A Novel Vector-Based Computer Tomography Alignment Measurement Protocol for Total Knee Arthroplasty

Area of Science:

• Orthopaedic surgery
• Medical imaging analysis
• Robotic surgery

Background:

• Total knee arthroplasty (TKA) component alignment impacts implant survival and outcomes.
• Computer tomography (CT) scans offer benefits over standard X-rays for joint assessment.
• A postoperative CT measurement protocol for robotic-arm assisted TKA (RATKA) was previously undefined.

Purpose of the Study:

• To assess the validity of a novel, vector-based CT alignment measurement protocol for RATKA.
• To compare final versus planned component alignment and placement.
• To evaluate inter-observer and intra-observer reliability of the CT protocol.

Main Methods:

• A CT-based technique using mathematical models calculated prosthetic alignments from anatomical landmarks.
• 30 postoperative CT scans from RATKA patients were analyzed using the proposed technique.
• Inter-observer and intra-observer reliability were assessed through repeated analyses.

Main Results:

• Mean measurement errors for component alignment and placement were low, with statistically significant differences noted for overall limb alignment (p=0.004).
• Femoral and tibial alignments showed minimal varus/valgus and flexion/slope errors.
• High reproducibility between observers and low variability (slopes 0.8-1.0, R>0.8) were observed.

Conclusions:

• A novel vector-based CT alignment measurement protocol for RATKA was successfully defined.
• The protocol demonstrated excellent accuracy in verifying planned component alignment and placement.
• The method offers a valuable tool for assessing component accuracy in RATKA studies using postoperative CT images.