Much effort has been aimed at strategies for patient optimization, perioperative standards of care, and postoperative risk stratification to reduce the incidence of SSI. Examples include, newer dressing modalities, antibiotic-impregnated bone cement, intra-wound powdered antibiotics, as well as novel suture types and techniques, all of which have shown great potential. However, the question remains as to whether these changes in practice have led to lower overall infections over the past few years. Therefore, the purpose of this study was to track the annual rates and trends of: 1) overall; 2) deep; and 3) superficial SSI following total hip arthroplasty (THA) using the most recent data (2012 to 2016) from a large nationwide database. The National Surgical Quality Improvement Program database was queried for all primary THAs (CPT code 27130) between 2012 and 2016, yielding 122,451 cases. Cases with reported superficial and/or deep SSIs were combined for an overall rate, and then independently analyzed as deep and superficial SSIs. The infection incidence for each year was calculated. After an overall 5-year correlation and trends, univariate analysis was also performed to compare the most recent year, 2016, with each of the preceding 4 years. Furthermore, a comparison of overall and deep SSI incidences from this study were compared to meta-analysis of pooled data from 2001 to 2011. Pearson correlation coefficients and chi-squared tests were used to determine correlation and statistical significance which was maintained at a p-value less than 0.05.Background
Methods
We report on an innovative surface grafting to highly crosslinked (HXLPE) bearing for THA using a biocompatible-phospholipid-polymer poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC). Such hydrophilic surfaces mimic articular cartilage and are hypothesized to improve lubrication and thereby reduce friction and wear. We performed in vitro testing of wear and friction of ceramic-on-polyethylene THRs with the PMPC treatment, and compared them with untreated controls. Highly cross-linked UHMWPE bearings, gamma-ray-irradiated at different levels with and without vitamin E (HXL Vit. E: 125 kGy, HXL: 75 kGy, respectively) were divided so half were PMPC treated (n=3 for all four groups). All were paired with identical 40 mm diameter zirconia-toughened-alumina ceramic heads. Testing was carried-out on an AMTI hip simulator for 10 million simulated walking cycles with standard lubricant and conditions (ISO-14242-1). Wear was measured gravimetrically at 21 intervals, and so was frictional torque with a previously described and tested methodology. PMPC treatment produced a statistically significant 71% in wear reduction of HXL poly (1.70±1.36 mg/Mc for PMPC vs. 5.86±0.402 mg/Mc for controls, p=0.013). A similar significant wear reduction was found for PMPC treated HXL with Vit. E liners (0.736±0.750 mg/Mc, vs. 2.14±0.269 mg/Mc, p=0.035). The improvements were associated with 12% and 5% reductions in friction of the HXL and Vit. E HXL respectively (statistically significant p=0.003, and marginal p=0.116, one tailed). These results were an important step in the quest for lower wearing, thin and strong UHMWPE liners for larger diameter femoral heads with the potential benefit of longevity and less risk of dislocation after surgery.
