Results of Conserve Plus Hip Resurfacing: prospective clinical, radiographic and ion study.

We report the 3- to 5-year clinical, radiographic and serum ion level results of a prospective consecutive cohort of 42 hip resurfacing arthroplasties using the Conserve Plus implant in 39 male patients that were operated on by a single surgeon in a community hospital. Average age was 53 years (range 34-67) at surgery.  There was one revision for a subcapital neck fracture. There were no surgery related complications. The survival of the implant was 95%.  Clinical evaluation showed excellent results with a modified Charnley score of 17.6/18, Harris Hip Score of 96.2/100, WOMAC  of 95.1/100, Oxford Score 15.3, and UCLA-Activity Score of 8/10. Radiographic analysis showed no implant at risk, no migration or signs of loosening, no neck narrowing and no osteolysis at final follow-up. Average cup inclination angle was 43.5° with 2 outliers (34° and 57°).  Ion level study showed average cobalt in serum 1.04 µg/l (range 0-4) for the whole group, 0.7 µg/l (range 0 -3) in patients with unilateral resurfacing and 2.0 µg/l (range 0 – 4) in patients with bilateral resurfacing.  All patients had ion levels within the safe zone

High rates of implant fracture of a generic polished tapered femoral stem

OBJECTIVES: Cemented polished tapered stems have demonstrated excellent long-term outcomes. Based on this concept, many generic tapered stems have been released into the market. The aim of this study was to evaluate implant-related complications of 1 specific stem design. METHODS: Between 2010 and 2017, 315 total hip replacements were performed using a Fortress stem (Biotechni, La Ciotat, France). Patient records and radiology were retrospectively reviewed for implant-related complications. A failure analysis was performed on the failed Fortress stems in order to determine the cause of premature failure. RESULTS: 7 (2.2%) patients sustained a fracture of the neck of the implant after a mean of 5 years (range 50-81 months). All fractures were atraumatic, originating at the introducer inlet of the stem. All fractured occurred in obese patients (BMI >33 kg/m2) with a small sized prosthesis. Of these, there were 5 135° and 2 125° stems. Fracture risk was 23% (7/30) for patients with a small sized stem and a BMI >30 kg/m2. All cases were revised using a cement-in-cement technique or a cementless modular revision stem. Failure analysis on the retrieved stems revealed a stress riser at the bottom of the introducer inlet. CONCLUSIONS: An alarmingly high rate of early implant fractures was seen using this specific type of cemented stem, particularly when using smaller implant sizes in obese patients. Although based on a proven design, a specific modification led to a stress riser in the neck area, which resulted in a high incidence of implant failure. This series underlines the importance of a stepwise introduction into the market of new orthopaedic devices even when based on established concepts. Generic stems may not behave as the original stem upon which it was designed.status: publishe