Background Cryoneurolysis of peripheral nerves uses localised intense cold to induce a prolonged block over multiple weeks that has the promise of providing potent analgesia outlasting the duration of postoperative pain following surgery, as well as treat other acute and chronic pain states. However, it remains unclear whether persistent functional motor deficits remain following cryoneurolysis of mixed sensorimotor peripheral nerves, greatly limiting clinical application of this modality. To help inform future research, we used a rat peroneal nerve injury model to evaluate if cryoneurolysis results in persistent deficits in motor function.
Methods Male Lewis rats (n=30) had their common peroneal nerves exposed bilaterally at the proximal lateral margin of the knee and subsequently underwent cryoneurolysis on one limb and sham treatment on the contralateral limb. Outcomes were evaluated on days 3, 14, 30, 90 and 180. The primary end point was motor function, based on ankle dorsiflexion torque. In addition, sensory function was tested based on von Frey’s filament sensitivity to the peroneal sensory distribution. A subset of animals was sacrificed following functional testing at each time point, and general tissue morphology, connective tissue deposition, and axon counts were evaluated.
Results Motor deficits in treated limbs were observed at 3 and 14 days but had resolved at time points beyond 1 month. Bilateral sensory deficits were also observed at 3 and 14 days, and also resolved within 1 month. Consistent with motor functional deficits, axon counts trended lower in treated nerves compared with contralateral controls at 3 days; however, axon counts were not significantly different at later time points.
Conclusions When applied to a mixed sensorimotor nerve, cryoneurolysis did not result in persistent motor deficits.
- interventional pain management
- postoperative pain
- acute pain
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Contributors SS: Planning, design, conduct, acquisition of data, data analysis and interpretation, and manuscript preparation. SB, ME, SD, EO, CH: Conduct, acquisition of data and manuscript revision. BMI: Conception, planning, design, data interpretation and manuscript preparation. RAG: Planning, design, conduct, data interpretation and manuscript revision. SW: Conception, planning, design, conduct, data interpretation and manuscript revision.
Funding Funding and equipment for this project provided by Epimed International (Farmers Branch, Texas).
Competing interests SS: The following companies have provided material and/or funding for his research directly to SS’s institution: Epimed International (Farmers Branch, Texas). BMI: The following companies have provided material and/or funding for his research directly to BMI’s institution: Epimed International (Farmers Branch, Texas); Myoscience (Fremont, California); SPR Therapeutics (Cleveland, Ohio); Infutronics (Natick, Massachusetts); Ferrosan Medical (Szczecin, Poland); and Heron Pharmaceuticals (San Diego, California). RAG: The following companies have provided material and/or funding for his research directly to RAG’s institution: Epimed International (Farmers Branch, Texas); Myoscience (Fremont, California); SPR Therapeutics (Cleveland, Ohio); Infutronics (Natick, Massachusetts); and Ferrosan Medical (Szczecin, Poland). SW: The following companies have provided material and/or funding for his research directly to SW’s institution: Epimed International (Farmers Branch, Texas); DelNova Inc (Chicago, IL).
Patient consent for publication Not required.
Ethics approval All animal work was prospectively approved by the University of California, San Diego Institutional Animal Care and Use Committee (La Jolla, California).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request from the authors. Please contact SS, PhD (firstname.lastname@example.org).
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