Prosthetic rehabilitation for bilateral transfemoral amputees using microprocessor-controlled knees with a novel training program: A study of two cases

Abstract

The use of microprocessor-controlled prosthetic knees facilitates safe and efficient ambulation in individuals with unilateral transfemoral amputation, contributing to their reintegration into daily life. We report rehabilitation outcomes in two individuals with bilateral transfemoral amputations that used Kenevo (Ottobock, Germany), a microprocessor-controlled prosthetic knee designed for low-activity users (K1/K2), as the first prosthesis. Gait training began in the most stable mode (A) and then progressed to modes B, B+, or C depending on gait stability. One patient subsequently trained with C-Leg 4 (Ottobock), a higher-functioning microprocessor-controlled prosthetic knee (K3/K4). Training durations were 8 months (1 month pre-prosthetic, 3 months stubby, 3 months Kenevo, and 1 month C-Leg 4) and 12 months (1 month pre-prosthetic, 2 months stubby, and 9 months Kenevo). The longer duration was due to the patient having a short residual limb and difficulty with outdoor ambulation. Both patients achieved independent walking with C-Leg or Kenevo and maintained prosthetic walking in the community after discharge. Ten-meter walk speeds were 0.77 and 0.93 m/s; 6-minute walk distances were 365 and 332 m; oxygen uptakes were 21.0 and 37.1 mL/kg/min. These cases suggest that initial training with Kenevo may support efficient rehabilitation in bilateral transfemoral amputees, while residual limb length may influence oxygen uptake during prosthetic ambulation.

Keywords

Prosthetic rehabilitation lower-limb amputation bilateral transfemoral amputation microprocessor-controlled prosthetic knees (MPKs)oxygen uptake energy consumption

Introduction

Few bilateral transfemoral amputees continue walking with their prostheses in the community.^1,2 One reason for this is the extremely high energy consumption while walking with prostheses. It has been reported that the energy consumption (oxygen uptake/oxygen consumption) of bilateral transfemoral amputees walking with prostheses is higher than that of healthy individuals walking or amputees in wheelchairs.^3–6 Energy consumption or fatigue during walking is an important factor in preventing bilateral transfemoral amputees from walking with prostheses as a means of transportation in the community.

Besides the problem of energy consumption during walking, specific training methods for bilateral transfemoral amputees have not been sufficiently established, and training for prosthetic walking requires a long time. There are limited reports on bilateral transfemoral prosthesis gait training, and for amputees to acquire a prosthetic gait, it is necessary to change the stability and function of the prosthetic knee according to their physical function and ability to walk with the prostheses during the training process. In the initial stage of training, prosthetic knees require high stability to prevent falls while standing and walking and to improve anxiety about falling. However, as training progresses and the ability to walk with prostheses improves, it is necessary to have a level of functionality that enables walking on uneven terrain, slopes, stairs, and other situations necessary for community ambulation.⁷ It has been reported that bilateral transfemoral amputees require approximately 2 years of training to acquire the ability to walk with their prostheses, even those with excellent basic physical fitness, such as veterans.⁸

Recently, microprocessor-controlled prosthetic knees (MPKs) have been increasingly used in transfemoral prostheses, and their effectiveness has been reported in patients undergoing unilateral transfemoral amputation. MPKs have been shown to reduce energy consumption during ambulation when compared to non–microprocessor-controlled prosthetic knees (NMPKs)⁹ and provide greater stability and safety when walking on level ground, uneven terrain, slopes, or stairs.^10,11 It has also been reported that the MPK that controls both the stance and swing phases decreases energy consumption during walking to a greater extent than the MPK in which only the swing phase is microprocessor-controlled and the stance phase is mechanically controlled.¹² A recent case report demonstrated that the use of MPKs (Kenevo®, C-Leg® 4; Ottobock, Duderstadt, Germany) was effective in reducing oxygen uptake during walking and alleviating walking burden in a middle-aged individual with bilateral transfemoral amputation.¹³ However, there have been few reports on training using MPKs as the first prosthesis in bilateral transfemoral amputees,^7,14,15 and a specific training method has not been sufficiently established. In addition, there are few reports on oxygen uptake in bilateral transfemoral amputees while walking with prostheses using MPKs.^8,13,16

The present report describes the application of Kenevo, a microprocessor-controlled knee designed for low-activity amputees (Medicare Functional Classification Levels K1 and K2),^17,18 as the initial prosthesis used in the rehabilitation of two individuals with bilateral transfemoral amputations, following a structured training protocol developed at the authors’ institution. Following the completion of gait training, prosthetic walking ability including oxygen uptake was measured. The purpose of this study is twofold: first, to present the outcomes of implementing a newly developed prosthetic training program for individuals with bilateral transfemoral amputations in two case studies and to conduct a preliminary evaluation of its validity and effectiveness; second, to assess the clinical progression and ambulatory function of these two individuals and to compare the findings with previously reported outcomes in the literature concerning individuals with bilateral transfemoral amputations.

Case presentation and methods

We de-identified all patient details in case presentation descriptions and obtained patient consent for the rehabilitation treatment presented in this report. This report is based on the Declaration of Helsinki. The subjects were informed in writing and orally prior to the study, and their consent was obtained. The reporting of this study conforms to CARE guidelines.¹⁹

Case 1 presentation

After consuming a large amount of alcohol, a man in his early 20s suffered compartment syndrome in both lower limbs and the left upper limb due to prolonged unconsciousness and was transported to a tertiary emergency hospital. He experienced cardiopulmonary arrest after arriving at the hospital, was resuscitated in the emergency room, and was treated in the intensive care unit (ICU). Transfemoral amputations of both legs were performed to save his life, but the left upper limb remained severely paralyzed because of compartment syndrome. Two months after disease onset, the patient was transferred to a local rehabilitation hospital where physical function and activities of daily living (ADL) training using a wheelchair were provided. Eight months after the onset of symptoms, the patient was transferred to the Hyogo Rehabilitation Center Hospital in Hyogo Prefecture, Japan to undergo prosthetic rehabilitation.

On physical examination, he was 120 cm tall and weighed 37 kg. The stump length was 24 cm on both sides, and there were no bilateral skin problems on the stump or residual limb. There were no flexion or abduction contractures in the bilateral hip joints, and the Thomas test was negative. The strength of both hip joint muscles was 4 on manual muscle testing (MMT). The left upper limb had an MMT 1-2 with almost no function. The right upper extremity showed no functional impairment.

Case 2 presentation

A man in his early 20s sustained severe work-related burns to both thighs, the right upper limb, and the trunk and was transported to a tertiary emergency hospital. On the same day, bilateral transfemoral amputations were performed as life-saving procedures, and the patient was admitted to the ICU. Skin grafts were subsequently applied to the left femoral residual limb, the right upper limb, and the trunk. Three months after the injury, the patient was transferred to our hospital to commence prosthetic rehabilitation.

Physical examination revealed that he was 104 cm tall and weighed 43 kg. The stump lengths were 12 and 19 cm on the right and left sides, respectively. Skin graft scars were observed at the left femoral stump end, right upper limb, and trunk, and all the wounds healed. For the hip joints, flexion contractures measured 15° on the right and 5° on the left, and abduction contractures were 20° on the right and 10° on the left (Figure 1(a)). The Thomas test was positive bilaterally, consistent with the presence of hip flexion contractures. The muscle strength of both hips was determined as MMT 3. The right upper extremity showed limited range of motion (ROM) of the elbow and wrist joints, and muscle strength was MMT 3. The left upper extremity showed no functional impairment.

Figure 1.

Case 2: (a) X-ray of the stump at the time of admission. The length of the right femoral stump was shorter than the left. Adduction of both hips was limited. (b) First day of stubby fitting. (c) First day of Kenevo fitting and (d, e, f, g) walking training in the parallel bars. Although the right stump was short, the patient was able to swing out symmetrically.

Prosthetic training program for bilateral transfemoral amputation using Kenevo and C-Leg 4

The structured prosthetic training program applied to the two patients is shown in Figure 2, which we devised for bilateral transfemoral amputees. This program starts with gait training using stubbies without knee joints. While confirming gait stability with physical therapy, the pylon of the stubbies was extended by 10 cm. The knee joint was incorporated when the pylon length reached 30 cm. Once a stable gait was achieved with a 30-cm pylon, training with Kenevo was initiated. Kenevo has four modes; while confirming stability with physical therapy, gait training was conducted starting with bilateral A mode (both the swing and stance phases are fixed), which has the highest stability. While confirming gait stability on level ground in physiotherapy, the modes progressed to B/B (swing phase hydraulic microprocessor-controlled, stance phase fixed), B+/B+ (swing phase hydraulic microprocessor-controlled, stance phase computer-controlled stance flexion), and C/C (both swing phase and stance phase hydraulic microprocessor-controlled), which have the most advanced gait functions. Once walking in a specific mode stabilized, the mode was changed one at a time, alternating between the two modes, and the stability was carefully evaluated (e.g. when changing from A/A to B/B, evaluate A/B and B/A to check the stability before setting it to B/B). Once the patient was able to walk stably on level ground, stairs, slopes, and uneven terrain in the C/C mode, we evaluated whether his walking speed exceeded 3 km/h (0.83 m/s). Because the maximum speed of Kenevo is 3 km/h, if the patient was able to walk at a speed greater than 3 km/h, based on the patient’s wishes and judgment of the rehabilitation team, the knee joint was changed to a C-Leg 4, which is more suitable for active patients (Medicare Functional Classification Levels K3 and K4),^17,20 and an evaluation was conducted to determine which was more appropriate. After prosthetic training was completed and the patient evaluated, the most appropriate Kenevo mode or C-Leg 4 was determined to be the permanent prosthesis for daily living.

Figure 2.

Prosthetic training program for bilateral transfemoral amputees using Kenevo. If the patient had difficulty acquiring a stable gait in any of the phases during Kenevo training, the mode in which the patient could walk stably was selected. C-Leg evaluation and training were optional.

Methods for clinical evaluation

For clinical evaluation, the 10-meter walk test (10MWT), 6-minute walking distance (6MD), and modified Borg Scale during prosthetic walking were measured at the time of prosthetic rehabilitation completion in each patient.^12,13,21,22

As for the measurement of oxygen uptake (VO₂; mL/kg/min) and oxygen cost (mL/kg/m), K5 (Cosmed, Rome, Italy) was used.²³ Walking distance was measured by 6MD on a 90-m level ground rectangular course. Measurements were performed according to the previous report^12,13 (Figure 3). Heart rate was measured before and after the measurement of oxygen uptake. Oxygen cost was calculated using the average walking speed (m/min) during the 6-minute walk.

Figure 3.

Measurement of oxygen uptake during prosthetic walking using the K5 system.

The Activities-specific Balance Confidence (ABC) scale was employed as a patient-reported outcome measure (PROM) at the most recent outpatient visit after discharge. The ABC scale is a self-reported measure assessing an individual’s confidence in performing various ambulatory activities without losing balance or experiencing unsteadiness. The scale consists of 16 items, each rated from 0% (no confidence) to 100% (complete confidence). Participants are asked to indicate their level of confidence in not losing balance while performing each activity. The overall score is calculated by averaging the ratings across all items, providing an indication of the individual’s balance confidence.²⁴

Results: Prosthetic training progress and clinical evaluation

Progress of prosthetic training in case 1

During the first month, the patient underwent physical therapy and voluntary training to improve muscle strength and basic fitness. During occupational therapy, upper limb function and ADL training were performed. After one month of training, the muscle strength of both lower limbs improved to MMT5. However, the left upper limb function did not improve. Bilateral stubby prostheses were fabricated using ischial ramal containment (IRC) sockets with silicone liners and pin suspension systems, and prosthetic training was subsequently initiated (Figure 4(a)). After 3 months of training with the stubby prosthesis, the patient was able to walk stably with a 30-cm pylon (Figure 4(b) and (c)). The left upper limb remained severely paralyzed even after rehabilitation, and when holding a cane in his left hand, it was necessary to fix it with a cuff belt; therefore, the stability of prosthetic walking was carefully evaluated. Three months after the start of prosthetic training, Kenevo training commenced in accordance with the established training program (Figure 2). The patient received prosthetic gait training and underwent functional evaluation using Kenevo, and after 3 months of rehabilitation, the patient achieved functional ambulation and was able to walk stably both indoors and outdoors using bilateral canes (the left equipped with a Velcro cuff), navigating flat surfaces, uneven terrain, slopes, and stairs while utilizing the C/C mode (Figure 4(d) to (f)).

Figure 4.

Case 1: (a) First day of stubby fitting. (b, c) While checking stability during walking, the stubbies were extended sequentially. (d) Indoor walking training using Kenevo. (e) Outdoor walking training. (f) Slope walking training and (g) outdoor walking training without walking aid using C-Leg.

At this point, the patient’s walking speed had reached 3.6 km/h. Based on the patient’s preference and the rehabilitation team’s assessment, the prosthetic knee joints were switched from Kenevo to C-Leg 4, followed by additional gait training and evaluation. After one month of C-Leg 4 training, he was able to walk both indoors and outdoors, as well as with the Kenevo without a cane (Figure 4(g)). Based on the comprehensive evaluation, the C-Leg 4 was determined to be the most appropriate prosthetic knee joint, as the patient reported greater stability and reduced fatigue during ambulation compared to the Kenevo. The prosthetic prescriptions were as follows: bilateral silicone liner pin suspension, IRC socket, C-Leg 4 knee joint, and energy-storing foot (Taleo; Ottobock). The total rehabilitation period was 8 months. The patient did not complain of anxiety about falling while walking, either with Kenevo or C-Leg 4, throughout the training. The patient was discharged from the hospital, and at the one-year follow-up, he was ambulating with prosthetic limbs for approximately 3 hours per day. For an additional 6 to 7 hours daily, he remained seated in a wheelchair while wearing the prostheses, which were purposefully utilized as needed to facilitate standing and other functional tasks. Due to architectural barriers within the home environment, ambulation with prosthetic limbs was challenging; therefore, he removed the prostheses and used a wheelchair to perform daily activities. He is currently undergoing re-employment training. Following hospital discharge, bilateral C-Leg 4 permanent prostheses were provided through the public prosthetic provision system.

Progress of prosthetic training in case 2

During the first month, the patient underwent physical therapy and voluntary training to improve joint ROM, muscle strength, and basic physical fitness. During occupational therapy, upper limb function and ADL training were performed. One month of training improved hip flexion and abduction contractures, and muscle strength in both lower extremities reached the MMT4+ level.²⁵ Additionally, the Thomas test for both hips became negative, indicating resolution of hip flexion contractures. Although there was some residual impairment of the right upper limb function, it improved to a level that allowed ADL. Prosthetic rehabilitation was initiated following the fabrication of bilateral stubby prostheses featuring IRC sockets, silicone liners, and pin suspension mechanisms (Figure 1(b)). After 2 months of training with the stubby prosthesis, the patient was able to walk stably with a 30-cm pylon, and Kenevo training was initiated (Figure 1(c)). As with case 1, gait training using the Kenevo prosthetic knee was conducted in accordance with the protocol outlined in Figure 2. In this case, the right thigh presented with a short residual limb, raising concerns about potential instability during the transition from stance to swing phase or in stance phase control. However, the use of the Kenevo provided sufficient stability to the right lower limb, enabling the patient to achieve a symmetrical gait (Figure 1(d) to (g)). After 4 months, he was able to walk steadily on level ground in the C/C mode. Subsequently, he was trained to walk on uneven terrain, slopes, and stairs. However, this patient refused the use of walking aids both indoors and outdoors; therefore, it took longer to complete the training than in case 1. In addition, owing to the short stump length on the right side, socket suspension failure occurred several times during prosthetic training, and it was necessary to adjust and remake the socket. At the time of completion of prosthetic training, the patient’s walking speed was approximately 3 km/h. Although his ambulatory performance reached a level that warranted consideration for transition to the C-Leg 4 prosthesis, the patient ultimately opted against this change. The decision was influenced by the extended adaptation period required during Kenevo training and his expressed preference to continue with the Kenevo system. Consequently, the Kenevo was judged to be the most appropriate prosthetic knee for this case. Regarding the prescription of the prosthetic foot component in this case, several options, including feet classified as K2 and K2-3 level components, were evaluated during the rehabilitation process. Among these, Pro-Flex® XC (K3-4; Össur, Reykjavík, Iceland)²⁶ was found to provide the most comfortable walking experience. In our national healthcare system, any combination of prosthetic components, including those across different K-level classifications, can be prescribed as long as an appropriate clinical evaluation is conducted. The prosthetic prescriptions were bilateral silicone liner pin suspension, IRC socket, Kenevo knee joint, and energy-storing foot (Pro-Flex XC). The total rehabilitation duration was 12 months.

As in case 1, the patient did not complain of anxiety regarding falling while walking throughout the training. The patient was discharged, and at the one-year follow-up, he used the prostheses for ambulatory activities for approximately one hour per day. For an additional 8 hours, he remained in a wheelchair while continuing to wear the prostheses, which were intermittently employed to assist with standing and other functional movements. Notably, the use of prostheses was essential for tasks such as getting in and out of an automobile. As in case 1, the architectural features of the home environment made ambulation with prostheses difficult. Consequently, the patient opted to remove the prostheses and relied on a wheelchair for daily living activities within the home. Bilateral Kenevo was provided as a permanent prosthesis by the work-related injury disability compensation fund. After hospital discharge, the patient began participating in parasports and subsequently competed in national-level para-swimming competitions.

Results of clinical evaluation on prosthetic walking and ABC scale as a PROM

Table 1 summarizes the ambulatory performance, oxygen uptake, and oxygen cost at the completion of prosthetic rehabilitation, as well as the ABC scale scores obtained at outpatient follow-up for both cases. In case 1, bilateral C-Leg 4 prosthetic knee joints were utilized, while bilateral Kenevo knee joints were employed in case 2. Ambulatory capacity was comparable between the two cases; however, oxygen uptake, oxygen cost, and perceived exertion during gait were greater in case 2. The ABC scale scores were similar across both cases.

Table 1.

Assessment results of prosthetic walking ability in each case. The Activities-specific Balance Confidence (ABC) scale consists of 16 items, each rated from 0% (no confidence) to 100% (complete confidence), evaluating the participant’s confidence in maintaining balance during various daily activities. The total score is calculated as the average of all item ratings.

	Case 1 (C-Leg)	Case 2 (Kenevo)
10MWT (m/s (km/h))	0.77 (2.7)	0.93 (3.5)
6MD (m (km/h))	365 (3.7)	332 (3.3)
VO₂ (mL/kg/min)	21.0	37.1
Oxygen cost (mL/kg/m)	0.35	0.67
mBS	5 (strong)	8 (very strong)
ABC scale	68.8	67.5

10MWT: 10-meter walk test; 6MD: 6-minute walking distance; ABC: Activities-specific Balance Confidence; mBS: modified Borg Scale; VO₂: oxygen uptake.

Discussion

A prosthetic training program utilizing the Kenevo as the initial prosthesis was developed for individuals with bilateral transfemoral amputations and implemented in two clinical cases. Both patients successfully acquired stable prosthetic gait and were able to maintain prosthetic ambulation in their community environments after hospital discharge. These findings indicate that prosthetic rehabilitation with the Kenevo, an MPK designed for users with lower activity levels, may be effective for individuals with bilateral transfemoral amputations, potentially facilitating earlier ambulation and reintegration into society compared to conventional timelines. Furthermore, for patients with appropriate indications, these results suggest that subsequent training with the C-Leg 4 may provide additional functional benefits in the later stages of rehabilitation.

Traditionally, one of the major challenges in prosthetic ambulation for individuals with bilateral transfemoral amputations has been the high energy cost associated with walking. However, this situation has been changing in recent years with the advancement of prosthetic technologies. While Crouse et al.⁴ reported that only the most physically fit individuals would be able to walk with prostheses following bilateral transfemoral amputation due to the high energy demands, more recent studies have demonstrated that the use of MPKs can reduce energy consumption during prosthetic ambulation, even in individuals with bilateral transfemoral amputations.^8,13,16 Notably, application of the Kenevo or C-Leg 4 has been shown to decrease oxygen uptake and physical exertion more effectively than conventional knee joints in such cases.¹³ Thus, the use of MPKs can reduce the physical burden on the prosthetic gait of bilateral transfemoral amputees and has advantages over existing NMPKs. The energy consumption while walking with the prosthesis in case 1 was similar to that reported by Jarvis et al.⁸ in veterans and in our previous report,¹³ suggesting that the patient could walk with relatively good energy efficiency as a bilateral transfemoral amputee. However, energy expenditure during walking was relatively high in case 2. This difference may be attributable to the shorter residual limb length observed in case 2 compared to case 1. Previous studies have reported that individuals with shorter femoral residual limbs exhibit higher energy expenditure during prosthetic ambulation.²⁷ In the two cases in this report, there were no marked differences in physical functions other than stump length, and the walking speeds were similar when evaluated using the 6MD, suggesting that the difference in stump length may have had a significant effect on energy consumption. The relationship between stump length and energy expenditure during prosthetic walking in bilateral transfemoral amputees requires further investigation.

As for the prosthetic walking ability and ADL from the perspective of PROMs, the ABC scale was used in this study. The ABC scale has been reported to be associated with quality of life in individuals with lower-limb amputations,²⁸ as well as with social participation and perceived mobility,^29,30 making it a relevant tool for evaluating functional and social aspects of daily life. The ABC scores were 68.8 in case 1 and 67.5 in case 2, comparable to previously reported values for individuals with unilateral transtibial or transfemoral amputations.^31,32 These findings suggest that individuals with bilateral transfemoral amputations using either the C-Leg 4 or the Kenevo maintained a high level of balance confidence in their daily lives and that MPKs may contribute to sustaining community-level activity. This outcome may support the validity and effectiveness of the rehabilitation program described in this report.

Another major challenge in the prosthetic rehabilitation of individuals with bilateral transfemoral amputations is the lack of universally applicable, standardized training programs that can be broadly implemented across clinical settings. Although there have been some case reports of prosthetic gait training for amputees using MPKs,^14,15 it has not been established as a universal training program. To improve the reproducibility and success rate of training, establishing a universal and standard training program for prosthetic rehabilitation of bilateral transfemoral amputees in clinical practice is important. A previously developed standardized rehabilitation program for individuals with unilateral vascular transtibial amputations was shown to reduce the time required to achieve stable prosthetic gait compared to conventional clinician-guided methods, with all participants achieving functional ambulation.³³ The program provides a structured model with clearly defined training methods and duration, ensuring consistent rehabilitation quality. In this study, the Kenevo could be used in all phases of gait training, from less difficult to more difficult, in stages by changing the mode. In addition, mode switching and adjustment could be completed within a few minutes, which proved highly effective in clinical settings. To adjust the difficulty level of walking using conventional prosthetic knee joints, it is necessary to prepare and replace multiple knee joints with different control mechanisms. This is time-consuming and may cause changes in the prosthesis alignment when the knee joint is replaced. This poses a significant burden for both amputees and rehabilitation teams. The ability to adjust the difficulty level of gait training through mode selection in the Kenevo could offer a practical solution to this challenge. The proposed prosthetic training approach for bilateral transfemoral amputees may have the potential to be established as a standardized rehabilitation program. While the validity and effectiveness of using the Kenevo as an initial training prosthesis were considered appropriate and beneficial in the two cases presented, further investigation is warranted to confirm its generalizability and clinical applicability.

An additional challenge in the prosthetic rehabilitation of individuals with bilateral transfemoral amputations is the prolonged duration required to achieve functional ambulation. Jarvis et al.⁸ reported on the rehabilitation outcomes of combat-injured military personnel, including individuals with bilateral transfemoral amputations, and noted that these patients required an average training period of 24 ± 5 months. In the present report, both cases involved patients with concomitant upper limb impairments in addition to bilateral transfemoral amputation; nevertheless, they achieved prosthetic ambulation and continued walking in the community after 8 and 12 months of training, respectively. These outcomes are comparable to previous reports^14,15 and suggest that the use of the Kenevo may contribute to a shorter rehabilitation period. However, as these findings are based on only two cases, the generalizability remains limited. Further validation of the proposed training method is required in a larger cohort.

Within the framework of this rehabilitation program, the selection between the C-Leg 4 and the Kenevo constitutes a critical issue that warrants further clinical investigation. Case 1 was assessed as possessing the physical capabilities necessary for C-Leg 4 use and was therefore considered a suitable candidate. Following evaluation and training, the subject successfully achieved stable ambulation with the C-Leg 4. In contrast, case 2 exhibited a walking speed of approximately 3 km/h during the training process, which may be considered within the range for potential C-Leg 4 candidacy. Following the completion of rehabilitation, the ability to walk at a speed exceeding this threshold was confirmed through objective gait assessments, including the 10MWT and the 6MD with using Kenevo. These results suggest the possibility that the subject’s physical function was consistent with a K3 level or higher, indicating that the C-Leg 4 might have been an appropriate option,²⁰ which may partly explain why the combination of the Kenevo and Pro-Flex XC, despite the mismatch in K-level,^18,34 provided the most comfortable gait for case 2. However, this subject experienced greater fatigue during ambulation, and oxygen uptake was higher than that of case 1. Consequently, it is likely that a slower walking speed would have been more comfortable for the subject when walking continuously for extended durations. Additionally, during the training process, case 2 encountered challenges with socket fitting due to a short residual limb on the right side, requiring an extended period to resolve the issue. Given these factors, the subject chose not to undergo C-Leg 4 evaluation or training after achieving a stable gait with Kenevo. In the training program outlined in this study, the criterion for transitioning to C-Leg 4 following Kenevo training was set at achieving a walking speed exceeding 3 km/h (0.83 m/s). Although both cases met this criterion, the prescribed prosthetic knee differed: C-Leg 4 in case 1 and Kenevo in case 2. When considering the transition from Kenevo to C-Leg 4, it would be essential to conduct a comprehensive assessment that accounts not only for walking speed but also for the patient’s preferences, gait comfort, training duration, and other relevant factors. Furthermore, thorough discussions between the prosthetic rehabilitation team and the patient are crucial for making an informed decision.

Conclusion

Two patients with bilateral transfemoral amputations underwent prosthetic rehabilitation through a novel prosthetic training program using Kenevo, an MPK for low-activity patients, as the first prosthesis. In one of the two cases, training with the C-Leg 4 was conducted following initial rehabilitation with the Kenevo. The findings of this study suggest that Kenevo may be a valid and effective knee joint for initial prosthetic training following bilateral transfemoral amputation. Energy expenditure during walking differed between the two patients, and the difference in the length of amputation may have influenced energy expenditure. Within the context of the rehabilitation program presented in this study, a more comprehensive evaluation may be beneficial when considering the transition from Kenevo to C-Leg 4. Such an assessment should take into account not only walking speed, but also the patient’s preferences, perceived gait comfort, and the duration of training required. A multifactorial approach may improve the selection of appropriate prosthetic knee joints for individuals with bilateral transfemoral amputations; however, further research is needed to establish definitive criteria for optimal joint selection.

Footnotes

Acknowledgements

We gratefully acknowledge the work of past and present members of our hospital. We would like to thank Editage () for English language editing.

Author contributions

M.T. was the patient’s primary physician and was responsible for the treatment and wrote the manuscript. T.C. created the training program applied in this study and provided a critical review of the manuscript. T.O. collected and analyzed the clinical data. I.T. and Y.A. led the patient’s prosthetic rehabilitation as physical therapists.

Data availability statement

All data supporting the findings of this study are included within the article.

Declaration of conflicting interests

The authors declare no conflicts of interest directly relevant to the content of this article.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

ORCID iD

Mitsunori Toda

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