Focal implants are much smaller than total or partial knee replacements.
What is a focal implant?
|A focal implant replaces a small part of a joint surface with an uncemented prosthesis made of cobalt-chrome, leaving the rest of the joint cartilage functioning as normal.|
Focal implants are available for the convex femoral condyles and also for the concave patello-femoral groove where the patella glides. They are appropriate in the middle age group for areas where damage is localised with healthy opposing cartilage surfaces, the mechanical alignment of the joint is good and meniscal function is not seriously compromised.
The clinical outcome of the different HemiCAP and UniCAP knee implants: A systematic and comprehensive review Malahias MA, Chytas D and Thorey F1. Orthop Rev (Pavia). 2018 Jun 14;10(2):7531.
Indications for focal implants
A key indication is for those patients who are in their middle years and who have focal joint cartilage damage, but who do not show any signs of joint space narrowing. Younger patients may instead be offered a biological solution such as autologous chondrocyte implantation (ACi) and older patients might be offered a knee replacement, but in between these two age groups a focal implant appears to have a significant role.
Another indication where younger patients may be considered, is if there is bone oedema associated with the cartilage damage, in which case any biological solution might fail.
Results of using a focal implant may be comparable to a biological implant, but there are cost and time savings.
A Comparison of the Outcomes for Cartilage Defects of the Knee Treated With Biologic Resurfacing Versus Focal Metallic Implants Pascual-Garrido C, Daley E, Verma NN and Cole BJ. Arthroscopy, 33 (2), 364-373 Feb 2017.