This is the third installment of our four-part series on Osseointegration, Bionic Solutions, and Clinical Outcomes, with Dr. Laurent Frossard. Other parts include:
- Part 1: Advantages of Osseointegration
- Part 2: Disadvantages of Osseointegration
- Part 4: Key Issues for Osseointegration Patients
You can obtain a PDF version of the transcript for this interview, complete with references, at Part_3 – Eight Ways to Improve Osseointegration.pdf.
For your search convenience, we have also included a raw text transcript beneath the embedded video below.
Finally, if you like the video, don’t forget to check out our Key Contacts & Related Information section at the bottom of this article.
Welcome back to our series on Osseointegration, Bionic Solutions, and Clinical Outcomes, Part 3, Eight Ways to Improve Osseointegration, with our guest, Dr. Laurent Frossard.
Dr. Frossard, at the end of the previous interview, you said that we know what we do not know. What do you mean by that?
Of course, there is a bench of fundamental discoveries that will help make all bionic solutions safely available on a wide scale. But science progresses through small increments, one little step at a time.
In the long run, improvements from basic science in antibiotics, stem cells, biomaterials — biofabrications, for example — are likely to make a significant impact to improve infections and improve the strength of the attachment.
In the meantime, there are several areas of improvement already identified that we should address. Most of them relate to the rehabilitation program.
What are these areas of improvement?
Well, we know the basic principles underlying the development of osseointegration. Basically, the rehabilitation program consists of putting pressure on the implant regularly.
At the moment, individuals perform load-bearing exercises using a short pylon attached to the implant. The progression of the load applied on the implant depends on pain as well as the type of implant, bone quality, and bodyweight.
But believe it or not, the compression prescribed is monitored with a basic weighting bathroom scale placed on a stool!
And for me, there is something fundamentally wrong with that. We are aiming at developing the next generation of bionic limbs using last-century technology to perform and monitor rehabilitation!
So, for me, clearly, there is a need for a much more efficient way to perform a pain-free rehabilitation program.
That makes sense. How do you propose that we improve monitoring?
Well, what we need to do is to develop a device that allows us to monitor, in real-time, the effects of the load applied on the bone.
First, this involves using wearable sensors to measure the load. I have done that load measurement a lot and that is the easy bit! We have the technology. We have the know-how.
Then, we need to use a digital twin version of the residuum. So, that model will have all the anatomical parts of the residuum including the bone, the nerves, the muscles, the fat tissues, and the skin. The model will make all these parts interacting with each other following the changes of load.
Now, no need to tell you that this type of computing is challenging. I am currently working with a team at Griffith University that specializes in this type of modeling. So, watch this space!
I am glad you mentioned the importance of loading. I have got to know your work on mechanical loading and osseointegration. I am particularly interested in the importance of prosthetic components, that is, your work on foot stiffness, angles of alignment, and
the use of microprocessor knees. How much do we know about the role of prosthetic components?
I am always surprised to find out that people outside the field of bioengineering are, in fact, reading that stuff because researching on mechanical loading is clearly the least sexy science you can ever imagine!
I have simply used a new state-of-the-art instrument to record actual daily activities. And it is one of the most informative data needed to improve the clinical understanding of osseointegration.
So, I do a lot of work trying to understand the loading applied by various components during rehabilitation and beyond.
My aim is to inform clinicians and engineers on how a prosthesis impacts the implant.
This involves using cutting-edge wearable technology embedded into the prosthesis. I am also developing new ways to compute the biomechanical data. For example, we have developed new metrics to measure the efficacy and safety of advanced prosthetic knees. We can also see if a prosthetic ankle unit behaves like an able-bodied ankle joint.
Ultimately, this work helps to refine the design of implant and rehabilitation programs. But, it also helps prosthetists to prescribe components that are most suited to particular users. Finally, it also justifies the prescriptions of high-end and costly components in a way that makes sense for healthcare administrators.
Do you think we know enough about the role of advanced prosthetic components like microprocessor knees?
Well, yes, we do, do, but only to a certain extent. Lots of information has been produced over the last 10 years. However, the data available were mainly collected during walking and scripted daily activities. So, they are only partially reflective of the true load applied on the implant during usual daily life. The other problem is that the components tested before then are no longer routinely prescribed. So, the data currently available are a little outdated.
The bottom line is that we need to know more about the actual mechanical load applied during rehabilitation and daily activities, particularly when the user is fitted with the most advanced prosthetic components, like microprocessor-controlled knees called MPKs.
Are you currently working on this topic as well?
Yes, I am. I have several projects of research in collaboration with the industry and regulators looking at the efficacy and safety of high-end components, including knees, ankles, and protective devices.
We are particularly interested to know if the current bionic components, initially designed for socket-suspended prostheses, are suitable for bone-anchored prostheses.
But, effectively, what we are doing is gathering critical information required for the design of the next generation of bionic limbs particularly suited for osseointegration.
From the point of view of prosthetic care and more particularly the fitting of the leg and these high-end components, can you explain the ripple effect of using an osseointegrated implant versus a socket?
Well, it is now well accepted that users with an osseointegrated implant must be fitted with advanced components like MPKs. There are several reasons for that.
The first one is that these components are needed to restore mobility and high functions. If we assume that the implant creates the capacity of a Formula 1, it makes sense to use a very powerful engine — go back to the metaphor of the car as in the first interview.
The second reason is that these components could contribute to reducing adverse events. They have features like auto-adaptive stance and swing control, as well as automatic stumble recovery, that make the leg a lot more predictable and stable. So, these components can reduce the incidence of falls quite significantly. This means less breakages of the implant and less secondary injuries for the users.
Outside the evidence gaps in monitoring the rehabilitation program and prosthetic loading, what are the other immediate areas of development?
One easy way to improve our clinical understanding of surgical and rehabilitation with osseointegrated implants would be to strengthen the way infections are recorded.
At the moment, superficial and possibly deep infections are poorly recorded. Users are very good at detecting early signs of infections (e.g., pain, discharge). Most users are geographically remote from their treatment team, so they tend to go see their GPs more often. These GPs who are, in most cases, unfamiliar with the treatment of infections for these types of patients with permanent stoma tend to be conservative. Hence, the prescription of strong courses of antibiotics.
Now, I don’t know if this is the right thing to do or not. I’m not a doctor. However, what is known is that patients are likely to report only partially these episodes several months after, later, during follow-up visits with their treating team. So, this is known as the “recall bias”. This is a well-known caveat in clinical studies. Because of that, I believe that we see only the tip of the iceberg when it comes to infections.
Another issue is the way infections are reported. There are several grading systems of infections. Emerging teams tend to create their own new system instead of using the ones already developed. Therefore, it is difficult to compare outcomes between surgical teams, let alone populating an international registry of clinical outcomes.
How can the current monitoring of infection be improved?
Well, the monitoring of adverse events could be facilitated by portable technology. It will be straightforward to develop an app that could record immediately all the adverse events including episodes of infection, intake of medication, and falls, for example.
Effectively, this is what any team worried about its credentials should do. The drive will be even stronger for the teams responsible for registered clinical trials.
By the way, I believe we should only consider evidence collected as part of registered clinical trials. I think this might be one way to make sure that the outcomes of all cases treated and all adverse events are correctly reported.
And how can the reporting of infection be simplified?
Well, this is a little bit trickier! Improving the reporting of infections might be a bit more challenging to tackle. It makes sense to me that the reporting of infection will be much more robust if every team could use a standard method. Quality of life and mobility are well reported, in fact disproportionally well reported, because they are standardized!
This means that all the stakeholders will have to come to the table and collegially agree on a reporting standard. That is challenging because these new standards might cast of different shade on the true strengths and weaknesses of some clinical practices.
Yes, I can see how that would be challenging. In the meantime, is there any other aspect to the procedure that we need to better understand?
Oh, year, there are plenty more we need to understand to facilitate access to a wider population and make bionic solutions widely accepted as the standard of care. We are a long way.
Another critical aspect of the treatment currently misunderstood is the very long-term care of patients with osseointegrated implants.
We know that the typical lifetime of a joint replacement, like a knee or a hip, is around seven years. Osseointegrated implants are more or less designed the same way. However, they must last the user’s lifetime.
The first patients were treated in Sweden by the Rickard Branemark’s in the 90s’, so just about 30 years ago. So, we are now just starting to gather lifelong outcomes. However, there are yet lots of unknowns about the long-term strength of the attachment to the bone, particularly the impact of aging.
Can you give us an example of what this could mean for, say, a young person fitted with an implant today?
Oh, absolutely! Let’s take an example of a lady fitted with an osseointegrated implant in her mid-40s’. Things go well for a good 15 to 20 years. But we do not fully grasp what will happen if her bones become weaker in her 60s’?
On paper, she could face two challenges. The lack of bone strength around the implant could lead to higher risks of breakage, loosening, and possibly infection.
Also, she will be at a much higher risk of fractures of the greater trochanter, particularly on the sound side that tends to be overused to compensate for prosthetic gait. So, what would happen if this lady is not able to walk and load her implant for an extended length of time?
Hopefully, this is a farfetched scenario. Nonetheless, it highlights that we need to see this procedure over a lifetime. Clinicians must develop a contingency plan to continue cleverly and safely stimulate the bone to address long phases of inactivity and the natural effects of aging.
I believe there is a need to consider alternative rehabilitation exercises beyond the initial post-operative program.
This seems like a very fascinating and complex subject. How do you balance out all the factors?
Well, during our last interviews, we have touched on the good, the bad, and the ugly, as well as the current evidence gaps and areas of development of bionic solutions. All these aspects should be considered at the onset of the decision making about opting for
osseointegration or not.
On one side, this is a truly life-changing decision that cannot be taken lightly. On the other side, it is easy to be overwhelmed by the complexity of the information to take into consideration. And at the end of the day, potential users are often stuck trying to solve a dilemma: are bionic solutions too good to miss or too bad to consider?
I probably cannot answer that question in most cases. However, it is possible for me to facilitate the process!
Again, Dr. Frossard, thank you for your incredible insights on these subjects. In Part 4 of this interview, we’re going to review the key issues for osseointegration patients?
For more information on Dr. Laurent Frossard, please visit his website.
For a complete description of bionic limb technologies, devices, and research, see our complete guides on bionic arms & hands and bionic legs and feet.