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Computer navigation improves surgical accuracy in ACL reconstruction
Literature review and new data show that surgeons place tunnels more accurately with navigation.
HOLLYWOOD, Fla. – Accurate tunnel positioning is crucial in a successful ACL reconstruction, but surgeons may not be placing the tunnels as accurately as they think.
With the number of ACL reconstructions performed each year – 175,000 this past year, according to Jason L. Koh, MD, associate professor of orthopedic surgery, Northwestern University Feinburg School of Medicine in Chicago – and an annual cost of more than $1 billion, the medical community cannot afford many revisions. Still, the American Orthopaedic Society for Sports Medicine reported a 10% to 20% ACL revision rate for 2005, he said.
“Obviously if you have imprecisely placed tunnels, you can have problems with range of motion, instability, synovitis, pain, graft impingement and graft failure,” Koh said. “And it’s also been related to arthritis in the long run and this high revision rate.”
Literature has shown that computer navigation can improve accuracy in ACL reconstruction, total knee reconstruction or hip reconstruction, according to Koh. What’s more, navigation provides surgeons the tools for documenting outcomes and to determine which patients are candidates for double-bundle reconstruction.
“The literature suggests that it’s difficult to obtain a perfect position consistently, even for an expert surgeon,” Koh said. “Intraoperative fluoroscopy may help with some of it, but it doesn’t give Isometer data, it doesn’t give impingement on the lateral wall data, and I would say it’s another piece of equipment and radiation in the room. And so, navigation may be a solution for this type of problem.”
Images: Koh JL |
Rates without navigation
Koh attributed the recent high revision rate to technical errors and poor tunnel placement. Because surgeons are concerned about possibly placing a tibial tunnel too anteriorly, they may end up going a little too posterior, “which can create it’s own set of problems like a too-vertical graft or a graft that actually hinges on the PCL and can cause either laxity or loss of flexion,” Koh said.
He presented navigation studies showing inaccuracy in ACL reconstruction at the Arthroscopy Association of North America 25th Annual Meeting.
In one study by Picard and colleagues, two surgeons performed ACL reconstruction on 20 foam knees. “The femoral tunnel was, on average, off by 4.2 mm from the ideal location,” Koh said. “The tibial tunnel was off by almost 5 mm from the ideal location.”
A British study by Sudhahar and colleagues compared the intraoperative estimates of two surgeons to postoperative X-rays of 32 knees.
“They found that, at least for the tibial tunnel, there was poor correlation of where they actually thought their tunnel was being placed in the medial lateral direction and no correlation in the anterior-posterior direction,” Koh said. Four tunnels, or 12.5%, were in extremely different positions than the surgeon expected.
The navigation systems
For these reasons, some orthopedic surgeons are turning to navigation systems to help them perform ACL reconstructions more accurately. Setting up and using the navigation system, as well as recording the data, is relatively easy, Koh said, and surgeons can still use their standard instruments and standard graft points for fixation.
All navigation systems include a reflective bulb or active markers tracked by an infrared camera, Koh said. He uses the Orthopilot Navigation System (Aesculap AG & Co. KG) because it attaches to the tibia and femur using K-wires, rather than screws.
“You identify extra-articular landmarks … and then you can do a preoperative anterior-posterior (AP) translation at a specified degree of knee flexion,” Koh said. To record the landmarks, surgeons must touch them with a probe and click a foot pedal.
The Orthopilot and other navigation systems also provide rotational data, calculate and define isometry, project the intercondylar notch on the plateau (impingement avoidance) and display impingement. “If there was impingement, it would tell you by how many millimeters, and it would show you red where the impingement was going to occur,” Koh said.
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Postoperatively, the system also indicates any improvement in AP translation and the total arc of motion, he added.
The systems’ cost is variable – and so is reimbursement for using the systems.
“There is a T-code for navigation, and it’s variably reimbursed at the moment, but there is a big effort to try to get additional reimbursement,” Koh said.
Koh presented his own data on navigated ACL surgery in 42 patients. He found a mean tunnel placement sited in the 10:30 to 1:30 positions. All tunnels were placed between 10:00 and 11:00 or between 1:00 and 2:00. “I’m trying to bring it down a little more lateral to obtain better rotational control,” Koh said.
He also found that he improved his tibial tunnel accuracy, placing them more anteriorly.
Koh found that the patients had a 14.97±3.51 mm AP translation preoperatively and an AP translation of 4.89±1.91 mm postoperatively.
“The other important thing [to remember] is that we demonstrated a significant improvement in rotational control using a standard single-bundle reconstruction,” Koh said. “The average rotational arc in the preop group was about 28°. For the postop group, their average rotational arc was about 17°. This perhaps could be even further improved if I dropped my tunnel a little bit more lateral.”
Koh also sees navigation as being extremely helpful in revision cases.
“I think it’s been really helpful for me in complex cases like revisions, or if you’re thinking about doing double-bundle reconstructions or single-bundle reconstructions of partially torn ACLs and ACLs that need to be revised,” Koh said. “And I suspect that in the long run, this may become standard practice.”
For more information:
- Koh JL. Computer navigation in ligament surgery. Presented at the Arthroscopy Association of North America 25th Annual Meeting. May 18-21, 2006. Hollywood, Fla.
- Picard F, DiGioia AM, Moody J, et al. Accuracy in tunnel placement for ACL reconstruction. Comput Aided Surg. 2001;6(5):279-89.
- Sudhahar TA, Glasgow MM, Donell ST. Comparison of expected vs. actual tunnel position in anterior cruciate ligament reconstruction. Knee. 2004;11(1):15-8.
- Dr. Koh has no direct financial interest in the products discussed in this article. He is a paid consultant for Aesculap.