SLR - November 2016 - Fahd Moeez

Treatment of Plantar Fasciitis with Botulinum Toxin: A Randomized, Controlled Study

Reference: Ahmad J. Ahmad SH, Jones K. Treatment of Plantar Fasciitis with Botulinum Toxin: A Randomized, Controlled Study. Foot Ankle Int. 2016 Sep. 14

Scientific Literature Review

Reviewed By: Fahd Moeez, DPM
Residency Program: NYU Lutheran Medical Center

Podiatric Relevance:
Plantar fasciitis impacts one in every 10 individuals in their lifetime with varying degrees of clinical symptoms. About two million individuals obtain medical treatment each year. First-line treatment includes conservative modalities, i.e., NSAIDS, corticosteroids injections, cast or CAM boot, night splints, orthoses and stretching exercises. Other therapies include extracorporeal shock wave therapy (ESWT) and platelet rich plasma (PRP) injections but are reserved for cases refractory to aforementioned treatments. Surgical intervention is offered to patients who have failed conservative treatment, but surgery is associated with risks of nerve injury, infections and issues with wound healing, decrease in arch height, lateral column pain and recurrence. Botulinum toxin (BT) blocks the presynaptic release of acetylcholine at the neuromuscular junction causing reversible muscular paralysis. Since plantar fascia lacks the neuromuscular junction, BT is thought to assist in plantar fasciitis by reversible paralysis of flexor digitorum brevis muscle. It also blocks the neurotransmitter Substance-P at neuromuscular junction to provide analgesia. Also, studies have shown anti-inflammatory effect of BT on soft tissue. The purpose of this study is to explore the use of botulism toxin through a long-term, randomized, double-blinded, placebo-controlled trial.

Methods: The trial was conducted between June 2012 and March 2015. The study included patients with acute or chronic plantar fasciitis with no prior use of BT injections. Out of the 89 patients, 50 patients were enrolled in the study to receive a single injection of either placebo (saline) or IncobotulinumtoxinA (IBTA). The selected patients were treated conservatively for six to 40 weeks prior to enrollment. Both the placebo and IBTA groups were similar in age, sex, preinjection Foot and Ankle Ability Measure (FAAM) and visual analog scale (VAS). The diagnosis of plantar fasciitis was confirmed with MRI, and all patients had weightbearing radiographs of the foot to rule out bony injuries.

Patients were randomized by an independent observer to receive a 1 ml injection of 100 U of IBTA or saline (placebo). The injections were sealed in 50 opaque envelopes with index cards marked as IBTA and Saline and then placed into a box. The independent observer blindly picked up each envelope from the box, drew the injection in 1-ml syringe and gave it to a board-certified neurologist. The neurologist had expertise in administering these injections with use of EMG. The EMG was used to confirm proper placement of needle by observing motor potentials as it had reached the FDB muscle near plantar fascia.

Additionally, patients received PT for a minimum of six weeks, which was extended six more weeks after the injection as recommended by the PT. Patients were also fitted with OTC arch supports (Lyncos) postinjection.

Results: The saline group included four, 16 and five patients with mild, moderate and severe plantar fasciitis diagnosed on MRI. At six months, the mean FAAM score for these patients improved from 35.9 to 40.9. The mean VAS decreased from 8.4 to 7.9. But the differences in functional and pain scores were not statistically significant (P=.32). Three patients in this group needed to drop out because of worsening pain and were treated surgically. At 12 months, the FAAM and VAS scores remained statistically insignificant in this group (P=.27).

The IBTA group included five, 14 and six patients having mild, moderate and severe plantar fasciitis diagnosed on MRI. The mean FAAM score at six months increased from 36.3 to 73.8. The mean VAS pain score decreased from 7.2 to 3.6. The p-value for these scores was statistically significant (P=.01). The FAAM score further improved to 79.5, and VAS pain decreased to 2.9 at 12 months with p value=.01. None of the patients in this group required surgery.

Conclusion: This study is one of the few randomized, double-blinded, prospective clinical trials that show significant improvement in pain and function following injection of IBTA. It also obviates the need for surgery after one-year follow-up. The study also suggests how reversible paralysis of the flexor digitorum brevis muscle helps in managing plantar fasciitis. This finding could have significant future implications in our understanding and management of this pathology. The author acknowledged this study has the limitation of having small sample size, and further long-term follow-up is needed to confirm their finding.

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