Foliation of the mouse cerebellum occurs primarily during the first 2 weeks after birth and is accompanied by tremendous proliferation of granule cell precursors (GCPs). We have previously shown that sonic hedgehog (Shh) signaling correlates spatially and temporally with fissure formation, and that Gli2 is the main activator driving Shh induced proliferation of embryonic GCPs. Here, we have tested whether the level of Shh signaling regulates the extent of cerebellar foliation. By progressively lowering signaling by removing Gli1 and Gli2 or the Shh receptor smoothened, we found the extent of foliation is gradually reduced, and that this correlates with a decrease in the duration of GCP proliferation. Importantly, the pattern of the remaining fissures in the mutants corresponds to the first fissures that form during normal development. In a complementary manner, an increase in the level and length of Shh signaling results in formation of an extra fissure in a position conserved in rat. The complexity of cerebellar foliation varies greatly between vertebrate species. Our studies have uncovered a mechanism by which the level and length of Shh signaling could be integral to determining the distinct number of fissures in each species.

PurposeThis study compares clinical and radiographic outcomes of operatively managed pediatric supracondylar humerus fractures between patients treated by pediatric orthopedists (POs) and patients treated by non-pediatric orthopedists (NPOs).Patients and methodsA retrospective cohort study of pediatric patients with surgically managed supracondylar humerus fractures was conducted. For clinical outcomes analyses, 3 months of clinical follow-up were required, resulting in a sample size of 90 patients (33 treated by NPOs, 57 by POs). For radiographic outcomes analyses, 3 months of both clinical and radiographic follow-up were required, resulting in a sample size of 57 patients (23 treated by NPOs, 34 by POs).ResultsThe rate of inadequate fracture fixation was higher for patients treated by NPOs (43.5 %) than for patients treated by POs (14.7 %; p = 0.030), but rates of clinical complications, malreduction, and postoperative loss of reduction did not differ. Treatment with open reduction was more common for patients treated by NPOs (33.3 %) than for patients treated by POs (3.5 %; p < 0.001). Total operating room time was longer for patients treated by NPOs (110.9 min) than for patients treated by POs (82.9 min; p < 0.001).ConclusionsWhile patients treated by POs differed from patients treated by NPOs with respect to several intermediate outcomes, including having a lower rate of open reduction and a lower rate of inadequate fracture fixation, there were no differences between POs and NPOs in the rates of the more meaningful and definitive outcomes, including clinical complications, malreduction, and postoperative loss of reduction.