Debridement of plantar callosities in rheumatoid arthritis: a randomized controlled trial

H. J. Davys, D. E. Turner1, P. S. Helliwell1, P. G. Conaghan1, P. Emery1 and J. Woodburn1

Foot Health Department, The Leeds General Infirmary and 1 Academic Unit of Musculoskeletal Disease, The University of Leeds, Leeds, UK.

Correspondence to: J. Woodburn, Academic Unit of Musculoskeletal Disease, University of Leeds, 36 Clarendon Road, Leeds LS2 9NZ, UK. E-mail: j.woodburn{at}leeds.ac.uk


    Abstract
 Top
 Abstract
 Introduction
 Participants and methods
 Results
 Discussion
 References
 
Objective. To compare forefoot pain, pressure and function before and after normal and sham callus treatment in rheumatoid arthritis (RA).

Patients and methods. Thirty-eight RA patients were randomly assigned to normal (NCT group) or sham (SCT) scalpel debridement. The sham procedure comprised blunt-edged scalpel paring of the callus which delivered a physical stimulus but left the hyperkeratotic tissue intact, the procedure being partially obscured from the patient. Forefoot pain was assessed using a 100 mm visual analogue scale (VAS), pressure using a high-resolution foot pressure scanner and function using the spatial–temporal gait parameters measured on an instrumented walkway. Radiographic scores of joint erosion were obtained for metatarsophalangeal (MTP) joints with and without overlying callosities. The trial consisted of a randomized sham-controlled phase evaluating the immediate same-day treatment effect and an unblinded 4-week follow-up phase.

Results. During the sham-controlled phase, forefoot pain improved in both groups by only 3 points on a VAS and no statistically significant between-group difference was found (P = 0.48). When data were pooled during the unblinded phase, the improvement in forefoot pain reached a peak after 2 days and gradually lessened over the next 28 days. Following debridement, peak pressures at the callus sites decreased in the NCT group and increased in the SCT group, but there was no statistically significant between-group difference (P = 0.16). The area of and duration of contact of the callus site on the ground remained unchanged following treatment in both groups. Following debridement, walking speed was increased, the stride-length was longer and the double-support time shorter in both groups; however, between-group differences did not reach levels of statistical significance. MTP joints with overlying callus were significantly more eroded than those without (P = 0.02).

Conclusions. Treatment of painful plantar callosities in RA using scalpel debridement lessened forefoot pain but the effect was no greater than sham treatment. Localized pressure or gait function was not significantly improved following treatment.

KEY WORDS: Plantar callosities, Callus debridement, Forefoot pain, Metatarsophalangeal joint, Gait parameters


    Introduction
 Top
 Abstract
 Introduction
 Participants and methods
 Results
 Discussion
 References
 
Acquired plantar hyperkeratotic lesions (callus) are associated with elevated mechanical stresses over prominent and deformed joints and they regularly occur in rheumatoid arthritis (RA) [1, 2]. Regular sharp scalpel debridement, usually undertaken by podiatrists, is a treatment of choice but there are no recommendations on the frequency or use of this treatment [1, 3]. A preliminary study showed short-lasting but significant reduction in forefoot pain over a 4-week period accompanied by potentially harmful increases in focal stresses at the treated callus site [1]. If callus acts as a physical irritant then debridement may explain why pain relief is achieved [1]. Reducing foot pain is associated with improved function and as patients walk faster, larger forces may be distributed over prominent areas such as treated callus sites thereby increasing local stresses [1, 2]. This mechanism has not been clearly elucidated.

The efficacy of callus debridement and its effects on local stresses and function have not been tested under controlled conditions. The current study design involves a sham treatment as a comparator to the normal treatment procedure.


    Participants and methods
 Top
 Abstract
 Introduction
 Participants and methods
 Results
 Discussion
 References
 
Objectives
The primary objective was to compare forefoot pain before and after normal and sham callus treatment. The secondary objectives were to compare the effects of these treatments on localized plantar pressures and the spatial–temporal gait parameters.

Recruitment of patients
Patients were eligible for inclusion if they had a definite diagnosis of RA and had symptomatic skin callosities overlying the plantar metatarsal heads that would have been routinely debrided by a podiatrist as part of normal foot care [4]. No patients were excluded on the basis of age, gender or race. Patients were ineligible if they had diabetes mellitus, neurological disease with lower limb symptoms or symptomatic peripheral vascular disease of the lower extremities. Patients were recruited from the Rheumatology Department at The Leeds General Infirmary. The study was undertaken with Local Research Ethics Committee approval and written approval was obtained from subjects.

Interventions
Patients were randomized to receive either normal callus treatment (NCT) or sham callus treatment (SCT). NCT comprised sharp scalpel debridement of the callosity. For the SCT, normal callus treatment was simulated with the podiatrist using a blunt-edged scalpel such that no callus tissue was debrided. Screens were used to obscure the patient's vision whilst treatment was in progress. A single podiatrist undertook all treatments. Patients continued to use their orthopaedic footwear or orthoses during the study period.

Outcomes
The primary outcome was pain in the signal foot as determined by the 100 mm visual analogue scale (VAS). Debridement removes plantar tissue and may therefore affect the contact area and focal stresses at the treated callus sites. Both the magnitude and timing of localized plantar forces and pressures can change if overall gait patterns alter [1, 5]. For these reasons, a high-resolution foot pressure scanner (Emed-SF, Novel GmbH, Munich, Germany) and an instrumented walkway (GaitRite, CIR systems, Clifton, NJ, USA) were used to measure secondary functional outcomes including contact area (cm2), peak pressure (kPa) and force (N) and contact time (ms) as pressure variables and walking speed (m/s), cadence (steps/min), stride length (m), cycle time (s) and double-support time (% of gait cycle) as spatial temporal gait parameters. Local plantar stresses may also be elevated by eroded metatarsal heads pressing within the skin, and for this reason radiographic damage at each metatarsophalangeal (MTP) joint with an overlying lesion was scored using the Scott modification of the Larsen method [6]. For both groups combined, a median erosion score was derived for each foot for MTP joints with and without overlying callus lesions. Finally, patients were monitored for adverse reactions and side-effects.

Design
The study had a randomized sham-controlled phase which compared pain before and immediately after the interventions. For ethical reasons, patients in the sham group had callosities debrided prior to leaving the clinic as they were already in receipt of regular foot care. Therefore, the second phase of the study was unblinded and evaluated pain daily for 7 days and then once weekly for 4 weeks. Plantar pressures and spatial–temporal gait parameters were assessed during the sham-controlled phase.

Sample size and randomization
We used data from a pilot study to estimate sample size based on a minimum detectable difference between active and sham treatments of 20 points (S.D. 21.3) on a VAS. Therefore a total of 38 patients were required to enter this two-treatment parallel-design study given a probability of 80% that the study will detect a treatment difference at a two-sided 5.0% significance level, if the true difference between the treatments is 20.0 units. Randomization was undertaken using random number codes and a balanced block-of-four design. The allocation codes were sealed in opaque envelopes and issued sequentially by an independent observer.

Statistical methods
The relative effectiveness of the intervention was determined by comparing the change in primary outcome variables between baseline and post-treatment in the sham-controlled phase. This was based on the Hodges–Lehman estimate of the median difference with 95% confidence interval based on a two-sided Mann–Whitney U-test. In the unblinded phase, the change in pain scores between 1 and 28 days was pooled for both groups and the underlying trend summarized descriptively. Missing data were replaced by the last value carried forward.

The plantar pressure and spatial–temporal gait secondary outcomes were normally distributed and therefore compared using the unpaired Student's t-test. Since 10 comparisons were performed, P values were adjusted using Bonferroni correction. When P values were <0.005 (0.05/10), the decisions made in the corresponding tests were considered significant. MTP joint erosion scores at sites with and without overlying callus were compared separately using the Mann–Whitney U-test with the level of significance set at P<0.05.

Baseline comparisons revealed no statistically significant differences between the two groups for the demographic and disease characteristic or the primary and secondary outcome variables.


    Results
 Top
 Abstract
 Introduction
 Participants and methods
 Results
 Discussion
 References
 
Trial profile
Fifty-five patients attending the Rheumatology Podiatry Clinic were identified as potential participants in the study. Thirteen patients refused to participate. Four patients were ineligible: two with resolved symptoms, one had recently undergone foot surgery and one patient was unable to walk barefoot. At baseline 38 patients were randomly assigned to the NCT (n = 19) and SCT (n = 19) groups. At 4 weeks, one patient from the NCT group was lost to follow-up due to unrelated illness (Fig. 1).



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FIG. 1 Trial profile.

 
Demographic and clinical characteristics
The NCT group recruited 16 female and 3 male RA patients with a mean age of 60.2 yr (range 39–80 yr) and mean disease duration of 20.5 yr (range 6–37 yr). The SCT group recruited 17 female and 2 male patients with a mean age of 57.5 yr (range 35–70 yr) and mean disease duration of 19.4 yr (range 2–38 yr). There were 43 callosities distributed over 38 feet in the NCT group and 54 lesions distributed over 38 feet in the SCT group. Nine patients in the NCT group and 11 in the SCT group used orthopaedic footwear and orthoses.

Primary outcome
During the sham-controlled phase, forefoot pain improved in both groups following intervention but by only 3 points on a VAS scale and no statistically significant between-group difference was found (Table 1). When the data were pooled during the unblinded phase, forefoot pain continued to improve up to 2 days post-intervention (Fig. 2). From day 2 to week 3 the treatment effect gradually lessened, and by week 4, prior to returning to clinic, a sharp loss of pain relief was observed. In both groups, the improvement in forefoot pain never exceeded 15 VAS points at any follow-up.


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TABLE 1. Changes in outcome variables between baseline and post intervention during the sham-controlled phase of the trial. Values are medians (interquartile range) or mean (standard deviation)

 


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FIG. 2. Median (IQR) change in VAS forefoot pain scores from baseline to 4 weeks for NCT-normal callus treatment, and SCT-sham callus treatment groups with data pooled at day 1 to week 4. BL, baseline; Pin, post-intervention (sham or normal treatment); wk, week number.

 
Secondary outcomes
At the plantar forefoot callus sites, the contact area increased and the contact time decreased in both groups following normal or sham debridement but these changes were less than the reported measurement error of the system of ±5% (Table 1). Peak pressures decreased by <2% in the NCT group and increased by 9% in the SCT group, whilst peak force showed increases of 3 and 9% respectively at the callus sites following treatment. However, there were no statistically significant between-group differences reported for any of these pressure variables.

Immediately following normal or sham treatment, function improved in both groups characterized by increased walking speed (by 9% for the NCT and 12.3% for the SCT group), increased cadence (1% NCT, 3% SCT), longer stride length (6% NCT, 11% SCT) and shorter double-support time (–7% NCT, –10% SCT). In both groups no change (<1%) was observed in cycle times. However, for all of these functional outcomes, no statistically significant between-group differences were reported following normal or sham callus debridement.

The median modified Larsen scores were 4.75 [interquartile range (IQR) 4, 5] and 3.75 (IQR 2, 5) for MTP joints with and without overlying callus respectively and this was significantly different (median difference = –0.5; 95% CI of difference –1.5 to –2.0, P = 0.02).

Adverse reactions and side-effects
In the NCT group, small ulcers were found at two callus sites following debridement and were not associated with the treatment provided during the study. These patients were not excluded.


    Discussion
 Top
 Abstract
 Introduction
 Participants and methods
 Results
 Discussion
 References
 
Sharp scalpel debridement of painful forefoot plantar callosities in RA reduced pain and focal pressures and increased walking function, but these changes were no greater than for a sham procedure. The main features of the study were the sham treatment, concealed randomization and inclusion of mechanical and functional outcomes. The pragmatic design maximized the practical aspects of the study and included typical podiatry patients with advanced RA foot disease.

The normal callus treatment was in accordance with standard practice and no attempt was made to withdraw orthoses or orthopaedic footwear. These treatments may have biased our findings; however, their use was equally distributed between the groups. Improved pain and function in the sham group was reported and it is difficult to say whether this was a true or perceived placebo effect. The sham procedure included aseptic technique and scalpel application to the skin and such modes of treatment delivery are thought to influence the placebo effect [7]. However, the technique did deliver a physical stimulus to the callus lesion, although no hyperkeratotic tissue was removed; this may have had a therapeutic effect.

In the normal callus treatment group, improved pain and function were no different from the sham group. This finding is inconsistent with previous uncontrolled studies which report absolute changes of between 35 and 60 mm on VAS scales immediately following scalpel treatment [1, 2]. Immediate pain relief with this treatment is thought to be related to the removal of the callus which acts as a physical irritant, often likened by patients to ‘removing a pebble or marble’ from under the MTP joints. One explanation may be related to the study design, particularly non-specific effects in the patient–podiatrist relationship. Prior to entering the study all patients were receiving regular podiatry care and in the course of providing the study information, gaining consent and delivering the normal or sham treatment, patient expectation of the treatment may have changed. Furthermore, forefoot pain around the MTP joints may have been related to other causes such as synovitis, bursitis or from pressure within where eroded metatarsal heads press on unprotected skin due to fatty-fibro padding displacement [2]. Indeed, MTP joints with an overlying callus were more eroded, and this suggests a relationship may exist between local stresses, joint damage, callus formation and painful symptoms.

Normal care was not withheld from these patients since many had long-standing RA, with associated complications, including a history of foot ulceration. Sharp scalpel debridement was undertaken in the sham group and in the daily and weekly reviews, pain improved then slowly tapered off over a 4-week period and this is consistent with past observations [1]. During this period calluses reoccurred. Since these assessments were unblinded, change in pain scores may have been biased, although the absolute change is still less than previously reported, suggesting some residual effects of non-specific behavioural response [1, 3].

The findings revealed some important physical and functional characteristics of the treatment. Both groups showed functional changes alongside decreased peak pressures at the callus site of the NCT group and increased peak pressures in the SCT group. Reduction of focal stresses following callus debridement has been consistently demonstrated in the diabetic foot but not before in RA [1, 8, 9]. In diabetes this effect is important as callus is highly predictive of foot ulceration and its debridement significantly reduces these stresses and facilitates ulcer healing [8, 9]. Its significance in RA is less clear because pressure reduction was not statistically or clinically significant and there was no associated reduction in foot pain. Foot ulceration is less common and less severe in RA, and only two cases of small ulcers were noted in this cohort. Reduction of focal pressures may be beneficial in these cases but overall changes to mechanical stresses are clearly short-lived since the callosities nearly always return over a 4-week period.

We conclude that the causes of forefoot pain may not be solely attributed to plantar callosities, and under controlled conditions sharp scalpel debridement has no benefits over sham for pain relief, localized pressure reduction or functional improvement. Further research is necessary to determine effective strategies for treatment.


    Acknowledgments
 
Dr Woodburn's work was supported by a Medical Research Council Clinician Scientist Fellowship award. Professor Emery is an Arthritis Research Campaign Professor in Rheumatology.

The authors have declared no conflicts of interest.


    References
 Top
 Abstract
 Introduction
 Participants and methods
 Results
 Discussion
 References
 

  1. Woodburn J, Stableford Z, Helliwell PS. Preliminary investigation of debridement of plantar callosities in rheumatoid arthritis. Rheumatology 2000;39:652–4.[Abstract/Free Full Text]
  2. Dixon St J A. The rheumatoid foot. Proc R Soc Med 1970;63:677–9.[ISI][Medline]
  3. Redmond A, Allen N, Vernon W. Effect of scalpel debridement on the pain associated with plantar hyperkeratosis. J Am Podiatr Med Assoc 1999;89:515–19.[Abstract]
  4. Arnett FC, Edworthy SM, Bloch DA et al. The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis. Arthritis Rheum 1988;31:315–24.[ISI][Medline]
  5. Turner DE, Woodburn J, Helliwell PS, Cornwall ME, Emery P. Pes planovalgus in rheumatoid arthritis: a descriptive and analytical study of foot function determined by gait analysis. Musculoskeletal Care 2003;1:21–33.
  6. Edmonds J, Saudan A, Lassere M, Scott D. Introduction to reading radiographs by the Scott modification of the Larsen method. J Rheumatol 1999;26:740–2.[ISI][Medline]
  7. Kaptchuk TJ, Goldman P, Stone DA, Stason WB. Do medical devices have enhanced placebo effects? J Clin Epidemiol 2000;53:786–92.[CrossRef][ISI][Medline]
  8. Young MJ, Cavanagh PR, Thomas G, Johnson MM, Murray H, Boulton AJM. The effect of callus removal on dynamic plantar foot pressures in diabetic patients. Diabet Med 1992;9:55–7.[ISI][Medline]
  9. Pitei DL, Foster A, Edmonds M. The effect of regular callus removal on foot pressures. J Foot Ankle Surg 1999;38:251–5.[Medline]
Submitted 22 August 2004; revised version accepted 10 September 2004.



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