i.e. the material returns to its original shaped (termed
elastic deformation) or, if the force is more that the
yield point the material, the material will be perma-
nently deformed (termed plastic deformation). Plastic
deformation or catastrophic failure of an implant is
considered mechanical failure as they would result in
malunion, nonunion or complete failure of the osteo-
synthesis. The mechanical failure is not only related to
catastrophic failure but more often than not the failure
is related to cyclic fatigue of the implants. Cyclic fa-
tigue relates to the formation of micro-cracks in the
implant due to cyclic loading. Propagation of these
cracks will lead to mechanical failure of the construct
if bone healing has not progressed adequately.
We can prevent implant associated complications
through adequate clinical examination, proper pre-
operative planning, good surgical skills and critical re-
view of the post-operative radiographs. Each one of
the above mentioned factors will be discussed as it
pertains to implant failure in the post-operative period.
Adequate Patient Examination and Preoperative
Preparation
All patients should be liberally clipped and an adequate
surgical scrub performed. Prophylactic antibiotic ad-
ministration is advised if surgical implants are placed
and is administered intravenously 30 – 60 minutes
before the surgical incision. The antibiotic is repeated
every 90 minutes for the duration of the surgery. The
author’s antibiotic of choice is cefazolin at a dose of
20 mg/kg IV. These above mentioned steps are critical
to prevent superficial and deep surgical site infection
which might predispose to early implant failure due to
resorption of bone at the bone implant interface. The
prevention of infection becomes increasingly difficult
with open fractures.
Open fractures are fractures where the bone is ex-
posed to environmental contamination due to a dis-
ruption of the soft tissue covering the bone. In human
surgery a significant decrease in infection rate is noted
if a broad spectrum intravenous antibiotic is adminis-
tered within 3 hours of the initial traumatic incident.
Once the patients are medically stabilised, surgical de-
bridement and wound lavage should be initiated. Early
surgical stabilisation with soft tissue reconstruction of
the soft tissue defect is widely accepted as the treat-
ment of choice.
External coaptation (bandaging) of open fractures is
not advocated. Although open factures have been
successfully treated with bone plates the ideal is to se-
lect a fixation method that allows a surgical approach
away from the initial wound. In addition, it is advised to
remove the implants after bone healing has occurred.
Bearing these factors in mind, external skeletal fixators
are ideally suited for open fractures
Preoperative Planning
Two orthogonal views of the long bone associated
with the fracture is a prerequisite for adequate sur-
gical planning. Radiographs of the contralateral limb
might be beneficial to select the appropriately sized
implant. By religiously planning all osteosynthesis
procedures preoperatively, efficiency is increased
and operative stress is decreased. Patients will bene-
fit from the mental rehearsal of the operative plan by
the improved outcome and safety of the procedure.
Operative planning can be divided into tactics and
logistics. Where the tactics refer to the surgical steps
employed to achieve the goals and logistics refers
to the resources employed during the operation (for
example the positioning of the patient, the proposed
implants, need for a tourniquet or intra-operative
fluoroscopy. Good logistical planning will decrease
surgical errors and improve operative ergonomics,
thereby decreasing operative and anaesthetic time,
which can have a direct influence on the develop-
ment of surgical site infections.
In the absence of digital software which can be
used for surgical planning, a plan can be made with
a goniometer, transparencies to lay over the radio-
graph, a felt tipped pen and a set of relevant tem-
plates of surgical implant (scaled correctly). The aim
of the surgical planning should be to reconstruct the
weight bearing axis in such a way that the normal
alignment and function of the bone is maintained.
Surgical planning also involves the anticipation of
“hurdles” associated with the fracture repair. If these
are encountered intra-operatively and no allowance
has been made in advance, the outcome is generally
a prolonged anaesthetic time, increased soft tissue
trauma or technical errors.
The signalment of the patient is important to consid-
er before selecting the correct osteosynthesis tech-
nique. Factors like weight, age, concurrent soft tissue
injuries, presence of other illnesses and breed of pa-
tient (activity level and intended use) need to be con-
sidered. Patient age is a large determinant of the bi-
ological environment of the fracture; young animals
have an active periosteum whereas geriatric animals
have prolonged healing times. This biological envi-
ronment is also dependant on the energy as sociated
with the inciting cause, high velocity/ high energy
forces generally leads to comminuted fractures with
impaired vascularity.
Additionally, each fracture needs to be critically as-
sessed in order to determine the mechanical forces
acting on the fracture. These forces are bending,
rotation, compression (shear) and distraction forces.
(Figure 1)
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