Pre-operative evaluation

Transcription

1 Pre-operative evaluation Andrea Meyer-Lindenberg Clinic of Small Animal Surgery and eproduction 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 MI / arthroscopy / miniarthrotomy 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 Fault in positioning m/l view - superimposion of femur condyles - fibula visible - fibula in the upper third with distinct distance to the tibia slight - Internal rotation - moderate correct 1

2 caudo-cranial view - Positioning sternal recumbency Hindlimb extended caudally include: stifle, tibia, tarsus central beam centered on stifle joint Caudo-cranial view - Patella central in trochlea groove - Fabellae bysected by femoral cortices - medial border of the calcaneus aligned with distal intermediate ridge of the tibia Caudo-cranial view - medial border of calcaneus - distal intermediate ridge of the tibia (deepest point of sulcus tali) Fault in positioning cd/cd view inwards / outwards rotation patella not centered Calcaneus false position alter the position repeat X-ray compensate positoning mistakes Torsional deformity diagnosis on caudo-cranial radiographs - Torsion of tibia - deformities of the distal femurs (Varus) - deformities of the proximal tibia (Valgus) Tibiatorsion internal torsion - e.g. Labrador, ottweiler - inward rotation of the paw - Calcaneus displaced laterally Correction within the scope of TPLO is possible 2

3 Tibiatorsion external torsion - large breeds - outward rotation of the paw - calcaneus displaced medially Assessment of limb alignment Frontal plane no deformity mmpta: 94 medial proximal mechanical tibia angle mmdta: 96 medial distal mechanical tibia angle Dismukes, Vet. Surg, 2008 Valgus-Deformity prox. Tibia proximo-distal displacement of femoral condyles mpmta: 103 mmdta: 87 Varus-Deformity distal femur caudo-cranial displacement of the femoral condyles double condyle sign correct positioning Dismukes, Vet. Surg, 2008 Varus (Femur) and Valgus (Tibia) deformity Cranio-caudal and proximo-distal displacement of femur condyles (Tibial plateau angle) Anatomy - proximal tibia: two joint parts - medial condyle - lateral condyle => angle of slope towards caudodistal cranial * Cranio-caudal and proximo-distal displacement of femur condyles between both condyles - Eminentia intercondylaris - Tub. intercondylare laterale - Area interkond. centralis (*) - Tub. Intercondylare mediale mediolateral caudal 3

4 mediolateral Measurment of TPA (Tibial plateau angle) (Tibial plateau angle) 1. mechanical axis of the tibia Anatomy (important points) - cranial margin midpoint between the two (medial and lateral) intercondylar tubercles Centre of Os tali - Tub. Tibiae - Margin of joint surface - cranial / caudal edge of med. tibial condyle Tibia plateau line - Midpoint between medial and lateral intercondylar tubercles 2. identifying tibia plateau 3. TPA - draw a line perpendicular to tibial mechanical axis angle between slope of medial tibial condyle (Tibia Plateau) and perpendicular to the tibial mechanical axis - Standard method - tibial plateau line - joining cranial and caudal edges of the medial tibial condyle TPA between 22 and 27 Estimation of the size of osteotomy - Size of the sawblade - template mathematically correct rotation 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 wide 3. Size of the osteotomy sufficient for placing the plate Centralisation of osteotomy - Optimal rotation point of stifle - instant center of rotation (IC) A: cranial B: caudal C: proximal D: distal E: central proximo-cranial displacement disto-caudale displacement caudo-proximal displacement cranio-distal displacement no displacement = Osteotomy position optimal Kowaleski Vet Surg

5 Size and shape of the tuberositas tibiae distance from onset of Lig. patellae to osteotomy (D2) - trapezoid - width increasing from proximal to distal D2-1 cm at least D2 Mistakes - reversed trapezoid - tibial tuberosity too narrow * Osteotomy too far distal => danger of fracture => femoral-tibial-impingment Size of the proximal fragment - enough place for plating 30 mm sawblade - Checklist Size of osteotomy - not damage any structures CENTE THE OSTEOTOMY - preserve tibial tuberosity width CHECK THE TUBEOSITY THICKNESS AND SHAPE - leave room for plate application CHECK THE SIZE OF THE POXIMAL FAGMENT Estimation of the otation Estimation of the TPA Estimation of the sawblade size Schedule table mm otation Post OP-TPA of 6 Next steps: (transfer correct osteotomy from x-ray to surgery) measure distance of the planned osteotomy from a reference point origin of the Lig. patellae to osteotomy cut 5

6 Using 2 marks Marking of the osteotomy points Marking of the Osteotomy Points Measurement D1 : Distance from origin of the Lig. patellae to the most proximal point of the osteotomy Measurement D2 : Distance from origin of the Lig. patellae to the osteotomy point on line perpendicularly to tibial tuberosity Measurement D3: From caudal tibial plateau to the most caudal aspect of the osteotomy - needle marks caudal border (joint cavity) of medial collateral ligament From the X-ay Planning to Surgery Follows in the next lecture: Mike Kowaleski Thank you very much for your attention! 6