Changes in femoral cortical porosity after reaming and intramedullary canal preparation in a canine model.

This study examined changes in femoral cortical porosity resulting from femoral canal preparation during cemented total hip arthroplasty (THA). Twenty-four canines were randomly assigned to 3 groups: (1) reaming only, (2) cementing without pressurization, and (3) cementing with pressurization. Femoral cortical porosity was measured from histologic samples of the femurs at 7 positions. Reaming during canal preparation significantly increased cortical porosity. Cementing further increased cortical porosity, whereas pressurization of cement helped to counteract the increase in cortical porosity caused by cementing alone. Cortical porosity was considered to be a marker for bone mineral density (BMD) during the early phase of peri-implant healing around cemented stems. To maximize bone mineral density after cemented total hip arthroplasty, we suggest using implants that do not require reaming and pressurizing cement appropriately.

Interactivity and reward-related neural activation during a serious videogame.

This study sought to determine whether playing a "serious" interactive digital game (IDG)--the Re-Mission videogame for cancer patients--activates mesolimbic neural circuits associated with incentive motivation, and if so, whether such effects stem from the participatory aspects of interactive gameplay, or from the complex sensory/perceptual engagement generated by its dynamic event-stream. Healthy undergraduates were randomized to groups in which they were scanned with functional magnetic resonance imaging (FMRI) as they either actively played Re-Mission or as they passively observed a gameplay audio-visual stream generated by a yoked active group subject. Onset of interactive game play robustly activated mesolimbic projection regions including the caudate nucleus and nucleus accumbens, as well as a subregion of the parahippocampal gyrus. During interactive gameplay, subjects showed extended activation of the thalamus, anterior insula, putamen, and motor-related regions, accompanied by decreased activation in parietal and medial prefrontal cortex. Offset of interactive gameplay activated the anterior insula and anterior cingulate. Between-group comparisons of within-subject contrasts confirmed that mesolimbic activation was significantly more pronounced in the active playgroup than in the passive exposure control group. Individual difference analyses also found the magnitude of parahippocampal activation following gameplay onset to correlate with positive attitudes toward chemotherapy assessed both at the end of the scanning session and at an unannounced one-month follow-up. These findings suggest that IDG-induced activation of reward-related mesolimbic neural circuits stems primarily from participatory engagement in gameplay (interactivity), rather than from the effects of vivid and dynamic sensory stimulation.

Variability in nucleus accumbens activity mediates age-related suboptimal financial risk taking.

As human life expectancy continues to rise, financial decisions of aging investors may have an increasing impact on the global economy. In this study, we examined age differences in financial decisions across the adult life span by combining functional neuroimaging with a dynamic financial investment task. During the task, older adults made more suboptimal choices than younger adults when choosing risky assets. This age-related effect was mediated by a neural measure of temporal variability in nucleus accumbens activity. These findings reveal a novel neural mechanism by which aging may disrupt rational financial choice.

BDNF genotype modulates resting functional connectivity in children.

A specific polymorphism of the brain-derived neurotrophic factor (BDNF) gene is associated with alterations in brain anatomy and memory; its relevance to the functional connectivity of brain networks, however, is unclear. Given that altered hippocampal function and structure has been found in adults who carry the methionine (met) allele of the BDNF gene and the molecular studies elucidating the role of BDNF in neurogenesis and synapse formation, we examined the association between BDNF gene variants and neural resting connectivity in children and adolescents. We observed a reduction in hippocampal and parahippocampal to cortical connectivity in met-allele carriers within both default-mode and executive networks. In contrast, we observed increased connectivity to amygdala, insula and striatal regions in met-carriers, within the paralimbic network. Because of the known association between the BDNF gene and neuropsychiatric disorder, this latter finding of greater connectivity in circuits important for emotion processing may indicate a new neural mechanism through which these gene-related psychiatric differences are manifest. Here we show that the BDNF gene, known to regulate synaptic plasticity and connectivity in the brain, affects functional connectivity at the neural systems level. In addition, we demonstrate that the spatial topography of multiple high-level resting state networks in healthy children and adolescents is similar to that observed in adults.

Combined single-stage osseous and soft tissue reconstruction of the tibia with the Ilizarov method and tissue transfer.

OBJECTIVE: To determine the outcome of single-stage soft tissue and osseous reconstruction using the Ilizarov method and soft-tissue transfer. DESIGN: A retrospective review. SETTING: : A university-affiliated, tertiary-care center. PATIENTS/INTERVENTION: We identified 11 patients from a retrospective review from January 1994 to July 1999 who underwent single-stage soft tissue and osseous reconstruction using the Ilizarov method. All 11 patients had an initial traumatic mechanism to their tibia and had previous operative intervention before the combined procedure. The Ilizarov procedure was performed for infected tibial nonunion (8 cases), or complex fracture with soft-tissue loss (3 cases). MAIN OUTCOME MEASUREMENTS: Soft tissue transplant survival, union, range of motion, leg length discrepancy, the Association for the Study and Application of the Method of Ilizarov (ASAMI) score, radiographic parameters. RESULTS: There were 8 concomitant free tissue flaps and 3 local pedicled flaps. Two patients had primary bone grafting, and 5 others had addition of an antibiotic impregnated bone substitute. There were 8 cases of elective reconstructive surgery and 3 cases of acute traumatic fracture. The mean duration of Ilizarov application was 26 weeks (range, 7 to 42). Eight tibiae united primarily, and 3 healed after delayed bone grafting. There were 2 major flap complications. Both were successfully managed with repeat surgery. One patient sustained a repeat open fracture and subsequently received an amputation. According to the ASAMI score, there were 9 excellent results, 1 good result, and 1 poor result. CONCLUSION: Our study suggests that concomitant osseous and soft-tissue reconstruction with the Ilizarov technique and free or pedicled flaps is a viable option for patients with composite tissue defects.

Methods of operative fixation of the acromio-clavicular joint: a biomechanical comparison.

PURPOSE: Three different methods of fixation used in acute disruption of the acromio-clavicular (AC) joint-namely, the coraco-clavicular Bosworth screw (CC Screw), a coraco-clavicular sling of Mersilene #5 tape (CC Sling), and a Hook Plate-were compared to baseline to see which could most closely replicate the stiffness of healthy cadaveric AC specimens (Intact). HYPOTHESIS: It is hypothesized that the Hook Plate method, as compared with the other reconstructions tested, will be most similar mechanically to the intact AC joint with respect to present outcome measures. METHODS: Five matched pairs of fresh-frozen cadaveric specimens were tested. Stiffness was tested with superior cyclic loads to 70 N. The stiffness for each specimen was initially tested with all the ligaments in place (Intact). The AC and CC ligaments were then sectioned, and stiffness was tested, in varying order, with reconstructions using the CC Screw, the CC Sling, and the Hook Plate. Failure testing consisted of taking either the CC Screw or Hook Plate to failure within each matched pair. RESULTS: The CC Screw and the CC Sling, respectively, showed stiffnesses of 46 +/- 23 N/mm and 15 +/- 8 N/mm, which was significantly different from the Intact specimen (P < 0.05). The Hook Plate had a stiffness of 26 +/- 17 N/mm, most comparable to the Intact joint stiffness of 25 +/- 8 N/mm (P = 0.785). With failure testing, the CC Screw failed at a significantly higher load than the Hook Plate (744 +/- 184 N vs 459 +/- 188 N) (P = 0.034). CONCLUSION: The CC Screw demonstrated the greatest stiffness with repetitive loading to 70 N. The Hook Plate had a stiffness most similar to the normal physiologic state of the AC joint. The CC Sling was significantly less stiff than the Intact joint or the other methods of fixation. SIGNIFICANCE: Although the stiffest construct is the CC Screw, Hook Plate fixation allows physiologic motion without pathological deformation and most closely resembles the stiffness of the native AC joint for the current test procedure used.