Cementless tibial components may lead to less TKR stability
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The use of cementless tibial components in total knee replacement surgery led to a greater risk for subsidence in patients, according to published findings.
Nils Oscar Nivbrant, MBBS, of the department of surgical and perioperative sciences at Umea University in Sweden and the Fiona Stanley Hospital in Australia, and colleagues sought to compare tibial component stability, change in surrounding bone mineral density (BMD) and clinical outcomes of TKRs performed with posterior-stabilized Advanced Coated System knee prostheses (Implantcast) fixed with and without cement.
Nivbrant and colleagues analyzed data from a prospective single-center, blinded, clinical trial composed of 100 patients (mean age, 68 years). Two experienced arthroplasty surgeons split conducting patient operations.
Investigators stratified patients into either a cemented or cementless tibial fixation. Radiostereometric analysis and dual X-ray absorptiometry were performed during inpatient stay and between 3 and 24 months for monitoring of tibial component migration and periprosthetic BMD.
Nivbrant and colleagues observed late and continuing migration in patients with cementless fixation.
At 24 months follow-up, mean subsidence was greater in the cementless group compared with the cemented group (1.22 vs. 0.06 mm; P < .01), the results showed. Mean maximum total point motion at 24 months was greater in the cementless group compared with the cemented group (2.04 vs. 0.48 mm; P < .01).
The cemented group had greater BMD loss in the medial, lateral and anterior periprosthetic regions compared with the cementless group, researchers wrote.
Two tibial components required revision in the cementless group, including one for loosening. Clinical scores improved equally in both groups.
“Late ongoing subsidence and high maximum total point motion raise concerns about the fixation stability of cementless (advanced coated system) posterior stabilized knee replacements,” Nivbrant and colleagues wrote. “Cemented tibial fixation were stable despite BMD reduction surrounding the tibial components.”
Perspective
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Denis Nam, MD, MSc
A recently published study in The Journal of Bone and Joint Surgery by Nivbrant and colleagues demonstrated a concerning degree of late tibial component subsidence of a posterior-stabilized, cementless design. In their single-center, blinded, prospective randomized control trial, a total of 97 TKRs were performed with either a cemented or cementless tibial component using the Advanced Coated System Fixed-Bearing Posterior Stabilized prosthesis (Implantcast). Radiostereometric analysis (RSA) was used for analysis. They found late and continuing migration with the cementless prosthesis with a mean maximum total point motion at 24 months of 2.04 mm.
Cementless fixation in total knee arthroplasty remains an area of interest due to technologic advancements allowing the creation of porous surfaces resembling trabecular bone, the potential for a biologic interface that could remodel over time and elimination of third-body debris from cement. However, there remain relevant concerns of the risk of fibrous ingrowth, component subsidence and increased aseptic loosening. Thus, it is crucial that new implant designs be introduced in a phased manner and the authors should be commended on performing this excellent analysis. While the aforementioned study raised concerns regarding this specific prosthesis and component design, it must also be emphasized that not all implant designs are created equal. Cementless TKA should not be abandoned due to the findings attributed to one specific design. The risk of tibial component loosening is clearly multifactorial, as numerous variables, such as tray stiffness, implant material, surface coating, keel design and fixation, component alignment, ligamentous balancing and many other factors, can influence the success or failure of a particular prosthesis.
Recently, Sporer and colleagues reported RSA results of a cruciate-retaining, cementless tibial component and showed reliable biologic fixation with minimal component subsidence at 24 months Thus, the study by Nivbrant and colleagues adds to the growing body of literature around cementless TKA designs, but it remains critical that each cementless design is evaluated on an individual basis.
Reference:
Sporer S, et al. Bone Joint J. 2019;doi:10.1302/0301-620X.101B7.BJJ-2018-1466.R1.
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