Botulinum Toxin A (Botox) Injections
When people hear the word 'botox' the immediate association is facial injections for anti-wrinkle treatment and magazine gossip on the latest celebrity to suffer a "bodge job" from one too many botox injections. Prior to this modern use of botox, no one really knew what botox was except for medical professionals that use it to treat their patients. Botulinum toxin A (Botox) injections were originally used to treat neurological conditions resulting in spastic paralysis (stiffening of muscles) such as cerebral palsy. Aside from their use for treating neurological conditions and more recently for aesthetic enhancement, they have also started to be used for the treatment of musculoskeletal conditions including plantar fasciitis.
How can Botox injections treat plantar fasciitis?
Botox injections are used to relax muscles and other soft tissue. As it is widely accepted that tightness in the calf muscles is a causative factor in plantar fasciitis, botox injections aim to relax contracture (tightening) in these muscles thus reducing tensile strain on the plantar fascia as a result of muscle relaxation. Additionally, they can be injected into the muscles of the foot to achieve the same effect. The mechanism of action of this toxin involves blocking the release of acetylcholine (the chemical that motor neurons of the nervous system release in order to activate muscles) at the neuromuscular junctions resulting in flaccid (floppy) paralysis.
Evidence
Below is a narrative review of the literature on botox injectons for plantar fasciitis.
A level 1, double-blinded, randomised control trial (good quality study) compared Botox vs. Corticosteroid injection for treatment of plantar fasciitis ( Elizondo-Rodriguez et al 2013).
Group 1 - Botox injection and plantar fascia stretching (19 patients)
Group 2 - corticosteroid injection and plantar fascia stretching (17 patients)
Results were recorded at 2 weeks, 1, 2, 4, and 6 months. There were no significant improvements in either group after the initial 2-week review. Both groups showed significant improvements in pain scores at 1 month. At the 2, 4 and 6 months follow up the Botox group had significantly better scores than the steroid group. At the final 6 month review the average pain score for the Botox group was 1.1/10 reduced from 7.1/10 (difference = 6) and 3.8/10 reduced from 7.7/10 (difference = 3.9) in the steroid group.
This study found that Botox injections were a superior treatment option than corticosteroid injections for the treatment of plantar fasciitis for short-term and mid-term (Elizondo-Rodriguez et al 2013). A limitation of this study is that patients were not followed up over a longer period (at least 12 months) which would inform us whether Botox is also successful in long-term management for plantar fasciitis. A particular point of interest from this study is that the botox injections where not injection in/around the plantar fascia but into the calf muscles. Following the injections, the calf muscles went into a state or relaxation. It is believed that this relaxation reduced the additional strain placed on the plantar fascia which results from increased calf muscle tension. This approach seeks to address the purported cause, unlike steroid injections which aim at treating the symptoms.
A similar study compared Botox injections with corticosteroid injections. This study was also a randomised control trial with 28 patients in each group. Like the Elizondo-Rodriquez study (2013) they found both Botox and corticosteroid injections successful at the 1-month review, however, the difference between the two treatments became larger at 6 months with the Botox group continuing to improve whilst the steroid group got slightly worse (Diaz-Llopis et al 2012).
Diaz-Llopis followed up their original study in 2012. They conducted a 12 month follow up in the Botox group to see if they had sustained improvements in the long term which they did. This provides evidence to support the use of Botox as a long-term treatment option (Diaz- Llopis et al 2013).
The site of the botox injection in the Diaz-Llopis study differed from the Elizondo-Rodriguez et al study. Instead of injecting into the calf muscles, Diaz-Llopis and colleagues injected the botox into the plantar fascia attachment to the heel bone and further along the arch of the foot. They decided to use this injection technique based on a previous study by Babcock et al (2005). By using the same injection technique enabled them to see if they would get the same/similar success. Another recent RCT study also found botox to be superior to steroid injections (Samant et al 2018).
The study by Babcock et al (2005) compared Botox injections with placebo. This was a double-blinded, randomised, placebo-controlled study in 27 patients with plantar fasciitis. The results were recorded at 3 weeks and 8 weeks and observed significant changes in the Botox group compared to the placebo-controlled group. A limitation of this study is the short term follow up.
Other studies have also compared botox injections with placebo and found botox to be significantly better than placebo (Huang et al 2010; Amad et al 2017). Amad and colleagues found Botox injections to be superior to placebo in a double-blind, randomised control trial of 50 patients (25 each group). They found Botox to be significantly better than placebo at 6 month and 12 month reviews. The Botox group also showed significant reduction in plantar fascia thickness which demonstrates healing of the degenerative plantar fascia. This was not seen in the control group. A further benefit of Botox is that it did not reduce heel fat pad thickness which is a commonly reported complication with steroid injections (Ahmad et al 2017).
On the other hand a similar study compared Botox injections with placebo, however, they found only marginal differences between the two groups . 63.1% of the Botox group perceived an improvement versus 55% of the placebo group (Peterlein et al 2012).
One study compared extracorporeal shockwave therapy (ESWT) with botox injections. This is an interesting study as ESWT has become a well established and successful treatment option for plantar fasciitis. Botox injections are currently considered a novel treatment with less research into its effectiveness, therefore comparing this treatment with an established treatment can be considered a good test. The study randomised patients into two groups with 36 in each group. The researchers found both treatments to be effective, in that both treatment groups demonstrated improved pain scores following treatment, however the ESWT came out on top, with great reductions in pain compared with the botox group. A limitation of the study design is that the researchers reviewed patients between 1-2 months after receiving treatment. Previous studies on botox injections demonstrate continued improvements in pain scores with more time. It is possible that the botox group may have seen greater improvements in pain scores if they reviewed the group at 6 months and 12 months, however the same can be said for the ESWT group (Roca et al 2016).
Risks
Botox injections are generally a safe treatment and major side effects are uncommon when administered in the hands of a suitably qualified clinician. Although very unlikely, there is a possibility that the effect of botulinum toxin may spread to other parts of the body and cause botulism-like signs and symptoms. Call your doctor right away if you notice any of these effects hours to weeks after receiving Botox:
Muscle weakness all over the body
Vision problems
Trouble speaking or swallowing
Trouble breathing
Loss of bladder control
Verdict
Overall it would appear that the current evidence for Botox injections as a treatment for plantar fasciitis is sufficient to support its use. Nearly all the current studies of moderate to high quality demonstrate significant success with this treatment option. Despite this, Botox injections are not a common treatment option and are not widely available for treating this condition, not at least in the UK and is something which deserves greater attention in clinical practice. This injection therapy should replace the commonly used steroid injection which has lower success rate in the long term and increased risk of harmful effects such as plantar fascia rupture. It remains unclear on what the most effective injection technique is. The majority of the studies adopted the technique of injecting the plantar fascia and surrounding tissue directly, whilst other studies have injected the calf muscles. To determine which technique is better we would need to see a study that compares these two techniques head to head.
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