Development and preclinical trials of a wire-driven end effector device for frozen shoulder treatment

Several different flexible end effectors have been developed to solve the problem of approaching the lesion in a minimally invasive surgery. In this paper, we developed a wire-driven end effector device to treat frozen shoulder. Since the device is for capsular release surgery, it has a suitable bend radius for the surgery. It is a cylindrical cannula that can fit various surgical tools and can be sterilized after use. The end effector is made of an elastic material called PAI (polyamide-imide) with its outer diameter and total length being 4 and 19 mm. It is controlled by wires that are connected to a motor. Through quantitative evaluation, we confirmed that the end effector can bend up to 90° in an upward or downward direction. Through qualitative evaluation, we confirmed that the device can easier access all regions of the glenoid in a shoulder model than conventional electrocautery. An experiment on a cadaver followed, which allowed us to discuss the real life performance, operation, and areas of improvement of the device with surgeons. From the experiments, we confirmed that our target region, the IGHL (inferior glenohumeral ligament), is within the reach of our device. The surgeon also evaluated that the control of the device caused no inconvenience.