Factors associated with mortality after proximal femoral fracture.

Proximal femoral fractures are a serious complication, especially for elderly patients. Therefore, we have aimed to answer the following research question: What is the postfracture mortality rate in the elderly population and what are associated risk factors? For this, proximal femoral fractures that occurred between 1 January 2009 and 31 December 2019 were identified from the Medicare Physician Service Records database. The Kaplan-Meier (KM) method with the Fine and Gray subdistribution adaptation was used to determine rates of mortality. A semiparametric Cox regression model was applied, incorporating 23 measures as covariates to identify risk factors. The estimated 1 year mortality rate was 26.8% after head/neck fracture, 28.2% after intertrochanteric fracture, and 24.2% after subtrochanteric fracture. Male sex, age over 70 years, chronic obstructive pulmonary disease (COPD), cerebrovascular disease, chronic kidney disease, a concomitant fracture, congestive heart failure, diabetes mellitus, hypertension, insulin use, ischemic heart disease, morbid obesity, osteoporosis, tobacco dependence, and median household income were determined as risk factors for increased mortality. An early assessment of individual risk factors accessible for therapeutic treatment is crucial in the management of proximal femur fractures to aid in attempts at reducing the high mortality apparent in the elderly US population.

Comparative Epidemiology of Revision Arthroplasty: Failed THA Poses Greater Clinical and Economic Burdens Than Failed TKA.

BACKGROUND: Revision THA and TKA are growing and important clinical and economic challenges. Healthcare systems tend to combine revision joint replacement procedures into a single service line, and differences between revision THA and revision TKA remain incompletely characterized. These differences carry implications for guiding care and resource allocation. We therefore evaluated epidemiologic trends associated with revision THAs and TKAs. QUESTIONS/PURPOSES: We sought to determine differences in (1) the number of patients undergoing revision TKA and THA and respective demographic trends; (2) differences in the indications for and types of revision TKA and THA; (3) differences in patient severity of illness scoring between THA and TKA; and (4) differences in resource utilization (including cost and length of stay [LOS]) between revision THA and TKA. METHODS: The Nationwide Inpatient Sample (NIS) was used to evaluate 235,857 revision THAs and 301,718 revision TKAs between October 1, 2005 and December 31, 2010. Patient characteristics, procedure information, and resource utilization were compared across revision THAs and TKAs. A revision burden (ratio of number of revisions to total number of revision and primary surgeries) was calculated for hip and knee procedures. Severity of illness scoring and cost calculations were derived from the NIS. As our study was principally descriptive, statistical analyses generally were not performed; however, owing to the large sample size available to us through this NIS analysis, even small observed differences presented are likely to be highly statistically significant. RESULTS: Revision TKAs increased by 39% (revision burden, 9.1%-9.6%) and THAs increased by 23% (revision burden, 15.4%-14.6%). Revision THAs were performed more often in older patients compared with revision TKAs. Periprosthetic joint infection (25%) and mechanical loosening (19%) were the most common reasons for revision TKA compared with dislocation (22%) and mechanical loosening (20%) for revision THA. Full (all-component) revision was more common in revision THAs (43%) than in TKAs (37%). Patients who underwent revision THA generally were sicker (> 50% major severity of illness score) than patients who underwent revision TKA (65% moderate severity of illness score). Mean LOS was longer for revision THAs than for TKAs. Mean hospitalization costs were slightly higher for revision THA (USD 24,697 +/- USD 40,489 [SD]) than revision TKA (USD 23,130 +/- USD 36,643 [SD]). Periprosthetic joint infection and periprosthetic fracture were associated with the greatest LOS and costs for revision THAs and TKAs. CONCLUSIONS: These data could prove important for healthcare systems to appropriately allocate resources to hip and knee procedures: the revision burden for THA is 52% greater than for TKA, but revision TKAs are increasing at a faster rate. Likewise, the treating clinician should understand that while both revision THAs and TKAs bear significant clinical and economic costs, patients undergoing revision THA tend to be older, sicker, and have greater costs of care.

Mortality, cost, and downstream disease of total hip arthroplasty patients in the medicare population.

The purpose of this study is to compare the differences in downstream cost and health outcomes between Medicare hip OA patients who undergo total hip arthroplasty (THA) and those who do not. All OA patients in the Medicare 5% sample (1998-2009) were separated into non-THA and THA groups. Differences in costs and risk ratios for mortality and new disease diagnoses were adjusted using logistic regression for age, sex, race, socioeconomic status, region, and Charlson score. Mortality, heart failure, depression, and diabetes were all reduced in the THA group, though there was an increased risk for atherosclerosis in the short term. The potential for selection bias was investigated with two separate propensity score analyses. This study demonstrates the potential benefit of THA in reducing mortality and improving aspects of overall health in OA patients.

Monotonic and fatigue behavior of five clinically relevant conventional and highly crosslinked UHMWPEs in the presence of stress concentrations.

Five formulations of clinically relevant UHMWPE (conventional, moderately crosslinked annealed and remelted, and highly crosslinked annealed and remelted) were investigated in a physiologically relevant environment. Their monotonic stress-strain behavior in the presence of notches of two different severities and at two different displacement rates was examined using a custom developed video based system. It was found that both an elevation of yield stress and a truncation of orientation hardening took place under monotonic loading and that these changes were found to be material and elastic stress concentration factor dependent. The fatigue behavior of these materials was examined using the same geometries via a stress-life approach with failure defined as fracture of the specimen in the 1000 to 100,000 cycle lifetime range. The results were modeled using the Basquin relationship (σ=AN(b), where σ=stress and N=lifetime, and A and b are experimentally derived constants) via maximum likelihood estimation methods to account for specimen runout (no failure at 250,000cycles). The conventional material was found to have a greater slope, b, and intercept, A, than the crosslinked materials as well as appearing to have less variance in its failure distributions.

Mortality, cost, and health outcomes of total knee arthroplasty in Medicare patients.

There are little data that quantify the long term costs, mortality, and downstream disease after Total Knee Arthroplasty (TKA). The purpose of this study is to compare differences in cost and health outcomes between Medicare patients with OA who undergo TKA and those who avoid the procedure. The Medicare 5% sample was used to identify patients diagnosed with OA during 1997-2009. All OA patients were separated into non-arthroplasty and arthroplasty groups. Differences in costs, mortality, and new disease diagnoses were adjusted using logistic regression for age, sex, race, buy-in status, region, and Charlson score. The 7-year cumulative average Medicare payments for all treatments were $63,940 for the non-TKA group and $83,783 for the TKA group. The risk adjusted mortality hazard ratio (HR) of the TKA group ranged from 0.48 to 0.54 through seven years (all P<0.001). The risk of heart failure in the TKA group was 40.9% at 7years (HR=0.93, P<0.001). The results demonstrate the patients in the TKA cohort as having a lower probability of heart failure and mortality, at a total incremental cost of $19,843.

Notched fatigue behavior of PEEK.

Poly(ether-ether-ketone) (PEEK) has been used as a load bearing orthopaedic implant material with clinical success. All of the orthopaedic applications contain stress concentrations (notches) in their design; however, little work has been done to examine the fatigue behavior of PEEK in the presence of a notch. This work examines both stress-life (S-N) fatigue behavior and the fracture behavior of unfilled PEEK under tension-tension loading in circumferentially grooved round bar specimens with different elastic stress concentration factors. It was found that the majority of the loading was elastic in nature, and that there was only a small portion on the lifetime where there was a detectable change in structural behavior prior to gross fracture. Fractographic analysis via SEM further elucidated the potential fracture micromechanisms. Additional analysis was conducted to estimate the percent of the lifetime spent in crack initiation vs. propagation, and it was found that the specimens spent the majority of the time in the crack initiation phase.

Comparison of periprosthetic tissue digestion methods for ultra-high molecular weight polyethylene wear debris extraction.

There is considerable interest in characterization of wear debris from polyethylene (UHMWPE) bearing components used in total joint replacement. To isolate UHMWPE wear debris, tissue samples must be excised from regions adjacent to revised UHMWPE implant components, followed by exposure to one of many available tissue digestion methods. Numerous studies demonstrate successful digestion, but the relative efficiency of each method is not clear. The purpose of this study was to evaluate a variety of conditions for tissue digestion to provide a quantitative comparison of methods. Porcine and human hip tissues were exposed for 24 h to basic, acidic or enzymatic agents, filtered and digestion efficiency calculated based on the percentage of initial to final tissue weight. Of the conditions tested, 5 M NaOH, 5 M KOH, 15 M KOH or 15.8 M HNO(3) yielded the most complete porcine hip tissue digestion (<1% residual tissue weight; p < 0.05). Proteinase K and Liberase Blendzyme 3 did not effectively digest tissue in a 24 h period. Similar to results from the porcine dataset, human tissues digestion was most efficient using 5 M NaOH, 5 M KOH or 15.8 M HNO(3) (<1% residual tissue weight; p < 0.05). To verify that particle surface modifications did not occur after prolonged reagent exposure, GUR415 and Ceridust 3715 particles were immersed in each solution for 24 h. Overall, this study provides a framework for thorough and efficient digestive methods for UHMWPE wear debris extraction.

The noisy ceramic hip: is component malpositioning the cause?

Noisy ceramics bearing surfaces are a recently recognized problem in total hip arthroplasty. Component malposition as a potential cause has been proposed. Squeaking occurred in 28 (2.7%) of 999 patients undergoing ceramic on ceramic total hip arthroplasty at our institution. Patients were matched, in a 1:2 ratio by anthropometric and demographic variables and also prosthesis size and type. The acetabular position was measured using radiographs and computed tomography. There was no statistically significant difference in cup inclination (P = .25) or version (P = .38) between groups. Four hips that have been revised were available for retrieval analysis. Stripe wear and metal transfer to ceramic components were observed. Etiology of squeaking ceramic total hip arthroplasty remains elusive. Although malposition could be an important contributing factor, the latter cannot be the sole reason based on our findings. Further investigation to elucidate the etiology is warranted.

Genetic selection of peptide inhibitors of human immunodeficiency virus type 1 Vpr.

Human immunodeficiency virus 1 (HIV-1) encodes a gene product, Vpr, that facilitates the nuclear uptake of the viral pre-integration complex in non-dividing cells and causes infected cells to arrest in the G(2) phase of the cell cycle. Vpr was also shown to cause mitochondrial dysfunction in human cells and budding yeasts, an effect that was proposed to lead to growth arrest and cell killing in budding yeasts and apoptosis in human cells. In this study, we used a genetic selection in Saccharomyces cerevisiae to identify hexameric peptides that suppress the growth arrest phenotype mediated by Vpr. Fifteen selected glutathione S-transferase (GST)-fused peptides were found to overcome to different extents Vpr-mediated growth arrest. Amino acid analysis of the inhibitory peptide sequences revealed the conservation of a di-tryptophan (diW) motif. DiW-containing GST-peptides interacted with Vpr in GST pull-down assays, and their level of interaction correlated with their ability to overcome Vpr-mediated growth arrest. Importantly, Vpr-binding GST-peptides were also found to alleviate Vpr-mediated apoptosis and G(2) arrest in HIV-1-producing CD4(+) T cell lines. Furthermore, they co-localized with Vpr and interfered with its nuclear translocation. Overall, this study defines a class of diW-containing peptides that inhibit HIV-1 Vpr biological activities most likely by interacting with Vpr and interfering with critical protein interactions.

Comparison of the properties of annealed crosslinked (Crossfire) and conventional polyethylene as hip bearing materials.

In 1998, orthopaedic manufacturers started to introduce highly crosslinked ultra-high molecular weight polyethylene (UHMWPE) for total hip replacement bearings. Today's highly-crosslinked UHMWPEs materials are irradiation processed with a total dose ranging between 50 and 105 kGy, depending upon the manufacturer. Each manufacturer has adopted a different route for producing their highly crosslinked UHMWPE that includes a combination of three important processing steps: an irradiation step, an intra or post-irradiation thermal processing step, and a sterilization step. This paper reviews the choices available to an implant designer when developing a highly-crosslinked UHMWPE as an orthopaedic bearing material. We suggest that the application of annealing rather than re-melting in the thermal processing step allows the retention of important mechanical properties in the finished material. This approach will be illustrated with test data on Crossfire (Stryker Howmedica Osteonics, Mahwah, NJ), an annealed, highly-crosslinked UHMWPE developed specifically for total hip replacements. We compare the physical, mechanical, and wear properties of Crossfire with that of conventional (N2-Vac) UHMWPE and with materials produced using published melt irradiation technology. At the short term (2 and 3 years) the results demonstrated through clinical follow-up, clinical results for Crossfire, are encouraging. Longer follow-up is necessary to confirm the benefits to patients from reduction of debris released from the articulation.