Subsolar abscess/solar penetration
Septic joint/bursa/sheath
Severe tendon or ligament strain / rupture Subluxation / luxation

Radial paralysis
Upward fixation of the patella Cellulitis
Rhabdomyolysis (“tying up”) 

•    Horse may be recumbent because exhausted / winded

•  Lameness may improve rapidly if fracture non-displaced

•  Look for wounds

•  In large animals, crepitus is only evident if fracture displaced

•  Can take several days for fracture to be evident radiographically (consider scintigraphy) 

  - take enough x ray views 

Incomplete/Complete fracture Displaced/Non-displaced

Avulsion fracture
Chip (one joint surface involved)

Slab (two joints involved)
Stress fractures 

salter harris fractures 

• Soft tissue injury and fracture comminution related to loading rate

• Trauma energy is dependent on second power of loading rate

• This energy is released when bone fractures

  – High velocity (high loading rate/energy) – Low velocity (low loading rate/energy)

• Viscoelastic properties! Bones become stiffer when loaded at higher rate

  – Can you walk over fresh cement? 

Mare treading on foal’s leg

Low speed so low energy

Clean break 

Racehorse galloping
High speed so high energy
Energy release during fracture results in comminution (multiple fragments) and extensive soft tissue damage 

• Wolffs Law

• Remodelling vs Modelling

• Microcrack formation with fatigue

  • –  During process of remodelling – bone is

    weakened –> microfractures occur

  • –  During fatigue –> muscles relax –> tendons

    which provide support to joints relax –> abnormal range of movement –> increased strains –> microcracks coalesce -> catastrophic fractures 

Direct Bone Healing

• –  Stable in-contact bone (gap < 1mm)

• –  Osteoclasts remove damaged bone

• –  Osteobasts create new Haversian systems directly across fracture line

  
  

  0. Indirect Bone Healing

  • –  Gap or movement between bone ends

  • –  Periosteal callus forms to stabilise

  • –  Gap haematoma -> fibrous tissue -> mineralisation

  • –  Intense remodelling 

   

Delayed union
• Healing is progressive but at lower rate

– 4 months in adults, 3 months in foals

• Non-union

• Healing/repair process has stopped but bony continuity has not been restored

• –  vascular non-union: (capable of biologic repair but displacement, instability)

• –  avascular non-union: (loss of fragments, aseptic necrosis)

• –  infected non-union: 

  
  

  • Mal-union

• Healing of bone in an abnormal position (functional or non-functional) 

• Rigid stabilisation

• Lack of infection (preferred)

• Adequate blood supply

– Prevent secondary compromise by adequate restraint 

Splint bone (MC/MT II/IV);
Distal phalanx
(Skull fractures) 

Common fractures in racehorse practice:

Cervical fractures; distal third metacarpal; carpal; proximal phalanx;pelvis  

What factors determine whether a fracture can be successfully treated ? 

How much weight does the bone normally bear? (e.g. metacarpal II; third carpal bone; femur)

Is a joint involved?
Degree of comminution & displacement Contamination; chronicity
(Owner/Trainer expectations) 

•   Common racehorse injury - sagittal ridge of distal MC “screws” into proximal P1 at speed

•  Sudden onset severe lameness

•  Lameness may improve within

  days if non-displaced – don’t be

  caught out !

•  Swelling, pain on passive

  manipulation and fetlock effusion

•  Crepitus only evident if very comminuted 

Treatment options range from fixation using one or several lag screws to arthroscopic fragment removal or half-limb cast.

Prognosis depends on fracture type and quality of repair, but many horses will return to racing, and repair is usually undertaken with that aim, not just salvage

Prerequisite for successful surgical repair is at least one strut of bone which extends from fetlock to pastern 

Direct hoof trauma

•  concussion (kicking wall)

•  landing on uneven

  surface/object

•  nail penetration through sole

•  fast work on hard tracks

  (Standardbreds / trotters)

  Less common:
  hyperextension of coffin joint Osteitis
  laminitis 

Acute severe lameness - may increase in first 24 hrs.

Increased digital pulsation May have:

Heat in foot
Solar pain on hoof testers
Pain on flexion
May have coffin joint effusion, but only if

fracture is articular

Signs subside slowly – horses usually walk sound after 4-8 weeks; can remain lame at diagnosed 

Radiography

Standard views of foot, but may see some fractures only on oblique views e.g. flexed D450 L-PaM oblique

+/- Nerve blocks MRI ? Scintigraphy ? 

(non-articular wing fracture)

• Treat by hoof immobilisation

Average healing time = 11 months Good to excellent prognosis 

(articular wing fracture)

Conservative treatment

•  average healing time 12

  months

•  50% prognosis for return to soundness

•  worse prognosis for older horses - neurectomy ?

  Surgical Tx possible 

Surgical Treatment

- requires good aseptic technique

- requires expertise and experience (& CT guidance?)

- 104 / 117 Type 2, 3 and 4 fractures returned to work (Pettersson 1996)

Conservative Treatment

- salvage procedure or for failed surgical repairs (50 % prognosis) 

Lag screw fixation if large

Arthroscopy/arthrotomy for removal if smaller

prognosis guarded to fair

Main long-term complication = OA of DIP joint 

Type V fracture (comminuted fracture)

•  Prognosis poor

•  Usually some bad underlying

  pathology

  Type VI fracture (solar margin fracture)

  •  Often secondary to laminitis

  •  Other common cause is penetrating foreign body

  •  Conservative treatment unless infected

  •  Treat primary cause 

Depends on fracture type & intended use

Conservative - hoof immobilisation

hoof cast

bar shoe

rim shoe +/- acrylic filled 

Proximal, mid or distal splint bone fractures

- Fracturesofthedistalthird

• -  occur spontaneously; avulsion fractures?

• -  external trauma, such as kicking (especially to the

  lateral splint bone) or interference (especially to the medial splint bone in forelimbs).

  - Proximal fractures

- caused by kicks to the lateral aspect of a hindlimb. concurrent injury of adjacent structures ! MT3, Suspensory Ligament 

Distal Fx/non-complicated prox. Fx.

conservative management. Approx. 76 percent
of distal splint bone fractures without concurrent desmitis return to previous exercise (50 percent in horses with desmitis)

Proximal intra-articular Fx and joint instability

internal fixation (plate fixation) Fx of mid portion

segmental ostectomy, excellent outcome

Open fractures

treated initially as open wounds, systemic and regional AB,
lavage; chance for successful healing is 3.5 times worse than with closed Fx.

Removal

of the distal 2/3 of a splint bone is safe
< proximal 1/3 of the splint bone remaining internal fixation.

Entire Mt4 can be removed however the surgical outcome
with this procedure is only fair (60 percent) for return to previous exercise.

Comminuted fractures of Mt4: usually no difference in surgical versus conservative treatment outcome (survival and return to exercise) other than conservative treatments tend to be cheaper.

Affected animals have characteristic “dropped elbow” stance due to disruption of stay apparatus

(DDx from humerus fracture & radial paralysis)

However, successful surgical treatment improves prognosis and allows earlier return to exercise therefore is optimal in most cases 

Repair of olecranon fractures

Surgical repair of Types III-V

A plate is contoured to the caudal aspect of the ulna after fracture reduction.

Aim for at least three screws proximal to the fracture and 4 distal

Plate removal is not necessary unless complications occur or the animal is < 18 months old

Assisted recovery is vital ! 

Rest alone
Casts
Lag screws
DCP/LCP
Intramedullary nails
Interlocking nails
Arthroscopic removal Standing debridement External Fixators

Transfixation pin casts 

• You cannot obtain pus from the foot (after 1-2 days of poulticing max.)

• Horse is lame at the walk (perhaps it has improved a bit)

• There is obvious limb deviation

• There is pain or oedema over a bone, with or without a wound

• There is a history of a kick or other severe trauma

• It is a racehorse