KNEE
Knee Joint Replacements
Total knee replacement has been one of the major advances in Orthopaedic Surgery
in the last thirty years. The most successful implants have been those of the
total condylar design and its modifications as found in the ST Ledger KneeTM, first introduced in 1974.In order to obtain improvements in knee flexion, stability and variations of
the tibial component which have not always been advantageous.
It is becoming generally accepted that the tibial component should have the following
features.
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The polyethylene should be machined from a solid block and not neat pressed or moulded, as this may lead to premature flaking.
- The thickness of the polyethylene should be greater than 6mm.
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Tibial wear should be minimised by having good congruity of joint surfaces without undue constraint decreases contact stresses and improve tibial wear characteristics. The 'uphill principle' or sloping tibial surface aids the process as well as giving some added stability in the sagittal plan.
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A central fixation post or 'keel' on the under side of the tibial component reduces the likelihood of tibial implant subsidence.
Other features which may be of value are, laterally placed studs on the under
side of the tibial tray, which confers extra rotational stability by a factor
of twenty, and a posterior cruciate retaining capability.
Many modern implants use the concept of a metal backed tibial tray with a 'snap
fit', modual tibial bearing insert. This latter aspect of design means that greater
flexibility in sizing can be achieved while keeping inventory requirements to
a minimum.
Although there has been little improvement in total knee replacement design throughout
the nineteen eighties, nevertheless our knowledge does give a predictable outcome,
provided that accepted and well tried principles of design are adhered to.
The St. Leger KneeTM system incorporates design concepts which are well proven and accepted. This
has resulted in a range of features which offer the surgeon predictable reliability
combined with the latest modular technology.
Please click here to access the St Ledger KneeTM Catalogue and Operative Technique
Please click here to access details of St Ledger KneeTM Clinical Investigations
Please click here to access the St Ledger KneeTM Brochure
The Femoral Component
Femoral components are offered in left or right options to ensure optimum fit.
Fixation pegs enhance Medial/Lateral stability.
Multi radius Condylar surfaces ensure that maximum rollback is achieved for greater
flexion.
A wider Patella groove ensures ease of Patella Tracking.
The Tibial Components
The minimum polyethylene thickness is 7mm which is well within accepted limits
for minimal Tibial wear and creep.
Carefully designed Condylar seats ensure a high degree of congruity with the
Femoral component, so minimising Tibial wear through lower contact stresses, without
undue constraint.
A range of five tibial thicknesses (7, 9, 11, 13 and 15mm) provide the surgeon
with optimum flexibility when assessing soft tissue tension and Flexion/Extension
characteristics.
Modual platic Tibial inserts offer maximum size flexibility.
Interchangeability of Femoral and Tibial components offer flexibility and better
patient fit.
Maximum resistance of the Tibial subsidence and rotation is achived by central
stem and outlying peg configuration of the Tibial component.
ARTHROPLASTY
EXTREMITIES
