Abstract
Background:
Focused extracorporeal shock waves (ESWT) has been used in the treatment of plantar fasciitis with heel spurs. The optimal location for administering treatment, however, has not been determined. The purpose of this study was to determine whether fluoroscopy-guided location of a heel spur or patient location of the maximal point of tenderness is more effective in administering ESWT.
Methods:
In a prospective, examiner-blinded trial, 41 patients were randomized into two groups for treatment by ESWT: group 1, location of the heel spur for ESWT by fluoroscopy, and group 2, patient location for ESWT by maximal point of tenderness. Each group had three session of ESWT at 1-week intervals. The success rates between the two groups were assessed at 6 and 12 weeks.
Results:
No significant differences were noted between the groups.
Conclusions:
Despite the small number of patients in the study, patient location for positioning the focus in ESWT in treatment of plantar fasciitis with a heel spur is recommended.
INTRODUCTION
Shock waves are single-pulse sound waves that spread quickly with a sudden rise in pressure and release energy at the interface of two media. 17 Musculoskeletal extracorporeal shock wave therapy (ESWT) has been used for treatment of calcifying tendinitis of the shoulder, 7,11 plantar fasciitis, 14,24 lateral epicondylitis, 13,32 and nonunions. 15,26 The effectiveness of ESWT in the treatment of plantar fasciitis is controversial. There are several studies demonstrating benefit of the treatment, 6,8,16,18,24,25,29,31 and a few, but well-designed trials, showing that low-energy ESWT is ineffective in the treatment of heel pain. 5,14,28 However, there is no trial demonstrating the superiority of high-energy shock waves compared to low-energy shock waves in that disease. Further conservative methods and operative procedures have been used for treatment; 2 –4,10,12,34 however, well-designed study trials are rare.
Many different theories exist about the etiology of plantar fasciitis. Furthermore, the relationship between subcalcaneal pain and heel spurs has not been definitely established. Previously it was stated that subcalcaneal pain is not caused by the spur of bone, which is the end result of recurrent strain on the plantar fascia. 1 In fact, a spur may be present in 50% of patients with painful heel, 30 but only 39% of those with heel spurs reported any history of pain. 27
Location devices using either ultrasound 5 or fluoroscopy 22 have been introduced to center the shock-wave application over the heel spur. Because of the uncertainty about whether the heel spur is the cause of pain, it is questionable if focusing on the spur is the correct location. Another form of focusing the shockwaves is location by the patient in which maximal energy is focused on the area of most pain, without using any instrumental location system. The aim of this study was to determine the clinical differences between location by the patient and location by computer-assisted fluoroscopy in the treatment of painful plantar heels with focused extracorporeal shock waves.
MATERIAL AND METHODS
Our study was a prospective, randomized, examiner-blind, single-center study. Twenty-six women and 16 men were recruited after passing the inclusion criteria (Table 1). One man was excluded because he had received a local injection with a steroid within 12 weeks after shock-wave therapy. Thus, 41 patients completed the study.
Inclusion and exclusion criteria
The mean age in group 1 was 52 ± 8 years and in group 2 it was 57 ± 14 years. The mean Body Mass Index was 30.4 ± 4.3 and 29.8 ± 4.3, respectively. Patients in group 1 received 4.3 different other conservative treatment modalities, and group 2 patients received 4.0 (ultrasound, insole supports, injections, acupuncture). Differences between the groups were not statistically significant.
Patients were recruited in a university hospital from December, 2000, to April, 2002. All patients were informed of and consented to the location methods. The population was randomized into two groups (group 1, location by fluoroscopy and group 2, location by the patient) by an online randomizer. The caregiver opened an envelope with randomization numbers immediately before the first treatment. Both groups were treated with the same lithotripter Storz Modulith SLK (Storz Medical Products Kreuzlingen, Switzerland). Extracorporeal shock waves were applied by using a contact gel Gerosonic (Gerot Pharma. Vienna, Austria). Local anesthesia was not given. In group 1 (20 patients) a three-dimensional computer-assisted navigation device device (Lithotrack, Storz Medical Products Kreuzlingen, Switzerland) was used to locate the plantar heel spur with maximal precision. The center of the heel spur was located by fluoroscopy in two planes according the constructor's instructions. Then the head of the lithotripter was docked medio-plantarly to the heel by using the computer-assisted navigation device. In group 2 (21 patients) the location was determined according to cooperative patient biofeedback of the maximal point of tenderness. Here the lithotripter was docked medioplantarly to the heel after the point of tenderness had been marked with a pen by the examiner. After the application of shock waves was started, the patients could focus the shock waves to the maximal point of tenderness by moving their feet minimally. In all patients, 1000 impulses of constant energy flux density (0.08mJ/mm2, low-energy) with a frequency of 4 Hz were administered at each session. Three sessions were performed at intervals of 1 week. All patients had a radiographically proven plantar heel spur.
The investigator delivering the treatment was not involved in followup, and only he knew the treatment. The clinical outcome was assessed by an observer blinded to the treatment group allocation. Followup examinations were carried out at 6 and 12 weeks after the last treatment session. The success rate was determined after 12 weeks (primary endpoint). Success was defined by a Roles and Maudsley score of 1 or 2. 14 The modified Roles and Maudsley score includes four grades of pain and activity. 21 In addition, the Roles and Maudsley score was determined at 6 weeks. The interval of painless walking (in minutes), pain intensities (at rest, at night, at pressure, and at weightbearing), on a visual analogue scale (VAS, 0 for no pain and 100 for unbearable pain), 20 and subjective changes were noted at 6 and 12 weeks (secondary endpoints). Patients were asked about their pain, whether symptoms improved, increased, or remained the same as before treatment. Additionally, painless plantar pressure was measured on the affected side and contralateral, healthy, side by having the patient stand on a scale. The weight applied to the scales was measured in kilograms. The classification was as follows: 1 = equal weightbearing on both sides; 2 = up to 25% reduction of weightbearing compared to the unaffected side; 3 = up to 50% reduction; 4 = up to 75% reduction; 5 = up to 100% reduction. Duration of treatment sessions and duration of fluoroscopy application (in group 1) were assessed.
Statistical Analysis
Repeated measure analysis was performed for each variable to compare both location modalities and the duration of treatment within groups. Demographic data were analyzed with an unpaired, two-sided Student's test. The success of treatment was calculated with a two-sided Fisher's exact test. Data were analyzed with SAS and GraphPad Prism 2.01 (statistical analysis software, Cary, N.C.). The level of significance was set at 0.05.
RESULTS
Primary end point
The primary end point could be assessed in all patients (Table 2). 15 patients in Group 1 and 14 patients in Group 2 had a Roles and Maudsley score of 1 to 2 at 12 weeks. The mean value for all patients of Group 1 was 1.9 ± 1.0 and fr patients of Group 2 it was 2.0 ± 0.9. The differences were not significant.
Roles and Maudsley Score
Roles and Maudsley score at 6 weeks. 13 patients in Group 1 and 14 patients in Group 2 had a Roles and Maudsley score of 1 or 2 at 6 weeks. The differences were not significant (Table 2).
Results of the Roles and Maudsley score at 6 and 12 weeks
1 corresponds to an excellent result without pain and full range of mobility and activity; 2 corresponds to a good result with occasional pail and full range of mobility and activity; 3 corresponds to a fair result with pain after activity; 4 corresponds to a poor result with limitation in daily activities. The subjective pain assessment by each patient is documented for the 6-week and 12-week followup.
Subjective Pain Assessment
Subjective results were better at 6 weeks than before treatment in 14 patients in group 1 and 18 patients in group 2. At 12 weeks, 16 patients in group 1 and 19 patients in group 2 reported better results compared to before treatment. These differences were not statistically significant (Table 2).
Interval of Painless Walking
A significant improvement (p < 0.01) was recorded in both groups 12 weeks after treatment. The difference between the groups was not statistically significant (Table 3).
Pain Intensity at Rest
There were no significant differences for this parameter between the groups nor for the duration of therapy within the groups (Table 3).
Pain Intensity at Night
A significant improvement was noted at 6 and 12 weeks (p < 0.001) after treatment compared to before treatment and from the first to the second (p < 0.004) followup in both groups. The location modality had no significant influence on pain intensity at night (Table 3).
Pain Intensity at Pressure
Significant improvement was observed in both groups from therapy to first and second followup (p < 0.0001). Also here, location had no significant influence (Table 3).
Pain Intensity at Weightbearing
Pain decreased significantly in both groups at 6 and 12 weeks (p < 0.0001), but not significantly from 6 to 12 weeks. No significant differences were noted between groups 1 and 2 (Table 3). The number of other conservative treatment modalities (insoles) had a significant influence on pain intensity on weightbearing. The higher the number of therapies the more effective was ESWT on reducing pain on weightbearing (p = 0.015).
Results of the secondary end point parameters
Painless Plantar Pressure by Scales
Before treatment eight patients in group 1 and 13 in group 2 had painless plantar pressure up to 50% of the contralateral, unaffected foot. At 6 weeks, 12 patients in group 1 and 16 patients in group 2 had painless pressure (up to 50% of the contralateral unaffected foot), and at 12 weeks, 17 patients in group 1 and 19 patients in group 2 had painless pressure (up to 50% of the contralateral, unaffected foot). The values calculated as continuous data are shown in Table 3. The improvement from pretreatment to 6 and 12 weeks was statistically significant (p < 0.001) in both groups. The severity before treatment had a significant influence on the outcome (p < 0.001). Thus, group 1 was statistically significantly better because they had more severe symptoms before treatment (p = 0.017).
Duration of Therapy Session and Radiation Application
The shorter duration of three therapy sessions in group 2 was statistically significant (p < 0.0001). In all 3 sessions of Group 1, fluoroscopy was in use for an average of 68 seconds.
Other Variables
Age, sex, and body-mass-index had no significant influence on results. Complications were not observed.
DISCUSSION
The efficacy of EWST for recalcitrant plantar fasciitis is controversial. 5,6,8,14,16,18,24,25,28,29,31,33 ESWT has been approved for the treatment of plantar fasciitis by the Food and Drug Administration 18 and can be recommended to patients before performing an invasive procedure, particularly because of its minimal adverse effects 23 and since nonoperative and operative treatment have, for the most part, limited high-level evidence based studies.
In reviewing the literature, the location of the shock wave focus was done mostly by ultrasound 5,8,14,31 or radiographic devices. 16,19,22,24 The shock wave focus was positioned to the tip or center of the calcaneal spur or to the thickest portion of the plantar fascia adjacent to the calcaneus. The exact site of origin of pain in painful heel syndrome is not yet understood. Therefore, we wanted to know whether an exact location device for positioning the shock wave focus is necessary and whether there is any benefit of using fluoroscopy compared to a subjective location by patient biofeedback.
We found no meaningful difference in clinical outcome between the location modalities. Although the success rates, with excellent or good results using the Roles and Maudsley score at 3 months, were slightly better in group 1 than group 2 (75% compared to 67%) no statistically significant differences could be detected.
A limitation of our study is the small number of participants. We performed a power analysis of the success rate with the current data. A sample size for each sample of 504 was calculated with the aim of detecting a significant difference in the success rates of 75% and 66% with a power of 80% and a = 0.05. The highest number of patients (272) in evaluating the effect of ESWT in plantar fasciitis was in a study by Haake et al. 14 The time of recruitment was 2 years, and nine centers were involved in that study. A trial with at least 1008 patients would be needed to have a statistical power to evaluate differences related to location modalities. Most of the outcome parameters revealed better results for group 2, although no statistically significant differences could be demonstrated. The differences in the time spent for the therapy sessions was relevant but expected. The time-consuming positioning of the focus by fluoroscopy caused the longer therapy time in group 1. Obviously, the radiation is a burden that favors patient location for treatment. However, the results of painless plantar pressure were significantly better in group 1, although more severe primary values before treatment had improved the results at 6 and 12 weeks generally.
Although most of the parameters showed improved results at followup compared to before treatment and the overall success rate of all 41 patients (71%) was higher than the placebo (40%) and treatment (46%) groups of the trial performed by Haake et al. 14 no further conclusions about the general efficacy of ESWT in the treatment of plantar fasciitis can be made by our study.
We found no noticeable differences in the clinical outcome between the groups. However, due to the longer lasting therapy sessions and the burden of additional radiation with fluoroscopy, we recommend patient location as a safe and effective technique for positioning the focus of ESWT in the treatment of plantar fasciitis with a calcaneal spur. Our results are only valid for therapeutic variables (low-energy treatment) and the device applied.