e‑Lavage.
During hip replacement surgery or major orthopedic procedures, bone material is milled away. The resulting chips and tissue remnants must be reliably removed from the surgical site. Irrigation systems such as e-Lavage are used to clean the bone side of the implant so that the cement adheres better and the implants are therefore better anchored.
Until now, complete disposable systems have often been used for this purpose. This means that the handpiece, tubing, drive, power supply, etc. are all disposed of after an operation. This costs money and resources.
H&B wanted to improve this standard and develop a partially reusable irrigation system. The idea is that only the components that come into contact with patients and irrigation fluid are disposed of. These include, for example, the tube set and sterile cover. Reprocessing is not necessary because the drive unit is not contaminated and has no contact with the patient. This reduces the amount of material used without compromising hygiene, performance, or handling.
H&B provides the strong foundation in mechanics and production. As a development partner, we contribute electronics, embedded software, and testing to ensure a safe, reusable drive system.
In cooperation with H&B, we took on the hardware and software development of the drive unit and a 4-channel Li-ion charging station for intraoperative use. The goal was to design a classic single-use system in such a way that key components could be used multiple times while maintaining the same energy efficiency, safety, and usability.
Our tasks in the field of electronics included selecting a suitable microcontroller, dimensioning the DC/DC converter including EMC-optimized PCB layout, defining the interfaces between hardware and software, and evaluating boundary conditions from industrial design to power consumption. In addition, we kept an eye on manufacturability and manufacturing costs, collaborated on the assembly and service concept, and provided options for later software updates.
The drive unit delivers a peak power of 30 W from a single Li-ion cell with a nominal voltage of 3.7 V. The electronics stabilize the supply to the BLDC motor at 12 V. The basis is a DC/DC converter with an input voltage range of 2.6 to 4.2 V and a stabilized output voltage of 12.1 V, designed for high efficiency. The motor is operated at approx. 2.5 A at 12 V, and the battery provides a current of approx. 8.1 A at 30 W. The currents are not constant over time; current peaks of over 22 A can occur. A battery protection circuit monitors the Li-ion cell and intervenes when discharge currents exceed 22 A, also protecting against deep discharge.
The drive unit has a design measuring approximately 140 mm × 25 mm × 30 mm, making it compact enough to be easily integrated into the ergonomic handpiece.
For the charging station, we have implemented a holder for four drive units with a quick-charge function. Charging currents of up to 3 A are provided per channel, and the total power of 60 W is dissipated via free convection. The power supply is designed for international markets. Connectors and pogo pins are optimized for very low contact transition resistances. An LED charging indicator with a synchronous fade effect supports handling in everyday surgical practice.
The scope of the project also includes tools for an automatic test station. These include a USB adapter for connecting the drive unit to the test station, as well as test and commissioning adapters. The charging station is powered by an external AC/DC power supply with an output voltage of 24 V DC at 2.5 A. The internal power supply is 5 V with a power of 55 W. The electronics are designed discretely with THT components. A charge controller controls 4 drive units with a Li-ion charge controller IC up to a charging current of 3 A. The LED display is controlled directly via the software, and an interface for LAN communication is also available. The embedded software is implemented in C.
“In the e-Lavage project, we developed the drive electronics, the 4-channel Li-ion charging station, and the embedded software in C. This included selecting the microcontroller, dimensioning the DC/DC converter, designing the charging technology, EMC-optimized layouts, and tools for the automatic test station. Close coordination with H&B’s mechanical engineers was crucial in order to combine high flushing performance, reusability, and installation space requirements.”
Stefan Schiefelbein
Head of Device Technology, B&W Engineering
The close collaboration between mechanics and electronics was typical of the cooperation with H&B. At the start of the project, we jointly defined functions, battery type, LED type and color, as well as requirements for ergonomics and haptics. Both teams then worked in parallel in their respective disciplines and regularly brought their results together, for example when the microcontroller had to be relocated for thermal reasons or additional safety functions were added. Step by step, a system was created in which all boundary conditions interacted harmoniously.
E-Lavage meets requirements such as high and adjustable flushing performance, quiet operation, sustainability throughout its entire life cycle, ergonomic design, a sterile overall system with a removable and rechargeable drive unit, and cost-efficient manufacturing.
The project involved physical and digital mockups in a stage-gate process, collaborative engineering between usability, mechanics, electronics, and software, usability tests and evaluations, a design history file for documentation, and preparation for MDR approval and protection and trademark rights by H&B.
Developing a partially reusable irrigation system meant balancing functional, regulatory, and economic requirements. In B&W Engineering, we had a reliable development partner with whom we were able to work as a team to transform high-level technical concepts into a solution ready for series production. B&W complemented us perfectly with its in-depth and long-standing experience in medical software and electronics development. The cooperation was characterized by openness, pragmatism, and a shared commitment to quality—crucial for the successful progress of the project.”
Tobias Morlok
Head of Medical Technology Development