Incomplete seating of the liner with the Trident acetabular system: a cause for concern?

We reviewed the initial post-operative radiographs of the Trident acetabulum and identified a problem with seating of the metal-backed ceramic liner. We identified 117 hips in 113 patients who had undergone primary total hip replacement using the Trident shell with a metal-backed alumina liner. Of these, 19 (16.4%) were noted to have incomplete seating of the liner, as judged by plain anteroposterior and lateral radiographs. One case of complete liner dissociation necessitating early revision was not included in the prevalence figures. One mis-seated liner was revised in the early post-operative period and two that were initially incompletely seated were found on follow-up radiographs to have become correctly seated. There may be technical issues with regard to the implanting of this prosthesis of which surgeons should be aware. However, there is the distinct possibility that the Trident shell deforms upon implantation, thereby preventing complete seating of the liner.

Impaction bone grafting in revision hip surgery.

We retrospectively reviewed the use of impaction bone grafting with cement for the fixation of femoral and acetabular components in revision hip arthroplasty. Seventy hips formed the basis of the study, with a mean follow-up time of 37 months. Sixty-eight percent of the femurs showed severe bone loss (Endoklinik grades 3 and 4). The mean Harris hip and Merle D'Aubigne Postel scores were 84 and 15.4, respectively. Massive subsidence occurred in only one femoral revision (>10 mm) and cup migration >5 mm in 6 cases. Loosening was seen in 1 revision for sepsis but none for aseptic loosening. Five complications were identified that were related to the surgical technique. We therefore support the use of this technique in revision surgery in patients with extensive bone loss.

Analysis of polyethylene thickness of tibial components in total knee replacement.

BACKGROUND: Excessive wear of the polyethylene bearing surfaces of tibial components has become an important factor in early failure of total knee arthroplasty. Inadequate thickness of the polyethylene insert is one cause of excessive wear, and various minimum thicknesses have been recommended in order to reduce contact stresses within the polyethylene. However, the true thicknesses of modular polyethylene tibial inserts typically are not stated accurately by the manufacturers in their product information. The purpose of this study was to determine whether the information about the thickness of tibial inserts supplied by the manufacturers is adequate. METHODS: Five of the thinnest available polyethylene tibial inserts from five different manufacturers were selected. The minimum thickness of each was measured with use of a Sigma electronic micrometer comparator to an accuracy of +/-0.005 mm. RESULTS: The stated thicknesses of the polyethylene tibial inserts were 8, 9, and 10 mm, values that differed markedly from the actual minimum thicknesses, which ranged from 5.5722 to 6.2048 mm (mean values). CONCLUSION: The thickness of polyethylene tibial inserts has been implicated as a potential cause of excessive wear and early failure of total knee replacements. This paper highlights the fact that the information supplied by the manufacturers is inaccurate and potentially misleading; in one case, the true thickness was much less than the recommended minimum thickness. We recommend that the minimum thickness of the tibial components as well as the combined thickness of the polyethylene insert and the metal tibial tray be specified in the product information and on the packaged insert.

A new spin on cytocentrifugation.

The patented Cytopro system design makes significant advances in the convenience and reliability of cytocentrifugation. The chamber and pad are designed to facilitate prewetting and to better control fluid flow rates. The sealed rotor is durable, convenient, and reliable with significant patented features impacting sample quality and convenience of operation.

Stanmore total hip replacement in younger patients: review of a group of patients under 50 years of age at operation.

Fifty-seven Stanmore Total Hip replacements were implanted between 1974 and 1986 in patients under the age of 50 years. We have reviewed the results in terms of survivorship and function, and assessed the reasons for revision. Of the original 57, 22 (39%) have been revised at an average of 12 years from implantation, usually for aseptic loosening. Most of them had originally been implanted for osteoarthritis. Prostheses cemented with second-generation techniques have lasted significantly longer, and acetabular loosening emerged as a continuing problem. The overall survivorship was 90% at 10 years and 68% at 15 years. Cemented hip replacement appears to be a viable option in younger patients and the Stanmore implant is comparable with other cemented prostheses in this age group.

Influence of fluid absorption time on cell recovery in cytocentrifugation.

OBJECTIVE: To determine the absorption time required to give complete cell recovery in cytocentrifugation. STUDY DESIGN: A simplified model for cell recovery was outlined that relates cell recovery to the relative magnitude of cell sedimentation velocity (SV) and fluid velocity (FV) during cytocentrifugation. The recovery of blood leukocytes was measured at various relative values of the SV/FV ratio and plotted to provide an indication of the effect of the ratio on recovery and to identify the conditions necessary to yield complete cell recovery. RESULTS: As SV/FV approaches zero, cell recovery also approaches zero. As the SV/FV ratio increases, recovery increases toward a maximum of 100%. The fluid absorption time is a key factor in the SV/FV ratio, which also includes centrifugal force and sample volume. A preliminary evaluation of commercial equipment yielded a wide range of absorption characteristics. In addition, fluid flow can be slowed and the SV/FV ratio increased by adding macromolecules--e.g., bovine serum albumin--to the sample fluid. CONCLUSION: Cytocentrifugation has the capability of nearly complete cell recovery if conditions are selected that yield a high SV/FV ratio. Such recovery usually requires slowing the fluid flow rate beyond what is normally obtained in most commercial equipment.

Effect of sample volume on cell recovery in cytocentrifugation.

The purpose of this study was to improve cell recovery and distribution in cytocentrifugation by optimizing sample volume. The experimental design used equal cell numbers in different diluent volumes from 25 to 500 microL. As the diluent volume increased, the fractional recovery of cells also increased, from 10% to a virtual 100%, even though the number of cells per sample remained constant. Optimal cell recovery was achieved with sample volumes between 200 and 500 microL. The importance of using a 200-microL volume with samples of high cellularity as well as those of low cellularity, such as cerebrospinal fluid, is discussed.

The A-V Impulse System reduces deep-vein thrombosis and swelling after hemiarthroplasty for hip fracture.

We performed a prospective randomised controlled trial of the A-V Impulse System in 82 patients treated by hemiarthroplasty for subcapital fracture of the femoral neck. The incidence of proximal deep-vein thrombosis as assessed by Doppler ultrasonography was 23% in the control group and 0% in those using the device (p less than 0.01). Calf and thigh circumferences were measured in both groups at seven to ten days after operation. In the treatment group there was a mean relative reduction of postoperative swelling of the thigh by 3.27 cm (p less than 0.001) and of the calf by 1.55 cm (p less than 0.001). The A-V Impulse System appears to be a safe and effective method of reducing the incidence of proximal deep-vein thrombosis, and of postoperative swelling.

Dietary hormonal modification of growth, intestinal ATPase, and glucose transport in tilapia.

The effect of growth stimulatory and inhibitory dietary applications of hormones [3,5,3'-triiodo-L-thyronine (T3) and 17 alpha-methyltestosterone (MT)] on Na+-K+-adenosinetriphosphatase (ATPase) activity and glucose transport by upper and lower intestinal brush-border membrane vesicles of tilapia (Oreochromis mossambicus) were characterized. Both enzyme activity and glucose transport were greater in growth-stimulatory treatments and lower in growth-inhibitory treatments than in the control. Growth on stimulatory hormone treatments increased apparent glucose influx kinetics (one-half maximum glucose influx, maximum glucose influx, and apparent diffusion coefficient) in both intestinal segments, whereas inhibitory treatments reduced these parameters in upper intestine but had no effect on these parameters in lower intestine. All hormone treatments increased the stoichiometry of Na-glucose cotransport from 1:1 in the control to 2:1 under test conditions. It is suggested that observed patterns of altered growth are due, in part, to hormonally modified intestinal nutrient transport and Na+-K+-ATPase activities.

Proton-stimulated Cl-HCO3 antiport by basolateral membrane vesicles of lobster hepatopancreas.

Purified epithelial basolateral membrane vesicles were prepared from lobster hepatopancreas by sorbitol gradient centrifugation. Na+-K+-adenosinetriphosphatase, alkaline phosphatase, and cytochrome-c oxidase enzyme activities in the final membrane preparation were enriched 9.6-, 1.4-, and 0.4-fold, respectively, compared with their activities in the original tissue homogenate. Vesicle osmotic reactivity was demonstrated using 60-min equilibrium 36Cl uptake experiments at a variety of transmembrane osmotic gradients. 36Cl uptake into vesicles preloaded with HCO3 was significantly greater than into vesicles lacking HCO3. This exchange process was stimulated by a transmembrane proton gradient (internal pH greater than external pH). Proton-gradient-dependent Cl-HCO3 exchange was potential sensitive and stimulated by an electrically negative vesicle interior. 36Cl influx (4-s exposures) into HCO3-loaded vesicles occurred by the combination of 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid sensitive, carrier-mediated transfer and "apparent diffusion." 36Cl influx was a hyperbolic function of both internal [HCO3] and internal [Cl]. The two internal anions displayed a 100-fold difference in apparent affinity constants with HCO3 being strongly preferred. 36Cl influx was stimulated more by preloaded monovalent than by divalent anions. Na was an inhibitor of proton-dependent anion antiport, whereas K had no effect. A model for HCl-HCO3 antiport is suggested that employs combined transmembrane concentration gradients of Cl and HCO3 to power anion exchange and transfer protons against a concentration gradient.

Prevention of rotation of the femoral head during internal fixation of subcapital fractures.

A simple technique for preventing rotation of the femoral head during fixation of a subcapital fracture with an AO dynamic hip screw system is described.

Glucose transport by lobster hepatopancreatic brush-border membrane vesicles.

Epithelial brush-border membrane vesicles (BBMV) were made from lobster hepatopancreas by using Mg2+ precipitation. Alkaline phosphatase, Na+-K+-ATPase, and cytochrome c oxidase activities in these vesicles were enriched 15.0-, 1.0-, and 0.19-fold, respectively, compared with activities of a washed original homogenate pellet, indicating a relatively pure apical membrane preparation reduced in basolateral or organelle contamination. Complete vesicular closure was confirmed with electron microscopy and equilibrium [3H]D-glucose uptake experiments using various transmembrane osmotic gradients. Glucose uptake was stimulated by a transmembrane Na+ gradient but not by an identical K+ gradient or by a Na+ gradient in the presence of phloridzin. Electrogenicity of Na+-dependent glucose transport was confirmed in two ways. First, an anion permeability sequence indicated glucose uptake was stimulated in the following order: SCN- greater than Cl- greater than gluconate- greater than SO4(2-). Second, an outwardly directed valinomycin-induced K+ diffusion potential, rendering the vesicle interior electrically negative, enhanced glucose uptake compared with K+-loaded vesicles lacking the ionophore. Glucose influx occurred by a combination of carrier-mediated transfer, illustrating Michaelis-Menten kinetics, and nonsaturable "apparent diffusion." pH (same on both sides) strongly influenced Na+-dependent glucose uptake according to the sequence: pH 6.0 greater than pH 7.4 greater than pH 8.0. Increased proton concentration lowered the Michaelis constant for glucose transport and increased the apparent diffusional permeability of the membrane to the sugar. Maximal carrier-mediated glucose transport rate was largely unaffected by pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcified left atrial myxoma with floppy mitral valve.

A heavily calcified left atrial myxoma in a man aged 53 was diagnosed from the plain chest x-ray film and confirmed by echocardiography. There was also moderate mitral regurgitation caused by a floppy mitral valve. Before a systemic embolus is considered to have arisen from a floppy mitral valve, echocardiography must be performed.