SEATTLE – Postoperative femoral nerve blocks prolong quadricep and hamstring weakness after anterior cruciate ligament reconstruction in young athletes, and delay recovery, according to investigators from the Mayo Clinic in Rochester, Minn.
Because of that, "I’ve stopped using them," said investigator Dr. Amy McIntosh, a pediatric orthopedic surgeon in Rochester.
M. Alexander Otto/Frontline Medical News
Dr. Amy McIntosh
In a retrospective study of patients no older than 18 years, her team found that 68% (42 of 62 patients) who got the block – weight-based bupivacaine HCl in all cases – were cleared for sports at 6 months, meaning that their operated knee was at least 85% as strong as their uninjured knee, and at least 90% as functional. Among children who didn’t get the blocks after anterior cruciate ligament reconstruction (ACL), 90% (56 of 62) were ready to return to sports, a significant difference. Overall, unblocked kids were 4.4 times more likely to be cleared at 6 months.
"Kids who didn’t clear at 6 months usually took another 3-4 months. At a year, everybody looked about the same," Dr. McIntosh said at the American Orthopaedic Society for Sports Medicine annual meeting.
Also at 6 months, kids who got the nerve block had significantly greater mean deficits in fast isokinetic knee extensions, a measure of quadricep strength (17.6% in the operated knee vs. 11.2% in the uninjured knee), and fast (9.9% vs. 5.7%) and slow (13.0% vs. 8.5%) isokinetic flexion, a measure of hamstring strength. It didn’t seem to matter if they got a one-shot femoral nerve block or a continuous pump infusion.
Dr. McIntosh initially lobbied Mayo anesthesiologists to use femoral blocks in kids, opting first for the pump. "Then I saw that those kids had a lot of quad atrophy and were taking a longer time to get off their crutches, so I started going to the one-shot block, but they still had quad atrophy, and took a little longer to get off their crutches and get their normal gait back. Now, after seeing this data, I’m done with it," she said.
She’s not alone. Long considered a benign and effective method for short-term pain control, surgeons have been reconsidering the blocks because of similar findings in adults.
"I tell patients [and parents] that they have to decide if they want great pain control up front, or a little more pain in the first few days after surgery," but a quicker return to sports. When offered the choice, young athletes opt against the block because it will likely mean missing an entire season. "That’s what matters to these kids," Dr. McIntosh said.
The nerve block group and control groups were evenly matched; children in both were about 16 years old, on average, with a mean body mass index of about 24 kg/m2. There were slightly more girls in the study than boys.
Most of the kids in both groups had patellar tendon autografts, and the rest had hamstring autografts. Those who got nerve blocks had shorter tourniquet (82 vs. 93 minutes), operative (134 vs. 155 minutes.), and anesthesia times (177 vs. 200 minutes).
Dr. McIntosh said he had no relevant financial disclosures. The project was funded internally.