Ossification of the Proximal and Middle Phalangeal Condyles: Radiographic Aid in Phalangeal Neck Fracture Reduction.

BACKGROUND: Phalangeal neck fractures are commonly dorsally displaced and angulated. Surgical treatment is often necessary to restore the retrocondylar recess. The purpose of this study was to determine whether radiographic landmarks can serve as a reference tool for assessing phalangeal neck fracture alignment based on age and sex. METHODS: In total, 1061 lateral finger radiographs that were interpreted as "normal" by pediatric radiologists in children aged 1 to 18 years were retrospectively reviewed. The proximal and middle phalanges of each digit had a line drawn along the volar cortex [termed the volar phalangeal line (VPL)] and a second perpendicular line was drawn at the level of the phalangeal condyle. A ratio of the anterior to posterior aspects of the phalangeal condyle was determined at the intersection of these lines. Sex of the patients was noted to determine whether it influenced the temporal course of ossification. A linear regression model was utilized to determine the annual coefficient of growth for the phalangeal condyles. RESULTS: There is a temporal course of ossification of the proximal and middle phalangeal condyles. As children increase in age, the VPL will intersect the phalangeal condyle more dorsally due to the eccentric ossification. In children above 9 years of age, the VPL will reliably intersect the middle one third of the phalangeal condyle. No clinically significant difference exists between the ratios of the proximal and middle phalanges. Sex was not associated with a difference in growth. The greatest growth increase was observed in the 8 to 9-year-old interval. CONCLUSIONS: The phalangeal condyles ossify in an eccentric manner and the VPL will intersect the phalangeal condyle more dorsally with increasing age. The VPL and knowledge of where it should intersect the phalangeal condyle can be used as a reference guide for evaluating the reduction of proximal and middle phalangeal neck fractures in children. LEVEL OF EVIDENCE: Level III.

More is less: a disinhibited prefrontal cortex impairs cognitive flexibility.

The prefrontal cortex (PFC) is critical for decision making, and it becomes dysfunctional in many neuropsychiatric disorders. Studies in schizophrenia patients and relevant animal models suggest loss of PFC inhibitory interneuron function. For instance, rats with a neonatal ventral hippocampal lesion (NVHL) show a deficient modulation of PFC interneurons by dopamine (DA). Whether the PFC becomes disinhibited in this model and alters decision making remains to be determined. Here, we recorded neural activity in the medial PFC of NVHL rats during a reward-discounting choice task that activated DA systems. Rats were trained to sample odors that instructed them to select one of two feeders that delivered unequal amounts of liquid. Putative pyramidal neurons in the PFC were hyperactive whereas task-related field potential oscillations were significantly reduced in NVHL rats, consistent with impaired interneuron activation by DA during odor sampling leading to disorganized processing. Cognitive flexibility was tested by examining response bias and errors after reversing reward outcomes. NVHL rats demonstrated impaired flexibility as they were less able to track changes in reward outcome and made more response errors than controls did. Reducing cortical excitability with the metabotropic glutamate receptor 2/3 agonist LY379268 (1 mg/kg, i.p.) improved behavioral flexibility in NVHL rats but not controls. Furthermore, D2 dopamine receptors were involved, as the antagonist eticlopride (0.02 mg/kg, i.p.) reduced the ability to switch only in control animals. We conclude that NVHL rats present PFC disinhibition, which affects neural information processing and the selection of appropriate behavioral responses.