Mortality after hip resurfacing versus total hip arthroplasty in young patients: a single surgeon experience.

BACKGROUND: The aims of this study were to investigate the following questions: (I) what are the mortality rates in patients age 55 years and younger who underwent a hip resurfacing arthroplasty (HRA) versus a standard total hip arthroplasty (THA)? (II) is the type of operation independently associated with mortality? METHODS: The database of a single high-volume surgeon was reviewed for patient's age 55 years and younger who underwent a hip arthroplasty between 2002 and 2010. This yielded 505 HRA patients and 124 THA patients. Chi-square analysis was performed to identify a 5-year mortality rate difference between the two cohorts. Multivariable Cox-Regression analyses were used to determine whether the type of operation was independently associated with mortality. RESULTS: There were 8 mortalities (1.6%) in the HRA cohort and 11 (8.9%) in the THA cohort, a statistically significant difference (P<0.001) on univariate analysis. Low mortality rates produced underpowered multivariate models. CONCLUSIONS: We have demonstrated that patients age 55 and younger who undergo HRA have a significantly lower mortality rate than those undergoing THA. This is consistent with multiple previously published large database studies.

Alternative Reimbursement Models: Bundled Payment and Beyond: AOA Critical Issues.

The Bundled Payments for Care Improvement (BPCI) initiative was begun in January 2013 by the U.S. Centers for Medicare & Medicaid Services (CMS) through its Innovation Center authority, which was created by the U.S. Patient Protection and Affordable Care Act (PPACA). The BPCI program seeks to improve health-care delivery and to ultimately reduce costs by allowing providers to enter into prenegotiated payment arrangements that include financial and performance accountability for a clinical episode in which a risk-and-reward calculus must be determined. BPCI is a contemporary 3-year experiment designed to test the applicability of episode-based payment models as a viable strategy to transform the CMS payment methodology while improving health outcomes. A summary of the 4 models being evaluated in the BPCI initiative is presented in addition to the awardee types and the number of awardees in each model. Data from one of the BPCI-designated pilot sites demonstrate that strategies do exist for successful implementation of an alternative payment model by keeping patients first while simultaneously improving coordination, alignment of care, and quality and reducing cost. Providers will need to embrace change and their areas of opportunity to gain a competitive advantage. Health-care providers, including orthopaedic surgeons, health-care professionals at post-acute care institutions, and product suppliers, all have a role in determining the strategies for success. Open dialogue between CMS and awardees should be encouraged to arrive at a solution that provides opportunity for gainsharing, as this program continues to gain traction and to evolve.

Update on Biomaterials.

Biomaterials are essential to the use and development of successful treatments for orthopaedic patients. Orthopaedic surgeons need to understand the expected clinical performance and the effects of implants in patients. Recent attempts to improve implant durability have resulted in adverse effects related to biomaterials and their relationship to patients. Examples of these adverse effects in hip arthroplasty include wear and corrosion of metal-on-metal bearings, trunnions, and tapered modular neck junctions. Conversely, polymers and ceramics have shown substantial improvements in durability. Improved implant compositions and manufacturing processes have resulted in ceramic head and acetabular liners with improved material properties and the avoidance of voids, which have, in the past, caused catastrophic fractures. Cross-linking of polyethylene with radiation and doping with antioxidants has substantially increased implant durability and is increasingly being used in joint prostheses other than the hip. Additive manufacturing is potentially a transformative process; it can lead to custom and patient-specific implants and to improvements in material properties, which can be optimized to achieve desired bone responses. Orthopaedic surgeons must understand the material properties and the biologic effects of new or altered biomaterials and manufacturing processes before use. In addition, a clear benefit to the patient must be proven based on superior preclinical results and high-quality clinical investigations before orthopaedic surgeons use new or altered biomaterials.

Preclinical computational models: predictors of tibial insert damage patterns in total knee arthroplasty: AAOS exhibit selection.

Computational models that predict clinical surface damage of the tibial insert during activities of daily living are emerging as powerful tools to assess the safety and efficacy of contemporary total knee arthroplasty designs. These models have the advantage of quickly determining the performance of new designs at low cost, and they allow direct comparison with the performance of classic, clinically successful designs. This study validated finite element and kinematic modeling predictions through comparison with preclinical physical testing results, damage patterns on retrieved tibial inserts, and clinically measured knee motion. There is a mounting body of evidence to support the role of computational modeling as a preclinical tool that enables the optimization of total knee arthroplasty designs and the auditing of component quality control before large-scale manufacturing is undertaken.

Biomechanical properties of fixed-angle volar distal radius plates under dynamic loading.

PURPOSE: To evaluate and compare the biomechanical properties of 8 different locked fixed-angle volar distal radius plates under conditions designed to reflect forces seen in early fracture healing and postoperative rehabilitation. METHODS: We evaluated the Acumed Acu-Loc (Acumed, Hillsboro, OR), Hand Innovations DVR (Hand Innovations, Miami, FL), SBi SCS volar distal radial plate (Small Bone Innovations, Morrisville, PA), Synthes volar distal radius plate and EA extra-articular volar distal radius plate (Synthes, Paoli, PA), Stryker Matrix-SmartLock (Stryker Leibinger, Kalamazoo, MI), Wright Medical Technology Locon VLS (Wright Medical Technology, Arlington, TN), and Zimmer periarticular distal radius locking plate (Zimmer, Warsaw, IN). After affixing each plate to a synthetic corticocancellous radius, we created a standardized dorsal wedge osteotomy. Each construct had cyclic loading of 100 N, 200 N, and 300 N for a total of 6000 cycles. Outcomes, including load deformation curves, displacement, and ultimate yield strengths, were collected for each construct. RESULTS: The Wright plate was significantly stiffer at the 100 N load than the Zimmer plate and was stiffer at the 300 N load than 4 other plates. The Zimmer and Hand Innovations plates had the highest yield strengths and significantly higher yield strengths than the Wright, SBi, Stryker, and Synthes EA plates. CONCLUSIONS: Given the biomechanical properties of the plates tested, in light of the loads transmitted across the native wrist, all plate constructs met the anticipated demands. It seems clear that fracture configuration, screw placement, cost, and surgeon familiarity with instrumentation should take priority in selecting a plating system for distal radius fracture treatment. CLINICAL RELEVANCE: This study provides further information to surgeons regarding the relative strengths of different plate options for the treatment of distal radius fractures.

Reporting and notification of adverse events in orthopaedics.

Surgeons should know how to alert the US FDA when an adverse event occurs with a device that has been approved by the FDA. Documentation of such events is critically important to help identify trends concerning a particular device, thereby helping surgeons and other health care professionals avoid similar events. The FDA created the MedWatch program to aid health care professionals in reporting adverse events. Orthopaedic surgeons can use the program to get up-to-date alerts and help protect their patients.

Clinical fracture of cross-linked UHMWPE acetabular liners.

Highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is increasingly used as a bearing material in total hip replacements. Cross-linking of UHMWPE has been shown to increase wear resistance but decrease its fracture resistance. We analyzed the clinical fracture failure of four cross-linked UHMWPE total hip replacement components of four different designs via microscopic observation of the fracture surfaces, and found that in all cases fractures initiated at stress concentrations in an unsupported region of the component (termed the elevated rim). Finite element analyses (FEA) of each individual implant design were then conducted. Results from this analysis demonstrated that the predicted magnitude and orientation of maximum principal stress due to mechanical loading of the elevated rim was sufficient to propagate initiated fatigue cracks in each case. FEA also predicted that cracks may arrest after some amount of growth due to a steep stress gradient near the initiation site. Further, while anatomical positioning of the implant and material properties affect the risk of fracture, we examined whether these failures are strongly related to the notched elevated rim design feature that is common to the four failed cases presented here. We believe that cross-linked UHMWPE remains an excellent bearing material for total hip replacements but that designs employing this material should mitigate stress concentrations or other design features that increase the risk of fracture.

Clinical performance of highly cross-linked polyethylenes in total hip arthroplasty.

Aseptic loosening secondary to wear-debris-induced osteolysis has been identified as the leading cause of late failure of total hip arthroplasty. Highly cross-linked polyethylene acetabular liners were developed as one approach to reducing this wear. Preclinical laboratory wear testing showed a number of cross-linked polyethylenes to have dramatically less wear than the polyethylene that had been in use for several decades. After the initial bedding-in phase (one to two years), the percent reductions in the wear rate, as indicated by the amount of penetration of the head into the socket evident on serial radiographs, have been comparable with what was predicted from preclinical hip-simulator testing of the highly cross-linked polyethylenes. To our knowledge, there have been no reports of clinically relevant osteolysis that was clearly attributable to wear of a highly cross-linked polyethylene acetabular liner. However, the clinical performance of these materials should be closely monitored with long-term follow-up.

Surface stress: a factor influencing ultra high molecular weight polyethylene durability in mobile-bearing knee design.

The continuing global interest in the use of total and unicompartmental mobile-bearing knee designs is manifest by an appreciation of their clinical performance. Like their fixed plateau counterparts, mobile-bearing knees are influenced by patient and surgical variables as well as design, material, and manufacturing choices. This article is a focused description of tibiofemoral surface stress distributions, as a predictor of in vivo material durability for three contemporary designs at positions encountered during daily activity.

Fixation strength comparison of onlay and inset patellar implants.

Patellar implant fixation continues to be one of the most troublesome areas in total knee arthroplasty (TKA). It has been reported that patellofemoral complications in TKA are responsible for almost half of all re-operations. The literature review revealed the rate of primary all-polyethylene patellar implant loosening ranging 1%-4.2% [Berend ME, Ritter MA, Keating EM, Faris PM, Crites BM. The failure of all-polyethylene patellar components in total knee replacement. Clin Orthop 2001;388:105-11, Chew JT, Stewart NJ, Hanssen AD, Luo ZP, Rand JA, An KN. Differences in patellar tracking and knee kinematics among three different total knee designs. Clin Orthop 1997;345:87-98, Barrack RL, Wolfe MW, Waldman DA, et al. Patellar resurfacing in total knee arthroplasty: a five to seven year follow-up of prospective, randomized, double-blind study. Proceedings of Sixty-Seventh Annual Meeting of the American Academy of Orthopaedic Surgeons 2000. p. 547]. The loosening rates for metal-backed or following patellar component revisions were considerably higher [Chew JT, Stewart NJ, Hanssen AD, Luo ZP, Rand JA, An KN. Differences in patellar tracking and knee kinematics among three different total knee designs. Clin Orthop 1997;345:87-98, Jordan LR, Sorrells RB, Jordan LC, Olivo JL. The long-term results of a metal-backed mobile bearing patella. Clin Orthop 2005;436:111-8, Berger RA, Lyon, JH, Jacobs JJ, Barden RM, Berkson EM, Sheinkop MB, et al. Problems with cementless total knee arthroplasty at 11 years followup. Clin Orthop 2001;392:196-207, Ritter MA, Pierce MJ, Zhou H, Meding JB, Faris PM, Keating EM. Patellar complications (total knee arthroplasty). Effect of lateral release and thickness. Clin Orthop 1999;367:149-57] Onlay and inset patellar components with variable fixation surface geometry are currently available for clinical use. The purpose of this study was to quantify the shear disassociation strength for both onlay and inset patellar fixation techniques. The variation in host material was minimized by the use of synthetic patellae, which has been previously validated in implant fixation studies. The testing revealed that inset patellar fixation resistance to shear disassociation was 25% higher than onlay patellae (p=0.0002).