Bodybuilding and Partial Knee Replacements (otherwise called a little knowledge can be a dangerous thing)

My rant:

One of the most frustrating obstacles I have encountered in life is academic protectionism. I refer to academic protectionism as the following:

  1. Scientific or philosophical journals and publications which are not available to the general public
  2. Inability to obtain sufficient educational resources which are not available to large portions of the population

In order to have access to these journals and publications you must have what is considered to be the ‘appropriate’ credentials which means you have to have an advanced degree from a properly credited academic institution. The access criteria to graduate programs are limited and appear to be reserved for young kids that plan to make their careers in a specific field. I was told at Colorado University in Boulder that I could not be accepted in the PhD philosophy program because they only had a few openings each year and they prefered to give them to younger people. Furthermore, they told me that the state requires financial assistance for each inductee and, even though I was willing to turn down assistance and personally pay for my education in full, they would have to offer it to me before I could reject it thus causing the rejection of my inductance to the program (ever hear of catch-22). I also find a bit of, shall we say, age discrimination in the expectation that kids who have more years than me would be expected to work in the field longer than me and are more likely to be accepted. Additionally, I have been told by academics that people are most intelligent in their early years, less than 30 years old, and do their greatest work in these years. It is true that there are only so many professors and they can only oversee so many student efficiently but that problem can be solved with a more well funded educational system (more professors = more students). Additionally, some folks are just smarter than others. This may mean they catch on faster, are able to remember details better and able to assimilate the information better. No doubt this is true but closing the access to those that have the motivation to learn without the best of all the aforementioned qualities could actually hurt the field (I would cite Einstein who had basic math problems in his youth). Additionally, older folks that may have certain disadvantages over youthful minds may also have certain advantages denied to youth by lack of age, experience, wisdom and not giving a damn about appearances. J I also find, for me anyway, age seems to help me focus and give attention to detail (I don’t even have a “smart phone”). As far as I can see many of the above ignoble factors are chiefly due to one reason:

  1. To protect capitalistic interests of the researchers and industry

The educational system and professional climate seem to favor closure in order to maximize financial interests. There are positive and negative reasons for this:

  1. Positive: Entry, access and production is controlled and therefore dues, grants and private business opportunities are accessible only to members and thereby, effectively maximize profit (i.e., the diamond industry). These factors may be solely due to meritocracy as the party line tells us but I would submit that, as Kuhn famously noted, many other factors are at work in these paradigms.
  2. Negative: Litigation and loss of profit can be protected by the jurisprudence industry (perhaps the Sophists did defeat the Academy)

The issue:

I recently found that the cartilage in my medial (inside) knee is pretty much non-existent. I suppose this could have something to do with genetics and my bodybuilding and personal trainer history. In my forties I did competitive bodybuilding. I was leg pressing 1,200 to 1,400 pounds with 10 or more sets and 10 or more reps per set. I was also doing squats with multiple reps and sets in the 500 pound range. I have tried to behave more sanely in my fifties but still do more than half that poundage. Ok, enough of the origins of the problem.

My academic background is a bachelors’ degree in Electrical Engineering and three different graduate philosophy programs. I also worked for years in hardware and software technology.

In spite, of not having access to publications in bioengineering I have researched UKA (unicompartmental knee arthroplasty; see this) which is what my doctor recommends to ultimately fix the cartilage. I do believe, after doing some preliminary research, that the MAKOPlasty solution is the best one in the market. The chief reason for this is because it is performed and customized to each patient at the time of the surgery by computer guided tools. Moreover, my concern has been to understand how much and what kind of weight lifting I can do in the future and how to balance this with the longevity of the prosthesis. Initially, I discovered that the official weight that should be lifted is 40 pounds. Since this is much less than most people weigh and would also need to be normalized to varying body weights to make any sense, I assumed that this is merely due to the sophistry of lawyers. After reading many personal accounts of folks lifting much more than that for years I came to the conclusion that the realistic numbers are not published and not accessible to the average ‘industry-assumed, dumb ass’.

There appear to be few studies in the area I am interested in. However, I did find this study. This study is obviously funded by the cement manufacturer so that should give some perspective to the following discussion. Additionally, since clinical trials take a long time and are costly these results come from finite element analysis (FEA) which is software simulation. FEA has proved reliable in the past as a good predictor when correlated to actual clinical testing.

ADDTIONALLY, my legal disclaimer without paying a lawyer to write it is:

I am not a professional or even active in this specific field of bioengineering so I may well have it all wrong. These are simply my own ‘dumb-ass’ observations.

(I would also add, screw the industries that refuse knowledge to the general public and restrict access to knowledge…beat the doors down if you have to folks) J

Here are conclusions that this study seems to validate:

  1. See the study for a longer description of tibial inlay and outlay components but in short, the tibial is the lower bone in the knee. A kind of strike plate made of plastic can either be scored into the tibial bone at the time of the surgery or placed on top the bone. Inlay seems to be better than outlay …(further reasons cited below).
  2. The component has a prong that goes down further into the tibia after ‘drilling’ (not necessarily a drill, more below) a hole for it in the tibia
  3. The inlay method is stronger.
  4. The study recommends the brand named cement, RESTORIS because it has better penetration into the bone (up to 6mm).
  5. The inlay that is scored out for the whole component appears to be better when it is deeper (3mm as opposed to 1mm) …(further reasons cited below).
  6. The deeper inlay appears to have less pain over time than the shallower inlay …(further reasons cited below).
  7. The deeper inlay has less chance of loosening or ‘debonding’ (coming off the tibia).
  8. Bone is denser and less cancellous (matrix, as more porous, less dense, perhaps more microscopic holes in it) as the scoring gets deeper into the tibia).
  9. Pain is less over time with the deeper inlay. I suppose a more porous bone can bond to scoring on the bottom of the plastic component and perhaps with functional movement acquire more microscopic breaks in the bone bonding which could result in more pain (?).
  10. The plastic component can settle or sink further into the bone with a shallower inlay due to the less dense bone. This can lead to loosening of the component, dislodging of the component and decrease the strength of the bond for the inlay and the prong.
  11. One drawback of deeper scoring into the tibia is that if and when revision (otherwise called redoing the implant) is performed, the “deeper cement penetration would be a slightly more complicated revision”. The tradeoff is “a good cement penetration can postpone or significantly reduce the likelihood of that revision”.
  12. The study is based on the assumption that “creating thicker cement/cancellous bone interdigitation during an inlay procedure is possible through the meticulous use of a custom pulsed lavage [pulsed jet to ‘drill the hole’] technique”. Apparently, there is a specific kind of pulsed jet to ‘drill the hole’ which is better than others.
  13. It is better to apply cement to the inlay itself and the resected cavity (the scored hole in the tibia). It is better to “cement[ing] the two components separately and maintaining a compressive force on the implant until the cement has cured”. Even Home Depot supports this conclusion.
  14. This comment was made in the study, “A 2100N load (approximately 60% of a total joint load of 4.5 x BW through the medial compartment)”. I believe N is forced measured as newtons. If this is true then, if 2100N is 60% of the total joint load then the total joint load is 3500N. According to the conversion 3500N is 787 pounds. It is important to note that this is force applied in the inferior direction (straight on the simulated tibial joint I think). Therefore, the more sheer force that is applied to the joint this number appears to be reduced at the rate of the square root of 3 (so fairly substantial fall off as more sheer force is applied). Apparently, joint failure is measured as a von mises criterion (wonder if there is any relation to the economist?) – that number is basically when the joint has catastrophic failure (yuk). I suppose if all this is true then the joint could theoretically take 787 pounds before you would need to go the emergency room for a quickie revision. See this, this, this especially if you have a math fetish.

Here are few other observations from my research:

  1. Since weight lifting is severely reduced from the poundage I would like to use after this surgery, negatives (reflexion, stretching the muscle) should be used for better muscle tearing at lower weights. See this.
  2. Reduce instantaneous stresses due to fast changes (i.e., smoother lifting with slower changes from contraction to reflextion and vise-versa). Instantaneous force pulses can go really high, really quickly and over time these pulses will decrease the lifespan of the prosthesis. Even walking on the stairs can create these instantaneous force spikes. I also found this interesting.

The study also gives your surgeon these suggestions:

Recommended Tibial Inlay

Component Implantation

1. Use high pressure pulsed lavage or similar technique to remove fatty deposits from the cancellous porous structure. A right angle attachment works very well. Dry the surface with a sponge filling the cavity under firm digital pressure. The open porous structure improves cement interdigitation.

2. A wet cloth may be placed behind the tibia to catch escaping cement during impaction.

3. Immediately apply cement to the resected cavity using a cement gun. Cement should be inserted as soon as it becomes workable (not shiny and sticky).

4. Apply cement to the inlay bottom and peripheral cement channel.

5. Immediately place the inlay tibial component into the cavity and compress it evenly and forcefully using finger or flat instrument pressure (e.g. freer elevator or the inlay impactor).

6. Carefully remove all excess extruded cement.

7. If a wet cloth was used posteriorly, remove it.

8. Apply and maintain distributed pressure on the central articular surface of the inlay, which can be accomplished by direct finger compression or with the assistance of an inlay impactor. Distributed pressure is important, particularly in the anterior/posterior direction, to avoid tilting of the component in the sagittal plane within the prepared cavity during cement curing. This pressure may extrude additional cement, which should now be removed.

However, in the interest of not pissing off your surgeon I would not give him/her a pop quiz on this. In any case, you will be knocked out during the procedure so peeking is not allowed.

Questions I would have for the surgeon (if he still wants to be my surgeon after this):

  1. Are we doing a 3mm inlay?
  2. Are we using RESTORIS cement on the inlay and the prong?
  3. Are we cementing both the inlay and the bone before setting the inlay?
  4. Are we using this special ‘custom pulsed lavage’ which increases adhesion?
  5. The computer assist for the surgery should be a requirement.

The unanswered question no one will touch:

What is the absolute poundage I should lift with this prosthesis? To be fair this cannot really be answered because it depends on:

  1. …how long you are hoping the prosthesis will last. Remember if you weigh 300 pounds and have high body fat, you are effectively weight lifting everyday without the benefit of being in shape. If your life span is shortened because you are only lifting the prescribed 40 pounds (which could only be done while lying in bed) the lawyers will be happy but the prosthesis will do you no good if you’re dead.
  2. …the type of activities you are doing. Hiking, running, bad form weight lifting will increase the pulse forces on your prosthetic and decrease its life (I think biking would be good but I only do mountain biking so that may not be so good…orthopedists like it though).
  3. I suppose I could still do one, and only one, 1,400 pound leg press but it would probably not be worth it.

I would love to get any feedback on this but I find most folks would rather not be bothered…

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