Orthoses in Spinal Cord Injury Rehabilitation Management and Improving Quality of Life

Abstract

Damage to a part of the spinal cord or nerves at the ends of the spinal canal causes spinal cord injuries which affect the individual to perform their normal functioning. The spinal cord injury results in complete or incomplete alteration in strength, sensation, and body function below the level of injury. It impacts the postural balance and confines the affected individual with limitations. The independent or optimal activity of living (ADL) management of spinal cord injury patients is challenging. Orthoses play an important role in the multidisciplinary approach to managing spinal injury patients and successful rehabilitation. Different orthoses are applied to spinal cord injury patients to achieve/regain movement, balance, pain relief, etc. The objective of this chapter is to brief about the orthotic rehabilitation management of spinal cord injury patients and its advancement prospects in future.

1. Introduction

The purpose of orthoses in spinal cord injury (SCI) patients is to increase stability, support, movement, and physical activity to make them independent during sitting, standing, and walking [1]. The spinal cord is the main channel through which sensory and motor information is communicated between the brain and the body [2]. It is the injury of the spinal cord from the foramen magnum to the cauda equina causes neurological lesions with severe socioeconomic impact on the affected individual. The majority of the SCI cases reported are due to road traffic accidents (RTA), violence, gunshot, high fall, sports and knife injury [3, 4]. The communication system between body and brain is disrupted, and the brain fails to make it to the body parts below the level of injury and vice versa. For example, an injury at the level of L3 results in paralysis of hip and leg muscles and may cause paraplegia [5]. About 40 million people every year worldwide suffer from spinal cord injury with greater proportion in developing countries and 20–35 years of age group [4, 6]. The location of lesion and severity determine the clinical and functional outcome in a spinal cord injury patient. Injuries at the cervical level cause tetraplegia, while lesions at the lower thoracic region are associated with paraplegia [7]. The neurological assessment after 72 hours of injury is an important predictor to determine the functional recovery of injury, that is, injury was complete or incomplete [8].

The spinal cord injury patients may experience voluntary recovery of sensory and motor functions. The first 3 months are most crucial for functional recovery and maximum recovery achieved by 9 months of injury. Nevertheless, long-term outcomes of spinal cord injury are closely related to the level and severity of the injury, and additional functional recovery may occur up to 12–18 months of injury [9]. SCI is categorized according to the level of function and sensation loss and causes loss of movement and sensation below the level of injury that limits standing and walking in the patients [10]. The cervical region of the spinal cord is the most affected (50%) region with single most common site being C5. The thoracic level injury stands second (35%) and lumbar third (11%) [11]. To achieve the power to walk is the main aim of orthotic management in SCI patients, which always depends on the level of injury and subsequently involved muscle powerlessness, sensory lack, spasticity, and lack of body control. The absence of motion in the hip, knee, and spastic ankle plantar flexion in the swing phase causes pathological gait [12]. Orthoses are medical devices that are applied externally to prevent contracture, increase function, maintain the functional position of a body segment, stabilize the body, and assist weak muscle, and its function/application results in increased motor control and balanced gait. It is also applied to preserve the results of surgical procedures for successful rehabilitation and prevent reoccurrences [13]. Early rehabilitation is important to restrict the loss of muscle strength and joint contracture and maintain bone density to secure normal functioning, and orthotists play an important role in an interdisciplinary rehabilitation team [4].

2. Spinal segments

The spinal cord is composed of nervous tissues that lengthen from the brainstem to the conus medullaris (upper lumbar region). Proximally it is a tubular structure that ended with a tapering cone distally. It connects distally to coccyx by a fibrous extension of pia mater called filum terminale. The spinal cord is protected by cerebrospinal fluid (CSF), soft tissue membrane, osseous vertebral column, and meninges. The spine length varies from 43 to 45 cm. The spinal cord is categorized into five segments that are cervical, thoracic, lumbar, sacral, and coccygeal. It contains 31 total nerve root segments—eight cervical, twelve thoracic, five lumbar, five sacral, and one coccygeal [14].

2.1 Cervical region

It is the proximal part of the spine and contains seven vertebrae (C1–C7) and eight cervical nerves (C1–C8). The lesion in the region causes quadriplegia affecting chest function, upper and lower limbs. It also affects the respiratory system and bladder and bowel control.

2.2 Thoracic region

The thoracic region is the longest region of the spine and holds 12 thoracic vertebrae (T1–T12) and 12 thoracic nerves (T1–T12). Thoracic spine also protects the blood vessels and nerves that run along the spinal cord. Injuries in the thoracic region generally affect the chest and lower limbs. It can also affect respiratory, bladder, and bowel function.

2.3 Lumbar region

The lumbar region, known as the lower back, runs from the chest to pelvis and consists of five vertebral vertebrae (L1 to L2) and five lumbar nerves. SCI in this region affects the hip and leg region and can affect bladder and bowel function.

2.4 Sacral region

It is large, flat, and triangular in shape. The sacral spine is composed of five fused sacral vertebrae (S1–S5) and five nerves. It is embedded between hip bones and controls pelvic organs such as the bladder and bowel. Injury to this region generally affects the hip and legs and may affect the bladder and bowel in a higher level of sacral injury (Figure 1) [5].

Figure 1.

Spinal cord segment.

3. SCI evaluation/scoring system

1. Based on the forces which produced injury to the vertebral column have been developed [15].

   It describes the fractures and dislocation of the spinal cord based on the force direction of the produced injury. The said classification system considers the etiological factors and the mechanism through which the etiological factors, work principal, anatomical and pathological characteristics of the injury, and an indication using which alignment, stability, and restoration can be achieved with safety. It helps surgeons in opting for the simplest and safest way of restoring stability and alignment [15].

2. Based on the extent of neurological deficit in terms of sensory and motor function loss (Michaelis, 1969; Jocheim, 1970; Cheshire, 1970) [16].

3. Based on American Spinal Injury Association (ASIA) Scale:

American Spinal Injury Association (ASIA) exam determines the normal and affected body parts based on the injury level. It uses common clinical techniques to perform the test with minimal equipment (pin, cotton wisp), and minimal clinical settings are required. To allow a valid comparison of scores throughout the care process, the ideal position to perform the test is to lie down the patient in supine position (except rectal examination to be done in side lying). It classifies SCI into complete or incomplete injury.

The sensory is executed testing the key points in each of the twenty-eight (28) dermatomes from C2 to S4–5 on both left and right sides of the body. The bony anatomical landmarks are used to refer to the location and two features of sensation are examined: light touch and pin prick [17]. Light sensation is tested with vision blocked. However, pin prick sensation is performed with a disposable safety pin with one end pointed and the other rounded. The pointed end is used to test the sharpness while the rounded end of the pin is for dull sensation. The main aim of the examiner is to determine the patient’s ability to differentiate between sharp and dull sensations at each sensory point. All these testings are separately scored on a three-point scale with comparison to the sensation on the patient’s cheek:

0 = Absent.

1 = Altered/Impaired/Partial sensation.

2 = Normal/Intact sensation.

NT = Not testable.

The optional method of sensory function consideration is joint movement appreciation and position sense and awareness of deep pressure and deep pain, which are graded on the same sensory scale, i.e., absent, impaired, or normal [2]. The testing of key muscles functions plays an important role in the motor examination of spinal cord injury patients. It corresponds to ten (10) paired myotomes from C5 to T1 and L2-S1. Utilizing the standard supine position and stabilization of each muscle are followed examined in a rostral-caudal sequence. Improper positioning and destabilization of muscle may result in faulty grading. The strength of muscle is graded on a six-point scale [18]:

0 = Total paralysis.

1 = Visible/Palpable contraction.

2 = Range of motion (ROM) with gravity eliminated-active movement.

3 = Full ROM against gravity-active movement.

4 = Full ROM against gravity and moderate resistance in a muscle-specific position.

5 = Full ROM against gravity and full resistance in a muscle-specific position as compared with unimpaired individual.

5* = Full ROM against gravity and enough resistance to be considered/observed normal if inhibiting factors such as pain, disuse, etc., are absent.

NT = Not testable (may be due to severe pain, contracture of ROM, immobilization, amputation, etc.) [2].

The Frankel HL classified ASIA Impairment Scale (AIS) into “complete” or “incomplete” injury based on sacral sparing definition, that is, the presence of sensory and motor function in the most caudal sacral segments. The absence of sensory and motor function in the lowest sacral segments (S4–5) is called absent sacral sparing (complete injury) while preservation of motor and sensory function at S4–5 is defined as the presence of sacral sparing (incomplete injury).

The following ASIA-AIS are applied to grade the degree of lesion or impairment;

ASIA A = Complete – Loss of sensory and motor function in sacral segment at S4–5.

ASIA B = Sensory incomplete – Complete absence of motor function below the level of sacral segment S4–5. But some sensory functions are present.

ASIA C = Motor incomplete – Presence of some motor power below the lesion (grades 0–2) but has no practical use to the patient.

ASIA D = Motor functional – Motor functions are preserved below the level of injury, and the patient can walk with the support of assistive devices. Key muscles have grade 3 or more power.

ASIA E = Normal – Both sensory and motor functions are intact and normal muscle functions are available. But abnormal reflexes may have been present [4, 19, 20].

4. Functional goals

The level and degree of SCI determine the abilities of patients and functional goal. Assistive devices such as walkers, wheelchairs, crutches, etc., are important tools to make them mobile and active in social life. An appropriate wheelchair maintains normal posture and assists in long-distance travel. Each patient needs to be assessed properly for the appropriate devices and orthosis that may vary on the level of injury, motor function preserved, and the patient’s power [21].

The orthoses are important in the incomplete SCI condition where the patients can ambulate. The lesion at T12 is considered as the beginning of functional ambulation. Parallel bar standing movement and balance exercises can be possible only if trunk and pelvis are stabilized, and posterior shell orthoses can fulfill the requirements. Standing and movement assisted with orthoses reduces spasticity (muscle tone), improves bowel and bladder function, and reduces chances of ulcers, osteoporosis, and depression [22]. In the chronic phase of rehabilitation, the main aim is to achieve optimal independence and movement for both complete and incomplete injury. The factors that affect ambulation are lesion level, spasticity, weight, age, and general health condition. Orthoses can be applied for the patient with T10 and above injury level to exercise ambulation to maintain or improve muscle volume or bowel and bladder function. T11-L2 injured patients can move with limitations (within the home) with the assistance of assistive devices. Patients with more distal injury can ambulate socially [4, 23]. Orthoses are important in achieving movement in the chronic phase. Outside parallel bar movement is possible with orthoses and crutches if the patient has pelvic control. Optimal ambulation can be achieved in a patient with C8-T12 injury by hip guidance orthosis (HGO). The selection of material and inclusion of technological advancement such as power inbuilt is essential in achieving ambulation with less energy expenditure, improving the duration of wear and distance travel [24]. Orthoses with functional electrical stimulation (FES) make more comfortable movement in SCI patients [25].

In the past years, the movement with robot has emerged as a new approach. It has evidence of improving functional outcomes in subacute SCI patients [26]. The purpose of using robotic orthosis is to enhance recovery through repetitive functional movement. It has also shown results in improving secondary health conditions such as spasticity, pain, bowel and bladder function, and bone density (Table 1) [28].

S. No.	Level of injury	Abilities	Functional goal
01.	C1–C3	Head and Neck limited movement	Completely dependent. High support (head, back and posture) manual wheelchair for movement A powered wheelchair with head or chin control may be indicated.
	C4	Moderate shoulder and elbow function may be possible	Hand and wrist orthosis may be used for contracture prevention. Adaptive devices may help in feeding independence.
02.	C5	Dependent and assisted activity of daily living (ADL)	Positioning hand orthosis. Wheelchair (powered) with a joystick may help in movement.
03.	C6	Has power to move arms and wrist.	Powered wheelchair may help in long-distance movement. Assistive devices (customized) can help in independent ADL to some extent.
04.	C7	Upper extremity optimal independent functioning. Added power to strengthen elbow.	Manual wheelchair can be accessible.
05.	C8–T1	Limited natural hand function.	Manual wheelchair assistance for movement.
06.	T2–T6	Increased trunk control and chest muscle function.	Limited walking with extensive assistive devices.
07.	T7–T12	Increased motor function due to improved abdominal control.	Limited walking with extensive assistive devices.
08.	L1–L2	Increased motor function in hip and knee. Independent ADL and self-care	Short distance movement with assistive devices. Wheelchair for long distances.
09.	L3–L5	Independent bowel and bladder function.	Increased social interaction with assistive devices such as ankle foot orthosis (AFO), crutches.
10.	S1–S5	Independent function.	Increased ability to walk with an appropriate orthosis.

Table 1.

Functional goal according to level and degree of SCI [4, 27].

5. Orthoses

The application of orthoses for SCI patients has the objective to promote the healing of the spine at injury site and support the affected muscle, joint, and limb/or body parts for functional gain. Orthoses can assist the SCI rehabilitation in the following ways:

• Immobilize the spinal column movement to promote early healing and prevent further damage.

• Develop postural alignment.

• Stabilize the spinal cord and maintain alignment.

• Do passive stretching of tight muscles and release spasticity.

• Assist movement in paralyzed muscles and joints.

• Transfer load to the ground to reduce the pain at joints [29, 30, 31].

5.1 Spinal orthoses

About 60% of spinal injuries affect the cervical region of the spine with predominance in upper cervical vertebrae. The nonsurgical management includes immobilization of the cervical spine through rigid orthosis. Halo vest immobilizer (HALO brace) and Minerva Jacket (cervicothoracic orthosis) are commonly used orthoses for the nonsurgical management of the cervical spine. Halo brace is also used postsurgery to stabilize the spine. It was developed by Perry and Nickel in 1959, who had applied to immobilize the occipitocervical fusion in poliomyelitis patients. The Halo vest size is determined by circumference measurement of the chest at the xiphoid process. The placement of the ring should be one and a half centimeters above the eyebrows with equal space from ring to cranium circumferentially. The anterior and posterior pins should be placed surgically with a povidone-iodine solution (using sterile technique) opposite to each other. It protects cervical injury patients from neurological injury.

The Halo brace has a rigid ring that attaches to the outer cortex of the cranium through four sharp-pointed pins to bear the major load. The cranial pin sites are the most prevalent site of complication that includes penetration, scalp infection, and skull fracture [32, 33].

Minerva orthosis is a kind of molded orthosis that restricts the motions of cervical and cervicothoracic regions. The proximal part extends up to the occipital part of the head and distally to the lower part of the thoracic region (T12) [34].

It is indicated for comparatively/relatively stable cervical injuries in the lower region. It is frequently applied in postoperative stabilization in cervicothoracic region. Minerva jacket provides a rigid command of mid and low cervical spine movement. The lightweight polypropylene (PP) materials make it more acceptable with a liner to mandible support and its extension to posterior side of the head (Figures 2 and 3) [37].

Figure 2.

HALO brace [35].

Figure 3.

Minerva brace [36].

The sterno-occipito-mandibular immobilizer (SOMI) orthosis is applied to restrict the flexion, extension, lateral bending, and axial rotation in SCI. It has rigid anterior cheat piece connected to the shoulder through straps across back side of patient. The mandibular support is removable and can be removed during eating. It is indicated in relatively stable injury [37, 38].

Other semi-rigid collars such as Philadelphia, Miami, Aspern coller and Malibu brace can be indicated in the case of stable cervical fractures and post-surgical phase. These collars provide less movement restriction. These are less expensive but provide muscle relaxation [37].

The choice of selection of orthosis for nonsurgical treatment modalities for cervical trauma depends on factors such as injury type, risk of displacement, neurological type, patient’s health, and compliance.

Cruciform anterior spinal hyperextension (CASH) brace is used in thoracic and lumbar vertebrae fracture to control the flexion but does not limit the lateral bending and rotation. It is a comfortable design to limit the flexion from T6 to L1 (Figure 4) [38, 39].

Figure 4.

CASH brace.

JEWETT hyperextension brace provides support to the thoracic and lumbar spine by preventing flexion and twisting. It has little better control than CASH orthosis. Anteriorly it has sternal and pubic bad and in posterior side single adjustable band to support and provide three-point pressure control of the orthosis. It is indicated for T6-L1 vertebral body fracture. The CASH and JEWETT orthoses are known as flexion control orthoses [40].

Taylor Brace is a Thoraco-lumbosacral orthosis (TLSO) that controls the spine’s flexion and extension in the thoracic, lumbar and sacral region due to its long posterior bands. The abdominal corset is attached to increase intracavity pressure. The axillary straps are attached proximally to control the upper thoracic region. It is indicated to produce extension in the sagittal plane.

Knight Taylor brace contains additional thoracic and lateral bars that additionally control the lateral flexion of the thoracic and lumbar spine. It is indicated for anterior compression fracture of the vertebral body and postsurgical thoracolumbar spine stability.

To achieve the full control of flexion, extension, and lateral and rotation control, custom-molded full BODY JACKET (TLSO) made up of polypropylene (PP) can be effective. It increases intracavitary pressure to help offload the spinal column. It minimizes the pressure distribution over the per unit area due to full body contact; therefore, it is an ideal application for neurological conditions. It is indicated for thoracic compression fracture or postsurgery from T3 to L3 region.

5.2 Lower limb orthoses

Functional mobility is the major challenge in spinal cord injury. Patients having loss of lower limb function can use a wheelchair or orthosis to ambulate in society. Assisted standing and walking with orthosis have the benefit to SCI patients [41]. The visible benefits are feeling of well-being, improvement in circulation, reflex activity, bowel and bladder function, pressure sore prevention, improved digestive system, reduced muscle spasm, and psychological support. The majorities of patients enjoy standing and accomplished limited walking [42].

The lower limb orthoses enable the SCI patients to walk and stand with the support of their weakened/lost muscle and joint function. The application of orthoses depends on the level of injury, the patients’ preserved abilities, and the required mechanism to support the individual. The orthoses applied to assist the weakened or paralyzed limbs for standing and walking are

• ankle foot orthosis (AFO),

• knee-ankle foot orthosis (KAFO),

• hip-knee ankle foot orthosis (HKAFO),

• externally powered orthoses,

• functional electrical stimulation (FES), and

• hybrid orthosis [43].

The appropriate selection of orthosis depends on objective assessment and evaluation independence, energy cost, mechanical reliability, stability analysis, and preserved muscle power and joint range of motion (ROM) of the SCI patients [44]. The lower limb orthosis implications are indicated for maintaining joint range of motion, muscle strengthening, standing, walking, and bowel and bladder functional improvement [45]. AFOs are frequently applied to SCI patients to provide support for the weak muscles around the ankle joint to stabilize the ankle joint. It assists the patient in effective push-off during stance and restricts toe-dragging during the swing, which minimizes the risk of fall. AFO assists in safer and more efficient walking to the patients of SCI from L4-S2 [46, 47]. The Vannini-Rizzoli stabilizing orthosis (VRSO) can be applied to SCI patients having an injury at T6 or lower. It immobilizes the leg, ankle, and foot in plantar flexion (15 degrees) and stabilizes the knee in the upright position. VRSO improves mobility using other assistive devices such as parallel bar, walker, and crutches [48].

The KAFOs consists of different types of knee joints and locking/unlocking mechanism that are prescribed as per the individual need of the SCI patient. It is indicated for lesion below T10 [49]. KAFOs provide the required external support for motor and sensory loss. Before prescribing it, joint ROM, muscle strength, spasticity, sensation, and proprioception must be assessed properly. Quadriceps weakness, knee instability, and knee hyperextension are indicated for KAFO. It controls abnormal involuntary movement, prevents unwanted movement, and stabilizes the weak segment of the limb [50, 51]. The different type of KAFOs is available with free, locking, and spring-assisted knee joints. Flexion-extension control, medial-lateral control, and stance control KAFOs are also available. The swing phase control orthoses available in the market are E-Mag and Free Walk stance control (Otto Bock), Microprocessor-controlled KAFOs, C-brace computer-controlled KAFO (Otto Bock), etc. [52].

The extension of KAFO with the hip joint and pelvic or waistband is known as HKAFO. It is recommended for SCI patient who has requirement for the home to limited ambulation. It is also used for standing purposes inside parallel bar [53]. HKAFOs also help in preventing contractures of the hips, knee, and ankles. It assists in swing-through and swing-to gait with the help of the forearm or axillary crutches [54]. The available HKAFO orthoses are hip guidance orthosis (HGO), advanced reciprocating gait orthosis (ARGO), and hip and ankle linkage orthosis (HALO).

The orthosis with functional electrical stimulation (FES) is used externally to stimulate the paralyzed muscles to restore the lost function and is known as a hybrid orthosis. The three different types of stimulations used are electrical stimulation of the ventral roots, electrical stimulation of peripheral nerves, and electrical stimulation of the muscles [55]. Two types of hybrid orthosis are available: one based on mechanical designs (HGO, RGO, ARGO) and the other based on new designs that are modular hybrid, wrapped spring clutch, and spring brake orthosis. Premature muscle fatigue, increased weight, and cumbersome mechanism of orthosis are the limitations of FES [12]. The lower limb exoskeleton with an inbuilt external power supply is also used in SCI ambulation. It is known as powered gait orthosis (PGO). PGOs are used as a gait training system to provide ambulation in clinics or home. It provides active joint ROM, improved walking speed, step length, and joint kinematics in SCI patients. Currently, there are only limited options of powered orthosis available [56].

5.3 Upper limb orthoses

The upper limb orthotic prescription depends on the level of spinal cord injury and preservation of function. The main function of upper limb orthotic management is to maintain hand and limb position to improve the routine daily activity of living (ADL). Upper limb orthosis helps in spasticity reduction, edema control, supports/assists functional tissues, and controls positional changes of the limb [57, 58]. The orthosis is provided to assist the SCI patients with reduced limb function and strength. The upper limb orthosis can be categorized into static and functional. The main function of a static splint is to allow and maintain a corrected position to gain some functional activity. The function may include typing, writing, and holding. The resting hand orthoses are applied to maintain the anatomical structure and position [59]. The wrist splints increase the function in ADL. The primary aim of the orthosis is to prevent overstretching of wrist extensors with a stable base. The other orthoses that may be used in SCI management are long opponens, short opponens, and MP blocking orthosis [60].

6. Biomechanical principles

The biomechanical principles are applied to orthotic devices to achieve efficient, safe, and functional ambulation. The application of principles depends on the mechanical function to be achieved, individual physical condition, and normal human locomotion. The biomechanical principles assist in improving control, correction, stabilization, or dynamic movement [61, 62]. In general, orthotic biomechanics involves pressure, equilibrium, and lever arm principles. Force application is an important factor in orthotic devices. The force applied to the body through orthotic devices changes the alignment and exerts pressure over particular point. Therefore, the force distributed to the larger area reduced the pressure.

$$\mathrm{F}=\mathrm{P}/\mathrm{A}\text{.}$$E1

Three-point pressures are widely accepted in orthotics to control angular movement. The single prime force is counterbalanced by two other forces applied in opposite directions, and the resultant force equals zero. A four-point force system is applied to restrict translational movement and control comparative displacement of one segment compared with another. Orthotic devices act as a lever arm to produce angular forces. The longer lever arm minimizes the pressure per square area to control the forces around the joint [38, 63]. The strength and stiffness of material also impact the biomechanical consideration in orthotic fabrication [64]. In spinal orthotics, it encircles the trunk to form a cylindrical structure around the vertebral column to reduce the spinal pressure. It also limits the spinal segment movement and reminds the wearer to maintain the desired posture to avoid pain or discomfort (Figures 5 and 6) [38].

Figure 5.

Three-point pressure mechanism [65].

Figure 6.

Four-point pressure mechanism [66].

7. Discussion

The earlier studies have evidence that orthotic treatments are fruitful in spinal cord lesions. It gives the way to align the misalignment and ease pressure from the injured area of the spine [67]. A significant achievement has been made in achieving ambulation through biomechanically mechanized orthotic devices. The individually customized devices according to the SCI and functional assessment of individual assist in standing and walking. However, there is a need to develop more lightweight and allergen-free materials to minimize the demanding energy cost for the purpose [45]. The enhancements in mechanical design of orthoses and inclusion of externally powered function have improved ambulation in SCI patients. However, more effort is needed to minimize the rejection rate due to increased energy expenditure demand and poor biomechanical design [68]. The powered orthoses reduce the energy demands and effort during movement. However, its application for the mass population is poor due to its high cost and accessibility [12].

8. Conclusion

Every SCI patient exhibits complex pathophysiology, and much work is still needed to make the advanced care. The orthoses assist the SCI patient in achieving ambulation and recovery. The gained knowledge in the research laboratory must be translated to clinical application in individuals to enhance their quality of life. Early intervention of orthoses is also very important to gain maximum motor and sensory functional outcomes. The research on finding the solution for less energy expenditure, more lightweight design is the need of the hour to minimize the rate of orthoses rejection. The availability of orthoses on time with environmental accessibility is equally important to achieve the optimal outcome in SCI.

Acknowledgments

The authors are grateful to Dr. Roshan Bijlee KN, the Director of Composite Regional Centre for Skill Development Rehabilitation and Empowerment of Persons with Disabilities, Kozhikode, Kerala, India, for his constant technical support.

Conflict of interest

The authors declare no conflict of interest.