Effects of microprocessor-controlled prosthetic knees on self-reported mobility, quality of life, and psychological states in patients with transfemoral amputations

Abstract

Objective

This study aimed to determine the effects of the microprocessor-controlled prosthetic knee (MPK) joint on self-mobility, body perceptions, depression, and quality of life in patients with unilateral transfemoral amputations (TFAs).

Methods

Thirty consecutive patients (28 males, mean age=38.5 years, age range=22–57) who had previously used non-MPKs and who were approved to use swing and stance phase-control MPKs were included in this 12-week clinical study. Before the MPK use and after the three-month follow-up, prosthetic use and locomotor capabilities were evaluated using the Houghton Scale and the Locomotor Capabilities Index (LCI-5), respectively. Body perception was assessed using the Amputee Body Image Scale (ABIS). The depressive symptoms and quality of life were evaluated using the Beck Depression Inventory (BDI) score and the 36-Item Short- Form Health Survey (SF-36), respectively.

Results

After MPK use, statistically significant ameliorations were observed in all outcome measures. The basic and advanced LCI-5 increased from 26.7±2.2 and 24.8±5.2 to 27.6±1.2 (p=0.007) and 27±2.1 (p=0.004), respectively. Houghton scores improved from 9±1 to 10.3±0.8 (p=0.000). The ABIS and BDI scores decreased from 43.2±10.9 and 5.7±6.6 to 37.1±8.9 (p=0.000) and 3.8±4.5 (p=0.015), respectively. Also, the SF-36 physical function and vitality subscales increased from 71.2±24.0 and 75.5±14.6 to 85.6±16.6 (p=0.001) and 81.7±14.1 (p=0.015), respectively.

Conclusion

MPK use provides significant improvements in the locomotor capabilities, quality of life, and activities of daily living to patients with TFAs as well as improves their body image perceptions and depressive symptoms.

Level of Evidence

Level III, Self controlled study

Introduction

Transfemoral amputation (TFA) is a life-altering event that can affect a person’s ability to perform several functions associated with independent living. The selection of an appropriate prosthetic component for patients with TFAs is a critical variable in rehabilitation, and it is a complex clinical decision that includes several factors, such as satisfying specific needs to reach optimal functioning (1, 2). Additionally, the choice of an appropriate prosthetic knee is important for patients with TFA, and a wide variety of prosthetic knee options are available. A microprocessor-controlled prosthetic knee (MPK) continuously controls the flexion and extension of the knee joint using a microcomputer system throughout the stance phase and/or swing phase of each gait cycle. MPK prostheses allow the prosthetic knee to respond to the user’s instantaneous needs to change his or her cadence and walking speed, while adjusting in response to extrinsic conditions, thereby mimicking the behavior of a healthy extremity (3).

Increased metabolic energy expenditures, decreased walking speeds, increased stumble and fall frequencies, and increased difficulty negotiating uneven terrains, hills, and stairs have been observed in previous studies conducted with patients with TFA (4–7). In addition to these physical capacity impairments, a limited number of studies have reported a deterioration in health-related quality of life (HRQoL). Compared to non-MPK use, it is possible to control the swing phase with variable walking speeds and to provide a high level of safety during the stance phase when using MPKs. This allows unilateral patients with TFA to ambulate with a pattern similar to a neutral gait, resulting in increased walking speeds on uneven terrains and decreases in the self-reported prevalence of stumbles and falls (8–10).

In addition to the technical and functional adaptations to an individual’s functional skills, activity level and daily activity participation of the amputee are also important. Current rehabilitation interventions for patients with TFAs are largely focused on improving body function and balance. However, one should also consider how the psychological aspects of prosthetic use impact patients’ daily activities (11). Although some studies have examined the effects of MPKs on the biomechanical variables in detail, there is insufficient evidence regarding the effects of MPKs on the performance of daily activities and HRQoLs in patients with TFA who have not previously used MPKs (2). Due to the lack of widespread knowledge regarding MPKs, the present study aimed to determine their effects on the activities and participation, HRQoL, body perceptions, and depressive symptoms of transfemoral amputees transitioning from non-MPKs to MPKs.

Materials and Methods

This 12-week clinical trial was conducted in the Department of Physical Medicine and Rehabilitation at a rehabilitation hospital. All the participants provided informed written consent before enrollment, and the study protocol was approved by the Local Ethics Committee (approval number 2016/5) in conformity with the Declaration of Helsinki.

A total of 30 consecutive patients who were approved for MPK use and met the inclusion criteria participated in our study. Unilateral TFA amputees, aged 20–60 years, who had been using non-MPK prostheses for at least one year and who were suitable for swing and stance phase-control MPK use (K3 or K4 activity level according to the Medicare Functional Classification Levels and a student or active employee) were included in this study. Patients with peripheral vascular disease due to diabetes mellitus and therefore undergoing transfemoral amputation were not included in the study. Those patients with previous MPK use histories, wounds and/or pain around the stump, disease, or drug use that could affect neuromuscular performance and balance, and stage 3 or 4 knee and/or hip osteoarthritis in the non-disabled lower extremity were excluded from the study.

Initial evaluations were performed with the non-MPK prostheses that the patients had been using at the time of admission. The patients were informed about the use of the prosthesis and skincare, and the training program was designed on how to walk with the prosthesis, along with training for stairs and ramp descent and ascension. Balance and coordination exercises were also developed. After 15 days, patients were seen for post-training approval; however, evaluations with the MPK prosthesis were performed three months after the patients began using the MPK prostheses in their daily activities. No attempt was made to standardize the prostatic components of the existing mechanical control prosthesis or the prescribed MPK prostheses once patients were included in the study. The subjects’ prosthetic sockets, suspension systems, and foot conditions were not the same for both the MPK and non-MPK conditions.

Outcome measures

The demographic characteristics, amputation levels, etiologies, and patients’ previously used non-MPK prostheses were recorded. Before the MPK use and during the three-month follow-up period, prosthesis use was evaluated using the Houghton Scale, locomotor capabilities were evaluated using the Locomotor Capabilities Index (LCI-5), while body perception was evaluated using the Amputee Body Image Scale (ABIS) under the supervision of an investigator. Depressive symptoms were evaluated using the Beck Depression Inventory (BDI), and the HRQoL was measured using the 36-Item Short Form Health Survey (SF-36).

The Houghton Scale is a self-administered questionnaire that reflects an individual’s perception of prosthetic use in patients with lower extremity amputations (12). It consists of four questions. The maximum score for this scale is 12, and higher scores are associated with increased performance and comfort. The Houghton Scale has moderate internal consistency and good test-retest reliability with self-reported functional ability scales and performance assessments (12, 13). This scale is responsive to change in prosthetic use in lower limb amputees after rehabilitation (12). Self-reported mobility was assessed with LCI-5. The LCI evaluates the basic and advanced locomotor abilities of lower limb amputees while wearing the prosthesis (14). The LCI-5, the five-level version of LCI, comprises of 14 questions ranging from 0 to 4. The total maximum scores are 28 for basic activities and 28 for advanced activities, and higher scores are associated with increased locomotor skills and independence (15). The self-reporting measure of the LCI-5 has good test-retest reliability and validity in persons with amputation during prosthetic training and at follow-up (15, 16). LCI-5 has been shown to have psychometric properties similar to the original version with a lower ceiling effect and larger effect size (15). The ABIS comprises of 20 items that evaluate body perception disorders in amputees with questions about an amputee’s perceptions and beliefs about his or her body experiences (17). The scale produces scores that range from 20–100, in which higher scores indicate higher body image disturbances. The ABIS is a reliable measurement tool for assessing the impaired body perceptions of patients with TFA (18). The SF-36 is a commonly used and well-documented HRQoL instrument. It has eight subscales, including physical functioning, physical role, bodily pain, general health, mental health, emotional role, vitality, and social functioning (19). A higher score indicates a better quality of life, and the reliability and validity of the SF-36 are well established (20). The severity of each participant’s depressive symptoms was assessed using the BDI, which is a preferred diagnostic and follow-up measurement inventory for the assessment of depression. This scale consists of 21 categories that evaluate the physical, emotional, cognitive, and motivational symptoms of depression, such as hopelessness, irritability, guilt, feelings of being punished, fatigue, and weight loss (21). This scale has well established psychometric properties. The validation of the national version of BDI has been established (22).

Statistical analysis

For the descriptive statistics of the data, the mean, standard deviation, median, minimum, maximum, frequency, and ratio values were used. The Kolmogorov-Smirnov test was used to assess the data distribution, and the Wilcoxon test was used to analyze the dependent variables. All of the analyses were conducted using the Statistical Package for Social Sciences for Windows version 22.0 (IBM SPSS Corp.; Armonk, NY, USA).

Results

Of the 30 patients included in this study, 28 were males, and the mean patient age was 38.5±10.1 years old. The mean time since amputation was 20.7±10.0 years. The average non-MPK prosthesis usage duration was 14.4±7.1 years. The demographic and clinical characteristics of the patients are shown in Table 1.

Table 1.

Demographic and clinical variables for the participants

		Min–Max	Median	Mean±SD /n-%
Age (years)		22.0–57.0	36.5	38.5±10.1
BMI (kg/m2)		16.1–36.7	26.1	25.9±4.0
Sex	Male			28 93.3
	Female			2 6.7
Education Level	Primary school			8 26.7
	High school			6 20.0
	University			16 53.3
Job type	White-collar worker†			13 46.5
	Blue-collar worker††			8 28.6
	Sportive activities†††			6 21.4
Amputee extremity	Right			18 60.0
	Left			12 40.0
Time since amputation (years)		5.0–40.0	20.0	20.7±10.0
Non-MPK prosthetic experience (years)		3.0–30.0	15.0	14.4±7.1
Reason for amputation	Traumatic			20 66.7
	Congenital deformities			4 13.3
	Malignant knee tumors			3 10.0
	Vascular pathologies (non-diabetic)			2 6.7
	Osteomyelitis			1 3.3
Non-MPK prosthesis knee conditions	Mechanical lock			15 50.0
	Hydraulic knee unit			10 33.3
	Pneumatic knee unit			5 16.6
Non-MPK prosthesis suspension systems	Suction			16 53.3
	Active vacuum system			7 23.3
	Passive vacuum system			4 13.3
	Liner pin lock			3 10.0

BMI: body mass index;

^†, Administrative and managerial professions;

^††, Industrial, commercial;

^†††, Professional;

Non-MPK, Non-Microprocessor-controlled prosthetic knee joint; SD: Standard deviation; Min: minimum; Max: maximum

The non-MPK prosthesis details are described in Table 1. All MPK prostheses [C-Leg® (Otto Bock HealthCare, Duderstadt, Germany), Plié® 2.0 (Freedom Innovations, Irvine, CA, USA), Rheo Knee® (Össur, Reykjavik, Iceland), Orion® (Endolite, Blatchford Group, UK)] provided microprocessor control of both the swing and stance phases of gait. Regarding the suspension systems of MPKs, 31% had a suction system, 25% had a passive vacuum system, 21.5% had an active vacuum system without knee sleeves, 14.3% had a low distal vacuum system without knee sleeves, and 7.2% had pin lock systems. Prosthetic sockets of MPK prostheses were similar to the mechanical conditions (ischial containment, ischial support, quadrilateral). Energy storing and return (ESAR), carbon fiber prosthetic feet were prescribed following the model of MPK prosthesis.

There were significant increases in the Houghton Scale scores and the basic and advanced LCI-5 scores, as well as significant decreases in the ABIS and BDI scores during the three-month follow-up evaluations after MPK use when compared with non-MPK use. Significant improvements were found in physical function, vitality, and general health subscales (p<0.05); however, significant differences were not detected in the emotional role, mental health, social role, physical role, and pain scores (p>0.05) at the three-month assessment with the MPK use when compared with the non-MPK use (Table 2).

Table 2.

Changes in outcome measures comparing the microprocessor-controlled prosthetic knee joint and non-microprocessor-controlled prostheses

Outcome Measure Scores	Non-MPK	MPK	p
	Mean±SD	Mean±SD
Hougton scale	9.0±1.0	10.3±0.8	0.000
LCI-5 basic	26.7±2.2	27.6±1.2	0.007
LCI-5 advanced	24.8±5.2	27.0±2.1	0.004
ABIS	43.2±10.9	37.1±8.9	0.000
BDI	5.7±6.6	3.8±4.5	0.015
SF-36
Physical functioning	71.2±24.0	85.6±16.6	0.001
Physical role	90.8±23.2	96.3±15.0	0.090
Emotional role	88.9±29.5	91.4±19.8	0.598
Vitality	75.5±14.6	81.7±14.1	0.015
Mental health	79.5±19.8	83.4±14.7	0.242
Social functioning	86.7±19.4	90.7±15.3	0.280
Pain	90.0±16.5	90.8±14.4	1.000
General health	75.3±23.4	84.6±15.3	0.038

NMPK: Non-microprocessor-controlled prosthetic knees; MPK: Microprocessor-controlled prosthetic knee joint; LCI: Locomotor Capabilities Index; ABIS: Amputee Body Image Scale; BDI: Beck Depression Index; SF-36: 36-Item Short Form Health Survey; SD: Standard deviation

Discussion

Our data suggest that the MPKs improved the patients’ abilities to perform locomotor abilities and activities of daily living, and they showed positive effects on body perception, vitality, and depressive symptoms of the participants. A wide variety of outcome measures have been used in studies evaluating the effectiveness of MPKs, but it is also important to consider how an amputee carries out his or her activities of daily living. At present, scientific data regarding the effects of MPK use on the performance of daily activities are insufficient. Additionally, a systematic review emphasized that future studies should determine the possible added functional value of MPKs, specifically focusing on activities and participation (2). In our study, several outcome measures were used, and the MPK’s effects on the psychosocial dimension, including mobility, prosthesis compliance, body perception, and mood, in addition to its effects on mobility, were evaluated.

Similar to the results of our study, previous studies have shown that there were improvements in self-reported mobility with MPK use in unilateral patients with TFA when compared with non-MPK use (9, 23–25). MPKs improve the gait and functional abilities of patients with TFA, and they allow for speed change adaptations. The gait symmetry is also better with MPK use (26, 27). Moreover, MPKs have significant effects on advanced locomotor capabilities of patients with TFA (16). Patients with TFA who have difficulties due to the loss of knee function, especially during stair ascent, tend to use self-selected step-over-step strategies with MPKs during stair descent, like the normal pattern observed in individuals without amputations (28). Similarly, there is evidence for increased gait speed on uneven surfaces and improvements in gait pattern during stair ascent and descent in patients with TFA with MPK use (3, 8, 9, 24–29). In our study, there were significant improvements after MPK use in the advanced activity scores, as assessed using the LCI-5, comprising of stair ascent and descent, walking outside on the uneven ground, and walking outside in inclement weather.

It is essential to assess and improve the HRQoL in patients with TFA to ensure that their prosthetic rehabilitations are comprehensive and successful. In patients with unilateral TFAs, when compared with those of age- and sex-matched individuals, there are significantly lower scores in all of the SF-36 subscales; therefore, the HRQoL is impaired (30, 31). In our study, there were improvements in the physical functioning and vitality subscales during the assessment period; however, there were no significant differences in the other subscales related to MPK use. In previous studies, there was an increase in the self-reported well-being of patients with TFA with stance and swing phase-control MPK use, when compared with non-MPK use, but these findings were not significant (3, 9, 25). However, the interventions and outcome measurement methods varied considerably between the studies (32). In addition, the SF-36 physical component and mental component summary scores showed statistically similar results between the patients with TFA and healthy Turkish controls, except with regard to the social functioning subscale (33). Nevertheless, the HRQoL of the patients with TFA in this study were unknown before the MPK use. In contrast, an average of one year of MPK use may contribute to a patient’s better adaptation to daily life activities. When evaluating the results of our study, one should consider the fact that assessments performed over three months may not reflect the positive improvements in the HRQoL subscales, such as the emotional role, mental health, and social functioning.

The consequences of impaired HRQoL and body perception in patients with TFA who undergo physical and psychosocial changes are interrelated concepts. It has been shown that depression, perceived prosthetic mobility, social support, prosthesis problems, and social activity participation influence the HRQoL after a lower limb amputation (34). Moreover, psychosocial factors influence the prosthetic rehabilitation of individuals with amputations. Although depression and anxiety are relatively high for up to two years after an amputation, they appear to decline to general population norms later (35). When considering the mean amputation time in our study, the depressive symptoms evaluated using the BDI were mild. However, social discomfort and body image anxiety have also been found among some individuals with amputations, and these have been associated with decreased participation in activities, depression, and anxiety (34). An amputee’s body perception is significantly affected by social values emphasizing vitality, physical appearance, and fitness (31). However, MPK patients have higher self-confidence and social participation levels due to their functional abilities and independence. It has also been reported that there are positive changes in the body perception and self-confidence of MPK patients, along with improvements in role participation and functional activity performances (36, 37). Similarly, when compared with non-MPK use, our study has shown significant improvements in depressive symptoms and body perceptions, along with the improvements in locomotor capabilities due to MPK use.

The use of swing and stance phase-control MPK has been shown to increase the subject-reported preferences and satisfaction when compared to non-MPK use in patients with unilateral TFAs (3, 9). In our study, these were not evaluated using separate questionnaires; however, it was considered that increases in subject-reported preferences and satisfaction might contribute to improvements in vitality, body perception, and depression. In a recent study, higher self-efficacy scores were related to higher prosthetic use and mobility levels; however, there was no significant difference between MPK use and non-MPK use in individuals with lower limb amputations (11). One should consider that the data used in this study were not extracted from a specific population but a previously applied survey involving a wide sample of older patients with TFA. The participants in our study were younger and with greater functional capabilities, which was in line with our established MPK use inclusion criteria. The target population in our study were active in their daily lives. Therefore, they could differentiate between MPK use and non-MPK use in terms of the psychosocial aspects.

In addition to a limited number of studies evaluating the HRQoL of patients with TFA, we found no studies that similarly evaluated the changes in their self-reported functional status, HRQoL, body perceptions, and depressive symptoms after MPK use. Nevertheless, our study did have several limitations that should be considered when interpreting the results. These include the small sample size, lack of a long-term follow-up, and lack of standardization with regard to the previously used non-MPK prostheses and currently used MPK prostheses. In this study, the effectiveness of swing and stance phase-control MPKs with various types of suspension mechanisms and prosthetic feet were investigated. It should be considered that prosthetic components with varying properties may have effects on performance during ascent and/or descent on uneven surfaces, stairs, and inclined surfaces. Furthermore, when considering the differences in the prostheses used and the environmental and individual factors, the self-reported measurements were used in the same patients after transitioning from a non-MPK to an MPK. In this respect, this study evaluated the effects of the prescribed MPK use over previously existing mechanically controlled prostheses rather than evaluating the specific characteristics of a single MPK and related knee condition. Additionally, we did not conduct a regression analysis, and thus, the results of outcome assessments may be influenced by confounding factors.

The differences between the prosthetic components of non-MPK and MPK prostheses may also be viewed as a limitation of this study. Due to the design of this study and ethical considerations, patients who used prescribed MPK prostheses and were approved for use were included in the study; therefore, patients could not use the same prosthetic socket, suspension mechanism, and prosthetic foot with their previous prostheses or change these choices. In some studies, the prosthetic sockets and suspension systems of the subjects were not changed to investigate specific bio-mechanic properties, such as peak stance and swing knee flexion angles and the knee flexion moment of the knee conditions (38, 39). However, in some studies that evaluated the quality of life, perceived self-efficacy, and specific self-reported outcomes, details regarding pre- and post-MPK prostheses were not provided (11, 33). Additionally, the existing mechanically controlled prostheses used by TFA amputees and the prescribed MPK prostheses with various prosthetic components may reflect the preferences and performance of the TFAs more accurately.

In conclusion, MPK prostheses have a positive effect on body perception, vitality, and depression when compared to non-MPK prostheses. These prostheses were also associated with improved performances in gait and daily activities throughout the short assessment period. Evaluating the activities, participation, and psychosocial aspects are important when determining the target TFA population for MPK use. In addition to the biomechanical advantages it provides, an MPK should be considered for appropriate amputees to reintegrate these individuals into society. Considering the limitations of this study, further studies with larger sample sizes that evaluate the effects of a variety of previously used non-MPKs, the efficacies of different MPK types, and the long-term effects of MPKs on the HRQoL should be conducted.

HIGHLIGHTS.

• MPK use provides significant improvements in the locomotor capabilities and activities of daily living to patients with TFAs.

• MPK prostheses have positive effects on body perception, vitality, and depressive symptoms when compared to non-MPK prostheses.

• Evaluating the activities, participation, and psychosocial aspects are important when determining the target TFA population for MPK use.