Revealing the polar lipidome, pigment profiles, and antioxidant activity of the giant unicellular green alga, Acetabularia acetabulum.

Marine algae are one of the most important sources of high-value compounds such as polar lipids, omega-3 fatty acids, photosynthetic pigments, or secondary metabolites with interesting features for different niche markets. Acetabularia acetabulum is a macroscopic green single-celled alga, with a single nucleus hosted in the rhizoid. This alga is one of the most studied dasycladalean species and represents an important model system in cell biology studies. However, its lipidome and pigment profile have been overlooked. Total lipid extracts were analyzed using hydrophilic interaction liquid chromatography-high resolution mass spectrometry (HILIC-HRMS), tandem mass spectrometry (MS/MS), and high-performance liquid chromatography (HPLC). The antioxidant capacity of lipid extracts was tested using DPPH and ABTS assays. Lipidomics identified 16 polar lipid classes, corresponding to glycolipids, betaine lipids, phospholipids, and sphingolipids, with a total of 191 lipid species, some of them recognized by their bioactivities. The most abundant polar lipids were glycolipids. Lipid classes less studied in algae were identified, such as diacylglyceryl-carboxyhydroxymethylcholine (DGCC) or hexosylceramide (HexCer). The pigment profile of A. acetabulum comprised carotenoids (17.19%), namely cis-neoxanthin, violaxanthin, lutein and ß,ß-carotene, and chlorophylls a and b (82.81%). A. acetabulum lipid extracts showed high antioxidant activity promoting a 50% inhibition (IC50 ) with concentrations of 57.91 ± 1.20 µg · mL-1 (438.18 ± 8.95 µmol Trolox · g-1 lipid) in DPPH and 20.55 ± 0.60 µg · mL-1 in ABTS assays (918.56 ± 27.55 µmol Trolox · g-1 lipid). This study demonstrates the potential of A. acetabulum as a source of natural bioactive molecules and antioxidant compounds.

Metastatic Epithelial-Myoepithelial Carcinoma in a Female Presenting with Neck Mass and Lytic Lesion in Acetabulum: A Diagnostic Challenge on Cytology.

Epithelial-myoepithelial carcinoma (EMC) is a rare, low-grade, malignant salivary neoplasm. Establishing an accurate cytological diagnosis is often challenging owing to its rarity, bland cytologic appearance and variable representation of cell populations in the smears. The diagnostic struggle is more so when the aspiration is from a metastatic site with an unknown primary, as in such cases the list of differential diagnoses expands further. A 58-year-old female presented with a low-back pain from last one month. On examination, she also had a level III, right cervical swelling for the last 20 years. Radiology revealed a lytic lesion in the left acetabulum. She had undergone surgery 35 years ago for a right-sided upper neck swelling, the medical records of which were not available. Fine needle aspiration (FNA) from the cervical swelling was performed. The smears were cellular and showed predominantly dispersed, round to polygonal tumor cells with mild pleomorphism, eccentric nuclei, coarse chromatin, occasional nucleoli and moderate cytoplasm with some showing vacuolations. The cell-block section revealed tumor cells arranged in the form of tubules lined by dual layer of tumor cells without any chondromyxoid stroma. On immunocytochemistry, the luminal cells showed positivity for CK7 (epithelial marker) and the abluminal cells showed positivity for p63 (myoepithelial marker). Based on these features, a final diagnosis of metastatic epithelial-myoepithelial carcinoma was rendered. The present report highlights the characteristic cytomorphological and immunocytochemical features of EMC and reiterates the diagnostic accuracy of FNAC for diagnosis of such challenging cases.

The comparative analyses of decalcification procedures and methyl benzoate pre-treatment on tissue preservation and antigenicity in human acetabular labra.

The histological processing of musculoskeletal tissue might be challenging. The alteration of tissue composition e.g. by calcification of soft tissue in the elderly, after trauma or surgical interventions makes the histological processing of fixed tissue difficult. Additional steps of decalcification are then needed that probably affect the staining quality. In the present work, the effects of different decalcification agents and the intermedium methyl benzoate on histological staining methods and immunohistochemistry have been compared. Acetabular labra were fixed with 4% paraformaldehyde, left untreated or decalcified using 30% ethylenediaminetetraacetic acid (EDTA; Chelaplex®) or 6% trichloroacetic acid (TCA) for 1-4 days to investigate the effects of decalcification duration. Moreover, samples were pretreated with methyl benzoate or conventionally paraffin embedded independent of decalcification procedure and duration. The specimens were evaluated using hemalaun-eosin, Azur II- methylene blue staining or immunohistochemistry against ankyrin B to visualize nerve fibers. Decalcification with Chelaplex® or TCA reduced cutting artifacts without affecting the tissue morphology and proteoglycan staining but decreased antigenicity in immunohistochemistry. Interestingly, methyl benzoate further reduced cutting artifacts without altering tissue morphology and elevated antigenicity for Chelaplex® decalcified tissue samples in immunohistochemistry. The decalcification with Chelaplex® or 6% TCA preserves tissue morphology and proteoglycan staining similar to non- decalcified tissue but facilitates section processing. In immunohistochemistry both decalcification agents decreased antigenicity. Chelaplex® decalcified, methyl benzoate treated samples yielded an improved antigenicity.

In-vitro oxidation model for UHMWPE incorporating synovial fluid lipids.

Post-irradiation melting of ultra-high molecular weight polyethylene (UHMWPE) reduced the oxidation potential of UHMWPE in vivo. After mid-term (5-10 years) use in vivo, there is detectable oxidation in irradiated and melted joint implant retrievals. The absorption of the synovial fluid lipid squalene was identified as a possible factor initiating oxidation. We investigated the role of lipids in UHMWPE oxidation by asking: (1) Do other synovial fluid lipids initiate oxidation in irradiated and melted UHMWPE?; (2) What is the effect of the absorption of multiple lipids on UHMWPE oxidation?; (3) How does lipid-initiated oxidation in vitro compare to what is observed in long-term retrievals? We diffused emulsified single and mixed lipids into irradiated and melted UHMWPE and accelerated aged them. We analyzed the oxidation in these samples and in four long-term highly crosslinked, irradiated, and melted Longevity™ UHMWPE liner retrievals (in vivo for up to 190 months) using Fourier Transform Infrared Spectroscopy (FTIR). We showed that lipids other than squalene could initiate oxidation in UHMWPE and that the types of absorbed lipids determined the amount of resultant oxidation. Although mixed lipids doping and accelerated aging reproduced the average and maximum oxidation values and oxidation products observed in vivo, the oxidation depth profile and its effect on cross-link density was different. One reason for this was the variability of oxidation in retrievals, suggesting additional factors contributing to oxidation. The understanding of oxidative processes in vivo and the development of clinically relevant in vitro protocols to evaluate implant materials is crucial for their long-term performance. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1833-1839, 2018.

Gene signatures in osteoarthritic acetabular labrum using microarray analysis.

BACKGROUND: Osteoarthritis (OA) is the most common chronic joint disease. This study aimed to uncover underlying mechanisms of OA pathogenesis and explore the potential biomarkers of osteoarthritic acetabular labrum. METHODS: The microarray data GSE60762 was utilized, containing five OA acetabular labrum samples and three healthy control samples. Data were preprocessed by oligo package and the differentially expressed genes (DEGs) were identified using limma package with predefined criteria, followed by functional enrichment analysis by the GoFunction in R Bioconductor, and protein-protein interaction (PPI) network analysis. RESULTS: As a result, 141 DEGs (44 were up-regulated and 97 were down-regulated) were identified between OA and healthy acetabular labrum cells. Up-regulated genes including CDH2 and WNT5A were significantly enriched in intracellular signal transduction function, while down-regulated genes such as KDR, FLT1 and CDH5 were remarkably correlated with cardiovascular system development. FLT1, KDR, CDH2 and CDH5 were the striking nodes in the PPI network. CONCLUSION: CDH2, WNT5A, KDR, FLT1 and CDH5 might serve as the biomarkers of OA prognosis. Intracellular signal transduction and cardiovascular system development might play significant roles in the destruction of labrum during OA progression. However, more experimental validations are warranted to confirm our findings.

A visual-aided wireless monitoring system design for total hip replacement surgery.

To improve the positioning accuracy of implants in Total Hip Replacement (THR) surgeries, a visual-aided wireless monitoring system for THR surgery is proposed in this paper. This system aims to measure and display the contact distribution and relative pose between femoral head and acetabulum prosthesis during the surgery to help surgeons obtain accurate position of implants. The system consists of two parts: the Sensors Array Measuring System (SAMS) and the display part. The SAMS is composed of a sensors array (including contact sensors and an image sensor), signal conditioning circuits, a low power microcontroller (MCU), and a low-power transceiver. The SAMS is designed to estimate the relative pose of femoral head component to acetabular component. The display part processes the data from sensors and demonstrates the contact distribution and the pose of the prothesis during the surgery in 3-D graphics. The two parts of the system communicate with each other on an RF link at the band of 400 MHz. The signal conditioning circuits have been designed and fabricated in 0.18 µm CMOS process. Testing results show that the resolution of the signal conditioning circuits is 60.1 µ Vpp (1.35 g) with ±100 mVpp input. The chip can operate under 1.2-to-3.6 V supply voltage for single battery applications with 116-160 µ A current consumption. The system has been verified by the simulation with rotation quaternion and translation vector. The experimental results show that the contact distribution and relative pose of the two components could be measured and demonstrated in real time. The relative error of rotation is less than 8% and the actual relative error of translation is less than 10%.

Cementless hydroxyapatite coated hip prostheses.

More than twenty years ago, hydroxyapatite (HA), calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants. Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990. The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem. The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long term survival, provided that certain requirements are met: good design selection, sound choice of bearing surfaces based on patient life expectancy, meticulous surgical technique, and indications based on adequate bone quality.

Metal-on-metal hip resurfacing: correlation between clinical and radiological assessment, metal ions and ultrasound findings.

PURPOSE: We report the clinical, radiological and wear analysis of 52 consecutive MoM hip resurfacings (performed on 49 younger patients) to a mean follow-up of 9.2 years. METHODS: Every patient underwent X-ray and clinical evaluation (HHS). Ultrasonography of the hip was performed in all patients in order to identify possible cystic or solid mass in periprosthetic tissue. In case of mass >20 mm, further MRI was performed to better analyse the characteristics of lesion. RESULTS: Five patients (five hips) had a revision. The overall survival rate was 90.38 %. The average HHS at follow-up examination was 95.5 points. No progressive radiolucent areas and no sclerosis or osteolysis around the implants were found. The US and RMI imaging showed a pseudotumour formation in two patients (correlated with high metal ion levels in blood and urine), both asymptomatic. CONCLUSION: A significant positive correlation between inclination of the acetabular component and serum metal ion levels was found (r = 0.64 and r = 0.62 for cobalt and chromium, respectively).

Effect of simplifications of bone and components inclination on the elastohydrodynamic lubrication modeling of metal-on-metal hip resurfacing prosthesis.

It is important to study the lubrication mechanism of metal-on-metal hip resurfacing prosthesis in order to understand its overall tribological performance, thereby minimize the wear particles. Previous elastohydrodynamic lubrication studies of metal-on-metal hip resurfacing prosthesis neglected the effects of the orientations of the cup and head. Simplified pelvic and femoral bone models were also adopted for the previous studies. These simplifications may lead to unrealistic predictions. For the first time, an elastohydrodynamic lubrication model was developed and solved for a full metal-on-metal hip resurfacing arthroplasty. The effects of the orientations of components and the realistic bones on the lubrication performance of metal-on-metal hip resurfacing prosthesis were investigated by comparing the full model with simplified models. It was found that the orientation of the head played a very important role in the prediction of pressure distributions and film profiles of the metal-on-metal hip resurfacing prosthesis. The inclination of the hemispherical cup up to 45° had no appreciable effect on the lubrication performance of the metal-on-metal hip resurfacing prosthesis. Moreover, the combined effect of material properties and structures of bones was negligible. Future studies should focus on higher inclination angles, smaller coverage angle and microseparation related to the occurrences of edge loading.

Wear of 36-mm BIOLOX(R) delta ceramic-on-ceramic bearing in total hip replacements under edge loading conditions.

Ceramic-on-ceramic bearings have become of great interest due to the substantial improvements in the manufacturing techniques and material properties and due to polyethylene wear debris-induced osteolysis and the issues with metal wear debris and ion release by metal-on-metal bearings. Edge loading conditions due to translational malpositioning (microseparation conditions) have been shown to replicate clinically relevant wear mechanisms and increase the wear of ceramic-on-ceramic bearings; thus, it was necessary to test new bearing materials and designs under these adverse conditions. The aim of this study was to assess the effect of increasing head size on the wear of BIOLOX(®) delta ceramic-on-ceramic bearings under edge loading conditions due to rotational (steep cup inclination angle) and translational (microseparation) malpositioning. In this study, six 36-mm ceramic-on-ceramic bearings (BIOLOX delta, CeramTec, Germany) were tested under standard and edge loading conditions using the Leeds II hip simulator and compared to the 28-mm bearings tested and published previously under identical conditions. The mean wear rate under standard gait conditions was below 0.1 mm(3)/million cycles for both the 28-mm and the 36-mm ceramic-on-ceramic bearings, and increasing the inclination angle did not affect the wear rates. The introduction of microseparation to the gait cycle increased the wear rate of ceramic-on-ceramic bearing and resulted in stripe wear on the femoral heads. Under microseparation conditions, the wear rate of size 36-mm bearings (0.22 mm(3)/million cycles) was significantly higher (p = 0.004) than that for size 28-mm bearings (0.13 mm(3)/million cycles). This was due to the larger contact area for the larger bearings and deprived lubrication under edge loading conditions. The wear rate of BIOLOX delta ceramic-on-ceramic bearings under microseparation conditions was still very low (<0.25 mm(3)/million cycles) compared to earlier generation ceramic-on-ceramic bearings (BIOLOX forte, 1.84 mm(3)/million cycles) and other bearing materials such as metal-on-metal bearings (2-8 mm(3)/million cycles).

Advanced material modelling in numerical simulation of primary acetabular press-fit cup stability.

Primary stability of artificial acetabular cups, used for total hip arthroplasty, is required for the subsequent osteointegration and good long-term clinical results of the implant. Although closed-cell polymer foams represent an adequate bone substitute in experimental studies investigating primary stability, correct numerical modelling of this material depends on the parameter selection. Material parameters necessary for crushable foam plasticity behaviour were originated from numerical simulations matched with experimental tests of the polymethacrylimide raw material. Experimental primary stability tests of acetabular press-fit cups consisting of static shell assembly with consecutively pull-out and lever-out testing were subsequently simulated using finite element analysis. Identified and optimised parameters allowed the accurate numerical reproduction of the raw material tests. Correlation between experimental tests and the numerical simulation of primary implant stability depended on the value of interference fit. However, the validated material model provides the opportunity for subsequent parametric numerical studies.

Sex determination from the acetabulum: test of a possible non-population-specific discriminant function equation.

In a recent study of pelvic dimorphism, Steyn and Patriquin demonstrated that sex classification accuracies for a combined sample of South African blacks, South African whites, and Greeks living on Crete, differed very little from those obtained separately for the three groups. These results suggest that population-specific formulae may be unnecessary when using pelvic dimensions to discriminate sex, and according to the authors, the formulae derived in their study from a large and ethnically diverse sample should provide reliable standards for determining sex in a variety of populations. The purpose of the present study was to assess the accuracy of the discriminant function equation for acetabular diameter published by the aforementioned authors on a documented skeletal sample from France. The overall allocation accuracy obtained utilizing the pooled-group equation (84.1%) did not differ appreciably from that achieved using a sample-specific formula developed from the French dataset employed in this study (85.4%). This result is of practical importance to forensic anthropologists working in France, and elsewhere, particularly in situations where there is some question as to the population affinity of the skeletal remains. Future studies should continue to combine pelvic and non-pelvic data from disparate populations, to develop additional osteometric standards for discriminating sex with high accuracy across human groups.

Comparison of periprosthetic tissue digestion methods for ultra-high molecular weight polyethylene wear debris extraction.

There is considerable interest in characterization of wear debris from polyethylene (UHMWPE) bearing components used in total joint replacement. To isolate UHMWPE wear debris, tissue samples must be excised from regions adjacent to revised UHMWPE implant components, followed by exposure to one of many available tissue digestion methods. Numerous studies demonstrate successful digestion, but the relative efficiency of each method is not clear. The purpose of this study was to evaluate a variety of conditions for tissue digestion to provide a quantitative comparison of methods. Porcine and human hip tissues were exposed for 24 h to basic, acidic or enzymatic agents, filtered and digestion efficiency calculated based on the percentage of initial to final tissue weight. Of the conditions tested, 5 M NaOH, 5 M KOH, 15 M KOH or 15.8 M HNO(3) yielded the most complete porcine hip tissue digestion (<1% residual tissue weight; p < 0.05). Proteinase K and Liberase Blendzyme 3 did not effectively digest tissue in a 24 h period. Similar to results from the porcine dataset, human tissues digestion was most efficient using 5 M NaOH, 5 M KOH or 15.8 M HNO(3) (<1% residual tissue weight; p < 0.05). To verify that particle surface modifications did not occur after prolonged reagent exposure, GUR415 and Ceridust 3715 particles were immersed in each solution for 24 h. Overall, this study provides a framework for thorough and efficient digestive methods for UHMWPE wear debris extraction.

Tubular acetabular intraosseous contrast tracking in MR arthrography of the hip: prevalence, clinical significance, and mechanisms of development.

OBJECTIVE: The purpose of this study was to describe tubular intraosseous tracking of contrast medium in the acetabular fossa, to our knowledge a previously undocumented imaging finding in MR arthrography of the hip, and to discuss its prevalence, clinical significance, and possible mechanisms of development. CONCLUSION: Tubular acetabular intraosseous contrast tracking is a common MR arthrographic finding that seems to have little clinical significance. Although the exact pathophysiologic mechanism is unknown, we presume repeated pumping of joint fluid through the nutrient foramina of the acetabular fossa may be one mechanism.

Cemented cup stability during lever-out testing after acetabular bone impaction grafting with bone graft substitutes mixes containing morselized cancellous bone and tricalcium phosphate--hydroxyapatite granules.

Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. In the near future the amount of bone grafts available for surgical purposes will be insufficient. Ceramic calcium phosphates [tricalcium phosphate (TCP) and hydroxyapatite (HA)] have been widely considered as potential bone graft substitutes or bone graft extenders. In the past, mechanical experiments have been performed to determine implant stability of bone grafts and ceramic TCP-HA granules mixes under a compressive load. However, in-vivo migration studies suggest that shear loading may be equally important. This in-vitro study investigated the initial stability of cups reconstructed with various mixes of bone grafts and ceramic TCP-HA granules in a lever-out situation, where shearing is the predominant loading mode. It was found that the cups reconstructed with mixes of bone graft and TCP-HA granules exhibited greater mechanical stability than the cups reconstructed with bone grafts only. It is concluded that from a mechanical standpoint, when considering shear force resistance, 50-50 per cent volume mix and 25-75 per cent volume mix of morselized cancellous bone graft and TCP-HA granules both provide adequate initial cup stability and can be used for acetabular reconstructions with the bone impaction grafting technique.

Acetabular augmentation at six- to 30-year follow-up. A biochemical and histological analysis.

In developmental dysplasia of the hip, a deficient acetabulum may be augmented by placing local autogenous iliac osseous graft, or the ilium itself, over the head of the femur with the expectation that the added bone will function as a bearing surface. We analysed this bone obtained en bloc during subsequent surgery which was performed for degenerative osteoarthritis in three patients at 6, 25 and 30 years after the initial augmentation procedure. In each patient, the augmentation comprised of red cancellous bone covered on its articulating surface by a distinct layer of white tissue. Microscopy of this tissue showed parallel rows of spindle-shaped cells lying between linearly arranged collagen bundles typical of joint capsule. Biochemical analysis showed type I collagen, the principal collagen of joint capsule and bone, with no significant quantity of type II collagen, the principal collagen of cartilage. While the added bone produced by acetabular augmentation was durable, histological and biochemical analyses suggested that it had not undergone cartilage metaplasia. The augmented acetabulum articulates with the head of the femur by means of an interposed hip joint capsule.

Quantitative analysis of UHMWPE wear debris isolated from the periprosthetic femoral tissues from a series of Charnley total hip arthroplasties.

Submicrometer and micrometer-sized UHMWPE wear particles have been associated with osteolysis and failure of total hip replacements. A previous study by Tipper et al. examined the wear debris isolated from the acetabular periprosthetic tissues from 18 Charnley total hip replacements, and compared this data to the tribological variables of the prostheses. The present study aimed to isolate the UHMWPE wear debris from the femoral periprosthetic tissues from 10 of the same cohort of patients, and compare it with the debris isolated from the corresponding acetabular tissues. A variety of particle morphologies were observed, discrete submicrometer particles, along with flakes and fibrils. The particle size distributions ranged from 0.1 to >250 microm, however, the largest particles were only found in samples when the femoral head damage was characterised as low (R(pm) < 0.2 microm). The mode of the frequency distribution of particles was in the range of 0.1-0.5 microm for all the femoral tissues. Considerable variations were found in the mass distributions of the wear particles as a function of size for different patients. The net mass of debris isolated from the femoral tissues was significantly lower (p < 0.05, Student's t-test) than from the corresponding acetabular tissues. This along with considerable spatial variation in the net mass of debris isolated from the different regions of the same sample of acetabular tissue, indicates that the transportation of the debris has a marked effect on the net mass of debris accumulated in different tissues.

Teicoplanin in the prevention of infection in total hip replacement.

Perioperative antibiotic prophylaxis has been shown to be effective in reducing postoperative wound infections. The rising incidence of infections secondary to methicillin-resistant strains of Staphylococcus aureus. S. epidermidis and S. enterococcal prompted us to administer Teicoplanin to infection in elective total joint arthroplasty. In 111 patients Teicoplanin was given in a single intravenous dose of 10 mg/kg prior to surgery. In the postoperative period no deep infection of the prosthetic device was found in a 14-month follow-up. In two patients the following organisms were isolated from superficial infections of the wound: S. epidermidis (methicillin-sensitive), Pseudomonas aeruginosa, and Enterobacter sp. In no patient was revision surgery necessary. The serum concentration of Teicoplanin was within the therapeutic range during surgery, and tissue levels of Teicoplanin in cancellous (6.2 mg/kg, range 3.8-10.9 mg/kg) and cortical (7.1 mg/kg, range 2.6-12.1 mg/kg) bone during surgery in 16 patients exceeded the minimum inhibitory concentration of 90% (MIC90) of methicillin-resistant strains reported for methicillin-resistant strains. In our experience a single dose regimen of Teicoplanin is a safe and effective method of antibiotic prophylaxis in hip joint replacement, particularly when methicillin-resistant bacteria are present.

Pharmacokinetic model for cefazolin distribution during total hip arthroplasty in dogs.

OBJECTIVES: To compare cefazolin pharmacokinetics in serum and concentrations in tissues during total hip arthroplasty in dogs with and without hip dysplasia, and to calculate the optimal dosage of cefazolin for prophylactic use during total hip arthroplasty. ANIMALS: 10 dogs with hip dysplasia and 3 clinically normal dogs. PROCEDURE: Blood samples and tissue specimens from the coxofemoral joint capsule, acetabulum, and femur were obtained during unilateral total hip arthroplasty. Cefazolin concentrations in serum and tissue specimen supernatant were determined, using high-performance liquid chromatography, for use in pharmacokinetic analysis. Mathematical simulation of serum cefazolin concentration was used to to predict the optimal dose. RESULTS: Mean pharmacokinetic constants (SEM) were 0.146 (0.013) min-1 for alpha, 4.47 min for t1/2 alpha 0.015 (0.004) min-1 for beta, 46.83 min for t1/2 beta. Significant different was not detected for cefazolin distribution and elimination between dogs with and without hip dysplasia. Additional, significant difference was not observed in pharmacokinetic parameters describing distribution and elimination between the first and second doses of cefazolin. The predicted optimal dosage regimen was 8 mg/kg of body weight, i.v. every hour or mg/kg, i.v. every 2 hours. CLINICAL RELEVANCE: For prophylactic i.v. treatment during total hip arthroplasty, use of cefazolin at a dosage of 8 mg/kg every hour or 22 mg/kg every 2 hours should maintain serum cefazolin concentrations at least 10x the minimum inhibitory concentration for 3 to 4 hours.