Nowadays, foot switches are used in almost every operating theatre to support the interaction with medical devices. Foot switches are especially used to release risk-sensitive functions of e.g. the drilling device, the high-frequency device or the X-ray C-arm. In general, the use of foot switches facilitates the work, since they enable the surgeon to use both hands exclusively for the manipulation within the operation procedures. Due to the increasing number of (complex) devices controlled by foot switches, the surgeons face a variety of challenges regarding usability and safety of these human-machine-interfaces.

In the future, the approach of integrated medical devices in the OR on the basis of the open communication standard IEEE 11073 gives the opportunity to provide a central surgical cockpit with a universal foot switch for the surgeon, enabling the interaction with various devices different manufacturers. In the framework of the ongoing OR.NET initiative founded on the basis of the OR.NET research project (2012–2016) a novel concept for a universal foot switch (within the framework of a surgical workstation) has been developed in order to optimise the intraoperative workflow for the OR-personnel.

Here, we developed three wireless functional models of a universal foot switch together with a standardised modular interface for visual feedback via a central surgical cockpit display. Within the development of our latest foot switch, the requirements have been inter alia to provide adequate functionalities to cover the needs for the interventions in the medical disciplines orthopaedic surgery, neurosurgery and ENT.

The evaluation has been conducted within an interaction-centered usability analysis with surgeons from orthopaedics, neurosurgery and ENT. By using the Thinking Aloud technique in a Wizard-of-Oz experiment the usability criteria effectiveness, learnability and user satisfaction have been analysed.

Regarding learnability 83.25% of the subjects stated that the usage of the universal foot switch is easy to learn. An average of 77,2% of users rated the usability of the universal foot switch between good and excellent on the SUS scale. The intuitiveness of the graphical user interface has been approved with 91.75% and the controllability with 83.25%. Finally, 86% of the subjects stated a high user satisfaction.

Pertrochanteric femoral fractures are common and intramedullary nailing with a proximal femoral nail (PFNA®) is an accepted method for the surgical treatment. Accurate guide wire and subsequent hardware placement in the femoral neck is believed to be essential in order to avoid mechanical failure. Malpositioned implants may lead to rotational or angular malalignment or “cut out” in the femoral neck. Hip and knee arthritis might be a potential long-term consequence. The conventional technique might require multiple guidewire passes, and relies heavily on fluoroscopy.

A computer-assisted surgical planning and navigation system based on 2D-fluoroscopy was developed in-house as an intraoperative guidance system for navigated guide wire placement in the femoral neck and head. To support the image acquisition process, the surgeon is supported by a so-called “zero-dose C-arm navigation” module. This tool enables a virtual radiation-free preview of the X-ray images of the femoral neck and head. The aim of this study was to compare PFNA® insertion using this system to conventional implantation technique. We hypothesised that guide wire and subsequent implant placement using our software decreases radiation exposure to the minimum of two images and reduces the number of drilling attempts. Furthermore, accuracy of implant placement in comparison to the conventional method might be improved and operation time shortened.

We used 24 identical intact left femoral Sawbones® to simulate reduced pertrochanteric femoral fractures. First, we performed placement of the PFNA® into 12 Sawbones using the conventional fluoroscopic technique (group 1). Secondly, we performed placement of the PFNA® into 12 Sawbones guided by the computer-assisted surgical planning software (group 2). In each group, we first performed open and secondly minimal-invasive intramedullary nailing in six sawbones each. For minimal-invasive guide wire placement, a surgical drape imitated soft tissue coverage. Conventional and navigated technique used a C-arm fluoroscope (Siemens IsoC 3D®, Erlangen, Germany) in conventional 2D mode. Guidewire and subsequent blade placement in the femoral neck was evaluated. We documented: 1: the number of fluoroscopic images; 2: the total number of drilling attempts; 3: implant placement accuracy (3.1. Tip apex distance (TAD); 3.2. visible penetrations of the femoral neck and head; 3.3. blade-corticalis bone distance in the anteroposterior and lateral plane) and the 4: operation time.

The number of fluoroscopic single shots taken to achieve an acceptable PFNA®-blade position was reduced significantly with computer-assistance by 71.5% (p<0.001) in the open and by 72,4% (p<0.001) in the minimally invasive technique. In each operation two X-rays for final documentation were taken. The average number of drilling attempts for the computer-guided system was significantly (p<0.05) less than that of the conventional technique in the minimally invasive procedure. The average number of drilling attempts showed no difference between the computer-assisted and conventional techniques in the open procedure. Accuracy of implant placement showed no difference between the computer-assisted and the conventional group. Computer assistance significantly increased the mean operation time for fixation of pertrochanteric femoral fractures with a PFNA® by 79.8% (p<0.001) in the open technique and by 54.4% (p<0.001) in the minimally invasive technique.

Use of our computer-guided system for fixation of pertrochanteric femoral fractures by a PFNA® decreases the number of fluoroscopic single shots and of suboptimal guide wire passes while maintaining blade placement accuracy that is equivalent to the conventional technique. Computer-assisted surgery with our system increases the operation time and has just been tested in non-fractured sawbones. Although these results are promising, additional studies including fractured sawbones and cadaver models with extension of the navigation process to all steps of PFNA® introduction and with the goal of reducing the operation time are indispensable before integration of this navigation system into the clinical workflow.

Fluoroscopic guidance is common in interventional pain procedures. In spine surgery, injections are used for differential diagnosis and determination of indication for surgical treatment as well. Fluoroscopy ensures correct needle placement and accurate delivery of the drug. Also, exact documentation of the intervention performed is possible. However, besides the patient, interventional pain physicians, surgeons and other medical staff are chronically exposed to low dose scatter radiation. The long-term adverse consequences of low dose radiation exposure to the medical staff are still unclear. Especially in university hospital settings, where education of trainees is performed, fluoroscopy time and total radiation exposure are significantly higher than in private practice settings. It remains a challenge for university hospitals to reduce the fluoroscopic time while maintaining the quality of education.

Multiple approaches have been made to reduce radiation exposure in fluoroscopy, including the wide spread use of pulsed fluoroscopy, or rarely used techniques like laser guided needle placement systems. The Zero-Dose-C-Arm-Navigation (ZDCAN) allows an optimal positioning of the c-arm without exposure to radiation. For training purposes, relevant anatomical structures can be highlighted for each interventional procedure, so injection needles can be best positioned next to the target area.

The Zero-Dose-C-Arm-Navigation (ZDCAN) module was developed to display a radiation free preview of the expected fluoroscopic image of the spine. Using an optical tracking system and a registered 3D-spine model, the expected x-ray image is displayed in real-time as a projection of the model. Additionally, selected anatomical structures including nerve roots, facet joints, vertebral discs and the epidural space, can be displayed. A seamless integration of the ZDCAN in a c-arm system already used in clinical practice for years could be achieved. For easy use, a tool was developed allowing the admission and use of regular single-use syringes and spinal needles. Accordingly, these can be used as pointers in the sterile area, a sterilization of the whole tool after every single injection is not required. We evaluated the efficiency and accuracy of this procedure compared to conventional fluoroscopically guided interventional procedures. In sawbones of the lumbar spine, facet joint injections (N = 50), perineural injections (N = 46) and epidural injections (N = 20) were performed.

Highlighting the target area in the radiation free preview model, an optimal positioning of the c-arm could be achieved even by unskilled medical staff. The desired anatomical structures could be identified easily in the x-rays taken, as they were displayed in the 3D model aside. As already seen evaluating a previous version of the ZDCAN module for the lower limb, the total number of x-ray images taken could be reduced significantly. Compared to the conventional group, the number of x-ray images required for facet joint injections could be reduced from 12.5 (±1.1) to 5.7 (±1.1), from 5.4 (±1.8) to 3.8 (±1.3) for perineural injections and from 4.1 (±0.9) to 2.1 (±0.3) for epidural injections. Total radiation time was reduced accordingly. Likewise, the mean time needed for the interventional procedure could be reduced from 168.3 s (±19.1) to 131.4 s (±16.8) for facet joint injections, was unchanged from 97.7 s (±26.0) to 104.7 s (±31.0) for perineural injections and from 60 s (±14.9) to 52 s (±7.1) for epidural injections.

The ZDCAN is a powerful tool advancing conventional fluoroscopy to another level. Using the radiation free preview model, the c-arm can easily be positioned to show the desired area. The accentuated display of the target structures in the preview model makes the introduction to fluoroscopy guided interventional procedures easier. This feature might reduce the learning curve to achieve better clinical results with lower radiation dose exposure. Thus, the ZDCAN can be a tool to improve education in university hospital settings for physicians as well as for medical staff while reducing radiation dose exposure in general use.