Is It Possible to Obtain Reliable MPTA and LDFA Values Using Imageless Navigation in Total Knee Arthroplasty? Comparison Between Preoperative CT Scan Measurements and Intraoperative Bone Morphing Before and After Articular Cartilage Removal (CAR-NAV-AL)

Background:

Accurate alignment is critical for the long-term success of Total Knee Arthroplasty (TKA). Newer robotic and navigated systems rely on bone morphing to define the patient's anatomy per-operatively. However, the impact of cartilage thickness and the intrinsic accuracy of these systems compared to 3D CT-based planning remain subjects of clinical interest.

Objectives:

The primary objective is to compare the Medial Proximal Tibial Angle (MPTA) and the Lateral Distal Femoral Angle (LDFA) measured by:

Preoperative CT scan (Reference standard).

Peroperative image-less navigation (bone morphing) with intact cartilage.

Peroperative image-less navigation (bone morphing) after cartilage removal.

Methodology:

This is a prospective, monocentric, interventional study. All included patients will undergo a standard preoperative 3D CT scan as part of the surgical planning. During the TKA procedure, the surgeon will use the navigation system to perform bone morphing at two specific stages:

Initial stage: On the joint surface with the cartilage still present.

Secondary stage: After the surgical removal of the articular cartilage.

Comparison:

The data collected peroperatively will be compared to the CT scan measurements. The study will evaluate the "fidelity" (accuracy) of the navigation system and analyze whether the presence or absence of cartilage significantly alters the reliability of the digital bone model created by the system.

Expected Outcomes:

The results will help determine the degree of confidence surgeons can place in imageless navigation for achieving precise anatomical alignment without the systematic use of preoperative 3D imaging.