Evidence supports the use of cementless tibial component fixation in total knee replacement but there is a paucity of literature on posterior stabilized designs. This randomized study of posterior stabilized total knee replacements compared cemented and cementless tibial fixation with regard to component migration, bone remodeling, and clinical outcomes.
This prospective single-center, blinded, randomized clinical trial included 100 patients with a mean age of 68 years (range, 45 to 87 years). Operations were performed by either of 2 experienced arthroplasty surgeons using the Advanced Coated System (ACS) prosthesis (Implantcast). Patients were randomized to cemented or cementless tibial fixation; other variables were standardized. Radiostereometric analysis (RSA) and dual x-ray absorptiometry (DXA) were performed during the inpatient stay and at 3, 12, and 24 months to monitor tibial component migration and periprosthetic bone mineral density (BMD). Clinical scores including the Oxford Knee Score and Short Form-12 were assessed prior to surgery and during follow-up.
Late and continuing migration was found with cementless fixation. At 24 months, the mean subsidence was significantly greater for the cementless group (1.22 mm) compared with the cemented group (0.06 mm) (p < 0.01). The mean maximum total point motion at 24 months was 2.04 mm for the cementless group and 0.48 mm for the cemented group (p < 0.01). The cemented group had more BMD loss than the cementless group in the medial, lateral, and anterior periprosthetic regions. Two tibial components were revised in the cementless group, including 1 for loosening. Clinical scores improved equally in the 2 groups.
Late ongoing subsidence and high maximum total point motion in our patients who underwent cementless tibial fixation raise concerns about the fixation stability of ACS cementless posterior stabilized knee replacements. Cemented tibial components were stable. Thus, we advise caution regarding the use of cementless tibial components and recommend tibial fixation with cement for the ACS posterior stabilized total knee replacement.
Level of Evidence:
Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.