Chapter 11 Veterinary Orthotics and Prosthetics 283The case for prosthetic limbs
Given the potential consequences of limb loss
and the recent availability of prosthetic limbs
for dogs, it seems prudent to offer this option for
those patients and clients amenable to this
approach. The biomechanics of the quadruped
make design of prosthetic limbs an interesting
challenge. The end goal is to provide a limb that
allows as close to normal quadrupedal ambula
tion as possible. Angulation differences between
the thoracic and pelvic limb, the mechanical role
of different limbs in ambulation, breed differ
ences, as well as level of subtotal amputation
must all be considered.
The key for any prosthesis is suspension and
retention of the device on the residual limb.
Dogs create tremendous forces on their limbs
during trotting, running, playing, and other
daily activities. Device retention can be a chal
lenge in the canine patient and proper design
is critical to success. Currently there are two
types of prosthetic limbs available: exopros
theses (socket‐based) and endo‐exoprostheses
(e.g., Percutaneous Fixation To the Skeleton,
PerFiTS™; Figure 11.16).
Exoprostheses provide a socket within
which the residual limb rests; an extension
provides contact to the ground via some form
of foot component (Figures 11.10, 11.11, and
11.14). Importantly, in a properly designed
exoprothesis, the total body force exerted
through the limb and prosthesis is not borne
on the distal end of the residual limb. This
improves comfort and provides some protec
tion for the residuum through the distribution
of forces through a larger surface area. The
advantage of exoprosthetic limbs over
endoprostheses is their relatively low cost,
simplicity of application, and adaptability to
many levels of limb loss from foot to mid
antebrachium or crus. Another advantage is
the lack of a surgical implant, which could
loosen or fail.
Endoprostheses employ a skeletally inte
grated implant to which a prosthesis is attached
(Figure 11.16). There are two important advan
tages to this approach. First, there is no mechan
ical delay in gaiting; the forces applied to the
prosthesis by virtue of gaiting are directly trans
mitted to the skeleton without a delay due to
transmission first through fur, skin and muscle.
An additional advantage is the potential for
fewer soft tissue irritations because there is no
socket. Although confounding, skin trauma is
not an intractable sequelae of socket prosthesis
in humans and animals. This is important
because not all patients are amenable to interos
seous techniques due to cost, injury level, or
currently limited availability. In time these dis
advantages may be overcome.
Rehabilitation is critical for the prosthesis patient
during the adaptation period, whether using an
exoprosthesis or an endo‐exoprosthesis. For either
patient there is no direct, anatomic contact to the
ground, therefore control of the limb (GRF and
TBF) is reversed. Control of the limb via the pros
thesis comes from the top down (proximal intact
limb) rather than ground up (prosthetic foot in the
absence of a normal foot) and results in delayed
feedback. Through gait patterning and proprio
ceptive retraining, along with strengthening,
the prosthesis patient relearns proprioception,Figure 11.16 This PerFITSTM limb is an example of an
endoprosthesis that employs a skeletally integrated
implant to which a prosthesis is attached. Source: Image
courtesy of Professor Noel Fitzpatrick.