Foot Orthoses in Patients With Sciatica

A multi-centre randomised controlled clinical trial has been designed according to the CONSORT guidelines. The design was carried out by the research group (5 researchers, Ph.D and Degree in Podiatry, from the University of Seville and 2 researchers, Medicine Doctors, from the university hospital "Virgen de Valme", in Seville, Spain). The patients will be diagnosed and recruited from the aforementioned hospital. The data will be gathered in the Clinical Area of Podiatry of the University of Seville.

The main inclusion criteria will be to have a medical diagnosis of chronic sciatica (CS) caused by lumbar disc herniation (LDH). All participants who voluntarily take part in the study will be given an informative document where the nature, objectives, and potential risks of the investigation are explained. When the participants have read it and any doubts have been resolved, the informed consent will be given for them to sign.

Firstly, clinical and demographic data will be collected, including age, gender, weight, height, years since diagnosis and current pharmacological management. Patients with CS will be explored and the Foot Posture Index (FPI) (a validated method for quantifying standing foot posture), and the Manchester scale for hallux valgus will be recorded for both the right and left foot. Plantar pressure will be obtained using the footscan® Advanced Pressure Measurement System (RsScan Lab LTD, UK). Standard podiatric care will be provided to the patients at the assessment session and when finished the follow up three months later, if needed. Participants will be requested not to have further foot interventions.

After the biomechanical examination, phenolic foam molds will be made of the patient's feet under weight-bearing conditions. The patient's foot will be manipulated before being introduced into the phenolic foam so as to place the subtalar joint in the most neutral position possible, always maintaining the forefoot plantar plane parallel to the ground. In the case of FPI values between +6 and +12, the examiner will hold the distal third of the participant's leg and apply external rotational force to the leg until the mirror of the pedoscope shows incipient loss of the first ray footprint that is, that the first metatarsal begins to elevate. At that moment, the examiner will stop applying external rotational force to the leg. The examiner will repeat this manoeuvre several times, as the external rotation applied to the foot in contact with the glass will be the same as that applied when introducing the foot into the phenolic foam. The same procedure but with internal rotation of the leg will be carried out for FPI values between -12 to -1. For feet with FPI values between 0 and +5, the examiner's hands will apply resistance against pronation or supination in order to maintain the foot in a normal posture.

For foot orthoses delivery one researcher will verify the fitting of the orthosis to the patient's foot. Then the orthosis will be set into shoes. Finally, the participants will be asked if the insoles cause them pain or discomfort in every session. Both interventions have the same protocol.

The software AleatorMetod.xls, available at www4.ujaen.es/~mramos/EPIP/AleatorMetod.xls, will be used to randomly allocate the participants into two groups, and this allocation will be concealed in envelopes. The simple randomisation process will be carried out according to the order of appointment, so that the first patient treated will be number 1. The participants themselves will choose the day and time to attend the Podiatric Clinical Area without knowing the order number that participants have or the corresponding random assignment. Group A will be the experimental group and will receive the custom-made foot orthoses and Group B will be the control group and will be given the placebo treatment. Both groups will be followed up for 3 months, and the data related to foot pain, be recorded monthly by phone. This phone call will remind the participants to appropriately use the orthoses during the follow-up period.

The primary outcome is pain within the foot, lower extremity and lumbar region. Visual analogue scale will be used to record pain at baseline and at the end of the follow-up period, and self-reported pain intensity once a month by phone call will be assessed with an 11-point NPRS with 0 = no pain to 10 = pain as bad as it can be.

Secondary outcomes will be disability related to foot pain, and quality of life. Disability related to foot pain will be measured using the Manchester Foot Pain and Disability Index (MFPDI) at baseline and at the end of the follow-up period. The values of this index range from 0 to 38, with higher values corresponding to greater disability. The SF-12 questionnaire will be used to collect data about the quality of life. This has values between 0 and 100, with higher values corresponding to a lower quality of life.

All the participants will be blinded, as will not know what group belong to and the type of orthoses that will be given in the study (intervention or placebo). Patients will only be informed that the research will evaluate this treatment to manage pain in patients with CS caused by LDH. The participants will be requested to use the foot orthoses assigned seven days a week for a minimum of eight hours per day for three months. The researcher who performs the measurements at days 0, 30, 60, and 90 will not be the same researcher who conducts the randomisation, adapts the foot orthoses, and gives them to the participants. Thus, researchers will be blinded as well. Adverse events will be recorded as part of the monitoring and appropriate safety measures. The participants will be asked about any problems with the foot orthoses and their adaptation to the footwear.

The minimum sample size was calculated using the following formula to compare mean values between populations:

n = (2s^2 (z_(α/2) + z_β))/d^2, where s2 is the sample variance, α is the type I error, β is the type II error, and d is the minimum difference to be detected. According to previous studies, the variance of the visual analogue scale for pain is equal to 400, and the difference found is 16. Therefore, the following result was obtained: n = (2s^2 (z_(α/2) + z_β))/d^2 = 〖2 ∙ 400 ∙ (1.96+0.84)〗^2/16^2 = 24.5 = 25 Thus, at least 25 people will be needed in each group to compare the mean values. In this study, 100 patients will be initially recruited, with 50 in each group, in consideration of possible losses.

The analysis of the data will becarried out using the statistical software IBM SPSS Statistics (IBM, Armonk, NY, USA). The descriptive data will provide the mean values and the standard deviations or the absolute frequencies and percentages depending on whether the variables are scalar or categorical. Shapiro-Wilk tests will be conducted for the inferential analysis to determine the most appropriate test to use. When the data show a normal distribution by groups, a t-test for independent samples will be carried out. Mann-Whitney's U test will be used for the independent samples when there is no normal distribution. For those study variables that will be measured four times, the tests will be conducted in pairs for related samples as well. The t-test will be used if the variables show a normal distribution in the four measurements, and Wilcoxon's signed-rank test will be used for related samples when do not. When statistically significant differences are found according to the P-value, the effect size will be calculated using Cohen's d or Rosenthal's r to analyse the magnitude of the differences. The differences will be classified according to the following for both parameters: below 0.2: no effect; 0.2-0.5: small effect; 0.5-0.8: medium effect; and above 0.8: large effect. The analyses will be based on an intention-to-treat data set.

In the case of the variables for which randomisation produces differences between groups at the initial assessment, repeated-measures analyses of covariance (ANCOVAs) with the baseline scores as covariates will be performed to enable comparisons of post-intervention data after adjusting for those differences in the initial scores.

The confidence level a priori is 95%. For missing data (participant withdrawal or interim missing data), the convenience of several missing data models (i.e., 'missing at random', 'missing completely at random' or 'missing not at random') will be classified by the trial personnel (according to available trial data). The most appropriate missing data model will be selected.

Data monitoring will be evaluated in collaboration with an external Statistician, who will also review all the issues related to data collection and analysis during the research process.