A Prospective, Longitudinal, Descriptive Study of the Effect of a Customized Wheelchair Cushion on Clinical Variables, Satisfaction, and Functionality Among Patients with Spinal Cord Injury

The Instituto Nacional de Rehabilitación (Rehabilitation National Institute) (INR) developed a prototype wheelchair cushion (INR cushion) designed to adjust to the anthropometry of the user’s ischiogluteal area and prevent pressure ulcer formation while maintaining or promoting functionality.   A prospective, longitudinal, descriptive study was conducted from February 2010 to February 2011 to evaluate the effect of using the INR cushion on clinical variables, functionality, and user satisfaction. Sixteen patients were recruited (9 male, 7 female, average age 31.8 [range 22–47] years, average body mass index 25 [range 22–34], average time in a wheelchair 10.1 [range 3–26] years) who met the study protocol inclusion criteria of being pressure ulcer-free for at least 6 months and capable of propulsion and transfer without assistance, chronic spinal cord injury (>2 years), and without chronic-degenerative diseases or cognitive problems. Each participant received the cushion for a 2-month evaluation. Eight clinical variables were assessed: trunk control, posture, spasticity, transfer capacity, comfort, skin reaction, propulsion capacity, and pressure release capacity. The clinical assessment was performed using validated scales and instruments: Modified Ashworth Scale (MAS), Functional Independence Measure™ (FIM), Norton Scale, and assessment of skin reaction. Interface pressures were measured using force sensing array, and participants completed a structured interview to assess user expectation, perceived functionality, perceived quality, and likelihood of recommending the device. Two patients withdrew due to appointment conflicts; of the remaining 14, significant differences between the user’s experience with other products and the INR were found with regard to pressure redistribution (P = 0.012); all participants but 1 graded the INR as good in all interview categories. No participants developed a pressure ulcer during the study. The customized cushion was especially functional among patients with incomplete thoracic and cervical injuries, high FIM scores, and moderate levels of activities of daily living. Taller patients (P = 0.01) and patients with higher degrees of spasticity (P = 0.007) were less satisfied with functionality. The results of this study contributed to the redesign process of the cushion. These findings may be useful to establish predictors, both subjective and clinical, for patient utilization of wheelchair cushion use.

Pressure ulcers are among the most frequent complications of spinal cord injury, due not only to the decrease in patient mobility and sensory function, but also to dysautonomia, spasticity, fecal and urinary incontinence, malnutrition, and depressive states.^1,2 Pressure ulcers have both social and economic repercussions. Salcido and Lorenzo³ estimate the cost of ulcer treatment, depending on the degree, fluctuates between $2,000 and $40,000 (US dollars).³ In addition to financial costs, pressure ulcers confound the rehabilitation process, extend hospital stay, and may provoke depressive states in patients with spinal cord injury.⁴

  In Pérez et al’s⁴ retrospective study performed at the Instituto Nacional de Rehabilitación (INR) in Mexico regarding pressure ulcer frequency in spinal cord injury patients (N = 211, 76.8% men, average age 32.3 ± 13.8 years), 61% of patients had a pressure ulcer at some point in their lives, most frequently patients with neurological thoracic level (n = 81) or cervical level damage (n = 39). The results obtained by Pérez et al⁴ are similar to those reported in Japan by Sumiya et al.⁵ Their cross-sectional, observational research studied the characteristics of 218 spinal cord injury patients (201 men, average age of 43.3 ± 11.80 years) using wheelchairs. Thirty-nine patients had some type of ulcer and were not satisfied with the wheelchair cushion they were using when the study was conducted, pointing to the necessity of using a cushion that satisfies the user’s need for pressure distribution and support. Regan et al⁶ performed a systematic review of studies related to the prevention of pressure ulcers and recommended use of wheelchair cushions as a prevention strategy. According to Regan et al’s findings, a single type of cushion does not meet the needs of every spinal cord injury patient; a cushion should be selected based on an assessment of the pressures between the cushion and the user and the clinical prescription and user characteristics and preferences; the cushion could be prescribed by physicians, rehabilitation professionals, and/or the multidisciplinary rehabilitation team. Furthermore, the review⁶ underscored the need to understand how to reduce pressure in body zones with a high incidence of ulcers.

  Studies regarding cushions anthropometrically adjusted to the ischiogluteal zone of the patient and used as surfaces for the prevention of pressure ulcers are particularly enlightening. In an experimental study, Sprigle et al⁷ specifically examined the efficiency of this kind of cushion versus the nonindividualized cushions the patient used habitually in 10 persons with spinal cord injury regarding clinical variables such as posture, balance, skin reaction, interface pressure, propulsion, and spasticity. The main findings suggest an anthropometrically adjusted cushion improves weight distribution, reduces tissue strain, and constitutes one of the best approaches for pressure ulcer prevention. These results match an experimental study by Rosenthal et al,⁸ where 47 nondisabled persons tested the pressure distribution capacity of a total contact seat-type cushion (a cushion anatomically adjusted to the ischiogluteal area). Study participants described comfort and an increase in their capacity to remain sitting when using this kind of cushion.

  At the INR,⁹ a cushion customized anthropometrically to the ischiogluteal region was designed and evaluated by 9 persons without disability and 9 with spinal cord injury. The results showed the cushion reduced pressure in the ischiatic tuberosity zone to <60 mm Hg after 30 minutes in both groups. The group with spinal cord injury used the cushion in daily life situations such as job, academic, and sports activities, finding it useful and satisfactory because it served the purpose for which it had been designed.

  To assess the satisfaction level of using this technical aid, Kittel et al¹⁰ performed a descriptive, qualitative study to evaluate the perceptions of the recommended wheelchair in 3 patients with spinal cord injury. The authors found one of the main factors associated with abandonment of the prescribed wheelchair in favor of another one (usually propelled by others) is dissatisfaction with the functional limitations of the aid, inappropriate selection, and lack of patient experience with the device.

  According to Serrano-del Rosal and Loriente-Arín,¹¹ who performed an observational study with data from the Primary Care Services User Survey with the Andalusian Public Health Service, satisfaction with a product or given service also is related to perceived quality. These authors note the perception of satisfaction within a health service is based on a person’s subjective judgment, where both necessity and expectation play a role. A health service user’s satisfaction is complex and multidimensional and can be expressed globally — that is, the health service user can express his/her judgment about the health service delivered as one entity without considering the different aspects that constitute a health service or the different aspects of value (eg, facilities, service organization, medical intervention). The authors found that to evaluate and subsequently improve the quality of the services, user satisfaction must be quantified and that a patient may abandon treatment if dissatisfied with the quality of the service or treatment received.

  Similarly, users must be satisfied with technical aids and devices to avoid their abandonment. As such, quantifying user satisfaction becomes necessary; as noted by Kittel et al,¹⁰ this can be accomplished through the evaluation of their functionality. In an interview-style survey¹² regarding attachment and abandonment, Phillips and Zhoa¹² addressed the predictive factors related to abandoning technical aids among a sample of 227 adults with some disability. For example, a device that sits in the closet may have been abandoned, switched (eg, from a cane to a walker), or the manufactured material or brand changed. The authors developed a survey to assess attachment and abandonment, dividing technical aids into categories of use. Among their findings, the factors for which the technical aid is abandoned include changes in the user’s needs, availability of the equipment from the supplier, equipment performance (including fulfillment of the user’s expectations regarding reliability, durability, and comfort), and consideration of the user’s opinion during the selection process. The authors found in the specific case of wheelchairs 38 of every 99 users abandoned their use. However, the study was limited; it did not differentiate reasons for abandonment (ie, user’s dissatisfaction versus evolution of the disability). The authors state dissatisfaction with a technical aid, as well as its correct function, is a critical element in its perceived success or failure.

  According to results of a cross-sectional study by Samuelsson and Wressle¹³ in 3 assistive-device centers in Sweden, the effects of using a technical aid are more noticeable than any other kind of clinical intervention. Participants included 262 persons with different motor disabilities and additional elderly people, all users of wheelchairs and walkers. Study participants completed a Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST) 2.0 questionnaire. The study highlighted the need to measure the satisfaction with technical aids because their use and utility in the rehabilitation process depends on the client and can influence decision-making regarding related recommendations and services. However, currently no studies have quantified the association between clinical characteristics of the spinal cord injury patient’s perception of functionality and satisfaction with a wheelchair cushion.

  The purpose of the current study was to evaluate the effect of a cushion designed and developed at the INR on clinical variables and individual perceptions of functionality and satisfaction in spinal cord injury patients.

For this prospective, longitudinal, descriptive study, participating physicians recruited patients who used the INR of the Spinal Cord Injury Service. The study was conducted over 1 year (February 2010 to February 2011): 6 months for patient recruitment, 1 month to manufacture the wheelchair cushions, 2 months for patient use, and 3 months for data analysis. Participants were selected according to the following inclusion criteria: wheelchair users capable of propulsion and transference without assistance; having a chronic spinal cord injury (>2 years); free of pressure ulcers for at least 6 months before the study; and no associated chronic-degenerative diseases or cognitive problems. Study candidates had to be willing to use the wheelchair cushion developed by the INR (at no cost to the user) for a minimum of 2 months. The Institutional Ethics Committee approved the study protocol, which also respects the Declaration of Helsinki. All participants provided written informed consent.

  Before the manufacture of the INR cushions, every eligible candidate was clinically evaluated for a wheelchair cushion according to the variables proposed by Sprigle et al⁷ (balance, posture, pressure relief and repositioning, transfer ability, propulsion of the wheelchair, comfort, effect of spasticity, posture, and skin reaction). The physicians participating in the study performed the clinical evaluation for each volunteer using validated scales and instruments.

  Individualized cushion. Every patient received a cushion conformed to each personal ischiogluteal anthropometry,⁹ which was attached to the wheelchair (INR wheelchair cushion). The cushions were developed by researchers of the Rehabilitation Engineering Laboratory of the INR^9,14 and manufactured in the Prosthetics and Orthotics Laboratory (INR). The manufacture of the cushions is based on the prosthetic lower limb fitting technique^14,15 using thermoformed polypropylene as a base for the anthropometry of the individual’s ischiogluteal zone. This anthropometry is obtained from a mold taken of the user by means of a seating simulator (Prairie Reflection® model PSS 97 Molding Frame, Prairie Seating Corporation, Skokie, IL).

  The polypropylene base is designed to reduce pressure in the zones predisposed to pressure ulcers; the body contact area is enhanced using a layer of commercial polyurethane foam to cover the base (see Figure 1). Because the cushion is a recently developed product, both manufacturing and user testing processes must be continually verified and improved; delivery takes approximately 5 days.

  To adjust the cushion to the patient, size, weight, and the wheelchair habitually used are considered. Some wheelchairs required modifications to ensure the feet were always supported.

  Variables assessed. All variables were evaluated for both the cushion previously used by the patients and the INR wheelchair cushion. Patients were encouraged to use the INR wheelchair cushion in all activities of daily living (ADLs), using it from 8 to 16 hours daily. This fact was verified by the manufacturing team.

  Trunk control.^7,16 Because no validated clinical tests existed to assess trunk control for spinal cord injury patients, this factor was evaluated by physical examination by an expert who determined control to be adequate or inadequate depending on the patient’s ability to remain seated and react to external stimuli while maintaining balance in a sitting position. This variable was evaluated for both the cushion previously used by the patients and the INR wheelchair cushion.

  Posture. Posture was evaluated according to Sprigle et al.⁷ Trunk symmetry was determined using touch examination and observation, and the pelvis was examined for obliquity or angles that might cause asymmetry.

  Interface pressure. An interface pressure map, the Force Sensing Array (FSA®) system (Vista Medical, Winnepeg, Canada) was used to verify symmetry in pressure distribution (see Figure 2). The sensors’ matrix deploys a topographical and numerical map of the pressures applied on every point through an arrangement of 16 x 16 resistive sensors. Every sensor is 2.5 cm x 2.5 cm in area; sensors are contained in a thin, flexible material that is placed between the user and the cushion. The information is obtained through the system interface and software. Measurements were ascertained when the INR wheelchair cushion was delivered to verify an average pressure of 60 mm Hg⁹ in the ischiastic tuberosity zone. The patient was seated 20 minutes in his/her INR wheelchair cushion while the manufacturing team verified the interface pressure. If an average pressure >60 mm Hg was detected, the INR wheelchair cushion was adjusted. The second interface measurement was performed after 2 months and lasted 20 minutes.

  Spasticity. The modified Ashworth Scale,¹⁷ which measures resistance to passive stretching, was used to assess the following factors and assign a corresponding value: normal muscle tone (0); slight hypertonia (1) — slight increase in muscle tone manifested by a catch and release or by minimal resistance at the end of the range of motion when the affected part(s) is moved in flexion or extension; increase of muscle tone manifested by a catch and release, followed by minimal less than a half of the range of motion (1+); moderate hypertonia (2) — increase in muscle tone in most of the range of motion although the affected part can move passively with ease; intense hypertonia (3) — prominent increase of the muscle tone, with difficulty performing passive movements; and extreme hypertonia (4) — the affected part remains rigid, both for flexion and extension.

  Transference capacity. User ability to transfer independently from a wheelchair to another surface, such as another chair or a bed, was evaluated using the Functional Independence Measure™ (FIM).¹⁸ The FIM is a scale used to quantify the degree of functional independence of a disabled person in the performance of ADLs. The scale contains 18 items related to different aspects of a person’s functional capacity: feeding, self-care, bathing, dressing of the lower body, dressing of the upper body, grooming, sphincter control, bed-chair-wheelchair transfer, toilet transfer, locomotion, stairs, cognitive comprehension, expression, social interaction, memory, and resolution of daily life problems. Every item can be graded from 0 to 7 according to the degree of functional independence found and the aid the patient needs to perform such activities: 0 = activity does not occur; 1 = needs total assistance; 2 = needs maximum assistance (patient can perform 25% to 49% of the task); 3 = needs moderate assistance (patient can perform 50% to 74% of the task); 4 = needs minimum assistance (patient can perform 75% or more of the task), 5 = needs supervision or setup, 6 = modified independence (patient requires the use of a device); and 7 = complete independence.¹⁸ The minimum/maximum grades are 18/126. A higher score implies greater independence.

  Skin reaction. An expert examined the skin in the ischiogluteal zone and, using the Norton Scale (which considers patients’ general state, mental state, activity, mobility, and incontinence to determine pressure ulcer risk),¹⁹ assessed the presence of pressure points, blotches, or any other sign that could precede the formation of a pressure ulcer. Each characteristic is assessed on a scale of 1 to 4; the grades are totaled to establish the risk score that rages from 5 to 20. A score of 14 or less indicates at-risk status. The Norton scale was only used at the beginning of the study.

  Propulsion capacity. The ability of the participant to move the wheelchair by him/her-self was assessed using the FIM.

  Pressure release capacity. The participant’s ability to shift/redistribute weight by himself in order to release pressure was assessed using the FIM. This ability was assessed in the dimensions: bed chair transfer, toilet transfer, shower transfer. The score ranges from 7 (complete independence) and 6 (patient requires uses of a device, but no physical assistance) to the lowest score of 0 (the activity does not occur).

  Comfort. This variable was assessed only in the INR wheelchair cushions during the test and adjustment phase and was evaluated using the structured interview^20,21 designed to evaluate the satisfaction and functionality of the cushion regarding comfort.

  Procedure. After 2 months of use for 8 to 16 hours daily (depending on the patient’s activity level), clinical variables were assessed using the scales and instruments described. In addition, a structured interview designed specially to evaluate satisfaction and functionality of the customized cushion^20,21 was conducted. This interview was developed according to the structured interview methodology, a qualitative format used to ascertain the opinion of users about a product or service. This approach allowed the researchers to gather more information than closed-ended questions²⁰ because reference can be made to previous experiences, providing the opportunity to refine the product based on negative comments. The face-to-face (interviewer-interviewee) technique also creates empathy.²⁰

  The structured interview design was based in the Models of Satisfaction of the American Customer Satisfaction Index (ACSI)²⁰ and the Mexican Satisfaction Index User (IMSU)²¹ that were designed to quantify the service or product user´s satisfaction. Both models take into account the person’s subjective judgment about the service or product received as a whole and the person’s subjective judgment about the service received when the different aspects that constitute the service or product are considered.

  The structured interview was conducted to quantify the user’s judgment of the wheelchair cushion. It took into account the 4 different dimensions or aspects that form the product.

  The first section considers the user’s expectation about the quality of the product to be received (the INR cushion) as well as the quality of his previous wheelchair cushion. The 2 items are graded from 1 to 10 (maximum score is 20 points).

  The second section deals with the perceived functionality when the patient is using the INR wheelchair cushion and is divided in 8 clinical variables as proposed by Sprigle et al,⁷ each item graded from 1 to 10 points (maximum score 80 points).

  The third section considers the quality perceived of the INR wheelchair cushion as a product, the satisfaction perceived when it is used to prevent pressure ulcers, and the perceived functionality when used during ADLs. This section has 3 items, each graded from 1 to 10 (maximum score 30 points).

  The fourth dimension considers the user’s inclination to recommend the INR wheelchair cushion based on the user’s satisfaction with the product during the project and his/her confidence the INR wheelchair cushion will provide good service to other users. In this fourth section, each item is graded from 1 to 10 (maximum score 20 points).

  The 1- to 10-point scales are based on the Analogous Visual Scale,²² an easy tool for patient use. Scores are grouped into 3 categories based on the user’s subject judgment. A score of 1 to 4 signifies the user perceived the lowest quality in the service or product and that it did not fulfill their expectation. A score of 5 to 7 shows the user perceives a low or medium quality in the service or product, has doubt about the services or product, or it did not fulfill their expectations. A score of 8 to 10 implies the user perceives quality in the service or product, has the disposition to recommend the service or product, or feels confident using the service or product.

  Data collection and analysis. Data collected during this study were stored in an exclusive archive for this study. A paper archive was collected for each participant, then data were stored in an electronic archive. Access to this file was limited to registered participant researchers. Patient anonymity was protected by assigning each participant a consecutive identification number.

  Statistical analysis. All data were analyzed with the SPSS 15 software program (Chicago, IL), and the Kolmogorov-Smirnov normality test was applied. Results were considered statistically significant when P <0.05.

  In the case of pressure distributions, the medium pressure of the ischiastic tuberosity zone obtained by FSA using the previous cushion was compared to average pressures obtained with the customized cushion. The Kolmogorov-Smirnov normality test was applied and provided a positive result for normality; consequently, a Student’s t-test was used. Results were considered statistically significant when P <0.05.

  A Mantel and Haenzel test, chi-squared test, or Wilcoxon t-test was used to determine the association between perceived functionality when performing ADLs and satisfaction with the use of the INR wheelchair cushion compared to the previous product with regard to: 1) the degree of spasticity and the change in satisfaction with the use of the prototype cushion and 2) the degree of spasticity and the perception of decrease in spasticity. Pearson correlation tests were used to examine the relationship between height and perceived satisfaction when using the INR wheelchair cushion.

Because the cushions were provided free of charge to the patient (the design and development of the product were sponsored by the Consejo Nacional de Ciencia y Tecnología [Science and Technology National Council]), the sample was limited to 16 patients.

  Patient characteristics. Table 1 shows the demographic and anthropometric characteristics of the 16 patients. Because 2 patients did not complete the study due to health problems that did not allow them to keep their appointments for the delivery of the cushion, the sample was reduced to 14. Before the delivery of the prototype cushion, 8 patients had a Norton score of 16 points, 4 patients had a score of 14 points, 3 patients had 15 points, and 1 patient had a score of 17 points, indicating patients are at high risk to develop a pressure ulcer.

  Transfer capacity and spasticity. No significant differences were found between the previous cushion and the INR wheelchair cushion with respect to transfer capacity. The average FIM score of the sample with the previous cushion was of 107.2 ± 17.3 points (range 77–124) versus 110.1 ±14.0 points (range 84–123) with the INR wheelchair cushion (P >0.05).

  Using the modified Ashworth scale, at the beginning of the study 5 patients had a spasticity degree from 2 to 3, and 11 patients presented a degree of +1 to 0. After study cushion use among the 14 study patients, 10 presented with a spasticity degree from +1 to 0, and 4 patients showed a spasticity degree 2 to 3; therefore, no difference in spasticity before and after the study was observed.

  Pressure distribution. FSA pressure distributions differed significantly. The average pressures in the ischiastic tuberosity zone were 72.19 ± 24.24 mm Hg (range 129.42–44.38 mm Hg) on cushions previously used by the patients and 58.22 ± 27.27 mm Hg (range 103.32–19.11 mm Hg) on the INR cushions, a significant difference (P = 0.012).

  Posture. Patients who did not use any kind of cushion or a cushion whose material could not be determined presented pelvis asymmetry or obliquity, confirmed by observing the pressure maps. In patients who used air or gel cushions, posture was mostly symmetrical with an aligned pelvis (see Figure 2). These patients reported the INR wheelchair cushion suited them better and felt more comfortable in their wheelchair. In the structured interview in the item “posture,” the sample average score was 9 points with the INR cushion, while the average with the previous cushion was 8, but those results were not statistically different.

  Balance. In the structured interview in the item related to balance, 10 patients (9 with complete thoracic injuries and 1 with complete spinal injury) scored balance 8 to 10; they were confident with their balance before using INR wheelchair cushion. Four of these patients graded balance 5 to 7 when they used the INR wheelchair cushion; they perceived discomfort or did not feel confident in their wheelchair, and when they performed some balance activities, they preferred to continue using their old wheelchair cushion. No statistically significant difference was found between cushions.

  Patient satisfaction. Patients were asked to grade satisfaction on their old and their new cushions during the structured interview (see Table 2). Every patient (13) but 1 graded the cushion as good in perceived functionality of the INR wheelchair cushion in the performance of ADLs (see Table 2).

  The change in perceived satisfaction between the use of the previous cushion and the use of the INR wheelchair cushion was associated with the perceived functionality in performing the ADLs, where the higher the grade given to the INR wheelchair cushion’s functionality, the greater the change in the score of satisfaction with the cushion (Mantel and Haenzel test, P = 0.006).

  With regard to spasticity, the change in perceived satisfaction between the previous cushion and the INR wheelchair cushion was associated with the degree of spasticity measured with the Modified Ashworth scale (see Table 3). The greatest change in grades in perceived satisfaction when using the INR wheelchair cushion occurred in patients with less spasticity. A significant difference between these scores was noted (chi-squared test, P = 0.015).

  The degree of spasticity associated with the grade assigned to the item related to perception of spasticity decreased among INR wheelchair cushion users (see Table 4). Patients presenting a spasticity degree between +1 and 3 assigned a grade of 6–7 to the item addressing perception of spasticity decrease. The patients who presented a spasticity degree between 0 and 1 assigned a grade of 8–9 to the same item; thus, a significant difference between the degree of spasticity and the grade was noted (Mantel and Haenzel test, P = 0.03).

  According to the interview results, an association was noted regarding the perception of spasticity decrease. The 10 patients with spasticity perceived a decrease regarding spasticity in their pelvic limbs (Mantel and Haenzel test, P = 0.03).

  Regarding the items related to propulsion and transfers, no significant differences were found in the trunk control assessment and the FIM before and after use of the INR wheelchair cushion. Two patients stated their propulsion was worse after changing to the INR cushion, and the rest of the sample graded propulsion as good. Six patients stated they perceived limitations in transfers (low to medium scores), and 5 said they thought the seat was high (low to medium scores). Further exploration was conducted to determine whether the user’s height could be associated with the perceived satisfaction when using the INR wheelchair cushion — the items with low to medium scores included balance, transfers, and propulsion, which could be related to the INR wheelchair cushion’s height (5 cm in average). Another factor to take into account is that most of the patients owned their wheelchairs and minimum or no adjustments were made regarding height, despite the biomechanical changes of adding the new cushion. In terms of gender, a tendency with moderate correlation (r = -0.64) was noted in shorter men, who assigned higher satisfaction grades to the customized cushion and in shorter women, where a strong correlation (r = -0.82) was noted (see Figure 3).

Scores relating to results of satisfaction and functionality assessment  are shown in Table 5 and Table 6.

None of the participants developed a pressure ulcer during the course of the study.

Although a wheelchair cushion can help distribute pressure and preserve correct posture, it must not interfere in the performance of ADLs. Three patients with inadequate trunk control graded posture and balance as good on the INR, but 3 patients with adequate trunk control and the highest mobility scores related to independence and locomotion (in the initial FIM, they stated they could climb up and down some stairs or avoid edges with their wheelchair), scored posture and balance as 5 to 7 — they did not feel confident using the INR wheelchair and preferred their old cushion when performing activities involving posture and balance. Moreover, 1 patient reported he could no longer manage to climb or go up stairs.

  Patients with a higher degree of spasticity were less satisfied with the cushion and they found it less functional. This finding may confirm the observation by Sprigle et al⁷ that patients who experience spasms may lose their position in the cushion and may not have the capacity to relocate themselves. Also, spasticity and functionality are related to the perception of quality of life in the spinal cord injury patient,^23,24 which may have affected the functionality grading scores of the cushion in this group of patients.

  No significant change in FIM was found between the initial and 2-month follow-up. Six patients graded capacity to transfer using the customized cushion as low, regardless of level of injury. Three patients graded mobility lower in the FIM. The low transfer capacity scores are not unexpected; however, 3 patients had a high mobility grade but rated transfer capacity as low. Upon further investigation, this was found to be related to a specific feature of the customized cushion that complicated transfers in extreme cases of low and high mobility. These data were taken into account for the redesign phase of the cushion. It is important to note this was not found with regard to locomotion or propulsion capacity.

  Height as a factor. In general, shorter patients were more satisfied with the cushion, which may be due to the fact that in some cases patients perceived better reach and noted a favorable change in their posture. The 5 tallest patients perceived instability and felt limited when performing their ADLs.

  ADLs and product satisfaction. The customized cushion masked wheelchair deficiencies, such as or incorrectly prescribed chairs/cushions regarding size or what was needed relevant to the level of their injury. These perceptions were reflected mainly in the functionality grade. In addition, perception of functionality to perform ADLs and the satisfaction in the use of the INR wheelchair cushion were related to the kind of wheelchair. In general, and independent of the level of injury, the patients who used this wheelchair cushion found it facilitated performance of ADLs, with the patients with higher levels of injury and lower scores of FIM grading the customized cushion higher in functionality and satisfaction. Patients with a lower level of injury and higher FIM scores were prudent regarding functionality when grading the item related to transference; in some cases, the cushion represented a complication, and they had to ask for support to perform their ADLs. With regard to balance, some patients with higher FIM scores and lower levels of injury reported cushion design complicated maneuvers with the wheelchair.

  The items receiving the highest grades were the 1) capacity to release pressure and 2) skin reaction regarding ability to address areas at risk for pressure, important concerns. Because pressure distribution was effective, patients who used the cushion did not develop pressure points or ulcers, quantitatively shown using the FSA equipment (see Figure 2). Posture and comfort items also received good scores; in general, patients were comfortable and exhibited better posture than when using the previous cushion.

  Developing an objective assessment and taking into consideration the user’s perception of this new cushion design may help diminish its abandonment. As Phillips and Zhoa¹² found, including the user in device decisions and considering their perceptions of whether the device lives up to expectation in terms of comfort, reliability, and safety tends to decrease abandonment of use. In this study, as the design team received the user’s feedback about the cushion, they could make adjustments in the cushion’s design to address balance and transfer issues, thus avoiding cushion abandonment.

  Although the literature includes studies comparing different wheelchair cushions in groups of spinal cord injury patients,^24-27 studies related to the efficiency of cushions to prevent pressure ulcers in groups with spinal cord injury,^28,29 and studies about customized cushions,³⁰ no evidence is available on user opinion regarding cushion satisfaction and functionality. The specifically designed instrument to evaluate satisfaction and functionality (structured interview) together with the clinical assessments provided useful and important information to facilitate wheelchair cushion redesign.

The limitations of this study were small sample size, lack of a concurrent control group, and the time required to manufacture the customized cushions. In addition, the instrument used to evaluate satisfaction and functionality has not been validated.

The results obtained in this study suggest a customized wheelchair cushion can help redistribute pressure and provide support but mainly in patients with high thoracic and incomplete cervical injuries, either adequate or inadequate trunk control, and in the performance of moderate ADLs. In other words, patients can perform 50% to 74% of their ADLs without assistance. In patients with an active daily life style, including the practice of sports, a customized cushion may complicate performance, which could lead the patient to abandon use of the cushion. Feedback provided by cushion users will help improve the cushion’s design.

  Studies on wheelchair cushion clinical variables, user satisfaction, and functionality are necessary to ensure continued use and help detect factors that predict abandonment or acceptance of therapeutic advancements.

The authors are grateful to the National Council of Science and Technology for the support for carrying out project under code SALUD-2006-key 1-45395; the Division of Neurological Rehabilitation and the Orthesis and Prosthesis Laboratory of the National Rehabilitation Institute of Mexico; the Program of Master in Quality Engineering of the Universidad Iberoamericana; and the participants of the Fundación Humanista de Ayuda a Discapacitados IAP.

The National Council of Science and Technology (CONACYT, by its Spanish acronym) provided a grant to support the project under code SALUD-2006-key 1-45395. The Division of Neurological Rehabilitation oversaw patient recruitment and clinical monitoring. The Orthesis and Prosthesis Laboratory of the National Rehabilitation Institute of Mexico provided facilities to manufacture the INR cushions. The Program of Master in Quality Engineering at Universidad Iberoamericana provided academic advice for the client satisfaction assessment. Some participants of the Fundación Humanista de Ayuda a Discapacitados IAP were involved as prospective study participants.

Dr. Vilchis-Aranguren is a physician, Servicio de Rehabilitación y Medicina Física, Hospital General de Zona #16, Unidad de Medicina Familiar (HGZ 16, UMF), (IMSS), Cancún, Quintana Roo, Mexico. Ms. Gayol-Mérida is a medical researcher, Laboratorio de Ingeniería de Rehabilitació; Dr. Quinzaños-Fresnedo is Head of the Neurological Rehabilitation Division; and Dr. Pérez-Zavala is Chief of the Spinal Cord Injured Service, División de Rehabilitación Neurológica, Instituto Nacional de Rehabilitación, Mexico City. Ms. Galíndez-Novoa is a professor, Departamento de Ingenierías, Universidad Iberoamericana (UIA), Mexico City; and Escuela de Ingeniería, Instituto Tecnológico y de Estudios Superiores de Monterrey (ITESM), Campus Santa Fe, Mexico City. Please address correspondence to: Jimena Quinzaños-Fresnedo, MSc, Division of Neurological Rehabilitation, Av. México-Xochimilco no. 289, Col. Arenal de Guadalupe, Tlalpan, Mexico City, Mexico 14389; email: jimenaqf@hotmail.com.