Two-Year Outcome Comparison of Custom Versus Conventional Total Knee (TKA) Implants

A Retrospective Cohort Study

Brandon Passano, MD; Ji Won Lee, MSN; Brian Gallagher, MD; Sameer Desale, MS; Henry R. Boucher, MD


Curr Orthop Pract. 2022;33(5):447-451. 

In This Article

Abstract and Introduction


Background: Custom implants have drawn increasing interest from surgeons seeking the promise of improved coronal alignment, decreased operative time, and improved outcomes. Currently, there is no clear evidence to support those claims. This study sought to investigate whether utilization of custom implants and instrumentation would lead to a greater improvement in 2-year patient-reported outcomes compared with conventional total knee arthroplasty (TKA).

Methods: This is a retrospective cohort study of 287 knees that underwent either custom TKA (n=150) or conventional TKA (n=137). Primary outcome measures included changes in Oxford Knee Score (OKS) and Short-Form 12 (SF-12) mental and physical component scores at preoperative versus 2-year follow-up. A mixed effects model was utilized to make comparisons between improvements in score. The complication and revision rates were compared.

Results: There was a significant improvement in all three patient-reported outcome measures from preoperative to 2-year follow-up in both the custom and conventional instrumentation group. There were no significant differences in the magnitude of improvement between the custom and conventional groups for OKS, SF-12 mental, or SF-12 physical (P=0.07, 0.19, and 0.13, respectively) at 2-year follow-up. There were no significant differences in the complication rate (P=0.69) or revision rate (P=0.60) at 2-year follow-up.

Conclusions: At a minimum follow-up of 2 years, the authors found no significant differences in patient-reported outcome measures including the OKS, SF-12 mental and physical scores between custom and conventional TKAs. Additionally, there were no significant differences in complication or revision rates.

Level of Evidence: Level III.


The number of primary and revision total knee arthroplasties (TKAs) are expected to increase exponentially to 3.48 million procedures annually by 2030.[1] However, approximately 19% of patients are dissatisfied with their results.[2] Factors associated with dissatisfaction are related to long-term pain and function as well as short-term postoperative outcomes.[2]

Correct biomechanical implant alignment is critical in a TKA because it has been shown to improve function and pain as well as decrease rates of postoperative complications.[3] Over the past decade, customized implants have been introduced to optimize postoperative biomechanics by matching the patient's natural prearthritic anatomy. Using CT or MRI mapping techniques, software-generated three-dimensional models are rendered to design patient-specific implants and cutting blocks. Planning software is utilized to select and adjust component size, thickness, alignment, and translation. Customizing components theoretically offers advantages such as preservation of bone stock, improved implant fit, avoidance of resection laxity, restoration of radii of curvature, and improved patellofemoral tracking. These factors attempt to recreate the patient's natural joint kinematics to produce superior outcomes.

The benefits of custom implants are debated. Studies have demonstrated benefits of custom implants over conventional implants and techniques such as better approximation of the natural kinematics and coronal alignment of the knee,[4–8] improved radiographic outcomes,[4–8] and fewer outliers.[6] However, there have been mixed results in the literature regarding custom TKAs' effect on blood loss, transfusion rates, length of stay, adverse events, operative time, discharge to a secondary facility, and cost effectiveness.[9,10] Additionally, the impact of custom TKA on patient-reported outcome measures (PROMs) has not been well defined in the literature.[10,11] Reimann et al.[12] demonstrated better daily function and patient satisfaction for those with customized implants at 2 years compared with controls. To the authors' knowledge, this is the only study that has examined the effect of custom knee implants on PROMs.

To address that gap, this study investigated outcomes from a custom TKA implant, which uses a CT-generated three-dimensional model of the knee to create individualized tibial and femoral components, polyethylene inserts, and custom cutting jigs. The purpose was to examine differences in PROMs with a custom total knee implant compared with the conventional implants. Outcomes of interest included Oxford Knee Scores (OKS), SF-12 mental and physical scores, revision rate, and complication rate. The authors hypothesized that the custom implants would have greater improvement in PROMs compared with conventional implants.