Homeopathic arnica for prevention of pain and bruising: randomized placebo-controlled trial in hand surgery (2024)

Abstract

INTRODUCTION

Homeopathy is based on the law of similars (‘like cures like’)which states that a substance that causes specific symptoms in a healthyperson can be used to treat those symptoms in a sick person. Remedies undergoa process called ‘potentization’ which describes stepwise dilutionfrom the ‘mother tincture’ combined with ‘succession’(vigorous shaking). The underlying assumption is that the more dilute a remedythe greater its potency, even though according to Avogadro's number, withpotencies beyond 12C (12 centesimal dilutions) the chance of a single moleculeremaining in the final solution tends to the infinitesimal.

The alpine plant Arnica montana is recommended by homeopathicpractitioners for treating injuries on account of its alleged ability tocontrol bruising, reduce swelling and promoterecovery¹.Homeopathic arnica is popular with patients undergoing surgery, who hope itwill reduce postoperative complications. However, despite favourable anecdotalreports² there islittle scientific evidence of itsefficacy³. Areduction in the pain associated with routine dental extractions has beenreported in placebo-controlled trials of homeopathicarnica^4,5,6,but two double-blind randomized trials demonstrated no effect on pain,swelling or bleeding after surgical removal of impacted wisdomteeth^7,8.Other trials have shown no beneficial effects on postoperativehaematomas⁹ or onrecovery fromhysterectomy¹⁰,acute strokeillness^11,12or childbirth¹³.Tentatively positive results were reported from a small study in patients withacute trauma¹⁴. Arecent trial of homeopathic arnica administered in conjunction with herbalarnica ointment was reported to show no effect on swelling or grip strengthbut a reduction in pain following carpal tunnel releasesurgery¹⁵.

As well as producing inconsistent results, many of these trials havemethodological limitations that make the findings unreliable. A rigorous trialon the subject would therefore be valuable in determining whether homeopathicarnica can aid recovery from surgery. This study was designed as a preliminaryinvestigation of the effect of this preparation on sequelae of hand surgery.If a beneficial effect of arnica (or a positive trend) was demonstrated, alarger trial would then be started.

METHODS

All patients between the ages of 18 and 70 years undergoing elective handsurgery for carpal tunnel syndrome by one surgeon (VSD) at the Royal Devon& Exeter Hospital or a private plastic surgery clinic were eligible forthe trial. Patients were excluded if they were currently taking homeopathicremedies, reported previous hypersensitivity to homeopathy, were takingaspirin, or were unable to complete the study diary or attend follow-upappointments. Patients were not included in the trial a second time if theysubsequently underwent surgery on their other hand. Patients listed forelective surgery for carpal tunnel syndrome were sent information and wereinvited to meet the investigators to discuss the study; each patient's generalpractitioner was also informed. Patients who wished to participate and who metthe study criteria were allocated the next available study number.

Patients received a medication bottle, identifiable only by study number,containing either high (30C) or low (6C) potency homeopathic arnica tablets orindistinguishable placebo. Tablets were to be taken three times daily forseven days preoperatively and fourteen days postoperatively. Patients wereadvised to refrain from handling the tablets or from eating, drinking, smokingor brushing teeth within 20 minutes of taking the tablets and were asked tosuck the tablets rather than simply swallow them. Homeopathic and placebotablets were supplied by A Nelson & Co Ltd. Medication bottles werelabelled with study numbers derived from a computer-generated randomizationlist in blocks of three by an individual not involved with running the trial.The randomization list was kept in a sealed envelope in a locked drawer untilthe end of the trial. All patients and investigators, including the surgeon,physiotherapists and data analysts, remained blind to treatment allocationuntil after data analysis.

All patients were admitted as day cases and received conventionalpreoperative and postoperative care. The operations were done under localanaesthesia. Afterwards the hand was rested on a palmar plaster splint tomaintain the wrist in slight dorsiflexion, allowing the fingers to be gentlymobilized within the dressing and the hand elevated in a high sling. Oralanalgesic medication, either paracetamol or diclofenac, was routinelyprescribed on the hospital discharge form. All patients were seen by thephysiotherapist at four, nine and fourteen days post-surgery (or the closestpossible day). At day four the splint was removed and digits and wrists weremobilized. A Futura aluminium wrist splint was given to the patients to wearfor a further week. Sutures were removed at day fourteen.

The primary outcome measures were pain and bruising, and the secondarymeasures were swelling and use of analgesic medication. Pain was assessed withthe short-form McGill Pain Questionnaire(SF-MPQ)¹⁶completed by the patient at recruitment (to provide a measure of pain fromcarpal tunnel syndrome) and on days four, nine and fourteen post-surgery. TheSF-MPQ includes a visual analogue scale(VAS)¹⁷ to indicatethe intensity of pain and a list of fifteen descriptive words (e.g. stabbing,gnawing, shooting). The VAS is sensitive to changes in painintensity¹⁸. Thepain descriptors are each rated on a 4-point scale (0=none, 1=mild,2=moderate, 3=severe) yielding a total score ranging from 0 to 45. Patientskept a daily pain diary throughout the trial, including VAS scores; they alsorecorded use of analgesics and any adverse events. To quantify bruising, aphotograph of the patient's wrist at the distal crease was taken by thephysiotherapist on days four, nine and fourteen post-surgery under standardlighting conditions. Scanned images were analysed with Adobe Photoshop 4.0software. For each patient, frames representative of normal skin (thenar zone)and of the bruised areas (operative site) were selected. The distribution ofred and blue pixels within each frame was calculated. This information,displayed as a histogram of the number of pixels (y-axis) against anincreasing scale of colour brightness from 0 to 255 (x-axis), enabledan objective and quantitative comparison of the colour of the bruised areawith the colour of the normal skin. This method was developed for objectivemeasurement of burn scarhypertrophy¹⁹ andhas been successfully used to assess healing at skin graft donorsites²⁰. For eachpatient the extent of bruising was also assessed independently by two plasticsurgeons blind to treatment allocation on a 3-point scale (0=none,1=mild—moderate, 2=severe) as a check on the validity of colourseparation analysis in assessing bruising.

To quantify swelling, wrist circumference was measured at the distal wristcrease before anaesthetic infiltration and on days four, nine and fourteenpost-surgery. Three readings were taken of each measurement. Adherence to thestudy medication was assessed by tablet counts at the end of the study.Patients were asked to tick boxes in the study diary as a further record oftablet taking. The success of patient blinding was assessed by a question inthe study diary on the last day of the trial, asking patients to indicatewhich treatment they believed they had received (arnica, placebo, don'tknow).

RESULTS

The flow of patients through the trial is displayed inFigure 1. Of the 64 patientsrecruited to the trial, 62 were included in the analysis. One patient in thearnica 6C group did not undergo the scheduled surgery so was no longereligible for the trial and one patient from the arnica 30C group withdrew fromthe study before undergoing surgery because she believed that the tablets werecausing her to feel ‘unhappy or low’. 8 other patients reportedadverse events—3 in the placebo group (heartburn; sore throat andflu-like symptoms; faintness and headache); 3 in the arnica 30C group (drymouth; headache; feeling ‘throbby’ in head/neck); 2 in the arnica6C group (drowsiness; sore tongue). Adherence was incomplete in all threegroups. As judged by tablet counts at the end of the trial, the number ofpatients who had taken less than 90% of their tablets was 9/20 for the arnica6C group, 7/22 for the placebo group and 6/20 for the arnica 30C group.Self-reported adherence was much higher, with only 2 patients indicating thatthey had taken less than 90% of the tablets. In total there were data missingat one or more timepoints on at least one outcome for 10 patients—3 ofthese were from the arnica 6C group, 5 from the placebo group and 2 from thearnica 30C group. Patient blinding seemed to remain intact throughout thestudy. 7/20 patients in the arnica 6C group, 3/22 in the placebo group and7/20 in the arnica 30C group correctly identified their treatment allocationat the end of the trial. The randomization procedure resulted in similarpatient characteristics in each group for most variables(Table 1). However, the arnica6C group contained more male patients and had lower VAS scores for carpaltunnel syndrome pain than the other two groups.

Results of the primary outcome measures of pain and bruising are presentedin Tables ​Tables22 and​and3.3. Postoperative pain did notdiffer between the groups at day 4 according to VAS scores(χ²=4.81, d.f.=2, P=0.79) or MPQ descriptor scores(χ²=2.48, d.f.=2, P=0.29). Similarly, bruising did notdiffer between the groups at day 4 in terms of blue (χ²=1.61,d.f.=2, P=0.45) or red (χ²=3.89, d.f.=2,P=0.14) channel brightness. The null hypothesis was thereforeaccepted.

There was support from the results of the secondary outcome measures ofswelling and use of analgesic medication, which are presented in Tables​Tables44 and​and55 andFigure 2. Neither swelling(χ²=1.25, d.f.=2, P=0.54) nor number of tablets(χ²=1.63, d.f.=2, P=0.44) differed between the groupsat day four. The only group difference that approached statisticalsignificance was on the MPQ descriptors total score (χ²=6.72,d.f.=2, P=0.04) where the placebo group had lower scores than thearnica 30C group at day nine (U=122.0, P=0.01, Mann—Whitney Utest). Figure 3 displays thedaily pain VAS scores from the study diary.

DISCUSSION

Despite its reputation as a useful intervention for preventing the effectsof anticipated trauma (e.g. surgery) or for treating unexpected trauma (e.g.accidental injury), homeopathic arnica was no better than placebo in reducingpostoperative complications. These results are compatible with the negativefindings from otherstudies^{7,8,9,10,11,12,13,15}.

This trial was designed to be a methodologically rigorous investigation ofthe specific effects of two potencies of homeopathic arnica. Attempts weremade to select outcome measures that were objective and/or adequatelyvalidated. In particular, by employing colour separation analysis it wasintended to assess bruising in a more objective quantitative manner thanprevious studies that have relied only on crude and subjectiveratings^9,22.

These results do not support the routine use of homeopathic arnica forpreventing or reducing postoperative complications such as bruising, swellingand pain. However, they do not rule out the possibility that individualpatients could benefit. Homeopathic practitioners identify specific patientcharacteristics (e.g. fear of being touched, denial of illness, difficultysleeping due to a hard bed, anxiousdreams²) that helppredict who will respond to arnica. This trial did not apply traditionalhomeopathic principles in this way. However, in one trial of surgical patientswhere the homeopathic remedy was chosen to match the patient's constitution,arnica was selected in 21 of 24 cases and no differences from placebo weredemonstrated⁸.

The use of non-parametric tests reduces the likelihood of detectingstatistical differences since they are less powerful than parametric testsparticularly with smaller samples. However, a type II error does not appear toaccount for the results of this trial, where differences between groups are sosmall that they would have no clinical relevance even if statisticallysignificant. Furthermore, there is no clear trend or consistent pattern thatfavours any of the interventions, indicating that measurement and random errorcan explain any perceived differences.

Poor adherence to the trial regimen was seen in over one-third of thesample. However, it seems unlikely that this explains the lack of differencebetween arnica and placebo since homeopathic practitioners often recommendthat a single dose of arnica before and after surgery is sufficient to hastenrecovery². From thestudy diaries it seems that more tablets were missed in the latter days of thetrial when patients are likely to have fully recovered.

A final point to consider in attempting to explain the lack of differencebetween arnica and placebo groups is the surgical model used in this trial.There was little bruising, pain and swelling in any of the groups, so perhapsthe skill of the surgeon offered little scope for arnica. However, arnica isreputed to be effective in every case of trauma, howeverslight²; some of therigorous trials cited above have tested arnica in bigger operations withoutsignificanteffects^{7,8,9,10,11,12,13}.Conversely, it might also be argued that major tissue injury is too severe tobenefit from the subtle effects of homeopathy; the present choice of surgicalmodel represented a compromise between minor and major trauma.

In view of the ineffectiveness of homeopathic arnica observed in this andother trials, how can we account for its remarkable reputation for healinginjury? The probable explanation is positive selection bias. Some patientsrecover very quickly from surgery. If those taking arnica attribute their goodrecovery to the homeopathic remedy and this apparent association is widelyreported, it is easy to see how the reputation can build. Since theexperiences of patients who recover well without taking arnica and those whor*ceive no benefit from arnica are less likely to be reported, the mythbecomes reinforced.

Acknowledgments

We thank Joanne Barnes for her assistance in designing this trial, ChrisStone for his help with the colour separation analysis and Theresa Sheldon whocollected data for this trial. Funding was provided by the Dr Susil Kumar andJamila Mitra Charitable Trust (UK); homeopathic and placebo tablets weresupplied by A Nelson & Co Ltd.

References