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The evidence is compelling that the placebo effect is due to biochemical effects, and is not a purely psychological phenomenon.
The evidence is compelling that the placebo effect is due to biochemical effects, and is not a purely psychological phenomenon.


Endogenous opioids are involved. The placebo effect is reversed by naloxone. It is enhanced by antagonism of cholecystokinin receptors. Placebo analgesia can mimic the respiratory depression side effect seen with exogenous opioids, and this side effect is reversible with naloxone.<ref>Amanzio M, Pollo A, Maggi G, Benedetti F. Response variability to analgesics: a role for non-specific activation of endogenous opioids. Pain. 2001 Feb 15;90(3):205-215. doi: 10.1016/S0304-3959(00)00486-3. PMID: 11207392.</ref>
There are a variety of centres in the brain stem that send descending signals to various spinal segments and cause diffuse inhibition. This is called the diffuse noxious inhibitory control (DNIC). The role of the DNIC is suppress less important ascending information so that the nociceptive information is highlighted, and this is called centre-surround inhibition (see [[Nociception]])


There is also some evidence that catecholamines and cortisol are involved.
Suppression occurs with global stimulation of brainstem nuclei, causing inhibitory signals through descending pathways to all segmental levels of the spinal cord. Opioids work by globally inhibiting the descending pathways. The nociceptive information thus becomes obscured by the now uninhibited background noise.
 
Endogenous opioids appear to be involved in the placebo effect. There are several streams of evidence for this. The placebo effect is reversed by naloxone. The placebo effect is enhanced by antagonism of cholecystokinin receptors. Placebo analgesia can mimic the respiratory depression side effect seen with exogenous opioids, and this side effect is reversible with naloxone.<ref>Amanzio M, Pollo A, Maggi G, Benedetti F. Response variability to analgesics: a role for non-specific activation of endogenous opioids. Pain. 2001 Feb 15;90(3):205-215. doi: 10.1016/S0304-3959(00)00486-3. PMID: 11207392.</ref> There is also some evidence that catecholamines and cortisol are involved.


== Response Rate ==
== Response Rate ==
Line 58: Line 60:


== Magnitude ==
== Magnitude ==
Essentially every pain intervention has a placebo component. In placebo controlled trials, the magnitude of the effect of placebo analgesics is typically ~50-80% of the active agent. For example with a baseline pain of 6, and active agent might reduce it to 3, while a placebo might reduce it to 4 or 5.
Essentially every pain intervention has a placebo component.  
 
'''Analgesics'''
 
In placebo controlled trials, the magnitude of the effect of placebo analgesics is typically ~50-80% of the active agent. For example with a baseline pain of 6, and active agent might reduce it to 3, while a placebo might reduce it to 4 or 5. However in systematic reviews, analgesics tend to barely reach clinical significance for effect compared to placebo.
 
'''Surgery'''
 
In the context of surgical interventions the placebo treatment is called the "sham" treatment. In the study of orthopaedic surgery for the treatment of acute and chronic pain conditions, there have only been 7 sham controlled trials. All but one of these 7 trials found no difference between the intervention and sham. <ref name=":3">Buchbinder R, Osborne RH, Ebeling PR, Wark JD, Mitchell P, Wriedt C, Graves S, Staples MP, Murphy B. A randomized trial of vertebroplasty for painful osteoporotic vertebral fractures. N Engl J Med. 2009 Aug 6;361(6):557-68. doi: 10.1056/NEJMoa0900429. PMID: 19657121.</ref><ref>Bradley JD, Heilman DK, Katz BP, Gsell P, Wallick JE, Brandt KD. Tidal irrigation as treatment for knee osteoarthritis: a sham-controlled, randomized, double-blinded evaluation. Arthritis Rheum. 2002 Jan;46(1):100-8. doi: 10.1002/1529-0131(200201)46:1<100::aid-art10037>3.0.co;2-v. PMID: 11817581.</ref><ref name=":4">Kallmes DF, Comstock BA, Heagerty PJ, Turner JA, Wilson DJ, Diamond TH, Edwards R, Gray LA, Stout L, Owen S, Hollingworth W, Ghdoke B, Annesley-Williams DJ, Ralston SH, Jarvik JG. A randomized trial of vertebroplasty for osteoporotic spinal fractures. N Engl J Med. 2009 Aug 6;361(6):569-79. doi: 10.1056/NEJMoa0900563. Erratum in: N Engl J Med. 2012 Mar 8;366(10):970. PMID: 19657122; PMCID: PMC2930487.</ref><ref>Moseley JB, O'Malley K, Petersen NJ, Menke TJ, Brody BA, Kuykendall DH, Hollingsworth JC, Ashton CM, Wray NP. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med. 2002 Jul 11;347(2):81-8. doi: 10.1056/NEJMoa013259. PMID: 12110735.</ref><ref name=":5">Firanescu CE, de Vries J, Lodder P, Venmans A, Schoemaker MC, Smeets AJ, Donga E, Juttmann JR, Klazen CAH, Elgersma OEH, Jansen FH, Tielbeek AV, Boukrab I, Schonenberg K, van Rooij WJJ, Hirsch JA, Lohle PNM. Vertebroplasty versus sham procedure for painful acute osteoporotic vertebral compression fractures (VERTOS IV): randomised sham controlled clinical trial. BMJ. 2018 May 9;361:k1551. doi: 10.1136/bmj.k1551. Erratum in: BMJ. 2018 Jul 4;362:k2937. Smeet AJ [corrected to Smeets AJ]. PMID: 29743284; PMCID: PMC5941218.</ref><ref name=":6">Clark W, Bird P, Gonski P, Diamond TH, Smerdely P, McNeil HP, Schlaphoff G, Bryant C, Barnes E, Gebski V. Safety and efficacy of vertebroplasty for acute painful osteoporotic fractures (VAPOUR): a multicentre, randomised, double-blind, placebo-controlled trial. Lancet. 2016 Oct 1;388(10052):1408-1416. doi: 10.1016/S0140-6736(16)31341-1. Epub 2016 Aug 17. Erratum in: Lancet. 2017 Feb 11;389(10069):602. PMID: 27544377.</ref><ref>Moradi A, Pasdar P, Mehrad-Majd H, Ebrahimzadeh MH. Clinical Outcomes of Open versus Arthroscopic Surgery for Lateral Epicondylitis, Evidence from a Systematic Review. Arch Bone Jt Surg. 2019 Mar;7(2):91-104. PMID: 31211187; PMCID: PMC6510924.</ref>
 
The singular positive trial<ref name=":6" /> was for vertebroplasty and stands in contrast to the three other negative vertebroplasty sham controlled trials.<ref name=":4" /><ref name=":3" /><ref name=":5" /> It was also industry funded and only looked at pain reduction in at 8 weeks (44% vs 21% NRS <4/10 at 14 days). A cheeky systematic review of orthopaedic surgery as a field found that sham surgery was as effective as orthopaedic surgery for reducing pain and disability.<ref>Louw A, Diener I, Fernández-de-Las-Peñas C, Puentedura EJ. Sham Surgery in Orthopedics: A Systematic Review of the Literature. Pain Med. 2017 Apr 1;18(4):736-750. doi: 10.1093/pm/pnw164. PMID: 27402957.</ref>
 
'''Non-surgical Interventions'''
 
The placebo effect also occurs with less invasive procedures, and the placebo intervention is again called sham.
 
For example, several sham controlled studies have been done for lumbar facet joints injections. Intra-articular lumbar facet joint corticosteroid injection has been shown to have no greater effect than intra-articular saline injection.<ref>Carette S, Marcoux S, Truchon R, Grondin C, Gagnon J, Allard Y, Latulippe M. A controlled trial of corticosteroid injections into facet joints for chronic low back pain. N Engl J Med. 1991 Oct 3;325(14):1002-7. doi: 10.1056/NEJM199110033251405. PMID: 1832209.</ref> Corticosteroid, local anaesthetic, and a mixture are all equally effective when injected into lumbar facet joints.<ref>Lilius G, Laasonen EM, Myllynen P, Harilainen A, Grönlund G. Lumbar facet joint syndrome. A randomised clinical trial. J Bone Joint Surg Br. 1989 Aug;71(4):681-4. doi: 10.1302/0301-620X.71B4.2527856. PMID: 2527856.</ref> Facet joint injections were also found to be equal to facet nerve blocks.<ref>Marks RC, Houston T, Thulbourne T. Facet joint injection and facet nerve block: a randomised comparison in 86 patients with chronic low back pain. Pain. 1992 Jun;49(3):325-328. doi: 10.1016/0304-3959(92)90239-8. PMID: 1408298.</ref>
 
The study of interventions has tended to move towards using categorical data as a primary outcome rather than average response rate, as using average response rates can hide the positive response in a subgroup. In this lumbar transforaminal corticosteroid injection was found to be superior to a variety of sham interventions.<ref>Ghahreman A, Ferch R, Bogduk N. The efficacy of transforaminal injection of steroids for the treatment of lumbar radicular pain. Pain Med. 2010 Aug;11(8):1149-68. doi: 10.1111/j.1526-4637.2010.00908.x. PMID: 20704666.</ref>
 
For zygapophysial joint pain, when patients are adequately selected using controlled blocks, radiofrequency neurotomy has been found to be superior to sham,<ref>Nath S, Nath CA, Pettersson K. Percutaneous lumbar zygapophysial (Facet) joint neurotomy using radiofrequency current, in the management of chronic low back pain: a randomized double-blind trial. Spine (Phila Pa 1976). 2008 May 20;33(12):1291-7; discussion 1298. doi: 10.1097/BRS.0b013e31817329f0. PMID: 18496338.</ref><ref>Lord SM, Barnsley L, Wallis BJ, McDonald GJ, Bogduk N. Percutaneous radio-frequency neurotomy for chronic cervical zygapophyseal-joint pain. N Engl J Med. 1996 Dec 5;335(23):1721-6. doi: 10.1056/NEJM199612053352302. PMID: 8929263.</ref><ref>Moussa WM, Khedr W. Percutaneous radiofrequency facet capsule denervation as an alternative target in lumbar facet syndrome. Clin Neurol Neurosurg. 2016 Nov;150:96-104. doi: 10.1016/j.clineuro.2016.09.004. Epub 2016 Sep 5. PMID: 27618781.</ref> however the Nath study did not report any data from which categorical outcomes could be calculated. In the lumbar spine, studies that have not followed the evidence based Spine Intervention Society guidelines for selection and/or technique haven't found consistent outcomes.<ref>Schneider BJ, Doan L, Maes MK, Martinez KR, Gonzalez Cota A, Bogduk N; Standards Division of the Spine Intervention Society. Systematic Review of the Effectiveness of Lumbar Medial Branch Thermal Radiofrequency Neurotomy, Stratified for Diagnostic Methods and Procedural Technique. Pain Med. 2020 Jun 1;21(6):1122-1141. doi: 10.1093/pm/pnz349. PMID: 32040149.</ref> (See [[Lumbar Zygapophysial Joint Precision Treatment]])
 
'''Diagnostic Procedures'''
 
Diagnostic procedures are also susceptible to the placebo effect. Patients who think they are having diagnostic zygapophysial joint blocks have a significant false positive rate with the subcutaneous injection of saline.<ref>Schwarzer AC, Wang SC, Bogduk N, McNaught PJ, Laurent R. Prevalence and clinical features of lumbar zygapophysial joint pain: a study in an Australian population with chronic low back pain. Ann Rheum Dis. 1995 Feb;54(2):100-6. doi: 10.1136/ard.54.2.100. PMID: 7702395; PMCID: PMC1005530.</ref> Stellate ganglion blocks using normal saline<ref>Price DD, Long S, Wilsey B, Rafii A. Analysis of peak magnitude and duration of analgesia produced by local anesthetics injected into sympathetic ganglia of complex regional pain syndrome patients. Clin J Pain. 1998 Sep;14(3):216-26. doi: 10.1097/00002508-199809000-00008. PMID: 9758071.</ref> and intravenous infusions of normal saline<ref>Verdugo RJ, Ochoa JL. Abnormal movements in complex regional pain syndrome: assessment of their nature. Muscle Nerve. 2000 Feb;23(2):198-205. doi: 10.1002/(sici)1097-4598(200002)23:2<198::aid-mus9>3.0.co;2-4. PMID: 10639611.</ref> can relieve CRPS symptoms.


== Clinical Application ==
== Clinical Application ==

Revision as of 14:42, 13 September 2021

Placebo means a treatment that lacks a specific therapeutic effect. For a drug it is an agent that lacks any pharmacological effect. For a procedure it is an intervention that lacks any specific anatomical or physiological effect. Placebo treatment is not the same as no treatment. Normal treatment is the sum of natural history, placebo effect, and medical treatment.

Definitions

Adequately defining placebo is challenging. Any treatment or intervention can have both specific effects and non-specific effects.

  1. The specific effects are due to known physiological mechanisms.
  2. The non-specific effects are a paradox and are due to unknown mechanisms. The paradox is resolved if the unknown mechanisms of the nonspecific effects become known.

Any treatment effect that is not due to the specific, intended effects of a treatment is referred to as the placebo effect. The term placebo response is what the individual reports after receiving a placebo, with the results being due to the placebo effect.

The total effect of an intervention may be a combination of both its physiological known specific effects, and unknown non-specific placebo effect. An absolute placebo effect is when the intervention has no known therapeutic physiological effect or an intervention that is designed to simulate medical therapy but doesn't have a specific therapeutic effect. The opposite of a placebo effect is a nocebo effect, where harm occurs for non-specific unknown reasons.

Placebo analgesia is the reduction or disappearance of pain, through the placebo effect, when a placebo is given to a patient who is told that it is a painkiller.

Comparison with Other Effects

The placebo effect is a specific phenomenon that is sometimes confused with other effects.

Natural history: some conditions naturally improve over time because of healing or some other factor. The improvement in pain is a property of the disorder that the patient has not the placebo effect. These two effects are distinguished through comparing the outcomes of patients taking placebo and the outcomes of patients having no treatment ("no treatment group").

Regression to the mean: Patients with chronic pain may be more likely to present to a doctor and join a trial when their pain is on the more severe end of what they have been experiencing to date. Conversely, patients who are doing well compared to their average are less likely to present to doctors and enrol in trials. There is therefore an overrepresentation of patients who are in a severe period of their naturally fluctuating pain levels. Measurements of pain and function may not represent their normal state, but the state of their flare. Regression to the mean refers to the statistical phenomenon that on average their pain is likely to improve to their previous average level of pain, regardless of treatment. This is not a placebo effect, but simply reflects normal fluctuations in pain. This effect can be controlled through using appropriate selection criteria.

Hawthorne effect: When individuals are being observed there is a change in performance simply because they know they are being studied. This is a conscious or subconscious change.

Symptom Ambiguity and Biases: This can be controlled by using objective physiological measurements.

Cointervention: It is important to rule out the effects of co-intervention. For example the simple act of mechanically inserting a needle during inject may in itself produce analgesia.

Psychological Theories

There are four main psychological theories regarding the mechanism of the placebo effect.[1][2]

Classic Conditioning: This theory views the placebo response as a conditioned response to features of the treatment setting such as the doctor's style of dress, equipment, medication. Relief occurs because of past experiences of having relief from going to the doctor. This mechanism is hard to apply to chronic pain. If anything, patients with chronic pain are likely to have had repeated failures, and so would be conditioned not to respond. Viewing it from this negative viewpoint can be an explanation for nocebo responses and "placebo sag.'[1]

Response Expectancy Theory: This views the placebo response as being due to an expectation from the patient that a treatment will relieve their pain. This effect is magnified and reinforced if the treatment is undertaken in an impressive manner, and impressive setting. The placebo effect has been found to be enhanced through credibility of the doctor, therapeutic setting, treatment, administrative setting; and the nature of the interaction between the patient and doctor.[1]

Meaning Model: This model views that part the patients symptoms may be amplified due to fear. It looks at what factors are needed to address fear and thereby maximise the placebo response:

  1. The patient must feel listened to and receive a valid coherent explanation for their illness
  2. The patient must feel care and compassion from the doctor
  3. The patient must feel empowered.

By having these three factors, any fears are reduced and pain and function may improve simply as a result of that.[2] Delivering a treatment with confidence and conviction can also also allay fear.

Cognitive Dissonance Theory: The patient avoids holding two psychologically inconsistent beliefs: that the treatment would work and only very sick people don't improve. To reduce this dissonance the patient alters their perception of their symptoms.

Biochemical Mediators

The evidence is compelling that the placebo effect is due to biochemical effects, and is not a purely psychological phenomenon.

There are a variety of centres in the brain stem that send descending signals to various spinal segments and cause diffuse inhibition. This is called the diffuse noxious inhibitory control (DNIC). The role of the DNIC is suppress less important ascending information so that the nociceptive information is highlighted, and this is called centre-surround inhibition (see Nociception)

Suppression occurs with global stimulation of brainstem nuclei, causing inhibitory signals through descending pathways to all segmental levels of the spinal cord. Opioids work by globally inhibiting the descending pathways. The nociceptive information thus becomes obscured by the now uninhibited background noise.

Endogenous opioids appear to be involved in the placebo effect. There are several streams of evidence for this. The placebo effect is reversed by naloxone. The placebo effect is enhanced by antagonism of cholecystokinin receptors. Placebo analgesia can mimic the respiratory depression side effect seen with exogenous opioids, and this side effect is reversible with naloxone.[3] There is also some evidence that catecholamines and cortisol are involved.

Response Rate

A commonly quoted figure is that 35% is the standard incidence of placebo response rates, or otherwise stated as one third of patients will exhibit a placebo effect. However this figure, published in 1955, was the average placebo responses in 15 papers, with the range being 15-58%.[4] In fact, subsequent studies has found that the incidence of placebo response varies between 0 and 100% depending on the disease, environment, investigator, and other factors.[5] The "constant" 35% figure is a myth.

Furthermore, any given individual can be both a placebo responder and a placebo non-responder under different settings. There is no such thing as a personality or psychological trait that causes individuals to consistently respond to placebos.[6][1][2]

In patients with chronic spinal pain, there is no difference in the psychological profiles of patients who have true-positive responses to placebo-controlled diagnostic blocks and those who have placebo responses.[7] There is also no difference between patients who have successful outcomes after successful treatment with radiofrequency neurotomy with those who do not.[8]

Magnitude

Essentially every pain intervention has a placebo component.

Analgesics

In placebo controlled trials, the magnitude of the effect of placebo analgesics is typically ~50-80% of the active agent. For example with a baseline pain of 6, and active agent might reduce it to 3, while a placebo might reduce it to 4 or 5. However in systematic reviews, analgesics tend to barely reach clinical significance for effect compared to placebo.

Surgery

In the context of surgical interventions the placebo treatment is called the "sham" treatment. In the study of orthopaedic surgery for the treatment of acute and chronic pain conditions, there have only been 7 sham controlled trials. All but one of these 7 trials found no difference between the intervention and sham. [9][10][11][12][13][14][15]

The singular positive trial[14] was for vertebroplasty and stands in contrast to the three other negative vertebroplasty sham controlled trials.[11][9][13] It was also industry funded and only looked at pain reduction in at 8 weeks (44% vs 21% NRS <4/10 at 14 days). A cheeky systematic review of orthopaedic surgery as a field found that sham surgery was as effective as orthopaedic surgery for reducing pain and disability.[16]

Non-surgical Interventions

The placebo effect also occurs with less invasive procedures, and the placebo intervention is again called sham.

For example, several sham controlled studies have been done for lumbar facet joints injections. Intra-articular lumbar facet joint corticosteroid injection has been shown to have no greater effect than intra-articular saline injection.[17] Corticosteroid, local anaesthetic, and a mixture are all equally effective when injected into lumbar facet joints.[18] Facet joint injections were also found to be equal to facet nerve blocks.[19]

The study of interventions has tended to move towards using categorical data as a primary outcome rather than average response rate, as using average response rates can hide the positive response in a subgroup. In this lumbar transforaminal corticosteroid injection was found to be superior to a variety of sham interventions.[20]

For zygapophysial joint pain, when patients are adequately selected using controlled blocks, radiofrequency neurotomy has been found to be superior to sham,[21][22][23] however the Nath study did not report any data from which categorical outcomes could be calculated. In the lumbar spine, studies that have not followed the evidence based Spine Intervention Society guidelines for selection and/or technique haven't found consistent outcomes.[24] (See Lumbar Zygapophysial Joint Precision Treatment)

Diagnostic Procedures

Diagnostic procedures are also susceptible to the placebo effect. Patients who think they are having diagnostic zygapophysial joint blocks have a significant false positive rate with the subcutaneous injection of saline.[25] Stellate ganglion blocks using normal saline[26] and intravenous infusions of normal saline[27] can relieve CRPS symptoms.

Clinical Application

The placebo effect can be enlisted in clinical practice simply through practice style and behaviour of the doctor in an ethical way.[2]

Sustained Partnership: Having a long term relationship with patients can lead to better outcomes. The ethical attitudes that enhance the placebo response rate are expressing interest in the total person, providing longitudinal care, being adaptive to the patient's idiosyncrasies, and avoiding cookbook medicine. From the patients side they must feel like they are in a caring, sensitive, and empathetic environment, and also view the doctor as reliable and trustworthy. Share decision making is important.

Mastery: The patient should feel empowered, and change from feeling like a passive entity that is totally dependent on the doctor, to feeling like they are in control of their health. They should be encouraged to express their ideas, concerns, and expectations.

Story: This is the narrative that is weaved by the doctor in a way that the patient can understand. Management is often easier when there is a cohesive and coherent narrative. Patients get less analgesic response if they are unaware that they are receiving an analgesic. They do better if they are expressly told that they are receiving a strong painkillers.[6] It is vital that patients understand how the analgesic works, what they are for, and how to use them properly.

Placebo should not be used as sole therapy. Otherwise it can delay seeking more effective treatments, it can reduce the future response of active therapy, it can add to treatment cost, it can result in a nocebo effect, and it can be a constant reminder of illness.

References

  1. ↑ 1.0 1.1 1.2 1.3 Peck C, Coleman G. Implications of placebo theory for clinical research and practice in pain management. Theor Med. 1991 Sep;12(3):247-70. doi: 10.1007/BF00489609. PMID: 1721730.
  2. ↑ 2.0 2.1 2.2 2.3 Brody H. The placebo response. Recent research and implications for family medicine. J Fam Pract. 2000 Jul;49(7):649-54. PMID: 10923577.
  3. ↑ Amanzio M, Pollo A, Maggi G, Benedetti F. Response variability to analgesics: a role for non-specific activation of endogenous opioids. Pain. 2001 Feb 15;90(3):205-215. doi: 10.1016/S0304-3959(00)00486-3. PMID: 11207392.
  4. ↑ BEECHER HK. The powerful placebo. J Am Med Assoc. 1955 Dec 24;159(17):1602-6. doi: 10.1001/jama.1955.02960340022006. PMID: 13271123.
  5. ↑ Wall PD. The placebo effect: an unpopular topic. Pain. 1992 Oct;51(1):1-3. doi: 10.1016/0304-3959(92)90002-S. PMID: 1454391.
  6. ↑ 6.0 6.1 Voudouris NJ, Peck CL, Coleman G. Conditioned response models of placebo phenomena: further support. Pain. 1989 Jul;38(1):109-116. doi: 10.1016/0304-3959(89)90080-8. PMID: 2780058.
  7. ↑ Lord SM, Barnsley L, Wallis BJ, Bogduk N. Chronic cervical zygapophysial joint pain after whiplash. A placebo-controlled prevalence study. Spine (Phila Pa 1976). 1996 Aug 1;21(15):1737-44; discussion 1744-5. doi: 10.1097/00007632-199608010-00005. PMID: 8855458.
  8. ↑ Wallis BJ, Lord SM, Bogduk N. Resolution of psychological distress of whiplash patients following treatment by radiofrequency neurotomy: a randomised, double-blind, placebo-controlled trial. Pain. 1997 Oct;73(1):15-22. doi: 10.1016/s0304-3959(97)00060-2. PMID: 9414052.
  9. ↑ 9.0 9.1 Buchbinder R, Osborne RH, Ebeling PR, Wark JD, Mitchell P, Wriedt C, Graves S, Staples MP, Murphy B. A randomized trial of vertebroplasty for painful osteoporotic vertebral fractures. N Engl J Med. 2009 Aug 6;361(6):557-68. doi: 10.1056/NEJMoa0900429. PMID: 19657121.
  10. ↑ Bradley JD, Heilman DK, Katz BP, Gsell P, Wallick JE, Brandt KD. Tidal irrigation as treatment for knee osteoarthritis: a sham-controlled, randomized, double-blinded evaluation. Arthritis Rheum. 2002 Jan;46(1):100-8. doi: 10.1002/1529-0131(200201)46:1<100::aid-art10037>3.0.co;2-v. PMID: 11817581.
  11. ↑ 11.0 11.1 Kallmes DF, Comstock BA, Heagerty PJ, Turner JA, Wilson DJ, Diamond TH, Edwards R, Gray LA, Stout L, Owen S, Hollingworth W, Ghdoke B, Annesley-Williams DJ, Ralston SH, Jarvik JG. A randomized trial of vertebroplasty for osteoporotic spinal fractures. N Engl J Med. 2009 Aug 6;361(6):569-79. doi: 10.1056/NEJMoa0900563. Erratum in: N Engl J Med. 2012 Mar 8;366(10):970. PMID: 19657122; PMCID: PMC2930487.
  12. ↑ Moseley JB, O'Malley K, Petersen NJ, Menke TJ, Brody BA, Kuykendall DH, Hollingsworth JC, Ashton CM, Wray NP. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med. 2002 Jul 11;347(2):81-8. doi: 10.1056/NEJMoa013259. PMID: 12110735.
  13. ↑ 13.0 13.1 Firanescu CE, de Vries J, Lodder P, Venmans A, Schoemaker MC, Smeets AJ, Donga E, Juttmann JR, Klazen CAH, Elgersma OEH, Jansen FH, Tielbeek AV, Boukrab I, Schonenberg K, van Rooij WJJ, Hirsch JA, Lohle PNM. Vertebroplasty versus sham procedure for painful acute osteoporotic vertebral compression fractures (VERTOS IV): randomised sham controlled clinical trial. BMJ. 2018 May 9;361:k1551. doi: 10.1136/bmj.k1551. Erratum in: BMJ. 2018 Jul 4;362:k2937. Smeet AJ [corrected to Smeets AJ]. PMID: 29743284; PMCID: PMC5941218.
  14. ↑ 14.0 14.1 Clark W, Bird P, Gonski P, Diamond TH, Smerdely P, McNeil HP, Schlaphoff G, Bryant C, Barnes E, Gebski V. Safety and efficacy of vertebroplasty for acute painful osteoporotic fractures (VAPOUR): a multicentre, randomised, double-blind, placebo-controlled trial. Lancet. 2016 Oct 1;388(10052):1408-1416. doi: 10.1016/S0140-6736(16)31341-1. Epub 2016 Aug 17. Erratum in: Lancet. 2017 Feb 11;389(10069):602. PMID: 27544377.
  15. ↑ Moradi A, Pasdar P, Mehrad-Majd H, Ebrahimzadeh MH. Clinical Outcomes of Open versus Arthroscopic Surgery for Lateral Epicondylitis, Evidence from a Systematic Review. Arch Bone Jt Surg. 2019 Mar;7(2):91-104. PMID: 31211187; PMCID: PMC6510924.
  16. ↑ Louw A, Diener I, Fernández-de-Las-Peñas C, Puentedura EJ. Sham Surgery in Orthopedics: A Systematic Review of the Literature. Pain Med. 2017 Apr 1;18(4):736-750. doi: 10.1093/pm/pnw164. PMID: 27402957.
  17. ↑ Carette S, Marcoux S, Truchon R, Grondin C, Gagnon J, Allard Y, Latulippe M. A controlled trial of corticosteroid injections into facet joints for chronic low back pain. N Engl J Med. 1991 Oct 3;325(14):1002-7. doi: 10.1056/NEJM199110033251405. PMID: 1832209.
  18. ↑ Lilius G, Laasonen EM, Myllynen P, Harilainen A, Grönlund G. Lumbar facet joint syndrome. A randomised clinical trial. J Bone Joint Surg Br. 1989 Aug;71(4):681-4. doi: 10.1302/0301-620X.71B4.2527856. PMID: 2527856.
  19. ↑ Marks RC, Houston T, Thulbourne T. Facet joint injection and facet nerve block: a randomised comparison in 86 patients with chronic low back pain. Pain. 1992 Jun;49(3):325-328. doi: 10.1016/0304-3959(92)90239-8. PMID: 1408298.
  20. ↑ Ghahreman A, Ferch R, Bogduk N. The efficacy of transforaminal injection of steroids for the treatment of lumbar radicular pain. Pain Med. 2010 Aug;11(8):1149-68. doi: 10.1111/j.1526-4637.2010.00908.x. PMID: 20704666.
  21. ↑ Nath S, Nath CA, Pettersson K. Percutaneous lumbar zygapophysial (Facet) joint neurotomy using radiofrequency current, in the management of chronic low back pain: a randomized double-blind trial. Spine (Phila Pa 1976). 2008 May 20;33(12):1291-7; discussion 1298. doi: 10.1097/BRS.0b013e31817329f0. PMID: 18496338.
  22. ↑ Lord SM, Barnsley L, Wallis BJ, McDonald GJ, Bogduk N. Percutaneous radio-frequency neurotomy for chronic cervical zygapophyseal-joint pain. N Engl J Med. 1996 Dec 5;335(23):1721-6. doi: 10.1056/NEJM199612053352302. PMID: 8929263.
  23. ↑ Moussa WM, Khedr W. Percutaneous radiofrequency facet capsule denervation as an alternative target in lumbar facet syndrome. Clin Neurol Neurosurg. 2016 Nov;150:96-104. doi: 10.1016/j.clineuro.2016.09.004. Epub 2016 Sep 5. PMID: 27618781.
  24. ↑ Schneider BJ, Doan L, Maes MK, Martinez KR, Gonzalez Cota A, Bogduk N; Standards Division of the Spine Intervention Society. Systematic Review of the Effectiveness of Lumbar Medial Branch Thermal Radiofrequency Neurotomy, Stratified for Diagnostic Methods and Procedural Technique. Pain Med. 2020 Jun 1;21(6):1122-1141. doi: 10.1093/pm/pnz349. PMID: 32040149.
  25. ↑ Schwarzer AC, Wang SC, Bogduk N, McNaught PJ, Laurent R. Prevalence and clinical features of lumbar zygapophysial joint pain: a study in an Australian population with chronic low back pain. Ann Rheum Dis. 1995 Feb;54(2):100-6. doi: 10.1136/ard.54.2.100. PMID: 7702395; PMCID: PMC1005530.
  26. ↑ Price DD, Long S, Wilsey B, Rafii A. Analysis of peak magnitude and duration of analgesia produced by local anesthetics injected into sympathetic ganglia of complex regional pain syndrome patients. Clin J Pain. 1998 Sep;14(3):216-26. doi: 10.1097/00002508-199809000-00008. PMID: 9758071.
  27. ↑ Verdugo RJ, Ochoa JL. Abnormal movements in complex regional pain syndrome: assessment of their nature. Muscle Nerve. 2000 Feb;23(2):198-205. doi: 10.1002/(sici)1097-4598(200002)23:2<198::aid-mus9>3.0.co;2-4. PMID: 10639611.
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