Causes of failure of ceramic-on-ceramic and metal-on-metal hip arthroplasties.

BACKGROUND: Few large series of hard bearing surfaces have reported on reasons for early failure. A number of unique mechanisms of failure, including fracture, squeaking, and adverse tissue reactions, have been reported with these hard bearing surfaces. However, the incidence varies among the published studies. QUESTIONS/PURPOSES: To confirm the incidences, we identified the etiologies of early failures of hard-on-hard bearing surfaces for ceramic-on-ceramic and metal-on-metal THAs. METHODS: We retrospectively reviewed records of 2907 THAs with hard-on-hard bearing surfaces implanted between 1996 and 2009; 1697 (58%) had ceramic-on-ceramic and 1210 (42%) had metal-on-metal bearing surfaces. We recorded bearing-related complications and compared them to nonspecific reasons for revision THA. The minimum followup of the ceramic-on-ceramic and metal-on-metal cohorts was 6 months (mean, 48 months; range, 6-97 months) and 24 months (mean, 60 months; range, 24-178 months), respectively. RESULTS: The overall revision rate for ceramic-on-ceramic THA was 2.2% (38 of 1697), with aseptic loosening accounting for 55% of revisions (femur or acetabulum). The bearing accounted for 13% of the revisions in the ceramic-on-ceramic THA cohort. The overall metal-on-metal revision rate was 5.4% (65 of 1210), 17 involving adverse tissue reactions related to the metal-on-metal bearing surface (17 of 1210, 1.4% of cases; 17 of 65, 26% of revisions). CONCLUSIONS: Twenty-six percent of the revisions from metal-on-metal and 13% of ceramic-on ceramic were bearing related. The overall short- to medium-term revision rate was 2.2% and 5.4% for ceramic-on-ceramic and metal-on-metal, respectively. The most common etiology of failure was loosening of the femoral or acetabular components. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence

Decreased Incidence of Periprosthetic Joint Infection in Total Hip Arthroplasty with Use of Topical Vancomycin

Background: Periprosthetic joint infections following total hip arthroplasty (THA) can cause significant patient morbidity and carry with them a substantial cost burden to the healthcare system.  The purpose of this study was to assess whether the addition of topical vancomycin decreased the incidence of superficial and deep infections after primary total hip arthroplasty?      Methods: We performed a retrospective analysis of patients who underwent primary THA with (1070 hips) and without (815 hips) the use of topical vancomycin.  Records were reviewed to determine incidence of PJI. Infections were categorized as deep or superficial. Medical comorbidity data was evaluated for known risk factors including diabetes, rheumatoid arthritis, and BMI. Records were further reviewed to determine surgical approach used and bacterial cause of PJI.      Results: The overall incidence of infection in the control group was 1.47% (12 hips) and significantly decreased to 0.47% (5 hips) with the addition of topical vancomycin (p=0.022). Deep infections also decreased from 0.86% (7 hips) in the control group to 0.09% (1 hip) in the vancomycin group (p=0.011).  There was no difference in BMI or percent of patients with diabetes between groups.       In all patients, regardless of vancomycin use, the incidence of infection in the direct lateral approach was higher (2.04%, 9 hips) than the anterior approach (0.055%, 8 hips)  (p=0.004).   Conclusions:  We found a lower incidence of periprosthetic joint infection after THA with the addition of topical vancomycin. We also found a decreased incidence of infection in patients who had surgery through an anterior approach compared with those who had a direct lateral approach

Minimal stress shielding with a Mallory-Head titanium femoral stem with proximal porous coating in total hip arthroplasty

<p>Abstract</p> <p>Background</p> <p>As longevity of cementless femoral components enters the third decade, concerns arise with long-term effects of fixation mode on femoral bone morphology. We examined the long-term consequences on femoral remodeling following total hip arthroplasty with a porous plasma-sprayed tapered titanium stem.</p> <p>Methods</p> <p>Clinical data and radiographs were reviewed from a single center for 97 randomly selected cases implanted with the Mallory-Head Porous femoral component during primary total hip arthroplasty. Measurements were taken from preoperative and long-term follow-up radiographs averaging 14 years postoperative. Average changes in the proximal, middle and diaphyseal zones were determined.</p> <p>Results</p> <p>On anteroposterior radiographs, the proximal cortical thickness was unchanged medially and the lateral zone increased 1.3%. Middle cortical thickness increased 4.3% medially and 1.2% laterally. Distal cortical thickness increased 9.6% medially and 1.9% laterally. Using the anteroposterior radiographs, canal fill at 100 mm did not correlate with bony changes at any level (Spearman's rank correlation coefficient of -0.18, 0.05, and 0.00; p value = 0.09, 0.67, 0.97). On lateral radiographs, the proximal cortical thickness increased 1.5% medially and 0.98% laterally. Middle cortical thickness increased 2.4% medially and 1.3% laterally. Distal cortical thickness increased 3.5% medially and 2.1% laterally. From lateral radiographs, canal fill at 100 mm correlated with bony hypertrophy at the proximal, mid-level, and distal femur (Spearman's rank correlation coefficient of 0.85, 0.33, and 0.28, respectively; p value = 0.001, 0.016, and 0.01, respectively).</p> <p>Conclusion</p> <p>Stress shielding is minimized with the Mallory-Head titanium tapered femoral stem with circumferential proximal plasma-sprayed coating in well-fixed and well-functioning total hip arthroplasty. Additionally, the majority of femora demonstrated increased cortical thickness in all zones around the stem prosthesis. Level of Evidence: Therapeutic Level III.</p

STROBE-X: A probe-class mission for x-ray spectroscopy and timing on timescales from microseconds to years

We describe the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probeclass mission concept that will provide an unprecedented view of the X-ray sky, performing timing and spectroscopy over both a broad energy band (0.2-30 keV) and a wide range of timescales from microseconds to years. STROBE-X comprises two narrow-field instruments and a wide field monitor. The soft or low-energy band (0.2-12 keV) is covered by an array of lightweight optics (3-m focal length) that concentrate incident photons onto small solid-state detectors with CCD-level (85-175 eV) energy resolution, 100 ns time resolution, and low background rates. This technology has been fully developed for NICER and will be scaled up to take advantage of the longer focal length of STROBE-X. The higher-energy band (2-30 keV) is covered by large-area, collimated silicon drift detectors that were developed for the European LOFT mission concept. Each instrument will provide an order of magnitude improvement in effective area over its predecessor (NICER in the soft band and RXTE in the hard band). Finally, STROBE-X offers a sensitive wide-field monitor (WFM), both to act as a trigger for pointed observations of X-ray transients and also to provide high duty-cycle, high time-resolution, and high spectral-resolution monitoring of the variable X-ray sky. The WFM will boast approximately 20 times the sensitivity of the RXTE All-Sky Monitor, enabling multi-wavelength and multi-messenger investigations with a large instantaneous field of view. This mission concept will be presented to the 2020 Decadal Survey for consideration

Unicompartmental Knee Arthroplasty: US and Global Perspectives.

Unicompartmental knee arthroplasty (UKA) is a treatment option for anteromedial osteoarthritis. Compared with total knee arthroplasty (TKA), UKA offers improved knee range of motion, functional recovery and decreased medical complications. Revision rates continue to be higher with UKA compared with TKA. With current UKA implants, there is no significant difference in mobile bearing or fixed bearing, or between cemented and cementless implants. Enabling technology, such as robotic-assisted surgery, has demonstrated improvements in component positioning, but no long-term difference in survival compared with traditional manual instruments