Cryoneurolysis for the Management of Chronic Pain in Patients With Knee Osteoarthritis; A Randomized Controlled Study
Phase: NA
Conditions: Chronic Pain, Osteoarthritis, Knee
Sponsor: Esbjerg Hospital - University Hospital of Southern Denmark

 
The Efficacy of Cryoneurolysis on Chronic Pain in Patients with Knee Osteoarthritis; A Double-blinded 
Randomized Controlled Sham Trial 
 
 
 
Date: 30-09-2024 
Clinicaltrials.gov; NCT03774121 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

STUDY PROTOCOL
Open Access
Cryoneurolysis for the management of
chronic pain in patients with knee
osteoarthritis; a double-blinded randomized
controlled sham trial
Niels-Peter Brøchner Nygaard1,2*
, Carsten Koch-Jensen3, Henrik Bjarke Vægter4,5, Niels Wedderkopp6,
Morten Blichfeldt-Eckhardt4,5 and Bibi Gram1,2
Abstract
Objective: Pain is the principal symptom in knee osteoarthritis (OA). Current non-operative treatment options have
only moderate effects and often patients experience persistent pain or side-effects. Novel advances in the field of
cryoneurolysis applies low temperatures to disrupt nerve signaling at the painful area, providing pain relief. The
primary aim of this randomized controlled trial (RCT) is to investigate if cryoneurolysis is superior to sham at
decreasing pain intensity 2 weeks after the intervention in patients with knee OA. Secondary aims are to explore
effects on pain, quality of life and functional performance over 24 months.
Methods: This two-arm, parallel-group RCT, approved by the Regional Ethics Committee, will randomly allocate
patients (n = 94) to a cryoneurolysis intervention group + standardized education and exercise (CRYO) or a sham
group + standardized education and exercise (SHAM) (1:1 ratio). Both groups will be assessed at baseline, 2 weeks
post intervention, post education and exercise and at 6, 12 and 24 months after cryoneurolysis. The primary
outcome is the NRS knee pain intensity score assessed 2 weeks post the intervention. Secondary outcome measures
include functional performance (chair-stand test, 40 m walk, stair test and maximum voluntary contraction of the
knee), patient reported outcomes (quality of life (EQ5D), Knee and osteoarthritis outcome scores (KOOS), among
others), use of analgesics, and adverse events over 24 months.
Impact statement: Cryoneurolysis could potentially provide an effective, safe and non-pharmacological therapeutic
option to treat pain in OA patients. The potential benefits include increased functional capacity and quality of life as
a result of significant pain relief and improved benefits of physical exercise.
Trial registration: Clinicaltrials.gov, NCT03774121, registered 3 March 2018, http://www.clinicaltrials.gov
Keywords: Cryoneurolysis, Osteoarthrities, Knee pain, Exercise
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data made available in this article, unless otherwise stated in a credit line to the data.
* Correspondence: Niels-peter.brochner.nygaard@rsyd.dk
1Research Unit of Health Science, Hospital of South West Jutland, University
Hospital of Southern Denmark, Esbjerg, Denmark
2Department of Regional Health Research, University of Southern Denmark,
Odense, Denmark
Full list of author information is available at the end of the article
Nygaard et al. BMC Musculoskeletal Disorders          (2021) 22:228 
https://doi.org/10.1186/s12891-021-04102-1

Background
Chronic pain represents a major challenge worldwide,
with significant clinical, social and economic implica-
tions. In Denmark and the rest of Europe, 20% of all
chronic pain conditions is related to osteoarthritis (OA)
[1]. There are over 300.000 people diagnosed with OA
per year in Denmark alone, and the incidence of this
pathology will increase significantly [2]. The pain and
loss of function associated with OA, results in a consid-
erable amount of years lived with disability [3] and has
significant socioeconomic consequences, estimated at 1 -
2.5% of the gross domestic product in western countries
[4]. Knee OA in particular, has a high prevalence rate
compared to other types of OA, and is also present in
the younger working age population [5].
The treatment of knee OA typically focuses on pain
relief, however, the effects of current conservative treat-
ment options remain small to moderate and most are as-
sociated with side effects [6]. In many cases, patients
may be subjected to partial/total knee arthroplasty
(TKA). TKA is considered to be an effective treatment
for end-stage knee osteoarthritis [7], however, more than
20% of patients receiving TKA, experience persistent
and unchanged pain post-surgery [8–10]. Therefore, ef-
fective and low-risk strategies are needed [11, 12]. Cryo-
neurolysis, which is the application of low temperatures
[−20 °C to −100 °C] to a target percutaneous peripheral
nerve, causing Wallerian degeneration [13, 14], disrupts
nerve function while structural elements of the nerve
bundle remain intact. This allows for complete regener-
ation and functional recovery of the nerve over time [15,
16] and has shown promising short and long-term re-
sults in a variety of chronic pain conditions such as lum-
bar facet joint pain [17], plantar fasciitis [18], occipital
neuralgia [19], post thoracotomy pain syndrome [20],
and Morton’s neuroma [21]. The ability to target the
genicular nerves to reduce pain around the knee has
been reported by studies applying radio frequency abla-
tion (RF) [22–24] but cryoneurolysis has in that respect
been associated with less adverse effects [25]. Radnovich
et al. targeted the infrapatellar branch of the saphenous
nerve (ISN) to reduce pain in patients with knee OA
[26]. The authors reported significant pain relief for up
to 150 days and no serious adverse effects. In another
study, Dasa et al. introduced preoperative cryoneurolysis
to the ISN and the anterior femoral cutaneous nerve
(AFCN) prior to TKA in patients with knee OA and ob-
served a statistically significant reduction in hospital stay
(days), and a decrease in prescribed opioids [27]. These
results provide clinical evidence, suggesting that cryo-
neurolysis treatment is a safe procedure, that may re-
duce both pain and symptoms in patients with knee OA
[14, 28]. Further adequately powered prospective ran-
domized controlled trials (RCTs) are needed to confirm
the efficacy and safety of cryoneurolysis treatment in pa-
tients with knee OA.
In Denmark, a standardized education and neuromuscu-
lar exercise program (GLA:D) has been implemented in the
national clinical guidelines by the Danish Health Authority,
for the treatment of knee and hip OA in clinical practice
[29]. Recent studies show that exercise reduce pain and im-
prove function in people with knee or hip OA [30, 31]. Des-
pite
of
these
reports,
the
beneficial
effects
remains
moderate with difficulties in maintaining these effects at
long-term follow-up [29]. In addition the implementation
of the exercise program is not optimal [12] and includes a
significant discontinuation rate for patients reporting high
pain levels [29]. In this line, pain and muscle weakness,
among others, have been reported to be major barriers for
physical exercise [32, 33]. The application of cryoneurolysis
treatment as an effective pain reducing treatment prior to
GLA:D might provide significant pain relief and improve
patients’ ability to produce force, resulting in improved ad-
herence, exercise effectiveness and long-term benefits [34].
Currently, no studies have reported the effects of cryoneur-
olysis treatment on pain and functional performance in
conjunction with a standardized education and exercise
programme (GLA:D), in patients with knee OA.
Objective
The primary objective of this RCT is to investigate if
cryoneurolysis is superior to sham at decreasing pain in-
tensity 2 weeks after the intervention in patients with
painful knee OA.
The secondary objective is to explore the safety and ef-
fectiveness of cryoneurolysis followed by GLA:D and to
assess long term effects.
Methods
This study protocol describes the design of an ongoing
parallel-group RCT conducted at the Department of
Neurology, University Hospital of Southern Denmark, Es-
bjerg, Denmark. The study protocol conforms to the
Standard Protocol Items: Recommendations for Interven-
tional Trials (SPIRIT) (see also appendix, Table 2), and
The Consolidated Standards of Reporting Trials of Non-
pharmacological Treatments (CONSORT NPT) will be
used as a guideline for reporting this trial. The study is
conducted according to the declaration of Helsinki and is
approved by The Regional Committees on Health Re-
search Ethics for Southern Denmark (S-20180089) and
registered in ClinicalTrials.gov (NCT03774121).
Participants and recruitment procedure
This study is recruiting patients with pain and knee OA
that are referred to GLA:D by their general practitioner,
prior to assessment of surgery eligibility at the hos-
pital (Fig. 1).
Nygaard et al. BMC Musculoskeletal Disorders          (2021) 22:228 
Page 2 of 10

Patients are screened according to the eligibility cri-
teria outlined below, and the diagnosis is confirmed by
further examination by an orthopaedic surgeon confirm-
ing knee OA and OA related pain. Eligible patients are
invited to proceed to a second visit where nerves around
the knee are identified using ultrasound (US) and elec-
trical nerve stimulation followed by a diagnostic genicu-
lar nerve block. If patients experience a ≥50% decrease
in knee pain intensity (NRS) as a result of the nerve
block, they will be randomly allocated to either a cryo-
neurolysis intervention group (CRYO) or a sham group
(SHAM).
Inclusion criteria
– Referred to GLA:D [29] by a physician.
– Age ≥18 years
– Chronic knee pain for a minimum duration of 6
months.
– Pain intensity ≥4 on the Numeric Rating Scale
(NRS).
– Radiographic confirmation of osteoarthritis; Grade
2-4 changes according to the Kellgren-Lawrence
classification system.
– A decrease of ≥50% in NRS scores with diagnostic
genicular nerve block.
– Written and oral understanding of Danish.
Exclusion criteria
– History of systemic inflammatory conditions such as
rheumatoid arthritis.
– Previous recipient of cryoneurolysis for the knee.
– Use of hyaluronic acid within the previous 30 days.
– Injection of corticosteroid within the previous 3
months.
– Clinically significant structural abnormities affecting
locomotion and knee function aside from
osteoarthritis and which might cause chronic knee
pain.
– Body mass index ≤18 and ≥40 kg/m2.
– In treatment for other pain conditions.
– Pregnancy
– Coagulopathy
– Uncontrolled serious disease (cancer, diabetes, etc.)
– Disease associated with reactions to cold, such as
cryoglobulinemia, cold urticarial and Renaud’s
syndrome.
Randomization
Randomization
is
performed
as
computer-generated
block randomization with a 1:1 allocation ratio using
random block sizes of 2, 4 and 6. The randomization re-
strictions will not be disclosed to ensure allocation
concealment and the sequence will be performed by an
external co-investigator. To account for the placebo ef-
fect and reduce the risk of bias, the patients, therapists
and data-manager will be blinded to the allocation.
Blinding will be assured using a sham trial that includes
the same procedures as cryoneurolysis treatment but
without any freezing temperatures.
The allocation code is concealed in a sealed envelope,
that will be available for the surgeon performing the
cryoneurolysis procedure only. In case of unexpected is-
sues and if deemed absolutely necessary by the investiga-
tors and physician, unblinding will occur according to
emergency unblinding procedures that will maintain the
integrity and confidentiality of the study.
Interventions
Active and sham cryoneurolysis
The interventions involve two visits.
First visit Radiographic confirmation and clinical deter-
mination of knee OA as pain generator followed by the
identification of the infrapatellar branch of the saphe-
nous nerve (IBSN) and anterior femoral cutaneous nerve
(AFCN). Predefined areas for each nerve are marked dir-
ectly on the patient [35, 36]. The area is searched using
a transcutaneous electrical nerve stimulation (TENS)
wand. Areas where the patient reported a response are
marked, and then retraced with incrementally lower
current to further specify nerve location. The location is
finally visually confirmed using ultra-sound. Nerve struc-
tures can be distinguished by its hypoechoic nerve fasci-
cles among the hyperechoic epineurium forming a
honeycomb-like structure in short-axis view. A diagnos-
tic nerve block using Ropivacain (5 mg/ml) is performed
at each location guided by ultra-sound. All patients
reporting a decrease of ≥50% in NRS pain scores are
scheduled for a second visit for cryoneurolysis.
Second visit Ropivacain (5 mg/ml) is injected before
treatment, locally at the insertion-point, 4-6 cm from
target nerve locations. This allows for continuous patient
feedback during the following procedures. The cryoneur-
olysis probe (Iceseed 1.5, Galil Medical Ltd.) is inserted
in proximity of the target nerve, guided by ultrasound
visualization to accurately determine the location of the
nerve and to account for adjacent neurovascular struc-
tures and variations in anatomical structures. Cryoneur-
olysis are performed with a single freeze cycle; 30s at an
effect of 20%, and 2 min 30s at 60% effect. After each
freezing cycle, 1 min active thaw and 1 min passive thaw
is used. The machine used for cryoneurolysis is a Visua-
lICE, (Galil Medical Ltd.), which utilizes Argon as a
coolant and Helium to thaw. This technology allows for
reversible destruction of nerves, also known as Wallerian
Nygaard et al. BMC Musculoskeletal Disorders          (2021) 22:228 
Page 3 of 10

degeneration, that prevents nerve signaling and poten-
tially alleviate pain and motor dysfunction in a number
of medical conditions.
The sham intervention includes the same procedures as
described above but using a sham probe that does not allow
for any freezing temperatures. Thus, visible marks as a re-
sult of the procedures will be similar in both groups.
GLA:D
Following the cryoneurolysis intervention, both groups
will participate in GLA:D [29] for a duration of 8 weeks
provided by specialized physiotherapists. The GLA:D
program consists of patient education and neuromuscu-
lar exercise. Patient education consists of three sessions
over the course of 2 weeks given by trained physiothera-
pists and focus on giving the patient knowledge on
osteoarthritis and treatment with exercise. Following pa-
tient education, patients participates in a 6-week group-
based NEuroMuscular Exercise program (NEMEX) with
a total of 12 sessions, each session lasting for 60 min
[31]. Patients who do not wish to or are not able to par-
ticipate in the supervised exercise program, have the
choice to perform the program at home, with detailed
instructions by the physiotherapist. The NEMEX of the
GLA:D program is performed in groups and with the
supervision of an experienced physiotherapist specialized
in training of musculoskeletal disorders.
Outcomes
The patients will be assessed at baseline, 2 weeks post
intervention, after completion of GLA:D and 6, 12- and
24- months post cryoneurolysis. The tests will include
both patient-reported outcomes (PRO) and objective
functional performance tests. The effects of group
CRYO and group SHAM will be compared at each
timepoint (Table 1).
Primary outcome
The primary outcome is the change in patient reported
knee pain intensity assessed using the numeric rating
scale (NRS) from baseline to 2 weeks post cryoneurolysis
compared between group CRYO and SHAM. NRS con-
sists of an 11-point scale between 0 and 10-, anchored
by two verbal descriptors, “no pain” for the score of 0
and “worst pain imaginable” for the score of 10. Respon-
dents are asked to rate their pain intensity on average
within the past 24 h. The NRS instrument has been vali-
dated in diverse populations and has been widely applied
in clinical and research settings [37].
Secondary outcomes
Functional performance will be evaluated by the 30 s
chair-stand test, the 40 m fast-paced walk test, the 9-step
stair-climb test and isometric knee MVC force [38].
The 30 s chair-stand test [39] consists of repeated sit-
to-stand movement for a duration of 30 s. The starting
position is seated, with feet placed flat on the floor,
shoulder width apart and with the arms crossed on the
chest. The position change to standing, with hips and
knees fully extended, followed by sitting back down, with
bottom fully touching the seat. The test is performed
with usual footwear and the chair should be with a
straight back, with no arms, placed against a wall. In
cases where the movement cannot be performed even
once, the hands are allowed to be placed on the legs or a
regular mobility aid can be used – the result is then re-
ported as an adapted test score. The outcome is the total
number of complete chair stands performed for the dur-
ation of the task (one chair stand represents a stand
followed by a sit movement).
The 40 m fast paced walk test [40] consists of walking
as fast as possible, but still safely, along a 10 m marked
walkway, then turning around a cone / tape and return.
This is then repeated for a total distance of 40 m. The
test is performed with usual footwear and regular walk-
ing aid is allowed and recorded. The outcome is
expressed as speed. i.e. walking distance (40 m) divided
by the time to perform the task (s). Timing is paused
during turns.
The 9-step stair-climb test [41] consists of the ascend
and descend a flight of stairs as fast as possible, but still
safely. The flight of stairs preferably has 9 steps, step
height appx. 20 cm, with handrails. The test is performed
with usual footwear and regular walking aid is allowed
and recorded. The outcome is the total time to perform
the task (s).
Quadriceps strength will be assessed measuring iso-
metric MVC force of the knee extensors (Bofors Elektro-
nik, Karlskoga, Sweden). Patients will be seated in a
chair with knee and hip flexed at 90° and with the pelvis
and chest restrained by straps. A non-extensile chain at-
tached to the back of the chair and connected to a force
transducer will be placed just proximal to the malleolus.
The patient will then be asked to perform three knee ex-
tensions pushing as hard as possible against the chain,
with 1 min rest in between. The highest peak value out
of the three MVCs will be taken as the MVC force.
In addition to pain intensity, PRO-data will be col-
lected using PainData, which is an electronic question-
naire system and database with multiple integrated
questionnaires, including:
– Knee Injury and Osteoarthritis Outcome Score
(KOOS). To assess patients’ opinion about their
knee and associated problems [42].
– EQ-5D. To assess generic quality of life [43].
– Pain Catastrophizing Scale. To assess the extent of
catastrophic thinking [44].
Nygaard et al. BMC Musculoskeletal Disorders          (2021) 22:228 
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Fig. 1 Flow chart
Nygaard et al. BMC Musculoskeletal Disorders          (2021) 22:228 
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– Patient Health Questionaire (PHQ9). To assess the
extent of depression [45].
– Generalized Anxiety Disorder (GAD7). To assess the
extent of anxiety [46].
– Pain intensity (NRS) and location (electronic
drawing on a 2D model).
– Self-reported use of analgesics.
Adverse events will also be reported and are defined as
any undesirable experience during the trial leading to
contact with the healthcare system (general practitioner,
emergency room or hospital). All adverse effects will be
assessed during follow-ups using both pre-specified
symptom inventories and open-ended questions.
Sample size
The planned number of trial participants is based on the
null-hypothesis, assuming no difference between cryo-
neurolysis treatment and sham. Estimating the sample
size for a two-sample means test with a level of signifi-
cance at 0.05, assuming a common standard deviation
(SD) of 3 in NRS pain intensity scores indicates that for
the intention-to-treat (ITT) population, 74 individuals is
required to obtain a power of at least 80% to establish a
minimal clinically important difference (MCID) of 2 in
NRS pain scores [47]. The MCID and common standard
deviation is based on previous findings with a similar pa-
tient group and intervention [48]. With an expected
drop-out rate of 20%, a total of 94 individuals will be in-
cluded in the project, 47 in each group.
Statistical methods
To evaluate the distributions of the continuous out-
comes, visual inspection of the studentized residuals
will be applied to evaluate whether the assumption
of normality is reasonable. Data will be reported as
differences between group means (means ± standard
deviations, 95% CIs) if normal distributed, otherwise
as
medians
with
interquartile
ranges.
Categorical
data will be reported as numbers and proportions.
An Intention-To-Treat (ITT) analysis will be used
for all allocated patients. Mixed linear regression
with the assumption of unstructured covariance will
be used to model the effect of the cryoneurolysis
treatment over time and to take into account the re-
peated measures by including individuals as random
variables. Time, group of treatment (cryoneurolysis or
SHAM) and the Group, time interaction will be used
as
fixed
effects
to
estimate
different
patterns
of
change over time. The results will be illustrated using
marginal effects that will be calculated using the mar-
gins command of STATA16. If the 95% CIs do not
overlap, data will be considered statistically signifi-
cant. A statistically significant difference of at least
two in NRS scores between groups, will be inter-
preted as a MCID.
Table 1 Timeline of the study – outcomes and variables assessed during the trial period
Timepoint
Study period
Enrolment
Allocation
Post-allocation
Follow-up
-4w
-1w
0w
2w
10w
na
24w
48w
96w
Enrolment:
Eligibility screening
X
Informed consent
X
Genicular nerve block
X
Allocation
X
Interventions:
Cryoeurolysis (CRYO)
X
Sham treatment (SHAM)
X
GLA:D (SHAM & CRYO)
X
X
Assessments:
Pain
X
X
X
X
X
X
Functional performance
X
X
X
X
X
X
KOOS
X
X
X
X
X
X
EQ5D
X
X
X
X
X
X
Adverse effects
X
X
X
X
X
X
Analgesics
X
X
X
X
X
X
w Weeks, na Not applicable (GLA:D start time may vary)
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Data monitoring
The current project will not require a formal data moni-
toring committee. This decision is based on the minimal
known risks associated with the intervention and little
expected disturbance to the clinical equipoise. Any ad-
verse effects will be recorded and reported according to
the guidelines to the Regional Committee on Health Re-
search Ethics for Southern Denmark within 7 days. Once
a year the lead investigator will report all expected and
unexpected adverse effects that have occurred during
that period, with an evaluation of patient safety.
The leading investigators will review the trial processes
and data continuously. In addition, a status report will
be sent for approval to the Danish Health Authority
each year.
Data management
All data will be kept electronically and filed according to
a participant code. Data entry will always be handled by
the same investigator, who will use unambiguous and
standard terminology based on predefined study forms.
Complete back-up of all data will be performed regularly
and stored on OPEN’s servers in the Region of Southern
Denmark,
using
Research
Electronic
Data
Capture
(REDCap). REDCap store data via an encrypted connec-
tion with restricted access and fulfil the demands for
data security. Data will be stored for a duration of 10
years. The project will be reported to the Danish Data
Protection Agency and will be handled according to the
regulations of the Act on Processing of Personal Data.
The full data set will be available to the lead investiga-
tors only.
Ethics
The study is conducted according to the declaration of
Helsinki and is approved by The Regional Committees
on Health Research Ethics for Southern Denmark (S-
20180089)
and
registered
in
ClinicalTrials.gov
(NCT03774121). Given the study design, eligibility cri-
teria and safety measures, the current project does not
include special risks for the participating patients. The
majority of risks does not require medical attention and
serious adverse effects as a result of local anesthetics and
cryoneurolysis are very rare. In contrast cryoneurolysis
could potentially provide an effective, safe and minimally
invasive option to treat pain in OA patients.
The inclusion of a sham group is necessary to test the
hypothesis because of the large reported placebo effects
in invasive interventions [49]. In addition, the associated
risks are minimal and the nature of misleading, in
regards to the administration of the sham trial, will be
adequately disclosed and accepted by the patient during
the informed consent process. The sham group is imple-
mented according to current standards [50].
Discussion
Impact and significance of the study
Current pain-relieving therapies show small to moderate
effects and a significant portion of patients who receive
surgery (TKA) report unchanged pain intensity levels
post-surgery. This indicates that there is a need for add-
itional therapies that could supplement or improve the
existing therapies. A significant difference in the change
in pain intensity between sham and intervention post
cryoneurolysis treatment would indicate that cryoneuro-
lysis is an effective non-pharmacological therapeutic op-
tion to treat pain in OA patients. Outcome measures
include both pain, social and psychological factors and
functional capacity, which allows for a thorough under-
standing of treatment effects. The novel addition of
GLA:D in combination with cryoneurolysis will elucidate
whether feasibility and effectiveness of exercise increase
if pain is attenuated and if the potential pain-relieving
effects of cryoneurolysis can be extended. The potential
benefits include increased functional capacity and quality
of life as a result of significant pain relief and improved
benefits of physical exercise, ultimately postponing or
making surgical intervention unnecessary. This could
have a significant impact on patients’ lives as well as sig-
nificant socioeconomic consequences and could change
the clinical landscape in the treatment of OA. Finally, an
important perspective, is the application of cryoneuroly-
sis in other areas – such as managing pain, related to
surgery, to improve rehabilitation.
If the results indicate that cryoneurolysis does not
elicit additional pain relief when compared to sham, it
might indicate that cryoneurolysis treatment is not suit-
able for the treatment of OA related pain or at least not
in the way it is applied in the current study.
Importantly, the freezing protocol in this study results
in reversible nerve damage, allowing for the reinnerva-
tion of the sensory receptors over time [15, 16]. It also
means that pain sensation might return over time [17,
26, 51, 52]. To maintain long-term pain-relieving effects,
this study is the first to combine cryoneurolysis with a
standardized education and exercise program. The anal-
gesic effects of exercise are well established, however,
the effects remain moderate and difficult to maintain
over time [29]. Cryoneurolysis of the genicular nerves al-
lows for potential long-term pain relief (> 3 months),
without affecting motor control, which could help exer-
cise feasibility and effectiveness - providing long-term
benefits of both cryoneurolysis and exercise [34]. In the
current study, patients are referred to GLA:D by their
general practitioner and is performed independently of
the study at specialized physiotherapists, post cryoneuro-
lysis treatment. Differences in practice and starting time
might occur between patients depending on the physio-
therapist and some may choose to perform parts of their
Nygaard et al. BMC Musculoskeletal Disorders          (2021) 22:228 
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training at home. These factors might confound the out-
come of the exercise program but is consistent with clin-
ical practice. The primary investigator facilitates GLA:D
participation.
Strength and limitations
This study is a blinded randomized controlled sham trial
that includes long-term follow ups allowing for an evalu-
ation of the long-term effects of treatment. The sham
intervention includes the same procedures as in cryo-
neurolysis treatment, emulating both physical marks and
sensory experiences such as sound and vision. Despite of
this, some performance bias cannot be excluded, and
some attrition bias might occur, due to patients seeking
treatment elsewhere – expectedly from the sham group.
The inclusion of a sham group is necessary to test the
hypothesis because of the large reported placebo effects
in OA trials [49]. Treatment with cryoneurolysis is still
in its early stage and further studies are needed to deter-
mine methodological strategies optimizing its potential
therapeutic effects. To achieve long-term pain relief, sig-
nificant degeneration of the sensory nerves is required.
The extent of nerve damage depends on several factors
including temperature, contact area, freezing rate, expos-
ure time, thawing strategy and cell type. The current
study applies a conservative freezing protocol, that is
relatively short ~ 3 min, a single freezing cycle and not
at full effect (slower freezing). This might reduce poten-
tial risks associated with the procedure but might also
attenuate treatment effects. Other studies use up to sev-
eral cycles and freezing periods up to 10 min, which
might induce pain relief for a longer duration due to in-
creased nerve degeneration. These studies, however,
tend to focus more on tissue destruction rather than de-
generation. Further studies are needed to determine op-
timal freezing protocols relative to different use cases.
Appendix
Table 2 WHO data registration items
Data category
Information
Protocol version
Version 1 - 21 January 2021
Primary Registry
Clinicaltrial.gov
Date of Registration
12-03-2018
Sources of Monetary
Danish Health Authority, Danish Rheumatism Association
Primary Sponsor
Department of Neurology, Hospital South West Jutland, Esbjerg Denmark
Secondary Sponsor
Research Unit of Health Sciences, Hospital South West Jutland, Esbjerg Denmark
Contact for Public Queries
Niels-Peter Broechner Nygaard
Contact for Scientific
Queries
Niels-Peter Broechner Nygaard
Country of Recruitment
Denmark
Health Condition
Osteoarthritis (DM17)
Interventions
Cryoneurolysis
Sham
GLA:D
Key inclusion and exclusion
criteria
Inclusion: Referred to GLA:D, Chronic pain > 6 months, Pain intensity ≥40 mm on the NRS pain scale, OA confirmed by
radiography, 50% reduction of pain after diagnostic nerve block
Exclusion: Systemic inflammatory disease, In treatment for other pain conditions, uncontrolled serious disease (cancer,
diabetes, etc.)
Study type
Interventional
Allocation; Randomized controlled; Parallel assignment; Single-blinded (patients and data-manager)
Primary purpose; Safety and effectiveness
Date if first enrollment
26-06-20,189
Sample size
n = 94
Recruitment status
Recruiting
Primary outcome
Change in Pain intensity score (NRS) after cryoneurolysis, compared between intervention and sham
Key secondary outcomes
Functional performance
Quality of Life
Adverse effects
Nygaard et al. BMC Musculoskeletal Disorders          (2021) 22:228 
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The target nerves, the identification of the target nerves
and placement of the cryo probe is equally as important
and might have a significant impact on the results. The
temperature gradient away from the probe increases
drastically [4, 7]. The typical isotherm with the needle
(IceSeed 1.5, Galil Medical) used in this study has a
temperature
of
−40 °C
in
an
area
equivalent
to
11x20mm. Already at 20x27mm the temperature has
risen to −20 °C and at 33x38mm the temperature is up
to 0 °C [8]. Thus, to attain temperatures necessary for a
relevant impact on sensory nerves for long-term pain re-
lief [−20 °C - 100 °C], probe placement relative to the
nerve is crucial. The current study uses a combination
of anatomical landmarks, electrical nerve stimulation
and ultrasound to accurately determine nerve locations
and to account for variation in surrounding anatomical
structures. This both increase precision and safety of the
procedure. Nevertheless, it is in some cases difficult to
identify and differentiate nerve structures with ultra-
sound which might cause variable results. The procedure
is in this study performed by the same surgeon through-
out, trained to identify neural structures and to perform
cryoneurolysis. In addition, local anesthesia is used lo-
cally only at the injection site, 4-6 cm from the ‘target’
nerve. This allows for continuous feedback on the effect
of treatment.
Dissemination of results
The obtained results will be made publicly available
within 1 year after the end of the project. This will in-
clude publication of the obtained results in international
scientific peer-reviewed journals - adhering to the rec-
ommendations of the Vancouver convention. Published
papers will have open access to ensure a broad distribu-
tion and the results will be presented at international
scientific conferences. The results will also be presented
for the general public and distributed across public plat-
forms (e.g. regional and national press, internet sites,
etc.) if copyright allows.
Acknowledgements
Not applicable.
Authors’ contributions
NPBN; Major contributor to the conceptualization of the research idea and
protocol. Primary contributor to the manuscript. Performs the acquisition
and analysis of the results. Study management. CKJ; Major contributor to the
conceptualization of the research idea and protocol. Performs the surgical
intervention. Study management. HBV; Contributor to the conceptualization
of the research idea and protocol. Manages patient-reported outcome data-
base. NW; Contributor to the conceptualization of the research idea and
protocol. Inclusion and diagnostics of patients. MBE; Contributor to the
conceptualization of the research idea and protocol. Technical contributor to
the surgical intervention and for the evaluation of pain. BG; Major contributor
to the conceptualization of the research idea and protocol. Major contributor
to the manuscript. Study management. All authors contributed to, read and
approved the final manuscript.
Funding
The study was funded by the Danish Rheumatism Association and the
Danish Health Authority. The funding sources does not have a role in the
design of the study and collection, analysis and interpretation of data and in
writing the manuscript. External peer-review took place during the funding
process.
Availability of data and materials
Not applicable.
Ethics approval and consent to participate
The study is conducted according to the declaration of Helsinki and is
approved by The Regional Committees on Health Research Ethics for
Southern Denmark (S-20180089).
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1Research Unit of Health Science, Hospital of South West Jutland, University
Hospital of Southern Denmark, Esbjerg, Denmark. 2Department of Regional
Health Research, University of Southern Denmark, Odense, Denmark.
3Department of Neurology, Hospital South West Jutland, University Hospital
of Southern Denmark, Esbjerg, Denmark. 4Pain Research Group, Odense
University Hospital, Odense, Denmark. 5Department of Clinical Research,
Faculty of Health Sciences, University of Southern Denmark, Odense,
Denmark. 6Department of Orthopedics, Hospital South West Jutland,
University Hospital of Southern Denmark, Esbjerg, Denmark.
Received: 21 January 2021 Accepted: 19 February 2021
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