Regional ossification-centre union and physeal closure

An ossification centre appearing, two centres joining, and a growth plate closing against the shaft are different events. The ages on this sheet are canine reference ranges. Breed and the interface being assessed matter.

At the distal humerus, the medial and lateral condylar centres join before the whole epiphysis joins the shaft. Table 73.2 gives about 6 weeks for centre union; Chapter 50 gives about 3 months. These are different textbook estimates of the same internal union. Yonamine and colleagues also recorded centre union at 3 months in laboratory Beagles. Table 73.2 gives 6–8 months for epiphysis-to-shaft fusion. The olecranon joins at 6–10 months, the proximal radius at 6–11 months, and the distal radius and ulna at 8–12 months.

At the proximal femur, the greater trochanter joins at 6–10 months, the femoral head at 7–11 months, and the lesser trochanter at 8–13 months. The original 6, 7 and 8-month cues are the early ends of those ranges. Distally, the trochlea joins the condylar centres at about 3 months. The whole distal femoral epiphysis joins the shaft later, at 8–11 months.

At the proximal tibia, the medial and lateral condylar centres unite at about 6 weeks. The proximal epiphysis joins the shaft at 6–12 months. The tibial tuberosity joins the condyle at 6–8 months; its union to the shaft is listed at 6–12 months in the table. Chapter 63 describes later tuberosity physeal closure, beyond 12 months, in large-breed dogs.

At the distal tibia, the medial malleolar centre joins the distal epiphysis at about 5 months. The distal tibial growth plate closes against the shaft at 8–11 months. Internal centre union therefore does not mean that all growth at that end has stopped.

References

hand-drawn ACVS Phase One notes; Johnston and Tobias, Veterinary Surgery: Small Animal, 2nd edition, Table 73.2 and Chapters 50 and 63; Yonamine et al., 1980. These textbook ranges are reference ages rather than individual closure dates.