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• Letter in response to: Custom insoles versus sham and GP-led usual care in patients with plantar heel pain: results of the STAP-study-a randomised controlled trial
  André Augusto Martines Teixeira Mendes, Marcelo Cardoso de Souza
  Published on: 14 October 2020

• Published on: 14 October 2020

  Letter in response to: Custom insoles versus sham and GP-led usual care in patients with plantar heel pain: results of the STAP-study-a randomised controlled trial

  • André Augusto Martines Teixeira Mendes, Physiotherapist, MSc , Professor, Faculty Anhanguera de Taubaté. Taubaté, São Paulo, Brazil.
  • Other Contributors:
    • Marcelo Cardoso de Souza, PT, PhD. Professor of Postgraduate Program in Rehabilitation Sciences – Federal Universi

  We read with great interest the study by Rasemberg and colleagues1 and appreciate the pragmatic research method illustrating the routine of clinicians in many countries. However, some points drew our attention and motivated this letter.
  A recent systematic review with meta-analysis2 investigated three types of insoles: customized, prefabricated, and sham. The authors included 19 trials (a total of 1,660 participants) and demonstrated that custom insoles did not reduce pain or improve function in the short-term. In the medium-term, the customized insoles were more effective than sham in reducing pain; however, with no improvements in function. In the long-term, the custom insoles did not reduce pain or improve the participants' function.
  At this point, we achieve the first question: what kind of customization did these studies address? When analyzing the studies included in this review, we noticed that customizations were based on Root's subtalar joint neutral theory, in which insoles should keep the subtalar joint aligned in a neutral position, and the internal longitudinal arch supported to optimize its height and control its descent during the mid-stance support phase. This does not seem ideal if we consider the foot mechanics and some particular movements, such as the windlass for impact absorption and propulsion of the foot3,4.
  When customizing an insole to keep both the foot and ankle in a neutral position, the clinician assumes that every...

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  We read with great interest the study by Rasemberg and colleagues1 and appreciate the pragmatic research method illustrating the routine of clinicians in many countries. However, some points drew our attention and motivated this letter.
  A recent systematic review with meta-analysis2 investigated three types of insoles: customized, prefabricated, and sham. The authors included 19 trials (a total of 1,660 participants) and demonstrated that custom insoles did not reduce pain or improve function in the short-term. In the medium-term, the customized insoles were more effective than sham in reducing pain; however, with no improvements in function. In the long-term, the custom insoles did not reduce pain or improve the participants' function.
  At this point, we achieve the first question: what kind of customization did these studies address? When analyzing the studies included in this review, we noticed that customizations were based on Root's subtalar joint neutral theory, in which insoles should keep the subtalar joint aligned in a neutral position, and the internal longitudinal arch supported to optimize its height and control its descent during the mid-stance support phase. This does not seem ideal if we consider the foot mechanics and some particular movements, such as the windlass for impact absorption and propulsion of the foot3,4.
  When customizing an insole to keep both the foot and ankle in a neutral position, the clinician assumes that every foot is aligned and neutral to improve function and avoid or minimize pain. However, when analyzing the study by Rasemberg et al.1 and contrasting with the results of two systematic reviews2,5, we concluded that the position does not seem useful for the treatment of plantar fasciitis.
  In our opinion, the manuscript also lacks detail regarding feet typology and the type of correction applied to each orthosis–and these are our second point.
  Even though the number of volunteers is representative and proper randomization was applied, the authors did not report the foot type classification, which somewhat confuses the clinical interpretation. Assuming that normal, planus, and cavus feet have different characteristics, it is likely that the participants reacted differently to the proposed treatments. Also, the insole was not described in detail, and it is challenging to understand the correction type used for each volunteer, which may interfere with data analysis and clinical decisions.
  All volunteers referred to the podiatrist received the orthosis, but did they need this correction? It is like prescribing glasses for people without vision problems. It is not clear whether podiatrists could exclude volunteers who did not need correction, which may have also influenced the results. Thus, the following question remains: Did the intervention worsen those volunteers who did not need corrections, and results were pulled down?
  Burns et al.6 compared the effects of customized and sham insoles in patients with bilateral cavus foot and foot pain. In this study, the insole customization did not aim to modify the hindfoot position. The longitudinal arch was supported, and an extrinsic heel post was introduced to limit the excessive lateral heel support. A superior effect of customized insoles on pain and physical function was found, indicating that specific interventions for specific foot types were efficient.
  Another study7 investigated the effects of customized insoles adapted in flip-flop sandals with corrections in individuals with plantar fasciitis for 12 weeks. The authors proposed different supports for the midfoot based on foot typology, thus maintaining the plantar arches function. A significant improvement in morning pain and pain at the end of the day was observed in the intervention group compared with controls.
  Therefore, we question the validity of the standard customization maintaining the neutral position regardless of the foot type and the dysfunctions.
  The third point regards the way the assessment of the study participants was conducted. Although we agree that the evaluation using pads with different thicknesses to determine the neutral position of the ankle is feasible and used by clinicians worldwide, it may not represent the real patient’s need since significant differences are present between static and dynamic evaluations using this method8. Thus, it is probable that the used measures were insufficient or inadequate for the pad prescriptions, even if supported by a 3D system.
  Regarding the sham insoles, we believe that the minimum effects generated by the insole thickness, softness, and different characteristics are important factors for both the comfort perception and pressure reduction sensation, and may have produced similar effects to the customized insole.
  In this sense, we invite you to reflect on the next steps in investigating the effects of insoles on plantar fasciitis, ending the cycle of custom-made insoles in a neutral position and beginning the new era of insoles prescribed for function and not for disease.

  References

  1- Rasenberg N, Bierma-Zeinstra SMA, Fuit L, et al. Br J Sports Med Epub ahead of print:doi:10.1136/ bjsports-2019-101409
  2- Whittaker GA, Munteanu SE, Menz HB, Tan JM, Rabusin CL, Landorf KB. Foot orthoses for plantar heel pain: a systematic review and meta-analysis. Br J Sports Med. 2018;52(5):322-328. doi:10.1136/bjsports-2016-097355
  3- Bruening DA, Pohl MB, Takahashi KZ, Barrios JA. Midtarsal locking, the windlass mechanism, and running strike pattern: A kinematic and kinetic assessment. J Biomech. 2018;73:185-191. doi:10.1016/j.jbiomech.2018.04.010
  4- Behling AV, Nigg BM. Relationships between the foot posture Index and static as well as dynamic rear foot and arch variables. J Biomech. 2020;98:109448. doi:10.1016/j.jbiomech.2019.109448
  5- Hawke F, Burns J, Radford JA, du Toit V. Custom-made foot orthoses for the treatment of foot pain. Cochrane Database Syst Rev. 2008;(3):CD006801. Published 2008 Jul 16. doi:10.1002/14651858.CD006801.pub2
  6- Burns J, Crosbie J, Ouvrier R, Hunt A. Effective orthotic therapy for the painful cavus foot: a randomized controlled trial. J AmPodiatrMed Assoc. 2006;96(3):205-211. doi:10.7547/0960205
  7- Costa ARA, de Almeida Silva HJ, Mendes AAMT, Scattone Silva R, de Almeida Lins CA, de Souza MC. Effects of insoles adapted in flip-flop sandals in people with plantar fasciopathy: a randomized, double-blind clinical, controlled study. ClinRehabil. 2020;34(3):334-344. doi:10.1177/0269215519893104
  8- Behling AV, Manz S, von Tscharner V, Nigg BM. Pronation or foot movement - What is important. J Sci Med Sport. 2020 Apr;23(4):366-371. doi: 10.1016/j.jsams.2019.11.002. Epub 2019 Nov 8. PMID: 31776068

  Contributors: All authors contributed equally to the letter.

  Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  Competing interests: None declared

  Patient consent for publication: Not required.

  Provenance and peer review: Not commissioned; externally peer reviewed.

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  Conflict of Interest:
  None declared.

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