Anatomical features of plantar fasciitis in various age cohorts: Based on magnetic resonance imaging

Abstract

Background

Due to the lack of further studies on the influence of age factors on plantar fasciitis, this study evaluates the characteristic observation points of magnetic resonance imaging in various age cohorts of patients with plantar fasciitis to help diagnosis.

Methods

A retrospective analysis of 160 cases of plantar fasciitis patients and normal subjects (who have the disease unrelated to plantar fasciitis) who have undergone an MRI examination in our institution. The two groups were separately divided into young adult subjects (36 to 44 years old), middle age adult subjects (45 to 59 years old), and older adult subjects (60 to 79 years old). Data was gathered regarding plantar fascia thickness, the coronal length of the plantar fascia at the calcaneal origin, the signal intensity of plantar fascia and surrounding structures, and the presence or absence of plantar calcaneal spurs, all of which were assessed objectively by the investigators.

Results

There were statistical differences in the thickness of plantar fascia between two groups of three age cohorts (Older adult patients: 0.59 ± 0.09 cm; Middle age adult patients: 0.49 ± 0.09 cm; Young adult patients: 0.47 ± 0.05 cm) (all p < 0.001). In addition, there were also statistical differences in the high signal intensity changes of the plantar fascia and surrounding soft tissues between two groups of three age cohorts (all p < 0.001). In older adult plantar fasciitis patients, with regard to plantar calcaneal spur discovery, there was a statistical difference between the two groups (Chi-square = 12.799. df = 1. p < 0.001).

Conclusion

In plantar fasciitis cases where a diagnosis is difficult, abnormalities in the soft tissue surrounding the plantar fascia in patients of low age are noteworthy. In older adult patients, the discovery of plantar calcaneal spurs with abnormal thickening of plantar fascia deserves attention, and abnormal MRI findings are more manifest. But the final diagnosis should be based on the medical history.

Level of Evidence

Level 3.

Keywords

plantar fasciitis heel pain magnetic resonance imaging age

Introduction

Heel pain is often caused by plantar fasciitis in adults. The pain in the medial plantar heel is often manifested when getting up in the morning or taking the first step after a long break. It can be gradually reduced over time for activity, which greatly affects the quality of patient’s life. Plantar fasciitis is often differentiated from rheumatoid nodules, calcaneal stress fractures, osteomyelitis, etc.^1–3 Some scholars studied that the vast majority of patients with plantar fasciitis are aged between 25 and 64, and clinical rate of patients aged between 45 and 64 is higher than those aged between 25 and 44.⁴ Various authors also mention the average age of patients with plantar fasciitis was significantly higher, and plantar fasciitis was first seen in childhood.^5–6 So will age factor influence imaging findings in MRI in patients with plantar fasciitis? Consequently, the interest of researchers in the study is a correlation between plantar fasciitis and age on MRI.

The etiology of plantar fasciitis is still unclear. Most scholars believe that the pathogenesis of plantar fasciitis is not caused by inflammation, but is more likely to be related to overuse and degeneration.^7,8 Plantar fasciitis is a common overuse injury, that accounts for the vast majority of musculoskeletal disorders in athletic populations, about 10% of runners. Repeated traction applied to the plantar fascia during long or incorrect walking or running may cause tear and repair of the fascia, thereby thickening the plantar fascia.^9–11 The degeneration of plantar fascia may have a greater impact on the elderly population: Some studies have found histopathological changes through plantar fascia surgical biopsy, confirming its degenerative processes, such as collagen decomposition, fibroblast changes, matrix destruction, and vascular changes, which may be the cause of clinical symptoms and imaging abnormalities in plantar fasciitis patients of old age cohort.^12,13

In some studies, ultrasound was used as the preferred medical imaging examination for the diagnosis of plantar fasciitis. MRI examination was regarded as a second-line imaging examination method because of its high cost.¹⁴ However, MRI is more clear about the observation of plantar fascia and its surrounding soft tissue structure, which could provide a more objective and accurate assessment of morphological changes related to plantar fasciitis, and help eliminate heel pain for other reasons.^15–17 Currently, there is still no consensus on the MRI examination diagnosis of plantar fasciitis. Characteristics of plantar fasciitis are obvious collagen degeneration, which is correlated with age.⁸ However, the influence of age on MRI observation of plantar fasciitis seldom has not been described in the present literature. Therefore, this study investigates the characteristic diagnostic observation points of MRI in plantar fasciitis patients to explore whether there are differences in patients of various age cohorts.

Methods

Plantar fasciitis patients and comparison subjects

All subjects who underwent an MRI examination were selected from our hospital. This study was conducted between January 2005 and June 2021.

Clinical diagnostic criteria of plantar fasciitis: Patients present with fixed heel pain, which was aggravated after morning rise, prolonged and strenuous activity, and can relieve with rest; Physical examination shows sharp tenderness at the calcaneus insertion. According to the latest age segmentation standard of the United Nations World Health Organization, a total of 64 (N = 64) patients with plantar fasciitis (35 females, 29 males, 8 young adult patients: 38–44 years old, 29 middle-aged adult patients: 45–59 years old, 27 older adult patients: 60–79 years old) were retrieved from the electronic medical record. They were included in the disease patients group. Some of them received non operative therapy, such as shock wave therapy, block therapy, and NSAIDs.

The MRI of patients with no plantar fasciitis diseases (referred to as normal subjects in this study) that had undergone MRI examination from April 2020 to April 2021 was adopted. Exclusion criteria: Previous calcaneal stress fractures, flat foot, pes cavus, Baxter syndrome, rheumatoid disease, ankle tunnel syndrome, diabetic foot disease, fat pad atrophy, heel pad contusion, Achilles tendon disease, calcaneal bursitis, and posterior tibial tendinitis. 96 (n = 96) normal subjects (50 females, 46 males, 40 young adult patients: 36–43 years old, 29 middle-aged adult patients: 45–58 years old, and 27 older adult patients: 60–76 years old) were selected as the normal group.

Setting up MRI observation points

It included the following: the thickness of the plantar fascia on the sagittal section, the coronal length of the plantar fascia at the calcaneal origin, the signal intensities of plantar fascia and surrounding soft tissues, the signal intensities of the calcaneal attachment and Achilles tendon, and the existence of plantar calcaneal spur. For the measurement of the plantar fascia on the sagittal plane, McNally and colleagues believed that the observation at the insertion point of the plantar fascia 1 cm away from the calcaneus attachment was appropriate.¹⁸ This study also chose this location to measure plantar fascia thickness. Morphological measurements were usually performed on T1-weighted sequences. And the signal strength was evaluated on fat-suppressed T2-weighted and T2-weighted sequences in the sagittal and axial orientation. The researchers evaluated the data using the PACS system.

Statistics

All measured numerical variables were expressed as mean ± standard deviation (SD), and categorical variables were expressed as characters and percentages. A group t-test was used to evaluate differences in the measurement of the thickness of the plantar fascia on the sagittal section and the coronal length of the plantar fascia at the calcaneal origin on the coronal section. The level of significance was set at p = 0.05. Chi-square tests were used to evaluate the differences among the morphology and signal intensities of the plantar fascia, surrounding soft tissues, the calcaneal attachment and Achilles tendon, and the existence of plantar calcaneal spur. The level of significance was set at p = 0.001. All statistical analyses were carried out using IBM SPSS Statistics 17.0 (Chicago, Illinois).

Result

With regard to the thickness of sagittal plantar fascia there were statistical differences between the three groups, Young adult age cohort (t = 12.872, p < 0.001), Middle age adult cohort (t = 12.183, p < 0.001), Older adult cohort (t = 12.583, p < 0.001). There were significant differences between the disease patients group and the normal group in the high signal intensity changes of the plantar fascia and surrounding soft tissues in three age cohorts, Young (Chi-square = 41.070,19.794. all df = 1. all p < 0.001), Middle (Chi-square = 34.402,25.379. all df = 1. all p < 0.001), Older (Chi-square = 30.000,14.509. all df = 1. all p < 0.001).

In the young adult age cohort, however, there was no statistically significant difference between the disease patients group and the normal group in the coronal length of the plantar fascia at the calcaneal origin (t = 1.871, p = 0.084), the discovery of plantar calcaneal spurs and the increase of signal intensity in calcaneal attachment and Achilles tendon (Chi-square = 2.793, 7.301. all df = 1. p = 0.095, 0.007). But the finding of plantar calcaneal spurs was statistically significant in the older adult cohort. (Chi-square = 12.799. df = 1. p < 0.001).

The specific values and ratios are shown in Tables 1 and 2.

Table 1.

Comparison of morphologic measurements in three age cohorts (x ± SD) (cm). There are significant differences of parameters between two groups in three age cohorts. Young adult cohort: There were statistical differences in the thickness of sagittal plantar fascia between two groups (t = 12.872, p < 0.001). Middle age adult cohort: There were statistical differences in the thickness of sagittal plantar fascia between two groups (t = 12.183, p < 0.001). Older adult cohort: There were statistical differences in the thickness of sagittal plantar fascia between two groups (t = 12.583, p < 0.001).

Age cohort	Group	Thickness¹	Coronal length²
Young	Match	0.21 ± 0.04	2.58 ± 0.35
Young	Observation	0.47 ± 0.05³	2.77 ± 0.25
Middle	Match	0.24 ± 0.05	2.68 ± 0.34
Middle	Observation	0.49 ± 0.09³	2.83 ± 0.43
Older	Match	0.26 ± 0.10	2.78 ± 0.33
Older	Observation	0.59 ± 0.09³	2.94 ± 0.34

Independent samples t test (p < 0.05) match versus observation.

¹on sagittal section of plantar fascia.

²on coronal section of plantar fascia.

³variables with statistical differences between groups.

Table 2.

Comparison of signal intensity of MRI observation points and calcaneal spur in three age cohorts. There were statistical differences in the high signal intensity changes of the plantar fascia and surrounding soft tissues in three groups (Young adult cohort: Chi-square = 41.070, 19.794. all df = 1. all p < 0.001. Middle age adult cohort: Chi-square = 34.402, 25.379. all df = 1. all p < 0.001. Older adult cohort: Chi-square = 30.000, 14.509. all df = 1. all p < 0.001). In the older adult cohort, with regard to plantar calcaneal spur discovery, this was statistical differences between groups (Chi-square = 12.799. df = 1. p < 0.001).

Age cohort	Group	PA (n)	ST (n)	CAAT (n)	PCS (n)
Young	Match	0 (0.0%)	2 (6.3%)	5 (12.5%)	6 (15.0%)
Young	Observation	8 (100.0%)*	7 (87.5%)*	5 (62.5%)	3 (37.5%)
Middle	Match	6 (20.7%)	7 (24.1%)	13 (44.8%)	11 (37.9%)
Middle	Observation	28 (96.6%)*	26 (89.7%)*	16 (55.2%)	17 (58.6%)
Older	Match	5 (18.5%)	12 (44.4%)	10 (37.0%)	9 (33.3%)
Older	Observation	25 (92.6%)*	25 (92.6%)*	19 (70.4%)	22 (81.5%)*

Chi-square tests (p < 0.001) match versus observation. PA, plantar fascia; ST, surrounding soft tissues; CAAT, calcaneal attachment and Achilles tendon; PCS, plantar calcaneal spur; X*, variables with statistical differences between groups.

Discussion

The plantar fascia consists of collagen fibers and elastic tissue. From the medial side of the calcaneus tuberosity, the medial, central, and lateral bands are separated to the distal end (Figure 1). Central band is divided into shallow and deep branches in each longitudinal bundle near the metatarsal head, and ends in the plantar plate and sesamoid bone at the first to the fifth metatarsal distal end. Among the three bands, it is the thickest and most important. The medial and lateral tendon bundles of the lateral band respectively stop at the fourth metatarsal plate and the fifth metatarsal base. The medial band is mostly located in the medial and middle cuneiform bones, covering abductor hallucis fascia and maintaining continuity with sub tendinous extensor retinaculum and flexor retinaculum under lateral dorsoaponeurosis.^10,15

Figure 1.

(a): The plantar fascia on the sagittal section of a normal subject shows a thin hypointensity band structure (white arrow). (b): On the coronal section, the medial (black arrow), central (double white arrow), and lateral (white arrow) portions of the plantar fascia. (c): White arrows indicate the coronal length of the plantar fascia at the calcaneal origin.

This study adopted the above common lesions (the thickness of the plantar fascia on the sagittal section, the length of the plantar fascia at the calcaneal origin on the coronal section, the signal intensities of the plantar fascia, surrounding soft tissues, the calcaneal attachment and Achilles tendon, and the existence of plantar calcaneal spur.) for MRI observation. The thickening and high signal intensity of plantar fascia is usually considered typical changes of plantar fasciitis^17,19(Figures 2 and 3), which can be common in plantar fasciitis patients of three age cohorts (Table 1, Table 2). The best assessment of plantar fascia and surrounding attachments can be made along the plantar fascia length of sagittal imaging.⁷ The average thickness of normal sagittal plantar fascia was 3.22 mm in some authors’ studies.¹⁹ In this study, the average thickness of normal plantar fascia is 2.46 mm, while it is 5.17 mm in plantar fasciitis patients. When the thickness of fascia measured near calcaneus insertion exceeds 5 mm, the diagnosis of plantar fasciitis should be considered.^17,19 The thickening of the plantar fasciitis is greatest in older patients, with a marked fusiform thickening. The thickening of the plantar fasciitis in patients may be associated with degeneration of the plantar fascia, combined with misposture such as over-rotation of the foot or overuse injury. Sari et al. proposed a new parameter, the coronal length of plantar fascia originating from the calcaneus on MRI of plantar fasciitis, but did not evaluate it under pathological conditions.²⁰ Therefore, this new parameter was included in this study to evaluate the patients with plantar fasciitis (Figure 1). However, this parameter has no statistical significance in the comparison of the three age cohorts (p < 0.05), and has no great reference value in this study.

Figure 2.

From a 40-year-old female patient with left foot of plantar fasciitis: (a): Showing the thickening of the plantar fascia and slight hyperintensity near the calcaneal origin (white arrow). (b): Showing obvious high signal intensity enhancement of the superficial flexor digit minimi brevis (white arrow).

Figure 3.

From a 75-year-old male patient with right foot of plantar fasciitis: (a): Showing uneven high signal intensity enhancement of heel fat pad (double white arrow), obvious hyperintensity of the calcaneal attachment (black arrow) and slight signal intensity enhancement in the Achilles tendon (white arrow). (b): Showing the plantar fascia thickening and hyperintensity in the fascia (white arrow), and a plantar calcaneal spur (black arrow).

Ehrmann et al. concluded that asymptomatic volunteers also had common MRI manifestations of plantar fasciitis on T1-weighted sequences images.²¹ MRI can assess the surrounding pathological tissues and identify involved muscles or small hematomas in the soft tissues.²² Some studies have found that the most common MRI findings of plantar fasciitis are uneven high signal intensity enhancement in deep and shallow soft tissue edema around the fascia.^15,17 The plantar fascia is connected with surrounding and even distal muscles by connective tissue.⁹ MR Imaging of 64 patients with plantar fasciitis in our study showed that 61 patients (95.3%) revealed increased signal strength within the plantar fascia on T2-weighted images, and 58 patients (90.6%) depicted the signal intensity changes in the soft tissues around the fascia, all of whom displayed imaging abnormalities. In the normal group, 85 cases (88.5%) and 80 cases (83.3%) were normal on both tests. See Table 2 for specific values and proportions. Clearly, our research supports this finding.

The plantar calcaneal spur is a condition that is under discussion. It is considered that corresponds to the origin of intrinsic muscles, such as flexor digitorum brevis. This study found that plantar calcaneal spur is more common in older adult patients with plantar fasciitis (Figure 3). In other studies, Menz et al. confirmed that the plantar calcaneal spur is common in the elderly and related to heel pain.²³ It is undeniable that the discovery of the plantar calcaneal spur in plantar fasciitis patients is more common with age. The plantar calcaneal spur is likely associated with plantar fasciitis. Moderate thickening of the plantar fascia is a normal feature of aging. Therefore, the discovery of plantar calcaneal spur is important for MRI diagnosis.

Plantar fasciitis and Achilles tendons absorb the static and dynamic mechanical impact from the body to sustain foot load and maintain a normal foot arch. Studies showed that with age, the insertion point of the Achilles tendon in the calcaneus changed, reducing the amount of tissue connecting the Achilles tendon to the periosteum, and reducing the continuity of the Achilles tendon-calcaneus-plantar fascia complex. These become pathological factors of heel pain in plantar fasciitis.^24,25 Although the authors found calcaneal attachment and high signals in the Achilles tendon in patients with plantar fasciitis (Figure 3), this study cannot prove its reliability in the diagnosis of plantar fasciitis.

Finally, the strengths of our study include the large sample of patients, and the comparison on MRI of age matching between the disease patients group and the normal component. Some important weaknesses need to be considered. First, all cases in this study did not include patients with acute plantar fasciitis. Second, this is a retrospective study, old MRIs, and the clinical situation is not clear so we cannot surmise about plantar fasciitis. Third, due to limitations of imaging and technology, some new findings are not adopted by the authors. For example, the measurement of the calcaneal crescent on MRI can help diagnose of patients with plantar fasciitis.²⁶

Conclusion

The thickness of sagittal plantar fascia and high signal intensity of plantar fascia and surrounding soft tissue was different between groups. The soft tissue abnormalities around plantar fascia in young adult patients were more significant than those in the normal group. In older adult patients, the discovery of plantar calcaneal spurs with abnormal thickening of plantar fascia deserves attention, and abnormal MRI findings are more manifest.

Footnotes

Author contributions

Lei Zhang contribute to conception and design of study. Lei Zhang, Mingyang Cai contribute to write and edit this manuscript. Lei Zhang, Mingyang Cai, Yiwen Gan, Jixiang Xiong, Zhangrong Xia, Peixin Yang, Xinghao Sun and Huining Tang contribute to protocol and project development of study. All authors read and approved the final manuscript.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The study received grants from National Natural Science Foundation of China (Youth Science Foundation Project), Project Number: 82004458; Traditional Chinese Medicine Research Project of Sichuan Traditional Chinese Medicine Administration, Project Number: 2020JC0138; Orthopedics (Shangantong) special scientific research project of Sichuan Medical Association, project number: 2020SAT26; Central Funds Guiding the Local Science and Technology Development General Program of Sichuan Provincial Science and Technology Department, project number: 2021ZYD0078; Scientific Research Cultivation Project of The Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University, project number: 2022-CXTD-08.

Ethical approval

Ethical approval was given by the medical ethics committee with the following reference number KY2021078-FS01.

Data availability

The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.

ORCID iDs

Lei Zhang

Guoyou Wang

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