Joel C. Higgins

Producing Accurate Platelet Counts for Platelet Rich Plasma: Validation of a Hematology Analyzer and Preparation Techniques for Counting

Platelet rich plasma (PRP) has been shown to clinically accelerate healing of both soft and hard tissues. As a result, it has gained increasing popularity. However, the clinical effectiveness of each type of PRP preparation method can vary in technique and efficiency, and current methods to evaluate the platelet concentration efficiency of PRP systems have several limitations. Therefore, the purpose of this study was to validate an automated hematology analyzer, the Cell-Dyn 3700, to accurately count platelets in concentration ranges of approximately 2,000,000-4,800,000 platelets/μL. PRP platelets were counted by way of a manual counting method and on the Cell-Dyn 3700, and the statistical evaluation indicated no difference between the groups (P > 0.05). Dilution of the PRP was not required, and accurate platelet counts could be achieved up to platelet concentrations of 4,800,000 platelets/μL. PRPs must be resuspended on a rocker for at least 5 minutes before platelet counts, and the entire PRP sample must be resuspended to allow for equal distribution of platelets before counting. With use of the validated Cell-Dyn 3700, a platelet concentrate system was used to prepare 153 PRPs. The baseline whole blood platelet concentration (328,000 platelets/μL ± 69,000 platelets/μL) and the average PRP samples (2,645,000 platelets/μL ± 680,000 platelets/μL) were compared, resulting in an eightfold increase in concentration and an average platelet percent recovery of approximately 76%. Automated hematology analyzers can be used to accurately count platelets in PRP given the system has been validated appropriately and the PRP samples are prepared properly to provide adequate platelet suspension.

Time- and depth-dependent changes in crosslinking and oxidation of shelf-aged polyethylene acetabular liners

Since crosslinking and oxidation of ultrahigh-molecular-weight polyethylene (UHMWPE) have important roles in determining the wear resistance of UHMWPE total joint components, the time and depth dependence of crosslinking and oxidation of new shelf-aged (2-11 years), ready-to-implant acetabular liners were studied by using solvent extraction and Fourier transform infrared spectroscopy. The ultrastructure of these materials also was examined by using low-voltage scanning electron microscopy in an oil-free vacuum. Oxidation levels increased with time and with depth (p < 0.0001) from the surface of the older liners to a maximum value at about 1-2 mm below the surface, then decreased. They were minimal at the midsection of the liners. The crosslinking of these liners decreased with time and depth (p < 0.0001) and was inversely proportional to the level of oxidation. High and depth-dependent oxidation levels were observed in all older liners made from GUR 415 and 412 resins but were distinctly absent from a comparably aged (i.e., 9 years) liner made from 1900 CM-resin. Some liners showed varying degrees of inhomogeneous and discontinuous morphologic ultrastructure in addition to varying amounts of porosity while others had a more homogeneous ultrastructure. Oxidation and crosslinking of polyethylene are time- and depth-dependent processes that are mutually competitive. We suggest that resin choice and perhaps consolidation-related variables lead to differences in polyethylenes ultrastructure. These ultrastructural differences in polyethylenes inhomogeneities, that is, the type (interconnected or closed-cell) or extent may affect the oxidation resistance of polyethylene. While oxygen diffusion to free radicals in polyethylene already is known to explain some of these time- and depth-dependent effects, perhaps such ultrastructural variations also may facilitate or retard oxygen diffusion in this material. Resin-based ultrastructural variability partially may explain the variability in the clinical performance of polyethylene total joint implant components. Thus resin choice or processing modifications related to polyethylenes ultrastructure may increase its oxidation resistance and ultimately improve the clinical wear performance of polyethylene total joint orthopedic implants.

Using Isostatic Pressing Techniques to Mold Uhmwpe

Ultra High Molecular Weight Polyethylene (UHMWPE) has been and is currently the standard for bearing material used in the orthopedic industry. The components are produced using a variety of manufacturing methods, many of which can have an effect on the longevity and performance of the device. Recently there has been extensive research into the causes of loosening of orthopedic devices. One area that has been targeted as a cause for loosening is reactions to particulate debris from the bearing surfaces of these appliances. As biological reactions to particulate become better understood, there has been an increased emphasis on the quality of the UHMWPE forms used for orthopedic bearing surfaces. Due to this increased awareness, various manufacturing and quality control improvements have been made throughout the industry.