The article authors include Diana Margarita Molinares, MD, Timothy Davis, MD, Daniel Fung, MD, John Chung-Liang Liu, MD, Stephen Clark, Pt, DPT, David Daily, PT, and James Mok, MD. The researchers examined 50 healthy volunteers between the ages of 21 years old and 35 years old who were placed at the 25 degree right lateral jack-knife or the right lateral decubitus position.
Historically, the lateral jack-knife position has been used for direct lateral lumbar fusions to improve access to L4-5 and L3-4 disc space. This is the first paper linking neural compromise and post-positioning nerve deficit to the jack-knife position. The lateral appraoch allows for larger interbody spacers to be inserted which helps with coronal balance of the spine and provides superior indirect decompression posteriorly.
For the study, the patients were in the assigned position for 60 minutes and underwent motor testing immediately after the 60 minutes were up, and every 15 minutes thereafter, five times.
The researchers found:
1. Motor deficits were observed in the non-dependent lower limb for all patients in the 25 degree right lateral jack-knife group, and none of the patients in the right lateral decubitus position group.
2. There were statistically significant differences found between the two groups in the 10-repetition maximum test immediately after the 60 minutes were over and 60 minutes after positioning.
3. The 25 degree right lateral jack-knife group reported 10 percent to 70 percent — with an average of 34.8 percent — decrease in knee extension strength. They reported a 20 percent to 80 percent — with an average of 43 percent — decrease in hip flexion strength in the nondependent limb.
4. Nearly all — 98 percent — of the patients in the 25 degree right lateral jack-knife group had sensory abnormalities and 36 percent of the patients still exhibited sensory deficits after the 60-minute recovery period.
5. None of the participants reported symptoms during the follow up calls seven days after positioning.
“Twenty-five degrees of right lateral jack-knife positioning for 60 minutes results in neurapraxia of the nondependent lower extremity. Our results support the hypothesis that jack-knife positioning alone can cause postoperative neurological symptoms,” concluded the study authors.
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