Computer or No Computer for Minimally Invasive Surgery
For a long time orthopedic surgeons have turned to the medial parapatellar approach for total knee arthroplasty. In other words, the most commonly used total knee replacement is often an invasive procedure, coupled with long hospital stays and lengthy rehabilitation. However, this methodology is changing. In today’s world where people want better results faster, surgeons are now facing pressure to perform surgery using minimally invasive techniques.
The idea behind minimally invasive surgery (MIS) for total knee arthroplasty is that there will be less recovery time, shorter hospital stays, and smaller scars. However, there is some concern about the minimal visibility that comes with this type of surgery. The more conventional parapatellar surgery involves large incisions that give the surgeon maximum visibility. In comparison, the minimally invasive technique utilizes much smaller incisions, which limits visibility. Thus, a computer assisted MIS has been created to decrease the potential for error.
The claim is that the minimally invasive computer assisted technique (MIS CA) has many benefits over normal minimally invasive technique that does not utilize computer navigation.
To test this claim, a study recently published in the Journal of Arthroplasty examined “the number of mechanical axis outliers and tibial and femoral component coronal axis outliers in postoperative radiographies or computed tomographic scans.” The study defines outliers as more than 3 degrees of deviation for neutral alignment. Also used to measure which technique is better were parameters like: length of surgery, complications, knee flexion, Knee Society scores, and Knee Society functional scores 6 months after the operation.
As one would expect, the study demonstrated that there were many more outliers in the coronal plane tibial component and mechanical axis when the MIS was performed WITHOUT the computer navigation. It will take long term outcome studies over 10-15 years to show improved longevity with navigated knees. This is the expected result of better alignment.
The length of surgery was prolonged for navigated cases in a teaching hospital by as much as 30 minutes. In an experienced surgeons’ practice, navigation adds 5-7 minutes to the surgery time.
There were no significant differences in complications between the groups.
As for the remaining parameters, knee flexion, Knee Society scores, and Knee Society functional scores, six months after the operation, no statistically significant difference was determined based on the different types of MIS surgery.
Making sense of it all
So, based on this study what conclusions can we come to?
The use of MIS surgery and multimodal pain control has decreased the average length of hospital stays after total knee replacement surgery. The average hospital stay has gone from 4 days down to 1.5 days with 20% of patients going home the same day as surgery. The average return to work has gone from 6 weeks post op to 4 weeks post op. If this short term improvement came at the cost of poor alignment and compromised longevity it would not be worth it. With navigation and MIS surgery both short term recovery and expected long term survival are enhanced.