Getters for improved technetium containment in cementitious waste forms.

A cementitious waste form, Cast Stone, is a possible candidate technology for the immobilization of low activity nuclear waste (LAW) at the Hanford site. This work focuses on the addition of getter materials to Cast Stone that can sequester Tc from the LAW, and in turn, lower Tc release from the Cast Stone. Two getters which produce different products upon sequestering Tc from LAW were tested: Sn(II) apatite (Sn-A) that removes Tc as a Tc(IV)-oxide and potassium metal sulfide (KMS-2) that removes Tc as a Tc(IV)-sulfide species, allowing for a comparison of stability of the form of Tc upon entering the waste form. The Cast Stone with KMS-2 getter had the best performance with addition equivalent to ∼0.08wt% of the total waste form mass. The observed diffusion (Dobs) of Tc decreased from 4.6±0.2×10-12cm2/s for Cast Stone that did not contain a getter to 5.4±0.4×10-13cm2/s for KMS-2 containing Cast Stone. It was found that Tc-sulfide species are more stable against re-oxidation within getter containing Cast Stone compared with Tc-oxide and is the origin of the decrease in Tc Dobs when using the KMS-2.

Factors predicting failure of patella fixation.

BACKGROUND: Surgical fixation of patella fractures is frequently indicated due to disruption of the quadriceps mechanism. Operative technique varies; however, failure rates can be high. The purpose of this study was to compare the effectiveness of various techniques for the fixation of patella fractures and the etiology of fixation failure. METHODS: We retrospectively reviewed 173 patella fractures treated operatively at two Level I trauma centers. Patients with less than 90 days of follow-up, inadequate radiographic studies, and partial or total excision were excluded. Failure was defined as hardware breakage, nonunion, or displacement of fragments from their initial reduced position. Twelve factors were examined independently for predictive value using both univariate and multivariate analyses. A comparison between groups based on reoperation and hardware removal was also performed. RESULTS: One hundred nine patients met the inclusion criteria, and 13 were found to have failed (12%). Both older patient age (p < 0.02) and use of K-wires, with or without tension-band wires (p < 0.04), were found to be significant predictors of failure. Increasing follow-up time was the only significant predictor of reoperation (p < 0.001) and hardware removal (p < 0.001). CONCLUSIONS: As anticipated, increasing age was found to correlate with higher failure rates. Use of K-wires with or without tension-band wires correlated with higher failure rates, compared with the use of screws, both K-wires and screws, or other fixation. Increasing follow-up time predicted both reoperation and hardware removal, with patients having symptomatic hardware and other complications naturally returning to clinic for evaluation and treatment.

Autologous bone grafting on steroids: preliminary clinical results. A novel treatment for nonunions and segmental bone defects.

Clinical management of delayed healing or nonunion of long bone fractures and segmental bone defects poses a substantial orthopaedic challenge. Surgical advances and bone tissue engineering are providing new avenues to stimulate bone growth in cases of bone loss and nonunion. The reamer-irrigator-aspirator (RIA) device allows surgeons to aspirate the medullary contents of long bones and use the progenitor-rich "flow-through" fraction in autologous bone grafting. Dexamethasone (DEX) is a synthetic steroid that has been shown to induce osteoblastic differentiation. A series of 13 patients treated with RIA bone grafting enhanced with DEX for nonunion or segmental defect was examined retrospectively to assess the quality of bony union and clinical outcomes. Despite the initial poor prognoses, promising results were achieved using this technique; and given the complexity of these cases the observed success is of great value and warrants controlled study into both standardisation of the procedure and concentration of the grafting material.

The orthopaedic implications of diphosphonate therapy.

Diphosphonates are among the many commonly prescribed drugs for osteoporosis management. These synthetic analogues of physiologically occurring inorganic pyrophosphate bind to the hydroxyapatite crystals of bone. Diphosphonates act by decreasing the amount of osteoclast-mediated bone resorption by inducing apoptosis and disrupting the mevalonate biosynthetic pathway. Prospective clinical trials have shown that diphosphonates increase bone mineral density and reduce the risk of fracture. Diphosphonates are generally well tolerated, with a low incidence of side effects. They may be administered orally or intravenously; infusions are the most potent. Few studies have directly studied the effect of diphosphonates on the rate of fracture or time to union. Concern exists regarding the long-term safety of diphosphonates, particularly in patients with osteoporosis. New evidence suggests that long-term therapy may increase the risk of fracture of the femoral shaft, with possible morphologic and prodromal warning signs. Further prospective research into the consequences of diphosphonate-mediated suppressed bone turnover is needed to elucidate a safe duration of treatment.