Effect of radiation, heat, and aging on in vitro wear resistance of polyethylene

Radiation cross-linking increases the wear resistance of polyethylene used in total hip replacement. Radiation also generates residual free radicals, which are detrimental to long-term properties of polyethylene. Two approaches are used to stabilize the residual free radicals and terminally sterilize the components. One is postirradiation annealing with gas sterilization and the other is postirradiation melting with gamma sterilization in nitrogen. The hypothesis of the current study is that postirradiation annealing followed by gamma sterilization in nitrogen will result in more free radicals in polyethylene than gamma sterilization either in air or in nitrogen alone. To test this hypothesis, concentration of residual free radicals was quantified in polyethylene that was annealed and gamma sterilized in nitrogen and control polyethylenes gamma sterilized in air versus in nitrogen. Three crosslinked polyethylenes that were melted and gas sterilized also were included in the study. The effects of residual free radicals were studied by accelerated aging. Oxidation levels and weight loss in bidirectional pin-on-disk tests were determined before and after aging. Polyethylene that was subjected to postirradiation annealing and gamma sterilization resulted in 58% more residual free radicals than control polyethylenes. Weight loss of the annealed polyethylene increased by 16-fold on accelerated aging and had three times higher oxidation levels than that measured in control polyethylenes after aging. In contrast, polyethylenes that were stabilized with postirradiation melting and terminally gas sterilized showed no detectable residual free radicals. Accelerated aging did not affect the weight loss and oxidation levels of melted polyethylenes.     

Widespread central nervous system cavernous malformations associated with café-au-lait skin lesions. Case report

The simultaneous presence of cavernous malformations in the brain and spinal cord is a very rare finding and is typically associated with familial cavernous malformations. Although they are uncommon, various skin lesions can manifest in patients with familial cavernous malformations. The authors report on a 60-year-old man in whom more than 100 lesions consistent in appearance with cavernous malformations, including several intramedullary spinal cord lesions, were found throughout the neuraxis. This patient also displayed prominent café-au-lait skin lesions, but had no additional signs of neurofibromatosis or other neurocutaneous disorders. Analysis of his DNA revealed a novel mutation in the KRIT1/CCM1 gene, thereby confirming the diagnosis of familial cavernous malformation. The presence of these lesions in every major compartment of this patient's central nervous system underscores their indiscriminate nature and the need to screen throughout the neuraxis in patients in whom familial cavernous malformations are suspected. The findings in this case add to the growing list of skin lesions associated with genetically confirmed familial cavernous malformations. In patients presenting with seizures, focal neurological deficits, or hemorrhagic stroke, the presence of unusual skin lesions should prompt consideration of familial cavernous malformations, and appropriate screening should be performed.     

Radiologic case study. Abrasion chondroplasty mimicking avascular necrosis

Arthroscopic abrasion arthroplasty, subchondral drilling, and microfracture continue to be performed with some frequency in younger patients with focal chondral defects and occasionally for patients with moderate degenerative knee arthritis. The plain radiographic appearance after those procedures may mimic avascular necrosis, but MRI is a sensitive method used to exclude the diagnosis of avascular necrosis and evaluate the extent to which fibrocartilaginous repair tissue has formed. When combined with an appropriate clinical history, dedicated articular cartilage imaging sequences improve the sensitivity and specificity that MRI provides in these patients with chondral knee injuries.     

Preoperative blood volume deficit influences blood transfusion requirements in females and males undergoing coronary bypass graft surgery

STUDY OBJECTIVE: To evaluate whether preoperative blood volume and postoperative blood loss influence blood transfusion in females and males undergoing coronary artery bypass graft (CABG) surgery. DESIGN: Prospective study. SETTING: Anesthesiology department of a teaching hospital. PATIENTS: 57 CABG patients (21 females and 36 males). MEASUREMENTS: Blood volume was determined using the radioactivity dilution method. Preoperatively, each patient received intravenous (IV) injection of 1 mL Albumin I(131) tracer having 25 microcuries of radioactivity. Five-milliliter blood samples were collected at different intervals. From these samples, hematocrit (Hct) value, preoperative total blood volume, red blood cell (RBC) volume, and plasma volume were determined. Postoperatively, some consenting patients received another 1 mL dose of the tracer, and the postoperative blood volumes were determined. If a patient received a blood transfusion, the units of packed red blood cells (PRBCs), platelets, or fresh frozen plasma (FFP) transfused were recorded. For each patient we recorded the gender, age, weight, height, body surface area (BSA), preoperative Hct, duration of surgery, and discharge Hct. RESULTS: Preoperatively, the mean total blood volume, RBC volume, and plasma volume, respectively, were 2095 mL/m(2), 631 mL/m(2), and 1,465 mL/m(2) in females; and 2,580 mL/m(2), 878 mL/m(2), and 1,702 mL/m(2) in males. The preoperative blood volumes were significantly lower (p < 0.01) in females than in males. There was no significant difference between males and females in the extent of blood loss during CABG. Intraoperatively, females received PRBC transfusion of 1.38 units, significantly more (p < 0.01) than the 0.39 units received by males. During the entire hospital stay, females received 4.33 units of PRBC, significantly more than (p < 0.02) the 1.33 units received by males. Significantly more (p < 0.01) females (12 of 21) received intraoperative PRBC transfusion than did males (6 of 36). Multiple logistic regression analysis of the data showed that PRBC transfusion was significantly correlated with the preoperative total blood volume and RBC volume. CONCLUSION: The greater need for blood transfusion in females than in males during CABG is primarily attributable to significantly lower preoperative total blood volume and RBC volume in females.     

Klotho Lacks an FGF23‐Independent Role in Mineral Homeostasis

Fibroblast growth factor‐23 (FGF23) is a bone‐derived hormone regulating vitamin D hormone production and renal handling of minerals by signaling through an FGF receptor/αKlotho (Klotho) receptor complex. Whether Klotho has FGF23‐independent effects on mineral homeostasis is a controversial issue. Here, we aimed to shed more light on this controversy by comparing male and female triple knockout mice with simultaneous deficiency in Fgf23 and Klotho and a nonfunctioning vitamin D receptor (VDR) (Fgf23/Klotho/VDR) with double (Fgf23/VDR, Klotho/VDR, and Fgf23/Klotho) and single Fgf23, Klotho, and VDR mutants. As expected, 4‐week‐old Fgf23, Klotho, and Fgf23/Klotho knockout mice were hypercalcemic and hyperphosphatemic, whereas VDR, Fgf23/VDR, and Klotho/VDR mice on rescue diet were normocalcemic and normophosphatemic. Serum levels of calcium, phosphate, and sodium did not differ between 4‐week‐old triple Fgf23/Klotho/VDR and double Fgf23/VDR or Klotho/VDR knockout mice. Notably, 3‐month‐old Fgf23/Klotho/VDR triple knockout mice were indistinguishable from double Fgf23/VDR and Klotho/VDR compound mutants in terms of serum calcium, serum phosphate, serum sodium, and serum PTH, as well as urinary calcium and sodium excretion. Protein expression analysis revealed increased membrane abundance of sodium‐phosphate co‐transporter 2a (NaPi‐2a), and decreased expression of sodium‐chloride co‐transporter (NCC) and transient receptor potential cation channel subfamily V member 5 (TRPV5) in Fgf23/Klotho/VDR, Fgf23/VDR, and Klotho/VDR mice, relative to wild‐type and VDR mice, but no differences between triple and double knockouts. Further, ex vivo treatment of live kidney slices isolated from wild‐type and Klotho/VDR mice with soluble Klotho did not induce changes in intracellular phosphate, calcium or sodium accumulation assessed by two‐photon microscopy. In conclusion, our data suggest that the main physiological function of Klotho for mineral homeostasis in vivo is its role as co‐receptor mediating Fgf23 action. © 2017 American Society for Bone and Mineral Research.     

Outcomes following parotidectomy for metastatic squamous cell carcinoma with microscopic residual disease: implications for facial nerve preservation

Background.

Metastatic cutaneous squamous cell carcinoma (SCC) of the parotid is an aggressive disease, requiring combined modality treatment of surgery and adjuvant radiotherapy to achieve cure. This study aims to determine whether facial nerve preservation followed by radiotherapy is a reasonable option in patients with microscopic residual disease involving the facial nerve.

Methods.

One hundred seventy‐six patients with metastatic cutaneous SCC involving the parotid were analyzed.

Results.

In this cohort, 15 patients who underwent nerve‐sparing surgery and adjuvant radiotherapy were found to have involved margins adjacent to the facial nerve. Comparing this group to patients with clear margins showed no difference in local recurrence or survival. Only 3 patients in this group developed local recurrence, and all successfully salvaged by further surgery.

Conclusion.

This study suggests that patients with metastatic cutaneous SCC to the parotid with microscopic residual disease involving the facial nerve and normal function can be successfully treated with a facial nerve–sparing approach and timely postoperative radiotherapy. © 2008 Wiley Periodicals, Inc. Head Neck, 2009     

Large femoral bone loss after hip revision using the uncemented proximally porous-coated Bi-Metric prosthesis: 22 hips followed for a mean of 6 years

Background and purpose Periprosthetic bone loss after uncemented femoral hip revision is a matter of concern. We have used a proximally porous- and hydroxyapatite-coated prosthesis (Bi-Metric) in revision since 1989 and now we report the bone changes. This prosthesis is intended to distribute the forces more evenly and to avoid proximal femoral unloading.Methods 22 patients were unilaterally reoperated because of aseptic loosening. Only patients with a healthy contralateral hip were included. Mean age at revision was 69 (55–80) years. Bone defects were graded by Gustilo-Pasternak and Endo-Klinik classifications. Clinical assessment was performed with Harris hip score. We used radiographs and dual-energy X-ray absorptiometry to evaluate migration, femoral remodeling, and bone mineral density after 72 (30–158) months.Results The mean Harris hip score was 74 (30–100) points at follow-up. Mild thigh discomfort was present in 1 patient and moderate thigh pain in 3 patients. There was no loosening or subsidence. Osteolysis seen at revision had diminished in 19 of the 22 hips at follow-up. We noted a large reduction in bone mineral density. It was most pronounced in Gruen regions 1, 2, 6, and 7.Interpretation Revision with this stem is a reliable procedure; however, we noted a large degree of proximal bone loss that could lead to later mechanical complications or fractures.     

Third-body wear testing of a highly cross-linked acetabular liner: the effect of large femoral head size in the presence of particulate poly(methyl-methacrylate) debris

The hip simulator wear performance of an electron beam cross-linked and subsequently melted ultrahigh molecular weight polyethylene against femoral heads of 28-, 38-, and 46-mm diameter in the presence of poly(methyl-methacrylate) particulate debris was contrasted with that of conventional polyethylene against a 46-mm diameter head. Over 5 million cycles of testing, the average wear rate of the conventional polyethylene liners was 29.3 +/- 3.0 mg per million cycles. All highly cross-linked components exhibited marked reduction in wear, with the highest wear measuring 0.74 +/- 0.85 mg per million cycles. This study, using a clinically relevant third-body material, showed the electron beam cross-linked material to be far more resistant to this third-body wear than conventional ultrahigh molecular weight polyethylene, even when very large diameter femoral heads were used.     

Minimal Acute Rejection after Lung Transplantation: A Risk for Bronchiolitis Obliterans Syndrome

Bronchiolitis obliterans syndrome (BOS) is a major cause of lung allograft dysfunction. Although previous studies have identified mild to severe rejection (grade>or=A2) as a risk factor for BOS, the role of minimal rejection (grade A1) remains unclear. To determine if A1 rejection by itself is a risk factor for BOS, we performed a retrospective cohort study on 228 adult lung transplant recipients over a 7-year period. Cohorts were defined by their most severe rejection episode (none, A1 only, and >or=A2) and analyzed for the subsequent development and progression of BOS using univariate and multivariate time-dependent Cox regression analysis. In the univariate model, the occurrence of isolated minimal rejection was a risk factor for all stages of BOS. Similarly, multivariate models that included HLA mismatch, cytomegalovirus pneumonitis, community acquired viral infection, underlying disease and type of transplant demonstrated that A1 rejection was a distinct risk factor for BOS. Furthermore, the associated risk with A1 rejection was slightly greater than the risk from >or=A2 and treatment of A1 rejection decreased the risk for subsequent BOS stage 1. We conclude that minimal rejection is associated with an increased risk for BOS development and progression that is comparable to A2 rejection.