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STL 20070915
The role of computer assisted surgery
(CAS)
Søren Toksvig-LarsenDept Orthopedics Hässleholm Hospital
Lund University
Sweden
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WHAT’S WRONG WITH THIS SCENARIO 2007?
• Orthopaedic Surgeon:
• Mallet and a Goniometer
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WHAT’S WRONG WITH THIS SCENARIO 2007?
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introduction
The purpose of modern technique:The purpose of modern technique:
• improve the duration of implantsimprove the duration of implants
• reduce the human errorreduce the human error
• simplification of the surgical techniquesimplification of the surgical technique
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Not necessarily make every case better
• prevent the outliersprevent the outliers
• explore the possibilities of enhancedexplore the possibilities of enhanced
ROM, stability, and alignment– knowing the functional Kinematics
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My background
Istituti Ortopedici Rizzoli
EU projects
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CAOSCAOSComputer Assisted Orthopaedic Computer Assisted Orthopaedic
SurgerySurgery
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Robot surgery”active”
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Formula 1
Robot surgery
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3-D op technique
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ProblemToo troublesome
Feed back systemsSafety systems
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Why continue Why continue using modern technique??using modern technique??
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Who is a non-responderMy problemMy problem
Non respondersNon responders
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Satisfaction - TKA
18 % were dissatisfied or uncertain
• O. Robertsson et al. 2000
Distribution of satisfaction, percent
0
20
40
60
80
100
Female Male Female Male
OA RA
Very sat isf ied
Satisf ied
Uncer tain
Unsat isf ied
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Possible Malalignment
Rotational malalignment
Translational malalignment
Varus Valgus Flexion Extension Internal rotation External rotation
Medial Lateral Proximal Distal Anterior Posterior
CAOSCAOS1212º freedom for each componentº freedom for each component
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Navigation
“passive”
Surgical set up
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Navigation gives information Navigation gives information during surgery to position the during surgery to position the
instruments and implants instruments and implants according the “anatomy”according the “anatomy”
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Knee Navigation workflow
HIP center
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Knee Navigation workflow
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NAV as other computers”shit in, shit out”
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Record Alignment
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More sophisticated instruments
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Tibia cut
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Gap balancing/tension
??????????????????????????
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Navigation
Fewer outliersFewer outliers
• Positioning of TKA with and without navigationSparmann et al. JBJS-Br 2003
– improved mechanical, frontal and sagital femoral axis and frontal tibial axis
– 240 patients (120 CAOS, 120 conventional)
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Navigation
60 cases TKA superior results for the CAOS group compared to the
conventional grouphowever
no statistically difference for • the mechanical axis• the tibial axis, the femural axis• a tendency for valgus positioning the femural component in the
CAOS group– Miehlke et al. Z. Orthop 2001
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• A prospective randomised study– 50 TKA knees, Genesis knee
Conclusion
CAOS excellent, but not better than conventional» J. Victor D. Hoste (Efort 2003)
TKA navigation
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•A prospective randomised study
–50 knees, Genesis knee
–Accuracy CAOS – excellent
Outcome Conventional CAOS
•Torniquet time 56 min 72 min p 0.002
•Operative time 70 min 93 min p<0.001
•Blood loss 3.3 g/dl 4 g/dl ns
•Patellar alignment no tilt>5º no tilt>5º
•Patellar alignment no subluxation no subluxation
•Tibial slope 3.5º 3º
»J. Victor D. Hoste (Efort 2003)
TKA navigation
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Sample-sizes needed in prospective randomised trialsSample-sizes needed in prospective randomised trials
• Detect a difference in outcome of 2.5% (i.e., 92.5 vs. 95 %) Detect a difference in outcome of 2.5% (i.e., 92.5 vs. 95 %) after 10 years with 80 % power at a 5 % level of after 10 years with 80 % power at a 5 % level of significanse.significanse.
• 2000 patients are required!!!2000 patients are required!!!
???Does it matter??????Does it matter???
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OVERALL SYSTEM ERROR 2 mmthe average difference between point distance in the virtual scene and the
corresponding point distance in the real world, is given by:
ACQUISITION ERROR: 1 mm
errors in surface position produced by the segmentation algorithm
SIMPLIFICATION ERROR: 0.4 mm
ACCURACY OF THE TRACKING SYSTEM: 0.5 mm
REGISTRATION ERROR: 1 mm
ACCURACY OF THE POSITION SENSOR: 1.0 mmdefined as the standard deviation of a set of measures with respect to the “real” value, obtained by means of a calibration instrument.
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Intraoperative cutting errors
Some of my experience using navigation
Pinning the cutting block can change the position of the block 1 - 2 degree
The cutting process can change the surface additional 1 - 2 degree
Can partly be corrected using navigation
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Evaluation
Methods with a lower accuracy than the CAOS systems
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z
Alignment – outliers (2-D)
Femural component too extended
valgus positioning the femural component
Less bloodloss
Individuality
Tibial rotation
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So far
The purpose of modern technique:The purpose of modern technique:
• improve the duration of implantsimprove the duration of implants
• reduce the human errorreduce the human error
• simplification of the surgical techniquesimplification of the surgical technique
NOT ACHIEVEDNOT ACHIEVED
But it willBut it will
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The CAOSThe CAOS technique technique
The cost-effective problemsThe cost-effective problems
• Longer operation timeLonger operation time
• Additional surgical interventionAdditional surgical intervention
• Complications?Complications?
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The CAOSThe CAOS technique technique
The cost-effective problemsThe cost-effective problems
• Big investment/costs to run the Big investment/costs to run the equipmentequipment
•Troublesome techniqueTroublesome technique
saved co
sts fo
r revisio
ns
saved co
sts fo
r revisio
ns
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New technique
A new technique becames viable if it makes a process or service deliveries either
–easier –faster –cheaper–better
–2 of these benefits would make a technology more popular
–For arthroplasty all 4 are required??!!
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