Goniometric Assessment of Muscle Tone of Preterm Infants and Impact of Gestational Age on Its Maturation in Indian Setting

CONTEXT: The normative data on muscle tone of preterm infants by goniometric assessment in Indian setting are scarce. AIM: The aim of this study it to provide a normative objective data of muscle tone of preterm infants by gestation using goniometer. SETTINGS AND DESIGN: This was a prospective, observational study including preterm infants admitted in a tertiary care hospital from North India. SUBJECTS AND METHODS: The objective dimension of muscle tone assessment of 204 healthy preterm infants was done; 61 infants completed follow-up till 40 weeks’ postconceptional age (PCA) and were compared to term infants. STATISTICAL ANALYSIS USED: SPSS (version 16.0) was used. The intergroup comparison was done through ANOVA, and the localization of differences between the groups was determined through multiple comparisons by post hoc test. RESULTS: Mean gestational age was 34.3 ± 1.7 weeks. Angles were as follows: adductor = 100.1 ± 8.7, popliteal = 118.9 ± 8.6, dorsiflexion = 39.0 ± 9.0, heel to ear = 121.90 ± 7.90, wrist flexion = 46.0 ± 10.2, and arm recoil = 122.2° ± 16.6°. The evolution of muscle tone as indicated by heel-to-ear angle shows progressive maturation from 32 weeks’ gestation while adductor angle, popliteal angle, and arm recoil mature predominantly after 36 weeks’ gestation. Comparison of preterm infants to term at 40 weeks’ PCA demonstrated significantly less tone in all except posture and heel to ear. CONCLUSIONS: Goniometric assessment provides a objective normative data of muscle tone for preterm infants. Maturation of heel to ear and posture evolves from 32 weeks onwards and are the earliest neurologic marker to mature in preterm infants independent of the gestational age at birth.