12] was used to compute a set of desired joint angles for tracking based on the marker trajectories from gait analysis, in order to measure the changes of muscle-tendon length during gait. We measured the lengths of 2 muscle-tendon units: the knee flexor, semimembranosus; and the ankle plantar flexor, medial head of gastrocnemius. To normalize, muscle-tendon lengths were divided by the muscle lengths when the hip, knee, and ankle were in the anatomic position, with the joint angle of hip
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flexion, abduction, and rotation, KF, and ankle dorsiflexion at 0 [13]. A minimum of 3 steps from a multistep trial was averaged to establish the maximal muscletendon length during gait cycle. Statistical Analyses The mean, standard deviation (SD), and range of clinical and biomechanical parameters were calculated. Spearman rank correlation coefficients were computed to estimate association of KF angle at IC and SLS with clinical and biomechanical parameters. Multivariate linear regression of the 2 parameters most highly correlated with each outcome measure, KFIC and KFSLS, was performed. The 2-tailed significance level was set at a < 0.05. Statistical analyses were computed with IBM SPSS statistics, version 21.0 (IBM Corporation, Armonk, NY). Colinearity of clinical and biomechanical parameters was assessed using variance inflation factors; parameters were considered noncolinear for variance inflation factors
Original Research
Biomechanical and Clinical Correlates of Stance-Phase Knee Flexion in Persons With Spastic Cerebral Palsy Dong-wook Rha, MD, Katelyn Cahill-Rowley, MS, Jeffrey Young, MD, Leslie Torburn, DPT, Katherine Stephenson, MS, Jessica Rose, PhD
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Correlates of Stance-Phase Knee Flexion
position during stance phase of gait in CP is not well understood. The aim of this study was to identify clinical parameters and gait biomechanics that may influence KF angle at IC (KFIC) and the minimum KF angle during single-limb support (SLS) (KFSLS) in persons with spastic CP. Parameters that contribute to KFIC and KFSLS may differ, and understanding these primary contributions can better inform treatment decisions.
Methods Gait analysis data from patients with spastic CP who were tested in the Motion & Gait Analysis Lab at Lucile Packard Children’s Hospital at Stanford, CA, from September 2010 to October 2013 were retrospectively reviewed and analyzed. Inclusion criteria for participants were (1) age between 5-20 years, (2) diagnosis of spastic CP, (3) no history of orthopedic surgery, rhizotomy, or use of a baclofen pump, (4) no history of any kind of chemoneurolysis within 6 months of gait analysis, (5) the ability to walk independently without assistive devices for at least 6 m with Gross Motor Function Classification System (GMFCS) levels IeIII, and (6) exhibited excessive knee flexion of at least 20 at IC in at least one limb. The more-involved limb, defined as the limb with greater KFIC, was included in this study. Approval for this analysis was obtained through the Stanford University Institutional Review Board.
Clinical Parameters All clinical measures were routinely recorded as part of the gait analysis by a single experienced senior physiotherapist. The Selective Control Assessment of the Lower Extremity (SCALE), a clinical tool developed to quantify voluntary SMC in patients with CP [7], assesses hip flexion/extension in the side-lying position and knee extension/flexion, ankle dorsiflexion/plantar flexion, subtalar inversion/eversion, and toe flexion/extension in a sitting position. These 5 motions were graded at each joint as “normal” (2 points), “impaired” (1 point), or “unable” (0 points) for a maximum of 10 points per leg. Popliteal angle was measured supine with the contralateral hip in a neutral position [8]. The angle of hip flexion contracture, KF contracture, and ankle dorsiflexion were also measured in the supine position using a goniometer and defined as having a fixed contracture of 5 or greater. When measuring the hip flexion contracture, the contralateral hip was flexed to the chest to stabilize the hip and control for any compensatory pelvic anterior tilt. Ankle plantar flexion contracture was measured with the knee extended.
Gait Kinematics Walking was tested barefoot at a self-selected speed along a 6-m path, and marker trajectories were recorded with an 8-camera optometric system for 3-dimensional (3D) motion analysis (Motion Analysis Corporation, Santa Rosa, CA) at a sampling rate of 100 Hz to measure the kinematic data (angle of each joint) during the gait cycle. A modified Helen Hayes marker set for lower limbs was used: 18 reflective markers were placed on the sacrum, the left and right anterior superior iliac spines, the lateral mid-shaft femur, the lateral knee joint axis, the lateral mid-shaft shank, the lateral malleolus, the calcaneus, the dorsum of foot between the second and third metatarsal heads, the left and right acromion, and the left scapula. For a static calibration trial, 4 additional markers were placed on the right and left medial knee joint axis and medial malleolus. The knee joint center was defined as the midpoint between the lateral and medial knee joint spaces, just inferior to the femoral condyles, and the ankle joint center was defined as the midpoint between the lateral and medial malleolus. Based on the previously described model, OrthoTrak software, version 6.6.4 (Motion Analysis Corporation) was used to calculate joint kinematics, an average of 3 representative trials. Hip, knee, and ankle sagittal plane kinematics were analyzed in relation to KFIC and KFSLS. Muscle-Tendon Length The muscle-tendon length was estimated using the Lower Limb Extremity Model 2010, a 3D computer model of the lower extremity [9]. This model incorporated muscle architecture data collected by Ward et al [10] from 21 adult cadavers and includes geometric representation of the bones, kinematic descriptions of the joints, and Hill-type models for 44 muscle-tendon compartments in the lower limb extremity. We performed inverse kinematics of motion capture data with this model using OpenSim, a freely available biomechanics simulation application [11]. The model was scaled to match the anthropometry of each subject based on the relative distances between pairs of markers measured experimentally and the corresponding markers in the model. The muscle attachments scaled with the segments. Least-squares formulation [12] was used to compute a set of desired joint angles for tracking based on the marker trajectories from gait analysis, in order to measure the changes of muscle-tendon length during gait. We measured the lengths of 2 muscle-tendon units: the knee flexor, semimembranosus; and the ankle plantar flexor, medial head of gastrocnemius. To normalize, muscle-tendon lengths were divided by the muscle lengths when the hip, knee, and ankle were in the anatomic position, with the joint angle of hip
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flexion, abduction, and rotation, KF, and ankle dorsiflexion at 0 [13]. A minimum of 3 steps from a multistep trial was averaged to establish the maximal muscletendon length during gait cycle. Statistical Analyses The mean, standard deviation (SD), and range of clinical and biomechanical parameters were calculated. Spearman rank correlation coefficients were computed to estimate association of KF angle at IC and SLS with clinical and biomechanical parameters. Multivariate linear regression of the 2 parameters most highly correlated with each outcome measure, KFIC and KFSLS, was performed. The 2-tailed significance level was set at a < 0.05. Statistical analyses were computed with IBM SPSS statistics, version 21.0 (IBM Corporation, Armonk, NY). Colinearity of clinical and biomechanical parameters was assessed using variance inflation factors; parameters were considered noncolinear for variance inflation factors
