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. 2025 Mar 8;17(3):e80270.
doi: 10.7759/cureus.80270. eCollection 2025 Mar.

Clinical and Economic Case for Patient-Specific Total Knee Arthroplasty: A Prospective Study

Eli Johnson  1 , Ethan Cottrill  2 , Tara Mann  3 , James Willey  4 , Cambre Kelly  3 , Daniel Dunaway  4
Affiliations

Clinical and Economic Case for Patient-Specific Total Knee Arthroplasty: A Prospective Study

Eli Johnson et al. Cureus. .

Abstract

Introduction: Total knee arthroplasty (TKA) is a common surgical intervention for severe knee arthritis resulting in joint or cartilage destruction, with success largely depending on prosthetic design and surgical technique. This study compares two Cruciate Retaining (CR) TKA systems, the iTotal® Identity CR system (ConforMIS; Wilmington, MA), a patient-specific knee (PSK) system, with the Triathlon® Total Knee System (Stryker; Kalamazoo, MI), a standard off-the-shelf (OTS) system, hypothesizing that the PSK system results in better clinical outcomes and reduced costs.

Methods: This single-center, prospective study included 188 patients (217 knees) who underwent TKA with either the PSK or OTS system from August 2017 to February 2021. Participants were enrolled if they had a clinical indication for total knee replacement and were deemed suitable candidates for either system. All participants were adults (18+ years) and capable of providing informed consent. Data on operative times, complications, patient-reported outcomes, and cost metrics were collected and analyzed.

Results: Compared to the OTS group, the PSK group had a significantly shorter average total operating room (OR) time (85.2 vs. 95.9 minutes, p < 0.001), tourniquet time (50.2 vs. 64.3 minutes, p < 0.001), OR instrument setup time (5.0 vs. 11.9 minutes, p < 0.001) and OR instrument tear down time (1.5 vs. 7.0 minutes, p < 0.001). At preoperative baseline, the PSK participants had a worse mean Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) score (40.73 vs. 49.6, p <0.001) and worse Knee Society Scores (KSS) (50.9 vs. 62.7, p <0.001) compared to the OTS group. Finally, the PSK group demonstrated greater mean improvement postoperatively in both the KOOS-JR (37.33 vs. 24.61, p <0.001) and the KSS (113.1 vs. 98.1, p <0.001) scores, compared to the OTS group.

Conclusions: The PSK system demonstrated advantages in operative efficiency and improved patient-reported outcomes at the three-month follow-up compared to a standard OTS knee replacement system. These findings highlight potential benefits in adopting patient-specific implants in TKA, with implications for both clinical outcomes and healthcare cost savings. However, further research with longer follow-up periods in diverse patient populations is necessary to fully understand the long-term implications of patient-specific knee replacement systems.

Keywords: cruciate-retaining tka; economic impact; patient-specific; total knee arthroplasty; total knee replacement (tkr).

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Conflict of interest statement

Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. Western Institutional Review Board issued approval Study No: 1175797; Protocol No: 20171188; Online Tracking No.:11-1893574. The process of consent was conducted in accordance with the guidelines set forth by the Institutional Review Board and good clinical practice, ensuring that participants were fully informed about the study's purpose, procedures, potential risks, and benefits before voluntarily agreeing to participate. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: This work was supported by funding from ConforMIS, Inc. Financial relationships: Tara Mann declare(s) employment and stock/stock options from restor3d, Inc. restor3d acquired ConforMIS, the sponsor of this study, in September 2023. Tara Mann is an employee of restor3d. A portion of her compensation is in the form of equity (restricted stock awards and stock options). Cambre Kelly declare(s) employment and stock/stock options from restor3d, Inc. restor3d acquired ConforMIS, the sponsor of this study, in September 2023. Cambre Kelly is an employee of restor3d. A portion of her compensation is in the form of equity (restricted stock awards and stock options). Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. Study characteristics.
OTS, Off-the-shelf; PSK, Patient-specific Knee; TKA, Total knee arthroplasty.
Figure 2
Figure 2. Operating room tray comparison.
The OTS system requires six to eight compared trays to a single tray used by the PSK system. OTS, Off-the-shelf; PSK, Patient-specific knee.
Figure 3
Figure 3. Operative data.
A. Comparison of operative times between PSK and OTS systems. B. Comparison of trays used between PSK and OTS groups. * Indicates a statistically significant difference (p < 0.001). Total OR time is defined as wheels in to wheels out and is not the cumulative total of tourniquet time, OR instrument setup time, and OR instrument tear down time. OTS, Off-the-Shelf; PSK, Patient-Specific Knee; OR, Operating room..
Figure 4
Figure 4. Outcome data.
A. KOOS-JR comparison between PSK and OTS groups preoperative and approximately three-months postoperatively. B. KSS comparison between PSK and OTS groups preoperative and approximately three-months postoperatively. * Indicates a significant difference (p < 0.001). KOOS-JR, Knee injury and Osteoarthritis Outcome Score for Joint Replacement; KSS, Knee Society Score; OTS, Off-the-shelf; PSK, Patient-Specific Knee.
Figure 5
Figure 5. Temporal change in outcome data.
Comparison of the difference in outcome data between the PSK and OTS groups over time. * Indicates a significant difference (p < 0.001). OTS, Off-the-shelf; PSK, Patient-specific knee.
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