膝部旋轉性的客觀測量法－－「LARS旋轉測量儀」

Measurement of Knee Rotation with LARS Rotational Laxiometer

過去，膝部旋轉性不穩定的測量，並沒有客觀的方法，只能使用理學檢查粗略、主觀地評估。目前有一套電子水銀旋轉性的測量儀器「LARS旋轉測量儀」，對於脛骨相對於股骨旋轉的測量，準確性可到達0.1度。可惜的是我們並沒有正常人口的膝蓋旋轉角度的統計數據。國外也只有一篇文獻記載「LARS旋轉測量儀」，測量外國人口正常膝蓋的旋轉角度。目前並無國人這方面的資料。我們國內膝蓋韌帶斷裂合併後外側旋轉性不穩定損傷的病人不少。過去因為無一客觀的方法能精確的測量，因理學檢查須要經驗及比較主觀。許多病人有可能被這種主觀的方式而延誤。我們因而設計了這個研究，希望能量出自己國人的一套有統計意義的膝蓋旋轉角度的數據，藉以幫助這類病人的準確及早期診斷。我們共有兩位有經驗的測量人員，測量了三十位國人。我們測量膝蓋彎曲在90度及30度的右膝外轉角度平均分別為15.8度及16.9度；而左膝為17.6及20.0度。膝蓋彎曲90度及30度，兩膝旋轉角度差平均為3.0度及4.2度，而膝蓋彎曲以90度及30度，兩側膝蓋旋轉角度比例平均為0.20及0.28˚ 測量人員本身及兩位之間的再度檢測並無統計學上的差異。根據我們的數據，膝蓋彎曲90度及30度兩膝旋轉角度若大於5.1度及6.3度。或者兩膝旋轉角度于膝蓋彎曲90度及30度比例若大於0.28及0.36就要提高警覺病人可能合併膝部後外側旋轉性不穩損傷。在檢查及治療膝部韌帶受傷的病患時、要特別注意。

In knee ligament injury, only the antero-posterior laxity could be measured quantitatively. The measurement of rotational instability could be done by physical examination only. No objective measurement is available.Recently, Jonathan Beacon from United Kingdom with cooperation of LARS Inc. has developed a rotational Laxiometer which is a device based on an electronic mercury goniometer The rotation of the tibia in relation to femur could be measured degree by degree as precise as 0.1.We measured 30 normal Chinese-origin Taiwanese by 2 trained examiners. Mean external rotation angle in right knee at 90˚ and 30˚ are 15.8˚ and 16.9˚, in left knee are 17.6˚ and 20.0˚ respectively. The mean side to side difference of the knee at 90˚ is 3.0˚ and 30˚ is 4.2˚. Ratio of side to side difference in relative to external rotation angle of normal side was analyzed. At 90˚, the ratio is 20%, and 28% at 30˚.The data while considering factors of intra-examiner and intra-examiner measured here are of no significant different. We may define value of greater than 6.3˚ side to side difference at 30˚ flexion and 5.1˚ at 90˚ flexion as the borderline of increased rotational laxity. The ratio of the side to side difference in relative to the external rotation angle of normal side shouldn't be greater than 28% at 90˚ flexion and 36% at 30˚ flexion, otherwise increased of rotational laxity should be alerted.