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Last year, surgeons performed more than three and a half million total knee replacements around the globe, making them one of the most common joint replacement procedures (also known as arthroplasties).1 When it comes to the implants that are used, there are many different types, but only a few prominent ways to connect the implants to the bone.
So, how do surgeons decide which technique is best?
Cemented fixation—in which implants are attached to the body with bone cement—has traditionally been the predominant method. More recently, press-fit implants, also known as cementless implants, have emerged as a viable option for many patients. Cementless implants are made of material that promotes new bone growth; they use biologic fixation, in which the implants are press-fit onto the bone. The bone then grows into the implant’s porous surface, ultimately attaching the two together without cement—or, in the case of hybrid fixation, with minimal cement.2
Since cementless techniques emerged in the 1980s, they have become predominant for hips, with 90% of hip replacements for osteoarthritis using cementless techniques, according to a study in the Journal of the American Academy of Orthopaedic Surgeons.3 But what about knees?
“There are different stresses across a knee compared to a hip, which have led to implant design and manufacturing limitations historically,” says Robert (RB) Jones, M.D., an orthopaedic surgeon at Mercy Clinic in Springfield, Missouri who has performed approximately 1,200 joint replacement surgeries in the last year. “But now, it really seems like we've cracked this code, so we've been able to engineer more biocompatible components with better manufacturing techniques, like 3D printing options.”
What are the benefits of cementless knee implants?
Patient outcomes are an important consideration, “especially as more active patients are getting joint replacements at younger ages,” says Dr. Jones. These types of knee replacements have shown encouraging survivorship.4
He also suggests that cementless fixation can eliminate potential thermal injuries.5 He explains that when cement cures, there is an exothermic chemical reaction when it goes from a liquid putty to hard cement.
“When that happens, the cement becomes hot enough that you can't hold it in your hand because it would burn you,” Dr. Jones says. Likewise “we know that it may create a thermal injury to the bone. So, if you penetrate with too much cement, we think that it can contribute to pain in the early post-op period, or it could even damage tissue.”
Press-fit techniques can also reduce the occasional muscle and nerve damage associated with the tourniquet use that cement techniques often require.6
There are several advantages of cementless fixation for healthcare providers, too. For one, eliminating cement can reduce surgical staff's exposure to cement fumes.7 “If there's any concern that a healthcare provider is pregnant, most hospitals will cycle them out of the room to avoid them smelling the fumes,” Dr. Jones says.
Eliminating cement also reduces time in the OR because there is no time spent waiting for cement to harden, ultimately providing the opportunity for doctors to do more surgeries. This time adds up for busy surgeons like Dr. Jones, who does up to a dozen knee replacements daily.
Why do some surgeons prefer cement fixation?
While there are many benefits to cementless knee implants, many surgeons still prefer cement fixation methods because of their long history of successful surgeries.8
“In arthroplasty, we're all about wildly successful surgeries that are trying to minimize complications. We judge success and failure in total joints over decades, not weeks, months or years,” Dr Jones says.
As such, because many surgeons were trained to use a certain type of implant, they stick with the technology they are comfortable with to ensure success and avoid mistakes.
What’s more, there’s abundant clinical evidence on the safety of cemented fixation, and cementless techniques are newer, which means there’s not as much evidence yet.
Every patient and surgeon is different, and there isn’t one perfect implant that will fit every scenario. Surgeon expertise and patient-specific factors will continue to lead decisions on whether to use cemented or cementless fixation.
Another potential barrier to adoption is the perceived cost differences between cement and cementless implants, because newer implant technology can have higher up-front costs.9 That said, as Dr. Jones points out, “there are also potential cost savings by avoiding cement-related materials such as mixers and tubing. Plus, initial expenses may be offset by eliminating the time that staff spends waiting up to 15 minutes for cement to dry and improving cleanup and turnover time between patients.”
Indications for cementless versus cemented knee replacements
When deciding whether a patient is better suited for cement or cementless fixation, Dr. Jones focuses on implant stability and fitment—in other words, how well the implant matches the shape and size of the patient's natural knee joint.
If a patient’s surrounding bones are not stable enough to use a biologic fixation, “cement works wonderfully in those instances,” he says.
When Dr. Jones started introducing cementless options to his practice years ago, he used age as an important indication because younger patients had harder, good-quality bones. But as he saw more and more success with cementless fixation, he eliminated the age requirement. “The line in the sand, so to speak, is now less age related,” he says. “The question now is: Are the cuts and the bone preparations precise? Is the fitment perfect? And if it is, I don't have an age cap any longer.”
Now, he estimates that 90% of the knee procedures he performs are cementless; he has done 1,000 cementless knee replacements with the ATTUNE™ AFFIXIUM™ Cementless FB Knee.
Every patient and surgeon is different, and there isn’t one perfect implant that will fit every scenario. Surgeon expertise and patient-specific factors will continue to lead decisions on whether to use cemented or cementless fixation. Overall, Dr. Jones describes cementless fixation10 as an efficient and effective option for most patients.
“It's satisfying when you can do a good, cementless knee replacement efficiently, safely, with a great outcome,” Dr. Jones says. “It takes one of my favorite surgeries, and one of the things that I think every orthopedic surgeon loves to do, and just makes it that much better.”
References:
1 “The Global Knee Market: Insights and Projections for 2024 and Beyond,” Life Science Intelligence, Accessed November 1, 2024. https://www.lifesciencemarketresearch.com/insights/the-global-knee-market-insights-and-projections-for-2024-and-beyond#:~:text=In%202023%2C%20approximately%203.6%20million,of%20patients%20and%20healthcare%20providers.
2 Prasad AK, Tan JHS, Bedair HS, Dawson-Bowling S, Hanna SA. “Cemented vs. cementless fixation in primary total knee arthroplasty: a systematic review and meta-analysis.” EFORT Open Rev. 2020 Nov
13;5(11):793-798. doi: 10.1302/2058-5241.5.200030. PMID: 33312706; PMCID: PMC7722941.
3 Matthias J, Bostrom MP, Lane JM. “A Comparison of Risks and Benefits Regarding Hip Arthroplasty Fixation.” J Am Acad Orthop Surg Glob Res Rev. 2021 Nov 1;5(11):e21.00014. doi: 10.5435/JAAOSGlobal-D-21-00014. PMID: 34726640; PMCID: PMC8565793.
4 Helvie, Peter F. et al. “Cementless Total Knee Arthroplasty Over the Past Decade: Excellent Survivorship in Contemporary Designs,” The Journal of Arthroplasty, Volume 38, Issue 6, S145 - S150.
5 Polizzotti G, Lamberti A, Mancino F, Baldini A. “New Horizons of Cementless Total Knee Arthroplasty.” J Clin Med. 2023 Dec 30;13(1):233. doi: 10.3390/jcm13010233. PMID: 38202240; PMCID: PMC10780266.
6 Ahmed I, Chawla A, Underwood M, Price AJ, Metcalfe A, Hutchinson C, Warwick J, Seers K, Parsons H, Wall PD. “Tourniquet use for knee replacement surgery.” Cochrane Database Syst Rev. 2020 Dec 8;12(12):CD012874. doi: 10.1002/14651858.CD012874.pub2. PMID: 33316105; PMCID: PMC8094224.
7 C. Kakazu, M. Lippmann, A. Karnwal, Hazards of bone cement: for patient and operating theatre personnel, BJA: British Journal of Anaesthesia, Volume 114, Issue 1, January 2015, Pages 168–169, https://doi.org/10.1093/bja/aeu433
8 “Study Finds Cementless Knee Replacement Outcomes Comparable to Standard Knee Implant, Less Time Needed in OR,” Hospital for Special Surgery, Accessed November 1, 2024. https://news.hss.edu/study-finds-cementless-knee-replacement-outcomes-comparable-to-standard-knee-implant-less-time-needed-in-or/
9Lawrie CM, Schwabe M, Pierce A, Nunley RM, Barrack RL. “The cost of implanting a cemented versus cementless total knee arthroplasty.” Bone Joint J. 2019 Jul;101-B(7_Supple_C):61-63. doi: 10.1302/0301-620X.101B7.BJJ-2018-1470.R1. PMID: 31256655.
10 Vendittoli PA, Riviere C, Hirschmann MT, Bini S. “Why personalized surgery is the future of hip and knee arthroplasty: a statement from the Personalized Arthroplasty Society.” EFORT Open Rev. 2023 Dec 1;8(12):874-882. doi: 10.1530/EOR-22-0096. PMID: 38038379; PMCID: PMC10714387.
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