Introduction To the Term
First of all lets look at what is actually meant by the term “custom” knee replacement. Are you getting a custom implant? The answer is “no”. You are getting a customized cutting guide that supposedly will ensure perfect placement for your knee implant. And while this intuitively seems like a very good thing, let’s examine this topic further.
History
Here is a brief history of somewhat recent innovations to the traditional model of conventional “off the shelf” implants
1) Gender Specific Implants- smaller and more tapered “off the shelf” versions
2) Computer Navigation- this aids in alignment but has nothing to do with the size and shape of the implant itself.
3) Custom Knee Replacement: Cutting guides are created by imaging the patients knee (CT or MRI) and then forming a cutting guide specifically for that patient. Some guides specify where the surgeon should cut the bone while other types guide the insertion of pins so that standard cutting guides can be used more accurately or so the theory goes.
So who are the major players in the market?
Biomet (Signature System/Vanguard)
ConforMIS (IFit/ITotal)
DePuy (TruMatch/Sigma)
OtisMed (OtisKnee/Triathlon) a division of Stryker
Smith & Nephew (Visionaire/Journey)
Wright Medical (Prophecy/Advance)
Advantages
The purported advantages over conventional surgical guides are as follows:
- Improved alignment
- Decreased operative time
- Increased patient throughput
- Decreased instrumentation
- Reduced risk of fat embolism and intra-operative bleeding due to minimal bone removal (i.e., no intra-medullary canal reaming)
- Decreased tissue loss
- Shorter recovery
- Reduced postoperative pain
- Decreased incidence of infection
- Lowered costs
Sounds great doesn’t it? Sign me up! It all seems to make perfect sense. Why would I not want a custom fit? What could go wrong?
But……..wait
Product Recalls
On January 23, 2012, Biomet sent a recall notice to its customers explaining two lots of Signature guides were incorrectly labeled. Biomet instructed its customers to return any affected product and notify hospital personnel if the affected guides had been further distributed.
Incorrectly labeled… yikes…you mean my personalized guide was someone else’s personalized guide?
Also if anyone remembers the Stryker lawsuit regarding their ShapeMatch cutting guide that I discussed in a previous blog post, it should be enough to give you pause.
Additionally, here is the list of problems with customized knee replacement cutting guides that were reported to the MAUDE database (A collection of reports from voluntary user facilities).
- Incorrect/difficult template fit (48)
- Template caused over-rotation (39)
- Template caused incorrect cut (20)
- Broken template during surgery (10)
- Broken tool (8)
- Sterilization-induced template malfunction (2)
- Bone fracture (1)
- Missing instrumentation (1)
Little Conclusive Evidence That They Are Better At This Point
The ECRI institute released an Emerging Technology Evidence Report April 2012 for Total Knee Replacement Using Patient Specific Templates.They concluded that the evidence is insufficient to demonstrate the claims made for use of the guides.
Screenshot images taken from ECRI report The first table shows data comparing custom knee replacements to computer navigation and the second table shows custom knee replacements vs conventional instrumentation. The yellow panel area is for inconclusive results.
So who is behind the ECRI? Their mission is as follows… to research the best approaches for safety, quality, and cost-effectiveness in healthcare, ultimately enabling your organization to improve patient care.
But one must always follow the money when evaluating the so-called neutrality of non-profits.
Their website states that they have three funding sources.
| Although ECRI Institute occasionally receives charitable grants to support our work, the majority of our funding is derived from three sources:1) Memberships from organizations—This membership model allows ECRI Institute to conduct research and provide information and advice, which is shared across our various memberships.2) Clients who engage us in custom planning and consulting projects such as quality system assessments, accident investigations, or strategic technology planning.3) Contracts, most often from government agencies—Examples include the U.S. Agency for Healthcare Research and Quality for the National Guidelines Clearinghouse and The Pennsylvania Patient Safety Authority, for whom we develop and maintain the Patient Safety Reporting System. |
Private contracts, government contracts and memberships from clients. Geez sounds like a for profit business to me. Although I am not ruling out this data source, I would look further because a high volume of government contracts or big industry contracts just doesn’t seem unencumbered to me.
You can find their entire report Here
Additionally the most recent study on patient cutting guides was completed by the Journal of Bone and Joint Surgery The authors concluded that…
“There were no significant improvements in clinical outcomes or knee component alignment in patients treated with patient-specific cutting blocks as compared with those treated with standard instruments. The group treated with patient-specific cutting blocks had a significantly higher prevalence of mal-alignment in terms of tibial component slope than the knees treated with standard instruments.”
Dr. Tarlow, who we have mentioned (Arizona Total Joint Surgeon who maintains his own blog), concurs with this report.
“Routine use can not be supported in uncomplicated knee replacement. Patients should not be influenced by marketing efforts suggesting widespread adoption of these products. “
In Summary:
Can things go wrong with conventional surgery..of course. I’m I trying to say that a customized template is a bad thing…not at all.
My purpose is to offset the deceptive quality of current marketing that lures people into uncritically adoption and acceptance.
Is a custom knee replacement the next best thing since sliced bread? The jury is still out.
5 replies to "Custom Knee Replacement: Next Best Thing Since Sliced Bread?"
I know this is late but will reply anyway for others who might read, The answer to Benjamin’s question is somewhat complex. First off many people will not be able to match the range in non-operative knee. There are a lot of reasons for this, type of knee implant, the surgeons technique (some surgeons are known for producing “tight” knees), therapy technique, and diligence. Swelling and tightness can be a nuisance for 6 months or more. Benjamin is worried that a traditional knee may have slightly limited his ultimate ROM however the important thing to remember is a traditional knee has been highly tested having been implanted in thousands of people and with high survival rates (number years of worry free service). This is a much more important result than a few extra degrees ROM in an untested or brand new model. I understand the desire to have the new knee be just like the old one but so far that is not the case. I would go with the tested knee every time. Don’t be the guinea pig!
I continue to wonder if I also have some poorer quality of overall movement with my July 2015 total knee replacement with the vanguard cr model done in traditional fashion. I did lots of PT. My max of flexion was 135 at 6 weeks and today am basically still in that range. Extension is 0 degrees. Just still feels a bit stiff with slight discomfort when I walk. Have developed pains like shin splints about 4-5 months ago in same leg while walking on hard floors at that time. Told by an ortho friend that is due to calf muscular tightness.
Keep wondering if I should have gotten a custom knee like the conformist. I am a 67 year old semi retired family doc
Would greatly appreciate any comments !
Sorry for the delay in response. But for others who may have questions in this regard, to be honest 135 in certainly average rom depending on the MD’s surgical technique. I have found that the Dr’s technique has more influence on rom than the implant itself. It usually results from balancing the ligaments, some doctors produce a “tigher” knee than others. For calf muscle tightness stretching and foam rolling should help. If not a postural exam by a PT may should some imbalances that could be corrected to alleviate the strain.
Thank you for your service. I will being a TKR soon and agree with you completely. The provider I see uses Biomet. Can you give me the names older models Knee replacements that have not had complications/
Thanka lot
The best thing to do is to have a discussion with your doctor about the fast track approval process and whether he uses implants that are new in the last 5-7 years. They do incentivize doctors to use the newer models to get the sales and marketing numbers going. If he is testy about your questioning it might be time to get a second opinion. This discussion should yield the information and protection you are seeking. The best ones don’t use stuff right off the shelf with fast track approval 510K (see my article on this if you want to know more)