It is well documented that the number of people living with an amputation is increasing,1,2 with the most recent estimates from 2005 suggesting that 41,000 individuals in the United States are living with major upper-limb loss.1 A study examining US service members from 2001 to 2011 reported that 14% of amputations involved the upper limb.3 Literature reports of rejection rates of upper-limb prostheses vary from 0% to 50% due to factors such as lack of perceived functional gains, prosthesis weight, and socket discomfort among others.4–6 Prosthetic prescription currently depends to varying degrees on patient input, the experience of treating clinicians with available components, literature on component function, manufacturer's claims, and reimbursement methods.7 The purpose of this updated systematic review was to determine if new evidence supporting the differences between myoelectric (MYO) and body-powered (BP) prostheses in the areas of functionality, control, and sensory feedback, cosmesis, and rejection has emerged since the previous review conducted in 2013.7
Similar to the previous literature review,7 a systematic search was conducted using 9 databases for publications of articles from 2014 to 2016. As in the initial review, the databases were searched using broad key words related to upper-limb prostheses: myoelectric, body-powered, externally powered, transradial, transhumeral, upper limb, prosthesis, and artificial limb.
Inclusion and exclusion criteria were established to select publications that were relevant to the review's purpose statement, which was to compare MYO and BP prostheses to help guide evidence-based clinical decisions. Editorial, case study/series, observational research designs, or literature reviews published between 2014 and 2016 were included. Conference proceedings, white papers, theses, dissertations, progress reports, non-English articles, partial hand/finger articles, surgical articles, modeling articles, pediatric articles, and electromyography (EMG)-only articles were excluded from the review. In addition, articles describing prostheses not currently commercially available such as the DEKA arm, able-bodied–only studies, or publications describing sensation capabilities were excluded because they did not pertain to the review's purpose statement.
ASSESSMENT OF METHODOLOGICAL QUALITY
The study design and methodological quality of those publications that met the inclusion and exclusion criteria were independently assessed by at least two of three reviewers according to the protocol developed by the American Academy of Orthotists and Prosthetists (AAOP) State-of-the-Science Evidence Report Guidelines.8 Reviewers discussed pertinent issues until consensus on study design and methodological quality was obtained for the included publications.
Each reviewer rated each study according to the AAOP Study Design Classification Scale that describes the type of study design. The State-of-the-Science Conference (SSC) Quality Assessment Form was used to rate the methodological quality of studies classified as experimental (E1–E5) or observational (O1–O6). The form identifies 18 potential threats to internal validity with the first 4 (E3–E5) or 5 (O1–O6) criteria not applicable for given classification and 8 potential threats to external validity.8 Threats were evaluated and tabulated.
EMPIRICAL EVIDENCE STATEMENTS
Based on results from the publications included in the updated review, empirical evidence statements (EESs) that compared BP and MYO prostheses were either developed or had their strength reevaluated. Reviewers rated the level of confidence of each EES as “high,” “moderate,” “low,” or “insufficient,” based on the updated number of publications contributing to the statement, the methodological quality of those studies, and whether the contributing findings were confirmatory or conflicting as similarly outlined by others.9 Note that in addition to peer-reviewed studies, editorials and systematic reviews were also included to the moderate and low confidence level descriptions due to the lack of observational and experimental studies available in the literature on the topic.
The updated literature review yielded 43 unique articles. After screening the inclusion and exclusion criteria, 33 publications were excluded. Ten articles were reviewed and scored for content and quality and an additional 7 articles were then excluded. This resulted in three publications included in the qualitative synthesis10–12 (Table 1).
The reviewed studies were classified into 1 of 9 defined study designs as described by the AAOP Study Design Classification Scale.8 Two publications were classified as O3, cross-sectional studies, and one was classified as E5, a controlled before-and-after study. Sample sizes range from 2 to 22 prosthesis users with additional able-bodied subjects studied for comparison. In total, this updated systematic review included 31 subjects with amputation and 33 able-bodied controls.
OUTCOME MEASURES FOR ASSESSMENT OF UPPER LIMB
The following outcomes were measured in the included publications: the SHAP test, surveys,10 movement time, force control, box and blocks test, duration of hand opening,11 range of motion, absolute kinematic variability, kinematic repeatability (adjusted coefficient of multiple determination) for trunk motion, shoulder flexion/extension, shoulder abduction/adduction, and elbow flexion/extension.12
METHODOLOGICAL QUALITY ASSESSMENT
Two of the included studies had moderate and one had low internal validity. Threats to internal validity preventing attainment of high scores included a lack of blinding and lack of reporting effect sizes. Strengths noted in internal validity were clearly outlining eligibility criteria and acclimation as well as the use of reliable outcome measures and the attainment of statistical significance.
Two of the included studies yielded moderate level external validity and one achieved high external validity. Threats to external validity included lack of documentation regarding clinical significance and generalizability of the sample. Strengths to external validity included clear sample and outcome descriptions and conclusions supported by study results (Table 2).
Ultimately, Sensinger et al.10 a controlled before-and-after trial (E5) had low overall quality, whereas de Boer et al.11 and Major et al.,12 both cross-sectional studies (O3), demonstrated moderate overall study quality.
EMPIRICAL EVIDENCE STATEMENTS
The previous systematic review of MYO and BP prostheses developed 11 EESs. The additional publications included in this review update added evidence to two of these EES:
- “Intuitive prosthetic control may require use of multiple control strategies, such as BP, MYO, or hybrid, that require less visual attention and ability to make coordinated motions of two joints but should be evaluated for each individual upper-limb prosthesis user.”7
- “Prosthetic rehabilitation plan addressing critical factors such as EMG site selection, controls and task training, and comfort by cohesive team will improve function and long-term success of electrically powered prosthesis users.”7
The updated systematic review added more evidence to two previous EESs that describe the potential need for multiple control strategies in an individualized prosthetic care pathway and the importance of a comprehensive rehabilitation plan to prosthetic success.
Sensinger et al.10 concluded that users performed better on the SHAP test when they could switch between voluntary opening and voluntary closing modes of their BP prostheses. This conclusion supports the EES that intuitive prosthetic control may require use of multiple control strategies and should be evaluated for each individual upper-limb prosthesis user.
The publication by de Boer et al.11 studied intermanual transfer effects of experienced below-the-elbow MYO prosthesis users and concluded that intermanual transfer has relevance regarding training of persons with upper-limb amputation. This supports the previous EES suggesting that control scheme familiarity can make either BP or MYO prostheses more advantageous. This publication also supports the EES regarding a prosthetic rehabilitation plan that addresses critical factors including control and task training that will improve function and long-term success of electrically powered prosthesis users.
Major et al.12 concluded that training dedicated to optimization of compensatory dynamics may be necessary to improve the functionality of transradial prosthesis users. This adds evidence to both the previously mentioned EESs regarding control scheme familiarity and a prosthetic rehabilitation plan that factors in control and task training.
Additional studies might have been included; however, their generalizability to the study purpose and population was sufficiently unclear. For instance, publications including only able-bodied subjects using a simulator were excluded. This is because current literature does not demonstrate that the degree of impairment is comparable between simulated prosthetic use in able-bodies and actual prosthetic use among persons with amputation.
DEKA arm studies were also excluded. The DEKA arm has multiple different control strategies relevant to the study topic. However, the system is not representative of classic MYO systems and has heretofore only been available to a limited population. Further, it is not commercially available at this time.
Since the previous systematic review evaluating differences in MYO and BP upper-limb prostheses, new evidence has emerged, which strengthens evidence suggesting that intuitive prosthetic control may require the use of multiple control strategies for each individual upper-limb prosthesis user. Evidence has also since emerged indicating that prosthetic rehabilitation addressing critical factors will most likely improve function and long-term upper-limb prosthetic success. It seems that, at this time, there is inadequate evidence to support an overall advantage of BP upper-limb prosthetic control or MYO prosthetic control. Rather, individual patient attributes, goals, and functional needs largely determine, which control strategy and prosthetic type is optimal for each patient with upper-limb amputation.
1. Ziegler-Graham K, MacKenzie EJ, Ephraim PL, et al. Estimating the prevalence of limb loss in the United States: 2005 to 2050. Arch Phys Med Rehabil
2. Resnik L, Meucci MR, Lieberman-Klinger S, et al. Advanced upper limb prosthetic devices: implications for upper limb prosthetic rehabilitation
. Arch Phys Med Rehabil
3. Kruger LM, Fishman S. Myoelectric and body-powered prostheses. J Pediatr Orthop
4. Dougherty PJ. Research and future developments in upper and lower limb prostheses. Curr Orthop Pract
5. Biddiss E, Chau T. Upper limb prosthesis
use and abandonment: A survey of the last 25 years. Prosthet Orthot Int
6. Gaine WJ, Smart C, Bransby-Zachary M. Upper limb traumatic amputees. Review of prosthetic use. J Hand Surg Br
7. Carey SL, Lura DJ, Highsmith MJ, et al. Differences in myoelectric and body-powered upper-limb prostheses: Systematic literature review. J Rehabil Res Dev
8. Hafner B. American Academy of Orthotists and Prosthetists (AAOP) State-of-the-Science Evidence Report Guidelines
. Washington, DC: American Academy of Orthotists and Prosthetists; 2008.
9. Sawers AB, Hafner BJ. Outcomes associated with the use of microprocessor-controlled prosthetic knees among individuals with unilateral transfemoral limb loss: a systematic review. J Rehabil Res Dev
10. Sensinger JW, Lipsey J, Thomas A, Turner K. Design and evaluation of voluntary opening and voluntary closing prosthetic terminal device. J Rehabil Res Dev
11. de Boer E, Romkema S, Cutti AG, et al. Intermanual transfer effects in below-elbow myoelectric prosthesis
users. Arch Phys Med Rehabil
12. Major MJ, Stine RL, Heckathorne CW, et al. Comparison of range-of-motion and variability in upper body movements between transradial prosthesis
users and able-bodied controls when executing goal-oriented tasks. J Neuroeng Rehabil