Evaluation of in vivo wear of vitamin E-diffused highly crosslinked polyethylene at five years: a multicentre radiostereometric analysis study.

AIMS: The primary aim of this study was to compare the wear properties of vitamin E-diffused, highly crosslinked polyethylene (VEPE) and one formulation of moderately crosslinked and mechanically annealed ultra-high molecular weight polyethylene (ModXLPE) in patients five years after primary total hip arthroplasty (THA). The secondary aim was to assess the clinical results of patients treated with VEPE by evaluating patient-reported outcome measures (PROMs), radiological evidence of fixation, and the incidence of mechanical failure. PATIENTS AND METHODS: A total of 208 patients (221 THAs) from four international centres were recruited into a prospective study involving radiostereometric analysis (RSA) and the assessment of clinical outcomes. A total of 193 hips (87%) were reviewed at the five-year follow-up. Of these, 136 (70%) received VEPE (vs ModXLPE) liners and 68 (35%) received ceramic (vs metal) femoral heads. PROMs and radiographs were collected preoperatively and at one, two, and five years postoperatively. In addition, RSA images were collected to measure PE wear postoperatively and at one, two, and five years after surgery. RESULTS: We observed similar bedding in one year postoperatively and wear two years postoperatively between the two types of liner. However, there was significantly more penetration of the femoral head in the ModXLPE cohort compared with the VEPE cohort five years postoperatively (p < 0.001). The only variables independently predictive of increased wear were ModXLPE (vs VEPE) liner type (ß = 0.22, p = 0.010) and metal (vs ceramic) femoral head (ß = 0.21, p = 0.013). There was no association between increased wear and the development of radiolucency (p = 0.866) or PROMs. No patient had evidence of osteolysis. CONCLUSION: Five years postoperatively, patients with VEPE (vs ModXLPE) and ceramic (vs metal) femoral heads had decreased wear. The rates of wear for both liners were very low and have not led to any osteolysis or implant failure due to aseptic loosening.

Promising early results for trabecular metal acetabular components used at revision total hip arthroplasty: 42 acetabular revisions followed with radiostereometry in a prospective randomised trial.

AIMS: The aim of this study was to compare the incidence of aseptic loosening after the use of a cemented acetabular component and a Trabecular Metal (TM) acetabular component (Zimmer Inc., Warsaw, Indiana) at acetabular revision with bone impaction grafting. PATIENTS AND METHODS: A total of 42 patients were included in the study. Patients were randomised to receive an all- polyethylene cemented acetabular component (n = 19) or a TM component (n = 23). Radiostereometric analysis and conventional radiographic examinations were performed regularly up to two years post-operatively or until further revision. RESULTS: The proximal migration was significantly higher in the cemented group. At two years, the median proximal migration was 1.45 mm and 0.25 mm in the cemented and TM groups, respectively (p = 0.02). One cemented component was revised due to dislocation. There were no revisions in the TM group. CONCLUSION: Lower proximal migration in the TM group suggests that this design might be associated with a lower risk of aseptic loosening in the long term compared with an all polyethylene cemented component. Longer follow-up is required to confirm the clinical advantages of using this component at acetabular revision. Cite this article: Bone Joint J 2017;99-B:880-6.

Kinetics and thermodynamics studies on the interaction of D-amino acid oxidase and sodium n-dodecyl sulphate in the presence and absence of flavin adenine dinucleotide.

The kinetics and thermodynamics of denaturation of D-amino acid oxidase by sodium n-dodecyl sulphate (SDS) was studied in the presence and absence of additional amounts of flavin adenine dinucleotide (FAD) at various temperatures (310-325 K) in 0.02 M sodium pyrophosphate at pH = 8.3. The activity measurement data was gathered with thermodynamic data for further interpretation. The corresponding data shows higher stability for DAO against temperatures and potent denaturants like SDS.

Stability of D-amino acid oxidase: denaturation by guanidine hydrochloride and urea.

The guanidine hydrochloride-induced and urea-induced denaturations of swine D-amino acid oxidase (EC 1.4.3.3) dimer were studied by the measurements of the difference absorption spectra in the near-ultra violet region and specific activity. Spectral measurements were made at different pH values (8.3 and 3.2) and temperatures (27, 37 and 47 degrees C). It has been observed that (1), enzyme looses all its activity in concentrated solutions of the denaturants, and (2), the product of urea and guanidine hydrochloride denaturation is only partially unfolded as judged by the measurements of the intrinsic viscosity and exposures of the tyrosyl, tryptophyl and sulphhydryl residues.

Denaturation of Bacillus amyloliquefaciens alpha-amylase with urea.

The urea induced denaturation of the Bacillus amyoliqefaciens alpha-amylase (E.C. 3.2.1.1) was studied by absorption measurements in the near ultra-violet region and specific activity measurements. Spectral measurements were made at pH 6.9 and over the temperature range 20-80 degrees C. It has been observed that urea induced a cooperative transition. In the absence of denaturant, the Gibs energy changes were in the range of 8-15 kcal mol(-1). alpha-amylase lost 80% of its activity in the concentrated solution of urea. alpha-amylase was more thermostable than other mesophilic enzymes.