Custom TKA: what to expect and where do we stand today?

The concept of custom total knee arthroplasty (TKA) is explored with specific attention to current limitations. Arguments in favor of custom TKA are the anatomic and functional variability we encounter in our patients. The biggest conceptual challenge is to marry the need for correction of deformity with the ambition to stay as close as possible to original anatomy.

A Pubmed search was performed on the following terms: 'patient specific implant', 'custom made implant', 'custom implant', 'total knee arthroplasty' and 'total knee replacement'. These studies were evaluated for the following intra- and post-operative variables: blood loss, hospital stay, range of motion, patient-reported outcome measures, limb and implant alignment, implant fit, tibiofemoral kinematics, complications and revision rates.

Out of 1117 studies found with the initial search, a total of 17 articles were included in the final analysis. In eight out of the 17 (47%) studies, either the research was commercially funded or one of the authors had a conflict of interest related to the work. 11 out of 17 studies included a control group in their study setup. Of those studies that included a control group, both superior and inferior results compared to off-the-shelf implants have been reported.

Custom knee implants are the next step in matching the geometric features of the prosthesis to the anatomy of the individual patient, after several iterations that added asymmetry and sizes in the existing implants. Several companies have proven that it is feasible to produce these implants in a safe way. An overview of current literature reveals the lack of strong methodological studies that prove the value of this new technology. Custom knee implants face conceptual and practical difficulties, some of which might be overcome with technological advances, such as robotics and artificial intelligence.