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Pre-operativeevaluation

Andrea Meyer-LindenbergClinic of Small Animal Surgery and Reproduction

Ludwig-Maximilians-University Munich

Importance of pre-operative planning• Evaluate patient before selecting

– type of osteotomy– implant– surgical approach

• Analyze and predict the difficulties• Perform predictable and precise

corrective osteotomy- most important: time

- think, draw, write• good quality radiographs

- orthogonal radiographic views- including proximal and distal joint- good quality radiographs

• Paper, pencil, templates(software – digital templating)

Evaluation of patient• lameness hindlimb• swelling of the stifle• positive drawer sign / henderson-test• radiographic assessment

• confirm CrCL rupture– joint effusion– osteoarthrosis

• diagnose other pathologies• assess limb alignment• measurement of tibial plateau angle (TPA)

• diagnosis of meniscal pathology• MRI / arthroscopy / miniarthrotomy

Standard radiographs• good positioning• medio-lateral view

- Positioning• 90° bending of knee and tarsus• Trochanter majus, fibulahead and

Malleolus lateralis are adjacent to X-ray table

• Central ray centered on knee joint(Eminentiae)

• medio-lateral view- superimposion of femur

condyles

- fibula visible

- fibula in the upper third withdistinct distance to the tibia

Standard radiographs Fault in positioning – m/l view

slight - Internal rotation - moderate correct

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• caudo-cranial view- Positioning

• sternal recumbency• Hindlimb extended caudally• include: stifle, tibia, tarsus• central beam centered on stifle joint

Standard radiographs

• Caudo-cranial view

- Patella central in trochlea groove- Fabellae bysected by femoral

cortices- medial border of the

calcaneus aligned withdistal intermediate ridgeof the tibia

Standard radiographs

• Caudo-cranial view- medial border of calcaneus- distal intermediate ridge of the tibia

(deepest point of sulcus tali)

Standard radiographs

• inwards / outwards rotation • patella not centered• Calcaneus false position• alter the position• repeat X-ray• compensate positoning

mistakes

Fault in positioning – cd/cd view

Torsional deformity

• diagnosis on caudo-cranialradiographs- Torsion of tibia- deformities of the distal femurs (Varus)- deformities of the proximal tibia (Valgus)

→ Correction within the scopeof TPLO is possible

Tibiatorsion

• internal torsion- e.g. Labrador, Rottweiler- inward rotation of the paw- Calcaneus displaced

laterally

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• external torsion- large breeds- outward rotation of the paw- calcaneus displaced

medially

R

Tibiatorsion

• Frontal plane• no deformity

Assessment of limb alignment

mMPTA: 94°medial proximal mechanicaltibia angle

mMDTA: 96°medial distal mechanicaltibia angle

Dismukes, Vet. Surg, 2008

Valgus-Deformity prox. Tibia• proximo-distal

displacement of femoral condyles

• mPMTA: 103°• mMDTA: 87°

R

R

Dismukes, Vet. Surg, 2008

• caudo-cranialdisplacement of thefemoral condyles

• double condyle sign• correct positioning

Varus-Deformity distal femur

Varus (Femur) and Valgus (Tibia) deformity• Cranio-caudal and

proximo-distaldisplacement of femur condyles

R

→ Cranio-caudal and proximo-distaldisplacement of femur condyles

Measurement of TPA(Tibial plateau angle)

• Anatomy- proximal tibia: two joint parts

- medial condyle- lateral condyle

=> angle of slope towards caudodistal

→ between both condyles- Eminentia intercondylaris

- Tub. intercondylare laterale- Area interkond. centralis (*)

- Tub. Intercondylare mediale

*

cranial

mediolateral

caudal

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Measurement of TPA(Tibial plateau angle)

• Anatomy (important points)- cranial margin

- Tub. Tibiae

- Margin of joint surface- cranial / caudal edge of

med. tibial condyle→ Tibia plateau line

- Midpoint between medial and lateral intercondylartubercles

mediolateral Measurment of TPA (Tibial plateau angle)

• 1. mechanical axisof the tibia

– midpoint between the two(medial and lateral)intercondylar tubercles

– Centre of Os tali

• 2. identifying tibia plateau- Standard method

- tibial plateau line- joining cranial and caudaledges of the medial tibialcondyle

Measurement of TPA• 3. TPA

- draw a line perpendicular to tibialmechanical axis

→ angle between slope of medial tibial condyle (Tibia Plateau) and perpendicular to the tibialmechanical axis

Measurement of TPA

TPA between22° and 27°

Planning of the Osteotomy• Estimation of the size of osteotomy

- Size of the sawblade- template

mathematically correctrotation point*- at the most proximal point of the mechanical axis(on level Eminentiae)

but:

1. No injury of articular cartilage, inter- meniscal-ligaments, Lig. patellae

2. Tub. tibiae sufficently wide3. Size of the osteotomy

sufficient for placingthe plate

*

• Centralisationof osteotomy- Optimal rotation point of stifle

- instant center of rotation (ICR)

Planning of the Osteotomy

A: cranial proximo‐cranial displacementB: caudal disto‐caudale displacementC: proximal caudo‐proximal displacementD: distal cranio‐distal displacementE: central no displacement = 

Osteotomy position optimalKowaleski Vet Surg 2005

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• Size and shape of thetuberositas tibiae

• distance from onset of Lig. patellae to osteotomy (D2)

- trapezoid- width increasing from

proximal to distal

• D2 - 1 cm at least

D2

Planning of the Osteotomy• Mistakes

- „reversed trapezoid“- tibial tuberosity too narrow

Osteotomy too far distal

=> danger of fracture=> femoral-tibial-impingment

*

Planning of the Osteotomy

• Size of the proximalfragment- enough place for plating

• 30 mm sawblade

Planning of the Osteotomy

• Size of osteotomy- not damage any structures→ CENTER THE OSTEOTOMY

- preserve tibial tuberosity width→ CHECK THE TUBEROSITY THICKNESS

AND SHAPE

- leave room for plate application→ CHECK THE SIZE OF THE PROXIMAL

FRAGMENT

Planning of the Osteotomy - Checklist

Estimation of the Rotation• Estimation of the TPA √• Estimation of the sawblade size √

↓

Schedule table↓

mm Rotation Post OP-TPA of 6°

• measure distance of theplanned osteotomy froma reference point

• origin of the Lig. patellae

• to osteotomy cut

Planning of the Osteotomy• Next steps:

(transfer correct osteotomy from x-ray to surgery)

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• Using 2 marks• Marking of the osteotomy points

Measurement „D1“:Distance from origin of theLig. patellae to the most proximalpoint of the osteotomy

Measurement „D2“:Distance from origin of theLig. patellae to the osteotomy point on line perpendicularly to tibialtuberosity

Planning of the Osteotomy

Measurement D3:From caudal tibial plateau to the most caudal aspect of theosteotomy- needle marks caudal border(joint cavity) of medial collateralligament

• Marking of the Osteotomy Points

Planning of the Osteotomy

From the X-Ray Planning to Surgery

Follows in the next lecture: Mike Kowaleski Thank you very much for

your attention!