The traditional method for normalizing quantitative strength data is to divide force or torque by body mass. We have previously shown that this method is not appropriate for able-bodied children and young adults and that normalization using allometric scaling is more effective. The purpose of the current study was to evaluate the effectiveness of applying existing normalization equations for lower extremity strength to children, adolescents, and young adults with cerebral palsy (CP) and, if appropriate, to develop CP-specific normalization equations using allometric scaling. We measured the maximum torque generated during hip abduction/adduction, knee extension/flexion, and ankle dorsiflexion/plantar flexion in 96 subjects with spastic diplegia CP ages 4–23 years. Traditional mass normalization (Torque/Mass1.0) and allometric scaling equations from children without disability (Torque/Mass1.6 for hip and knee; Torque/Mass1.4 for ankle) were not effective in eliminating the influence of body mass. Normalization using CP-specific allometric scaling equations was effective using both muscle-specific and common (Torque/Mass0.8 for ankle plantar flexors; Torque/Mass1.4 for all others) scaling relationships. For the first time, normalization equations have been presented with demonstrated effectiveness in adjusting strength measures for body size in a group of children, adolescents, and young adults with CP.
Tishya A. L. Wren and Jack R. Engsberg
Jack R. Engsberg, Richard E. A. Van Emmerik, Sandy A. Ross and David R. Collins
This investigation developed a measure of motor control at the ankle for persons with CP using relative phase. Twenty-nine subjects, 14 with spastic diplegia cerebral palsy (CP group) and 15 without disability (WD group) were tested once. Video data were collected as a seated subject performed four full range of ankle plantar and dorsiflexion movement tasks (right ankle, left ankle, ankles in-phase with each other, and ankles antiphase to each other) at four different frequencies (self-paced, 0.5, 0.75, 1.0 Hz). The relative phase measure was able to discern the differences between the two groups of children. The CP group had poorer motor control than the WD group, based upon the measure. Both groups had more difficulty performing the antiphase than the in-phase movements. The investigation adds to the body of knowledge in that the concept of relative phase was used as a measure of motor control at the ankle in persons with CP. Results indicated that the measure was adequately sensitive to quantify differences between a group with CP and a group without disability. Clinically the measure could eventually be used as both an assessment and outcome tool.
Jack R. Engsberg, Sandy A. Ross and Tae S. Park
This study was conducted to determine whether an objective and quantitative measure for active ankle range of motion would be sensitive to differences between persons of able body and those with cerebral palsy (CP), and between pre- and postselective dorsal rhizotomy (SDR). Twelve children with spastic diplegia CP were tested before undergoing an SDR, and again after 8 months of intensive physical therapy (SDR group). Fourteen other children with spastic diplegia were tested initially and again 8 months following no intervention but maintaining their existing level of physical therapy (CP group). Twenty age-matched children of able body were tested once (AB group). A video system recorded active sagittal plane ankle movements as the seated child independently performed maximum dorsiflexion and plantarflexion. The data were tracked and analyzed to determine end-range dorsiflexion and plantarflexion, and total active ankle range of motion. Repeated-measures ANOVA and Tukey post hoc tests were used to test for significant differences among and between groups, p < 0. 05. Results for the SDR group indicated a significant increase in end-range dorsiflexion and total range of motion following the surgery, with no changes in any measures for the CP group. Results for both groups with CP indicated differences vs. the AB group. The measure provided additional information from what has previously been reported for active ankle range of motion. The integration of this measure with other objective measures for quantifying impairments and presurgical function may be useful in predicting post-SDR gait status and other functional activities.
David A. Hampton, Kevin W. Hollander and Jack R. Engsberg
A theory for equinus gait in cerebral palsy (CP) is that the strong plantarflexors prevent the weak dorsiflexors from achieving dorsiflexion, thereby causing the ankle to be in a plantarflexed position. Recent work has indicated that both the ankle dorsiflexors and plantarflexors are weak. The purpose of this research was to theoretically and experimentally demonstrate that equinus deformity gait could be a compensatory strategy for plantarflexor weakness. It was hypothesized that children with CP utilize an equinus position during gait as a consequence of their weakness. A two-dimensional, sagittal plane model estimating plantarflexor forces through the Achilles tendon was developed. Five able-bodied (AB) children were tested utilizing heel-toe and progressively increasing toe walking strategies. Four children with CP were tested as they walked using their equinus gait. Results demonstrated that AB children assuming the toe walking stance progressively reduced the plantarflexor force when compared to their heel-toe walking trials. However, their toe walking strategy could not reduce the plantarflexor force level to that of the children with CP during the gait cycle. It was concluded that the equinus deformity posture complemented the CP children's plantarflexor weakness. Therefore, by implementing a concomitant strategy to maintain a reduced force state, equinus deformity could be used as a compensatory mechanism for individuals with plantarflexor weakness.
Jack R. Engsberg, Kenneth S. Olree, Sandy A. Ross and Tae S. Park
This investigation quantified maximum active resultant joint torques in children with spastic diplegia cerebral palsy and nondisabled children. An isokinetic dynamometer rotated the limb (10°/s) while the resultant knee joint torques (both assistive and resistive) during knee extension and flexion in 6 nondisabled children and 26 children with cerebral palsy were recorded. Torque-angle data were processed to calculate maximum values during extension and flexion and work done during the movements. An independent t test determined if significant differences existed between groups (p < .05). Maximum extensor and maximum flexor torques and work during extension and flexion were significantly less for the children with cerebral palsy. Results supported previously published research indicating that children with spastic diplegia were weaker than nondisabled children. Additional information regarding the weakness of the children with spastic diplegia near the end range of extension motion is presented.
Jack R. Engsberg, Sandy A. Ross, Kevin W. Hollander and T.S. Park
Hip spasticity and strength from 44 children with cerebral palsy (CP) and 44 children with able bodies (AB) were compared. For spasticity, a KinCom dynamometer abducted the passive hip at 4 different speeds and recorded the resistive adductor torques. Work values for the torque-angle data were calculated at each speed. Linear regression derived the slope for the line of best fit for the work-velocity data to determine the spasticity measure. For strength, the KinCom rotated the hip from maximum adduction to maximum abduction at a speed of 10°/s while the child performed a maximum abduction concentric contraction. Tests were reversed to record maximum adduction. Maximum torques and work by the abductors and adductors were calculated. Spasticity in the adductors for the CP group was significantly greater than values recorded for the AB group. All strength measures were significantly less than the AB group. Results provide objective information, quantifying hip spasticity and strength in children with CP.
Jack R. Engsberg, Joanne M. Wagner, Angela K. Reitenbach, Kevin W. Hollander and John W. Standeven
This investigation developed a measure of motor control for the knee extensors in adults with cerebral palsy (CP). Four adults with CP and 4 able-bodied (AB) adults participated. A KinCom dynamometer rotated the knee from approximately 90º of knee flexion to 10º/s less than the participant’s maximum knee extension at a speed of 10º/s, while the participant attempted to match a 44.5-N “target” force. The average, standard deviation, and median frequency of the force-time data were used to describe the test results. The individual force values for the AB group were near the target force and clustered together. The values for the CP group were also near the target force, but displayed greater variation. The average standard deviation for the CP group was more than three times larger than that of the AB group. The average median frequency for the CP group was less than that of the AB group. Results pointed to differing strategies for each group as they attempted to match the target force. The AB group attempted to match the target force with frequent small-magnitude force changes, while the CP group attempted to match the target force with fewer oscillations of greater magnitude. The methods employed in the present investigation are initial attempts to quantify one aspect of motor control, a visually guided tracking task.
Susan K. Grimston, Jack R. Engsberg, Reinhard Kloiber and David A. Hanley
Increased incidence of stress fracture has been reported for amenorrheic runners, while some studies have reported decreased spinal bone mass in amenorrheic runners. Based on results from these studies, one tends to associate decreased spinal bone mass with an increased risk of stress fracture. The present study compared regional bone mass and external loads during running between six female runners reporting a history of stress fracture (seven tibial and three femoral neck) and eight female runners with no history of stress fracture. Dual photon absorptiometry measures indicated significantly greater spinal (L2-L4) and femoral neck bone mineral density in stress fracture subjects (p<0.05) but no differences between groups for tibial bone density. Normalized forces recorded from Kistler force plates indicated significantly greater vertical propulsive, maximal medial, lateral, and posterior forces for stress fracture subjects during running (p<0.05).
Jack R. Engsberg, Lawrence G. Lenke, Keith H. Bridwell, Mary L. Uhrich and Connie M. Trout
This investigation determined relationships between coronal vertical alignment (CVA) and sagittal vertical alignment (SVA) variables calculated from radiographs and surface markers representing bony landmarks. Biplanar radiographs were taken on 28 subjects (standing) after 2 metallic surface markers were placed on the skin superficial to C7 and S2. The CVA-R and SVA-R were measured on the radiographs. Similar variables were calculated from the surface markers (CVA-P-R, SVA-P-R). Correlation between CVA-R and CVA-P-R was 0.894 (p < 0.000), and between SVA-R and SVA-P-R was 0.946 (p < 0.000). Results lead to three recommendations: (1) obtain surface marker data when radiographs are taken to establish relationships between the two sets of data, (2) take care in providing instructions to the subjects if measures are to be taken at different times, and (3) observe caution in interpreting results when simultaneous x-ray and surface marker data were not recorded.
Jack R. Engsberg, Kathy G. Tedford, James A. Harder and Jocelyn P. Mills
This investigation compared stance, swing, and double support times of a recent below-the-knee amputee (BKA) child’s gait with the gait of normal children and with that of experienced BKA children. Kinematic data were collected for 11 normal children, 2 experienced BKA children, and a novice BKA child. Results indicated there were significant differences between the steps of prosthetic and nonprosthetic limbs and between normals and BKAs. Initially the gait of the novice BKA differed from that of experienced BKAs. After 94 days the gait of the novice BKA was not significantly different from that of the experienced BKAs. It was concluded that since the structure and function of the prosthetic limb is not the same as normal, (a) it may be appropriate for the BKA child to have an asymmetrical gait pattern, and (b) rehabilitation may be directed toward teaching the recent BKA child to walk more like experienced BKAs than like normal children.