Continued stabilization of trabecular metal tibial monoblock total knee arthroplasty components at 5 years-measured with radiostereometric analysis.
OBJECTIVE
The trabecular metal tibial monoblock component (TM) is a relatively new option available for total knee arthroplasty. We have previously reported a large degree of early migration of the trabecular metal component in a subset of patients. These implants all appeared to stabilize at 2 years. We now present 5-year RSA results of the TM and compare them with those of the NexGen Option Stemmed cemented tibial component (Zimmer, Warsaw IN).


METHODS
70 patients with osteoarthritis were randomized to receive either the TM implant or the cemented component. RSA examination was done postoperatively and at 6 months, 1 year, 2 years, and 5 years. RSA outcomes were translations, rotations, and maximum total point motion (MTPM) of the components. MTPM values were used to classify implants as "at risk" or "stable".


RESULTS
At the 5-year follow-up, 45 patients were available for analysis. There were 27 in the TM group and 18 in the cemented group. MTPM values were similar in the 2 groups (p = 0.9). The TM components had significantly greater subsidence than the cemented components (p = 0.001). The proportion of "at risk" components at 5 years was 2 of 18 in the cemented group and 0 of 27 in the TM group (p = 0.2).


CONCLUSIONS
In the previous 2-year report, we expressed our uncertainty concerning the long-term stability of the TM implant due to the high initial migration seen in some cases. Here, we report stability of this implant up to 5 years in all cases. The implant appears to achieve solid fixation despite high levels of migration initially.
School of Biomedical Engineering, Dalhousie University, Halifax, Canada. wilsondaj@gmail.com
David A J
DA
Wilson
Glen
G
Richardson
Allan W
AW
Hennigar
Michael J
MJ
Dunbar
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001843:Bone Cements; D002484:Cementation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000601:surgery*; D011095:Polyethylenes; D011474:Prosthesis Design; D059869:Radiostereometric Analysis; D018401:Sample Size; D013977:Tibia; D013997:Time Factors; D016896:Treatment Outcome
D001843:Bone Cements; D011095:Polyethylenes