Total knee arthroplasty after anterior cruciate ligament reconstruction with the use of image-based robotic technology and functional alignment

Abstract

Background: Total knee arthroplasty (TKA) in patients with prior anterior cruciate ligament reconstruction (ACLR) presents unique challenges due to altered knee kinematics, residual instability, and fixation implants that may interfere with implant positioning. Image-based robotic-assisted TKA enables the functional alignment (FA) strategy that accounts for individual bony anatomy, ligamentous laxities, and anterior compartment characteristics.

Surgical technique: This technique involves a CT-based robotic workflow where femoral and tibial components are planned based on patient-specific alignment and soft tissue balance. Intraoperative assessment with a digital tensioning device guides fine-tuning of flexion and extension gaps, ensuring balanced implant positioning while minimizing soft tissue releases. Fixation implants from prior ACLR are identified using robotic navigation, allowing for targeted adjustments such as selective removal or controlled elevation of components to avoid excessive bone loss. Patellar tracking is dynamically evaluated with a probe, facilitating real-time adjustments to optimize mediolateral tracking and anterior offset.

Discussion: Given the altered biomechanics in post-ACLR knees, FA may provide a physiological alignment by accommodating native laxities and reducing the risk of residual instability. Additionally, robotic guidance allows for precise management of fixation implants, ensuring optimal implant positioning and bone preservation. While further studies are needed, robotic-assisted FA represents a promising approach for enhancing outcomes in TKA for post-ACLR patients.

Keywords: Functional alignment; Functional knee positioning; Personalized alignment; Robotic knee; Total knee.

Figure 1

Intraoperative identification of the tibial fixation staple using the image-based robotic system. The robotic probe is utilized to locate the fixation staple, which was entirely covered by bone and not visible through direct visualization. The system provides real-time spatial feedback, displaying the distance to the bone and mapping reference points for accurate positioning. The inset image on the right shows the corresponding CT scan with the staple’s location, ensuring precise intraoperative identification.

Figure 2

Intraoperative verification of tibial component rotation using robotic guidance. The rotation of the tibial implant is assessed with reference to Akagi’s line. The use of the probe ensures accurate rotational positioning before final implantation.

Figure 3

Preoperative planning of the femoral component and boxing cut using an image-based robotic system. CT-based imaging was utilized to precisely position the femoral implant while ensuring the cutting box aligned with the head of the femoral fixation screw. The robotic system provided detailed visualizations in transverse, coronal, and sagittal planes.

Figure 4

Intraoperative verification of the mediolateral positioning of the femoral implant using a robotic-assisted system. The robotic probe was utilized to confirm the precise mediolateral placement of the femoral component before proceeding with the box cut. This step ensured accurate localization of the femoral fixation screw head, preventing blind bone removal and allowing for a controlled resection while preserving bone stock.