足弓發育及抑制痙攣的生物力學研究

Abstract

背景：目前已有1000多篇科學論文探討扁平足議題，然而人類如何在兒童時期發展出足弓沒有完整的縱向研究；痙攣是一種神經病理現象，影響中風和脊髓損傷患者運動功能表現，並導致關節攣縮，如何有效抑制痙攣是臨床上的大議題。本研究的目的是建立一個新的扁平足分類，據此研究兒童足弓狀態的轉變，並確定與之發展相關的預後因子；並嘗試使用脈衝射頻（PRF）於背根神經節，檢測對痙攣抑制和運動表現的改變。 方法：1)前瞻性收錄小學一年級兒童的身體結構、體適能及足弓指數，進行了兩次評估；使用Chippaux-Smirak指數（CSI）的雙峰頻率分佈來定義扁平足和非扁平足。探討兒童身體結構和體適能測試，包括20米短跑，站立式跳遠和單腳平衡在扁平足及非扁平足兒童的差異、發生足弓改變及維持扁平足的差異。2) 24隻經脊髓損傷後並存活28天之大鼠，以右後肢痙攣為實驗模型，隨機分為PRF組或假手術組。PRF以2赫茲雙頻25ms持續300秒(500k赫茲，5V電壓強度)施加在右側L5背根神經節上。在PRF或假手術後的前一天、第3天、第7天和第14天，以450deg / s的被動踝背屈運動，測量右肱三頭肌的肌肉張力；並通過Basso，Beattie和Bresnahan（BBB）評分來評估運動功能。 結果：1) CSI 0.6為雙峰分布，其交叉值可區分扁平足及非扁平足，此交叉值不隨年齡、性別和體重而變化。以此足弓分類發現a)扁平足女童在單腳平衡中的表現明顯劣於非扁平足女童（前者單腳平衡測驗中位數為4.0秒，後者為4.3秒，p = 0.04，95％信賴區間0.404-0.484）。b)混合足型兒童在性別、體重、BMI及單腳平衡表現之百分比，介於雙側扁平兒童和雙側非扁平足兒童之間。c)第二年轉為非扁平足者的兒童在單腳平衡項目表現明顯改善（進步增加2.5秒，而維持扁平足者則進步1.7秒，p = 0.03）。 2) PRF後第3天肌張力明顯下降，於第14天後逐漸恢復到治療前狀態，而在假手術組中，肌肉張力在術後為持續顯著增加；PRF後BBB評分從10降至8，並在第14天後恢復到PRF前水平，而假手術後BBB評分則維持不變。 結論：兒童足弓指數的雙峰分佈，及其特殊的轉變模式，與身體自然生長不同。足弓發展與單腳平衡之間的密切關係，顯示結構與功能之間的潛在聯繫。PRF對痙攣下的肌肉張力產生顯著且可逆的抑制，但可能伴隨運動功能的惡化。這個發現警示PRF降痙治療，應考量患者的痙攣狀態及運動功能，在療效及併發症之間求取平衡，顯示可微調劑量的PRF植入裝置，而非體外一次性刺激，是未來所需。

Background: More than 1,000 scientific papers have been devoted to flatfoot issue. However, how human build foot arches has not been studied thoroughly before. Spasticity affects motion and leads to joint contracture in patients with stroke and spinal cord injury. The purposes of flatfoot study were to establish a new classification of flatfoot and to study the transition of foot arch status in children and to identify the associated factors. The spasticity study tested spasticity suppression and locomotion change after pulsed radiofrequency (PRF) at the dorsal root ganglion of rats. Methods: 1) In a prospective longitudinal study, two surveys of body structure, physical fitness and foot arch index were conducted in 1228 school aged children from 2012 to 2014. The bimodal frequency distribution of the Chippaux-Smirak index (CSI) of footprints was used to define flatfeet and non-flatfeet. The body structures and physical fitness tests, including 20-meter dash, standing long jump and one leg balance, were compared between flatfooted children and non-flatfooted children, children who transited from flatfooted to non-flatfooted and children remained in flatfooted. 2) Twenty-four rats that survived for 28 days after thoracic spinal cord injury and showed spasticity in the right hind limb were separated randomly to a PRF group or Sham operation group. PRF consisted of 2 Hz biphasic 25 ms trains of PRF (500 kHz, 5 V intensity) applied on the right L5 dorsal root ganglion for 300 seconds. Muscle tension of the right triceps surae was measured at 450deg/s of passive ankle dorsiflexion on the day before and 3, 7, and 14 days after PRF or sham operation. Locomotive function was evaluated by obtaining Basso, Beattie, and Bresnahan (BBB) scores. Results: 1) A constant intersection value of 0.6 in the CSI could distinguish the two modes of children, and values were constant by age, sex, and weight. a) Flatfoot girls had significantly inferior performance in the one leg balance than non-flatfoot girls (median, 4.0 seconds in flatfoot girls vs. 4.3 seconds in non-flatfoot girls, p=0.04, 95% CI 0.404-0.484). b) Children with mixed feet were just between the children with bilateral flatfeet and children with bilateral non-flatfeet in percentage of sex, body weight, BMI and performance of one leg balance. c) Flatfooted children who were transiting to non-flatfooted showed significantly improved performance in one leg balance (+2.5 seconds vs. +1.7 seconds in children remaining in flatfooted, p=0.03), while sex and weight were not associated with the transition. 2) Muscle tension of the triceps surae decreased significantly 3 days after PRF, and gradually returned to baseline 14 days later. In the sham operation group, muscle tension increased significantly over 14 days. The BBB scores declined from 10 to 8 after PRF and returned to pre-PRF levels 14 days later, while scores remained constant after sham operation. Conclusion: Development of children’s foot arches is a transition process that is characterized by bimodal distribution and all-or-none changes and is not attributable to body growth. The close relationship between foot arch development and one leg balance suggests underlying structure-function connection. PRF produced significant and reversible suppression in spasticity, but this was accompanied by deterioration in locomotive function. Thus, caution should be exercised in considering the benefits and costs in suppressing spasticity in ambulatory patients, and implanted devices that apply titratable doses of PRF may be best to optimize patients’ needs.