Balance, Balance Confidence, and Falls Using Nonmicroprocessor and Microprocessor Knee Prostheses: A Case Study After Vascular Amputation With 12-Month Follow-Up : JPO: Journal of Prosthetics and Orthotics

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Balance, Balance Confidence, and Falls Using Nonmicroprocessor and Microprocessor Knee Prostheses

A Case Study After Vascular Amputation With 12-Month Follow-Up

Wong, Christopher Kevin PT, PhD, OCS; Wilska, Julie PT, DPT; Stern, Michelle MD

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JPO Journal of Prosthetics and Orthotics: January 2012 - Volume 24 - Issue 1 - p 16-18
doi: 10.1097/JPO.0b013e3182435f12
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Older people with vascular disease constitute the largest proportion of people undergoing leg amputations1 and have a greater risk of falling than the general public, with reported incidences of 31% during rehabilitation2 and 52% within the community.3 Falls among people with transfemoral amputation are significantly more common than after transtibial amputation,4 and nearly half report a fear of falling.3 With the high risk of falling for people with transfemoral amputations because of vascular disease, it is unsurprising that this group rates their balance confidence significantly lower.5

For people with amputation, subjective lack of balance confidence is a persistent problem related to a fear of falling, functional activity, participation in society, and the incidence of falls.2,3 The Activity-specific Balance Confidence (ABC) scale reliably assesses confidence in maintaining balance while performing daily mobility tasks.5 The self-reported 16-item questionnaire has been more predictive of prosthetic mobility and social participation than a history of actual falls3 and can be administered in a waiting room.5 The ABC may be vulnerable to subjective rater-overconfidence, however, which may explain the comparatively high fall incidence in people aged between 50 and 60 years.6

Increased falls has been associated with balance impairment, commonly measured with balance assessments including the Berg balance scale (BERG) and timed-up-and-go (TUG) test.7 The BERG consists of 14 balance tasks, such as stand-one-leg-eyes-open, rated on a 0 to 4 scale with a summated maximum score of 56 that has been widely used to determine the risks for falls.8,9 The TUG test combines sit-to-stand with walking and turning to reliably assess functional balance and mobility.10 Clinical measures of balance impairment may provide additional tools beyond self-rated balance confidence to determine the risk for falls and prosthetic use.

Whether different prosthetic knees can improve balance and reduce falls for people after vascular amputation remains uncertain. Stumbles and falls assessed with the self-report Prosthesis Evaluation Questionnaire decreased over 2 months when using a microprocessor knee (MPK) compared with a non-MPK prostheses in community-dwelling people with mostly nonvascular amputation.11 One elderly man with nonvascular amputation had no falls using a MPK for 1 year although he fell previously using a non-MPK prosthesis, but no objective balance assessment was performed.12 Subjectively, 88% of users report greater confidence with a MPK compared with a non-MPK prosthesis.13 Self-report assessments may be biased, however.

The studies of people with vascular amputations using MPK or non-MPK prostheses to affect balance ability, balance confidence, and fall prevention are lacking. This case study documents balance, balance confidence, fall and activity participation history in a person with transfemoral amputation because of vascular disease who used both MPK and non-MPK prostheses, with 1-year follow-up.


A 53-year-old African American man voluntarily signed informed consent to participate in this study approved by the Columbia University Medical Center Institutional Review Board. He was recruited at an urban medical center amputee support group meeting and was assessed at three sessions over 14 months.

Before undergoing a transtibial amputation due to peripheral vascular disease, the subject was employed as a surgical technician and independently performed all household and recreational activities including swimming, bowling, and gym exercise. His amputation was revised to a transfemoral amputation 5 months after his transtibial amputation. Three months later, he received his first prosthesis, outfitted with a hydraulic non-MPK prosthesis (Mauch® Knee, Ossur at and participated in 2 weeks of inpatient rehabilitation. He returned home with part-time home health aide assistance for 6 weeks before becoming independent. He did not return to work or leisure activities because he did not feel capable.

On entry into the study, the subject had used his prosthesis for 17 months, which had begun with outpatient physical therapy. Although he had become an unlimited independent community ambulator using a cane, as defined by the K-3 Medicare functional level of ambulation for prosthetic users, he had fallen twice without injury in the previous year. On the first session, he completed an information questionnaire including functional level and falls history and the self-report ABC. Using his non- MPK prosthesis, he also performed a BERG balance assessment and TUG functional mobility test. Three weeks later at his second session, he used a MPK (C-Leg® microprocessor knee prosthesis, Otto Bock at for a 1-hour trial training session with a prosthetist and amputee demonstrator. After his 1-hour training, he was retested using the same assessments.

Two months later, he received his own MPK and started 24 outpatient physical therapy sessions over the next 3 months for gait, balance, and functional training. Follow-up balance, balance confidence, functional mobility, and fall history assessments were performed at his third session after 12 months of MPK use. All assessments were performed by the same clinician.


The subject demonstrated improved BERG, ABC, and TUG test scores with MPK use. The subject had no falls over 12 months and returned to participation in previous recreational activities including bowling and jogging (Table 1).

Table 1:
Assessment data


The subject's BERG score increased immediately following the initial 1-hour MPK training session and increased after 1 year by six points, representing clinically meaningful improvement.14 The increased BERG score represented a reduced fall risk from 40% to 50% (for score of 52) to 10% to 43% (for score of 46), based on associations between BERG and falls in retrospective and prospective groups of older people.8,9

The subject's initial 84% ABC score using the non-MPK was higher than older people receiving home care and demonstrated far more confidence than the 51% average ABC score for people with vascular amputation.15 With MPK use, his ABC score increased immediately by approximately 10%, which could reflect rater-overconfidence. His balance confidence level was maintained at 1-year follow-up, however, and was similar to groups of able-bodied community-dwelling elderly.15

His initial 15.7 seconds of TUG test time using the non-MPK also exceeded the mean for people with leg amputations: 19.4 to 24.5 seconds.5,10 He improved after the 1-hour MPK training, lowering his TUG test time to 14.5 seconds, the median for people after leg amputation.5 After 1-year of MKP use, his TUG test time had decreased further to 9.7 seconds, similar to the fastest times reported for people with leg amputation.10

Although his confidence grew immediately using the MPK, possibly reflecting an initial overconfidence, extended time to accommodate to the MPK and receive physical therapy appeared helpful in achieving clinical meaningful improvements in BERG and TUG test performance 1 year later. Consistent with past reports, he did not fall during the 1 year using the MPK.11,12 Perhaps, most important, he returned to participate in leisure activities like bowling, swimming, and amputee-focused outdoor exercise classes, trail walking, and jogging. His return to higher impact activities can be considered to have raised his Medicare level from K-3 to K-4.

As a single-case study, no conclusions can be drawn with regards to the causality of balance and functional improvements and any conclusions apply only to this case. Limitations include the lack of recorded prosthetic adjustments and C-leg parameter settings. Although outcome assessments were standardized, physical therapy interventions with the MPK and non-MPK were not. Information on what activities were performed and participated in was obtained solely from the subject.

Further controlled research with comparison groups receiving physical therapy with non-MPK or MPK prostheses without physical therapy would be required to determine what interventions improve balance and reduce falls. Further research is also suggested specifically into the effects of MPK use on balance, function, and falls in people with vascular amputations. Although functional ability, morbidity, and mortality complicate research of people with vascular leg amputations, these typically older people are the most at risk to fall and may benefit the most from fall prevention strategies.


For this man with transfemoral amputation because of vascular disease, balance, balance confidence, falls, and participation in leisure activities all improved during a year of MPK. Future research to identify and reduce risk of falls for people with vascular transfemoral amputation is needed before clinical conclusions can be drawn.


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lower limb; prosthetics; function; outcomes; vacuum; subatmospheric

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