The Rise of Cementless Total Knee Replacements
There are three hundred and sixty joints in the human body. Most work our whole lives without needing a surgeon. However, sometimes our anatomy needs assistance. Take the knee for example. The American Joint Replacement Registry recorded over two million arthroplasty procedures between 2012 and 2020.¹ Of these, 52.1 percent were Total Knee Arthroplasties (TKA).¹ Most of these cases used bone cement to fixate their implants. Recently though, an increasing number of TKAs have ditched the material altogether. Going cementless, as it were.
First used in 1958, bone cement helps knee replacements stay in place.² These polymeric mixtures solidify an implant’s connection to a patient’s bones. The cement fills intertrabecular spaces and cures to create a solid bond between the two.³ ⁴
Cementless implants use their surface to lock their initial position.⁵ This rough texture prevents micromotion, which reduces the ingrowth of bone.⁵ A process called osseointegration. Later, bone fuses with the implant creating a sturdy connection. Much the same result as a cemented implant.
However, only 1.9% of cases in 2012 were cementless, but as of 2020, that share of procedures had grown to 14.2%.¹ A dramatic change considering that cementless TKAs are nothing new. Their first documented use was back in 1980.⁵ But something has changed in orthopedics which may partially explain this increase.
Cementless implants depend even more than cemented ones on their patient’s bone health. Osteoporotic bone may not provide a tight enough fit for initial fixation.³ This limitation may be one of the reasons why cementless implants are gaining popularity. Between 2000 and 2014, the mean age for knee replacements dropped by 2.1 years to 65.9.⁷ And bones from younger patients typically have a higher bone mineral density (BMD).⁸ A factor that correlates with reduced fracture risk.⁹ Additionally, it’s hoped this greater density could increase implant lifespan. Perhaps even long enough to reduce the chance of revisions. However, additional studies are needed to demonstrate long-term outcomes in patients of this lower age range.
But nothing lasts forever, and implants are no exception. Over time both bone cement and cementless implants wear down. This process creates fragments in surrounding tissues. These particles can trigger inflammatory responses that resorb bone leading to loosening.¹⁰ It should be noted that there was no significant difference in revision rates or function in a study between these two types of implants.¹¹ Meaning that for some patients cementless implants could be a better fit and certainly no worse an option than cemented ones.
Cementless knee arthroplasties are becoming a more significant part of the orthopedic landscape. Younger populations with less osteoporotic bone mean implants must adapt to these patients’ needs. It would seem that cementless fixation may be rapidly filling this expanding niche.
Bibliography
1.
American Joint Replacement Registry (AJRR): 2021 Annual Report. American Academy of Orthopaedic Surgeons; 2021:20, 74.
2.
Prudhon JL, Verdier R. Cemented or cementless total knee arthroplasty? SICOT-J. 2017;3:70. doi:10.1051/sicotj/2017046
3.
Cluett J. How Artificial Knee and Hip Replacement Implants Are Held in Bone. Verywell Health. Published July 25, 2022. Accessed August 31, 2022. https://www.verywellhealth.com/how-are-joint-replacements-held-in-the-bone-2549505
4.
Atrium Health Wake Forest Baptist. Computer-assisted Total Knee Replacement. www.youtube.com. Published July 2, 2011. Accessed August 31, 2022. https://youtu.be/6HlTqzOoR3A
5.
Dalury DF. Cementless total knee arthroplasty. The Bone & Joint Journal. 2016;98-B(7):867–873. doi:10.1302/0301–620x.98b7.37367
6.
Vaishya R, Chauhan M, Vaish A. Bone cement. Journal of Clinical Orthopaedics and Trauma. 2013;4(4):157–163. doi:10.1016/j.jcot.2013.11.005
7.
Sloan M, Premkumar A, Sheth NP. Projected Volume of Primary Total Joint Arthroplasty in the U.S., 2014 to 2030. The Journal of Bone and Joint Surgery. 2018;100(17):1455–1460. doi:10.2106/jbjs.17.01617
8.
Warming L, Hassager C, Christiansen C. Changes in Bone Mineral Density with Age in Men and Women: A Longitudinal Study. Osteoporosis International. 2002;13(2):105–112. doi:10.1007/s001980200001
9.
Gundry M, Hopkins S, Knapp K. A Review on Bone Mineral Density Loss in Total Knee Replacements Leading to Increased Fracture Risk. Clinical Reviews in Bone and Mineral Metabolism. 2017;15(4):162–174. doi:10.1007/s12018–017–9238–4
10.
Cemented vs. Cementless Knee Replacement — R. Michael Meneghini, MD. www.meneghinimd.com. https://www.meneghinimd.com/specialties/cemented-vs-cementless-knee-replacement
11.
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 Reviews. 2020;5(11):793–798. doi:10.1302/2058–5241.5.200030
