Amputation of Finger by Horse Bite With Complete Avulsion ... - Healio

■ Case Report
Amputation of Finger by Horse Bite With
Complete Avulsion of Both Flexor Tendons
LIOR KOREN, MD; SHALOM STAHL, MD; ALEXEY ROVITSKY, MD; ELI PELED, MD
abstract
Full article available online at ORTHOSuperSite.com. Search: 20110627-26
Amputation of fingers with tendon avulsion occurs through a traction injury, and most
occur through a ring avulsion mechanism. Usually the flexor digitorum profundus is
torn out with the amputated finger. Replantation usually is recommended only when
the amputation is distal to the flexor digitorum superficialis insertion. Animal bites are
relatively common, with a decreasing order of frequency of dogs, cats, and humans.
Horse bites are relatively infrequent but are associated with crush injuries and tissue
loss when they occur.
1
This article describes a 23-year-old man with amputation of his middle finger at the
level of the proximal phalanx after being bitten by a horse. The amputated stump
was avulsed with the middle finger flexor digitorum profundus and flexor digitorum
superficialis torn from the muscle-tendon junction from approximately the middle of
the forearm. The patient had no other injuries, and he was able to move his other 4
fingers with only mild pain. As the amputated digit was not suitable for replantation,
the wound was irrigated and debrided. The edges of the phalanx were trimmed, and
the edges of the wound were sutured. Tetanus toxoid and rabies vaccine were administered,
along with intravenous amoxicillin and clavulanic acid. The patient was
discharged from the hospital 2 days later, with no sign of infection of the wound or
compartment syndrome of the forearm. This case demonstrates the weakest point in
the myotendinous junction and emphasizes the importance of a careful physical examination
in patients with a traumatic amputation.
2
Figure 1: Photograph showing the stump of the
third fi nger. Figure 2: Photograph showing the amputated
middle fi nger with the tendon attached up
to the myotendinous junction. The avulsed fl exor
digitorum profundus and fl exor digitorum superfi
cialis are attached to the amputated finger, and
a few muscle fi bers are attached to the tendons in
the proximal part.
Drs Koren, Rovitsky, and Peled are from the Department of Orthopedic Surgery B, and Dr Stahl is
from the Hand Surgery Unit, Rambam Health Care Campus and the Bruce Rappaport Faculty of Medicine,
Technion-Israel Institute of Technology, Haifa, Israel.
Drs Koren, Stahl, Rovitsky, and Peled have no relevant fi nancial relationships to disclose.
Correspondence should be addressed to: Eli Peled, MD, Department of Orthopedic Surgery B, Rambam
Health Care Campus, POB 9602, Haifa 31096, Israel (e_peled@rambam.health.gov.il).
doi: 10.3928/01477447-20110627-26
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■ Case Report
Amputation of fingers with tendon
avulsion from their musculotendinous
junction are caused by a traction
injury, most of which occur through a
ring avulsion mechanism. Ring avulsion
has been classified by Urbaniak et al 1 and
revised by Kay et al. 2 Several case reports
describe this specific injury. 2-6 When a
tendon is torn out with the amputated segment,
it is usually with the flexor digitorum
profundus. Replantation is recommended
only when the amputation is distal to the
flexor digitorum superficialis insertion.
This article presents a case of a 23-
year-old man with amputation of his
middle finger at the level of the proximal
phalanx after being bitten by a horse.
CASE REPORT
A 23-year-old right-handed man presented
after being bitten by a horse, with amputation
of his middle finger at the level of the proximal
phalanx (Figure 1). The amputated stump was
avulsed with the middle finger flexor digitorum
profundus and the flexor digitorum superficialis
from the muscle-tendon junction to the
middle of the forearm (Figure 2). The patient
reported pain in the proximal forearm. He had
no other injuries, and he was able to move his
other 4 fingers with only mild pain. The digit
was not suitable for replantation.
The wound was irrigated by saline and debrided.
The edges of the phalanx were trimmed,
and the edges of the wound were proximated by
single sutures nylon 4/0. Tetanus toxoid and rabies
vaccine were administered, and the patient
was given intravenous amoxicillin and clavulanic
acid. The patient was discharged from the hospital
2 days later with no sign of infection of the wound
or compartment syndrome of the forearm.
DISCUSSION
In their classification system for ring
avulsion injuries, Kay et al 2 described 4
categories:
● I—circulation adequate,
● II—circulation inadequate,
● III—circulation inadequate with fracture
or a joint injury, and
● IV—complete amputation.
1 2
Figure 1: Photograph showing the stump of the third fi nger. Figure 2: Photograph showing the amputated
middle fi nger with the tendon attached up to the myotendinous junction. The avulsed fl exor digitorum
profundus and fl exor digitorum superficialis are attached to the amputated fi nger, and a few muscle fibers
are attached to the tendons in the proximal part.
In their review of 55 cases of ring
avulsion injuries, Kay et al 2 found 3 had
adequate circulation and 8 had primary
amputation. Salvage was attempted in 44
cases; of these, 9 were amputated secondarily,
19 were successfully revascularized,
and 16 were successfully replanted.
In 1974, Ponnampalam 5 described a
case of a man working close to a conveyor
belt who caught his right thumb on a side
rail. The thumb was amputated at the base
of the distal phalanx along with 25 cm
of an avulsed flexor pollicis longus. The
wound of the stump was covered with skin
from the avulsed segment.
In their study describing their revised
classification, Kay et al 2 reported a case
of a 45-year-old man whose finger was
caught by a ring when he fell. The finger
was completely amputated at the level of
the distal middle phalanx. Although the
flexor digitorum profundus was avulsed
from the musculotendinous junction, the
flexor digitorum superficialis was intact.
The finger was replanted with shortening
and fusion of the distal interphalangeal
joint. At his final follow-up examination,
the patient was satisfied with the outcome.
In another case report, Huemer and
Dunst 6 described a 17-year-old adolescent
who suffered a ring avulsion injury
with amputation of the finger at the distal
interphalangeal joint with avulsion of the
flexor digitorum profundus from the myotendinous
junction. The torn-out tendon
was resected, and the amputated part of
the finger was replanted microsurgically.
The final result was 50° of motion at the
proximal interphalangeal joint and 30° of
motion at the distal interphalangeal joint.
A search of the English literature did
not reveal an injury that resulted in complete
avulsion of both the flexor digitorum
profundus and the flexor digitorum superficialis
at the musculotendinous junction.
A case of incomplete avulsion of both tendons
was reported by Docker and Titley 7
who described a 37-year-old woman who
fell and whose ring finger was caught in a
rack; the finger was amputated at the level
of the midshaft of the middle phalanx. The
distal finger was still attached to the hand
via 10 to 15 cm of the flexor digitorum superficialis
and flexor digitorum profundus
tendons that were not completely avulsed.
Interestingly, the patient developed compartment
syndrome of the forearm, which
was treated with a fasciotomy.
Animal bites are relatively common,
with a decreased order of frequency of
dogs, cats, and humans. Horse bites are
relatively infrequent, but when they occur,
they are associated with crush injuries and
tissue loss. 8,9 Failure has been reported to
occur with muscle strain injuries within
the muscle belly, at the myotendinous
junction, or within muscle near the myotendinous
junction. 10
Our case demonstrates the devastating
power of a horse bite and its traction force
in addition to its cutting force. This type
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ORTHOPEDICS | ORTHOSuperSite.com

AMPUTATION OF FINGER BY HORSE BITE | KOREN ET AL
of bite demonstrates the weakest point in
the myotendinous junction and emphasizes
the importance of a careful physical
examination of patients with a traumatic
amputation. If the patient arrives with just
the stump, the level of the tendon injury
might not be recognized at first.
REFERENCES
1. Urbaniak JR, Evans JP, Bright DS. Microvascular
management of ring avulsion injuries. J
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3. Boyes JH, Wilson JN, Smith JW. Flexor-tendon
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