Predicting reamputation risk in patients undergoing lower extremity amputation due to the complications of peripheral artery disease and/or diabetes.

BACKGROUND: Patients undergoing amputation of the lower extremity for the complications of peripheral artery disease and/or diabetes are at risk of treatment failure and the need for reamputation at a higher level. The aim of this study was to develop a patient-specific reamputation risk prediction model. METHODS: Patients with incident unilateral transmetatarsal, transtibial or transfemoral amputation between 2004 and 2014 secondary to diabetes and/or peripheral artery disease, and who survived 12 months after amputation, were identified using Veterans Health Administration databases. Procedure codes and natural language processing were used to define subsequent ipsilateral reamputation at the same or higher level. Stepdown logistic regression was used to develop the prediction model. It was then evaluated for calibration and discrimination by evaluating the goodness of fit, area under the receiver operating characteristic curve (AUC) and discrimination slope. RESULTS: Some 5260 patients were identified, of whom 1283 (24·4 per cent) underwent ipsilateral reamputation in the 12 months after initial amputation. Crude reamputation risks were 40·3, 25·9 and 9·7 per cent in the transmetatarsal, transtibial and transfemoral groups respectively. The final prediction model included 11 predictors (amputation level, sex, smoking, alcohol, rest pain, use of outpatient anticoagulants, diabetes, chronic obstructive pulmonary disease, white blood cell count, kidney failure and previous revascularization), along with four interaction terms. Evaluation of the prediction characteristics indicated good model calibration with goodness-of-fit testing, good discrimination (AUC 0·72) and a discrimination slope of 11·2 per cent. CONCLUSION: A prediction model was developed to calculate individual risk of primary healing failure and the need for reamputation surgery at each amputation level. This model may assist clinical decision-making regarding amputation-level selection.

Mortality prediction following non-traumatic amputation of the lower extremity.

BACKGROUND: Patients who undergo lower extremity amputation secondary to the complications of diabetes or peripheral artery disease have poor long-term survival. Providing patients and surgeons with individual-patient, rather than population, survival estimates provides them with important information to make individualized treatment decisions. METHODS: Patients with peripheral artery disease and/or diabetes undergoing their first unilateral transmetatarsal, transtibial or transfemoral amputation were identified in the Veterans Affairs Surgical Quality Improvement Program (VASQIP) database. Stepdown logistic regression was used to develop a 1-year mortality risk prediction model from a list of 33 candidate predictors using data from three of five Department of Veterans Affairs national geographical regions. External geographical validation was performed using data from the remaining two regions. Calibration and discrimination were assessed in the development and validation samples. RESULTS: The development sample included 5028 patients and the validation sample 2140. The final mortality prediction model (AMPREDICT-Mortality) included amputation level, age, BMI, race, functional status, congestive heart failure, dialysis, blood urea nitrogen level, and white blood cell and platelet counts. The model fit in the validation sample was good. The area under the receiver operating characteristic (ROC) curve for the validation sample was 0·76 and Cox calibration regression indicated excellent calibration (slope 0·96, 95 per cent c.i. 0·85 to 1·06; intercept 0·02, 95 per cent c.i. -0·12 to 0·17). Given the external validation characteristics, the development and validation samples were combined, giving a total sample of 7168. CONCLUSION: The AMPREDICT-Mortality prediction model is a validated parsimonious model that can be used to inform the 1-year mortality risk following non-traumatic lower extremity amputation of patients with peripheral artery disease or diabetes.

An equinus deformity of the ankle accounts for only a small amount of the increased forefoot plantar pressure in patients with diabetes.

Patients with diabetes mellitus may develop plantar flexion contractures (equinus) which may increase forefoot pressure during walking. In order to determine the relationship between equinus and forefoot pressure, we measured forefoot pressure during walking in 27 adult diabetics with a mean age of 66.3 years (sd 7.4) and a mean duration of the condition of 13.4 years (sd 12.6) using an Emed mat. Maximum dorsiflexion of the ankle was determined using a custom device which an examiner used to apply a dorsiflexing torque of 10 Nm (sd 1) for five seconds. Simple linear regression showed that the relationship between equinus and peak forefoot pressure was significant (p < 0.0471), but that only a small portion of the variance was accounted for (R(2) = 0.149). This indicates that equinus has only a limited role in causing high forefoot pressure. Our findings suggest caution in undertaking of tendon-lengthening procedures to reduce peak forefoot plantar pressures in diabetic subjects until clearer indications are established.

Postoperative management of transtibial amputations in VA hospitals.

Rigid plaster dressings and immediate postoperative prostheses (IPOP) in patients undergoing transtibial amputations have been reported to reduce pain and healing time, prevent knee flexion contractures, and expedite early ambulation compared to soft dressings. Yet, despite the reported benefits, surgical adoption of (conventional) rigid dressings and IPOP has been inconsistent. The purpose of this study was to determine the current postoperative transtibial amputation dressing practices in VA hospitals. A six-item questionnaire was sent to 134 surgeons at the 117 VA hospitals where transtibial amputations were performed in fiscal year 1999. Responses were received from 83% of the surgeons. During the 1999 study year, surgeons performing transtibial amputations used soft dressings on 67% of patients, conventional rigid dressings with no intent to apply a foot attachment on 14% of patients, removable rigid dressings on 14% of patients, and IPOP (almost exclusively without a foot) on 5% of patients. The application of a rigid dressing or IPOP did not correlate well with the total number of transtibial amputations performed by the surgeon, hospital bed size, or academic affiliation.

Mechanical properties of prosthetic limbs: adapting to the patient.

Lower-limb amputees have identified comfort and mobility as the two most important characteristics of a prosthesis. While these in turn depend on a multitude of factors, they are strongly influenced by the biomechanical performance of the prosthesis and the loading it imparts to the residual limb. Recent years have seen improvements in several prosthetic components that are designed to improve patient comfort and mobility. In this paper, we discuss two of these: VSAP and prosthetic foot-ankle systems; specifically, their mechanical properties and impact on amputee gait are presented.

Recreational activities of lower-limb amputees with prostheses.

Ninety-two (92) persons with lower-limb amputations who regularly used prostheses responded to a survey that included questions about preferred recreational activities. This article describes the variety of activities selected by these men and women aged 20 to 87 years. Of the activities that were of high importance, 74% to 88% could be performed. Those activities assigned moderate to low importance were less often reported as able to be performed. The activities that require high energy level were more problematic for performance. The diversity of identified activities (n= 166) underscores the value of learning about amputees' activity preferences when making prosthetic prescription decisions.

Can the presence of equinus contracture be established by physical exam alone?

The condition in which ankle dorsiflexion is restricted is known as equinus contracture (EC). Equinus contracture is purported to be associated with a number of clinical conditions. However, there are no data to support or refute a clinician's ability to diagnose EC by clinical exam. We prospectively evaluated the maximum ankle dorsiflexion with the knee fully extended in 68 people (34 patients with isolated fore- or midfoot pain and 34 asymptomatic subjects) both by clinical exam and by a custom-designed ankle goniometer. We compared the likelihood of agreement of the clinical impression (equinus, no equinus) to the maximum ankle dorsiflexion measured with the instrument at two different numerical definitions of EC (< or =5 degrees and < or =10 degrees of maximum dorsiflexion). When all subjects were included and equinus defined as < or =5 degrees of ankle dorsiflexion, a clinician's ability to detect the equinus when it is truly present is 77.8%. If equinus is defined as < or =10 degrees, this ability increases to 97.2%. Alternatively, if equinus is not present, as defined by < or =5 degrees, then a clinician's ability to correctly diagnose no equinus is 93.8%. If equinus is defined to < or =10 degrees, this ability decreases to 68.8%.

Trends in peripheral vascular procedures in the Veterans Health Administration, 1989-1998.

OBJECTIVE: To assess trends in peripheral vascular procedures performed in Veterans Health Administration (VHA) facilities. METHODS: All discharges with peripheral vascular procedures recorded for 1989-1998 were analyzed. The VHA user population was used to calculate age-specific rates. Trends were evaluated using frequency tables and Poisson regression. RESULTS: The VHA had 55,916 discharges with peripheral vascular procedures performed almost exclusively in men. Indications included peripheral vascular disease (53.7%), gangrene (19.3%), surgical complications (13.3%), and ulcers and infection (9.6%). The VHA age-specific rates were higher than US population rates for persons 45 to 64 years, similar for those 65 to 74 years, and lower for those 75 years and older. The age-specific rates declined slightly over the 10 years of observation, with the greatest decline noted in men age 45 to 65. CONCLUSION: The VHA provides almost 8% of all US peripheral vascular procedures in males. The VHA age-specific rates differ from the US rates with a shift to younger patients. The rates decreased for all age groups between 1989-1998.

Survival following lower-limb amputation in a veteran population.

GOAL: We sought to describe the common demographic and comorbid conditions that affect survival following nontraumatic amputation. METHODS: Veterans Administration hospital discharge records for 1992 were linked with death records. The most proximal level during the first hospitalization in 1992 was used for analysis. Demographic information (age, race) and comorbid diagnosis (cardiovascular, cerebrovascular, and renal disease) were used for Kaplan-Meier curves to describe survival following amputation. MAIN OUTCOME MEASURE: Death. RESULTS: Mortality risk increased with advanced age, more proximal amputation level, and renal and cardiovascular disease, and decreased for African Americans. No increased risk for persons with diabetes was noted in the first year following amputation but the risk increased thereafter. A higher risk of mortality in the first year was noted for renal disease, cardiovascular disease, and proximal amputation level. CONCLUSION: Survival following lower-limb amputation is impaired by advancing age, cardiovascular and renal disease, and proximal amputation level. Also, a small survival advantage is seen for African Americans and those with diabetes.

Back pain as a secondary disability in persons with lower limb amputations.

OBJECTIVE: To evaluate the frequency, duration, intensity, and interference of back pain in a sample of persons with lower limb amputations. DESIGN: Retrospective, cross-sectional survey. SETTING: Community-based survey from clinical databases. PARTICIPANTS: Participants who were 6 or more months post lower limb amputation (n = 255). INTERVENTION: An amputation pain survey that included several standardized pain measures. MAIN OUTCOME MEASURES: Frequency, duration, intensity, and interference of back pain. RESULTS: Of the participants who completed the survey (return rate, 56%), 52% reported experiencing persistent, bothersome back pain. Of these, 43% reported average back pain intensity in the mild range (1-4 on 0-10 rating scale) and 25% reported pain of moderate intensity (5-6 on 0-10 scale). Most respondents with back pain rated the interference of their pain on function as none to minimal. However, nearly 25% of those with back pain described it as frequent, of severe intensity (>or=7 on 0-10 scale), and as severely interfering with daily activities including social, recreational, family, and work activities. CONCLUSIONS: Back pain may be surprisingly common in persons with lower limb amputations, and, for some who experience it, may greatly interfere with function.

Effect of trans-tibial prosthesis pylon flexibility on ground reaction forces during gait.

This study explored the effects of trans-tibial prosthesis pylon flexibility on ground reaction forces (GRFs) associated with walking and step-down. Four (4) active subjects with unilateral trans-tibial amputation and pylon lengths ranging from 4.9 cm to 25.9 cm were studied wearing an aluminium (rigid) pylon and a nylon (more flexible) pylon. Ground reaction forces were collected for the amputated limb during walking at pre-measured self-selected velocity and when stepping down from a 20 cm box. Pylon material significantly affected the magnitudes and patterns of GRFs in both tests. During walking, the most notable differences were seen in the anteroposterior (AP) direction. With the flexible pylon, the AP propulsive peak was greater (p=0.031), and the irregularities in the AP force curve were reduced. Additionally, when walking with the flexible pylon, the vertical peak associated with weight acceptance occurred earlier (p=0.010), the vertical terminal stance peak occurred later (p=0.012), and stance time was longer (p=0.010). During step-down, the vertical loading rate (p=0.010) and the peak vertical force (p=0.010) were greater with the more flexible pylon. Subjective feedback indicated that subjects could distinguish between the two pylons and felt that the nylon component was more comfortable, more flexible, and would enable them to walk more quickly. These results suggest that the pylon may be an influential component of the prosthesis with respect to gait and comfort, and that some degree of flexibility is desirable.

Chronic phantom sensations, phantom pain, residual limb pain, and other regional pain after lower limb amputation.

OBJECTIVES: To determine the characteristics of phantom limb sensation, phantom limb pain, and residual limb pain, and to evaluate pain-related disability associated with phantom limb pain. DESIGN: Retrospective, cross-sectional survey. Six or more months after lower limb amputation, participants (n = 255) completed an amputation pain questionnaire that included several standardized pain measures. SETTING: Community-based survey from clinical databases. PARTICIPANTS: A community-based sample of persons with lower limb amputations. MAIN OUTCOME MEASURES: Frequency, duration, intensity, and quality of phantom limb and residual limb pain, and pain-related disability as measured by the Chronic Pain Grade. RESULTS: Of the respondents, 79% reported phantom limb sensations, 72% reported phantom limb pain, and 74% reported residual limb pain. Many described their phantom limb and residual limb pain as episodic and not particularly bothersome. Most participants with phantom limb pain were classified into the two low pain-related disability categories: grade I, low disability/low pain intensity (47%) or grade II, low disability/high pain intensity (28%). Many participants reported having pain in other anatomic locations, including the back (52%). CONCLUSIONS: Phantom limb and residual limb pain are common after a lower limb amputation. For most, the pain is episodic and not particularly disabling. However, for a notable subset, the pain may be quite disabling. Pain after amputation should be viewed from a broad perspective that considers other anatomic sites as well as the impact of pain on functioning.

Trends in lower limb amputation in the Veterans Health Administration, 1989-1998.

OBJECTIVE: To assess trends in lower limb amputation performed in Veterans Health Administration (VHA) facilities. METHODS: All lower limb amputations recorded in the Patient Treatment File for 1989-1998 were analyzed using the hospital discharge as the unit of analysis. Age-specific rates were calculated using the VHA user-population as the denominator. Frequency tables and linear, logistic, and Poisson regression were used respectively to assess trends in amputation numbers, reoperation rates, and age-specific amputation rates. RESULTS: Between 1989-1998, there were 60,324 discharges with amputation in VHA facilities. Over 99.9% of these were in men and constitute 10 percent of all US male amputations. The major indications were diabetes (62.9%) and peripheral vascular disease alone (23.6%). The age-specific rates of major amputation in the VHA are higher than US rates of major amputation. VHA rates of major and minor amputation declined an average of 5% each year, while the number of diabetes-associated amputations remained the same. CONCLUSION: The number and age-specific rates of amputations decreased over 10 years despite an increase in the number of veterans using VHA care.

The role of ankle plantar flexor muscle work during walking.

Impaired ankle plantar flexor (APF) function is a frequent cause of gait limitations, but the role of the APF in the forward propulsion of the body remains controversial. To better understand both the direct and indirect effects of the APF during push-off and through advancement of the leg, mechanical work and inverse dynamic analyses were performed on 8 normal subjects during level walking. During push-off, 23.1 joules (J) of energy were generated, primarily by the APF, but only 4.2 J of this energy is transferred into the trunk. Ankle plantar flexor work is primarily used to accelerate the leg into swing. Most of the energy, 18.6 J, is recovered by transfer into the trunk at the end of swing. The timing of the energy transfers relative to the trunk motion imply that the APF contributes to the forward kinetic energy of the trunk but that other mechanisms likely account for the work used to raise the trunk against gravity.

Mechanical work adaptations of above-knee amputee ambulation.

OBJECTIVE: To quantify the muscular adaptations of above-knee amputee patients' ambulation using an experimental and modeling approach. DESIGN: Nonrandomized controlled study. SETTING: A referral center for treatment of veterans with amputation. SUBJECTS: Eight normal ambulators and 8 nondysvascular above-knee amputee subjects wearing the same lightweight prostheses were studied with a gait analysis system, walking at self-selected speeds. MAIN OUTCOME MEASURES: Using an inverse dynamics linked segment model, the mechanical torque, power output, and work done were calculated at the hip, knee, and ankle joints. RESULTS: The mean concentric ankle plantarflexor work done was much greater for the normal subjects compared to the prosthetic limb in pushoff (25.2 +/- 3.7 J vs 4.9 +/- 2.1 J), but greatest for the intact limb of the amputee subjects (34.2 +/- 6.6 J). Also, the concentric hip extensor work done in early stance was greater for the intact limb of the amputee subjects than for normal subjects (9.9 +/- 5.5 J vs 3.6 +/- 2.6 J), presumably compensating for the coincident decreased pushoff of the prosthetic limb. Other compensatory mechanisms are also discussed. CONCLUSIONS: Increased joint torques and power outputs of the amputee subjects' intact limb compared to normal ambulation may be viewed as providing additional gait progression and upright stance during parts of the gait cycle when the amputated limb lacks needed active muscle support.

Energy transfer mechanisms as a compensatory strategy in below knee amputee runners.

Below knee amputee runners exhibit abnormalities in the mechanical work characteristics of the lower extremity musculature during stance phase. The most significant abnormality is a marked reduction in the mechanical work done in the stance phase prosthetic limb. Energy transfer across the hip joint to the trunk during deceleration of the swing phase leg may be an important energy distribution mechanism to compensate for the reduced work done during prosthetic stance phase. Five unilateral below knee amputee runners wearing the SACH prosthetic foot and 5 normal subjects were studied. All subjects ran at a controlled velocity of 2.8 ms(-1) while kinematic and ground reaction force data were collected. Using a four segment linked segment model and an inverse dynamics approach joint moments, muscle power outputs, mechanical work values and energy transfers across the hip were calculated. The total amount of energy transferred during swing phase and the energy transferred out of the swing phase leg into the trunk were both significantly greater than normal. Energy transfer mechanisms are important in influencing the lower extremity energetics during swing phase. In addition, the 74 percent increase in energy transfer out of the intact swing phase limb combined with the temporal characteristics of this energy flow suggests that energy transfer may be an adaptive mechanism that allows energy redistribution to the trunk which may partially compensate for the reduced power output of the stance phase prosthetic limb.

Rehabilitation in limb deficiency. 1. Gait and motion analysis.

This self-directed learning module highlights new advances in this topic area. It is part of the chapter on rehabilitation in limb deficiency in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article discusses normal gait, the influence of prosthetic alignment on amputee function, and the effects of prosthetic components on the metabolic costs and the biomechanical function of the amputee. The biomechanics of normal ambulation are presented as a background to enable the practitioner to gain an understanding of the typical gait adaptations that occur in below-knee and above-knee amputees. The effects of newer prosthetic components and socket designs on the biomechanical adaptations are reviewed. The metabolic costs of amputee ambulation are significantly greater than normal. The theoretical mechanisms for this are discussed, and the effects of newer socket designs, ultra-light-weight components, and energy-storing prosthetic components are presented.

Effect of alterations in prosthetic shank mass on the metabolic costs of ambulation in above-knee amputees.

The metabolic costs of above-knee amputee ambulation are significantly greater than normal. The role of prosthetic mass and mass distribution on the metabolic costs of walking has received limited study. The metabolic costs of eight unilateral traumatic above-knee amputees were therefore studied under varying mass conditions. All of the subjects were active young amputees with a common prosthetic prescription, which included a total contact ischial containment, suction suspension socket with a graphlite knee assembly and a hydraulic unit, with a Seattle Light Foot (Model and Instrument Development, Seattle, WA). Expired gases were collected during over-ground ambulation at their self-selected walking speed and at three control speeds (.6, 1.0 and 1.5 m/s). The expired volumes and gas concentrations were measured, and the metabolic cost (ml/kg/m) at each ambulation speed was calculated. Data were collected on two further sessions with the addition of 0.68 and 1.34 kg to the center of mass of the shank, after a 1 wk acclimatization period. Results show that in the unweighted condition, the self-selected walking speed had the lowest metabolic energy expenditure and that the addition of weight to the shank did not significantly alter the metabolic costs of ambulation at any of the speeds studied. The common request for lighter weight prostheses does not appear to be based on the metabolic costs of ambulation.

Gait parameters of children with spastic diplegia: a comparison of effects of posterior and anterior walkers.

The purpose of this study was to compare the effects of posterior and anterior walkers on the gait parameters of five children with spastic diplegic cerebral palsy. Computer-based kinematic analysis was used to investigate differences in gait. Gait laboratory data indicated that use of the posterior walker (1) facilitated more upright posture in these subjects, as seen in decreased trunk and hip flexion during stance phase; (2) decreased double stance time; and (3) increased walking velocity. According to parent report, both the parents and their children preferred the posterior walker. Most parents also reported that when using the posterior walker, their children walked more normally with increased stability and interacted more easily with other children.

Insights into amputee running. A muscle work analysis.

Five young, active, unilateral below knee amputees wearing the SACH prosthetic foot, and six normal subjects participated in the study. Subjects ran at a controlled velocity of 2.8 m/s +/- 10% over a ground reaction force plate while being filmed with a video camera. Joint moments, power outputs and mechanical work characteristics were then calculated. During stance phase the amputee prosthetic limb exhibited a marked reduction in total work. There was a reduction in the mechanical work at the knee and the prosthetic foot/ankle with a compensatory increase in mechanical work by the hip musculature. The intact stance phase limb mechanical work characteristics were not significantly different from normal. The hip flexors were the only muscle group in the swing phase prosthetic limb with a significant increase in muscle work compared with normal subjects. The intact swing phase limb in contrast exhibited a marked increase in concentric muscle work by the hip flexors and eccentric muscle work by the knee flexors in early swing phase, and an increase in concentric hip extensor and eccentric knee flexor muscle work in late swing phase. The major compensatory patterns, therefore, that allow below knee amputees to run appear to be an increase in stance phase hip muscle work on the prosthetic limb and increased hip and knee muscle work on the intact limb during swing phase.