Ch 61f avulsion of long digital and gastrocneamus muscle, Stifle arthrodesis Flashcards
Avulsion and Luxation of the Tendon of Origin of the Long Digital Extensor Muscle
- originates at the extensor fossa of the lateral femoral condyle and inserts on digits II through V
- function: flex the tarsocrural joint and extend the digits
- origin is almost entirely intra-articular
Avulsion:
Etiology, Pathogenesis, Pathophysiology, and Epidemiology
- immature large- and giant-breed dogs, likely resulting from low-grade trauma
- bone fragment(s) or may be entirely tendinous
- Iatrogenic laceration can occur during surgery
Clinical signs
- stifle joint effusion
- thickening overlying the lateral aspect
- ability to simultaneously fully flex the stifle, fully extend the tarsocrural joint, and completely flex the digits without tension
- Radiograph
- confirmed arthroscopically or by arthrotomy
luxation:
Etiology, Pathogenesis, Pathophysiology, and Epidemiology
- can accompany patellar luxation
- complication of TPLO
- Spontaneous luxation uncommon
- occurs in a caudal direction
- may be associated with marked lameness.
- no lameness, but an audible click or snapping sound (during the stance phase of the gait
- displacement can be felt lateral aspect of joint
Treatment, Outcome, and Prognosis: Avulsion
tendon is not necessary for stifle joint stability
- If the injury is recent, reattachment with a screw and spiked washer (treatment of choice)
- in chronic, excision of the hypertrophic bone is indicated to mitigate the chance of delayed or fibrous union
- reattachment to the soft tissues of the proximal tibial will return function to the muscle with no consequences
- exercise restriction for 4 to 6 weeks
prognosis
- for return to normal function is good
Treatment, Outcome, and Prognosis: Luxation
- Repair = replacing the ruptured thin band of tissue that confines the tendon
- Bone tunnels through the cranial and caudal bony prominences surrounding the extensor groove are created
- Nonabsorbable sutures create a mattress suture between the bone tunnels, trapping the tendon within the groove.
prognosis
- for return to function is good.
Avulsion of the Origin of the Gastrocnemius Muscle
- gastrocnemius muscle is a powerful flexor of the stifle joint and extensor of the tarsocrural joint.
- two muscle bellies that originate on the lateral and medial supracondylar tuberosities of the femur
- contains a sesamoid bone (fabella) within its origin
- lateral fabella is larger and nearly spherical
- medial fabella is smaller and more angular
- gastrocnemius tendon, the major component of the common calcanean tendon.
function of gastrocnemius (2)
- flexor of the stifle joint
- extensor of the tarsocrural joint.
Etiology, Pathogenesis, Pathophysiology, and Epidemiology
- probably occurs as a result of low-grade trauma and typically includes avulsion of the associated fabella
- lameness with varying degrees of tarsocrural joint hyperflexion (plantigrade stance)
- Swelling of the caudal aspect of the stifle
rads
- displacement of one or both fabellae with associated regional soft tissue swelling
Treatment, Outcome, and Prognosis
- surgical reattachment at the anatomic origin.
- muscle can be reattached with a soft tissue suture repair if abundant
- suture placed around the fabella is anchored to a bone tunnel/anchor in the femur
- Alternatively, a screw and a spiked washer
- protected for 2 to 3 weeks with a soft-padded bandage, splint, or cast
- weeks 4 to 6, a gradual return to normal activities
prognosis
- is good
- complications include failure of repair and recurrence
Stifle Joint Arthrodesis
indicated
- comminuted intra-articular fractures, acute stifle joint luxation,
- chronic stifle joint luxation or subluxation,
- severe osteoarthritis
- severe patellar luxation that is refractory
- successful arthrodesis will preserve pain-free limb function
- limb is typically circumducted or carried at gaits faster than walking, and knuckling of the paw may occur
proper angle of stifle arthrodesis for dogs and cats
- 135 to 140 degrees for dogs
- 120 to 125 degrees for cats
surgery
principles of arthrodesis (removal of all articular cartilage,menisci, condylectomy, and rigid internal fixation
- bilateral approach
- osteotomy of the tibial tuberosity allows complete access + create a smooth surface for plate fixation on the cranial tibia
- Kirschner wires distal femur and proximal tibia, perpendicular to the long axis
- Two additional Kirschner wires can be placed to guide the osteotomies
- for 140 degree jonint: 2nd k-wires are placed 20-degree angles to the initial wires ([180 degrees − 140 degrees = 40 degrees]/2 = 20 degrees angulation of each Kirschner wire)
- oscillating bone saw, bone cut parallel to placement of the Kirschner wires at 20-degree angles
- preserve the popliteal blood vessels
- removed only enough to enure bone stock and limb length are preserved
- temporary stabilization is achieved with crossed Kirschner wire
- Kirschner wires that were used to guide the osteotomies should be parallel > ensure correct angle and to avoid limb rotation
- bone plate long enough to span at least 60% to 70% of both bones (to mitgate fracture due to stress concentration)
- Compression should be applied
- least one plate screw should be placed in lag fashion across the osteotomies.
- one or two independent screws should be placed in lag fashion across the osteotomies
- tibial tuberosity is attached adjacent to the bone plate
post op
Most patients do not need external support (plate functions as a tnesion band device, though results in significant bending force on the bone adjacent (immediately proximal and distal)
- if the bone surfaces are not congruent, or if inadequate compression, fatigue failure of the bone plate may occur.
- confinement enforced until recheck radiographs are obtained at 6 weeks
- fusion typically occurs 8 to 12 weeks
- Periosteal new bone ends of the bone plate = reduces the likelihood of fracture.
-
prognosis
complications (4)
- prognosis for pain-free limb function is good
complications
- delayed or failure of fusion
- infection
- fracture
- osteoarthritis of the hip or tarsus resulting from biomechanical alteration in gait
