BFO perspective: Modeling medical implants in a human body

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Asiyah Yu Lin

Oct 25, 2020, 1:06:34 PM10/25/20
Hi all, 

This may be a topic of interest for you:
A human body with a medical implant -- an extended human body.
There is a process of the body's interaction with the implant, as the immune system will consider it as a foreign body. 
The extended human body is now not a pure organic thing, and it is mixed with some implants made of non-organic material to fulfill some functions of the body. Sometimes, it is not for an essential function for the body to survive. Some implants are purely for cosmetic purposes, such as breast implants in cosmetics cases. 
Other things such as Tattoo, or belly ring, nose ring, or even earrings --> do you count it as a part of the body?
There maybe no boundary between the implants and human body.
Sometimes, the implants degrade, the chemical molecules will enter the human body.

Is this implant only specific for human being? Maybe some implants were implanted in some pets? What about plants?

How do we model this using BFO? Can you provide some insights?


Lindsay Cowell

Oct 25, 2020, 1:16:44 PM10/25/20

In IDO, we use the term “extended organism” which I think comes for OGMS. Perhaps take a look there.



Lindsay G. Cowell, PhD 

Division of Biomedical Informatics

Department of Population and Data Sciences

Department of Immunology

University of Texas Southwestern Medical Center at Dallas

5323 Harry Hines Blvd.

Dallas, TX  75390-9066


F4.218, MC9066

phone: 214-648-2289

fax: 214-648-2064



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Alan Ruttenberg

Oct 25, 2020, 4:38:27 PM10/25/20
Hi Asiyah, Lindsay :-)

For OHD (based on OGMS)  we defined: 

prosthetic role: IRI:
Definition: A material to be added role that inheres in a material entity that replaces some missing body part

Definition: A processed material that bears a prosthetic role

Works for some things, like prosthetic limbs or tooth implants and breast implants, but probably not for others, like pacemakers or CGMs or your jewellery examples.

For some of those (e.g. pacemaker) I expect we would want a similar term but defined in terms of adding a material entity that supplements a bodily function.

We consider prosthestic teeth to be part of a body. I'm not sure about removable arms, though I lean slightly towards considering them part. My intuition: tattoos are part, but not piercing jewelry. I don't consider immune system acceptance or rejection to be an appropriate criterion, for at least the reason that the immune system, in the case of autoimmune diseases, can reject parts of the body even if not foreign. Also, it would be odd to consider a transplanted heart not to be part of the recipient. Perhaps the underlying criterion is whether the non-developmental part is a functional part. However, another workable distinction, should you need one, would discriminate between parts that developed in the course of the organism's natural development, vs. not.

It's a safe bet to consider many of these (but maybe not the jewellery) as parts of an extended organism. IIRC the term was introduced to cover things like skin infections and parasites, and external microbiome. I don't recall whether it was intended for bacterial symbionts that are part of the microbiome, or internal infectious disorders. The definition:

extended organism: An object aggregate consisting of an organism and all material entities located within the organism, overlapping the organism, or occupying sites formed in part by the organism

As I look at the definition, it doesn't really take a position about whether something like the microbiome or prosthetic tooth are part of the organism or only part of the extended organism. It uses the weaker "located in". All the parts that developed naturally are located in the organism too: part_of->located_in
I don't think jewellery examples satisfy the overlapping criterion, but perhaps do the occupying sites criterion. Lindsay?

Hope this helps,

Asiyah Yu Lin

Oct 26, 2020, 12:16:58 AM10/26/20
Hi Alan and Lindsay, :D

Thanks for your response! It helps indeed. The tatoo maybe considered as something that is being injected into the body and does not create extra space. Tattoo is different from dermal fillers, which creates extra space in your body for cosmetic purposes. 

I think the prosthetic role's definition needs a little improvement: A material to be added role that inheres in a material entity that replaces some missing body part 
Not all breast implants replace missing body parts. Please think about the case of orthopedics devices, such as infusion of the disc to treat some chronic back pain. 

I think a prosthesis has to achieve some function

Below is the defintion from 21CFR, although it is regulations, it may provide you some ideas for definition.  
(d) Implant means a device that is placed into a surgically or naturally formed cavity of the human body. A device is regarded as an implant for the purpose of this part only if it is intended to remain implanted continuously for a period of 30 days or more, unless the Commissioner determines otherwise in order to protect human health.

  For this definition, a sponge accidentally left inside the body may not be considered as an implant or prosthesis.   

It is also hard to model the "intended use" concept in medical devices. Any thoughts?



Pierre Grenon

Oct 26, 2020, 12:00:42 PM10/26/20
to BFO Discuss
Hello Asiyah,

I'm not entirely sure about the context and whether you are proposing 'extended human body' and testing the cogency of the definition/description or if you are trying to make sense of something you found somewhere in the light of BFO. But you are asking how to model, in BFO, certain aggregates that involve an organism (human or other) and something that is not biological and, in the general case, that is located somehow in or near the organism, is that right?

First, I am not aware that 'extended organism' is something BFO has any ability to discern, this is because it sounds at first sight like you would need a definition of 'organism' in the first place and that is a biological matter and not a formal one. BFO consistently uses 'organism' as an example of object is all one can say, as far as I am aware --- when doing so there seems to be an underlying assumption that organisms of the relevant complexity are made of parts that are or are originating in living tissues, I'm not sure that's a claim that's made though.

Yet, strictly speaking in BFO, all the stuff you put together in your examples come across as aggregates, perhaps all as aggregates of objects. Objects have some causal unity. My interpretation of this is that, on a purely structural view, a body with a foreign body of any sort within it creates an aggregate and by some criterion of causal unity that aggregate may be maximal in the language of BFO 2. In principle, that does not mean that the resulting aggregate is an organism (although this is pending the definitional issue for organism) and it does not mean either that the added material, encompassed somehow by the organism, is part of the organism. On the other end of the problem, there is no way of imposing strict limits on what can be added (pretty much any aggregate somehow connected in a relevant sense, whatever it is, can be an 'extended organism'). This last claim may be perfectly fine and correct but then there is a risk of trivialising the tentative 'extended organism' --- is a naked person an organism and a person with clothes an extended organism, for example? What about a person with clothes in a car?

Alan mentions, with caution, one criterion for the integrity of organisms (species) that ties to the developmental process. Another, perhaps more important criterion is the physiologicial unity of organisms and the existence of physiological processes therein. It seems credible to me that no artifact is involved in a purely physiological process (but again, that may be only a domain specific definitional issue). The closest cases of examples in which you have aggregates of organisms and artefacts that come close to a functioning biological system would be when the artefact sustains, facilitates or triggers physiological mechanisms -- the pacemaker seems a good example of that, a mechanical aortic valve is another. But I think the story is here of relations between processes of different sorts (because their participants are of different sorts) at the level of domain analysis (these distinctions are not perceptible at the formal level).

Because of this and because there is virtually no purely structural (as in physical structure) way of distinguishing between cases of an organism having foreign parts within/around it to account for more than mereotopological differences, you will not be able to do justice to medical devices and implants without either referring to certain types of processes or certain types of SDCs.

One way of addressing purposeful placement is to use the processes that led to the implantation. It becomes a matter that is definitional of the process that some outcome was or was not intended following a procedure of sort. In practice, when modelling this, you ideally want to reuse something that allows you to offload as much as possible as you can (if you already have access to a well defined 'surgical procedure' with an account of intended outcome, this may be enough). In doing so you may be able to distinguish cases in which a mechanical aortic valve has been put in place from cases in which a sponge has been left behind.  

Another (complementary) way may be to use the SDCs for the implant --- the aortic valve has a role (broader approach) or maybe a function (more detailed approach) that fits the context you are trying to capture. The same offloading principle applies, not least because SDCs are involved and exhibited in other processes. Note that there will be bodily processes, even just mechanical ones like mastication to account for the role of dental implants or walk for lower limb prosthesis, and other processes that may have no interesting narrow biological properties such as elaborate communication through bodily modifications or concealment for smuggling, say.

While it can be made definitional, I see no forthcoming account of parthood between non-living objects and organisms that does not challenge the physiological integrity of organisms and it seems that differences between deliberate and accidental augmentation do not coincide with (physiologically and broadly biologically) beneficial or hurtful. There is a clear ethical and psychological dimension to the problem that I have entirely ignored as I only mean to highlight ways in which, according to my understanding, the distinctions you seem to be trying to draw are more or less well supported by the formal aspects in BFO.

Finally, some people recently mentioned on this list desires to be dealing more explicitly with systems --- since afterall organisms are living systems and your interest is in preserving the system part for aggregates involving these and non-organismal parts, it may be an interesting route.

I'd suggest for the short term to attend to the relevant processes and SDCs that could allow you to capture the distinctions you are trying to make.  This may be tackled by answering questions such as:
- What are the procedures leading to an implant?
- What are the prerequisites and success and failure criteria for these procedures?
- What are the participants? Who carries them? On who? What artefacts are involved?
- What are the processes in which the role or the function of the implant exhibit themselves?

Once you've addressed these, I'm not sure what benefit there is to use an 'extended human body' or 'extended organism' universal. What does it bring you in your context?

With many thanks and best regards,

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