Diagnosis-

This calf sustained a fracture in the distal diaphyseal region of the left 
metacarpal bones.  The fracture is simple, oblique, and now open to the 
environment due to the presence of sores and bacteria cultured from the 
fracture site.  The fracture and sores were sustained at the time of birth due 
to the techniques used to deliver the calf.  The fracture was never properly 
reduced at initial treatment and was improperly bandaged and casted leading 
to tissue necrosis and sloughing. The calf has a valgus deformity due to the 
improper reduction of the fracture ends.

This fracture is defined as a delayed union, one that has not healed in the 
expected time (3 months).  There are many local factors that would cause 
this : instability, vascular compromise, large fracture gaps, interposed soft 
tissues, infection, and inappropriate fixation techniques.  This calf has an 
unstable, improperly fixated fracture, with a large gap and infection of the 
fracture site.  As of these could have been contributing to the delayed union.

Ideally, for fracture healing to occur, there would be a rigid fixation, a good 
blood supply and no infection.  A good vascular supply is necessary for 
proper healing, first by the pleuropotential cells becoming fibroblasts and 
laying down fibrous tissue between fracture ends.  This fibrous tissue is then 
broken down and replaced by dystrophic calcified tissue, which is then 
replaced by bone through ossification.  If there is less blood supply and more 
fracture movement, the pleuropotential cells instead become chondroblasts 
and form cartilage which must be replaced by bone through endochondral 
ossification, a slow process.  If there is very poor blood supply, there is no 
new bone formation, this is associated with dead bone at the site.  

Fortunately this delayed union maintains some good blood supply.  This is 
evident radiographically by the bony callus formation at the fracture ends.  
So this would be a viable delayed union, classified as hypertrophic.  This is 
beneficial for the prognosis because osteogenic potential is still present.

Additionally, a positive culture of Staph and E.coli was obtained from the 
fracture site.  This indicates osteomyelitis, infection of the bone.  Some of 
the radiographic changes, such as bony sclerosis, and the presence of 
draining tracts are compatible with this diagnosis.  There is no evidence of 
sequestrum that would need to be removed, and we will treat this by 
antibiotics.  The physis is not involved, which is important for this growing 
animal.