Ultrasonic diagnosis of meniscus lesions

Controversy exists about the value of ultrasonography of meniscal tears. We therefore examined 101 knee joints of 99 patients in a prospective study. Prior to the arthroscopy the menisci were scanned from an independent team by using 7.5 and 10.0 MHz ultrasound waves. 81 meniscal tears were seen at arthroscopy; 36% of these tears could not be detected with the scanner (? false negative results) while 20% of intact menisci showed positive echogenic structures, which were analysed as meniscal tears. It seems that ultrasonography of the menisci is still of experimental use without any clinical importance.     

New surface modification for Ti-6Al-7Nb alloy: oxygen diffusion hardening (ODH)

PVD-TiN coating and N+ implantation of Ti-6Al-7Nb alloy resulted in surface hardening to a depth of less 3 microns. The new oxygen diffusion hardening (ODH) treatment increased the hardness gradually to 50 microns. PUD-TiN showed an improvement in the tribological properties, while N+ implantation increased the PE wear rate. The wear rate of the ultrahigh-molecular-weight as well as the friction coefficient were reduced to one-half of the values achieved with the combination of CoCrMo-alloy when paired against the ODH-treated surface. In pairing with ZrO2-containing bone cement the ODH-treated surface showed only a minimal reaction.     

Long-term wear of ceramic matrix composite materials for hip prostheses under severe swing phase microseparation

The purpose of this study was to evaluate the long-term wear performance of alumina matrix composite (AMC) heads against alumina matrix composite inserts and alumina matrix composite heads against alumina (Al) inserts with the use of a hip-joint simulator incorporating severe swing phase joint microseparation. The wear of AMC on Al produced an average wear rate of 0.61 mm3/million cycles over the 5-million-cycle test duration. The wear of AMC on AMC produced an average wear rate of 0.16 mm3/million cycles over the 5-million-cycle test duration. Both the AMC on alumina and AMC on AMC produced significantly lower wear than previously tested HIPed alumina, where an average wear rate of 1.84 mm3/million cycles was reported over 5 million cycles. The wear mechanisms and wear debris of AMC on AMC and AMC on Al were similar to those observed in previous alumina retrieval studies with stripe wear caused by intragranular fracture and wear debris consisting of predominantly uniform 10-20-nm-sized particles and a few irregular particles up to 3 microm in size.     

Alumina-alumina artificial hip joints. Part II: characterisation of the wear debris from in vitro hip joint simulations

Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses. The introduction of microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of approximately 0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2-27.5 nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1-35nm). however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.021 microm) and scanning electron microscopy (SEM) (0.05-->10 microm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05-3.2 microm size range. and TEM revealed particles in the 5-90 nm size range, indicating that microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.     

Fatal meningoencephalitis due to Bacillus anthracis

Abstract: We report the first case of fatal anthrax meningoencephalitis in Hong Kong over the past 60 years. A 13 year-old boy presented with right lower quadrant pain, diarrhoea and progressive headache. Lumbar puncture yielded gram positive bacilli initially thought to be Bacillus cereus, a contaminant. He was treated with ampicillin and cefotaxime, but died 3 days after hospitalization. The organism isolated from blood and cerebrospinal fluid was later identified as Bacillus anthracis.     

Survival and developmental disability in infants with birth weights of 501 to 800 grams, born between 1979 and 1994

OBJECTIVE: Because the survival rate has increased for extremely low birth weight neonates, many have raised the concern that the rate of developmental disability among survivors will also increase. To address this concern, we analyzed changes over time in survival and major neurosensory impairment in a sample of extremely low birth weight infants born between July 1, 1979, and June 30, 1994. METHODS: The study sample included 513 infants with birth weights of 501 to 800 g who were cared for in either of the two neonatal intensive care units that serve a 17-county region in northwest North Carolina and who were born to mothers residing in that region. At 1 year of age (corrected for gestation), survivors were examined by a pediatrician and were tested using the Bayley Scales of Infant Development. Major neurosensory impairment was defined as cerebral palsy, a Bayley Mental Developmental Index <68, or blindness. A total of 209/216 (97%) of survivors were examined at 1 year of age. Epoch of birth was defined as follows: epoch 1, July 1, 1979 to June 30, 1984; epoch 2, July 1, 1984 to June 30, 1989; and epoch 3, July 1, 1989 to June 30, 1994. RESULTS: Survival rates for epochs 1, 2, and 3 were, respectively, 24/120 (20%), 63/175 (36%), and 129/218 (59%). In contrast, the proportions with a major neurosensory impairment did not increase over time; rates for successive epochs were 6/24 (25%), 17/61 (28%), and 26/124 (21%). Rates of cerebral palsy were 3/24 (13%), 12/61 (20%), and 9/124 (7%); rates of delayed mental development were 4/24 (17%), 12/61 (20%), and 17/124 (14%); and rates of blindness were 2/24 (8%), 0/62, and 5/124 (4%), respectively. CONCLUSIONS: This analysis suggests that the increasing survival of extremely low birth weight neonates since the late 1970s has not resulted in an increased rate of major developmental problems identifiable at 1 year of age.     

The role of COX-2 in heart pathology

Cyclooxygenase-2 (COX-2) is a key enzyme in the production of prostaglandins, and an important anti-inflammation drug target. Recent focus has been placed on the role of COX-2 in heart function and pathology, due to the finding that specific COX-2 inhibitors significantly increased the risk of heart disease in chronic users. However, the exact role of COX-2 in cardiac physiology and disease remains controversial due to the conflicting data reported. Roughly equal numbers of reports have shown either a detrimental role or a protective role for COX-2 in heart in experimental models. Here we attempt to provide a background on the more general roles of COX-2 in pathophysiology, as well as molecular mechanisms employed to control COX-2 expression. This background provides a basis for better understanding the functional role of COX-2 in human heart pathologies, based on the results of COX-2 pharmacological inhibitor studies in humans as well as COX-2 expression in human heart disease. Furthermore, we will explore the experimental evidence implicating different intracellular molecular signaling cascades that regulate COX-2 expression in cardiomyocytes. All of this data permits a more mechanistic understanding of the published studies using pharmacological inhibitors of COX-2 in experimental models of heart pathology. Lastly, we will examine the use of genetic manipulation of COX-2 in mice as one of the future avenues in an attempt to resolve the role of COX-2 in cardiac physiology and pathology.     

Reduced variability of acetabular cup positioning with use of an imageless navigation system

Positioning the acetabular component is one of the most important steps in total hip arthroplasty; malpositioned components can result in dislocations, impingement, limited range of motion, and increased polyethylene wear. Conventional surgery makes use of specialized alignment guides provided by the manufacturers of the implants. The use of mechanical guides has been shown to result in large variations of cup inclination and version. We investigated acetabular cup alignment with the nonimage-based hip navigation system compared with a conventional mechanically guided procedure in 12 human cadavers. Postoperative cup position relative to the pelvic reference plane was assessed in both groups with the use of a three-dimensional digitizing arm. In the navigated group, a median inclination of 45.5 degrees and a median anteversion of 21.9 degrees (goals, 45 degrees and 20 degrees) were reached. In the control group, the median inclination was 41.8 degrees and the median anteversion was 24.6 degrees. The ninetieth percentile showed a much wider range for the control group (36.1 degrees-51.8 degrees inclination, 15 degrees-33.5 degrees anteversion) than for the navigated group (43.9 degrees-48.2 degrees inclination, 18.3 degrees-25.4 degrees anteversion). This cadaver study shows that computer-assisted cup positioning using a nonimage-based hip navigation system allowed for more consistent placement of the acetabular component.