Cementless Fixation in TKA: Early Study Results
The study is intended to evaluate early radiographic fixation status and changes and clinical outcomes when a modular tibial component with a trabecular metal coating is used in cementless fixation of a total knee implant.
Raj K. Sinha, MD, PhD, and Cristian Balcescu
The authors have no disclosures relevant to this article.
Editor’s Note: This article is an except of the authors’ study, Early Results of a Modular Cementless Tibial Component for Total Knee Arthroplasty, published in the journal Reconstructive Review. The full article can be found here.
Cementless components in total knee arthroplasty (TKA) have been used for 3 decades with mixed results, especially for fixation. As such, cemented components have continued to be endorsed as the gold standard [1-5].
However, cementless fixation remains attractive, especially for younger and more active patients in whom cemented fixation may be less durable, with a greater risk of polyethylene wear/osteolysis from third-body wear [1,6,7].
An optimum implant, therefore, would be cementless and reliably achieve durable bony fixation.
Previous cementless devices suffered from poor design characteristics such as improper pore size, debonding of the porous coating, and excessively thin polyethylene inserts . Newer technologies such as hydroxyapatite coating have been reported to achieve better osseointegration at early follow-up with limited subsidence . Similarly, non-modular trabecular metal (TM) tibial components have demonstrated excellent fixation and mid-term durability [10,11].
This study evaluates the early radiographic fixation status and changes and clinical outcomes of a modular tibial component with a TM coating intended for cementless fixation.
A total of 24 primary TKAs indicated for painful osteoarthritis unresponsive to conservative medical therapy were performed in 21 patients (5 females, 16 males) by the senior author (RKS) from 2007 to 2009. Three patients had bilateral TKAs, with 2 patients having simultaneous bilateral TKAs. All surgeries were performed using a mini-midvastus approach, with an uncemented Zimmer® NexGen® Trabecular Metal™ Tibial Tray, a cemented posteriorly stabilized Zimmer® NexGen® LPS-flex femur, and cemented all-polyethylene patellar components. In no case was the TM tray abandoned for a cemented component.
To our knowledge, this is the first report on a modular trabecular tibial component intended for cementless fixation during TKA.
In general, this design reliably achieved early bony fixation (Figure 1). No components were revised, and 1/24 was probably radiographically loose or fibrous stable.
This low failure rate compares favorably with other cementless designs. For example, Moran et al found a 19% failure rate due to aseptic failure of the tibial component in a series of 108 primary TKAs in 96 patients after an average follow-up of 64 months using an uncemented, porous-coated system (PCA designed by Howmedica, Rutherford, New Jersey) .
Additionally, Goldberg et al observed a 13% failure rate in 124 TKAs in 99 patients after an average follow-up of 11 years in the surviving knees (Miller- Galante I, designed by Zimmer, Warsaw, Indiana), although only 1 revision was cited as being due to tibial component loosening .
Berger et al observed a 19% failure rate (7% due to tibial loosening) in a series of 108 TKAs (Miller- Galante I, designed by Zimmer, Warsaw, Indiana), performed on 82 patients after follow-up greater than 7 years, and average 11-year follow-up of surviving knees .
This modular version also compares favorably with its non-modular counterpart. Patients did not have prolonged pain postoperatively, and at latest follow-up, behaved like typical TKA patients.
Given the short follow-up, no comments can be made regarding durability of fixation. Longer-term study will be needed.
In addition, the femoral component was a high-flex PS design, possibly loading the implant posteriorly to a higher degree than a non-high-flex or CR design would. Initial mechanical fixation, however, appeared to be adequate to achieve bony ingrowth.
Lastly, although the TM fixation surface has enjoyed success in multiple applications, the data from this study utilizing this particular tibial component design cannot be extrapolated to other tray designs or to femoral components.
Nevertheless, use of a modular tibial tray designed for cementless fixation appears to be safe and effective.
Raj K. Sinha, MD, PhD, is from STAR Orthopaedics, La Quinta, California. Cristian Balcescu is from UCLA School of Medicine, Los Angeles, California.
Sinha RK, Balcescu C. Early Results of a Modular Cementless Tibial Component for Total Knee Arthroplasty. 2014; 4(3):27-30. doi: 10.15438/rr.4.3.27. Copyright 2014, Joint Implant Surgery & Research Foundation. Used with permission.
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