Lecture 17: Surgery of the Carpus, Metacarpus, Phalanges, and Sesamoids

palmigrade stance

occurs when foot is positioned such that palmar surface of metacarpus contacts ground

valgus position

foot is an outward deviation

varus position

foot is an inward deviation

carpal fractures

• rare in companion animals

• often disabling because carpal joint serves a major weight-bearing function

what happens when carpal fractures are not treated?

joint incongruity and development of OA leads to severe lameness

what is the most frequently diagnosed fracture of carpal bones in companion animals?

radial carpal bone fractures

radial carpal bone fractures

• may involve chronic lameness without history of trauma

• 3 common fracture patterns occur → speculated these results from incomplete ossification of radial carpal bone

what is the most common breeds to have chronic radial carpal bone fractures?

boxers and sporting breeds

accessory carpal bone fractures

• occur in racing greyhounds and sled dogs

• mostly occurs in right leg

• considered avulsion injuries

medical or conservative management of carpal fractures

not indicated!

surgical treatment for radial carpal bone

• small chip fragments that cannot be stabilized → removed

• large fragments-anatomically reduced and rigidly stabilized with lag screws or a combination of lag screws and K-wires

• dogs with chronic fractures → best treated with carpal arthrodesis

the carpus is composed of

proximal and distal row of carpal bones

radial carpal bone anatomy

• articulates primarily with radius

• serves as major weight-bearing area

what is the most common injury of the carpus?

hyperextension injury

conservative management for carpal hyperextension

• rarely successful

• arthrodesis → best treatment

• pancarpal or partial carpal arthrodesis

pancarpal or partial carpal arthrodesis for carpal hyperextension

• remove cartilage

• autogenous cancellous bone graft

• rigid fixation

postop care for carpal hyperextension

• coaptation with splint for up to 6 weeks is indicated for most dogs

• screws for reconstruction of radial carpal bone are not removed unless cause problems

prognosis for carpal fractures

fair to good for return to function

prognosis for carpal arthrodesis

• fair for partial

• good for pancarpal arthrodesis

carpal laxity syndrome

• dogs 5-27 weeks; males 2:1

• treat by appropriate diet, controlled exercise, recovery 1-4 weeks

sesamoid bones

small, round or oblong bones found adjacent to metacarpophalangeal joints

metacarpal bone fractures

• common in dogs and cats

• result from a direct blow or force to paw or from hyperextension injuries

sesamoid fractures

• in racing greyhounds and rottweilers

• occur after excessive tension on digital flexor tendons

• sesamoid bones 2 and 7 of forelimb are most often affected

proximal sesamoid fragments are removed if

they are causing chronic lameness

what is this?

sesamoid fracture of 2 and 7

dogs with sesamoid fractures have a history of

acute lameness that subsided but recurred with exercise

luxations of metacarpophalangeal joints or interphalangeal joints

• typically occur in working dogs or racing greyhounds

• chronic instability leads to DJD and less than optimal function

acute luxations in working or racing dogs are best treated with

open reduction and suturing of joint capsule and collateral ligaments

chronic luxations of 2nd or 5th toe can be treated with

amputation

diagnosis of phalange masses

• radiographs → osteolysis and soft tissue swelling

• fine needle aspirate for cytology

• recommended treatment is digit amputation

digit amputation

• make elliptical skin incision

• preserve pad

• remove the sesamoid bones

digit arthrodesis

• expose joint

• open joint capsule

• remove articular cartilage

• contour small plate to dorsal surface of bones

• attach plate using lag screw

• temporarily hold bones in position with K-wires and tension band