It is the goal of all prosthetic interventions to maximize patient function. Research has shown that physical mobility is the only independent factor that significantly affects quality of life in amputees when compared with nondisabled persons.1 Although they theoretically have the highest probability of achieving normal functioning,2 patients who have undergone amputation due to an avulsive trauma generally have secondary injuries that complicate their recoveries. For transtibial amputees, injuries typically include extensive damage to the patellar tendons and hamstring group. It is possible to accommodate for the resulting gait deficiencies with a patella-tendon-bearing (PTB) socket connected to an ischial weightbearing thigh cuff (IWBTC) with external knee joints and check strap (Figure 1). In this type of prosthesis, the external knee joints and check strap combine to prevent knee hyperextension in the PTB socket, accommodating the hamstring group weakness. The forces responsible for hyperextension on the residuum are countered by the check strap.3
Alternatively, there is an emerging technology that shows promise as a replacement for traditional prosthesis designs: elevated vacuum (EV). Also known as subatmospheric, EV prostheses consist of an elastomeric liner, total surface bearing socket, mechanical or electronic vacuum pump, and a sealing sleeve. Designs can also include an elevated vacuum locking system, a safety feature which provides suspension should the vacuum seal be breached. EV systems have been found to distribute forces evenly over the residuum, so there is an exceptionally high suspension force without the high pressure areas seen in PTB sockets.4 It is thought that EV systems maximize surface contact between the socket wall and the liner, enabling high frictional forces that augment suspension and fit. This phenomenon was recently proven in a study of traumatic transtibial amputees where those wearing EV prostheses demonstrated significantly less vertical movement of the tibia during gait and strenuous activities than those in traditional sockets.4,5 For a highly active transtibial amputee, intimate socket fit and effective force distribution are integral to the performance of daily activities, as they are imperative to suspension, comfort, proprioception, function, and limb health. Furthermore, a recent study found that skin problems on the residual limb are uncommon with vacuum system users.6 Finally, one study indicates that EV could enable better stance phase and step length symmetry when compared with PTB designs in transtibial amputees, and the researchers involved explain those results with the fact that EV can provide better total skin surface contact,7 enabling more mechanical and sensory control over the prosthetic limb. Clearly, EV has the potential to greatly increase patient functional achievement.
Despite the possibilities of EV, the lack of valid research in this area limits the evidence for its use. This fact is highlighted by Van der Linde et al.'s literature review which found a lack of unbiased information about the effects of different components, including sockets, on patient functional status.8 The majority of clinical studies that do exist on the topic have used standardized gait assessment protocols with limited ecological validity, making them inappropriate to use in making a prosthetic prescription.8 No published reports were found documenting the long-term effect of EV technology on patient function. Very little unbiased, valid research has been found comparing PTB sockets and EV sockets. Therefore, the purpose of this report is to show the long-term functional development of one patient during his transition from a transtibial prosthesis featuring PTB socket, with IWBTC, external knee joints, and check strap to an EV system.
The subject in this case is a patient at Dayton Artificial Limb in Dayton, Ohio. He is a highly active 40-year-old male with a left amputation at the transtibial level. His amputation is the result of an avulsive traumatic accident in 1992, in which the patient's limb was caught in a grain augur. The injury caused extensive patellar tendon and hamstring group damage. At the time of reporting in May 2010, the patient was 165 cm tall and weighed 108 kg. He did not smoke and consumed two alcoholic drinks a week. He had not been diagnosed with any other physical health conditions.
Shortly after his amputation, the patient was fit with a PTB socket connected to an IWBTC with external knee joints and a check strap (Appendix). He was classified a functional level K3 and participated in 3 months of physical therapy and prosthetic training. He wore this prosthesis for 16 years, with routine fittings and replacements. He required no assistive devices and walked approximately four miles a day on varied terrain as required by his profession as a farmer.
Throughout the prosthetic process, the patient reported discomfort around the fibula head, mid-patellar tendon, and at the proximal brim of the IWBTC. The fibula head and mid-patellar tendon area pain were managed with pads and socks, but those areas remained discolored, indicating that they were areas of high pressure. He also exhibited minor but persistent circumduction and gait asymmetry. He began experiencing more difficulties with his prosthesis in January 2010. Specifically, the patient complained of pain and stiffness in his sound side knee joint that were likely due to the gait asymmetry, and his limb displayed contact dermatitis, a condition that can be caused by factors involved in the residual limb and socket interface such as weight distribution and shear force.9 The negative effects of the prosthesis resulted in its occasional disuse. The patient expressed a lack of confidence in daily activities such as getting down from a tractor, climbing a ladder, and walking on uneven ground.
The patient's residuum was manually examined by the prosthetist in May 2010 at a routine fitting, and his limb displayed increased range of motion and muscle mass compared with the results of similar routine evaluations by the prosthetist since he began using his PTB with IWBTC prosthesis. In a gait evaluation by the prosthetist at that appointment, the patient demonstrated better control of knee hyperextension, and the prosthetist saw increased anterior-posterior and medial-lateral stability in the form of decreased stabilizing motion in the knee joint likely explained by increased muscular compensation. Furthermore, the patient reported a desire to wear a less cumbersome prosthesis that would allow him more freedom of movement. Based on the patient's increased dynamic stability and interest in a new prosthesis, the treating physician ordered an EV prosthesis for the patient. The transition to an EV system was also made in order to simplify the prosthetic use and management for both the patient and the clinician. A total-surface-bearing socket can be fabricated at a central fabrication facility in a matter of hours, compared with the week required to create a custom-laminated PTB socket with IWBTC.
The EV prosthesis included a total surface bearing socket (Prosthetic Design, Dayton OH), silicone liner (Prosthetic Design, Dayton OH), Harmony HD mechanical pump (Otto Bock, Minneapolis MN), EVLS™ suspension (Prosthetic Design, Dayton Ohio), Derma ProFlex sealing sleeve (Otto Bock, Minneapolis MN), and Pacifica foot (Freedom Innovations, Irvine CA) (Figure 2).
To measure the effectiveness of the EV prosthesis in increasing the patient's functional capabilities, he was administered three assessments 1 week, 1 month, and 1 year after he received the EV prosthesis, in addition to routine visual observations of gait and balance performed by the prosthetist and physical therapist (Table 1). An attempt was made to implement the most reliable and ecologically valid instruments for the patient's functional assessment.
First, the patient self-reported his functional capabilities with the Locomotor Capabilities Index 5 (LCI5), a measure of a lower limb amputee's perceived capabilities with a prosthesis. It was originally developed as part of the Prosthetic Profile of the Amputee questionnaire10 and consists of 14 basic and advanced activities on a five-point ordinal scale. It has demonstrated good internal consistency, test-retest reliability, and construct validity when used with adults with lower limb amputation and shows good correlation with the Prosthetic Evaluation Questionnaire's (PEQ) mobility section.10–12 It has been shown to be able to detect changes in functional limitations throughout rehabilitation,12 making it appropriate for this report. The second assessment was the Instrumental Activities of Daily Living (IADL) index, which is a tool used to measure function in a wide range of patient groups.13 Although not a measure of locomotor ability, it does yield information about a patient's general ability to perform daily tasks. The third assessment was a qualitative interview developed by the clinical facility and used with all patients with questions about residual limb health, sound limb health, hours a day of prosthetic use, pain levels, and daily activities.
After 1 month with the EV prosthesis, the patient completed the Amputee Mobility Predictor with a prosthesis (AMPPro). The AMPPro is a highly reliable instrument designed to objectively measure function in amputee subjects so that clinicians can implement the most appropriate components to achieve an optimal gait.14 An advantage of the AMPPro is that it provides clinicians with information concerning balance, strength, mobility, agility, and functional limitation needs. It was chosen as an assessment for this report because it has been shown to be a clinically feasible, reliable, and valid instrument available for objectively measuring function in amputee subjects.14,15 In addition, the AMPPro takes less time and is easier to score than the PEQ.14 The AMPPro is better able to show effects over time compared with spatiotemporal measures such as the 6-minute walk test, the 10-meter walk test, and the timed up and go test.15 To show the effect of continued use of the EV prosthesis, the AMPPro was administered for a second time after the patient had been using the EV prosthesis for 3 months and again after 1 year of use.
During the initial fitting session in May 2010, the patient was able to ambulate without aid within 5 minutes of donning the EV prosthesis (Figure 3). He reported that he liked the stability that it provided around his knee as he walked.
One week after the initial fitting, the patient came in for a final fitting and delivery of the EV prosthesis. He reported that initially blisters developed on the distal end of the residuum as a result of inconsistencies in his donning technique. The sores healed within 2 days of continued use of the EV prosthesis. The results of the 1 week, 1 month, and 1 year assessments are shown in Table 2.
At his 1-week appointment, the patient reported that he wore this EV prosthesis for 10 hours a day with adequate knee joint stability and was feeling more confident with the prosthesis. His residual limb was in excellent condition, with no discoloration or irritation. The patient scored a perfect 56 on the LCI5 and a perfect 8 on the IADL index.
One month into use of the EV prosthesis, the patient was again administered the interview and functional assessments. He reported better linkage between the residuum and prosthesis and was not experiencing any inflammation in his sound side knee joint. Gait evaluation by the physical therapist revealed improved symmetry and knee joint stability compared with the 1-week assessment, as observed while the patient ambulated in the examination room. The patient stated that he wore the prosthesis for 16 hours a day and walked approximately six miles every day. The patient again received perfect scores on the LCI5 and IADL, demonstrating the significant ceiling effects of those assessments. The patient completed the AMPPro. He scored 44 out of 47 possible points, classifying him as a K4 ambulator. He was unable to stand on his prosthesis side foot unsupported, stand with his eyes closed for 30 seconds, or smoothly vary cadence during the gait tasks.
After 1 year of use, the patient's functional status was evaluated. In the interview, he reported satisfaction with the EV prosthesis and stated that during the planting season, he was routinely able to wear it for 24 hours a day. He described that he was able to confidently get up and down from his combine, climb ladders, and walk over uneven ground in the fields. He displayed symmetrical gait as he ambulated around the examination room, as observed by the physical therapist and prosthetist. His residual limb appeared healthy, with hair-regrowth evident over the entire surface. He again received perfect scores on the LCI5 and IADL. He scored a 46 on the AMPPro, missing one point for being unable to stand unassisted on his prosthetic foot.
DISCUSSION AND CONCLUSIONS
This patient maintained a high activity level when using the PTB with IWBTC prosthesis, but he was experiencing negative effects, namely gait abnormalities, skin irritation at high pressure areas, and joint pain, effects which are common to lower limb amputees.6,9,16 These effects resulted in noticeable functional deficiencies expressed in his lack of confidence in more challenging locomotor tasks. Therefore, the clinician's goal was to reduce the negative secondary effects and enable the patient to improve his functional status. Most importantly, it was hoped that the patient would benefit from the gait normalizing effect that had been seen with other transtibial EV patients4,6,17 which would reduce the stress on his sound side knee. Less vertical movement in the socket could also eliminate the contact dermatitis that he experienced with the PTB with IWBTC prosthesis.6,9
The interview and functional assessments allowed the patient's prosthetist to track his development as he became accustomed to the EV prosthesis. His responses and scores indicated that his functional capabilities indeed increased as he learned to use the EV prosthesis. Qualitatively, the patient expressed balance confidence and stability within 1 week of transitioning from the PTB with IWBTC. This result was unexpected, as it was assumed that the patient would require approximately 1 month to build up hamstring strength necessary for stability. However, the patient's assertion is consistent with Ferraro's study of transtibial vacuum users6 and could be due to the high suspension forces possible with vacuum systems.4 Although the LCI5 and IADL assessments were largely unsuited to his high functional level, the improved balance task performances on the AMPPro suggest that he saw increased proprioception with the prosthesis. This also could have contributed to his confidence during locomotor tasks and explained the high scores on the LCI5.
In addition to balance, his gait normalized throughout the process. He displayed new abilities to vary cadence and display step length symmetry in the first year of use, according to the prosthetist's observations during evaluations, consistent with his improved score on the gait tasks of AMPPro. Most likely, these developments were enabled by both the increased range of motion possible without the IWBTC and the increased linkage that he reported between the residual limb and the prosthetic socket, as suggested by Beil et al.4 In turn, the pain and swelling in his sound side knee were not reported after 1 month of EV prosthesis use, since he was able to distribute his weight evenly between his sound leg and the prosthesis.
Significantly, all skin issues were resolved within 1 week of switching to the EV prosthesis, and his residuum remained healthy even under extreme use conditions. This progress can also be explained by the high suspension forces which kept his limb from moving vertically in the socket4,5 and is consistent with Ferraro's finding that improved skin health is common in amputees using EV.6 Furthermore, the areas of high pressure around the fibula head, mid-patellar tendon, and at the proximal brim of the IWBTC had always caused redness on the patient's residual limb when he wore the PTB with IWBTC, and the patient expressed pain at these areas as a result. With the EV prosthesis, the patient's limb was no longer discolored and he reported no pain, supporting Beil's theory that pressure is better distributed in EV prostheses.4
With his EV system, the patient was able to walk more, wear his prosthesis longer, climb ladders, jump down from a tractor, and traverse uneven ground on a regular basis. For this patient, the transition from a PTB with IWBTC system to an EV system dramatically improved his functional outcome and overall satisfaction with the prosthesis.
The primary limitation in this case study is the lack of an established baseline for comparison with the PTB with IWBTC. Although this report was primarily concerned with the patient's functional development during rehabilitation with the EV prosthesis, it would have been beneficial to provide quantitative results of the AMPPro and LCI5 for when the patient wore the PTB with IWBTC prosthesis. The patient's performance with the PTB with IWBTC prosthesis was presented qualitatively here as a justification for the transition to EV, but the quantitative data are needed as a baseline. Then, a true comparison of the PTB with IWBTC prosthesis and the EV prosthesis could be presented and this research used more effectively in the broad discussion of the benefits of EV compared with other systems.
Additional work is needed in the use of vacuum in the prosthetic profession. Case reports comprise an important step to justifying the efficacy of vacuum systems, and more are needed that include qualitative data provided by the patient, prosthetist, and physical therapist and quantitative data gathered through standard functional assessments. Furthermore, this patient's outstanding results on the LCI5 were unexpected. The LCI5 is considered a difficult measure appropriate for high-activity amputees, so further research needs to be performed in the area of quantitative gait and balance assessment of high-activity amputees. Finally, additional clinical studies are needed that document the functional development of large numbers of patients as they use EV systems, because such studies would benefit the profession as a whole by identifying technologies that directly improve patient outcomes.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
The authors thank Luci Busch, CPO, of Dayton Artificial Limb Clinic who contributed skills and materials vital to this research and Tracy Slemker, CPO, of Prosthetic Design and Dayton Artificial Limb Clinic who was critically involved in the editing and publication of this work. The authors also thank the patient who volunteered to be the subject.
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KEY INDEXING TERMS: lower limb; prosthetics; function; outcomes; vacuum; subatmospheric