Fracture: overview

• Cause: fractures are caused when the force applied to the bone exceeds the ultimate strength of the bone. 
• The type of fracture depends on the size and direction of the force applied to it and the shape, size and structure of the bone involved.
• Separation of the fracture fragments and, therefore, the degree of instability, depends on the severity of the fracture and tension forces from surrounding tissues and attachments.
• Types: fractures can be separated into 6 broad groups:
  • Oblique.
  • Transverse.
  • Comminuted.
  • Spiral.
  • Segmental.
  • Epiphyseal.
• Fractures may be:
  • Either Open - skin wound communicating with fracture site.
  • Or Closed - overlying skin is intact.
• Signs: vary according to site, type, degree of instability, severity of fracture, whether 'open' or 'closed'.
• Treatment: conservative management, external coaptation Fracture fixation: casts, external  Fracture: external fixation or internal fixation Fracture: internal fixation  - depends on site, type, severity of fracture.
• Prognosis: dependent upon site, type, severity, method of repair, age, concurrent injuries or pathology.

General

• History of trauma.
• Pain.
• Swelling.

Specific

• Loss of function.

• Instability.
• Crepitus - depends on distraction of fracture fragments.

• Signs of predisposing condition - see Predisposers.

• Cardiac arrhythmias.
• Shock.
• Collapse.
• Respiratory abnormalities if fracture associated with trauma.
• Neurologic abnormalities (central and peripheral).

Epiphyseal

• Young animal <12 months (skeletally immature), however, male neutered cats can have open physes for significantly longer.

• Internal fixation is the most costly.

• External fixation at a moderate cost.

• Conservative management is relatively inexpensive.

• The more severe the fracture, the greater the causal forces (usually) and the associated damage to surrounding tissues and other systems.

• Direct trauma, eg HBC (RTA) (most common), gun shot, air gun pellet.
• Compression, eg fall from height.
• Bending or shearing forces, eg trapped limb.

General

• Neoplasia.
• Generalized bone disease.
• Presence of internal fixation device, eg bone plate Fracture fixation: plate, screws Fracture fixation: lag screw, wire Fracture fixation: wire.
• Bone defects, eg holes, cysts, notches.
• Previous fracture.

Specific

Epiphyseal

• Open growth plate (skeletally immature animal) Epiphyseal trauma and older male neutered cats.

• Fractures are caused when the force applied to the bone exceeds the ultimate strength of the bone.
• See also fracture healing Fracture: healing.

• Fractures can be separated into 6 broad groups:
  • Incomplete - greenstick.
  • Oblique.
  • Transverse.
  • Comminuted.
  • Spiral.
  • Segmental.
  • Associated with growth plate (physis) (Salter-Harris classification) .
• Fractures may be:
  Either Open (compound) - skin wound communicating with fracture site - Grades I, II, III.
  Or Closed (simple) - overlying skin is intact.
• Fractures may be:
  Either Complete - total disruption of bone continuity.
  Or Incomplete - partial continuity of bone maintained, eg greenstick fracture (young animals), fissure fracture (adults).
• Relative displacement of fracture fragments:
  • Distraction/avulsion - pull of tendon/ligament/muscle attachments separate bone fragments.
  • Compression - compressive force shortens bone, eg vertebra.
  • Depression - concave deformity of bone, eg skull, from applied force.
  • Impaction - fractured bone ends driven into one another.
• Type depends upon:
  • Size and direction of the force applied.
  • Bone structure.
  • Bone shape.
  • Site.

 Force

• Torsion  →  spiral fractures.
• Shearing/tension/bending  →  transverse fractures.
• Compression/bending  →  oblique fractures with/without comminution.
• High energy stress, eg HBC (RTA) or gun shot often  →  severe comminution and damage to surrounding tissue.
• A combination of the above forces are usually acting in any one instance   →   variable fracture patterns.

Bone structure

• The resistance of a particular bone to external forces is dependent upon the composition of that bone, ie the proportions of cortical:cancellous bone:
  • Cortical bone - strong against compression; weak against shearing perpendicular to long axis.
  • Cancellous (trabecular) bone - strong against compression; weak against tension.
• Long bones have a wide metaphysis of cancellous bone - suited to absorb large amounts of compression energy.

Bone shape and size

• Cylindrical shape resists torsion, eg long bones.
• Square shape (rounded angles) resists bending, eg majority of bones.
• Cross sectional area, length and the shape of the bone as it relates to the neutral axis, however most cats are fairly similar in size.

Site

• The type of stresses acting on a bone will vary according to the site of the bone, eg:
  • Vertebrae/long bone metaphyses - compression.
  • Patella/traction epiphyses - tension.
  • Humeral condyle - shearing.
  • Long bone diaphyses - bending.
  • Tibia/humerus - torsion.
• Exposure/degree of protection by surrounding tissue affects fracture incidence/type, eg distal limbs have little covering tissue to absorb external forces  →  high incidence of limb fractures in general trauma, eg HBC (RTA) and risk of comminution and beiong open.

• Depends on bone involved.

General

• History of trauma.
• Pain.
• Swelling.

Specific

• Loss of function.
• Soft-tissue injury.

• History of predisposing condition - see Predisposers.

• Signs of other tissue damage.
  It is almost impossible for a bone to fracture without considerable damage occurring to adjacent soft tissues - always examine whole animal carefully, see also Trauma   Trauma: overview. 
• Site dependent, eg:
  • Limb Femur: fracture - acute onset lameness, limb shortening +/- deviation.
  • Spine Spine: fracture/luxation - nervous signs.
  • Jaw Mandible: fracture - eating abnormalities, facial distortion, dental malocclusion, hypersalivation.
  • Tail - abnormalities of function and carriage.
  • Ribs - signs of thoracic involvement.
  • Pelvis Pelvis: fracture - urinary tract injury possible; signs may vary from a single limb lameness to an inability to stand on the hind limbs +/- neurological signs.

• Instability.
• Crepitus - dependent upon distraction of fracture/fragments or interposition of soft tissue.

• Signs of predisposing condition - see Predisposers.

• Assess other injuries, eg respiratory function, vascular integrity, neurological function Neurological examination.

Radiography

• Two views under general anesthesia including both proximal and distal joints.
• Visualization of fracture site; classification of fracture type; involvement of associated tissues in multiple injuries.
• Stressed, eg hock fractures.
• Involvement of associated tissues in multiple injuries, eg ligament rupture.
• May be useful to have contralateral limb region as comparison in young animals with open physes, comminuted fractures to establish original limb length, and in regions with complex or unfamiliar anatomy such as the tarsus or carpus.

Stabilize patient

• Analgesia Analgesia: overview.
• Opioids are first line analgesia. Underlying hypoperfusion (cardiovascular shock) or renal disease should be ruled out or corrected prior to administration of NSAIDs. NSAIDs once deemed safe, are particularly useful in orthopedic trauma, particularly with soft-tissue swelling Therapeutics: musculoskeletal system.
• Correct blood loss; identify source of bleeding, and provide supportive fluid therapy Fluid therapy: for hemorrhage.
• Treat shock Shock.
• Treat other injuries, eg thoracic Thorax: trauma, urinary, eg kidney, bladder Bladder: trauma rupture, ureter Ureter: trauma.

Fracture

General considerations

• Patient status:
  • Age.
  • Size.
  • General health.
  • Expected lifestyle.
  • Other injuries, eg nerve damage.
• Fracture site.
• Fracture type and severity.
• Available equipment and implants.
• Surgical expertize.
• Cost.
• Open fractures will require urgent debridement and stabilization.
• The aim of fracture repair is to rapidly restore function of the bone.
• Urgency of fracture repair varies according to site: spinal fractures may require immediate decompression; intra-articular fractures/growth plate injuries should be stabilized within 48 h.
  Early orthopedic repair in a stable patient reduces the incidence of post-operative complications, however they must be cardiovascularly stable and suitable for anesthesia. Fracture repair of diaphyseal fracture can be delayed up to 5 days if absolutely necessary.

Specific considerations

• The techniques available for treatment of fractures are:
  • Conservative management.
  • Internal fixation Fracture: internal fixation.
  • External fixation Fracture: external fixation.

Conservative management

• An option in patients which can be strictly cage rested; where the fracture site is not amenable to external fixation, eg proximal femoral fractures; and internal fixation is not a feasible alternative, eg financial restraint, poor general health of patient/co-existing or predisposing condition.
  High risk of 'false joint' formation, non-union, limb deformity.
• Analgesia essential Analgesia: overview.

• Always take post-operative radiographs (orthogonal view).
• Repeat radiograph every 6 weeks to assess healing progress in adults and every 2-4 weeks in young.

Monitoring

• Repeat radiograph every 6 weeks to assess healing progress.
• Assess return of function 2 weeks post-operatively and thereafter monthly.

General

• Early orthopedic repair in a stable patient reduces the incidence of post-operative complications.
• It is important that nerve lesions be identified before fracture treatment - prognosis will be affected:
  • Neuropraxia - good prognosis.
  • Plexus avulsion - guarded prognosis.
  • Nerve severence - poor prognosis.
  • A pertinent neurological assessment should be performed immediately after initial triage Triage assessment as best performed prior to giving opioid analgesia.

Conservative management

• Site-dependant.
• Almost always malunion, however may be functional.
• High risk of non-union, limb deviation, limb shortening/deformity, 'false joint' formation.
• Pelvic fractures - malunion  →  pelvic canal narrowing  →  dystocia and/or obstipation  →  megacolon (common complication).
• External coaptation best for fractures below the elbow and stifle due to the conformation of the limb. Most appropriate for fractures with inter-digitation, minimally displaced fractures, ideally when a paired bone (fibula, ulna) also intact. Often better option in yong due to reduced healing and therefore coaptation time. Regular monitoring essential to minimize soft-tissue injuries associated with coaptation. Cats can be more difficult to achieve reliable external coaptation than dogs.

External/internal fixation

• See External fracture fixation Fracture: external fixation.
• See Internal fracture fixation Fracture: internal fixation.

• Conservative management: gradual return of function over >6 weeks. Often normal function never achieved owing to deformity, non-union or malunion.
• See External fracture fixation Fracture: external fixation.
• See Internal fracture fixation Fracture: internal fixation.

• See fracture healing Fracture: healing.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Nolte D M, Fusco J V & Peterson M E (2005) Incidence of and predisposing factors for nonunion of fractures involving the appendicular skeleton in cats: 18 cases (1998-2002). JAVMA 226 (1), 77-82 PubMed.
• Scott H (2005) Repair of long bone fractures in cats. In Practice 27 (8), 390-397 VetMedResource.
• Harari J (2002) Treatments for feline long bone fractures. Vet Clin North Am Small Anim Pract 32 (4), 927-947 PubMed.

Other sources of information

• Tobias K & Johnston S  (2011) Veterinary Surgery: Small Animal. 1st edn. W B Saunder & Co. pp 565-571, 647-656.
• Montavon P M, Voss K & Langley-Hobbs S J (eds) (2009) Feline Orthopedic Surgery and Musculoskeletal Disease. Saunders ISBN: 978-0-7020-2986-8.