In particular as compared to our previous problems there were:-
no cases of secondary patellar resurfacing
no cases of tibial subsidence
With regard to tibial subsidence I no longer use cement in soft bone I just use bone graft – same as Karel Hamelynck
MUAs were 1.85% for 10 year results now 1% so I should have had 2 cases
So what about the spinouts and patellar resurfacings?
500 1000 0 1500 2000 2500 3000 3500 4000 93 94 95 96 97 98 99 00 01 02 03 04 05 Years Number of procedures First 575 10 Spinouts out of 900 Cases - 1.1% Change in practice 3 Spinouts out of 3025 cases 0.1% My experience with Rotating Platform Spinouts Summary - Rotating Platform spinouts CORR 425: 207-211; Aug 2004
Generally caused by Surgical error
Which usually produces Flexion Gap Instability
Leave the collateral ligaments alone! 9 of the 13 were valgus
Seldom a problem in mild deformity
Management should not involve major revision
Ideally should be treated closed - cast in extension for 8 weeks
Is generally not recurrent
2 recurrent dislocations out of 4500 cases (0.04%)
Why is spinout more common in valgus knees LATERAL SIDE Slack in flexion Popliteus LCL Gastrocnemius Flexion gap Normal ligament tension
At the end of 2006 we therefore embarked on a prospective, randomised controlled single blinded study
With the LCS complete duofix tibia being compared to the standard tibial component with porocoat – same femur
100 patients in each group
Essentially to see whether the radiolucent lines are abolished and whether there is less pain in the first few months because of more rapid bony ingrowth
The definitive results will not be available until 2008.
So cemented or cementless – why are the results so good in terms of loosening and wear?
Traditional theory of LOW CONTACT STRESS
Congruent 0-30 degrees
Large surface area
Mean Wear Rates Transactions of 50 th Annual Meeting of the Orthopaedic Research Society, Vol. 29, San Francisco, California, March 7-10 2004. Linear wear is much less than multi-directional!
Fixed bearing Multidirectional motion of femoral component relative to bearing RP Mobile bearing Bearing rotation decoupled: Linear rotation at tibial counterface with reduced rotation at femoral counterface Wear in Fixed vs Rotating Platform The LCS Rotating Platform reduces wear and cross shear by decoupling multidirectional motions to more linear motions at two interfaces