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

Abstract

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.

Figure 1

An illustration of the stance phase of walking with the dominant flexor and extensor muscle groups that are involved in the three phases is produced. The dominant muscle groups are identified in red if they contract concentrically and in purple if they contract eccentrically. A) Early stance phase lasts from ipsilateral heel strike to contralateral toe off thus covering the first double support phase (initial 20% of stance). The right leg is accepting majority of body weight as it descends from previously being in single support on the left leg. In this phase the right hip extensors concentrically contract to extend the hip, the knee extensors eccentrically contract to allow the knee to bend and the ankle dorsiflexors eccentrically contract to maintain ankle dorsiflexion. B) Mid-stance phase lasts from contralateral (here left) toe off until contralateral heel strike. During single support the body is at its highest point over the extended ipsilateral leg. The body has maximum potential energy preparing to fall forward for the next double support. Limited muscular contractions are needed during this phase except when the knee extensors contract concentrically to extend the knee and straighten the leg. C) Late stance lasts from contralateral heel strike to ipsilateral toe off. It is the final 20% of stance and is the second double support phase. In this phase the body is propelled forward onto the extended left leg mainly by the action of the ankle plantar flexors. Functionally, these muscles contract concentrically and accelerate the leg and the trunk forward and upward over the left leg thus providing forward progression and weight support.

Figure 2

The ensemble-average joint torque curves of the affected limb for the PAD patients (PAD-PF and PAD-P; N=24 limbs) and the healthy controls (Control; N=20 limbs) during the stance phase for the (a) ankle and (b) knee joints. Note: ADT ankle dorsiflexion torque, APT ankle plantar flexion torque, KET extensor torque, KFT flexor torque. Torques are normalized to body mass in kg. Error bars represent the standard deviation of the mean values. Note: ^b p < .05, significant differences between groups (PAD-PF Affected limb vs. Control). ^dp < .05, significant differences between groups (PAD-P Affected limb vs. Control). ^ep < .05, significant differences between testing conditions (PAD-PF vs. PAD-P).

Figure 3

The ensemble-average joint power curves of the affected limb for the PAD patients (PAD-P and PAD-PF; N=24 limbs) and the healthy controls (Control; N=20 limbs) during the stance phase for the (a) ankle and (b) knee joints. Note: A1 ankle power absorption in late midstance, A2 ankle power generation in late stance, K1 knee power absorption in early stance, K2 knee power generation in early stance, K3 knee power absorption in late stance. Error bars represent the standard deviation of the mean values. Note: ^b p < .05, significant differences between groups (PAD-PF Affected limb vs. Control). ^dp < .05, significant differences between groups (PAD-P Affected limb vs. Control). ^ep < .05, significant differences between testing conditions (PAD-PF vs. PAD-P).

Figure 4

The ensemble-average joint power curves of the non-affected limb for the PAD patients (PAD-PF and PAD-P; N=24 limbs) and the healthy controls (Control; N=20 limbs) during the stance phase for the (a) ankle and (b) knee, joints. Note: A1 ankle power absorption in late midstance, A2 ankle power generation in late stance, K1 knee power absorption in early stance, K2 knee power generation in early mid-stance, K3 knee power absorption in late stance. Error bars represent the standard deviation of the mean values. Note: ^b p < .05, significant differences between groups (PAD-PF Affected limb vs. Control). ^dp < .05, significant differences between groups (PAD-P Affected limb vs. Control). ^ep < .05, significant differences between testing conditions (PAD-PF vs. PAD-P).