Amputations I – 3

Amputations 3
Krukenberg’s Amputation This kineplastic operation transforms the
transradial residual limb into radial and ulnar pincers capable of strong
prehension and excellent manipulative ability due to the retention of
sensation. Due to psychologic considerations, it is generally restricted to
blind bilateral amputees who cannot use visual cues to operate their
prostheses (Fig. 2).

Elbow Disarticulation/Transhumeral Amputation Functionally, both
levels require two acts to develop prehension, making these amputations
significantly less functional and making the prosthesis heavier than the
prosthesis for amputation at the transradial level. The length and shape of
elbow disarticulation provides improved suspension and lever arm capacity
compared to the transhumeral amputation. The drawback is cosmetic, because
the elbow will be too far distal and the forearm shank too short for the
limbs to be of equal length. Prosthetically, the best function with the
least weight at the lowest cost is provided by hybrid prosthetic systems
combining myoelectric, traditional body-powered, and body-driven switch
componentry for elbow disarticulation or transhumeral amputation.

Patients with a complete unreconstructable brachial plexus injury can
achieve function by amputation of the insensate dead-weight arm, leaving a
sensate residual limb which can be fitted with a prosthesis. If no
voluntary shoulder motion remains, shoulder fusion allows scapulothoracic
motion to drive the prosthesis.

Shoulder Disarticulation/Forequarter Amputation These levels of
amputation provide minimal function, because the patient must sequentially
control two joints and a terminal device. Limited function can be achieved
with a manual universal shoulder joint positioned by the opposite hand,
combined with a lightweight hybrid prosthetic components.

Lower Limb

Two major recent advances in lower limb prosthetics are socket design
and fabrication, and dynamic-response feet. New plastics allow sockets to
be lighter and more flexible, and therefore, more comfortable.
Computer-assisted design and fabrication allow more efficient fabrication
with the newer materials. The standard quadrilateral prosthetic socket for
transfemoral amputees is gradually being replaced by the newer ischial
containment socket designs, which more efficiently transfer load by total
contact. Silicone sleeves, used primarily in transtibial levels, improve
comfort and suspension. Dynamic response feet now provide spring and
push-off to the amputee’s gait, probably lessening the energy demands for
walking or running.

Toes The great toe, primarily, and the lesser toes act as
stabilizers during stance phase. Ischemic patients generally ambulate with
an apropulsive gait pattern, so they suffer little disability from toe
amputation. Traumatic amputees will lose some late stance-phase stability
with toe amputation. When amputation of the great toe is necessary, an
attempt should be made to salvage the proximal aspect of the proximal
phalanx with the insertion of the flexor hallucis brevis in order to
maintain some stabilizing function. Isolated second toe amputation should
be amputated just distal to the proximal phalanx metaphyseal flare to act
as a buttress that prevents late hallux valgus.

Ray Resection Single outer (first or fifth) ray resection functions
well in standard shoes. Resection of more than one ray leaves a narrow
forefoot that is difficult to fit in shoes. Central ray resections are
complicated by prolonged wound healing, and rarely outperform midfoot
amputation.

Midfoot Amputation There is little functional difference between
transmetatarsal and tarsal-metatarsal (Lisfranc) amputation. The long
plantar flap used in these amputations acts as a myocutaneous flap and is
preferred to fish-mouth dorsal-plantar flaps. Transmetatarsal amputation
should be performed in the distal shaft to retain lever arm length, or
through the proximal metaphyses to prevent late plantar pressure ulcers
under the residual bone ends. A percutaneous Achilles tendon lengthening
should be performed with the Lisfranc amputation to balance the foot to
prevent the late development of equinus or equinovarus. Late dynamic varus
occurring during stance phase of gait can be corrected with lateral
transfer of the tibialis anterior tendon. Midfoot amputees rarely require
the stability of high-topped shoes, generally being sufficiently stable
with standard tie shoes.