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

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.

Inclusion criteria

Patients aged 18 years or older.

Patients with primary or secondary knee osteoarthritis requiring a Total Knee Arthroplasty (TKA).

Patients for whom the surgical planning requires a pre-operative 3D CT scan.

Patients who have been informed about the study and have signed the written informed consent.

Patients affiliated with or beneficiaries of a social security scheme.

Exclusion criteria

Revision Total Knee Arthroplasty (re-operation).

Major bone loss or significant bone deformity that prevents reliable anatomical landmarking.

History of prior knee surgery that could interfere with the navigation system trackers (e.g., retained hardware in the femur or tibia).

Pregnant or breastfeeding women.

Persons deprived of liberty or under legal guardianship.

Patients with a known allergy to any component used during the standard surgical procedure.