Lower extremity nerve function, calf skeletal muscle characteristics, and functional performance in peripheral arterial disease

Abstract

Objectives: To determine whether poor lower extremity nerve function is associated with less-favorable calf muscle characteristics and greater functional impairment in people with and without peripheral arterial disease (PAD).

Design: Cross-sectional.

Setting: Three Chicago-area medical centers.

Participants: Four hundred thirteen participants with PAD (ankle-brachial index (ABI) < 0.90) and 255 without.

Measurements: Electrodiagnostic testing of the peroneal nerve was performed. Calf muscle cross-sectional area and percentage fat were measured using computed tomography at 66.7% of the distance between the distal and proximal tibia. Six-minute walk performance was measured.

Results: Adjusting for age, sex, race, ABI, leg symptoms, smoking, physical activity, comorbidities, and other covariates, lower peroneal nerve conduction velocity (NCV) was associated with lower calf muscle area (first quartile 4,770.3 mm(2) , fourth quartile 5,571 mm(2) , P < .001) and poorer 6-minute walk distance (first quartile 989.2 feet, fourth quartile 1,210.8 feet, P < .001) in participants without diabetes mellitus with PAD. Lower peroneal NCV was associated with lower calf muscle area (first quartile 5,166.0 mm(2) , fourth quartile 6,003.8 mm(2) , P = .01) and poorer 6-minute walk distance (first quartile 866.4 feet, fourth quartile 1,082.5 feet, P = .01) in participants with diabetes mellitus and PAD as well. In participants without PAD, lower peroneal NCV was not associated with lower calf muscle area but was associated with poorer 6-minute walk distance only in participants without diabetes mellitus (first quartile 1,317.0 feet, fourth quartile 1,570.4 feet, P-trend < .001).

Conclusion: Lower peroneal nerve function is associated with smaller calf muscle area and greater functional impairment in individuals with PAD. Future study is needed to determine whether improving peroneal NCV prevents loss of calf muscle and functional decline in people with PAD.

Figure 1

Adjusted associations between peroneal nerve function and calf muscle characteristics in diabetic and non-diabetic individuals with PAD (n=441).* *■Non-diabetic individuals with PAD (n=301) ■Diabetic individuals with PAD (n=140) Analyses were adjusted for age, sex, race, ankle-brachial index, body-mass index, smoking, alcohol consumption, leg symptoms, comorbidities, physical activity, leg revascularization, and the study cohort. ‡P<0.05 for pairwise comparison to reference group. §P<0.01 for pairwise comparison to reference group. NCV=nerve conduction velocity, PAD=peripheral arterial disease

Figure 2

Development of functional impairment in individuals with peripheral arterial disease Proposed framework for the associations of PAD with impaired nerve function, adverse calf muscle characteristics, and functional impairment and decline in PAD. Denervation refers to damage to the distal motor nerve axons supplying muscle resulting in pathologic changes in muscle. Decreased muscle innervation refers to the loss of nerve conduction resulting in reduced muscle function.