Navigational and Conventional UKA: The differences
Arthritis is one of the top diseases that plagues the aging population; with osteoarthritis being the main assailant. Although sometimes mild, this disease can quickly turn into a painful menace that inhibits daily activities.
One type of osteoarthritis that often leads to meniscal disruption, ligament instability, or limb deformity is unicompartmental arthritis. This subset of arthritis affects only one compartment of the joint, and it usually attacks the articular cartilage in the medial or lateral part of the tibiofemoral joint.
When unicompartmental arthritis hits the advanced stages and surgery becomes necessary, patients have to choose between unicompartmental knee arthroplasty (UKA) and total knee arthroplasty. UKA has recently become the preferred method due to its 10-year survival rate of 95%.
Now that computer navigated UKA was been implemented, some studies have tried to exemplify the difference between conventional UKA and computer navigated UKA; however most show little statistical difference.
A recent study published in the Journal of Arthroplasty aimed to show the statistical difference between the two surgeries. To do so the study focused on using similar instrumentation for both surgeries, and then compared the radiologic and clinical results and survival rate after an average 9 year follow up period.
The study hypothesized that the navigational UKA would result in better limb alignment and implant position, along with better clinical outcomes and an improved survival rate, as compared to the conventional UKA.
The patients monitored in the study had a range of predominant medial compartment pain usually attributed to arthritis, and isolated medial compartment arthritis managed by medial unicompartmental arthroplasty. In the end 68 patients were divided up, half receiving navigational UKA and half receiving conventional UKA.
To minimize variation the same surgeon performed all of the surgeries. Patients also received very similar surgical procedures; with the exception that one utilized the computer navigation system. Each patient also underwent the same postop rehabilitation protocols. Postoperative clinical and radiographic assessments were then performed at 6 and 12 months followed by annual doctor visits.
Clinical visits were performed pre- and postoperatively to check range of motion, osteoarthritis index scores, and pain scores. The radiographic exams were also performed pre- and postoperatively and included anteroposterior and lateral radiographs of the knee and full-length weight-bearing radiographs. These clinical and radiographic exams were crucial in determining the alignment, positioning, and survival rate of the prosthesis.
When looking at the radiographic results it is clear that there was little variation between the navigational and conventional groups in relation to alignment and positioning. However, there were more outliers and more postoperative complications in the conventional group than in the navigational group. Opposite to the radiographic results, the clinical results did show a significant difference in the osteoarthritis index scores and pain scores. There were also more revisions required in the conventional group than the navigational group.
Overall the study was only slightly more successful at determining which type of surgery is better long-term. Although the navigation system showed improved radiographic outcomes to reduce outliers, no consensus can be reached about whether navigational UKA has long-term benefits over conventional UKA. Although the study exemplified better clinical outcomes for the navigational group, there was only a slight difference in the 10-year survival rate in favor of navigation UKA, 97.1% compared to 94.1%.
Furthermore, because the study showed that there were less outliers in the navigational group, it can be assumed that the accuracy of implantation is improved when navigation is used.
The most significant difference in this study was shown in the clinical results. The navigational group showed much better osteoarthritis index scores and pain scores than the conventional group. These results suggest that higher accuracy of implantation and better alignment go hand in hand with clinical outcomes.
As expected, the navigational UKA helped improve accuracy and positioning of the prosthesis, and it helped reduce the number of outliers. However, it cannot be concluded that navigational UKA is significantly better than conventional UKA. In fact, more studies are needed to give the results found in this study more significance.
Healy, William L., and Richard Iorio. “Unicompartmental Arthritis of the Knee | The Journal of Bone & Joint Surgery.” Unicompartmental Arthritis of the Knee | The Journal of Bone & Joint Surgery. The Journal of Bone & Joint Surgery.
Kyoo Song, Eun, Mohite N, Seung-Hun Lee, Bo-Ram Na, and Jong-Keun Seon. “Comparison of Outcome and Survival After Unicompartmental Knee Arthroplasty Between Navigation and Conventional Techniques with an Average 9-Year Follow-Up.” The Journal of Arthroplasty 31.4 (2015): 395-400.