Growth plate fractures and disorders Flashcards
Growth plate function
Growth plate is the site of longitudinal bone growth
Longitudinal bone growth occurs via endochondral ossification
Anything that interferes with growth plate function before growth plate closure can have an impact on overall bone length and/or alignment
Two main types of growth plate
Pressure growth plates – found at the ends of long bones responsible for most of bone growth e.g. distal radial growth plate
Traction growth plates – found where muscles insert or originate & these contribute little to bone growth e.g. tibial tuberosity
Which is more likely to occur in immature animals - physeal fractures or luxations?
The physis is 3-5 times weaker than the attachment of ligaments & joint capsule to bone so physeal fractures are much more likely in immature animals than luxations.
Salter Harris classification
Classified injuries of the ‘pressure’ physes in man to give prognostic information.
The classification is not very useful in prognosticating the outcome in small animals.
Instead each injury should be evaluated individually and a guarded prognosis given until evidence for continued growth is seen radiographically
Type I physeal fractures
Physeal separation – metaphysis displaced from epiphysis
Transverse fracture through growth plate (physis).
Account for close to 40% of physeal fractures in dogs and cats.
Type II physeal fractures
Small corner of metaphysis fractured
Fracture through the growth plate and the metaphysis that spares the epiphysis.
Account for close to 40% of physeal fractures in dogs and cats.
Type III physeal fractures
Fracture through epiphysis and physis. Metaphysis unaffected.
Around 3% of physeal fractures are type III.
Rare
Type IV physeal fracture
Fracture through epiphysis, physis extending into metaphysis.
Accounts for 19% of physeal fractures in dogs and cats.
Type V physeal fracture
Compression or crush injury of growth plate
Resulting in a decrease in the perceived space between the epiphysis and the diaphysis on x-ray.
Type VI physeal frcture
Bony bridge across growth plate – angular deformity
Rare
Principles for repair of physeal fractures
Early surgery is important
Warn O about risk of complications
More important that articular suface integrity is maintained than function of physis
Fragments often small and delicate - careful surgery, especially with epiphyseal fragment (most germinal cells remain there)
Some can be managed by external coaptation
Should repair using implants that minimally disrupt physis - small smoot k wires perpendicular to physis is ideal
Should affect <10% SA of the growth plate
Implants that cross the physis should be avoided e.g. bone plates or lag screws
Removal of implants once fracture has healed
Proximal Humeral Growth plate fractures
Rare
Salter Harris type I & II (commonest) - the distal humerus displaces in a caudoproximal direction. Check neurological function. Reduce and repair with a single IM pin or Kwire.
Salter Harris type III (very rare) - may involve both the humeral head and the greater tubercle. These are articular fractures and need ORIF with K wire and lag screws.
Distal Radial & Ulna Physeal Fractures
Fractures through the growth plate are occasionally seen in immature animals.
The fracture is usually a Salter Harris type I or II.
More importantly there may be a concurrent Type V ulna growth plate injury that will not be recognised on early radiographs and may result in premature closure of the distal ulna growth plate and subsequent angular deformity.
Owners should always be warned of the likelihood or possibility of growth plate damage and subsequent angular limb deformity in any immature animals suffering limb trauma
Treatment – cross pins or open reduction and external coaptation. In minimally displaced fractures with an intact ulna external coaptation alone may be used.
Distal Tibial Physeal fractures
The physeal fragment is often very small and usually not big enough to apply a T plate, therefore fracture is usually stabilised with cross pins.
Reduction of the fracture can be difficult so early repair is recommended.
As only small weak implants can be used to repair the small fragments (adaptation osteosynthesis) some post operative support – a cast or splint - is needed until repair has been documented radiographically.
Femoral head fractures
These are not uncommonly seen in both dogs and cats.
Fractures can occur through the growth plate of the femoral head. These fractures will commonly result in disruption to the blood supply of the femoral head.
Signalment
* Cats or dogs usually skeletally immature – from 3-10mths of age
* Males or females of any breed affected
Early repair is imperative
Surgical approach – craniolateral or by osteotomy of the greater trochanter
Techniques for repair – parallel K wires or lag screws or a combination of both.
FHNE – last resort treatment.
Post operative care – restricted exercise until there is radiographic evidence of fracture healing
Radiography – a classic ‘apple coring’ of the femoral neck occurs which is a result of remodelling and resorption of bone during the healing phase. This is evident radiographically as a narrowing of the femoral neck at approximately 4 weeks post op – these changes should gradually resolve.
Prognosis – slightly guarded as the growth plate will often close prematurely resulting in a short femoral neck and coxa vara. Non union will occur if the fracture repair is unstable. If fracture repair fails then a FHNE should be performed (or possibly a THR)
