Alternative bearings allow for the increased utilization of large femoral heads in total hip arthroplasty. This study demonstrated the effect of increasing femoral head size on the force required for dislocation during intraoperative assessment. Using a standard posterior approach, 10 cadaver hips underwent total hip arthroplasty; components were implanted in a standard fashion. The extremity was attached to a custom jig to replicate intraoperative assessment (internal rotation with 90° of hip flexion/neutral adduction). This range of motion (ROM) was repeated in triplicate using femoral head sizes of 28mm, 32mm, 36mm, 40mm, and 44mm. The ROM to dislocation (degrees) and torque (N*m) required were recorded. With increasing head sizes, there was a significant increase in torque required for dislocation (p<0.0001). The least square means torques (N*m) for each femoral head size (28-44mm) were 2.07, 2.15, 2.42, 2.74, and 3.65N*m. The corresponding least square means ROMs prior to dislocation were 43.5°, 46.2°, 50.8°, 54.3°, and 59.5°. There was a significant difference in ROM between nonadjacent head sizes (i.e., 28mm and 44mm) (p<0.0001). Total hip implant stability is multifactorial. Increasing femoral head size may confer stability during intraoperative assessment by increasing both the ROM prior to dislocation and the force required for dislocation.

BACKGROUND:Cigarette smoke exposure during prenatal and early postnatal periods increases the incidence of a variety of abnormal behaviors later in life. The purpose of this study was to identify the possible critical period of susceptibility to cigarette smoke exposure and evaluate the possibe effects of cigarette smoke during early life on brain-derived neurotrophic factor/neurotrophic tyrosine kinase receptor B signaling in the brain.METHODS:Three different age of imprinting control region mice were exposed to cigarette smoke or filtered air for 10 consecutive days beginning on either gestational day 7 by maternal exposure, or postnatal days 2 or 21 by direct inhalation. A series of behavioral profiles and neurotrophins in brain were measured 24 hours after mice received acute restraint stress for 1 hour on postnatal day 59.RESULTS:Cigarette smoke exposure in gestational day 7 and postnatal day 2 produced depression-like behaviors as evidenced by significantly increased immobility in both tail suspension and forced-swim test. Increased entry latencies, but not ambulation in the open field test, were also observed in the gestational day 7 and postnatal day 2 cigarette smoke exposure groups. Genetic analysis showed that gestational day 7 cigarette smoke exposure significantly altered mRNA level of brain-derived neurotrophic factor/tyrosine kinase receptor B in the hippocampus. However, behavioral profiles and brain-derived neurotrophic factor/tyrosine kinase receptor B signaling were not significantly changed in PND21 cigarette smoke exposure group compared with FA group.CONCLUSIONS:These results suggest that a critical period of susceptibility to cigarette smoke exposure exists in the prenatal and early postnatal period, which results a downregulation in brain-derived neurotrophic factor/tyrosine kinase receptor B signaling in the hippocampus and enhances depression-like behaviors later in life.

OBJECTIVES:Reducing unnecessary radiation exposure from medical imaging is paramount. This study assessed whether a laser aiming guide for C-arm fluoroscopy reduced the number of exposures needed to obtain an acceptable image, thereby reducing total fluoroscopy time for hip, knee, and ankle fluoroscopy.METHODS:An obese cadaver was placed supine on a radiolucent surgical table. Images were obtained by licensed radiologic technologists using a calibrated OEC 9900 Elite C-arm with laser targeting (LT) and without LT (NLT). Dosimeters were placed 1, 3, and 6 ft (30.5, 91.5, and 183 cm) away from the center of the C-arm at 90-degree angles at 2 levels, simulating thyroid and gonadal exposure. Posterior-anterior (PA) images of the bilateral lower extremities were obtained with each technician acquiring 24 centered images (hip, knee, and ankle) using both LT and NLT C-arm fluoroscopy.RESULTS:Total fluoroscopy time was reduced by 19% when using LT with a 39% reduction for the knee and a 29% reduction for the ankle. The addition of LT improved the likelihood of obtaining a centered image for knees and ankles but not for hips. The gonadal dosimetry data were significantly higher than the thyroid dosimetry badges at 1 ft. At the 3-ft zone, only trace amounts of radiation were detected; the 6-ft zone reported no radiation exposure in either group.CONCLUSIONS:LT helped with imaging knees and ankles with statistically significant reductions in fluoroscopy time and a statistically significant improvement of image quality defined as obtaining a centered PA image faster. The dosimetry badges detected minimal exposure at 3 ft and no detectable exposure at 6 ft at both levels.

The purpose of this study was to determine the minimum number of throws needed for knot security for square knots using 5 common suture materials and 3 common sizes by in vitro single load to failure biomechanical testing. The hypothesis was that each suture combination studied would share a common minimum of at least 5 throws to guarantee security. Five suture materials (FiberWire [Arthrex, Inc, Naples, Florida], Monosof, Surgipro, Maxon, and Polysorb [Covidien, Mansfield, Massachusetts]) with varying suture sizes (#5, #2, 0, 2-0, and 4-0) were tied in vitro, varying the number of square knot throws (3, 4, 5, and 6). Twenty knots for each combination were statically loaded to failure in tension; whether the knot failed by fracture or slippage and the tensile strength at knot failure was determined. For the tested materials, at least 5 flat square throws should be used to confer knot security based on a binomial proportion score 95% confidence interval (CI) 0.84 to 1.0 or at least 4 throws for a 95% CI of 0.76 to 0.99. FiberWire requires 6 flat square throws per knot for security at either 95% CI level. Unless a surgeon has specific knowledge of experimental evidence that fewer throws are necessary for a specific application, the default should be a minimum of 4 throws, with 5 conferring additional security in most situations, and FiberWire requiring 6 throws.

The emission of fossil fuel carbon dioxide (CO2) to the atmosphere is implicated as the predominant cause of global climate change; therefore, advanced CO2 capture technologies are of the utmost importance. In this study, innovative amine-multilayered sorbents were fabricated using layer-by-layer (LbL) nanoassembly technology via alternate deposition of a CO2-adsorbing amine polymer (e.g. polyethylenimine or PEI) and an oppositely-charged polymer (e.g. polystyrene sulfonate or PSS). We found that the developed sorbents could be used for CO2 capture and that LbL nanoassembly allows us to engineer their CO2 capture performance through the fabrication variables (e.g. deposition polymers, deposition media, and number of bilayers). PEI/PSS was found to be the best polymer combination for developing sorbents with relatively high CO2 capture capacity. The amine-multilayered solid sorbents possessed fine microstructures and may have similar polymer deposition within and on the surface of solid sorbents. These amine-multilayered sorbents had much faster CO2 desorption rates compared to sorbents prepared using the current PEI-impregnation approach. Such fast CO2 desorption could make sorbents a good option for CO2 removal from power plants and even the atmosphere.

Our objective was to assess the rejuvenation effect of extracellular matrix (ECM) deposited by human bone marrow stromal cells (hBMSCs) on hBMSC expansion and tissue-specific lineage differentiation potential. Passage 5 hBMSCs were expanded on ECM or conventional plastic flasks (Plastic) for one passage. Cell number was counted and immunophenotype profiles were assessed using flow cytometry. Selected integrins and proliferation-related pathway signals were assessed using Western blot. The expanded cells were evaluated for their chondrogenic potential in a pellet culture system with TGF-β3-containing chondrogenic medium using gross morphology, histology, immunostaining, biochemical analysis, real-time polymerase chain reaction, Western blot, and biomechanical testing. ECM-expanded hBMSCs were further evaluated for their osteogenic potential using Alizarin Red S staining and alkaline phosphatase activity assay and for their adipogenic potential using Oil Red O staining. ECM-expanded hBMSCs exhibited an enhanced proliferation capacity and an acquired robust chondrogenic potential compared to those grown on Plastic. ECM expansion decreased intracellular reactive oxygen species and increased stage-specific embryonic antigen-4 expression in hBMSCs. ECM expansion also upregulated integrins α2 and β5 and induced a sustained activation of Erk1/2 and cyclin D1. Interestingly, upregulation of TGF-β receptor II during cell expansion and chondrogenic induction might be responsible for an enhanced chondrogenic potential in ECM-expanded hBMSCs. We also found that ECM-expanded hBMSCs had an increased osteogenic potential and decreased adipogenic capacity. ECM deposited by hBMSCs may be a promising approach to expand BMSCs from elderly patients for the treatment of large-scale bone defects through endochondral bone formation.

BACKGROUND CONTEXT: Prior studies by our group have shown that nicotine delivered via a transdermal nicotine patch significantly enhanced posterior spinal fusion rates in rabbits. This runs contrary to previously published studies by other groups in which nicotine administration decreased fusion rates. Hence, there may be a dose-dependent effect of nicotine on posterior spinal fusion outcomes.

BackgroundCigarette smoke exposure in utero and during early postnatal development increases the incidence of asthma and airway hyperresponsiveness (AHR) later in life, suggesting that a possible critical period of developmental sensitivity exists in the prenatal and early postnatal periods.ObjectiveWe investigated mechanisms of susceptibility during critical developmental periods to sidestream smoke (SS) exposure and evaluated the possible effects of SS on neural responses.MethodsWe exposed three different age groups of mice to either SS or filtered air (FA) for 10 consecutive days beginning on gestation day (GD) 7 by maternal exposure or beginning on postnatal day (PND) 2 or PND21 by direct inhalation. Lung function, airway substance P (SP) innervation, and nerve growth factor (NGF) levels in broncho alveolar lavage fluid were measured after a single SS exposure on PND59.ResultsMethacholine (MCh) dose response for lung resistance (RL) was significantly elevated, and dynamic pulmonary compliance (Cdyn) was significantly decreased, in the GD7 and PND2 SS exposure groups compared with the FA groups after SS exposure on PND59. At the same time points, the percent area of SP nerve fibers in tracheal smooth muscle and the levels of NGF were significantly elevated. MCh dose–response curves for RL and Cdyn, SP nerve fiber density, and the level of NGF were not significantly changed in the PND21 exposure group after SS exposure on PND59.ConclusionsThese results suggest that a critical period of susceptibility to SS exposure exists in the prenatal and early postnatal period of development in mice that results in increased SP innervation, increased NGF levels in the airway, and enhanced MCh AHR later in life.

BACKGROUND CONTEXT: A previous pilot study by our group demonstrated that nicotine administration via transdermal nicotine patch showed consistent serum nicotine levels whereas administration via the more commonly utilized mini-osmotic pump resulted in large variations in serum levels of nicotine of rabbits. In other work, we have previously demonstrated that nicotine delivered via a transdermal patch enhanced posterior spinal fusion rates in rabbits. This is contrary to studies published by other groups where nicotine administration decreased fusion rates. Hence, there may be a dose-dependent effect of nicotine on posterior spinal fusion outcomes.

Stem cells derived from synovial lining-synovial lining--derived stem cells or SDSCs--are a promising cell source for cartilage tissue engineering. We hypothesized that negatively selected SDSCs would form cartilage constructs and conventionally passaged SDSCs would be contaminated with macrophages, inhibiting SDSC-based chondrogenesis. We mixed SDSCs with fibrin gel and seeded the cells into polyglycolic acid scaffolds. After 3 days of incubation with a proliferative growth factor cocktail (containing transforming growth factor beta1 [TGF-beta1], insulin-like growth factor I [IGF-I], and basic fibroblast growth factor [FGF-2]), the cell-fibrin-polyglycolic acid constructs were transferred into rotating bioreactor systems and cultured with a chondrogenic growth factor cocktail (TGF-beta1/IGF-I) for up to 4 weeks. Tissue constructs based on negatively selected SDSCs had cartilaginous characteristics; were rich in glycosaminoglycans and collagen II; exhibited high expression of mRNA and protein for collagen II, aggrecan, and Sox 9; exhibited a negligible level of mRNA and protein for collagens I and X; and had an equilibrium modulus in the range of values measured for native human cartilage. Conventional passage yielded SDSCs with contaminating macrophages, which adversely affected the quality of tissue-engineered cartilage. We thus propose functional cartilage constructs could be engineered in vitro through the use of negatively isolated SDSCs.

Fracture Toughness is More Sensitive to Bone Remodeling Parameters than Strength and Toughness Timothy L. Norman1,2, Xidong Chen1, Garrett Noble1, Dan Porter2, Vince Kish2, Carola Pechey3, Clifford Les3, Yener Yeni3 1Engineering and Computer Science, Cedarville University, Cedarville, OH; 2Orthopaedics, West Virginia University, Morgantown, WV; 3Bone and Joint Center, Henry Ford Hospital, Detriot, MI tnorman@cedarville.edu

Abundant epidemiological data shows that maternal smoking during pregnancy or second-hand smoke exposure during neonatal life and infancy increases the incidence of respiratory illnesses later in life. However, underlying mechanisms initiated in early life but affecting adult disease remain undefined. Neurotrophins, including nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), are neurotrophic factors essential in promoting and maintaining differentiation, growth, and survival of central and peripheral nervous system. The goal of this proposal is to examine the potential role of neurotrophin release in mediating long-term effects of prenatal and early postnatal smoke exposure. Our studies showed that an initial exposure to smoke during prenatal and early postnatal periods significantly changed lung function, substance P (SP) innervation in trachea and the level of NGF in BAL fluid after re-exposure to smoke on adult (postnatal day (PD) 60). In controls, smoke exposure (PD 28) with a subsequent re-exposure at PD 60 did not affect lung function or SP innervation or NGF levels. PCR array revealed enhanced expression of multiple genes including NGF and its receptor by smoke exposure only during early prenatal periods. These data suggest that a critical period of exposure exists in early periods of development. Increased expression of NGF and its receptor in airway caused by smoke exposure may enhance susceptibility to respiratory illnesses in adult. These findings have obvious and significant implication both for smoking during pregnancy and the effects of second hand tobacco smoke exposure. The study provides evidence that prenatal and early postnatal life are periods of enhanced susceptibility to detrimental effects of cigarette smoke. These effects appear to be mediated through the release of neurotrophic factors like NGF which regulate growth and maturation of the airway during these susceptible periods.

Background context Decreased effectiveness in spinal fusion procedures in patients who smoke before, during, or after the operation has been noted in several clinical studies. In previous work, direct current (DC) electrical stimulation has been shown to enhance intertransverse process fusion in a rabbit model. Purpose To test the efficacy of DC stimulation on bone healing in spinal fusion in rabbits exposed to nicotine. Study design/setting A randomized and controlled interventional study. Methods Thirty male New Zealand white rabbits received a single level posterolateral, intertransverse process fusion with autologous iliac crest bone. One group (control) acted as a control without nicotine or electrical stimulation. A second group (Nic) received a continuous dose of nicotine via a transdermal patch to simulate a heavy smoker, and a third group, nicotine/stimulator group (Nic/Stim), additionally received a 100-microamp DC stimulator. The fusion masses (L5-L6) and the adjacent unfused control segment (L4-L5) were evaluated radiographically, manually, and biomechanically. Results The Nic group showed significantly higher fusion rate compared with the control group. The Nic/Stim group also demonstrated significantly higher fusion rate and X-ray trabeculation compared with the control group. However, the Nic/Stim group was not significantly higher than the Nic group in fusion rate or X-ray trabeculation. Conclusions Nicotine significantly improved fusion rate compared with controls, and DC stimulation significantly increased X-ray trabeculation of nicotine treated rabbits compared with controls.

This study measured the changes in moment arm length of thumb motor tendons after simulated ligamentous instability and subsequent reconstruction of the trapeziometacarpal joint. Excursions of thumb motor tendons were measured simultaneously with the trapeziometacarpal joint angulation during flexion to extension and abduction to adduction motion. Tendon moment arms were calculated based on joint and tendon displacement techniques in the intact joint, after sequential sectionings of the capsuloligamentous restraints, and after the reconstruction procedure of Eaton and Littler. The results showed that moment arms of the abductor pollicis longus and extensor pollicis brevis tendons increased significantly as compared with those for normal joints during flexion to extension motion after sectioning the palmar capsuloligamentous components. After the ulnopalmar structures were cut, the moment arm of the extensor pollicis longus tendon had a statistically significant increase during abduction to

This study discusses the anatomical basis for reverse first to fifth dorsal metacarpal arterial flaps. The arterial pattern and size of the first to fifth dorsal metacarpal arteries were examined in 20 fresh cadaver hands. Their connections to the palmar arterial system at the metacarpal head were observed, and the location, number and diameter of skin perforators from each dorsal metacarpal artery were measured. The first to fourth dorsal metacarpal arteries were found in all specimens; the fifth dorsal metacarpal artery was found in 19 of our 20 specimens. The mean diameters of the first to fifth arteries at their bifurcation site were 0.6, 0.8, 0.5, 0.4 and 0.2 mm, respectively. Each artery gave off four to eight skin perforators (diameter: 0.1-0.3 mm) between the metacarpal head and base. The first to third dorsal metacarpal arteries consistently connected to the palmar arterial system, and connections between the fourth and fifth dorsal metacarpal arteries and the palmar system were found in 65% and 40% of specimens.

In this study, fluorescently labeled ATDC5 and bone marrow derived preosteoblastic cells were embedded in agarose gel and poked with a micropipette under a confocal microscope. Image stacks of cross sections of cells were taken before and after poking and the largest cross sectional areas were analyzed. After adjusting for photobleaching effects by equalizing the area of a nearby unpoked cell (by adjusting threshold values of the images) the area of the poked cell before and after poking was measured and the percentage change in area was calculated. The percentage change in cross sectional area was 25 ± 15% for ATDC5 cells and 31 ±13% for bone marrow derived cells (n= 5 for each type of cell). The decrease in area was statistically significant for each cell type (p<0.05). There was no difference in the reduction in areas between the two types of cells (power >80%). These results are consistent with the theory that some of the cell water is free and some are structured or restricted. This method can be utilized to determine fluid pressure in cells. This is significant because it is believed that changes in intracellular fluid pressure can play a role in cellular mechanotransduction.

ATDC5 cells, a prechondrocytic cell line, were cultured in 2% agarose gel-cell constructs. A major reorientation of actin structure (stress-fiber to punctate) was observed during the chondrogenesis of these cells. 2D finite element models of cell (considered as a composite with embedded actin fibers) in a 500μ3 gel were created for days 1 (prechondrocytes), 5, 8 & 12 (chondrocytes) of culture. The response of the cells to uniaxial compression of the gel-cell construct was studied. The model predicted that, as a result of rearrangement of actin, the cells became more compliant and less anisotropic. When the gel size was reduced to 20μ3, RUTL (Ratio of radial deformations of cell in the Transverse direction to Loaded direction) became significantly different between prechondrocytes and chondrocytes. The difference in force required to compress a 20μ3 gel-cell construct containing a prechondrocyte vs a chondrocyte to 15% deformation was 103nN (152.3 vs 48.8 nN). This information can be used to build MEMS based devices that can mechanically distinguish between the different cell types.

INTRODUCTION: Cementless implants achieve long-term fixation and consequent clinical stability primarily via biologic means – bony ingrowth into a porous-coated intramedullary implant surface. The adequacy of this biologic fixation depends upon numerous factors, including the initial or short-term fixation of the implant with respect to the adjacent bone (1,5,6). Short-term fixation refers to the post-operative limitation of relative motion between implant surface and the adjacent bone. Micromotion may be limited by utilizing a rough implant coating in concert with a distal stem press-fit. However, the holding power of the press-fit over time is dependent upon the viscoelastic nature of cortical bone (2). The objective of this study was to experimentally evaluate the effect of transverse cortical bone viscoelasticity on initial diaphyseal fixation of an implant for various degrees of press-fit (diametral interference ( )) and surface coating. It was hypothesized that viscoelastic relaxation increases with press-fit amount. It was also hypothesized that if bone was stressed above a certain level during press-fit, implant fixation would be reduced. METHODS: Eleven femoral pairs were utilized in this study (females 63.1 3.9, males 53.6 8.9). The target cortical index range, as calculated from anterior-posterior x-ray films was 40-60%, which was also representative of the hip replacement population (3,4). The right and left femurs were cut into three 4 cm long diaphyseal bone sections that were reamed until “chatter” (resistance to reaming from cortical bone) was felt. After reaming, a cylindrical CoCrMo alloy intramedullary test specimen (DePuy, A Johnson and Johnson Company) was selected that corresponded to line-to-line (same size stem as ream), 0.5 mm press-fit (a stem with a diameter 0.5 mm larger than the reamer) and a 1.0 mm pressfit (a stem with a diameter of 1.0 mm larger than the reamer). The actual press-fit was then calculated form the difference between the reamer diameter and the measured stem diameter. Three stem surface conditions were manufactured including 20 grit, small bead coating (60/80 mesh Porocoat porous coating) and large bead coating (24/35 two layer coating). With the bone held in place on an annular loading platform, the test specimens were inserted into the bone segments using standard operating room tools and procedures. Once inserted, the loading platform was placed between the cross-heads of a servo-mechanical testing machine (Materials Testing System, Minneapolis, MN) and loaded under stroke control at 1 mm/min. Actuator load and deflection were recorded and plotted for determining the push-out load. The push-out load was defined as the maximum load attained prior to slipping of the stem within the canal. The push-out load was determined for specimens at time=0 hours (Pt=0) and after 24 hours (Pt=24) of soaking in a physiological bath. From these two quantities, the viscoelastic Load Radio was found as Load Ratio = P0/P24. The Load Ratio was a measure of the viscoelastic effect on the “holding strength” of the stems. Statistical analysis was performed using JMP (SAS Institute, Cary, NC) and significance was set at p<0.05. RESULTS: Results indicated that there was no significant relationship between push-out loads and press-fit at t=0 and t=24 hours (Figure 1). However, a nonlinear regression analysis of the pooled Load Ratio versus press-fit data indicated a significant (p<0.0002, r = 0.43) quadratic relationship (Figure 2). Therefore, more relaxation occurred between t=0 and t=24 hours resulting in less push-out load as press-fit increased. The analysis also indicated that small bead coated (i.e. Porocoat) stems have significantly greater push-out loads at t=0 hours (p<0.01) and t=24 hours (p<0.04) compared to large bead coated stems. The small bead coated stems also demonstrated greater push-out loads than the 20 grit stems but the difference did not reach statistical significance. DISCUSSION: Results from experiments showed that relaxation significantly increased with press-fit, i.e. there was a greater reduction in push-out loads at higher press-fit as hypothesized. It was found that stability of the stem was not related to press-fit amount, indicating that after achieving press-fit, no additional gains or losses in stability were obtained by increasing press-fit, contradicting our second hypothesis. In finite element analysis conducted in our lab, results suggest an implantbone interference fit threshold ( =0.10mm) above which there would be no advantage in short-term push-out strength. This is indicative of an interference “threshold;” that is, a value of interference above which no significant benefit in terms of holding power is obtained. The results of this study showed that cortical bone viscoelasticity in the transverse plane of the diaphyseal femur has a diminishing effect on the contact pressure between the endosteal bone surface and the press-fit implant. This effect becomes significantly more pronounced as press-fit increases. However, there was no significant relationship between press-fit amount and pushout load. Therefore, for a particular implant size, there is a degree of press-fit beyond which no additional gains or losses in short-term fixation are realized. Additional study into this phenomena is warranted in view of the clinical implications. ACKNOWLEDGMENT: This project was supported by funding from DePuy, A Johnson & Johnson Company. REFERENCES: (1) Bauer TW, Schils J. Skeletal Radiol 28:483-97, 1999. (2) Blaha JD. In The Adult Hip, pp. 1085-1092, 1998. (3) Gruen TA. Acta Orthop Belg 63:20-7, 1997. (4) Gruen TA et al., 23 Annual Meeting of American Society of Biomechanics, 1999. (5) Pilliar RM et al., Clin Orthop 208:108-13, 1986. (6) Rosenberg A. Orthopedics 12:1223-33, 1989. Listing for additional author affiliation **DePuy, A Johnson & Johnson Company, Warsaw, IN ***Zonal Concepts, Wesley Chapel, FL ****University of Rochester, Rochester, NY *****University of Michigan, Ann Arbor, MI

BACKGROUND CONTEXT: Postoperative C5 nerve root palsy is a potential complication following the operative treatment of cervical stenosis. Though none has been proven, several etiologies of this problem have been proposed including surgical technique, cervical alignment, reperfusion injury, root tethering from dorsal shift of the cord, and the short length of the C5 root relative to other levels.