Biomedical Engineering Reference
In-Depth Information
cruciate sacrificing form. Since this design is easier to implant reliably than the
Bicruciate retaining device form, some surgeons used the posterior cruciate
retaining form even when a viable anterior cruciate is present by sacrificing the
anterior cruciate.
This device was later replaced by an A/P gliding, robust, unit bearing replacing
the dual meniscal bearing of the earlier device as illustrated in Fig. 6.76.
a'
a
Since a' > a the
Posterior Cruciate
Ligament tightens
causing femoral
rollback
(a) Full Extension, Bearing Forward
(b) 90° Flexion, Posterior
Displacement of the Bearing
Fig. 6.76
A-P Glide Bearing and Tibial Platform
The use of this device was, however, limited to use outside of the United States
since it was not approved by the FDA.
Further, due to simplicity of surgical instrumentation, concerns for continued
viability of the cruciates, and due to the inherent stability of the rotating platform
device, some surgeons chose to routinely sacrifice the cruciates and implant the
Cruciate Sacrificing Tibial Component in their entire patient population. Although
there are now long-term clinical trials involving thousands of patients, the clinical
justification for retaining or sacrificing, viable cruciate ligaments is not clearly
established. As a result the cruciate sparing devices were abandoned.
