Computer-Assisted Surgery Practice Questions

Q: A study compares outcomes of computer-navigated versus conventional total knee arthroplasty. Navigation group shows 95% implants within 3 degrees of neutral mechanical axis versus 80% in conventional group (p<0.05). However, 5-year functional outcomes and survival rates are similar. What is the most appropriate interpretation?

Improved radiographic alignment may not translate to short-term functional improvement but could affect long-term survival. ***Improved radiographic alignment may not translate to short-term functional improvement but could affect long-term survival*** - Navigation significantly improves **radiographic alignment** consistency (p<0.05), but high-quality evidence shows this does not always create immediate **functional differences** within 5 years. - While **short-term functional outcomes** are similar, reducing **outliers** to within 3 degrees of the neutral axis is theoretically linked to better **implant survival** beyond 10-15 years. *Navigation is inferior due to longer operative time without functional benefit* - Increased **operative time** is a known drawback, but it does not make the technique **inferior** if it achieves superior technical precision. - The term "inferior" is clinically inaccurate here as the study demonstrates **statistically significant** improvements in surgical accuracy. *Conventional technique should be abandoned* - **Conventional techniques** are still the gold standard because they provide identical **short-term survival** and clinical scores at a lower cost. - Abandonment is unjustified as long as the **clinical outcome** parity exists and long-term superiority of navigation is not yet definitively proven by this data. *The study proves navigation provides no clinical benefit* - Improved **mechanical axis** alignment is itself a technical clinical benefit that reduces mechanical stress on the polyethene liner. - A lack of difference in **5-year scores** does not prove a lack of benefit; it only indicates that **short-term follow-up** may be insufficient to detect long-term wear advantages.

Q: During computer-navigated total hip arthroplasty, the navigation system shows 38 degrees of cup abduction and 18 degrees of anteversion. However, the surgeon's visual assessment suggests more abduction. Intraoperative fluoroscopy confirms navigation data. What is the most likely cause of this discrepancy?

Incorrect pelvic tilt registration affecting surgeon's visual perception. ***Incorrect pelvic tilt registration affecting surgeon's visual perception*** - Visual assessment in total hip arthroplasty is highly susceptible to **pelvic tilt**; a change in tilt can dramatically alter the surgeon’s perception of **cup abduction** and **anteversion**. - Since **fluoroscopy** (an objective imaging tool) confirms the **navigation data**, the discrepancy must originate from a subjective error in visual judgment caused by the patient's physical orientation. *Navigation system calibration error* - While calibration errors can occur, they would not be consistent with **intraoperative fluoroscopy** confirmation of the navigation data. - Modern systems use rigid **registration points** that usually trigger an alert if the tracking integrity or calibration is lost. *Electromagnetic interference from surgical equipment* - Electromagnetic interference typically causes **tracking jitter** or signal loss rather than a stable, plausible-looking but incorrect numerical reading. - If interference were present, the navigation data would likely appear inconsistent or fail to correlate with the **fluoroscopic images**. *Fluoroscopy machine malfunction* - It is highly unlikely for a fluoroscopy machine to malfunction in a way that perfectly correlates with an incorrect navigation reading; instead, it serves as the **gold standard** for confirming implant position. - A malfunction would usually involve **imaging artifacts** or failure to capture images rather than providing a misleadingly precise anatomical visualization.

Q: A 55-year-old patient is scheduled for computer-assisted pedicle screw placement in lumbar spine. During registration, the navigation system shows a registration error of 3.5 mm. What should be the surgeon's action?

Re-register the anatomy to reduce error. ***Re-register the anatomy to reduce error*** - In **computer-assisted navigation**, a registration error exceeding **2.0 mm** is considered clinically unacceptable and unsafe for screw placement. - The surgeon must perform **re-registration** to identify potential issues such as loose **reference frames**, patient movement, or poorly chosen anatomical landmarks. *Switch to freehand technique* - While the freehand technique is an alternative, the primary goal of using navigation is to enhance **accuracy**; one should first attempt to troubleshoot the system before abandoning it. - Reverting to freehand without attempting to fix the navigation error ignores the potential benefits of **intraoperative imaging** already obtained. *Proceed with surgery as error is acceptable* - A **3.5 mm error** is significantly above the safety threshold and increases the risk of **pedicle breach**, nerve root injury, or vascular complications. - Proceeding with such high **deviation** defeats the purpose of precision-guided surgery and compromises patient safety. *Increase the screw diameter to compensate* - Increasing the **screw diameter** is dangerous and counterintuitive, as it would likely lead to a structural **pedicle wall blowout** if the trajectory is slightly off. - Accuracy must be maintained through **spatial alignment**, not by altering hardware size to cover up for navigation inaccuracies.

Question 1

A surgeon experiences pin-site fracture during reference array fixation in computer-navigated TKA in an osteoporotic patient. Subsequently, three more cases develop similar complications. What systematic approach should be implemented to prevent this complication?

Accepted Answer

Use unicortical pins instead of bicortical pins with reduced insertion torque protocol

Answer

Switch to electromagnetic navigation system

Answer

Abandon navigation in all osteoporotic patients

Answer

Increase pin diameter for better fixation

Question 2

A tertiary care center is planning to implement computer-assisted surgery program for joint replacement. They have limited budget and expertise. Which factor should be prioritized when selecting a navigation system?

Accepted Answer

Imageless navigation with good technical support and training program

Answer

Image-based system requiring dedicated CT scanner

Answer

Most expensive system with all features available

Answer

System with steepest learning curve to ensure only expert surgeons use it

Question 3

A study compares outcomes of computer-navigated versus conventional total knee arthroplasty. Navigation group shows 95% implants within 3 degrees of neutral mechanical axis versus 80% in conventional group (p<0.05). However, 5-year functional outcomes and survival rates are similar. What is the most appropriate interpretation?

Accepted Answer

Improved radiographic alignment may not translate to short-term functional improvement but could affect long-term survival

Answer

Navigation is inferior due to longer operative time without functional benefit

Answer

Conventional technique should be abandoned

Answer

The study proves navigation provides no clinical benefit

Question 4

During computer-navigated total hip arthroplasty, the navigation system shows 38 degrees of cup abduction and 18 degrees of anteversion. However, the surgeon's visual assessment suggests more abduction. Intraoperative fluoroscopy confirms navigation data. What is the most likely cause of this discrepancy?

Accepted Answer

Incorrect pelvic tilt registration affecting surgeon's visual perception

Answer

Navigation system calibration error

Answer

Electromagnetic interference from surgical equipment

Answer

Fluoroscopy machine malfunction

Question 5

A 55-year-old patient is scheduled for computer-assisted pedicle screw placement in lumbar spine. During registration, the navigation system shows a registration error of 3.5 mm. What should be the surgeon's action?

Accepted Answer

Re-register the anatomy to reduce error

Answer

Switch to freehand technique

Answer

Proceed with surgery as error is acceptable

Answer

Increase the screw diameter to compensate

Computer-Assisted Surgery — MCQs

Computer-Assisted Surgery — MCQs

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