Revision Rates for Aseptic Loosening in the Obese Patient: A Comparison Between Stemmed, Uncemented, and Unstemmed Tibial Total Knee Arthroplasty Components

Background

Total knee arthroplasty (TKA) is an effective treatment option for high body mass index (BMI) patients achieving similar outcomes to nonobese patients. However, increased rates of aseptic loosening in patients with a high BMI have been reported. Component fixation is a concern when performing TKA in the obese patient. To address this concern in cemented TKA, extended tibial stems have been used. Uncemented implants that take advantage of biologic osseointegration have also been advocated. This retrospective study examined the use of and revision rates of extended cemented tibial stems and uncemented implants compared with conventional cemented implants in our high BMI patient population.

Methods

We retrospectively reviewed a prospectively maintained database of 3239 primary Attune TKAs (Depuy, Warsaw, Indiana). All obese patients (BMI > 30 kg/m2) with > 30 months of follow-up were included in our analysis. Those who underwent cemented TKA using a tibial stem extension (Group 1) (n = 145) and those where cementless implants were used (Group 2) (n = 100) were compared to a control group (n = 1243) using a standard cemented implant. Primary outcome measures were all-cause revision, revision for aseptic loosening, and revision for tibial loosening. Kaplan-Meier survival analysis and Cox regression models were used to compare the primary outcomes between groups.

Results

In total, there were 1512 knees that met the inclusion criteria. The mean follow-up was 6.8, 5.1, and 5.3 years for cemented, stemmed, and cementless groups, respectively. There were 37 all-cause revisions identified. Seven were for aseptic loosening (2 tibial, 1 femoral, and 4 involving both components); all of these were in the standard cemented implant group. There were no revisions in the stemmed or cementless implant groups. Survival analysis did not show any significant differences between groups for either all-cause revision or for aseptic loosening.

Conclusions

This retrospective analysis showed that there were no revisions required for aseptic loosening when a cemented, stemmed, or uncemented implant was used in obese patients. These findings show that cementless and extended stem implants are a reasonable option in obese patients.