Android Controlled Limb Lengthen Device

This information on this website  is shared as open source for a device we have created  for remote monitoring of limb lengthening by the  Ilizarov method .  This disclosure is for discussion and experimention only.  It has not been certified as a medical device and therefore should not be used clinically.

This image show Professor Ilizarov the inventor of  this revolutionary limb lenthening proceedure without having to do open surgery

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This is a NUS Biomedical Engineering final year capstone project done by Euphie Chan during during the academic year 2015-2016 under the guidance of Prof Casey Chan. 

In this project, an automated bone transport device has been developed in order to overcome the current limitations faced in performing Ilizarov bone transport. Illizarov bone transport is used in treating critical size bone defect where the bone loss is beyond the intrinsic capacity of the bone to heal spontaneously. Bone transport involves corticotomy of the affected bone away from the removed bone defect area and gradual transport of the bone segment towards a docking site. Bone regeneration occurs at the distraction site by intramembranous ossification under slow distraction. 

Figure 1. Bone Transport Example
Critical Segmental Bone loss in distal tibia, after corticortomy in the proximal tibia, a segment of of tibial shaft is transported distally by slow distraction using the Ilzarov method to replace the bone loss in the distal tibial

Although successful, there are several limitations associated with current bone transport technique. Currently distraction is done manually by the patient after being discharged from hospital, there might be inconsistent distraction as patient fails to follow the distraction instruction. The patient is scheduled to meet the doctor normally once a month where difficulties is found in monitoring the patient’s condition. Distraction not done consistently might lead to serious consequences which involve a second surgery to separate the bone. Furthermore, manual distraction limits the possibilities in exploring and evaluating potential distraction protocol. For instances, the combination of compression with distraction has shown to be improving the outcome of bone healing. The manual distraction makes the research and clinical implementation of distraction with more intervention, such as compression, tedious and inconvenient for the patient and researcher. Therefore, the development of bone transport device that addresses the related limitations is necessary. 


We propose an automated bone transport device using external fixator, android app, microcontroller, drive system, distance sensor and motion sensor. The proposed device is designed to ensure consistent distraction and monitoring of patient when he/she is discharged home. The device also aims to provide researchers and physician an accurate and simple way in selecting distraction options. 

Proposed Solution

The main gut of our solution is the Arduino an open-source electronics platform based on easy-to-use hardware and software.  It is used as an eletronic rapid prototyping platform.

The proposed solution consists of three main parts: an Android app, an Arduino device and external fixators. The Android app should allow the user to input the parameters for bone transport treatment, including distraction rate, distraction frequency, compression rate and compression duration, which will be sent to Arduino device via Bluetooth. The Arduino device then controls the stepper motor to perform bone transport. An Infrared (IR) sensor and Inertial Measurement Unit (IMU) are proposed to be implemented into the Arduino device in order to detect the distracted bone length and affected limb motion. The feedback data should be sent to the Android app via Bluetooth so that the patient and physician can monitor the treatment progress. 

Results - Our Device

 The circuit for Arduino device and the arrangement of external fixator components in 3D drawing are shown in Figure 2 and 3. Figure 4 shows the photo of real prototype. 

Figure 2. Circuit of Arduino Device.

Figure 3. 3D drawing of external fixator 

Figure 4. Real Prototype.

The Android app seeks user permission to turn on Bluetooth once started. The user can then search for the Bluetooth devices nearby such as an Android handphone or tablet and choose the Arduino device listed to connect with as shown in Figure 5. After choosing the Arduino device, the Android app establishes Bluetooth connection with the Arduino device and starts a new activity as shown in Figure 6. New activity “Control” allows user to input the four parameters for bone transport treatment. The Android app provides multiple options for distraction frequency, compression rate and compression duration. The options are arranged in a dialog window for user to choose when “Please select” is clicked on as shown in Figure 7. 

Figure 5. Android app lists all the Bluetooth device nearby.

Figure 6. New activity allows user to set bone transport treatment parameters. 

Figure 7. Multiple options are available for the parameters. 

After setting all the parameters, the user can sent the data to Arduino by clicking on “START TREATMENT” button. Arduino then commands the stepper motor to perform bone transport as instruction received. IR sensors and IMU detects the distracted bone length and affected limb motion and send the data to Android App every 2 seconds once the Bluetooth connection is established. The data is stored in SQL Database. The user can view the data by choosing “TREATMENT DIARY” button as shown in Figure 6. The feedback information is presented over time in graphical form, depicted in Figures 8 and 9.  The user can retrieve the data by day by clicking the calendar button and choose a date from the datepicker window as shown in Figure 10. 

Figure 8. Feedback data are arranged in graph. 

Figure 9. Feedback data are arranged in graph. 

Figure 10. The app allows user to retrieve the data of a particular day. 


We have made available the source code as open source for the benefit of patients, engineers and physicians.

Github open source code for Android app here:

Disclaimer, our prototype design is only a prove of concept and it has not been certified for clinical use.
If you want to modify or use our design on patients, you have to obtain medical device clearance prior to using it on patients.