Computer navigation may avoid TKA component placement errors, revisions

Surgeon finds navigation helps with complicated cases, but adds nearly 15 minutes operative time.

Issue: August 2008

Findings from retrievals and meta-analyses support using computer navigation during total knee arthroplasty to minimize long-term failures.

According to Douglas A. Dennis, MD, navigating total knee arthroplasty (TKA) improves component alignment and may reduce polyethylene wear and late component loosening. “There are now numerous published articles in the literature that clearly document improved component position and alignment with the use of computer-assisted navigation,” he said at the American Academy of Orthopaedic Surgeons 75th Annual Meeting.

Among the positive aspects of navigation Dennis discussed were: computer-assisted TKA is associated with reduced intraoperative blood loss compared to standard techniques; it allows for precise titration of ligamentous releases; it does not require cannulation of the intramedullary (IM) canal, which reduces the risk of intracranial embolization; and it is very helpful in cases with intramedullary deformity where the use of conventional instrumentation is not possible as with fracture malunions, fracture hardware etc.

Among the negatives: It increases time in the operating room.

“A literature review showed that computer navigation adds 9 to 15 minutes to TKA cases,” Dennis told Orthopedics Today. He explained that the added time is worth it because the system generates information that is valuable for soft tissue gap balancing and symmetry.

This patient’s left total knee arthroplasty was performed with computer navigation and showed excellent alignment along the mechanical axis. However, the right knee operated on with a standard technique had slight varus alignment relative to the mechanical axis.

This patient had a distal femoral osteotomy prior to computer-assisted TKA and needed only limited intraoperative hardware removal. The final alignment was excellent without performing a repeat osteotomy, surgeons said.

Varus stress at 9° is applied to the knee via computer navigation. It demonstrates passive correctability of the deformity and informs the surgeon that limited medial soft tissue releasing will be required.

Images: Dennis DA

Safer surgery

Numerous reports have documented that malalignment is associated with numerous adverse problems such as premature component loosening and polyethylene wear. Dennis contends that computer assistance can help surgeons optimally place components, and therefore dramatically reduce the risk of malalignment and other postoperative complications.

He cited a meta-analysis of reports on 3,500 post-TKA patients by Fehring and colleagues. They looked at component alignment relative to the mechanical axis and found a 9% rate of malalignment of 3° or more when computer navigation was used vs. 32% without it.

Dennis said, “I believe it can also add safety, as well as accuracy to minimally invasive surgery where conventional visualization is often impaired.”

One study of 108 knees randomized for minimally invasive TKA with computer navigation vs. TKA performed with a standard approach without computer navigation found good radiographic alignment in 92% of MIS navigated cases vs. 68% of cases performed using conventional means.

“Even more importantly, they were able to perform all of these minimally invasive surgeries … without major complications,” he said.

Proficiency with computer-assisted TKA can improve overall results and speed up the learning curve, Dennis added. “It is, however, an evolving technology and I think we can see increased efficiency and reduced costs in the future.”

Immediate assessment

Dennis discussed one case where computer assistance helped him decide whether an osteotomy would correct a 54-year-old woman’s knee deformity to neutral or if TKA alone might achieve the needed correction. She had a varus distal femoral osteotomy more than a decade ago and presented with a residual deformity.

“The computer can provide you with immediate and accurate assessment on the passive ability to correct the deformity and the amount of medial collateral ligament release that will be required,” Dennis explained.

Had he decided to do an osteotomy in this case, the computer would have been helpful in determining the magnitude of symmetric intra-articular osseous resection that would have been needed to correct the deformity.

“This was certainly helpful to perform this case and obtain good alignment without the need for corrective osteotomy,” he noted.

For more information:

Douglas A. Dennis, MD, can be reached at Colorado Joint Replacement, 2535 S. Downing St., Suite 100, Denver, CO 80210; 720-524-1367; e-mail: kslutsky@co-ortho.com. He receives research support, miscellaneous funding and royalty payments from, and is a consultant to DePuy, a Johnson & Johnson Company and receives research support and miscellaneous funding from Zimmer and Ceramatec.

References:

Dennis DA. Computer assisted navigation. Symposium C: Technical tips and innovation for total knee arthroplasty. Presented at the American Academy of Orthopaedic Surgeons 75th Annual Meeting. March 5-9, 2008. San Francisco.

Fehring TK, Mason JB, Moskal J, et al. When computer-assisted knee replacement is the best alternative. Clin Orthop Relat Res. 2006;452:132-136.