considerations in knee artroplasty
DESCRIPTION
TRANSCRIPT
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CONSIDERATIONS IN TKA
JAVIER MATA
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HISTORY OF TKA
• Total knee arthroplasty is one of the most important advances in orthopaedics during the last 30 years.
• Patients with severe arthritis have reduced pain, correction of deformity and improved function as well as life quality after TKA implantation.
• Today, increasing interest is showed in the mobile bearing type of knees. Long term results will have to prove that they are better!
• Several surgical points need to be considered !!!
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The Surgeon Is One Of TheMost Important Factors
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ANATOMY AND SOFT TISSUES
• A thorough knowledge of the knee anatomy, bones,mechanical, anatomical axis,ligaments and soft tissues must clearly be understood ( John Insall ).
• Total knee arthroplasty is the correct alignment of the components and soft tissue balancing. The last is the formula 1 “Fine Tuning”.
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THE PEFECT KNEE IS BALANCED
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The vertical axis.
The mechanical axis.
The anatomical axis
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WHICH KNEE SHOULD WE USE ? ?
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TODAY,THINGS ARE CHANGING
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WHAT ABOUT CLINICAL RESULTS?
WHAT DOES THE CURRENT KNEE MARKET HAVE ?
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Clinical Results
Some Notable Long Term (>10 Year) Clinical Results
TC 90.77%1
IB (Post Stabilised) Mark II 93.6%1
PFC 96.2%LCS (Meniscal) 94.7%2
Kinematic 95.0%TCCK * 97.5%3
IB (Post Stabilised) Mark I * 98.0%1
* Uniform Compressed Polyethylene
1 Survivorship of cemented TKA. Insall, AOAS San Francisco 19972 Orthopaedics. Sept 96. R.B. Sorrells3 Swedish Knee Register. AAOS, San Francisco 1997
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Year % Survival References 15 98 Ritter - Current Concepts 1999
11.4 95 Emerson – Journal of Arthroplasty 2000
>10 98 Clinical Orthopaedics Dec. 95- 2001 AGC Knees Ritter et.al.
10 97.5 Swedish Knee Register - AAOS 1997
>7 97 Finish Knee Register - 988 AGC Knee 1995
>8 98.2 Oxford Group U. Kingdom – 1996 Published this Year
>10 96 Emmerson M.D. USA 1996
AGC Clinical Results
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ARE WE GOING FOR A C.R. OR P.S. TOTAL KNEE?
• Retaining the posterior cruciate ligament is more natural, but in practice more difficult to achieve good tension.Or it is too tight or too loose. Rarely the correct tension( Stiehl)
• Implanting a PS knee gives the surgeon reproducible mechanical rollback.It is an easier operation!
• The available literature suggests that PS TKA is superior in results than CR TKA.
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WHAT TYPE OF INCISION?
• Medial approach(varus or valgus knees)• Lateral approach(lateral knees)• Subvastus approach(varus knees)• Midvastus approach(varus knees)• Tibial tubercle osteotomy(L. Whitside)• Rectus snip(vastus turndown)
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MEDIAL APPROACH
• Varus Deformities.• We start with a straight line incision if possible.• Medial parapatellar.• About 1 cm medial to the tibial tubercle.• Deep M.C.L.• Superficial M.C.L.• Semimembranosus.• Subluxation of the tibia(rotation).• patello-femoral ligament.
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MEDIAL APPROACH
• Valgus Deformaties.• Straight line skin incision.• Medial parapatellar.• Anterior deep M.C.L.• Illiotibial band.• Straight anterior subluxation.• Lateral capsular ligament.• Arcurate ligament.• Popliteus&L.C.L.
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L
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LATERAL APPROACH
• Valgus Deformities (Keblish)• Straight line skin incision.• Lateral parapatellar.• Lateral capsular ligament.• Partial tubercle release.
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SUBVASTUS APPROACH
• Varus knees.• Straight line skin incision.• Medial parapatellar( not going into the quads).• Elevate proximally.• Avoid saphenous nerve.• Sometimes difficult patella exposure with
obese patients
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MID VASTUS APPRAOCH
• Varus knees( Engh)• Same as subvastus but here we go slightly
into the vastus medialis.
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L
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TIBIAL TUBERCLE OSTEOTOMY
• Straight line skin incision.• Medial parapatellar.• Tibial tubercle osteotomy of about 10cm.• Leave soft tissues intact laterally.• Fixation with wires,screws,staples etc..
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RECTUS SNIP OR VASTUS TURNDOWN
• Straight line skin incision.• Medial parapatellar.• Transverse cut into the quads.• Medial closure.• No lateral release.
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GOOD KNEE EXPOSURE
• It is very important to achieve good knee exposure. This will facilitate the whole procedure.
• First thing to do, is to take all protruding osteophytes away. This from the femur and the tibia.
• If partial ligament release is necessary, do it. Disadhere the ligaments.
• So, restore the anatomy.
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ESTABLISH YOUR REFERENCES
• What is the valgus angle going to be?• Mark and draw the epicondylar axis line for
correct femoral exorotation. Check with the Whitsides line.
• Restore the joint line.Use available anatomical reference landmarks.
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Epicondylar axis line and Whitsides’ line
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Where is the “Joint Line” ?
• About 16 to 18mm from the fibula head.• 46mm off the medial distal femur at the
adductor tubercle ( A. Hofmann )• About 27mm distal off the medial femoral
epicondyle.• Look for the old meniscal scar in the joint
capsule= joint line
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ANTERIOR REFERENCING
• Most of the knee instrumentations use anterior referencing of the femoral component.
• Here we respect the anterior part of the femur.• If , between 2 sizes, we can downsize.• The counterpart is that we cut more posterior
femoral condyle off. This elevates the joint line in flexion.
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POSTERIOR REFERENCING
• We respect the posterior femoral condyles, thus re-establish the joint line in flexion.
• The counterpart is that we cannot downsize, if between sizes. Otherwise we will notch the anterior femoral cortex.
• There are instruments that compromise, like the Fudge A/P sizer.
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The “ Fudger” A/P sizer permits downsizing if between 2 sizes
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PERFORM ACCURATE BONE CUTS
• The key to success is the sawblade.• Go for the femur or the tibia. It’s surgeons
preference.• Restore the mechanical axis, joint line and
do a good soft tissue balance.• Achieve in flexion and extension exact
rectangles.
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Be in the right place when drilling into the
femur or tibia!!
• Look at your X rays to establish your entry points into the bone.
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TIBIAL PREPARATION
• You can prepare your tibial cut extramedullary or intramedullary.
• Be sure to check this cut because it is one of the most important cuts in TKA.
• A tibial cut should be perpendicular to it’s mechanical axis.
• A neutral cut is the best. Slight valgus cut is tolerated
• A VARUS CUT IS BAD
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When using a posterior slope,
you must watch out!!!Internal rotation will result in a valgus cut of the tibia.
External rotation will result in a varus cut of the tibia
Be sure to be in exact A/P when using a tibial resection guide.
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Extramedullary tibial resection guide over the top
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Intramedullary resection guide
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In varus knees, you will cut off more laterally than medially.
In valgus cases, you will cut about the same amounts medially and laterally.
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The posterior cortical axis is 10° internally rotated.
The inermalleolar axis is 15° externally rotated.
The tibial crest is neutral.
The tuberosity is just lateral
Reference landmarks
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INSTRUMENTATION
• Use the instrumentation correctly but don’t depend fully on it.
• Be like Einstein,use your brains and common sense.
• Establish correct flexion and extension gaps.How? Use spacer blocks or tensioners to achieve this.
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This is the correct way
Not correct
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CHECK YOUR FLEXION AND EXTENSION GAPS:
THEY MUST BE EXACT !!!!
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Flexion and extension spacers
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PATELLA TRACKING
• Patella tracking is extremely important in TKA.The following points are important to achieve good patella tracking.
• Surgical approach,correct femoral size,lateralisation,correct exorotation of the femoral component,slight exorotation and lateralisation of the tibial component,medialisation of the patella component.( AAOS comments )
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PATELLA PREPARATION
• Surgeons have different approaches to implant a patella component.
• Some do it free hand.• Others resurface or inlay the patella button.• Some don’t and leave the natural patella in
situ.• Most do a “Denervation” around the natural
patella.
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Check the natural, eroded patella size
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Resurfacing the patella
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Inlay patella technique
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‘ Cut ‘ the cement away
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TRIAL REDUCTION
• It is imperative to achieve full extension and good flexion with the trial components in place during the operation.
• Try the Bob Booths full extension test.• Try the gravity test for evaluation of the
flexion.• Try the P.O.L.O. test.• If using a PS knee, try and luxate the femur
from the tibia(hop over test).
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CEMENTING
• Take good and meticulous care in cementing the components in place.
• Do not pressurize in full extension otherwise you will end up with an anterior tibial slope of your tibial component.Hold the leg at about 30 degrees of flexion.
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METICULOUS IRRIGATION IS ESSENTIAL!!!!
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GO FOR A CLEAN AND DRY BONE SITUATION
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PRESSURIZE THE CEMENT INTO THE BONE
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GRACIAS