Intrinsic Muscle Atrophy and Toe Deformity in the Diabetic Neuropathic Foot
A magnetic resonance imaging study
- Sicco A. Bus, MSC1,
- Qing X. Yang, PHD23,
- Jinghua H. Wang, PHD2,
- Michael B. Smith, PHD23,
- Roshna Wunderlich, PHD1 and
- Peter R. Cavanagh, PHD14567
- 1Center for Locomotion Studies, Penn State University, University Park, Pennsylvania
- 2Center for NMR Research, Penn State University College of Medicine, Hershey, Pennsylvania
- 3Department of Radiology, Penn State University College of Medicine, Hershey, Pennsylvania
- 4Department of Kinesiology, Penn State University, University Park, Pennsylvania
- 5Department of Biobehavioral Health, Penn State University, University Park, Pennsylvania
- 6Deparment of Medicine, Penn State University College of Medicine, Hershey, Pennsylvania
- 7Department of Orthopaedics and Rehabilitation, Penn State University College of Medicine, Hershey, Pennsylvania
Abstract
OBJECTIVE—The objectives of this study were to compare intrinsic foot muscle cross-sectional area (CSA) in patients with diabetic polyneuropathy and nondiabetic control subjects and to examine the association between intrinsic muscle CSA and clawing/hammering of the toes in neuropathic feet.
RESEARCH DESIGN AND METHODS—High-resolution T2-weighted fast spin-echo images and parametric T2 multiple spin-echo images were acquired using multiple spin-echo magnetic resonance imaging (MRI) of frontal plane sections of the metatarsal region of the foot in a sample of eight individuals with diabetic polyneuropathy and eight age- and sex-matched nonneuropathic nondiabetic control subjects. The configuration of joints of the second toe was obtained using a three-dimensional contact digitizer.
RESULTS—Remarkable atrophy was found in all the intrinsic muscles of neuropathic subjects as compared with nondiabetic control subjects. Quantitative T2 analysis showed a 73% decrease in muscle tissue CSA distally in the neuropathic subjects. Muscle comprised only 8.3 ± 2.9% (means ± SD) of total foot CSA compared with 30.8 ± 3.9% in control subjects. No significant differences were found between the groups in the metatarso-phalangeal and proximal and distal interphalangeal joint angles of the second ray. Moreover, clawing/hammering of the toes was found in only two of eight neuropathic subjects.
CONCLUSIONS—Although sensory neuropathy is often emphasized in considerations of diabetic foot pathology, our results show that the consequences of motor neuropathy in the feet are profound in people with diabetes. This has implications for foot function and may play a significant role in postural instability. However, intrinsic muscle atrophy does not necessarily appear to imply toe deformity.
- CSA, cross-sectional area
- DIP, distal interphalangeal
- MNCV, motor nerve conduction velocity
- MRI, magnetic resonance imaging
- MT, magnetization transfer
- MTH, metatarsal head
- MTP, metatarso-phalangeal
- PIP, proximal interphalangeal
- TE, echo time
- TR, repetition time
- VPT, vibration perception threshold
Footnotes
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Address correspondence and reprint requests to Peter R. Cavanagh, PhD, Department of Biomedical Engineering ND20, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH 44195. E-mail: cavanagh{at}bme.ri.ccf.org.
Received for publication 21 December 2001 and accepted in revised form 13 May 2002.
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