Summary

Robotic-assisted TKAs obtained adequate patellar alignment, with patellar height, inclination, translation, and joint line within the values established in the literature.

Abstract

Introduction

Robotic assistance has revolutionized knee arthroplasty surgery, allowing greater precision in the positioning of the femoral and tibial components, however, it does not directly assist patellar positioning.

Objective

Evaluate patellar alignment in robotic-assisted total knee arthroplasty (TKA) to correlate whether the greater precision in the femoral and tibial components translates into correct patellar alignment. Our hypothesis is that robotic-assisted total knee arthroplasty with patellar resurfacing allows adequate patellar alignment in the axial, coronal, and sagittal axes.

Methods

Retrospective cohort study. 50 patients who underwent TKA with robotic arm assistance in the same center by 2 surgeons were included. Patients had postoperative radiographs taken at least 3 months after their surgery. Patients with poorly taken radiographs were excluded. The pre- and post-operative X-rays were analyzed to perform the following evaluations of patellar alignment: Tilt, translation, height (measured with modified Insall-Salvati and Caton-Deschamps) and the level of the joint line (according to the references of the adductor tubercle and medial epicondyle). All evaluations were performed by a musculoskeletal radiologist. A descriptive analysis of postoperative patellar alignment was carried out and compared with reference values established in the literature.

Results

The X-rays were performed on average 3.5 months postoperatively, with an average flexion of 36° (3°) in the lateral X-ray and 32° (2°) in the axial X-ray. Patients had an average patellar height measured by Insall-Salvati of 1.5 ( 0.14) (normal value = 1.2–2.1), Caton-Deschamps 0.86 ( 0.17) (normal value = 0.6-1.2). The average patellar tilt was 5° (7.6) (normal value = <5°). The average translation was 4.3 mm (4.76) (normal values = <5mm). A maintenance in the height of the joint line was obtained (compared to the preoperative X-ray) with an average variation in distance from the adductor tubercle of 2.2mm (normal value = <4mm) and average variation in lateral epicondyle distance of 5.2mm (normal value = <8mm).

Conclusions

Robotic-assisted TKAs obtained adequate patellar alignment, with patellar height, inclination, translation, and joint line within the values established in the literature.