MDR moratorium: A halftime report

In 2017, the European Commission has agreed on and published a new regulatory framework for medical devices to substitute the present Medical Device Directive, thereby increasing the scrutiny on medical device manufactures and supply consistent and practicable rules EU-wide. 

In the beginning, the MDR was often understood as a major burden for both established and new medical device companies due the increased requirements for pre-clinical data and post-market surveillance. Originally, manufacturers of medical devices were given a three year transition period until May 26th 2020 to duly adapt their internal processes and products to the new regulation. 

During the transition period, however, it became clear that the MDR is not only a challenge for manufactures, but that notified bodies and competent authorities themselves encountered a variety of obstacles as well leading the entire transition onto a rather rocky road. In late 2019, only a small fraction of notified bodies was designated for MDR due to a significant delay within the designation process. The MDCG (Medical Device Coordinating Group) was also way behind their schedule for relevant guidance documents intended to clarify and substantiate the European Commission’s expectations on how to follow the new rules, and the European database for medical devices (Eudamed) seems to be delayed by a matter of years even. And then: Covid-19. 

European Comission deciding for a 12 month extension

As a result, the European Commission decided to extend the transition period by one year. This extension period has now reached half time, but still: only 17 out of 48 notified bodies that have applied for designation until recently have actually been designated yet.[1] In addition, although quite a number of guidance documents has been published already, the list of guidance documents under development is constantly growing. While there were 30 MEDDEV guidelines available under the MDD, more than 40 MDCG guidances have been published up to now – some of them have already been revised – and another 36 documents are currently on the schedule.[2] In summary, it appears that a lot of open questions and uncertainties are still to be addressed even half a year after reaching the original MDR-deadline. 

Logically, the Medical Device Regulation (MDR) has been the main topic among medical device manufacturers from all divisions for the past years now and with its implementation still in progress, the debate on how the elevated expectations for quantity and quality on clinical data will actually affect the industry still lives on. Of note, the transition from MDD to MDR comes with considerable costs for established manufacturers not only in regard to the time and personnel required for implementing the changes, or the increased service fees from the notified bodies, but especially in regard to the revised general safety and performance requirements (formally: essential requirements). A recent survey from a German EDC service provider indicates that medical device companies spend approximately 5% of their annual revenue for MDR compliance alone.[3] It has thus often been feared that a considerable number of products will drop out from the market – especially those for orphan diseases and rare conditions – for their manufacturers to cope with the rising costs and that innovation of new products decelerates due to this increased level of required clinical data, making the life especially difficult for young businesses and start-up companies.  

Our approach at medical magnesium

Being founded in 2015, our team at medical magnesium was faced with the upcoming regulatory changes early onWe implemented the future requirements into our current proceduresanticipated the need for sufficient clinical data on our MDR projects early on and allocated our resources accordingly. This allowed us to dynamically render our process to the respective needs and shift our focus even on short notice. Half-time through the transition, we thus managed to achieve our first main goals as a medical device company on the fly by receiving the CE mark for our first devices under the MDD. Our believe in procedural dynamics and open discussion among all company departments (from development to clinical affairs) allowed us to anticipate the MDR moratorium early on and specifically guide our resources onto certain projects to speed up the process of product validation and certification. As a result, we had been able to draft and submit the complete technical file for our latest mm.X implant, the mm.CS, early before deadline and have finally received the CE mark for our third class III implant. 

Being able to achieve these goals during this rather turbulent time of MDR transition and the ongoing health crisis not only fills us with pride. It lets us believe that small business can certainly stand their ground in the MDR regulated medical device market and allows us to face the future confidently. 


Author: MG 




Mechanics of resorbable magnesium: Overview among implant materials

Mechanics of materials are characterized in certain parameters such as utimate tensile strength, elongation and more. This a very engineering focused way of describing features. In trauma care other features are highlighted:

• Bending resistance until breakage of the fracture plate,
• Easy and controllable insertion of screws,
• Torque resistance of the screw drive before the screw drive is rounded,
• Safe and stable bone fragment repostioning and many more.

As magnesium is a light metal and the use as biomaterial is relatively new, we will think through some implant design features and compare it to existing implant materials.

General implant material comparison

A lot of the material behaviour and the derived implant behaviour can be read in the Tension-Elongation Diagram. We have brought an actual exemplary test result from our lab:

The x-axis describes the elongation of the material, the resulting tensile strength is displayed on the y-axis. The tensile strength is displayed in measured Force divided by the cross section of the rod. The unit of the resulting tension is Newton (Force) by Section (mm²) or N/mm².

To visualize this: A force of 500N (Meaning the gravity force of appr. 50kg) applied on a rod with a diameter of 2mm would result in a tension of 500N/ (1mm²*π) = 166 N/mm²
In this example, a 2mm magnesium rod can withstand the gravity load of 100kg or 1000N before plastic deformation starts and it begins to deform. Up to this point it will always return into its original geometry (like a spring). Loads above this limit result in a plastic, permanent deformation.

Using fracture plates, it is of essential importance to allow small bending operations to precisely match the anatomical shape of the fractured bone. The design of the alloy behaviour must therefore leave room for a plastic deformation in a controlled manner, this can be found in the diagram in the plastic deformation after the elastic phase.

Prominent polymer materials such as PEEK display a value of 100 N/mm², translated to a 2mm rod allow a load of 30kg. Resorbable materials like PLLA or PLDLA normaly reach their limit at around 50 N/mm². Biocomposite materials, such as used by most sports medicine companies, even reach lower limits as the mixed ceramic material such as ß-TCP further weakens the structure.

In comparison to resorbable materials, modern surgical permanent titanium materials reach out to 800-1000 N/mm² with the known usual possibilities of bending manipulation., which allows a downsizing of trauma implants. In comparison cortical bone reaches up to 250 N/mm².

The mechanical resistance of magnesium is in the middle in between polymers and titanium materials. In comparison to polymers, which are favorable to break instantly (ductile behaviour) , magnesium implants allow anatomical bending for a safe configuration.

Implant screws: Interface design

A trauma implant always has, in most cases, two or three, interfaces: The is the implant-Instrument interface, the so-called drive, an optional screw-plate interface and the screw bone interface.

The implant-instrument interface is incorporated in the screw head. The torque to protrude the screw into the bone is transmitted through a small surface. This results in a lot of load on this section. Polymer designs have trouble to transmit the required torque and establish a resulting compression force due to their low mechanical resistance. In comparison with titanium, magnesium implants require special attention concerning the drive design. The required insertion torques, around 1-2Nm for 2.7mm cortical bone screws, represent values closer to the mechanical limits.

As bioabsorbable magnesium screws are inserted into hard cortical bone, we only apply the more stable drive shape designs. Most of our products will feature a star shaped drive interface. In internal testing we have measured the maximum torques before screw-driver cams out and the drive is finally “stripped” or “rounded”, meaning a total failure of the interface.

In a total perspective, a mechanical chain has always one component which represents the weakest link. In screw design, this should always be the drive. The instrument (driver) shall not break, as it is expensive and possibly harmful to the user and the patient (because of possible sharp pieces). If the screw head shears off completely, a headless threaded pin is hardly removable. In comparison to titanium implants, in an “emergency” magnesium implants can be overdrilled using standard surgical drills.

As a result, the magnesium designs, require a larger drive (meaning transmitting surface) than comparable titanium implants to ensure the same usability. The maximum torque which can be applied by manual insertion is very much influenced by the handle of the screwdriver. After these lessons, we put a lot of stress on the right sizing for the screwdriver handle and have applied torque limiter whenever useful.

The world of resorption adds very interesting new aspects into the equation. We will look more closely into this in another blog post.

Author: KR