Robotic Assistance Is Not Associated With Decreased Early Revisions in Cementless TKA: An Analysis of the American Joint Replacement Registry
Authors: Kirchner Gregory J. , Stambough Jeffrey B. , Jimenez Emily , Mullen Kyle , Nikkel Lucas E. 
Published: November 2024

Background
Previously, we conducted a retrospective study of American Joint Replacement Registry (AJRR) data that examined the 2-year odds of revision between robotic-assisted and nonrobotic-assisted TKA, and we found no benefit to robotic assistance. However, proponents of robotic assistance have suggested that robot platforms confer more accurate bone cuts and precise implant sizing that might promote osteointegration of cementless implants by limiting micromotion at the bone-implant interface that could lead to aseptic loosening. Therefore, it seems important specifically to evaluate the odds of revision among patients with cementless implants only within our previous study population.

Questions/purposes
(1) After controlling for potentially confounding variables, such as surgeon, institution, and patient comorbidity profile, was robotic assistance associated with a decreased odds of 2-year revision of cementless TKA for any reason compared with cementless TKAs performed without robotic assistance? (2) After again controlling for potentially confounding variables, was robotic assistance associated with a decreased odds of 2-year revision of cementless TKA for particular revision indications (such as aseptic loosening, infection, instability, or pain) compared with the cementless TKAs performed without robotic assistance?

Methods
Using the AJRR, a retrospective cohort of patients ≥ 65 years of age with osteoarthritis who underwent primary TKA with cementless femur and tibial components from January 2017 through March 2020 was identified. Procedures performed with hybrid fixation (cement only on the tibia but not on the femur, or vice versa) were excluded. The AJRR was selected because it is the largest arthroplasty registry in the world by annual procedure volume, and it contains a data linkage with inpatient and outpatient Medicare claims data to ensure near-complete 2-year follow-up. A total of 9220 patients were identified, and robotic assistance was used in 45% (4130) of procedures. Patient age did not differ between groups (72 ± 5 years versus 72 ± 5 years; p = 0.29). However, the robotic-assisted cohort had a slightly higher proportion of female patients (56% [2332 of 4130] versus 53% [2693 of 5090]; p = 0.002) and higher Charlson comorbidity index (CCI) (2.9 ± 0.9 versus 2.8 ± 0.9; p = 0.003). Therefore, a mixed-effects model was used to analyze the ORs for all-cause linked revision with robotic assistance and was adjusted for age, gender, CCI, surgeon, and institution. Subanalyses were performed on indications for revision. A power analysis demonstrated the ability to measure a difference as small as one-half SD between risk of revision within each cohort (specifically, moderate effect sizes based on Cohen d).

Results
After controlling for potentially confounding variables, such as surgeon, location of surgery, and patient comorbidity profile, we found no difference regarding odds of all-cause revision between robotic-assisted and nonrobotic-assisted cementless TKA (OR of robotic-assisted versus nonrobotic-assisted cementless TKA 0.8 [95% CI 0.5 to 1.3]; p = 0.41). There were no differences in reasons for revision between robotic-assisted and nonrobotic-assisted cementless TKA, such as mechanical loosening (OR 3.2 [95% CI 0.8 to 12]; p = 0.09) and infection (OR 1.5 [95% CI 0.8 to 2.6]; p = 0.19).

Conclusion
We found no evidence that robotic assistance improves the odds of cementless implant survival free from revision at 2 years. Importantly, the differences in odds of revision beyond 2 years as a function of robotic assistance in cementless TKA remains unknown and warrants further population-level investigation, but until or unless robotic assistance proves its value in well-designed studies in terms of endpoints that patients can perceive (such as pain, function, or survivorship), we recommend against widespread adoption until further evidence becomes available. Additionally, we encourage surgeons and healthcare facilities using robotic assistance in cementless TKAs to study its impact on patient outcomes, if any.

Level of Evidence
Level III, therapeutic study.