早產兒和足月兒於站姿和行走下姿勢控制的發展

Abstract

早產兒是發生動作及姿勢控制障礙的高危險群。雖然早產兒發展出獨立站立和行走的能力常較足月兒晚，然而目前對於此發展階段間早產兒的姿勢控制卻仍未知。本研究目的要探討早產兒與健康足月兒於站立及行走時的姿勢控制的發展。受試嬰幼兒包括八位早產兒以及九位健康足月兒，自獨立行走前兩個月到行走後三個月期間，每個月接受一次站姿測試，並於開始獨立行走後也接受行走測試。在站姿測試裡，受試嬰幼兒接受兩種不同站立情境的測試：左手觸碰/沒有觸碰一個固定支撐平面。實驗中以力板測量嬰幼兒站立時的壓力中心於前後、左右方向的位移，並計算距離相關、速度相關及頻率三個面向的參數。在行走測試中，嬰幼兒行走於一公尺長的力板走道上，測量其壓力中心的位移以探討嬰兒於步態啟動時的姿勢控制。分析參數包含步態起始的時間，壓力中心於前後、左右方向的最大位移和達到最大位移的發生時間。研究結果顯示早產兒和足月兒的站立穩定度會隨著站與走的經驗增加而上升，在距離相關、速度相關、與頻率參數都顯示顯著改變，但距離相關變數的改變僅發生在前後方向。額外的手觸摸可減少站立時的姿勢晃動，但此穩定效果主要出現於獨立行走前一個月至行走後三個月之間，在放手行走前兩個月時則不明顯。此外，早產兒使用手支撐來維持直立站姿穩定度的效果較足月兒不佳，早產兒在步態起始過程中壓力重心往前的位移大於足月兒。隨著行走經驗的增加，嬰幼兒行走時壓力中心往前的位移也逐漸增加，而在左右方向的位移則沒有明顯變化。雖然早期的站姿與行走時的姿勢控制發展主要發生於前後方向，嬰幼兒在站姿及步態起始時的姿勢穩定度卻是於左右方向有顯著相關。本研究顯示健康的早產兒在早期站立和行走階段所展現的姿勢控制發展和足月兒相似，然而早產兒的姿勢控制中的感覺動作整合能力可能較足月兒差。嬰幼兒在早期站立及行走下的姿勢控制發展主要發生在前後方向，但因站立和行走時姿勢控制目的的異同，此二動作行為在左右方向的姿勢控制彼此相關，但在前後方向則不相關。

Preterm infants are at risk for postural and motor deficits. Walking is the most significant motor milestone acquired during infancy and is often delayed onset in preterm infants. The purpose of this study was to investigate the development of postural control in standing and walking during infancy and how it may be affected by preterm birth. Eight preterm and nine full-term infants were tested monthly for their quiet standing posture and walking performance from two months before walking onset to three months post walking. During the standing test, the infant stood independently in two conditions: with or without the hand touching a contact surface. Displacements of infants’ center of pressure (COP) in the anterior-posterior (AP) and medial-lateral (ML) directions were analyzed with distance-related, velocity-related, and frequency measures. In the walking test, the infant walked on a 1-m long walkway formed by force platforms. COP displacements during the first gait cycle were analyzed to examine the infant’s postural control in gait initiation. Duration of gait initiation phases, peak amplitudes of COP sway in AP and ML directions, and the timing to the peaks during gait initiation were analyzed. The results showed that, with increasing experience in standing and walking, both preterm and full-term infants increased their postural stability in quiet stance as revealed in distance-related, velocity-related, and frequency measures of COP sway. The developmental change of distance-related measures of COP sway only occurred in AP but not ML direction. Additional hand touch significantly attenuated standing postural sway as early as from one month before walking onset to three months post walking, but the touch effect was not so robust at two months before walking onset. Comparing to full-term infants, preterm infants showed poorer sensorimotor integration in using hand touch to help stabilize upright stance. For gait initiation, preterm infants demonstrated significantly larger forward COP sway than full-term infants did. Peak amplitude of infants’ COP forward sway during gait initiation significantly increased with increasing walking experience while no significant developmental change was observed in ML direction. Furthermore, infants’ postural stability in ML, but not AP, direction during quiet stance was significantly associated with postural stability during gait initiation. Our findings suggest that healthy preterm infants demonstrate similar postural control development with full-terms infants during early standing and walking. However, preterm infants may exhibit poorer sensorimotor integration in postural control. Early postural development in standing and walking mostly involves changes of postural control in the sagittal plane. Infants’ postural control of standing and walking are related in frontal plane stability, the aspect where the two postural behaviors share the same purpose.