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Study finds inherent risk for nerve injury with RF cautery in primary cruciate substituting TKA
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Three statistically significant risk factors for developing postoperative neuropathy when using intraoperative saline-irrigated bipolar radiofrequency hemostasis for total knee arthroplasty are female gender, low body mass index, and those with rheumatoid arthritis, according to a retrospective review comparing hemostasis with this device to electrocautery.
“Our study found inherent, but low risk of nerve injury,” said principal investigator Steven T. Lyons, MD, a staff orthopedic surgeon at Florida Orthopedic Institute in Tampa, Fla., who pointed out that many other physicians use bipolar radiofrequency (RF) for hemostasis successfully without similar findings. “I think it’s not a problem with the device as much as it is a problem with technique,” said Lyons.
Reasons unclear
Lyons said he has no idea why these three factors pose a risk. “But a fourth risk factor, which is probably the largest risk factor and the common thread in all my patients during total knee replacement, is the complete removal of the posterior cruciate ligament,” Lyons told Orthopedics Today. “This exposes the posterior compartment of the knee a lot more. Anatomically, the tibial nerve is right behind the posterior compartment of the knee, where we treat with the RF device. Therefore, I think it is prudent to use extreme caution, specifically in the center of the knee, when cauterizing using the RF device.”
 Bipolar radiofrequency (RF) being used just posterior to the intercondylar notch. Images: Lyons ST |
Prior to 2007, Lyons had not encountered this kind of nerve injury complication in his patient database. “It was a very specific type of injury, if you will – limited to a numbness on the bottom of the foot,” he said. A few of the complaints were associated with foot drop, “but most were simply random numbness on the bottom of the foot. Because this was a bit out of the ordinary from what I normally witness, I tried to determine the new modifier that could have caused this.”
Comparative review
The only new modality Lyons had introduced in 2007 was bipolar RF hemostasis, which he deployed for total knee replacement between July 2007 and October 2008. For the review, he compared his 241 consecutive cases of integrated saline/RF energy during this time period with his previously 241 consecutive primary TKR cases of electrocautery to achieve hemostasis conducted between October 2006 and July 2007. The two groups were demographically and clinically comparable.
 RF treatment used in the posterior compartment of the knee. |
Outcomes were presented at the annual meeting of the American Academy of Orthopaedic Surgeons (AAOS) in New Orleans. Overall, 3.73% (nine of 241 cases) in the RF group had neuropathies documented by electromyography (EMG). Furthermore, 14% of the RF group had sensory changes in the medial plantar nerve, 29% had problems with the lateral plantar nerve, and 57% had the entire bottom of the foot affected.
“No nerve injuries occurred in the comparison group,” Lyons said. Conversely, no vascular injuries were detected in the RF group.
“Among thin, females with rheumatoid arthritis, one needs to tread very carefully using a bipolar RF device in the back of the knee to cauterize for hemostasis,” said Lyons, a clinical assistant professor of orthopedics at the University of South Florida, who no longer routinely uses bipolar RF cautery for hemostasis in knees, but does for hips. “However, I will use RF in knees of patients who are Jehovah’s Witnesses, patients who are anemic, or have conditions to prevent significant blood loss.” – by Bob Kronemyer
References:
- Lyons, ST; Morrison, K. Sensory neuropathy associated with cauterization using bipolar radio frequency device in primary TKA. Paper 162. Presented at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons. March 9-13. New Orleans.
- Steven T. Lyons, MD, Florida Orthopedic Institute, 7171 N. Dale Mabry Highway, Suite 502, Tampa, FL 33614; 813-936-5075; e-mail: slyons14@gmail.com.
