Background Chronic metatarsalgia (CM) causes significant pain and disability, affecting quality of life. Foot orthoses (FOs) including medially wedged designs with a metatarsal pad decrease excessive plantar pressure under the metatarsal heads, which is a suggested risk factor for developing CM. This FOs model may be effective in diminishing pain and improving function in these individuals. Thus, the objective of this trial will be to compare the effects of medially wedged FOs with a metatarsal pad and sham FOs on pain and foot function in individuals with CM.

Methods/design This participant- and assessor-blinded superiority randomized controlled trial (RCT) with two parallel groups will be conducted in Trois-Rivières, Canada. Sixty-four participants with CM will be recruited from the Université du Québec à Trois-Rivières outpatient podiatry clinic and via social media invitations. They will be randomized into intervention (customized FOs) or control (sham FOs) groups and will be evaluated at baseline and after 6 and 12 weeks. The primary outcome will be: (1) mean pain during walking for the most painful foot during the past week. The secondary outcomes will be: (1) Foot Function Index, (2) Global rating of change and (3) the 5-level EQ-5D.

Discussion Medially wedged FOs with a metatarsal pad are expected to provide a greater reduction in pain and improvement in foot function compared to sham FOs. This trial will help guide FOs prescription recommendations for managing foot pain in individuals with CM in the future.

Foot musculoskeletal disorders cause significant impairments and disabilities for those affected. Among the various types of foot pain, chronic metatarsalgia (CM) is the most prevalent. Metatarsalgia represents 88% of all causes of foot pain, with a prevalence of 13 to 36% in adults. It is characterized by persistent pain to one or more metatarsophalangeal joints, resulting from harm (whether of mechanical origin or not) to the anatomical structures associated with the joint, including bone, cartilage, capsule and ligaments, tendons, bursae and subcutaneous tissue, and skin. Chronic metatarsalgia significantly reduces the quality of life of those affected, physically, psychologically, and socially. Different treatment modalities are used for CM, such as stretching exercises, footwear modifications, and foot orthoses (FOs). The first-line treatment is conservative, and surgery should be considered only when conservative treatment fails. Nevertheless, there is little high-level evidence (level I) to support the efficacy of conservative treatments for CM.

The reduction of the mechanical overload under the metatarsal heads during locomotion is a fundamental aspect of CM treatment, and it strongly correlates with pain reduction. Foot orthoses are commonly used devices to reduce pain and improve function in individuals with musculoskeletal disorders. They reduce forefoot plantar pressure during locomotion in individuals with CM and redistribute plantar pressure more evenly. Metatarsal pads, a common FOs modification, effectively redistribute forefoot plantar pressure and thus reduce pain caused by excessive metatarsal loads. Adding a medial wedge to FOs (inclination in the frontal plane) further reduces forefoot peak pressure in healthy adults. While FOs tested so far are generally effective in managing CM, their effects can be inconsistent across patients, some patients did not find them effective. From a biomechanical standpoint, FOs reduce mechanical overload; however, it is crucial to determine whether they also effectively reduce pain and improve foot function. Randomized controlled trials (RCT) are considered the gold standard for evaluating treatment effectiveness and efficiently translating research findings into clinical practice. This study design will allow us to assess whether, in addition to their biomechanical effects, FOs provide clinical benefits for individuals with CM.

All details are here : https://doi.org/10.1371/journal.pone.0340905

Inclusion Criteria:

1. are aged 18 years or over,
2. have bilateral or unilateral metatarsalgia under one or more of the lesser metatarsal heads for at least 3 months (pain score of ≥ 4 out of 10 on a Visual Analogue Scale (VAS)) that is aggravated by weight-bearing activities,
3. are able to walk without assistive devices (e.g., cane, walker),
4. are willing to wear shoes that will accommodate their FOs on a daily basis and
5. are willing to minimize the use of other interventions (e.g., pain medications, physical therapy) during the trial period

Exclusion Criteria:

1. have arthritis,
2. have neurological diseases (e.g., intermetatarsal neuroma) or other mechanical pain, plantar corns (e.g., intractable plantar keratoma),
3. have a history of orthopedic foot surgery,
4. have prior use of customized FOs,
5. have cognitive impairments,
6. are pregnant.