Introduction
Inflammation of the plantar fascia is the most common soft tissue complication in the foot area and one of the leading causes of foot pain [1, 2]. This complication is caused by excessive and repeated pressure on the heel, which causes damage to the plantar fascia [2]. This complication can disrupt daily living activities, reduce patients’ quality of life, and impose high costs on the health system [3]. Treatments for plantar fasciitis usually include non-surgical procedures, such as weight loss, topical corticosteroid injections, physical exercise and physiotherapy modalities, and orthoses [4].
One standard treatment method for problems, such as plantar fasciitis is to pay attention to the risk factors of the complication (risk factor) and design therapeutic interventions to control and reduce the risk factors associated with lesions [5]. Previous review studies have shown that decreased dorsiflexion movement in the ankle and metatarsophalangeal joints are a risk factor for plantar fasciitis [2, 6]. Stretching the plantar muscles and fascia increases the dorsiflexion amplitude of the ankle and metatarsophalangeal joints, reduces pain, and increases motor function and satisfaction in patients with this complication [6, 7]. One of the measures to apply stretch on soft tissue structures involved in plantar fasciitis is the use of orthoses [8]. Orthopedic treatments for this complication of plantar fasciitis generally include medical insoles and night splints [2]. While medical insoles reduce pressure on the heel in the weight-bearing position [9], night splints are commonly used to prevent muscle contraction and stiffening of the soft tissues around the ankle and foot [10]. Therapeutic recommendations using night splints are based on the contraction of the calf muscles and the shortness of the plantar fascia at rest, which reduces the flexibility of soft tissues and thus increases the vulnerability of the tissue to forces (such as the force of body weight in standing position) [11]. Therefore, two types of night splints can be considered to apply stretch to these tissues: one type of splint to apply stretch to the calf muscle set and the other type of splint to apply stretch to the plantar fascia. Previous research has mainly compared the effect of one type of splint (calf muscle stretch) with other conservative treatments (especially medical insoles) and has not widely considered the effects of using a plantar fascia stretching splint on this complication [12]. The present study aimed to compare the effects of using a night splint to stretch the calf muscles with a night splint to stretch the plantar fascia on the range of motion of ankle and foot joints, pain intensity, and quality of life in patients with plantar fasciitis.
Materials and Methods
Thirty people with inflammation from those who were referred to orthopedic outpatient clinics voluntarily entered the clinical study in parallel groups. Inclusion criteria included morning pain and stiffness at the origin of the plantar fascia (under the heel) and a pain score higher than three based on the visual pain scale, which was exacerbated by passive thumb extension (Windlass test). People with a history of surgery, fractures, or peripheral nerve involvement in the lower extremities were excluded. Participants were divided into three study groups based on age and body mass index [13]. Study groups included group 1 (night splint of calf muscle stretching and daily use of heel pad), group 2 (night splint of heel fascia and daily use of heel pad), and group 3 (control group without night splint and daily use of heel pad). Measurements related to the pre-test session were performed at the baseline and before the interventions started. After four weeks of interventions, individuals were called to perform the measurements in the post-test. Before entering the study, the volunteers were informed about the details of the project and provided written consent was signed.
The night splint for stretching the calf muscles (Figure 1-a) consisted of a prefabricated plastic orthosis, including the ankle-foot orthosis that kept the ankle at 5 degrees of dorsiflexion (Code B0904, Bahgam Co., Isfahan, Iran). The night splint to stretch the plantar fascia was a neoprene sock-shaped support (Figure 1-b) that brought the toes close to the dorsum surface of the leg with an adjustable strap (Salamat Teb Co., Tehran, Iran). The heel pad was made of flexible silicone rubber (Figure 1-c), which was made of softer material in the area under the heel (code 21600, Teb & Sanat Co., Tehran, Iran). All three orthoses used in this study were given to the participants based on measurements.
The primary outcomes of this study included pain intensity, quality of life, and range of motion of the metatarsophalangeal and ankle joints. The Visual Analogue Scale was used to assess pain intensity in the pre-test and post-test. The Persian version of the 36-Item Short Form Survey (SF-36) questionnaire was used to record patients’ quality of life, which assesses the physical and mental health of a person in various activities during the past month [14]. The flexibility of the calf and plantar fascia muscles was measured by dorsiflexion goniometry of the ankle and first metatarsophalangeal extension (thumb), respectively [15]. 
Each measurement of the angles was repeated three times, and the mean values were used for statistical analysis. analysis of covariance (ANCOVA) was used to compare the data in the three study groups. The alpha error rate for all statistical tests was considered 0.05.
Results
The study participants were 27 females and three males, equally distributed among the study groups. The recipient group of splint for calf muscle stretching was 46.4±8.6 years old, 169.4±4.8 cm tall, and 69.3±13.1 kg. These values were 45.2±10 years old, 165.6±8.8 cm tall, and 70±12.6 kg in plantar fascia stretch splint recipients and 45±6.8 years old, 169.4±5.16 cm tall, and 74.1±10.2 kg in the control group. All participants completed the study steps, including the pre-test, use of orthoses, and post-test. Also, none of the participants used any other therapeutic interventions during the study except oral anti-inflammatory drugs (prescribed by a specialist). The independent t-test showed an insignificant difference between the variables of age, height, and weight of the three groups (p>0.05).
The results of ANCOVA (factor analysis of the study group) indicated a statistically significant difference between the study groups in the post-test in pain intensity (η2=0.44, p=0.001, F=9.35) and the amount of first metatarsophalangeal joint extension (η2=0.27, p=0.017, F=4.76). The three study groups showed a statistically insignificant difference between the quality of life score and the degree of ankle dorsiflexion (Table 1).


The Bonferroni test for pair-to-pair comparison within the group showed that all three study groups expressed lower pain intensity in the post-test compared to the pre-test. Also, in the group receiving calf muscle stretch splint, the amount of first metatarsophalangeal joint extension in the post-test significantly increased compared to the pre-test (1.69 to 2.5: 95% confidence interval (CI), p=0.002) (Table 2).


The rate of pain reduction in calf stretch splint recipients was higher compared to plantar fascia stretch splint recipients (0.24 to 2.8: 95% CI, p=0.016) and control group (0.75 to 3.15: 95% CI, p=0.001) (Table 2). The difference between the other groups was related to the first leg’s metatarsophalangeal extension. This variable showed no difference in the three groups in the pre-test (p>0.05). Post-test comparisons between groups showed that the use of night splint stretching compared to the control group increased the range of motion of the first metatarsophalangeal joint (0.56 to 7.1: 95% CI, p=0.02) (Table 2).
Discussion
This study showed that using orthoses (including silicone heel pads and night splints to stretch the calf and plantar fascia) could reduce the severity of pain in people with plantar fasciitis. Simultaneous use of stretching night or fascia splint with heel pad inside the shoe showed a better effect than using heel pad alone in reducing participants’ pain. Also, the rate of pain improvement in the calf stretch splint group was higher than in the fascia stretch splint group. These results suggest that night splints of the ankle and plantar can accelerate the improvement of painful complications in a short period by increasing the flexibility of the foot’s soft tissues.
 The results of this study were in line with the reports of previous studies stating that short-term stretching of the tissues around the ankle, especially the Achilles tendon, can effectively improve the complication of the plantar fascia [16, 17]. The use of night orthoses to position the ankle has long attracted the attention of researchers in this field. In 1991, a case-series article on the benefits of using night splints in the plantar fascia was published for the first time [18]. At the end of the study, 11 patients (out of [14] recovered from pain due to plantar fascia inflammation [18]. Then, a tiny clinical trial compared the effects of night splint against oral medication and heel pad (study control mode) and confirmed the benefits of using night splint [19].
Our study also showed that using a plantar fascia stretch splint could reduce pain in people with plantar fasciitis. Because the plantar fascia is located along the Achilles tendon and the forces from the robust calf set are transferred, it is also considered in stretching interventions [16]. If there is no flexibility in the fascia, this tissue may be exposed to small and sudden tears (mainly in athletes) [12]. Scientific evidence regarding splints’ night stretching of the plantar fascia was limited to two previous studies [20, 21]. Barry et al. used a sock-like night splint in their study that covered from the tip of the foot to below the knee and stretched the toes by stretching the straps [20]. Barry considered the stretch of the calf set in the standing position. It was reported that the splint group had a shorter recovery period than the standing stretch group [20]. Lee et al. used a sock splint with a similar height to the present study and considered using a softer insole under the heel for the control group [21]. Lee et al. reported that in the splint group, leg function and pain intensity improved more after two and eight weeks [21]. Our study did not confirm these results because there was an insignificant difference between groups compared to fascia stretch splint and heel pad (medical insole), but both groups reported significantly less pain after four weeks. One possibility of insignificant changes in the outcomes of physical function or flexibility of the calf set may be related to the short duration of the present study. It has been reported that complete recovery of this complication takes about 12 months, which is even longer in chronic cases [22]. Feedback from patients in the post-test study also indicated that the interventions were “helpful” rather than “therapeutic.” Pain intensity scores in the post-test, despite a significant decrease compared to the pre-test, showed that patients’ pain remained significant. Accordingly, all interventions (even control mode) have been effective in reducing the severity of pain, but splint calf was more effective. Observing an increase in the amount of toe extension after using a calf stretch splint is also in support of previous theories that fascia is located along the Achilles tendon and confirmed the effect of manual stretching of the calf muscles on improving fascia flexibility [23].
Conclusion
The results of this study should be interpreted by taking into account the following limitations: First, the duration of the complication is one of the determining factors in determining the prognosis. This study variable was omitted because the study participants were available and did not have medical records. Second, in this study, providing the same shoes for the participants was impossible; each had to use his shoes. Third, in this study, facade intervention was not used, and for the control group, one of the most effective foot orthoses [24] was used to treat the complication (silicone pad). Although this issue reduced the ethical considerations for the study, it makes it difficult to deduce the net effect of night splints on the study’s outcome. Finally, and most importantly, in this study, despite providing verbal advice to participants for regular use of interventions, direct monitoring of this issue was impossible.
The results of this study provide basic concepts to confirm the feasibility and effectiveness of using plantar fascia stretch splints in treating plantar fasciitis. Therefore, in future studies, we can pay attention to the design and optimization of plantar fascia stretch splints, examining the comfort level, patient admission, longer-term effects of using these splints, and evaluating the reliability of the effects through studies with larger sample size.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Isfahan University of Medical Sciences (Code: IR.MUI.REC.1395.3.726). The informed consent was obtained from each participant before study. The participants were given the permission to cancel their participation at any stage of study. The forms contained the personal information was coded to ensure the confidentiality of information

Funding
The paper was extracted from the MSc. thesis of the first, Department of Orthotics and Prosthetics, School of Rehabilitation Sciences, Isfahan University of Medical Sciences, Isfahan, Iran (No. 395276).
Authors' contributions
Conceptualization and supervision: Ebrahim Sadeghi-Demneh; Methodology: Ebrahim Sadeghi-Demneh, Behzad Akhavan-Broujeni; Investigation, writing-original draft, and writing-review & editing: Both authors; Data collection: Behzad Akhavan-Broujeni; Data analysis: Ebrahim Sadeghi-Demneh; Funding acquisition and resources: Ebrahim Sadeghi-Demneh, Behzad Akhavan-Broujeni. 

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
The authors express their gratitude from the participants of the research and members of university research council.

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