Background: In the murine model of suture fusion, it is widely accepted that the posterior frontal suture progresses from a state of patency on day 25 through complete fusion by day 45. The present study was performed to evaluate the process of normal posterior frontal suture fusion and to quantitate patterns of suture morphology in prefusion and postfusion mouse calvariae. Methods: The calvariae of mice euthanized on day 25 (n = 7) and day 45 (n = 7) of postnatal life were analyzed by micro-computed tomography with 21-mm sections from each posterior frontal suture and analyzed by a nonblinded investigator for patency or fusion in the ectocranial, central, and endocranial segments. Results: Both the ectocranial and central surface of the posterior frontal suture demonstrate a statistically significant difference in percentage fusion on day 25 versus day 45 of postnatal life. When compiled as a single suture complex, patterns of patency and fusion across the three defined levels showed a distinct trend toward patency at 25 days (19.8 ± 4.4 percent) and fusion at 45 days (48.6 ± 6.7 percent), but this relationship was not absolute. Conclusions: Although it has previously been thought that the posterior frontal suture in the mouse is fully patent on day 25 and fused on day 45, micro-computed tomographic analysis of the suture suggests otherwise. Accurate characterization of the timing and pattern of fusion in the mouse posterior frontal suture is an essential component to our understanding of the murine model, which serves as a widely studied analogue for suture fusion in humans.
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