Passive mechanical properties of the gastrocnemius after spinal cord injury.

INTRODUCTION: In this study we compared passive mechanical properties of gastrocnemius muscle-tendon units, muscle fascicles, and tendons in control subjects and people with ankle contractures after spinal cord injury. METHODS: Passive gastrocnemius length-tension curves were derived from passive ankle torque-angle data obtained from 20 spinal cord injured subjects with ankle contractures and 30 control subjects. Ultrasound images of muscle fascicles were used to partition length-tension curves into fascicular and tendinous components. RESULTS: Spinal cord injured subjects had stiffer gastrocnemius muscle-tendon units (stiffness index: 74.8 ± 27.0 m(-1) ) than control subjects (54.4 ± 17.7 m(-1) ) (P = 0.004). Muscle-tendon slack lengths, as well as slack lengths and changes in length of fascicles and tendons, were similar in the two groups. CONCLUSIONS: People with ankle contractures after spinal cord injury have stiff gastrocnemius muscle-tendon units. It is not clear whether this reflects changes in properties of muscle fascicles or tendons.

Half of the adults who present to hospital with stroke develop at least one contracture within six months: an observational study.

QUESTIONS: What is the incidence of contractures six months after stroke? Can factors measured within four weeks of stroke predict the development of elbow, wrist, and ankle contractures six months later? DESIGN: Prospective cohort study. PARTICIPANTS: Consecutive sample of 200 adults with stroke admitted to a Sydney hospital. OUTCOME MEASURES: Loss of range of motion in major joints of the body was measured using a 4-point ordinal contracture scale. In addition, elbow extension, wrist extension, and ankle dorsiflexion range of motion were measured using torque-controlled procedures. Potential predictors of contracture were age, pre-morbid function, severity of stroke, muscle strength, spasticity, motor function, and pain. Measurements were obtained within four weeks of stroke and at six months after stroke. RESULTS: 52% of participants developed at least one contracture. Incidence of contracture varied across joints from 12% to 28%; shoulders and hips were most commonly affected. Muscle strength was a significant predictor of elbow, wrist, and ankle joint range. Prediction models explained only 6% to 20% of variance in elbow, wrist, and ankle joint range. CONCLUSION: About half of all patients with stroke develop at least one contracture within six months of stroke. Incidence of contractures across all joints ranged from 12% to 28%. Muscle strength is a significant predictor of elbow, wrist, and ankle contractures but cannot be used to accurately predict contractures in these joints.