Department of Rheumatology, University College, London and
1 Department of Health Sciences and Clinical Evaluation, Alcuin College, University of York, Heslington, York YO10 5DD, UK
Correspondence to:
F. Crawford.
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Abstract |
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Methods. Systematic review of the published and unpublished literature. Electronic search of Medline, BIDS and the Cochrane database of clinical trials. An assessment of the quality of the reporting was made of studies included in the review. Main outcome measure: patients' pain scores. Study selection: randomized controlled trials, published or unpublished, that evaluated treatments used for plantar heel pain. Foreign language papers were excluded.
Results. Eleven randomized controlled trials were included in the review. These evaluated some of the most frequently described treatments (steroid injections and orthoses) and some experimental therapies (extracorporeal shock wave therapy and directed electrons). The methodological assessment scores of the published trials were low; small sample sizes and failure to conceal the treatment allocation from study participants prevents more definitive statements about the efficacy of treatments. In 10 of the included trials, patients in both the intervention and control arms reported improved pain scores at the final outcome measure.
Conclusions. Although much has been written about the treatment of plantar heel pain, the few randomized controlled trials involve small populations of patients and do not provide robust scientific evidence of treatment efficacy.
KEY WORDS: Heel, Pain, Treatment, Efficacy, Systematic review.
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Introduction |
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Methods |
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Medline, from 1966 to June 1998, was searched using a generic search strategy described by Dickersin et al. [5] combined with 10 condition-specific items [6]. Additional searching was undertaken using the BIDS database, from hand searching The Chiropodist, The Journal of British Podiatric Medicine, The Foot and the reference lists of all located reports. Contact was made with university podiatry departments to request unpublished theses on heel pain held in their libraries.
A methodological assessment tool based on the 21 items within the Consolidated Standards of Reporting Trials (CONSORT) statement was developed and used to evaluate the design, conduct, analysis and generalizability of trials, and to assess their internal validity [7]. Two reviewers (FC and DA) independently applied these criteria to each reported trial (which had been blinded to obscure the authors) and scored them out of 21 according to the number of methodological assessment items reported. Particular attention was paid to issues of trial design and implementation judged most likely to compromise the main study findings, specifically, the blinding of health professionals and patients to treatment allocation [8]. The objectivity (blinding) of outcome measurements and loss to follow-up were also assessed (Table 4). The identified trials were scrutinized for outcome measures of patients' heel pain. Disagreements were resolved by discussion.
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Results |
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The search of the BIDS database, our hand search and the reference lists of reports identified a further 115 reports of treatments for plantar heel pain, none of which were randomized controlled trials. A total of 153 reports were excluded from the review (Table 3). The conservative and surgical treatments described in both the included and excluded reports appear listed in order of frequency (Tables 1 and 2
).
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Details of the eleven trials included in the review grouped according to intervention
We found no information in these articles on the natural course of the disease and the diagnostic features of heel pain varied enormously. Table 4 shows the methodological scores and sources of bias in the trials, whilst Table 5
gives details of the trials' participants and outcomes.
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Steroid injection vs saline injection (Blockey [12]).
Painful heels were either injected with 25 mg hydrocortisone acetate or saline injection. All patients were also given a sponge heel pad.
Steroid injections alone vs pads alone vs steroid injections and pads (Kriss [21]).
In this three-arm trial, patients received either an anti-pronatory insole or a steroid injection of triamcinolone hexacetonide (Lederspan) 20 mg mixed with 2% lignocaine or both.
Physical therapies
Low-intensity laser therapy (Basford et al. [10]).
Affected feet were irradiated either with a 30 mW continuous-wave 0.83 µm GaA1As IR diode laser or a disabled laser probe. Treatment consisted of three periods of 33 s `sweeps' at both the origin of the plantar fascia and the medial border.
True ultrasound vs placebo ultrasound (Crawford and Snaith [14]).
Episodes of heel pain were allocated to either true ultrasound at a dosage of 0.5 W/cm2 , pulsed 1:4, 3 Mz for 8 min, or placebo ultrasound when only the timer was set. All patients received eight treatments in 4 weeks.
Ionophoresis with dexamethasone vs ionophoresis with saline (Gudeman et al. [16]).
Group 1 patients were treated with placebo ionophoresis (buffered saline) while group 2 patients received ionophoresis with dexamethosone. All patients also received six sessions of ice and stretching programmes over a 23 week period.
Bioelectron MKII (Nolan [20]).
This experimental device produced a beam of electrons, delivered onto the surface of the skin via a probe. The manufacturers claimed that this reduced tissue acidity and restored the inflamed area to normal pH. Patients were randomized to receive either a functioning or a disabled device. After instruction, patients used the device at home, administering treatment for 5 min three times daily over 21 days.
Extracorporeal shock wave therapy (ESWT) vs placebo (Rompe et al. [18]).
ESWT was applied using an experimental device, the Siemens Osteostar. The device made contact with feet in the treatment group only, feet in the placebo group had the device held at a 1 cm distance. In the treatment group, the energy density was 0.06 mJ/mm2 three times in weekly intervals.
Extracorporeal shock wave therapy 1000 impulses vs 10 impulses (Rompe et al. [22]).
ESWT was applied using an experimental device, the Siemens Osteostar. Patients in group 1 received 1000 impulses three times at weekly intervals, patients in group 2 received 10 impulses in the same time period. This second study of ESWT by Rompe et al. involved the largest number of patients in any of the trials in this review.
Insoles and night splints
PPT insoles vs PPT insoles with magnetic foil (Caselli et al. [13]).
Patients in the treatment group wore PPT Rx (type of mass-produced insole) firm moulded insoles containing a Nikken magnetic foil placed in the heel. Control group patients wore the same insole without the magnetic foil. All patients wore the insole for 4 weeks, with no co-interventions.
Night splints (Powell et al. [17]).
In their allocated intervention month, each patient received a night splint made of polypropylene with the ankle placed in 5° of dorsiflexion. Foam was used distally on the splint to give 30° dorsiflexion at the MTP joints.
Summary statistics (mean pain scores with standard deviations) were available for only five reports [14, 20, 21, 23]. The outcomes for all trial participants are reported in Table 6. Seven studies reported excluding individuals with seropositive and seronegative conditions, [1214, 1719, 22], and a further three excluded patients taking either steroids or NSAIDs, or both [10, 20, 21].
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In the five trials that did find statistically significant improvements in pain, the evaluation of ionophoresis and dexamethosone compared with ionophoresis and saline [16] showed an improvement in the outcomes of the dexamethosone group at 1 month only. At outcomes taken thereafter, no differences were detected.
In the trial by Kriss [21], the results showed that patients who received steroid injections alone had the greatest improvement in pain levels. The main threats to the internal validity of this trial was the patients', health professionals' and evaluators' knowledge of the treatment allocation (Table 4).
In both trials of ESWT [18, 22], the health professionals were aware of the treatment allocation. The authors suggest that the painful nature of ESWT therapy meant it was unlikely that patients were unaware of the treatment allocation in the larger study, and in the smaller study the equipment did not make contact with the feet of patients in the placebo group.
Although the cross-over trial of night splints [17] reported improvements in patients' heel pain during the treatment phase, both patients and health professionals were aware of the treatment allocation. It is not reported whether the evaluator of outcomes was objective.
The small sample sizes and failure to conceal treatment allocations from some or all trial participants means that there are substantial threats to the validity of the conclusions produced by these trials.
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Conclusion |
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The main problem with the trials included in the review was the insufficient attention to eliminating bias by concealing treatment allocation from all trial participants. None of the trials that produced statistically significant results concealed the treatment allocation from the health professionals. Without attention to the issue of concealment, internal validity is threatened, reducing the trial's value in establishing the true efficacy of interventions.
The quality of reporting of trials reviewed was generally poor with methodological assessment scores ranging from 5 to 15 out of a possible 21. The two highest methodological assessment scores were both reports of trials contained in unpublished degree dissertations [20, 21] whose authors were free from the word limitations imposed by medical journals. There was no apparent relationship between the trials' methodological scores and the conclusions they reached.
The lack of homogeneity of treatments compared in the trials prevented us from pooling data, which, given the small number of patients in the trials, might have produced evidence for the treatment of painful heels (Table 4). The paucity of summary statistics either published in the reports or made available after direct contact with the authors made any alternative analysis difficult. It was not possible to produce robust evidence of effectiveness for any of the treatments evaluated in the included randomized controlled trials.
These shortcomings mean that moderate degrees of benefit from the treatments may well have been missed (as have any detrimental effects). In future, trials evaluating treatments for heel pain may need to be multicentred, and the reports of all trials (but especially small studies) need to contain detailed summary statistics to enable pooling of data (meta analysis).
The trials included in this review suggest that many observed treatment effects can be explained either by placebo effects or by the spontaneous resolution of symptoms. As the natural evolution of heel pain is not fully understood, we were interested that (with the exception of the cross-over study by Powell et al. [17]) all trials included in this review reported some improvement in patients' mean pain scores in both treated and non-treated populations (Table 6). Given the relatively short treatment period in some trials and the long duration of some patients' pain (Table 5
), it is possible that the observed effects can be explained due to the placebo effect patients can experience simply from participating in a trial.
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Acknowledgments |
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References |
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