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)
Femoral neck fractures
These have a better prognosis than femoral head fractures as the growth plate is unaffected and the blood supply to the femoral head is less damaged.
Repair – lag screws (and Kirschner wires).
Premature physeal arrest
may occur if there is injury to the germinal cells or blood supply to the physis.
Compression damage or fractures traversing the growth plate are more likely to cause growth arrest than epiphyseal fractures
Not just Salter Harris type V and VI injuries which result in premature growth plate closure, all physeal injuries can lead to premature closure and owners should be warned accordingly at the time of the initial injury.
Magnitude of problem of premature growth plate closure
Age: 95% of growth is complete by 7 months of age so an injury in a 7 month old dog will have much less effect than a similar injury in a 3 month old animal
Which growth plate is affected: premature closure of the distal ulna physis will have a greater affect than premature closure of the distal humerus due to the intimate relationship between the radius and ulna.
The different growth plates at the opposite ends of each bone are often responsible for different percentages of the total growth.
For example the proximal radius is responsible for approximately 40% of total growth and the distal for 60%, the proximal ulnar physis is responsible for 15% of total ulna growth and the distal ulnar physis for 85%.
Principles for corrective surgery for premature growth plate closure/angular limb deformity
Restore joint congruity
Restore paw to a functional position
Correct rotational deformity
Correct angular deformity
Restore limb length
Osteotomy
an elective surgical division of the bone.
Ostectomy
resection of a piece of bone
Common angular deformities
Premature closure of the distal ulna growth plate - radius curvus
Premature Closure of The Distal Radial Growth Plate
Premature Closure of the Distal Radius and Ulna Growth Plates
Premature Closure of the Distal Femoral And / Or the Proximal Tibial Growth Plate
Premature Closure of The Caudal Proximal Tibial Growth Plate
Premature Closure of The Distal Tibial Growth Plate
Premature closure of the distal ulna growth plate
The distal ulna growth plate is the most commonly affected of all the growth plates.
The conical shape of the distal ulnar physis is unique to the dog - in all other animals the radial and ulnar physes are flat and predisposed to shearing fractures.
The canine distal ulnar physis is unable to shear so shear forces are transformed into compressive forces.
Large dogs seem to be most frequently affected, often bilaterally and there may not be a history of trauma.
Cessation or slow growth is ’normal’ in some chondrodystrophic breeds such as Basset Hounds, Dachshunds or Skye Terriers.
Retained cartilage cores occasionally seen in Giant and large Breeds may also lead to premature closure.
Affected animals present with Radius Curvus.
The radius continues to grow while the ulna acts as a bowstring.
Radius curvus
Cranial & then medial bowing of the radius
Carpal valgus
External rotation of the foot (supination) and
Subluxation of the humeroulnar joint and radiocarpal bone
Presenting complaint for radius curvus
either for lameness due to elbow subluxation or because owners have noticed the angular deformity.
Diagnostic imaging for radius curvus
Must include the whole antebrachium including the elbow and carpal joints. Both limbs should be radiographed for comparison and to check for bilateral problems.
Treatment options for radius curvus in a young dog
(< 6 months with residual growth potential)
i. Cut ‘bow-string’ and stop growth - Partial ulna ostectomy with temporary transepiphyseal bridging (TTB) of the craniomedial aspect of the distal radial growth plate. Use staples or 2 screws and a figure of 8 wire for the TTB.
ii. Cut ‘bow-string’ - Removal of the distal ulna growth plate with part of the distal ulna
Treatement options for radius curvus in a skeletally mature dog
Definitive correction - Ulna osteotomy and corrective osteotomy of radius. Corrective radial osteotomy may involve either a cuneiform osteotomy or an oblique osteotomy.
