What is the procedure that uses a computed tomography (CT) scan for knee replacement, considered to have better outcomes compared to traditional knee replacement surgery?

CT-Based Navigation for Total Knee Arthroplasty

The procedure that uses CT scans for knee replacement is called CT-based navigation for total knee arthroplasty (TKA), which aims to improve component positioning but has not consistently demonstrated superior clinical outcomes compared to conventional techniques.

Understanding CT-Based Navigation for TKA

• CT-based navigation is a computer-assisted surgery (CAS) technique that uses computed tomography imaging to guide the precise placement of knee replacement components 1
• This technique helps surgeons achieve more accurate alignment of the prosthetic components by providing real-time feedback during surgery 1
• CT is particularly useful for assessing rotatory alignment of prosthesis components, which is critical for proper knee function 1

How CT-Based Navigation Works

• Pre-operative CT scans of the patient's knee are obtained and loaded into a computer system 2, 3
• During surgery, the system creates a virtual model of the patient's knee and tracks surgical instruments in relation to the patient's anatomy 3
• The navigation system provides real-time feedback to the surgeon about component positioning, allowing for adjustments to achieve optimal alignment 1, 3

Purported Benefits vs. Evidence

• Proponents claim CT-based navigation improves implant alignment and reduces outliers (components positioned >3° from ideal alignment) 4, 3
• However, research shows mixed results regarding clinical benefits:
  • Studies have found no statistically significant difference in prosthesis alignment between CT-navigated and conventional TKA 5
  • The number of outliers was not consistently decreased with navigation 5, 6
  • No significant differences in short-term clinical outcomes have been found between navigated and conventional TKA 6

Clinical Outcomes

• Functional outcomes as measured by Knee Society Scores show no statistically significant difference between CT-navigated and conventional TKA at follow-up periods 5, 6
• Patient satisfaction does not consistently favor CT-navigated procedures; in one study, 40.6% of patients preferred their conventionally-aligned knee versus 21.9% who preferred their computer-assisted knee 5
• Complication rates are similar between CT-navigated and conventional TKA 6

Limitations and Considerations

• CT-based navigation typically requires longer surgical time compared to conventional techniques 6
• The technique has a learning curve of approximately 16 cases before a surgeon can reproduce results comparable to experienced surgeons 4
• CT-based navigation is more expensive and time-consuming than conventional techniques 2
• Metal artifacts from implants can limit the usefulness of CT for post-operative evaluation 1

Alternative Imaging Approaches

• Newer CT technology with metal artifact reduction techniques may expand the utility of CT for evaluation of TKAs 1
• Ultrasound can be used effectively to evaluate soft tissues around the knee without metal artifact interference 1
• MRI has higher soft-tissue contrast resolution than CT and may be superior for assessing soft-tissue complications, though it is limited by metallic susceptibility artifacts 1

Post-Operative Imaging Recommendations

• Radiographs remain the initial imaging modality of choice for routine follow-up of TKA patients 1
• CT may be used to assess rotatory alignment of prosthesis components and to reveal changes in surrounding bone not apparent on radiographs 1
• For suspected periprosthetic soft-tissue abnormalities, MRI without contrast or ultrasound are the preferred imaging modalities 1