Currently, therapists have difficulty assessing and describing hand sensory deficits.
The gold-standard tool to quantify hand tactile sensitivity is the esthesiometer.
The Semmes-Weinstein esthesiometer presents nylon monofilaments of approximately the
same length and of varying diameters. The diameter and length are used to control
the force applied. The minimal diameter detected is used to classify the sensory function[1]. However, not only tactile sensitivity, but also the ability to detect weight and
compressibility variations are involved in hand function.
The sensation of touch on skin is provided by mechanoreceptors in the epidermis and
dermis skin layers. There are four types of mechanoreceptors: Merkel receptors detect
pressure from small objects, on a frequency between 0.3 and 3.0 Hz. Meissner corpuscles
detect flutter, e.g. when rubbing objects against the skin or skin movement across
a surface, on a frequency between 3.0 to 40.0 Hz. Ruffini cylinders detect pressure
and stretching of the skin, on higher frequencies, between 15.0 and 400.0 Hz2. Merkel
disks and Ruffini cylinders are associated with slowly adapting fibers that respond
as long as the stimulus is present. Meissner corpuscles respond to stimulation with
a burst of firing at the beginning and end of stimulation, therefore, they are called
rapidly adapting fibers[2].
The sensory system works in constant interaction with the motor system. Such interaction,
which is not assessed by the Semmes-Weinstein protocol, allows the perception of objects
(known as haptic perception, or stereognosis), which is achieved by the active exploration
of surfaces, by moving hands[3],[4], and is fundamental in daily life activities. Therefore, tests involving haptic
perception could include broader response scoring. This would allow a more detailed
description of normality range (considering development[5],[6],[7], aging[8],[9] and learning[9]) and the comparison between patients with sensory dysfunctions and healthy controls[1],[3],[4].
Younger children tend to hold objects for less time than older children, and to perform
less rotations for tactile examination. The sensory exploration time in children aged
four months is five times longer than the visual examination time[5]. This fact demonstrates the intersection of different receptors from childhood to
optimize perception.
One year old children can differentiate small changes (of approximately 10 g) in weight[10]. As people get older, degradation in tactile sensory acuity is noted[8]. Skin loses elasticity and tactile nerve endings suffer ruptures of muscle fibers,
which change in size, distribution and shape. The number of skin receptors tend to
diminish[7] and even previous extensive tactile experience is insufficient to preserve sensory
function during aging[8],[9].
Sensory central and peripheral modifications may be associated with clinical manifestations.
Grunwald[3],[4] related changes in the right posterior parietal cortex, the same region of tactile
perception, in patients with anorexia. Hands sensory function may be altered in a
great variety of neurological disorders, e.g. stroke, brachial plexus injuries, metabolic
diseases. Specifically for patients with stroke, many scales have been developed to
assess sensorimotor functions: Nottingham Sensory Assessment, Fugl-Meyer and Rivermead
Assessment of Somatosensory Performance. However, all these scales are also classificatory[11],[12].
Morash et al. showed that blind individuals have better haptic performance than healthy
controls, particularly when the use of multiple fingers is allowed in a tactile exploration
task[13]. Mueller et al. showed that occupation-related long-term sensory training enhances
roughness discrimination[14]. Conversely, recent data shows that the tactile search for changes involves less
memory than visual search for changes, because the working memory has higher availability
for the visual system and the haptic perception has a poorer working memory capacity[15].
To better understand the normal variations, and development, aging, training, or diseases
consequences on hand sensorimotor function, it is crucial to develop standardized
instruments to evaluate and categorize hand haptic perception, considering different
receptors functions and inputs. The objective of this study was to develop an instrument
to assess hand haptic perception, generate scores and measure timed performance, and
to submit the instrument to experts evaluation.
METHOD
Test and manual development
Group meetings - Five therapists discussed possible tasks to be included in the Hand Haptic Perception
Instrument (HHPI), in 16 one-hour meetings. Several materials were tested until therapists reached a
consensus about the best options for each task. An illustrated manual was also developed.
Submission to referees
In this stage, the instrument was evaluated by experts, who assessed the technical
knowledge involved, test quality and relevance, routines for data collection, material
quality and manual clearness (overall appearance, figures, technical content).
This part of the study was conducted with 30 experts (13 physiotherapists, 5 physicians,
5 occupational therapists, 4 biologists and 3 psychologists), who had obtained a minimum
score of 8 (on a 0-10 scale), according to Fehring´s criteria[16]. All experts had Ph.D. degree on health sciences, mean age 49.1 years (SD 9.3),
26 women. The mean Fehring´s score was 8.5 (SD 0.6). Experts were randomly divided
into 3 groups of 10. No differences on age or Fehring´s score were found between the
three groups.
The ten experts from group 1 analyzed the material and manual of the HHPI, and received
the evaluation forms, which contained a Likert-scale questionnaire[17]. Each question was scored 1 for poor and 5 for very good. The corrections suggested
by group 1 were discussed and incorporated in 3 meetings, by the same 5 therapists
who developed HHPI ([Table]).
Table
Experts evaluation criteria.
|
Criteria
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1 (very poor)
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2 (poor)
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3 (regular)
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4 (good)
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5 (very good)
|
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Overall manual appearance
|
|
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General content and updated texts
|
|
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Overall manual quality
|
|
|
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Text clarity
|
|
|
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|
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Figures relevance
|
|
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|
|
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|
Material adequacy for depression domain
|
|
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Material adequacy for elevation domain
|
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Material adequacy for texture domain
|
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Material adequacy for density domain
|
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Material adequacy for barognosis domain
|
|
|
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Material recognition for shape domain
|
|
|
|
|
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|
Total score
|
|
|
|
|
|
In the next stage, ten experts from group 2, analyzed HHPI and their corrections were
discussed in three meetings. After the feedback from group 2, group 3 gave their suggestions,
discussed on the three last meetings, in which accepted corrections were incorporated
to the final version of the test.
RESULTS
Experts suggestions and test corrections
Group 1: Twelve modifications were suggested and nine of them were accepted. The structures
on depression, elevation, shape recognition and barognosis domains were modified.
Group 2: Three modifications were suggested and only one was accepted. The figures of depression
identification task were altered again.
Group 3: Experts recommended future studies to develop adaptations for children, older adults
and patients.
HHPI characteristics
The HHPI aims to assess, score and time hand sensorimotor function, involving: Merkel
receptors, which detect pressure from small objects; Meissner corpuscles, which detect
rubbing against the skin or skin moving across a surface; and Ruffini cylinders, which
detect pressure and stretching. Therefore, the domains depression, elevation, texture,
density, barognosis and recognition of shapes were approached.
Assessment must be conducted in quiet, well illuminated room with a [table] and two chairs. The examiner is positioned in front of the examinee. The examinee
must be blindfolded while exploring tasks materials, except the weight from barognosis
and compressibility domains. Materials consist of testing structures for each domain,
evaluation chart for data collection, blindfold, pencil, rubber, A4 sheets of paper,
stopwatch, camera with tripod.
We suggest this test to be filmed, because recording will allow the analysis of the
exploratory movements on each task. Time measurement must be started after a verbal
command authorizing the beginning of the test and stopped after the conclusion, or
when the maximum time is reached (three minutes per step). Time can be measured clinically
(when the test is performed), or digitally, by watching the test films.
We suggest following the sequence described on the evaluation chart to facilitate
data organization and a two-minute rest between each domain. Texture domain may promote
temporary skin dysesthesia, and should be the last one to be performed.
Depression domain
Purpose: To assess the ability to perceive a figure made by surface depression, to generate
mental image and reproduce it by drawing on a paper and then pair it with a printed
figure.
Materials: Three wooden squares (13 x 13 cm) with 3 mm wide and deep depression figures with
geometric forms ([Figure 1]). Task 1 is considered easy, task 2 is considered medium and task 3, difficult.
Figure 1Above and left: figures used on depression domain (easy, medium and difficult steps).
Above and right: figures of elevation domain (easy, medium and difficult). Below left:
structures used on textures domain - first horizontal row: sandpapers with smoother
texture, second row: sandpapers with intermediate texture and third horizontal row,
rougher sandpapers. Below at center: density structures: foams of different densities
covered by orange leather. Below right: Styrofoam structures of different weights,
covered with yellow glossy paper, used on barognosis domain.
Assessment and registration: Response analysis, according to the (1) replication, scored as 1, if lines were correctly
represented, otherwise, scored as zero; (2) proportion, scored as 1 if proportion
is correct or 0 if it is incorrect and (3) location on the paper 1 if location is
correct or 0 if it is incorrect. Then, the examinee has to identify the figure on
a sheet with three similar figures, represented in 13 x 13 cm squares. Correct answers
are scored as 1. The time must be measured and registered on each step, as additional
qualitative information.
Elevation domain
Purpose: To assess the ability to perceive the position of three lines made by surface elevation
(parallel, perpendicular and overlapped), to generate mental images and reproduce
them by drawing.
Materials:Wooden 13 x 13 cm structures, containing single or double stitching lines, covered
by paper and Contact® plastic ([Figure 1]). Difficulty levels are easy, with three double stitching parallel rows, medium,
with two overlapping stitching lines and one single stitching line below and difficult,
with three single stitching lines, diverging ([Figure 1]).
Assessment and registration:Scored according to the (1) replication, scored as 1, if lines were correctly represented,
otherwise, scored as zero; (2) proportion scored as 1 if proportion is correct or
0 if it is incorrect and (3) location on the paper, scored as 1 if location is correct
or 0 if it is incorrect. Considering that this domain has three steps and that each
step has one figure (easy, medium and difficult), the total score of this phase is
nine. Then, the examinee has to identify the figure on a sheet with three similar
figures with the same size of the tested ones. Correct answers are scored as 1. Therefore,
the total score ranges from 0 to 10. Time is registered as qualitative information.
Texture domain
Texture, compressibilityand barognosishave similar goals: The examinee must order, from left to right, three structures
in accordance with the characteristics of texture, density or barognosis. The tests
will take place in three steps: high, medium and low variation in textures, compressibility
and weight. The last step will assess the perception of differences between structures
with high/low roughness, density or weight. The tests ends when the examinee finishes
ordering the structures or when the examinee reaches the maximum time for exploration
of three minutes. Correct answers are scored as 1 and incorrect, as 0.
Materials: Nine sandpapers with different textures: 1 (water granulation 280), 2 (iron grit
granulation 150), 3 (abrasive mass 60), 4 (abrasive mass 80), 5 (abrasive mass 100),
6 (abrasive mass 120), 7 (abrasive mass 150), 8 (abrasive mass 180) and 9 (abrasive
mass 220). The sandpapers were glued on 13.0 x 13.0 x 0.3 cm wooden boards.
Assessment and registration:The test starts with three stacked sandpapers (2, 4 and 6 or 3, 5 and 7). The examinee
must organize the order of the sandpapers, from the smoother to the rougher. Each
correct sequence is scored as 1. In the second task, the examinee must distinguish
between sandpapers 1, 2 and 3 (smoothest ones) and the third, between 7, 8 and 9 (roughest
ones). Score ranges from 0 to 3, for each one of the three tasks. One extra point
is added if the examinee can differ between the softest and roughest structures, or
between distinct compressibilities (compressibility domain), or distinct weights (barognosis
domain).
Compressibility domain
Materials: Nine different types of foams, with densities D13, D23, D26, D28, D28 SOFT, SOFT
D30, D33, D35, D45, SK ULTRASOFT, RIGICEL and FILTRAL were glued on 13.0 x 13.0 x
0.3 cm wooden boards, and covered with leather ([Figure 1]).
Assessment and registration: The examinee palpates the pieces and organizes the structures from the softest (highest
compressibility) to the hardest (lowest compressibility), from left to right. The
maximum time allowed is three minutes. First task includes pieces 2, 4 and 6 or 3,
5 and 7; second task includes pieces 1, 2 and 3; and the third task, pieces 7, 8 and
9 ([Figure 1]).
Barognosis domain
Materials: Nine styrofoam 6.5 x 2.5 cm cubes, containing fishing weights from 0.6 g to 5.4
g inserted inside them, covered with Contact® plastic ([Figure 1]).
Assessment and registration: The examinee selects three cubes according to the task difficulty level. The examinee
is instructed to pick up a cube on each hand. Then, the examinee must perform aleatory
movements with both hands, wrists and elbows, to increase the proprioceptive information
given by the cubes in order to compare their weights. Then, the cubes must be ordered
from the lightest to the heaviest, from left to right, on a maximum time of three
minutes. The first task involves the pieces 2, 4 and 6 or 3, 5 and 7, the second task,
pieces 1, 2 and 3 and the third task, pieces 7, 8 and 9 ([Figure 1]).
Shape recognition domain
Recognition of flat shapes
Objective: After palpating a cardboard flat geometric shape, the examinee must reproduce the
figure by drawing, and then select the same figure from three options given.
Materials: Three cardboard geometric shapes (square, oval and hexagon).
Assessment and registration: After palpating the piece, the examinee is instructed to draw it. Then, the examinee
must replicate the figure by drawing. The drawing is evaluated considering replication
and proportion, scored as zero (wrong) or 1 (correct). Then, the examinee must locate,
on a sheet of paper with three similar figures, which one represented the figure previously
palpated. There are three difficulty levels (easy: square; medium: oval and difficult:
hexagon).
Recognition of short and tall shapes
Objective: After palpating a short geometric shape, the examinee must find a corresponding structure
among other geometric shapes with the same height, in groups of four pieces glued
on a wooden board.
Materials: Twelve 0.15 cm (short) and twelve 1.00 cm (tall) wooden shapes (easy: square, triangle,
rectangle, circle; medium: oval, trapezoid, hexagon, octagon and difficult: irregular
polygons) glued on a wooden board ([Figure 2]).
Figure 2Shape Domain. Above: Paper Flat Figure step. Easy: triangle, average: square and difficult:
arrow. In the middle, the structures used on slight elevation step. First horizontal
row: easy, second row: medium and the third row: difficult. Below, structures of geometrical
shapes used on great elevation step, with the same levels of difficulty of the slight
elevation test.
Assessment and registration: The examinee must palpate the shape offered by the examiner. After that, the figure
must be identified among the structures of the corresponding level (easy, medium or
difficult), glued on a wooden board.
DISCUSSION
The present study aimed to develop an instrument for hand perception testing, made
with affordable materials, in order to provide reproducibility on clinical and/ or
research conditions. Within the process of developing HHPI, the strategy of organizing
groups of referees, according to Fehring´s criteria, was crucial to reach a higher
level of quality[16]. The 30 referees, distributed in three groups of 10 each, evaluated the test and
gave suggestions, which resulted on the gradual improvement of the instrument.
Based on the suggestions, we tested and modified initial ideas and materials. For
instance, on barognosis domain, we increased the structures weight difference. First,
weights ranged from 0.2 g to 0.6 g. Following the referees suggestions, we modified
to a 0.6 g to 5.4 g weight range.
Regarding the tasks, firstly, we intended to use nine structures (three easy, three
medium and three difficult). The referees suggested the inclusion of only three groups
of structures, one of each difficulty level, otherwise testing would be too long.
The option to allow the manipulation and exploration of the objects without the interference
of the examiner was based on a study about the role of movement explorations on the
perception of length with free and restricted mobility. The authors found better results
when the object was explored freely[18],[19].
The examiner verbal command became simpler and clearer. The verbal commands for each
task were detailed explained on the manual. On barognosis domain, we added the verbal
information that the examinee should move the cubes with hands, wrists and elbows
movements to compare their weights[10].
HHPI included the assessment of distinct neural pathways, from touching to drawing
and from touching to visually identifying the figure between three possible options.
We believe that this will make the test useful not only for patients with peripheral
sensorimotor deficits, but also with central primary or associative sensorimotor disorders[20]. Besides, timed performance, which is additional qualitative measure, will enrich
the discussion of motor strategies. Filming the tasks will provide complementary information
for such analysis, allowing the description of the exploratory strategies. HHPI can
be used to complement the current gold-standard tests, which focus specifically on
tactile, thermic, vibratory and pain perception.
The present paper aimed to present a new instrument, and future studies will describe
normality variations on healthy population, clarifying differences on haptic performance,
according to dexterity, development, aging, previous hand training, motor strategies.
We also intend to perform subsequent reliability and validity analyses.
In conclusion, we developed a new instrument, named HHPI, which evaluates hand distinct
sensory receptors functions and generates scores and timed performance. The instrument
testing process, with groups of referees, allowed the analysis of HHPI adequacy to
measure haptic perception.
