Catastrophic Early Failure and Fragmentation of a Modern Moderately Cross-linked Polyethylene Acetabular Liner.

A 60-year-old man who underwent uncomplicated staged bilateral total hip arthroplasty for femoral head osteonecrosis presented with mechanical catching of his left total hip arthroplasty 3 years after index surgery. Radiographs revealed eccentricity of the left femoral head, concerning the failure of a modern moderately cross-linked polyethylene liner. Catastrophic polyethylene liner failure with significant wear, fragmentation, and femoral head abrasion was noted during revision surgery. The original liner and head were replaced, and the patient has exhibited no complications, pain, or difficulty ambulating 6 months postoperatively. This report highlights one potential novel mechanism for the failure of the Exactech Connexion GXL liner (Exactech Inc., Gainesville, FL), an implant recently reported to have a higher-than-expected failure rate, potentially due to insufficient packaging and increased oxidative processes.

Early Polyethylene Failure in a Modern Total Hip Prosthesis: A Note of Caution.

BACKGROUND: Historically, there has been excellent survivorship of total hip arthroplasty with newer implants expected to outperform prior generations. Review of our institutional database identified problems with one particular cross-linked polyethylene liner in mid-term follow-up, which has not been reported in the literature. We report on the technical aspects of this liner, as well as the clinical and radiographic factors associated with early failure of this bearing in our practice. METHODS: A retrospective review of our institutional database was performed from January 2009 to June 2019 of patients who presented with significant osteolysis in the setting of prior total hip arthroplasty with a contemporary polyethylene liner. Demographic and radiographic measures were collected for all patients. RESULTS: Twelve patients were identified, with nine undergoing revision surgery. All patients demonstrated radiographic osteolysis at the time of revision surgery. The average time to diagnosis of failure was 55.9 months (range: 12-120 months). Average cup position preoperatively was 44 degrees inclination (range: 36-53 degrees) and 21 degrees anteversion (range: 10-34 degrees). Nine patients underwent revision of the acetabular component, with two also undergoing femoral component revision. The Manufacturer and User Facility Device Experience database revealed 22 reported cases of wear-related failure from 2009 to 2019. CONCLUSIONS: Considering that no identifiable risk factors related to patient demographics or implant position were identified, the Exactech Connexion GXL liner may be prone to a high rate of early failure from wear and severe secondary osteolysis. We recommend close surveillance of patients with this bearing surface.

An epidermal equivalent assay for identification and ranking potency of contact sensitizers.

The purpose of this study was to explore the possibility of combining the epidermal equivalent (EE) potency assay with the assay which assesses release of interleukin-18 (IL-18) to provide a single test for identification and classification of skin sensitizing chemicals, including chemicals of low water solubility or stability. A protocol was developed using different 3D-epidermal models including in house VUMC model, epiCS® (previously EST1000™), MatTek EpiDerm™ and SkinEthic™ RHE and also the impact of different vehicles (acetone:olive oil 4:1, 1% DMSO, ethanol, water) was investigated. Following topical exposure for 24h to 17 contact allergens and 13 non-sensitizers a robust increase in IL-18 release was observed only after exposure to contact allergens. A putative prediction model is proposed from data obtained from two laboratories yielding 95% accuracy. Correlating the in vitro EE sensitizer potency data, which assesses the chemical concentration which results in 50% cytotoxicity (EE-EC50) with human and animal data showed a superior correlation with human DSA05 (µg/cm(2)) data (Spearman r=0.8500; P value (two-tailed)=0.0061) compared to LLNA data (Spearman r=0.5968; P value (two-tailed)=0.0542). DSA05=induction dose per skin area that produces a positive response in 5% of the tested population Also a good correlation was observed for release of IL-18 (SI-2) into culture supernatants with human DSA05 data (Spearman r=0.8333; P value (two-tailed)=0.0154). This easily transferable human in vitro assay appears to be very promising, but additional testing of a larger chemical set with the different EE models is required to fully evaluate the utility of this assay and to establish a definitive prediction model.