Ch 61d Patella bone fracture and ligament dz

Question 1

Etiology, Pathogenesis, Pathophysiology, and Epidemiology

Answer 1

fracture
- trauma (direct blow to the cranial stifle)
- in cats, stress fractures can occur, presumably resulting from jumping
- complication of TPLO

Patellar ligament tears
- deep laceration or direct trauma
- quadriceps femoris muscle contraction simultaneously occurs with forced stifle joint flexion

• patella is located within the tendon of insertion of the quadriceps femoris muscle, it is subjected to strong tensile forces; fixation must be engineered to withstand these forces
• Failure to address these distractive forces will likely result in nonunion of the fracture and poor limb function

Question 2

Diagnosis

Answer 2

• lameness is severe, and physical examination reveals pain and swelling
• Patellar ligament rupture results in involuntary stifle joint flexion (joint cannot be extended)
• patella alta
• ## assess the stifle joint for injury of the collateral ligaments, menisci, or cruciate ligaments

Question 3

Treatment of a Patellar Fracture

Answer 3

• nondisplaced or minimally displaced apical, basilar, or body fractures; displaced transverse body fractures; and comminuted fractures
• Chronic may be difficult to reduce due to contracture of the quadriceps> prone to fixation failure or refracture because of tension

Non/minimally displaced apical or basilar fractures
- conservatively (rest) until union is achieved
- excised if the fragment(s) is small or nonunion

non/minimally displaced body
- Kirschner wire placed from base to apex in a predrilled hole and by tension-band wire fixation.
- circumferential cerclage wire around patella + circumferential wire within tendons

Displaced transverse body fractures
- Kirschner wire and single or double tension-band wire
- small dogs and cats 20 gauge
- large dogs 18 or 16 gauge

comminuted fracture
- anatomic reconstruction using Kirschner wire(s) and tension band attempted, but further fracture or fixation failure may occur.
- Small fragments that are too small are discarded
- single large fragment results in better function than patellectomy.

Question 4

Patella fracture - external protection

Answer 4

1. transarticular external skeletal fixation > converted to hinged after 4 to 6 weeks.
2. mattress sutures placed through the patella or proximal&raquo_space; tibial tuberosity, using wire or nylon
3. Plating > small flexible plate attached to the tibial tuberosity and quads tendon by placing sutures through the plate holes

Question 5

Treatment of Patellar Ligament Rupture

Answer 5

• to restore extensor function to the stifle joint
• mattress suture: 16 to 20 g wire or large 80 to 100lb nylon within quad tendon or through patella, and through a drill hole in the tibial tuberosity
• tedon repair: locking loop pattern with 2-0 - 2 nonabsorbable suture + simple sutures for tendon apposition

ligament defects
- augmented with autogenous fascia lata grafts sutured into the defect or spanning from the patella to the tibial tuberosity

protected
- transarticular splint
- TA ESF
- patellar ligament plating

Question 6

Outcome, Prognosis, and Complications (3)

Answer 6

• crate confinement and short leash walks for 6 to 8 weeks
• implant migration or breakage and may cause soft tissue irritation and lameness
• mattress sutures commonly break 4 to 6 weeks postoperatively

complications
- fixation failure
- nonunion
- fracture at fixation devices

Prognosis
- poor to good, depending on the complexity
- patellar ligament rupture is fair to good

Question 7

Patellar fracture and dental anomaly syndrome (PADS)

cats

Answer 7

• congenital bone disease of cats
• often 1-3yrs
• characterized by atraumatic bone fractures (most commonly the patella)
• Patella # usually transverse with sclerosis
• often bilateral
• persistence of deciduous teeth
• impaction of permanent teeth.
• Jaw swelling due to osteomyelitis is often the reason presented
• DSH
• osteomyeltitis in first 4 years of life – mandible 4x more common than maxilla
  
  • prompt, aggressive sx treatment of osteomyelitis and extraction of teeth recommended
  • change to bone consistent with osteopetrosis associated with osteoclast deficiency or dysfunction

other fractures
- Humeral intercondylar fissure/fractures (8.7% of PADs)
- pelvic (27% of PADs)
- tibia
- precede or procede patella fracture
- charactersistic of stress fractures

Patella treatment
- pin and tension ban repair of transverse fractures in cats suspected of having PAdS is notoriously unsuccessful (up to 86% failure)
- Circumferential sutures or wiring have been reported as having a better success rate
- aim is not to achieve bony fracture union, but to re-establish the quadriceps mechanism.
- patellar fractures are unlikely to heal (non-union

Question 8

cat patella healing

Answer 8

• relative lack of radiographic union may be because sesamoid bones produce a fibrous rather than an osseous union.
• may never show radiographic evidence of healing or require a considerably long period of time to do so
• Hence, clinical outcome may be more important than radiographic union in patellar fracture cases
• Tx therefore focused on reconstructing the quadriceps mechanism and holding the bone fragments close together

STUDY: in 34 cats, only 1/52 patellar fractures showed radiographic evidence of fracture healing and this was seen on radiographs taken 3 years following surgery

Question 9

Biomechanical evaluation of
three fixation methods in a feline
transverse patella fracture model
Min-Yeong Lee 2023

Answer 9

27 feline cadaveric pelvic limbs
Group 1; single Kirschner wire (0.9 mm) and figure-of-eight wiring (20 G)
Group 2 ; circumferential and figure-of-eight wiring with orthopaedic wire (20 G).
Group 3; as group 2, but with #2 FiberWire.

This study shows that the combination of circumferential and figure-of-eight techniques with FiberWire is more resistant to displacement than metal wire in this ex vivo feline patella fracture model

Question 10

Combined internal fixation and transarticular
external skeletal fixation to treat traumatic
patellar fractures in five dogs
M Sprocatti 2022

NZVJ

Answer 10

Type IA lateral triangulated or modified Type II) was used in combination with internal fixation with pins and/or orthopaedic wire, supported by nylon leader line (patella-to-tibia mattress suture)

TA-ESF for a median of 6 weeks was not associated with major complications and long-term outcomes were satisfactory for all cases

combination of strong distractive forces, limited vascular supply, and low osteogenic potential leads to poor healing capacity for patellar fractures, and fixation failure is commonly reported

only one case (Case 5)
reached complete radiographic union. Lack of radiographic
union did not appear to have a negative
influence on the final outcomes

TA-ESF and casts, revealing structural cartilage degeneration after only 4 weeks of immobilisation

passive ROM did not, however, provide a positive
effect on joint cartilage in a previous experimental
study

Prospective
studies are needed to compare different
fixation methods and evaluate the impact of fixation
on radiographic healing and clinical outcome.