Barri L. Schnall

Transfemoral amputations: the effect of residual limb length and orientation on gait analysis outcome measures.

BACKGROUND The level of function achieved following a transfemoral amputation is believed to be affected by surgical attachment of the remaining musculature, resulting orientation of the femur, residual limb length, and eventual prosthetic fit. METHODS Twenty-six subjects underwent gait analysis testing in the current preferred prosthesis more than twenty-four months postamputation. The femoral length and orientation angles of each subject were measured from standing postoperative radiographic scanograms. The subjects were separated into groups for analysis on the basis of the femoral shaft angles and the residual limb length ratios. Gait analysis was performed to collect kinematic and temporospatial parameters. RESULTS A good correlation was observed between residual femoral length and trunk with regard to forward lean (r = -0.683) and lateral flexion (r = -0.628). A good correlation was also observed between residual femoral length and pelvic motion with regard to pelvic tilt (r = -0.691) and obliquity (r = -0.398). A moderate correlation was observed with speed (r = 0.550), indicating that subjects with shorter residual limbs experienced a greater excursion in the torso and pelvis, while walking at a slower self-selected pace. A significant correlation (r = 0.721, p < 0.001) was observed between the femoral shaft abduction angle and the residual femoral length; the shorter the residual limb, the more abducted it was. CONCLUSIONS The length of the residual femur substantially influences temporospatial and kinematic gait outcomes following transfemoral amputation, and appears to be more important than femoral orientation with regard to these parameters.

Metabolic analysis of male servicemembers with transtibial amputations carrying military loads

For servicemembers who have sustained amputations and wish to return to Active Duty, performing common military tasks is essential. The purpose of this study was to examine the metabolic requirements of servicemembers with transtibial amputations wearing a loaded rucksack and walking at a steady speed. We tested 12 servicemembers with unilateral transtibial amputations and 12 uninjured controls on a treadmill at two walking speeds (1.34 and 1.52 m/s) while they carried a 32.7 kg load. Oxygen consumption was recorded. Results showed that metabolic demand for the injured servicemembers was significantly higher (8.5% at 1.34 m/s and 10.4% at 1.52 m/s) than for controls. An understanding of energy expended during load carriage by this study population is critical for decisions regarding return-to-duty requirements. Although significant differences existed between uninjured controls and those with amputations, it is important to note that those differences are less than previously published. This finding, coupled with the fact that servicemembers with transtibial amputations have redeployed, implies that, despite statistical significance, results may not be clinically relevant. Future work should include more taxing conditions to identify a threshold for potential limitations.

Medial knee joint contact force in the intact limb during walking in recently ambulatory service members with unilateral limb loss: a cross-sectional study

Background Individuals with unilateral lower limb amputation have a high risk of developing knee osteoarthritis (OA) in their intact limb as they age. This risk may be related to joint loading experienced earlier in life. We hypothesized that loading during walking would be greater in the intact limb of young US military service members with limb loss than in controls with no limb loss. Methods Cross-sectional instrumented gait analysis at self-selected walking speeds with a limb loss group (N = 10, age 27 ± 5 years, 170 ± 36 days since last surgery) including five service members with transtibial limb loss and five with transfemoral limb loss, all walking independently with their first prosthesis for approximately two months. Controls (N = 10, age 30 ± 4 years) were service members with no overt demographical risk factors for knee OA. 3D inverse dynamics modeling was performed to calculate joint moments and medial knee joint contact forces (JCF) were calculated using a reduction-based musculoskeletal modeling method and expressed relative to body weight (BW). Results Peak JCF and maximum JCF loading rate were significantly greater in limb loss (184% BW, 2,469% BW/s) vs. controls (157% BW, 1,985% BW/s), with large effect sizes. Results were robust to probabilistic perturbations to the knee model parameters. Discussion Assuming these data are reflective of joint loading experienced in daily life, they support a “mechanical overloading” hypothesis for the risk of developing knee OA in the intact limb of limb loss subjects. Examination of the evolution of gait mechanics, joint loading, and joint health over time, as well as interventions to reduce load or strengthen the ability of the joint to withstand loads, is warranted.

Kinematic Analysis of Males with Transtibial Amputation Carrying Military Loads

The biomechanical responses to load carriage, a common task for dismounted troops, have been well studied in nondisabled individuals. However, with recent shifts in the rehabilitation and retention process of injured servicemembers, there remains a substantial need for understanding these responses in persons with lower-limb amputations. Temporal-spatial and kinematic gait parameters were analyzed among 10 male servicemembers with unilateral transtibial amputation (TTA) and 10 uninjured male controls. Participants completed six treadmill walking trials in all combinations of two speeds (1.34 and 1.52 m/s) and three loads (none, 21.8, and 32.7 kg). Persons with TTA exhibited biomechanical compensations to carried loads that are comparable to those observed in uninjured individuals. However, several distinct gait changes appear to be unique to those with TTA, notably, increased dorsiflexion (deformation) of the prosthetic foot/ankle, less stance knee flexion on the prosthetic limb, and altered trunk forward lean/excursion. Such evidence supports the need for future work to assess the risk for overuse injuries with carried loads in this population in addition to guiding the development of adaptive prosthetic feet/components to meet the needs of redeployed servicemembers or veterans/civilians in physically demanding occupations.

Functional Gait Analysis Before and After Delayed Military Trauma-related Amputation: A Report of Three Cases

The current conflicts in Iraq and Afghanistan have produced a large number of service members with severe combat-related injuries. Eighty-two percent of service members with combat-related injuries have sustained extremity trauma, which accounts for 54% of wounds overall1. Of all the lower-extremity amputations performed at military treatment facilities, approximately 13% (125 of 975) were the result of delayed or “elective” procedures2. Recent studies have shown that the outcomes of extensive salvage procedures for severely injured limbs are not necessarily definitive in a nonmilitary population3 and that early amputation can be preferable to limb salvage in many such instances3-12. Some military and nonmilitary population studies have considered a delayed amputation as occurring within as little as twenty-four hours postinjury, while other studies have cited a range over years4,13,14. Up to 15% of combat-related amputations have occurred later than twelve weeks postinjury, and the military medical community has adopted this as a reasonable timeframe during which initial operative efforts at limb salvage can be attempted2,14. Given the incidence of trauma-related amputation in the active duty military population, as well as the likely underreported frequency of similar scenarios in civilian trauma settings3,8,15-17, the goal of this report is to provide an analysis of gait in combat-injured patients before and after delayed amputation. Our institutional review board approved the retrospective review of the data presented in this manuscript. The three patients included in this case series were informed that data would be submitted for publication, and they all gave consent. Case 1. A forty-one-year-old male U.S. Navy navigator was involved in a midair collision and was ejected from his aircraft. Upon landing, he sustained a Gustilo …

Mechanical and dynamic characterization of prosthetic feet for high activity users during weighted and unweighted walking

Many Service members and Veterans with lower-limb amputations have the potential for high function and the desire to resume physically demanding occupations that require them to carry heavy loads (e.g., military service, firefighters, farmers, ranchers, construction workers). However, it is currently unclear which prosthetic feet best accommodate heavy load carriage while also providing good overall function and mobility during unweighted activities. The main objective of this study was to investigate the ability of currently available prosthetic ankle-foot systems to accommodate weighted walking by examining the mechanical characteristics (i.e., forefoot stiffness) and dynamic function (i.e., rocker radius, effective foot length ratio, and late-stance energy return) of prosthetic feet designed for high activity users. Load versus deflection curves were obtained for nine prosthetic ankle-foot systems using a servohydraulic test frame and load cell. Effective roll-over shape characteristics and late-stance energy return measures were then obtained using quantitative gait analysis for three users with unilateral, transtibial amputation. Results from mechanical and dynamic testing showed that although forefoot stiffness varied across the nine feet investigated in this study, changes measured in roll-over shape radius and effective foot length ratio were relatively small in response to weighted walking. At the same time, prosthetic feet with more compliant forefoot keel structures appeared to provide more late-stance energy return compared to feet with stiffer forefoot keel structures. These results suggest that prosthetic ankle-foot systems with compliant forefoot keel structures may better accommodate weighted walking by reducing the metabolic cost of physically demanding activities. However, to more fully understand the biomechanical and functional implications of these results, other factors, such as the residual-limb strength of the user and the overall stiffness profile of the prosthetic foot, should also be considered.

Knee adduction moment peak and impulse do not change during the first six months of walking with a prosthesis

BACKGROUND Individuals with unilateral lower limb loss are at increased risk for developing knee osteoarthritis in their contralateral limb. The mechanisms underlying this phenomenon are unknown, but large or unusual loads on the limb are thought to contribute to osteoarthritis development. Yet, to our knowledge, there have been no longitudinal assessments of knee joint kinetics to assist with identifying the origin or progression of such loads. RESEARCH QUESTION This study aimed to examine knee joint kinetics of individuals with lower limb loss as a function of time from independent ambulation. METHODS Eight male Service Members with unilateral lower limb loss (3 transfemoral/5 transtibial) completed gait analyses, walking at self-selected speed and cadence, at 0, 2, and 6 months following initial independent ambulation. RESULTS Although there was a significant time effect on stride length (p = 0.047), there were no pairwise differences (all p ≥ 0.152). Additionally, there was not a significant effect of time on the peak (p = 0.666), loading rate (p = 0.336), or impulse (p = 0.992) of knee adduction moment (KAM), peak knee flexion moment (KFM) (p = 0.128), or the peak (p = 0.485) or loading rate (p = 0.130) of vertical ground reaction force (VGRF). SIGNIFICANCE The results of the current study demonstrate that major features of knee joint loading do not change over the first 6 months of independently walking with a prosthesis. The magnitude of these loads are similar to loads observed in individuals with lower limb loss further from injury/initial ambulation, but the present results do not imply that no changes occur after 6 months.

Functional Outcomes of Service Members With Bilateral Transfemoral and Knee Disarticulation Amputations Resulting From Trauma

As longitudinal studies for those with bilateral transfemoral amputation (BTFA) or knee disarticulation (KD) are lacking, it is important to quantify performance measures during rehabilitation in an effort to determine reasonable expectations and trends that may influence the rehabilitation process. At initial evaluation (date of first independent ambulation) and follow up (median 135 [range = 47-300] days later), 10 participants with BTFA/KD completed 6 minute walk testing and Activity Specific Balance Confidence and Lower Extremity Functional Scale questionnaires. Of these, six participants also completed stair ambulation; ascent time and stair assessment index (SAI) scores were calculated. Patients utilized their prescribed prostheses at each visit. Participants were able to cover a significantly greater distance (135.3 [70.1] m) in 6 minutes at the follow-up visit (*p = 0.005). The change in SAI scores for stair ascent and descent was not statistically significant (p = 0.247). Stair ambulation confidence scores were significantly greater at the final visit (*p = 0.034). Stair negotiation appears to plateau early; however, confidence builds despite absence of functional gains over time. Service members with BTFAs/KDs are able to achieve functional community ambulation skills. Thus, this investigation suggests that clinicians can realign rehabilitation paradigms to shift focus towards community distance ambulation once safe stair ascent and descent is achieved.