可偵測骨科骨板之固定螺絲鎖緊力之 被動無線感測裝置

Abstract

骨板固定系統(locking plate and screw system)是用於骨科中固定四肢骨時所使用，強化病人的四肢骨強度。若骨板固定系統之螺絲於手術時或手術後復健期間鬆動，會減弱四肢骨患部固定效果，使骨頭融合的成效降低。而目前術後檢測的方法，只能透過X光由前向、側向或斷層掃描(CT)擷取患部影像來觀察骨板系統中螺絲固定狀況。此方法在短期內骨頭並未成長時並不精確，也不適合密集多次觀察，否則會使病人接受過多的輻射劑量。而本計畫之目標即是開發可偵測骨科骨板之固定螺絲鎖緊力之被動無線感測裝置，可提供用於小腿骨之骨板系統螺絲固定狀況及鬆動位置之即時監測能力。此感測裝置將以電感電容 (LC) 電路原理進行無線被動的感測，由於LC電路之共振頻率與其電感及電容值有關，所以利用一墊片式 (washer) 感測器，使螺絲鎖緊力影響此感測器之電容值，然後藉由量測LC電路共振頻率的變化，進而得知螺絲鎖緊力。此LC式被動感測裝置不但可以以無線讀取訊號，且無需裝設電池，僅外部讀取裝置需要連接電源，因此非常適合置放於人體體內。但感測裝置會受到感測端和讀取端間介質影響共振頻率及感測距離，需要依靠共振頻率變化量推估其鎖緊力變化量，同時感測距離也需要再提升，但比起以往X-ray觀測螺絲固定狀況，此感測裝置可以提供不同螺絲鎖緊力之量化數值，更精確地提供小腿骨上螺絲的固定狀況訊息給醫療人員，有助於提早判斷是否需接受其他改善療程。

Locking plate and screw system are used in orthopedic fixed limb bone which strengthens the patient's limb bone after surgery. If the locking plate and screw system are loosened during surgery or after surgery, the fixation effect of the limb bone is weakened, and the effect of bone fusion is reduced. The current detection method is X-ray. Using X-ray from the forward, lateral or tomography (CT) can detect the affected area of the image to observe the locking plate and screw. This method does not accurate when the bones don't grow in the short term. The method is also not suitable for intensive observation because the patient will accept too much radiation dose. The aim of this project is to develop a passive wireless sensor that detects the locking force of the fixed screw on the bone plate. It can provide immediate monitoring of the screw fixation for the bone. This sensor is a wireless passive sensor based on the principle of the inductor capacitance (LC) circuit. By using LC circuit principle, we can use the change of frequency to estimate the locking force of locking plate and screw system through this device. This sensor is a passive sensor, so it can be read without the battery installed. It is very suitable for placing into the human body. But the sensor will be affected by the medium between the reader and sensor. We need to rely on the change of resonance frequency to estimated change of locking force .Then the sensing distance also need to improve. Compared with the previous method(X-ray), this sensor can provide an accurate value of screw locking force. It can help to find locking plate and screw system loosening after surgery and can be treated as soon as possible.