The effect of adding tobramycin to Simplex P cement on femoral stem micromotion as measured by radiostereometric analysis

Abstract

Background Previous in vitro research on addition of antibiotics to bone cement has found no statistically significant deterioration in mechanical properties. However, no clinical studies have compared the performance of tobramycin-laden bone cement with that of standard bone cement (Simplex P).

Patients and Methods 23 patients (25 hips) were randomized to receive an Exeter (Stryker Orthopaedics) femoral stem cemented with either Simplex P (standard) or Simplex T (tobramycin-laden) cement. There were 2 years of follow-up, with scheduled radiostereometric (RSA) examinations.

Results All stems migrated distally and showed some degree of retroversion. No clinically significant differences in stem subsidence or retroversion were found between the Simplex T and Simplex P cement groups after 2 years. Overall subsidence was less than in previous studies, probably due to a postponed initial post-surgical examination. Rates of subsidence in both cement groups were consistent with those from previous studies of Exeter stems.

Interpretation Subsidence of the femoral stem after 2 years was similar in the Simplex T (tobramycin-laden) and Simplex P (standard) groups.

EB: main investigator, main surgeon, preparation of manuscript. MP: conducted radiographic examinations, preparation of manuscript. TG: conducted radiographic examinations, measurements, analysis of data, and preparation of manuscript. TT: interpretation and final review of manuscript, contribution of surgical cases.

We thank Stryker Orthopaedics for their financial support of this study. This study was partially and unconditionally funded by Stryker Orthopaedics. The authors received no benefits or payment. We also thank Nathanael M Kesler who conducted radiographic examinations and measurements, and also Drs Colin Burnell and David Hedden who contributed surgical cases and contributed to the design of the study. We are grateful to Michelle Hofer for acquiring the radiographic images.