Effect of positioning on the incidence of abnormalities of muscle tone in low-risk, preterm infants

Abstract

BACKGROUND. The preterm infant is subject to the force of gravity: when its body lies pressed against the mattress on which it is placed.

Aims: The purpose of this study was to investigate short-term effects of varied post-natal lying positions in order to prevent neuromuscular and postural abnormalities.

Methods: 60 low risk preterm infants of 31-36 weeks gestational age were enrolled for this randomised clinical trial. Initially each child underwent neurological and psychomotor assessments which included tonus and reflex protocols as well as behavioral, sensory motor and postural examinations. The lying positions of the treated group were varied (back, prone, and side) using a specially designed moldable mattress that maintained the functional position of the infant's body. The control group was placed on their stomachs, (the standard lying position used in 1994) with a standard orthopaedic bolster support under their hips. All infants underwent a second round of examinations upon discharge to assess any changes in neurological and psychomotor outcomes.

Results: The sensory-motor skills examinations showed significant abnormalities in the control group: (1) dominance of the extensor muscles due to muscle shortening, (2) hyper abduction and flexion of the arms, and (3) global neuromuscular rigidity. Psychomotor and neurological exams of the control and treatment groups showed delayed developmental muscular acquisitions for infants in the control group.

Conclusion: Regular changes in posture, while retaining correct functional positions, allowed maintenance of normal neuromuscular and osteo-articular function and permitted the development of spontaneous and functional motor activity in low-risk perterm infants.