Morphologic changes of the fifth phalange secondary to smartphone use

1 Introduction

Over the last decade, there has been an increase in the use of smartphones for the use of different applications [1, 2]. A study in Sweden found that 99% of the population aged 15 to 24 has a mobile device, and of these 82% have a Smartphone [3]. In Mexico, 71.5% of the population has some type of mobile phone, and 66.3% of them have a Smartphone [4]. Children, teenagers, and young adults are of particular interest due to the increase use of these devices for a variety of activities [1, 5]. Studies show that over 90% of young adults use mobile phones daily in leisure and 41.6% of all young adults use mobile phones daily at work [6–9]. Data regarding possible adverse effects on the hand due to excessive use of the mobile phone is limited [10]. Studies on effects it may cause on the upper extremity are needed [8, 9].

Studies have already associated the movements of the hand when texting with musculoskeletal symptoms[2, 11]. A study revealed that 65% of Finns under the age of 30 had frequently experienced constant pain in the hand they used most to handle the devices [6]. Other authors have established a relation between upper extremity symptoms and use of smart devices or entertainment units as different syndromes: “overuse injury”[12], “repetitive strain injury”[13], “Nintendinitis” [14], “Blackberry Thumb” [5], “Wiitis” [15] and even some have been described as “Whatsappitis” [16]. Tendinous injuries of the first phalanx, shoulders, back, and neck, and correlate them with the posture used when sending text messages [3, 17]. One study reported increased TNF-R1, a serum marker of inflammatory processes, and tendinopathy of the abductor pollicis brevis muscle by magnetic resonance in high volume “texters” [18]. However, data on morphological changes in the hand that may be caused by the use and weight of smartphones is limited.

The objective of this study was to evaluate the participation of the fifth finger in the manipulation of smartphones related to its holding technique in a young population and determine if an asymmetry was being caused. Data was analyzed for comparison between genders, age, BMI, years of use, time of daily use, and holding technique.

2 Methods

An observational, cross-sectional, and comparative study was carried out. University students who used smartphones and signed informed consent were included. Those with traumatic or congenital alteration of the upper extremity, refusal to participate in the study or lack of signed informed consent were excluded.

A survey was conducted to obtain: Age, gender, height, weight, approximate time of cell phone use per day, number of years using a smartphone, and holding technique when texting. Three options were provided for holding with one hand, and three for two hands, in order to assess the participation of the fifth finger (Fig. 1).

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Fig. 1

Illustration of holding techniques for smartphones. A. The phone is held with one hand, using the middle face of the distal interphalangeal joint of the little finger as support. B. The phone is held with one hand, without supporting it with the little finger. C. The cell phone is held with one hand using as support the entire medial surface of the little finger. D. Hold the phone with both hands, using the medial aspect of the distal interphalangeal joints of both little fingers as support. E. Hold the phone with both hands, without resting it on the little fingers. F. Hold the phone with both hands using as support the entire medial surface of the little finger of a hand.

Once the survey was completed, photographs (Canon Rebel T5 18.0 megapixel camera) were taken from the dorsal region of the hand and the small (5th) finger, in order to assess the degree of asymmetry between both hands. They were placed over a fixed sheet of millimeter paper, illuminating with a LED lamp EL211. The camera was fixed on a tripod to avoid differences in distance, and the sheet was marked with a point to confirm alignment with the hand. Participants were asked to place their hand without exerting pressure on the sheet, in a position in which the fifth finger was just below the lens of the camera.

A digital vernier was used on a millimeter sheet at a fixed aperture of 5 cm and photographed to calibrate the imageJ program. A triangle was drawn on the surface of the finger, using as apexes the nail bed, the proximal interphalangeal joint and the medial portion of the middle phalanx forming a scalene triangle (Fig. 2a). The area between the base of the triangle and the lateral contour border of the finger was measured in squared millimeters (Fig. 2b). Comparison for asymmetry (mm2) and miniferet (mm) were obtained between the dominant and non-dominant hand.

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Fig. 2

2A Technique used in the evaluation of photographs. First, two points were drawn at the angles of the nail bed to be used as reference for a line drawn at the base of the nail. Secondly, a pair of lines were drawn at the proximal and distal wrinkle of the proximal interphalangeal joint, then a parallel line drawn at the midpoint between them. Thirdly, a point placed at the middle of a line drawn perpendicular to the lines used for point 1 and 2 lines. 2B: The area of the concavity on the lateral border of the 5th finger was then highlighted and measurements taken using the imageJ software.

A total of 143 participants (44.1% women and 55.9% men) were recruited. Mean age was 20±2 years with a range between 16 and 29 years. The mean number of years owning a smartphone was 3.81 years with a mean daily use of 3.8 hours (Table 1). Of these, 85.3% predominantly used their right hand and 14.7% their left hand.

No significant differences were found between the areas measured for asymmetry of soft tissue and miniferet of both fingers of the subjects regarding age, gender, body mass index, hours per day of use, and years of ownership using T test for independent samples (Table 2). When performing an ANOVA test to compare the types of one- and two-handed holding techniques with the areas of asymmetry and miniferet of both hands, no statistically significant difference was found. The most common one-handed holding technique was type B (38.5%), followed by C (32.9%) and A. The most common two-handed technique was type F (42.0%), followed by the D (29.4%) and E (28.7%) (Table 3).

Our results show no statistical significance in the inferential analysis. However, the descriptive data give rise to the discussion of several remarkable points.

The population that uses the smartphone with their right hand had a higher mean in the area of asymmetry. This coincides with other authors who have described that holding techniques could be associated as a risk factor to develop morphological changes [19].

The type F holding technique with two hands was the most prevalent. In this position, the weight of the device rests on the lateral border of the small finger during activities such as texting [7]. A similar position was the second most common for one-handed holding. Although there was no statistical significance found in our study between holding technique and area of asymmetry, many participants express a subjective deformity due to this. This variable should be considered in future studies to determine the correct ergonomic positions in the use of these devices. Recent studies focused on other risk factors have omitted this [16].

Our population consisted mainly of students, with a mean age of 20 years. It’s possible these had no significant changes due to a short ownership period of 3.81 years and starting its use at a more mature age. Studies with a greater number of years of use have shown the presence of multiple alterations associated with the use of smartphones [21]. A study with an older population may present significantly different results [3].

Ossification of the phalanges may also play a role. Although our study only evaluated soft tissue, a population of children and teenagers who have a high use of smartphones and lack the bone and joint maturity, may present significant changes as they enter adulthood. Future studies will be needed with possible evaluation of bone structures to establish this. Many studies have reported an increase in use of smart-devices among young populations [22]. It is important con consider the effects and possible malformations it may cause in coming decades.

Our study was limited by its sample size and age. A more chronic use of the devices may also confirm the risk of deformity in the small finder when held with type C and F techniques.

5 Conclusion

No asymmetric changes were evident between left and right small fingers in relation to the holding position of a smartphone in a young adult population.

Conflict of interest

None to report.

Funding

There was no external funding; resources were provided by the University.