Regional Differences and Age Related Changes in the Thickness of the Plantar Aponeurosis

Research Article

Austin J Anat. 2020; 7(1): 1094.

Regional Differences and Age Related Changes in the Thickness of the Plantar Aponeurosis

Misiani MK, Amuti TM*, Kipkorir V, Murunga A, Awori K, Ogeng’o JA and Saidi HS

Department of Human Anatomy, University of Nairobi, Kenya

*Corresponding author: Amuti TM, Department of Human Anatomy, University of Nairobi, PO Box 30197- 00100, Nairobi, Kenya

Received: July 25, 2020; Accepted: October 30, 2020; Published: November 06, 2020

Abstract

Background: Decrease in the foot’s biomechanical efficiency occurs with age possibly due to age-related alterations in the Medial Longitudinal Arch (MLA) and Plantar Aponeurosis (PA). Even though this relationship has been inferred, it has not been described. Thus, study aimed to determine the same.

Materials and Methods: Sixty feet were sourced, following which, the dorsum height and truncated foot length were measured and divided to derive the AHI (Arch Height Index). The PA was then exposed by dissection and the thickness of its enthuses and three bands were measured. Data was coded into SPSS where means were calculated. Age related differences in the truncated foot length, dorsum height, AHI and the PA’ enthesis and 3 bands was determined using ANOVA. P-value≤0.05 was considered significant at 95% confidence interval.

Results: The mean truncated foot length, dorsum height, AHI and PA enthesis thickness were 20.57mm, 7.9mm, 0.392 and 3.34mm respectively. There was no statistical significant difference among the age groups on the dorsum height, truncated foot length. Statistical significant difference was however noted on the AHI and enthesus. As for the bands, the central, lateral and medial sections had mean values 2.65, 2.08 and 1.2mm respectively. Moreover, statistical significant differences based on age grouping was, only, in the thickness of the central band and the medial band. There was no linear association between the AHI and the thickness of the PA.

Conclusion: The aging differences in the observed parameters may be due to adaptability to the configuration of the MLA.

Keywords: Enthesis; Plantar aponeurosis; Arch height index; Truncated foot length

Introduction

The Plantar Aponeurosis (PA), the deep fascia of the foot [1], is the main stability factor for maintenance of the Medial Longitudinal Arch (MLA) of the foot [2]. Together with the MLA, the PA aids in efficient propulsion of thrust from the hindfoot to the forefoot in locomotion via the “windlass” mechanism [3]. In this role, the biomechanical properties of the PA are dependent on its viscoelasticity, partly a function of its thickness [4]. Pertinent to this, the structure of the PA is responsive to biomechanical stresses which are determined by the conformation of the medial longitudinal arch [5]. Further, as the main stability factor for the MLA, the PA influences the configuration of the MLA [6].

This configuration of the MLA can be represented by the Arch Height Index (AHI), which is defined as the ratio of dorsum height to truncated length of the foot. The dorsum height is the height of the foot at 50% of the length of the foot while truncated length of the foot is the distance from the tip of the heel to the first metatarsophalangeal joint [7]. A high AHI results in a stiffer MLA [3] which in turn leads to a reduction of the ability of the PA to act as a mechanical truss in the “windlass” mechanism [8]. On the other hand, a low AHI leads to an increase in the movement of the foot in the sagittal plane which is associated with thickening of the PA [9]. The change in the thickness of the PA in response to the configuration of the MLA is due to its adaptability to the varied biomechanical strains precipitated by these different conformations of the MLA [5]. On the other hand, the thickness of the PA influences the configuration of the MLA [6]. A relationship between the AHI and the thickness of the PA is therefore inferred though it has not been described. Moreover, there is scarcity of information on the age-related changes in the AHI that may lead to changes in the thickness of the PA.

The biomechanical efficiency of the foot reduces with age [10] due to changes in the configuration of the MLA and implies consequent modifications of the structure of the PA [11]. These modifications include changes in its thickness (Craig et al., 2001). Such changes in the thickness of the PA are seen in diabetes [6] and Plantar Fasciitis (PF) [12] and they result in altered foot biomechanics [11,5]. It is however not known whether similar changes in the thickness of the PA contribute to the age-related decrease in the foot’s biomechanical efficiency. This study therefore also sought to describe the changes in the thickness of the PA that occur with age. Our null hypothesis was that the thickness of the plantar aponeurosis neither has regional differences nor age related changes.

Materials and Methods

A total of fresh 120 feet of 60 subjects aged between 20 and 56 years were used in this cadaveric study. These were obtained from Chiromo Funeral Parlour in the Department of Human Anatomy, University of Nairobi. Ethical approval was granted by the Kenyatta National Hospital/University of Nairobi Ethics and Research Committee and the Kenyan constitution. Further, consent was sought from each family members and benefits of the study explicitly explained to them prior to any dissections. All procedures were carried out in accordance with the principles laid out in the Declaration of Helsinki 1964. Subjects who had feet that had suffered trauma, had been operated on or had deformities were excluded from the study.

With the foot resting on the table, the truncated length of the foot (the length without the phalanges) was measured to the nearest millimeter using a measuring ruler (Haco® Industries Kenya Limited, Nairobi). A wooden block was placed against the sole of the foot vertically and the dorsum height measured, using the same ruler, to the nearest millimeter Figure 1. To minimize intra-observer errors, three measurements of the same dimension were taken and an average of these recorded. The AHI was calculated as the ratio of the dorsum height to the truncated foot length [7].