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Abstract

Background:

Given the growing number of variable-damping prosthetic knee and ankle components and broad number of potential biomechanical outcomes, a systematic review is needed to assess advantages of damped knee and ankle units over non-damped prostheses.

Objectives:

This study provides an overview of the biomechanical outcomes associated with the use of prosthetic knees and ankles with damping mechanisms in individuals with lower limb amputation.

Study design:

Literature review.

Methods:

A systematic search was performed through PubMed, Science Direct, Web of Science, Cochrane, and Scopus databases from June 1994 to March 2016. The level of evidence of each article was assessed using a 13-element checklist for evaluating non-randomized controlled trials for quality assessment. Afterward, the studies were classified as A-level, B-level, or C-level based on total score and positive scores from certain key categories.

Results:

In total, 22 papers remained for the quality assessment based on the inclusion criteria. In total, 15 studies scored sufficiently high quality scores to be classified. One article scored as A-level, eight as B-level, and six as C-level. In total, 10 studied knees and 5 examined ankles. Sample sizes ranged from 5 to 28 subjects.

Conclusion:

Available studies were evaluated in detail and biomechanical outcomes were extracted from the studies that met criteria. Results of this review indicate that study methodology and outcome measures were heterogeneous across reviewed papers. This could be an explanation for inconsistent findings of the reviewed studies. Only self-selected gait speed showed a consistent difference when dampers were applied to the leg. Thus, further research is required in this area.

Clinical relevance

This study provides an overview of evidence related to prosthetic knee and foot/ankle components with damping attachments. Research related to biomechanical outcomes is of great importance for researchers and practitioners in this area. The studies drew mixed conclusions, but walking speed was consistently different for damped versus non-damped components.

Keywords

Ankle prosthesis knee prosthesis damping amputee gait

Background

Prosthetic components, especially ankle–foot and knee systems, are designed to imitate the function of the lost physiological structures.^1,2 The proper choice of prosthetic components can determine the quality of the restoration of function.³ Several studies have revealed physiological and biomechanical problems with conventional prosthetic components, which have motivated the emergence of new designs such as hydraulically damped ankle and knee devices.^4,5

Over the past decades, computer-controlled, variable-damping prosthetic knees have been introduced. Advantages of variable-damping knee designs over passive mechanical prosthetic knees may mainly be associated with adaptation to various walking speeds and enhanced stability and balance.^6–9

Recently, ankle–foot prostheses with damping properties have been introduced. Foot dampers could affect the gait biomechanics in individuals with limb loss,¹⁰ which could indirectly lead to a higher freely chosen walking speed.¹¹ Some researchers have worked on viscoelastic models of prosthetic feet composed of dampers and springs.^12,13 Wirta et al.¹⁴ studied the effect of different ankle–foot devices on below-knee gait and reported a preference for devices with greater damping and shock absorption at heel strike. Also, it has been revealed that reduction in peak angular acceleration of the prosthesis at heel strike is a significant feature of foot-ankle function.¹⁵

Given the growing number of variable-damping components and a broad number of biomechanical outcome measures that have been used to assess the devices, a systematic review is needed to assess the advantages of damped knee and ankle units over non-damped prostheses. The purpose of this study, therefore, was to provide an overview of the biomechanical outcomes associated with the use of prosthetic knee and ankle components with damping mechanisms in individuals with lower limb amputation.

Methods

Search strategy

A systematic search was performed through PubMed, Science Direct, Web of Science, Cochrane, and Scopus databases from June 1994 to March 2016. The following keywords and their combinations were used for the search: amputee, lower limb, trans-femoral, trans-tibial, above the knee, below the knee, foot, knee, ankle-foot, prosthesis, artificial limb, hydraulic knee, hydraulic ankle, pneumatic knee, pneumatic ankle, damping, gait analysis, motion analysis, and walking. Syntax may vary slightly depending on the database, but the general search string resembled the following: ((lower limb OR transfemoral OR transtibial OR above knee OR below knee OR foot OR knee OR ankle-foot) AND (amput*)) AND ((lower limb OR transfemoral OR transtibial OR above knee OR below knee OR foot OR knee OR ankle-foot) AND (prosthe* OR artificial limb) AND (hydraulic knee OR hydraulic ankle OR pneumatic knee OR pneumatic ankle OR damping)) AND (gait analys* OR motion analys* OR walking OR performance). The cited references were also investigated to extend the search.

Study selection

First, authors assessed the title and abstract of the articles to define whether the article was related to the study question. Furthermore, the inclusion criteria were as follows:

Peer-reviewed studies written in English;

Randomized controlled trial, cohort study, case report, or case series;

Population with transfemoral, knee disarticulation, or transtibial amputation;

Evaluation of prosthetic knee and foot components with damping mechanisms during level ground walking;

Outcome measures including gait kinetics, kinematics, spatial, temporal, and pressure parameters.

Quality assessment

A 13-element checklist for evaluating non-randomized controlled trials developed by Van der Linde et al.⁵ was used to examine the level of evidence of each article (Appendix 1, on-line version only). This checklist was originally adapted from two other checklists for quality assessment of randomized controlled trials and included 13 criteria divided into three categories for assessing the selection of patients (A1–A4), intervention and assessment (B5–B9), and statistical validity (C10–C13). A criterion scored “1” if the answer was yes or valid and scored “0” if the answer was no or invalid. The criterion was also scored “0” if it was not applicable. Two reviewers performed the quality assessment independently. In case of disagreement, a subsequent independent review was performed to reach a consensus.⁵ Afterward, the studies were classified as below:

A-level studies. Score of 11 points or more including 6 points from A and B criteria and a positive score for criterion B7 (blinding) and B8 (timing of the measurement, adaptation);

B-level studies. Score between 6 and 10 points and a positive score for criterion B8;

C-level studies. Score of at least six points of A and B criteria with an invalid score on criteria B7 and B8.

Results

Search results

The initial search resulted in a total of 273 abstracts, among which 72 papers were duplicated. After applying the inclusion criteria, 18 papers remained for the full text review. Additionally, reference search of the papers resulted in 10 more papers, among which four abstracts fulfilled the inclusion criteria. Finally, 22 studies were assessed based on the checklist in this systematic review (Figure 1).

Figure 1.

Procedure for article selection.

Study selection

After quality assessment, 15 studies obtained a sufficiently high score to be assigned to A-, B-, and C-levels. The other seven studies did not gain enough points to be classified in a level and were excluded from the final review.

Only one study was classified as A-level, receiving a total score of 11 points, in which the subjects were blinded to the intervention and were given enough time to adapt to prosthetic changes (positive score for criteria B7 and B8). However, eight studies were classified as B-level and six studies as C-level. The main difference between the B- and C-level studies was the positive score for the adaptation time (B8 criterion). B-level studies received 8–10 points and had a positive score of B8, whereas C-level studies obtained 8–10 points with a negative score of B8. The results of the quality assessment are demonstrated in Tables 1 and 2.

Table 1.

Results of quality assessment for papers related to prosthetic knees.

Authors	Subjects				Parameters	Selection					Intervention						Statistical validity				Total score	Level of evidence
Authors	No.	Cause	Level	Age (years)	Parameters	A1	A2	A3	A4	A	B5	B6	B7	B8	B9	B	C10	C11	C13	C	Total score	Level of evidence
Boonstra et al.¹⁶	28	Trauma, tumor, arterial occlusion	TF	15–63	Range of motion (ROM), temporal parameters, center of gravity (CoG) position	1	0	1	1	3	1	1	1	1	1	5	1	1	1	3	11	A
Kirker et al.¹⁷	16^a	Trauma, congenital abnormality	TF	18–66	Walking speed, step length symmetry	1	1	0	0	2	1	1	0	1	1	4	1	0	1	2	8	B
Datta et al.¹⁸	10	Trauma	TF	23–46	Walking speed, temporal and spatial gait symmetry	1	1	1	0	3	1	1	0	1	1	4	1	0	1	2	9	B
Johansson et al.⁷	8	Trauma, infection, congenital, cancer	TF	29–54	Temporal parameters, joints angle, moment, power and work	1	1	1	1	4	1	1	0	0	1	3	1	0	1	2	9	C
Segal et al.¹⁹	8	Trauma	TF	28–60	Temporal, kinematic and kinetic parameters	1	1	0	1	3	1	1	0	1	1	4	0	0	1	1	8	B
Kaufman et al.²⁰	15	Trauma, cancer, peripheral vascular disease, congenital	TF	26–57	Knee moment and flexion degree in initial stance	1	1	1	0	3	1	1	0	1	1	4	1	0	0	1	8	B
Jepson et al.²¹	5	?^b	TF	28.8–55.7	Temporal and spatial gait parameters, symmetry	1	0	1	0	2	1	1	0	1	1	4	1	0	1	2	8	B
Bellmann et al.²²	9	Trauma, osteosarcoma	TF	22–49	Kinetic and kinematic parameters	1	1	1	1	4	1	1	0	0	1	3	1	0	1	2	9	C
Lythgo et al.²³	5	?^b	TF	58.8 (11.9)	Spatial and temporal gait parameters, symmetry index	1	0	1	1	3	1	1	0	1	1	4	1	0	1	2	9	B
Kaufman et al.²⁴	15	Trauma, cancer, peripheral vascular disease, congenital	TF	26–57	Kinetic and kinematic symmetry	1	1	1	0	3	1	1	0	1	1	4	1	0	0	1	8	B

In this study, only 6 subjects out of 16 attended for gait analysis.

The cause of amputation is not mentioned in the article.

Table 2.

Results of quality assessment for papers related to prosthetic ankles.

Authors	Subjects				Parameters	Selection					Intervention						Statistical validity				Total score	Level of evidence
Authors	No.	Cause	Level	Age (years)	Parameters	A1	A2	A3	A4	A	B5	B6	B7	B8	B9	B	C10	C11	C13	C	Total score	Level of evidence
Portnoy et al.²⁵	10	Trauma	TT	42 (12)	Cadence, peak and root mean square internal von Mises stresses, loading rate	1	1	1	0	3	1	1	0	1	1	4	1	0	0	1	8	B
De Asha et al.²⁶	20	?^a	TT	47.4 (12.5)	Walking speed, COP parameters, angular velocity of the prosthetic shank	1	1	1	1	4	1	1	0	0	1	3	1	1	1	3	10	C
De Asha et al.¹⁰	8	?^a	TT	44.8 (10.7)	Walking speed, joint kinetics	1	1	1	1	4	1	1	0	0	1	3	1	0	1	2	9	C
De Asha et al.¹¹	19	?^a	TF TT	42 (14.8) 47 (10.3)	Temporal and spatial gait parameters, COP parameters, angular velocity of the prosthetic shank, COM forward velocity and position, inter-limb asymmetry	1	1	1	1	4	1	1	0	0	1	3	1	0	1	2	9	C
Johnson et al.²⁷	21	Trauma Infection cancer	TT	42 (12.8)	Minimum toe clearance (MTC) Joint angles at MTC Prosthetic limb hip-hiking Walking speed	1	1	1	1	4	1	1	0	0	1	3	1	1	1	3	10	C

COP: center of pressure; COM: center of mass.

The cause of amputation is not mentioned in the paper.

Findings of the selected studies

The selected studies were divided into two categories based on the effect of prosthetic knee and ankle with damping mechanism on gait parameters. In total, 10 studies compared the effect of different prosthetic knees and five papers examined the impact of prosthetic ankles. The primary outcomes of these studies are presented in Tables 3 and 4. The reviewed studies included a sample size ranging from 5^21,23 to 28 subjects¹⁶ with transfemoral amputation among the knee studies. The range among the ankle studies was 8–21 transtibial subjects.^10,27 The cause of amputation was reported as trauma, tumor, arterial occlusion, peripheral vascular disease, congenital abnormality, or infection in 10 studies and it was not mentioned in the other five papers. The mean age range for knee studies was 15–66 and 42–47 years for ankle studies.

Table 3.

Outcomes related to prosthetic knee joints.

Author	Intervention	Adaptation period	Findings	Level of evidence
Boonstra et al.¹⁶	3R20 Tehlin knee	2 weeks	Fast walking speed was significantly higher with the Tehlin knee than the 3R20 Swing-phase duration and stride time of prosthetic side were shorter with Tehlin knee Hip joint ROM was not different between two knee joints Knee joint ROM and 10° flexion duration during swing phase were smaller for Tehlin knee The CoG position was the same for both knee joints	A
Kirker et al.¹⁷	Intelligent knee Pneumatic swing phase-control knee	4–7 months for intelligent knee	No significant change in walking speeds was observed using two knee joints Step length was more symmetrical with the intelligent knee than the pneumatic knee joint at slow and fast walking speeds	B
Datta et al.¹⁸	Intelligent knee Pneumatic swing phase-control knee	6 weeks	No significant differences in parameters between two knee joints were found	B
Johansson et al.⁷	C-leg Rheo knee Mauch SNS	10 h	The walking speeds were not different across the three prostheses Rheo knee was associated with longer step times Mauch showed larger stance negative hip work, greater swing positive hip work, larger peak hip flexion moment at terminal stance, and larger peak hip power at toe-off. Rheo showed a smaller peak hip extension moment during late swing C-leg had higher peak knee extension angle in terminal swing and lower angular velocity at toe-off. The Mauch had significantly higher peak knee extension moment and peak knee power absorption at toe-off. Peak knee flexion moment in terminal swing was significantly lower for the Rheo Mauch and Rheo showed significantly larger peak ankle plantar flexion angles and peak foot compressions during early stance, significantly lower peak ankle dorsiflexion angles during mid to terminal stance and lower peak ankle plantar flexion moment at 30% of the gait cycle	C
Segal et al.¹⁹	Mauch SNS C-leg	3 months	Self-selected walking speed with the C-leg was significantly higher (p = 0.004) compared with the Mauch SNS (1.31 ± 0.12 m/s vs 1.21 ± 0.10 m/s) Prosthetic limb step length was less for the C-leg compared with the Mauch SNS which resulted in increased symmetry between limbs for the C-leg Peak swing knee flexion angle decreased for the C-leg compared with the Mauch SNS while was not significantly different from that of intact limb Early stance knee flexion moment increased for the C-leg compared with the Mauch SNS, but remained significantly reduced (p = 0.01) compared with healthy subjects and intact limb. The C-leg vertical ground reaction force decreased compared with the Mauch SNS (96.3% ± 4.7% vs 100.3% ± 7.5% body weight)	B
Kaufman et al.²⁰	Mauch SNS or equivalent C-leg	10–39 weeks	Gait improvement including knee flexion degree and internal extension moment during initial stance was seen with C-leg, While Mauch SNS caused knee hyperextension and internal flexion moment	B
Jepson et al.²¹	Adaptive knee Endolite prosthetic Catech	8 weeks	No significant changes in parameters between two prostheses were seen	B
Bellmann et al.²²	C-leg Energy knee Rheo knee Adaptive 2	2 h	C-leg and Hybrid knee showed significant differences in self-selected and higher walking speeds Maximum knee flexion angle increased variably from slow to the fast walking speed and C-leg was the lowest Swing-phase angular velocity of the Rheo Knee was the slowest followed by Adaptive 2, the C-leg and the Hybrid knee No significant differences in joint moments were observed.	C
Lythgo et al.²³	3R90 3R92	14–47 days	Gait speed with the 3R92 was lower than with the original devices and 3R90 prosthesis No significant differences were found in other parameters	C
Kaufman et al.²⁴	Mauch SNS CaTech Black Max Century2000 C-leg	18 (8) weeks	No significant difference in hip, knee, and ankle kinematic symmetry with the knee prostheses were found Significant improvement was seen in gait symmetry at the hip, knee, and ankle with C-leg	B

ROM: range of motion; CoG: center of gravity.

Table 4.

Outcomes related to prosthetic ankle joints.

Author	Intervention	Adaptation period	Findings	Level of evidence
Portnoy et al.²⁵	ESR Echelon	1 month	No significant changes in cadence between two prosthetic feet were observed Peak internal stresses and loading rates were significantly decreased in amputated leg with Echelon compared with ESR foot	B
De Asha et al.²⁶	habF hyA-F	45 min	Walking speed was higher with hyA-F than with habF (1.17 ± 0.15 vs 1.12 ± 0.14 m/s) COP velocity, posterior COP displacement, and COP variability were significantly reduced with hyA-F compared with habF Angular velocity of the prosthetic shank during the double support increased for hyA-F	C
De Asha et al.¹⁰	rigF hyA-F	45 min	Customary walking speed was significantly higher with hyA-F than rigF (1.18 ± 0.18 m/s vs 1.09 ± 0.19 m/s) Intact limb hip flexion moment, ankle dorsiflexion moment, total and negative ankle work, and total intact joint works were significantly reduced with hyA-F compares with rigF Residual knee peak power and negative work increased using the hyA-F Ankle negative power was higher with hyA-F in initial stance while positive power was less with hyA-F	C
De Asha et al.¹¹	rigF hyA-F	45 min	Walking speed was significantly faster with the hyA-F Negative COP displacement and slowing the COM velocity were reduced with the hyA-F	C
Johnson et al.²⁷	habF hyA-F	45 min	Mean MTC increased for both limbs when using the hyA-F compared with habF (2.17 vs 1.90 cm) Prosthetic side MTC variability increased using the hyA-F Both limb swing-phase hip at prosthetic MTC was significantly more flexed when using the hyA-F compared with habF (25.8° vs 22.8°, p = 0.001) Mean walking speed was greater when with hyA-F (1.12 ± 0.14 vs 1.17 ± 0.14) Swing-phase hip flexion at prosthetic limb MTC increased with walking speed (r = 0.09, p = 0.04), while decreased for knee flexion and hip-hiking	C

ESR: energy storage and return prosthetic feet; rigF: Dynamic response foot; hyA-F: Dynamic response foot with an articulating hydraulic ankle attachment; habF: Rigid or elastic articulating attachment habF:4—foot; COP: center of pressure; COM: center of mass; MTC: minimum toe clearance.

The prosthetic knee devices used in the studies included microprocessor-controlled knees, hydraulic/pneumatic fluid-controlled knees, and mechanical friction control knees (Table 3). The foot/ankle studies included a carbon foot combined with a hydraulic articulation (Table 4). Time allowed for adaptation to the prosthetic component varied from 2 h to 39 weeks among the knee studies and was 45 min to 4 weeks for ankle studies.

In general, temporal and spatial gait parameters and symmetry indexes, lower limb joint angles, moments, power and work, anterior–posterior center of mass (COM) velocity and position, and posterior displacement of center of pressure (COP) were the primary assessed biomechanical parameters (Tables 1 and 2).

Discussion

The objective of this study was to provide a review of biomechanical outcomes associated with the use of prosthetic knees and ankles with damping systems in individuals with lower limb loss.

The 15 papers included in this review fell into categories A through C according to the Van der Linde et al.⁵ scale for quality assessment. Although the scale allows for papers scoring six or higher, all papers included in this review scored eight or higher. This does not appear to be unusual, as the papers included in the review by Van der Linde et al. scored eight or higher as well with the exception of two (of 40 total) that scored seven. The nature of the classification system, with combinations of scores from certain categories as well as particular criteria of emphasis, seems to limit the likelihood of papers scoring six or seven being included as level C or higher.

The results of this review revealed that only one knee study blinded the participants to the type of prosthetic knee by covering it.¹⁶ Mohr et al.²⁸ studied the vertical jump in two groups of basketball players when they were or were not aware of their shoe weight differences. The results showed that the performance of the non-blinded group significantly increased with lighter shoes but it did not change across the blinded group. This result was attributed to psychological effects such as positive and negative expectancies toward the shoe weight differences. It is more challenging to conduct a blind experimental design when comparing prosthetic components, given that prosthetic sockets and components are usually visually apparent. Nonetheless, it is suggested to blind the participants to the type of intervention whenever feasible to minimize the possible bias.

Duration to adapt to a new prosthetic device is another important criterion and varied greatly among knee and ankle studies. English et al.²⁹ suggested a period of 1–3 weeks to achieve a consistent walking pattern and obtain the optimal gait outcome with new prosthetic ankle and knee. In all, 80% of the papers on knee joints met this adaptation time threshold. However, this period was not commonly considered in ankle studies in which only 33% of studies met the threshold. This factor could affect the extent to which the participants learned to walk and accommodate to changes in their new prostheses. Some studies only evaluated immediate response to a new component; thus, the adaptation time might not apply to them.

Many articles lost points in the rating because of the number of subjects. The ratio of the sample size to the number of independent variables for 87% of the reviewed articles was not sufficient enough to get the score (C11, Appendix 1).

Prosthetic ankle joints

In a B-level study, Portnoy et al.²⁵ showed socket pressures and loading rate of the residual limb reduced when walking with a specific type of hydraulic foot (Echelon). This might protect the distal end of the residual limb from high stresses and also increase the amputee comfort during walking. In four C-level studies conducted by one research team, an increase in self-selected walking speed was reported when walking with a hydraulic foot (Echelon).^10,11,26,27 This could be explained by the evidence reported in those studies in which COP variability and negative COP displacement, defined as the total retrograde distance traveled by COP in a gait cycle, were reduced with the hydraulic foot.^11,26 Additionally, walking with a hydraulic foot could increase the angular velocity of the prosthetic shank throughout double support, lessening the deceleration of COM velocity and, consequently, increasing gait speed.¹¹

It was demonstrated that subjects with unilateral lower-leg amputations rely more on the contralateral leg to compensate for prosthetic leg limitations.⁴ The results of one C-level study showed that compensatory joint kinetics significantly reduced with a hydraulic ankle compared to a rigid one and allowed the amputees to exert more load on the prosthetic side.¹⁰ Additionally, Johnson et al.²⁷ demonstrated that a hydraulic foot prosthesis provides a dorsiflexed position of the prosthetic foot at the instant of toe-off and throughout the swing phase and therefore improves the toe clearance. Here, it is good to note that prosthesis dorsiflexion at the instant of toe-off happens as opposite to the sound foot and thus may reduce push-off.

Although the results of reviewed papers in general demonstrate an improved gait while walking with a hydraulic foot, some interpretation of the conclusions is necessary. The aforementioned C-level articles appear to be conducted by a single research team, and part of the subject descriptions such as mean age, level of amputation, and the prosthetic foot types are very similar across papers. Furthermore, for all of the Echelon articles, the participants were not blinded to the prosthetic type, so they might have experienced more confidence and relied more on the advanced prosthetic feet. This possibility supports the necessity of blinding to the type of intervention when feasible.

Prosthetic knee joints

Reviewed articles on knee prostheses reported conflicting results related to temporal and spatial gait parameters. In the only study with A-level quality, a pneumatic swing-phase control (Tehlin) knee was compared with a non-damped mechanical control knee (3R20). Improvement in walking speed was shown for the Tehlin knee in the form of a shorter stride time and a more symmetrical swing-phase duration for the prosthetic leg.¹⁶ Most of the studies compared older versions of hydraulic or pneumatic damping knees with the new generation of microprocessor units. In only two studies, the walking speed was reported higher with a specific type of microprocessor knee, that is, C-leg. However, in the study by Bellmann et al.,²² the participants were existing C-leg users and had only 2 h of adaptation with other knee joints. Segal et al.¹⁹ concluded that because subjects had longer acclimation periods, they could demonstrate faster walking speed with C-leg. However, it is worth mentioning that novel prosthetic knees are claimed to normalize the stance and swing gait phases over a wide range of speeds. Bellmann et al.²² tested different knees during walking at three different speeds of low, normal, and fast. They concluded that those wearing the C-leg (linear hydraulic) did not experience many changes in knee flexion even though walking speeds changed.

Two B-level studies showed more symmetrical step length with the intelligent knee than a pneumatic or hydraulic knee joint.^17,19 However, others found no changes in temporal and spatial gait symmetry between these knee joints. This was attributed to the higher level of maintenance required for the intelligent compared to the hydraulic and pneumatic knee or the learning factor associated with using a new prosthesis. ^18,21Therefore, more evidence is needed to conclude whether knee prostheses with damping control systems can provide more symmetrical step length during walking.

For transfemoral amputees, the knee flexion moment is smaller than normal because the prosthetic knee does not substitute for the quadriceps muscle.³⁰ However, Segal et al.¹⁹ reported that the microprocessor-controlled C-leg enhanced the knee flexion moment significantly compared with the mechanical knee. During the loading phase, normal physiological knee flexion acts as a shock absorber that can prevent wear and tear of joints,³⁰ which has been reported to have a range of 15°–18° in healthy subjects or the intact leg of lower limb amputees.³⁰ Designed to enable controlled knee flexion during stance phase, microprocessor-controlled knees were shown not to change peak knee flexion angle during stance when compared to the intact limb or other prosthetic knees.¹⁹ A possible reason would be that amputees tend not to perform knee flexion, probably because of fear of buckling and falling.^19,31

Some differences were documented with damped prosthetic knee and ankle joints compared to those without a damper. Overall, walking speed was influenced when the dampers were added to the leg. One way to leverage the potential advantages of damping components is to change the damper based on the walking speed. This finding may be partially attributed to variability of results from different studies, small sample sizes that do not show significant differences among the various knee joints, as well as methodological limitations such as blinding. Therefore, more research is needed to compare different biomechanical outcomes of prosthetic knees at a range of walking speeds.

Conclusion

Some differences were documented with damped prosthetic knee and ankle joints compared to those without a damper. Overall, walking speed showed the highest difference when dampers were applied to the leg. Additionally, considering the level of studies based on this review, more studies are needed to identify differences among the various available joints, especially in the area of hydraulically damped ankle–foot devices. Future work is needed to compare the outcomes of transfemoral amputees and to evaluate how the combination of damped knee and ankle joints would affect performance.

Footnotes

Author contribution

All authors contributed equally in the preparation of this manuscript.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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The effect of damping in prosthetic ankle and knee joints on the biomechanical outcomes: A literature review

Abstract

Background:

Objectives:

Study design:

Methods:

Results:

Conclusion:

Clinical relevance

Keywords

Background

Methods

Search strategy

Study selection

Quality assessment

Results

Search results

Study selection

Findings of the selected studies

Discussion

Prosthetic ankle joints

Prosthetic knee joints

Conclusion

Footnotes

Author contribution

Declaration of conflicting interests

Funding

References