Sara A. Myers

Claudication distances and the Walking Impairment Questionnaire best describe the ambulatory limitations in patients with symptomatic peripheral arterial disease

BACKGROUND Claudication secondary to peripheral arterial disease leads to reduced mobility, limited physical functioning, and poor health outcomes. Disease severity can be assessed with quantitative clinical methods and qualitative self-perceived measures of quality of life. Limited data exist to document the degree to which quantitative and qualitative measures correlate. The current study provides data on the relationship between quantitative and qualitative measures of symptomatic peripheral arterial disease. METHOD This descriptive case series was set in an academic vascular surgery unit and biomechanics laboratory. The subjects were symptomatic patients with peripheral arterial disease patients presenting with claudication. The quantitative evaluation outcome measures included measurement of ankle-brachial index, initial claudication distance, absolute claudication distance, and self-selected treadmill pace. Qualitative measurements included the Walking Impairment Questionnaire (WIQ) and the Medical Outcomes Study Short Form-36 (SF-36) Health Survey. Spearman rank correlations were performed to determine the relationship between each quantitative and qualitative measure and also between the WIQ and SF-36. RESULTS Included were 48 patients (age, 62 +/- 9.6 years; weight, 83.0 +/- 15.4 kg) with claudication (ABI, 0.50 +/- 0.20). Of the four WIQ subscales, the ankle-brachial index correlated with distance (r = 0.29) and speed (r = 0.32); and initial claudication distance and absolute claudication distance correlated with pain (r = 0.40 and 0.43, respectively), distance (r = 0.35 and 0.41, respectively), and speed (r = 0.39 and 0.39 respectively). Of the eight SF-36 subscales, no correlation was found for the ankle-brachial index, initial claudication distance correlated with Bodily Pain (r = 0.46) and Social Functioning (r = 0.30), and absolute claudication time correlated with Physical Function (r = 0.31) and Energy (r = 0.30). The results of both questionnaires showed reduced functional status in claudicating patients. CONCLUSIONS Initial and absolute claudication distances and WIQ pain, speed, and distance subscales are the measures that correlated the best with the ambulatory limitation of patients with symptomatic peripheral arterial disease. These results suggest the WIQ is the most specific questionnaire for documenting the qualitative deficits of the patient with claudication while providing strong relationships with the quantitative measures of arterial disease. Future studies of claudication patients should include both quantitative and qualitative assessments to adequately assess disease severity and functional status in peripheral arterial disease patients.

Gait variability is altered in patients with peripheral arterial disease

OBJECTIVE Claudication is the most common presentation of peripheral arterial disease (PAD), producing significant ambulatory compromise. Claudicating patients, most of whom are elderly, have reduced mobility and poor health outcomes, including an increased risk of falls. The gait of elderly fallers is characterized by increased variability. Increase in the variability of the locomotor system makes the gait more noisy and unstable. The purpose of this study is to investigate gait variability in patients with PAD. METHODS Nineteen symptomatic PAD patients (age, 63.6 +/- 9.8 years; body mass, 82.1 +/- 18.5 kg; height, 1.71 +/- 0.06 m) walked on a treadmill in the absence of pain or claudication symptoms while joint flexion and extension kinematics were captured. Results were compared with results obtained from 17 matched healthy controls (age, 65.2 +/- 12.5 years; body mass, 82.0 +/- 25.9.5 kg; height, 1.73 +/- 0.08 m). Relative joint angles were calculated for the ankle, knee, and hip flexion/extension, and the stride-to-stride variability of joint flexion and extension was calculated from at least 30 consecutive footfalls. Variability was expressed using the largest Lyapunov exponent, standard deviation, and coefficient of variation. Independent t tests were used to compare gait variability between groups. RESULTS Symptomatic PAD patients had significantly higher largest Lyapunov exponent values and coefficient of variation values for all joints, and higher standard deviation values at the ankle and the hip (P < .05). CONCLUSION Symptomatic PAD patients have increased gait variability at the ankle, knee, and hip joints at baseline ambulation in the absence of claudication pain. Our findings indicate significant baseline deterioration in the locomotor system of symptomatic PAD patients. This deterioration results in increased noise and instability of gait and is a potential contributing factor to the falls and mobility problems experienced by symptomatic PAD patients.

Peripheral arterial disease affects kinematics during walking

OBJECTIVE Claudication is the most common manifestation of peripheral arterial disease (PAD) producing significant ambulatory compromise. The purpose of this study was to use advanced biomechanical analysis to characterize the kinematic ambulatory pattern of claudicating patients. We hypothesized that compared with control subjects, claudicating patients have altered kinematic gait patterns that can be fully characterized utilizing advanced biomechanical analysis. METHODS The study examined fourteen PAD patients (age: 58 +/- 3.4 years; weight: 80.99 +/- 15.64 kg) with clinically diagnosed femoro-popliteal occlusive disease (Ankle Brachial Index (ABI): 0.56 +/- 0.03, range 0.45 to 0.65) and five healthy controls (age: 53 +/- 3.4 years; weight: 87.38 +/- 12.75 kg; ABI >or= 1). Kinematic parameters (hip, knee, and ankle joint angles in the sagittal plane) were evaluated during gait in patients before and after the onset of claudication pain and compared with healthy controls. Joint angles were calculated during stance time. Dependent variables were assessed (maximum and minimum flexion and extension angles and ranges of motion) and mean ensemble curves were generated. Time to occurrence of the discrete variables was also identified. RESULTS Significantly greater ankle plantar flexion in early stance and ankle range of motion during stance was observed in PAD patients (P < .05). Time to maximum ankle plantar flexion was shorter and time to maximum ankle dorsiflexion was longer in PAD patients (P < .05). These differences were noted when comparing PAD patients prior to and after the onset of claudication with healthy controls. The analysis of the kinematic parameters of the knee and the hip joints revealed no significant differences between PAD patients and controls. CONCLUSION PAD patients with claudication demonstrate significant gait alterations in the ankle joint that are present prior to the onset of claudication pain. In contrast, the joint motion of the hip and knee did not differ in PAD patients when compared with controls. Further research is needed to verify our findings and assess the impact of more proximal disease in PAD patients as well as the effect of revascularization on joint kinematics.

Bilateral claudication results in alterations in the gait biomechanics at the hip and ankle joints.

Claudication is the most common symptomatic manifestation of peripheral arterial disease (PAD), producing significant ambulatory compromise. The purpose of this study was to use advanced biomechanical gait analysis to determine the gait alterations occurring in claudicating patients both before and after onset of claudication pain in their legs. Hip, knee, and ankle joint moments were measured in claudicating patients (age: 64.46+/-8.47 years; body mass: 80.70+/-12.64kg; body height: 1.72+/-0.08m) and were compared to gender-age-body mass-height-matched healthy controls (age 66.27+/-9.22 years; body mass: 77.89+/-10.65kg; body height: 1.74+/-0.08m). The claudicating patients were evaluated both before (pain-free (PF) condition) and after (pain condition) onset of claudication pain in their legs. Thirteen symptomatic PAD patients (26 claudicating limbs) with bilateral intermittent claudication (IC) and 11 healthy controls (22 control limbs) were tested during level walking at their self-selected speed. Compared to controls, PAD hip and ankle joints demonstrated significant angular kinematics and net internal moment changes. Alterations were present both in PF and pain conditions with several of them becoming worse in the pain condition. Both PF and pain conditions resulted in significantly reduced peak hip extensor moment (5.62+/-1.40 and 5.63+/-1.33% BWxBH, respectively) during early stance as compared to controls (7.53+/-1.16% BWxBH). In the pain condition, PAD patients had a significantly reduced ankle plantar flexor moment (7.56+/-1.41% BWxBH) during late stance as compared to controls (8.65+/-1.27% BWxBH). Furthermore, when comparing PF to pain conditions, there was a decreased peak plantar flexor moment (PF condition: 8.23+/-1.37 vs. pain condition: 7.56+/-1.41% BWxBH) during late stance. The findings point to a weakness in the posterior compartment muscles of the hip and calf as being the key factor underlying the PAD gait adaptations. Our findings establish a detailed baseline description of the changes present in PAD patients joint angles and moments during walking. Since IC is primarily a gait disability, better understanding of the abnormalities in joint and muscle function will enhance our understanding of the gait impairment and may lead to novel, gait-specific treatments.

Abnormal joint powers before and after the onset of claudication symptoms.

OBJECTIVE Claudication is the most common manifestation of peripheral arterial disease, producing significant ambulatory compromise. Our study evaluated patients with bilateral lower limb claudication and characterized their gait abnormality based on advanced biomechanical analysis using joint torques and powers. METHODS Twenty patients with bilateral claudication (10 with isolated aortoiliac disease and 10 with combined aortoiliac and femoropopliteal disease) and 16 matched controls ambulated on a walkway while 3-dimensional biomechanical data were collected. Patients walked before and after onset of claudication pain. Joint torques and powers at early, mid, and late stance for the hip, knee, and ankle joints were calculated for claudicating patients before and after the onset of claudication pain and were compared to controls. RESULTS Claudicating patients exhibited significantly reduced hip and knee power at early stance (weight-acceptance phase) due to decreased torques produced by the hip and knee extensors. In mid stance (single-limb support phase), patients had significantly reduced knee and hip power due to the decreased torques produced by the knee extensors and the hip flexors. In late stance (propulsion phase), reduced propulsion was noted with significant reduction in ankle plantar flexor torques and power. These differences were present before and after the onset of pain, with certain parameters worsening in association with pain. CONCLUSIONS The gait of claudication is characterized by failure of specific and identifiable muscle groups needed to perform normal walking (weight acceptance, single-limb support, and propulsion). Parameters of gait are abnormal with the first steps taken, in the absence of pain, and certain of these parameters worsen after the onset of claudication pain.

Joint torques and powers are reduced during ambulation for both limbs in patients with unilateral claudication

OBJECTIVES Symptomatic peripheral arterial disease (PAD) results in significant gait impairment. In an attempt to fully delineate and quantify these gait alterations, we analyzed joint kinematics, torques (rotational forces), and powers (rotational forces times angular velocity) in patients with PAD with unilateral claudication for both the affected and nonaffected legs. METHODS Twelve patients with unilateral PAD (age, 61.69 +/- 10.53 years, ankle-brachial index [ABI]: affected limb 0.59 +/- 0.25; nonaffected limb 0.93 +/- 0.12) and 10 healthy controls (age, 67.23 +/- 12.67 years, ABI >1.0 all subjects) walked over a force platform to acquire gait kinetics, while joint kinematics were recorded simultaneously. Data were collected for the affected and nonaffected limbs during pain free (PAD-PF) and pain induced (PAD-P) trials. Kinetics and kinematics were combined to quantify torque and powers during the stance period from the hip, knee, and ankle joints. RESULTS The affected limb demonstrated significantly (P <.05) reduced ankle plantar flexion torque compared to controls during late stance in both PAD-PF and PAD-P trials. There were significant reductions in ankle plantar flexion power generation during late stance for both the affected (P <.05) and nonaffected limbs (P <.05) compared to control during PAD-PF and PAD-P trials. No significant differences were noted in torque comparing the nonaffected limbs in PAD-PF and PAD-P conditions to control for knee and hip joints throughout the stance phase. Significant reductions were found in knee power absorption in early stance and knee power generation during mid stance for both limbs of the patients with PAD as compared to control (P <.05). CONCLUSION Patients with PAD with unilateral claudication demonstrate significant gait impairments in both limbs that are present even before they experience any claudication symptoms. Overall, our data demonstrate significantly reduced ankle plantar flexion torque and power during late stance with reduced knee power during early and mid stance for the affected limb. Further studies are needed to determine if these findings are dependent on the location and the severity of lower extremity ischemia and whether the changes in the nonaffected limb are the result of underlying PAD or compensatory changes from the affected limb dysfunction.

Gait variability patterns are altered in healthy young individuals during the acute reperfusion phase of ischemia-reperfusion.

BACKGROUND The role of ischemia reperfusion contributing to functional impairment in lower extremity peripheral arterial disease (PAD) patients has not previously been elucidated. The evaluation of gait variability patterns has proven useful in many pathologic populations. Therefore, the purpose of this study is to isolate and determine the specific effect of the acute reperfusion phase of ischemia-reperfusion on gait variability in young individuals with no vascular disease. MATERIALS AND METHODS Thirty healthy young individuals walked on a treadmill during baseline and the acute reperfusion phase of ischemia-reperfusion conditions while lower extremity joint kinematics were captured. Stride to stride variability was assessed using the largest Lyapunov exponent, approximate entropy, standard deviation, and coefficient of variation. Differences in gait variability between conditions were assessed using dependent t-tests. RESULTS The largest Lyapunov exponent values and approximate entropy values were significantly higher in the acute reperfusion phase of ischemia-reperfusion condition for the ankle, knee, and the hip. Coefficient of variation was significantly higher at the hip and standard deviation was higher at the knee and the hip during the acute reperfusion phase of ischemia-reperfusion condition. CONCLUSIONS The acute reperfusion phase of the ischemia-reperfusion cycle alters gait variability patterns at the ankle, knee, and the hip in healthy young individuals. Our findings indicate increased noise and irregularity of gait variability patterns post-ischemia. In young healthy individuals who do not have neuromuscular impairments, significant gait alterations are present during walking after a period of interruption of blood flow.

Abnormal Accumulation of Desmin in Gastrocnemius Myofibers of Patients with Peripheral Artery Disease Associations with Altered Myofiber Morphology and Density, Mitochondrial Dysfunction and Impaired Limb Function

Patients with peripheral artery disease (PAD) develop a myopathy in their ischemic lower extremities, which is characterized by myofiber degeneration, mitochondrial dysfunction and impaired limb function. Desmin, a protein of the cytoskeleton, is central to maintenance of the structure, shape and function of the myofiber and its organelles, especially the mitochondria, and to translation of sarcomere contraction into muscle contraction. In this study, we investigated the hypothesis that disruption of the desmin network occurs in gastrocnemius myofibers of PAD patients and correlates with altered myofiber morphology, mitochondrial dysfunction, and impaired limb function. Using fluorescence microscopy, we evaluated desmin organization and quantified myofiber content in the gastrocnemius of PAD and control patients. Desmin was highly disorganized in PAD but not control muscles and myofiber content was increased significantly in PAD compared to control muscles. By qPCR, we found that desmin gene transcripts were increased in the gastrocnemius of PAD patients as compared with control patients. Increased desmin and desmin gene transcripts in PAD muscles correlated with altered myofiber morphology, decreased mitochondrial respiration, reduced calf muscle strength and decreased walking performance. In conclusion, our studies identified disruption of the desmin system in gastrocnemius myofibers as an index of the myopathy and limitation of muscle function in patients with PAD.

Adaptation and Prosthesis Effects on Stride-to-Stride Fluctuations in Amputee Gait

Twenty-four individuals with transtibial amputation were recruited to a randomized, crossover design study to examine stride-to-stride fluctuations of lower limb joint flexion/extension time series using the largest Lyapunov exponent (λ). Each individual wore a “more appropriate” and a “less appropriate” prosthesis design based on the subjects previous functional classification for a three week adaptation period. Results showed decreased λ for the sound ankle compared to the prosthetic ankle (F1,23 = 13.897, p = 0.001) and a decreased λ for the “more appropriate” prosthesis (F1,23 = 4.849, p = 0.038). There was also a significant effect for the time point in the adaptation period (F2,46 = 3.164, p = 0.050). Through the adaptation period, a freezing and subsequent freeing of dynamic degrees of freedom was seen as the λ at the ankle decreased at the midpoint of the adaptation period compared to the initial prosthesis fitting (p = 0.032), but then increased at the end compared to the midpoint (p = 0.042). No differences were seen between the initial fitting and the end of the adaptation for λ (p = 0.577). It is concluded that the λ may be a feasible clinical tool for measuring prosthesis functionality and adaptation to a new prosthesis is a process through which the motor control develops mastery of redundant degrees of freedom present in the system.

Patients with peripheral arterial disease exhibit reduced joint powers compared to velocity-matched controls

Previous studies have shown major deficits in gait for individuals with peripheral arterial disease before and after the onset of pain. However, these studies did not have subjects ambulate at similar velocities and potential exists that the differences in joint powers may have been due to differences in walking velocity. The purpose of this study was to examine the joint moments and powers of peripheral arterial disease limbs for subjects walking at similar self-selected walking velocities as healthy controls prior to onset of any symptoms. Results revealed peripheral arterial disease patients have reduced peak hip power absorption in midstance (p=0.017), reduced peak knee power absorption in early and late stance (p=0.037 and p=0.020 respectively), and reduced peak ankle power generation in late stance (p=0.021). This study reveals that the gait of patients with peripheral arterial disease walking prior to the onset of any leg symptoms is characterized by failure of specific and identifiable muscle groups needed to perform normal walking and that these gait deficits are independent of reduced gait velocity.