Fracture: overview in Cats (Felis) | Vetlexicon (2024)

• 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 fixationor internal fixationFracture: internal fixation - depends on site, type, severity of fracture.
• Prognosis: dependent upon site, type, severity, method of repair, age, concurrent injuries or pathology.

Presenting signs

General

• History of trauma.
• Pain.
• Swelling.

Specific

• Loss of function.

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

• Signs of predisposing condition - see Predisposers.

Acute presentation

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

Age predisposition

Epiphyseal

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

Cost considerations

• Internal fixation is the most costly.

• External fixation at a moderate cost.

• Conservative management is relatively inexpensive.

Special risks

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

Etiology

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

Predisposing factors

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 traumaand older male neutered cats.

Pathophysiology

• Fractures are caused when the force applied to the bone exceeds the ultimate strength of the bone.
• See also fracture healingFracture: 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:
  EitherOpen (compound) - skin wound communicating with fracture site - Grades I, II, III.
  OrClosed (simple) - overlying skin is intact.
• Fractures may be:
  EitherComplete - total disruption of bone continuity.
  OrIncomplete - 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.

Publications

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).JAVMA226(1), 77-82 PubMed.
• Scott H (2005)Repair of long bone fractures in cats.In Practice27(8), 390-397 VetMedResource.
• Harari J (2002)Treatments for feline long bone fractures.Vet Clin North Am Small Anim Pract32(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.