1. m. mardani kivi guilan university of medical sciences 2
TRANSCRIPT
The primary function of the patella is to increase the lever arm of the extensor mechanism around the knee, improving the efficiency of quadriceps contraction.
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Extensor lever arm is greatest at 2020 degrees of flexion and the quadriceps force required for knee extension increases significantly in the last 2020 degrees of extension.
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Patella provides 50% increase in knee extension strength compared with that after patellectomy.
Patellofemoral joint sustains some of the greatest contact pressures of all the joints of the body.
Normal walking generates 50% body weight joint reaction forces which increase to 88 times body weight for jumping from a small height.
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Of all the indications for resurfacing, inflammatory arthritisinflammatory arthritis has been the most widely accepted. Most authors have recommended routine resurfacing for all patients with R.AR.A..
Lighter patients tending to do well with un-resurfacing patella.
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Bilateral arthroplasty no difference in stair-climbing ability or incidence of anterior knee pain.
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No difference in Ant. Knee pain, functional score or revision rates between resurfaced and un-resurfaced groups.
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Revisions in Non-resurfaced
group
Revisions in resurfaced
group
AuthorKnee
implant used
Min. F/Up (yr)
No. Knees
All reasons
Patello-femoral
problems
All reasons
Patello-femoral
problemsBourne et
alAMK 6.3 100 6 2 2 1
Feller et alPCA
modular3 40 0 0 2 0
Schroeder et al
Not specified
2 40 2 2 1 1
Barrack et al
Miller Galante II
5 93 7 7 0 0
wood et alMiller
Galante II2 198 15 15 9 9
Waters PFC 2 474 11 11 3 3
Totals 4 types3.4
(mean)954
(100%)41
(4.3%)37 (3.9%)
17 (1.8%)
14 (1.5%)
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AMK: Anatomic Modular Knee; PFC: Press Fit Condylar; PCA: Porous Coated AMK: Anatomic Modular Knee; PFC: Press Fit Condylar; PCA: Porous Coated AnatomicAnatomic
The prosthetic patella should be medialized to approximate the median eminance of the normal patella.
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“No thumb” test of patellar tracking should be used as a guide of patellar instability (before retinacular closure)
If the patella can be subluxated half of its diameter over the medial femoral condyle, the retinaculum is probably not too tight.
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If there is any abnormality in patellofemoral tracking deflatedeflate the torniquet and examine again 48% (Marson) or 31% (Husted) it will be normal.
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Correction should be toward the reason. if there is not any component mal-positioning lateral release lateral release should be done.
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