Joint Angular Velocity in Spastic Gait and the Influence of Muscle-Tendon Lengthening.

Joint Angular Velocity in Spastic Gait and the Influence of Muscle-Tendon Lengthening Granata KP, Abel MF, Damiano DL (Kluge Children's Rehabilitation and Research Center, University of Virginia, Charlottesville, Va), J Bone Joint Surg Am. 2000;82:174-186.

The purpose of this study was to examine the influence of muscle-tendon surgery on lower-extremity joint kinematic data and electromyographic data during gait of children with spastic cerebral palsy. Another goal was to compare lower-extremity kinematic data and electromyographic data during gait of children with spastic cerebral palsy who underwent muscle-tendon lengthening surgeries with the data of age-matched children whose development was healthy.

A total of 40 children with spastic cerebral palsy who received muscle-tendon surgeries between February 1994 and October 1996 at the University of Virginia Children's Medical Center were included in the study. Seventy-three age-matched children whose development was healthy were also evaluated. Children with moderate to severe mental retardation, extrapyramidal motor involvement, or concurrent medical conditions that required an operation or hospitalization within 6 months before the study were excluded. Children with severe torsional deformities that would warrant osteotomies were also excluded from this study.

The mean age at the time of surgery was 8.3 years (range = 3.7-14.8 years). Twenty-nine children received distal hamstring lengthening: 18 of the 29 children received medial and lateral lengthenings and the other 11 children received medial lengthening only. Thirty children received transection of the gastrocnemius-soleus muscle. Sixteen children received releases of the proximal gracilis and adductor longus muscles. In 14 children, only a single muscle-tendon group was lengthened bilaterally (6 children had distal hamstring muscle lengthenings only and 8 had gastrocnemius-soleus muscle lengthenings only). Other procedures included: transfer of the rectus femoris muscle to the hamstrings (6 children), transection of the iliopsoas muscle (3 children), transfer of the posterior tibial tendon (2 children), subtalar stapling (4 children), and osteotomy of the first metatarsal (1 child). All surgeries were performed by the same orthopedic surgeon.

The children with spastic cerebral palsy were evaluated prior to and approximately 9 months after the muscle-tendon surgeries. A total of 80 limbs were evaluated prior to and after the surgeries. However, because of missing data, a total of 154 legs from children with spastic cerebral palsy were included in this study. The children whose development was healthy were evaluated once. A total of 146 legs from this group of children were included in this study.

Each child was required to walk barefoot at self-selected speeds along a 10-m walkway while being filmed by a VICON 6-camera motion analysis system that calculated joint angular velocity data. Lower-extremity segments were identified by 15 reflective markers. A minimum of 3 trials were processed and averaged using the VICON Clinical Manager software (version 1.21). For each child, temporal and distance parameters and total joint excursions in the sagittal plane were calculated at the hip, knee, and ankle for each child. Joint angular velocities were calculated and normalized to the stride duration to remove cadence artifact. For each child, the researchers also determined peak joint angular velocities for flexion and extension and joint angle and joint angular velocity at foot-strike, midstance, and toe-off.

Electromyographic data were collected from all children with spastic cerebral palsy and from 17 legs of children whose development was healthy using bipolar surface electrodes over the rectus femoris, biceps femoris, gastrocnemius, and tibialis anterior muscles. Electromyographic data were normalized to the mean activity level observed throughout the gait cycle. Muscle co-activation about the knee (quadriceps femoris versus hamstring muscles) and ankle (gastrocnemius versus tibialis anterior muscles) was evaluated to assess the balance of muscle activity before and after the muscle-tendon surgeries.

The authors reported that children with spastic cerebral palsy were able to walk with larger strides (lengthened by 10 cm) and faster (velocity increased by 10 cm/s) after the muscle-tendon surgeries. For the joint angle data, the authors found significantly less knee flexion in children with spastic cerebral palsy after surgery. However, at foot contact and toe-off, the knee angles of children with spastic cerebral palsy were still significantly different from those of the children whose development was healthy. The authors also reported that hip and ankle joint movements in children with spastic cerebral palsy after the surgery became more similar to those of children whose development was healthy.

Significant differences in joint angular velocities were found between children with spastic cerebral palsy and children whose development was healthy. Children with spastic cerebral palsy did not show significant changes in joint angular velocities after the muscle-tendon surgery. The authors reported that, after the surgery, ankle joint angular velocities from foot contact to midstance in children with spastic cerebral palsy were more similar to those of children whose development was healthy. For the children with spastic cerebral palsy, muscle-tendon surgeries reduced abnormal plantar-flexion velocity at foot-contact through midstance.

The authors categorized motion data into 3 groups: data for the children whose development was healthy, presurgical data for children with spastic cerebral palsy, and postsurgical data for children with spastic cerebral palsy. Mathematically predicated categories were compared with actual group assignments. The authors reported that joint angle data correctly differentiated the 3 groups. Joint angular velocity data were able to accurately differentiate only between the children whose development was healthy and the children with spastic cerebral palsy, but not between the presurgical and postsurgical condition of the children with spastic cerebral palsy. The authors suspected that muscle-tendon lengthening has a limited capacity to modify joint angular velocity.

For the electromyographic data, the authors reported significant reduction of gastrocnemius activity during weight acceptance after the surgeries for children with spastic cerebral palsy. The most pronounced effect was in children who had surgeries on the gastrocnemius muscle. After the surgeries, hamstring versus quadriceps femoris muscle co-activity at toe-off was significantly reduced for children with spastic cerebral palsy.

The authors stated that joint angular velocity is an accurate way to examine gait of children by decreasing intersubject variability and reducing angle bias errors. The authors reported that reduced joint angular velocity observed in children with spastic cerebral palsy may have resulted from co-activation of antagonists or reduced muscle-tendon extensibility. Detailed discussion about joint angle and joint angular velocity changes observed in the hip, knee, and ankle joint as the result of muscle-tendon surgery was presented. According to the authors, muscle-tendon surgeries successfully modified joint angles observed while children with spastic cerebral palsy walked at self-selected speeds, but surgery did not influence the joint angular velocity profiles.

Wen Ling, PT, PhD New York University New York, NY