Cementless Total Knee Arthroplasty Matches Cemented Survivorship at Five Years

Evolution of Fixation Strategies in Primary Total Knee Arthroplasty

Total knee arthroplasty remains the definitive intervention for end-stage osteoarthritis, yet the optimal method for component fixation continues to be a subject of clinical debate as patient demographics shift toward younger, more active individuals [1]. While cemented fixation has historically served as the gold standard, the leading causes of revision surgery, such as aseptic loosening (the failure of the bond between the implant and bone without infection) and periprosthetic joint infection, drive the search for more durable interfaces [2]. Surgeons are increasingly managing patients with higher body mass indices and complex comorbidities, factors that can significantly influence postoperative quality of life and implant longevity [3, 4]. Although technological adjuncts like robotic assistance and kinematic alignment (a surgical approach that restores the patient's native joint line and rotational axes) have refined surgical precision, the fundamental stability of the bone-implant interface remains the primary determinant of long-term success [5, 6]. This study provides a mid-term comparison of cemented and cementless fixation to determine if contemporary porous metal designs can match the established reliability of the cemented technique.

Comparative Cohort and Implant Design Specifications

The researchers conducted a retrospective review of 483 primary total knee arthroplasties performed at a single institution between May 1, 2018, and May 31, 2019. This study population was divided into two distinct cohorts based on the fixation method employed: 261 cemented procedures and 222 cementless procedures. To isolate the impact of the fixation interface and minimize confounding variables related to prosthetic geometry, the surgical teams utilized the same contemporary implant design for every patient in both groups. This consistency in hardware allows for a more direct assessment of how biologic fixation (the process where bone grows into the porous surface of an implant to secure it without cement) compares to traditional polymethylmethacrylate cementation. For the practicing clinician, this study design reduces the noise often found in registry data where multiple implant geometries may skew results.

Five-Year Revision Rates and Survivorship Analysis

The researchers established a minimum follow-up period of 5.0 years to evaluate the intermediate-term durability of the prosthetic interface, with a mean follow-up of 5.8 years (range, 5.0 to 6.4). During this observation window, both fixation strategies demonstrated high rates of component retention. The 5-year all-cause revision survivorship was 98.5% in the cemented group and 99.5% in the cementless group. These findings suggest that the biologic fixation achieved through contemporary porous metal designs provides a stable foundation that is clinically comparable to the immediate mechanical bond of polymethylmethacrylate cement at the five-year mark. For surgeons considering the transition to cementless designs, these data provide reassurance that early failure is not increased with biologic fixation.

Radiographic Stability and Absence of Aseptic Loosening

The radiographic evaluation of the study cohorts provided critical evidence regarding the mechanical stability of the bone-implant interface. The researchers reported zero cases of aseptic loosening in either the cemented or cementless groups during the follow-up period. Furthermore, there was no radiographic evidence of component subsidence (the sinking or shifting of the prosthetic component into the underlying cancellous bone) identified in either group. Detailed imaging analysis also focused on the presence of non-progressive radiolucent lines, which are thin gaps appearing between the implant and the bone on imaging that do not widen over time. These lines were observed in 28 (10.7%) of the cemented knees and in 22 (9.9%) of the cementless knees, with no statistically significant difference between the groups (P > 0.05). Because these lines remained non-progressive, they were not associated with clinical failure. The study concluded that cementless fixation demonstrates excellent minimum five-year survivorship and radiographic outcomes equivalent to cemented fixation, offering a viable alternative for primary total knee arthroplasty without compromising mid-term stability.

References

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