COMPARISON OF MID-TERM CLINICAL OUTCOMES FOLLOWING PRIMARY TOTAL HIP ARTHROPLASTY WITH OXINIUM VERSUS COBALT CHROME FEMORAL HEADS

Abstract

The use of metal on polyethylene articulations was a key development in establishing total hip arthroplasty as a successful and reproducible treatment for end stage osteoarthritis. In order to ensure implant durability in relatively younger populations, there is a need for alternative, wear resistant bearing surfaces. Oxidized Zirconium (Oxinium, Smith & Nephew, Inc., Memphis, TN) is a relatively new material that features an oxidized ceramic surface chemically bonded to a tough metallic substrate. This material has demonstrated the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture. The purpose of the current investigation was to assess early clinical outcomes following primary total hip arthroplasty with Oxinium versus Cobalt Chrome femoral heads.

One-hundred primary THA procedures were prospectively performed in 100 patients. There were 52 males and 48 females. Using a process of sealed envelope randomization, patients were divided into 2 groups. Group 1 consisted of fifty patients, each receiving primary THA implants with an Oxinium femoral head (OX). The mean age of each patient was 51 years (SD 10.8, Range 22–74) with 26 males and 24 females. Group 2 also consisted of 50 patients. Within this group again each patient received primary THA implants however with a cobalt-chrome femoral head (CC). Demographics were similar with mean age 51 years (SD 11.0, Range 19–76) and again 26 males and 24 females.

The current study reports clinical outcome measures for both the OX and CC groups at a minimum follow-up of 2 years postoperatively. At the time of latest follow-up, stem survival for both groups was 98%. There was a significant improvement in all clinical outcome scores between preoperative and 2 year postoperative time periods for both bearing groups (p< 0.003). There were no significant differences between bearing groups for any of the clinical outcome scores at final follow-up (p> 0.159). Mean Harris Hip Scores at 2 years postoperatively were 92 and 92.5 for OX and CC, respectively (range; 65–100 OX, 60–100 CC). For SF-12, both the Physical Component Summary Scale (PCS) and the Mental Component Summary Scale (MCS) are reported. Mean PCS scores at final follow-up were 45.2 and 49.21 for OX and CC (range; 27.1–56.7 OX, 26.3–61.8 CC). Mean MCS scores were 53.8 and 52.57 for OX and CC (range; 39.2–65.5 OX, 34.3–64 CC). Mean final WOMAC scores are reported as 84.9 and 87 for OX and CC, respectively.

The current data suggest that total hip arthroplasty utilizing Oxinium femoral heads is safe and effective. Additional follow-up of the current cohort will be performed in order to fully assess mid- to long-term clinical outcomes.