History of Cryoanalgesia
Cold has been used to relieve pain since the days of Hippocrates in ancient Greece. Modern cold therapy, or cryoanalgesia, has been around since the 1950s and is a trusted technology for treating pain.
Cryoanalgesia (also known as cryoneurolysis) is the destruction of the signal carrying parts of a nerve. It is a small subset of treatments under the broad umbrella of cryotherapy.
Until now, traditional cryotherapy treatments were invasive and used large complicated machines.
The iovera° system has innovated the delivery of cryoanalgesia. With the iovera° system, healthcare providers are able to deliver a concentrated, focused cold zone only to the targeted nerve through a handheld device. This procedure is well tolerated and from animal studies does not damage or destroy the surrounding tissue.2
Cryoanalgesia with the iovera° system
To understand how cryoanalgesia is achieved with the iovera° system, it is important to first understand the varying degrees of nerve injury and the temperatures at which they occur. Sunderland described and classified the basic types of nerve injuries to assist in the prognosis and treatment strategy for these injuries.3,4
Sunderland Nerve Injury Classification4–6
Neuropraxia – interruption of conduction; Short recovery time
|+10°C to -20°C|
Axonotmesis – Loss of continuity of the axon; Wallerian degeneration; preservation of endo- peri- and epineurium
|-20°C to -100°C|
Neurotmesis – Loss of continuity; Some loss of continuity of epineurium and perineurium; endoneurium may or may not be disrupted (ie, liquid nitrogen)
|-140°C and colder|
Not possible with the iovera°
Transection (Severe neurotmesis) – Gross loss of continuity
|Not possible with the iovera°|
Adapted from Ilfeld BM, et al. 2016.
Axonotmesis involves loss of the relative continuity of the axon and its covering of myelin but preserves the connective structure of the nerve (the endoneurium, perineurium and epineurium).
- Wallerian degeneration occurs distal to the site of injury
- When axonotmesis affects a sensory nerve, the sensory deficits occur distal to the site of lesion
- Axonal regeneration in animal models occurs at a rate of 1 to 2 mm per day7, after which sensory signaling is restored
Figure taken from Ilfeld BM, et al. 2016.
1. Radnovich R, et al. Osteoarthritis Cartilage. 2017;25(8):1247-1256.
2. Hsu M, Stevenson FF. Wallerian degeneration and recovery of motor nerves after multiple focused cold therapies. Muscle Nerve. 2015;51(2):268-275.
3. Sunderland S. A classification of peripheral nerve injuries producing loss of function. Brain. 1951;74(4):491-516.
4. Sunderland S. Nerves and Nerve Injuries. London, United Kingdom: Churchill Livingstone; 1968:180.
5. Seddon HJ. Three types of nerve injury. Brain. 1943;66(4):237-288.
6. Ilfeld BM, et al. Expert Rev Med Devices. 2016;13(8):713-725.
7. Evans PJ. Cryoanalgesia: the application of low temperatures to nerves to produce anaesthesia or analgesia. Anaesthesia. 1981;36(11):1003-1013.